WO2020070704A1

WO2020070704A1 - Wearable active robot with spinal polyarticular chain

Info

Publication number: WO2020070704A1
Application number: PCT/IB2019/058467
Authority: WO
Inventors: Andrea BALDONI; Simona CREA; Nicola Vitiello
Original assignee: Scuola Superiore Di Studi Universitari E Di Perfezionamento Sant'anna
Priority date: 2018-10-05
Filing date: 2019-10-04
Publication date: 2020-04-09
Also published as: IT201800009210A1

Abstract

The present invention is in connection with an underactuated wearable active robot in which at least one of the derivated motion output is linked with a polyarticulated kinematic chain adapted to correspond with the vertebral column of a user.

Description

WEARABLE ACTIVE ROBOT WITH SPINAL POLYARTICULAR CHAIN

DESCRIPTION

Technical field of the invention

Background of the invention

The term wearable active robot in the present description is used to generically indicate any mechanically implemented prosthetic or exoskeletal device intended to be worn by a user to aid motion or to replace a limb and/or body portion.

As is known, the constructive complexity of such robots tends to make them bulky and heavy; therefore, difficulties arise with the known robots in practical use, especially for certain subjects (for example elderly or frail individuals), who may even be unable to wear the robot. In any case, this kind of robot tends to be uncomfortable or heavy to wear for all other subjects.

The technology is therefore shifting with a view to seeking to reduce the size and weight of wearable robots. The reduction of weight and dimensions in exoskeletal robots would not only allow more user-friendly use but also greater tolerability of the robot itself. In fact, very heavy or even simply bulky robots are poorly accepted by the user, either because of the difficulty of use, or because of the strong aesthetic and emotional impact they cause in use.

However, no satisfactory technical solutions have been found to date that allow this goal to be reached: in fact, constructive simplicity is not easy to obtain because these aid systems often require complex, multiple functionalities. Furthermore it must be considered that any constructive simplicity obtained must not represent a deterioration in the reliability and functionality of the system.

Summary of the invention

It is an object of the present invention to solve the above mentioned problems in connection with weight and structural complexity with the same functionality and reliability of the current robots.

A particular object of the present invention is to provide a wearable active robot which allows a simplification of the mechanical power transmission chain of the robot while simultaneously maintaining a high functional reliability.

A further object of the present invention is to provide a robot that attains an overall weight reduction.

These and other objects are achieved by a wearable active robot according to the first of the appended claims. Further features of the invention are defined by the dependent claims.

Brief description of the drawings

The characteristics and advantages of the robot according to the present invention will become apparent from the following description of an embodiment thereof, provided by way of non-limiting example with reference to the appended drawings wherein:

- figure 1 represents schematically and with conceptual blocks underactuation means applied to the robot according to the invention;

- figure 2 is again a schematic block representation of a wearable robot equipped with the underactuation means of figure 1 ;

- figure 3 schematically shows a block diagram of a specific embodiment of the invention in which the underactuation means comprise torque sensor means;

- figures 4a and 4b show at respectve different angles a specific embodiment of a wearable robot having underaction means linked with three articulated modules and namely two hip modules and a spinal module;

- figure 4c shows in detail an articulated module adapted to be worn on a user’s back;

- figure 5 depicts a detail of the underactuation means of the robot of figures 4a and 4b;

- figure 6 shows an embodiment of a SEA (series elastic actuator) architecture;

- figures 7a and 7b conceptually show two possible different embodiments of the underactuation means of the previous figures.

Detailed description of the invention

With reference to the above mentioned features and in particular for the time being to figures 1 and 2, the invention provides underactuation means generally indicated with the reference numeral 1 , installed onboard to a wearable active robot globally indicated with the reference numeral 2.

A wearable active robot means here generically any actuated prosthetic or exoskeletal device intended to be worn by a user to aid motion or to replace a limb and/or body portion.

The underactuation means 1 comprise a single actuation unit 10 that produces a torque at a primary motion output 100 to drive at least two articulated modules 20, 21 of the robot adapted to correspond, in use, with respective mono- or poly-articular body joints of a user.

The actuation means comprise one or more actuators commanded by an energy source controlled by an electronic controller (not shown). The term actuator can be understood as linear actuators but also, for example and not limited to, electric motors, electro-active polymers, hydraulic power systems such as a hydraulic pump.

Furthermore, as articulated exoskeletal module it is here meant any actuated joint of the robot having at least one degree of freedom, such as for example knee, ankle, elbow, wrist joints. However, polyarticular structures comprising kinematic chains are also comprised in this definition; structures of this kind are adapted to be particularly associated with the back and markedly with the spinal articulation of the user to follow and reproduce, in this case, the movements of the user's spine, or with the pelvis to reproduce the movement of the pelvis-hip joint. An example of a poly- articulated structure adapted to the application in association with the pelvis-hip joint is described in patent application n. WO2017216663 by the same applicant, herein incorporated for reference.

An example of a polyarticular structure specifically adapted to the association with the user's spine will instead be made hereafter in the present description.

As mentioned above, the actuation unit 10 defines the motion output 100 to which a first motion distribution element 11 is connected. The first motion distribution element 11 therefore receives as an input 100’ the torque generated as an output by the actuation unit 10.

The first motion distribution element 11 also defines two differential derivative motion outputs 110 and 111 , each adapted to connect with a respective articulated module 20, 21 of the robot or with a second motion distribution element 12, 12’ in turn operatively interfaced with at least two further articulated exoskeletal modules 20', 2 , 20", 21".

Therefore, the actuation unit 10, although defining a single primary motion output 100, obtain by themselves the movement of at least two articulated modules 20, 21 , thanks to the interposition of the first motion distribution element 11 which receives the motion input from the actuation means and distributes it in differential mode (that is, as a differential gearing) to the two derivative outputs 110, 111 and therefore, consequently, to the articulated exoskeletal modules operatively connected thereto The articulated exoskeletal modules that can be actuated with the single actuation unit 10 are therefore potentially infinite. For example, reference should be made to the schematization of robots of figure 2 where a further motion distribution element and specifically a second distribution element 12’ and a third motion distribution element 12” are connected to each derivative motion output 110, 111 of the first motion distribution element 11. Second and third groups of actuated modules of the robot 20', 21 ', 20”, 21” are in turn connected to the differential motion outputs 120', 12T, 120", 121” of each of said second and third distribution elements. Therefore, in this case, four articulable exoskeletal modules are implemented with the actuation means 10. If on the other hand the second 12’ and third motion distribution element 12” in turn had fourth and fifth motion distribution elements connected, the potentially feasible exoskeletal modules starting from the single primary output 100 defined by the actuation unit 10 would be in even greater numbers. This underactuation system thus obtains the drive of complex robotic structures with a constructive simplicity that has never been reached by the currently known robots.

The underactuation system can advantageously comprise torque sensor means

13 interposed between the first motion distribution element 11 and the actuation unit 10, therefore in correspondence with the primary motion output 100.

These sensor means can comprise, for example but not limited to, a transmissive element with elastic response for the transmission of a torsional stress associated with at least one position encoder to determine its torsional bending and therefore the torque, being it known the stiffness factor of the elastic transmission element. The architecture that comprises sensor means of this type in series with an actuation unit is known as SEA (series elastic actuator).

Figure 6 shows an embodiment of a SEA architecture. The torsional elastic transmissive element is indicated in the figure with the number 130. The actuation unit in turn comprises a motor 10a and a crankshaft 10b which defines a low range motion output 10c. This low range motion output of the crankshaft 10b is interfaced to a first connection flange of the transmissive element 130a; a second flange 130b longitudinally opposite to the first one is connected to a cup-like connection element 131 which supports on its outer periphery the primary motion output 100 of the actuation means 10. Further, the sensor means comprise two encoders in this specific embodiment, of which a first encoder 132 is mounted so as to read the movement on the first flange 130a and a second encoder 133 is mounted so as to read the movement on the second flange 130b. The difference in measurement read between the two encoders allows evaluating the torsional flexion of the elastic transmission element and therefore, being it known the stiffness factor, the torque transmitted to the cup-like connection element and therefore on the primary motion output 100. Possibly only one encoder can be provided, for a direct reading of the torsional flexion.

The sensor means 13 are therefore adapted to detect the torque actually absorbed by the first motion distribution element. This actually absorbed torque also includes any external perturbation that is exerted in feedback on the actuation means from the derived motion outputs. For example, this external perturbation is a feedback action exercised by a user wearing a robot on which the system is installed. In fact, if the user has residual mobility, he or she can move the joint and consequently the module at the associated joint. This movement enters as a force exerted from the outside in the differential, algebraically adding the input power received by the differential through the single primary motion output. The sensor 13 therefore detects a deviation between the power actually managed by the differential and that supplied by the actuator unit. This deviation, except for the deviation due to the internal frictions of the mechanisms and to possible errors, is therefore a function of the external perturbation mentioned above.

The sensor means are typically interfaced with a control unit configured for feedback control of the actuation means as a function of this deviation and consequently also as a function of the external perturbation received from at least one of the two derivative outputs.

This feedback control allows making the robot "transparent" in relation to any force exerted by the user directly on the articulable module, a force which, in the absence of such control, would be undesirably and in a substantially uncontrolled way redistributed by the motion distribution element, based on the differential distribution criterion, to one or more articulable exoskeletal modules connected thereto.

Specifically, the SEA architecture is able, by reading the deformation of the torsional elastic transmissive element located downstream of the actuation unit and upstream of the motion distribution element, to give the control unit the information on the torque value transmitted in that section and therefore allows closing the control loop in a timely manner as regards the active provision for the necessary motor task. This architecture also allows the robot to be controlled in feedback if the user wishes to be able to impose motion from the outside. If an irreversible transmission were provided, all the movement imposed by a derivative output of the motion distribution element would have the same and opposite reaction on the other output, which clearly could not move freely. Sensor means upstream of the motion distribution element therefore allow the motor to compensate the contribution of the resisting torque by nullifying the algebraic difference of the motion generated by the two derivative outputs subjected to an input force supplied from the outside, i.e. by the user himself.

In a preferred embodiment, the motion distribution element is then a differential of a mechanical type i.e. materialized by an epicycloidal gearing.

The differential can also be of a pneumatic/hydraulic type as shown in figures 7a and 7b. In greater detail, in this case the actuation unit 10 comprises a hydraulic pump and the motion distribution element is materialized by a piping having a fluid inlet 100’ that corresponds to the motion input, while the derivate outlets 110 e 111 represent the motion outputs. Each motion output is the input of a hydraulic motor that actuates a respective joint.

Reference will now be made to the embodiment illustrated in figures 4a, 4b and

5. In this example the actuation unit comprises an electric engine 10a in series with a spring 10b having sensors at its ends, so as to defined a SEA architecture as the one mentioned above. The primary motion output 100 takes the form of a first meshing member. This primary motion output 100 is linked with a first differential 11 which has a second meshing member 110’ adapted to mesh with the first meshing member 100 to receive the torque delivered by the actuation unit 10. Specifically, the first and second meshing members are geared wheels, even if other equivalent functional solutions can be provided.

The first differential 11 provides two differential motion outputs, of which a first derivative output 110 and a second derivative output 111. The first derivative output 110 is linked with a first articulated module 20. The second derivative output 111 is linked with a second differential 12.

The first derivative output 110 is a meshing member such as a pulley adapted to operatively engage with a respective pulley 20a that represents a motion input of the first articulated module 20, as shown specifically in the figures from 4a to 4c. In this specific case, the pulley 20a supplies the input motion to an articulated kinematic mechanism adapted to be associated with the spinal joint, i.e. to the vertebral column of a user.

Again in this specific example, the articulated kinematic mechanism comprises an exoskeletal kinematic chain adapted to assist the movement of a polyarticular bone chain. The exoskeletal kinematic chain, thus defining a back portion exoskeleton, comprises a frame to be worn at the hip region of the user an a plurality of exoskeletal links 20b, one of which is fixed with the frame.

The kinematic chain further comprises a number of exoskeletal rotoidal joints 20d; each exoskeletal rotoidal joint allows a relative rotation between two exoskeletal links adjacent thereto, around a rotation axis X.

Each exoskeletal rotoidal joint is arranged at a given distance from the previous exoskeletal rotoidal joint along the spinal exoskeleton, the distance being constant for each value of the relative rotation.

Each exoskeletal link 20b is further connected to a correspondent vertebra of the spinal column through a kinematic constraint such as to permit the transmission of at least one force component F_n orthogonal with the link and/or the corresponding vertebra.

At each exoskeletal rotoidal joint a pulley 20a’ is arranged which is adapted to rotate about a corresponding pivot axis, and at least one inextensible cable 20c in contact by friction with each pulley 20a' and fixed with an end link opposite to the frame exoskeleton end. The relative derivative motion output is adapted to pull the at least one cable 20c so as to bring the exoskeletal links to rotate around the respective exoskeletal rotoidal joints. Possibly two or more cables can be provided which are alternately driven so as to bring the exoskeletal links to rotate clockwise and/or counter-clockwise around respective exoskeletal rotoidal joints

The second derivative output 111 consists of a meshing member (specifically a geared wheel, even if also in this case the implementation of other functionally equivalent solutions cannot be excluded).

This second derivative output 111 is connected with the motion input 12a of the second differential 12, represented by a matching meshing member. The second differential further provides a first 121 and a second motion output 122. These two further derivative motion outputs 121 and 122 mesh with respective motion inputs 21a and 22a of a second 21 and a third articulated exoskeletal modules 22 to provide rotational movement. In particular, the two motion inputs 21a, 22a consist of pulleys which have a degree of freedom in rotation according to an axis thereof that is perpendicular to the axis of the second differential motion output. These pulleys supply the motion to an articulated kinematism which defines the second and third articulable modules 21 and 22 which in this specific case are adapted to be associated with the pelvis-hip articulation of the user. These articulated modules 21 and 22 are for example of the type described in the previous above cited patent application in the name of the present applicant, i.e. WO2017216663. In greater detail, the articulated exoskeletal modules 21 and 22 consist each of a kinematic chain that allows the transmission of rotary motion between an active rotating member materialized by each of the motion input pulleys 21a and 22a, and a distal rotating member. The two rotating members have axes that can assume any relative orientation. The distal rotating member is also materialized by a respective pulley, shown in the figures and indicated with the references 210a and 222a. The first rotating member is therefore adapted to rotate about its own pivot axis X. The second rotating member is in turn adapted to rotate about its own pivot axis Y.

The kinematic chain further comprises a plurality of connection members 21b, 22b each of which comprises at least one passage having at least one rotating element; each connection member further comprises at least one interface adapted to connect the connection member to an adjacent one and to one of the rotating members, generating a rotational constraint around a pivot axis Z thereof.

The chain then comprises a transmission element (not visible), such as a cable or a belt, adapted to extend along a determined path to transmit a rotary motion between the two rotation members.

Therefore, the kinematic chain is adapted to pass between an adjustment configuration in which each connection member is adapted to rotate about its own pivot axis Z to adjust its angular position with respect to an adjacent connection member or to one of the rotation members, and a drive configuration in which when the first rotation member rotates about its own pivot axis X, the distal rotation member performs a proportional rotation about its own axis Y; in the drive configuration each connection member is designed not to rotate about its own pivot axis Z.

The robot according to the invention attains a number of advantages in term of overall weight reduction and structural complexity. In particular, thanks to the underactuation of two or more joints of the robot, this not only is structurally much simpler than the presently known robots, but is also lighter and more compact, without detriment of functionality and reliability.

Furthermore, the ratio of costs, weight, bulk, the number of driven or drivable joints being the same, is remarkably lower, with respect to the robots of the previous state of the art.

The robot can further comprise braking means associated with the underactuation system and in particular at both the outputs thereof. The braking means, e.g. but not necessarily disc brakes, have the function of modulating the power delivered between one or the other output of the system itself as a function of the movement that the user must perform. Such breaking means obtain thus a further control level inasmuch by acting on one or both the brakes associated with the two outputs one can further share and/or distribute the drive delivered in output by the motion distribution elements.

The association of a SEA-type architecture to a motion distribution element achieves further advantages in particular as far as the control of the wearable robot is concerned even facing external perturbations caused by gestures carried out by the same user. As mentioned, thanks to the SEA implementation it is possible to make the robot“transparent” to this kind of stresses, leaving then the user with great freedom and capability of movement in spite of his/her wearing the robot.

Thanks to the back exoskeleton as described, it is also possible to assist the movement of the whole spinal column of the user with a single motion actuation; in fact, thanks to the motion drive along the spinal kinematic chain as a result of the engagement between the at least one cable and the pulleys it is possible to drive the plurality of exoskeleton links, starting from a single motion input.

Furthermore, the association between this back/spinal exoskeleton with the exoskeletal articulated pelvis-hip modules as described, and with the underactuation system (comprising in turn an actuation unit and a motion distribution element for distributing the drive in a differential manner) permits to achieve a complex robotic architecture starting from a single actuator, with a clear structural simplification and lower overall weight.

The present invention has been described with reference to a preferred embodiment thereof. It is to be understood that there may be other embodiments that relate to the same inventive core within the scope of protection of the claims provided below.

Claims

1. An active robot adapted to be worn by a user, the robot comprising at least two articulated exoskeletal modules (20, 21 , 22) adapted to correspond to respective mono-or poly-articular body joints of said user when the robot itself is worn, said robot further comprising onboard a single actuation unit (10), adapted to control in actuation at least two of said articulated modules; wherein one of said articulable modules is a poly-articular kinematic chain (20), comprising a single motion input driven by said actuation unit and adapted to correspond with the user's vertebral column.

2. The active wearable robot according to claim 1 , comprising: - said actuation unit (10) which defines a primary motion output (100); - at least one first motion distribution element (11) connected to said primary motion output (100) to receive the motion generated therefrom in input and distribute it in differential mode through at least two derivative motion outputs (110, 111); wherein at least one of said two or more articulated modules (20, 21 , 22) is associated with each of said two derivative motion outputs (110, 111).

3. The active wearable robot according to claim 2, wherein said motion distribution element is a differential gearing (11).

4. The active wearable robot according to claim 2, wherein said motion distribution element is a hydraulic-type differential materialized by a piping bifurcation which defines a fluid inlet and at least two fluid outlets.

The active wearable robot according to claim 3, wherein downstream of said actuation unit torque sensor means (13) are arranged to detect a deviation between the torque delivered by said single primary motion output (100) and the torque actually absorbed by said motion distribution element.

5. The active wearable robot according to claim 5, wherein said sensor means comprises a transmissive element (130) with torsional elastic response and at least one position sensor to determine the torsional flexion of said transmissive element (130).

6. The active wearable robot according to any of claims 2 to 6, wherein one of said derivative motion outputs (110, 111) is connected to a second differential mode motion distribution element (12), said second differential mode distribution element defining two further derivative motion outputs.

7. The active wearable robot according to claim 7, wherein said two or more articulated modules (21 , 22) further comprise two articulated kinematic mechanisms adapted to correspond with a pelvis-hip joint of the user.

8. The active wearable robot according to any of the previous claims, wherein said kinematic chain comprises a number of rotoidal exoskeletal joints (20d) each of which is such as to allow a relative rotation between two exoskeletal links (20b) adjacent to said joint, about a pivot axis thereof.

9. The active wearable robot according to claim 9, wherein at each rotoidal exoskeletal joint of said kinematic chain a pulley (20a¹) is arranged which is adapted to rotate about a corresponding pivot axis, the kinematic chain further comprising at least one inextensible cable (20c) in contact by friction with each pulley (20a¹) and connected to an exoskeletal link at an end of said kinematic chain opposite to a connection end integral with the user.

10. The active wearable robot according to claim 10, wherein said actuation unit is adapted to drive said at least one cable (20c) so as to bring said exoskeletal links (20b) to rotate about the respective rotoidal exoskeletal joints (20d).

11. The active wearable robot according to claim 11 , wherein said kinematic chain comprises two or more cables (20c) adapted to be alternately driven so as to bring said exoskeletal links to rotate around the respective rotoidal exoskeletal joints (20d) in a clockwise and/or counter-clockwise direction.