Series elastic actuator, method, and system for using thereof

Abstract

An actuation unit (100) designed as a Series Elastic Actuator (SEA) includes a casing (102), at least one elastic element (104), a reducer element (106) and a motor (108). The series elastic chain is composed mainly by the reduction stage casing (102) and the elastic element (104). The motor (108) is laterally arranged with respect to the reducer element (106) to minimize the axial encumbrance and linked with a transmission mechanism (107) to a reducer input shaft (128). Elasticity is obtained by the at least one elastic element (104) exerting a tangential force on a reducer holder (130) to emulate a torsional spring characteristic. The spring deformation can be measured in real-time by measuring the relative rotation between the casing (102) and the reducer holder (130) by an encoder (140).

Description

SERIES ELASTIC ACTUATOR, METHOD, AND SYSTEM FOR USING THEREOF

[0001] CROSS-REFERENCE TO RELATED DISCLOSURES

[0002] This application incorporates by reference: International application No. PCT / IB2014 / 062735, filed on June 30, 2014, and published as WO 2015 / 001469 Al on January 8, 2015; International application No. PCT / IB2016 / 050639, filed on February 8, 2016, and published as WO 2016 / 128877 Al on August 18, 2016; International application No. PCT / IB2019 / 053598, filed on May 2, 2019, and published as WO 2019 / 211791 Al on November 7, 2019; International application No. PCT / US2020 / 029573, filed on April 23, 2020, and published as WO 2020 / 219712 Al on October 29, 2020; International application No. PCT / IB2021 / 058139, filed on September 7, 2021, and published as WO 2022 / 053934 Al on March 17, 2022; International application PCT / IB2023 / 052820, filed on March 22, 2023, and published as WO 2023 / 180958 Al on September 28, 2023; International application No. PCT / IB2023 / 061070, filed on November 2, 2023; and US Provisional Application No. 63 / 615,538, filed December 28, 2023.

[0003] FIELD OF THE DISCLOSURE

[0004] The disclosure relates to an actuation system for wearable robotics.

[0005] BACKGROUND

[0006] Motor disorders associated with aging present challenges for individuals that require mobility assistance, especially in walking and activities of daily living. Robotic orthoses and exoskeletons provide a promising solution to assist elderly people and other individuals living with motor deficits. These orthoses usually have an anthropomorphic form and are worn by the subject. For active assistance purposes, such a robotic orthosis can include an actuation mechanism, which generates mechanical power and transfers that power to the affected joint segment.

[0007] An example of a robotic orthosis is an active pelvis orthosis (APO), which is a wearable orthosis arranged to improve gait energy efficiency especially as affected by impairments of the hip. The APO may be of the type described in WO 2016 / 128877, which employs a sophisticated system of links, actuator, and other components to allow the human flexionextension axis to align with the control systems to give the user hip abduction-adduction rotation, and internal-external rotation assistance. Another example of a robotic orthosis is a sensorized upper limb exoskeleton, which is a wearable device arranged for rehabilitation andassistance of users affected by upper-limb impairments. The upper limb exoskeleton may be of the type described in WO 2023 / 180958, which delivers anti-gravitational support at the shoulder level, enables upper-limb configuration limits for shoulder and elbow ranges of motion, and reads kinematic data that may be analyzed by users and clinicians.

[0008] Known actuation mechanisms used in robotic orthoses include electric, pneumatic, hydraulic, and passive actuators. Notably, the scientific community has taken advantage of Series Elastic Actuators (SEAs) for various applications. Traditional SEAs feature a passive elastic element in series with a motor and gearbox, wherein the motor gearbox is placed directly before or beyond the elastic element.

[0009] The elastic element of a SEA generates a compliant mechanical interface between the motor and the load. The elasticity generally provides reduced reflected inertia and increased shock absorption and energy storage capabilities. However, one of the criticalities in implementing this type of actuator is the choice and construction of the elastic element. Disadvantages of using a traditional SEA include a reduction of the positioning bandwidth and an increase in the number of mechanical parts with a consequent overall weight increase. Additionally, a prevalent axial encumbrance can be observed in traditional SEAs that presents a challenge for these types of actuators to be used in more compact, wearable designs.

[0010] The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate examples of some technology where embodiments of the actuator described herein may be utilized.

[0011] SUMMARY

[0012] Embodiments of the disclosed device, system, and method relate to an actuator unit or actuation unit having an improved series elastic actuator (SEA). The present disclosure is directed to a series of elastic actuators, methods, and systems for use in wearable robotics (e.g., exoskeletons). An object of the present disclosure is to provide an improvement over the traditional SEAs discussed above, in particular from the standpoints of ergonomics and convenience of use, such as weight reduction, compactness, and customized elastic elements acting together as a torsional spring to connect the motor and the gearbox to the actuation apparatus frame.

[0013] In an embodiment, the actuation unit, or actuation system, comprises a casing, a first elastic element, a reducer element (e.g., stator), and a motor. The first elastic element isarranged in series between the casing and the reducer element. The motor includes an output shaft linked to an input shaft of the reducer element by a transmission mechanism (i.e., by means of a belt drive, gear drive, chain drive, or the like). Advantageously, the motor is laterally arranged with the reducer element at the first and second rotational axes, respectively (i.e., the rotational axis of the motor is parallel to the rotational axis of the reducer). This reduces axial encumbrance for more compact applications in wearable robotics.

[0014] The transmission mechanism of the actuation unit can comprise a pulley system, including a first pulley attached to the output shaft of the motor. The first pulley is also connected to the belt and rotatable about the first rotational axis. A second pulley is attached to the input shaft of the reducer element. The second pulley is also connected to the belt and is rotatable about the second rotational axis. In an embodiment, the casing comprises a belt tensioner arranged between the first and second pulleys to maintain adequate tension along the belt. Alternative embodiments of the transmission mechanism, as described herein, can include a gear train assembly.

[0015] In an embodiment, the first elastic element is a linear or bending spring mounted to the casing and a reducer holder of the reducer element. The first elastic element may be arcuate in shape and curve outward from transmission mechanism between the output shaft of the motor and the input shaft of the reducer element. A second elastic element may also be arranged in series between the casing and the reducer element and mounted to the casing and the reducer holder. In an embodiment, the first elastic element is mounted to the casing by a first pin anchor. The first elastic element may also be mounted to the reducer holder by another pin anchor or by a fixed anchor. In an embodiment, the second elastic element is mounted to the casing by a fixed anchor. The second elastic element may also be mounted to the reducer holder by another fixed anchor or by a pin anchor.

[0016] The actuation unit preferably comprises one or more encoders for measuring relative rotation between different components. One of the main features of the disclosed SEA architecture is the precise force / torque control obtained through an encoder that measures the deflection of the elastic element. In an embodiment, the actuation unit comprises a first encoder to measure spring deformation of the first elastic element in real-time by measuring relative rotation between the casing and the reducer holder. The first encoder may be mounted to the reducer holder at the second rotational axis. A second encoder may be provided to measure the relative rotation between the casing and a second output shaft of the reducer element.

[0017] In an embodiment, the reducer holder is arranged to rotate with respect to the casing by at least one bearing. The reducer holder may be barrel-shaped or configured as a flange. The reducer holder may also be configured to contain at least a portion of the second pulley.

[0018] In an alternative embodiment of the actuation unit, the reducer holder is realized together with the casing. The two bodies of the same part could be linked by thin elastic bridges (e.g., radial or variously shaped) to create an elastic behavior similar to the one of the springs. The actuation unit may also comprise an encoder configured to measure the displacement of the elastic bridges by measuring the relative rotation between the first segment and the reducer holder about the second rotational axis.

[0019] These and other aspects of the disclosed actuation apparatus, as well as the methods of operation and functions of the related elements of structure and the combination of parts, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying figures, all of which form a part of this specification.

[0020] For purposes of summarizing the disclosed actuation apparatus, certain aspects, advantages, and novel features of the actuation apparatus have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the actuation apparatus. Thus, the actuation apparatus may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0021] GLOSSARY

[0022] As used, the terms “rigid,” “flexible,” “compliant,” and “resilient” may distinguish characteristics of portions of certain features of the actuation system. The term “rigid” should denote that an element of the actuation system, such as a frame, is generally devoid of flexibility. Within the context of " rigid features,” it should indicate that they do not lose their overall shape when force is applied and may break if bent with sufficient force. The term “flexible” should denote that features are capable of repeated bending such that the features may be bent into non-retained shapes, or the features do not retain a general shape, but continuously deform when force is applied. The term “resilient” may qualify such flexible features as generally returning to an initial general shape without permanent deformation. As for the term “semi-rigid,” this term may connote properties of support members or shells thatprovide support and are free-standing; however, such support members or shells may have flexibility or resiliency.

[0023] The term “approximately” means a value within a statistically significant range of value or values, such as the stated length, distance, weight, height, angle, or force.

[0024] The term “elastic” means being capable of spontaneously recovering in size and shape after deformation.

[0025] The term “encoder” is understood to have its ordinary and usual meaning to one skilled in the art, and, unless specified, may refer to absolute and incremental encoders. The encoder may encompass a device or sensor used to detect position. The encoder may be mechanical, optical, magnetic, or electromagnetic induction type.

[0026] The terms “substantial” or “substantially” mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including, for example, tolerances, measurement error, measurement accuracy limitations, and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. The terms “substantial” or “substantial” mean ±10% in some embodiments, ±5% in some embodiments, and ±1% in others.

[0027] The term “user” generally refers to a person, wearer, patient, or operator using a device with the actuation unit.

[0028] The term “transmission mechanism,” as used herein, refers to a mechanical power transmission device or apparatus configured to convey movement, power, and / or energy between two points (e.g., between a motor and a reducer element).

[0029] It will be understood that, unless a term is defined to possess a described meaning, there is no intent to limit the meaning of such term, either expressly or indirectly, beyond its plain or ordinary meaning.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] References will be made to embodiments of the disclosure, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the disclosure is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the disclosure to these particular embodiments. Items in the figures are not necessarily drawn to scale.

[0032] Further characteristics and advantages of the invention will emerge clearly from theensuing description referring to the annexed drawings, which are provided purely by way of non-limiting examples and in which:

[0033] Figs. 1A illustrates a block diagram that provides a general architecture for an embodiment of the actuation unit.

[0034] Figs. 1B-1C illustrate side and top perspectives of the general architecture for an embodiment of the actuation unit with a belt transmission.

[0035] Figs. 1D-1E illustrate side and top perspectives of the general architecture for an embodiment of the actuation unit with a geared transmission.

[0036] Figs. 2A-2B illustrate diagrams of elasticity obtained with elastic elements exerting a tangential force on a reducer frame.

[0037] Fig. 3 illustrates a side cross-sectional view of an embodiment of the actuation unit.

[0038] Figs. 4A-4D illustrate top cross-sectional views of actuation units having various elastic element configurations.

[0039] Figs. 5A-5B illustrate perspective views of a casing for an embodiment of the actuation unit.

[0040] Fig. 6A illustrates a side cross-sectional view of an embodiment of the actuation unit.

[0041] Fig. 6B illustrates a perspective view of the first segment of the actuation unit in Fig. 6A.

[0042] Fig. 6C illustrates a perspective view of the first segment of the actuation unit in Fig. 6A with a fixed anchor configuration for the elastic elements.

[0043] Fig. 6D illustrates a perspective view of the first segment of the actuation unit with a geared transmission.

[0044] Fig. 7 illustrates a diagram for obtaining torsional stiffness in embodiments of elastic elements utilized in the disclosed actuation unit.

[0045] Fig. 8 illustrates a graph of the stiffness characterization of elastic elements from the disclosed actuation unit.

[0046] Figs. 9A-9B illustrate top and perspective views of an alternative embodiment of the actuation unit having a reducer holder realized together with the casing.

[0047] Fig. 10A illustrates an application of the actuation unit with an active pelvic orthosis.

[0048] Fig. 10B illustrates an application of the actuation unit with an upper-body exoskeleton.

[0049] DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0050] While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments are shown in the drawings and are described below in detail. The dimensions, angles, and curvatures represented are to be understood as exemplary and are not necessarily shown in proportion. It should be understood, however, that there is no intention to limit the disclosure to the specific embodiments disclosed. Still, on the contrary, the intention is to cover all modifications, alternative constructions, combinations, and equivalents falling within the spirit and scope of the disclosure. In the various figures, similar elements are provided with similar reference numbers. The reference numbers used herein are provided merely for convenience and, hence, do not define the sphere of protection or the scope of the embodiments.

[0051] Fig. 1A illustrates a general architecture of a series elastic actuator (SEA) system 10. The SEA system 10 comprises at least one elastic element 30 (e.g., linear or bending spring) mounted in series with a casing 20 and a reducer element 40. Due to the elasticity of the elastic element 30, the SEA system 10 allows for inherent compliance with human joints. Additionally, in embodiments where the elastic element 30 is looped with a position encoder (e.g., encoder 140), the elastic element 30 may be used to obtain reliable, precise torque measurements. As depicted in the block diagram, the reducer element 40 is placed in series between the elastic element 30 and a load 60. However, unlike traditional SEA architectures where the motor-gearbox is placed directly before or beyond a sensorized spring, the SEA system 10 features a motor 50 placed laterally with respect to the reducer element 40 to minimize the axial encumbrance. The motor 50 is linked to the reducer element 40 by means of a belt 70.

[0052] Figs. 1B-1C illustrate side and top perspectives of the general architecture for an embodiment of the SEA system 10 having two elastic elements 30, 32 arranged with a belt transmission mechanism. From the perspective of Fig. IB, the following passage refers to the first elastic element 30; however, the same applies to the second elastic element 32. The first elastic element 30 is mounted in series to the casing 20 and to a frame 42 of the reducer element 40. The first elastic element 30 of the SEA system 10 generates a compliant mechanical interface between the motor 50 and the load 60, wherein the load 60 is connected to a reducer output shaft 46 of the reducer element 40. The elasticity of the first elastic element 30advantageously provides reduced, reflected inertia and increased shock absorption and energy storage capabilities. The motor 50 (e.g., brushless) transmits rotation and torque for the SEA system 10 at an output shaft 52. The output shaft 52 is connected to an input shaft 44 of the reducer element 40 by means of a belt 70. The reduced axial encumbrance achieved by laterally arranging the motor 50 and reducer 40 and connecting them by the belt 70 allows for the SEA system 10 to be used in various compact, simplified applications for wearable robotics. The belt 70 may be a band, chain, or similar structure connecting to the output shaft 52 and the input shaft 44 (e.g., by a pulley system).

[0053] Alternatively, as illustrated in Figs. 1D-1E, the belt 70 may be removed and replaced in embodiments that employ a gear transmission mechanism with a gear train 80 having interacting gear components. The gear train 80 includes a driving gear 86 connected to the output shaft 52, a driven gear 82 connected to the input shaft 44, and at least one transmission gear 84 to transfer power and rotational motion from the motor 50 to the reducer 40. The reduced axial encumbrance achieved by laterally arranging the motor 50 and reducer 40 and connecting them by the gear train 80 also allows for the SEA system 10 to be used in various compact, simplified applications for wearable robotics.

[0054] Figs. 2A-2B illustrate diagrams of the elasticity obtained with the first and second elastic elements 30, 32 (e.g., linear or bending springs) exerting tangential force (dFl, dF2) on the reducer frame 42 by displacement (dll, dl2) of the first and second elastic elements 30, 32 to emulate torsional spring characteristics. The elastic element 30 could be configured and dimensioned as a classical torsional spring; however, this configuration is not convenient for axial dimensions. The elastic element 30 is arranged as a linear or bending spring in a preferred embodiment; however, one skilled in the art will recognize that various types of springs can be used (e.g., mono-leaf springs, coil springs, and the like). The elastic deformation is measured in real time by measuring the relative rotation (d0) between the casing 20 and the reducer frame 42, with at least one encoder. As depicted, the relative rotation (d0) is measured about the rotational axis (Al) defined by the frame 42. Like the encoders described in International application No. PCT / IB2023 / 061070, the same being incorporated by reference in its entirety, the encoder (e.g., encoder 140) may be used to compute the torque (drl, dr 2) generated by the SEA system 10 based on the stiffness values of the first and second elastic elements 30, 32.

[0055] Fig. 3 illustrates a side cross-sectional view of an embodiment of the actuation unit 100. The actuation unit 100 comprises a casing 102, at least one elastic element 104, reducer element 106, and motor 108. In an embodiment, the casing 102 includes a first segment 112 and asecond segment 114. The first segment 112 is generally constructed as a housing for the reducer element 106 and the motor 108, and the second segment 114 is generally constructed as a cover to protect internal components of the actuation unit 100. In an embodiment, the first segment 112 forms a chamber 116 to contain the motor 108. In an embodiment, the motor 108 is mounted to first segment 112 by a fastener 123 (e.g., screw); however, the motor 108 may be mounted within the chamber 116 using alternative fastening means such as bolts, washers, anchors rivets, or other mechanical fasteners or using welding, riveting, or clinching. The output shaft 120 of the motor 108 extends through an aperture 118 formed by the first segment 112 and into the receptacle 126 within, or space formed by, the second segment 114.

[0056] The actuation unit 100 comprises a transmission mechanism 107 arranged to convey power from the motor 108 to the reducer element 106. In an embodiment, the transmission mechanism 107 is a pulley system. The motor 108 transmits rotation about a first axis II and torque at the output shaft 120 of the actuation unit 100 to a first pulley 122. The first pulley 122 is connected to the output shaft 120 and is positioned above the chamber 116 of the first segment 112. A belt 110 connects the first pulley 122 to a second pulley 124, the second pulley being arranged to rotate at a second axis 12 of rotation. The belt 110 is generally provided as an endless drive member, such as an elastic band, chain, toothed belt, or another type of endless drive member. Alternatively, the belt 110 may be replaced by geared components, wherein the first and second pulleys 122, 124 are arranged as gears with interacting teeth for transmitting power or force between the motor 108 and the reducer element 106. The first and second pulleys 122, 124 are generally provided as wheels; however, they could alternatively be configured and dimensioned as sprockets, toothed pulleys, or any other types of rotational member.

[0057] The second pulley 124 is connected to an input shaft 128 of the reducer element 106. The reducer element 106 (e.g. , stator) is housed within a reducer holder 130. The reducer holder 130 is generally barrel shaped, arranged to rotate about the second axis 12, and located within the first segment 112 of the casing 102 using at least one bearing 134. At least one bearing 134 may be a rolling element that reduces rotational friction and supports the weight of the reducer element 106. In an embodiment, one or more fasteners 133 may be used to attach the reducer holder 130 to the reducer element 106 on a frame 132 of the reducer element 106. In an embodiment, the output rod 136 of the reducer element 106 extends through an opening 138 formed by the first segment 112 to connect with a load (e.g., an assistive device for an exoskeleton).

[0058] In an embodiment, the actuation unit 100 comprises first and second encoders 140, 142 configured to measure values of rotation and deformation of the at least one elastic element 104 and reducer holder 130. The values obtained then allow for computing the torque generated by the actuation unit 100. The first encoder 140 is configured to measure rotational displacement between the casing 102 and reducer holder 130. As depicted in Fig. 4A, the first encoder 140 may be mounted to the casing 102 and configured to measure values from a positional element 144 (e.g., magnet) mounted on the reducer holder 130. The second encoder 142 is configured to measure the displacement between the casing 102 and output rod 136 of the reducer element 106.

[0059] Figs. 4A-4D depict various spring configurations of the elastic elements 104, 105 mounted on the first segment 112 of the casing 102. The first scheme SI, as illustrated in Fig. 4A, generally represented by the icon in drawing, illustrates a pin-to-pin configuration. The first elastic element 104 is mounted to the casing 102, proximal to the first pulley 122, by a first pin anchor 146. The first elastic element 104 is likewise mounted to the reducer holder 130, proximal to the second pulley 124, by a second pin anchor 148. The first and second pin anchors 146, 148 allow for some minor rotational movement at the attachment points but do not allow translational movement. In an embodiment, the pin anchors 146, 148 may be provided as mechanical fasteners (e.g., nails, tacks, screws) and / or may be formed, in whole or in part, as part of the first segment 112 of the casing 102. The first and second pin anchors 146, 148 are thus limited to respective axial forces at first and second end points of the first elastic element 104. The second elastic element 105 may also feature a pin-to-pin configuration, wherein the second elastic element 105 is mounted (i) to the casing 102 by a third pin anchor 150 and (ii) to the reducer holder 130 by a fourth pin anchor 152.

[0060] Connection through a pin or pine-like fastener (e.g., first pin anchor 146) offers the advantage of facilitating the manufacturing of the elastic element 204 and streamlining the assembly procedure of the actuation unit 100. Furthermore, achieving the required stiffness of the elastic elements 104, 105 is made more straightforward as they function as separate parts without experiencing stress concentration resulting from a rigid connection. Examples of pin anchors include pins, nails, screws, rivets, bolts, and the like.

[0061] Fig. 4B depicts a second scheme S2 having a fixed-pin configuration. Like the first scheme SI, the first elastic element 104 is mounted to the reducer holder 130 by a pin anchor 148. However, in the second scheme S2, the first elastic element 104 is mounted to the casing 102 by a first fixed anchor 154. The first fixed anchor 154 provides a more rigid connectionthat constrains the first elastic element 104 to the casing 102 and prevents translational and rotational movement at the first end of the first elastic element 104. Thus, in this embodiment, there is a more rigid connection at the casing 102 than at the reducer holder 130. The second elastic element 105 may also feature a fixed-pin configuration, wherein the second elastic element 105 is mounted (i) to the casing 102 by a fixed anchor 158 and (ii) to the reducer holder 130 by a pin anchor 152. In an embodiment, the fixed anchors 154, 158 may be provided as mechanical fasteners (e.g., nails, tacks, screws) and / or may be formed, in whole or in part, as part of the first segment 112 of the casing 102.

[0062] The use of a “rigid” connection (e.g., first fixed anchor 154) may eliminate friction in the coupled parts (e.g., elastic element to casing or elastic element to reducer holder). However, the design effort required to produce parts from a single material increases. In the context of mass production, a rigid connection could be represented as a solution ensuring greater repeatability in the performance of the system. Examples of fixed anchors can include the use of multiple pins, nails, screws, rivets, bolts, and the like.

[0063] Fig. 4C depicts a third scheme S3 comprising a pin-fixed configuration, wherein the first elastic element 104 is mounted to the casing 102 by a first pin anchor 146 and is mounted to the reducer holder 130 by a fixed anchor 156. Thus, in this embodiment, there is a more rigid connection at the reducer holder 130 than at the casing 102. The second elastic element 105 may also feature a pin-fixed configuration, wherein the second elastic element 105 is mounted (i) to the casing 102 by a pin anchor 150 and (ii) to the reducer holder 130 by a fixed anchor 160.

[0064] Fig. 4D depicts a fourth scheme S4 comprising a fixed-fixed configuration, wherein the first elastic element 104 is mounted to the casing 102 by a first fixed anchor 154. The first elastic element 104 is likewise mounted to the reducer holder 130 by a second fixed anchor 156. The second elastic element 105 may also feature a fixed-fixed configuration, wherein the second elastic element 105 is mounted (i) to the casing 102 by a fixed anchor 158 and (ii) to the reducer holder 130 by a fixed anchor 160. Advantageously, the fixed anchors provide more secure attachments with multiple contact points. One skilled in the art will recognize that the type of anchor or attachment used to connect the elastic element 104 to the casing 102 and reducer holder 130 may depend on the material used for the elastic element 104. For example, different materials have different buckling forces and stresses that depend on the type of connection (i.e., pinned or fixed).

[0065] The elastic elements 104, 105 depicted in Figs. 4A-4D provide an illustrative shape to show a spring-like configuration; however, the elastic elements 104, 105 may be designed with different configurations. For example, the elastic elements 104, 105 may be arcuate or convex in shape, curving outward away from the transmission mechanism 107 (e.g., the pulleys 122, 124 and belt 110). Again, a fundamental variant for obtaining the desired characteristics of the elastic elements 104, 105 lies in the material or materials used; the most suitable materials are the metals generally used in mechanical constructions. They include steel, aluminum alloys and titanium alloys. There may be identified in the Young's modulus of the selected material, the fundamental parameter for obtaining the desired rigidity characteristics of the elastic elements 104, 105. Besides the desired rigidity, the material selection to be used directly follows the amount of mechanical load (e.g., load 60) that the elastic elements 104, 105 should be capable of bearing and the degree of dimensional compactness to be obtained.

[0066] Figs. 5A-5B depict an embodiment of the actuation unit 200 having a compact casing 202. The casing comprising first and second segments 212, 214 that may be joined together to house and protect various elements (pulleys, belts, shafts, etc.) of the actuation unit 200. The motor 208 is housed within a chamber 216 of the first segment 212 and is accessible from the bottom of the first segment 212. An output interface 237 may also be accessible on the bottom of the first segment 212 for outputting torque and force from the reducer element 206. The lateral placement of the motor 208 next to the reducer element 206, housed within the first segment 212, minimizes the overall axial encumbrance of the actuation unit 200 and allows the actuation unit 200 to be used in compact applications of wearable robotics.

[0067] Figs. 6A-6B depict cross-sectional and perspective views of the actuation unit 200 having an exemplary pin-to-pin configuration of elastic elements 204, 205. The actuation unit 200 comprising the casing 202, first and second elastic elements 204, 205, reducer element 206, and motor 208. The motor 208 is housed within the first segment 212 of the casing 202 and may be fastened within a chamber 216 of the first segment 212 by one or more fasteners 233. The fastener may be a screw, bolt, clip, and / or another rigid connecting element. The motor 208 generates torque at an output shaft 220 that extends through an aperture 218 formed by the first segment 212 and that connects to a first pulley 222. The first pulley 222 is connected to a second pulley 224 by a belt 210. The belt 210 may have a polyurethane construction resistant to pollutants and abrasion and feature a carbon fiber tensile cord. In an embodiment, the belt 210 may have a nylon construction for favorable mechanical properties, fatigue resistance, and weight reduction. In an embodiment, the actuation unit 200 may comprise a belttensioner 211 mounted on the first segment 212 and between first and second pulleys 222, 224. The belt tensioner 211 is configured and dimensioned to rotate and maintain proper tension of the belt 210 between the first and second pulleys 222, 224.

[0068] In an embodiment, the second pulley 224 defines a projection 225 that extends through the reducer element 106 to an output interface 237. The reducer input shaft 228 of the reducer element 206 is mounted to the second pulley 224. The reducer holder 230 houses the reducer element 206 and is configured to rotate with displacement of first and second elastic elements 204, 205. The reducer holder 230 is also configured to house the second pulley 224. In an embodiment, one or more bearings 234 may be provided between the second pulley 224 and the reducer holder 230. Bearings 234 may also be provided between the reducer holder 230 and second segment 214 and between an output shaft 236 of the reducer element 206 and the first segment 212. In a preferred embodiment, an encoder 240 is mounted to the reducer holder 230 and above the second pulley 224. An encoder 242 may also be provided at the output interface 237 between the output shaft 236 and the first segment 212. In an embodiment, the output shaft 236 is carried by a flange 231 rotatable with respect to the casing 202 through a bearing 235.

[0069] As depicted in Fig. 6B, the actuation unit 200 comprises a pin-to-pin configuration with first and second elastic element 204, 205. The first elastic element 204 is mounted to the first segment 212 of the casing 202 by a first pin anchor 246. The first elastic element 204 bows outwardly between the first and second pulleys 222, 224 from the first pin anchor 246 to a second pin anchor 248 mounted on the reducer holder 230. Likewise, the second elastic element 205 is mounted to the first segment 212 of the casing by a third pin anchor 250. The second elastic element 205 curves from the third pin anchor 250 to a fourth pin anchor 252 mounted on the reducer holder 230. Advantageously, the elastic elements can be configured as a monoleaf springs or a parabolic leaf spring to accommodate various interspersed components, e.g., the transmission mechanism. One skilled in the art will recognize that various spring configurations may be provided, similar to the embodiments provided in Figs. 4A-4D, to achieve elastic elements 204, 205 with desirable deformation characteristics.

[0070] Figs. 6C-6D depict perspective views of the actuation unit 200 having an exemplary fixed-fixed configuration of elastic elements 204, 205. Similar to the fourth scheme S4 depicted in Fig. 4D, the first elastic element 204 features a fixed-fixed configuration and is mounted to the casing 202 by a first fixed anchor 254 and further mounted to the reducer holder 230 by a second fixed anchor 256. The second elastic element 205 also features a fixed-fixedconfiguration, wherein the second elastic element 205 is mounted (i) to the casing 202 by a fixed anchor 258 and (ii) to the reducer holder 230 by a fixed anchor 260. One skilled in the art will recognize that the type of anchor or attachment used to connect the elastic element 204 to the casing 202 and reducer holder 230 depends on the type of material used for the elastic element 204. Advantageously, arranging the elastic elements 204, 205 to be fixed at both extremities does not require pretension and avoids backlash. In this case, the elastic elements 204, 205 behave like beams rather than compression springs because of the fixed anchors.

[0071] While Figs. 6A-6C illustrate embodiments of the actuation unit 200 comprising a transmission mechanism 207 arranged with a belt 210 and pulleys 222, 224, Fig. 6D illustrates an embodiment of the actuation unit 200 comprising a transmission mechanism 207 with a gear train 280. In particular, the actuation unit 200 features a gear train 280 to transmit rotational motion and torque from the motor 208 to the reducer element 206. In an embodiment, the gear train 280 includes a driving gear 286 connected to the motor output shaft 220. The driving gear 286 initiates the rotation and transmits power to one or more transmission gears 284, and the one or more transmission gears 284 are connected to an output gear (e.g., driven gear 82), which is mounted to the reducer input shaft 228 of the reducer element 206. Advantageously, the gears of the gear train 280 receive less friction and can achieve higher speeds at a quicker rate than pulley systems. The gear train 280 can also have a longer lifespan and produce more power than pulley systems. In an embodiment, the gears of the gear train 280 are composed of copper alloys, iron alloys, aluminum alloys, thermoplastics, or any combination thereof.

[0072] Fig. 7 shows a diagram for obtaining torsional stiffness in embodiments of elastic elements utilized in the disclosed actuation unit 200. Given the linear stiffness of the push-pull spring pair (i.e., elastic elements 204, 205), one may obtain the equivalent torsional stiffness ‘K_Torsional’ of the actuation unit 200 using the following equation:^Torsional 2 X T X Knnear

[0073] Wherein ‘K_Linear’ is defined as the linear stiffness of the elastic element and ‘r’ is defined as the radius of the pin or fixed connection point (e.g., second pin anchor 248) of the elastic element (e.g., first elastic element 204) to the reducer holder (e.g., reducer holder 230). Fig. 8 depicts exemplary results of a characterization test of the elastic elements 204, 205 based on the diagram and equation from Fig. 7. The desired stiffness value of the elastic elements 204, 205 depends on several aspects, such as the resolution of the encoders 240, 242 used for reading the deformation. Additionally, the material or materials used in the mechanical construction of the elastic elements 204, 205 include steel, aluminum alloys and titaniumalloys.

[0074] In general, the resulting torsional stiffness that allow the use of the system as an actuator for wearable robots may range between hundreds and thousands of Nm / rad (e.g., 200-5000 Nm / rad). The exact value depends on the specific application (i.e., human joint, joint speed, level of forces) and on the choice of the resolution of the encoder used to measure the spring deflection. In the disclosed embodiments, the linear stiffness of the elastic elements may range between 200 N / mm and 1000 N / mm for achieving a proper performance with a compact design.

[0075] Figs. 9A-9B depict an alternative embodiment of actuation unit 300. The first segment 312 of the casing 302 is realized with the reducer holder 330. The first segment 312 is linked to the reducer holder 330 by thin, elastic bridges 304 of the same monolithic part to create an elastic behavior similar to that provided by elastic elements 104, 204 in aforementioned embodiments. In an embodiment, the elastic bridges 304 may be radial shaped; other shapes (e.g., curved, angled) may be used to provide elastic behavior specific to the application. In an embodiment, the reducer holder 330 is barrel-shaped or formed as a flange, still being realized together, or formed with the casing 302. The actuation unit 300 may also comprise an encoder 340 and positional element 344 configured to measure the displacement of the elastic bridges 304 by measuring the relative rotation between the first segment 312 and the reducer holder 330 about the second rotational axis 12. The reducer holder 330 may also interface with a bearing 334 to enable rotation of the reducer element (e.g., reducer element 106, 206) with respect to the reducer holder 330. The actuation unit 300 further comprises a transmission mechanism as a belt 310 between first and second pulleys 322, 324.

[0076] Figs. 10A-10B illustrate exemplary applications that may utilize the actuation units discussed above. In Fig. 10A, an active pelvic orthosis 401 is provided with an actuation unit 400 to assist in movement at the hip joint. In Fig. 10B, an upper-body exoskeleton 501 is provided with an actuation unit 500 to assist in movement at the shoulder joint. The disclosed actuation unit is suitable for several applications in robotics; however, given the compact design, it represents an important solution for actuating wearable robots. One skilled in the art will recognize that the actuation unit may also act on other human joints (i.e., elbow, knee) and is not solely limited to the disclosed example and embodiments.

[0077] The features and / or components of one embodiment, example, or figure discussed, shown, or suggested hereinabove may be combined with features and / or components of otherembodiments, examples, or figures discussed, shown, or suggested herein to provide embodiments, examples, or implementation variations that are not explicitly verbally or visually described or shown herein.

[0078] One skilled in the art will realize that the disclosed elastic element assembly may be composed of multiple deformable parts in parallel and series among each other to develop further embodiments. These and other alternatives will readily occur to the skilled artisan in view of the present disclosure and are encompassed within the subject matter of the present disclosure.

[0079] It is to be understood that even though numerous characteristics and advantages of various embodiments of the present disclosure have been outlined in the foregoing description, together with details of the structure and function of various embodiments thereof, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

CLAIMS1. An actuation unit (100) comprising: a casing (102); a reducer element (106) having an input shaft (128); a first elastic element (104) arranged in series between the casing (102) and the reducer element (106); and a motor (108) having an output shaft (120) linked with a transmission mechanism (107) to the input shaft (128) of the reducer element (106); wherein the motor (108) is laterally arranged with the reducer element (106) at first and second rotational axes (II, 12), respectively; and wherein the first elastic element (104) is mounted to the casing (102) and a reducer holder (130) of the reducer element (106).

2. The actuation unit (100) of claim 1, further comprising a second elastic element (105) arranged in series between the casing (102) and the reducer element (106), the second elastic element (105) being mounted to the casing (102) and the reducer holder (130).

3. The actuation unit (100) of claim 1, further comprising a first encoder (140) to measure spring deformation of the first elastic element (104) in real-time by measuring relative rotation between the casing (102) and the reducer holder (130).

4. The actuation unit (100) of claim 1, wherein the transmission mechanism (107) comprises a first pulley (122) attached to the output shaft (120) of the motor (108) and a second pulley (124) attached to the input shaft (128) of the reducer element (106), the first pulley (122) and second pulley (124) being connected via belt (110).

5. The actuation unit (100) of claim 1, wherein the transmission mechanism (107, 207)comprises a gear train (280) arranged to transmit power from the motor (108, 208) to the reducer element (106, 206).

6. The actuation unit (100) of claim 1, wherein the first elastic element (104) is mounted to the casing (102) by a first pin anchor (146).

7. The actuation unit (100) of claim 2, wherein the second elastic element (105) is mounted to the casing (102) by a pin anchor (150).

8. An actuation unit (200) comprising: a casing (202); a first elastic element (204) arranged in series between the casing (202) and a reducer element (206); a second elastic element (205) arranged in series between the casing (202) and the reducer element (206); a motor (208) having a first output shaft (220) linked with a transmission mechanism (207) to an input shaft (228) of the reducer element (206); wherein the motor (208) is laterally arranged with the reducer element (106) at first and second rotational axes (II, 12), respectively; wherein the first elastic element (204) is mounted to the casing (202) and a reducer holder (230) of the reducer element (206); wherein the first elastic element (204) is arcuate in shape and curves outward from the transmission mechanism (207) between the output shaft (220) of the motor (208) and the input shaft (228) of the reducer element (206).

9. The actuation unit (200) of claim 8, further comprising:a first encoder (240) to measure relative rotation between the casing (202) and the reducer holder (230); and a second encoder (242) to measure relative rotation between the casing (202) and a second output shaft (236) of the reducer element (206).

10. The actuation unit (200) of claim 8, wherein the transmission mechanism (207) comprises: a first pulley (222) attached to the first output shaft (220) of the motor (208), the first pulley (222) being rotatable about the first rotational axis (II); a second pulley (224) attached to the input shaft (228) of the reducer element (206), the second pulley (224) being rotatable about the second rotational axis (12); and a belt (207) connected to both the first pulley (222) and the second pulley (224) and arranged to transfer power between the motor (208) and the reducer element (206); wherein the second rotational axis (12) is parallel to the first rotational axis (II).

11. The actuation unit (200) of claim 8, wherein the first elastic element (204) is mounted to the reducer holder (230) by a first pin anchor (246).

12. The actuation unit (100, 200) of claim 8, wherein the first elastic element (104, 204) is mounted to the casing (102, 202) by a first fixed anchor (154, 254).

13. The actuation unit (200) of claim 8, wherein the transmission mechanism (207) comprises a gear train (280) arranged to transmit power from the motor (208) to the reducer element (206).

14. The actuation unit (200) of claim 8, wherein the casing (202) comprises a first segment (212) and a second segment (214), the first segment (212) configured to house the motor (208) within a chamber (216).

15. The actuation unit (200) of claim 8, wherein the reducer holder (230) is arranged to rotate with respect to the casing (202) by at least one bearing (234).

16. The actuation unit (200) of claim 9, wherein the first encoder (240) is mounted to the reducer holder (230) at the second rotational axis (12).

17. The actuation unit (200) of claim 10, wherein the reducer holder (230) is barrel-shaped and configured to contain at least a portion of the second pulley (224).

18. An actuation unit (100, 300) comprising: a casing (102, 302); a reducer element (106) comprising an input shaft (128); and a motor (108) having an output shaft (120) linked with a belt (110, 310) to the input shaft (128) of the reducer element (106) by first and second pulleys (122, 124), respectively; wherein the motor (108) is laterally arranged with the reducer element (106) at first and second rotational axes (II, 12), respectively; wherein the casing includes a first segment (112, 312) and a second segment (114); and wherein at least one elastic bridge (104, 304) is formed with the first segment (112, 312) and a reducer holder (130, 330), the at least one elastic bridge (104, 304), the first segment (112, 312), and the reducer holder (130, 330) being of one material.

19. The actuation unit (100, 300) of claim 18, wherein the at least one elastic bridge (104, 304) radially extends between the first segment (112, 312) and the reducer holder (130, 330).

20. The actuation unit (100, 300) of claim 18, further comprising a first encoder (340) configured to measure relative rotation between the first segment (112, 312) and the reducer holder (130, 330) about the second rotational axis (12).

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