Artificial wrist

Abstract

An artificial wrist (1) is provided, comprising: a first body (2) constrained to a support; a second body (3) adapted to be constrained to a gripper (10a); an actuator (4) connecting and moving the bodies (2, 3); the actuator (4) comprises an air chamber (41) defining a longitudinal trajectory (4a), a first end integral with the first body (2) and a second end integral with the second body (3); and a filament (42) helically wound on the air chamber (41) defining a winding pitch and having ends integral with the air chamber (41) so that, when the air chamber (41) deforms, there is a deformation of said filament (42) defining an increase in the winding pitch and thus an angular displacement between said third and fourth ends with consequent torsion of the air chamber (41) and thus a rotation between the bodies (2, 3).

Description

[0001] DESCRIPTION

[0002] ARTIFICIAL WRIST

[0003] The present invention relates to an artificial wrist of the type specified in the preamble of claim 1.

[0004] In particular, the invention is adapted to be used for connecting an end-effector (such as a gripper) to a support (for example a suitably prosthetic robotic arm), allowing mutual motion between end-effector and support. In detail, the artificial wrist is adapted to be used in the industrial field.

[0005] Artificial wrists for manipulating objects and used to couple an end-effector (usually a gripper for gripping one or more objects) to a robotic arm or a user's residual stump are currently known.

[0006] The known artificial wrists summarily provide a base element constrained to the support, a mobile element relative to the base element and for constraint to the robotic arm; and a hinge defining a rotation axis between the elements and thus between support and device.

[0007] An example of an artificial wrist is described in US2007260328.

[0008] In this artificial wrist, the hinge is constituted by a gearwheel integral with the gripper and configured to engage a coupling body to the arm so as to control a rotation of the hinge and thus of the wrist through said gear wheel.

[0009] A second example of an artificial wrist is described in CN111631846.

[0010] The wrist described herein is composed of a rotating structure and a tilting structure, the rotating structure comprises a wrist base, a first drive motor, a first transmission system and a rotating platform, with the first drive motor driving the rotating platform to rotate through the first transmission system; the tilting structure further comprises a second drive motor, a second transmission system and a tilting platform, with the second drive motor driving the tilting platform to perform tilting through the second transmission system.

[0011] Another example of an artificial wrist is described in US8795387.

[0012] US8795387 describes a wrist to be attached between arm and end-effector. The wrist has a proximal section, a central section rotatably fixed to the proximal section with a first joint, and a distal section rotatably fixed to the central section with a second joint. The second joint includes a second articulation axis that is substantially orthogonal and non-intersecting with the first articulation axis. The distal section also includes, at its distal end, a terminal device fastening mechanism. The first and second joints each include a proximal portion, a distal portion, a pin and a locking mechanism adapted to allow angular selection between the proximal and distal portions and their locking.

[0013] The known technique described includes some important drawbacks.

[0014] In fact, artificial wrists are equipped with complex mechanics and difficult to implement compared to the reduced encumbrances required by artificial wrists.

[0015] Another drawback is that artificial wrists require limited encumbrances and weights to make their use practical and comfortable, but, as is easily understood from the examples reported above, they have a great number of elements which impose considerable weight and high encumbrance.

[0016] Another aspect is represented by the fact that the known artificial wrists are capable of emulating only a few movements of, for example, a human wrist. Consequently, they impose particular movements on the robotic arm to perform the correct gripping of an object.

[0017] In this situation, the technical task underlying the present invention is to devise an artificial wrist capable of substantially overcoming at least part of the cited drawbacks.

[0018] Within said technical task, an important object of the invention is to achieve an artificial wrist having a reduced weight and limited encumbrances.

[0019] Another important object of the invention is to make an artificial wrist that is easy to make and, above all, allows simple execution of movements that are currently difficult to perform.

[0020] The technical task and the specified objects are achieved by an artificial wrist as claimed in the appended claim 1. Preferred embodiments are described in the dependent claims.

[0021] The features and advantages of the invention are clarified below by the detailed description of preferred embodiments of the invention, with reference to the accompanying drawings, in which:

[0022] Fig. 1 shows, to scale, a perspective view of the artificial wrist according to the invention;

[0023] Fig. 2a illustrates, to scale, a side view of the artificial wrist according to the invention; Fig. 2b shows a sectional view, to scale, of the side view of Fig. 2a;

[0024] Fig. 3 is a perspective view, to scale, of an end-effector provided with the artificial wrist according to the invention;

[0025] Fig. 4a presents, to scale, a side view of the end-effector of Fig. 3;

[0026] Fig. 4b shows a sectional view, to scale, of the side view of Fig. 4a;

[0027] Fig. 5 highlights a detail in an end-effector that can be associated with the artificial wrist according to the invention; and

[0028] Figs. 6a-6e describe a possible gripping procedure of an object performed with an end-effector provided with the artificial wrist according to the invention.

[0029] In this document, the measurements, values, shapes and geometric references (such as perpendicularity and parallelism), when associated with words such as “approximately” or other similar terms such as “substantially” or “about”, are to be understood as subject to measurement errors or inaccuracies due to production and / or manufacturing errors and, above all, as subject to a slight deviation from the value, measurement, shape or geometric reference to which it is associated. For example, such terms, when associated with a value, preferably indicate a deviation not exceeding 10% of the value itself.

[0030] Furthermore, when used, terms such as “first”, “second”, “upper”, “lower”, “main” and “secondary” do not necessarily identify an order, a priority of relationship or relative position, but may simply be used to more clearly distinguish between different components.

[0031] Unless otherwise indicated, “perpendicular”, “transversal”, “parallel” or “normal” or other terms of geometric positioning between geometric elements (for example axes, directions and lines) are to be understood with reference to their mutual geometric position between the corresponding projections. Said projections are defined on a single plane parallel to the plane(s) of lie of said geometric elements.

[0032] The measurements and data reported in this text are to be considered, unless otherwise indicated, as carried out in the ICAO International Standard Atmosphere (ISO 2533:1975).

[0033] Unless otherwise specified, as results from the following discussions, it is considered that terms such as “processing”, “computing”, “determination”, “calculation”, or the like, refer to the action and / or processes of a computer or similar electronic computing device that manipulates and / or transforms data represented as physical quantities, such as electronic quantities of registers of a computer system and / or memories, into other data similarly represented as physical quantities within computer systems, registers or other storage, transmission or information display devices.

[0034] With reference to the Figures, the artificial wrist according to the invention is globally denoted by the number 1.

[0035] It is adapted to be used for connecting an end-effector 10 (in detail a gripper 10a) to a support, for example a robotic arm, allowing at least one rotation between endeffector and support.

[0036] The artificial wrist 1 , as illustrated in Figs. 1 , 2a and 2b, comprises a first body 2 adapted to be constrained to a support; a second body 3 adapted to be constrained to an end-effector 10; and an actuator 4 connecting the bodies 2 and 3 to one another allowing mutual motion between said bodies 2 and 3 and therefore between support and gripper 10a.

[0037] The bodies 2 and 3 may be of known type.

[0038] The first body 2 defines a first longitudinal axis 2a suitably barycentric.

[0039] It may comprise first fastening means configured to constrain the first body 2 integrally to the support.

[0040] The second body 3 defines a second longitudinal axis 3a suitably barycentric.

[0041] It comprises second fastening means configured to constrain the second body 3 integrally to the gripper 10a.

[0042] The first and second fastening means may be of known type.

[0043] The actuator 4 defines a longitudinal trajectory 4a.

[0044] It is configured to control at least one rotation between the bodies 2 and 3 and more particularly at least a mutual torsion thereof, that is, a rotation of the first body around the first axis 2a and / or a rotation of the second body around the second axis 3a. Precisely, the actuator 4 is configured to control at least one rotation of the second body 3 relative to the first body 2 and therefore of the gripper 10a relative to the support. More precisely still, it is configured to control at least a torsion of the second body 3 relative to the first body 2 and therefore a rotation of the second body around the second axis 3a.

[0045] The actuator 4 is configured to define said mutual torsion between the bodies 2 and 3 as a function of a variation of its length along the longitudinal trajectory 4a. Advantageously, the actuator 4 is configured to define, suitably as a function of a variation of its length along the longitudinal trajectory 4a, also at least one additional deformation distinct from said torsion.

[0046] In at least one application case, such as that described below with reference to the gripping procedure of an object resting, in detail anchored, on a support surface, such additional deformation may provide an additional rotation between the bodies 2 and 3 distinct from said mutual torsion around an additional rotation axis perpendicular to the longitudinal trajectory 4a. Preferably, said additional deformation may be identified by a first additional rotation around a first additional rotation axis perpendicular to said trajectory 4a and a second additional rotation around a second additional rotation axis perpendicular to said first additional rotation axis and to said trajectory 4a.

[0047] It is emphasised that this additional deformation may not be actively controlled by the actuator 4 and therefore defined by other conditions and / or by the interactions with the working environment of the artificial wrist 1 .

[0048] The actuator 4 comprises at least one air chamber 41 defining the longitudinal trajectory 4a and, along said longitudinal trajectory 4a, a first end integral with the first body 2 and a second end integral with the second body 3.

[0049] In particular, it may comprise a single air chamber 41 .

[0050] The longitudinal trajectory 4a may be barycentric to the air chamber 41 and therefore to said cavity.

[0051] The trajectory 4a may define a subtended segment and thus connecting the first axis 2a to the second axis 3a.

[0052] In particular, the tangent to the longitudinal trajectory 4a at the first end is parallel and preferably substantially coincident with the first axis 2a.

[0053] The tangent to the trajectory 4a at the second end is parallel and preferably substantially coincident with the second axis 3a.

[0054] The longitudinal trajectory 4a and therefore the air chamber 41 may be arched (preferably being double-curved as in Fig. 6d) or alternatively rectilinear.

[0055] The air chamber 41 is subtended between the bodies 2 and 3.

[0056] The chamber 41 is identifiable as a hollow body defining a housing for a fluid hermetically sealed. Preferably, the fluid is a gas such as air.

[0057] The chamber 41 is identifiable as a tubular hollow body: alternatively, the chamber 41 is bellows-shaped and, as known, comprises a series of ridges (portions at greater radial distance from the trajectory 4a) alternated with bottoms (portions at lower radial distance from the trajectory 4a).

[0058] The hollow body and therefore the air chamber 41 may have a thickness, calculated perpendicularly to the trajectory 4a, substantially comprised between 30 mm and 1 mm, in detail between 20 mm and 5 mm, and more precisely between 12 mm and 5 mm.

[0059] The external diameter of the air chamber 41 may be at least twice the internal diameter of the chamber 41.

[0060] It is configured to vary its extension, suitably at least along the trajectory 4a, in accordance with a variation of the internal pressure of the air chamber 41 , that is, of the pressure exerted by the fluid contained in said chamber 41 , defining a motion between the bodies 2 and 3.

[0061] The air chamber 41 therefore defines a rest configuration (Figs. 1 , 2a-2b, 4a-4b, 6a- 6b) in which it has a minimum volume and at least one working configuration (Figs. 6c-6e) in which the chamber 41 has a volume greater than the minimum volume. In detail, the chamber 41 has a minimum axial extension in the rest configuration and an axial extension greater than said minimum axial extension in the at least one working configuration.

[0062] It is specified that the expression “axial extension” identifies a length calculated along the longitudinal trajectory 4a.

[0063] In the rest configuration, the longitudinal trajectory 4a is preferably rectilinear.

[0064] In the working configuration, the longitudinal trajectory 4a may be rectilinear (Fig. 6e) or arched (Figs. 6c-6d).

[0065] In said rest configuration, the internal pressure of the air chamber 41 is equal to a rest pressure, for example equal to the atmospheric pressure.

[0066] In the working configuration, the internal pressure of the chamber 41 is different and preferably higher than said rest pressure.

[0067] The actuator 4 also comprises at least one filament 42. Preferably, the actuator 4 comprises a single filament 42.

[0068] Each filament 42 is helically wound on the chamber 41 along the longitudinal trajectory 4a defining a winding pitch. It has a helical development having said trajectory 4a as its axis and said winding pitch as its pitch. Each filament 42 is identifiable as an elongate body defining a third end and a fourth end. It therefore extends continuously between the third and fourth end.

[0069] The third end is integral (for example glued) to the first body 2 or alternatively to the chamber 41 near the first end. In detail, the third end is integral with the air chamber 41 at the first end.

[0070] The fourth end is integral (for example glued) to the second body 3 or alternatively to the chamber 41 near the second end. Preferably, it is integral with the air chamber 41 at the second end.

[0071] The integral constraint of the third and fourth ends causes a deformation of the air chamber 41 to induce a deformation of the filament 42 which, in turn, generates a deformation of the air chamber 41. Therefore, the chamber 41 , when it assumes an internal pressure different (preferably higher) than said rest pressure and expands, controls an elongation of the axial extension of the filament given, substantially exclusively, by an increase of the winding pitch. By virtue of this, there is an angular displacement between the third and fourth ends and therefore a torsion of the chamber 41 around the longitudinal trajectory 4a. The torsion of the air chamber 41 , in turn, determines a rotation between the bodies 2 and 3. Precisely, since the tangent to the longitudinal trajectory 4a is parallel to the first axis 2a at the first end and to the second axis 3a at the second end, the torsion of the air chamber 41 gives rise to a rotation of the first body 2 around the first axis 2a and / or a rotation of the second body 3 around the second axis 3a. Preferably, such torsion determines a rotation of only the second body 3 around the second axis 3a relative to the first body 2 which remains static.

[0072] In addition to said torsion, as better described below, the deformation of the air chamber 41 may also determine at least one additional rotation and in detail said first and said second additional rotation.

[0073] It is noted that the stiffness of the filament 42, also thanks to the helical development, is such that a deformation of the chamber 41 corresponds to at least one variation of the axial extension of the filament 42 determined, substantially exclusively, by a variation of the winding pitch of the filament 42. Moreover, the filament 42 also allows a deformation of the longitudinal trajectory 4a and therefore of the chamber 41 such as a curvature.

[0074] In order to allow to control such torsion of the air chamber 41 , the filament 42 has a stiffness with respect to the air chamber 41 such as to allow said filament 42 to tighten the chamber 41 and to allow the same filament 42 to mainly control an angular displacement between third and fourth ends, and thus between first and second ends, so as to impose at least one torsion to the air chamber 41 .

[0075] Summarising, the filament 42 limits and preferably prevents a deformation of the section (perpendicular to the longitudinal trajectory 4a) so that a variation of the internal pressure of the air chamber corresponds, preferably exclusively, to a variation of the axial extension of the air chamber 41 and thus of the filament 42, thereby generating said torsion and suitably allowing at least said additional rotation. The Young’s modulus of the filament 42 is greater than the Young’s modulus of the air chamber 41 . In detail, the Young’s modulus of the filament 42 is at least equal to 100 times, in detail 1000 times, more precisely 10,000 times the Young’s modulus of the air chamber 41. For example, the Young’s modulus of the filament 42 is comprised between 10,000 and 120,000 times the Young’s modulus of the air chamber 41.

[0076] The air chamber 41 may be made of elastomeric material, in detail preferably of silicone rubber such as that commercially known as Dragon skin® 10 by Smooth- On Inc.

[0077] The filament 42 may be made of cotton, nylon or copper suitably impregnated with, for example, silicone.

[0078] The filament 42 may have a circular section with diameter substantially comprised between 0.1 mm and 3 mm and preferably between 0.4 mm and 0.3 mm.

[0079] The winding pitch of the filament 42 may be substantially less than 50% of the external diameter of the air chamber and suitably comprised between 75% and 30% of the internal diameter of the chamber 41 .

[0080] The winding pitch may be substantially comprised between 15 mm and 2 mm and in detail between 7 mm and 5 mm.

[0081] Each filament 42 may be embedded in the air chamber 41 (that is, in said tubular body).

[0082] Alternatively, it is wound externally to the chamber 41 and therefore constrained to the lateral wall of the air chamber 41 . It is noted that, in the case of a bellows-shaped air chamber, the filament 42 may be constrained to the air chamber 41 at only the ridges; or only the bottoms. The air chamber 41 may comprise, for each filament 42, a groove configured to house said filament 42 and made on the external surface of said air chamber 41 . The groove has a helical development at least equal to that of the filament 42.

[0083] The groove may be obtained along the lateral wall, suitably external, of the air chamber. It is noted that, in the case of bellows-shaped air chamber 41 , the groove may be obtained at only the ridges or only the bottoms.

[0084] The groove has a section smaller than that of the filament 42 so as to house at least part of the section of the filament 42 which may thus protrude from the lateral surface of said chamber 41.

[0085] The actuator 4 may also comprise a coating 43 configured to externally coat the air chamber 41 and therefore enclose and lock the filament 42 to the chamber 41 , suitably in said groove.

[0086] The coating 43 is configured to penetrate into the groove filling it together with the filament.

[0087] The coating 43 is configured to impregnate the filament, so as to ensure integration between chamber 41 and filament 43.

[0088] The coating 43 may be made of elastomeric material, in detail preferably of silicone rubber such as that commercially known as Ecoflex® 30 by Smooth-On Inc.

[0089] The actuator 4 may also comprise a connector 44 configured to place the air chamber 41 (that is, the housing defined by it) in fluid communication with a fluid supply system.

[0090] The connector 44 may be placed in correspondence with the first body 2.

[0091] The supply system, for simplicity not shown in the figure, is configured to vary (that is, increase and decrease) the pressure of the fluid inside the air chamber 41 and thus control a change in configuration of the same air chamber 41 . It may comprise a compressor, a vent valve or other known means configured to carry out said pressure variation.

[0092] The supply system may be part of the artificial wrist 1 (for example integral with either the first body 2 or the second body 3). Alternatively, it may be part of the endeffector 10 and / or of a robotic arm comprising said artificial wrist.

[0093] The invention also introduces an innovative end-effector 10.

[0094] The end-effector 10 (Figs. 3, 4a and 4b) comprises at least one, preferably a single, artificial wrist 1 and preferably a gripper 10a configured to perform the gripping of an object 1a.

[0095] The gripper 10a is constrained, suitably integrally, to the wrist 1 at the second body 3.

[0096] The gripper 10a comprises at least two fingers 20 movable with respect to one another so as to perform the gripping of an object 1a; and a palm 30 to which said fingers 20 are constrained. In detail, the gripper 10a comprises three fingers 20 angularly equally spaced.

[0097] Each finger 20 defines a preferred extension direction 20a.

[0098] Each finger 20 defines a proximal end at the palm and a distal end from the palm 30.

[0099] Each finger 20 defines an extended position (Figs. 3, 4a-4b, 6a) in which the preferred extension direction 20a is not suitable to perform the gripping of an object 1a and for example curved or preferably rectilinear; and one or more gripping positions (Figs. 6b-6e) in which the direction 20a is arched, suitably more than in the extended position, so as to allow the gripping. Preferably, in the extended position the fingers 20 of a gripper 10a have preferred extension directions 20a (curved or preferably rectilinear) diverging from one another from the palm 30.

[0100] Each finger 20 is identifiable as a hollow body configured to vary its posture according to the internal pressure of the finger itself.

[0101] It comprises a contact layer 21 defining a first surface 21 a of contact with said object 1a and a second surface 21b opposite to the first surface with respect to the same contact layer 21 ; and a plurality of enclosures 22 protruding from the second surface 21 b.

[0102] The contact layer 21 and therefore the surfaces extend along the preferred extension direction 20a. In detail, they are mutually spaced along said direction 20a. Each enclosure 22 defines, together with the contact layer 21 and more precisely with the second surface 21 b, a cell 22a configured to deform according to a variation of the internal pressure. The enclosures 22 and thus the cells 22a may be aligned along the preferred extension direction 20a.

[0103] The enclosures 22 and thus the cells 22a may have a protrusion height, calculated along the normal to the second surface 21b, monotonically decreasing from a maximum value at the proximal end to a minimum value at the distal end.

[0104] The cells 22a may have the same section calculated perpendicularly to said normal to the second surface 21b.

[0105] The cells 22a, and thus the enclosures 22, are configured to expand according to a variation of the internal pressure of the cells 22a, that is, of the pressure of the fluid contained in the cells 22a, determining a change in position of the finger 20. In particular, the contact layer 21 has a greater stiffness than the enclosures 22 so as to have substantially a lateral deformation of the cells 22a, that is, a deformation of the cells 22a and thus of the enclosures 22 greater at the lateral walls of the cells 22a extending between the second surface 21b and the apical portions of the enclosures 22. Such lateral deformation causes the lateral walls of the enclosures 22 to come into mutual contact, curving the layer 21 and thus causing the transition to the gripping position.

[0106] In the extended position, the internal pressure of the cells 22a is equal to a supplemental rest pressure, for example, equal to the atmospheric pressure.

[0107] In the gripping position, the internal pressure of the cells 22a is different and, preferably, greater than said supplemental rest pressure.

[0108] Preferably, the fluid in the cells 22a is a gas such as air. In particular, the fluid in the cells 22a is the same as that in the air chamber 41 .

[0109] Each finger 20 may also comprise at least one duct 23 configured to place said cells 22a in fluid communication, which thus have the same internal pressure.

[0110] Said duct 23 is preferably obtained at the first surface 21a.

[0111] Each finger 20 may also comprise a contact sensor 24 of the first surface 21a with the object 1 a.

[0112] Said contact sensor 24 is configured to detect the contact of the finger 20 with the object 1a and in particular the contact pressure between finger 20 and object 1a (that is, the gripping force of the gripper 10a on the object 1a).

[0113] The palm 30 comprises a central portion 31 configured to be constrained to the artificial wrist 1 and in detail to the second body 2; and for each finger 20 a connection portion 32 of said finger 20 to the central portion 31.

[0114] The central portion 31 defines a preferred extension axis. Suitably barycentric, and substantially coincident with the second axis 3a when the palm 30 is constrained to the second body 3.

[0115] The central portion 31 is interposed between the connection portions 32 so as to space the fingers 20 from one another and in particular the proximal ends of the fingers 20.

[0116] The central portion 31 may comprise connection means 31a to a fluid supply system, suitably the same as or different from the system of the artificial wrist 1 introduced above.

[0117] The supply system is thus configured to vary the pressure exerted by the fluid inside the cells 22a defining a change in position of the fingers.

[0118] The central portion 31 may comprise at least one distribution block 31b configured to place the cells 22a of the various fingers 20 in fluid communication with one another and preferably with said supply system.

[0119] It is noted that a gripper 10a preferably has the cells 22a of all the fingers 20 in mutual fluid communication and thus at the same internal pressure; while the air chamber 41 is not in mutual fluid communication with the cells 22a and may therefore have a different internal pressure.

[0120] The distribution block 31b preferably comprises a toroidal air chamber; an inlet section configured to place the toroidal air chamber in fluid communication with said supply system; and for each finger 20 an outlet section placing the toroidal air chamber in fluid communication with the cells 22a of the finger 20 through the connection portions 32.

[0121] Each connection portion 32 comprises a channel configured to place the cells 22a in fluid communication with the distribution block 31b and thus with the supply system.

[0122] Finally, the invention comprises an end-effector 10 and a robotic device comprising a robotic arm suitably constrained to the artificial wrist 1 at the first body 2.

[0123] The robotic arm may be of known type and is therefore not further described.

[0124] At least one among artificial wrist 1 , end-effector 10, and robotic arm comprises a control board.

[0125] Said control board may be in data connection with the supply system so as to control a change in configuration of the artificial wrist (controlling a variation of the internal pressure in the air chamber 41) and / or of the position of the fingers 20 (controlling a variation of the internal pressure in the cells 22a) preferably based on the contact sensor 24.

[0126] It is noted that the control board may comprise a database of the objects comprising one or more objects 1a, each of which is associated with a gripping value, that is, the pressure and / or force that a finger 20 must exert on the object 1a to perform its gripping and allow its handling; and suitably a threshold defining the maximum internal pressure and thus the maximum axial extension of the air chamber 41 .

[0127] Said control board may also be in data connection with the robotic arm so as to control the movement of the end-effector 10.

[0128] The operation of the artificial wrist 1 and thus of the end-effector 10 and the robotic arm described above in structural terms is as follows.

[0129] This operation introduces a new gripping procedure of an object implementable by an end-effector 10 equipped with an artificial wrist 1 and thus by a robotic arm provided with said end-effector 10.

[0130] Initially, the artificial wrist 1 is in a rest configuration and the fingers 20 of the gripper 10a are in the extended position.

[0131] Preferably, the object 1a is resting on a support surface 1b. For example, the object 1a is an object constrained to the support surface 1 b and thus to be detached from said surface 1b such as a vegetable, a fruit or a mushroom to be picked-up.

[0132] The gripping procedure comprises an identification step in which the object 1a to be picked is indicated to the control board, which then identifies the gripping value associated with it in the object database (said identification is performable in a known manner and is therefore not described in this document).

[0133] The procedure comprises an approachment step (Fig. 6a) of the end-effector 10 to the object 1a to be picked, suitably resting, and in detail constrained, to said support surface 1 b.

[0134] In this step, the end-effector 10, suitably moved by the robotic arm, places the fingers 20 in contact with the object 1a.

[0135] It is noted that in this step the wrist 1 is in the rest configuration with the trajectory 4a rectilinear and preferably the fingers 20 are in the extended position.

[0136] The procedure then comprises a gripping step (Fig. 6b) in which the gripper 10a performs the gripping of the object 1a.

[0137] In this gripping step each finger 20 moves to a gripping position. In detail, the supply system, suitably controlled by the board, defines a variation and in particular an increase of the internal pressure in the cells 22a. Consequently, the cells 22a and thus the enclosures 22 expand, determining a change in position of the fingers 20 which move closer to the object 1a. The gripping step ends when the contact sensor 24 detects a contact pressure and / or force with the object 1a equal to the gripping value of the object 1a and therefore the supply system, suitably controlled by the board, ends the variation of the internal pressure in the cells 22a which thus remain in the gripping position.

[0138] In the gripping step, the robotic arm remains substantially static.

[0139] At this point, the procedure comprises a detachment step (Figs. 6c-6d) of the object 1a from the support surface 1b.

[0140] The gripping and detachment steps may be carried out in parallel.

[0141] Alternatively, the gripping step precedes the detachment step and therefore, during the gripping step, the artificial wrist 1 is in the rest configuration with the longitudinal trajectory 4a rectilinear; while the detachment step is carried out with the fingers in the gripping position reached in the gripping step.

[0142] In this step, the wrist 1 moves from the rest configuration to a working configuration. In detail, the air chamber 41 deforms by altering its axial extension as a result of a variation of the internal pressure in the same chamber 41 suitably given by the supply system preferably controlled by the board. In response to said variation in axial extension, the filament 42 also varies its axial extension by altering, substantially exclusively, its winding pitch. Consequently, since the third and fourth ends of the filament 42 are integral with the air chamber 41 (or alternatively with the bodies 2 and 3) the variation of the axial length of the filament 42 determines an angular displacement between the third and fourth ends which in turn causes a torsion of the chamber 41 around the trajectory 4a and thus a rotation between the bodies 2 and 3.

[0143] In detail, the air chamber 41 expands as a function of the increase of the internal pressure in the air chamber 41 increasing, preferably exclusively, its axial extension along the trajectory 4a. This increase in axial extension of the air chamber 41 causes the filament 42 to also increase the axial extension by increasing, substantially exclusively, its winding pitch. Consequently, the axial elongation of the filament 42 determines an angular displacement between the third and fourth ends which in turn causes a torsion of the chamber 41 around the trajectory 4a and thus a rotation of the second body 3. In fact, while the first body integral with the robotic arm remains stationary, the second body 3 integral with the gripper 10a, and thus with the object 1a, rotates dragging the gripper 10a in rotation, and thus the object 1a, which rotates with respect to the surface 1b detaching itself (for example performing the detachment / harvesting of the mushroom from the ground).

[0144] In the detachment step, the robotic arm and thus the first body 2 may remain substantially static. Consequently, the variation of the axial extension of the air chamber 41 defines a deformation of the longitudinal trajectory 4a and thus at least said additional rotation. In detail, the increase of the axial extension of the air chamber 41 , being blocked at the first end by the static first body 2 and at the second end by the support surface 1b at the second body 3, determines said additional deformation and in particular at least one additional rotation defining a curvature of the chamber 41 and the filament 42 with consequent rotation of the gripper 10a, and thus of the object 1a, around at least said additional rotation axis. More in detail, said increase of the axial extension of the chamber 41 determines, preferably simultaneously, a first additional rotation and a second additional rotation and thus a rotation of the gripper 10a, and thus of the object 1a, around the first and the second additional rotation axis.

[0145] At this point, the gripping procedure comprises a moving away step (Fig. 6e) of the object 1a from the support surface 1 b.

[0146] In this step, the end-effector 10, suitably moved by the robotic arm, moves the object 1a away from the contact surface 1b.

[0147] Consequently, the object 1a, not being in contact with the surface 1b, does not block along an axial direction the second body 3 which therefore allows the longitudinal trajectory 4a and the air chamber 41 to return to being rectilinear.

[0148] The artificial wrist 1 and thus the end-effector 10 and the robotic arm according to the invention achieve important advantages.

[0149] In fact, the artificial wrist 1 differs from known artificial wrists in that it is equipped with an extremely simple mechanism, easy to make and above all with reduced encumbrances.

[0150] Another advantage lies in the fact that the wrist 1 allows a high mobility of the endeffector 1 which, therefore, can be easily adapted to multiple uses.

[0151] For example, the artificial wrist 1 is capable of allowing the gripper 10a a smooth combined flexion-torsion movement without this in any way reducing the effectiveness of the gripping of the object 1a. This aspect finds application, for example, in agriculture where the wrist 1 defines an innovative gripping procedure which, as described above, is characterised by a flexion-torsion movement that allows delicate uprooting of crops such as, for example, mushrooms.

[0152] This simplicity is also determined by the possibility of controlling the artificial wrist 1 and the end-effector 10 simply by varying only their internal pressure. This avoids the complexity of the control system required in known end-effectors and wrists as well as the necessary complicated mechanical systems.

[0153] The invention is susceptible to variations falling within the scope of the inventive concept defined by the claims.

[0154] For example, the end-effector 10 may provide that the central portion 31 and the second body 2 are made in one piece.

[0155] In another example, the gripper 10a may have the fingers 20 not in mutual fluid communication and therefore the cells 22a of one finger 20 at an internal pressure different from those of another finger 20.

[0156] In another example, the actuator 4 may comprise a plurality of air chambers 41 . Said air chambers 41 may be aligned along the longitudinal trajectory.

[0157] Consequently, the actuator 4 may comprise either a single filament 42 subtended between the first end of the first chamber 41 (or the first body 2) and the second end of the last chamber 41 along said trajectory 4a (or the second body 3); or one filament 42 for each chamber 41.

[0158] Alternatively, said air chambers 41 may be parallel and have the same axial extension in the rest configuration. In this case, the actuator 4 may comprise either a single filament 42 winding around all the air chambers 41 ; or one filament 42 for each chamber 41.

[0159] Furthermore, said air chambers 41 may always have the same internal pressure or may assume different internal pressures and thus be differently deformed, defining a motion between the bodies 2 and 3 resulting from said deformations.

[0160] In this context, all details may be replaced by equivalent elements, and the materials, shapes and dimensions may be of any type.

Claims

C LAI M S1. Artificial wrist (1 ) comprising:- a first body (2) adapted to be constrained to a support;- a second body (3) adapted to be constrained to a gripper (10a);- an actuator (4) constraining said first body (2) to said second body (3) allowing mutual motion of said bodies (2, 3); and characterised in that said actuator (4) comprises:- at least one air chamber (41 ), each of which defining a longitudinal trajectory (4a) and along said longitudinal trajectory (4a) a first end integral with said first body (2) and a second end integral with said second body (3); said air chamber (41 ) being configured to expand along said longitudinal trajectory (4a) in accordance with a variation of internal pressure in said air chamber (41), defining a motion between said bodies (2, 3);- at least one filament (42) o helically wound on said air chamber (41) along said longitudinal trajectory (4a) defining a winding pitch and o having■ a third end integral with one of said first body (2) and said air chamber (41) near said first end, and■ a fourth end integral with one of said second body (3) and said air chamber (41) near said second end, so that, when said air chamber (41 ) deforms, there is a deformation of said filament (42) defining an increase in said winding pitch and thus an angular displacement between said third and fourth ends which causes a torsion of said air chamber (41) around said longitudinal trajectory (4a) and thus a rotation between said bodies (2, 3).

2. Artificial wrist (1) according to claim 1 , wherein said filament (42) has a stiffness with respect to said air chamber (41) such as to allow said filament (42) to tighten said air chamber (41 ) and enable said filament (42) to mainly control said angular displacement between said third and fourth ends.

3. Artificial wrist (1 ) according to claim 2, wherein said winding pitch is less than 50% of the external diameter of said air chamber (41 ) and comprised between 75% and 30% of the internal diameter of said air chamber (41); and wherein saidwinding pitch is substantially comprised between 15 mm and 2 mm and in detail between 7 mm and 5 mm.

4. Artificial wrist (1 ) according to at least one of the preceding claims, wherein said air chamber (41) comprises, for each said filament (42), a groove configured to house said filament (42) and formed on the external surface of said air chamber(41 ); and wherein said actuator (4) comprises a coating (43) which fills said groove locking said filament (42) in said groove.

5. Artificial wrist (1 ) according to at least one of the preceding claims, wherein said filament (42) is made of cotton and said coating (43) impregnates said filament(42).

6. End-effector (10) configured to perform the gripping of an object (1a) and comprising said artificial wrist (1) according to at least one of the preceding claims and a gripper (10a) integral with said second body (3).

7. End-effector (10) according to the preceding claim, wherein said gripper (10a) is pneumatic and comprises three fingers (20); and wherein each finger (20) defines a preferred extension direction (20a) and comprises a contact layer (21) defining a first surface (21a) of contact with said object (1a) and a plurality of enclosures (22) protruding from the second surface (21b); wherein each of said enclosures (22) defines a cell (22a) configured to deform in function of a variation of internal pressure in said cell (22a), defining for said finger (20) an extended position wherein said preferred extension direction (20a) and thus said finger (2) are not suitable to perform the gripping of said object (1a), and at least one gripping position wherein said preferred extension direction (20a) and thus said finger (2) are suitable to perform said gripping of said object (1a).

8. Gripping procedure of an object (1a) from a support surface (1b) of said object (1a), characterised in that it comprises:- said end-effector (10) according to at least one of claims 5-6;- said air chamber (41) defines a rest configuration wherein said air chamber (41 ) has along said longitudinal trajectory (4a) a minimum axial extension and at least one working configuration wherein said air chamber (41 ) has an axial extension greater than said minimum axial extension;- a gripping step wherein said gripper (10a) performs the gripping of said object(1a) from said support surface (1b) and said air chamber (41) is in said rest configuration;- a detachment step wherein said air chamber (41 ), moving from said rest configuration to said working configuration, increases its axial extension defining an increase of the winding pitch of said filament (42) and thus a torsion of said air chamber (41 ) around said longitudinal trajectory (4a) which drags in rotation said second body (3), said gripper (10a), and thus said object (1a) with respect to said support surface (1 b); and- wherein in said detachment step said increase of said extension of said air chamber (41), being said object (1a) resting on said support surface (1b), determines a curvature of said air chamber (41 ) with consequent rotation of said gripper (10a) and thus of said object (1a) around at least one rotation axis perpendicular to said longitudinal trajectory (4a).

9. Procedure for gripping an object (1a) according to the preceding claim, comprising a robotic device comprising said end-effector (10) and a robotic arm constrained to said first body (2); said procedure also comprising an preachment step wherein said robotic arm positions the end-effector (10) in correspondence with said object (1a) constrained to said support surface (1b); and wherein said robotic arm remains static at least in said detachment step.

10. Gripping procedure of an object (1a) according to at least one of preceding claims 8-9, wherein said gripper (10a) is pneumatic and comprises three fingers (20); and wherein each finger (20) defines a preferred extension direction (20a) and comprises a contact layer (21 ) defining a first surface (21a) of contact with said object (1a) and a plurality of enclosures (22) protruding from the second surface (21 b); wherein each of said enclosures (22) defines a cell (22a) configured to deform depending on a variation of internal pressure in said cell (22a), defining for said finger (20) an extended position wherein said preferred extension direction (20a) and thus said finger (2) are not suitable to perform the gripping of said object (1a), and at least one gripping position wherein said preferred extension direction (20a) and thus said finger (2) capable of performing said gripping of said object (1a); and wherein in said gripping step said fingers (20) move from said extended position to said gripping position performing said gripping of said object (1a).

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