US20020173364A1

US20020173364A1 - Apparatus for measuring dynamic characteristics of golf game and method for asessment and analysis of hits and movements in golf

Info

Publication number: US20020173364A1
Application number: US09/858,829
Authority: US
Inventors: Bogie Boscha
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-05-17
Filing date: 2001-05-17
Publication date: 2002-11-21
Also published as: US20020173365A1

Abstract

The apparatus of the invention consists of three force sensors built into the head of the club head, a main electronic unit built into the shaft or grip of the club and electrically connected to the sensors within the club, and a remotely located data acquisition, processing and displaying unit connected with the electronic units within the club via an IR or RF transmitter which is a part of the main electronic unit. A first force sensor measures a force in the direction perpendicular to the front face of the club head (axis X′). The second sensor measures a force in the direction perpendicular to axis X′ in the plane of the club head face which either contains the longitudinal axis of the shaft or is parallel thereto (axis Y′). The third sensor the direction perpendicular to the plane X′-Y′. The data collected during the game from the aforementioned self-contained system makes it possible to conduct complete dynamic analysis of swings and hit and correlate the results of this analysis with actual movements of the ball. The data and results of the analysis can be presented on the display of the data acquisition and processing system in a simple graphical or digital form convenient for observation and understanding by a player.

Description

CROSS REFERENCES TO RELATED APPLIOCATIONS

“Not Applicable”.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

“Not Applicable”.

REFERENCE TO “MICROFICHE APPENDIX”

“Not Applicable”.

BACKGROUND OF THE INVENTION.

1. Field of the Invention

The present invention relates to the field of golf and, in particular, to apparatus for measuring dynamic characteristics of golf game and to a method for assessment and analysis of hits and movements in golf. More specifically, the invention relates to a system based on the use of force sensors which are built into the head of a golf club and are connected in a wireless manner to a remotely controlled display system.

2. Description of the Related Art

Golf is one of the most popular sports in the world for people of all ages and skill levels. According to the definition from Encyclopedia Britanica, the game consists of playing the ball on a teeing ground and trying to put it into a hole by successive strokes in accordance with the rules. The stipulated round consists of 18 holes, and most golf courses have 18. Standard 18-hole courses measure from 6500 to 7000 yards (5900 to 6400 meters). Some courses have only nine holes; these are played twice in a stipulated round. The clubs are designed for the various positions in which the ball may come to rest and for the various distances to the hole. The objective is to put the ball into the hole with fewest strokes.

Golf balls have a maximum weight of 1.62 ounces (45.93 grams) and a minimum diameter of 1.68 inches (4.27 centimeters).

The golf clubs are different in length and suppleness of shaft, weight, size and shape of head, the angle at which the shaft ends and the head begins (the lie), and the angle of the face of the club from the vertical (the loft). In the average, good players set there are usually either three or four woods clubs and nine or ten irons. No two clubs in a set are the same.

It is understood that the hit applied to the ball determines the entire trajectory of the ball flight and the result of the game in general. Obtaining of quantitative information about the dynamics of the hit makes it possible to correct the results of the game during the play. It is known that the game of golf involves the use of various golf clubs having heads of different geometries and shapes. Along with other factors, such as the characteristics of swing, swing speed, the geometry of the club head determines the nature of hit and the initial angle of the ball trajectory. It is also known that in a simplified form the phenomenon of impact can be characterized via the law of momentum conservation. This means that the velocity and the direction of a golf ball after the hit can be represented via the following expression: P=M·{overscore (V)}, where in a first approximation M is the mass of the club head, and {overscore (V)} is the velocity vector of the club head at the moment of impact. It is understood that in an ideal case vector {overscore (V)} determines direction of the ball flight after the impact applied to the ball from the club head. Theoretically, the law of momentum conservation must predetermine the initial velocity and direction of ball flight. In reality, however, the ideal condition described above can never be realized in practice. First of all, this is because in the ideal case the vector of the impact from the club head must pass exactly through the center of the ball mass (i.e., the center of the ball), which is difficult to realize in practice with each impact. Second of all, any deviation from the aforementioned ideal impact will generate a lateral displacements of the ball trajectory from the desired path, as well as rotation of the ball caused by the aforementioned lateral displacements and by deformation of the ball, which can never be ideally elastic.

In other words, the conditions described above will always cause deviations from ball trajectory from t the he desired one. Therefore obtaining of quantitative characteristics of the hit applied from golf club to the golf ball based on real measurements rather than on the player's sensations is an important factor for revealing an actual correlation between the characteristics of the impact and results of the game.

Attempts have been made heretofore to described dynamics of the golf motions. For example, U.S. Pat. No. 5,297,796 issued to Peterson; Jon R. on Mar. 29, 1994 describes a visual monitoring system for a golfer to simultaneously watch his/her golf swing while the swing is being made. The system includes one or more video cameras and a video monitoring screen mounted below a transparent surface where the swing is being made with a golf club for viewing the swing without distorting the head of the golfer during the golf swing.

A disadvantage of the system of U.S. Pat. No. 5,297,796 consists in that it is an external system that employs a plurality of television or video cameras placed around the golfer to capture what part of the swing is desired to be seen. The presence of cameras on the field and the presence of the video monitoring screen below a transparent surface where the swing is being made may confuse the player and cause him/her to play unnaturally, as if he/she will unconsciously be afraid to hit the camera and the screen with the ball. Thus the aforementioned system only imitates the game for training purposes. Furthermore, the system is expensive and is limited in its capacity.

U.S. Pat. No. 5,688,183 issued on Nov. 18, 1997 to Sabatino, et al. described a golf club head velocity monitor disposed at or near the golfer's hands. Accordingly, the velocity measuring apparatus of that invention embodied as a small, lightweight, self-contained device secured, e.g., to a golfer's hands in the manner of a wristwatch, or may be secured to a standard golf glove in place of the ordinarily supplied ball-marking button, or may be secured to the golf club shaft in the vicinity of the grip. According to this invention, the system may contain several sensors from which club head velocity measurements may be inferred. These sensors are disposed in a substantially fixed relationship to the golf club during a swing to be monitored. The sensors are preferably acceleration sensors. One sensor may measure the centripetal acceleration along the shaft of the golf club; other sensors may measure acceleration in a plane which is generally perpendicular to the golf club shaft. Using two or more sensors, the club face orientation and/or direction of motion at impact with a ball may be determined.

A disadvantage of the device of U.S. Pat. No. 5,688,183 consists in that the presence of sensors on the player's wrist will restrict movements of the player's hand and the measurements will produce unnatural results.

Attempts have been made to solve the above problems by incorporating the sensor into the club head. Thus U.S. Pat. No. 5,646,345 issued on Jul. 8, 1997 to Butler, Jr. describes an acceleration-responsive device attached to the club head. The device includes a support for a rod between two spaced portions of the support. A weighted disc is mounted for movement on the rod and is held by a spring at one end of the rod. An indicator is also mounted for movement on the rod adjacent the disc. A tube is coupled to the support to facilitate swinging movement of the device where, due to the acceleration thereof, the disc is moved along the rod and pushes the indicator along the rod. When the swinging movement ceases, the disc is returned to the one end of the rod, while the indicator remains at the position to which it was moved. A scale reading of a decal adjacent the moved indicator provides a indication of the acceleration attained during the swinging of device. This reading can be applied to a graph to assist the user of device in the selection of golf clubs having a shaft stiffness most appropriate for the user's physiological particularities.

The club of the type described in U.S. Pat. No. 5,646,345 differs from a regular golf club, so that the training of the golfer with this club or selection of the club suitable for the golfer's playing habits will not match real conditions. However, neither this system, nor any other known system provides satisfactory description of the dynamics of the golf ball hit with complete registration and analysis of the golfer's performance characteristics under natural field conditions of the game and with the use of a club maximally close to the real one.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide a self-contain compact and accurate system built into the golf club head and remotely connected in wireless manner to a system for automatically registering in a real time the dynamics of the golfer's swing and hit. Another object is to provide the system of the aforementioned type which can be realized in real field conditions of the golf game without any distortions of the game nature and without causing in a golfer any feeling leading to unnatural behavior. Still another object is to provide a system of the aforementioned type which collects the maximum possible data of different game characteristics sufficient for analysis and complete correlation of the game characteristics with the game results. Another object is to provide a method for collecting data on dynamics of the golf game, transmitting them wirelessly to a data acquisition and processing unit, and displaying the collected data in a simple and clearly understandable form.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a general view of the system of the invention illustrating a golf club, golf ball, and a data acquisition and display unit. [0020]
FIG. 2 is a sectional view of the club head along the line II-II of FIG. 1. [0021]
FIG. 3A is an example of a block diagram of the sensor assembly suitable for measuring forces in the X′-Y′ plane. [0022]
FIG. 3B is a block diagram of a custom-designed infrared receiver. [0023]
FIG. 4 is another embodiment of the invention which utilizes a digital transceiver operating in RF range of frequencies. [0024]
FIG. 5 is a schematic view of the golf club and of the ball in the X-Y plane in connection with the dynamics movements of the golf club and of the ball. [0025]
FIG. 6[0026] a is a schematic view in which the swing characteristics of the golf club are presented as a function of an instant angular position Φ of the club with respect to the coordinate X.
FIG. 6[0027] b is a is a schematic view in which the swing characteristics of the golf club are presented as a function of an instant angular position Φ of the club with respect to the coordinate Z.
FIG. 7[0028] a is an example of a golfswing graph in the form that can be presented on the display of the apparatus of the invention: the graph illustrates consecutive steps of a “free” swing performed without collision with the ball, the curve showing a sharp peak corresponding to a position of the ball in case if the club would collide with the ball.
FIG. 7[0029] b is a graph similar to the one shown in FIG. 7a and illustrating one of the swings in case of collision with the ball.

DETAILED DESCRIPTION OF THE INVENTION

A general view of the system of the invention for measurement, acquisition, and processing of dynamic data of the golf game is shown in FIG. 1. The system consists of a [0030] sensor assembly 20, e.g., three or two unit acceleration sensors, built into the head 22 of a golf club 24. The club may be of any type used in the game, such as driver, iron, wedge, etc. The sensor assembly 20 is preferably a group of microsensors of the type ADXL210 produced by Analog Devices, Inc., Ma, USA. The sensor assembly 20 has small dimensions, which allow it to be easily built into the interior of the golf club head 22, and a small mass as compared to the mass of the club head. In order to incorporate the microsensors 20, the head 22 has a cavity 26. It is understood that the cavity 26 has dimensions much smaller than the size of the head 22.
[0031] Reference numeral 27 designates a hollow shaft with a grip 29 closed at the top end with a cap 31.
FIG. 2 is a sectional view of the [0032] club head 22 along the line II-II of FIG. 1. It can be seen from FIG. 2 that X′-X′ component of the microsensor assembly 20 is oriented within the head cavity 26 so that it is positioned on the same line X-X with the direction of impacts normally applied from the head 22 to a golf ball 28 at the moment hit. Other sensor components are also oriented in the direction of their respective axes. It is also seen that the sensor assembly 20 is rigidly fixed within the head cavity 26 by a threaded insert 30 inserted into the cavity 26 and attached to the head 22.
In the [0033] club 24 of the invention the shape and dimensions of the club and its head 22 are the same as those of a conventional club.
For convenience of the description of motions that occur in the golf game, it is advantageous to introduce a fixed system of coordinates the origin of which is located in the point O that coincides with the position of the center of gravity of the [0034] ball 28 directly prior the instant of impact applied to the ball from the club 24.
Thus, the aforementioned axis X-X (FIG. 2) is a horizontal axis which conventionally should coincide with the horizontal surface of the golf field. Respectively, the axis Y-Y is a vertical axis perpendicular to the X-X axis, and Z-Z is a lateral axis perpendicular to the plane formed by the axes X-X and Y-Y. It is obvious that the axis Z-Z is also a horizontal axis. It is also understood that the trajectory of the [0035] ball 28 after the hit can be described by a set of coordinates in the X,Y,Z system. This system of coordinates is required for representing the final position of the ball 28 on the golf field when the ball is at rest after completion of its motion. This means that the position of the axis X-X is defined by at least two points, i.e., the initial position of the ball prior to the hit and the position of the target hole in the field. However, in order to describe and analyze the dynamics of impact, i.e., the dynamics of interaction of the club head 22 with the ball 28, it would be advantageous to introduce another coordinate system with the original O′ in the center of mass of the head 22. This coordinate system is fixed with respect to the club head 22 and is characterized by three mutually orthogonal axes X′-X′, Y′-Y′, and Z′-Z′, where axis X′-X′ is the axis which is perpendicular to the surface of the head face 36 and characterizes the direction of hit; the Y′-Y′ axis is perpendicular to the axis X′-X′ and coplanar or parallel to the club shaft 27, and the Z′-Z′ axis is perpendicular to the plane formed by the axis X′-X′ and Y′-Y′.
It is important that the position of the [0036] sensor 20 within the cavity 26 of the club head 22 be rigidly fixed with respect to the plane X′-Y′.
Reference numeral [0037] 38 (FIG. 1) designates an electronic unit for receiving measurement data from the sensor assembly 20 and for wirelessly transmitting these data to a remotely located data processing unit 40 for processing and displaying the obtained data. The electronic block 38 is located in the tubular shaft 29 of the club 24 and is connected to the sensor 20 by conductors 42 guided through the interior of the shaft 29. A battery 41 for supplying electric power to the electronic block 38 and the sensor assembly 20 is located inside the grip 29 in its upper end directly under the cap 31 so that it could be conveniently removed from the grip together with the cap 31.
Now the [0038] sensor 20, and the units 38 and 40 will be described in more detail.
In fact, the [0039] aforementioned sensor 20 consists of three components or unit sensors for measuring forces in the directions of axis X′-X′, Y′-Y′, and Z′-Z′. These unit sensors are capable of measuring accelerations of the club head 22 in the direction of the aforementioned axes.
The [0040] sensor assembly 20 used in the measurement system of the invention is a pair of identical bi-directional sensor accelerometers. These sensors were chosen for use in a real device tested by the applicant for the following reasons:
2 Axis of Acceleration Sensing on a Single IC Chip [0041]
10 milli-g Resolution [0042]
Duty Cycle Output with 1 ms Acquisition Time [0043]
Low power >0.5 mA [0044]
Direct Interface to Popular Microprocessors [0045]
BW Adjustment with a Single Capacitor [0046]
+2.7V to +5.25V Single Supply Operation [0047]
1000 g Shock Survival (in destructive test) [0048]
The ADXL210 is a low-cost, low-power, complete 2-axis accelerometer with a measurement range of ±10 g and can measure both dynamic acceleration (during head movement and impact) and “static acceleration” (e.g., “g”). [0049]
The outputs are digital signals with duty cycles (i.e., a ratio of pulse-width to period) are proportional to acceleration in the direction of two axes being sensed (X′-X′ and Y′-Y′). The outputs can be measured directly by the main [0050] electronic block 38.
The [0051] sensor assembly 20 is mounted in a miniature PC board 45 (FIG. 2). A block diagram of the sensor assembly 20 for measuring forces in the X′-Y′ plane is shown in FIG. 3A. It can be seen that the sensor assembly consists of an X′-sensor unit 20 a and a Y′-sensor unit 20 b which are connected, via respective demodulators 44 and 46, to a counter 48 via a duty cycle modulator 50. The counter 48 requires an A/D converter or logic (not shown). The output period of the sensor is adjustable from 0.5 ms to 10 ms via a single resistor 52. If a voltage output is desired for presentation of measurement results in the directions of axes X′ and Y′, a voltage output proportional to acceleration is available from the X′_FILT pin 54 and the Y′_FILT pin 56, respectively. The bandwidth of the ADXL210 acceleration sensor may be set from 0.01 Hz to 5 kHz via capacitors 58 (for X′ axis) and 59 (for Y′ axis).
The second sensor assembly, which measures forces that occur at the moment of hit in the Y′-Z′ plane is identical to the one described above for hit in the X′-Y′ plane. Therefore the block diagram of the second sensor assembly is not shown. It will differ from the diagram of FIG. 3[0052] a in that the unit sensors 20 b and 20 c are used instead of 20 a and 20 b for measuring forced in the direction of axes Y′-Y′ and Z′-Z′.
As has been mentioned above, the sensors measure a force acting in the directions of sensor orientation. Since the force is proportional to accelration F=m·a, where m is a mass of the club head and a is acceleration of the club mass center), the results of measurements can be represented as accelerations. Integration of acceleration produces velocity. The next step, integration of the velocity, produces trajectory of the club movement. Interrelations between the force, speed, path of movement, and time make it possible to obtain a complete description of the dynamic behavior of the club in time. All these operations are performed with the use of the electronics of the system of the invention in real time and the results can be visually illustrated in various forms on the [0053] display 51 of the system (FIG. 1).
It is understood that accuracy and speed of calculations depend on the construction and quality of the electronic units of the system. Therefore the elements of the electronic part of the system have to be selected with reference to the specific requirements so that the number of steps of integrations could be sufficient for complete representation of the entire process. In other words, the quicker is the electronics, the smoother are the curves on the display. [0054]
The Y′-Y′ axis chip output [0055] 60 (FIG. 3A) is used to measure the swing parameters. This measurement is determined by the position of the club head 22, and hence of the sensor assembly 20, above the ground in a vertical plane. On the other hand, the X′-X′ axis chip output 62 is used to measure the off-center hits that results in slice or draw. In golf, the “slice” is a shot struck which curves pretty severely from left to right (for a right-handed golfer), and the “draw” is a shot when a right-handed player hits a control hook, which goes from right to left. Information taken from the X′-X′-axis output 62 and from the Y′-Y′-axis output 60 is sent from the sensor assembly 20 to a main electronic unit 38 (FIG. 1) which is located in the club grip 29 and is connected to the sensor via wires 42 (2 twisted pair for signals and one for voltage). The Z′-Z′ axis chip output (not shown) is used to measure parasitic deviations of the ball movement in the lateral direction from the ideal or central hit.
The ADXL210 sensor assembly is specifically designed to work with low-cost microprocessors. [0056]
The main [0057] electronic unit 38 consists of a microprocessor 70 located in the grip 29 of the golf club 24 (FIG. 1), an interface unit 72 for connection to the sensor assembly 20, the aforementioned battery 41 with the switch 68, and an IR transmitter (not shown) which is a part of the microprocessor 70. Since the microprocessor 70 of the type required for the application in the golf-club control system of the invention is commercially available, e.g., in the form of an MSP430 microprocessor of Texas Instruments, the internal structure of this microprocessor is omitted from the description. The interface 72 is located in the grip 29 and can be custom-made for connection to the sensor assembly 20. The commercially produced ADXL210-type sensor and the microprocessor MSP430 are interfaceable.
This microprocessor was chosen due to its miniature dimensions and low-power characteristics (+1.8 to 3.6 V, 250 μA at 1 MHz). The main [0058] electronic unit 38 is powered from the same battery 41 as the sensor assembly 20. The power supply to the main electronic unit 38 and to the sensor assembly 20 is controlled by a switch 68 located in a recess (not shown) on the side surface of grip 29 in order to protect the system from accidental switching on during transportation or storage of the club 24. The main electronic unit 38 processes the data received from the sensor assembly 20 and presents this data in a digital form. The MSP430 microprocessor 70 is interfaced to an infrared transmitter (not shown) which is capable of transmitting the aforementioned digital output data shown by arrows G to the data processing unit 40 for processing and displaying the obtained data.
The data processing and displaying [0059] unit 40 is located remotely either in the form of a IR receiver 47 in combination with a display unit 51, e.g., in form of a laptop-type personal computer placed in the field of direct vision of the player for observation of the results of the game or in the form of a pocket-size mini-display.
The [0060] IR receiver 72 can be represented by a MAX3120 IrDA 1,2-compatible infrared transceiver commercially produced by MAXIM, California. This receiver is suitable and optimized for battery-powered space-constrained applications. It consumes only 120μA while supporting data rates up to 115 kbps over a wide 3 V to 5.5 V operating range. This unit is extremely compact and can be used in conjunction with light-emitting diodes built into miniature and hand-,as well as with the palm-top computer displays.
The [0061] signal receiving unit 47 is a custom-designed infrared receiver the block diagram of which is shown in FIG. 3B. The unit is plugged into the PC RS232 interface of the data processing and displaying unit 40 and is characterized by the following features:
1) Powered from the laptop or palmtop serial port (does not require a separate battery or external power supply); [0062]
2) Obeys the Infrared Data Association (IrDA) protocol; [0063]
3) Generates a 16×Baud clock from the received infrared signal; [0064]
4) Contains RS232 compatible driver for data transmission to the laptop or palmtop. [0065]
All the elements of the [0066] signal receiving unit 47 are mounted on a single printed circuit board and comprise the pin diode PD connected to the following sequentially arranged main elements: an infrared transceiver MAX3120, two timer modules, i.e. TLC555(1) and TLC555(2), IRDA encoder/decoder, and MAX233A driver.
FIG. 4 illustrates another embodiment of the invention which utilizes a digital transceiver operating in RF range, e.g., 900 MHz or 2.4 GHz. These ranges coincide with those used in commercial wireless telephone communication systems. As shown in FIG. 4, which is partial sectional view of the upper part of the club, the top end of a club grip [0067] 74 is closed with a cap 76 which supports an electric battery 78 inserted into the interior of the grip 74. The battery 78 is electrically connected to a main electronic unit 80. The detailed construction of the main electronic unit 80 used in this embodiment is omitted since, in principle, it is the same as in the embodiment shown in FIG. 1 and differs from it only in that the transmitter operates in the RF range instead of infrared range of frequencies.
Correspondingly, a remotely located [0068] data processing unit 82 has a receiver 86 operating in the same frequency range as the main electronic unit 80. An example of such a transmitter-receiver pair is any commercially available compact radio telephone having a telephone transmitter mounted into the grip 74 and the telephone receiver mounted into the remotely located data processing unit 82.
The remotely located data processing unit [0069] 40 (FIG. 1) or 82 (FIG. 4) consists of a central processing unit 45 (FIG. 1) or 84 (FIG. 4), such as a conventional laptop or palmtop with appropriate displays 51 (FIG. 1) or 90 (FIG. 4), a signal receiving unit 47 (FIG. 1) or 86 (FIG. 4), and a modem-type converter 49 (FIG. 1) or 88 (FIG. 4). Reference numeral 92 designates a battery switch.
In order to use the system of the invention for monitoring the golf game or for training purposes, it is require merely to place the remotely located data processing unit [0070] 40 (FIG. 1) or 82 (FIG. 4) into a position convenient for use. For this purpose, the display unit 51 (FIG. 1) or 90 (FIG. 4) can be placed within the vision field of the player or can be located in a different place for analyzing the result of the game after the game is completed. For example, the pocket-size palmtop can be kept in the player's pocket, and the larger-size displays can be located in the couch's office or on the ground in front of the player.
Prior to the use, the system is switched on by activating the switch [0071] 68 (FIG. 1) or 92 (FIG. 4) when the club is held in contact with the ball at the starting point O′ of the back swing (FIG. 2). For the ball, the normal position is the origin of the X, Y, Z coordinate system, while for the club the normal position the one in which the center of mass of the head 22 is located in the origin of the X′, Y′, Z′ coordinate system. In other words, the player is visually aimed at the ball to orfient the club head face square to the ball's center of mass to establish the intended trajectory of the ball flight.
The dynamics of the golf club movements and of the ball prior to the impact on the ball as well as after the impact will now be considered with reference to FIG. 5 which is a schematic view of the [0072] golf club 24 and the ball 28 in the X-Y plane. The example shown in FIG. 5 relates to the maximum swing of the golf club for developing the maximum force of the hit, which ensures the longest trajectory of the ball flight and thus allows for more representative analysis.
Let us assume that the [0073] club 24 is raised to the highest position on axis Y (vertical position where Y=H) and prior to initiation of the club movement the center of the mass of the club 24 is located in a point I having coordinates X₀and Y₀. In this point the velocity vector {overscore (V)} is equal to 0. In each moment of time the movement of the club 24 can be presented as an instant rotation of the 24 around an instant center of rotation which is located in the area of the golfer's shoulder. In this case, the radius of rotation is approximately equal to the length of the club plus the part of the hand which rotates. When the golfer starts moving the club 24 and moves the center of mass of the club head 22 from the initial point I with coordinates X₀, Y₀to the point A with coordinates X₁, Y₁, the instant center of rotation of the club is shifted from the point O_Ito the point O_A. The instant linear velocity vector at this moment can be represented as {overscore (V)}_A. Similarly, as the club swing is continued, the center of mass of the club head 22 is shifted from the point A with coordinates X₁, Y₁to the point B with coordinates X₂, Y₂, the instant center of rotation of the club is shifted from the point O_Ato the point O_B. The instant linear velocity vector at this moment can be represented as {overscore (V)}_B, and so on. Thus the trajectory of the center of mass of the club head 22 is shown in FIG. 5 in the form of a curve TR in the X-Y plane. If necessary, the trajectory can also be presented in the Y-Z and X-Z planes, so that combination of all these three presentations can be plotted into a three-dimensional view on the display.
It is more convenient, however, to present the swing characteristics as a function of an instant angular position Φ of the club with respect to the coordinate X. This graph is shown in FIG. 6, which illustrates the function {overscore (V)} (Φ). It can be seen that the velocity {overscore (V)} increases in non-linear manner as the swing progresses reaching a certain high value {overscore (V)}[0074] _collisiondirectly prior to the hit. The moment of hit on the ball 28 is shown as a sudden drop in velocity of the club 24. According to our assumption, the hit corresponds to Φ=90° with the square face of the club head. The drop on the curve {overscore (V)} (Φ) occurs due to elastic deformations of the club head 22 during collision with the ball 28. It can be seen from FIG. 6a that after the moment of collision and relaxation of club head deformations, the velocity is still growing for a certain short period of time due to movement of the golfer's hand by inertia. FIG. 6a is a schematic view in which the swing characteristics of the golf club are presented as a function of an instant angular position Φ of the club with respect to the coordinate X. After this short period of acceleration the velocity is rapidly reduced as the golfer discontinues the club swing.
It can be seen from FIG. 5 that the instant centers of rotation of the club head mass travels within a certain limited area in the zone of the golfer shoulder. In other words, as the zone of deviations for the centers of rotation of the club head mass is small, the approximation shown in FIG. 5 is justifiable. [0075]
It should be noted that the [0076] club 24 does not move purely in the X-Y plane but also experiences some movement in the X-Z plane or Y-Z plane of the aforementioned X,Y,Z coordinate system. It is understood that at the moment of hit the Z coordinate should be equal to 0. However, in a real game, the trajectory of the club swing will never be ideally in the X-Y plane, and some deviations in the Z-axis direction will always take place. These deviations will generate Z-component of the impact which will lead to lateral scatterings from the desired direction with Z=0. The Z(Φ) function is shown in FIG. 6b which is a schematic view presenting swing characteristics of the golf club as a function of an instant angular position Φ as a function of X.
It is well known that the length of any ballistic trajectory, which is the case of the ball flight as well, is determined by the initial velocity and the angle at the initial point of the trajectory. The aforementioned angle depends on the angular position of the club head face in the X-Y at the moment of hit. Since the swing is always approximately the same, the trajectory of the ball is determined by the selection of a specific club head. This is because the club heads of different types are characterized by different inclinations of the club head faced with respect to the club shaft. [0077]
The club known as driver has a club head plane inclined to the shaft at an angle that in the case of the ideal central hit on the ball ensures the maximum length of the ball trajectory. In other word, a hit in which the direction of hit transfer from the club to the ball occurs along a line which connects the center of mass of the head with the center of the ball mass is considered as a central hit. The central hit with the maximum destination for the ball is achieved at the most optimal angle of hit equal to 45°. If the hit deviates from the central, the ball will not reach the target. Such deviations are measured by the X′-X′ and Y′-Y′ sensosr. [0078]
Such analysis is conventional, since the real game is characterized by a great variety of moves, swings, types of clubs, and golfer's habits. For example, some strikes may have the center of rotation of the club head mass in the apex of a cone with a swinging motion of the club around the apex as the center. In other cases the center of rotation performs movements close to linear movements, etc. [0079]
In spite of the aforementioned deviations from the theory of the golf dynamics described above, the system of the invention is advantageous in that for each individual golfer the dynamics of the game at various stages of the game can be presented in a quantitative form as a set of data transmitted from the [0080] sensor 20 built into the club head 22 to the main electronic unit 38 and shown in the display 40 in any convenient digital or graphical form obtained after processing the data. For example, the data acquired by the system can be presented in the form of graphics shown in FIGS. 5 and 6.
Another example of graphic presentation of the golf dynamics data is shown in FIGS. 7[0081] a and 7 b.
FIG. 7[0082] a is an example of a golfswing graph in the form that can be presented on the display of the apparatus of the invention. Thus, curve 101 (FIG. 7a) shows beginning of the golf back swing. The sensor begins to sense a negative force to get activated. The back swing motion starts at point O′ (FIGS. 2 and 7a), where the golf club face 36 is in contact with the ball 28. The negative force is developed due to beginning of the back swing. In the back swing the trajectory of the club head moves to the left of FIG. 7a till point I (X₀, Y₀) (FIG. 5). In FIG. 7a the time for the back swing has to be measured on the same scale as for the forwards swing but in the opposite direction. The entire cycle of back and forward swings takes no more than 3 sec. The forward swing, which is described by a curve 102 in FIG. 7a, is initiated at point I (X₀, Y₀) (FIG. 5) and ended at point E (FIG. 5) where movement of the club 24 is discontinued. Peak 103 on the graph of FIG. 7a corresponds to the position of the ball 28. The curve 102 shows a free swing, i.e., a swing without collision with the ball.
FIG. 7[0083] b is a graph similar to the one shown in FIG. 7a. However, this curve illustrates a swings (curve 104) in case of collision with the ball. The point of collision is marked by a reversed peak 105. After the collision with the ball at point 105, the club continues to move forward by inertia with gradual decrease in speed to zero at point 106.
The [0084] curve 108 in FIG. 7b corresponds to a back swing similar to 101 in FIG. 7a. Arrows in the curves of both graphs show directions of the movements. Electronically, the system of the invention operates in the manner described below.
When a golfer addresses the [0085] ball 28, i.e., takes a position for hitting the ball 28 on completion of set up with the club head 22 next to the ball 28, the golfer may activate the system either by pushing on the switch 68 (FIG. 1) or activating the system by voice (if a voice-activation system is available). The swing is normally is performed within about 3 sec from this moment.
The infrared signals are transmitted from the main [0086] electronic unit 38 located in the club 24 (FIG. 1) to the receiver shown in FIG. 3B. The signals are conventionally shown by arrows G in FIG. 1. For the case of RF transmission, the signals transmitted from the main electronic unit 74 to the receiver 82 are conventionally shown by arrows G′ in FIG. 4. The timer TLC555(2) is configured to generate 16× baud clock for infrared receiver MAX3120. The timer TLC555(1) is used to synchronize the baud clock of the timer TLC555(2) to the start of each received byte of the signal. It does this by holding the reset input to the timer TLC555(2) which is active until the first IR pulse is received. This is assumed to be the start bit of a received byte. When the timer TLC555(1) senses this event, it generates a pulse (1 byte wide for a preset baud rate). This pulse is fed to the timer TLC555(2) rest input. This allows the timer TLC555(2) to start generating 16× clock pulses for the IRDA encoder/decoder module. When the timer TLC555(1) times out (1 byte times), it then resets the timer TLC555(2) out (1 byte time) and waits for the next byte to repeat the cycle. Precision components (or potentiometers) are connected to the timers (reset pulse and 16× clock) for desired baud rate.
Thus it has been shown that the invention provides a self-contain compact and accurate system built into the golf club head and remotely connected in wireless manner to a system for automatically registering in a real time the dynamics of the golfer's swing and hit. The aforementioned system can be realized in real field conditions of the golf game without any distortions of the game nature and without causing in a golfer any feeling leading to unnatural behavior. The system collects the maximum possible data of different game characteristics sufficient for analysis and complete correlation of the game characteristics with the game results. The invention also provides a method for collecting data on dynamics of the golf game, transmitting them wirelessly to a data acquisition and processing unit, and displaying the collected data in a simple and clearly understandable form. [0087]
Although the invention has been shown in the form of specific embodiments, it is understood that these embodiments were given only as examples and that any changes and modifications are possible, provided they do not depart from the scope of the appended claims. For example, the sensors and other parts of the electronics can be installed outside the club and attached to the rear face of the club head. The display unit can be installed on the golf card in front of the driver's seat. The main electronic unit may send to the golfer through a feedback circuit a sound signal informing about results of the hit. Although two sensor assemblies were mentioned and described for measuring forces and accelerations along three mutually perpendicular axes, only one bi-directional sensor assembly can be used for approximated analysis of the golf dynamics. If necessary, the electronics of the system can be activated by a voice signal. [0088]

Claims

1. An apparatus for measuring dynamic characteristics of golf game consisting in that a golf club hits a golf ball for delivering said ball to a target location, said apparatus comprising:

a golf club having a shaft, a grip at the upper end of said shaft, and a club head at the lower end of said shaft, said club head having a center of mass and a face plane for contact with said club ball;

at least one bi-directional sensor assembly comprising:

a first force sensor rigidly connected to said club head and oriented along a first line passing though said center of mass of said club head for measuring a force in the direction of said first line and a normal to said face plane; and

a second force sensor rigidly connected to said club head and oriented along a second line perpendicular to said first line and located in said face plane or in a plane parallel thereto;

a main electronic unit rigidly connected to said golf club and electrically connected to said at least one bi-directional sensor assembly, said main electronic unit comprising a signal transmitting unit;

a power supply unit with switching means for supplying an electric power to said at least one bi-directional sensor assembly and to said main electronic unit, said power supply unit being supported by said golf club; and

a data acquisition and display unit located remotely from said golf club and comprising a signal receiving unit for wirelessly receiving signals from said signal transmitting unit, a data processing unit, and a display unit for displaying the data being processed in said data processing unit.

2. The apparatus of claim 1, wherein said shaft has a first interior cavity inside said shaft, said club head has a second interior cavity inside said club head, said grip has a third interior cavity inside said grip, said bi-directional sensor assembly being located in said second interior cavity and rigidly fixed therein, and said main electronic unit being located in a location selected from said first interior cavity and said third interior cavity.

3. The apparatus of claim 2, wherein said signal transmitting unit and said signal receiving unit are selected from a group of IR and RF signal transmitting units and signal receiving units, respectively.

4. The apparatus of claim 1, wherein said data acquisition and display unit comprises a data processing and displaying unit selected from a group consisting of a PC, a laptop, and a palmtop.

5. The apparatus of claim 3, wherein said data acquisition and display unit comprises a data processing and displaying unit selected from a group consisting of a PC, a laptop, and a palmtop.

6. The apparatus of claim 1, further provided with a third force sensor rigidly connected to said club head and oriented along a third line passing though said center of mass of said club head for measuring a force in the direction of said face plane and a normal to a plane formed by said first line and said second line, said third force sensor forming in combination with said second force sensor a second bi-directional sensor assembly.

7. A system for measuring dynamic characteristics of golf game consisting in that a golf club hits a golf ball for delivering said ball to a target location, said system comprising:

a golf club having a shaft with a first cavity, a grip with a second cavity at the upper end of said shaft, and a club head with a third cavity at the lower end of said shaft, said club head having a center of mass and a face plane for contact with said club ball;

a first force sensor located in said third cavity and rigidly fixed to said club head, said first force sensor being oriented along a first line passing though said center of mass of said club head for measuring a force acting on said center of mass of said club head in the direction of said first line and of a normal to said face plane; and

a second force sensor rigidly connected to said club head and oriented along a second line perpendicular to said first line and located in said face plane or in a plane parallel thereto, said first force sensor and said second force sensor forming a first bi-directional sensor assembly;

a third force sensor rigidly connected to said club head and oriented along a third line passing though said center of mass of said club head for measuring a force acting on said center of mass of said club head in the direction of said face plane and of a normal to a plane formed by said first line and said second line, said third force sensor forming in combination with said second force sensor forming a second bi-directional sensor assembly;

a main electronic unit rigidly connected to said golf club and located in a location selected from said first cavity and said second cavity, said main electronic unit being electrically connected to said first bi-directional sensor assembly and to said second bi-directional sensor assembly, said main electronic unit comprising a signal transmitting unit;

a power supply unit with switching means for supplying an electric power to said first bi-directional sensor assembly, said second bi-directional sensor, and to said main electronic unit, said power supply unit being located in a location selected from said first cavity and said second cavity; and

8. The apparatus of claim 7, wherein said signal transmitting unit and said signal receiving unit are selected from a group of IR and RF signal transmitting units and signal receiving units, respectively.

9. The apparatus of claim 7, wherein said data acquisition and display unit comprises a data processing and displaying unit selected from a group consisting of a PC, a laptop, and a palmtop.

10. The apparatus of claim 8, wherein said data acquisition and display unit comprises a data processing and displaying unit selected from a group consisting of a PC, a laptop, and a palmtop.

11. A method for assessment and analysis of hits and movements of a golf club comprising the steps of:

providing a self-contained system comprising: a golf club having a shaft, a grip at the upper end of said golf shaft, and a club head at the lower end of said shaft, said golf club head having a center of mass and a face for contacting a golf ball during the play, said system further comprising at least one bi-directional sensor assembly built into said golf club and comprising a first force sensor rigidly connected to said club head and oriented along a first line passing though the center of mass of said club head for measuring a force in the direction of said first line and of a normal to said face plane and a second force sensor rigidly connected to said club head and oriented along a second line perpendicular to said first line and located in said face plane or in a plane parallel thereto; a main electronic unit built into said golf club and electrically connected to said at least one bi-directional sensor assembly, said main electronic unit comprising a signal transmitting unit; a power supply unit with switching means for supplying an electric power to said at least one bi-directional sensor assembly and to said main electronic unit, said power supply unit being supported by said golf club; and a data acquisition and display unit located remotely from said golf club and comprising a signal receiving unit for wirelessly receiving signals from said signal transmitting unit, a data processing unit, and a display unit for displaying the data being processed in said data processing unit;

establishing a fixed three-axes orthogonal coordinate system with the first origin in said center of mass of said golf ball prior to the instant of impact applied to said ball from said golf club;

establishing a moveable three-axes orthogonal coordinate system with the second origin in said center of mass of said club head;

registering positions of said second origin by said at least one bi-directional sensor assembly at sequential periods of time during movements of said golf club prior to hit on said ball to form a golf dynamic data;

transmitting said golf dynamic data from said main electronic unit via said data transmitting unit to said data receiving unit;

processing said data in said data processing unit; and

displaying said data in said display unit.

12. The method of claim 11, wherein said golf dynamic data are said forces acting in the directions of axes of said moveable three-axes orthogonal coordinate system in sequential moments of time.

13. The method of claim 12, wherein said golf dynamic data is transmitted from said data transmitting unit to said data receiving unit in the form of IR signals.

14. The method of claim 12, wherein said golf dynamic data is transmitted from said data transmitting unit to said data receiving unit in the form of RF signals.

15. A method for assessment and analysis of hits and movements of a golf club comprising the steps of:

providing a self-contained system comprising: a golf club having a shaft, a grip at the upper end of said golf shaft, and a club head at the lower end of said shaft, said golf club head having a center of mass and a face for contacting a golf ball during the play, said system further comprising;

two bi-directional sensor assemblies built into a golf club and comprising a first force sensor rigidly connected to said club head and oriented along a first line passing though the center of mass of said club head for measuring a force applied to said club head in the direction of said first line and of a normal to said face plane, a second force sensor rigidly connected to said club head and oriented along a second line perpendicular to said first line and located in said face plane or in a plane parallel thereto, and a third force sensor oriented along a third line perpendicular to a plane formed by said first plane and said second plane; a main electronic unit built into said golf club and electrically connected to said two bi-directional sensor assemblies, said main electronic unit comprising a signal transmitting unit; a power supply unit with switching means for supplying an electric power to said at least one bi-directional sensor assembly and to said main electronic unit, said power supply unit being supported by said golf club; and a data acquisition and display unit located remotely from said golf club and comprising a signal receiving unit for wirelessly receiving signals from said signal transmitting unit, a data processing unit, and a display unit for displaying the data being processed in said data processing unit;

establishing a fixed three-axes orthogonal coordinate system with the first origin in the center of gravity of said golf ball prior the instant of impact applied to said ball from said golf club;

registering positions of said second origin by at least one of said two bi-directional sensor assemblies at sequential periods of time during movements of said golf club prior to hit on said ball to form a golf dynamic data;

processing said data in said data processing unit; and

displaying said data in said display unit.

16. The method of claim 15, wherein said moveable three-axes orthogonal coordinate system having a first axis in a direction of said first line, a second axis in a direction of said second line, and a third axis in a direction of said third line.

17. The method of claim 16, wherein said data is transmitted from said data transmitting unit to said data receiving unit in the form of IR signals.

18. The method of claim 16, wherein said data is transmitted from said data transmitting unit to said data receiving unit in the form of RF signals.

19. The method of claim 17, wherein said graphical form comprising at least one curve in a coordinate system in which an abscissa is a time and an ordinate is an acceleration developed by said center of mass of said club head.