WO2001017466A2 - A lower limb prosthesis - Google Patents

Abstract

A lower limb prosthesis has a pelvic attachment, thigh (5) and shin components interconnected by a knee joint, and, interconnecting the pelvic attachment and the thigh component, a hip joint (4) which includes an adaptive hip flexion drive mechanism (8, 9). This mechanism is arranged to apply a dynamically variable flexion moment to the hip joint, and comprises an adaptive resilient energy storing device which stores energy during hip extension and returns the stored energy during subsequent flexion. The energy storage device comprises an electronically controlled piston and cylinder assembly, the piston rod of which is, itself, a telescopic mechanism for limiting the duration of the swing phase.

Description

A LOWER LIMB PROSTHESIS

This invention relates to a prosthesis, and more particularly to a lower limb prosthesis for a hip-distarticulation amputee.

Hip disarticulation amputees have particular difficulty in achieving an acceptable walking gait with a limb prosthesis, principally due to the fact that when the limb reaches the rollover part of the stance phase, i.e. towards the end of the stance phase when the foot begins to lift from the ground to start the swing phase, the amputee has to exert significant effort to initiate swing of the prosthesis. This is uncomfortable and also results in an unnatural limb movement. The amputee has to twist the pelvis excessively in order to transfer sufficient energy to the prosthesis, and to lift the prosthesis during the swing phase.

Prostheses have been developed to reduce such difficulties. These prostheses use energy storing mechanisms, usually leaf or coil spring arrangements, for storing energy during the stance phase and returning it at rollover to initiate the swing phase. The energy required to be transferred from the amputee to the prosthesis is thereby reduced. However, improved operation tends only to be achieved at fixed or predetermined walking speeds. Indeed, to maintain satisfactory operation, such a limb may have a mechanism to limit the thigh flexion/extension angle and angular speed which has the effect of limiting stride and walking speed, impairing the amputee's mobility.

According to a first aspect of the invention, there is provided a lower limb prosthesis comprising a pelvic attachment, thigh and shin components interconnected by a knee joint, and, interconnecting the pelvic attachment and the thigh component, a hip joint including an adaptive hip flexion drive mechanism arranged to apply a dynamically variable flexion moment to the hip joint.

According to a second aspect of the present invention, there is provided a lower limb prosthesis for a hip disarticulation amputee, the prosthesis having an adaptive control system which comprises: an energy storing mechanism located in a proximal region of the prosthesis and arranged to store energy generated during part of a stance phase, and to return at least part of the stored energy at rollover to initiate a swing phase, the mechanism including a control device for controlling the amount of energy stored by the mechanism; a sensor for generating electrical sensor signals in response to movement of the prosthesis; and processing means electrically coupled to the sensor and the control device, the processing means being arranged to generate setting signals for the control device, the setting signals being generated in accordance with a set of control data generated during a teach mode, and measurement data values representative of the speed of operation of the prosthesis which are calculated in response to the sensor signals, the control data representing a relationship between speed of prosthesis operation and parameter values representing selected settings of the control device, whereby during operation of the prosthesis the energy storing mechanism is automatically adjusted according to the detected speed of limb operation.

By generating, during a teach mode, control data which represents a relationship between selected settings of the energy storing control device and speed of limb operation, the wearer is able to define, for different speeds of walking, control device settings which provide for an improved, if not optimal limb operation. During a playback mode of operation, the processing means of the adaptive control system generates setting signals for the control device, in accordance with the generated control data and the detected speed of limb operation, to adjust the amount of energy stored and returned by the energy storing mechanism. As the amputee operates the limb in a playback mode, the adaptive control system of the prosthesis provides a required level of swing phase initiation and assistance for delivering the improved, if not optimal, limb operation.

The prosthesis is particularly suited for hip disarticulation amputees, wherein the prosthesis includes a pelvic attachment, which may include a hip alignment portion, located at a proximal end of the limb, and a thigh portion attached to the alignment portion, the control mechanism interconnecting the pelvic attachment and the thigh portion so as to control relative movement therebetween. The thigh portion may be attached to further prosthetic components, extending distally for connection to a prosthetic foot.

The energy storing mechanism may comprise a piston-and-cylinder assembly which, over at least part of the stance phase, compresses a gas, usually air, and wherein at rollover, the compressed gas drives the piston in a return stroke to initiate the swing phase. Part or all of the stored energy is returned at rollover. The piston and cylinder assembly may include a valve, and the control device of the mechanism may comprise an electric motor which is coupled to the valve. The piston rod of the assembly may be pivotally attached to the hip alignment portion with the cylinder pivotally attached to the thigh portion at a position distal to the hip joint.

In the preferred embodiment the processing means of the adaptive control system comprises: data generating means operable in the teach mode and the playback mode of the processing means automatically and repeatedly to generate the measurement data values in response to the sensor signals; control device setting means operable in both modes to feed the setting signals to the control device for adjusting a parameter of the energy storing mechanism to control the amount of energy stored, the setting means further being operable in the teach mode to feed the setting signals to the control device according to the parameter values generated in the processing means in response to command signals input to the processing means; means for processing the parameter values together with the associated said measurement data values to generate the control data; and storage means for storing the control data, the setting means being further operable during the playback mode as the limb is operated to process the resulting measurement data values in conjunction with the stored set of control data to generate the said setting signals for the control device. The command signals are inputted to the processing means by a remote operator control unit, a receiver forming part of the prosthesis being coupled to the processing means for receiving the command signals. In this way it is possible for a prosthetist to calibrate the control system by a series of relatively short walking tests using the remote operator control unit without the constraints imposed by having to stay close to the patient.

In the preferred system in accordance with the invention, the processing circuit includes saving means responsive to a further command signal received via the receiver from the remote control unit to feed automatically to the storage means signals representative of the measurement data value and the parameter value associated with a selected instant in time for each of a plurality of different limb operation speeds. In addition, the data generating means may be arranged to store a step period value in a storage element repeatedly during the teach mode, the stored value in the storage element thereby being updated continuously to provide a signal representative of the step period existing immediately before a further command signal as mentioned above is received. The data generating means may also be continuously operable to generate the step period values as a running average of a plurality of step periods, and the circuit preferably include means for calculating automatically a series of step period boundary values based on optimum step period values determined during the teaching mode to define a series of speed ranges, this occurring automatically when the saving means responds to the further command signal from the operator unit.

In effect, the processing circuit in the limb provides on-line interactive processing in the teach mode in the sense that the operator control unit allows a command signal to be issued which initiates a test routine or test "window". The test routine or window is terminated by the saving means in response to the above-mentioned further command signal. Whenever the receiver is switched on, it is preferred that the processing circuit continuously provides data measurement values representative of the speed of limb operation and uses the stored control data set to set the control device of the energy storing mechanism using the setting means. When a command signal is issued to initiate the test routine or window, in particular a command signal which designates a particular walking speed, the processing circuit allows the operator to set the control device using the operator control unit, the set parameter value being stored in a special register so that when the further command signal is issued it is the parameter value in the special register that is saved. The test routine for that designated speed having been terminated, the control data set is recalculated and the processing circuit reverts to automatic setting of the control device using the recalculated control data set. The prosthesis may then continue in the teach mode until the control unit issues another command signal, e.g. for a different walking speed, again initiating a test routine or window, and so on until a satisfactory control data set is produced. This data set can then be stored in a more permanent form, thereby ending the teach mode. Thus the teach mode may be regarded as including a plurality of operator defined test windows for different walking speeds, between which the system automatically sets the control device. The control device parameter is preferably the moment applied to the thigh portion by the energy storing mechanism, which is related to the pressure of gas compressed within the piston and cylinder assembly.

The values of the control device parameter obtained at different walking speeds at the selected instants referred to above may be used by the processing circuit to calculate automatically interpolated parameter settings to provide a complete set of parameter settings to correspond to the different step period ranges. Typically, the teach mode allows the operator to designate three walking speeds so that three average step period values are measured and stored together with three corresponding parameter values. In the preferred embodiment, the processing circuit is arranged to calculate from the stored data four boundary or threshold step period values defining boundaries between five speed ranges, which can be referred to as slow, medium slow, normal, medium fast, and fast. These boundary values are stored in a non-volatile memory along with the three optimum parameter values which represent valve settings determined during the walking tests and two automatically calculated intermediate parameter values to yield a set of five valve settings for use during the playback mode according to which of the five step period ranges the step period corresponds at any given time during use of the prosthesis. It is preferred that the communication link between the operator unit and the receiver is a one-way radio frequency link. The control unit may simply possess keys for designating walking speeds (e.g. slow, normal, fast), one or more controls for increasing and decreasing the control device parameter value, and a control for saving selected parameter values determined during the walking tests in conjunction with concurrently measured step period values. The sensor may be a magnetic proximity sensor associated with the piston and cylinder assembly, comprising a permanent magnet mounted on or associated with the piston and a magnetically sensitive transducer mounted on or associated with the cylinder, or vice versa, to produce pulsed electrical signals, one pulse being generated for each step taken. From this pulsed signal it is possible to determine the step period. It is to be understood that, while the step period is used in the description as a measure of the speed of walking, it is also possible to use signals directly or indirectly representing the step rate or speed.

The prosthesis may comprise a device for limiting the stride length of the wearer. This may comprise a device within the energy storing mechanism for limiting the amplitude of hip flexion thereby limiting the duration of the swing phase. In the preferred embodiment, the piston and cylinder assembly contains a limiting mechanism, whereby the piston rod of the assembly comprises a first rod member attached to the hip alignment portion and a second rod member attached to the piston, the first rod member being connected telescopically to the second rod member so as to allow relative longitudinal movement therebetween, an adjustable stop limiting the amount of relative longitudinal movement between the two rod members. The limiting mechanism may be disabled to allow large hip flexion angles, e.g. when the wearer is sitting.

The prosthesis satisfies biomechanical requirements in that it is mechanically stable during walking, producing a minimal anterior-posterior moment about the hip joint, and an optimal medial-lateral bending moment throughout the limb. For these and for cosmetic reasons, the adaptive control system is preferably located within a region, or envelope, having a medial-lateral width of 75mm, a medial-lateral height of 200mm, and a medial-lateral depth of 70mm. The size meets ergonomic as well as dimensional constraints for the design of functional components.

According to a second aspect of the invention, there is provided an adaptive control system for a lower limb prosthesis, the control system comprising: an energy storing mechanism for location in a proximal region of the prosthesis for storing energy generated during part of the stance phase of the walking cycle and for returning at least part of the stored energy at rollover to initiate a swing phase, the mechanism including a control device for controlling the amount of energy stored by the mechanism; a sensor for generating electrical sensor signals in response to movement of the prosthesis; and processing means electrically coupled to the sensor and the control device, the processing means being arranged to generate setting signals for the control device, the setting signals being generated in accordance with a set of control data generated during a teach mode, and measurement data values representative of the speed of operation of the prosthesis which are calculated in response to the sensor signals, the control data representing a relationship between the speed of operation and parameter values representing selected settings of the control device, whereby during limb operation in a playback mode, the energy storing mechanism is automatically adjusted according to the detected speed of operation.

According to a third aspect of the invention, there is provided a method of controlling an artificial limb for a hip disarticulation amputee, the limb comprising an energy storing mechanism associated with a hip joint for storing energy during part of the stance phase of the walking cycle for return at rollover, and a control system for adjusting the amount of energy stored, wherein, during a teach phase of the method, movement of the limb is automatically and repeatedly monitored by electronic means forming part of the control system with a series of measurement data values related to the speed of operation of the limb being generated in the electronic means, a remote control unit is operated in conjunction with a receiver forming part of the limb during operation of the limb to transmit command signals to the limb which are processed by the electronic means to generate setting signals for adjusting the energy storing mechanism with the object of improving limb operation, data generated in the electronic means and representing selected settings of a control device forming part of the energy storing mechanism are processed in the electronic means together with the associated said measurement data values to generate a set of control data representing a relationship between speed of limb operation and control device settings, and the set of control data is then stored in the electronic means, and in which method, during a playback phase, the movement of the limb is automatically and repeatedly monitored by the electronic means in conjunction with the stored set of control data to generate appropriate control device setting signals for automatically adjusting the energy storing mechanism according to the speed of limb operation.

Preferred features of the above described method are set out in the appended dependent claims.

The invention will now be described, by way of example, with reference to the drawings in which:

Figure 1 is a partly cross-sectioned side view of an upper portion of a lower limb prosthesis comprising an adaptive control system, in accordance with the invention;

Figures 2A to 2F are a set of diagrams showing a hip disarticulation amputee with the prosthesis of Figure 1 in different states, Figure 2A corresponding to the standing condition, Figures 2B to 2E showing walking conditions, and Figure 2F showing a sitting condition;

Figures 3 A and 3B are partly cross sectioned side elevations of the prosthesis of Figure 1 in different stages of hip flexion;

Figures 4A, 4B and 4C are partly sectioned side views of a telescopic piston rod forming part of a piston and cylinder assembly of the prosthesis of Figure 1;

Figures 5 A and 5B are diagrammatic lateral and anterior elevations showing an envelope inside which at least an energy storing mechanism of the prosthesis is located.

Figure 6 is a block diagram of a prosthesis control system; Figure 7 is a plan view of an operator control unit;

Figure 8 is a flow chart illustrating start-up and shut-down phases of a program forming part of the control system;

Figure 9 is a teach mode speed measurement flow chart of the program;

Figure 10 is a teach routine flow chart of the program; and

Figure 11 is a playback routine flow chart of the program including playback mode speed measurement.

Referring to Figure 1, a lower limb prosthesis for a hip disarticulation amputee has a hip alignment device 1 connected to a hip socket 2 using a conventional single bolt alignment former 3 which allows both tilt and rotation of lower parts of the prosthesis about the hip socket 2. The alignment device carries a hip joint pivot 4 for attachment of a thigh member 5 of the prosthesis. It should be noted that although the preferred joint is a uniaxial joint, with the pivot axis of the joint extending in the medial-lateral direction outside the confines of the pelvis and, therefore, spaced from the natural hip axis, its is also possible to use a polycentric multi-axial joint to provide an instantaneous pivot axis translated to a position above the pelvic perimeter, near to a position where the amputee's natural hip joint would be located. The alignment portion 1 is pivotally connected at pivot 4 to the thigh member 5 which extends distally to a prosthetic knee (not shown in Figure 1), which is in turn connected to a prosthetic shin and foot member (also not shown). Also connected to the hip alignment portion 1 at a second pivot 6 having a medial-lateral axis spaced generally posteriorly from the hip joint pivot axis defined by pivot 4 is the piston rod 7 A, 7B of a piston-and-cylinder assembly having a piston 8 and a cylinder 9, the cylinder 9 being connected to the thigh member 5 by a third pivot 10 having a medial-lateral axis located distally of the axis of pivot 4. The piston-and-cylinder assembly is a pneumatic device which constitutes an energy storing mechanism for storing energy during part of the stance phase of the walking cycle, the energy being returned during rollover to initiate and assist the swing phase of the limb. It will be appreciated that references to 'rollover' refer to that part of a walking cycle in which the amputee's weight begins to transfer from one limb to the other, i.e. towards the end of the stance phase and just prior to the swing phase. Energy is stored by the piston-and-cylinder assembly by means of the piston 8 compressing air within the cylinder 9. As will be described in detail below, the stored energy is returned at rollover so as to initiate and assist the swing phase anterior swing of the thigh member 5. As will be appreciated, the amount of energy stored (and therefore returned) by the piston-and-cylinder assembly depends on the pressure of the air in the cylinder 9. This is controlled by a needle valve 12 which is adjusted by an electrical stepper motor 11. The needle valve 12 lies in a passage 13 in the body of the cylinder 9, the passage 13 interconnecting the interior of the cylinder 9 (on the opposite side of the piston 8 from the piston rod 7 A, 7B) with the atmosphere via passage 14. Operation of the motor 11 causes the needle member to move into or out of the passage 13.

Referring to Figure 2A, when the amputee is standing still the hip joint is partly flexed.

Referring to Figures 2B to 2D, during the walking cycle the latter part of the stance phase is characterised by rollover terminating at the point shown in Figure 2B where the foot is about to leave the ground (i.e. at the end of the stance phase) to initiate the swing phase. The next stance phase begins at heel strike as shown in Figure 2C, and the cycle continues to mid-stance, shown in Figure 2D. The operation of the piston-and-cylinder assembly during the various walking phases is best understood by reference, in addition, to Figure 2E, which shows the limb in the above-mentioned three conditions, namely (i) at heel strike, (ii) at mid-stance phase, and (iii) during rollover, and also with reference to Figures 3A and 3B which show the relative positions of the upper prosthesis components during rollover and at heel strike respectively.

During the stance phase, air is compressed by the piston and cylinder assembly to a pressure which is determined by the control device, i.e. the motor 1 1 which controls the needle valve 12. The limb may include a facility for relieving the pressure manually so that the upwards force from the piston 8 does not cause discomfort whilst the amputee is standing. Most of the compression occurs at the start of the stance phase in which a large amount of energy is transferred through the hip socket 2 to the piston 8 as the pelvis begins naturally to rotate and tilt. Figure 3 A shows the proximal part of the limb at rollover, the piston 8 having compressed the air in the cylinder 9 due to maximum extension of the hip joint, as shown by Figure 2E(iii). At this point, most of the amputee's weight is transferred from the prosthesis to the other leg. Accordingly, the pressure, or energy stored by the piston-and-cylinder assembly forces the piston rod 7 A, 7B to deliver a return stroke upwards, thereby causing the thigh member 5, which is pivotally connected to the hip alignment portion 1, to move forwards. In this way, the swing phase is positively initiated by the returned energy. The returned energy also assists completion of the swing phase. Thus, the amputee benefits by only having to exert a relatively small effort to complete the swing phase. Figure 3B shows the proximal part of the prosthesis at the end of the swing phase, i.e. at the point of heel-strike as shown at (i) in Figure 2E. It can be seen from Figure 3B that the return stroke of the piston results in the thigh member being moved forwards. When the foot of the prosthesis is placed on the ground, the next stance phase commences and the piston 8 compresses air once more in the cylinder 9.

The piston and cylinder assembly acts as a stride length limiting device in that the assembly and its mounting are arranged such that the piston stroke normally allows hip flexion to occur only to the extent required for normal weight-bearing activities, but insufficiently for sitting. Sitting is allowed for by arranging for the piston rod to be telescopic. More specifically, the piston rod has coaxial inner and outer portions 7A and 7B, the inner portion 7 A being retracted within the outer portion 7B during normal use. A detent arrangement prevents withdrawal of the inner piston rod member 7A unless a pulling force beyond a certain magnitude is exerted via pivot 6. Thus, when the amputee wishes to sit down, the locking function of the detent is overcome by leaning forward with the prosthesis on the ground, thereby applying a sufficient flexion moment to release the detent and allow further flexion. The detent mechanism will now be described with reference to Figures 4A, 4B and 4C.

The inner piston rod member 7A is, itself, formed as two coaxial parts, these being a central shaft 7AC, having an inner flange 7AF and an annularly grooved head 7AH, and a bearing sleeve 7 AS. The flange and the head are at a distal end of the central shaft 7AC. Fixed on the shaft at its proximal end is a pivot housing 7AP for housing the pivot 6 connecting the piston and cylinder assembly to the hip alignment device 1 (Figure 1). The central shaft 7AC is slidable within the bearing sleeve 7AS. This sleeve 7AS surrounds the central shaft 7AC and, itself, bears on an inner annular abutment 7AA which is a sliding fit on the central shaft 7 AC. An annular space formed between the central shaft 7AC and the bearing sleeve 7AS accommodates a compression spring 7AB acting between the flange 7AF on the shaft 7AC and the abutment 7AA on the bearing sleeve 7AS to bias the shaft against axial pulling forces applied via pivot 6.

The piston rod bearing sleeve 7AS has apertures housing a plurality of ball bearings 7AD which, during normal use of the prosthesis, are in registry with a relatively large diameter portion of the central shaft head 7 AH, as shown in Figure 4 A, and are received in a semi circular cross-section annular groove 7BG in the piston rod outer member 7B. Accordingly, during normal use the piston rod inner member 7A is locked in a retracted position within the piston rod outer member 7B so that, when the piston and cylinder assembly is under compression or light tension, the hip flexion angle is limited by the stroke of the piston 8. This is the locked condition illustrated in Figure 4 A.

When the piston 8 reaches the limit of its travel within the cylinder 9 and a tension is applied via pivot 6 beyond a predetermined level determined by the stiffness of the spring 7AB, the central shaft 7 AC is withdrawn by a small extent from the bearing sleeve 7AS to bring the annular groove 7AG into registry with the ball-bearings 7AJD whereupon these are free to drop out of the part circular groove 7BG in the piston rod outer member 7B as shown in Figure 4B. The piston rod inner member 7A is, as a result, no longer locked within the piston rod outer member 7B and continued pulling via pivot 6 causes the piston rod inner member 7A to be withdrawn from the outer member 7B, as shown in Figure 4C, allowing further flexion of the hip joint.

Upon compression of the piston and cylinder assembly (for instance, when the amputee stands up from the sitting position), the piston rod inner member 7A moves back within the piston rod outer member 7B. When it reaches the point where the ball bearings 7AD can re-engage in the part circular cross-section groove 7BG in the piston rod outer member, the spring force acting on the flange 7AF of the central shaft 7 AC causes the latter to slide inwardly relative to the bearing sleeve 7AS, once more pushing the ball bearings into the groove 7BG and locking the central shaft 7AC within the sleeve 7 S.

It is in the above described manner that the thigh portion 5 of the prosthesis can swing sufficiently relative to the alignment portion, and the pelvic attachment of the prosthesis as a whole, to and from the position shown in Figure 3C.

For reasons of prosthesis stability, certain dimensional aspects are considered when locating the adaptive control system within the prosthesis. The hip joint formed at the proximal end of the prosthesis is suitably aligned with both the knee joint and the ankle joint such that the resulting load line provides for a stable walking operation. In particular, to aid knee joint stability between heel strike and late stance, just prior to rollover there should be a minimal moment about the hip joint in the anterior-posterior plane. Furthermore, in order that the limb remains stable in the stance phase, the bending moment about the knee joint in the medial-lateral plane is also preferably minimised. These biomechanical features minimise gait deviation and hip 'hiking-up'. To satisfy the conflicting aims of ergonomic acceptability of the upper portion of the prosthesis, dimensioning to allow sufficient energy to be transferred to the energy storing mechanism, and allowing a full range of suitable hip movements, it is desirable that at least the mechanical components of the control system, i.e. the hip alignment portion 1 , the thigh member 5 and the piston-and-cylinder assembly, be located within an envelope 19 having the dimensions shown in Figures 5A and 5B. Figure 5A is a lateral view of the proximal portion of the prosthesis attached to the amputee 20 on the anterior side. In this view, dimension d, the generally anterior projection of the upper end portion of the envelope from the socket, is preferably 50 mm and dimension c, i.e. the anterior-posterior depth of the envelope, is preferably 70 mm. Referring to Figure 5B, which is an anterior view, dimension a is preferably 200 mm. This represents the preferred maximum proximal-distal extent of the mechanism. Dimension b, the preferred maximum medial-laterial extent, is 75mm. In order that the energy storing mechanism fits within this envelope, conventional components are used which are of the appropriate size. In particular the cylinder of the piston-and-cylinder arrangement is chosen to have a diameter of 50 mm. This enables the assembly to fit comfortably within the envelope described above, whilst ensuring that sufficient energy is stored in the cylinder to be able to initiate the swing phase. In the preferred embodiment, electronic circuitry of the control system is also be located within this envelope.

In order to provide an optimum amount of energy return from the piston-and cylinder assembly for different walking speeds, the limb comprises an adaptive control system. The system operates by enabling the wearer of the limb to initiate a so-called 'teach mode' in which the prosthetist operates a remote control unit to adjust the prosthesis until an appropriate setting of the control device is achieved for a particular walking speed. Thus the wearer is able to adjust the prosthesis to provide a required rate of energy return in order to match the wearer's walking speed. As will be described in detail below, this is performed for a number of different walking speed settings. When all the required data is set by the control system, the operator may initiate a 'playback' mode in which the wearer is able to operate the limb as normal, with the control system controlling the energy storing mechanism so that it is automatically adjusted according to the detected speed of limb operation.

The control device, i.e. the stepper motor, is driven by the combination of a microcomputer and receiver which together form assembly 22 (see Figure 1). The microcomputer determines thigh flexion and extension movements by means of a magnetic proximity sensor comprising a first part, preferably a transducer 24A, mounted in or associated with the cylinder 9 and a second part, preferably a permanent magnet 24B, mounted on or associated with the piston 8. The electronic circuitry 22 and the stepper motor 11 are powered by batteries (not shown). The receiver has a receiving antenna formed as a conductor track on the printed circuit board bearing components of the microcomputer and receiver.

The electronic circuitry 22 is shown in more detail in Figure 6. More particularly, the circuitry comprises the receiver 30 coupled to an antenna 28 and a processor circuit 32 which receives demodulated signals via input 34 and controls the receiver via output 36. A non-volatile memory in the form of an EEPROM 38 stores walking speed and valve setting data 38 produced by the processor circuit 32, and writes such data to the processor circuit 32 when required.

The processor circuit 32 includes an output driver for driving the stepper motor 20 which in turn moves the needle valve 12, and it has an input for receiving pulses from the sensor 24 comprising transducer 24 A and magnet 24B (see Figure 1).

The receiver 30 preferably receives radio frequency (RF) signals via the receiving antenna 28 from an operator control unit 40 shown in block diagram form in Figure 6 and in plan view in Figure 7. The control unit 40 has a control code generator 42 responsive to operation of keys 44 on the face of the control unit 40. The control codes generated by the generator 42 are applied as modulation to an RF output signal transmitted by an RF transmitter 46 via a transmitting antenna 48 within the control unit 40 for transmission to the receiving antenna 28 on the limb. A battery 49 housed within the control unit 40 powers both the control code generator 42 and the transmitter 46.

Referring to Figure 7, the keys of the remote control unit 40 are divided into four groups. The first group comprises START and EXIT keys which are used by the operator to start and exit a teach mode of the control system for programming optimum valve settings for different walking speeds. The receiver 30 on the limb has a beeper (not shown) which sounds whenever one of the keys 44 is pressed and a corresponding signal is received, allowing the prosthetist to check the receiver is on and within range. A second group of keys is for designating particular walking speeds. These SELECT SPEED keys comprise a SLOW key, a FAST key, and a NORM (normal) key. Thus, when the operator wants to carry out a walking test at a normal speed, he presses the NORM key and the system then performs a teach sequence for that particular speed. The SLOW and FAST keys are used similarly for designating walking tests as slow and fast tests respectively.

During the walking tests, the prosthetist adjusts the amount of air to be compressed and so the amount of energy stored and so returned by the piston and cylinder assembly using a group of ADJUST VALVE keys comprising an OPEN key and a CLOSE key for respectively decreasing the returned energy and increasing the returned energy. A SAVE key and a CANCEL key are used for saving optimum settings. In this manner the prosthetist can improve and, indeed, optimise the functioning of the control device at different limb operation speeds. In effect, the system is calibrated so as to be able to adjust the energy storing mechanism automatically in the playback phase to suit the individual wearer.

The receiver 30 or processor circuit 32 may include means (not shown in the drawings) for giving a visual or audible signal when the receiver is switched on andor when particular keys are pressed on the operator control unit.

Operation of the system will now be described with reference to Figures 8 to 1 1. Referring firstly to Figure 8, which shows start-up and shut-down phases of a program run by the microcomputer to cause the system to run in a teach mode, activation of the receiver 30, which remains off during a playback mode of the system to save battery power, is performed by extending the prosthesis at the hip in a particular manner. Specifically, the patient extends the limb fully, counts 10 seconds, then flexes the hip within 10 seconds, and extends it again. This produces a particular sequence of signals from the sensor shown as 24A, 24B in Figure 1 which are recognised by the processor circuit 32 as an activation code, and the receiver 30 is switched on via line 36. Having activated the receiver 30, the software causes the processor circuit 32 to monitor the receiver output (step 52) for a signal from the operator control unit. In the absence of any signal for longer than a predetermined period (e.g. 30 seconds), the processor circuit 32 causes the receiver to be switched off again (steps 54 and 56). Absence of the signal from the operator control unit also causes the processor to operate the playback routine (step 58), which will be described below.

As soon as the signal from the operator control unit is detected, the processor circuit undergoes a valve homing procedure (step 60). This is a procedure to allow the stepper motor and needle valve of the hip control device to be set with respect to a predetermined reference position. In fact, the stepper motor 20 (Figure 1 ) is fed with 40 valve closing step signals to move the needle valve 12 to the fully closed position. This is designated the zero reference position by the processor circuitry. A default value of a valve setting for the inactive state or slowest walking speed, or a previously saved valve setting for the inactive state or the slowest walking speed stored in the EEPROM store 38 is then read into the processor circuit 32 which has a register set up for the setting. This causes the stepper motor to move from the zero reference position to the appropriate valve setting. The valve homing procedure of step 60 is now complete. It has the result that the valve is set initially to a datum setting.

The processor circuit 32 now waits for the program START signal from the operator control unit (step 62). If this is received, the microprocessor circuit operates a teach routine (step 64) which will be described below. If not, the receiver is switched off. The end of the teach routine 64 also switches off of the receiver (step 56).

When the processor circuit 32 is operating in the teach mode, the processor circuit 32 continuously monitors movements of the limb in order to determine whether the limb is inactive, or, if the patient is walking or running, the speed of such walking or running. Thus, referring to Figure 9, the flexion sensor is monitored in a monitoring step 70 insofar as pulses from the sensor are received in the microprocessor circuit 32. The spacing between the pulses is measured by a counter loop; (only two successive pulses are required to establish a measurement). These pulse intervals are processed to determine whether the movement of the limb is characteristic of the activation sequence described above. If so, the start-up routine 74 is activated (as described above with reference to Figure 8). In all other cases, a running average of the step period is calculated (step 76). If the step period represented by the running average is greater than two seconds, a speed register set up by the processor circuit is reset (step 78) and the next step period is counted. If no movement is detected for a predetermined period such as four seconds, the stepper motor is caused by the program to drive the valve to a value stored in the EEPROM store for standing or sitting.

Averaging (step 76) may be performed by creating a predetermined number, e.g. six, of calculation registers and successively feeding them a corresponding number (six) of step period counts, each register commencing with a different step. Thus, a first calculation register receives the counts for, say, steps 1, 2, 3, 4, 5, and 6. The second calculation register stores the counts for steps 2, 3, 4, 5, 6, and 7, the third register receives the counts for steps 3, 4, 5, 6, 7, and 8, and so on, the contents of each register being added and divided to produce a respective average value so as to yield a running average by reading the successive calculated averages one after the other at the same rate as the registers are being filled. In practice, the average is calculated by counting how many steps are taken between resets of the registers, ignoring the first and second step periods, adding together the next four and dividing by four. Other methods of calculating a running average can be used. The running average is stored in a walking speed register which is being continuously updated with the new average values. In the teach mode, updating continues only so long as the values are representative of the patient walking.

It will be appreciated that, having determined the walking speed in the above described manner, and given stored data in the form of a look-up table of valve settings associated with particular walking speeds, it is possible during use of the prosthesis to set the valve dynamically according to walking speed. The manner in which this stored data, is produced will now be described with reference to Figure 8, which shows the teach routine performed by the processor circuit 32 which, it will be recalled, appears in the start- up and shut-down flow chart of Figure 6 as step 64. The teach routine involves determination of settings for the basic operations of a prosthesis using the operator control unit to designate certain walking speeds as "slow", "normal", or "fast", the patient being led through a series of walking tests at the different speeds while the opening of the needle valve of the energy storing mechanism is adjusted by remote control using the operator control unit until a satisfactory swing phase is obtained in each case. The optimum valve settings so obtained are stored by "saving" corresponding signals, and performing calculations to derive intermediate values so that data is stored in "final" registers set up by the processor circuit 32 representing five speed ranges and five corresponding valve settings. When the receiver is switched off (step 56, Figure 8) this data is read into the EEPROM (38 in Figure 4).

Now referring to Figure 10, the teach mode begins with checking for receipt of a CANCEL signal from the operator control unit (step 90), receipt of such a signal causes the final registers to be cleared and refilled from the EEPROM store (step 92). Next, the program seeks a speed selection signal from the operator control unit. If this is received, a speed selection pointer is set either to slow, normal, or fast according to the signal received. In the absence of such a signal, the pointer defaults to normal (steps 94 and 96).

Accordingly, the processor circuit 32 now knows the selected speed to which the next part of the procedure relates. In step 98, the circuit looks for depression of either the OPEN (decrease energy return) or CLOSE (increase energy return) keys. Receipt of the signal corresponding to either causes the processor circuit to check the default settings of the standing and sitting register (referred to above in connection with the valve homing procedure) to determine the difference between the current valve position and the default setting so that the change in valve position resulting from one push of the OPEN key or the CLOSE key is appropriately adjusted to the produce the same subjective effect substantially regardless of valve opening. Accordingly, if the current valve position is between, say, zero and 15 steps from the default position, a multiplier is set to cause the stepper motor to move at one step per key push. If, on the other hand, the current valve position is between 16 and 20 steps from the default position, the stepper motor is caused to move at two steps per key push, and so on with increasing steps for increasing difference from the default value. In effect, the multiplier is set to produce a logarithmic relationship between the valve movement and the valve opening with respect to the default position. These steps are representative in Figure 8 by steps 98 and 100. A "selected position" register set up by the processor circuit 32 now receives the new valve setting, and the stepper motor is driven to cause the valve to move appropriately (steps 102 and 104). At this point the current value of the running average of the step period is read into a selected speed register representing the chosen designated speed (slow, normal, or fast) (step 106).

Next, the program checks for receipt of the SAVE signal from the operator control unit (step 108), and in the absence of such a signal returns to the beginning of the loop represented by steps 90 to 108. Initially, the teach routine allows the operator to try a succession of different valve openings until the optimum setting is reached. At this point, the prosthetist presses the SAVE key to cause the program to proceed to step 1 10 in which the contents of the selected speed register, i.e. signals representing the last received running average step period and the last set valve position, are written to calculation registers. Of course, this step period and valve setting corresponds to just one of the selected speeds slow, normal, or fast. The calculation registers will already contain corresponding settings for the other two selected speeds, obtained either from previous walking tests or as default values.

Next, the processor circuit performs in step 112, calculation of boundary values for five speed ranges and five valve settings. This means that, in this preferred embodiment, the step periods measured for slow, normal, and fast walking tests are considered to represent the centre values of first, third, and fifth step period ranges, while step period values halfway between the slow and normal periods and normal and fast periods respectively are considered to represent the centre values of second and fourth step period ranges. The boundary values are calculated accordingly.

The three valve settings obtained from the calculation registers are considered to represent the optimum valve settings for walking speeds corresponding to step periods within the first, third, and fifth ranges respectively, while settings midway between the valve settings stored in the calculation register are considered as the optimum settings for speeds corresponding to step periods within the second and fourth step period ranges. Again, these intermediate valve settings are calculated in the calculation step 112. At the same time inactive and fail safe settings of the valve are generated which correspond to the setting for the slowest speed range for inactive standing, stationary and medium value setting for fail safe condition. This calculated step period range and valve setting data (five values for each plus inactive and emergency (low battery voltage) valve settings) are written to the final register each time a calculation is performed, i.e. after each SAVE command.

At this point, the prosthetist may have completed the walking tests, in which case he presses the program EXIT key which is sensed by the processor circuit in its checking step 116, causing the contents of the final register to be read to the EEPROM store (step 118) so that the program continues with the shut-down routine represented by steps 56 and 66 of Figure 4 (step 120). If the prosthetist has not finished, no EXIT signal is received, and the teach routine is repeated from step 90 through to step 1 16 again.

It will be appreciated that the EEPROM now contains stored data representing five valve settings for five consecutive speed ranges which represent the optimum settings for the individual patient and which can be used during normal use of the prosthesis. It will be appreciated that a different number of speed ranges and corresponding valve settings can be used, the step period and the valve setting values being calculated appropriately. Indeed, discrete ranges may be dispensed with and the results of the walking tests may be used to define a continuous relationship between walking speed and valve opening, i.e. so that the valve opening can be altered in a stepless manner.

It is possible to incorporate a checking step in the teach routine whereby when the EXIT key is pressed, the program reads the relative magnitudes of the measured "slow", "normal" and "fast" step periods to check that the step periods are in the correct order of magnitude and, if necessary, reallocates the "slow", "normal" and "fast" designations for the step period and corresponding valve setting values to put the step periods into the correct order. Incorrect ordering can happen when, for example, the walking tests are carried out at spaced apart times, and when the patient is tested alternately tired and not tired. If the valve settings are in an incorrect order of magnitude, the software is arranged such that one or both of the slow and fast settings is altered to be the same as the normal setting to avoid inconvenience for the patient until the tests are repeated.

The playback routine will now be described with reference to Figure 1 1. Referring to Figure 11, the processor circuit first monitors the sensor in step 130 and measures and processes the output in step 132 so that, after checking whether the receiver is activated in step 134 (see the description above for the activation procedure), the speed register can be updated with what can be referred to as the instantaneous value of the step period providing the receiver is off (step 136). In other words, rather than writing a calculated average step period value to the speed register as in the teach mode, the playback routine causes each measured step period to be written directly to the speed register so that changes in the patient's pattern of movement can be picked up immediately.

If the receiver is activated, however, checks are performed to determine whether to enter the teach mode. Accordingly the receiver output is monitored (step 138) for the presence of a signal from the operator control unit. If a start signal is detected (step 140), the valve homing procedure described above with reference to Fig. 8 (step 146) is carried out. In the absence of such a receiver output signal, the speed register is updated with the so-called instantaneous step period value and then, while the playback routine is operating, the receiver output is monitored over a period of time, here four minutes, for the presence of an operator control unit signal, as shown in Fig. 11 as step 142. If a receiver output signal is detected during this period, again, the valve homing procedure is carried out. If not, the receiver is switched off (step 144) and the playback routine continues.

When a start signal is detected, whether immediately or during the four minute period, and the valve homing procedure 146 has been carried out, the receiver causes entry 148 into the teach routine described above with reference to Fig. 10. If no program start signal is detected, the receiver is switched off and the playback routine is continued.

The next step in the playback routine, after updating of the speed register, is reading the speed register for the latest step period (step 150), followed by the comparison of the step period with zero (step 152). It should be understood that the contents of the speed register are zero so long as no movement of the thigh member 5 is detected by the sensor 24A, 24B (Fig. 1) within a predetermined time interval. Thus, if the speed register output is zero for greater than four seconds, the prosthesis is considered to be inactive, in which case the inactive valve setting stored in the EEPROM store is read to a current valve register and the stepper motor is driven to the corresponding valve setting (steps 154, 156). The program then links back to step 132. If, however, movement is detected, and the speed register output is greater than zero for at least four seconds, the step period is compared with the boundary values of the step period ranges stored in the EEPROM (step 158) to determine whether the indicated range is different from the range already set in a select register (step 160). If no difference is detected, the program links back to the beginning of the playback routine. If a difference is detected, the select register is up-dated (step 162), the corresponding valve setting for the new range is read from the EEPROM store and written to the current valve register (step 164) and the motor is driven to the setting corresponding to the value in the current valve register (step 156). The program then returns back to the beginning of the playback routine.

The system has the advantage that since the operator control unit communicates via a wireless link the operator can monitor the patient's performance from the most suitable position, and does not necessarily need to walk with the patient whenever a command signal is to be generated. Full automation of determination of walking speed and continuous measuring and updating of the walking speed by the processor circuit removes much of the effort involved in determining walking speed. The consequent significant simplification also reduces the extent of specialised training required of the prosthetist, and reduces the time necessary to reach optimum valve settings. As a result, it is possible in many cases for the patient to carry out the teaching procedure without intervention by the prosthetist, the patient benefiting by direct feedback without the need for interpretation by the prosthetist. In addition, the much reduced adjustment period significantly reduces the possibility of patient fatigue influencing the results.

In summary, significant features of the above-described adaptive prosthesis control system include a controllable energy storing device for mounting in a lower-limb prosthesis with a hip joint, for initiating and/or assisting the swing phase of the walking cycle, a step sensor 24 for generating a walking step signal indicative of the step period during walking, an electronic processing circuit associated with and electrically coupled to the energy storing device and the step sensor, a receiver electrically coupled to the processing circuit for receiving electromagnetically or acoustically radiated command signals, and an operator unit arranged to generate and radiate the command signals. The command signals include adjustment signals for adjusting the energy storing device which are transmitted by the operator unit under the control of an operator. The processing circuit includes storage means, speed indicating means operable automatically both in a teach mode and a playback mode to convert the walking step signal periodically into a step period value, and control device setting means responsive during the teach mode to the adjustment signals picked up by the receiver to cause alteration of a parameter of the energy storing device and to generate signals indicative of a value of the parameter. The processing means further comprises saving means responsive to a further command signal received via the receiver from the operator unit to feed automatically to the storage means signals representative of the step period value and the parameter value associated with a selected instant in time for each of a plurality of different walking speeds in order to produce a set of stored data representing required parameter settings for the different speeds. The processing means also include playback means operable in the playback mode to cause the energy storing device parameter to be adjusted at required times in accordance with the step period values derived from walking step signals sensed at those times by the step sensor and in accordance with the corresponding parameter settings of the stored data.

The system allows continuous processing and averaging of the walking speed or step period. In the teach mode the operator is able to alter the energy storing parameter, i.e. the pressure of air within the cylinder so as to change the amount of energy stored and returned by remote control, and to react in real time to each alteration by making further alterations. When a suitable setting for a particular speed of limb operation is achieved, the processing means can be remotely commanded to "save" that setting and automatically to calculate a new set of control data based on the new setting and previous settings for other walking speeds. The processing means is thus able to perform on-line calculation of control data for use in the playback mode. The processing means on the limb is automatically able to gather and process data. All operator commands are carried out by remote control in the preferred system.

Claims

1. A lower limb prosthesis comprising a pelvic attachment, thigh and shin components interconnected by a knee joint, and, interconnecting the pelvic attachment and the thigh component, a hip joint including an adaptive hip flexion drive mechanism arranged to apply a dynamically variable flexion moment to the hip joint.

2. A prosthesis according to claim 1, wherein the drive mechanism comprises an adaptive resilient energy storage device arranged to store energy during hip extension and to return the stored energy during a subsequent flexion movement.

3. A prosthesis according to claim 2, wherein the energy storage device comprises a telescopic strut.

4. A prosthesis according to claim 3, wherein the thigh component comprises an elongate thigh member having a proximal end and a distal end , the proximal end being pivotally mounted on the pelvic attachment to define a hip axis of rotation, and wherein the telescopic strut is pivotally connected to the pelvic attachment to define a second axis which is substantially parallel to and located posteriosly of the hip axis, the telescopic strut being pivotally connected also to the thigh member at a location spaced distally from the hip axis, whereby expansion of the telescopic strut causes flexion of the hip joint about the hip axis.

5. A prosthesis according to claim 3 or claim 4, wherein the strut comprises a piston and cylinder assembly.

6. A prosthesis according to claim 5. wherein the piston and cylinder assembly acts as a pneumatic spring.

7. A prosthesis according to claim 5 or claim 6, wherein the piston and cylinder assembly includes a variable aperture valve controlling the flow of fluid to and/or from a chamber of the piston and cylinder assembly.

8. A prosthesis according to any of claims 1 to 7, including a sensing device for sensing a variable relating to the motion of the prosthesis and an adjustment unit arranged to adjust the drive mechanism in response to the sensed variable in order to vary the applied hip flexion moment.

9. A prosthesis according to claim 8 and claim 2, wherein the adjustment unit is operable to vary the amount of the said stored energy.

10. A prosthesis according to claim 8 and claim 7, wherein the adjustment unit comprises an electronic control circuit coupled to the sensing means, and an electrical actuator connected to the variable aperture valve for varying the valve aperture.

11. A lower limb prosthesis for a hip disarticulation amputee, the prosthesis having an adaptive control system which comprises: a mechanism located in a proximal region of the prosthesis and arranged to store energy generated during part of a stance phase, and to return at least part of the stored energy at rollover to initiate a swing phase, the mechamsm including a control device for controlling the amount of energy stored by the mechanism; a sensor for generating electrical sensor signals in response to movement of the prosthesis; and processing means electrically coupled to the sensor and the control device, the processing means being arranged to generate setting signals for the control device, the setting signals being generated in accordance with a set of control data generated during a teach mode and measurement data values representative of the speed of operation of the prosthesis which are calculated in response to the sensor signals, the control data representing a relationship betweeen speed of prosthesis operation and parameter values representing selected settings of the control device, whereby during operation of the prosthesis the energy storing mechanism is automatically adjusted according to the detected speed of limb operation.

12. A prosthesis according to claim 11, wherein the prosthesis comprises a hip alignment portion located at a proximal end of the prosthesis, and a thigh portion attached to the alignment portion to form a hip joint, the energy storing mechanism being coupled to the alignment portion and the thigh portion to affect the relative movement therebetween.

13. A prosthesis according to claim 1 or claim 2, wherein the energy storing mechanism is a piston-and-cylinder assembly which, for part of the stance phase, compresses a gas, and wherein, at the rollover phase, part of the compressed gas produces a return stroke of the piston to initiate the swing phase.

14. A prosthesis according to claim 13, wherein the piston-and-cylinder assembly has a valve, and the control device is an electric motor which is coupled to the valve.

15. A prosthesis according to claim 3 or claim 4, wherein a piston rod of the piston-and-cylinder assembly is pivotally attached to the hip alignment portion and the cylinder is pivotally attached to the thigh portion at a position distal to the hip joint.

16. A lower limb prosthesis according to any of claims 1 1 to 15, wherein the processing means comprises: data generating means operable in a teach mode and a playback mode of the processing means automatically and repeatedly to generate the measurement data values in response to the sensor signals; control device setting means operable in both modes to feed the setting signals to the control device for adjusting a parameter of the control device to control the amount of energy stored, the setting means further being operable in the teach mode to feed the setting signals to the control device according to the parameter values generated in the processing means in response to command signals input to the processing means; means for processing the parameter values together with the associated said measurement data values to generate the control data; and storage means for storing the set of control data, the setting means being further operable during the playback mode as the limb is operated to process the resulting measurement data values in conjunction with the stored set of control data to generate the said setting signals for the control device.

17. A prosthesis according to claim 6, comprising a receiver coupled to the processing means for receiving command signals from a remote operator control unit.

18. A prosthesis according to any of claims 11 to 17, wherein the sensor is arranged to produce pulsed sensor signals, one pulse being generated for each step taken.

19. A prosthesis according to any of claims 1 1 to 18, wherein the data generating means is operable continuously during the teach mode to generate measurement data values which are running averages of step periods as the limb is operated.

20. A prosthesis according to any of claims 17 to 19, wherein the processing circuit further includes saving means responsive to a further command signal received via the receiver from the remote control unit to feed automatically to the storage means signals representative of the measurement data value and the parameter value associated with a selected instant of time for each of a plurality of different limb operation speeds.

21. A prosthesis according to claim 20, wherein the said means for processing are operable in response to each operation of the saving means to calculate automatically a series of measurement data boundary values based on measurement data values selected during the teach mode to define a plurality of measurement data value ranges.

22. A prosthesis according to claim 21, wherein the said means for processing are operable automatically to calculate interpolated parameter values to provide a set of parameter values to correspond to the measurement data value ranges.

23. A prosthesis according to any of claims 17 to 22, wherein the remote control unit has control means for increasing and decreasing the control device parameter.

24. A prosthesis according to any of claims 1 1 to 23, wherein the control system further comprises a mechanism for limiting the duration of the swing phase so as to limit the stride length.

25. A prosthesis according to claim 24, wherein the piston rod of the piston-and-cylinder assembly is the swing phase limiting mechanism, and wherein the piston rod comprises a first member attached to the hip alignment member and a second member attached to the piston, the first rod member being located telescopically within the second rod member so as to allow relative longitudinal movement therebetween, an adjustable stop limiting the amount of relative longitudinal movement between the two members during the swing phase.

26. A prosthesis according to claim 24 or claim 25, wherein the swing phase limiting mechanism may be disabled.

27. A prosthesis according to any of claims 16 to 26, wherein the control device parameter is the pressure of the gas compressed within the piston-and-cylinder assembly.

28. A prosthesis according to any of claims 11 to 27, wherein the processing means further comprises checking means for checking that the selected control device settings of the control data are correctly ordered in magnitude with respect to the corresponding stored measurement data values.

29. A prosthesis according to any of claims 11 to 28, wherein the energy storing mechanism is located within an envelope having a medial-lateral width of 75mm, a proximal-distal height of 200mm, and an anterior posterior depth of 70mm.

30. An adaptive control system for a lower limb prosthesis, the control system comprising: an energy storing mechanism located in a proximal region of the prosthesis for storing energy generated during part of the stance phase of the walking cycle and arranged such that part of the stored energy is returned to initiate the swing phase, the mechanism including a control device for controlling the amount of energy stored by the energy storage mechanism; a sensor for generating electrical sensor signals in response to movement of the limb; and processing means electrically coupled to the sensor and the control device, the processing means being arranged to generate setting signals for the control device, the setting signals being generated in accordance with a set of control data generated during a teach mode and measurement data values representative of the speed of operation of the limb which are calculated in response to the sensor signals, the control data representing a relationship betweeen speed of limb operation and parameter values representing selected settings of the control device, whereby during limb operation in a playback mode, the energy storing mechanism is automatically adjusted according to the detected speed of limb operation.

31. A method of controlling an artificial limb for a hip disarticulation amputee, the limb comprising an energy storing mechanism associated with a hip joint for storing energy during part of the stance phase of the walking cycle for return at rollover and a control system for adjusting the amount of energy stored, wherein, during a teach phase of the method, movement of the limb is automatically and repeatedly monitored by electronic means forming part of the control system with a series of measurement data values related to the speed of operation of the limb being generated in the electronic means, a remote control unit is operated in conjunction with a receiver forming part of the limb during operation of the limb to transmit command signals to the limb which are processed by the electronic means to generate setting signals for adjusting the energy storing mechanism with the object of improving limb operation, data generated in the electronic means and representing selected settings of a control device forming part of the energy storing mechanism are processed in the electronic means together with the associated said measurement data values to generate a set of control data representing a relationship between speed of limb operation and control device settings, and the set of control data is then stored in the electronic means, and in which method, during a playback phase, the movement of the limb is automatically and repeatedly monitored by the electronic means in conjunction with the stored set of control data to generate appropriate control device setting signals for automatically adjusting the energy storing mechanism according to the speed of limb operation.

32. A method according to claim 31, wherein the selected settings of the control device correspond to different values of energy being stored by the energy storing mechanism.

33. A method according to claim 32, wherein the control device is a piston-and cylinder assembly and wherein operation of the control device comprises driving an electric motor to alter the degree of opening of a valve in the assembly.

34. A method according to claim 33, wherein the speed of operation of the limb is monitored using a sensor which produces a pulsed signal when the limb is operated, the processor circuit measuring the pulse repetition rate.

35. A method according to any of claims 31 to 34, wherein the measurement data values are continuously generated by the electronic means as a series of running averages of the step period during both the teach phase and the playback phase as the limb is operated.

36. A method according to any of claims 31 to 35, including generating in the remote control unit a further command signal, and, in the electronic means, causing, in response to the further command signal, selection and storage of the measurement data value and the control device setting associated with the instant in time the further command signal is transmitted, whereby control device settings and measurement data values can be selected and saved for a plurality of different respective speeds of operation.

37. A method according to claim 36, wherein the processing of the selected control device settings and measurement data values to generate the control data is performed in response to the said saving.

38. A method according to claim 36, wherein the processing of the selected control device settings and measurement data values comprises calculation of a series of measurement data boundary values based on the selected measurement data values to define a plurality of different consecutive measurement data value ranges, and wherein the processing of the control device settings comprises calculating interpolated settings to provide a set of control device setting values to correspond to the measurement data value ranges.

39. A method according to any of claims 34 to 38, wherein the command signals include control device incrementing signals for increasing or decreasing a parameter of the control device in steps.