Abstract
The invention relates to a method for controlling an orthopaedic joint device of a lower extremity. The joint device has an upper part (2) and a lower part (3) mounted in a hinged manner on the latter. Arranged between the upper part (2) and the lower part (3) is an energy converter (5) by which, during walking, kinetic energy from the relative movement between the lower part (3) and the upper part (2) is converted or stored and supplied again to the joint in order to support the relative movement, wherein kinetic energy within one movement cycle is converted and/or stored and, within the same movement cycle, is supplied again as kinetic energy to the joint device (1) in a controlled manner and staggered in time.
Claims
1-32. (canceled)
33. A method for controlling an orthopedic joint device of a lower extremity, the orthopedic joint device having an upper part and a lower part mounted in an articulated manner thereon, the method comprising: providing an energy conversion device arranged between the upper part and the lower part, the energy conversion device comprising a hydraulic cylinder with a piston arranged on a piston rod, and a spring arranged within one of the first and second chambers, the piston separating the hydraulic cylinder into a first chamber and a second chamber, a volume of the first chamber being reduced during a flexion movement of the lower part relative to the upper part and increased during an extension movement of the lower part relative to the upper part, the spring being loaded during the flexion movement and relaxed during the extension movement; converting and storing kinetic energy from relative movement between the lower part and the upper part with the energy conversion device; and feeding back the kinetic energy to the orthopedic joint device with the energy conversion device during a stance phase to assist with the extension movement; wherein within a movement cycle, kinetic energy is converted and stored and, within the same movement cycle, is fed back to the orthopedic joint device in a controlled manner after a time delay such that the energy feedback does not occur immediately after converting and storing of the kinetic energy.
34. The method as claimed in claim 33, further comprising feeding back the kinetic energy during at least one of initiation of a swinging phase to assist the flexion movement of the orthopedic joint device, after reaching a maximum flexion angle to assist the extension movement, and after the flexion movement following an initial heel contact to assist the extension movement.
35. The method as claimed in claim 33, wherein the kinetic energy is at least one of converted and stored during a flexion movement, the method further comprising feeding back the kinetic energy to initiate the swinging phase to at least one of assist the flexion movement and to maintain a bending velocity after a toe lift off.
36. The method as claimed in claim 33, wherein the kinetic energy is at least one of converted and stored after initiation of a swinging phase, the method further comprising feeding back the kinetic energy to assist a flexion movement of the orthopedic joint device after reaching a maximum flexion velocity.
37. The method as claimed in claim 33, wherein the kinetic energy is at least one of converted and stored before reaching an extension stop limit, the method further comprising feeding back the kinetic energy to at least one of initiate and assist a flexion movement of the orthopedic joint device.
38. The method as claimed in claim 1, further comprising feeding back the kinetic energy during a swinging phase of the joint device to increase or maintain the extension movement.
39. The method as claimed in claim 33, wherein the kinetic energy is stored during at least one of a standing phase at a beginning of a standing phase flexion with heel loading, before reaching an extension stop limit, and after initiating the standing phase flexion with forefoot loading.
40. The method as claimed in claim 33, wherein the kinetic energy is converted and stored with an initial heel impact, the method further comprising feeding back the kinetic energy as part of at least one of initiating and assisting a flexion movement of the orthopedic joint device.
41. The method as claimed in claim 33, wherein less of the kinetic energy is supplied to the orthopedic joint device with increasing walking speed.
42. The method as claimed in claim 33, wherein the converted kinetic energy is completely fed back to the orthopedic joint device in the movement cycle.
43. The method as claimed in claim 1, wherein at least one of the converting and storing of the kinetic energy is carried out only in predetermined phases during the movement cycle.
44. The method as claimed in claim 33, wherein a supply of stored kinetic energy is converted and fed back to assist the relative movement in the controlled manner.
45. The method as claimed in claim 33, wherein a supply of stored kinetic energy is changed by energy from the spring.
46. The method as claimed in claim 33, wherein the energy is stored in an energy store, the energy store being assigned an actuator, the actuator to fill the energy store to a minimum level if the relative movement is not sufficient.
47. The method as claimed in claim 46, wherein the energy store is assigned a releasing device, the releasing device to release the kinetic energy from the energy store.
48. The method as claimed in claim 1, wherein the kinetic energy fed back is dependent upon at least one of the following criteria: an angular position of the upper part in relation to the lower part; a position of at least one of the upper part and the lower part in space; an angular velocity of at least one of the upper part and the lower part; a relative velocity between the upper part and the lower part; a loading situation; and an acceleration of at least one of the upper part and the lower part.
49. The method as claimed in claim 48, wherein the kinetic energy is stored with the spring and is fed back from the spring dependent upon at least one of the criterion recited in claim 48.
50. The method as claimed in claim 33, further comprising adjusting a point in time of an intervention of the energy conversion device to change at least one of an amount of kinetic energy to be converted and an amount of kinetic energy supplied.
51. The method as claimed in claim 46, further comprising charging the energy store by an actuator if the energy conversion device is not active on account of the relative movement between the upper part and the lower part.
52. The method as claimed claim 1, wherein the relative movement is influenced by a damper device.
53. The method as claimed in claim 33, wherein feeding back the kinetic energy to the orthopedic joint device with the energy conversion device occurs only during the stance phase.
54. The method as claimed in claim 33, wherein feeding back the kinetic energy also occurs after extension during the stance phase to assist with flexion movement of the lower part relative to the upper part.
55. A method of controlling an orthopedic joint device of a lower extremity, the orthopedic joint device having an upper part and a lower part mounted in an articulated manner thereon, the method comprising: providing an energy store and an energy conversion device arranged between the upper part and the lower part; converting kinetic energy from relative movement between the lower part and the upper part with the energy conversion device; storing the converted kinetic energy from the energy conversion device in the energy store as stored energy; and feeding back the stored energy to the orthopedic joint device with the energy conversion device during a stance phase to assist with an extension movement of the lower part relative to the upper part by supplying the stored energy from the energy store to the energy conversion device; wherein within a movement cycle, kinetic energy is converted and stored and, within the same movement cycle, is fed back as the stored energy to the orthopedic joint device in a controlled manner after a time delay such that the energy feedback does not occur immediately after converting and storing of the kinetic energy, and the stored energy available for feeding back to the conversion device is supplemented by the energy store.
56. A method for controlling an orthopedic joint device of a lower extremity, the orthopedic joint device having an upper part and a lower part mounted in an articulated manner thereon, the method comprising: providing an energy conversion device arranged between the upper part and the lower part, the energy conversion device comprising a hydraulic cylinder with a piston arranged on a piston rod, the piston separating the hydraulic cylinder into a first chamber and a second chamber, a volume of the first chamber being reduced during a flexion movement of the lower part relative to the upper part and increased during an extension movement of the lower part relative to the upper part; converting and storing kinetic energy from relative movement between the lower part and the upper part with the energy conversion device; and feeding back the kinetic energy to the orthopedic joint device with the energy conversion device during a stance phase of walking in order to assist with the extension movement; wherein within a gait cycle, kinetic energy is converted and stored and, within the same gait cycle, is fed back to the orthopedic joint device in a controlled manner after a time delay such that the energy feedback does not occur immediately after converting and storing of the kinetic energy, and the energy feedback occurs only during specific phases of the gait cycle.
Description
[0036] Exemplary embodiments of the invention are explained in more detail on the basis of the accompanying figures, in which:
[0037] FIG. 1 shows a knee angle progression during a gait cycle;
[0038] FIG. 2 shows the progression of the knee angle velocity over a gait cycle;
[0039] FIG. 3 shows phases of possible take-ups and releases of energy of the knee joint during the gait cycle;
[0040] FIG. 4 shows a schematic representation of a joint device with an energy storage device for flexion assistance;
[0041] FIG. 5 shows a joint device with a device for extension assistance;
[0042] FIG. 6 shows a joint device with a spring mounted in a cam;
[0043] FIG. 7 shows a joint device with a flywheel mass as an energy store;
[0044] FIG. 8 shows a variant of the joint device with extension control;
[0045] FIG. 9 shows a joint device with two springs;
[0046] FIG. 10 shows a joint device with an elastic cord as an energy store;
[0047] FIG. 11 shows a variant of FIG. 1 with a displaceable spring attachment;
[0048] FIG. 12 shows a variant with a spring arranged in the lower part;
[0049] FIG. 13 shows a variant of FIG. 3 with an interposed actuator;
[0050] FIG. 14 shows a variant with a twisted filament as an energy store;
[0051] FIG. 15 shows a representation of drive moment progressions for different walking speeds:
[0052] FIG. 16 shows a representation of different paths of displacement against a joint angle for various walking speeds;
[0053] FIG. 17 shows a representation of a lever arm progression against a joint angle; and
[0054] FIG. 18 shows a representation of a flexion damping setting of a damper against a knee angle.
[0055] In FIG. 1, a schematic representation of the progression of the knee angle over time is shown. The representation comprises a gait cycle, that is to say beginning from the setting down of the heel up until the renewed setting down of the heel of the same leg.
[0056] After the initial touching down of the heel with a stretched knee joint, that is to say at a knee angle of 180, the knee joint initially bends a little in the standing phase, which is referred to as standing phase flexion. As soon as the foot is set down completely on the ground, the knee joint is stretched, so that a knee angle of 180 is established. In the course of the bending movement toward the end of the standing phase, the knee angle decreases. The perpendicular, dashed line denotes the end of the standing phase, and consequently the point in time at which the tip of the foot leaves the ground. This point in time is known as toe off. In the then-following swinging phase, the lower part swings further toward the rear and pivots in relation to the upper part up to the minimum knee angle of 120. There follows a reversal of movement; the lower leg with the prosthetic foot is brought forward and pivots up to the stretching stop limit, which lies at a knee angle of 180. In this stretched position, the touching down of the heel will generally take place.
[0057] In FIG. 2, a schematic representation of the knee angle is superposed with the knee angle velocity v. The knee angle profile corresponds in this case to that described in FIG. 1. During the initial standing phase flexion, the knee angle velocity v increases briefly. During the stretched phase, that is to say at a knee angle of 180, the knee angle does not change; likewise, the knee angle velocity v remains constant at 0 per second. The bending of the knee joint toward the end of the standing phase leads to a rise in the knee angle velocity v up to a maximum at the toe off. The further swinging-back movement of the lower part takes place with a slowing speed, until at a minimum knee angle a reversal of movement commences and the lower part executes an extension movement. Accordingly, the knee angle velocity extends below the zero line up to the point in time at which extension damping commences, in order not to allow the lower part to swing into the stretching stop limit without deceleration. Accordingly, the knee angle velocity v is reduced until the lower part has reached the stretching stop limit and the knee angle is again 180. The knee angle velocity v is then 0.
[0058] In order to enter the region of great knee bending more quickly, it is possible and necessary in certain portions of the gait cycle to increase the knee angle velocity, for example in order to facilitate swinging through of the leg. The maximum knee bending may in this case remain the same or else be increased, if there is extension assistance, in order that the lower leg is brought forward quickly enough. In FIG. 3, the knee angle over time during a gait cycle is represented once again. In it, regions in which kinetic energy from the relative movement between the lower part and the upper part can be converted or stored are marked; these regions are provided with the reference sign o. Furthermore, regions in which it may be advantageous to supply stored energy once again to the system, in order to assist extension or flexion, are marked by the reference sign i. During the initial standing phase bending, kinetic energy can be taken up, in order to feed it back, for example in the extension phase then immediately following. It is likewise possible to buffer-store the energy taken up in the bending phase or else toward the end of the stretching phase to supply it once again during a further energy take-up phase, so that the lower part is for example flexed or extended more quickly, in order to achieve the effect that is respectively desired. The supplying of the converted or stored energy after a controlled time delay takes place within the same movement cycle during predetermined phases i, it being preferred to use deceleration phases to convert and/or store energy and acceleration phases to feed this energy back after a controlled time delay. The control preferably takes place electronically; in principle, however, mechanical control is also possible.
[0059] Provided as supplying phases i are, in particular, the extension movement after the initial heel contact, the assistance of the bending to initiate the swinging phase, the maintenance of the flexion velocity after the toe off and also the assistance of the flexion movement after reaching the maximum flexion angle.
[0060] In FIG. 4, an example of an orthopedic joint device 1 is shown in a schematic representation. The orthopedic joint device 1 has an upper part 2 and a lower part 3. The lower part 3 is mounted on the upper part 2 pivotably about a pivot axis 4. The flexion takes place in the direction of the arrow; an energy conversion device 5 is arranged on the extension side. The energy conversion device 5 has a hydraulic cylinder 51, in which a piston 52 is arranged on a piston rod 53. The piston 52 is used for separating two chambers 55, 56 hydraulically from one another. In the lower chamber 55 there is arranged a compression spring. The two chambers 55, 56 are coupled to one another by way of a hydraulic line 57. In the hydraulic line 57 there is arranged a controllable valve 58, by way of which the flow rate from the upper chamber 56 into the lower chamber 55 can be controlled. At the upper end of the piston rod 53 there is arranged a sawtooth-like beveled form-fitting element 531, which is in engagement with a pivotably mounted toothed rack 59, which likewise has toothing in the form of sawteeth formed so as to correspond to that of the form-fitting element 531. During an extension movement of the lower part 3 in relation to the upper part, the piston 52 is pushed in. In order to initiate flexion assistance, the valve 58 is opened to such an extent that the valve 58 allows a faster piston movement than the joint device. For tensioning the spring 54, the piston rod 53 is pushed downward. This takes place during an extension movement of the lower part 53 in relation to the upper part. If the lower part 3 flexes in relation to the upper part 2, the teeth of the toothed rack 53 slide along on the bevel of the form-fitting element 531 on account of their orientation; during the extension of the lower part 3, the spring 54 is compressed, since sliding of the toothed rack 59 is not possible due to the substantially horizontal areas of contact. For flexion assistance, for example in the initiation of the swinging phase, that is to say with a relatively greatly bent lower part 3, the form-fitting element 531 is in engagement relatively far down on the toothed rack 59 and assists the movement of the lower part 3 in the direction of the arrow. For flexion assistance, the valve 58 is mechanically or electrically controlled in dependence on an ascertained joint angle position or mechanically or electrically controlled in dependence on a joint angle velocity. If the valve 58 is opened, the spring 54 can relax, since the hydraulic fluid can flow out of the upper piston chamber 56 through the hydraulic line 57 into the lower chamber 55.
[0061] In FIG. 5 there is shown a joint device in which the direction of action is reversed in comparison with the embodiment according to FIG. 4. The spring 54 is arranged around the piston rod 53; the form-fitting element 531 and similarly the arrangement of the teeth in the toothed rack 59 are oriented in the opposite direction, so that there is extension assistance. The piston 52 is drawn out when there is flexion, and has an assisting effect for the extension when the valve 58 allows a piston movement, which the spring 54 assists. This may take place in particular when there is a reversal of the flexion movement into an extension movement. For controlling the assistance of the extension movement, the toothed rack 59 or ratchet may be mechanically decoupled or the valve 58 may intervene in a damping manner.
[0062] In FIG. 6, a further variant of the invention is represented, one in which a spring 6 is compressed by way of a cam 7 when there is flexion of the joint, in order to release the energy again when there is further bending. Consequently, kinetic energy can be stored during a flexion movement, for example during the heel strike, and be fed back to the joint device 1 for the initiation of the swinging phase for the assistance of the flexion movement and/or for the maintenance of the bending velocity after the toe off. During the extension movement, the spring 6 remains ineffective on account of the guidance in the cam 7.
[0063] A further variant of the joint device 1 is shown in FIG. 7. In this case, a flywheel mass 8, which is accelerated when there is flexion of the lower part 3 in relation to the upper part 2, is provided as the device for converting and storing kinetic energy. As the flexion velocity slows down, the flywheel mass 8 releases the rotational energy again, so that, after reaching the maximum flexion velocity, that is to say after the toe off, or the swinging through in the extension phase, energy is supplied to the joint device 1 to assist the respective movement.
[0064] In FIG. 8, the device 5 for converting and storing kinetic energy is constructed in a way similar to that described in FIG. 4, but without the form-fitting element 531 at the upper end of the piston rod 53 and without the toothed rack 59. With such a device it is possible to operate extension control, in particular to set the extension stop limit. If the joint device is stretched completely, the piston 52 is moved to the maximum extent into the lower chamber 55. The compression spring 54 is tensioned to the maximum extent. The energy stored in this way can be released on opening of the valve 58 for flexion assistance, so that assistance is provided at the end of the standing phase for the initiation of flexion. The further the piston rod 53 is in this case moved out, the greater the knee angle at which the extension control acts, since the upper end of the piston rod 53 or a component assigned to it comes into early contact with the stop surface in the upper part 2.
[0065] In FIG. 9, a further variant of the invention is shown. In addition to the configuration according to FIG. 4, the energy conversion device 5 provides a second toothed rack 593 and a second form-fitting element 533. The second toothed rack 593 is arranged pivotably on the lower part 3; the second form-fitting element 533 acts on the spring 54 in the lower piston chamber 55. The piston 52 with the piston rod 53 is pushed in by way of the toothed rack 59 when there is extension. The spring 54 stores the kinetic energy as potential energy. Depending on the intended assistance, either the spring 541 on the piston rod or the spring 54 away from the piston rod is compressed.
[0066] The energy conversion device 5 may be assigned a speed-dependent coupling, which at increased knee angle velocities v provides reduced friction between force transmission elements, so that the rate of conversion or storage is inversely proportional to the pivoting velocity of the lower part 3 in relation to the upper part 2.
[0067] FIG. 10 shows an orthopedic joint device in the form of a prosthetic knee joint with an upper part 2, in which an upper leg shaft 20 for receiving an upper leg stump is arranged. A lower part 3 is fastened in an articulated manner distally in relation to the upper part 2, so that the upper part 2 can be pivoted in relation to the lower part 3. Formed on the rear of the upper part 2 is a bracket 21, arranged on which there is on the one hand a damper device 50 in the form of a hydraulic or pneumatic damper and on the other hand an energy store 54 in the form of an elastic cord. The elastic cord is connected by way of a transmission gear mechanism 11 to an actuator 10 in the form of an electric motor. The electric motor is arranged in a lower leg tube, which is fastened to the lower part 3. The energy store 5 in the form of the elastic cord is fastened to the transmission gear mechanism 11 and a bracket 12; if the motor 10 is activated, it acts by way of the transmission gear mechanism 11 on the bracket 12 and can either tension or relax the elastic cord 54, in that the bracket 12 is displaced in the distal or proximal direction or is turned in one direction or the other, in order to roll up or unroll the elastic cord. The bracket 12 consequently forms a displaceable mounting point of the energy store 5, whereby it is possible in the case of an extension movement of the lower part 3 to set the beginning of a tensioning operation of the elastic cord 54. The bracket 12 can be used to realize a displaceable, elastic stretching stop limit, which is adjusted by way of the actuator 10. The energy store 54, formed as a spring, is tensioned by way of an extension movement of the lower part 10 and takes up part of the kinetic energy of the lower part 3. This may take place for example at the end of the swinging phase or after the heel strike and the standing phase flexion. The spring 54 is tensioned in the course of the standing phase extension and continues to be kept tensioned during the standing phase.
[0068] In the terminal standing phase, the stored energy can be released again to assist the initiation of the swinging phase; the elastic cord 54 is drawn in and converts the potential energy into mechanical work, in order to assist the flexion of the lower part 3. If more energy is to be stored in the energy store 54, the actuator 10 pretensions the elastic cord 54, in that the bracket 12 is displaced distally or in the rolling-up direction; if less energy is to be stored, the bracket 12 is displaced proximally or the cord is unrolled. In the exemplary embodiment represented, the energy storage device 54 is at the same time the conversion device 5, in which the mechanical work from the relative movement is converted into potential energy.
[0069] In addition to the conversion device 5 or the energy store 54, a separate damper 50 is provided in the form of a hydraulic or pneumatic damper, which is of an adjustable design, so that the damper device 50 can be used to influence the damping during walking, both in the direction of flexion and in the direction of extension.
[0070] For controlled assistance in the initiation of the swinging phase, it is provided that changing of the pretensioning of the elastic cord 54 takes place by way of the actuator 10, the transmission mechanism 11 and the displacement or turning of the bracket 12, in order to keep a better check on the release of energy. It has been found that a spring alone as the energy store has the effect of introducing too great a force too quickly, which can be perceived by the patients as unpleasant. In order to keep a check not only on the time period over which energy is introduced but also the amount of energy and the power output, a manipulation can be performed on the energy store 54 in dependence on the angular position of the upper part 2 in relation to the lower part 3, the angular position of the upper part 2 and/or the lower part 3 in relation to one another or in space, the angular velocities or the walking speed, in order to limit the power output and additionally control the time sequence of the release of energy. By relaxing the spring 54 it is possible to introduce less energy into the joint device 1; by pretensioning the spring 54, it is possible to maintain assistance of the flexion over a longer time period and over a greater flexion angle, in order to achieve the desired harmonious gait pattern.
[0071] A variant of the invention is shown in FIG. 11, one in which a displacement at the distal mounting point takes place instead of the relaxing or tensioning of the spring 54 substantially in its longitudinal extent. The upper fastening point is guided in a displaceable spring attachment 25, which by way of the actuator 10 is displaceable back and forth in the direction of the double-headed arrow. Depending on the point of articulation and the direction of movement, the elastic cord 54 is tensioned or relaxed. Both in FIG. 10 and in FIG. 11, the energy from the extension movement is stored in the elastic cord 54. After ending of the extension movement, it is possible that the motor 10 can subsequently retension the cord 54 if the expected energy to be applied is not sufficient to bring about desired assistance in the initiation of flexion. The pretensioning advantageously takes place whenever the joint device 1 is in a completely extended state, in order to have to work as little as possible against a pretensioning movement. It is possible by the adjustment either of the pretensioning of the elastic cord 54 or of the proximal mounting position to set the stretching angle from which the conversion device 5 becomes active, whereby how much energy is to be stored in the energy store 5 can also be set.
[0072] In FIG. 12, a variant of the joint device 1 is shown, one in which the conversion device 5 in the form of the spring 54 is arranged in the lower leg tube. The actuator 10 is connected to the spring 5 and can either compress it or wind it up, depending on the configuration of the spring as a compression spring or a spiral spring. The spring 5 is coupled by way of a thrust rod 11 to a limit stop 16, which is fastened to the upper part 2. By activation of the motor 10, the bottom point of the spring 5 can be changed, whereby the thrust rod 11 can be used to set when the spring 5 comes into contact with the limit stop 16. The earlier the thrust rod 11 comes into contact with the limit stop 16, the greater the path of adjustment and the compression of the spring 5, so that correspondingly more energy is stored in the spring 5. Accordingly, when it is converted back, more energy is transmitted from the spring by way of the thrust rod 11 to the limit stop 16, so that increased flexion assistance can be achieved. In order to influence the release of energy, the spring 5 is either tensioned or relaxed in the event of movement assistance.
[0073] In FIG. 13 there is shown a variant that corresponds substantially to FIG. 12; however, the actuator 10, possibly with a spindle drive and freewheeling in one direction, is arranged between the spring 5 and the thrust rod 10, so that the bottom point of the spring 5 remains fixed, but the spring 5 can be pretensioned with the motor 10. If flexion assistance is initiated, the motor 10 must join in the rotation, in order to release the energy and transmit it by way of the thrust rod 11 and the stop limit 16 to the joint device, whereby particularly good control over the release of energy can be achieved. It is similarly possible to stop the release of energy, which may be advisable if a situation has been misjudged.
[0074] In FIG. 14, a twisted filament is shown as the energy store 54 and conversion device 5, in the case of which shortening is achieved by a twisting of filaments. By increasing or decreasing the twisting, the contact point from which the twisted filament builds up tensile forces can be set. Between the motor 10 and the twisted filament 54, an axial decoupling 13 is provided.
[0075] Apart from the embodiment shown of the energy store as a spring, by using a transmission gear mechanism and a generator it may possibly also be designed as an electrical energy store in the form of a battery, a storage battery or a capacitor. For converting the stored electrical energy back, the generator is switched as a motor, so that driving and assistance of the relative displacement of the lower part 3 in relation to the upper part 2 can take place. To increase the amount of energy, a generator may be assigned to the electrical energy store; it is similarly possible to provide a further energy store, which serves as a buffer into which excess electrical energy is fed or from which energy that is additionally required is provided.
[0076] The springs as energy stores 54 may be designed as tension springs, compression springs, torsion springs or elastomer elements, which from a certain stretching angle, which is set by the actuator 10, come into contact and from this point in time both convert mechanical work into energy and feed it back for movement assistance. The spring in this case takes up the energy from the movement in the direction of extension, and serves at the same time as a decelerating device and extension stop limit. With the initiation of the swinging phase, the energy is released again and helps the user to initiate the swinging phase. The actuator 10 can be used to adjust the point in time of the contact of the spring in the case of the release of energy, so that different, controlled forms of assistance are possible for different walking speeds. It is similarly possible that the respective spring is retensioned by way of the motor 10, if the energy stored by the preceding movement is not sufficient to provide sufficient assistance; for example, in the case of particularly slow walking or going down steps, the mechanical work may not be sufficient to tension the spring sufficiently. As shown in FIG. 12, the spring 5 may be assigned a releasing device 14, by way of which the initiating time for the release of the stored energy can be additionally ensured.
[0077] In order to ensure the initiation of the release, the joint device 1 may include a safety device, which is formed by the hydraulics in the damper 50 or by a control of the motor 10, which ensure that the spring energy applied is reduced again in time.
[0078] On account of the fact that the kinetic energy in the extension is at least partially stored, the assistance provided by the motor can operate very sparingly. The battery for the actuator 10 can be made small and lightweight, as can the actuator 10 itself, since the actuator 10 has sufficient time when retensioning in the standing phase to tension the spring, and the feeding in of the energy does not have to take place as quickly as the release for the initiation of the swinging phase. The motor 10 controls the release of energy from the spring, possibly in conjunction with the separate damper 20. The flexion assistance provided by the energy store helps in achieving the necessary bending angle in the case of alternating climbing up stairs and when overcoming obstacles, and saves hip work.
[0079] In FIG. 15, the drive moment for different walking speeds are shown against the joint angle . The representation is for three different walking speeds, the respective walking speeds being represented by different symbols in the diagram; the lowest walking speed is identified by a triangle, the medium walking speed by a circle and the highest walking speed by an X. The drive moment is the effective drive moment in Nm, that is to say the energy stored by the storage device 5 and fed back, less the losses such as damping or friction. It is evident that initially a very high drive moment is used in order to be able to provide the flexion assistance at the beginning. With an increasing joint angle , here the knee angle, which is measured from a maximum extension position, the drive moment to be applied initially falls steeply, remains constant over a small angular range, briefly rises again and then, up to maximum flexion, falls to zero. It is evident that the flexion assistance at low walking speeds, represented by the triangle, is greater than at high walking speeds. The drive moment progression, as it is shown in FIG. 15, cannot be produced by retensioning or relaxing a spring without the influence of a motor, since, according to the invention, after a strong drop in the drive moment, the moment is maintained over a further time period up until reaching the maximum angle.
[0080] FIG. 16 shows a diagram in which the tension path of the motor 10 is plotted against the joint angle . Various walking speeds are presented, once again identified by a triangle, a circle and an X; the lowest walking speed is represented by a triangle. The representation relates to the translational movement of the motor 10 in the case of the embodiments of FIGS. 10, 12 and 14. The path of displacement according to FIG. 16 is adjusted such that the drive moment curve according to FIG. 15 can be achieved. The respective progression is different for each spring chosen and, depending on the property of the spring, can lead to a greater or smaller path of displacement. The aim is to achieve a displacement, and consequently tensioning, of the spring that is as small as possible. At the start of the initiation of bending, it is evident that the motor allows the spring to slide back, in order to achieve the fastest possible force reduction, in order that the feeling of controlled flexion continues to be maintained. At greater angles, the spring is tensioned again, in order to maintain the force or increase it again. Here, too, it is significant that, at slower walking speeds, increased assistance is necessary. The release of the spring, and consequently of the energy, for flexion assistance and the driving of the motor take place at the same time, so that it is possible to keep a check over the entire progression of the flexion assistance.
[0081] FIG. 17 shows the changing of the lever arm according to an embodiment of FIG. 11 against the joint angle for different walking speeds. Here, too, at the same time as the release of the spring the motor 10 is activated, in order to adjust the lever arm. Initially, the lever arm is quickly reduced, in order to bring about a reduction in the force; subsequently, the lever arm is increased again, in order to apply force and assist the flexion movement over a greater angular range a.
[0082] In FIG. 18, the flexion damping setting of the damper device 50 is shown against the joint angle for various speeds. As a departure from the previous figures, the lowest walking speed is identified by a square, the medium speed by a triangle and the highest walking speed by a rhomboid. A medium flexion damping setting of the damper device 50 is initially provided, decreasing as the joint angle increases. At high walking speeds, raising of the flexion damping may take place toward the end of the swinging phase, in order to avoid excessive bending of the lower part 3. By changing the flexion damping setting in the damper unit 50, it is possible in conjunction with the motor control to carry out effective and safe, as well as simple, control of the introduction of energy for movement assistance.
[0083] Apart from the embodiment shown as flexion assistance, the device may in principle also be used for extension assistance; the statements made in relation to flexion assistance also apply correspondingly to extension assistance, it also being possible and intended that flexion assistance and extension assistance are arranged together in a joint device.
