WO2024080924A1

WO2024080924A1 - A gripper member and a gripper system

Info

Publication number: WO2024080924A1
Application number: PCT/SG2023/050675
Authority: WO
Inventors: Yifan Wang; Yuchen Zhao
Original assignee: Nanyang Technological University
Priority date: 2022-10-12
Filing date: 2023-10-05
Publication date: 2024-04-18

Abstract

Disclosed herein is a gripper member and a gripper system including the gripper member. The gripper member includes a pair of supporting members and a palm. Each of the pair of supporting members is a bendable actuator. The palm includes a first surface partially defining a chamber. The first surface partially defines a chamber. Opposing sides of the first surface are coupled to the pair of supporting members along a respective length of the pair of supporting members. The first surface extends between the pair of supporting members. The palm includes a filler disposed in the chamber.

Description

A GRIPPER MEMBER AND A GRIPPER SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to the Singapore application no. 10202251349K filed October 12, 2022, the contents of which are hereby incorporated by reference in their entirety for all purposes.

TECHNICAL FIELD

[0002] This application relates to a gripper member and a gripper system suitable for gripping a wide variety of objects.

BACKGROUND

[0003] Advances in robotics enable challenging tasks to be accomplished by robots made of soft and compliant materials, such as jamming grippers for picking up an object. Typically, jamming grippers are required to push down on the object before picking up, and this pushing force may deform or damage soft items and such pushing force may even be larger than the gripping force. Therefore, jamming grippers are often configured for specific objects of certain characteristics, thus limiting the scope of use/application.

SUMMARY

[0004] In one aspect, the present application discloses a gripper member. The gripper member includes a pair of supporting members and a palm. Each of the pair of supporting members is a bendable actuator. The palm includes a first surface partially defining a chamber. The first surface partially defines a chamber. Opposing sides of the first surface are coupled to the pair of supporting members along a respective length of the pair of supporting members. The first surface extends between the pair of supporting members. The palm includes a filler disposed in the chamber.

[0005] A stiffness of the palm may be variable and responsive to a jamming of the filler in the chamber, and the palm may be bendable responsive to a bending of the pair of supporting members. The jamming may be responsive to a negative pressure in the chamber. Each of the pair of supporting members may extend along a first axis and may be operable to at least partially bend the first surface about a second axis, in which the second axis is transverse to the first axis.

[0006] In another aspect, the present application discloses a gripper system. The gripper system includes: a gripper device and a controller in signal communication with the gripper device. The gripper device may include a plurality of the gripper member, e.g., two or more gripper members. The controller is configured to control the gripper members to cooperatively handle an object.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Various embodiments of the present disclosure are described below with reference to the following drawings:

[0008] FIG. l is a schematic diagram illustrating a gripper system according to embodiments of the present disclosure;

[0009] FIG. 2 is a perspective view of one embodiment of a gripper device according to an embodiment;

[0010] FIG. 3 is an exploded view of a gripper member according to an embodiment;

[0011] FIG. 4 is a sectional top view of FIG. 3 showing view A- A;

[0012] FIG. 5 is a front view of the gripper member of FIG. 3;

[0013] FIG. 6 is a side view of the gripper member of FIG. 3; [0014] FIG. 7 is a front view of a gripper member according to another embodiment;

[0015] FIG. 8 is a front view of a gripper member according to another embodiment;

[0016] FIG. 9 is a sectional view of FIG. 2 showing view B-B;

[0017] FIG. 10 is a detailed view of FIG. 9 showing view C;

[0018] FIG. 11 is a perspective view of a filler according to an embodiment;

[0019] FIG. 12 is a perspective view of a filler according to another embodiment;

[0020] FIG. 13 is a perspective view of a filler according to yet another embodiment;

[0021] FIG. 14 is a perspective view of a palm of a gripper member conforming to an object according to an embodiment;

[0022] FIG. 15A is a side view of a gripper device gripping an object according to an embodiment;

[0023] FIG. 15B is a side view of the gripper device of FIG. 15A gripping another object;

[0024] FIG. 15C is a side view of the gripper device of FIG. 15A gripping another object;

[0025] FIG. 15D is a side view of the gripper device of FIG. 15A gripping another object;

[0026] FIG. 16 shows images of a gripper device of the present disclosure picking up various objects;

[0027] FIG. 17 illustrates a measurement setup and respective measurement results of gripping forces of various gripper devices of the present disclosure;

[0028] FIG. 18 illustrates the maximum gripping forces of the various gripper devices applied to various objects during gripping; and.

[0029] FIG. 19 illustrates a measurement setup and respective measurement results of pinching forces of various gripper devices of the present disclosure. DETAILED DESCRIPTION

[0030] The following detailed description is made with reference to the accompanying drawings, showing details and embodiments of the present disclosure for the purposes of illustration. Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments, even if not explicitly described in these other embodiments. Additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0031] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0032] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance as generally understood in the relevant technical field, e.g., within 10% of the specified value.

[0033] As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

[0034] For the sake of brevity, the term "handling" may be used interchangeably with any one or more of the terms "gripping", "picking", “grasping”, "holding", "picking", "transporting", "lifting", "transferring", etc., as will be understood from the context. For the sake of brevity, as used herein, the term "pressure" may be understood with reference to ambient pressure. For example, "positive pressure" may refer to a pressure that is higher than ambient pressure, and "negative pressure" may refer to a pressure that is lower than ambient pressure. Depending on the context, the term "positive pressure" may refer to an increase in pressure and the term "negative pressure" may refer to a decrease in pressure.

[0035] To aid understanding and not to be limiting, a detailed description of various embodiments of a gripper device 100 and a gripper system 50 will be described below with reference to the appended figures. The gripper device 100 may also be described as a gripper that can handle one or more objects of differing physical properties (e.g., dimensions, shape, softness, etc.) without applying excessive forces that may damage the one or more objects. For the sake of brevity, the following will describe various examples with respect to the handling of one object, but it will be understood that multiple objects may be handled simultaneously by one gripper system in various examples.

[0036] FIG. 1 is a schematic diagram of a gripper system 50 according to various embodiments of the disclosure. According to some embodiments, the gripper system 50 includes one or more gripper devices 100 that may individually or cooperatively provide one or more first surfaces 212 to contact the object 60 to be handled. The first surface 212 is characterized by a variable stiffness. For example, in a less stiff state, the first surface 212 is flexible or soft enough to behave like a fabric. For example, in some states, the first surface 212 may have a shape complementary to the shape of the object 60. For example, in some states, the shape of the first surface 212 is adaptable to or mouldable by the shape of the object 60. In other words, in some states, the first surface 212 may be compliant. The variable stiffness of the first surface 212 is controllable by controlling an extent of jamming of the filler in the chamber. For example, if the filler in the chamber is jammed, the first surface 212 is correspondingly stiff and does not change in shape until the filler is released from the jammed state. According to some embodiments, the one or more first surfaces provide a relatively large area of contact or area of support for the exemplary object 60, such that any irregular shaped objects may be robustly held and transported. In other examples, the gripper system 50 may be configured to first apply a small contact force or pinching force on the obj ect 60, followed by a relatively larger lifting force to lift the object 60. The first surface 212 and the palm 210 can stiffen to provide the large lifting force This advantageously allows delicate items such as a fruit to be gripped or picked up without bruising the fruit. Beneficially, the gripper system 50 may also be used to grip or pick up a wide variety of objects with different characteristics, such as various materials, geometries, distribution in weight, surface finishes, etc.

[0037] In some embodiments, as illustrated in FIG. 1, the gripper system 50 includes a gripper device 100 in signal communication with a controller 52. The gripper device 100 may include a frame 110 coupled to one or more gripper members 200. The example in FIG. 1 illustrates an example of the gripper system 50 having two gripper members 200. The gripper members 200 may be actuatable to cooperatively grip an object 60. In some embodiments, the gripper members 200 may be actuated to bend or curve towards the object 60 to pick up the object 60 from a surface 62. Each of the gripper member 200 includes a pair of supporting members 220. Each of the gripper member 200 includes a palm 210 defining a chamber 214 therein. The palm 210 includes a first surface 212, with the first surface 212 partially defining the chamber 214 in the palm 210, e.g., the first surface 212 forming a part of the chamber wall 213. The first surface 212 is coupled along the respective length of the supporting members. The chamber 214 is fluidically/pneumatically sealable such that a relative pressure difference between the interior of the chamber 214 and the exterior of the chamber 214 can contribute to a change in a stiffness of the first surface 212. The bending of the palm 210, e.g., the bending of the chamber wall 213 or the first surface 212, may be driven by pneumatically actuating the supporting members 220. The pneumatic actuation of the palm 210 (also interchangeably referred to as the pneumatic actuation of the chamber 214) causes the chamber wall 213 or the first surface 212 to harden, e.g., becoming more rigid and less compliant. As used herein, such an increase in stiffness of the palm 210 may be referred to as a jamming transition. The gripper members 200 may present the respective one or more first surfaces 212 oriented to enable contact and conformance to an object 60 between the gripper members. The first surface 212 may form a significant portion of the gripper member area (approximately 83% of the total area). The controller 52 may be configured to control the gripper members 200 to operatively grip the object 60. In various examples, the gripper members 200 may be actuated pneumatically by a pressure pump 56 in fluid communication with the gripper members 200, with the pressure pump 56 controllable by the controller 52.

[0038] In some embodiments, the gripper device 100 is a jamming gripper. Each of the gripper members 200 may include a chamber 214 with jamming materials or one or more fillers 240 disposed in the chamber. In some examples, the filler 240 in a chamber may include a substantially planar or planar lattice member. Responsive to a vacuum or a negative pressure in the chamber, e.g., formed by use of a vacuum pump 58, the filler becomes “jammed” (e.g., packed closer together), causing the first surface 212 contacting the object 60 to adapt in compliance with the shape of the object 60. The first surface 212 may be described as forming at least a part of a palm as, similar to the palm of a hand, the first surface may wrap around the object or form a cup to hold the object. The gripper member 200 may be described as a variablestiffness member. In some embodiments, the gripper device 100 may be coupled with a robotic arm 54 or an end-effector of a robotic arm 54. The robotic arm 54 may be configured to move the gripper device 100. In some embodiments, the controller 52 may also be in signal communication with the robotic arm 54 to control a position of the gripper device 100 relative to the surroundings.

[0039] In some embodiments, the gripper system 50 may include one or more suction nozzles 59 configured to lift the object 60. In some embodiments, the suction nozzle 59 may be incorporated with the gripper device 100, for example, coupled to the gripper device 100 to enable a compact solution. The suction nozzle 59 may be detachably coupled to the gripper device 100 such that the suction nozzle 59 can be installed or uninstalled, according to the different types of handling required. Alternatively, the suction nozzle 59 may be provided independently from the gripper device 100 such that the suction nozzle 59 may be changed or replaced according to operational requirements, for example, including but not limited to, nozzle size, suction pressure, etc. Provision of the suction nozzle 59 beneficially allows thin and soft objects such as a sheet of paper or fabric, etc., to be first lifted up to expose a "lower" surface that can be supported by one or more gripper devices 100. It may be appreciated solely using a conventional gripping action from the side may result in deforming a soft and thin sheet-like object. The suction nozzle 59 may be operated such that it does not need to physically contact the object. In some embodiments, the suction nozzle 59 may also be in fluid communication with the vacuum pump 58, with the vacuum pump 58 providing a suction pressure to the suction nozzle 59.

[0040] FIG. 2 illustrates a gripper device 100 according to various embodiments of the present disclosure. The gripper device 100 includes a frame 110 coupled to a pair of gripper members 200a/200b. The frame 110 may be formed with grooves 112 for slidable engagement between the frame 110 and each of the pair of gripper members 200a/200b, such that a spacing between the pair of gripper members 200a/200b is adjustable. The spacing between the pair of gripper members 200a/200b may be adjustable to suit the size of the object. The frame 110 may also include a coupling hole 114 for coupling with a robotic arm 54. In some embodiments, the gripper members 200a/200b may be generally planar members, each in its default state defining a respective gripper plane 80a/80b. In operation to pick up the object, the gripper members 200a/200b may be actuated to move towards each other and away from the respective gripper planes 80a/80b. In other embodiments, for purpose of picking up particulate objects (e.g., beads, grains, etc.), one or both of the gripper members 200a/200b may be bent or curved away from the respective gripper planes 80a/80b to form a scoop for scooping the particulate objects.

[0041] FIG. 3 illustrates a non -limiting embodiment of the gripper member 200 in greater detail. The gripper member 200 may be generally planar in a default state, e.g., it may define a generally flat or planar gripper plane 80 when in a non-operational state. The gripper member 200 includes a palm 210 characterized by a variable stiffness. The palm 210 may include a contact surface such as a first surface 212 that can be brought into contact with an object. In some embodiments, the palm 210 or at least the first surface 212 is formed from an elastic material, such as a silicone elastomer. The first surface 212 may be frictionally enhanced, to facilitate a secure grip on the object. The first surface 212 may extend between opposing sides 216 of the palm 210.

[0042] Referring again to FIG. 3 and FIG. 4, the gripper member 200 may include a coupling member 230 coupled to the palm 210 and the pair of supporting members 220. The coupling member 230 may be coupleable to the frame 110 of the gripper device 100, for example, to the grooves 112 formed in the frame 110 of the gripper device 100. Further, the coupling member 230 may be formed with channels 232 enabling fluidic communication between the chamber 214 and a first nozzle 234. Fluidic communication between a vacuum pump and the chamber 214 may be enabled via the first nozzle 234. The coupling member may also provide fluidic communication between each of the actuating chamber 224 with respective second nozzle 236. Fluidic communication between a pressure pump and each of the actuating chamber 224 is enabled via the second nozzle 236.

[0043] As illustrated in the enlarged views of FIG. 5 and FIG. 6, the first surface 212 may include a plurality of serrated edges or a plurality of folds. This provides the first surface 212 with room to stretch as the gripper member 200 deforms. The folds may be variously configured. In some examples, the folds may be formed with a triangular and/or zig-zag crosssection extending along the first axis 82. In some examples, the zig-zag cross-section may form an alternating angle (a) of 60°, with a wall thickness (t) of 1 mm and a pitch length (p) of 2.3 mm.

[0044] In some embodiments, when the first surface 212 is brought into contact with the object, a curvature of the first surface 212 may be changed or deformed in order to conform to the object. For example, each of the pair of supporting members extending along the first axis may be operable to at least partially bend the first surface 212 about a second axis in which the second axis is transverse to the first axis. For example, the first surface 212 may be bendable about the first axis 82 as well as to bend about the second axis 84 to conform with the object, in which the deformation of the first surface 212 may be partially contributed by actuation of at least one of the supporting members and partially contributed by pneumatic operation of the palm (e.g., relative pressure changes in the chamber). In some embodiments, the first surface 212 is deformable to form a topologically complex surface, wherein the topological surface includes at least one three-dimensional valley or at least one indented region relative to the gripper plane 80. As used in the present disclosure, the term "topologically complex surface" refers to a non-planar surface, e.g., may include one or multiple local peaks and local valleys, disposed across a surface.

[0045] Referring again to FIG. 3, according to various embodiments, the palm 210 may include a chamber 214 formed interior of the palm 210. In some embodiments, the chamber 214 is at least partially defined by the first surface 212. In some embodiments, the chamber 214 may be disposed neighbouring or adjacent to the first surface 212.

[0046] In various embodiments, as shown in FIGS. 9 and 10, a filler 240 may be disposed in the chamber 214. The chamber 214 may be configured to be fluidly sealed, such that when a negative pressure is applied to the chamber 214, the chamber 214 is in a jammed state. When the chamber 214 is not in the vacuum state or jammed state, it is in an unjammed state wherein the first surface 212 is less stiff or more compliant. In some embodiments, in the unjammed state, parts of the filler 240 may move relative to one another. In a jammed state, the parts of the filler 240 become immobilized relative to one another upon being packed closer together. In the jammed state, the filler 240 may be more packed or denser. In some embodiments, in the jammed state, the filler 240 holds up or defines a shape of the chamber 214. In some embodiments, in the jammed state, the first surface 212 may be sustained in a shape that is at least partially defined by the distribution of filler 240 about the object. It may be appreciated that a modulus of elasticity (stiffness) of the first surface 212 is thus lower than a modulus of elasticity (stiffness) of the filler 240 material, such that in the jammed state, the filler 240 is operable to sustain the first surface 212 in a curved or deformed shape.

[0047] In various embodiments of the present disclosure, the gripper member 200 includes a pair of supporting members 220 or actuators coupled respectively to the pair of opposing sides 216 of the palm 210. The supporting members 220 may be formed from a silicone elastomer, such as Smooth-On Mold Star 30. In an example, the supporting members 220 are fixed to the opposing sides 216 of the palm 210 by adhesive. In some embodiments, one of or both of the supporting members 220 may extend along respective opposing sides 216 of the palm 210, substantively covering the opposing sides 216 of the palm 210. In the default state, each of the pair of the supporting members 220 may be disposed aligned with the gripper plane 80, or in other words, the supporting members 220 are disposed coplanar with the gripper plane 80. In some embodiments, the supporting members 220 are coupled, for example via adhesive, midplane of the palm 210. In some examples, the supporting members 220 do not need to come into contact with the object 60 in order for the gripper member 200 to handle the object.

[0048] In some embodiments, each of the pair of the supporting members 220 may be pneumatically operable members, each having a respective actuating chamber 224. The supporting members 220 may be formed from two elastomer sheets or shells, defining the actuating chamber 224 therebetween. Further, the supporting members 220 may also include a strain limiting layer respectively, such as a piece of paper or nylon fabric, disposed between the two elastomer sheets or shells for strain limiting the actuation of the supporting members 220. [0049] In some embodiments, a plurality of slots 222 may be formed on at least one side of the each supporting member 220. Each of the slot 222 may define a respective slot width (W). Each of the supporting member 220 may be actuated to bend or curl responsive to a change in a pressure in the respective actuating chamber 224, i.e., an increase or decrease in pressure, in each of the actuating chamber 224. Responsive to an increase in pressure in each of the actuating chambers, the respective supporting member 220 bends to widen each of the plurality of slots, in other words, to widen the respective slot width (W). Alternatively, the supporting members 220 may be actuated via other means, such as via electrically driven actuators, cable driven actuators, magnetically driven actuators, etc.

[0050] Therefore, by way of coupling the supporting members 220 to respective opposing sides 216 of the palm 210, the palm 210 may be deformed under the actuation of one or both of the supporting members 220. In addition to conforming to an object, actuation by the supporting members 220 may also result in a change in a curvature of the first surface 212, or in other words, bending the first surface 212. In some embodiments, changing the curvature of the first surface 212 may include bending 90 at least one part of the first surface 212, such as a tip portion 212a of the first surface 212, away from the gripper plane 80. In some embodiments, referring to FIG. 5 and FIG. 6, the changing of the curvature of the first surface 212 may include bending the first surface about a first axis 82 and concurrently bending the first surface about a second axis 84.

[0051] In some embodiments, the first surface 212 may be a quadrilateral surface, such as a rectangular surface, this providing a relatively larger first surface for gripping. In other embodiments, as illustrated in FIG. 7 and FIG. 8, the first surface 212 may include a narrow end 212b for coupling with the coupling members 230 and an opposing wide end 212c. The narrow end 212b limits the restrictive effect of the coupling member 230 on the conformability of the first surface 212 or the palm 210. In other embodiments, the first surface 212 may be a polygonal surface having multiple sides, such as an octagon as illustrated in FIG. 8. The first surface 212 may include ends 212d not directly coupled to the coupling members 230. This allows the ends 212d to be free from the restrictive effect of the coupling members 230, thus improving conformability of the first surface 212.

[0052] Further referring to FIG. 10, in addition to the filler material 240 disposed in the chamber 214 of the palm 210, one or more polymer sheet 250 may be disposed in the chamber 214 of the palm 210. The polymer sheet 250 may be disposed between the first surface 212 and the filler 240 such that when the chamber 214 is in the jammed state, the polymer sheet 250 is in full contact with the filler material 240, resulting in a higher bending stiffness in comparison to not having the polymer sheet 250. In an example, the polymer sheet 250 may be a piece of 0.1mm thin polyethylene terephthalate sheet.

[0053] FIG. 11 illustrates a filler 240 according to an embodiment of the disclosure. The filler 240 may be configured in a planar form. In some embodiments, the filler 240 includes a plurality of interlinked truss units 242 or a structured fabric. The filler 240 may be formed by a stereolithography 3D printer with rigid material. In some embodiments, each of the truss unit 242 includes truss members 244 collectively defining a hollow interior space 246. It may be appreciated that the interlinking/interlocking between the truss units 242 enhances the stiffness variation of the filler 240. In an example, the truss units 242 may be octahedron truss units. The octahedron truss unit may have a diameter of 0.7mm and a length of 4.5 mm. A side of each octahedron truss may be truncated and attached to a planar pad 248 as support. Provision of the planar pad 248 facilitates the 3D printing process and may beneficially avoid potential puncture to the palm 210. In some embodiments, two layers of interlinked truss units 242 may be stacked and disposed in the chamber 214. The pad 248 may be disposed facing the wall of the chamber 214. In some examples, the filler 240 may occupy a rectangular volume in the chamber 214 of approximately 10cm by 8cm by 1cm.

[0054] Referring to FIG. 12, in alternative embodiments, the filler 240 may include a plurality of sheets 241 stacked together to form a thickness. In other embodiments as illustrated in FIG. 13, the filler 240 may include a plurality of fibers 243 disposed parallel to each other to form a thickness.

[0055] FIG. 14 illustrates a single gripper member 200 in operation according to some embodiments of the present disclosure. For the sake of brevity, only one gripper member 200 is described and a skilled person would appreciate that one or more gripper members 200 may cooperate in a complementary manner in operation. In operation, the palm 210 may be actuated by the supporting members 220 such that the first surface 212 is moved towards the object 60 until the first surface 212 contacts an exterior of the object 60. In the example as shown in FIG. 14, the first surface 212 may deform to bend about the first axis 82 as well as to bend about the second axis 84 in conformance with the object 60. Further, the first surface 212 may form an indentation 216 of a topological surface when conforming to the object 60. As can be understood from the foregoing description, the term "deformation" as used in the present disclosure loosely refers to a change in shape and/or volume of an article. The "deformed" article may be the result of any one or more of a bending and/or a soft, flexible, compliant state of the article. In various examples, the gripper member 200 is deformable by a combination of a bending and/or a change in a degree of stiffness, in which the bending and the change in stiffness can be effected independently of one another. In various examples, the palm 210 or the first surface 212 is deformed or bent/unbent by a bending/unbending of the supporting members 220. In various examples, the palm 210 or the first surface 212 is deformed or stiffened by a jamming transition of the palm 210.

[0056] In some examples, a negative pressure or a vacuum may be applied to the chamber 214 and cause the gripper member 200 to be in the jammed state with the filler 240 at least partially holding the first surface 212 against the object 60. Application of the negative pressure is optional. For example, negative pressure may be applied if the gripping force from the gripper member 200 in the unjammed state alone is insufficient to grip the object. [0057] Optionally, prior to actuating the palm 210 to contact the obj ect 60, the suction nozzle 59 as described above may be configured to provide a suction force on the object 60, such as a sheet of fabric, to lift the object 60. This advantageously prevents any potential deformation or damages to the sheet of fabric in the operation of gripping from the sides of the object.

[0058] FIGS. 15A to 15D illustrate examples of the gripper device 100 gripping different objects. It may be appreciated that under the concurrent actuation of the supporting members of both gripper members 200a/200b, different objects 60 may result in different deformation to each palm 210 of respective gripper members 200a/200b. Thereafter, the deformation may be sustained by jamming the gripper members 200a/200b, providing rigidity to the respective palms 210. The gripper members 200a/200b may be held in position to lift the object 60. The gripping force applied on the object 60 may include a frictional force between the object 60 and the first surface 212, as well as a clamping force or supporting force provided by the palm 210 on the object 60.

[0059] Referring to FIG. 15 A, if the object 60 is generally flat along the gravity direction without any protrusion for holding, the gripping force may be predominantly frictional forces between the first surface 212 and the object 60. Referring to FIG. 15B, if the object 60 includes a sloped (tapering) surface along the gravity direction, the gripping force may include both the frictional forces as well as the supporting forces on the object 60. Referring to FIG. 15C, if the object 60 is relatively small in size (relative to the palms 210), the gripping force may include predominantly clamping forces of the palm on the obj ect 60. Referring to FIG. 15D, if the obj ect is large with a rounded surface providing at least one anchor point for support, the gripping force is predominantly the supporting force provided by the first surface 212 to the object 60. Object Gripping Performance

[0060] The gripper system’s versatility was experimentally demonstrated by successfully picking up 12 common and representative objects using the gripper device 100, as shown in FIG. 16. In the example, a positive pressure of 120 kPa to the supporting members such that the palms may conform and grip the object. When necessary, the chamber is provided with negative pressure of -90 kPa to activate j ammed state. The gripper is then lifted at a constant speed of 0.5 m/min. It was shown in the test that the gripper device can successfully pick up a grape berry (10 g, image (a) of FIG. 16), a bok choy or vegetable (78 g, image (b) of FIG. 16), an apple (192 g, image (c) of FIG. 16), a pitaya (454 g, image (d) of FIG. 16), a bag of vegetable fries (55 g, image (e) of FIG. 16), a stapler (35 g, image (f) of FIG. 16), and a hand cream (124 g, image (g) of FIG. 16). This demonstrated the ability of the present gripper system to handle a wide range of objects of varying size and weight, as well as soft and deformable food packages.

[0061] For small lightweight objects such as the grape berry and the stapler, frictional forces may be sufficient to grip them. For heavier objects such as the pitaya, jamming is required to stiffen the palm so that a strong geometric constraint may be imposed to enclose the object and passively provide the gripping force. Further, the gripper device 100 may pick up delicate objects such as a badminton shuttlecock (4 g, image (h) of FIG. 16) and a ping pong ball (3 g, image (i) of FIG. 16). The gripper device 100 was able to pick up these objects without causing the feathers of the shuttlecock to bend or forming indentations on the ball. In addition, the gripper device 100 may grip slender or slippery objects such as a chocolate bar (54 g, image (j) of FIG. 16), a bottle (404 g, image (k) of FIG. 16), and a wet hydrogel sphere (83 g, image (1) of FIG. 16).

Maximum Gripping Force

[0062] A universal testing machine (Mark-10 F305) was used to pull the gripper device off a fixed object (as shown in image (a) of FIG. 17), and the pulling force is measured as a function of displacement. The gripper device was mounted onto a moving force sensor of the testing machine, and the weight of the gripper device is offset so that the pulling or pushing forces experienced by the gripper device can be measured. Image (b) of FIG. 17 shows the 12 objects of different shapes and sizes used in the experiment. The objects tested included spheres, cubes, and cylinders, oriented either horizontally or vertically. The diameters of the spheres and cylinders are 7cm and 5cm respectively, and the lengths of the cubes are 3 cm.

[0063] For a single run of the experiment, the gripper device was first lowered to a fixed position and the supporting members or actuators were pressurized to 120 kPa to grasp the object. This position was chosen such that for the spheres and horizontal cylinders, as illustrated in charts (c) to (f) of FIG. 17, the palms of the gripper member completely enclosed the object; and for cubes and vertical cylinders, the palms cover up to the edges of the object. The vacuum level in the chamber of the palm was controlled at either 0 kPa or negative 90 kPa, such that the effect of jamming on gripping force was measured. The gripper device was pulled or lifted upwards at a constant speed of 2 mm/s until the object detached from the gripper device, with the test repeated 5 times for each object. Two qualitatively different responses were observed for spheres (as shown in chart (c) of FIG. 17) and for horizontal cylinders (as shown in chart (d) of FIG. 17), with the gripping forces first increasing with the pulling distance to reach a maximum value, thereafter, decreasing to zero when the gripper device lost contact with the object. For cubes (chart (e) of FIG. 17) and vertical cylinders (chart (f) of FIG. 17), the gripping forces were lower in comparison to the case for spheres and cubes, and remained relatively constant throughout the pulling process. Without being limited by theory, it is believed that two main mechanisms contribute to the maximum gripping force, namely: geometric interlocking and frictional contacts. For cubes and vertical cylinders, frictional contacts substantially contribute to the gripping force. For spheres and horizontal cylinders, the interlocking effect substantially dominates the gripping force. As additional effort is needed to break the geometric constraints provided by the bent or deformed palms, the gripping forces for the spheres and the horizontal cylinders are larger than cubes and vertical cylinders. In addition, upon jamming, the increased palm stiffness results in stronger constraints and hence significantly larger gripping forces were measured when gripping spheres and horizontal cylinders. The maximum gripping force increased 4.6 times for the 7 cm sphere and 3.5 times for the 7 cm horizontal cylinder. For cubes and vertical cylinders, the gripping forces changed slightly before and after jamming. In these cases, the gripping forces were mainly from frictional contact, and the results suggest that the pinch forces, i.e., the forces with which the palms actively pinch the object, remain almost unchanged when jammed. The experiments show that a wide variety of objects can be picked up by the gripper device as disclosed.

[0064] FIG. 18 illustrates the maximum gripping forces achievable with different examples of the gripper member. Example Fl corresponds to the gripper member of FIG. 5 with the polymer sheet and filler material (interlinked lattice units or structured fabric) as shown in FIGS. 10 and 11. Example F2 corresponds to an example with a structured fabric and without the polymer sheet. Example LI corresponds to the gripper member of FIG. 5 with paper sheets for the filler material as shown in FIG. 12. Example T1 corresponds to the gripper member of FIG. 7 with a polymer sheet and filler material (interlinked lattice units or structured fabric) as shown in FIGS. 10 and 11.

Pinch Force Test

[0065] To estimate the gripper’s pinch force, pinch force tests were performed on the gripper palm, as shown in image (a) of FIG. 19. The pinch force as a function of the pressure in the supporting member or the actuator pressure for the three palm designs (Fl, F2 and LI) are shown in the plot (b) of FIG. 19, and the effect of jamming shown in plots (c), (d), and (e) of FIG. 19 respectively. All pinch forces increase as a function of pressure of the supporting member with the results of both palms averaged. When the palm is unjammed, the LI gripper member has the maximum pinch force of 0.58N at 120 kPa; and the F2 gripper member has a pinch force of 0.38 N, higher than the pinch force of 0.32N for Fl gripper member at 120 kPa. Advantageously, the pinch forces for each of the examples are relatively low which makes it suitable for gripping soft and delicate objects.

[0066] A ratio between the maximum gripping force (7 cm horizontal cylinder in the jammed state) and pinch force at 120 kPa when jammed, are about 42 for the Fl gripper member, 62 for the F2 gripper member, and 33 for the LI gripper member respectively, all surpassing current state-of-the-art in jamming-based variable-stiffness finger or membrane grippers. The large ratios show that the present gripper device is able to apply a relatively low force for picking up delicate objects, while being able to passively provide a large gripping force or supporting force in the jammed state.

[0067] In one aspect, the present application discloses a gripper member. The gripper member includes a pair of supporting members and a palm. Each of the pair of supporting members is a bendable actuator. The palm includes a first surface partially defining a chamber. The first surface partially defines a chamber. Opposing sides of the first surface are coupled to the pair of supporting members along a respective length of the pair of supporting members. The first surface extends between the pair of supporting members. The palm includes a filler disposed in the chamber.

[0068] A stiffness of the palm may be variable and responsive to a jamming of the filler in the chamber, and the palm may be bendable responsive to a bending of the pair of supporting members.

[0069] The jamming may be responsive to a negative pressure in the chamber. Each of the pair of supporting members may extend along a first axis and may be operable to at least partially bend the first surface about a second axis, in which the second axis is transverse to the first axis. A curvature of the first surface may be responsive to a positive pressure in the pair of supporting members. The first surface may be sustained in a deformation in response to a jamming of the filler via a negative pressure in the chamber. The first surface in a default state may define a gripper plane, in which the first surface may be deformable away from the first plane. The first surface may be deformable to form a topologically complex surface. A modulus of elasticity of the first surface may be lower than a modulus of elasticity of a material of the filler. The first surface may include a plurality of folds.

[0070] The gripper member may further include a polymer sheet disposed in the chamber, in which the polymer sheet is disposed between the first surface and the filler. The filler may include a plurality of interlinked truss units, in which each of the truss unit defines a hollow interior space. The filler may include a plurality of sheets stacked together to form a thickness. The filler may include a plurality of fibers disposed parallel to each other.

[0071] Each of the pair of supporting members may include a respective actuating chamber, in which each of the pair of supporting members is bendable responsive to a change in pressure in the respective actuating chamber. Each of the pair of supporting members may include a plurality of slots formed on at least one side of each respective supporting member, in which, responsive to the change in pressure in the respective actuating chamber, the respective supporting member is bendable to widen the plurality of slots.

[0072] In another aspect, the present application discloses a gripper systemm. The gripper system includes: a gripper device and a controller in signal communication with the gripper device. The gripper device includes two gripper members, each of the two gripper members being any as described above. The controller is configured to control the two gripper members to cooperatively handle an object.

[0073] The gripper system may further include a suction nozzle, in which the suction nozzle is configured to lift the object via a suction force. The gripper system may further include a robotic arm coupled to the gripper device, in which the gripper device is movable by the robotic arm. The gripper system may further include a vacuum pump in fluid communication with a respective chamber of each of the two gripper members. [0074] All examples described herein, whether of apparatus, methods, materials, or products, are presented for the purpose of illustration and to aid understanding, and are not intended to be limiting or exhaustive. Modifications may be made by one of ordinary skill in the art without departing from the scope of the invention as claimed.

Claims

CLAIMS A gripper member, comprising: a pair of supporting members, each of the pair of supporting members being a bendable actuator; and a palm, the palm including: a first surface partially defining a chamber, opposing sides of the first surface being coupled to the pair of supporting members along a respective length of the pair of supporting members, the first surface extending between the pair of supporting members; and a filler disposed in the chamber. The gripper member as recited in claim 1, wherein a stiffness of the palm is variable and responsive to a jamming of the filler in the chamber, and wherein the palm is bendable responsive to a bending of the pair of supporting members. The gripper member as recited in claim 1 or claim 2, wherein the jamming is responsive to a negative pressure in the chamber. The gripper member as recited in any one of claims 1 to 3, wherein each of the pair of supporting members extends along a first axis and is operable to at least partially bend the first surface about a second axis, the second axis being transverse to the first axis. The gripper member as recited in any one of claims 1 to 4, wherein a curvature of the first surface is responsive to a positive pressure in the pair of supporting members. The gripper member as recited in any one of claims 1 to 5, wherein the first surface is sustainable in a deformation in response to a jamming of the filler via a negative pressure in the chamber. The gripper member as recited in any one of claims 1 to 6, wherein the first surface in a default state defines a gripper plane, and wherein the first surface is deformable away from the first plane. The gripper member as recited in any one of claims 1 to 5, wherein the first surface is deformable to form a topologically complex surface. The gripper member as recited in any one of claims 1 to 6, wherein a modulus of elasticity of the first surface is lower than a modulus of elasticity of a material of the filler. The gripper member as recited in any one of claims 1 to 7, wherein the first surface includes a plurality of folds. The gripper member as recited in any one of claims 1 to 8, further comprising a polymer sheet disposed in the chamber, the polymer sheet disposed between the first surface and the filler. The gripper member as recited in any one of claims 1 to 9, wherein the filler comprises a plurality of interlinked truss units, wherein each of the truss unit defines a hollow interior space. The gripper member as recited in any one of claims 1 to 9, wherein the filler comprises a plurality of sheets stacked together to form a thickness. The gripper member as recited in any one of claims 1 to 9, wherein the filler comprises a plurality of fibers disposed parallel to each other. The gripper member as recited in any one of claims 1 to 12, wherein each of the pair of supporting members comprises a respective actuating chamber, and wherein the each of the pair of supporting members is bendable responsive to a change in pressure in the respective actuating chamber. The gripper member as recited in claim 13, wherein each of the pair of supporting members comprises a plurality of slots formed on at least one side of each respective supporting member, and wherein responsive to the change in pressure in the respective actuating chamber, the respective supporting member is bendable to widen the plurality of slots. A gripper system comprising: a gripper device, the gripper device including two gripper members, each of the two gripper members being as recited in any of claims 1 to 16; and a controller in signal communication with the gripper device, wherein the controller is configured to control the two gripper members to cooperatively handle an object. The gripper system as recited in claim 17, further comprising a suction nozzle, wherein the suction nozzle is configured to lift the object via a suction force. The gripper system as recited in claim 17 or claim 18, further comprising a robotic arm coupled to the gripper device, the gripper device being movable by the robotic arm. The gripper system as recited in claim 18, further comprising a vacuum pump in fluid communication with a respective chamber of each of the two gripper members.