Method for controlling an artifical knee joint

Abstract

The invention relates to a method for controlling an artificial knee joint comprising: an upper part (10) and a lower part (20) which are articulatedly mounted on one another so as to be pivotable about a pivot axis (15); and an actuator (30) which is coupled to the upper part (10) and the lower part (20) and influences a movement state of the upper part (10) and / or the lower part (20), wherein the actuator (30) is coupled to a control device (40) which is coupled to at least one sensor (50) and activates, deactivates, or modulates the actuator (30) on the basis of sensor values from the at least one sensor (50), wherein, when walking on a downwardly inclined surface, a stance phase flexion following an initial contact is countered with a resistance, and a stance phase extension is supported by the actuator (30) depending on the surface inclination (α).

Description

[0001] Method for controlling an artificial knee joint

[0002] The invention relates to a method for controlling an artificial knee joint having an upper part and a lower part, which are pivotably mounted to one another about a pivot axis. The method comprises an actuator coupled to the upper part and the lower part, which influences a movement state of the upper part and / or lower part. The actuator is coupled to a control device that is coupled to at least one sensor and activates, deactivates, or modulates the actuator based on sensor values ​​from the at least one sensor. The lower part is designed, in particular, as a lower leg component.

[0003] Orthopedic joint devices include, in particular, orthoses, exoskeletons, or prostheses that comprise an upper part and a lower part articulated to it. In orthoses and exoskeletons, the upper and lower parts are attached to a still-existing limb, for example, using shells, straps, belts, cuffs, or other fastening devices. Orthoses and exoskeletons can guide movements, limit pivoting around a joint axis, prevent pivoting movements, or support or fix the alignment of limbs relative to one another. In polycentric joints, the pivot axis is the instantaneous center of rotation, which shifts depending on the pivoting movement. In addition, orthoses can be equipped with damping devices to dampen pivoting movements around the joint axis.The damping devices can be provided with a control so that, depending on sensor data, a modified damping can be provided in the flexion direction and / or extension direction.

[0004] It is also known to assign mechanical energy storage devices to the upper or lower part, so that movement can be supported by releasing the stored energy from the energy storage device. Mechanical energy storage devices include, in particular, springs, elastomer elements, and pneumatic and hydraulic energy storage devices.

[0005] Prostheses replace a missing or no longer existing limb and serve to provide functionality that is as close as possible to that of the natural limb. Furthermore, prostheses serve to provide the most natural appearance possible for the prosthetic user. A prosthetic upper part is designed, for example, as an osseointegrable component, a prosthetic socket, or as a component attached to a prosthetic socket, where the prosthetic socket serves to secure it to a limb or limb stump. The prosthetic joint, for example a prosthetic knee joint or a prosthetic ankle joint, connects the upper part to a lower part, which in turn may have further prosthetic components, such as a lower leg tube or a prosthetic foot.

[0006] Particularly in orthoses, exoskeletons and prostheses of the lower extremities, but also of the upper extremities, dampers, in particular hydraulic dampers or other resistance devices are arranged between the upper and lower parts. These dampers provide different resistances in individual states or movement situations based on sensor data. Such resistance devices are often designed as linear actuators that provide a defined resistance to a flexion movement and / or extension movement. The resistance is changed, for example, by changing the position of valves. When the flow cross-section is reduced, the corresponding resistance to a movement increases. Passively damped, in particular passively hydraulically damped prostheses or orthoses work purely dissipatively. Energy is taken from the movement of the upper part relative to the lower part, whereby very high moments orForces can be generated. At the same time, passive damping in an open state, for example when no valves are closed or throttles are activated, has only very low resistance. The working range of such an orthosis or prosthesis is limited in that no energy can be fed into the movement in order to support it or actively counteract the movement or make a change from a static state. In addition, orthoses, exoskeletons and prostheses with motor drives are known from the state of the art, so-called active orthoses or prostheses, in which a movement is initiated, supported or braked by activating, deactivating or modulating the drive. For this purpose, stored electrical energy from a battery or accumulator is converted in the actuator.Motor drives also serve to influence the movement behavior between the components of the orthosis or prosthesis, for example, to slow down a pivoting movement. Motor drives can be operated in braking mode or as part of a generator circuit; they can also be coupled with a mechanical energy storage device.

[0007] Both purely passive devices such as dampers and semi-active devices such as energy storage devices and motor drives influence the movement behavior of the upper and / or lower parts and are actuators that influence a state of motion of the upper and / or lower parts. The actuators can initiate a movement, reverse a movement, assist a movement, or resist a movement. The state of motion of the upper and / or lower parts is also influenced if a load is counteracted, a static state is maintained, or a change in a state of motion due to external forces is prevented or suppressed. This can happen, for example, if a uniform pivoting movement is to be maintained and external forces act in the direction of movement or against the direction of movement.

[0008] EP 2 869 792 B1 discloses a method for controlling an orthopedic joint device of a lower extremity comprising an upper part and a lower part articulated thereto, between which an energy conversion device and / or a storage device is arranged, via which kinetic energy from the relative movement between the upper part and the lower part is converted and / or stored during walking. This energy can be fed back to the joint to support the relative movement, wherein within a movement cycle of the joint device, kinetic energy is converted and / or stored and, within the same movement cycle, is fed back to the joint device in a controlled manner and with a time delay as kinetic energy. The conversion rate and / or storage rate of the energy conversion device or storage device is inversely proportional to the pivoting speed of the lower leg.

[0009] WO 2016 / 169 850 A1 relates to a method for controlling a damping change in an artificial joint of an orthosis, an exoskeleton, or a prosthesis of a lower extremity, comprising a resistance unit between an upper and a lower part, which are pivotally attached to each other. The resistance is changed via a resistance unit when a sensor signal from a control unit associated with the adjustment device activates the adjustment device. The resistance is changed depending on the position and / or length of the leg tendon or its temporal derivatives.

[0010] WO 2016 / 169 848 A1 also relates to a method for controlling a damping change of an artificial knee joint, in which the flexion resistance is reduced during the swing phase. During walking or standing, the course of at least one load characteristic acting on an orthosis or prosthesis to which the artificial knee joint is attached is recorded. If a maximum of the load characteristic course is determined during the stance phase or standing and a threshold value of the load characteristic below the maximum is subsequently detected, the flexion damping during the stance phase is reduced to a swing phase damping level.

[0011] Walking on surfaces with varying inclines requires constant adaptation to the current conditions, especially to varying surface inclines. Walking on a downward slope, such as walking downhill on a surface, requires special support from the artificial knee joint. Active and passive artificial knee joints enable walking downhill on a surface by providing high flexion resistance. The knee joint bends sharply under the body weight of the user, allowing a controlled lowering during the stance phase. This movement is called "yielding."At the end of the stance phase on the treated side, as the load is transferred to the contralateral side, the flexion resistance is reduced. This generates greater ground clearance in the swing phase and the foot does not "stick" to the ground in the terminal stance phase. The resistance to flexion in the stance phase can be either constant or with an increase in resistance with increased flexion. On very flat surfaces, "yielding" is not beneficial because the body sinks too much, so that the movement pattern used here is that of walking on level ground. This leads to a swing phase being triggered in the terminal stance phase. Due to the incline of the ground, the person applying the device must apply an additional extension moment in order to keep the joint extended in the stance phase or to bring the knee joint back into extension after flexion in the stance phase.This is necessary because, with the current technology, activation is not possible with a bent knee joint. This results in a propulsive movement and an increase in walking speed with each step, which is perceived as particularly unpleasant by the user.

[0012] The object of the invention is to provide a method which provides improved support to the person using it and in particular to enable a smooth transition from walking on level ground to walking down a ramp.

[0013] This object is achieved by a method having the features of the main claim. Advantageous embodiments and further developments of the invention are disclosed in the subclaims, the description, and the figures.

[0014] The method for controlling an artificial knee joint with an upper part and a lower part, which are pivotally mounted to one another about a pivot axis, with an actuator which is coupled to the upper part and the lower part and influences a state of movement of the upper part and / or upper part, wherein the actuator is coupled to a control device which is coupled to at least one sensor and activates, deactivates or modulates the actuator on the basis of sensor values ​​of the at least one sensor, is characterized in that when walking on a downwardly inclined surface, a stance phase flexion is opposed after an initial contact by a resistance and a stance phase extension is supported by the actuator depending on the inclination of the surface.The actuator actively supports stance phase extension when walking on a downwardly inclined surface, combined with controlled stance phase flexion depending on the surface gradient. The type of support and the control of the actuator's support for stance phase extension are adapted to the surface gradient. In particular, as the surface gradient increases, a larger flexion angle is enabled during the stance phase and / or the knee joint is extended less during the stance phase extension. This can be achieved, for example, by reducing support for the extension movement earlier and initiating the swing phase at a larger knee flexion angle.

[0015] In one embodiment, when walking on a downwardly inclined surface, partial stance phase extension and swing phase initiation occur with the knee joint not fully extended. The extent of knee extension during the stance phase extension can be controlled by the actuator by applying resistance to knee extension. The resistance can also be increased to such an extent that knee extension is completely blocked. Alternatively or additionally, with active support of knee extension by the actuator, the extent of knee extension can be controlled by the applied extension moment, in particular by the amplitude of the extension moment and / or the temporal progression, for example, an earlier or later reduction or increase of the extension moment.An extension movement can also be initially supported by an extension moment, the extension moment subsequently reduced, and then resistance to the extension movement applied. The swing phase is initiated with the knee joint flexed in the stance phase by reducing the flexion resistance and / or by generating a knee flexion moment through the actuator, which causes a flexion movement.

[0016] The degree of stance phase extension, achieved by supporting the extension movement and, if necessary, resisting it, is particularly negatively correlated with the slope of the ground. This means that with a steeper slope, the knee joint is extended less, whereas with a less steep slope or a flat ramp, the knee joint is extended further before the initiation of the swing phase. Accordingly, with a flat ramp, a swing phase is only initiated or permitted after a comparatively large extension has occurred after the knee flexion and the knee flexion angle has decreased to the desired level.The control system can be designed so that the relative knee extension, defined as the difference between the maximum knee flexion angle during stance flexion and the minimum knee flexion angle during stance extension before the initiation of the swing phase, is correlated with the ground slope. However, the minimum knee flexion angle during stance extension, and thus before the initiation of the swing phase, can also be correlated with the ground slope.

[0017] In one embodiment, partial extension only occurs when the ground slope exceeds a certain threshold. If the ground slope is below this threshold, the knee joint is essentially fully extended.

[0018] In one embodiment, knee extension during the stance phase is stopped once the ground slope exceeds a certain threshold. Knee flexion can be slowed down to achieve a plateau phase of the knee angle or to temporarily slow down the knee flexion. The swing phase is initiated from a loaded flexion movement or a plateau phase, particularly by reducing the knee extension moment during the terminal stance phase.

[0019] In one embodiment of the method, support for the extension movement is positively correlated with stance phase flexion, meaning that with increasing stance phase flexion, greater or stronger support for the extension movement occurs. Furthermore, support is increased up to a threshold of the ground inclination with increasing stance phase flexion angle. The greater the ground inclination, the greater the support; however, above a certain ground inclination, there is no increase in support for the stance phase extension.

[0020] In one embodiment, the support is positively correlated with the maximum stance phase flexion angle up to a limit value of the ground inclination.

[0021] In one embodiment, the knee extension moment is increased monotonically with knee flexion in at least one region of the stance phase flexion. In an actuator with an energy storage device, in particular a spring-loaded device, work can be performed on the energy storage device during the stance phase flexion in order to transfer energy into the energy storage device. The moment can be applied partially or entirely by a linear or non-linear spring mechanism, for example an elastomer, coil, and / or fluid spring. Alternatively or additionally, the moment is applied by an electromechanical drive and / or a damper. A drive can emulate elastic or viscoelastic behavior.

[0022] In one embodiment, the support for stance phase extension is not applied unchanged, but is reduced during stance phase extension, so that with a decreasing knee flexion angle, i.e. with increasing extension, reduced support is achieved. For this purpose, for example, the external extension moment is reduced depending on a decreasing knee flexion angle. In one embodiment, after the support in stance phase extension has been completely reduced, resistance is applied to the knee extension movement. The reduction in support and / or the resistance to an extension movement can be correlated in terms of its extent and / or its temporal course with the ground gradient. In particular, the reduction in extension support and / or the resistance to extension can be negatively correlated with the ramp gradient.As the ramp incline increases, the resistance to extension at the end of the extension movement can initially be reduced and thereafter the extension support can no longer be completely reduced.

[0023] In a further development, swing phase initiation is supported or permitted by the actuator depending on the ground inclination. Active initiation of the swing phase can, for example, occur by applying a flexion moment that supports the swing phase initiation. A swing phase can be permitted by reducing the flexion resistance. In one embodiment, support for swing phase initiation is progressively reduced as the ground inclination increases until no internal flexion moment is applied by the knee joint in the terminal stance phase. As the ground inclination increases, the maximum applied flexion moment can, for example, be reduced in the terminal stance phase and / or pre-swing phase, a flexion moment can be applied later and / or reduced earlier and / or the work and / or power performed by the actuator can be reduced.On steep ground slopes, an external flexion moment acts during the terminal stance phase, particularly when the knee joint is only partially extended, and the knee joint begins to flex as soon as the internally applied extension moment is less than the external flexion moment. The timing of swing phase initiation can be influenced by reducing flexion resistance. In one embodiment, support for swing phase initiation, either by reducing flexion resistance or by an active drive, is initiated and carried out before the artificial knee joint is in an extension stop or before the knee joint has reached an extension stop. This prevents the knee joint from having to be fully extended before a swing phase can be initiated.This would mean that when walking on a downward-sloping ramp, the body of the person using the device would have to be levered over the outstretched leg, which corresponds to an unphysiological gait pattern and can sometimes be dangerous.

[0024] In one embodiment, resistance is applied to the knee joint during the pre-swing phase or part of the pre-swing phase. In the pre-swing phase, the knee joint flexes under the body weight. Bending too quickly can lead to premature weight transfer to the contralateral side, greater loading on the contralateral side, or a lowering of the body's center of gravity. Bending too quickly can be prevented by applying flexion resistance or an extension moment. Flexion resistance in the pre-swing phase can also occur after an active initiation of a swing phase by applying an internal flexion moment. The flexion resistance is advantageously reduced as the load decreases and / or during the flexion movement. In one embodiment, the applied flexion resistance is positively correlated with the slope of the ground.On very flat ramps it is possible that no bending resistance is applied.

[0025] In one embodiment of the method, the resistance against a stance phase flexion is adjusted depending on the ground inclination, because in particular with a greater inclination in the downward direction a higher flexion resistance is set at a larger knee flexion angle.

[0026] In a further development of the method, the achievable stance phase flexion angle is increased in a positive correlation with the ground inclination, so that on a more steeply inclined ground the maximum achievable stance phase flexion angle is also increased.

[0027] In one embodiment, the knee extension moment is increased as a function of the knee flexion movement, so that, depending on the external knee flexion moment, which depends on the ground slope, an increase in the maximum knee flexion angle is achieved with increasing ground slope. Alternatively or additionally, the achievable maximum flexion angle can be increased by increasing the extension moment later or more slowly during knee flexion.

[0028] The maximum pivot angle of the lower part is advantageously adjusted during the swing phase depending on the ground incline, since it is advantageous to allow or achieve a larger maximum pivot angle of the lower part when the ground incline is greater in the downward direction. A larger maximum knee angle increases ground clearance when the leg swings through under the body. Due to the downward incline of the ground, the contralateral foot touches down at a lower height, which would reduce ground clearance while maintaining the maximum knee angle. A larger pivot angle is allowed or achieved, for example, by applying a greater flexion moment in the preswing phase and / or swing phase flexion, by allowing a flexion moment to act for a longer time, by applying less flexion resistance and / or by increasing flexion resistance later.For example, a maximum flexion angle during the swing phase can be increased from 65° to 80° with increasing ground inclination. After the swing phase reversal, swing phase extension can be controlled depending on the ground inclination and / or the maximum flexion angle by applying extension moments and / or extension resistances, so that the knee joint reaches a desired extension position at the right time before initial contact. In particular, at higher maximum knee flexion angles, stronger or longer extension support and / or a lower or delayed onset of extension resistance can be applied.

[0029] Artificial knee joints have an extension stop that blocks further extension movement. The extension stop can be a mechanical stop that can be changed by adjusting the position of one or more stop elements. With a hydraulic design of a damper or drive, the extension stop can be adjusted by completely closing a corresponding hydraulic line. A functional extension stop can also be provided by applying a sufficiently large resistance force via an actuator. Such an extension stop can be adjusted depending on the ground incline. With a greater ground incline, the extension stop is shifted in the flexion direction, i.e. the lower part hits the extension stop at a greater knee flexion angle.

[0030] An extension resistance is adjusted depending on the slope of the ground. The extension resistance is increased, especially on steeper slopes, to prevent the knee from extending too far during the subsequent movement after initial contact. The extension movement is thus stopped or slowed down earlier, resulting in a more flexed knee joint when the foot rolls on a downwardly inclined surface.

[0031] The ground inclination can be determined using measured speeds and / or distances, in particular through path integration, accelerations, segment angles, segment angle profiles, the ground reaction force or components thereof, moments and lever arms around joint axes and / or segments, the profile of a force application point, in particular the ground reaction force, movement data from preserved body segments and / or joints, in particular the ipsilateral femoral stump and / or the contralateral leg, and / or environmental sensors. The temporal profiles, temporal derivatives, and / or partial derivatives of the recorded variables can also be used for control purposes. Machine learning or artificial intelligence methods can also be used for control purposes, in particular for determining the ground inclination from the available sensor data.The determination of the ground inclination is carried out in particular by a combination of several detection methods and by using all sensor values ​​that are already present in the prosthesis, orthosis or exoskeleton.

[0032] The ground inclination can be explicitly determined and used for control purposes. Alternatively or additionally, the actuator can be controlled based on at least one determined variable that correlates with the ground inclination. This allows a correlation between the ground inclination and the control target variables, such as the maximum achievable knee angle during stance phase flexion, the extent of stance phase extension, or the extent of support for swing phase initiation, to be achieved without explicitly determining the ground inclination. For example, control can be based on segment angles, the knee angle, and the ankle moment, the curves of which are typically correlated with the ground inclination and thus also allow control that correlates with the ground inclination.

[0033] The ground slope is defined as the local slope below the lower section or a height difference between two endpoints spaced apart in the direction of travel. For example, the height difference of the previous step can be used to determine the expected height difference of the next step, or at least to store this as an expected value in the control system. The ground slope can be determined as a continuous variable. The control system can also be continuously adapted to the ground slope. Alternatively or additionally, the ground slope can be assigned to discrete classes, for example, discrete value ranges of ground slopes. The control system can also be adapted to the ground slope in discrete steps.For example, different control parameters and / or target values ​​can be stored for inclines below 5%, inclines between 5% and 10%, and inclines above 10%. The control adjustment can occur continuously over time or from step to step. The relative adjustment of the control over time or from step to step can be limited to prevent sudden changes in the control. The control or individual control parameters can be adjusted autonomously over time, for example, based on a cost function to be minimized, in order to achieve adaptation to the user, properties of the prosthesis or orthosis, and / or other influencing factors such as the footwear used.

[0034] If a prosthetic foot is articulated to the lower part, a further development provides for the maximum plantar flexion angle of the prosthetic foot to be adjusted depending on the ground slope. In particular, the maximum plantar flexion angle is positively correlated with the ground slope. With a greater ground slope, the maximum plantar flexion angle is increased; with a less downward ground slope, the maximum plantar flexion angle of the prosthetic foot relative to the lower part is reduced.

[0035] The actuator can comprise a drive and / or a force storage device and be designed in combination with a passive resistance device such as a damper or a brake. This enables effective use of the various options for influencing the relative movement of the upper and lower parts. An active component, such as an electric motor or a spring-loaded mechanism, can provide active support, for example, during stance phase extension or to initiate swing phase flexion. The passive resistance device, such as a hydraulic damper, a device for charging the mechanical force storage device, a magnetorheological damper device, or a brake, is used to absorb large forces and moments during stance phase flexion.Accordingly, the individual components only need to be optimized and dimensioned for their respective tasks and an electric motor does not have to offer any resistance to stance phase flexion or can be operated at optimal operating points.

[0036] In one embodiment, the actuator is coupled to a human-machine interface and is activated, deactivated or modulated on the basis of biosignals, so that a change in the damping behavior and the movement behavior of the artificial knee joint is achieved that is voluntarily controlled by the person using it.

[0037] In one embodiment, the maximum flexion angle during the swing phase is positively correlated with the ground slope: the greater the ground slope, the greater the maximum flexion angle, to facilitate a full swing. In one variant, the maximum achievable stance phase extension angle is positively correlated with the ground slope: the greater the ground slope, the earlier the stance phase extension is decelerated or stopped.

[0038] In one embodiment, the height difference between the ipsilateral foot position during two stance phases is used as the ground slope. Alternatively, the height difference between the ipsilateral and contralateral foot position in the respective stance phase is used.

[0039] In one embodiment, in addition to the ground gradient, the step length, walking speed and / or cadence are also used to control the actuator.

[0040] Exemplary embodiments of the invention are explained in more detail below with reference to the figures. They show:

[0041] Figure 1 - a schematic representation of a prosthetic leg; Figure 2 - a schematic representation of a leg orthosis;

[0042] Figure 3 - a movement sequence when walking on a downward sloping surface

[0043] Figure 4 - a knee angle curve when walking on differently inclined surfaces;

[0044] Figure 5 - a knee moment curve when walking on differently inclined surfaces;

[0045] Figure 6 - a knee moment curve over the knee angle when walking on differently inclined surfaces;

[0046] Figures 7 to 9 - further knee angle curves in the stance phase flexion and extension when walking on differently inclined surfaces;

[0047] Figures 10 to 15 - further knee moment curves when walking on differently inclined surfaces; and

[0048] Figure 16 - schematic representations of actuators with energy storage devices.

[0049] Figure 1 shows a schematic representation of a prosthetic knee joint as part of a prosthesis, and Figure 2 shows an orthotic knee joint as part of an orthosis. The prosthetic knee joint has an upper part 10 and a lower part 20, which are pivotally mounted on one another about a pivot axis 15. In a design as a prosthesis, a prosthetic foot 60 is arranged at the distal end of the lower part 20. In the design of the artificial knee joint as an orthotic knee joint, as shown in Figure 2, the lower part 20 is designed as a lower leg splint on which no foot part is arranged, but on which an optional foot part 60 can be arranged, represented by a broken line. In the case of a KAFO (knee ankle foot orthosis), a foot part 60 is arranged on the lower part 20, on which a foot can be placed. However, this can also be omitted to create a pure knee orthosis.In the embodiment as a prosthetic leg according to Figure 1, a prosthetic socket or other device for receiving a femoral stump or for securing it to a person is arranged or formed on the upper part 10. In the embodiment according to Figure 2, the orthosis is secured to a leg via fastening means 101, 201, which are designed, for example, as straps, shells, or the like, in order to removably secure the orthosis to the leg.

[0050] An actuator 30 is arranged as a linearly acting hydraulic actuator between the upper part 10 and the lower part 20. In the illustrated embodiment, the hydraulic actuator 30 is designed with a hydraulic chamber or a cylinder that is arranged or formed in a housing or base body 31. A piston 32 is displaceably mounted in the cylinder. The piston 32 is displaceable along the longitudinal extent of the cylinder and is fastened to a piston rod 33 that protrudes from the housing or base body 31. The piston 32 divides the cylinder into chambers that are fluidly connected to one another via at least one hydraulic line. The base body 31 or the housing can be pivotally mounted on the lower part 20 at a fastening point 23 in order to prevent canting of the piston 32 during a pivoting movement of the upper part 10 relative to the lower part 20.The end of the piston rod 33 facing away from the piston 32 is attached to the upper part 10, in the illustrated embodiment to an extension arm to increase the distance from the pivot axis 15, at an upper attachment point 21. During flexion, the piston 32 is pressed downward, so that the volume of an extension chamber decreases. Correspondingly, the volume of a flexion chamber increases, reduced by the volume of the retracting piston rod 33. An electric motor 36 can be arranged in or on the housing 31 to generate pressure within one of the chambers. This motor drives a pump 37 to apply pressure to the hydraulic fluid within one of the two chambers and thereby move the piston 32 within the cylinder in one direction or the other. This causes a flexion movement or, in particular, an extension movement of the orthopedic device in the form of the prosthetic leg.The electric motor 36 for driving the pump 37 is an option that can be used in one embodiment in combination with the linear damper. An alternative design of the actuator provides a rotary hydraulic system or an electric motor, e.g., with a gear, instead of a linear hydraulic system. A combination of several of the aforementioned actuators in conjunction with passive resistance devices is also implemented in one embodiment.

[0051] Arranged within or on the housing 31 is an adjustment drive 34, which is coupled to at least one control valve 35, via which the hydraulic resistance in the linear hydraulic system 30 can be varied if the resistance is to be controlled during use via hydraulic damping. The adjustment drive 34, like the entire actuator 30 with the motor 36, is coupled to a control device 40, which, based on sensor values, activates, deactivates, or modulates the actuator 30, and in particular the motor 36 and the adjustment drive 34, in order to provide adapted resistance and hydraulic support for an extension movement and, if necessary, a flexion movement.If the resistance device is not designed as a hydraulic damper but as a magnetorheological resistance device, the change in the resistances is not achieved by adjusting valves 35, but by activating, deactivating or modulating a magnetic field, the adjustment drive 34 is then the electromagnet or the magnetic coil.

[0052] At least one sensor 50 for detecting the spatial orientation of the lower part 20 and the upper part 10, respectively, is arranged on both the upper part 10 and the lower part 20. In particular, the sensor 50 for detecting the spatial orientation is arranged only on the upper part 10. This sensor 50, which can be designed, for example, as an IMU (inertial measurement unit), is used to determine the solid angle or the absolute angle to a fixed spatial orientation, for example, the direction of gravity, during use of the prosthetic knee joint or the orthotic knee joint. Instead of being designed as an IMU for detecting spatial positions, the sensor 50 can also detect other status data, in particular status data relating to the artificial knee joint. Another sensor 50 is schematically shown as a hexagon and is designed as a human-machine interface (MMI) sensor for recording human biosignals.When used in a prosthesis, this is preferably attached to the upper part 10 in order to interact with the body. When designed as an orthosis, the MMI sensor can also be arranged on other components. In principle, an MMI sensor can also be attached separately to the body and wirelessly coupled to the control device 40, e.g., via a radio connection. The status data recorded includes, in particular, positions, angular positions, speeds, accelerations, forces, moments, as well as their progressions or changes. The determined solid angle of the upper part 10 and / or the lower part 20 or another status variable is compared with a threshold angle.When a threshold value stored in a controller 40 for the respective sensor value or a variable derived therefrom is reached or exceeded, the adjustment drive 34 and / or the motor 36 is modulated, activated or deactivated in order to change the flow resistance in the hydraulic system and the support force in the extension direction by the motor 36 and the pump 37 in the actuator 30 in the design as a hydraulic actuator, the viscosity in a magnetorheological design and the drive torque or the braking force in an electromechanical drive.

[0053] The actuator 30 in an artificial knee joint serves to modulate a flexion movement and an extension movement in order to generate or support an appropriate or desired movement sequence. An extension movement is supported if necessary and advantageously decelerated shortly before reaching maximum extension to avoid a hard stop. In order to be able to drive the actuator 30, in particular the motor 36 and, if applicable, the adjustment drive 34, an energy storage device, in particular in the form of an accumulator, is also assigned to the actuator 30. The energy storage device can be arranged directly next to the actuator 30 or at another location in the orthopedic device where more space is available or where this appears advantageous due to the weight distribution.

[0054] One difference between the embodiment according to Figure 1 and the embodiment according to Figure 2 is that, according to Figure 2, an electromechanical drive with a motor 36 is provided, in which the electric motor 36 can apply a torque between the upper and lower parts, if necessary via a gear, in particular a force-locking or form-locking traction mechanism. Depending on the direction of rotation of the motor 36, flexion or extension of the knee joint can then be effected or supported via, for example, a V-belt or toothed belt and pulleys. The embodiment with the drive with an electric motor 36 via a mechanical power transmission device and parallel damping via a hydraulic damper can also be used in a prosthetic knee joint. As already explained in relation to Figure 1, the resistance device in an orthosis can also be embodied by a motor, e.g. in generator mode.

[0055] The direct mechanical coupling of the electric motor 36 as part of the actuator 30 to the upper part 10 and the lower part 20 can be achieved via a power transmission device, for example via a spindle drive, so that instead of a piston rod 33, a spindle is retracted or extended from the housing 31 by turning a spindle nut driven by the electric motor. Alternatively, the spindle can be coupled to the motor and move the spindle nut translationally and support a bending and / or stretching movement. In another embodiment, the motor 36 is coupled to the upper part 10 and the lower part 20 via a gear device, for example via a planetary gear, in order to effect or decelerate a displacement of the upper part 10 relative to the lower part 20. The gear device can have a variable transmission ratio.

[0056] Furthermore, the prosthesis or orthosis is provided with a control device 40 and at least one angle detection device in the form of a sensor 50. The angle detection device 50 detects the angle between the upper part 10 and the lower part 20 and is designed, for example, as a direct angle sensor that detects the angle directly. Alternatively, the angle between the upper part 10 and the lower part 20 can be determined by evaluating the sensor data from two spatial position sensors 50. Both methods can also be used simultaneously or in a complementary manner. All sensors arranged on the prosthesis or orthosis are coupled to a control device 40, and their sensor values ​​serve as the basis for controlling the actuator 30, in particular the motor 36 and the adjustment drive 34 of a resistance device if this is designed as a passive damper, or as input signals for a motor control system.In the case of magnetorheological damping, the sensor values ​​serve to control the magnetic field or its variation. Based on the sensor data, in particular the spatial positions and / or angular positions as well as position data and data on the load, orientation, acceleration, and / or deformation of other components or the MMI 50, the actuator 30 is controlled, for example, to activate, deactivate, or modulate the electric motor 36, to generate or support a relative movement between the upper part 10 and the lower part 20, in particular to apply an extension moment in a controlled manner, but also to reduce or increase a pivoting resistance and / or to limit an end stop.

[0057] Figure 3 schematically shows the movement sequence when walking on an inclined surface. A person fitted with a prosthesis is standing on a surface sloping downwards at an angle of inclination α and places the fitted leg with the prosthesis on the ground. The prosthesis has an upper part 10 and a lower part 20, which are articulated together about a pivot axis 15. A foot part 60 is attached to the lower part 20, which, in the illustrated embodiment, is pivotable about an ankle joint axis 65 in order to be able to perform plantar flexion and / or dorsiflexion. As an alternative to the illustrated embodiment with a prosthesis, an orthosis can also be used as an orthopedic device, in particular a knee-ankle-foot orthosis (KAFO). The illustrated situation comprises the stance phase, which begins at time t0 with the heel strike and ends at time t3 with the toe-off.The stance phase is followed by the swing phase, during which the foot part 60 is in the air and not subjected to any ground reaction force. The heel of the foot part is placed on the ground at time t0 with a straight leg, the knee angle being 0°. Alternatively, the knee joint can be slightly bent, for example 4°. Due to the fact that when walking on a downwardly inclined surface, knee flexion with a knee angle or knee flexion angle greater than 0° is often present throughout the entire movement sequence, with the degree of flexion and the course of the flexion over the stance phase changing with the inclination or the angle of inclination a of the surface, support of an extension movement or extension of the knee joint by an actuator is advantageous. The manner, when and how this support takes place is explained below.

[0058] From the moment the heel touches the ground, plantar flexion of the foot part 60 occurs, combined with knee flexion, so that the knee angle increases. The foot striking phase is associated with the so-called stance phase flexion, during which a load response occurs and weight is shifted from the unsupported leg to the supported leg. At time t1, the foot part 60 is fully placed on the ground and the prosthetic knee joint is flexed. The actuator can control the extent and timing of the stance phase flexion, for example, so that at time t1 an optimal extent of stance phase flexion is permitted for the slope of the ground. The maximum stance phase flexion is particularly greater than when walking on level ground.As the gait cycle continues, the body's center of gravity is moved forward and is located anterior to the ankle joint axis 65 at the end of the terminal stance phase at time t2. When walking on level ground, the knee joint typically extends fully after stance phase flexion, so that the knee joint is in full extension at the end of the terminal stance phase. The knee angle would be 0°. However, due to the incline of the ground, it is advantageous not to extend the knee joint fully after stance phase flexion, but rather to only support or allow partial knee extension, so that the knee joint is still flexed at the end of the terminal stance phase, as shown at time t2. Dorsiflexion is still performed by moving the body's center of gravity forward while the foot part 60 is placed on the ground until the heel lifts off.In the preswing phase, between times t2 and t3, the knee joint flexes again, whereby the flexion movement can be actively supported or decelerated. At the end of the stance phase, as shown at time t3, the knee joint is strongly flexed, whereby greater knee flexion and a larger knee angle can be present than would be the case when walking on level ground. The forefoot or toe area is still in contact with the ground, the heel is raised and the knee joint is flexed. At the end of the stance phase, the swing phase begins, which immediately follows toe-off at time t3. During the swing phase, the knee joint flexes further to ensure sufficient ground clearance. The maximum flexion angle in the swing phase, which is shown at time t4, can in particular be greater than when walking on level ground.

[0059] Figures 4 and 5 show knee moment curves for different ground inclinations from a first initial contact at time t0, through the toe-off at time t1, to a second initial contact at time t2. Curve a) shows the knee angle curve and knee moment curve for walking on a level surface or a surface with a very slight ground incline, curve b) on a surface inclined downwards by 5°, curve c) on a surface inclined downwards by 10°, and curve d) the knee angle curve and knee moment curve on a surface inclined downwards by 15°. The curves are each plotted over the gait cycle and start with the heel strike. The knee angle is 0° in the fully extended position; knee flexion increases the knee angle, so that the knee angle is a knee flexion angle.The knee moment is the so-called internal knee extension moment, which is applied by the actuator and counteracts the external knee moment acting on the knee joint due to the movement and the relative position of the components. An internal knee moment is applied by an actuator and influences a movement or makes it easier or more difficult to initiate a movement.

[0060] The maximum knee flexion angle when walking on level ground, as shown in curve a), is reached in the stance phase between 15% and 20% of the gait cycle. After the initial flexion following heel strike, the knee angle decreases again during the further course of the stride after full foot landing and rollover. Before initiation of the pre-swing at approximately 40% of the gait cycle, the knee joint is fully extended, corresponding to a knee angle of 0°. Subsequently, the pre-swing phase is initiated with renewed flexion until, after toe-off or toe separation at time t1, the swing phase begins at approximately 50% of the gait cycle. With increasing ground slope, the knee no longer reaches full extension before initiation of the pre-swing at 30% to 40% of the gait cycle, and the knee angle no longer reaches 0°. At a ground slope of 15° according to curve d), a plateau of the knee angle occurs at

[0061] 20 - 30% of the gait cycle before further flexion occurs, which corresponds to the preswing phase.

[0062] The internal knee extensor moment when walking on level ground and on surfaces with varying downward inclines is initially increased during stance phase flexion to achieve controlled flexion. The maximum extensor moment is typically reached towards the end of stance phase flexion, a maximum in each case occurring at approximately 15% of the gait cycle. The extensor moment is then reduced again. When walking on level ground and on gentle ramps, up to 5°, for example, the extensor moment is completely reduced during stance phase extension and a flexion moment is subsequently applied to resist knee extension, which is the case at approximately 30% of the gait cycle. With a greater downward incline, the knee extensor moment is advantageously not completely reduced.The preswing phase is advantageously supported on shallow ramp inclines up to, for example, 5° by applying an internal flexion moment, especially at the beginning of the flexion movement. For steep ramp inclines, such as 10° or 15°, resistance to flexion movement is applied during the preswing phase to prevent collapse due to the typically high external flexion moment and to achieve a harmonious swing phase initiation up to toe-off.

[0063] Figure 6 shows knee angle-knee moment curves for level walking a) and downhill walking on a surface with a surface incline of between 5° and 15° with curves b), c) and d). The step starts with the heel strike with a slight forward bend of the knee joint of ~4°. With knee flexion in the example shown, the knee moment and knee angle increase in an almost linear relationship, which corresponds to a spring-like behavior, whereby the relationship or stiffness is similar for all surface inclines. With increasing surface incline, the maximum knee angle in the stance phase flexion increases. The knee joint then extends again when walking on level ground and on inclines up to 10°. With increasing surface steepness, both the extent of stance phase extension and the internal flexion moment at the end of stance phase extension are reduced. At a 10° incline, no more flexion moment is generated; at a 15° incline, the internal extension moment is reduced from approx.30° knee angle is reduced, and there is no extension, but essentially a plateau phase in the knee angle. The area under the curve between initial contact and knee brake increases with increasing ground steepness, which corresponds to an increasing dissipative effect. The maximum knee angle in the swing phase also increases with ground slope.

[0064] During the physiological movement sequence of walking on level ground, the knee joint performs stance phase flexion and extension, returning to almost full extension in the terminal stance phase. On downwardly inclined surfaces, the extent of stance phase flexion increases and the knee joint is no longer brought into full extension. Above a certain incline, extension no longer occurs, but rather a short plateau phase or a continuously flexed knee angle profile ensues. To implement such movement sequences on different surface inclines in a prosthetic knee joint or orthotic knee joint, it is necessary to actively support stance phase extension, which requires an active knee joint with a drive and / or a force storage device.The internal knee moment, which is applied by the drive such as the motor and / or energy storage, is adapted to the respective gait situation and the course of the gait cycle depending on the inclination of the ground.

[0065] The ground inclination can be determined via path integration, segment angles, e.g. foot angle, thigh angle or lower leg angle, the course of segment angles to each other, relative angles, e.g. ankle, knee and / or hip angles, the COP course, in particular in combination with the foot or lower leg angle, the ground reaction force or components thereof, joint moments and / or normal distances of the ground reaction force around joint axes or reference points, environmental sensors, in particular radar or lidar, the movement of the contralateral leg, in particular in relation to the ipsilateral side and the like.

[0066] The subgrade slope can be determined quantitatively, e.g., as a class or as a value in %; however, indicators that correlate with the subgrade slope can also be used. The subgrade slope can be the local slope of the subgrade below the supporting foot or a height difference between two points, e.g., between the positions of the foot at two consecutive initial contacts.

[0067] Alternatively or additionally, it is possible that the ground slope is not explicitly determined, but rather that control is based on sensor values ​​such as segment angle, joint angle, moment, and force curves, and the relationship with the ground slope arises from the interaction between the user, the prosthesis control, and the ground. The COP, the knee lever, the lower leg angle, the thigh angle, the leg tendon angle, or even the knee angle are particularly suitable for this purpose. Time derivatives of any order or partial derivatives, e.g., changes in the lower leg angle depending on changes in the thigh angle, of these variables can also be used for control.

[0068] In one embodiment, a knee extension moment in the stance phase flexion is initially increased with knee flexion, for example in a linear relationship, which corresponds to a springy effect. When walking on level ground and on very slight ground inclines, this behavior can be sufficient to stop a flexion movement and initiate an extension movement. The maximum knee flexion angle is a consequence of the knee moment characteristics and the load profile as well as the rolling over the prosthesis. As the ground incline increases, the heel acts for longer and the forefoot for later, whereby the knee joint flexes more strongly while the knee angle and knee moment remain the same. As the ground incline increases further, the knee extension moment is no longer increased or is even reduced by the control system with increasing knee flexion from a certain point in time, e.g. when a certain knee angle is reached.This makes it possible for the knee joint to flex further. In this case, the knee extension moment no longer follows a linear elastic characteristic surface. Knee extension is then achieved, for example, as soon as the person using the exercise initiates sufficiently high hip extension or the COP is far enough anterior during the rolling movement. When walking on level ground or on a very gentle incline of up to approx. 10°, extension is initially actively supported and then decelerated towards the end. Deceleration in the late stance phase extension is necessary because an external knee extension moment is typically generated by the forefoot. Without controlled deceleration, the knee joint would snap into the extension stop. The extension knee moment is thereby continuously reduced in the stance phase with extension, e.g. in a linear relationship.Active extension and braking can, for example, occur in such a way that the lower leg remains virtually still during extension or does not rotate too far forward or backward. It is also possible to control knee extension in such a way that rolling over the forefoot takes place in a particularly favorable manner, whereby the mechanical properties of a spring made of fiber-reinforced plastic, e.g. carbon springs in prosthetic feet or orthoses, can be optimally utilized. After full or partial extension, the swing phase can be released or the swing phase can be actively initiated by the control system. As the ground gradient increases, the braking flexion moment is continually reduced until the knee joint no longer generates any internal flexion moment in the terminal stance phase.On steep ground slopes, an external flexion moment acts during the terminal stance phase, and the knee joint begins to flex as soon as the internally applied extension moment is less than the external flexion moment. Flexion initiation can be achieved by a corresponding reduction of the extension moment, with the user being able to influence this themselves via the hip moment.

[0069] It may be necessary to apply very high resistance to stance phase extension or even to completely stop it, for example, by means of a lock. A flexion moment generated by the actuator can already provide such resistance. Alternatively or additionally, an extension resistance or a lock on extension can also be applied using hydraulics or similar means.

[0070] In one embodiment, a supporting flexion moment in the pre-swing, which serves to support the swing phase, is reduced as the ground slope increases, and if necessary, resistance is applied to the flexion movement as the ground slope increases further. While walking on level ground requires overcoming the resistance of the forefoot or an external extension moment to initiate the swing phase, which can be facilitated by a flexion moment in the knee, this effect decreases as the ground slope increases. This is because the COP only moves from the heel to the forefoot at larger knee angles or a greater forward tilt of the lower leg, and the knee axis is already very far anterior at this point.If the knee joint is not fully extended in the terminal stance phase with increasing ground steepness, the knee joint axis will be far anterior even in the late stance phase, and the knee joint will begin to flex due to body weight alone as the internal extension moment is reduced. If an additional flexion moment were to be applied in this case, the prosthesis or orthosis would collapse beneath the body. Accordingly, the internal flexion moment is reduced as the ground steepness increases, and flexion in the pre-swing period is even resisted. For example, an active swing phase initiation when walking on level ground can be reduced initially, and then a strategy similar to the "swing on ramps" function can be applied. The transitions are advantageously smooth.

[0071] In one embodiment, a mechatronic foot is used together with the knee, for example a combined knee-ankle prosthesis or a KAFO. The ankle joint can be passive without a drive, active with a drive, or semi-active with an adjustment device, e.g. for adjusting the ankle angle in the unloaded or lightly loaded state. The foot can allow plantar flexion in response to loading in order to achieve an earlier foot flat. With increasing ground gradient, the extent of plantar flexion can be increased. The control is based on the determined ground gradient. Increasing plantar flexion can also be achieved by reducing plantar flexion resistance with increasing ground gradient or by controlling plantar flexion depending on the ground reaction force or the lower leg angle.Faster or stronger plantar flexion reduces the duration and magnitude of the external knee flexion moment in the load response and has a less powerful driving effect. In one embodiment, the flexion and extension behavior is controlled in such a way that a harmonious trajectory of the hip or torso is achieved, for example, a uniform lowering and a uniform forward progression. The hip position in relation to the foot and its course can be estimated in the stance phase, for example, via the leg tendon, in particular via its length and orientation. It is advantageous if the hip is neither raised nor lowered too much during the stance phase. A good trajectory runs parallel to the ground, for example, and thus depends on the incline of the ground.If knee flexion is stopped too early, the extension moment is increased too quickly, or knee extension is initiated too early, the body is decelerated and feels "levered out," which is perceived as unpleasant. Excessive extension at the end of the stance phase extension, for example, full extension on steep inclines, also leads to the body sinking less harmoniously, and the user feels as if the hip is being hyperextended or that the posterior edge of the socket is pressing uncomfortably into the residual limb.

[0072] In one embodiment, the flexion and extension behavior is controlled as a function of the ground reaction force in relation to one or more preserved body parts, in particular as a function of the estimated hip moment or shaft tipping moment. Analogous to harmonic sinking, the hip moment or tipping moment should be as harmonious as possible. The internal, knee-extending moment can influence the ground reaction force vector so that it is tilted further forwards or backwards and the external moment acting on the hip joint or shaft can be influenced. For example, an extension moment in the knee during stance phase flexion can initially be increased with increasing knee angle. If it is determined later that the hip flexion moment is too low or the hip extension moment is too high, the extension moment can be increased less or even reduced. The same applies to the shaft tipping moment.Alternatively or additionally, forces and / or moments between the stump and the shaft can also be determined directly via sensors and used for control purposes.

[0073] In one embodiment, the maximum knee angle in the swing phase increases with increasing ground slope. When walking on level ground, the knee joint is fully extended in the terminal stance phase. From this position, the knee joint flexes under load, which corresponds to the pre-swing or forward swing phase, and swings to a maximum knee angle of approximately 65° after the toe-off. The extent of knee flexion can be influenced and controlled via the knee flexion moment and knee extension moment in the pre-swing and / or swing phase. As the ground slope increases, the knee joint is no longer fully extended in the terminal stance phase, but the pre-swing occurs from an already flexed position. At the same time, the toe-off shifts to higher knee angles.In order to ensure sufficient ground clearance at the time of toe-off even with high knee angles, it is advantageous to increase the maximum knee angle in the swing phase as the ground slope increases, for example by reducing the extension moment in the swing phase. The maximum swing phase angle can also be determined by the knee angle, the knee angular velocity or other variables at the time of toe-off. The swing phase flexion can also be controlled in such a way that the relative extent of swing phase flexion from toe-off to the reversal of movement from flexion to extension is reduced as the ground slope increases. In combination with a larger knee angle at toe-off, a higher maximum knee angle in the swing phase can still result. On very steep surfaces, knee extension can occur immediately after toe-off. Swing phase extension can be delayed if necessary.be supported by an extension moment to ensure that the knee joint is sufficiently extended before the following initial contact.

[0074] Extension and / or bending moments can be applied via resistance devices such as dampers, brakes, magnets, and the like. Moments can also be generated via energy storage devices such as springs, hydraulics, pneumatics, or other elastic elements, or via active actuators that perform work, such as motors, spindle drives, or the like. A combination of passive and active components is also possible, e.g., a damper with a motor; a damper with an energy storage device and a motor; or a damper with an energy storage device.

[0075] For example, the extension moment in the stance phase can be applied by a spring that is tensioned during stance flexion and relaxes during extension. The movement behavior can be additionally controlled by dissipative elements arranged in parallel and / or series. In a spring-accumulator hydraulic system, a hydraulic resistance can act in parallel or in series. A parallel resistance can apply a higher torque than via the spring alone, with some of the energy being dissipated. A series-acting resistance, in particular a bypass, can reduce the torque and the spring accumulator can be charged or discharged less. For example, in a stance phase flexion, a spring can initially be tensioned and then, for example during particularly high knee flexion, the extension resistance can be limited or even reduced by a bypass valve, even though further knee flexion is taking place.A bypass valve can also be open throughout the entire flexion and / or extension movement, dissipating some of the kinetic energy. The torque can also be modulated via a parallel active actuator, for example, by applying a torque in the same direction as or opposite to the energy storage.

[0076] In one embodiment, the prosthesis or orthosis can be controlled via a human-machine interface (HMI), e.g. via EMG. The HMI makes it possible to intentionally influence the behavior of the prosthesis. Intuitive, unconscious control is also possible via such an HMI. A wide variety of properties can be changed via the HMI, such as torque, damping, stiffness, and the like. In conjunction with a control system for walking downhill on a surface, different aspects of the movement sequence can be influenced via the HMI. For example, depending on the control via the HMI, the extent of stance phase flexion or the resistance to stance phase flexion can be influenced. For example, the extent of support for the extension movement or the duration of the extension movement until the initiation of the pre-swing can also be influenced.In a simple design, control is achieved via one or two electrodes placed on the front and, if applicable, the back of the thigh. The behavior of the prosthesis or orthosis is modulated by the muscle tension of one or both muscles. For example, a stronger or longer contraction of the quadriceps during the stance phase can produce a higher or longer-acting extension moment in the knee. In particular, the time of an increase or decrease in torque can be determined via muscle tension. The time of modulation can usually be determined very well by the user via a contraction, whereas precise and reproducible modulation of the tension intensity is frequently not possible, at least not in an untrained state.Alternatively or additionally, variables that correlate with the ground slope can be derived via the HMI, which can then be used to control the system depending on the ground slope. For example, muscle and / or nerve signals can be recorded, such variables can be derived using classification or artificial intelligence methods, and the actuator control can be adapted to the ground slope.

[0077] Alternatively or in addition, the control approaches described above can also be applied on downward slopes that are not level, such as steps or ledges. Here, too, a flexion movement in the stance phase can be followed by partial extension before the pre-swing and swing phases begin.

[0078] Figure 7 shows knee angle curves in the stance phase from initial contact to toe-off for two different ground inclinations cd and a2 > cd . After initial contact, stance phase flexion is permitted up to the knee flexion angle cpK,max, which is the case for the ground inclination cd at time t1. The maximum knee flexion angle increases with increasing ground inclination. The larger knee flexion angle at greater ground inclination lowers the body more, which is advantageous for the movement sequence. With greater ground inclinations, faster knee flexion can also be permitted, as shown in the figure. After stance phase flexion, partial stance phase extension up to the angle cpK,min is induced or permitted, which is the case for the ground inclination cd at time t2. The swing phase initiation then follows.The relative knee extension AcpK is the difference between the maximum knee angle cpK,max and the minimum knee angle (pK,min). Both the relative knee extension and the minimum achievable or achieved knee angle can be adjusted depending on the ground slope. With the greater ground slope a2 in the example shown, there is both a lower relative extension and a lower absolute extension, so that the minimum knee angle before swing phase initiation is greater than with the lower ground slope cd. The lower knee extension with increasing ground slope is advantageous in order to lower the body further on steeper ground or to raise it less sharply, whereas the body's center of gravity is lowered less sharply on flatter ground slopes.

[0079] Figure 8 shows knee angle curves in the stance phase from initial contact to toe-off for two different ground inclinations cd and a2 > cd . At the lower ground inclination cd, after stance phase flexion, partial stance phase extension is induced before swing phase initiation is permitted or induced. The extension movement can be partially assisted by the actuator and / or the extension movement can be resisted. At the greater ground inclination, which corresponds to a steep ramp, for example with a 10° incline, maximum stance phase flexion is achieved and subsequently swing phase initiation is permitted or induced without stance phase extension occurring. On steep ramps, stance phase extension would lead to an unpleasant lifting of the body.Because the knee joint is not extended during the stance phase, an external flexion moment typically acts on the knee joint throughout the entire stance phase. In this case, the swing phase can be initiated by reducing the flexion resistance or the extension moment. Stance phase extension can also be prevented by a flexion moment or by blocking the extension movement, even if an external extension moment is acting. Furthermore, instead of the plateau phase shown, it is possible to temporarily slow down the stance phase flexion or to allow a continuous flexion movement, which is not shown in Figure 8. These two control variants can be applied as the ground slope continues to increase.

[0080] Figure 9 shows knee angle progressions from swing phase initiation to the terminal swing phase before initial contact for two different ground inclinations cd and a2 > cd . With increasing ground inclination, a higher maximum swing phase angle cpK,max is achieved or permitted. In the example shown, a faster swing phase extension is also achieved in order not to increase the overall duration of the swing phase despite the larger maximum knee angle in the swing phase and to bring the knee joint into sufficient extension in time before initial contact, which in the example shown corresponds to a slightly bent knee position.

[0081] Figure 10 shows knee moment curves from initial contact to the end of the terminal stance phase for two different ground inclinations cd and a2 > c . In the example shown, no moment is generated at the time of initial contact. Only when the knee joint flexes in the stance phase flexion is the internal extension moment TK applied by the actuator increased. The extension moment influences the knee flexion speed and the maximum achieved knee angle in the stance phase flexion. After a maximum extension moment iK,max is reached, the extension moment is reduced again. With a low ground inclination cd, it is advantageous to apply a lower maximum knee extension moment than with a steeper ground inclination a2, especially in combination with an increase in the achievable knee flexion angle in the stance phase with increasing ground inclination.The temporal progression of the internal extensor moment can also be varied with the slope of the ground. For example, an extensor moment can be increased or reduced more quickly with a steeper slope, as shown in the example. As the slope of the ground increases, the external knee flexion moment typically lasts longer, partly because the point of application of force moves further towards the middle of the foot. A greater knee flexion angle can also lead to a greater knee flexion moment, since the knee axis is further anterior with a greater knee flexion angle and the lever arm for the ground reaction force is increased. Last but not least, with a steeper slope of the ground, the greater difference in height from step to step can result in a greater impact when transferring body weight to the affected side, which can also lead to a greater external flexion moment.By increasing the internal extension moment with increasing ground inclination, the increasing external flexion moment can be counteracted and a harmonious knee flexion behavior can be achieved during the stance phase. As the leg rolls over, the internal extension moment is advantageously reduced again, particularly in correlation with the ground inclination. In the example shown, for the low ground inclination cd, the extension moment is completely reduced, followed by a flexion moment, whereas for the greater ground inclination a2, the knee extension moment is only partially reduced.The reduction of the knee extension moment and, if necessary, the application of a flexion moment, for example a resistance to knee extension, is carried out in particular in such a way that a maximum knee flexion angle is not exceeded in the stance phase, partial extension of the knee joint is achieved and / or a harmonious knee movement is achieved, in particular a rapid snapping of the knee joint in the extension direction is prevented.

[0082] Figure 11 shows two further knee moment curves from initial contact to the end of the terminal stance phase for two different ground inclinations cd and a2 > cd . The extension moment iK is reduced after the maximum extension moment has been reached at time t1 and a knee flexion moment is subsequently applied, which is shown as a negative moment TK. The knee flexion moment initially acts as resistance to an extension movement in the stance phase extension and leads to the initiation of the swing phase from time t2. The knee flexion moment is negatively correlated with the ground inclination, so that for a low ground inclination cd a higher resistance to the extension movement and / or a higher support of the flexion movement is applied in the preswing phase than for a greater ground inclination a2. During the preswing phase the flexion moment is advantageously reduced again and, if necessary, resistance is also applied to the flexion movement.As the ground slope increases, the temporal progression of the moment applied by the actuator can be adjusted, in particular, the flexion moment in the preswing phase can be reduced earlier. As the ground slope increases, the external extension moment at the end of the swing phase typically decreases. By reducing the flexion moment in the late stance and preswing phases with increasing ground slope, a particularly harmonious movement progression and harmonious swing phase support can be achieved, in particular, partial stance phase extension can be achieved and an abrupt initiation of the swing phase can be prevented on steeper ground slopes.

[0083] Figure 12 shows two further knee moment curves from initial contact to the end of the stance phase for two different ground inclinations cd and a2 > c . With a shallow ground inclination cd, the extension moment TK is completely reduced after reaching an initial maximum during stance phase extension, and a flexion moment is generated subsequently. The applied flexion moment initiates the swing phase at time t2, which is actively supported in an initial phase, i.e. work is performed by the actuator. In contrast, for a steeper ground inclination a2, the swing phase initiation is not actively supported by a flexion moment, but rather the swing phase initiation is achieved by reducing the extension moment, particularly in combination with a larger knee flexion angle at the end of the terminal stance phase. The swing phase initiation occurs at time t2, as soon as the external flexion moment exceeds the internal extension moment.In the preswing phase, knee flexion is particularly resisted. While it is beneficial to actively support the initiation of the swing phase on flat ground slopes, it is more beneficial to initiate the swing phase against resistance on steeper ground slopes. This allows the ipsilateral side to be loaded for longer, the impact on the contralateral side upon initial contact is reduced, and a harmonious movement pattern is achieved. Supporting the swing phase to the extent that is required on a flat ground slope or when walking on level ground would lead to an abrupt flexion of the knee joint and a sinking of the body, as well as an inevitable premature transfer of weight to the contralateral side.

[0084] Figure 13 shows two knee moment curves during the stance phase, plotted against the knee angle for two different ground inclinations. The left-hand illustration shows the curve for a first ground inclination cd, the right-hand illustration for a greater ground inclination a2. The internal extension moment applied by the actuator corresponds to a positive moment TK, and a flexed knee joint to a positive knee angle cpK. The extension moment is increased during the stance phase flexion and reduced again during the stance phase extension, in each case from time t1 to t2. In one embodiment, the work performed on the actuator, shown as hatched areas, increases during the stance phase flexion and extension with increasing ground inclination. Alternatively or additionally, the power absorbed by the actuator increases with increasing ground inclination.This is achieved in particular by reducing the extension moment in stance phase extension compared to that in stance phase flexion for the same knee angle, particularly in conjunction with a higher maximum flexion angle and / or a higher flexion angle at the end of the terminal stance phase. The work performed on the actuator can be converted into electrical energy and / or heat, for example. When walking downhill, the body's potential energy must be dissipated step by step. Typically, the difference in the body's potential energy per step increases with increasing ground gradient. Accordingly, it is advantageous to increase the energy recuperated and / or dissipated by the actuator as the ground gradient increases.

[0085] In one embodiment, a spring accumulator is arranged in relation to a resistance device in such a way that the resistance device can change the zero point of the spring accumulator in relation to the knee angle. The spring accumulator is arranged in particular in series with the resistance device and the zero point is shifted towards a larger knee angle during the stance phase flexion and / or extension, wherein the shift of the zero point increases in particular with increasing ground gradient. The spring accumulator can, for example, be designed as a fluid spring and the resistance device as a hydraulic resistance with at least one controllable throttle valve, which act in series with one another. The throttle valve can be designed in such a way that a lock can be achieved. When the knee joint is flexed, energy is transferred to the spring accumulator by compressing the fluid. The spring accumulator generates an internal extension moment.When the knee joint is extended, energy is again drawn from the spring actuator. Depending on the hydraulic resistance, which can be adjusted using the throttle, the zero point of the spring actuator shifts during the flexion and extension movement. For example, the zero point of the spring actuator may be at a knee angle of 4° before the flexion movement and increase to a knee angle of 15° during the flexion and extension movement due to a set resistance of the throttle. Energy is dissipated through the throttle effect. The hydraulic resistance and its temporal change can thus control the work performed on the actuator, and the extent of knee extension can also be influenced by shifting the zero point.The resistance device can also be designed as an electromechanical actuator, for example, as a motor or spindle drive, whereby the zero point of the spring-loaded device can be changed by controlling the electromechanical actuator. The energy performed by the electromechanical actuator can, in particular, be recuperated and fed into an accumulator.

[0086] Figure 14 shows two further knee moment curves in the preswing phase, plotted against the knee angle for two different ground inclinations. The left-hand illustration shows the curve for a first ground inclination cd , the right-hand illustration for a greater ground inclination a2. In the curves shown, the actuator generates a flexion moment in the preswing phase, which in the illustrations corresponds to a negative moment TK, whereby the initiation of the swing phase is actively supported. The flexion moment is reduced in particular with increasing knee angle and, if necessary, resistance to flexion is applied. In one embodiment, the work performed by the actuator in the preswing phase, which is shown in each case as a hatched area, is negatively correlated with the ground inclination. This can occur in particular together with an increase in the knee angle at the end of the terminal stance phase with increasing ground inclination.A reduction in the work performed is achieved primarily by reducing the maximum bending moment and / or reducing the bending moment earlier. Alternatively or additionally, the power generated by the actuator is reduced with increasing ground gradient. As the ground gradient increases, more energy must be absorbed by the actuator. It is advantageous to reduce the energy input in the preswing phase as the ramp gradient increases.

[0087] Figure 15 shows two further knee moment curves in the preswing phase versus the knee angle for two different ground inclinations cd and a2 > c . In the illustrations, in the preswing phase the actuator applies an extension moment, which corresponds to a positive moment TK, against a flexion movement. Such control is particularly advantageous on steep ramp inclines, where the application of a flexion moment would lead to a rapid collapse of the knee joint beneath the body, particularly in combination with only partial or no knee extension in the stance phase. In one embodiment, the work performed on the actuator in the preswing phase, which is shown as hatched areas, is positively correlated with the ramp inclination. The work performed on the actuator can be increased by applying a higher extension moment or by reducing the extension moment later.Such a control allows more energy to be absorbed by the actuator on steep ground slopes.

[0088] Starting from a very flat ground slope, the work performed by the actuator in the preswing phase can initially be reduced as the ground slope increases, and as the slope increases further, the work performed on the actuator can be increased.

[0089] Figure 16 shows different arrangements of an energy storage device 39 together with a resistance device 38 in the actuator 30, which is arranged between the upper part 10 and the lower part 20. Mechanical and fluid-mechanical energy storage devices enable particularly efficient storage and release of energy during the movement sequence. As shown, the spring-loaded device 39 and the resistance device 38 are part of the actuator 30 and are interconnected in the actuator so that both components can contribute to the work performed by the actuator. Depending on the arrangement, the force and / or energy flow can vary. The resistance device 38 can be either a purely dissipative device, such as a hydraulic damper, or an electromechanical actuator that can both decelerate and assist a movement.In the middle, a design is shown in which the resistance device 38 and the energy storage device 39 are arranged such that, when the upper and lower parts are stationary, energy can be exchanged between the resistance device and the energy storage device, in particular through a serial arrangement. For example, a spring element and an electromechanical drive can be arranged in series between the upper and lower parts. The movement of the electromechanical drive can compress or stretch the spring element. With such an arrangement, it is possible to control the pivoting between the upper and lower parts as well as the moment between the upper and lower parts and to enable harmonious downhill walking on inclined surfaces. Alternatively or additionally, in one design, the energy storage device 39 and the resistance device 38 can be arranged parallel to one another, as shown in the lower illustration.For example, a spring accumulator and a controllable throttle valve can be installed one behind the other in a hydraulic circuit of a hydraulic damper, so that the hydraulic fluid also flows through the throttle valve when flowing into the spring accumulator and / or out of the spring accumulator. Such an arrangement makes it possible to influence and harmoniously control the pivoting movement between the upper and lower parts, particularly for descending ramps. In addition to the resistance device 38 and the energy accumulator 39, further components and / or multiple energy accumulators 39 and / or resistance devices 38 can also be installed in the actuator 30. For example, a spring accumulator and a throttle valve can be arranged in a hydraulic damper such that they act in series with one another, while an electromechanical drive acts parallel to the hydraulic damper.

Claims

Patent claims 1. A method for controlling an artificial knee joint with an upper part (10) and a lower part (20) which are pivotally mounted to one another about a pivot axis (15), with an actuator (30) which is coupled to the upper part (10) and the lower part (20) and influences a state of movement of the upper part (10) and / or the lower part (20), wherein the actuator (30) is coupled to a control device (40) which is coupled to at least one sensor (50) and activates, deactivates or modulates the actuator (30) on the basis of sensor values ​​from the at least one sensor (50), characterized in that when walking on a downwardly inclined surface, a resistance is offered to a stance phase flexion after an initial contact and a stance phase extension is assisted by the actuator (30) depending on the surface inclination (a).

2. Method according to claim 1, characterized in that the support of the stance phase extension is negatively correlated with the ground inclination (a).

3. Method according to claim 1 or 2, characterized in that up to a limit value of the ground inclination (a) the support is positively correlated with a maximum stance phase flexion angle.

4. Method according to one of the preceding claims, characterized in that the support is reduced during a stance phase extension.

5. Method according to one of the preceding claims, characterized in that a swing phase initiation is supported by the actuator (30) as a function of the ground inclination (a).

6. Method according to claim 4, characterized in that the swing phase initiation is supported before reaching an extension stop.

7. Method according to one of the preceding claims, characterized in that the resistance to the stance phase flexion is adjusted as a function of the ground inclination (a).

8. Method according to one of the preceding claims, characterized in that the achievable stance phase flexion angle is changed in a positive correlation with the ground inclination (a).

9. Method according to one of the preceding claims, characterized in that the maximum pivoting angle of the lower part (20) in the swing phase is adjusted depending on the ground inclination (a).

10. Method according to one of the preceding claims, characterized in that an extension resistance is adjusted depending on the ground inclination (a).

11. Method according to one of the preceding claims, characterized in that the ground inclination (a) is determined via a path integration, segment angle, segment angle curves, the ground reaction force, the COP curve and / or an environmental sensor system.

12. Method according to one of the preceding claims, characterized in that the ground slope (a) is determined as the local slope below the lower part (20) or a height difference between two points spaced apart from one another in the direction of travel.

13. Method according to one of the preceding claims, characterized in that a prosthetic foot (60) is articulated on the lower part (20). is mounted and a maximum plantar flexion angle of the prosthetic foot is adjusted depending on the ground inclination (a).

14. Method according to one of the preceding claims, characterized in that the actuator (30) has a drive and / or energy storage device and a passive resistance device.

15. Method according to one of the preceding claims, characterized in that the actuator (30) is coupled to an HMI and is activated, deactivated or modulated on the basis of biosignals.

16. Method according to one of the preceding claims, characterized in that the maximum flexion angle in the swing phase is changed in a positively correlated manner with the ground inclination (a).

17. Method according to one of the preceding claims, characterized in that a maximum achievable stance phase extension angle is positively correlated with the ground inclination (a).

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