CA1203625A - Apparatus for detecting an absolute position and a process thereof - Google Patents
Apparatus for detecting an absolute position and a process thereofInfo
- Publication number
- CA1203625A CA1203625A CA000441231A CA441231A CA1203625A CA 1203625 A CA1203625 A CA 1203625A CA 000441231 A CA000441231 A CA 000441231A CA 441231 A CA441231 A CA 441231A CA 1203625 A CA1203625 A CA 1203625A
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- CA
- Canada
- Prior art keywords
- detecting
- value
- absolute position
- detectors
- period
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/003—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring position, not involving coordinate determination
Abstract
Abstract of the disclosure An apparatus and a process for detecting an absolute value relating to mechanical movement of a member to be measured from a reference point. The apparatus includes a detecting means with a plurality of detectors of which periods are different from each other. Each detector generates electric signal with its each period corresponding to movement of the member. The signals are stored in a memory. Then, absolute value of mechanical movement between one of detectors and the member is specified by using of two values. The one is equal to values of multiplication between the period of the signal corresponding to the detector and an integer. The other is the stored value in the memory corresponding to the detector. The value of the integer is decided by using periods and stored values corresponding to other detectors.
Description
~L~r9~s Title of the invention An apparatus for de~ecting an absolute position and a process thereof Background of the invention This invention relates to an apparatus for detecting an absolute position of an element and a process thereof and more particularly to an apparatus for determining an absolute value by use of signals from a plurality of detectors and a process thereof.
In ~he~prior art, for example, ~s ~isclosed in Japanese Patent ~o.1,091,345 issued on M~rch~31, 1982~ a detector detecting an absolute position of an element on a machine tool, obtains an absolute value as follows~ First, the number of rotations of the element in a direction of a coordinate axis, iOe~ the X axis, is derived from a driving unit for the X axis direction and that number is supplied to a reduction train with two (2) stages or three t3) stages. A
rotary detector is provided on a rotatable axle of each reduction stage so that a value within one revolution of the rotary detector is read out to obtain an absolute value from the combination of values detected by the rotary detectors.
The combination of values above is performed as follows.
Suppose that a table of a machine tool is moved in the X
axis direction. The number of revolutions derived from the X
axis driving unit is reduced to 1/10 between the first axis and second axis of an X axis absolute position detecting unit. Further, the reduced number of revolutions is again reduced to 1/10 between the second axis and third axis thereof. Furthermore, the reduced number of revolutions is reduced to 1/10 between the third axis and fourth axis ql~.
r; ' ~ . ~
:~L2~
thereof. In this instance, the four~h axis rotates less than one revolution over all the length of all measuring range in the X axis direction.
For example, suppose that the first axis rotates one revolution per 2mm which is the movement of the table in the X axis direction. The movement of the table corresponding to each revolution of the fourth axis is as follows.
In ~he~prior art, for example, ~s ~isclosed in Japanese Patent ~o.1,091,345 issued on M~rch~31, 1982~ a detector detecting an absolute position of an element on a machine tool, obtains an absolute value as follows~ First, the number of rotations of the element in a direction of a coordinate axis, iOe~ the X axis, is derived from a driving unit for the X axis direction and that number is supplied to a reduction train with two (2) stages or three t3) stages. A
rotary detector is provided on a rotatable axle of each reduction stage so that a value within one revolution of the rotary detector is read out to obtain an absolute value from the combination of values detected by the rotary detectors.
The combination of values above is performed as follows.
Suppose that a table of a machine tool is moved in the X
axis direction. The number of revolutions derived from the X
axis driving unit is reduced to 1/10 between the first axis and second axis of an X axis absolute position detecting unit. Further, the reduced number of revolutions is again reduced to 1/10 between the second axis and third axis thereof. Furthermore, the reduced number of revolutions is reduced to 1/10 between the third axis and fourth axis ql~.
r; ' ~ . ~
:~L2~
thereof. In this instance, the four~h axis rotates less than one revolution over all the length of all measuring range in the X axis direction.
For example, suppose that the first axis rotates one revolution per 2mm which is the movement of the table in the X axis direction. The movement of the table corresponding to each revolution of the fourth axis is as follows.
2 x 10 x 10 x 10 = 2000(mm) Therefore, the effective detecting range i.s 2 meters.
One revolution of the third axis corresponds to 200mm in the movement of the table while one revolution: of the second axis corresponds to 20mm in the movement of the tablen Thus, in this case, an absolute value within 2000mm of the table movement can be calculated from the sum of each value of the rotating angles within one revolution of the first, second, thi~d and fourth axes.
However, the disadvantages concerning the above are:
~a) The reduction train becomes larger in size and its inertia moment increased as the effec~ive measuring range is enlarged.
(b) The weighting factor of each value of the axes is different from each other. Thus, errors over one graduated scale on the fourth axis will be 10û0 times greater: in the first staye.
Accordingly, mechanical accuracy must always be maintained at a high degree even if Yibration or wear occurrs in the machine tool during operation thereof.
One revolution of the third axis corresponds to 200mm in the movement of the table while one revolution: of the second axis corresponds to 20mm in the movement of the tablen Thus, in this case, an absolute value within 2000mm of the table movement can be calculated from the sum of each value of the rotating angles within one revolution of the first, second, thi~d and fourth axes.
However, the disadvantages concerning the above are:
~a) The reduction train becomes larger in size and its inertia moment increased as the effec~ive measuring range is enlarged.
(b) The weighting factor of each value of the axes is different from each other. Thus, errors over one graduated scale on the fourth axis will be 10û0 times greater: in the first staye.
Accordingly, mechanical accuracy must always be maintained at a high degree even if Yibration or wear occurrs in the machine tool during operation thereof.
3 --It is a principal object of the present invention to provide an apparatus for detecting an absolute position in which a plurality of detectors each produces periodical electric signals in respons to predetermined mechanical movement of the member, the detectors having periods which are different from each other. Electric signals are oftained from the detecting means, which correspond to less than one period when the member is mechanically s~opped. The signals thus obtained are digitally stored and, an integral value determined wherein a relative po~ition between one of ~he detectors and the member is specified by a value multiplied by a value of integer N of the period corresponding to the one detector and a value of the le~s one period, and the integral value N is determined by using at least a period corresponding to another det~ctor of the detecting means and the digital quantity stored in the storing means~
It is another object of the present invention to provide a process for detecting an absolute position which comprises the steps of preparing a detecting means with a plurality of detectors which generate periodical electric signals corresponding to predtermined mechanicl movements which are different from each other to a member to be measured, generating the mechanical movement be~ween the detecting means and the membert storing the electric signals corresponding to each of the p~riod out o the detecting means, specifying a relative position involved in the mechanical movement between one of detectors of the detecting means and the member by using the value multiplied by integer N of the period corresponding to the one of detectors and the value which ls less than the period, and deciding the integral value N by u~ing period corresponding to another detector of the detecting means and the stored value which is from another detector.
"::
-` ~21D3~5 It is a further object of the present invention to provide a process for detecting an absolute position which comprises the steps of preparing a transmitting means of rotary type which includes a plurality of rotary detectors generating electric signals o which period is due to a rotary angle range based on one revolution or devided revolution equally thereof and axes rotating the detectors respectively at predetermined ratio, connecting the rotary transmitting means to the member ~o be measured for mechanical movement thereof, supplying the mechanical movement between the rotary detector and member to be measured under the condition specified, storing the electric signals corresponding to the respective period out of the each dekector, specifying a relative position relationship between the member and one of the detectors, being involved in mechanical movement, by using the value multiplied by integer N of the period corresponding to the one of detector and the value which is which is less than one period thereof, and deciding the integral value N by using the period corresponding to another detector of the detectors and the stored value from the another detector.
The foregoing and, other object~, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.
Brief description of the drawings.
Figure 1 is a diagram illustrating the principle of the present invention~
Figure 2 is a diagram of waveforms from detec~ors corresponding to the period illustrated in Figure 1, 3~ 2~;
Figure 3 is a diagram showing a layout o gear trains and a group of detectors which are of rotary type according to the present invention, Figure 4 is a block diayram for an ahsolute position detecting apparatus including three (3) gears and resolverst Figures Sa and 5b are diagrams illustrating an adjustment of phases of secondary outpu~s from resolvers shown in Figure 4, Figures 6a and 6b are diagrams illustratirlg counting of a position collating counter and zero cross adjustment for the phases of the outputs from the resolver in Figure 4, Figure 7 is a diagram for waveforms illustrating a process of detecting an absolute position by the apparatus shown in Figure 4, Figure 8 is a flow chart illustrating data processing in the central processing unit shown in Figure 4, Figure 9 is a block diagram of another embodiment of the present invention whîch shows a preerred absclute position detecting apparatus compared to that of Figure 4, Figure 10 is a diagram illustrating the function of a resolver with ten (10) poles as shown in Figure 9, Figures lla and llb ~are diagrams illustrating zero cross adju~tment of three (3) resolvers with ten (10) poles in Figure 9,~
Figure 12 is a diagram ~or waveforms illustrating a process of absolute position detection in Figure 9, ~3~Z$
Figure 13 is a flow chart illustrating a process of data processing in the central processing unit shown in Figure 9, Figure 14 is a diagram illustrating a process for calculating that position data is zero in Figure 9, Figure 15 is a diagram illustrating measured phase lag for the apparatus o Figure 9, and Figure 16 is a diagram for still another embodiment of the present invention.
Detailed de~cription of the invention Referring to Figure 1, reference numerals 21, 22 and 23 indicate one part of a detecting means, i.e. scales which are provided in parallel, respectively, in the X axis direction. The period of scale 21 is Pl which consists of five ~5~ graduated scales as one unit in the X axis direction. The period of scale 22 is P2 which consists of six (6) graduated scales as one unit in the X axis direction and the period of scale 23 i~ P3 which conqists of seven (7) graduated scales as one unit in the X
axis direction. A distance LAgs indicates an effective detecting range from the starting point OABS . In Figure 1, all the periods of scales 21, 22 and 23 are consistent with each other at the`point Lab~l which is the next consistent point from the starting point OAB~.
A detecting means 24 can move in the X axis direction, and supports detectors ~5, 26 and 270 The detec~ors 25, 26 and 27 output electric signals as the wave~orms 25a, 26a and 27a shown in Figure 2. These waves correspond ta the wave forms from a potentiometer of rotary type as one example of an ideal detector.
` ~3~5 Suppose that the central position of the detecting means 24 is at ~he point L(X) and each detector 25, 26 and 27 outputs values ~ Pl, ~ P2 and~P3, respectively, each of which values is less than one period of Plr P2 and P3. In Figure 1, the distance L~X) is obtained by the following expressions.
L~X) = Nl x Pl ~ ~Pl (1) L~X) = N2 x P2 ~ QP2 (2) L(X) = N3 x P3 + ~P3 (3) In the expressions, the values Pl, P2 and P3 are known amounts and the values ~ Pl, ~ P2 and ~ P3 are also measured values, i.e. known amounts. Thus, the corresponding value L(X) will be obtained where the value of integer 1, 2, 3~...n is substituted for Nl in the expression (1), successively. After that, the values L(X) will be substituted in~o the expressions (2) and (3) in order to obtain the values j equal to ~he Values Nl. For instanceV as shown in Figures 1 and 2, Pl is equal to ~ive (5). P2 is equal to six (6) and P3 is equal to seven (7~. On the other hand, the value ~ Pl is equal to three (3~P2 is equal to ~ive (5) and ~ P3 is equal to two (2)~ The numerals 1,2,3,4....n are substituted for Nl successively in the expression (1).
~uppose that Nl is equal to the numeral 1, (LX) = 1 x 5 + 3 = 8 (4) 8 = N2 x 6 ~ 5 (5~
8 = ~3 x 7 ~ 2 (6) NO integral numbers including zero (0), which are substituted for N2 and N3, can solve the expressions (5~ ~nd (~) .
Thus, the value Nl cannot be 1.
~2~
~ 8 --Suppose that Nl is equal to the numeral 2, L~X) = 2 x 5 + 3 = 13 (7) 13 = N2 x 6 ~ 5 (8) 13 = N3 x 7 + 2 (9) No integral numbers including zero (O), which are substituted for N2 and N3, can solve the expressions t8) and (9~. Thusr the value N1 cannot be 2.
Suppose that Nl is equal t3 the numeral 3, L(X) = 3 x 5 + 3 = 18 (10) 18 = ~2 x 6 + 5 ~11) I8 = N3 x 7 + 2 (12~
No integrals N2 and N3 can solve the expressions (11~ and (12~.
Suppose that Nl IS equal to the numeral 4, L(X) = 4 x 5 + 3 = 23 (13) 23~= N2 x 6 + 5 (14) 23 = N3 x 7 ~ 2 (15~
The expressions ~14) and (15) are solved in this case, i.e.
N2 is three (3) and N3 is three (3)~ as will be apparent from Figure 1. Fur~hermore~ the reason why only one group of N1, N2 and:N3 exists for the combination of Pl~ P2 and ~ P3 provided by the detecting means is illu~trated below.
Figures 1 and 2 show a detecting means of linear type which moves linearly with respect to the scales 21, 22 and 23 whereas the; rotary type thereof is illustrated in Figure 3 as an preferred embodiment. In Figure 3, a motor 31 ~26)3625 activates a driven member 34 which moves through a feed screw 35 in the X direction shown as an arrow. An axle 36 extending from the driving motor 31 is connected with a rotary axle 38 of rotary detecting means Sn. The rotary axis 38 is connected to an axle 37 of a gear Gn in order to be rotated, gear Gn having Tn teeth. As illustrated in Figure 3, the gear Gl, G2, G3....Gn..~.GN having teeth Tl, T2, T3, .... Tn,~..TN, respectively, are engaged with each other to comprise a gear train. Detectors Sl, S2, S3~ ..Ø Sn,...SN output signals ~ 2, ~3, .~ n,....
N, respectively, which correspond to the rotating positions of rotary axles 38 of each detector. Suppose, in Figure 3, the driven member 34 stays at a point in the X axis direction after rotation of the motor 31. The absolute value Pn of the position thereof will be found as follows where the detector Sn outputs the position data ~ n.
Pn = Rn ~ + ~n (~6) In the expression (I6), the symbol ~ indicates the moving degree of the driven member 34 in the X axis direction per revolution of the motor 31, the symbol Rn indicates the number of revolutions of the detector Sn from the reference point, which number is an integer. The symbol ~ n corresponds to the rotating angle position which is less than one revolution of the rotary axle 38 of the detector Sn , that is,~ which corresponds to the displacement of the driven member 34 in the X axis direction. The number of revolutions of the motor 31 is transmitted to each detector Si (i~n) as well as detector Sn through the gear train 33.
Thus, the following expression is solved.
~i = Ti Pn - iFiX~Ti Pn/~ (17) ~2~3625 where iFix ~A] is the integral portion of symbol A~
Furthermore, the sum of the teeth to be rotated until each gear Gl, G2, ...~.GN reaches ~he same position is obtain.ed by the following expression.
LCM~K~
Where the symbol K is equal to ~Tj-j = 1, 2, ...N ~
and the symbol LCM~K} means the least common multiple of K.
The maximum number of effective revolutions Kn of detector Sn is defined by the following expression9 Kn = LCMfR~ 1 (18~
Suppose that the Pn is the solution of Rn in the expression (17), {1, 2, ...N , ~n ~0, ly 2, ...Nl ~i = Ti (~n . ~ + ~n) - iFiX~TTi (pn ~ ~ ~n)/~ (19) Only pn exists in the above expression so that the value of ~n can be substituted into the following expression in order to obtain the absolute position Pn. That is, Pn = Pn ~ + ~n (20) Furthermore, the effective detecting range i.e. the maximum position for detecting Pn (max) is determined by the following expression.
Pn(ma~) = Kn a + ~n(max) (21) ~21~2~;i In the expression n(max) is the maximum ~alue detected by de~ector Sn. The expression (21) means that the value will vary linearly with the position Pn(max) according to the number of revolu~ions of gear G(n).
~s to the preferable selection for the number of teeth, ~a) Elements (the number of teeth) of ~he se~ K should not have any common factors, and tb) Pn(max) becomes larger where the number of teeth Tn of the gear G(n) connected to the detector Sn is the minimum in the set K .
In view of the above (a) and ~b), the expression (18) can will be converted to the followîng expression.
N
lJ TJ
_ J = 1 K~ - ~
'~ (22) Tn _ Ti ~ K (23) As the gears G(l) and G(m) are selected to have the relationship of a prime number to each other, the following expression is not sol~ed.
Tl = M Tm (M : a positive inte~er) Tl, Tm ~ K
Furthermore, the reason why only ~ n exists in the expression (l9) is illustrated as follows.
D31fi~
In Figure 3, the efEective rotating number En of detector Sn is solved by the following expression.
En - LCM5 ~ (243 Where Er~ = Krl + ~.
That is,r En effective rotating numbers exist which can satisfy the value an in the ~xpression 16.
In view of ~he expressions (16) and (17), suppose that ~n is, as a solution, equal to~lwhere i is equal to l. The ~ollowing expression will be established~
~l = T~ n a ~ ~ n) - iFiX [Ti ( P r, ~ ~ t (25) Suppose that El which corresponds ~o ~1 and Rn = pl ~ El is substituted for the right portion of the expression (17).
Thu~, the right portion of the expression (17) is equal to the following expression.
The right portion of expression (17) =
T1 1 (Pl+E~ +~n I--lFIX~--I (P1tEl ) J~ 1/ ~
'I'n (~ol ~+~n)+~n E~ i F iX~ +On)/~Tl ~ En ~ J
Tn(pl o J+~ lF~X~ (Pn +TI~E~ iFiX~T~E1~J
~2~3625 = ~1 (refer to the expression ~25~) = the let portion o the expression (17) where the element Tl El is integer and ~1 is equal to LCM lTn, T1~ /Tn.
Thus, possible Rns which can sati~fy the expression (17) are E~- in toto. Similarly, suppose, i is equal to 2, 3, Ø., n-l~ n~l, ..... , N, respectively, E n ~E n E n :~ n n From the above, for all the cases where i is equal to 1, 2~
3, ..., n-l, n+l, ...N, the capability to satisfy the expression (16) and (17) is indicated by the following expre~sion.
E n l En ~ ~n . - EI~ 1, En~l ~ N
L(;~M ~ K I
Tn L CM ( I,CM ~ Tn, Tl I L~ ( Tn, T2 1 .,.,, LC~M ~ Tn, TIY ) LCM I Tl" ~r2, ~^ T N~
Tn Tln LGM~LC~ITn 9Tl I ,LCMlTn ,T2 J 9~ L~ITn ,T2J]
LCM I T l f T2 , ~--T N j = 1 LCM~LCM~Tn ,Tl 1 ,LCMI'~n ,T2 ] ,-----LC~Tn,T~ ~
~ 14 -Thus, only one value ~ n exist, which satisfies the following expression.
O 1 ='T I ( Pn ~ J+On )--i F IX~T- ( Pn ~ n )/1 ) ~
Figure 4 illustrates an embodiment derived from the process for detecting an absolu~e position shown in Figure 3. For convenience of illustration, the numbers of teeth of the gear G(3), G(4) and G(5) are three (3), four (4) and five (5), respectively. A feed s~rew 67 for the X axis is directly connected to an output axle 66 of motor 49. A
driven member 65 moves in the X direction shown by the arrow by rotation of the motor 49. ~n axle 52 which rotates with an output axle 66 of motor 49 extends upwardly in order to rotate with a rotary axle 53 of a resolver 46. The gear G(3) is provided on an axle 53A which extends ~rom the rotary axl~ 53. Furthermore, resolvers 47 and 48 are provided in parallel to the resolver 46. A rotary axle 54 o resolver 47 is connected to an axle 54A of gear G(4) to rotate, which is engaged with the gear G(3). Similarly, a rotary axle 55 of resolver 48 is connected to an axle 5SA of gear G(5) to rotate, which is in turn engaged with the gear G(4). The primary exciting coils of resolvers 46, 47 and 48 are connected to an exciting circuit 50 through lines 56, 57 and 58 to supply exciting current thereto, respectively. A
selecting circuit 51 is connected to the exciting circuit 50 by lines 59 and 60, The selecting circuit 51 selectively supplies exciting current to the resolvers 46, 47 and 48 by way of a combination of selected signals SEL0 and SELl The secondary outputs of the resolvers 46, 47 and 48 are introduced into an isolator 45 through lines 62, 63 and 64 t respectively. Output signal EN (enable signals) of the isolator 45 is introduced into a register 42 through a circuit including a filter and comparator 44.
~,203~.æ~
A counter 41 for 10,000 counts is connected to a central processing unit (CPU) 43 through register 42 so that the number counted by the counter 41 at the time when the signal EN is produced is fed into the CPU 43 by lines 65 and 66.
The data fed into CPU 43 will beprocessed according to the following procedure as shown in Figure 8. In the isolator 45, a terminal AG of the primary side indicates an analog ground whereas a terminalLG of the secondary side indicates a logic ground.
Figures 5 through 7 illustrate transmission of signals from the resolvers 46l 47 and 48 to the register 42. Figure 5a shows waveforms of the secondary outputsPxl, Px2 and Px3 of resolvers 46, 47 and 48, respec~ively, when exciting signals consisting of sine wave and cosine wave are simultaneously supplied to the resolver~ above. Figure 5b shows wave forms in which three t3) wave forms are in phase with each other by adjustment of their mechanical angles. Fîgure 6a shows wave forms which indicate repeating of counts from zero (0) through 9999 by the counter 41 which runs as a collating position counter and can count 5 KHZ. Figure 6a shows setting up signals of the register 42 i.e. EN signals in Figure 4 which are fed from the filter and comparator 44.
Figure 6a finally shows waveforms of the secondary outputs of resolvers 46, 47 and 4B. It is apparent from Figure 6a that the setting up signals EN are formed at the time when the secondary output crosses the zero (O) level line in voltage. In Figure 6a, the value counted by counter 41 is not zero (0) at the time when setting sig~al EN rises.
However, the value counted by counter 41 shows zero (0) in the waveforms of Figure 6b. That is~ the value of collating position counter 41 iOe. æero (0) is set up in the register 42 at the rising point 50r the falling point) of outpu~
signals (Pxl, Px2, Px3~ of resolver 46g 47 and 48 which have been adjusted to be in phase. This is called zero ~ .
~3~
cross adjustment. The position obtained by the above procedure becomes the absolute origin.
Figure 7 illustrates how to obtain the coordinates Po where the driven member 65 is stopped at the absolute coordinates Po in the predetermined X direction by rotation of motor 49 shown in Figure 4. As shown in the upper right side of Figure 7, the secondary wave forms Pxl, Px2 and Px3 of resolvers 46, 47 and 48 are shifted in phase with respect to each other because of gear trains G(3~, G(4) and G(5). The zero cross position of each ~ignal is indicated by ~hesymbols Xl, X~ and X3, respectively. Each saw teeth waveform corresponding to the waveforms- Pxl, Px2 or Px3 in Figure 7 corresponds to the ~op waveforms in Figures 6a and 6b, respectively. As shown by the waveform Px3, Px2 or Pxl in Figure 7, the length of waveform Px3 is 3/5 of Pxl and the lenyth of waveform Px2 is 4/5 of Pxl.
The height of each waveform indicates the count in register 42 so that one time the value of Pxl, two times the value of Px2 and three times the value of Px3 are supplied to the CPU
~3.
Figure 8 illustrate~ a process for obtaining the absolute position based on the data Xl, X2 and X3 supplied to the CPU 43 of Figure 4.
AS illustrated in Figure 7, the absolute position Po is expressed by the following expression.
Po = Rx lOOOO + X3 (26~
wbere ~x indicates ~he number of rokating, necessarily an integer, o the rotary axle of resolver 46; which is from the absolute origin to the position Po. The driven member 65 moves lOOOO~m per each revolution of gear G(3).
~2~
The data X2 ob~ained by the signal Px2 is determined by the following expression.
X2 = 4-(RX ~ 10000 + X3) - A
where A = iFix[4(Rx 10000 -~ X3)/10000] 10000 (28) and iFix [a] indicates an integer of a. The data Xl ob~ained by the signal Pxl is determined by the following expressionO
Xl = 5(Rx 10000 + X3) - B (29) where B = iFiX[3(RX 10000 + X3)/10000] 10000 (30) Xn the fir~t ~I) part o~ Figure 8~ the numbers of RX which satisfy the measured values X3 and X2 simultaneously are determined with regard to the expression (~7). In the second (II) part of Figure 8, the value of RxO which satisfies the measured value Xl is selected from the numbers of RX.
In the flow chart of Figure 8, RX is set to be zero (0~ in Step 1 (as abridged STP hereafter) and k is set to be one (1) in STP 2 in order to set up an initial condition where an operation startîng signal is given after storing the measured data Xl, X2 and X3 in the memory of CPU. In STP 3 is determined whether or not the expression (27) is solved, which is obtained by calculation of the expression (28) since the value of RX is given to be zero.
STP 4 sets Rx(k) where the judgment is YE5 in STP 3. Where the judgment is: No therein. After STP 4, k is incremented by one in STP 5 and Rx is incremented by one in STP ~. ~x is checked to determine i~ its has reached its maximum number i.e. 20 which isgiven by the expression (24) and is the value ~%~3~æs obtained by the least common multiple 60 of the numbers of teeth 3, 4 and 5 divided by the number of teeth 3. STP 3 through STP 6 is repeated until RX reaches 20 i.e. No is decided in STP 7. During this process, the value Rx(k) and k are defined through STP 4 and STP 5, respectively, where the expression (27) is solved. STP ~ sets up N=l as the initial value when YES is decided in STP 7.
The value B is calculated by the expression t30) in STP 9 and, it is confirmed that the expression (29) is solved.
STP 10 follows YES in STP 9. In STP 10, the value Rx(N) is set up as Rxo. An absolute position Po will now be obtained by subs~ituting Rxo for Rx o~ the expression (26). Figure 8 shows only up to the choice of Rxo~
STP 11 confirms that the value N is equal to ~he value K-l.
The value k is the last i.e. the largest value which is defined in STP 5 of the first part (~j of the flow chart.
STP 12 increments the value N byone following YES in STP 11.
That is, the value Rx (1), Rx(2), ... Rx(k3, i.e. from small value to large value, all of which satisfy the value x3 and x2 of the expression (27) simultaneously, are designated in 5TP 9. STP 13 follows ~ES in STP 11 to indicate existence of an error in the measuring system~ This means that the expression (29) is still not solved even where the largest value Rx(k) is entered thereinto after checking the value- Rx from N=l in order in STP 9, i.e. it is not in normal measuring condition.
In the meanwhile, the above process for date processing is ef~ective to work out an accura~e absolute position where the expressions (27) and (29) are approximately solved. The reason for the above will be illustra~ed as follows~
The embodiment in Figure 4 shows the resolvers 46, 47 and 48 of which one revolu~ion results in one cycle, respectively.
Thus, the effec~ive de~ecting range fro~ the absolute origin will be determined by the following expression where K is set to be equal to 3, 4 and 5 and Tn is set to be e~ual to 3 in the expression (24).
~n = LCM~3~ 4~ 5~ = 63 = 20 (revolutions) This means that the motor 49 in Figure 4 rotates less than revolutions. As illustrated above, one revolution of motor 49 corresponds to 10000 ~m so that twenty (20) revolutions thereof correspond to two hundred mm, since 20(revolutions) x 10000 (~mjrev.) = 200,000~m = 200 mm A preferred embodiment is illustrated in Figure 9 in which the effective detecting range is two thousand (2000)mm .
The configuration shown in Figure 9 is similar to that of Figure 4. ~owever, the following differences exist between Figures 4 and 9. That is, the resolvers 103, 104 and 105 are of the type which include ten (10) poles are adopted and the counter 108 is fox 2000 counts. Further, the gears G(31), G(32) and G(33) include the number of teeth 31, 32 and 33, respectively~ Furthermore, outputs of filter and comparator 112 are colcked into a flip flop circuit 113 clock signal CK
from a clock pulse generator 122 to become EN signals ~enable signals) for a regis~er 109 through a ~AND gate 114.
Suppose that a driven member 102 moves lOOOO~m in the X axis direction while a motor 101 rotates one revolution as in Figure 4. As a result, the resolver 103 which includes ten (10) poles makes five (5) cycles of phase shift during its one revolution. Each period thereof correspond to two thousand (2000) ~ m as illustrated in Figure 10. Two ~housand coun~s of counter 108 corresponds to one period of the resolver 103. Figure 11 (a) shows the waveforms before adjustment of absolute origin whereas Figure 11 (b) shows them after adjustment. Figure 11 (a) shows the diference between the zero poink of counter 108 and the zero cross point of the secondary output waveforms of the resolvers 103, 104 and 105, respectively, whereas Figure 11 ~b) shows coincidence between the ~ontent of counter 108 and the zero cross point of the secondary ou~put waveforms. In this case, a pulse signal EN is adop~ed as an instructing signal in order to feed the content of counter 108 to register 109.
Figure 12 illustrates a measuring process for an absolute position detec~ing device as in Figure 9. In Figure 12, suppose that the driven member 102 is intially located a~
the absolute origin under the condition that the resolvers 103, 104 and 105 and counter 108 are adjusted and then driven member 102 moved to the point Po. Under this condition, the r~solvers 103, 104 and 105 output signals no, mo and lo, respectively.
Thu~, the absolute position P0 will be determined as follows, with reference to Figure 12.
po = 2000~ t no : ~31) p = RN x 5 (32) where Rn indicates the revolution number ~an integer~ of the resolver 10.~
Regarding resolver 104, the following expression is solved.
~2~
G(31) : G(32) = 31 : 32 Thus, the output mo of resolver 104 is as follows.
mo = 31 l2000~ + no) - C (33) C = iFiX~(20QO~ ~ no~/2000~ 2000 (34~
Regarding resolver 105, the following expression is solved.
G(31~ : G(33) = 31 : 33 Thus, the output lo of resolver 105 is as follows.
lo = 31(2QOOf~ no) - D (35) D = iFiX[31~2000p + no)~20001 2000 (36) Accordingly~ the value p will be obtained by putting the figures 0, 1, 2~ ...,, (1056-1) successively into the expressions ~33) and (34). After that, the only value~will be obtained as ~he valu ~ , which satisfies thP expressions (35) and (36).:~hen, the value p o is substituted into the expression ~31) in order to obtain the absolute position Po.
The flow chart shown in Figure 13 is devided into two parts.
The fir~t part of Figure 13 shows a proces~ to select the values~ , of which more than one will e~ist and satisfy the expressions (33) and (34) simultaneously while the second part of Fi~ure 13 shows a process to select the value~o out of the values ~ which are obtained in the ~irst partO The flow chart in Figure 13 shows a process which is basically similar to that of Figure 8. The differences betw~en the two flow charts ar~ as follows. That is, ~z~ , X3~ no, ~%03~æs N -~J, X2-~ mo, Xl-~ lo, A--~C, B--7D, Rxo - ~fo, Rx(N)-~(J).
Thus, a detailed explanation of each step of the flow chart will be omitted.
The following is an illustration for the effec~ive detec~ing range.
The expression below defines the range detected by the detec~in~ device shown in Figure 9.
Suppose that any absolute position P iæ set up, P = 2000 ~+ n = 5 RN
m = 32 (2000~ + n~ - C
C = iFiX[3~(2090 f ~ n~/2000] ~ 20Q0 t38) 1 = 33(2000 ~ + n) - D
D = iFiX131(2000~ + n)/2000] ~ 2000 where 1, m and n indicate measured position data at any position P.
Suppose that the values of data 1, m and n are to be zero including the absolute origin, from the expressions (38) and (39), ~= 332(2000~) ~ iFlX132f] 2000 0 = 33(200 ~) - iFiX[ ~ ] 2000 According1y, ~12~3625i = 3l ~- iFiX[32p]
O = 33 ~- iFiX~33p] (41) Functions F and G are introduced into the expressions (41) which will be changed as indicated below.
F(~) ~ 32 P - iFiX[31p] (42) G(~ - 33 p - iFiXr33~] (43) F(~) and G(p) are shown in Figure 140 Thus, with regard to Figure 14, the solutions of F(p) = O, G(p) ~ O are obtained as follows.
PF = 32 ~ (44) ~G = 33 P (45) where, ~ and ~ are zero ~0) or a positive integer~ Now, suppose that ~F is equal to ~G~ 32 ~ is equal to 33~ ~
O~ a 33 ~l :. ~ = 32~ ~= 33 where ~ is zero (O) or a positive integer.
Accordingly, P F = P ~ = 32 33 ~ C 105~ a~
where the values ~ and p are subs~ituted in~o the expressions (44) and (45~. That isr regarding~, the cases that position data become zero are as follows.
~æo~
= 0 ~ = 0 (absolute origin) = 1 p = 1056 ~ 2112 ~ ~ 3 ~- 316~
Accordlnyly, the effective detecting range Pmax (=2000~max +
nmax) is given by the expression below.
P max = ~F - 1 - 1055 nmax = 19 9 9 Thus, Pmax = 2000 x 1055 + 19~9 - 2111g99(~m) ~ 2000(mm) where ~ is equal to zeroO
The following is an illustration for determining errors in measur ment.
The illustration above regarding Figure 9 relates to a process in which errors for data lo, mo and no measured are excluded. However, in practice, these measured data lo, mo and no include errors due to quantization which are involved in electrical resolving power and mechanical errors from the gear traîn. Thus, the measured values are different rom the theoretical valuesn The following illustrates the range of errors.
Positioning data 1, m and n which are measured corresponding ~o the absolute position P from each of resolver~ 103, 104 and 105 of Figure 9, are i~dicated as follows, 1 ~ lT + ~1 (46) ~zO~æ~
m = mT ~ ~ m (47) n - nT + ~n (48) where lT, mT and nT indicate accurate values, while ~ m and ~ n indicate errors, respectively.
Thus, the expressions (33) and (34) are mo~ified as follows.
mT + ~m ~ 3~(2000 p ~ nT ~ ~n) - C (49) C = iFiXl32(2000~+ nT ~ ~ n) /2000] ~ 2000 (50) where mT is determined as follows.
mT ~ 3~(2000P + nT) - iFiX[3~(2000p ~ nT~2000] ~ 2000 (51) Accordingly, the error ~ m obtained by substituting the value mT of the expression (51) for the value mT of the expre~sion (4~) is calculated by the expression bel.ow.
~m = 32 dn - e (52 e = iFiX~3~(2000~ nT ~ ~ n) /2000] 2000 - iFiX[32~2000p ~ nT)/20003 ~ 2000 (53i Thus, the value e is egual to 0 or 2000~
~ m ~ 3-l2 ~ n ~2000 (54) Similarly/
~3~2~i ~1 = 3l ~ n ~{2000 (55~
Suppose that error due to ~uantization is ~, which value is 1 (~m/pulse), mechanical error is ~, which value is 2 (~m /pulse) and ~ n inc].udes the value&and ~ ~ all of which are substituted in the expressions (54) a~d (55)l then [~m] * ~- 3 1 ( 1 + 0 . 9 2 6 ) - 1.866 [~n]
[~1]* ~- 33~1 + 0.926)~ h~
~- 1.809 [~n]
where suppose ~hat [ n] is 1, then ~m]* = 1.866~m~ ~56 ~ * ~ + 1O80g(~m~ (57) where [~Q~ is defined as the actual error pulse number and [
~Q]* is defined as the actual error quantity.
Corresponding to the value Po which is determined by successive steps of the flow chart shown in Figure 13, [~n3 ~ ~ 1, and the followin~ conditions are necessary.
Regarding the value mo, <mT - 1.866>~ mo 5 1999 ~58) or <m~ ~ 1.866> ~ mo > d (59) ~26~
or mT - 1.866 ~ mo ~ mT ~ 1~866 (603 Regarding the value lo~
<lT - 1.809~ ~ lo ~ 1999 (61) or < lT + 10809> ~ lo > 0 (6~) or lT ~ 1~809 ~ lo lT ~ 1.809 ~63 where ~ S > is defined, when S ~ 0 ~ as S - iFiX [s/2000] 2000 or <S~ is defined, when S C 0 , as 2000 ~ ~
Each of the expressions ~5~) through (~0) will be selected corresponding to the measured value mo which is in the range from zero (0) to 1999. For example, the expression (58~
will be selected where the value mo i~ close to and less than the value 1999. The expre~sion (59) will be chosen where the value mo is close to zero (0). Furthermore, the expression (60) will be selected where the value mo is in the middle of the values zero (0~ and 1999. Similarly, one of the expressions ~61), (62) and (63) is chosen corresponding to the value lo. Briefly speaking, the expression~ (58) through (60) and the expressions (~1~
through (63) will not be solved where each of the measured data mo and lo include a value being more than the errors ( ~ ~ ~ in the detecting device shown in Figure 9, which is given in the form of a numeral.
Further, for instance, the value mT is necessary in order to solve the expression (5~ which is an inequality. The value mT will be calculated by ~he expres~ion (51) under the - 2~ ~
condition that nT is ~etermined to be nearly equal to no (nT
no) in the expression (51) and ~o, which is determined in the flow chart of E~igure 13, is substituted for p Furthermore, the following inequalities (58~) throu~h ~63A~
can be adopted since all of the values lo, mo and no are integers.
That is, the expression (58) corresponds to the following.
iFiX r ~ mT - 10866> ] c mo ~ 1999 ~58A) The expression (59) corresponds to ~he following.
iFiX [<mT - 1.866>] 2 ~o ~ 0 (59A~
The expression (60) corresponds to the following.
iFiX [mT - 1.866 ] ~ mo iFiX [mT + 1.866] (60A) The expression (61~ corresponds to the following.
iFiX [<lT - 1.809>] _ lo ~ 1999 ~61A) The expression (62) corresponds to the following.
iFiX [~lT ~ 1.809>] 2 lo 2 0 (62A) ~he expression (63) corresponds to ~he following~
iFiX [lT - 1.809] _ lo iFiX [lT ~ 1.809~ (63A) The capability o miscalculation for an accurate absolute position is illu~trated below, which is based on the existence of errors as indicated aboveO
As shown in Figure 15t the ratio of teeth nu~bers of each gear is 31 : 32 : 33 Further, each resolver 103, 104 and 105 includes ten (10) poles, respectively.
Thus~ where the gear G(32~ ro~atPs at 1~5 revolution after the gear G(31) con~inues to ro~ate in the same direction more than 1/5 revolution from the position at absolute origin, ~he number of pulses dm produced by ro~a~ion of the gear G(31) is calculated by the expression below~
dm = (52_ 31 ) O 13 ~52.5 Similarly~ the n~mber of pulses dl of the gear G533) to the ~ear G(31) is calculated by the following expression.
dl - (53- 5l ) 13 ~-121.2 Thus, [~m] <~ dm, ~1] ~< dl (64) This means that ~o will become accurate wher~ ~he expression (64) is satisfied even if there are errors ~ m( - loB66) and ~1( = l.B09) in the measured data lo and mo, and the data lo and mo including the errors are utilized when p o is determined in the flow chart of Figure 13. That is, p o is not subject to the influence of errorsn Further, the absolute position is determined by the following expression when ~o is decided.
Po - 2û00Po ~ no $
i.e~ P o is not affected by errors in the gear train since the value mo and lo are not used. In other words, in the expression of STP 3 in Figure 13, the value of right portion thereof will be changed by 62.5 as~is increased by one (1 so that errors w;ll not be made whenPsatisfying the value mo is clocked since the errors of mo are not comparable to the value 62.5. The same applies ~o (J) and lo of S~P 9.
Thus, from another po;nt o v;ew, there are no problems even if the value~ mo and lo include errors therein when~of STP 3 and p(J) of STP 9 are determined ~orrectly i.e. gears which are roughly worked will be able to be used and the furthermore, lives of gears will be increased even if they become gradually deteriorated in accuracy D
Resolvers of rotary type are illustrated in Figures 4 and 9 as detectors ~owever, in the present invention, any type of detectors can be utilized provided that the detectors have a regular period and the absolute quantitie~ thereof ~uch as lo, mo and no are able to be measured within one period.
That is, detectors of linear type like inductsyn ~trademark~
and magnetic scal~ can be utilized. Resolvers are not even limited to the rotary type.
Furthermore, systems for processing the measured data are illustrated in ~i9ures 8 and 13~ However, the systems are not limited in the present invention. For instanceO the expressions (1), ~ and t3) can be solved as simultaneous equations D
In the present invention, three t3) resolvers for measuring are activated by one motor which is used to move a member to be measured as illustrated in Figures 4 and 9 D Howeverl one of the resolvers can be removed by using signals from a detector for position feed back already provided in feeding $
controllers, such as a resolver, rotary encoder or the like fixed in a machining tool~ As illustrated in Figure 16~
resolvers 207, 208 and 209 for the detector are connected to the axles of pulse motors PM1, PM2 and PM3 in order to be rotated. In this case, the gear train is not necessaril~
pro~ided. Instead, the number of pulse P(~X) corresponding to movement ~X ins~ructed by a NC uni~ for the machining tool will be supplied to the pulse motor 203~ Further, the number o~ pulses Pt31/32 ~ X) will be supplied to the pulse motor 204 and still furthermore, the number o~ pulses P~31/33 ~ X) will be supplied to pulse motor 205.
Accordingly9 the movement X will be supplied to a pulse proportioner.
In Figure 16, a gear train 212 can be used instead of part 206 of pulse motors 204 and 205. In the embodiment of Figure 16, movement of the driven member is electrically transmitted to r~solvers etc. instead of being mechanically transmitted so that the limited space in a machine tool will be more efFectively used for fixing of resolvers therein. Further, in F;gure 16, the pulse motors 203~ 204 and 205 are used. However, a synchro is provided on the axle of motor 101.
The process of the present in~ention, which can determine the absolute position from a combination of measured data from detectors having a plurality of periods, is almost free from measuring errors since there is no weighting factor among measured data from the detectors~ Thus~ the moment of inertia in the gear train can be decreased and it is not necessary to correct errors due to attrition of gearsO
Further, as apparen~ from the embodiments in Figures 9 and 13, the absolute position is determined by two steps, one of which sets p o and the other of which determines Po by using ~o such as Po = 2000~o ~ no. That is, the absolute posi~ion ~ 32 -;s obtained at high accuracy since mechanical errors of the gear train are not included in no. Furthermore, the detecting device itself can be smaller in size with longer life. The numbers of teeth of gears have no common divisors as illustrated in Figures 4 and 9, so that the effective detecting range of the device can increased remarkably.
While the invention has been particularly shown and described with respect to a preferred embodiment thereof, it will be understood by those in ~he art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention~
It is another object of the present invention to provide a process for detecting an absolute position which comprises the steps of preparing a detecting means with a plurality of detectors which generate periodical electric signals corresponding to predtermined mechanicl movements which are different from each other to a member to be measured, generating the mechanical movement be~ween the detecting means and the membert storing the electric signals corresponding to each of the p~riod out o the detecting means, specifying a relative position involved in the mechanical movement between one of detectors of the detecting means and the member by using the value multiplied by integer N of the period corresponding to the one of detectors and the value which ls less than the period, and deciding the integral value N by u~ing period corresponding to another detector of the detecting means and the stored value which is from another detector.
"::
-` ~21D3~5 It is a further object of the present invention to provide a process for detecting an absolute position which comprises the steps of preparing a transmitting means of rotary type which includes a plurality of rotary detectors generating electric signals o which period is due to a rotary angle range based on one revolution or devided revolution equally thereof and axes rotating the detectors respectively at predetermined ratio, connecting the rotary transmitting means to the member ~o be measured for mechanical movement thereof, supplying the mechanical movement between the rotary detector and member to be measured under the condition specified, storing the electric signals corresponding to the respective period out of the each dekector, specifying a relative position relationship between the member and one of the detectors, being involved in mechanical movement, by using the value multiplied by integer N of the period corresponding to the one of detector and the value which is which is less than one period thereof, and deciding the integral value N by using the period corresponding to another detector of the detectors and the stored value from the another detector.
The foregoing and, other object~, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.
Brief description of the drawings.
Figure 1 is a diagram illustrating the principle of the present invention~
Figure 2 is a diagram of waveforms from detec~ors corresponding to the period illustrated in Figure 1, 3~ 2~;
Figure 3 is a diagram showing a layout o gear trains and a group of detectors which are of rotary type according to the present invention, Figure 4 is a block diayram for an ahsolute position detecting apparatus including three (3) gears and resolverst Figures Sa and 5b are diagrams illustrating an adjustment of phases of secondary outpu~s from resolvers shown in Figure 4, Figures 6a and 6b are diagrams illustratirlg counting of a position collating counter and zero cross adjustment for the phases of the outputs from the resolver in Figure 4, Figure 7 is a diagram for waveforms illustrating a process of detecting an absolute position by the apparatus shown in Figure 4, Figure 8 is a flow chart illustrating data processing in the central processing unit shown in Figure 4, Figure 9 is a block diagram of another embodiment of the present invention whîch shows a preerred absclute position detecting apparatus compared to that of Figure 4, Figure 10 is a diagram illustrating the function of a resolver with ten (10) poles as shown in Figure 9, Figures lla and llb ~are diagrams illustrating zero cross adju~tment of three (3) resolvers with ten (10) poles in Figure 9,~
Figure 12 is a diagram ~or waveforms illustrating a process of absolute position detection in Figure 9, ~3~Z$
Figure 13 is a flow chart illustrating a process of data processing in the central processing unit shown in Figure 9, Figure 14 is a diagram illustrating a process for calculating that position data is zero in Figure 9, Figure 15 is a diagram illustrating measured phase lag for the apparatus o Figure 9, and Figure 16 is a diagram for still another embodiment of the present invention.
Detailed de~cription of the invention Referring to Figure 1, reference numerals 21, 22 and 23 indicate one part of a detecting means, i.e. scales which are provided in parallel, respectively, in the X axis direction. The period of scale 21 is Pl which consists of five ~5~ graduated scales as one unit in the X axis direction. The period of scale 22 is P2 which consists of six (6) graduated scales as one unit in the X axis direction and the period of scale 23 i~ P3 which conqists of seven (7) graduated scales as one unit in the X
axis direction. A distance LAgs indicates an effective detecting range from the starting point OABS . In Figure 1, all the periods of scales 21, 22 and 23 are consistent with each other at the`point Lab~l which is the next consistent point from the starting point OAB~.
A detecting means 24 can move in the X axis direction, and supports detectors ~5, 26 and 270 The detec~ors 25, 26 and 27 output electric signals as the wave~orms 25a, 26a and 27a shown in Figure 2. These waves correspond ta the wave forms from a potentiometer of rotary type as one example of an ideal detector.
` ~3~5 Suppose that the central position of the detecting means 24 is at ~he point L(X) and each detector 25, 26 and 27 outputs values ~ Pl, ~ P2 and~P3, respectively, each of which values is less than one period of Plr P2 and P3. In Figure 1, the distance L~X) is obtained by the following expressions.
L~X) = Nl x Pl ~ ~Pl (1) L~X) = N2 x P2 ~ QP2 (2) L(X) = N3 x P3 + ~P3 (3) In the expressions, the values Pl, P2 and P3 are known amounts and the values ~ Pl, ~ P2 and ~ P3 are also measured values, i.e. known amounts. Thus, the corresponding value L(X) will be obtained where the value of integer 1, 2, 3~...n is substituted for Nl in the expression (1), successively. After that, the values L(X) will be substituted in~o the expressions (2) and (3) in order to obtain the values j equal to ~he Values Nl. For instanceV as shown in Figures 1 and 2, Pl is equal to ~ive (5). P2 is equal to six (6) and P3 is equal to seven (7~. On the other hand, the value ~ Pl is equal to three (3~P2 is equal to ~ive (5) and ~ P3 is equal to two (2)~ The numerals 1,2,3,4....n are substituted for Nl successively in the expression (1).
~uppose that Nl is equal to the numeral 1, (LX) = 1 x 5 + 3 = 8 (4) 8 = N2 x 6 ~ 5 (5~
8 = ~3 x 7 ~ 2 (6) NO integral numbers including zero (0), which are substituted for N2 and N3, can solve the expressions (5~ ~nd (~) .
Thus, the value Nl cannot be 1.
~2~
~ 8 --Suppose that Nl is equal to the numeral 2, L~X) = 2 x 5 + 3 = 13 (7) 13 = N2 x 6 ~ 5 (8) 13 = N3 x 7 + 2 (9) No integral numbers including zero (O), which are substituted for N2 and N3, can solve the expressions t8) and (9~. Thusr the value N1 cannot be 2.
Suppose that Nl is equal t3 the numeral 3, L(X) = 3 x 5 + 3 = 18 (10) 18 = ~2 x 6 + 5 ~11) I8 = N3 x 7 + 2 (12~
No integrals N2 and N3 can solve the expressions (11~ and (12~.
Suppose that Nl IS equal to the numeral 4, L(X) = 4 x 5 + 3 = 23 (13) 23~= N2 x 6 + 5 (14) 23 = N3 x 7 ~ 2 (15~
The expressions ~14) and (15) are solved in this case, i.e.
N2 is three (3) and N3 is three (3)~ as will be apparent from Figure 1. Fur~hermore~ the reason why only one group of N1, N2 and:N3 exists for the combination of Pl~ P2 and ~ P3 provided by the detecting means is illu~trated below.
Figures 1 and 2 show a detecting means of linear type which moves linearly with respect to the scales 21, 22 and 23 whereas the; rotary type thereof is illustrated in Figure 3 as an preferred embodiment. In Figure 3, a motor 31 ~26)3625 activates a driven member 34 which moves through a feed screw 35 in the X direction shown as an arrow. An axle 36 extending from the driving motor 31 is connected with a rotary axle 38 of rotary detecting means Sn. The rotary axis 38 is connected to an axle 37 of a gear Gn in order to be rotated, gear Gn having Tn teeth. As illustrated in Figure 3, the gear Gl, G2, G3....Gn..~.GN having teeth Tl, T2, T3, .... Tn,~..TN, respectively, are engaged with each other to comprise a gear train. Detectors Sl, S2, S3~ ..Ø Sn,...SN output signals ~ 2, ~3, .~ n,....
N, respectively, which correspond to the rotating positions of rotary axles 38 of each detector. Suppose, in Figure 3, the driven member 34 stays at a point in the X axis direction after rotation of the motor 31. The absolute value Pn of the position thereof will be found as follows where the detector Sn outputs the position data ~ n.
Pn = Rn ~ + ~n (~6) In the expression (I6), the symbol ~ indicates the moving degree of the driven member 34 in the X axis direction per revolution of the motor 31, the symbol Rn indicates the number of revolutions of the detector Sn from the reference point, which number is an integer. The symbol ~ n corresponds to the rotating angle position which is less than one revolution of the rotary axle 38 of the detector Sn , that is,~ which corresponds to the displacement of the driven member 34 in the X axis direction. The number of revolutions of the motor 31 is transmitted to each detector Si (i~n) as well as detector Sn through the gear train 33.
Thus, the following expression is solved.
~i = Ti Pn - iFiX~Ti Pn/~ (17) ~2~3625 where iFix ~A] is the integral portion of symbol A~
Furthermore, the sum of the teeth to be rotated until each gear Gl, G2, ...~.GN reaches ~he same position is obtain.ed by the following expression.
LCM~K~
Where the symbol K is equal to ~Tj-j = 1, 2, ...N ~
and the symbol LCM~K} means the least common multiple of K.
The maximum number of effective revolutions Kn of detector Sn is defined by the following expression9 Kn = LCMfR~ 1 (18~
Suppose that the Pn is the solution of Rn in the expression (17), {1, 2, ...N , ~n ~0, ly 2, ...Nl ~i = Ti (~n . ~ + ~n) - iFiX~TTi (pn ~ ~ ~n)/~ (19) Only pn exists in the above expression so that the value of ~n can be substituted into the following expression in order to obtain the absolute position Pn. That is, Pn = Pn ~ + ~n (20) Furthermore, the effective detecting range i.e. the maximum position for detecting Pn (max) is determined by the following expression.
Pn(ma~) = Kn a + ~n(max) (21) ~21~2~;i In the expression n(max) is the maximum ~alue detected by de~ector Sn. The expression (21) means that the value will vary linearly with the position Pn(max) according to the number of revolu~ions of gear G(n).
~s to the preferable selection for the number of teeth, ~a) Elements (the number of teeth) of ~he se~ K should not have any common factors, and tb) Pn(max) becomes larger where the number of teeth Tn of the gear G(n) connected to the detector Sn is the minimum in the set K .
In view of the above (a) and ~b), the expression (18) can will be converted to the followîng expression.
N
lJ TJ
_ J = 1 K~ - ~
'~ (22) Tn _ Ti ~ K (23) As the gears G(l) and G(m) are selected to have the relationship of a prime number to each other, the following expression is not sol~ed.
Tl = M Tm (M : a positive inte~er) Tl, Tm ~ K
Furthermore, the reason why only ~ n exists in the expression (l9) is illustrated as follows.
D31fi~
In Figure 3, the efEective rotating number En of detector Sn is solved by the following expression.
En - LCM5 ~ (243 Where Er~ = Krl + ~.
That is,r En effective rotating numbers exist which can satisfy the value an in the ~xpression 16.
In view of ~he expressions (16) and (17), suppose that ~n is, as a solution, equal to~lwhere i is equal to l. The ~ollowing expression will be established~
~l = T~ n a ~ ~ n) - iFiX [Ti ( P r, ~ ~ t (25) Suppose that El which corresponds ~o ~1 and Rn = pl ~ El is substituted for the right portion of the expression (17).
Thu~, the right portion of the expression (17) is equal to the following expression.
The right portion of expression (17) =
T1 1 (Pl+E~ +~n I--lFIX~--I (P1tEl ) J~ 1/ ~
'I'n (~ol ~+~n)+~n E~ i F iX~ +On)/~Tl ~ En ~ J
Tn(pl o J+~ lF~X~ (Pn +TI~E~ iFiX~T~E1~J
~2~3625 = ~1 (refer to the expression ~25~) = the let portion o the expression (17) where the element Tl El is integer and ~1 is equal to LCM lTn, T1~ /Tn.
Thus, possible Rns which can sati~fy the expression (17) are E~- in toto. Similarly, suppose, i is equal to 2, 3, Ø., n-l~ n~l, ..... , N, respectively, E n ~E n E n :~ n n From the above, for all the cases where i is equal to 1, 2~
3, ..., n-l, n+l, ...N, the capability to satisfy the expression (16) and (17) is indicated by the following expre~sion.
E n l En ~ ~n . - EI~ 1, En~l ~ N
L(;~M ~ K I
Tn L CM ( I,CM ~ Tn, Tl I L~ ( Tn, T2 1 .,.,, LC~M ~ Tn, TIY ) LCM I Tl" ~r2, ~^ T N~
Tn Tln LGM~LC~ITn 9Tl I ,LCMlTn ,T2 J 9~ L~ITn ,T2J]
LCM I T l f T2 , ~--T N j = 1 LCM~LCM~Tn ,Tl 1 ,LCMI'~n ,T2 ] ,-----LC~Tn,T~ ~
~ 14 -Thus, only one value ~ n exist, which satisfies the following expression.
O 1 ='T I ( Pn ~ J+On )--i F IX~T- ( Pn ~ n )/1 ) ~
Figure 4 illustrates an embodiment derived from the process for detecting an absolu~e position shown in Figure 3. For convenience of illustration, the numbers of teeth of the gear G(3), G(4) and G(5) are three (3), four (4) and five (5), respectively. A feed s~rew 67 for the X axis is directly connected to an output axle 66 of motor 49. A
driven member 65 moves in the X direction shown by the arrow by rotation of the motor 49. ~n axle 52 which rotates with an output axle 66 of motor 49 extends upwardly in order to rotate with a rotary axle 53 of a resolver 46. The gear G(3) is provided on an axle 53A which extends ~rom the rotary axl~ 53. Furthermore, resolvers 47 and 48 are provided in parallel to the resolver 46. A rotary axle 54 o resolver 47 is connected to an axle 54A of gear G(4) to rotate, which is engaged with the gear G(3). Similarly, a rotary axle 55 of resolver 48 is connected to an axle 5SA of gear G(5) to rotate, which is in turn engaged with the gear G(4). The primary exciting coils of resolvers 46, 47 and 48 are connected to an exciting circuit 50 through lines 56, 57 and 58 to supply exciting current thereto, respectively. A
selecting circuit 51 is connected to the exciting circuit 50 by lines 59 and 60, The selecting circuit 51 selectively supplies exciting current to the resolvers 46, 47 and 48 by way of a combination of selected signals SEL0 and SELl The secondary outputs of the resolvers 46, 47 and 48 are introduced into an isolator 45 through lines 62, 63 and 64 t respectively. Output signal EN (enable signals) of the isolator 45 is introduced into a register 42 through a circuit including a filter and comparator 44.
~,203~.æ~
A counter 41 for 10,000 counts is connected to a central processing unit (CPU) 43 through register 42 so that the number counted by the counter 41 at the time when the signal EN is produced is fed into the CPU 43 by lines 65 and 66.
The data fed into CPU 43 will beprocessed according to the following procedure as shown in Figure 8. In the isolator 45, a terminal AG of the primary side indicates an analog ground whereas a terminalLG of the secondary side indicates a logic ground.
Figures 5 through 7 illustrate transmission of signals from the resolvers 46l 47 and 48 to the register 42. Figure 5a shows waveforms of the secondary outputsPxl, Px2 and Px3 of resolvers 46, 47 and 48, respec~ively, when exciting signals consisting of sine wave and cosine wave are simultaneously supplied to the resolver~ above. Figure 5b shows wave forms in which three t3) wave forms are in phase with each other by adjustment of their mechanical angles. Fîgure 6a shows wave forms which indicate repeating of counts from zero (0) through 9999 by the counter 41 which runs as a collating position counter and can count 5 KHZ. Figure 6a shows setting up signals of the register 42 i.e. EN signals in Figure 4 which are fed from the filter and comparator 44.
Figure 6a finally shows waveforms of the secondary outputs of resolvers 46, 47 and 4B. It is apparent from Figure 6a that the setting up signals EN are formed at the time when the secondary output crosses the zero (O) level line in voltage. In Figure 6a, the value counted by counter 41 is not zero (0) at the time when setting sig~al EN rises.
However, the value counted by counter 41 shows zero (0) in the waveforms of Figure 6b. That is~ the value of collating position counter 41 iOe. æero (0) is set up in the register 42 at the rising point 50r the falling point) of outpu~
signals (Pxl, Px2, Px3~ of resolver 46g 47 and 48 which have been adjusted to be in phase. This is called zero ~ .
~3~
cross adjustment. The position obtained by the above procedure becomes the absolute origin.
Figure 7 illustrates how to obtain the coordinates Po where the driven member 65 is stopped at the absolute coordinates Po in the predetermined X direction by rotation of motor 49 shown in Figure 4. As shown in the upper right side of Figure 7, the secondary wave forms Pxl, Px2 and Px3 of resolvers 46, 47 and 48 are shifted in phase with respect to each other because of gear trains G(3~, G(4) and G(5). The zero cross position of each ~ignal is indicated by ~hesymbols Xl, X~ and X3, respectively. Each saw teeth waveform corresponding to the waveforms- Pxl, Px2 or Px3 in Figure 7 corresponds to the ~op waveforms in Figures 6a and 6b, respectively. As shown by the waveform Px3, Px2 or Pxl in Figure 7, the length of waveform Px3 is 3/5 of Pxl and the lenyth of waveform Px2 is 4/5 of Pxl.
The height of each waveform indicates the count in register 42 so that one time the value of Pxl, two times the value of Px2 and three times the value of Px3 are supplied to the CPU
~3.
Figure 8 illustrate~ a process for obtaining the absolute position based on the data Xl, X2 and X3 supplied to the CPU 43 of Figure 4.
AS illustrated in Figure 7, the absolute position Po is expressed by the following expression.
Po = Rx lOOOO + X3 (26~
wbere ~x indicates ~he number of rokating, necessarily an integer, o the rotary axle of resolver 46; which is from the absolute origin to the position Po. The driven member 65 moves lOOOO~m per each revolution of gear G(3).
~2~
The data X2 ob~ained by the signal Px2 is determined by the following expression.
X2 = 4-(RX ~ 10000 + X3) - A
where A = iFix[4(Rx 10000 -~ X3)/10000] 10000 (28) and iFix [a] indicates an integer of a. The data Xl ob~ained by the signal Pxl is determined by the following expressionO
Xl = 5(Rx 10000 + X3) - B (29) where B = iFiX[3(RX 10000 + X3)/10000] 10000 (30) Xn the fir~t ~I) part o~ Figure 8~ the numbers of RX which satisfy the measured values X3 and X2 simultaneously are determined with regard to the expression (~7). In the second (II) part of Figure 8, the value of RxO which satisfies the measured value Xl is selected from the numbers of RX.
In the flow chart of Figure 8, RX is set to be zero (0~ in Step 1 (as abridged STP hereafter) and k is set to be one (1) in STP 2 in order to set up an initial condition where an operation startîng signal is given after storing the measured data Xl, X2 and X3 in the memory of CPU. In STP 3 is determined whether or not the expression (27) is solved, which is obtained by calculation of the expression (28) since the value of RX is given to be zero.
STP 4 sets Rx(k) where the judgment is YE5 in STP 3. Where the judgment is: No therein. After STP 4, k is incremented by one in STP 5 and Rx is incremented by one in STP ~. ~x is checked to determine i~ its has reached its maximum number i.e. 20 which isgiven by the expression (24) and is the value ~%~3~æs obtained by the least common multiple 60 of the numbers of teeth 3, 4 and 5 divided by the number of teeth 3. STP 3 through STP 6 is repeated until RX reaches 20 i.e. No is decided in STP 7. During this process, the value Rx(k) and k are defined through STP 4 and STP 5, respectively, where the expression (27) is solved. STP ~ sets up N=l as the initial value when YES is decided in STP 7.
The value B is calculated by the expression t30) in STP 9 and, it is confirmed that the expression (29) is solved.
STP 10 follows YES in STP 9. In STP 10, the value Rx(N) is set up as Rxo. An absolute position Po will now be obtained by subs~ituting Rxo for Rx o~ the expression (26). Figure 8 shows only up to the choice of Rxo~
STP 11 confirms that the value N is equal to ~he value K-l.
The value k is the last i.e. the largest value which is defined in STP 5 of the first part (~j of the flow chart.
STP 12 increments the value N byone following YES in STP 11.
That is, the value Rx (1), Rx(2), ... Rx(k3, i.e. from small value to large value, all of which satisfy the value x3 and x2 of the expression (27) simultaneously, are designated in 5TP 9. STP 13 follows ~ES in STP 11 to indicate existence of an error in the measuring system~ This means that the expression (29) is still not solved even where the largest value Rx(k) is entered thereinto after checking the value- Rx from N=l in order in STP 9, i.e. it is not in normal measuring condition.
In the meanwhile, the above process for date processing is ef~ective to work out an accura~e absolute position where the expressions (27) and (29) are approximately solved. The reason for the above will be illustra~ed as follows~
The embodiment in Figure 4 shows the resolvers 46, 47 and 48 of which one revolu~ion results in one cycle, respectively.
Thus, the effec~ive de~ecting range fro~ the absolute origin will be determined by the following expression where K is set to be equal to 3, 4 and 5 and Tn is set to be e~ual to 3 in the expression (24).
~n = LCM~3~ 4~ 5~ = 63 = 20 (revolutions) This means that the motor 49 in Figure 4 rotates less than revolutions. As illustrated above, one revolution of motor 49 corresponds to 10000 ~m so that twenty (20) revolutions thereof correspond to two hundred mm, since 20(revolutions) x 10000 (~mjrev.) = 200,000~m = 200 mm A preferred embodiment is illustrated in Figure 9 in which the effective detecting range is two thousand (2000)mm .
The configuration shown in Figure 9 is similar to that of Figure 4. ~owever, the following differences exist between Figures 4 and 9. That is, the resolvers 103, 104 and 105 are of the type which include ten (10) poles are adopted and the counter 108 is fox 2000 counts. Further, the gears G(31), G(32) and G(33) include the number of teeth 31, 32 and 33, respectively~ Furthermore, outputs of filter and comparator 112 are colcked into a flip flop circuit 113 clock signal CK
from a clock pulse generator 122 to become EN signals ~enable signals) for a regis~er 109 through a ~AND gate 114.
Suppose that a driven member 102 moves lOOOO~m in the X axis direction while a motor 101 rotates one revolution as in Figure 4. As a result, the resolver 103 which includes ten (10) poles makes five (5) cycles of phase shift during its one revolution. Each period thereof correspond to two thousand (2000) ~ m as illustrated in Figure 10. Two ~housand coun~s of counter 108 corresponds to one period of the resolver 103. Figure 11 (a) shows the waveforms before adjustment of absolute origin whereas Figure 11 (b) shows them after adjustment. Figure 11 (a) shows the diference between the zero poink of counter 108 and the zero cross point of the secondary output waveforms of the resolvers 103, 104 and 105, respectively, whereas Figure 11 ~b) shows coincidence between the ~ontent of counter 108 and the zero cross point of the secondary ou~put waveforms. In this case, a pulse signal EN is adop~ed as an instructing signal in order to feed the content of counter 108 to register 109.
Figure 12 illustrates a measuring process for an absolute position detec~ing device as in Figure 9. In Figure 12, suppose that the driven member 102 is intially located a~
the absolute origin under the condition that the resolvers 103, 104 and 105 and counter 108 are adjusted and then driven member 102 moved to the point Po. Under this condition, the r~solvers 103, 104 and 105 output signals no, mo and lo, respectively.
Thu~, the absolute position P0 will be determined as follows, with reference to Figure 12.
po = 2000~ t no : ~31) p = RN x 5 (32) where Rn indicates the revolution number ~an integer~ of the resolver 10.~
Regarding resolver 104, the following expression is solved.
~2~
G(31) : G(32) = 31 : 32 Thus, the output mo of resolver 104 is as follows.
mo = 31 l2000~ + no) - C (33) C = iFiX~(20QO~ ~ no~/2000~ 2000 (34~
Regarding resolver 105, the following expression is solved.
G(31~ : G(33) = 31 : 33 Thus, the output lo of resolver 105 is as follows.
lo = 31(2QOOf~ no) - D (35) D = iFiX[31~2000p + no)~20001 2000 (36) Accordingly~ the value p will be obtained by putting the figures 0, 1, 2~ ...,, (1056-1) successively into the expressions ~33) and (34). After that, the only value~will be obtained as ~he valu ~ , which satisfies thP expressions (35) and (36).:~hen, the value p o is substituted into the expression ~31) in order to obtain the absolute position Po.
The flow chart shown in Figure 13 is devided into two parts.
The fir~t part of Figure 13 shows a proces~ to select the values~ , of which more than one will e~ist and satisfy the expressions (33) and (34) simultaneously while the second part of Fi~ure 13 shows a process to select the value~o out of the values ~ which are obtained in the ~irst partO The flow chart in Figure 13 shows a process which is basically similar to that of Figure 8. The differences betw~en the two flow charts ar~ as follows. That is, ~z~ , X3~ no, ~%03~æs N -~J, X2-~ mo, Xl-~ lo, A--~C, B--7D, Rxo - ~fo, Rx(N)-~(J).
Thus, a detailed explanation of each step of the flow chart will be omitted.
The following is an illustration for the effec~ive detec~ing range.
The expression below defines the range detected by the detec~in~ device shown in Figure 9.
Suppose that any absolute position P iæ set up, P = 2000 ~+ n = 5 RN
m = 32 (2000~ + n~ - C
C = iFiX[3~(2090 f ~ n~/2000] ~ 20Q0 t38) 1 = 33(2000 ~ + n) - D
D = iFiX131(2000~ + n)/2000] ~ 2000 where 1, m and n indicate measured position data at any position P.
Suppose that the values of data 1, m and n are to be zero including the absolute origin, from the expressions (38) and (39), ~= 332(2000~) ~ iFlX132f] 2000 0 = 33(200 ~) - iFiX[ ~ ] 2000 According1y, ~12~3625i = 3l ~- iFiX[32p]
O = 33 ~- iFiX~33p] (41) Functions F and G are introduced into the expressions (41) which will be changed as indicated below.
F(~) ~ 32 P - iFiX[31p] (42) G(~ - 33 p - iFiXr33~] (43) F(~) and G(p) are shown in Figure 140 Thus, with regard to Figure 14, the solutions of F(p) = O, G(p) ~ O are obtained as follows.
PF = 32 ~ (44) ~G = 33 P (45) where, ~ and ~ are zero ~0) or a positive integer~ Now, suppose that ~F is equal to ~G~ 32 ~ is equal to 33~ ~
O~ a 33 ~l :. ~ = 32~ ~= 33 where ~ is zero (O) or a positive integer.
Accordingly, P F = P ~ = 32 33 ~ C 105~ a~
where the values ~ and p are subs~ituted in~o the expressions (44) and (45~. That isr regarding~, the cases that position data become zero are as follows.
~æo~
= 0 ~ = 0 (absolute origin) = 1 p = 1056 ~ 2112 ~ ~ 3 ~- 316~
Accordlnyly, the effective detecting range Pmax (=2000~max +
nmax) is given by the expression below.
P max = ~F - 1 - 1055 nmax = 19 9 9 Thus, Pmax = 2000 x 1055 + 19~9 - 2111g99(~m) ~ 2000(mm) where ~ is equal to zeroO
The following is an illustration for determining errors in measur ment.
The illustration above regarding Figure 9 relates to a process in which errors for data lo, mo and no measured are excluded. However, in practice, these measured data lo, mo and no include errors due to quantization which are involved in electrical resolving power and mechanical errors from the gear traîn. Thus, the measured values are different rom the theoretical valuesn The following illustrates the range of errors.
Positioning data 1, m and n which are measured corresponding ~o the absolute position P from each of resolver~ 103, 104 and 105 of Figure 9, are i~dicated as follows, 1 ~ lT + ~1 (46) ~zO~æ~
m = mT ~ ~ m (47) n - nT + ~n (48) where lT, mT and nT indicate accurate values, while ~ m and ~ n indicate errors, respectively.
Thus, the expressions (33) and (34) are mo~ified as follows.
mT + ~m ~ 3~(2000 p ~ nT ~ ~n) - C (49) C = iFiXl32(2000~+ nT ~ ~ n) /2000] ~ 2000 (50) where mT is determined as follows.
mT ~ 3~(2000P + nT) - iFiX[3~(2000p ~ nT~2000] ~ 2000 (51) Accordingly, the error ~ m obtained by substituting the value mT of the expression (51) for the value mT of the expre~sion (4~) is calculated by the expression bel.ow.
~m = 32 dn - e (52 e = iFiX~3~(2000~ nT ~ ~ n) /2000] 2000 - iFiX[32~2000p ~ nT)/20003 ~ 2000 (53i Thus, the value e is egual to 0 or 2000~
~ m ~ 3-l2 ~ n ~2000 (54) Similarly/
~3~2~i ~1 = 3l ~ n ~{2000 (55~
Suppose that error due to ~uantization is ~, which value is 1 (~m/pulse), mechanical error is ~, which value is 2 (~m /pulse) and ~ n inc].udes the value&and ~ ~ all of which are substituted in the expressions (54) a~d (55)l then [~m] * ~- 3 1 ( 1 + 0 . 9 2 6 ) - 1.866 [~n]
[~1]* ~- 33~1 + 0.926)~ h~
~- 1.809 [~n]
where suppose ~hat [ n] is 1, then ~m]* = 1.866~m~ ~56 ~ * ~ + 1O80g(~m~ (57) where [~Q~ is defined as the actual error pulse number and [
~Q]* is defined as the actual error quantity.
Corresponding to the value Po which is determined by successive steps of the flow chart shown in Figure 13, [~n3 ~ ~ 1, and the followin~ conditions are necessary.
Regarding the value mo, <mT - 1.866>~ mo 5 1999 ~58) or <m~ ~ 1.866> ~ mo > d (59) ~26~
or mT - 1.866 ~ mo ~ mT ~ 1~866 (603 Regarding the value lo~
<lT - 1.809~ ~ lo ~ 1999 (61) or < lT + 10809> ~ lo > 0 (6~) or lT ~ 1~809 ~ lo lT ~ 1.809 ~63 where ~ S > is defined, when S ~ 0 ~ as S - iFiX [s/2000] 2000 or <S~ is defined, when S C 0 , as 2000 ~ ~
Each of the expressions ~5~) through (~0) will be selected corresponding to the measured value mo which is in the range from zero (0) to 1999. For example, the expression (58~
will be selected where the value mo i~ close to and less than the value 1999. The expre~sion (59) will be chosen where the value mo is close to zero (0). Furthermore, the expression (60) will be selected where the value mo is in the middle of the values zero (0~ and 1999. Similarly, one of the expressions ~61), (62) and (63) is chosen corresponding to the value lo. Briefly speaking, the expression~ (58) through (60) and the expressions (~1~
through (63) will not be solved where each of the measured data mo and lo include a value being more than the errors ( ~ ~ ~ in the detecting device shown in Figure 9, which is given in the form of a numeral.
Further, for instance, the value mT is necessary in order to solve the expression (5~ which is an inequality. The value mT will be calculated by ~he expres~ion (51) under the - 2~ ~
condition that nT is ~etermined to be nearly equal to no (nT
no) in the expression (51) and ~o, which is determined in the flow chart of E~igure 13, is substituted for p Furthermore, the following inequalities (58~) throu~h ~63A~
can be adopted since all of the values lo, mo and no are integers.
That is, the expression (58) corresponds to the following.
iFiX r ~ mT - 10866> ] c mo ~ 1999 ~58A) The expression (59) corresponds to ~he following.
iFiX [<mT - 1.866>] 2 ~o ~ 0 (59A~
The expression (60) corresponds to the following.
iFiX [mT - 1.866 ] ~ mo iFiX [mT + 1.866] (60A) The expression (61~ corresponds to the following.
iFiX [<lT - 1.809>] _ lo ~ 1999 ~61A) The expression (62) corresponds to the following.
iFiX [~lT ~ 1.809>] 2 lo 2 0 (62A) ~he expression (63) corresponds to ~he following~
iFiX [lT - 1.809] _ lo iFiX [lT ~ 1.809~ (63A) The capability o miscalculation for an accurate absolute position is illu~trated below, which is based on the existence of errors as indicated aboveO
As shown in Figure 15t the ratio of teeth nu~bers of each gear is 31 : 32 : 33 Further, each resolver 103, 104 and 105 includes ten (10) poles, respectively.
Thus~ where the gear G(32~ ro~atPs at 1~5 revolution after the gear G(31) con~inues to ro~ate in the same direction more than 1/5 revolution from the position at absolute origin, ~he number of pulses dm produced by ro~a~ion of the gear G(31) is calculated by the expression below~
dm = (52_ 31 ) O 13 ~52.5 Similarly~ the n~mber of pulses dl of the gear G533) to the ~ear G(31) is calculated by the following expression.
dl - (53- 5l ) 13 ~-121.2 Thus, [~m] <~ dm, ~1] ~< dl (64) This means that ~o will become accurate wher~ ~he expression (64) is satisfied even if there are errors ~ m( - loB66) and ~1( = l.B09) in the measured data lo and mo, and the data lo and mo including the errors are utilized when p o is determined in the flow chart of Figure 13. That is, p o is not subject to the influence of errorsn Further, the absolute position is determined by the following expression when ~o is decided.
Po - 2û00Po ~ no $
i.e~ P o is not affected by errors in the gear train since the value mo and lo are not used. In other words, in the expression of STP 3 in Figure 13, the value of right portion thereof will be changed by 62.5 as~is increased by one (1 so that errors w;ll not be made whenPsatisfying the value mo is clocked since the errors of mo are not comparable to the value 62.5. The same applies ~o (J) and lo of S~P 9.
Thus, from another po;nt o v;ew, there are no problems even if the value~ mo and lo include errors therein when~of STP 3 and p(J) of STP 9 are determined ~orrectly i.e. gears which are roughly worked will be able to be used and the furthermore, lives of gears will be increased even if they become gradually deteriorated in accuracy D
Resolvers of rotary type are illustrated in Figures 4 and 9 as detectors ~owever, in the present invention, any type of detectors can be utilized provided that the detectors have a regular period and the absolute quantitie~ thereof ~uch as lo, mo and no are able to be measured within one period.
That is, detectors of linear type like inductsyn ~trademark~
and magnetic scal~ can be utilized. Resolvers are not even limited to the rotary type.
Furthermore, systems for processing the measured data are illustrated in ~i9ures 8 and 13~ However, the systems are not limited in the present invention. For instanceO the expressions (1), ~ and t3) can be solved as simultaneous equations D
In the present invention, three t3) resolvers for measuring are activated by one motor which is used to move a member to be measured as illustrated in Figures 4 and 9 D Howeverl one of the resolvers can be removed by using signals from a detector for position feed back already provided in feeding $
controllers, such as a resolver, rotary encoder or the like fixed in a machining tool~ As illustrated in Figure 16~
resolvers 207, 208 and 209 for the detector are connected to the axles of pulse motors PM1, PM2 and PM3 in order to be rotated. In this case, the gear train is not necessaril~
pro~ided. Instead, the number of pulse P(~X) corresponding to movement ~X ins~ructed by a NC uni~ for the machining tool will be supplied to the pulse motor 203~ Further, the number o~ pulses Pt31/32 ~ X) will be supplied to the pulse motor 204 and still furthermore, the number o~ pulses P~31/33 ~ X) will be supplied to pulse motor 205.
Accordingly9 the movement X will be supplied to a pulse proportioner.
In Figure 16, a gear train 212 can be used instead of part 206 of pulse motors 204 and 205. In the embodiment of Figure 16, movement of the driven member is electrically transmitted to r~solvers etc. instead of being mechanically transmitted so that the limited space in a machine tool will be more efFectively used for fixing of resolvers therein. Further, in F;gure 16, the pulse motors 203~ 204 and 205 are used. However, a synchro is provided on the axle of motor 101.
The process of the present in~ention, which can determine the absolute position from a combination of measured data from detectors having a plurality of periods, is almost free from measuring errors since there is no weighting factor among measured data from the detectors~ Thus~ the moment of inertia in the gear train can be decreased and it is not necessary to correct errors due to attrition of gearsO
Further, as apparen~ from the embodiments in Figures 9 and 13, the absolute position is determined by two steps, one of which sets p o and the other of which determines Po by using ~o such as Po = 2000~o ~ no. That is, the absolute posi~ion ~ 32 -;s obtained at high accuracy since mechanical errors of the gear train are not included in no. Furthermore, the detecting device itself can be smaller in size with longer life. The numbers of teeth of gears have no common divisors as illustrated in Figures 4 and 9, so that the effective detecting range of the device can increased remarkably.
While the invention has been particularly shown and described with respect to a preferred embodiment thereof, it will be understood by those in ~he art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention~
Claims (27)
1. An apparatus for detecting an absolute position of a moving member, comprising:
means for detecting predetermined mechanical movement of said member with a plurality of detectors each producing a periodical electric signal corresponding to a given distance, said detec-tors having periods different from each other, means for supplying electric or mechanical quantity corresponding to mechanical movement of a member to be measured to said detect-ing means, means for obtaining electric signals which correspond to less than one period of said respective ones of said periods from each said detecting means when said member is mechanically stopped, means for storing said signals obtained as digital values, and means for determining an integral value wherein a relative position between one of said detectors and said member is specified by a value multiplied by a value of integer N of said period corresponding to said one detector and a value of said less than one period, and said integral value N is determined by using at least a period corresponding to another detector of said detecting means and said digital quantity stored in said storing means.
means for detecting predetermined mechanical movement of said member with a plurality of detectors each producing a periodical electric signal corresponding to a given distance, said detec-tors having periods different from each other, means for supplying electric or mechanical quantity corresponding to mechanical movement of a member to be measured to said detect-ing means, means for obtaining electric signals which correspond to less than one period of said respective ones of said periods from each said detecting means when said member is mechanically stopped, means for storing said signals obtained as digital values, and means for determining an integral value wherein a relative position between one of said detectors and said member is specified by a value multiplied by a value of integer N of said period corresponding to said one detector and a value of said less than one period, and said integral value N is determined by using at least a period corresponding to another detector of said detecting means and said digital quantity stored in said storing means.
2. An apparatus for detecting an absolute position according to claim 1 wherein said means for determining an integral value includes calculating said absolute position by adding said value multiplied by N of said period corresponding to said one of detectors to said digital quantity obtained from said one of detectors under the condition that said integral value N is put into said specified relative position as a numerical value.
3. An apparatus for detecting an absolute position according to claim 1, wherein said detecting means comprises a position detector of linear type.
4. An apparatus for detecting an absolute position according to claim 1, wherein said detecting means comprises a position detector of rotary type.
5. An apparatus for detecting an absolute position according to claim 1, wherein said detecting means comprises in combination of position detectors of linear type and rotary type.
6. An apparatus for detecting an absolute position according to claim 1, wherein said detecting means generate phase modulation signals.
7. An apparatus for detecting an absolute position according to claim 1, further including a transmitting mechanism of rotary type with an axis and gear train for transmitting said movement to said detectors.
8. An apparatus for detecting an absolute position according to claim 1, further including an activating means of the type which rotates electrically for transmitting said movement to said detectors.
9. An apparatus for detecting an absolute position according to claim 1, further including:
mechanism of rotary type with an axle and gear train and an activating means of the type which rotates electrically for transmitting said movement to said detectors.
mechanism of rotary type with an axle and gear train and an activating means of the type which rotates electrically for transmitting said movement to said detectors.
10. An apparatus for detecting an absolute position according to claim 7, wherein said transmitting mechanism of rotary type includes a plurality of gears of which teeth numbers have no common divisor.
11. An apparatus for detecting an absolute position according to claim 8, wherein said activating means comprises a pulse motor.
12. An apparatus for detecting an absolute position according to claim 8, wherein said activating means comprises a synchro.
13. An apparatus for detecting an absolute position according to claim 1, wherein said storing means includes a counter counting a predetermined number in a predetermined time interval and a register storing a measured content as a measured data from said counter which corresponds to said electric signal obtained at the point.
14. An apparatus for detecting an absolute position according to claim 1, wherein said integral value determining means includes a computer determining said integral number N which satisfies a relationship among said integral value which is successively changed, said digital value which is measured and said period which corresponds to each of said measured values,
15. An apparatus for detecting an absolute position according to claim 6, said detecting means includes a change-over means in order to change supplying electric signals for exciting each of said detectors.
16. An apparatus for detecting an absolute position according to claim 1, wherein the smallest period of quantity of mechani-cal movement corresponding to integer N for calculation of absolute position is selected by comparing with said another period.
17. A process for detecting an absolute position of a moving member, comprising the steps of:
preparing a detecting means with a plurality of detectors which generate periodical electric signals corresponding to predeter-mined mechanical movements of said member, the periods being different from each other, generating said mechanical movement between said detecting means and said member, obtaining electric signals which correspond to less than one period of said respective ones of said periods of each said plurality of detectors when said moving member is mechanically stopped, storing said electric signals corresponding to each of said periods out of said detecting means, specifying a relative position involved in said mechanical move-ment between one of the detectors of said detecting means and said member by using the value multiplied by integer N of said period corresponding to said one of detectors and the value which is less than said period, and determining said integral value N by using a period corresponding to another detector of said detecting means and the stored value which is from another detector.
preparing a detecting means with a plurality of detectors which generate periodical electric signals corresponding to predeter-mined mechanical movements of said member, the periods being different from each other, generating said mechanical movement between said detecting means and said member, obtaining electric signals which correspond to less than one period of said respective ones of said periods of each said plurality of detectors when said moving member is mechanically stopped, storing said electric signals corresponding to each of said periods out of said detecting means, specifying a relative position involved in said mechanical move-ment between one of the detectors of said detecting means and said member by using the value multiplied by integer N of said period corresponding to said one of detectors and the value which is less than said period, and determining said integral value N by using a period corresponding to another detector of said detecting means and the stored value which is from another detector.
18. A process for detecting an absolute position according to claim 17, wherein said integral value N is determined by a ratio of said period corresponding to said another detector of said detecting means to said period corresponding to one of detectors and said stored value obtained from said another detector.
19. A process for detecting an absolute position according to claim 17, wherein the smallest period of quantity of mechanical movement corresponding to integer N for calculation of absolute position is selected comparing with said another period.
20. A process for detecting an absolute position according to claim 17, wherein the absolute value P is obtained by substituting the decided value N into the following expression P = N ? l1+ .DELTA.l1 where P is set to indicate a relative position relationship between said member and one of said detectors, l1 is set to indicate a period corresponding to another detector different from said one of detector, .DELTA.l1 is set to indicate a measured value being stored corresponding to said period and N is set to indicate an integral value.
21. A process for detecting an absolute position according to claim 17, further comprising:
confirming that measured data being stored is in a predetermined range of errors.
confirming that measured data being stored is in a predetermined range of errors.
22. A process for detecting an absolute position, comprising the steps of:
preparing a transmitting means of rotary type which includes a plurality of rotary detectors generating electric signals of which period is due to a rotary angle range based on one revolution or divided revolution equally thereof and axes rotating said detectors respectively at predetermined ratio, connecting said rotary transmitting means to said member to be measured for mechanical movement thereof, supplying said mechanical movement between said rotary detector and member to be measured under the specified condition, obtaining electric signals which correspond to less than one period of said respective ones of said periods of each said plurality of detectors when said moving member is mechanically stopped, storing said electric signals corresponding to said respective period out of said each detector, specifying a relative position relationship between said member and one of said detectors, being involved in mechanical movement, by using of the value multiplied by integer N of said period corresponding to said one of the detectors and the value which is less than one period thereof, and, determining said integral value N by using the period correspond-ing to another detector of said detectors and the stored value from said another detector.
preparing a transmitting means of rotary type which includes a plurality of rotary detectors generating electric signals of which period is due to a rotary angle range based on one revolution or divided revolution equally thereof and axes rotating said detectors respectively at predetermined ratio, connecting said rotary transmitting means to said member to be measured for mechanical movement thereof, supplying said mechanical movement between said rotary detector and member to be measured under the specified condition, obtaining electric signals which correspond to less than one period of said respective ones of said periods of each said plurality of detectors when said moving member is mechanically stopped, storing said electric signals corresponding to said respective period out of said each detector, specifying a relative position relationship between said member and one of said detectors, being involved in mechanical movement, by using of the value multiplied by integer N of said period corresponding to said one of the detectors and the value which is less than one period thereof, and, determining said integral value N by using the period correspond-ing to another detector of said detectors and the stored value from said another detector.
23. A process for detecting an absolute position according to claim 22, wherein said integral value N is determined by using a ratio of said period corresponding to said another detector of said detecting means to said period corresponding to said one of detectors and said stored value obtained from said another detector.
24. A process for detecting an absolute position according to claim 22, wherein the absolute value P is obtained by substit-ing the determined value N into the following expression P = N ? l1+ .DELTA.l1 where P is set to indicate a relative position relationship between said member and one of said detectors, l1 is set to indicate a period corresponding to another detector different from said one of detector, .DELTA.l1 is set to indicate a measured value being stored corresponding to said period and N is set to indicate an integral value.
25. a process for detecting an absolute position according to claim 22, wherein one of axle which rotates at highest rotation ratio therebetween is selected to be connected to mechanical movement of said member to be measured.
26. A process for detecting an absolute position according to claim 22, further comprising a step of:
confirming that measured data being stored is in a predetermined range of errors.
confirming that measured data being stored is in a predetermined range of errors.
27. A process for detecting an absolute position according to claim 22, further comprising a step of:
selecting the smallest period of mechanical movement corresponding to integer N rather than other period of that for computing an absolute position.
selecting the smallest period of mechanical movement corresponding to integer N rather than other period of that for computing an absolute position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57199882A JPS5988612A (en) | 1982-11-15 | 1982-11-15 | Method and apparatus for detecting absolute position |
| JP57-199882 | 1982-11-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1203625A true CA1203625A (en) | 1986-04-22 |
Family
ID=16415174
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000441231A Expired CA1203625A (en) | 1982-11-15 | 1983-11-15 | Apparatus for detecting an absolute position and a process thereof |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4611269A (en) |
| EP (1) | EP0109296B1 (en) |
| JP (1) | JPS5988612A (en) |
| CA (1) | CA1203625A (en) |
| DE (1) | DE3382301D1 (en) |
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| US8918807B2 (en) | 1997-07-21 | 2014-12-23 | Gemstar Development Corporation | System and method for modifying advertisement responsive to EPG information |
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| US9736524B2 (en) | 2011-01-06 | 2017-08-15 | Veveo, Inc. | Methods of and systems for content search based on environment sampling |
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| JPS5988612A (en) * | 1982-11-15 | 1984-05-22 | Toshiba Mach Co Ltd | Method and apparatus for detecting absolute position |
| JPS614918A (en) * | 1984-06-20 | 1986-01-10 | Toyota Motor Corp | Absolute sensor for rotational position detection of multiple rotation using resolver |
| JPS61110006A (en) * | 1984-11-05 | 1986-05-28 | Fanuc Ltd | Position detector |
| JPH067288Y2 (en) * | 1985-04-23 | 1994-02-23 | 株式会社エスジー | Absolute linear position detector |
| JPS6291808A (en) * | 1985-10-17 | 1987-04-27 | Toshiba Mach Co Ltd | Calculating method for angle of rotation of body of rotation |
| DE3860375D1 (en) * | 1987-03-18 | 1990-09-06 | Toshiba Kawasaki Kk | TURNING DETECTOR WITH A SYNCHRO. |
| US5272648A (en) * | 1987-05-20 | 1993-12-21 | Mitsubishi Jukogyo Kabushiki Kaisha | Method of detecting a position of a robot |
| JPS63286705A (en) * | 1987-05-20 | 1988-11-24 | Mitsubishi Heavy Ind Ltd | Position detecting method for robot |
| US4905004A (en) * | 1988-04-11 | 1990-02-27 | University of Texas system The Board of Regents | Cycle-portion encoder |
| US5103226A (en) * | 1989-12-05 | 1992-04-07 | Crown Equipment Corporation | Height sensor for turret stockpicker |
| JP3037770B2 (en) * | 1990-04-05 | 2000-05-08 | 帝人製機株式会社 | Absolute position detector |
| US5444613A (en) * | 1990-07-30 | 1995-08-22 | Teac Corporation | Device for generating a signal representative of the position of an angularly or linearly moveable member |
| US5204600A (en) * | 1991-02-06 | 1993-04-20 | Hewlett-Packard Company | Mechanical detent simulating system |
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| US5886519A (en) * | 1997-01-29 | 1999-03-23 | Mitutoyo Corporation | Multi-scale induced current absolute position transducer |
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| US7116100B1 (en) * | 2005-03-21 | 2006-10-03 | Hr Textron, Inc. | Position sensing for moveable mechanical systems and associated methods and apparatus |
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| US7985134B2 (en) | 2006-07-31 | 2011-07-26 | Rovi Guides, Inc. | Systems and methods for providing enhanced sports watching media guidance |
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| US8407737B1 (en) | 2007-07-11 | 2013-03-26 | Rovi Guides, Inc. | Systems and methods for providing a scan transport bar |
| US9166714B2 (en) | 2009-09-11 | 2015-10-20 | Veveo, Inc. | Method of and system for presenting enriched video viewing analytics |
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| US3764868A (en) * | 1971-06-10 | 1973-10-09 | Eaton Corp | Synchronizing plural motor control system for machines |
| US4330752A (en) * | 1979-05-14 | 1982-05-18 | Optimetrix Corporation | Position control circuit |
| US4342077A (en) * | 1980-07-17 | 1982-07-27 | Allen-Bradley Company | Numerical control servo drive circuit |
| US4377847A (en) * | 1981-02-17 | 1983-03-22 | Gould Inc. | Microprocessor controlled micro-stepping chart drive |
| US4429267A (en) * | 1981-06-22 | 1984-01-31 | Manhattan Engineering Company, Inc. | Digital positioning systems having high accuracy |
| JPS58106691A (en) * | 1981-12-21 | 1983-06-25 | 株式会社エスジ− | Multi-rotation type rotary encoder |
| JPS5988612A (en) * | 1982-11-15 | 1984-05-22 | Toshiba Mach Co Ltd | Method and apparatus for detecting absolute position |
-
1982
- 1982-11-15 JP JP57199882A patent/JPS5988612A/en active Pending
-
1983
- 1983-11-14 EP EP83306926A patent/EP0109296B1/en not_active Expired - Lifetime
- 1983-11-14 DE DE8383306926T patent/DE3382301D1/en not_active Expired - Fee Related
- 1983-11-15 US US06/552,365 patent/US4611269A/en not_active Expired - Lifetime
- 1983-11-15 CA CA000441231A patent/CA1203625A/en not_active Expired
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7996864B2 (en) | 1994-08-31 | 2011-08-09 | Gemstar Development Corporation | Method and apparatus for displaying television programs and related text |
| US8918807B2 (en) | 1997-07-21 | 2014-12-23 | Gemstar Development Corporation | System and method for modifying advertisement responsive to EPG information |
| US9015749B2 (en) | 1997-07-21 | 2015-04-21 | Rovi Guides, Inc. | System and method for modifying advertisement responsive to EPG information |
| US9635406B2 (en) | 1998-05-15 | 2017-04-25 | Rovi Guides, Inc. | Interactive television program guide system for determining user values for demographic categories |
| US9426509B2 (en) | 1998-08-21 | 2016-08-23 | Rovi Guides, Inc. | Client-server electronic program guide |
| US10984037B2 (en) | 2006-03-06 | 2021-04-20 | Veveo, Inc. | Methods and systems for selecting and presenting content on a first system based on user preferences learned on a second system |
| US9749693B2 (en) | 2006-03-24 | 2017-08-29 | Rovi Guides, Inc. | Interactive media guidance application with intelligent navigation and display features |
| US10694256B2 (en) | 2007-03-09 | 2020-06-23 | Rovi Technologies Corporation | Media content search results ranked by popularity |
| US9736524B2 (en) | 2011-01-06 | 2017-08-15 | Veveo, Inc. | Methods of and systems for content search based on environment sampling |
Also Published As
| Publication number | Publication date |
|---|---|
| US4611269A (en) | 1986-09-09 |
| JPS5988612A (en) | 1984-05-22 |
| DE3382301D1 (en) | 1991-07-04 |
| EP0109296B1 (en) | 1991-05-29 |
| EP0109296A2 (en) | 1984-05-23 |
| EP0109296A3 (en) | 1986-08-13 |
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