Decentralized Rotary Actuator

Abstract

An apparatus and method for actuating a joint of a human, animal or robot is disclosed. An elongated, longitudinally flexible and torsionally elastic body is provided, the body being used to transmit torque. The torque is transmitted via the body based at least in part on torsional deformation information of the body. In an embodiment, a flexible drive shaft is provided, wherein the flexible drive shaft includes the body as shown. In addition, the use of the flexible drive shaft as both a compliant element and a torque transfer element in a rotary actuator to actuate a mechanical joint is disclosed. In addition, the use of the flexible drive shaft for determining the impedance of a joint of a human or animal is also disclosed.

Description

Technical Field

[0001] The invention may relate in one aspect to the technical field of non-implantable prostheses (IPCA 61F 2 / 50), in particular to operating or controlling devices thereof (IPCA 61F2 / 68). The invention may relate in one aspect to deformation measurement and torsion control of a flexible drive shaft. Background Art

[0002] US2011 / 0040216A1, entitled "Exoskeletons for running and walking", describes a hip torque series elastic actuator. The series elastic actuator includes a spring connected in series with the output of a motor / gearbox. The spring acts as a sensor, filter, and impedance limiter.

[0003] The series elastic actuator requires the motor / gearbox to be close to and in-line with the joint axis of rotation. At least one point of actuation is displaced in the longitudinal direction, making actuation inherently more complex. For distal joints on the limbs, such as the knee, ankle, elbow, and wrist, the presence of the motor near the joint imposes a large inertial load on the limb and requires additional power. In addition, for such joints, a motor / gearbox that is in-line with the joint axis of rotation results in a bulky exoskeleton, i.e., a skeleton outside the body of a person or animal, further hindering smooth movement.

[0004] D. Sahebjavaher, "Validation of the UBC Powered Upper Limb Orthosis Simulator," PhD dissertation, University of British Columbia (2012), http: / / dx.doi.org / 10.14288 / 1.0103452 describes an exoskeleton including a flexible drive shaft for transmitting motor power to the joint gearbox. Paragraph 2.3.2.1 of Sahebjavaher states that for ergonomic reasons, it is important to minimize the weight of the exoskeleton to minimize power requirements, inertial loads, and keep the weight distribution of the device centered on the user's waist, and therefore, a flexible drive shaft is used.

[0005] Paragraph 3.2.1.3 of Sahebjavaher discusses the flexible drive shaft, which introduces complications in predicting the actual performance of the drive system due to its spring-damper-like properties. In addition, paragraph 3.2.1.3 further mentions that bends in the flexible drive shaft produce unpredictable results. Paragraph 3.2.1.3 also discloses that if the flexible drive shaft is not guided, the step response varies significantly and is not repeatable. In order to produce a consistent step response during operation of the orthosis, paragraph 3.2.1.3 proposes the need to guide the flexible drive shaft and strongly recommends the use of a tubular housing to suppress non-axial rotational motion and vibration over the entire length of the shaft.

[0006] MR Tucker et al., "Design of a wearable perturbator for human knee impedance estimation during gait", 2013 IEEE International Conference on Rehabilitation Robotics (ICORR) (2013), http: / / dx.doi.org / 10.1109 / ICORR.2013.6650372 discloses a knee joint perturbator, which experimentally estimates the knee joint impedance of a person in gait by applying angular velocity perturbations. The knee joint perturbator includes a portable lower limb exoskeleton designed to switch between a transparent mode and a speed control mode, and a bidirectional flexible drive shaft for remote actuation.

[0007] Tucker further discloses in paragraph III.D the use of parallel dual-grid strain gauges mounted on opposite sides of the crank of the exoskeleton to sense the interaction torque between the perturbator and the tibia of the leg. Tucker also presents in paragraph IV an experimental characterization of the dynamic properties of the flexible shaft under different bending and loading conditions.

[0008] The teachings of Sahebjavaher and Tucker require torque sensors at the joints to understand the applied torque and accurately drive the remote motors. Torque sensors are expensive and delicate devices that cause additional inertial loads when placed at the joints.

[0009] US2018 / 0133894A1 (also published as WO2016 / 204441A1) discloses an articulated robot actuator. The actuator includes two motors, a pair of joint actuation components, and a pair of spring components for transmitting torque between the motors and the joint actuation components. The spring component can be torsionally deformed, that is, it can include torsional strain. Due to the torsional deformation, a restoring force can be generated. The pair of joint actuation components can include an encoder located on its drive shaft to measure the rotation angle of the pair of joint actuation components, and the degree of torsional strain of the pair of spring components is measured based on the rotation angle of the pair of joint actuation components. The articulated robot actuator counteracts the torsional deformation of the spring component by measuring the degree of torsional strain of the spring component and controlling the motor according to the degree of torsional strain, thereby compensating for the torque caused by the torsional deformation of the spring component. Figure 5 of the document teaches that the encoders are all positioned at the distal end and deviate from the axis with the spring component. The document further teaches that the motor, the spring member and the pair of joint actuating members are located at the waist, whereby the pair of joint actuating members are coupled to the knee joint and / or the hip joint via rigid connecting members.

[0010] US2018 / 0133894A1 does not mention measuring the longitudinal bending deformation of the spring member, that is, the bending of the spring member around an axis perpendicular to the torque transmission axis. Since the joint actuation member is located at the waist, the spring member provides compliance and local torque transmission, but does not provide remote torque transmission to the joint. This is provided via a rigid connection member. Due to the local torque transmission, the embodiment of US2018 / 0133894A1 does not provide a device for guiding the spring member, measuring the spatial configuration of the spring member, and protecting the spring member.

[0011] The present invention is directed to addressing at least some of the above-mentioned problems. Summary of the invention

[0012] In a first aspect, the present invention provides an apparatus for actuating a joint of a human, an animal or a robot.

[0013] In a second aspect, the invention provides a method for actuating a joint of a human, an animal or a robot.

[0014] In a third aspect, the present invention provides the use of a flexible drive shaft as a compliant element and a torque transfer element in a rotary actuator for actuating a mechanical joint.

[0015] In a fourth aspect, the invention provides the use of a flexible drive shaft for determining the impedance of a joint of a human or animal.

[0016] In a fifth aspect, the present invention provides a system for determining the impedance of a joint of a human or animal.

[0017] The present invention is advantageous for a number of reasons. The elongated, longitudinally flexible and torsionally resilient body serves a dual purpose: decentralized torque transfer in a rotary (torsion) actuator (e.g., a rotary series elastic actuator) and a compliant element. Decentralization (relocation) of the motor, e.g., to a fixed external location for a fixed exoskeleton or to the waist for a portable exoskeleton, keeps the inertial load of the distal limb joint or robotic arm limited, thereby limiting power requirements and increasing user comfort and transparency. The body at least partially decouples the dynamics of the motor (including friction and inertia) and protects the motor from shocks introduced on the mechanical joints. In addition, due to its torsion resiliency, the body can improve energy efficiency by storing and returning energy. The body also allows relative motion of the motor and the mechanical joint.

[0018] Because of the compliance of the subject, the device further requires an accurate drive system to produce the desired output torque. Torque sensors are delicate and expensive devices and should therefore be avoided. When placed at or near the distal limb joints, they also introduce inertial loads, which is a further disadvantage. The present invention achieves accurate model-based torque control based on deformation information of the subject, thereby alleviating the need for torque sensors at or near the joints. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A A schematic diagram of a flexible drive shaft is shown. Figure 1B A schematic diagram of multiple concentric layers of windings with opposite pitch angles and directions is shown.

[0020] Figure 2A and Figure 2B The force test bench is shown. Figure 3 Its corresponding schematic overview is shown.

[0021] Figure 4A and Figure 4B The measured torque-deflection angle relationship for two flexible drive shafts in a straight configuration is shown. Fig. 7A and Figure 7B The correspondence of measured and predicted torque-deflection angle relationships in the straight configuration is shown. Fig. 8A and Figure 8B The correspondence of the measured and predicted pseudo-stiffness-deflection angle relationships in the straight configuration is shown.

[0022] Figure 5A A schematic overview of the relative position parameters used to calculate the bend radius is shown. Figure 5B The corresponding experimental setup is shown. Figure 5C Shown is the experimental setup for measuring the bending angle.

[0023] Figure 6The torque-angle relationship of the flexible transmission shaft at different bending radii (in mm) is shown. Fig.9A The correspondence of measured and predicted torque-deflection angle relationships for multiple bend radii is shown. Fig. 9B The bending factors and corresponding errors for the multiplicative torque model are shown.

[0024] Fig. 10A and Fig. 10B A system in which a flexible drive shaft indirectly drives a joint via a transmission system is shown ( Fig. 10A ) and systems in which the flexible drive shaft directly drives the joint ( Fig. 10B ) is a schematic overview of the .

[0025] Fig.11 A schematic diagram of a cascade control system including an inner speed control loop and an outer PID torque control loop is shown.

[0026] Fig. 12A A schematic overview of an embodiment of a device for actuating a joint of a human, an animal or a robot is shown, the device comprising a mechanical joint 302, a motor 301 for providing torque to the mechanical joint, and an elongated, longitudinally flexible and torsionally elastic body 303, wherein the device is configured to transmit torque from the motor 301 to the mechanical joint 302 via the body 303, wherein the device comprises a device configured to determine torsional deformation information (θ s -θ m ) sensor clusters 304a, 304b, and wherein the device is adapted to drive the motor 301 at least partially based on outputs from the sensor clusters 304a, 304b.

[0027] Fig. 12B A schematic overview of an embodiment of a device for actuating an ankle joint is shown. Fig.13 Humanoid position curves are shown for the hip, knee, and ankle joints. Fig.14 Shown in Fig. 10B Performance of the control system following the set point signal for the configuration shown. Fig.15 The corresponding Bode plots for various bending radii are shown. Fig.16 Shown is the measured impedance of a flexible drive shaft at various bend radii. Fig.17 The interactive torque-time curves of human-like external disturbance trajectories applied to the human hip, knee, and ankle joints are shown. Fig.18 The effect of the bending angle on the output torque-angle characteristics of the flexible drive shaft is shown. Fig.19 and Fig. 20 The estimated error curve is shown.

[0028] Fig.21A schematic overview of an embodiment of a device for actuating a joint is shown.

[0029] Fig. 22 A schematic overview of an embodiment of a data flow for driving a motor is shown.

[0030] Fig.23A and Fig. 23B The torques required at the hip and knee joints to accelerate and decelerate the ankle actuator during the gait cycle using a remote and torsionally compliant actuator (RTCA) according to an embodiment of the present invention (solid line) and according to a traditional co-linear scheme (dashed line) are shown, respectively. DETAILED DESCRIPTION

[0031] The present invention relates to a device and method for actuating a joint of a human, animal or robot. Use of a flexible drive shaft as a compliant element and torque transfer element in a rotary actuator for actuating a mechanical joint; Use of a flexible drive shaft to determine the impedance of a human or animal joint; System for determining the impedance of a human or animal joint. The invention is summarized in the corresponding sections above. In the following, the invention is described in detail, preferred embodiments are discussed, and the invention is illustrated by examples.

[0032] Unless otherwise defined, all terms used to disclose the present invention, including technical and scientific terms, have the meanings commonly understood by ordinary technicians in the field to which the present invention belongs. Through further guidance, including looking at the term definitions to better understand the teachings of the present invention.

[0033] As used herein, the following terms have the following meanings:

[0034] As used herein, "a", "an" and "the" have both singular and plural references unless the context clearly indicates otherwise. For example, "a compartment" means one or more compartments.

[0035] As used herein, "about" means that a measurable value such as a parameter, amount, duration, etc., encompasses a variation of less than + / -20%, preferably less than + / -10%, relative to the specified value. More preferably, less than + / -5%, even more preferably less than + / -1%, and still more preferably less than + / -0.1%, as long as such variation is suitable for implementing the disclosed invention. However, it should be understood that the value referred to by the modifier "about" itself is also specifically disclosed.

[0036] As used herein, "comprise" is synonymous with "include" and is inclusive or open-ended, specifying the existence of the following items, such as parts, and does not exclude the existence of other undescribed parts, features, elements, components, steps known in the art or disclosed herein.

[0037] As used herein, a "mechanical joint" refers to a non-human, non-animal joint comprising a first portion and a second portion that can be articulated relative to each other.

[0038] The present invention relates to a slender, longitudinally flexible and torsionally elastic body. "Longitudinal flexibility" can result in "bending deformation" of the body. "Longitudinal flexibility" allows for a variable "spatial configuration". "Torsional elasticity" can result in "torsional deformation" or "torsional strain" of the body. The various parts of the slender body include the local length direction along which the body extends locally. Those skilled in the art will understand that "torsional deformation" is associated with rotation around an axis of rotation parallel to the local length direction, and "bending deformation" is associated with rotation around an axis of rotation perpendicular to the local length direction. Therefore, "bending deformation" is related to the spatial configuration of the body. The limitation of a numerical range by endpoints includes all numbers and fractions contained in the range, as well as the listed endpoints.

[0039] The present invention provides a device for actuating a joint of a human, animal or robot. The device comprises a mechanical joint; a motor for providing torque to the mechanical joint; an elongated, longitudinally flexible and torsionally elastic body for transmitting torque from the motor to the mechanical joint; and a sensor cluster configured to determine torsional deformation information of the body. The device is particularly configured to drive the motor based at least in part on output from the sensor cluster.

[0040] The device is configured to drive a motor based at least in part on torsional deformation information from a sensor cluster. Preferably, the device is configured to drive a motor without directly measuring torque on the body. Preferably, the device is configured to drive a motor without measuring torque at a mechanical joint. Preferably, the device is configured to drive a motor without torque measurement between the body and the mechanical joint. Preferably, the device does not include a torque sensor between the body and the mechanical joint. Preferably, the device does not include a torque sensor at the mechanical joint. Preferably, the device does not include a torque sensor at the end of the body.

[0041] In another aspect, the present invention provides a method for actuating a joint of a human, animal or robot. An elongated, longitudinally flexible and torsionally elastic body is provided. The body includes a distal end and a proximal end. Torsional deformation information of the body is determined. An input for the proximal end of the body, such as an input torque, an input velocity or an input position, is determined based at least in part on a desired output torque at the distal end of the body and the torsional deformation information. The input is applied to the proximal end of the body. Therefore, the input position is a synonym for the input angle.

[0042] Preferably, the input is determined without measuring torque at a distal end of the body. Preferably, the input is determined without measuring torque at a mechanical joint. Preferably, the input is determined without measuring torque between the body and the mechanical joint.

[0043] In a preferred embodiment, the device is configured to determine an input for the proximal end of the body based at least in part on a desired output torque at the distal end of the body and an output from a sensor cluster, whereby the device is further configured to apply the input at the proximal end of the body via a motor.

[0044] The present invention is advantageous for a number of reasons. The elongated, longitudinally flexible and torsionally resilient body serves a dual purpose: decentralized torque transfer in a rotary (torsion) actuator (e.g., a rotary series elastic actuator) and a compliant element. Decentralization (relocation) of the motor, e.g., to a fixed external location for a fixed exoskeleton or to the waist for a portable exoskeleton, keeps the inertial load of the distal limb joint or robotic arm limited, thereby limiting power requirements and increasing user comfort and transparency. The body at least partially decouples the dynamics of the motor (including friction and inertia) and protects the motor from shocks introduced on the mechanical joints. In addition, due to its torsion resiliency, the body can improve energy efficiency by storing and returning energy. The body also allows relative motion of the motor and the mechanical joint.

[0045] Because of the compliance of the subject, the device further requires an accurate drive system to produce the desired output torque. Torque sensors are delicate and expensive devices and should therefore be avoided. When placed at or near the distal limb joints, they also introduce inertial loads, which is a further disadvantage. The present invention achieves accurate model-based torque control based on deformation information of the subject, thereby alleviating the need for torque sensors at or near the joints.

[0046] On the other hand, the present invention provides a system for determining the impedance of a joint of a human or animal. The system includes a mechanical joint that can be applied to the joint from the outside. The system also includes a slender, longitudinally flexible and torsionally elastic body. The body includes a distal end and a proximal end. The body can be directly or indirectly connected to the mechanical joint at the distal end. For example, a gearbox can be arranged between the distal end of the body and the mechanical joint. The system also includes a sensor cluster configured to determine torsional deformation information of the body. In addition, the system includes a processing unit, which is configured to determine the impedance of the joint based at least in part on the torsional deformation information from the sensor cluster.

[0047] Preferably, the system does not comprise a torque sensor at the mechanical joint. Preferably, the system does not comprise a torque sensor at the distal end of the body. Preferably, the system does not comprise a torque sensor between the body and the mechanical joint. Preferably, the processing unit is configured to determine the impedance of the joint without performing a torque measurement at the mechanical joint. Preferably, the processing unit is configured to determine the impedance of the joint without performing a torque measurement at the distal end of the body. Preferably, the processing unit is configured to determine the impedance of the joint without measuring a torque between the body and the mechanical joint.

[0048] Thus, the system of the present invention enables accurate impedance determination based on deformation information of the subject, thereby alleviating the need for torque sensors at or near the joints.

[0049] In a preferred embodiment, the apparatus is configured to determine the impedance of the joint based at least in part on the output from the sensor cluster.

[0050] Those skilled in the art will appreciate that there are common technical features in various aspects of the present invention. Those skilled in the art will further appreciate that different aspects of the present invention are interrelated. In the above description and the subsequent description, specific references to specific aspects of the present invention may be omitted. All features described above or below may belong to each different aspect, even if they have been described in conjunction with a specific aspect.

[0051] In a preferred embodiment, the torsional deformation information includes a relative angle of torsion between the distal end and the proximal end. Preferably, the sensor cluster is configured to determine the relative angle of torsion between the distal end and the proximal end. Preferably, the output of the sensor cluster includes one or more signals indicating the relative angle of torsion. Preferably, the sensor cluster includes two rotary encoders, preferably rotary optical encoders. Preferably, the rotary encoders are positioned in series at both the distal end and the proximal end of the subject. Based on the data from the encoders, the relative angle of torsion between the proximal end and the distal end of the subject can be determined. The one or more signals may include absolute angle measurements. Additionally or alternatively, the one or more signals may include the relative angle of torsion.

[0052] In a preferred embodiment, torsional deformation information and bending deformation information of the subject are determined. Preferably, the bending deformation information includes a bending angle or a bending radius. Preferably, the sensor cluster is configured to determine the torsional deformation information and bending deformation information of the subject. Preferably, the output of the sensor cluster includes one or more signals indicating the bending deformation information. Preferably, the device is configured to drive the motor based at least in part on the torsional and bending deformation information from the sensor cluster. Preferably, the input for the proximal end of the subject is determined at least in part based on the desired output torque at the distal end of the subject and the torsional and bending deformation information. Preferably, the processing unit is configured to determine the impedance of the joint based at least in part on the torsional and bending deformation information from the sensor cluster. Preferably, the sensor cluster includes a distance sensor, a displacement sensor or an additional rotary encoder for determining the bending deformation information.

[0053] The bending of the body affects the torque transmission characteristics of the body. Therefore, it may be important to consider both the torsional deformation information and the bending deformation information to drive the motor to obtain the desired output torque at the distal end of the body. In this way, an output torque closer to the desired output torque can be obtained at the distal end.

[0054] In a preferred embodiment, a torque model based on torsional and bending deformation information is used. Preferably, the device is configured to drive the motor at least partially based on the torque model, which is dependent on the torsional and bending deformation information. Preferably, the input to the proximal end of the subject is determined at least partially based on the desired output torque at the distal end of the subject and the torque model based on torsional and bending deformation information. Preferably, the processing unit is configured to determine the impedance of the joint at least partially based on the torque model based on torsional and bending deformation information. Preferably, the torsional deformation information here is the relative angle of torsion. In order to obtain sufficiently accurate modeling of the subject's behavior, a torque model is generally required. The torque model can be a linear or nonlinear torque model, preferably a nonlinear torque model.

[0055] Fig. 22A schematic overview of an embodiment of a motor for a drive device is shown. Preferably, the body is part of a flexible drive shaft. An output torque desired at a mechanical joint 181 is provided. The desired output torque at the joint can be based, for example, on a known gait cycle for the specific joint. The desired torque at the joint 181 can be converted into an expected output torque 182 at the distal end of the body. For example, this conversion may be required when a gearbox is positioned in series between the distal end of the body and the mechanical joint. With the aid of a sensor cluster 183, torsional and bending deformation information 184 of the body is obtained. Therefore, as described above, the torsional deformation information is usually a relative angle of torsion. Based on the desired output torque 182 at the distal end of the body and the torsional and bending deformation information 184 of the body, a torque model 185 (preferably a nonlinear torque model) is used to calculate the corresponding input 186 at the proximal end of the body. The input 186 at the proximal end of the body can be converted into information for driving a motor 187, such as a motor torque. Similarly, for example, the gearbox may have been positioned in series between the motor and the body. Alternatively or additionally, the output of the torque model can be drive information for the motor, such as motor torque, motor current, motor position (motor angle), or motor speed. The conversion from the input 186 at the proximal end of the body to the information for driving the motor 187 is then implicitly included in the torque model 185.

[0056] In a preferred embodiment, the dependence of the torque model (preferably a nonlinear torque model) on torsional deformation information and on bending deformation information is multiplicatively separable. When the torque model is multiplicatively separable, simulation of the subject behavior is easier, faster, and requires less computational resources. Furthermore, the multiplicatively separable model is sufficiently accurate for industrial application of the invention and demonstrates that the effects of bending and torsion on the subject behavior can be separately calculated and understood.

[0057] The elongated and longitudinally flexible body also has torsional elasticity, that is, the body has limited torsional rigidity. The torque-angle relationship of the body can be nonlinear. The torque-angle relationship of the body can depend on the direction of rotation, i.e. clockwise or counterclockwise. In a preferred embodiment, the torsional elastic body has a torsional rigidity of at most 10000N.m / rad, preferably at most 7499N.m / rad, more preferably at most 5623N.m / rad, more preferably at most 4217N.m / rad, more preferably at most 3126N.m / rad, more preferably at most 2371N.m / rad, more preferably at most 1778N.m / rad, more preferably at most 1334N.m / rad, more preferably at most 1000N.m / rad, more preferably at most 750N.m / rad, more preferably at most 562N.m / rad, and most preferably 422N.m / rad. Those skilled in the art will appreciate that the values ​​in the foregoing list are upper limits for the torque and angle components of the torque-angle relationship along a torsionally elastic body. The torsionally resilient body may include a torsional stiffness, i.e., the portion of torque and angle somewhere along the torque-angle relationship, of about 398 N.m / rad, about 316 N.m / rad, about 251 N.m / rad, about 200 N.m / rad, about 158 ​​N.m / rad, about 126 N.m / rad, about 100 N.m / rad, about 79 N.m / rad, about 63 N.m / rad, about 50 N.m / rad, about 40 N.m / rad, about 32 N.m / rad, about 25 N.m / rad, about 20 N.m / rad, about 16 N.m / rad, about 13 N.m / rad, about 10 N.m / rad, about 7.9 Nm / rad, about 6.3 Nm / rad, about 5.0 Nm / rad, about 4.0 Nm / rad, about 3.2 Nm / rad, about 2.5 Nm / rad, about 2.0 Nm / rad, about 1.6Nm / rad, about 1.3Nm / rad, about 1.0Nm / rad, about 0.79Nm / rad, about 0.63Nm / rad, about 0.50Nm / rad, about 0.40Nm / rad, about 0.32Nm / rad, about 0.25Nm / rad, about 0.20Nm / rad, about 0.16Nm / rad, about 0.13Nm / rad, about 0 .10Nm / rad, about 0.079Nm / rad, about 0.063Nm / rad, about 0.050Nm / rad, about 0.040Nm / rad, about 0.032Nm / rad, about 0.025Nm / rad, about 0.020Nm / rad, about 0.016Nm / rad, about 0.013Nm / rad, about 0.010Nm / rad or any value below or therebetween.

[0058] The flexible drive shaft may or may not have a housing. In a preferred embodiment, the body is a rotatable, elongated, longitudinally flexible and torsionally resilient inner shaft of the flexible drive shaft. Preferably, the device comprises a flexible drive shaft. Preferably, the method comprises the step of providing a flexible drive shaft. Preferably, the system comprises a flexible drive shaft. The flexible drive shaft comprises a rotatable, elongated, longitudinally flexible and torsionally resilient inner shaft, a housing, a distal end, a proximal end, and a connector on each of the distal end and the proximal end. Therefore, the body is a rotatable inner shaft. Preferably, the flexible drive shaft is a bidirectional flexible drive shaft. Preferably, the inner shaft comprises a winding. Preferably, the inner shaft comprises a plurality of substantially concentric winding layers. Preferably, the inner shaft comprises a plurality of continuous substantially concentric layers of windings, which comprise opposite pitch angles and directions. Preferably, the winding comprises a spring grade wire.

[0059] A flexible drive shaft is advantageous for a number of reasons. The housing provides a bearing surface and support for the rotatable inner shaft. It also prevents the inner shaft from twisting excessively when subjected to high loads. A flexible drive shaft has the further advantage that it has a higher efficiency than other conventional non-linear torque transfer components such as universal joints.

[0060] Figure 1A A schematic diagram of an embodiment of a bidirectional flexible drive shaft is shown. The flexible drive shaft comprises a rubber sheath 101 , an outer shell 102 and an inner core 103 . Figure 1B A schematic diagram of the inner core 103 of a bi-directional flexible drive shaft is shown. The inner core comprises a plurality of consecutive substantially concentric layers of windings comprising opposite pitch angles and directions. The windings comprise spring grade wire.

[0061] The characteristics of the flexible shaft are at least partially determined by the grade of the wire, the size of the wire, the number of layers, the number of wires in each layer, and the effective length of the flexible drive shaft. Usually, a compromise needs to be made between torsional stiffness and bending flexibility: if higher torsional stiffness is required, the bending flexibility and the minimum working bending radius of the flexible drive shaft are reduced. This limits the spatial configuration of the flexible drive shaft. The length of the flexible drive shaft usually does not affect the torque transmission, but affects the torsional stiffness: the greater the length, the lower the torsional stiffness.

[0062] The torque-angle relationship of a bidirectional flexible drive shaft is generally nonlinear and depends on the direction of rotation and bending deformation. When the flexible drive shaft is subjected to a torsional load, half of its inner spring-like wire layer attempts to expand as it unwinds, while the other layers above and below it attempt to contract as they are wound tighter. This action, in which the layers squeeze each other under load, provides a torsional stiffness characteristic. However, when the torque is applied in the direction that expands the outer layer, no other layer resists the torque. This operating direction, referred to as the loose outer layer (LOL) direction, will provide the lowest shaft stiffness. In contrast, the opposite direction, the tight outer layer (TOL) direction, will provide the highest shaft stiffness.

[0063] Characterization of the torque transfer characteristics of a flexible drive shaft under dynamic loading and / or deformation is important for accurately driving a mechanical joint or measuring impedance across a mechanical joint.

[0064] The bidirectional flexible drive shaft has an asymmetric torque-angle relationship for clockwise and counterclockwise rotation. In order to obtain a more symmetric torque-angle relationship, two flexible drive shafts can be connected in series so that when rotating, one of the flexible drive shafts always rotates in its outer tight (TOL) direction.

[0065] In another embodiment, the device and / or system includes two flexible drive shafts in parallel and configured to rotate in opposite directions when transmitting torque. In this embodiment, both shafts are fastened together, but spiral in opposite directions.

[0066] The presence of a flexible drive shaft does not preclude the presence of a rigid torque transfer shaft for portions that do not require bending. Thus, the device may or may not include a rigid torque transfer shaft in series with an elongated, longitudinally flexible and torsionally elastic body (e.g., an elastic body), such as a flexible drive shaft. Likewise, the system may or may not include a rigid torque transfer shaft in series with an elongated, longitudinally flexible and torsionally elastic body (e.g., an elastic body), such as a flexible drive shaft. For examples, see Fig. 12A .

[0067] In a preferred embodiment, the flexible drive shaft is used as a compliant element and a torque transfer element in a rotary actuator for actuating a mechanical joint. Preferably, the flexible drive shaft is used to transfer torque from a motor to a target mechanical joint, wherein the motor and the target mechanical joint are mechanically coupled via one or more additional joints, wherein the flexible drive shaft is used to transfer torque from the motor to the target mechanical joint through or on the one or more additional joints. Preferably, the input from the motor to the flexible drive shaft is at least partially based on torsional and / or bending deformation information of the flexible drive shaft.

[0068] In a preferred embodiment, the flexible drive shaft is used to determine the impedance of a joint of a human or animal. Preferably, the impedance is determined at least in part based on torsional and / or bending deformation information of the flexible shaft.

[0069] In a preferred embodiment, a transmission system, such as a gearbox or a cable pulley system, is provided between the distal end of the body and the mechanical joint. Preferably, the device includes a transmission system, such as a gearbox or a cable pulley system, located between the distal end of the body and the mechanical joint. Preferably, the system includes a transmission system, such as a gearbox or a cable pulley system, located between the distal end of the body and the mechanical joint. Additionally or alternatively, a transmission system, such as a gearbox or a cable pulley system, may be provided at the proximal end of the body. In that case, the device may additionally or alternatively include a transmission system, such as a gearbox or a cable pulley system, located between the proximal end of the body and the motor. In that case, the system may additionally or alternatively include a transmission system, such as a gearbox or a cable pulley system, located at the proximal end of the body.

[0070] A gearbox between the distal end of the body and the mechanical joint can increase the effective stiffness: when the gearbox is connected in series behind the flexible shaft, the effective stiffness of the body and gearbox combination is the torsional stiffness of the body multiplied by the square of the gearbox reduction ratio.

[0071] In a preferred embodiment, the device for actuating a joint of a person, animal or robot is a wearable robot for actuating a joint of a person or animal. Preferably, the wearable robot is an exoskeleton. The device can be a lower limb exoskeleton, an upper limb exoskeleton, a robotic arm, a prosthesis or a tactile device.

[0072] The present invention is further described by the following non-limiting examples, which further illustrate the present invention and are not intended to, and should not be construed to, limit the scope of the present invention.

[0073] Example

[0074] Example 1: Characteristics of a flexible drive shaft

[0075] 1.1 Force test bench

[0076] Figure 2A and Figure 2B A dynamometer test bench is shown, comprising a motor 201 , an encoder 202 , a retainer plate 203 and a torque sensor 204 . Figure 3 The corresponding schematic diagram is shown. M+GB represents the ability to provide torsional elasticity (quasi-stiffness K s ) The flexible drive shaft provides torque (angular rotation θ m ) motor and gearbox. The torque sensor measures the transmitted torque T at the far end (output end) of the flexible drive shaft. s. The motor is a rotary EC motor Maxon EC-4pole 30 produced by Maxon Motor AG, equipped with an integrated 86:1 gearbox and a 500 counts per revolution (CPT) encoder. The motor can provide 8N.m of continuous torque, up to 12N.m of intermittent torque, and a continuous speed of 192rpm. The motor is connected to the proximal end (input end) of the flexible shaft via a rod. The Maxon EPOS3 controller can drive the motor in speed control mode. The force test bench also includes two rotary optical encoders (2000CPT), located at both ends of the flexible drive shaft. The difference in the measured values ​​between the two rotary optical encoders provides a measure of the relative torsional deflection angle of the flexible drive shaft. The data is sampled at 1kHz with the help of a Beckhoff EK 1000 module.

[0077] 1.2 The flexible transmission shaft studied

[0078] The first flexible drive shaft studied is MasterFlex 08, which includes a diameter of about 8 mm, a length of about 86.5 cm, a maximum torque of about 6 N.m, and a total weight of about 1.2 kg. The second flexible drive shaft studied is Dremel225, which includes a diameter of about 3 mm, a length of about 20 cm, a maximum torque of about 0.22 Nm, and a total weight of about 0.3 kg. Therefore, the first flexible drive shaft has a higher torsional stiffness and a lower bending flexibility than the second flexible drive shaft.

[0079] 1.3 Straight Line Construction

[0080] Initially, the first and second flexible drive shafts are arranged horizontally and substantially without bending. The output ends of the flexible drive shafts are connected to torque sensors which are blocked at their output ends and measure the torque transmitted through the shafts. The encoder measures the position θ of the output end of the motor unit m , which provides information about the total deflection angle of the shaft. The motor is controlled in velocity mode and is set to follow a torque multi-sine signal with a flat spectrum from 0.01 Hz to 10 Hz and variable amplitude over the maximum range of each flexible shaft.

[0081] Figure 4A and Figure 4B The torque T of the first flexible drive shaft and the second flexible drive shaft are shown respectively s - Deflection angle θ m It can be seen that this relationship is asymmetric. The relationship includes three different areas:

[0082] Quasi-linear region, for negative deflection angles;

[0083] A dead band, where no torque is applied, for small deflection values; and

[0084] Non-linear region for positive deflection angles.

[0085] 1.4 Deformation structure

[0086] Bending deformation affects friction, torque capacity and thus torque transmission. Figure 5A The curved flexible drive shaft includes an entry portion and an exit portion substantially parallel to a common length direction and a curved portion therebetween. The curved portion includes a displacement Y perpendicular to the length direction, which is achieved over a length X in the length direction. By the formula R = (X 2 +Y 2 ) / (4Y), the bending radius R of the flexible drive shaft is calculated based on the relative positions (X, Y) of the two sides of the flexible shaft. For this characterization, the motor and torque sensor are set on two different platforms that can move relative to each other in a two-dimensional Cartesian plane. In addition, retainer plates are evenly distributed along the shaft to hold it properly and maintain the desired configuration during the experiment, see Figure 5B Again follow the instructions in Example 1, paragraph 1.3, to operate the motor.

[0087] Figure 6 The torque-deflection angle relationship of the first shaft at different bending radii R (in mm) is shown.

[0088] As an alternative or in addition to the bending radius R, the bending deformation information may include the bending angle like Figure 5C The bending angle can be measured via a rotary encoder 504 such as a rotary optical encoder. The experimental device also includes a torque sensor 502, a drive unit 507 and a flexible shaft 506. The device can simulate a knee joint 501 with a thigh 505 and a shank 503.

[0089] 1.5 Output Torque – Angular Modeling for Straight Line Construction

[0090] The flexible drive shaft is a non-ideal torsion spring. The relationship between the output torque and the deflection angle of the flexible drive shaft depends on the torsional deflection angle and the bending angle. In addition, the relationship is asymmetric. Surprisingly, these relationships of the flexible drive shaft show high repeatability regardless of the amplitude or frequency of the set point value command.

[0091] A two-component model is provided, which includes a negative component for negative deflection angles and a positive component for positive deflection angles. m -θ s , where θ for the executed tests s = 0, the torque T can be estimated for both positive and negative components using the Fourier series approximation and terms related to dynamics.s and quasi-stiffness K s :

[0092]

[0093] In order to take into account the influence of dynamics in the torque-angle curve, a dynamics-dependent term c is added that takes into account the rotational speed of the shaft.

[0094] Table 1 – Fitting model coefficients for the first flexible drive shaft and the second flexible drive shaft

[0095]

[0096]

[0097] Table 1 contains the fitted model coefficients for the first flexible drive shaft and the second flexible drive shaft. Fig. 7A (first flexible axis) and Figure 7B The corresponding experimental and model torque-angle relationships of the first and second flexible drive shafts are shown in (Second Flexible Shaft). The model shows a root mean square error of 0.029 ± 0.017 Nm relative to the torque value provided by the torque sensor. The normalized root mean square error is 0.315 ± 0.188%, with a maximum observed value of 1.27%. Fig. 8A (first flexible axis) and Figure 8B The corresponding experimental and model quasi-stiffness-angle relationships of the first flexible drive shaft and the second flexible drive shaft are shown in (Second Flexible Shaft).

[0098] 1.6 Output torque – angular modeling of bending deformation

[0099] Surprisingly, it is found that the model's dependence on the bending deformation R and the relative torsion angle Δθ is multiplicatively separable, i.e., T s (Δθ,R)=μ(R).T s (Δθ)and K s (Δθ,R)=μ(R).K s (Δθ), providing surprisingly accurate results.

[0100] Table 2 and Fig. 9B Included are the fitted bending deformation prefactors μ(R) for the first flexible drive shaft at various bending radii R, and the corresponding normalized root mean square errors between experimental data and model predictions. For various values ​​of the bending radius R, the corresponding experimental and model torque-angle relationships of the first flexible drive shaft are Fig.9A Shown in.

[0101] Table 2 – Fitted bending deformation prefactor μ(R)

[0102]

[0103] A simple method has been obtained to model the torque transfer rate (or quasi-stiffness) characteristics of two different flexible drive shafts, taking into account both their dynamic properties and spatial configuration. This allows accurate estimation of torque transfer through a flexible drive shaft based solely on torsional deflection and bending radius without the need for a torque sensor.

[0104] Example 2: Flexible drive shaft directly drives output joint

[0105] In the case of wearable robots, the most important parameters are the torque, velocity and stiffness achieved at the actuator output. When using a flexible drive shaft to drive the output joint directly or in series with a 1:1 drivetrain, see Fig. 10B , highly compliant actuators such as series elastic actuators (SEAs) are obtained, which allow accurate torque control with inherent safety characteristics at the output joint level. Advantages include torque control at the output based on position sensors (angle measurement), safety in case of load-induced shocks, and energy storage capabilities.

[0106] Fig.11 A cascade control system is shown, which includes an inner speed control loop and an outer PID torque control loop executed on the motor controller (EPOS3). Using the separable model T s (Δθ,R)=μ(R).T s (Δθ) The output torque is calculated.

[0107] Fig.14 The performance of the controller achieved when following a desired sinusoidal signal with an amplitude of 6 N.m and a frequency of 1 Hz is shown. For a set of 15 iterations, the tracking error shows a mean value (RMSE) of 0.7334 ± 0.0223 Nm, corresponding to a normalized error (NRMSE) of 6.11%, with an average delay of 25 ms. However, the average accuracy error between the torque estimate and the torque sensor is 0.0456 ± 0.005 Nm (0.37%).

[0108] The bandwidth of the same controller has also been evaluated.A multi-sine signal with a flat spectrum from 0.1 Hz to 10 Hz, variable amplitude of 5 N.m peak, was used as set point for the torque controller for bend radii of 450, 300 and 120 mm and for straight conditions. Fig.15 The approximate second-order transfer function G(s)=T is shown for three of the four conditions tested. estimated / T desiredBode plots of the transfer functions. These transfer functions were estimated using MATLAB's System Identification Toolbox and fit the measured data with close to 80% accuracy under all test conditions. When the cable is straight, the controller shows a bandwidth of 6.22 Hz (calculated as the cutoff frequency at -3 dB attenuation). As the cable is set to a smaller bend radius (higher bends), the bandwidth decreases to 5.87 Hz, 4.32 Hz, and 4.30 Hz for bend radii of 450, 300, and 120 mm, respectively.

[0109] Example 3: Impedance of a Flexible Drive Shaft Under Zero Torque Control

[0110] In order to perform good torque control in a robot that interacts with a person, an accurate actuation system with low impedance is required. The active orthosis must follow the joint motion so that the subject does not feel any resistance when the desired torque is set to zero. In order to check the output impedance of the flexible drive shaft under zero torque control (transparent mode), a motor was connected at its output as an external disturbance. The motor was set to position control mode to follow a chirp signal with a frequency push-sweep from 0.1 to 10 Hz and an amplitude of 20 degrees. The torque controller was set to 0 N.m so that the input motor reacts to the output disturbance in a way that the load does not feel any limitations. Similarly, the torque estimate is used as feedback for the torque control, giving a measure of the interaction torque between the load and the actuator. A torque sensor is set between the load motor and the flexible drive shaft to compare the interaction torque value with the estimated result.

[0111] The output impedance was calculated as a transfer function between the interaction torque (provided by the estimation) and the output speed produced by the load motor for three different conditions: a straight axis and bending radii of 450 and 200 mm. In this way, the effect of the bending radius on the output impedance was characterized. Fig.16 As shown, regardless of the bending radius, for low frequencies, the controller can make the impedance close to zero. As the frequency increases, the controller cannot fully follow the desired output impedance and begins to show a higher impedance until the resonance point is reached and the output impedance becomes the mechanical impedance of the flexible shaft. For lower bending radii, this output impedance increases more. In addition, as the cable bends, the maximum impedance value (resonance point) is achieved at a lower frequency. The output impedance of the flexible drive shaft depends not only on the controller, but also on the spatial configuration of the flexible drive shaft due to the increase in friction with the bending radius. The flexible drive shaft therefore behaves as a variable stiffness actuator because its output stiffness depends on the spatial configuration of the flexible shaft.

[0112] In order to test the interactive torque that a person would feel when using the proposed actuator and controller, the load motors were set to follow the position profiles of the human-like hip, knee, and ankle joints, e.g. Fig.13The results for the interaction torque are shown in Figure 2, taken from human data at a speed of 1.2 s / stride (considered a normal walking speed) (DA Winter, Biomechanics and Motor Control of Human Movement, 2009). Fig.17 where the measurement from the torque sensor is compared with the model estimate. The model accurately predicts the interaction torque. Therefore the proportional part of the PID control can be increased, thus improving the response of the system.

[0113] Example 4: Flexible drive shaft with transmission system at the output joint

[0114] In the case of wearable robots, the most important parameters are the torque, velocity, and stiffness achieved at the actuator output. By directly driving the output joint with a flexible drive shaft, such as Fig. 10B As shown, the output torque is limited by the maximum capacity of the flexible drive shaft. The torque that a flexible drive shaft can transmit is limited and depends mainly on the diameter. Therefore, if a higher torque is required, a thicker flexible drive shaft is required, which increases its size and weight and limits the maximum bending. Another option is to increase the output torque with the help of a transmission system at the output end, such as Fig. 10A As shown, where the reduction ratio is greater than 1. This allows for a thinner, lighter flexible drive shaft. In exchange, the output speed is reduced, the output stiffness is increased, and the compliance of the actuator is limited and the accuracy of the torque controller is reduced due to possible backlash or losses in the transmission system. In particular, the output stiffness increases with the square of the transmission ratio, increasing the output impedance of the device, losing the compliance characteristics of the actuator, and turning it into a rigid actuator.

[0115] In the corresponding test, a gearbox with a transmission ratio of 9:1 was placed at the far end of the flexible drive shaft. The gearbox was connected to a torque sensor to measure the resulting output torque. The transmission sensor can be multiplicatively considered in the torque model and again a good correspondence between the measured and predicted torque is obtained.

[0116] Example 5: Dynamic bending

[0117] In this example, the bending angle is used Instead of the bending radius R, the bending deformation is characterized by Figure 5C The motor 507 and the torque sensor 502 are arranged in two different aluminum profiles, which are used as the thigh 505 and the calf 503 respectively, and the aluminum profiles are connected by a passive hinge joint used as the knee joint 501. The flexible drive shaft 506 connects the motor with the torque sensor 502, and transmits the torque from the thigh to the ankle through the knee joint. The rotary optical encoder 504 measures the rotation angle of the knee This provides information about the bending angle of the flexible shaft. The shaft is firmly and evenly fixed to both bodies with the help of custom-made retaining plates.

[0118] The torque controller was set to follow a 1 Hz sinusoidal signal of 4 N.m amplitude while the angle of the joint was artificially changed to fixed angles of 0, 20, 40, 60, 70, 80 and 90 degrees while the output torque was measured by the torque sensor. The data was collected and implemented in an offline identification procedure with the help of deformation pre-factor to update the model estimate to account for the bending angle. The identified deformation prefactor ( value) is introduced into the dynamic lookup table, where Linear interpolation. In this way, the torque estimate is automatically set to update according to the bending angle measured by the knee encoder.

[0119] Fig.18 The effect of bending angle on the output torque-angle characteristic of the shaft is shown, and the proposed model uses a lookup table with linear interpolation to obtain a separable model. The ability to dynamically track these changes to respond to 4N.m and 1Hz sinusoidal signals according to the bending angle renew

[0120] Fig.19 shows the relationship between the estimation error and the bending angle, and Fig. 20 The corresponding time evolution of the estimation error and the bending angle when using the proposed dynamic model and when not using the model is shown. The maximum estimation error is 0.35Nm when using dynamic adaptation, while the maximum estimation error is 2.8Nm when ignoring the influence of the bending angle. By considering the bending angle, the proposed adaptive model reduces the accuracy error by 87.5%.

[0121] Example 6: Sensor cluster for body deformation information

[0122] This example describes a preferred embodiment of the sensor cluster of the device, method and system.Thus, the body is preferably part of a flexible drive shaft.

[0123] The sensor cluster includes two rotary encoders for determining torsional deformation information. The rotary encoder is preferably a rotary optical encoder, preferably with 2000 counts per revolution (CPT). 2000 CPT corresponds to an accuracy of 0.18°. One of the rotary encoders is positioned in series at the proximal end of the body, and the other of the rotary encoders is positioned in series at the distal end of the body. Based on the signals from the two rotary encoders, the relative angle of torsion between the distal end and the proximal end can be determined.

[0124] The sensor cluster includes one or more bending sensors for determining bending deformation information of the subject. The bending sensor can thus be a distance sensor, a displacement sensor, an attached rotary encoder, etc. The bending sensor can directly measure the deformation of the subject, or can measure the deformation of another component (such as a mechanical joint to which the subject is attached). If the subject includes multiple bending points along its length (and the corresponding wearable robot, orthosis or exoskeleton), each of these bending points can be equipped with the necessary bending sensor.

[0125] Example 7: Implementation of the device

[0126] Fig.21 A schematic overview of an embodiment of a device for actuating a joint is shown. The device comprises a mechanical joint 175, a motor 171 for providing torque to the mechanical joint 175, and a flexible drive shaft 172 located between the motor 171 and the mechanical joint 175 for transmitting torque from the motor 171 to the mechanical joint 175.

[0127] The device also includes sensor clusters 173a, 173b, 174. The sensor clusters include:

[0128] A first rotary optical encoder 173a, arranged in series between the motor 171 and the proximal end of the flexible drive shaft 172;

[0129] A second rotary optical encoder 173b, arranged in series between the distal end of the flexible drive shaft 172 and the mechanical joint; and

[0130] ·Bend sensor 174.

[0131] Based on the outputs from the first rotary encoder 173a and the second rotary encoder 173b, the relative torsion angle of the flexible drive shaft can be obtained. Based on the bending sensor 174, the bending deformation information of the flexible drive shaft, such as the bending angle α or the bending radius, can be obtained.

[0132] Thus, the motor can be positioned on the back of the torso 176 and the mechanical joint can be a knee mechanical joint 175 for rotating the shank 178 relative to the thigh 177.

[0133] Based on the nonlinear torque model 185 (see Fig.18 ) to drive the motor to calculate an input 186 at the proximal end of the flexible drive shaft, preferably an input speed, such as a motor speed, based on a desired output torque 182 at the distal end of the flexible drive shaft and the torsional relative angle and bending deformation information 184 of the flexible drive shaft. Fig.18 Due to the torque model, no torque sensor is required at the mechanical joint, at the distal end of the flexible drive shaft, or between the mechanical joint and the distal end of the flexible drive shaft.

[0134] Decentralization of the motors and driving the motors based on a torque model provides advantages as discussed above in the preceding description.

[0135] Example 8: Comparison with conventional collinear torque provision

[0136] The remote and torsional compliant actuator (RTCA), including a Maxon EC-4pole 30 motor, a MasterFlex 08 flexible drive shaft, two rotary encoders and a gearbox, has a total weight of 1.8 kg, of which 0.7 kg corresponds to the input motor plus gearbox combination, and can provide a maximum torque of 4 to 6 N.m, with a torque bandwidth ranging from 4.3 to 6.22 Hz, depending on the spatial configuration of the flexible shaft. Although the weight of the RTCA is comparable to other compliant actuators with similar torque ranges, the weight of the RTCA is evenly distributed on the limb instead of being concentrated on the joints, thereby improving the mass distribution of the exoskeleton. In addition, using the proposed output torque estimation model, the flexible shaft becomes a virtual torque sensor for the RTCA, which only uses position encoders to estimate and control the output torque delivered at the joint level without the need for actual torque sensors. Torque sensors are usually expensive, bulky and heavy, usually set at the joint position, and also have an adverse effect on the inertia of the system.

[0137] To investigate the effect of the tele-actuation scheme on the torque requirements, a lower limb exoskeleton was simulated using SimMechanics (MATLAB, MathWorks, Inc) where only the ankle joint was actuated. Human-like position trajectories were applied at the hip and knee joints (see Fig.13 ), and when implementing RTCA to drive the ankle joint (see Fig. 12B ) and when the actuator is placed directly in line with the ankle using the traditional solution, the torque required to actuate the joint is compared using inverse dynamics. Using anthropometric data, the exoskeleton is sized for a person with a height of 1.70m, with a thigh length of 0.416m and a calf length of 0.418m. The weight is distributed in the exoskeleton as follows:

[0138] For RTCA, the motor weight (0.7 kg) was modeled as a point mass at 0.1 m from the hip joint and connected to the thigh. The flexible shaft and the remaining components were modeled as a mass at 0.1 m from the knee joint.

[0139] For the co-linear solution, a total weight of 1 kg was estimated, which is 0.7 kg for an actuator implementing the same input motor-gearbox combination as the RTCA, and another 0.3 kg including the compliance element (usually a torsion spring) and the required auxiliary components.

[0140] Fig.23A and Fig. 23B The results of the simulation are shown. Fig.23A and Fig. 23B The torques required to accelerate and decelerate the ankle actuator at the hip and knee joints during the gait cycle are shown, respectively, using a remote and torsionally compliant actuator (RTCA) according to an embodiment of the present invention (solid line) and using a traditional co-linear approach (dashed line).

[0141] For the hip joint, when humanoid kinematic features are applied to the hip and knee joints, the peak torque required to accelerate and decelerate the ankle actuator is reduced from 2.67Nm in extension and 3.45Nm in flexion when using the proposed RTCA scheme when using conventional actuators at the ankle to 2.07Nm in extension and 1.56Nm in flexion. This means that the peak extension torque required for the hip joint has dropped by 22.5% and the peak flexion torque has dropped by 54.8%. For the knee joint, the maximum peak extension torque required is reduced from 3.39Nm to 0.89Nm (a reduction of 73.75%), and the bending torque is reduced from 1.32Nm to 0.35Nm (73.5%).

[0142] Finally, simulation results show that the torque required to accelerate the exoskeleton’s own weight can be greatly reduced using RTCA due to better weight distribution. For the ankle joint, results show a 55% reduction in peak required torque at the hip and a 74% reduction in peak required torque at the knee compared to a collinear conventional actuation scheme.

Claims

1. A device for actuating a joint of a human, an animal or a robot, the device comprising: Mechanical joints; a motor for providing torque to the mechanical joint; and An elongated, longitudinally flexible and torsionally elastic body, Thus, the device is configured to transmit torque from the motor to the mechanical joint via the body, wherein the device also includes a sensor cluster, the sensor cluster is configured to determine torsional deformation information of the body, so that the device is configured to drive the motor at least partially based on the output of the sensor cluster, characterized in that the device includes a flexible drive shaft, the flexible drive shaft includes a rotatable, elongated, longitudinally flexible and torsionally elastic inner shaft, an outer shell, a distal end, a proximal end, and a connector on each of the distal end and the proximal end, so that the body is the rotatable inner shaft, Wherein the sensor cluster is configured to determine bending deformation information of the body, and wherein the output includes one or more signals representing the bending deformation information.

2. The device according to claim 1, wherein: The body includes a distal end and a proximal end, wherein the sensor cluster is configured to determine a relative angle of torsion between the distal end and the proximal end, and wherein the output includes one or more signals representative of the relative angle of torsion.

3. The device according to claim 1, wherein: The bending deformation information includes a bending angle or a bending radius.

4. The device according to claim 2, wherein: The apparatus is configured to drive the motor based at least in part on a torque model that depends on the twist relative angle and the bending deformation information.

5. The device according to claim 4, wherein: The dependence of the torque model on the torsion relative angle and the bending deformation information is multiplicatively separable.

6. The device according to claim 1, wherein: The body includes a distal end and a proximal end, wherein the device is configured to determine an input to the proximal end of the body based at least in part on a desired output torque at the distal end of the body and the output from the sensor cluster, and wherein the device is further configured to apply the input at the proximal end of the body via the motor.

7. The device according to claim 1, wherein: The apparatus is configured to determine an impedance of a joint of the human, animal or robot based at least in part on the output from the sensor cluster.

8. The device according to claim 1, wherein: The torsionally elastic body has a torsional stiffness of at most 10000 N.m / rad.

9. The device according to claim 8, wherein: The torsionally elastic body has a torsional stiffness of at most 5623 N.m / rad.

10. The device according to claim 9, wherein: The torsionally elastic body has a torsional stiffness of at most 3162 N.m / rad.

11. The device according to claim 10, wherein: The torsionally elastic body has a torsional stiffness of at most 1778 N.m / rad.

12. The device according to claim 11, wherein The torsionally elastic body has a torsional stiffness of at most 1000 N.m / rad.

13. The device according to claim 12, wherein: The torsionally elastic body has a torsional stiffness of at most 750 N.m / rad.

14. The device according to claim 1, wherein: The device is a wearable robot for actuating joints of humans or animals.

15. The device according to claim 14, wherein: The device is an exoskeleton.

16. A method for actuating a joint of a human, an animal or a robot, the method comprising the steps of: Providing an apparatus according to any one of claims 1 to 15; determining torsional deformation information of the subject; determining an input to the proximal end of the body based at least in part on a desired output torque at the distal end of the body and the torsional deformation information; and The input is applied at the proximal end of the body.

17. Use of a device according to any one of claims 1 to 15 to actuate a mechanical joint.

18. Use of a device according to any one of claims 1 to 15 for determining the impedance of a joint of a human or animal.

19. A system for determining the impedance of a joint of a human or animal, the system comprising: The device according to any one of claims 1 to 15, wherein the mechanical joint is applicable externally to a joint of the human or animal; and A processing unit is configured to determine the impedance based at least in part on the torsional deformation information from the sensor cluster.

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