KR20190079790A - Variable stiffness gripper system - Google Patents

Abstract

According to an embodiment of the present invention, a variable rigid gripper system comprises: a variable rigid gripper formed long with a structure in which a soft body is each disposed between a plurality of rigid bodies, and having a tendon connected to the rigid body located at a front end of the rigid body and disposed through the other rigid bodies and the soft bodies among the rigid bodies; a gripper body wherein a rear end of the variable rigid gripper is connected to a front part, and having a variable rigid gripper each disposed at a plurality of installation locations provided on the front part; and a gripper controller disposed in the gripper body and connected to the tendons of the variable rigid grippers and providing an operation force to the tendons to change the rigidity and shape of the variable rigid gripper. Therefore, an objective of the present invention is to provide the variable rigid gripper system capable of improving gripping performance of an object by appropriately varying the rigidity as needed.

Description

[0001] VARIABLE STIFFNESS GRIPPER SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable rigidity gripper system, and more particularly, to a variable rigidity gripper system capable of appropriately varying rigidity to improve gripping performance of an object.

Generally, the gripper system is developing in the form of a multi-joint gripper similar to a human hand. The gripper system as described above is extensively utilized in fields such as an endoscope field or a robot field in which a gripping operation of an object is required.

Since the conventional gripper system has a structure in which the object and the finger are always in contact with each other regardless of the shape of the object, the efficiency of the gripping performance of the object deteriorates in terms of frictional force.

In addition, since the existing gripper system is designed based on a rigid body, perfect control is required in order to catch an object. If the gripper system is composed only of a rigid body, the stability of the gripper system can be secured, but a danger may occur depending on the intended use. For example, if a gripper system consisting of a rigid body is applied to the hands of a robot, the structural stability may be very good, but if the control is not very precise due to its own rigidity, .

In order to solve the problem of the rigid body-based gripper system as described above, a preference for a soft gripper system is increasing, and research on the system has been progressing recently.

For example, Korean Registered Patent No. 10-1359515 (entitled " variable stiffness structure ", issue date: 2014.02.25) discloses a variable stiffness structure capable of softening or strongly changing the stiffness of a structure Lt; / RTI >

Soft gripper systems have lower structural stability than rigid body based gripper systems but have a variety of other advantages. In other words, a soft gripper system is advantageous in that it can smoothly hold objects of various shapes, perform work with people, and deal with objects that are easily damaged, such as agricultural products, without damage.

However, the soft gripper system developed so far has a disadvantage in that there is a restriction on the weight of the object which can be used due to the limitation of the structure and the material.

Embodiments of the present invention provide a variable stiffness gripper system capable of appropriately varying stiffness as needed to improve gripping performance of an object.

Further, the embodiment of the present invention provides a variable stiffness gripper system capable of structurally improving the rigid body and the soft body of the variable rigidity gripper so as to effectively hold a heavy object.

Embodiments of the present invention also provide a variable stiffness gripper system that improves the structure for providing an actuating force on the tendons of the variable stiffness grippers so that the operation of the variable stiffness grippers can be smoothly controlled.

According to an embodiment of the present invention, a plurality of rigid bodies are arranged in a lengthwise manner and soft bodies are disposed between the rigid bodies, and the rigid bodies are connected to the rigid bodies located at the tip ends of the rigid bodies, A variable rigidity gripper provided with a tentatively arranged tendon; a gripper body having a rear end portion of the variable rigidity gripper connected to the front portion and a variable rigidity gripper disposed at a plurality of installation positions provided on the front portion, There is provided a variable stiffness gripper system including a gripper controller coupled to the grippers' tendons and providing operating force to the tendons to change the stiffness and shape of the variable stiffness grippers.

According to one aspect, a crease portion formed of an acid and a valley may be formed on the outer peripheral portion of the soft body. The pleated portion may be formed in a shape surrounding the outer peripheral portion of the soft body, and a plurality of the pleated portions may be provided continuously along the longitudinal direction of the soft body.

The corrugation may be formed in a cross-sectional shape of at least one of a triangle, a rectangle, a trapezoid, or an ellipse.

The soft body includes a first soft body disposed at a central portion between the rigid bodies so as to be positioned on the central axis of the variable rigid gripper and disposed so as to penetrate the tangential body and a first soft body disposed at a portion other than the center portion between the rigid bodies, And a second soft body disposed in a shape surrounding the outer periphery and having a corrugated portion.

According to one aspect, the rigid body disposed at the distal end of the variable rigidity gripper can be formed longer than the other rigid bodies, and a rubber member for increasing frictional force can be disposed on the surface.

 According to one aspect, one end of the tendon may be connected to a rigid body disposed at the distal end of the variable rigidity gripper, and the other end of the tendon may pass through other rigid bodies and soft bodies other than the rigid body, Lt; / RTI > The gripper body may be provided with a tendon passageway through which the tendons of the variable rigid grippers are disposed.

The gripper controller includes a controller frame disposed at a rear portion of the gripper body and configured to communicate with the tension passage, a tendon reel connected to the other end of the tendons passing through the tendon passage and disposed in a shape that the tendons are wound around the outer periphery, And a tension control motor coupled to the rotating shaft and rotating the tendering reel to provide an actuating force to the tendons to change the stiffness and shape of the variable rigidity grippers.

Here, the tendon reel may be disposed at a position facing the tendon passage.

And, the tendons can be arranged in a plurality of mutually spaced apart variable gripper grippers. The tendon reel and tendon control motors are provided in a number corresponding to the number of tendons arranged in the variable rigidity gripper and can be connected individually to the tendons.

Also, the variable rigidity grippers may be provided with the same arrangement of the tendons. Tendons arranged at the same position of the variable rigidity grippers among the tendons can be connected to the tender reels, respectively.

The variable rigidity gripper system according to the embodiment of the present invention is a structure in which the rigidity of the variable rigidity gripper and the shape of the variable rigidity gripper are varied by adjusting the tendons of the variable rigidity grippers connected to the gripper body, The rigidity and the shape of the variable rigidity grippers can be appropriately changed according to the shape, shape, and the like, and the gripping performance of the object can be greatly improved.

In addition, since the variable rigidity gripper system according to the embodiment of the present invention has the corrugated portion formed on the outer peripheral portion of the flexible body of the variable rigidity gripper, it is possible to prevent the flexible body from being pushed outward when the rigidity of the variable rigidity gripper varies, It is possible to smoothly flex the soft body when the shape of the variable rigidity gripper is varied and to reduce deformation of the soft body as the stiffness variable of the variable rigidity gripper is repeated.

Further, the variable rigidity gripper system according to the embodiment of the present invention is a structure in which the rigid body disposed at the distal end portion of the variable rigidity gripper is formed longer than the other rigid body and the rubber member is disposed on the surface, It is possible to improve the gripping performance of the object by the variable rigidity grippers, and it is possible to smoothly grasp even a heavy object.

In addition, since the variable rigidity gripper system according to the embodiment of the present invention is a structure that rotates the tendon reel by the tendon control motor to provide the operating force to the tendon, it is possible to appropriately control the operation of the tendon control motor, The rigidity and shape of the variable rigidity gripper can be precisely and finely varied.

1 is a diagram illustrating a variable stiffness gripper system according to an embodiment of the present invention.
2 is a view showing an example of the variable stiffness gripper shown in Fig.
3 is a cross-sectional view of a main portion of the variable rigidity gripper shown in Fig.
4 is a view showing an operating state of the variable stiffness gripper shown in Fig.
5 is a view showing another example of the variable stiffness gripper shown in Fig.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to or limited by the embodiments. Like reference symbols in the drawings denote like elements.

1 is a diagram illustrating a variable stiffness gripper system 100 according to one embodiment of the present invention. Fig. 2 is a view showing an example of the variable rigidity gripper 110 shown in Fig. 1, Fig. 3 is a sectional view showing a main portion of the variable rigidity gripper 110 shown in Fig. 2, Fig. 5 is a view showing an operating state of the variable rigidity gripper 110 shown in Fig. 5 is a view showing another example of the variable rigidity gripper 110 shown in FIG.

Referring to FIG. 1, a variable stiffness gripper system 100 according to one embodiment of the present invention includes a variable stiffness gripper 110, a gripper body 120, and a gripper controller 130.

Here, the variable stiffness gripper system 100 according to the present embodiment is constructed by using three variable stiffness grippers 110. However, the present invention is not limited thereto and four or more variable stiffness grippers 110 may be applied .

Referring to FIGS. 1 to 4, the variable rigidity gripper 110 according to the present embodiment is a member for grasping an object, and may be formed in a long finger shape. The variable rigidity gripper 110 may include the rigid body 200, the soft body 300, and the tendon 400.

The rigid body 200 is a member formed of a rigid material such as plastic or metal. In the present embodiment, three rigid bodies 200 are described as being spaced apart from each other in the longitudinal direction of the rigid gripper 110. However, The present invention is not limited thereto and can be variously changed according to the design conditions and conditions of the variable stiffness gripper system 100.

That is, the rigid body 200 may include a first rigid body 210, a second rigid body 220, and a third rigid body 230. The first rigid body 210 is a rigid body disposed at the distal end of the variable rigidity gripper 110 and may be formed longer than the other rigid bodies 220 and 230. The rubber rigid body 210 may include rubber A member (not shown) may be disposed. Therefore, the gripping force of the variable rigidity gripper 110 can be further improved by the first rigid body 210. [ The rubber member may be a rubber layer thinly coated on the surface of the first rigid body 210, or may be formed of a rubber pad attached with an adhesive.

The soft body 300 is a member formed of a soft material such as silicon or rubber, and can be disposed between a plurality of rigid bodies 200, respectively. That is, the soft body 300 may include the first soft body 310 and the second soft body 320. The first soft body 310 may be positioned between the first rigid body 210 and the second rigid body 220 and the second soft body 320 may be positioned between the second rigid body 220 and the third rigid body 220. [ (Not shown).

In addition, the outer peripheral portion of the soft body 300 may be formed with the corrugated portion 330 formed by the mountain and the valley. The corrugated portion 330 may be formed so as to surround the outer peripheral portion of the soft body 300 and may be continuously provided along the longitudinal direction of the soft body 300. Meanwhile, the corrugated portion 330 may have a cross-sectional shape of at least one of a triangle, a quadrangle, a trapezoid, and an ellipse. Hereinafter, in the present embodiment, it is assumed that the corrugated portion 330 has a triangular cross-sectional shape.

Accordingly, the soft body 300 may be formed in an outer shape similar to a bellows in which a corrugation is formed on the outer periphery. The softened body 300 is pushed between the rigid bodies 200 by the corrugated part 330 when the softened body 300 is compressed and the wrinkled part 330 is formed at the outer peripheral part of the softened body 300, The flexible body 300 can be pressed relatively easily by bending the flexible rigid gripper 110 while the soft body 300 is smoothly folded by the wrinkle portion 330 to stably fix the object And it is possible to prevent deformation of the soft body 300 as the soft body 300 is repeatedly pressed.

The tensile member 400 is a member formed in a wire shape and can control the rigidity of the variable rigidity gripper 110 or the shape of the variable rigidity gripper 110 by an exertion force externally applied thereto. A plurality of the tensors 400 may be disposed on the variable rigidity gripper 110, but in the present embodiment, two tensors 400 are arranged on the variable rigidity gripper 110.

The tensile member 400 is connected to the first rigid body 210 located at the forefront of the first, second and third rigid bodies 210, 220 and 230 while the other second and third rigid bodies 220 and 230 And the first and second soft materials 310 and 320, respectively. That is, one end of the tensile member 400 may be connected to the first rigid member 210 disposed at the distal end of the variable rigidity gripper 110, and the other end of the tendon 400 may be connected to the other rigid member 210 except for the first rigid member 210 The second and third rigid bodies 220 and 230 and the first and second soft materials 310 and 320 and then to the gripper controller 130 through the gripper body 120.

And, the tender 400 may include a first tender 410 and a second tender 420. The first and second tendons 410 and 420 may be formed of the same material and length, and may be disposed parallel to each other inside the variable rigidity gripper 110. In addition, the first and second tendons 410 and 420 may be disposed symmetrically with respect to the center axis of the variable rigidity gripper 110.

As shown in FIGS. 1 and 4, the first and second tenses 410 and 420 may be provided in the same three-dimensional shape as the three variable rigidity grippers 110 installed on the gripper body 120. The tendons 400 provided in the same arrangement in the variable rigidity grippers 110 can change the rigidity and shape of the variable rigidity grippers 110 equally in the direction of grasping the object. 4, the first tendon 410 may be disposed at a position opposite to the direction in which the variable rigidity grippers 110 are bent when the object is gripped, and the second tendon 420 may be disposed at a position The variable rigidity grippers 110 can be disposed at positions in the direction in which the variable rigidity grippers 110 are bent.

The first and second tenses 410 and 420 are formed in the first and second through holes 240 and 340 formed in the second and third rigid bodies 220 and 230 and the first and second soft bodies 310 and 320 Can be arranged to penetrate. That is, the first and second rigid bodies 220 and 230 may have a first through hole 240 for the first and second tandems 410 and 420 to pass therethrough, The second through holes 340 may be formed in the adults 310 and 320 so that the first and second tenses 410 and 420 are penetrated. The first through hole portion 240 and the second through hole portion 340 may be connected to communicate with each other.

Referring to FIG. 1, the gripper body 120 according to the present embodiment is a member for supporting variable rigid grippers 110 for gripping an object. The rear end of the variable rigidity gripper 110 includes a front portion 122, Lt; / RTI >

The variable rigidity gripper 110 may be disposed at a plurality of installation positions in the front portion 122 of the gripper body 120. As described above, in the present embodiment, it is described that the three variable rigidity grippers 110 are arranged in a triangular shape on the front portion 122 of the gripper body 120 and are bent toward the central portion of the variable rigidity grippers 110 do. That is, the variable stiffness gripper 110 may be composed of the first variable stiffness gripper 112, the second variable stiffness gripper 113, and the third variable stiffness gripper 114.

A tension passage (not shown) may be formed in the gripper body 120 so that the first and second tensors 410 and 420 of the variable rigidity grippers 110 are disposed to pass therethrough. The tendon passage may be formed long from the front portion 122 to the rear portion of the gripper body 120. One end of the tendon passageway is branched into three passages toward a portion where the rear ends of the first, second and third variable stiffness grippers 112, 114, 116 are connected, or the first, second and third variable stiffness grippers 112, And 116 may be formed as a single passageway including all the connected portions.

1 and 4, the gripper controller 130 according to the present embodiment is a member for controlling the rigidity of the first, second and third variable rigidity grippers 112, 114, and 116 and changing the shape thereof, The second and third tendons 410, 420 disposed on the first and second variable stiffness grippers 112, 114, 116, respectively.

Here, the gripper controller 130 may be disposed at a rear portion of the gripper body 120. The gripper controller 130 may be configured to transmit the actuating forces F1 and F2 to the first and second tendons 410 and 420 to vary the rigidity and shape of the first, second and third variable rigidity grippers 112, As shown in FIG.

For example, the gripper controller 130 may include a controller frame 132, tendon reels 134, 135, and a tension control motor 136, 137.

The controller frame 132 may be disposed on the rear portion of the gripper body 120 to support the tendon reels 134 and 135 and the tension control motors 136 and 137. The controller frame 132 may be provided with a passage communicating with the tendon passage.

The tendon reels 134 and 135 may be connected to the other ends of the first and second tendons 410 and 420 passing through the tendon passages and may be formed so that the first and second tendons 410 and 420 are wound around the outer periphery . That is, the tendon reels 134 and 135 have the first tendon reel 134 wound around the outer periphery of the first tendon 410 and the second tendon reel 135 wound around the outer periphery of the second tendon 420 .

Here, the first and second tensile reels 134 and 135 may have the same shape as each other, and may be disposed at a position facing the tendon passage. The first and second tensile reels 134 and 135 may be individually rotated by the first and second tandem control motors 136 and 137 to be described later. The actuating forces F1 and F2 provided to the first and second tendons 410 and 420 can be independently controlled.

The tension control motors 136 and 137 rotate the first and second tensile reels 134 and 135 to generate an action force F1 for changing the rigidity and shape of the first, second and third variable rigidity grippers 112, 114 and 116 , F2) to the first and second tendons 410, 420. The rotation axis 137a of the tension control motors 136 and 137 may be connected to the center of the tendon reels 134 and 135, respectively.

That is, the tension control motors 136 and 137 include a first tension control motor 136 connected to a first tension reel 134 and a second tension control motor 136 connected to the second tension reel 135, And a first tension control motor 137 connected thereto.

1 to 4, the tendon reels 134 and 135 and the tendon control motors 136 and 137 according to the present embodiment are provided on the number of tendons 400 disposed on the variable rigidity gripper 110, And may be provided in the same number as the tenns 400 corresponding thereto. Here, the plurality of tendons 400 may be individually connected to the tendon reels 134 and 135 one by one.

That is, in this embodiment, the first and second tensile reels 134 and 135 and the first and second tendency control motors 136 and 137 are provided corresponding to the first and second tendons 410 and 420, respectively. If the number of the tendons 400 arranged in the variable rigidity gripper 110 is increased to four or more, the number of the tendon reel and the tendon control motor may be the same as the number of the tendons 400 Or more may be used. At this time, the four or more tendons 400 may be classified into four or more variable rigidity grippers 110 disposed at positions corresponding to each other and individually connected to four or more tendon reels.

5 shows another example of the variable stiffness gripper system 100 'according to an embodiment of the present invention. In FIG. 5, the same reference numerals as those shown in FIGS. 1 to 4 denote the same members, and a detailed description thereof will be omitted. Hereinafter, the variable stiffness gripper system 100 shown in Figs. 1 to 4 will be described with reference to a point different from an example.

5, the variable stiffness gripper system 100 'according to the present embodiment differs from the variable stiffness gripper system 100 shown in Figs. 1 to 4 in that the soft stub 300' Respectively, and are arranged at the inner side and the outer side, respectively.

That is, the soft body 300 'may include the inner soft body 322 and the outer soft body 324.

The inner soft body 322 may be arranged in a cylindrical shape at a central portion between the rigid bodies 200 so as to be positioned on the central axis of the variable rigidity gripper 110. The inner soft body 322 may be provided with a second through hole 340 'for allowing the tender 400 to pass therethrough.

The outer soft body 324 may be disposed in a tubular shape so as to surround the central portion between the rigid bodies 200. That is, the outer softened body 324 may be arranged to surround the outer peripheral portion of the first softened body 300 between the rigid bodies 200. A wrinkle portion 330 may be formed on the outer peripheral portion of the outer softened body 324 as described above.

Therefore, in the present embodiment, the inner soft body 322 can be utilized relatively more for reversing the rigidity and shape of the variable rigidity gripper 110, and the outer soft body 324 can be used for the soft body 300 ' The soft body 300 'may be prevented from being pushed out or the soft body 300' may be smoothly bent during the compression of the soft body 300 '.

The soft body 300 'may include a first soft body 310' positioned between the first rigid body 210 and the second rigid body 220 and a second soft body 310 'positioned between the second rigid body 220 and the third soft body 220' And a second softened body 320 'positioned between rigid bodies 230.

Operation and effect of the variable rigidity gripper system 100 according to an embodiment of the present invention will be described as follows. Hereinafter, an example of the variable stiffness gripper system 100 according to an embodiment of the present invention will be described.

First, an object is positioned between the first, second, and third rigid grippers 112, 114, 116 to grip or lift the object using the variable rigidity gripper system 100.

1 and 4, when the first and second tentative control motors 136 and 137 are operated, the first and second tentative reels 134 and 135 rotate to rotate the first and second tendons 410 and 420 Are wound on the first and second tensile reels 134, 135. At this time, operating forces F1 and F2 corresponding to the forces acting on the first and second tandems 410 and 420 are transmitted to the first and second tandems 410 and 420, .

When the first and second tendons 410 and 420 are pulled by the operating forces F1 and F2 as described above, the first and second softened bodies 310 and 420 are rotated by the first and second rigid bodies 210, 320 are compressed between the first, second and third rigid bodies 210, 220, 230.

When the first and second softened bodies 310 and 320 are compressed, the rigidity of the first, second and third variable rigidity grippers 112, 114, and 116 is increased, so that it is possible to hold the object more stably.

As shown in FIGS. 1 and 4, when the first and second tendency control motors 136 and 137 are rotated at different speeds, the first and second tendon reels 134 and 135 rotate the first and second tendons 410 and 420 are also different from each other.

The first, second and third variable stiffness grippers 112, 114 and 116 are coupled to the first and second tendons 410 and 420, respectively, when the first and second tendons 410 and 420 are pulled by different operating forces F1 and F2, 420 are bent in a direction in which a relatively strong operating force F2 is applied.

That is, the operating force F2 in the direction of gripping the object among the operating forces F1 and F2 applied to the first and second tendons 410 and 420 is greater.

4, when the actuation force F2 applied to the second tendon 420 is greater than the actuation force F1 exerted on the first tendon 410, the variable stiffness gripper 110 is moved to the second tendon 410, It is possible to hold the object by bending in the direction in which the body 420 is located.

As described above, since the first, second and third variable stiffness grippers 112, 114, and 116 are bent in the direction of the object in a state of increased rigidity, the first, second and third variable stiffness grippers 112, 114, and 116, respectively.

Although the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And various modifications and changes may be made thereto without departing from the scope of the present invention. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the claims set forth below, fall within the scope of the present invention.

100: Variable Stiffness Gripper System
110: Variable stiffness gripper
120: Gripper body
130: Gripper controller
200: Rigid body
300: soft body
330:
400: Tendon
F1, F2: Operating force

Claims (10)

A flexible member having a tensile member which is elongated in a structure in which a soft body is disposed between a plurality of rigid members and which is connected to a rigid member located at a front end of the rigid members and disposed to pass through other rigid members and soft members, Rigid gripper;
A gripper body having a rear end portion of the variable rigidity gripper connected to the front portion and a variable rigidity gripper disposed at a plurality of installation positions provided on the front portion; And
A gripper controller disposed in the gripper body and associated with the tendons of the variable stiffness grippers, the gripper controller providing an actuating force to the tendon to vary the stiffness and shape of the variable stiffness gripper;
And a variable rigidity gripper system.
The method according to claim 1,
The outer peripheral portion of the soft body is formed with a corrugated portion formed of an acid and a valley,
Wherein the wrinkle portion is formed in a shape surrounding the outer peripheral portion of the soft body, and a plurality of the wrinkle portions are continuously provided along the longitudinal direction of the soft body.
3. The method of claim 2,
Wherein the wrinkle portion is formed in a cross-sectional shape of at least one of a triangle, a quadrangle, a trapezoid, and an ellipse.
3. The method of claim 2,
The soft-
A first soft material disposed at a central portion between the rigid bodies so as to be positioned on the central axis of the variable rigid gripper, the first soft material being arranged to penetrate the tendon; And
A second soft body disposed in a shape other than the central portion between the rigid members and surrounding the outer periphery of the first soft member and having a corrugated portion;
And a variable rigidity gripper.
The method according to claim 1,
Characterized in that the rigid body disposed at the distal end of the variable rigidity gripper is formed longer than the other rigid bodies and a rubber member for increasing frictional force is disposed on the surface.
6. The method according to any one of claims 1 to 5,
One end of the tendon is connected to the rigid body disposed at the distal end of the variable rigidity gripper and the other end of the tendon passes through the rigid body and the gripper controller after passing through the rigid bodies and soft bodies except for the rigid body,
Characterized in that the gripper body is formed with a tendon passageway through which the tendons of the variable rigid grippers are disposed.
The method according to claim 6,
The gripper controller,
A controller frame disposed at a rear portion of the gripper body and configured to communicate with the tendon passage;
A tendon reel connected to the other end of the tendons passing through the tendon passage and arranged in a shape that the tendons are wound around the outer periphery; And
A tension control motor connected to the center of the tension reel and providing an actuating force to the tendons to change the rigidity and shape of the variable rigidity grippers by rotating the tension reel;
And a variable rigidity gripper.
8. The method of claim 7,
Wherein the tentative reel is disposed in a position facing the tendon passageway.
8. The method of claim 7,
A plurality of tendons are arranged on the variable rigidity gripper so as to be spaced apart from each other,
Wherein the tendon reel and tendon control motors are provided in a number corresponding to the number of tendons arranged in the variable rigidity gripper and are connected to the tendons individually one by one.
10. The method of claim 9,
The variable rigidity grippers are provided with the same arrangement of tendons,
Characterized in that the tendon reels are connected respectively to tendons arranged at the same position of the variable rigid grippers among the tendons.

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