WEARABLE ACTIVE ASSISTING DEVICE

Abstract

The present invention relates to a wearable active assisting device comprising an actuator in use to provide a limb assistance and coupled to a limb to be actively assisted via at least one force transmission element to be elongated or shortened by the actuator; and a control having an input for signals from a plurality of sensors, a signal processing stage for processing input signals from the plurality of sensors, and an output stage for outputting a motor actuation signal in accordance with the processed sensor signals; wherein the control further has a limb assistance degree selection input for selecting a degree of limb assistance; and wherein the signal processor stage is adapted to continuously model an elongation of the at least one force transmission element to be elongated or shortened corresponding to a movement or posture currently detected by the plurality of sensors to output a continuous actuator actuation signal according to a modeled elongation of the at least one force transmission element to be elongated or shortened and in response to a selected minimum degree of limb assistance.

Claims

1. A wearable active assisting device comprising: an actuator; at least one force transmission element, wherein the at least one force transmission element is configured to be elongated or shortened by the actuator, wherein the actuator is configured to provide a limb assistance and is configured to be coupled to a limb to be actively assisted via the at least one force transmission element; a plurality of sensors; a control comprising an input for receiving signals from the plurality of sensors; a signal processing stage for processing input signals from the plurality of sensors; and an output stage for outputting a motor actuation signal in accordance with the input signals processed in the signal processing stage; wherein the control further comprises a limb assistance degree selection input for selecting a degree of limb assistance; and wherein the signal processing stage is adapted to continuously model an elongation of the at least one force transmission element to be elongated or shortened corresponding to a movement or posture currently detected by the plurality of sensors to output a continuous actuator actuation signal according to a modeled elongation of the at least one force transmission element to be elongated or shortened and in response to a selected minimum degree of limb assistance.

2. A wearable active assisting device according to claim 1, wherein a system response is determined according to physical characteristics of a human body.

3. The wearable active assisting device according to claim 1, wherein the control is adapted to model a force transmission element elongation.

4. The wearable active assisting device according to claim 1, wherein the plurality of sensors comprises one or more gyro-sensors, accelerometer sensors, magnetometer sensors, stretchable sensors, kinematic sensors, angle sensors, or a combination of any thereof.

5. The wearable active assisting device according to claim 4, wherein the plurality of sensors comprises at least one gyro-sensor and/or accelerometer sensor, wherein each of the plurality of sensors is configured to be positioned at each of a plurality of limbs or joints.

6. The wearable active assisting device according to claim 5, wherein a current force transmission element elongation is determined in response to sensor signals.

7. The wearable active assisting device according to claim 1, wherein the control is adapted to model a force transmission element elongation independent of any force or tension indicative signals indicative of a force and/or tension in the at least one force transmission element detected from the plurality of sensors.

8. The wearable active assisting device according to claim 1, wherein the control is adapted to model an elongation of the at least one force transmission element to be elongated or shortened in a manner taking friction of the at least one force transmission element and/or inertia into account.

9. The wearable active assisting device according to claim 1, further comprising a resilient elastic element provided in series with the force transmission element to be elongated or shortened, the resilient elastic element configured to be positioned between the limb to be actively assisted and the actuator, and wherein a restrictor for restricting the elongation of the resilient elastic element to a maximum allowed elongation is provided.

10. The wearable active assisting device according to claim 9, wherein the resilient elastic element has a modulus of resilience such that for a maximum residual force accepted in a selected minimum degree of limb assistance, the resilient elastic element is elongated by no more than the maximum allowed deviation between a standardized model and an extension correction.

11. The wearable active assisting device according to claim 1, wherein the at least one force transmission element to be elongated or shortened comprises a force transmission element, wherein a reel is provided to reel or unreel the force transmission element when shortening or elongating, and wherein the actuator is a step motor or a brushless motor.

12. The wearable active assisting device according to claim 1, wherein the force transmission element is guided in a slack sheath.

13. (canceled)

14. The wearable active assisting device according to claim 1, wherein in a minimum degree of assistance, the control is adapted to maintain the elongation at a residual force.

15. The wearable active assisting device according to claim 14, wherein the residual force is smaller than 30 N.

16. The wearable active assisting device according to claim 15, wherein the residual force is smaller than 20 N.

17. The wearable active assisting device according to claim 16, wherein the residual force is smaller than 10 N.

18. The wearable active assisting device according to claim 14, wherein the residual force induced by the force transmission element is larger than 0.5 N.

19. The wearable active assisting device according to claim 18, wherein the residual force induced by the force transmission element is larger than 1 N.

20. The wearable active assisting device according to claim 18, wherein the residual force induced by the force transmission element is between 0.5 N and 5 N.

21. The wearable active assisting device according to claim 14, wherein the residual force induced by the force transmission element occurs for at least for a part of a movement detected by the plurality of sensors.

22. The wearable active assisting device according to claim 21, wherein the residual force induced by the force transmission element occurs for at least 50% of a cyclic movement.

23. The wearable active assisting device according to claim 22, wherein the residual force induced by the force transmission element occurs for at least 66% of a cyclic movement.

24. The wearable active assisting device according to claim 23, wherein the residual force induced by the force transmission element occurs for at least 75% of a cyclic movement.

25. The wearable active assisting device according to claim 1, wherein the control is adapted to model the elongation such that when transitioning from a selected minimum degree of assistance to a degree of assistance higher than the minimum degree, a force transmission element slack of no more than 10 cm needs to be overcome by reeling.

26. The wearable active assisting device according to claim 25, wherein a force transmission element slack of no more than 7 cm needs to be overcome by reeling.

27. The wearable active assisting device according to claim 25, wherein a force transmission element slack of no more than 5 cm needs to be overcome by reeling.

28. The wearable active assisting device according to claim 1, wherein the active assisting device is adapted to assist in leg activity and the plurality of sensors comprises at least one gyro- and accelerometer sensor configured to be positioned at each of a plurality of limbs or joints.

29. The wearable active assisting device according to claim 28, wherein a current force transmission element elongation is determined in response to sensor signals.

30. The wearable active assisting device according to claim 1, wherein in response to the sensor signals the model is adapted to identify a current intended movement from the sensor signals, to determine a phase in the current movement identified, to model a change of the force transmission element elongation according to the expected progress of the current movement, and to output a motor actuation signal in response to the modeled elongation.

31. The wearable active assisting device according to claim 1, wherein the control is adapted to identify an activity as a current movement and wherein the control is adapted to determine a phase in the current activity as a stance phase or swing phase and/or determine foot-ground-contact and/or determine a phase in stair climbing and/or ascending and/or walking, uphill or downhill and/or sitting transitions.

32. A control for a wearable active assisting device, the wearable active assisting device comprising an actuator, the actuator configured to be actuatable to provide limb assistance and configured to be coupled to a limb to be actively assisted via at least one force transmission element to be elongated or shortened by a motor; the control comprising an input for signals from a plurality of sensors, a signal processing stage for processing the signals, and an output stage for outputting a motor actuation signal in accordance with the processed sensor signals; and wherein the control comprises a model stage adapted to model: the elongation of the at least one force transmission element in a manner keeping assistance at or below a threshold, a current movement and/or posture of a user detected by the sensors, and inertia and/or friction of the wearable active assisting device, and wherein the output stage is adapted to output the motor actuation signal in accordance with the current modeled elongation and a limb assistance required.

33. The control according to claim 32, wherein the control is adapted to model an elongation component in a continuous manner without reference to a predefined force/assistance profile.

34. The control according to claim 33, wherein the control is further adapted to determine an additional elongation component to be simultaneously applied in response to a detected and/or identified movement, wherein the additional elongation is simultaneously applied to the transparency mode elongation.

35. The control according to claim 34, wherein the detected and/or identified movement is a walking movement, a stair climbing movement, and/or a sitting transition movement.

Description

[0046] The present invention will now be explained with reference to the drawings. In the drawings:

[0047] FIG. 1 shows a schematic of a wearable active assisting device according to the present invention;

[0048] FIG. 2 shows a detail thereof showing a spring as resilient elastic element provided in series with a force transmission element to be elongated or shortened and a cuff arrangement to be placed around a limb but together with a restrictive for restricting the spring elongation to the maximum allowed elongation;

[0049] FIG. 3 shows an explanation of a model used by the control of the wearable active assisting device according to the invention;

[0050] FIG. 4 shows a schematic high level block diagram for modeling a transparency behavior of a wearable active assisting device according to the present invention;

[0051] FIGS. 5a-d show model components in more detail, namely a compliance compensation component;

[0052] FIG. 5b a velocity compensation component;

[0053] FIG. 5c a resilient element force compensation; and

[0054] FIG. 5d a position compensation component;

[0055] FIG. 6a a force-tendon length relationship for different forces ramped up repeatedly in a cyclic manner;

[0056] FIG. 6b shows in more detail of the force-tendon length-relation for a fixed force and repeated force ramps; note that the rather than the tendon length, the encoder counts of a rotating actuator are indicated;

[0057] FIG. 6c the force-tendon length-relation of FIG. 6 with an average behavior obtained after repeated cycling;

[0058] FIG. 6d a demonstration showing that a force applied to a tendon can be precisely controlled;

[0059] FIG. 6e the force-tendon length relation for different postures;

[0060] FIG. 7 illustrates that different tendon lengths are needed for minimum support and/or transparency mode in different postures;

[0061] FIG. 8 shows the forces acting on the knee-moment-arm during a transparency mode when moving slowly showing that only minimum forces are applied during transparency mode.

[0062] According to FIG. 1, a wearable active assisting device 1 comprises a motor 2 actuatable and used to provide assistance to a limb 3 of a user 4, the motor 2 being coupled to the limb 3 via at least one force transmission element 5 to be elongated or shortened by the motor and a control 6 having an input for signals 7a, 7b, 7c, 7d from a plurality of sensors 8a,8b, 8c, 8d, the controller having a signal processing stage for processing input signals 7a-7d from the plurality of sensors 8a-8d and an output stage 9 for outputting a motor actuation signal 10 in accordance with the processed sensor signals, wherein the control further has a limb assistance degree selection input 11 for selecting a degree of limb assistance; and wherein the signal processor stage of control 6 is adapted to model an elongation of the at least one force transmission element 5 to be elongated or shortened corresponding to a movement of the user as currently detected using the sensors 8a-8d and to output a motor actuation signal 10 according to a current model elongation of the at least one force transmission element 5 to be elongated or shortened and in response to a selected minimum degree of limb assistance.

[0063] It should be noted that while in the embodiment shown, the degree of limb assistance can be selected and the transparency mode implemented by the present invention is used as the minimum degree of limb assistance, this need not necessarily be the case. It is possible to generally keep the assistance precise, in particular intentionally below a maximum degree of assistance, for example in order to reduce the load on the components of the wearable active assisting device such as the motor, battery, tendons and so forth, and to increase longevity of the device.

[0064] Still, even in that case, the transparency mode described herein can be considered useful as the transparency mode can be used to define a base elongation starting from which additional assistance is provided. In this manner, for example the overall assistance during a cyclic movement can be more constant. In such a case, the wearable active assisting device might e.g. comprise a motor actuatable to provide joint assistance and coupled to a joint to be actively assisted via at least one force transmission element to be elongated or shortened by the motor; and a control having an input from a plurality of sensors, a signal processing stage for processing the signals and an output stage for outputting a motor actuation signal in accordance with the processed sensor signals; wherein the control comprises a model stage adapted to model the elongation of the at least one force transmission element in a manner keeping assistance at or below a threshold sensible by the user by taking into account both a current movement and a posture of the user as detected by the sensors and an inertia and/or friction of the wearable active assisting device counteracting a movement, and wherein the output stage is adapted to output the motor actuation signal in a accordance with the current modeled elongation and/or limb assistance required.

[0065] Now, returning to FIG. 1 and the embodiment shown therein, the user 4 is a human patient requiring a certain degree of assistance but using the wearable active assisting devices also during at least some periods where no active assistance is required.

[0066] The force transmission element is a tendon coiled and decoiled on a reel rotated by motor 2 so as to elongate or shorten the force transmission element. This can be seen inter alia in FIG. 7. While the precise way the wearable active assisting device is constructed and the force transmission element is guided along the body of the human user 4 is not shown in FIG. 1, reference can be had to WO 2018/122106 A1 in this respect. Possible although non-restricting examples of wearable active assistive devices in which the invention can be implemented are shown therein.

[0067] Also, many details such as the construction from different layers and so forth are shown in the cited document. These are also useful in the present invention, although not absolutely necessary. Thus, while a wearable muscle assisting device having a construction according to the cited document and having sensors according to the cited document and a control that other than as described herein closely corresponds to the cited document is perfectly usable for the present invention, it should be noted that the present invention is not restricted to a wearable active assisting device constructed as in WO2018/122106 A1 and that the basic ideas of the present invention can also be used with wearable active assisting devices having a different construction.

[0068] In the embodiment shown, the joints assisted are the knee and hip joints of the user, in particular of the right leg, and a first triaxial accelerometer sensor 8d is provided at the shank and a second triaxial accelerometer is provided at the thigh. Furthermore, angle sensors are provided to indicate the bending angle of the right hip, cf. sensor 8a and of the right knee, cf. sensor 8c. A further angle sensor may be provided at the ankle (not shown in FIG. 1). Different angles are also shown for different postures in FIG. 7.

[0069] The force transmission element 5 in the embodiment shown is a tendon made from inextensible material and anchored via a cuff 12 at the shank (cf. FIG. 2). Between the tendon 5 and the cuff 12 a rather resilient helical spring 13 provided. The coil spring 13 is anchored with one end thereof at the cuff 12 and with another end thereof at the end 5a of the tendon 5. Parallel to the helical spring 13 and guided within the coil spring 13 is a rope 14. The length of rope 14 is such that in the rope is slack up to the maximum accepted extension of resilient element 13. Such restriction is of course also implementable with resilient elements other than coil springs, e.g. with rubber bands.

[0070] As can be seen in FIG. 3, the length of the tendon running along the leg of the user 3 will depend on the posture of the user, in particular the bending angles of the knee and the hip; furthermore, if the motor is attached at the trunk of the user in a rather high position, the length will also depend on the posture of the trunk itself. It will be understood that the change of the length of tendon 5 will depend inter alia on the path along which the tendon runs close to the human body as implemented by the wearable active assisting device. Depending for example on whether the tendon is guided in front or behind the hip, the length will differ. This of course can be taken into account. This can be in particular done as shown in FIG. 3 by calculating a virtual tendon length by defining a virtual hip and a virtual leg only dependent on the current bending angles, indicated in FIG. 3 as angle α, angle β, angle γ.

[0071] Then, it will be obvious to the skilled person that any wearable assistive device will have some mass that also needs to be moved if the user wants to move a limb. For example, when moving the shank, the cuff 12 has to be moved as well as the spring 13, rope 14 together with parts of tendon 5 and so forth. Also, there will be some friction due to the garment-like structure of parts of the wearable active assisting device and the friction within the garment and due to other causes of friction as commonly understood.

[0072] Now, if a user is to be provided with zero assistance as the minimum assistance but without being adversely effected by the wearable active assisting device 1, then, the compensation components depicted in FIG. 4 should be taken into account and compensated for such as inertia and friction among other effects and disturbances. Otherwise, the user would have to apply additional forces simply to overcome the additional friction and inertia of the wearable active assisting device. It will also be obvious that the inertia to be overcome may depend on the specific movement. For example, where the shank is to be moved, the inertia to be compensated for will depend on whether the shank is to be supported during the beginning of the swing phase where a high acceleration is needed or during the middle of the swing phase where the velocity basically remains constant for a short time, so that no inertia forces need to be compensated. Also, friction forces may depend on the current velocity and current bending angle. (Note that while for explanation of friction and inertia effects, reference has been made to movement patterns and phases such as stance or swing, determination thereof is not necessary. Rather, determination of the speed of the shank asf. will suffice).

[0073] As shown in FIG. 4, the model stage modeling a transparency force will in a preferred embodiment take into account the current posture or position of different parts of the human body, namely the trunk, thigh, shank, and will also take into account the current velocity of the trunk, the thigh and the shank. Then, a friction for each component such as at the trunk, thigh and shank and the respective inertia can be taken into account, as well as a resilient element force component.

[0074] It will be obvious that the motor will also contribute to friction and inertia so that further to the sensors such as IMU (inertial measuring units) for the trunk, for the thigh and for the shank respectively, preferably a motor encoder signal should be taken into account as well. Using these signals, the position compensation force, the velocity compensation force, a friction compensation force and an inertia compensation force can be calculated from a position compensation component, the velocity compensation component, a friction compensation component and an inertia compensation component, respectively.

[0075] By adding these force components, an overall transparency force is determined that is used to give the user the impression that a wearable active assisting device neither assists nor hinders movement.

[0076] As can be seen in FIG. 5a, 5b, 5d in more detail, each IMU comprises gyro-sensors and acceleration sensors, in particular triaxial accelerometer sensors that are respectively designated as gyro thigh, acc thigh, gyro shank, acc shank; gyro trunk, acc trunk; gyro thigh, acc thigh, gyro shank, acc shank. From these sensor signals, a current thigh angle and a current shank angle is calculated which are both used in the determination of the velocity compensation component and in deriving a knee angle and a hip angle. From these angles, a virtual hip angle and a virtual leg length is then calculated based on a non-user-specific model resulting in a suggested length of the virtual tendon.

[0077] Repeating this determination over and over, a change in the virtual cable length over time is calculated.

[0078] The change of the virtual cable length over time can be compared with the current velocity of the motor derived from a motor encoder signal so as to determine whether or not the current velocity is the correct velocity needed to fully compensate current movement or not. As necessary, the current velocity can then be corrected.

[0079] In a similar manner, to determine a position compensation, again the trunk angle, the thigh angle and the shank angle are used and from these a knee angle is now determined. Knee angle and trunk angle are compared with a respective initial angle as the differences determine the change of length. Also, the initial thigh angle is taken into account. In this manner, it can be determined whether the current elongation is correct, or should be increased or should be decreased so as to avoid tensions or slack. Depending on the result of this determination, a force component relating to the current position is determined.

[0080] Finally, it is possible and preferred that the compliance of tissue and its effect on the displacement of the tendon when forces are being applied are taken into account in a manner compensating for the tissue compression of the human body when the tendon is applying forces onto it.

[0081] It should be noted that with preferred actuators it is possible to determine the winding or unwinding of a tendon using a counter counting rotational angle encoder signals from the actuator and to estimate the force applied to the tendon at the same time, e.g. from the current and/or voltage applied to the actuator. In this manner, a force-tendon length relation can be established and from this, the effects of tissue compression and the like can be estimated. Such relations can be determined repeatedly, taking into account that by tensioning the tendon the path it is guided along the body might slightly change, the textile parts of a wearable active assistive device might glide with respect to each other or change their position somewhat asf. leading to slight changes in the force-tendon length relation. Such variations in the behavior can be deduced for example from FIG. 6b. For the sake of precision, it is noted that in FIG. 6, reference is made to the encoder counts. While the encoder counts are closely related to the tendon length, it will be understood that due to the winding or unwinding of the tendon, a full rotation of an actuating motor will result in a smaller change in case the tendon is fully extended as compared to a case where the full rotation will result in a larger change of tendon length due to the larger diameter of the tendon almost fully wound up. Nonetheless, the general pattern can easily be seen and also, it is easy to correct such effects in a controller, in particular a microprocessor-based controller having certain software modules. Also, it can be seen from FIG. 6c that it is possible to derive an average behavior for increasing or rapidly decreasing forces as shown by the curve AB-BC-CA.

[0082] Also, it will be understood that different maximum forces applied will result in different changes, as is obvious for example from FIG. 6a, that increasing a force applied will result in a behavior different from the behavior observed when a force is decreased, as is also obvious from FIG. 6a or 6b, and that the effects described will be different in different postures, compare FIG. 6c. Thus, a general behavior and/or general influence of tissue compression asf. could be modeled; additionally and/or alternatively a behavior could be modeled taking specifically into account whether the force is applied for a first time after significant change of posture or whether application of force is repeated; additionally and/or alternatively a behavior could be modeled taking into account the maximum force currently or previously applied in a given posture; additionally and/or alternatively a behavior could be modeled taking into account a previous posture, in particular the posture(s) immediately preceeding the current posture. FIG. 6d shows a potential force profile to determine the stiffness model of a user. The depicted results in FIG. 6e show additionally the different length of slack in the system that can be compensated for.

[0083] The model could be based on average data gathered for a wide range of users and/or could be based on data gathered specifically for a single user, in particular for the specific user and the specific current way the device is worn, taking into account that day-to-day variations may occur and that these variations can be compensated for by establishing or estimating current force-tendon length relations. Note that thus, in a preferred embodiment a model can be determined that correlates forces being applied with measurements of tendon travel so that the system can take into account any potential high pressure points on the user by compensating them, (reeling out cable). It should also be noted that when compressed, the tissue will of course absorb some of the energy and that this can be modeled in a manner treating the tissue as a spring-damper system that by absorbing energy from the force transmitting element helps stabilize potential instabilities during control actions, also improving system response to a safety actuation when a sudden increases of assistance is required.

[0084] It should be noted that while the control is adapted to model a force transmission element elongation irrespective of the size and weight of the user, e.g. to determine an elongation necessary for a transparency mode irrespective of the size of a user, an exemption to this can be made with respect to modeling force-tendon length relations as these can be determined easily as is obvious from the above.

[0085] Now, while it would be possible to model the exact behavior of the wearable active assisting device for a specific user having a specific size, this would usually require a number of measurements that frequently would have to be repeated over and over again, for example because the legs of a patient are initially swollen following an accident, the swelling slowly decreasing over time.

[0086] Therefore, it is desirable to use the resilient element as explained with respect to FIG. 2 to use general parameters and to elongate or shorten the tendon only to a precision such that the spring 13 is not fully extended during a transparency mode. Only when actual assistance is needed, for example because a patient becomes exhausted, the tendon 5 will be shortened so much that element 14 is no longer slack. As the distance the tendon 5 has to be reeled in will be extremely small during transparency mode of the present invention, active assistance can be provided almost immediately and without causing a shock or jerk to the limb supported.