Exoskeleton lower limb

Abstract

Lower limb (1) of an ambulatory exoskeleton (2) comprising a connecting interface (30, 75) and a coupling device (35) which is connected by a first connection (37) to the lower limb (1) and by a second connection to the connecting interface (30, 75), in which the coupling device (35, 39) allows at least two movements of the connecting interface (30, 75) relative to the lower end (23) of the ambulatory exoskeleton (2), the two movements comprising at least a first movement chosen from the following: – a rotation of axis (037) substantially parallel to a transverse plane (Pt) of the user (100); – an axis rotation (O39) substantially parallel to a sagittal plane (Ps) of the user (100), and the lower limb (2) comprises means (40) for detecting a displacement of the connecting interface (30, 75) relative to the lower end (23) of the ambulatory exoskeleton (2).Method of controlling such a lower member (1) Figure for abstract: Figure 1.

Description

Title of the invention: TITLE Lower limb of exoskeleton Technical field

[0001] The invention relates to the field of exoskeletons and more particularly to the lower limbs of ambulatory exoskeletons and their walking intention sensors. STATE OF THE PRIOR ART

[0002] Conventionally, a lower limb of an ambulatory exoskeleton comprises a pelvic segment on which is articulated, around a hip, a first end of a leg segment and a foot segment articulated by means of an ankle to a second end of the leg segment. Control of the lower limb requires at least one actuator to control the flexion of the leg segment during walking and to take up the forces applied to the exoskeleton. The forces applied to the exoskeleton can have several origins: a load applied to the exoskeleton (load-bearing exoskeleton), a partial replacement of the user's movements (rehabilitation exoskeleton) as well as, generally, the majority of the exoskeleton's own weight.These efforts (mass of the exoskeleton to which can be added the load taken by it) are ideally transmitted to the ground via the foot segment which provides support on the ground, sparing the muscular structure of the user, in particular his ankle.

[0003] The leg actuator alone takes up the entire load, it consumes a lot of energy, including in static phases. The exoskeleton must therefore include energy storage means (hydraulic, thermal or electrical) sized accordingly and which impact the weight of the exoskeleton as well as its autonomy and inertia. Finally, in the event of a fault in the energy supply, the entire mass of the exoskeleton as well as its possible load rests on the user, which can be dangerous for the user.

[0004] When the exoskeleton moves from a static equilibrium state to an ambulatory phase, it is necessary to identify the user's intention to begin such an ambulatory phase. Conventionally, such an intention is recognized by measuring a reduction in effort (leg lift) on the actuator of the lower limb or an increase in the effort to be resumed (weight transfer to the supporting leg) when the user wishes to move from a static phase to an ambulatory phase. The user must then exert a stimulus effort of sufficiently significant amplitude for it to be detected by the actuator. Such a stimulus effort is generally proportional to the load taken up by the exoskeleton. There is generally a latency in the reaction of the exoskeleton which makes wearing the exoskeleton unsafe. comfortable and insecure for the user. Indeed, the user must fight against the exoskeleton to overcome a threshold of detection of the stimulus effort at each step. These disadvantages are a brake on the diffusion of exoskeletons in load-bearing applications. SUBJECT OF THE INVENTION

[0005] An object of the invention is to improve the comfort of use of a user of an ambulatory exoskeleton. Statement of the invention

[0006] For this purpose, a lower limb of an ambulatory exoskeleton is provided comprising at least one leg segment having a lower end arranged to come into direct contact with a support surface of the ambulatory exoskeleton to transmit vertical forces applied to the lower limb of the ambulatory exoskeleton. The lower limb of the ambulatory exoskeleton comprises a connection interface to a lower limb of a user as well as a coupling device which is connected by a first connection to the lower limb of the ambulatory exoskeleton and by a second connection to the connection interface. According to the invention, the coupling device allows at least two movements of the connection interface relative to the lower end of the ambulatory exoskeleton, the two movements comprising at least a first movement chosen from the following:

[0007] - a rotation of axis substantially parallel to a transverse plane of the user;

[0008] - a rotation of axis substantially parallel to a sagittal plane of the user, and

[0009] the lower limb comprises means for detecting a displacement of the connecting interface relative to the lower end of the ambulatory exoskeleton.

[0010] According to other particular, non-exclusive and optional embodiments of the invention: - the first connection and / or the second connection is of the embedding, pivot, finger ball joint or ball joint type; - the detection means comprise a bending sensor, an angular sensor, an inertial unit or an accelerometer;

[0011] the coupling device comprises a deformable structure whose apparent bending stiffness is between one and four hundred N / m. For the purposes of the present application, the apparent bending stiffness is the bending stiffness measured at an output point of a mechanical system of which a part would be embedded; - the deformable structure comprises a shaft pivotally mounted around an axis substantially parallel to the transverse plane; - the deformable structure comprises a spring; - the lower limb includes a sensor for detecting contact between the user's foot and the support surface; - the detection sensor includes an on / off type sensor, a pressure sensor or a distance sensor; - the connecting interface is rigidly attached to one of the user's feet; - the connecting interface comprises a sole provided with the means for its connection rigid at the user's foot; - the leg segment comprises a spring element extending between a pelvic segment of the exoskeleton and the lower end to exert a force which opposes a bringing together of the pelvic segment and the lower end.

[0012] The invention also relates to a method for controlling an ambulatory exoskeleton comprising a lower limb comprising at least one leg segment having a lower end arranged to come into direct contact with a bearing surface of the ambulatory exoskeleton to transmit vertical forces applied to the lower limb of the ambulatory exoskeleton, the lower limb comprising a connection interface to a lower limb of a user as well as a coupling device which is connected by a first connection to the lower limb of the ambulatory exoskeleton and by a second connection to the connection interface, in which the coupling device allows at least two movements of the connection interface relative to the lower end of the ambulatory exoskeleton, the two degrees of freedom comprising at least a first degree of freedom chosen from the following:

[0013] - a rotation of axis substantially parallel to a transverse plane of the user;

[0014] - a rotation of axis substantially parallel to a sagittal plane of the user, and

[0015] the lower limb comprises means for detecting a displacement of the connecting interface relative to the lower end of the ambulatory exoskeleton,

[0016] the method comprising the steps of: - detect a movement of the coupling device from an initial position; - control an actuator of the ambulatory exoskeleton to return the coupling device to the initial position.

[0017] Other characteristics and advantages of the invention will appear on reading the following description of a particular non-limiting embodiment of the invention. Brief description of the drawings

[0018] [Fig-1] [Fig. 1] is a schematic profile view of a user wearing a first embodiment of the lower exoskeleton limb according to the invention;

[0019] [Fig.2] [Fig.2] is a partial schematic perspective view of the detail of the lower limb of the [Fig.l];

[0020] [Fig.3] [Fig.3] is a partial schematic perspective representation of a lower portion of the lower limb of [Fig.l];

[0021] [Fig.4] [Fig.4] is a partial schematic representation in perspective of detail of an upper portion of the lower member of [Fig.l];

[0022] [Fig.5] [Fig.5] is a schematic perspective representation of the member lower part of [Fig.l] in a first phase of walking;

[0023] [Fig.6] [Fig.6] is a schematic perspective representation of the member lower part of [Fig.l] in a second phase of walking;

[0024] [Fig.7] [Fig.7] is a schematic perspective representation of the member lower part of [Fig.l] in a third phase of walking;

[0025] [Fig.8] [Fig.8] is a schematic perspective representation of the member lower part of [Fig.l] in a fourth phase of walking;

[0026] [Fig.9] [Fig.9] is a schematic perspective representation of the member lower part of [Fig.l] in a fifth phase of walking;

[0027] [Fig. 10] [Fig. 10] is a partial schematic representation in top view of the lower limb of [Fig.l] in a first state;

[0028] [Fig. 11] [Fig. 11] is a partial schematic representation in top view of the lower limb of [Fig.l] in a second state;

[0029] [Fig. 12] [Fig. 12] is a partial perspective schematic representation of a second embodiment of the lower member of the invention;

[0030] [Fig. 13] [Fig. 13] is a schematic representation of a third embodiment of the lower member of the invention;

[0031] [Fig.14] [Fig.14] a schematic representation in side view of a fourth embodiment of the lower member of the invention;

[0032] [Fig. 15] [Fig. 15] a schematic representation in side view of a fifth embodiment of the lower member of the invention;

[0033] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0034] With reference to Figures 1 and 2, the lower limb, generally designated 1, of the ambulatory exoskeleton 2, is worn by a user 100. The lower limb 1 comprises a pelvic segment 10 on which is articulated, around a first axis 025 and using a first joint 25, the first upper end 21 of a leg segment 20 comprising a spring blade 22. The second lower end 23 of the leg segment 20 comprises a cylindrical support 24, here a non-slip rubber support intended to come to bear on a support surface 1000 of the exoskeleton 2 and of the user 100. The lower limb 1 also comprises a shoe 30 connected by a coupling device - here a shaft 35 - to the support 24. The shaft 35 comprises a first end 36 which is mounted on the support 24 using a first pivot connection 37 of second axis 037 substantially parallel to a transverse plane Pt. A second end 38 of the shaft 35 is connected to the shoe 30 using a second connection of the embedding type. The shoe 30 makes it possible to rigidly secure the user's foot 130 to the lower limb 1.

[0035] The shaft 35 is here a polymer or rubber shaft whose stiffness is equal to 150 N / m. Thus, the shaft 35 allows in particular the following movements: - a rotation of the shoe 30 relative to the support 24 around the axis 037 and authorized by the pivot connection 37; - a rotation of the shoe 30 relative to the support 24 around a third axis 039 substantially parallel to a sagittal plane Ps, orthogonal to the axis 037 and authorized by the low stiffness of the shaft 35; - a translation in a direction orthogonal to the transverse plane Pt and authorized by the combination of the low stiffness of the shaft 35 and the pivot connection 37; - a translation in a direction parallel to the transverse plane Pt and secant with the sagittal plane which is authorized by the low stiffness of the shaft 35.

[0036] The pivot connection 37 is instrumented using a rotary encoder 40—here a rotary potentiometer. The encoder 40 measures the relative angular position of the shoe 30 and the support 24. From this angular position, an intention on the part of the user 100 to lift his foot 130 engaged in the shoe 30 can be deduced. The encoder 40 is connected to a control and command unit 50 carried by the pelvic segment 10 and powered by a battery 51 also carried by the pelvic segment 10.

[0037] A first cable 45 extends between the support 24 and the pelvic segment 10. More precisely, a first end 46 of the cable 45 is connected to a stirrup 26 screwed into the support 24.

[0038] As visible in [Fig. 3], the cable 45 is included in a plane PI comprising the axis 025 of the joint 25 in order not to create a parasitic torque on the pelvic segment 10. It is possible to completely eliminate the parasitic torques in abduction by passing the cable 45 through the center of rotation of the joint 25. Such an embodiment is shown in [Fig. 3]. The end 21 of the lower limb 1

[0039] -here the spring blade 22- comprises a first yoke 28 comprising two first ears 28.1 and 28.2 which cooperate in rotation respectively with two second ears 11.1 and 11.2 of a second yoke 11. The yoke 11 comprises a core 11.3 which extends between the ears 11.1 and 11.2 and which is connected to the pelvic segment. The first ears 28.1 and 28.2 bear against inner faces of the second ears 11.1 and 11.2 and are articulated relative to each other by an axis 12 which passes through the ears 28.1, 28.2, 11.1 and 11.2 of the yokes 28 and 11. The cable 45 extends between the two first ears 28.1 and 28.2 in a transverse bore 13 of the axis 12. The second end 47 of the cable 45 is connected to a drum 60 driven by a motor 61 controlled by the command and control unit 50.

[0040] The basin segment 10 comprises an interface 70 for carrying a payload 71.

[0041] For its connection to the user 100, the exoskeleton 2 comprises straps for connecting the pelvic segment 10 to the pelvis 110 of the user 100. The leg 120 of the user is, for its part, not connected to the exoskeleton 2.

[0042] In operation and prior to the installation of the exoskeleton 2 on the user 100, the motor 61 is controlled to adjust a deployed length of the cable 45 so that the distance d separating the pelvic segment 10 from the support 24 is substantially equal to the distance separating the pelvis 110 from the foot 130 of the user 100. A cable clamp 48 is then tightened to lock the cable 45 in position relative to the joint 25. The blade 22 is then prestressed. Once the exoskeleton 2 is attached to the user 100 and his foot 130 is engaged in the shoe 30, a load 71 is fixed on the interface 70. The blade 22 is sized so as not to bend under the weight of the exoskeleton 2 plus the weight of the load 71 after it has been prestressed.Depending on the characteristics of the blade 22 (material, section), the load supported by the user 100- and taken up here by his leg 120- can vary from 0% (total assistance) to 100% (no assistance) of the total load which includes the dead weight PE of the exoskeleton 2 and the weight of the load 71.

[0043] When standing, the blade 22 takes up vertical forces to which the exoskeleton 2 is subjected. The forces exerted by the blade are transmitted to the pelvic segment 10 by the joint 25. A minimal amount of energy is consumed by the exoskeleton 2 in this configuration since the motor 61 is not powered and does not consume energy ([Fig.4]).

[0044] When the user 100 wishes to walk, he transfers part of the load exerted on his foot 130 to his other foot and begins to lift the foot 130 secured to the shoe 30 ([Fig.5]). In doing so, he causes a deformation of the shaft 35 whose low stiffness does not constrain the movement of the shoe 30 relative to the support 24. The encoder 40 measures a change in the angular position of the first end 36 of the shaft 35 relative to the support 24 and transmits this information to the unit 50. The unit 50 analyzes this measurement and then controls the motor 61 to cause a winding of the cable 45 on the drum 60. To do this, the unit 50 powers the motor 61 to return the angular position of the shoe 30 relative to the support 24 to its initial position.

[0045] ([Fig.7]). When the user 100 wishes to rest his foot on the ground, the encoder 40 detects a change in the angular position of the first end 36 of the shaft 35 relative to the support 24 and transmits this information to the unit 50 ([Fig.8]). The unit 50 analyzes this measurement and then controls the motor 61 to cause the cable 45 to unwind from the drum 60. To do this, the unit 50 powers the motor 61 to return the angular position of the shoe 30 relative to the support 24 to its initial position ([Fig.9]).

[0046] This produces a lower limb 1 of an exoskeleton that consumes a tiny amount or even no energy when standing. The detection time for the transition from a static phase to an ambulatory phase is not felt by the user 100 because the first phase of lifting the foot 130 is done in a manner virtually free of perceptible stress (flexion of the shaft 35) for a sufficient period of time for the exoskeleton 2 to detect the intention and control the actuator to cause a movement of the lower limb 1. The control becomes transparent to the user who does not perceive any latency in the reactions of the exoskeleton 2 nor any resistance to his movements. Advantageously again, and as shown in FIGS. 10 and 11, the freedom of rotation around the axis 039 of the shoe 30 allows the abduction of the ankle 131 of the user 100.This additional freedom offered to the user 100 makes wearing the exoskeleton even more seamless in that it allows for natural pivoting and turning movements. The possibility of twisting movements of the shoe 30 around an axis parallel to the support surface 1000 also contributes to improving the comfort of the user 100 in using the exoskeleton 2, particularly on uneven terrain.

[0047] Elements identical or analogous to those previously described will bear an identical numerical reference in the following description of the second, third, fourth and fifth embodiments of the invention.

[0048] According to a second embodiment shown in [Fig. 12], the shoe 30 comprises a pressure sensor 31 which is thresholded to provide an all-or-nothing signal to the unit 50. Here, the switch is located at a support surface 32 of a heel 33 of the shoe 30. The detection of the intention of the user 100 to lift the foot 130 as well as the phase of resting the foot 130 on the support surface 1000 is then more robust and faster, which further improves the transparency of the control of the exoskeleton 2.

[0049] According to a third embodiment shown in [Fig.13], the end 38 of the shaft 35 is connected to a sole 75 intended to be rigidly connected to the foot 130 of the user 100, for example using shells 76.1 and 76.2 and straps not shown.

[0050] According to a fourth embodiment shown in [Fig. 14], the shoe 30 is connected to the support 24 by a recessed connection. The shaft 35 here comprises a flexion sensor 41 which is connected to the unit 50 and which provides a measurement of a displacement of the shoe 30 relative to the support 24. [Fig. 14] also represents another type of sensor for detecting contact between the foot 130 and the support surface 1000, here a contactor 34 secured to the shoe 30.

[0051] According to a fifth embodiment shown in [Fig. 15], the shoe 30 is connected to the support 24 by a recessed connection. The shaft 35 is replaced by a spring 39 - here a helical spring. An inertial unit 42 secured to the shoe 30 and connected to the unit 50 provides a measurement of a displacement of the shoe 30 relative to the support 24.

[0052] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0053] In particular,

[0054] - although here the lower limb comprises a shoe 30, the invention applies also to other types of connection interface to the user's lower limb such as an ankle brace or connecting straps to the calf;

[0055] - although here the exoskeleton only comprises one lower limb, the invention also applies to an exoskeleton with two lower limbs;

[0056] - although here the first end of the shaft is mounted on the support using a pivot connection, the invention also applies to other types of first connection such as for example a connection of the embedding type, finger ball joint or ball joint;

[0057] - although here the second end of the shaft is mounted on the support using a embedding type connection, the invention also applies to other types of second connection such as for example a pivot type connection, finger ball joint or ball joint;

[0058] - although here the shaft has a bending stiffness equal to one hundred and fifty N / m, :'inventions' also applies to a deformable structure having a different stiffness such as for example one between one and four hundred N / m;

[0059] - although here a change in angular position of the device is detected coupling, the invention also applies to the detection of other types of states of the coupling device such as for example stress or deformation in the flexible shaft;

[0060] - although here the lower limb comprises a threshold pressure sensor for provide an all-or-nothing signal to the control unit, the invention also applies to other types of sensor for detecting contact between the user's foot and the support surface, such as for example a switch, a non-threshold pressure sensor or a distance sensor;

[0061] - although here the pelvic segment and the shoe are connected to the user by straps, the invention also applies to other means of securing the segments from the exoskeleton to the user, such as rigid cylindrical elements or specific clothing attached to the segments of the exoskeleton;

[0062] - although here the leg segment comprises a spring blade and a cable, the invention also applies to a leg segment comprising a thigh segment articulated on a tibia segment which would connect the pelvic segment and the support, or even a non-pre-stressed support piece - and without internal articulation - whose length would be substantially equal to that of the user's leg at rest (i.e. in a static standing position);

[0063] - although here the leg segment comprises a spring blade, the invention applies also to other types of spring elements such as for example a stack of Belleville washers, an elastomer element, a gas spring, a coil spring (for example on the knee), a volute spring, a deformable parallelogram structure or even a pulley of elastic cables;

[0064] - although here the cable is connected to the support, the invention also applies to other connection points of the cable to the exoskeleton which are capable of causing a variation in the distance separating the ends of the leg segment such as for example a connection on the ankle, the tibia segment or the thigh segment;

[0065] - although here the actuation system is fixed to the pelvic segment, the invention also applies to other attachment points of the actuation system which are capable of causing a variation in the distance separating the ends of the leg segment such as for example an attachment on the hip, the upper leg, the tibia segment or the thigh segment;

[0066] - although here the lower member comprises a cable clamp abutting against an axis, the invention also applies to other devices for prestressing the spring element;

[0067] - although here the support comprises a rotary potentiometric sensor, the invention also applies to other types of walking intention sensor such as a pressure sensor, a force sensor or a rotoid sensor linked to an ankle segment joint, or even contactless measurement systems (e.g.: optical sensor, magnetic sensor, etc.);

[0068] - although here the spring blade is positioned at the back of the user's leg, the invention also applies to other implantations of the spring blade such as for example a spring blade positioned at the front of the user's leg (curvature towards the front), or on the outer side of the user's legs;

[0069] The spring blade can be articulated on the foot segment and / or the pelvic segment at points identical to or different from the articulation points of the leg segment on the foot and / or hip segment.

[0070] Advantageously, the cable 45 can be doubled by a second active or non-active cable. (i.e. taking up or not part of the tension of the cable 45) which contributes to operational safety and prevents the consequences of an accidental breakage of the cable.

[0071] Not all the joints of the segments of the exoskeleton have been described and can be adapted to the specific use of the exoskeleton. For example, the hip flexions can be either actuated, left free, or even coupled, depending on the case.

[0072] Similarly, the hip abduction joints may be, depending on the case, actuated, left free, or constrained (bilateral or unilateral stop, with or without spring).

Claims

Claims

1. Lower limb (1) of an ambulatory exoskeleton (2) comprising at least one leg segment (20) having a lower end (23) arranged to come into direct contact with a bearing surface of the ambulatory exoskeleton (2) to transmit vertical forces applied to the lower limb (1) of the ambulatory exoskeleton (2), the lower limb (1) of the ambulatory exoskeleton (2) comprising a connecting interface (30, 75) to a lower limb of a user (100) as well as a coupling device (35, 39) which is connected by a first connection (37) to the lower limb (1) of the ambulatory exoskeleton (2) and by a second connection to the connecting interface (30, 75), wherein the coupling device (35, 39) allows at least two movements of the connecting interface (30, 75) relative to the end lower (23) of the ambulatory exoskeleton (2),the two movements comprising at least a first movement chosen from the following: - an axis rotation (037) substantially parallel to a transverse plane (Pt) of the user (100); - an axis rotation (039) substantially parallel to a sagittal plane (Ps) of the user (100), and the lower limb (2) comprises means (40) for detecting a movement of the connecting interface (30, 75) relative to the lower end (23) of the ambulatory exoskeleton (2).,

2. Lower limb (1) of an ambulatory exoskeleton (2) according to claim 1, wherein the first connection and / or the second connection is of the embedding, pivot, finger ball joint or ball joint type.

3. Lower limb (1) of an ambulatory exoskeleton (2) according to claim 1 or 2, wherein the detection means comprise a flexion sensor (41), an angular sensor (40), an inertial unit (42) or an accelerometer.

4. Lower limb (1) of an ambulatory exoskeleton according to any one of claims 1 to 4, in which the coupling device (35, 39) comprises a deformable structure (35, 39) whose apparent bending stiffness is between one and four hundred N / m.

5. Lower limb (1) of an ambulatory exoskeleton according to claim 5, in which the deformable structure (35, 39) comprises a shaft (35) pivotally mounted about an axis (037) substantially parallel to the transverse plane (Pt).

6. Lower limb (1) of an ambulatory exoskeleton according to claim 5, in which the deformable structure (35, 39) comprises a spring (39).

7. Lower limb (1) of an ambulatory exoskeleton according to any one of the preceding claims, comprising a sensor (31, 34) for detecting contact between the foot (130) of the user (100) and the support surface (1000).

8. A lower limb (1) of an ambulatory exoskeleton according to claim 8, wherein the detection sensor comprises an on / off type sensor (31), a pressure sensor (34) or a distance sensor.

9. Lower limb (1) of an ambulatory exoskeleton according to any one of the preceding claims, in which the connecting interface (30, 75) is rigidly secured to a foot (130) of the user (100).

10. Lower limb (1) of an ambulatory exoskeleton according to claim 8, in which the connecting interface (30, 75) comprises a sole (75) provided with means for its rigid connection to the foot (130) of the user (100).

11. A lower limb (1) of an ambulatory exoskeleton according to any preceding claim, wherein the leg segment (20) comprises a spring element (22) extending between a pelvic segment (10) of the exoskeleton and the lower end (23) to exert a force which opposes a bringing together of the pelvic segment (10) and the lower end (23).

12. A method for controlling an ambulatory exoskeleton (2) comprising a lower limb (1) comprising at least one leg segment (20) having a lower end (23) arranged to come into direct contact with a bearing surface (1000) of the ambulatory exoskeleton (2) to transmit vertical forces applied to the lower limb (1) of the ambulatory exoskeleton (2), the lower limb (1) comprising a connecting interface (30, 75) to a lower limb of a user (100) as well as a coupling device (35, 39) which is connected by a first connection to the lower limb (1) of the ambulatory exoskeleton (2) and by a second connection to the connecting interface (30, 75), wherein the coupling device (35, 39) allows at least two movements of the connecting interface (30, 75) relative to the lower end (23) of the ambulatory exoskeleton (2),the two degrees of freedom including at least a first degree of freedom chosen from the following:, - an axis rotation (037) substantially parallel to a transverse plane (Pt) of the user (100); - an axis rotation (039) substantially parallel to a sagittal plane (Ps) of the user (100), and the lower limb (2) comprises means (40) for detecting a movement of the connecting interface (30, 75) relative to the lower end (23) of the ambulatory exoskeleton (2), the method comprising the steps of: - detecting a movement of the coupling device (35, 39) from an initial position; - controlling an actuator (61) of the ambulatory exoskeleton (2) to return the coupling device (35, 39) to the initial position.

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