Control of a passive prosthetic knee joint with adjustable damping

Abstract

Systems and methods for controlling a passive prosthetic knee joint with adjustable damping in the direction of flexion such that a prosthetic unit attached to the knee joint can be adapted for climbing stairs.

Claims

1. A method, comprising: providing a passive prosthetic knee joint and a prosthetic leg unit, the passive prosthetic knee joint being connected to the prosthetic leg unit, the prosthetic leg unit comprising a prosthetic foot; operating the passive prosthetic knee in a stair climbing mode comprising: detecting with at least one sensor of the passive prosthetic knee joint a lift phase of the prosthetic foot, the at least one sensor generating first sensor data associated with detecting the lift phase; adjusting a flexion damping level of the passive prosthetic knee joint in the lift phase in response to the first sensor data to a reduced level that is below a level used by the passive prosthetic knee joint during a lift phase of a swing phase control when walking on level ground; detecting with at least one sensor a foot placement phase of the prosthetic foot, the at least one sensor generating second sensor data associated with detecting the foot placement phase; increasing the flexion damping level of the passive prosthetic knee joint in the foot placement phase in response to the second sensor data from the reduced level to an increased level that is above the level that is used during a foot placement phase of the swing phase control when walking on level ground; and maintaining the increased level until a straightened hip is detected when in the foot placement phase.

2. The method of claim 1, wherein in the foot placement phase, an extension damping level is increased to an increased level that is above a level that is used for walking on level ground.

3. A method, comprising: providing a passive prosthetic knee joint and a prosthetic unit, the passive prosthetic knee joint being connected to the prosthetic unit, and the prosthetic unit comprising an artificial foot; controlling the passive prosthetic knee joint with adjustable damping in a direction of flexion such that the prosthetic unit can climb stairs, the controlling comprising: detecting with at least one sensor of the passive prosthetic knee joint a low-torque lift phase of the prosthetic foot, the at least one sensor generating first sensor data associated with detecting the low-torque lift phase; lowering the flexion damping in the low-torque lift phase in response to the first sensor data to below a level that is used during a swing phase control when walking on level ground; detecting with at least one sensor of the passive prosthetic knee joint a foot placement and hip-straightening phase, the at least one sensor generating second sensor data associated with detecting the foot placement and hip-straightening phase; increasing extension damping and flexion damping in the foot placement and hip-straightening phase in response to the second sensor data to a level above a damping of the swing phase control when walking on level ground; and maintaining the increased flexion damping in the foot placement and hip-straightening phase until a hip is fully straightened.

4. The method of claim 3, wherein the flexion damping in the foot placement phase is increased to a maximum value.

5. The method of claim 3, wherein the flexion damping is lowered as a function of an axial force acting on a lower leg shaft.

6. The method of claim 3, wherein an extension damping is set at a first level during the low-torque lift phase and set at a second level during the foot placement and hip-straightening phase.

7. The method of claim 3, wherein the at least one sensor includes a force sensor or a torque sensor.

8. The method of claim 3, wherein the low-torque lift phase is detected by the at least one sensor determining that no forefoot moment is present, which indicates no forefoot load.

9. The method of claim 3, wherein the flexion in the low-torque lift phase is provided by a pre-tensioned spring mechanism.

10. The method of claim 3, wherein the increase in the flexion and extension damping is initiated when the prosthetic foot, after being lifted, is placed down again.

11. The method of claim 3, wherein the flexion damping in the low-torque lift phase is lowered to a minimum value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An illustrative embodiment is explained in more detail below with reference to the figures.

(2) FIGS. 1 to 6 are schematic depictions showing the sequence involved in alternating stair-climbing with a passive knee joint prosthesis.

DETAILED DESCRIPTION

(3) FIG. 1 shows a prosthesis wearer 1 with a knee joint prosthesis 2 which is secured by upper attachment elements to a femoral stump. The prosthetic leg 20 stands with the healthy contralateral leg 4 in front of a step.

(4) To reach the next step up, a prosthetic foot 6 has to be guided over the step edge. An active bending of the hip, as is indicated by the arrow 7, assists the passive bending of the knee, which is shown by the arrow 8 and which, because of the mass inertia both of the prosthetic foot 6 and also of the connection element 3, occurs from the prosthetic knee joint 2 to the prosthetic foot 6. For this purpose, a minimum extension damping is required to ensure that, after a flexion of the hip, the prosthetic foot 6 does not swing forward and is not moved against the riser or under the step 5. In the lift phase, as shown in FIG. 2, the prosthetic foot 6 is guided upward, as far as possible in a perpendicular manner, this possibly being initiated by a slight rearward movement. The lift is detected with at least one sensor 10 (see FIGS. 1-3) via the flexion angle a between the connection element 3 and the thigh or via a reduction of the axial force in the connection element 3, without flexion of the prosthetic foot 6. It is also possible to detect the stair-climbing mode, and thus the lowering of the flexion damping to a value below the normal swing phase control, preferably to the minimum value, via a horizontal rearward movement of the prosthetic foot 6 in conjunction with a bending of the hip.

(5) After the step edge has been negotiated and the lift phase completed, as is shown in FIG. 2, a secure positioning of the prosthetic foot 6 on the step is required. For this purpose, the prosthetic foot 6 has to be moved forward, which can be achieved by extension as a result of the force of gravity. For this purpose, an extension damping can be reduced, if this has not already been done in the lift phase. A prosthetic knee joint 2 that is sufficiently damped in flexion and extension prior to straightening allows the prosthesis wearer 1 to position the prosthetic foot 6, by changing the hip angle. In the lowering and hip-straightening phase, the flexion and extension are preferably strongly damped to control the foot placement, and to prevent a spontaneous backward fall in the event that the hip-straightening torque is insufficient. The extension remains damped so as to be able to control the speed of straightening of the hip and knee. This is shown in FIG. 3.

(6) In FIG. 4, the foot placement phase is completed. The prosthesis wearer 1 can initiate straightening of the knee with a hip-straightening torque. The straightening of the knee can be assisted by an extension of the healthy foot.

(7) FIG. 5 shows the increasing straightening of the knee through application of a hip torque. The increasing straightening of the knee shortens the effective lever and facilitates the straightening of the knee through the straightening of the hip.

(8) FIG. 6 shows the complete extension of the leg provided with the knee joint prosthesis 2. The contralateral leg 4 is moved past the prosthetic leg 20 and placed on the next step up, such that alternating climbing of stairs is possible with the passive knee joint prosthesis.

(9) Accordingly, the control is configured in such a way that, during the lift of the prosthetic foot 6 a flexion resistance is set that results in a knee angle a, which allows the prosthetic foot 6 to be placed on the next step. Flexion support by spring mechanisms may facilitate the lifting movement and make it easier to negotiate the step height.

(10) If no action is to take place after the stair-climbing mode has been triggered by detection of a low-torque lift, a free extension is set, said free extension being set in a time-dependent manner. The time function can also be mechanical. The low-torque lift can be detected via the mass inertia, if the healthy leg is first set down and only the second step is intended to be negotiated by the leg provided with the prosthesis. If the prosthetic foot is first unloaded and the prosthetic knee joint then bent, the stair-climbing mode is set. Damping both in the direction of extension and also in the direction of flexion after the lift phase, that is to say during the hip-straightening phase, is maintained until a complete extension of the prosthetic knee joint is reached or detected.

(11) P1. A control of a passive prosthetic knee joint with adjustable damping in the direction of flexion such that a prosthetic unit, with upper attachment elements and with a connection element to an artificial foot, can be adapted for climbing stairs, said control involving the following steps:

(12) detecting a low-torque lift of the prosthetic food, and

(13) lowering the flexion damping in a lift phase to below a level that is suitable for walking on level ground.

(14) P2. The control in paragraph P1, characterized in that the extension and/or flexion damping, in a foot placement and hip-straightening phase, is increased to a level above a damping of a swing phase control for walking on level ground.

(15) P3. The control in paragraph P2, characterized in that the flexion damping in the foot placement phase is increased to a maximum value.

(16) P4. The control in paragraphs P2 or P3, characterized in that the flexion damping in the foot placement and hip-straightening phase is maintained until the hip is fully straightened.

(17) P5. The control in one of paragraphs P2 through P4, characterized in that the flexion damping is increased as a function of the change of the knee angle.

(18) P6. The control in one of the preceding paragraphs (P1-P5), characterized in that the flexion damping is increased or lowered as a function of the axial force acting on the lower leg shaft.

(19) P7. The control in one of the preceding paragraphs (P1-P6), characterized in that an extension damping is set during the lift phase and also during the foot placement and hip-straightening phase.

(20) P8. The control in one of the preceding paragraphs (P1-P7), characterized in that the low-torque lift is detected by a force or torque sensor.

(21) P9. The control in one of the preceding paragraphs (P1-P8), characterized in that the low-torque lift is detected by measuring a horizontal acceleration of the prosthetic foot and by recording a bending in the prosthetic knee joint.

(22) P10. The control in one of the preceding paragraphs (P1-P9), characterized in that a low-torque lift is detected by recording a torque at the front of the prosthetic foot.

(23) P11. The control in one of the preceding paragraphs (P1-P10), characterized in that the flexion in the lift phase is supported via a pretensioned spring mechanism.

(24) P12. The control in one of the preceding paragraphs (P1-P11), characterized in that the increase in the flexion and extension damping is initiated when the prosthetic foot, after being lifted, is placed down again.

(25) P13. The control in paragraph P12, characterized in that the foot placement is detected by an axial force measurement in the lower leg shaft or in the prosthetic foot.

(26) P14. The control in one of the preceding paragraphs (P1-P13), characterized in that the flexion damping in the lift phase is lowered to a minimum value.

(27) P15. The control in one of the preceding paragraphs (P1-P14), characterized in that, after the flexion damping has been lowered, a free extension is set with time control.

(28) P16. The control in paragraph P15, characterized in that the free extension is spring-assisted.

(29) P17. The control in paragraph P15 or P16, characterized in that the time control is effected mechanically or electronically.

(30) P18. A method for initiating and implementing a stair-climbing mode in a passive prosthetic knee joint connected to a prosthetic leg unit including a prosthetic foot comprising:

(31) detecting a low-torque lift of the prosthetic foot;

(32) initiating a lift phase, in which a flexion damping level of the knee joint is reduced to a level below that which is used for walking on level ground;

(33) detecting a placement of the prosthetic foot; and

(34) initiating a lowering phase, in which the flexion damping level is increased to a level above that which is used for walking on level ground.

(35) P19. The method of paragraph P18, wherein in the lowering phase, an extension damping level is increased to a level above that which is used for walking on level ground.

(36) P20. The method of paragraph P19, wherein the flexion damping and extension damping are increased to maximum levels in the lift phase.

(37) P21. The method of paragraph P18, wherein the flexion damping is reduced to a minimum level in the lift phase.

(38) P22. The method of paragraph P18 further comprising the step of, during the lowering phase, maintaining the flexion damping level until a straightened hip is detected.

(39) P23. The method of paragraph P18, further comprising the step of, during the lowering phase, detecting a knee angle and establishing, the flexion damping level as a function of the detected knee angle.

(40) P24. The method of paragraph P18 wherein at least one of the detecting steps comprises the step of detecting an axial force along the prosthetic unit.

(41) P25. The method of paragraph P18 wherein an extension damping level is established during each of the lifting and lowering phases.

(42) P26. The method of paragraph P18 wherein the step of detecting the low torque lift comprises measuring a horizontal acceleration of the prosthetic foot and by detecting a bend in the knee joint.

(43) P27. The method of paragraph P18 wherein the step of detecting the low torque lift comprises detecting a torque at the front of the prosthetic foot.

(44) P28. The method of paragraph P18 wherein the step of detecting the placement of the foot comprises measuring an axial force measurement along the prosthetic unit.

(45) P29. The method of paragraph P18 wherein after initiating the lifting phase, a time controlled free extension is set.