Method for controlling an orthopaedic joint device

Abstract

The invention relates to a method for controlling an orthopedic knee joint device comprising an upper part (10), a lower part (20), and a foot part (25) secured thereto, wherein at least the upper part (10) and the lower part (20) are pivotally mounted in an articulated manner relative to each other about a pivot axis (15), comprising an actuator (30) which is coupled to the upper part (10) and to the lower part (20) and influences a pivoting movement. The actuator (30) is coupled to a controller (40) which is coupled to at least one sensor (50) and activates, deactivates, or modulates the actuator (30) on the basis of sensor values of the at least one sensor (50). A movement of the foot part (25) is detected by detecting and analyzing a linear acceleration and / or change in position of the upper part (10), the lower part (20), and / or the foot part (25), and a flexion resistance in a swing phase or during a loading response of the foot part (25) is modified in comparison to a starting state prior to the movement.

Description

[0001] Method for controlling an orthopaedic joint device

[0002] The invention relates to a method for controlling an orthopaedic knee joint device having an upper part and a lower part and a lower part fastened thereto, wherein the upper part and the lower part 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 pivoting movement, 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.

[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 system so that, depending on sensor data, a modified damping can be provided in the direction of flexion and / or extension. It is also known to assign energy storage devices to the upper or lower part so that movement support can be provided by releasing the stored energy from the energy storage device. Prostheses replace a missing or no longer present limb and serve to provide functionality that is as close as possible to the functionality of the natural limb. In addition, prostheses serve to provide the most natural appearance possible for the prosthetic user. A prosthetic upper part is designed, for example, as a prosthetic socket or as a component attached to a prosthetic socket, where the prosthetic socket serves to secure it to a limb or a limb stump.The prosthetic joint, for example a prosthetic knee joint, connects the upper part with a lower part, which in turn can have further prosthetic components, for example a lower leg tube or a prosthetic foot.

[0004] 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 exhibits very low resistance in an open state, for example, when no valves are closed or throttles are activated. The operating range of such an orthosis or prosthesis is limited in that no energy can be directed into the movement to support it, actively counteract it, or initiate a change from a static state.

[0005] In addition, orthoses, exoskeletons, and prostheses with motorized drives are known from the state of the art. These are so-called active orthoses or prostheses, in which a movement is initiated, assisted, or decelerated by activating, deactivating, or modulating the drive. For this purpose, stored electrical energy from a battery or accumulator is converted into the actuator. The motorized drives also serve to influence the movement behavior between the components of the orthosis or prosthesis, for example, to decelerate a pivoting movement. Motorized drives can be operated in braking mode or as part of a generator circuit.

[0006] 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 the state of movement 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 movement 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 movement 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.

[0007] 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.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.

[0008] 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.

[0009] Prostheses or orthoses controlled by microprocessors adapt to different activities, environmental situations, or movement situations when walking. For example, different control strategies or control sequences are used for walking on level ground, walking down stairs, and walking down ramps. Furthermore, a distinction is made between standing and activities that involve locomotion. In order to achieve optimal support for the user in different situations, it is necessary, or at least advantageous, to be able to provide appropriate behavior from the orthopedic joint device upon initial contact with the limb being treated, i.e., the limb fitted with the orthosis or prosthesis, for example, the desired movement resistance, stiffness, or joint angle.The object of the present invention is therefore to provide a method for controlling an orthopaedic knee joint device with which it is possible to provide an optimal setting even in different and changing movement situations.

[0010] This problem is solved by a method having the features of the main claim. Advantageous embodiments and further developments are disclosed in the subclaims, the description, and the figures.

[0011] The method for controlling an orthopedic joint device with an upper part and a lower part and a foot part fastened to the lower part, wherein at least the upper part and the lower part 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 pivoting movement, 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 a displacement of the foot part is detected by recording and evaluating a linear acceleration and / or a change in position of the upper part, the lower part and / or the foot part and a flexion resistance in a swing phase or during a load response of the foot part is changed compared to an initial state before the displacement.The load response is the phase in a gait cycle or walking movement that includes the heel strike or initial ground contact and continues for up to 12% of a gait cycle or movement. The load response thus extends from the beginning of the stance phase up to approximately 25% of the stance phase, assuming that the stance and swing phases last approximately the same length. Using such a method, it is possible to detect a swing phase without a preceding movement or a movement sequence with a preceding swing phase activation via linear accelerations. This not only detects the swing phase itself, but also allows preparation for the subsequent stance phase to be initiated.Preparation for a change in resistance or position can already occur during the swing phase, allowing a change in resistance or position adjustment in the artificial knee joint of the orthopedic device to occur before landing and before the load response of the foot part. To do this, the actuator is activated, deactivated, or modulated, for example, to reduce resistance to flexion or to adjust a joint angle to improve or adjust the load response.

[0012] In one embodiment, the initial state is standing or, alternatively, a situation other than walking in which the foot part is in contact with the ground. Such a situation other than walking is, for example, sitting, starting a movement such as starting to walk, withdrawing a foot or the like. When the foot part, in particular a prosthetic foot or a foot socket of an orthosis, is in contact with the ground, the actuator should be adjusted, regardless of the preceding movement or the previous state, so that the next stance phase can be recognized as early as possible and an adaptation to the expected load can take place. In particular when standing, i.e. when both feet are on the ground and bearing weight, an adaptation to the expected load in the swing phase or during initial contact after a swing phase is advantageous.

[0013] In one embodiment, the displacement of the foot part comprises a lifting of the foot part, which is detected in particular by a drop in an axial force component in the foot part and / or the lower part, or in which a drop in an axial force component in the foot part and / or the lower part is used at least as part of a criterion for the lifting or the presence of a swing phase. Alternatively or additionally, a vertical acceleration of the foot part and / or the lower part can be determined and used as at least part of a criterion or as the sole criterion for the lifting or the presence of a swing phase and thus for determining that the foot part is being displaced.

[0014] In one embodiment, during the displacement, the resistance to flexion in the swing phase is left unchanged during a lifting phase of the foot part and / or the lower part, and before the foot part is placed on the ground, for example, during a lowering phase of the foot part, the resistance to flexion in the swing phase is reduced. Alternatively or additionally, a joint angle between the upper part and the lower part is adjusted during the swing phase before the foot part is placed on the ground in order to achieve the most favorable orientation of the lower part or the foot part relative to the upper part and, if applicable, the ground.

[0015] In one embodiment, at least one linear acceleration of the upper part, the lower part and / or the foot part is determined by at least one sensor. The linear acceleration can be configured in particular as a vertical acceleration or as a horizontal acceleration. The corresponding sensors enable either a direct acceleration measurement via

[0016] Inertial sensors or allow a determination by converting, for example, deflections with known dimensions.

[0017] In one embodiment, the linear acceleration of the foot part in the walking direction is determined, with a positive acceleration and / or a negative acceleration in the walking direction being used as the linear acceleration. A positive acceleration in the walking direction occurs when the foot part is moved forward with the toe tip and accelerated; a negative acceleration in the walking direction occurs when the foot part is moved backward with the toe tip pointing forward.

[0018] In one embodiment, the linear acceleration is measured at the foot part or calculated from a linear acceleration of the lower part in conjunction with an angular acceleration of the lower part. Alternatively, the linear acceleration can be calculated from a linear acceleration of the upper part in conjunction with a knee angle and an angular acceleration of the lower part.

[0019] One embodiment provides that an ankle moment is detected at the foot part and / or the lower part, and a reduction in the ankle moment is used as a criterion for the presence of lifting or a swing phase. An ankle moment is a resistance that counteracts a displacement of the foot part relative to the lower part about an axis that is essentially orthogonal to the sagittal plane, or causes a pivoting about this axis. If an ankle moment reduction occurs, this can be used as a criterion, or at least part of a criterion, for the presence of a swing phase, since an ankle moment reduction occurs at the end of the stance phase, for example, when the side of the patient not fitted with an orthopedic device, i.e. the unfit side, bears the entire body weight and the fitted side is lifted.This occurs at the end of each step when walking or, for example, when lifting the foot when climbing stairs. If a swing phase is present, it can be assumed that the foot section is being displaced and the flexion resistance can or must be changed compared to an initial state before the displacement. In particular, in conjunction with a vertical acceleration, the lifting of the foot section and the manner in which the foot section is lifted can be detected. The lifting of the foot section can also be detected solely by determining the vertical acceleration of the foot section, i.e. an acceleration against the direction of gravity, and can be used as a criterion for the lifting of the foot section or the presence of a swing phase. Since the foot section is usually permanently coupled to the lower part, the criteria for a reduction in axial force in the foot section or a vertical acceleration in the foot section also apply accordingly to the lower part.

[0020] In one embodiment of the method, when the foot section is moved, the resistance to flexion in the swing phase is left unchanged during a lifting phase, i.e. when the foot section or the lower section is moved upwards against the direction of gravity. Before the foot section is placed on the ground, the resistance to flexion is then reduced, with this reduction still taking place during the swing phase. Alternatively or additionally, a joint angle is set, whereby the joint angle can be either the joint angle of the knee joint or a joint angle of the foot section relative to the lower section. The joint angle of the foot section can also be set independently of the knee joint angle. The change in the joint angle occurs independently of the change in flexion resistance in a swing phase or during a load response of the foot section.

[0021] One embodiment provides that at least one linear acceleration of the upper part, the lower part and / or the foot part is determined by at least one sensor. The respective linear acceleration can be determined directly by a sensor provided for this purpose; a vertical acceleration is measured by a vertical acceleration sensor and a horizontal acceleration by a horizontal acceleration sensor. The determination can also be made indirectly, for example by recording joint angles or changes in joint angles and knowing the distances of relevant points to the axis of rotation, so that in conjunction with a spatial position sensor, for example, it is determined whether and to what extent the foot part is moving in a horizontal direction or is being accelerated in a direction. In particular, the linear acceleration of the foot part in the walking direction is determined. If a linear acceleration occurs in the walking direction, the foot orthe foot part is moved forward so that the flexion resistance can be changed.

[0022] In one embodiment, the linear acceleration is measured at the foot part or calculated from a linear acceleration of the lower part in conjunction with an angular acceleration of the lower part or a linear acceleration of the upper part in conjunction with a knee angle and an angular acceleration of the lower part.

[0023] A further development of the method provides that an ankle moment is detected at the foot part and / or the lower part, and that a reduction in the ankle moment is used as a criterion or as a sub-criterion for the presence of the lifting or swing phase. If a foot part is in the air, which can be a characteristic of the presence of a swing phase, no relevant external forces act on the foot part that could cause pivoting about an ankle joint axis. Thus, no ankle moment of the foot part is generated relative to the lower part, so that a reduction in the ankle moment can be used as a criterion for the end of a stance phase or for the presence of the lifting or swing phase.

[0024] One embodiment provides that a knee moment about the pivot axis of the lower part relative to the upper part is detected and a knee moment, in particular a knee moment in the flexion direction, is used as a criterion or a partial criterion for the presence of the lifting or the presence of a swing phase.

[0025] In addition, the orientation of the upper part, the lower part and / or the foot part in space can be used as a criterion or sub-criterion for the presence of lifting or the presence of a swing phase. If the lower part tilts backward in space as seen from the distal end of the lower part, this condition can be used as a criterion or sub-criterion for the presence of lifting or a swing phase. A backward tilt occurs, for example, at the end of a swing phase when walking on level ground, shortly before the foot part touches the ground. After toe off and the initial swing phase, the forward tilt of the lower part in space increases. With increasing extension after reaching the maximum flexion angle of the knee, the forward tilt decreases until it reaches a vertical orientation in space and becomes a backward tilt with increasing extension.If the lower part is in a backward inclination, especially in conjunction with the absence of an ankle moment, it can be concluded that the swing phase when walking on level ground has ended, so that this can be used as a criterion for a swing phase.

[0026] However, an orientation of the upper part, the lower part, and / or the foot part in space that lies outside a threshold value can be used as a criterion for the absence of a lifting or swing phase, or at least no swing phase or a situation that would require a change in flexion resistance. Advantageously, the sensor values ​​are determined and evaluated in real time to allow adjustment of the individual resistances or factors influencing a movement sequence during use of the orthopedic device.

[0027] A sensor reading duration outside a time window can be used as a criterion for the absence of a lifting or swing phase. If the upper part, lower part, and / or foot part remain in the same position for an extended period of time, it can be assumed that no change in flexion resistance, joint angle, and / or influence on the pivotability from upper part to lower part is necessary, so that, for example, a change only occurs during a movement with sufficient speed.

[0028] The flexion resistance can be set in the swing phase or during the load response to a resistance that corresponds to the flexion resistance at the initial contact during walking on the level, so that a standard resistance is set in a load response after the initial heel contact to allow stance phase flexion without the knee joint collapsing.

[0029] Exemplary embodiments of the invention are explained in more detail below with reference to the figures. Like reference numerals denote like components. Not all components are provided with reference numerals in all figures to maintain clarity. They show:

[0030] Figure 1 - a schematic representation of a prosthetic knee joint;

[0031] Figure 2- a representation of an initiation of a step from a standing position;

[0032] Figure 3 - a step initiation when walking downhill;

[0033] Figure 4 - a detection of step initiation;

[0034] Figure 5 - Courses of load, foot position and lower leg angle;

[0035] Figure 6 - State changes;

[0036] Figure 7 - a step initiation in combination with context recognition;

[0037] Figure 8 - an adjustment of a flexion resistance when starting to walk;

[0038] Figure 9 - a variant of Figure 8;

[0039] Figure 10 - an adjustment of an effective spring stiffness and damping when starting;

[0040] Figure 11 - a variant of Figure 10;

[0041] Figure 12 - a control of a degree of freedom; and

[0042] Figure 13 - a continuous adaptation of a characteristic to the context. Figure 1 shows a schematic representation of a prosthetic knee joint as part of a prosthesis. 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. A prosthetic foot 25 is arranged on the distal end 21 of the lower part 20. 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. Between the upper part 10 and the lower part 20, a resistance device 30 is arranged as a linearly acting hydraulic actuator. In the illustrated embodiment, the hydraulic actuator 30 is designed with a hydraulic chamber or a cylinder, which is arranged or formed in a housing or base body 31.A piston 32 is slidably 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 a hydraulic line. The base body 31 or the housing can be pivotally mounted on the lower part 20 at a fastening point 23 to prevent the piston 32 from tilting 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 fastened to the upper part 10 at an upper fastening point 210, in the illustrated embodiment to an extension arm to increase the distance from the pivot axis 15.During flexion, the piston 32 is pushed downwards, so that the volume of a flexion chamber decreases; correspondingly, the volume of an extension chamber increases, reduced by the volume of the retracting piston rod 33. An electric motor can be arranged in the housing 31 to generate pressure within one of the chambers. This electric motor drives a pump (not shown) to pressurize 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 an extension movement of the orthopedic device in the form of the prosthetic leg. The electric motor for driving the pump is an option that can be used in one embodiment in combination with the hydraulic actuator 30. In principle, a drive or motor is not necessary for a passive prosthetic knee joint.An alternative embodiment to the configuration of the actuator 30 as a passive linear damper, in particular a linear hydraulic damper, is a rotary damper, in particular a rotary hydraulic damper, a magnetorheological resistance device, or an electric motor, in particular in combination with a gear or a spindle drive. The electric motor can be operated in generator mode. A combination of several of the aforementioned resistance devices as an actuator is also implemented in one embodiment.

[0043] Arranged within or on the housing 31 is a drive 34, which is coupled to at least one control valve 35, via which the hydraulic resistance in the actuator 30 can be varied. The actuator 30, and in particular the drive 34, is coupled to a control device 40, which activates, deactivates, or modulates the drive 34 based on sensor values ​​in order to provide an adapted resistance through the passively designed actuator 30. If the actuator 30 is configured as a magnetorheological resistance device, the resistances are varied by activating, deactivating, or modulating a magnetic field; the drive 34 is then the electromagnet or the magnetic coil.When the actuator 30 is designed as an active drive with an electric motor, the change in resistance occurs by activating, deactivating or modulating voltages which influence the torque generated by the electric motor.

[0044] At least one sensor 50 for detecting the spatial orientation of the lower part 20 and the upper part 10 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 as an IMU (inertial measurement unit), for example, determines 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. Instead of being designed as an IMU for detecting spatial positions, the corresponding sensor 50 can also detect other status data, in particular status data relating to the artificial knee joint. Status data includes, in particular, positions, angular positions, speeds, accelerations, forces, as well as their progressions or changes.The determined solid angle of the upper part 10 and / or the lower part 20 or another state variable is compared with a threshold angle or threshold value. Upon reaching or exceeding a threshold value stored in a control device 40 for the respective sensor value or a variable derived therefrom, the drive 34 is modulated, activated, or deactivated to otherwise change the flow resistance in the actuator 30 in the hydraulic damper configuration, the viscosity, the braking force, the torque, the stiffness, or the force counteracting the flexion movement.

[0045] The actuator 30 in an artificial knee joint typically 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 impact. A flexion movement is decelerated or prevented during the stance phase and swing phase to ensure that the flexion is limited. In order to be able to drive the drive 34 to actuate the control valve 35, an energy storage device, in particular in the form of an accumulator, is also assigned to the drive 34. The energy storage device can be arranged directly next to the drive 34 or at another location in the orthopedic device where more space is available or where this appears advantageous due to the weight distribution.

[0046] Furthermore, the control device 40 and at least one angle detection device in the form of a sensor 50 are arranged on the prosthesis or orthosis. 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. Furthermore, a sensor 50 for detecting at least one linear acceleration is arranged on the foot part 25 in order to be able to directly detect horizontal and / or vertical accelerations of the foot part 25.All sensors arranged on the prosthesis or orthosis are coupled to the control device 40, and their sensor values ​​serve as the basis for controlling the drive 34 of the actuator 30 if the actuator 30 is designed as a damper, or as input signals for a motor control if the actuator 30 is designed as a motor. 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, the drive 34 is controlled in order to reduce or increase a pivoting resistance by the actuator 30. Not all sensors 50 have to be arranged on the orthopedic device in order to carry out the method.

[0047] Figure 2 shows a schematic representation of the initiation of a step or starting to walk from a standing position. At time t0, which is shown in the left-hand illustration of Figure 2, the user is in a standing position. The feet do not necessarily have to be at the same height, as shown here; other positions in a slight stride, straddling, leaning, bent, squatting, etc. are also starting positions for walking. The treated side is typically partially or fully weight-bearing, but this is not required; it can also, for example, hang freely beneath the body or crossed over the contralateral side. In this situation, the orthotic joint device has typical basic characteristics that are advantageous for standing or other starting positions. For example, high flexion resistance in the extended position or a spring characteristic with increasing flexion angle.The basic characteristic does not have to be constant, in the sense of a constant damping, but rather the system is in a state with a control specific to the initial situation.

[0048] A step can now be initiated with the supported side. To do this, the supported side is relieved of load and placed forward, which is shown at a time t?). Typically, the body's center of gravity is also shifted forward over the contralateral leg. At initial contact, which occurs at time t1e, the prosthesis or orthosis should have characteristics typical for initial contact when walking that differ from the characteristics of the basic position, in this case standing. In order to provide this characteristic already at the initial contact when starting to walk, especially with actuators that are not infinitely fast, the step initiation is already detected during the relief and the forward placement of the supported side and the characteristic is changed, for example, during the forward placement of the foot. This is achieved by adjusting the actuator.Ideally, the initial contact characteristics of the first step do not differ, or differ only slightly, from the initial contact characteristics of each subsequent step in a repeating, cyclical step sequence. Gait parameters such as speed, stride length, etc. can be taken into account in the characteristics.

[0049] Figure 3 shows step initiation or starting to walk downhill on an inclined surface. Here, too, the starting situation at time t0 is a more or less static standing position. When initiating a step when walking downhill, the correct characteristics at initial contact and subsequently in the early stance phase are even more important than when walking on level ground, as these largely determine how quickly the person using the step sinks in. An excessively high stretching moment or extension moment leads to a forward lever, while an insufficient stretching moment causes too rapid bending. Inappropriate characteristics can also be compensated for less by the person using the step than when walking on level ground. If a step is now initiated, i.e. the affected side is relieved of load, placed forward (t?) and then loaded again (tie), the optimal characteristics for walking downhill should already be active at initial contact.To do this, it is recognized that the supplied side is placed forward, and the characteristic is changed even before initial contact; e.g., by adjusting or changing the control of an actuator. Here, too, the characteristic at initial contact of the first step should, if possible, not differ or differ only insignificantly from the characteristic of each subsequent step in the gait cycle.

[0050] Detection of step initiation is shown in Figure 4. Initiation can be detected using various variables determined by sensors 50. Typical for step initiation are the unloading and forward positioning of the treated side, the pushing of the body forward over the contralateral side, the relative backward rotation of the treated side compared to the starting position, and the position of the foot in relation to the hip, particularly when the foot part is in front of the hip in the direction of walking. A lateral shift of the body's center of gravity to the contralateral side with unloading of the treated side is also an indicator of step initiation. One or more of these indicators can be used to detect step initiation. Sensor data serves as the basis for detection.The image shows the treated side in a standing position at the same height as the untreated side, as well as during the forward sitting position, with the foot section positioned in front of the untreated side in the direction of walking. The foot of the untreated, contralateral side remains unchanged during the forward sitting position.

[0051] The left image in Figure 4 shows the trajectories of the foot, knee joint and hip in the sagittal plane. Step initiation can be detected via one or more trajectories. The trajectories s(t) or at least a component thereof, e.g. horizontal or vertical, can be determined via distance measurements to the environment or to the contralateral side, via the change in position, e.g. using positioning systems or the integration of speed and / or acceleration variables. Step initiation can be detected based on the trajectory. Relative speed measurements can be used to detect that the supplied side is moving relative to the contralateral side or the environment, and this can be used to conclude that step initiation has occurred. It is also possible to observe the accelerations, e.g.Detect step initiation when forward acceleration and / or backward acceleration occur during the further course of the movement. In addition to the variables and any threshold values, the progression of one or more of these variables can also be used for detection.

[0052] Alternatively or additionally, the tilt of one or more components can be used to detect step initiation, both in the sagittal plane and in other planes. The right-hand image shows the position of the segments in the sagittal plane as well as the position of the leg tendon, which is drawn as a connecting line between the hip joint and the ankle joint. The thigh and leg tendon rotate backward when the footrest is placed forward. Before the footrest is placed on the ground, there is typically a slight backward tilt, after the footrest is usually placed in front of the body. These features can be used to detect step initiation.

[0053] The loading and unloading of the orthosis or prosthesis can be determined using a force sensor and used to detect step initiation, for example, to detect the time of unloading or the unloading state. Both forces and moments can be measured to determine the loading state. The course of the load, such as a rapid unloading, can also be used.

[0054] In particular, a combination of the determined translational and rotational variables can be used for detection, e.g., that the foot moves forward and the leg rotates backward. The changes or variables can relate to positions / locations, speeds, and accelerations. Detection of step initiation and changes in characteristics can also only occur when a certain minimum step length is present, which can be determined from the relative forward movement or rotation compared to the starting position and / or the position of the foot part relative to the body. In addition to detection using threshold values ​​and rule-based criteria, classification can be performed using AI algorithms. Individual features and / or variables can also be determined or estimated using AI algorithms.

[0055] Figure 5 shows typical curves of load, foot position, and lower leg angle during the sequence of standing, sitting forward, loading, and rolling forward when walking over time t. Shown are: t - time

[0056] S - Initial state / standing

[0057] I - State of step initiation

[0058] IC - Initial contact

[0059] B - Stance phase of the first gait cycle

[0060] XF - Position of the foot under the body <p s- Absolute lower leg inclination f - Load / axial force In the left-hand diagram, the person using the aid is in the starting position, in this case standing, at time t0. In the illustration shown, the aid is fully loaded, i.e. with around half the body weight of the person using it. Between t0 and ti, the aid is unloaded. Between ti and t2, the foot section is placed forward, whereby the lower leg rotates backwards and, at initial contact tie, shows a clear backward inclination. Also typical of the forward positioning of the foot section is the slight retraction of the foot or the opposite rotation of the thigh shortly before initial contact. At time t2, the forward positioning of the foot section is recognized as such and the characteristics of the aid are adjusted accordingly.Starting at the point of initial contact (tie), the aid is reloaded, and the user rolls forward over the assisted leg. The foot position (XF) remains constant after initial contact.

[0061] The illustration on the right shows a fundamentally similar process, although the device here allows knee flexion during the unloading phase from a standing position. This applies, for example, to passive default swing joints, which reduce flexion resistance when the load is released from a standing position. However, it can also be a special function that only reduces flexion resistance under specific conditions when the load is released from a standing position. Hip flexion and foot contact with the ground generate a knee flexion moment, which causes knee flexion. It is also possible for an active joint to generate a flexion moment when the load is released from a standing position, which can be interpreted as negative flexion resistance. Knee extension can be caused by gravity and inertia as well as by internally applied extensor moments.

[0062] For the sake of simplicity, the left-hand variant is assumed as the standard procedure in the following considerations. However, this is not intended to be a limitation.

[0063] Figure 6 shows state changes of the system during step initiation. The states shown refer to the states of the system, in particular the characteristics, the control of the actuator and states detected by the controller, and not necessarily to a control via a state machine. Within the cyclic movement of a gait cycle with a cyclic sequence A — > IC — > B — > — > A, for example, walking on a level surface, the

[0064] System before initial contact IC in state A, for example, swing phase extension with corresponding characteristics and actuator control. For example, extension is stopped at 4° forward bending, and a flexion resistance optimal for walking with stance phase flexion is already set. After initial contact IC, the system passes through state B, which corresponds, for example, to stance phase flexion, as well as other states, represented here only by ..., until the system returns to state A as part of the cyclic sequence. This sequence is used for both Figure 6 and Figure 7.

[0065] To ensure that the aid has optimal characteristics for the subsequent stance phase during the initial contact when starting to walk, i.e. when the foot is placed forward and weight is placed on the foot, the forward placement is detected and the characteristics are changed. The starting point is state S, which in the illustration corresponds to standing. Here, for example, the aid has a maximally extended knee angle and a high flexion resistance. If the foot on the assisted side is now placed forward from the starting position, this is detected by the control system and the aid then changes its characteristics in preparation for the upcoming initial contact. For example, similar to the characteristics in state A of the cyclic movement, the knee joint is flexed slightly (4°) and the flexion resistance is slightly reduced compared to standing to enable an easy glide into the stance phase flexion.Since an initially recognized forward placement of the foot does not necessarily correspond to a start, it is of course also possible to switch back to the characteristics of the initial situation, a transition from I to S, which is shown in illustration a) of Figure 6. This can be the case, for example, if the forward placement takes too long or if the foot part is only swung forward and back again and then placed under the body.

[0066] The characteristics upon initial contact from states I and A do not have to be identical. For example, the knee flexion angle during forward sitting can be set to 2°, while the knee flexion angle during swing phase extension of cyclic walking is set to 4°. However, if the control system triggers the same characteristic, regardless of whether it is a forward sitting from a standing position or a swing phase extension of cyclic walking, the result is the state diagram shown in Figure 6 (b).

[0067] If the initial contact is not explicitly detected, e.g. because there is no corresponding sensor for detection, the processes c) and d) result, in which the initial contact lies between states A and B.

[0068] Figure 7 illustrates step initiation combined with context recognition. Walking control is typically adapted to the context. This means that the assistive device has different characteristics when walking in different contexts, such as walking on level ground, walking downhill on inclines, walking downstairs, walking uphill on inclines, or climbing stairs. The context also affects starting to walk from a standing position. When standing on level ground, starting to walk on level ground occurs; when standing on an incline facing downhill, starting to walk downhill on inclines occurs, and so on.

[0069] This can be taken into account in the control system by context recognition even when the foot is placed forward from a standing position, and by adapting the characteristics to the context-specific stance phase. In Figure 7, for example, the cyclical sequence A1 — > IC1 — > B1 —>■ ... -^ A1 is shown for level walking and the cyclical sequence A2 — IC2 — > B2 — > ... — > A2 is shown for walking down slopes. ICi indicates further cyclical sequences. Not only is the forward placement of the foot recognized, but the context is also recognized or estimated from the input data of the control system using algorithms and the characteristics are adapted so that they are optimal for the stance phase of the corresponding context. The adaptation of the characteristics to the context can be discrete, so that one of several context-specific characteristics is selected. Alternatively, adaptation to the context can also take place continuously or.smoothed, which is explained in connection with Figure 13. Any adjustments of the characteristics to other parameters such as walking speed or stride length can, of course, also be taken into account.

[0070] Figures 8 and 9 show two example adjustments of a flexion resistance during walking. The states S, I, IC, B are shown in each case, as well as the control A of at least one actuator, in this case with R as the resistance against flexion. The description of the movement sequence and designations correspond to those of the previous figures. In this version, the aid has a load-dependent flexion resistance characteristic while standing. With sufficient load, the resistance RO is set to be optimal for standing. As the load decreases below a threshold value, the flexion resistance is continuously reduced starting from RO. The reduction can also go into the negative range, which corresponds to an internally applied flexion moment. Accordingly, the flexion resistance R is reduced with the unloading from t1 to t2.The characteristics when standing do not have to correspond to a constant resistance, but can be considered as generally fixed.

[0071] At time t2 it is detected that the foot has been placed forward. The flexion resistance is then increased to level R1, which is higher than the standing level and is particularly advantageous for the subsequent initial contact when starting to walk. This can be the case, for example, if the person using the aid can control the movement of the aid very well while standing at the existing resistance level RO, but during the initial contact when starting to walk and during the initial contacts of the following steps within the gait cycle the external flexion moments on the knee at level RO can no longer be controlled or can no longer be reliably controlled. Accordingly, the higher level R1 ensures sufficient stance phase protection right from the first initial contact when starting to walk. The level R1 can also be so high that knee flexion is actually not possible.The resistance curve shown from t2 to tIC is a sum of the actuator adjustment time, a desired temporal smoothing and / or a dependence of the resistance level on other variables, for example the step length or the backward inclination of the leg, both of which increase during the forward placement of the foot. A variant of Figure 8 is shown in Figure 9. In this embodiment, the characteristic during standing (tO) and unloading is a constant flexion resistance at level RO, but not the same level as in Figure 8. At time t2, the forward placement of the foot is detected and the flexion resistance is then reduced to a level R1. This is advantageous, for example, to enable a transition into stance phase flexion with the initial contact when starting to walk and with each subsequent initial contact within the gait cycle.The flexion resistance while standing would be too high for this purpose and would make stance phase flexion difficult or uncomfortable. The flexion resistance can be increased again later in the stance phase to limit the knee flexion speed or to achieve a flexion stop. Such control can be advantageous in different contexts, whereby the detailed design, e.g. of the initial resistance level or the increase in resistance, depends on the context. The resistance at initial contact when starting to walk should ideally be as close as possible to the behavior at initial contact within the gait cycle. Here, too, the resistance curve shown from t2 to tIC is the sum of the maximum adjustment speed of the actuator, the desired temporal smoothing and / or dependencies on other parameters.

[0072] Figure 10 shows an adjustment of the effective spring stiffness and damping during start-up. In this embodiment, the actuator has the characteristics of a parallel spring-damper system with adjustable spring stiffness c(pi) and damping d(r|). This can be realized, for example, via a motor drive that emulates damping and spring stiffness through appropriate control. However, it can also be a hydraulic damper with a spring accumulator whose stiffness and damping behavior can be changed. This combination is one of many embodiments and is therefore not intended to be limiting; rather, combinations of parallel and serial dampers, springs, etc. can be used.

[0073] When standing at time tO, the characteristic is essentially damping with a constant damping level dO; the spring stiffness is low. This is useful to enable unrestricted flexion of the knee joint from a standing position for sitting or kneeling. High spring stiffness would prevent this. At time t2, the forward placement of the foot is detected, and the damping is reduced and the spring stiffness increased in preparation for the subsequent initial contact when starting to walk. Low damping and high spring stiffness enable particularly comfortable stance phase flexion. Using a spring energy store, it is also possible to store energy during stance phase flexion instead of dissipating it via a damper.

[0074] A variant of Figure 10 is shown in Figure 11. In this embodiment, the actuator has at least one switching element or the actuator is a switching element that can, for example, couple and uncouple a spring, as shown on the left in Figure 11. Alternatively, a spring accumulator in a hydraulic system can be activated or deactivated via a switching valve by optionally connecting port P2 to PO or P1. When the spring is decoupled or deactivated, only slight resistance is present in this embodiment. When the spring is coupled or activated, the corresponding spring force is effective.

[0075] The starting position here is er = 0 , which corresponds to a decoupled spring or a deactivated spring actuator. The low resistance to movement can be useful for an aid that can be easily controlled by the user while standing, even without stance phase protection, and which gives them maximum freedom of movement. This is the case, for example, with orthoses for people with a high level of residual functionality or with exoskeletons for people without disabilities. During the initial contact of walking, in contrast, the spring element or the spring actuator should secure the stance phase. In order to ensure this security right from the initial contact when starting to walk, the forward placement of the foot is detected (time t2) and then, in preparation for the initial contact, the switching element is switched to position er = 1, which couples the spring or connects the spring actuator to the hydraulic piston.

[0076] In this case, the figure shows the desired switching position, which in this specific example is not varied with other parameters or smoothed over time. Due to the inertia of the system, the actual switching position would naturally only be reached with some time delay, which is why switching before the initial contact is detected is desirable.

[0077] Alternatively, a switching element could activate or release a lock, couple or release degrees of freedom, switch properties between two discrete values, e.g., damping, stiffness, friction, gear ratios, and the like, or switch between other discrete states. The switching element can also be part of an actuator that can also adjust other properties. For example, a passive or active resistance device can be arranged in parallel with a switchable spring or a switchable spring-loaded mechanism, which also functions when the spring is decoupled or the spring-loaded mechanism is deactivated.

[0078] Figure 12 shows how a degree of freedom is changed by the actuator when starting to walk. For example, a knee joint can be extended or flexed using a motor or a previously charged energy storage device. A degree of freedom can be limited using a resistance device. Derivatives of the degrees of freedom can be changed and / or limited in a similar way. The degree of freedom cp is shown, which is changed using the actuator. In the following exemplary embodiment, this is the knee angle. In the initial standing situation (t0), the auxiliary device is in a fully extended position. The knee joint is in position cp0. The arrangement and properties of the elements of the auxiliary device and the positioning of the knee axis result in an extending or minimally flexing knee moment when standing. This is advantageous for stable standing.However, during initial contact when walking, it is advantageous if the knee joint is in a slightly bent position. In particular, this can reduce the impact forces on the user and facilitate the initiation of stance phase flexion. If the aid is now released from a standing position and the foot is placed forward, this can be detected (t2) and the knee is bent by the actuator. This means that the slightly bent position cp1 is already present upon initial contact after starting to walk when the affected side first touches the ground. If knee flexion is permitted or actively supported during the process of releasing the load and placing the foot forward, the subsequent extension movement can be stopped at the desired slightly forward bent knee angle.Figure 13 shows a continuous adaptation of a characteristic to the context, which in the illustrated embodiment occurs continuously, i.e. there are smooth transitions between different contexts, which is expressed via the continuous parameter X. The context recognition can be implemented, for example, as fuzzy logic or as an AI algorithm with continuous probabilities for the contexts, which can be interpolated or weighted accordingly. Alternatively, the context recognition takes place by means of a parameterization that transitions smoothly into other contexts, such as a calculation or estimation of the ground gradient for walking downhill on inclines, which transitions smoothly into walking on level ground for an incline of 0°. A section through the plane X = constant corresponds to one of the preceding figures. The characteristic of the aid is accordingly continuously adapted using the parameter X.This can occur not only for the characteristics during the start of walking or the forward placement of the foot, but also for the characteristics within the various cyclic movements. For example, during the start of walking and during the stance phase of walking down slopes, a continuous adjustment of the characteristics can occur depending on the slope. However, it is also possible that continuous adjustments are followed by discrete branches and / or vice versa.

Claims

Patent claims 1. A method for controlling an orthopedic knee joint device with an upper part (10) and a lower part (20) and a foot part (25) attached thereto, wherein at least the upper part (10) and the lower part (20) 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 pivoting movement, 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 ​​of the at least one sensor (50), characterized in that a displacement of the foot part (25) by detecting and evaluating a linear acceleration and / or change in position of the upper part (10),of the lower part (20) and / or the foot part (25) is detected and a flexion resistance in a swing phase or during a load response of the foot part (25) is changed compared to an initial state before the displacement., 2. Method according to claim 1, characterized in that the initial state is standing or a situation other than walking in which the foot part (25) is placed on the ground.

3. Method according to claim 1 or 2, characterized in that the displacement comprises a lifting of the foot part (25), which is determined by a drop in an axial force component in the foot part (25) and / or lower part (20) and / or a vertical acceleration of the foot part (25) and / or the lower part (20) and is used as a criterion for the lifting or presence of a swing phase.

4. Method according to one of the preceding claims, characterized in that during the displacement the resistance to flexion in the swing phase is left unchanged in a lifting phase and before the foot part (25) is placed on the ground the resistance to flexion in the swing phase is reduced and / or a joint angle is adjusted.

5. Method according to one of the preceding claims, characterized in that at least one linear acceleration of the upper part (10), the lower part (20) and / or the foot part (25) is determined by at least one sensor (50).

6. Method according to one of the preceding claims, characterized in that the linear acceleration of the foot part (25) is determined in the walking direction.

7. Method according to one of the preceding claims, characterized in that the linear acceleration is measured at the foot part (25) or calculated from a linear acceleration of the lower part (20) in conjunction with an angular acceleration of the lower part (20) or from a linear acceleration of the upper part (10) in conjunction with a knee angle and an angular acceleration of the lower part (20).

8. Method according to one of the preceding claims, characterized in that an ankle moment is detected at the foot part (25) and / or the lower part (20) and an ankle moment reduction is used as a criterion for the presence of the lifting or a swing phase.

9. Method according to one of the preceding claims, characterized in that a knee moment about the pivot axis (15) is detected and a knee moment is used as a criterion for the presence of the lifting or a swing phase.

10. Method according to one of the preceding claims, characterized in that the orientation of the upper part (10), the lower part (20) and / or the foot part (25) in space is additionally used as a criterion for the presence of the lifting or a swing phase.

11. Method according to claim 10, characterized in that a backward inclination of the lower part (20) in space, seen from the distal end (21) of the lower part (20), is used as a criterion for the presence of the lifting or a swing phase.

12. Method according to one of the preceding claims, characterized in that an orientation of the upper part (10), the lower part (20) and / or the foot part (25) in space which lies outside a threshold value is used as a criterion for the absence of the lifting or a swing phase.

13. Method according to one of the preceding claims, characterized in that the sensor values ​​are determined and evaluated in real time.

14. Method according to one of the preceding claims, characterized in that a duration of sensor values ​​lying outside a time window is used as a criterion for the absence of the lifting or a swing phase.

15. Method according to one of the preceding claims, characterized in that the flexion resistance during the load response corresponds to the flexion resistance at the initial contact during walking on the plane.

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