METHOD FOR CONTROLLING A DAMPING MODIFICATION

Abstract

A method for controlling a damping modification in an artificial knee joint of an orthosis, an exoskeleton, or a prosthesis. The artificial knee joint has an upper part pivotally connected to a lower part. A resistance unit is secured between the upper part and the lower part in order to provide a resistance against a flexion or extension. The resistance unit is paired with an adjustment device to modify the resistance when a sensor signal of a control unit paired with the adjustment device activates the adjustment device. The flexion resistance is reduced for the swing phase. A curve of at least one load characteristic is detected when walking or standing; a maximum of the load characteristic curve when standing is ascertained; and the flexion damping is reduced to a swing-phase damping level during the standing phase when a threshold of the load characteristic below a maximum is reached.

Claims

1. A method for controlling a damping variation in an artificial knee joint of an orthosis, an exoskeleton or prosthesis, the method comprising: providing an artificial knee joint with an upper part and a lower part, which are fastened to one another in a manner pivotable about a pivot axis, a resistance unit fastened between the upper part and the lower part to provide a resistance to flexion or extension of the artificial knee joint, and an adjustment device assigned to the resistance device to vary the resistance when a sensor signal of a control unit assigned to the adjustment device activates the adjustment device; reducing the flexion resistance for a swing phase; capturing a profile of at least one load characteristic when walking or standing, the at least one load characteristic acting on the orthosis, exoskeleton or prosthesis; ascertaining a maximum of the at least one load characteristic profile during a stance phase or when standing; after reaching the maximum, reducing the flexion damping during the stance phase to a swing phase damping level if a threshold of the at least one load characteristic below the maximum is reached, wherein an initial value of the flexion damping prior to the reduction is set to a value which blocks flexion when standing or in the stance phase.

2. The method as claimed in claim 1, wherein at least one of an ankle moment and an axial force on the lower part are used as the at least one load characteristic.

3. The method as claimed in claim 1, wherein a threshold for triggering the swing phase damping is time variable.

4. The method as claimed in claim 1, wherein a threshold for triggering the swing phase damping is set depending on at least one of a walking speed, a roll-over speed and a walking situation.

5. The method as claimed in claim 1, wherein a threshold for triggering the swing phase damping is set depending on an unloading speed.

6. The method as claimed in claim 1, wherein a threshold for triggering the swing phase damping is set depending on an angle position of a prosthesis component or orthosis component.

7. The method as claimed in claim 1, wherein a threshold level for triggering the swing phase damping is selected from a range between 95% and 50% of a maximum value of the at least one load characteristic.

8. The method as claimed in claim 1, wherein the flexion damping is reduced depending on the profile of the at least one load characteristic.

9. (canceled)

10. The method as claimed in claim 1, wherein the flexion damping after a reduction is increased again when a value of the at least one load characteristic increases again.

11. The method as claimed in claim 1, wherein the profile of the at least one load characteristic comprises a substantially bell-shaped profile of the at least one load characteristic.

12. A method for controlling a damping variation in an artificial knee joint of an orthosis, an exoskeleton or prosthesis, the method comprising: providing an artificial knee joint with an upper part and a lower part, a resistance unit, and an adjustment device, the upper part being pivotally connected to the lower part, the resistance unit configured to apply a flexion resistance or an extension resistance, the adjustment device having a control unit, and the adjustment device configured to vary the flexion or extension resistance when a sensor signal of the control unit activates the adjustment device; reducing the flexion resistance for a swing phase; capturing a profile of at least one load characteristic on the orthosis, exoskeleton or prosthesis when walking or standing; determining a maximum of the profile during a stance phase or when standing; after reaching the maximum, reducing the flexion damping during the stance phase to a swing phase damping level if a threshold of the at least one load characteristic below the maximum is reached, wherein an initial value of the flexion damping prior to the reduction is set to a value which blocks flexion when standing or in the stance phase.

13. The method as claimed in claim 12, wherein at least one of an ankle moment and an axial force on the lower part are used as the at least one load characteristic.

14. The method as claimed in claim 12, wherein a threshold for triggering the swing phase damping is time variable.

15. The method as claimed in claim 12, wherein a threshold for triggering the swing phase damping is set depending on at least one of a walking speed, a roll-over speed and a walking situation.

16. The method as claimed in claim 12, wherein a threshold for triggering the swing phase damping is set depending on an unloading speed.

17. The method as claimed in claim 12, wherein a threshold for triggering the swing phase damping is set depending on an angle position of a prosthesis component or orthosis component.

18. The method as claimed in claim 12, wherein a threshold level for triggering the swing phase damping is selected from a range between 95% and 50% of a maximum value of the at least one load characteristic.

19. The method as claimed in claim 12, wherein the flexion damping is reduced depending on the profile of the at least one load characteristic.

20. The method as claimed in claim 12, wherein the profile of the at least one load characteristic comprises a substantially bell-shaped profile of the at least one load characteristic.

21. The method as claimed in claim 12, wherein the flexion damping after a reduction is increased again when a value of the at least one load characteristic increases again.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] An exemplary embodiment of the invention will be discussed in more detail below on the basis of the figures. In the figures:

[0026] FIG. 1 shows a schematic illustration of a prosthesis; and

[0027] FIG. 2 shows a load characteristic profile.

DETAILED DESCRIPTION

[0028] FIG. 1 shows, in a schematic illustration, a leg prosthesis with an upper part 1 to which a thigh socket 10 for receiving a thigh stump is fastened. A lower part 2 designed as a lower leg part is arranged pivotably on the upper part 1. The lower part 2 is mounted on the upper part 1 pivotably about a pivot axis 4. The lower part 2 has a lower leg tube 5, to the distal end of which there is fastened a prosthetic foot 3 in which there may be accommodated a device for determining the axial force A.sub.F acting on the lower leg tube 5 and the ankle moment M.sub.A acting about the fastening point of the prosthetic foot 3 to the lower leg tube 5.

[0029] In or on the lower part 2 there is arranged a resistance device 6 which may be formed for example as a damper or actuator and which is supported between the upper part 1 and the lower part 2 in order to provide an adjustable extension resistance and flexion resistance. The resistance device 6 is assigned an adjustment device 7, for example a motor, a magnet or some other actuator, by means of which the respective resistance within the resistance device 6 can be varied. If the resistance device 6 is formed as a hydraulic damper or pneumatic damper, it is possible by means of the adjustment device 7 for the respective flow cross section of a flow transfer channel to be increased or decreased in size or for the flow resistance to be varied in another way. This also may be realized by opening or closing valves or changing viscosities or magnetorheological properties. If the resistance device is formed as an electric motor operating as a generator, it is possible for an increase or decrease in the respective resistances to flexion or extension to be set through variation of the electrical resistance.

[0030] To be able to activate or deactivate the adjustment device 7, a control device 8 is assigned to the lower part 2, in particular is accommodated in a lower leg cover, by means of which control device a corresponding activation or deactivation signal is output to the adjustment device 7. The adjustment device 7 is activated or deactivated on the basis of sensor data, and the sensor data are provided by one or more sensors 9 which are arranged on the artificial knee joint. These may be angle sensors, acceleration sensors and/or force sensors. The sensors 9 are connected to the control device 8, for example by cable or by means of a wireless transmission device.

[0031] The entire step cycle from the heel strike to the new, next heel strike HS, and thus also the entire swing phase with the swing phase extension and the swing phase flexion, is monitored by means of the sensors 9.

[0032] FIG. 2 shows the profile of two load characteristics, namely the ankle moment M.sub.A and the actual force F.sub.A. The axial force F.sub.A acts on the lower part 2 in the direction of longitudinal extent of the lower part; the ankle moment M.sub.A acts in the region of a prosthetic foot 3 or foot part of an orthosis. The profile of the load characteristics is plotted over time T. A substantially bell-shaped profile of the load characteristics M.sub.A and F.sub.A emerges. The prior art has disclosed the reduction of the stance phase damping prior to reaching a maximum of the ankle moment M.sub.A or of the axial force F.sub.A in order to be able to effectuate a swing phase triggering. The trigger values to this end lie at 70% to 90% before reaching the maximum value M.sub.Amax or F.sub.Amax of the load characteristic. The trigger thresholds according to the prior art are determined in time and lie prior to the instant t.sub.max, at which the maximum value of the load characteristic is present or assumed.

[0033] According to the invention, provision is now made for prompting a flexion damping reduction only after reaching the maximum M.sub.Amax, F.sub.Amax. To this end, the load characteristics are captured while walking at a high sampling rate by way of sensors 9 over the whole step cycle. It is likewise possible to capture angle sizes, angle speeds or position variables such as absolute angles and evaluate the profile of these characteristics. After reaching a maximum of the load characteristic or load characteristics, the flexion damping is reduced before reaching the terminal stance phase and before the toe-off in order to facilitate a flexion of the artificial knee joint and in order to be able to provide a pattern of motion that approaches natural walking. The criterion for release, i.e. a reduction in the flexion damping, consequently initially is reaching the maximum value of the load characteristic, for example the maximum ankle moment M.sub.Amax and/or the maximum axial force F.sub.Amax. Subsequently, the further profile of the load characteristic is monitored or continued to be ascertained and a check is carried out as to whether a previously set but variable threshold, which is independent of the instant t.sub.max in time, is reached. The threshold is not determined in time but only dependent on the profile of the load characteristic. It is not necessary to quantitatively set the maximum value, just as little as it is necessary to estimate a step duration or load duration. As soon as the set threshold or the threshold that is determined on the basis of other sensor values is reached, there can be a swing phase triggering by reducing the flexion damping. For walking on a level surface, 90% of the maximum load or of the maximum moment is a usual value; however, this value depends on the walking speed, the nature of the ground underfoot and the use of walking aids. The threshold may vary between 95% of the maximum value of the load characteristic and 50% of the maximum value of the load characteristic. As a consequence, the threshold need not have a fixedly set magnitude; the manipulated variable may vary. By triggering the swing phase after reaching the maximum value of the load characteristic, the artificial knee joint is secured longer for a longer period of time, namely Δt.sub.v. The risk of a collapsing joint as a result of an early triggering of the swing phase, for example after a delayed step, is at least reduced as a result thereof.

[0034] The unloading speed or the roll-over speed while walking can be used for setting the threshold. It is likewise possible to use the roll-over angle, the walking direction, which can be ascertained by evaluating the change in angle of the lower part in relation to the vertical direction, the quality of the angle, i.e. whether a forward inclination or a backward inclination is present, and the absolute value in space for modifying the threshold and to set the respective threshold anew while walking. As a result, a reliable swing phase triggering that is adapted to the respective walking behavior can be achieved.

[0035] In the case of fast unloading, the swing phase is triggered earlier than in the case of slow unloading, which provides increased security against unwanted flexion, particularly in the case of slow walking. All explanations relating to a prosthesis apply accordingly to an orthosis. Then, a lower leg brace is used instead of a lower leg tube. Attachment to a patient is then not effectuated by way of a shaft, but by way of belts, cuffs or the like on the leg that is present.