Plastic surgery technology devices

Abstract

The present invention relates to an orthopedic technical device comprising an upper part (100) and a lower part (200) displaceably supported on the upper part, the lower part being coupled to an actuator (30) for displacing the lower part relative to the upper part, the actuator having an electric motor (40), an energy store (50) and a control device (60), wherein a first change-over switch (62) is arranged between the energy store and the electric motor, the first change-over switch being coupled to the control device and switching the supply voltage (Us) of the motor control part (66) of the electric motor between the output voltage (Uo) of the energy store and a voltage converter (80) having a supply voltage varied relative to the output voltage.

Description

[Technical Field]

[0001] The present invention relates to an orthopedic technical device comprising an upper part and a lower part displaceably supported on the upper part, the lower part being connected to an actuator which displaces the lower part relative to the upper part, the actuator having an electric motor, an energy store and a control device. [Background technology]

[0002] Orthopedic technical devices are in particular prostheses, orthoses and exoskeletons. Prostheses replace, as far as possible in terms of form and / or function, limbs or body parts that are absent or no longer present. The simplest prostheses have a purely cosmetic function or complement a limb, for example by replacing a distal phalanx. In the case of complex prostheses, several prosthetic components are connected to each other, attached to each other and in particular pivotally connected to each other via joints.

[0003] Locking devices have been developed to influence the relative movement of prosthetic components with respect to one another, and can be used to lock and unlock an extended prosthetic knee joint so that the prosthesis user can sit. Drives have been developed that transmit shoulder movements via a cable mechanism to the prosthetic hand, thereby allowing it to grasp and hold objects. Dampers, especially hydraulic dampers, and energy stores, especially in the form of springs, are arranged on the individual components to influence the movement behavior. The aim here is, inter alia, to achieve optimal functionality and, where appropriate, to enable the movement to occur as naturally as possible.

[0004] Actuation devices have been incorporated into prosthetic limbs to assist or dampen the movement of prosthetic components, thereby creating active prosthetic limbs. Corresponding embodiments exist for passive and active orthoses or exoskeletons, which are placed on existing limbs. Orthoses and exoskeletons that span joints can also be equipped with springs, animal powertrains, and / or motor drives.

[0005] A control device is arranged in an orthopedic technical device for controlling both passive and active prosthetic limbs, orthotics and exoskeletons, which generates control signals based on sensor values ​​or stored history to activate, deactivate or modulate a drive device or to change a resistance, for example by opening or closing a valve, releasing or cutting off stored energy from an energy store, switching on, switching off or modulating an electric motor, etc.

[0006] In active orthopedic technical devices with electric motor drives, the energy storage device usually consists of a battery or accumulator. In electric motor drives, there is a proportional relationship between the required supply voltage and the rotational speed of the drive, and between the torque of the drive and its motor current. Therefore, the maximum values ​​of the current and voltage of the energy supply determine the maximum torque and maximum rotational speed of the drive.

[0007] Therefore, in order to be able to provide both high torque and high rotational speed for driving the orthopedic technical device, a large energy storage device or electric motor must be used. This increases the weight of the orthopedic technical device, which places a limit on the size of the energy storage device and / or motor. An electric motor is an electromechanical converter that converts electrical energy into mechanical energy. By electric motors, in particular, DC motors, AC motors, piezoelectric actuators, motors operating on the Lorentz force, reluctance motors, and thermoelectric actuators are understood. Summary of the Invention

[0008] The object of the present invention is to provide an orthopedic technical device in which a relatively light energy store is sufficient or whose drive has a larger operating range.

[0009] This problem is solved by an orthopedic technical device having the features of the independent claims. Advantageous embodiments and developments of the invention are disclosed in the dependent claims, the following description and the figures.

[0010] An orthopedic technical device includes an upper part and a lower part displaceably supported on the upper part, the lower part being coupled to an actuator that displaces the lower part relative to the upper part, the actuator having an electric motor, an energy storage device, and a control device. A first changeover switch is arranged between the energy storage device and the electric motor, the first changeover switch is coupled to the control device, and the supply voltage of the motor control of the electric motor is switched between the output voltage of the energy storage device and a voltage converter with a supply voltage that is changed, in particular an increased, relative to the starting position. A changeover switch is arranged between the motor control device and the energy storage device, and the changeover switch is arranged on the control device, and the motor control is supplied either directly with the output voltage of the energy storage device or with an increased voltage. In addition to a certain rapidity of adjustment, an active orthopedic technical device must provide sufficient torque to be able to perform a desired movement or action or to be able to affect a movement situation in an intended way. In this case, fast movements can often be performed with low torque without significant load, while movements requiring high torque are usually performed slowly. Using the control device and the changeover switch, the output voltage can be passed directly to the electric motor in a first switch state, thereby supplying the motor with a large current at a relatively low supply voltage equal to the output voltage of the energy store. This allows the electric motor to generate a high torque. When a corresponding switching signal is output by the control device, the voltage converter is switched on or activated. The voltage converter changes the output voltage from the energy store, in particular increasing or decreasing it, and supplies the increased or decreased voltage as a supply voltage to the electric motor via the motor control. This increases the electric motor's speed or possible speed, or increases the electric motor's maximum speed, thereby reducing the maximum torque, or reduces the speed and correspondingly increases the maximum torque. Directly connecting the motor control to the energy store allows a large current flow to the motor. This allows the electric motor to generate a high torque at a low speed.If a higher rotation speed is required, a voltage converter switches to an increased supply voltage. The control device then sends a switching signal to adjust the supply voltage. The control device can detect the need for a higher voltage or torque increase in the motor and provide the appropriate supply voltage by switching the voltage converter. This can be done, for example, by evaluating sensors that detect the movement, load, condition, and / or position of the prosthetic or orthotic components, the surrounding environment, and / or the patient's non-wearing contralateral side, or changes therein. Sensors can also be evaluated so that further future profiles can be inferred from previous signal profiles.

[0011] In one embodiment, the output voltage of the voltage converter can be dynamically adjusted to allow a gradual changeover between the respective provided or required supply voltages. The output voltage of the voltage converter is dynamically adjusted to cover the voltage increase requirements of the individual phases of the step. The dynamically adjusted output voltage minimizes losses in the voltage converter caused by voltage boosting. The dynamic adjustability allows a gradual changeover between the respective provided supply voltages.

[0012] In one embodiment, the voltage converter is designed to be both up and down converting, i.e. to provide a stepped-up or stepped-down voltage as the supply voltage. Alternatively, in one embodiment, the voltage converter may comprise a step-up converter and a step-down converter to be able to provide each desired supply voltage.

[0013] In one embodiment, the voltage converter is bidirectional and includes a step-up converter and a step-down converter, or only one converter capable of both up- and down-conversion. Therefore, when energy is fed back to a battery or energy storage in the generator mode of the motor, the fed-back voltage can be adjusted. On the one hand, in forward rotation mode, the output voltage of the energy storage can be increased to a higher level to supply the motor control, while the step-down converter enables reverse rotation mode. In this case, the electric motor operates in generator mode when the supply voltage level increases. The step-down conversion allows the electric energy generated by the motor to be controlled and fed back to the energy storage for charging. The generator mode allows the generated electric energy to be fed back to the energy storage, while the electric motor operates in generator mode when the voltage level of the supply voltage increases. Therefore, in particular with a dynamically adjustable voltage converter, it is possible to reduce losses in the step-up or step-down converter when the motor voltage is down- or up-converted.

[0014] One development provides for a second changeover switch to be coupled to the control device for switching between the step-up converter and the step-down converter. The second changeover switch is particularly needed when the output of the voltage converter cannot be deactivated. In such an embodiment of the voltage converter, the second changeover switch must always be blocked when the first changeover switch is conductive, or must always be conductive when the first changeover switch is blocked.

[0015] In the start position of the first change-over switch, the output voltage of the energy store is present as the supply voltage for the motor control of the electric motor, which therefore initially operates at a low maximum speed and torque.Only when a corresponding control signal is present, for example based on a sensor, does the switch-over to an increased supply voltage take place.

[0016] In one embodiment, the changeover switch or switches are designed as part of the voltage converter, so that the switching can be partly or completely integrated into the voltage converter.

[0017] In one embodiment, the supply lines of the motor controller are electrically isolated from the voltage converter and the energy storage. The switching and voltage converter can be fully or partially integrated into the motor controller. In one embodiment, a changeover switch provides switching of the circuit configuration of the energy storage.

[0018] In one embodiment, the voltage converter consists of at least one semiconductor switch, at least one of which may be designed as part of the switching device.

[0019] One development provides for the control device to be designed so that the supply voltage of the motor controller is only increased once a speed threshold of the electric motor is exceeded. The supply voltage of the motor controller can depend on the motor speed, the motor torque, the motor current and / or their time course. It is not only necessary to measure the motor speed to detect whether the speed threshold is reached or exceeded, but also the rate of change of the relevant degree of freedom can be measured, from which the motor speed or the exceedance of the speed threshold can be inferred.

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of a prosthetic limb. [Figure 2] FIG. 1 is a schematic diagram of an orthosis. [Figure 3] FIG. 2 is a block diagram of a voltage supply. [Figure 4] FIG. 1 is a plot of gait data. [Figure 5] 1A-1C are exemplary plots of various operating ranges. [Figure 6]FIG. 10 is an alternative circuit diagram. [Figure 7] Energy and signal flow in the circuit diagram according to FIG. [Figure 8] This is a variation of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] In FIG. 1, a prosthetic knee joint is shown as part of a prosthetic orthopedic device, and in FIG. 2, as part of a prosthetic device. The prosthetic knee joint has an upper part 100 and a lower part 200, which are pivotally supported relative to one another around a pivot point 120. In one embodiment as a prosthetic limb, the lower part 200 has a prosthetic foot 205 arranged at its distal end. In the embodiment of the prosthetic knee joint as a prosthetic knee joint shown in FIG. 2, the lower part 200 is designed as a transtibial splint without a foot, but with the optional foot part 210 shown in dashed lines. In the case of a KAFO, the foot part 210 is arranged on the lower part 200, on which the foot can rest. However, this can be omitted to realize a pure knee orthosis. In the embodiment as a prosthetic leg according to FIG. 1, the upper part 100 is arranged or formed with a prosthetic socket or another device for receiving a femoral stump or for fixing to a person. In the embodiment according to Fig. 2, the brace is fixed to the leg via attachment means 101, 201, for example in the form of a belt or a shell, for removably fastening the brace to the leg. Another difference between the embodiment according to Fig. 1 and the embodiment according to Fig. 2 is that according to Fig. 2, an alternative drive is provided in which an electric motor 40 is coupled to a belt pulley, possibly via a transmission. Depending on the direction of rotation of the motor, flexion or extension of the knee joint can then be brought about or assisted via a V-belt or a toothed belt. The embodiment of the drive with an electric motor 40 via a mechanical force transmission and parallel damping by a hydraulic damper can also be used in prosthetic knee joints or other prosthetic devices.

[0023] An actuator 30, which is a linearly operating hydraulic motor, is arranged between the upper part 100 and the lower part 200. In the illustrated exemplary embodiment, the hydraulic actuator 30 is formed with a hydraulic chamber or cylinder 11, which is arranged or formed in a housing or base 10. A piston 12 is slidably supported in the cylinder 11. The piston 12 is attached to a piston rod 20 that is displaceable along the longitudinal extension of the cylinder 11 and protrudes from the housing or base 10. The piston 12 divides the cylinder 11 into several chambers that are fluidically connected to each other via hydraulic piping. To prevent tilting of the piston 12 when the upper part 100 pivots relative to the lower part 200, the base 10 or housing can be pivotally supported on the lower part 200. The end of the piston rod 20 opposite the piston 12 is attached to the upper part 100, in the illustrated exemplary embodiment, by a jib that extends the distance to the pivot axis 120. During flexion, the piston 12 is depressed, thereby reducing the volume of the flexion chamber and correspondingly expanding the volume of the extension chamber, which is reduced by the volume of the advancing piston rod 20. An electric motor 40 is arranged within the housing 10 to generate pressure in one of the chambers, which drives a pump (not shown) to apply pressure to the hydraulic fluid in one of the two chambers and thereby move the piston 12 in one direction or the other within the cylinder, thereby producing a flexion or extension movement of the orthopedic technical device in the form of a prosthetic leg.

[0024] In the illustrated exemplary embodiment, the actuator 30 is fixed to the lower part 200 via a mounting device 41. A sensor 70 is arranged on both the upper part 100 and the lower part 200 to detect the spatial orientation of the lower part 200 or the upper part 100. This sensor 70, which may be designed as an inertial measurement unit (IMU), detects a fixed spatial orientation during use of the knee prosthesis, such as a spatial angle or absolute angle relative to the direction of gravity. Instead of an IMU, the sensor 70 can detect other status data, in particular status data related to the knee prosthesis. The status data detected include, in particular, position, angular position, velocity, acceleration, force, and their progression or changes. The detected spatial angle of the upper part 100 and / or lower part 200 or other status quantities are compared with a threshold angle. When a threshold value stored in the controller for each sensor value or a quantity derived therefrom is reached or exceeded, the actuator 30 is activated or deactivated to change the flow resistance in the actuator 30.

[0025] The actuator 30 of the prosthetic knee joint is used to inhibit flexion and extension movements in order to generate or support an appropriate or desired movement pattern. Extension movements are optionally supported and preferably damped just before reaching maximum extension to avoid severe impacts. Flexion movements are damped or blocked during the stance and swing phases to ensure limited knee bending. To be able to drive the electric motor 40, the actuator 30 also has an energy store 50, particularly in the form of an accumulator. The energy store 50 can also be located in another location of the orthopedic technical device where more space is available or where it would be advantageous to distribute the weight.

[0026] Instead of the embodiment of the actuator 30 as a hydraulic motor with an electric motor 40 and a pump, the actuator 30 can also have a direct mechanical connection between the electric motor 40 and the upper part 100 and the lower part 200 via a force transmission device, for example a spindle, whereby the spindle, instead of the piston rod 20, is driven by the rotation of a spindle nut driven by the electric motor 40 and moved into or out of the housing 11. In one embodiment, the actuator 30 is coupled to the upper part 100 and the lower part 200 via a transmission, for example a planetary gear mechanism, in order to displace the upper part 100 relative to the lower part 200. Instead of the embodiment of the orthopedic technical device as a lower limb orthosis or prosthesis or exoskeleton, it can also be designed as an upper limb orthosis or prosthesis or exoskeleton. Other orthopedic technical devices having two mutually displaceable components whose relative movement is influenced by an electric motor also use the present invention.

[0027] Furthermore, the orthopedic technical device is provided with a control device 60 and at least one angle detection device 70 as a sensor. The angle detection device 70 detects the angle between the upper part 100 and the lower part 200, e.g., is designed as a direct angle sensor that directly detects the angle. Alternatively, the angle between the upper part 100 and the lower part 200 can be detected by evaluating the sensor data of the spatial position sensor 70. Both methods can be used simultaneously or complementary to each other. All sensors arranged in the orthopedic technical device are connected to the control device 60, and their sensor values ​​are used as the basis for controlling the actuators 30. Based on the sensor data, in particular the spatial and / or angular positions, as well as the position data, as well as data on the loads, orientations, accelerations, and / or deformations of other components, the actuators 30 are controlled, for example, to activate, deactivate, or inhibit the electric motor 40, for example, to reduce or increase the rotational resistance, define end stops, and / or generate or support relative movement between the upper part 100 and the lower part 200.

[0028] FIG. 3 shows a circuit diagram of the voltage supply of the electric motor 40 from an energy storage device 50. A control device 60 is arranged between the electric motor 40 and the energy storage device 50 and includes several components for supplying the electric motor 40 with the necessary or desired supply voltage Us. The energy storage device 50 outputs an output voltage Uo, which is initially supplied to a motor control device 66. The control device 60 includes a first changeover switch 62 and a direct motor control device 66, which detect and determine, based on data, particularly sensor data, what supply voltage Us is or needs to be supplied to the electric motor 40 to achieve optimal results. In one embodiment, the first changeover switch 62 is in a conducting position, in which the output voltage Uo is supplied directly from the energy storage device 50 as the supply voltage Us of the motor control device 66. Therefore, with the output voltage Uo as the supply voltage Us, the electric motor 40 can be supplied with a maximum motor current at a low motor voltage via the motor control device 66.

[0029] If the computer detects via the motor control 66 or another evaluation device that the electric motor 40 needs to increase its rotation speed, for example to quickly pivot the lower part 200 relative to the upper part 100 in an unloaded state, the motor control 66 sends a corresponding control signal to the voltage controller 86. The voltage controller 86 recognizes the switch position of the first change-over switch 62 and sends a corresponding command to the first change-over switch 62 and to the first voltage converter 82, which is designed as a step-up converter. The step-up converter 82 transforms the output voltage Uo of the energy store 50 to a higher level and then transmits this intermediate circuit voltage as a supply voltage Us to the electric motor 40 via the motor control 66. The control signal of the motor control 66 thereby provides a command for adjusting the required supply voltage Us. The switch-over to the supply voltage Us, which has a higher voltage compared to the output voltage Uo, is carried out by the first change-over switch 62, which provides the output voltage of the step-up converter 82 as Us. The switch-over process is advantageously assisted by the dynamically adjustable step-up converter 82. Thus, a gradual switchover between different voltage sources is possible. Furthermore, losses in the boost converter 82 are reduced. In particular, the output voltage Uo can follow the need for a voltage increase, resulting in smaller losses. The output voltage level only increases as much as necessary. At an increased supply voltage Us compared to the output voltage Uo, the maximum motor current is reduced, so that the electric motor 40 can achieve a higher rotational speed but provide relatively less torque.

[0030] In the embodiment shown, the voltage converter is of bidirectional design and, in addition to the boost converter 82, also comprises a step-down converter 84, which can be used to step down the boosted voltage or to extract energy from the motion captured by the motor 40 and return it to the energy store 50. For this purpose, the second change-over switch 64 is assigned to a voltage controller 86, so that the control device 60 controls the two change-over switches 62, 64 via the motor control unit 66 and the voltage controller 86 in the case of appropriate load, motion and energy states, in order to increase the output voltage Uo as required or to return it to the starting level again or, in generator mode, to return electrical energy from the motor 40 to the energy store 50 for recharging.

[0031] Figure 4 shows an exemplary progression of the torque at the knee shaft generated by the motor versus the rotational speed occurring during a step. Each circle represents a measurement point. The starting torque (in Nm) of the electric motor is plotted for each step against the rotational speed (in rpm). A relatively high torque of up to -25 Nm at low rotational speeds of 10 to -15 rpm correlates with a high adjustment speed (-50 to +60 rpm) with a starting torque of less than +-5 Newton meters. A characteristic feature of the use of active drives in knee prostheses is the large gap between the high torque and low rotational speed range and the low torque and high rotational speed range. In electric drives with electric motors, there is a proportional relationship between the required supply voltage Us and the drive's rotational speed, as well as between the drive's torque and its motor current. Therefore, the maximum values ​​of the current and supply voltage Us determine the maximum torque on the one hand and the maximum drive's rotational speed on the other hand. Energy storage devices typically consist of several cells in an accumulator system. For a given number of cells, the entire system can be optimized for higher currents by connecting several cells in parallel, or for higher voltages by connecting the cells in series. If both ranges, i.e., high torque and high rotational speeds, are to be achieved in the same way, additional cells must be added, which increases the volume and therefore the weight of the energy storage device.

[0032] Figure 5 shows an example plot of gait data for an active knee prosthesis powered by the circuit of Figure 3. The torque generated by the motor at the knee axis is plotted against the rotational speed during one step. Each circle represents a measurement point. Two operating ranges are plotted, as selected by the selector switches 62 and 64. The vertical rectangle represents the range with a supply voltage Us corresponding to the output voltage Uo, i.e., a range that allows for relatively high torque at a relatively low rotational speed. The horizontal rectangle represents the range in which the electric motor 40 operates at a supply voltage Us higher than the output voltage Uo, thus allowing for a higher maximum rotational speed but a lower maximum torque. The vertical rectangle represents the operating range in which the maximum starting current can be supplied to the electric motor 40 at the output voltage Uo, thereby covering a high torque range. The horizontal operating range represents the voltage range increased by the voltage controller 86 and boost converter 82 at a reduced maximum current, allowing for high rotational speeds with relatively low torque. The overlapping region of the two ranges is advantageously covered by the vertical operating range when the output voltage Uo is conducted directly without the interposition of the converter 82 .

[0033] The voltage converters 82, 84 are dynamically adjustable, and the step-down converter 84 converts the electrical energy generated from the movement during the phase of the increased motor voltage in generator mode of the electric motor 40 into a corresponding voltage for charging the energy store 50. If a direct connection with the energy store 50 exists, the electric motor 40 can charge the energy store 50 via the motor control 66 in the phases when the motor voltage Us is smaller than the output voltage Uo and the voltage converter 84 is deactivated. The boost allows the behavior of the orthopedic technical device to remain unchanged in terms of the achievable rotational speed even when the energy store 50 is empty and the voltage drops.

[0034] FIG. 6 shows a circuit diagram of a motor control as an alternative to the motor control according to FIG. 3, where the same reference numerals refer to the same components. In FIG. 7, the respective energy flows are indicated by solid arrows. Energy is supplied to the motor 40 from the energy store 50, or energy is supplied to the energy store 50 when the motor 40 is in generator mode. In this embodiment, the control device 60 also comprises a first changeover switch 62 and a second changeover switch 64, although the second changeover switch 64 is optional. The motor control 66 is controlled in a closed loop or open loop via a motor controller 88, which is also connected to the voltage controller 86 and exchanges control signals with it. The exchange of control signals is indicated by dashed arrows. The motor controller 88 also influences the motor control 66.

[0035] The top arrow in Fig. 7 shows the energy flow in generator mode or in reverse mode when the motor 40 is driven. The electrical energy generated by the motor 40 is returned to the energy store 50, for example when braking a prosthetic or orthotic joint. As long as a high current and a low voltage are present, the transfer takes place without the intervention of a voltage converter. Conversely, in the conventional mode shown by the second arrow from the top, energy is supplied directly from the energy store 50 to the motor 40 without any change, possibly using a step-down conversion, so that the motor 40 is supplied with a high current and a relatively low supply voltage.

[0036] The drive energy flow, where a higher or increased supply or motor voltage is required for the motor 40, is indicated by the third arrow from the top. To generate the increased motor voltage in forward rotation mode, electrical energy is directed from the energy storage device 50 through the controller 60 to the corresponding voltage converter 84. Conversely, in reverse rotation mode at increased motor voltage, indicated by the bottom arrow, electrical energy generated by the motor 40 in generate mode is directed through the step-down converter 84 and then transferred to the energy storage device 50.

[0037] In FIG. 8 a variant of FIG. 6 is shown in which the motor controller 88 is designed as an integral part of the motor control unit 66 .

[0038] In principle, the energy supply can also be completely separated from the motor control 66 or the motor 40 .

Claims

1. An orthopedic technical device comprising an upper part (100) and a lower part (200) displaceably supported on the upper part, the lower part (200) being coupled to an actuator (30) for displacing the lower part relative to the upper part (100), the actuator (30) having an electric motor (40), an energy store (50) and a control device (60), an orthopedic technical device, characterized in that a first change-over switch (62) is arranged between the energy store (50) and the electric motor (40), the first change-over switch (62) being coupled to the control device (60) and switching a supply voltage (Us) to a motor control unit (66) of the electric motor (40) between an output voltage (Uo) from the energy store (50) and an output voltage (Uo) from a voltage converter (80) having a supply voltage (Us) varied with respect to the output voltage (Uo).

2. 2. An orthopedic technical device according to claim 1, characterized in that the output voltage from the voltage converter (80) is dynamically adjustable.

3. 3. An orthopedic technical device according to claim 1 or 2, characterized in that the voltage converter (80) is capable of both step-up and step-down conversion or comprises a step-up converter (82) and a step-down converter (84).

4. 4. The orthopedic technical device according to claim 3, characterized in that a second changeover switch (64) for switching between the step-up converter (82) and the step-down converter (84) is coupled to the control device (60).

5. 5. The orthopedic technical device according to claim 1, wherein in the starting position of the first change-over switch (62), the output voltage (Uo) from the energy store (50) is present as a supply voltage (Us) to a motor control (66) of the electric motor (40).

6. Orthopaedic technical device according to any one of claims 1 to 5, characterized in that the first and second change-over switches (62, 64) are designed as part of the voltage converter (80).

7. 7. An orthopedic technical device according to claim 1, wherein the voltage converter (80) consists of at least one semiconductor switch, at least one of which is designed as a change-over switch (62, 64).

8. 8. The orthopedic technical device according to claim 1, wherein the control device (60) is designed in such a way that the supply voltage (Us) to the motor control unit (66) is increased only when the rotational speed of the electric motor (40) exceeds a threshold value.

9. 9. An orthopedic technical device according to any one of claims 1 to 8, characterized in that the supply voltage (Us) to the motor control (66) or to the motor (40) depends on the motor speed, the motor torque or the motor current and / or on the time course of the motor speed, the time course of the motor torque or the time course of the motor current.

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