Abstract
The invention relates to a method for controlling a joint (2, 28) of an orthopedic device that comprises a first part (8), a second part (4), which is arranged on the first part (8) such that it can be pivoted about a pivot axis (12), an active actuator (42), a self-locking transmission (16, 50) and an electric control unit for controlling the actuator (42), the electric control unit controlling the actuator (42) during the method in such a way that the second part (4) moves according to forces acting on it externally.
Claims
1. A method for controlling a joint (2, 28) of an orthopedic device that comprises a first part (8), a second part (4), which is arranged on the first part (8) such that it can be pivoted about a pivot axis (12), an active actuator (42), a self-locking transmission (16, 50) and an electric control unit for controlling the actuator (42), characterized in that during the method the electric control unit controls the actuator (42) in such a way that the second part (4) moves according to forces acting on it externally.
2. The method according to claim 1, characterized in that the joint (2) is an artificial ankle joint (2), the first part (8) is a lower leg part and the second part (4) a foot part.
3. The method according to claim 1, characterized in that the joint is an artificial knee joint (28), the first part (8) is an upper leg part and the second part (4) a lower leg part.
4. The method according to claim 1, characterized in that at least one load measurand is detected by means of at least one sensor that allows a statement to be made about the load on the transmission (16, 50) and/or the static friction between the first transmission element (16) and the second transmission element (50), wherein the electric control unit controls the actuator (42) depending on the load measurand detected.
5. The method according to claim 1, characterized in that at least one force measurand is detected by means of at least one sensor that allows a statement to be made about the external forces acting on the second part (4), wherein the electric control unit controls the actuator (42) depending on the force measurand detected.
6. The method according to claim 5, characterized in that a resulting movement and/or a resulting position of the second part (4) relative to the first part (8) is calculated from the force measurand detected and the electric control unit controls the actuator (42) in such a way that the resulting movement is carried out and/or the resulting position is reached.
7. The method according to claim 1, characterized in that the electric control unit can be brought into a first mode and into a second mode, wherein in the first mode it controls the actuator (42) in such a way that the second part (4) is moved according to forces that act on it externally and do not do so in the second mode.
8. The method according to claim 7, characterized in that the electric control unit is brought into the first mode when predetermined movements, movement patterns and/or states of movement have been detected and/or when an actuation element has been actuated.
9. The method according to claim 7, characterized in that the electric control unit is brought into the second mode when a predetermined criterion is met.
10. The method according to claim 9, characterized in that the criterion is met when an angle between the second part (4) and the first part (8) leaves a predetermined angle range; when the predetermined movements, movement patterns and/or states of movement are not or are no longer detected; when an actuation element has been actuated and/or after the electric control unit has been in the first mode for a predetermined period of time.
11. The method according to claim 9, characterized in that the predetermined criterion can be adjusted or changed.
12. A joint (2, 28) for an orthopedic device for carrying out a method according to claim 1.
13. The joint according to claim 12, characterized in that it has at least one sensor for detecting a load measurand, which comprises at least one expansion measuring strip, a spring force measure, a deformation sensor, a torque sensor, a pressure sensor and/or an axial load sensor.
14. The joint according to claim 13, characterized in that it has at least one sensor for detecting the force measurand, which comprises at least one force sensor, a position sensor, an inertial sensor and/or a gyroscope.
Description
[0029] In the following, a number of embodiment examples of the invention will be explained in more detail with the aid of the accompanying figures. They show
[0030] FIG. 1a schematic representation of a prosthetic foot with an ankle joint according to an embodiment example of the present invention.
[0031] FIG. 2schematic phases of a gait cycle,
[0032] FIG. 3schematic movements and positions of a leg w % bile sitting,
[0033] FIG. 4schematic representations of the range of motion whilst walking in a sloped plane,
[0034] FIG. 5schematic representations of the scope of movement of an ankle at different heel heights,
[0035] FIGS. 6a-6dvarious schematic positions of a leg while sitting down and standing up,
[0036] FIG. 7schematic representations of the control of a knee joint at various loads,
[0037] FIG. 8a schematic representation of the control unit in different modes, and
[0038] FIG. 9a schematic sectional view through a joint according to an embodiment example of the present invention.
[0039] FIG. 1 schematically depicts a prosthetic foot with an active ankle joint 2, which is designed according to an embodiment example of the present invention. It connects a second part 4, designed as a prosthetic foot with a foot base 6, to a first part 8, which is designed as an adaptor element on which a lower leg element can be arranged. A housing 10 contains a self-locking transmission and an actuator as well as an electric control unit, which is configured to conduct a method described here. The second part 4 is arranged on the first part 8 such that it can be pivoted about a pivot axis 12. The actuator, designed as a motor, is supplied with energy via a battery 14. In the embodiment example shown, the motor is able and configured to displace a spindle 16 upwards and downwards, and thus to change a pivot angle between the second part 4 and the first part 8.
[0040] FIG. 2 schematically shows four phases of a gait cycle. The first phase in the far left-hand representation in FIG. 2 corresponds to the first phase of the next step in the far right-hand representation in FIG. 2. This first phase is the so-called heel strike. The ankle joint 2, depicted only schematically, is in principle designed in the same way as the joint shown in FIG. 1. A heel 18 comes into contact with a ground 20. In this phase, the joint is operated in the first mode, so that the electric control unit controls the actuator in such a way that the second part 4 moves in accordance with the externally acting forces. Said forces cause a forefoot 22 to lower until the foot base 6 is fully on the ground 20. The respective phase of the gait cycle is determined via sensors, which can be arranged at various positions of the prosthetic foot and/or the ankle joint 2. The electric control unit is brought into the first or second mode on the basis of the sensor data.
[0041] In the second representation from FIG. 2, the rollover phase is shown, in which the foot base 6 lies fully on the ground 20 and a lower leg 24 moves forward. In all the phases depicted in FIG. 2, the movement is from the position indicated by a solid line into the position indicated by a dashed line. In this case too, the electric control unit is operated in the first mode, so that the actuator cancels the self-locking effect of the transmission and the second part 4 moves relative to the first part 8 as if it were being moved by the externally acting forces.
[0042] In the third representation in the middle of FIG. 2, the phase of pushing off from the ground 20 is shown. Sensors detect that a predetermined dorsal stop is reached, i.e. an angle between the first part 8 and the second part 4 assumes a predetermined value. In the embodiment example shown, the electric control unit is then brought from the first mode into the second mode, so that the self-locking effect of the transmission is no longer cancelled. The joint no longer moves according to the forces acting externally on the joint, but blocks, so that the foot can push off from the ground 20.
[0043] In the penultimate representation in FIG. 2, the swing phase is shown in which the foot loses contact to the ground. In the process, the forefoot 22 is raised, wherein the position reached during this movement is pre-set. The movement is caused by the actuator, i.e. the motor in the present case. In an especially preferred embodiment, an active plantar flexion of the foot, i.e. a lowering of the forefoot 22 and therefore an active push-off, is carried out when the foot is pushing off from the ground 20. This increases an angle between the second part 4 and the first part 8 at which the actuator moves the second part 4 relative to the first part 8. If this is the case, it is advantageous to raise the forefoot again in the swing phase by way of a dorsal flexion and to reach the desired position for the next heel strike. Alternatively, it is also possible to not carry out a plantar flexion when the foot is pushing off. In this case, it is not necessary, but indeed advantageous, to carry out a dorsal flexion during the swing phase.
[0044] In the embodiment example shown, sensors, such as pressure sensors, are arranged on the foot base 6 or load sensors at different points on the ankle joint 2 by which, as is generally known from the prior art, different phases of a gait cycle can be detected. Depending on whether a free movement of the second part 4 relative to the first part 8 is desired, the electric control unit is brought into the first mode or the second mode.
[0045] FIG. 3 schematically shows the representation of a leg prosthesis with an upper leg 26, a knee 28, a lower leg 24, an ankle joint 2 and a foot 30. The ankle joint 2 is configured to be controlled according to a method in accordance with an embodiment example of the present invention. The left-hand representation in FIG. 3 shows the situation in which the wearer of the prosthesis is sitting. The knee 28 is almost at a right angle and the foot base 6 of the foot lies fully on the ground. In this situation, it is beneficial to operate the electric control unit in the first mode, so that the second part 4, i.e. the foot 30 in the present example, can move according to the externally acting forces. This is schematically depicted by the two arrows 32.
[0046] The middle representation in FIG. 3 shows that the wearer of the prosthesis is pivoting the lower leg 24 relative to the upper leg 26, so that the knee 28 exhibits a greater angle. The foot 30 is slightly raised, but has not changed its angle relative to the lower leg 24. In the right-hand representation from FIG. 3, the foot 30 touches down and moves along the arrow 32 from the middle representation in FIG. 3, so that the foot base 6 once again lies fully on the ground. This is possible because the electric control unit is operated in the first mode and the actuator controlled in such a way that the second part 4 moves corresponding to the externally acting forces relative to the first part 8. As a result, the user can at all times adjust to a position that is comfortable for them. This would not be possible by controlling the ankle position, as is known from the prior art. Here, the ankle position would be adjusted solely via the motor, but in this case the information on the desired position would be missing.
[0047] FIG. 4 schematically shows the influence of the slope of a ground 20 on which the wearer of the prosthesis is walking. Again, a leg prosthesis with the lower leg 24, the knee 28, the ankle joint 2 and the foot 30 is schematically depicted, the ankle joint 2 again being configured to be controlled according to a method for controlling the joint in accordance with an embodiment example of the present invention. The foot 30 forms the first part 8 and the lower leg 24 forms the second part 4. In each case, dashed lines depict a plantar stop 34 and a dorsal stop 36, which indicate the maximum range of motion of the ankle joint. In the left-hand representation in FIG. 4, the wearer of the prosthesis is standing on an even and horizontal surface; in the right-hand representation in FIG. 4 the ground 20 is sloped. This changes the range of motion required between plantar stop 34 and dorsal stop 36. During the phases 1 to 3 of the gait cycle, which are shown in FIG. 2, the ankle joint 2 moves in such a way that the foot 30 is moved relative to the lower leg 24 within this range of motion. In this range, the electric control unit is operated in the first mode, so that a self-locking effect of the transmission is cancelled. As soon as one of the stops 34, 36 is reached, which is detected via sensors, for example, and passed on to the electric control unit, the electric control unit is brought from the first mode into the second mode, so that the self-locking effect of the transmission is not cancelled. If, for example, the slope of the ground 20 is now determined via further sensors, the actual value of the angle can be adjusted and changed for the plantar stop 34 and/or the dorsal stop 36.
[0048] FIG. 5 shows the influence of a heel height of a schematically depicted heel 38 of a shoe. The left-hand representation in FIG. 5 corresponds to the left-hand representation in FIG. 4. The foot 30 lies fully on the ground 20 and the dorsal stop 36 and the plantar stop 34 limit the range of motion that the lower leg 24, i.e. the first part 8, has relative to the foot 30, i.e. the second part 4, when the electric control unit is operated in the first mode. If the wearer of this prosthesis now puts on a shoe with a heel 38, there is no initial change to the range of motion and the actual values of the various stops 34, 36. This is shown in the middle representation of FIG. 5. However, the change in heel height causes a change, for example, to the angle between the foot 30 and the lower leg 24 at which the heel of the foot 30 comes into contact with the ground 20 during the heel strike. If the heel height is detected via a sensor, the stops 34, 36, which are not mechanical stops, but rather simply electronic or virtual stops, can be adjusted. This is shown in the right-hand representation of FIG. 5.
[0049] FIGS. 6a to 6d depict various situations during sitting down and standing up with a leg prosthesis. It has the upper leg 26 and the lower leg 24, between which the knee 28 is located. In FIG. 6, the knee 28 is suitable and configured to be controlled according to the present invention. FIG. 6a depicts an extended leg such as occurs, for example, during standing and walking, especially for patients with low degrees of mobility. In this case, the knee joint 28 is preferably blocked and consequently the self-locking effect of the transmission is not cancelled. The electric control unit is operated in the second mode.
[0050] In FIG. 6b, sensors have detected, for example, that the wearer of the prosthesis wants to sit down. To this end, it is advantageous for the self-locking effect of the transmission, which is located in the knee joint 28, to be cancelled, so that the knee joint 28 can move according to the externally acting forces. This is possible in both directions, which is schematically depicted by the arrows 32.
[0051] FIG. 6c shows the situation when sitting. The electric control unit remains in the first mode, like in FIG. 6b, and the knee joint 28 can move freely along the two arrows 32. FIG. 6d, on the other hand, depicts the process of standing up. This can also be detected via sensors, for example. When standing up, it is advantageous if the knee joint 28 supports the wearer of the prosthesis while they are standing up. The self-locking effect is consequently active and the actuator is controlled by the electric control unit in such a way that a desired end position is reached. The knee joint is controlled as the active knee joint it is. In addition, the self-locking effect prevents a renewed, unwanted flexion if the active control of the joint happens to fail, so that the knee joint depicted is secure in all situations.
[0052] FIG. 7 shows a way of identifying whether the electric control unit is being operated in the first mode, as depicted in the left-hand representation of FIG. 7, or in the second mode. For example, if only a small load is detected on the prosthetic leg, the self-locking effect is cancelled and the electric control unit operated in the first mode. The knee joint 28 can be moved along the arrows 32 in both directions according to the externally acting forces. The situation is different when a large load is acting on the prosthetic leg, as is shown in the right-hand representation in FIG. 7 by the arrow 40. Under this high load, cancelling the self-locking effect of the transmission would be a safety hazard for the wearer of the prosthesis, so that the electric control unit of the joint is operated in the second mode.
[0053] FIG. 8 schematically shows how the control unit works in the two different modes. A controller first determines, in the electric control unit or a separate electric control unit, whether the electric control unit is operated in the first mode, i.e., the upper string in FIG. 8, or in the second mode, i.e., the lower string of FIG. 8, based on sensor data recorded by sensors, not depicted. In the upper string, the externally acting forces are detected via sensors and evaluated in the electric control unit, i.e. the motor control unit or a controller. The motor, i.e. the actuator, is then controlled in such a way that it cancels the self-locking effect of the transmission and allows a movement according to the externally acting forces.
[0054] In the lower string of FIG. 8, in which the electric control unit is operated in the second mode, it is not necessary to detect the externally acting forces in order to control the actuator. Here, the self-locking effect of the transmission is active and the actuator or motor is controlled in such a way that a desired position is reached or maintained.
[0055] FIG. 9 shows a schematic sectional view through a prosthetic foot with an ankle joint 2, a first part 8 and a second part 4. The second part 4 is arranged about a pivot axis 12 on the first part 8. An active actuator 42 in the form of a motor is arranged on the first part 8, said actuator being configured to rotate a first shaft 44. In the embodiment example shown, the rotation of the first shaft 44 is transmitted via a timing belt 46 to a second shaft 48, which likewise is set in rotation. The spindle 16, which comprises an outer thread, is located on said second shaft. A screw sleeve 50 is located on the second part 4, the former comprising an inner thread designed to correspond to the outer thread of the spindle 16. Together, the spindle 16 and the screw sleeve 50 form a self-locking transmission.
REFERENCE LIST
[0056] 2 ankle joint [0057] 4 second part [0058] 6 foot base [0059] 8 first part [0060] 10 housing [0061] 12 pivot axis [0062] 14 battery [0063] 16 spindle [0064] 18 heel [0065] 20 ground [0066] 22 forefoot [0067] 24 lower leg [0068] 26 upper leg [0069] 28 knee [0070] 30 foot [0071] 32 arrow [0072] 34 plantar stop [0073] 36 dorsal stop [0074] 38 heel [0075] 40 arrow [0076] 42 active actuator [0077] 44 first shaft [0078] 46 timing belt [0079] 48 second shaft [0080] 50 screw sleeve
