Soft gripper and soft gripper system

Abstract

Disclosed herein is a soft gripper system and a soft gripper. The soft gripper comprises: a plurality of gripper fingers, each of the plurality of gripper fingers comprising: a finger base defining a first surface and a second surface opposing the first surface, the finger base defining a network of pneumatic channels; an actuator coupled to the first surface, the actuator defining a pneumatic channel; a plurality of suction members coupled to the second surface, the plurality of suction members in fluid communication with the network of pneumatic lines, wherein the finger base is biased to a curved state, wherein the actuator is actuatable to displace the finger base away from the curved state responsive to a first negative pressure in the pneumatic channel, wherein each of the plurality of suction members provides a respective suction pressure responsive to a second negative pressure in the network of pneumatic lines.

Description

SOFT GRIPPER AND SOFT GRIPPER SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to Singapore patent application no. 10202401061Y which was filed on 12 April 2024, the contents of which are hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] This application relates to the field of material handling, and more particularly to a soft gripper, and a soft gripper system.BACKGROUND

[0003] Labor shortage, particularly for unskilled repetitive pick and place tasks, presents a significant obstacle in general cluster grasping. An exemplary application is in traditional and vertical farming settings. Automation has the potential to not only mitigate labor shortages but also optimize operational costs, playing a pivotal role in meeting global food demands efficiently. However, this transition is not without its complexities. For instance, the process of harvesting, characterized by a wide array of labor-intensive tasks such as handling leaves and branches, employing tools for precise stem cutting, and plucking fruits, would require intricate orchestration of robotic arms and tools. This demands the precise regulation of forces through tactile feedback during crop handling.SUMMARY

[0004] According to an aspect, disclosed herein is a soft gripper. The soft gripper comprises: a plurality of gripper fingers, each of the plurality of gripper fingers comprising: a finger basedefining a first surface and a second surface opposing the first surface, the finger base defining a network of pneumatic channels; an actuator coupled to the first surface, the actuator defining a pneumatic channel; a plurality of suction members coupled to the second surface, the plurality of suction members in fluid communication with the network of pneumatic lines, wherein the finger base is biased to a curved state, wherein the actuator is actuatable to displace the finger base away from the curved state responsive to a first negative pressure in the pneumatic channel, wherein each of the plurality of suction members provides a respective suction pressure responsive to a second negative pressure in the network of pneumatic lines.

[0005] According to another aspect, disclosed herein is a soft gripper system. The soft gripper system comprises the soft gripper as described above and a pneumatic pressure source in a controllable fluid communication w'ith each gripper finger of the soft gripper.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Various embodiments of the present disclosure arc described below with reference to the following drawings:

[0007] FIG. 1 is a schematic diagram of a soft gripper system according to various embodiments;

[0008] FIG. 2 is a sectional view' of a soft gripper in a curved state according to various embodiments;

[0009] FIG. 3 is a sectional view of the soft gripper of FIG. 2 in an opened state;

[0010] FIG. 4 is a bottom view of FIG. 3;

[0011] FIG. 5 is a top view' of FIG. 3;

[0012] FIG. 6 is a schematic diagram of fluid communication between a pneumatic pressure source and a soft gripper according to various embodiments;

[0013] FIG. 7 is a sectional view of a suction member according to various embodiments;

[0014] FIG. 8 is a sectional view of the suction member of FIG. 7 handling an object;

[0015] FIG. 9A is a top view of a soft gripper according to various embodiments;

[0016] FIG. 9B is a top view of another soft gripper according to various embodiments;

[0017] FIGs. 10A to 10D are schematic diagrams of a soft gripper system during operation according to various embodiments;

[0018] FIG. 1 1 shows a scooping soft gripper according to an exemplary embodiment, the scooping soft gripper comprises an array of suction cups with compliant stems designed to conform and attach to a cluster of items;

[0019] FIG. 12 shows a bellow actuated scooping mechanism of the scooping soft gripper of FIG. 11, used to enclose a cluster of items after initial grasping using suction;

[0020] FIG. 13 shows the elements of the scooping soft gripper of FIG. 1 1 , with magnified sectional view of the passive suction cup: (i) Compliant stem, (ii) Suction cup, and (iii) Passive Film;

[0021] FIG. 14 is an illustration of a vacuum channels for all the suction cups of the array connected to a single vacuum inlet. Dimensions of the ray bounding box: 9.5 cm by 6 cm;

[0022] FIG. 15 shows a force-displacement measurement setup for material tests on passive suction cup;

[0023] FIG. 16 shows the test results for suction cups without passive film for test bases at three angles. The combination of SS960 for the suction cup and DS30 for its stem yielded the highest suction force;

[0024] FIG. 17 shows the test results for the best-performing combination of SS960 cup and DS30 stem and determining the optimum passive film material. EF10 emerged as the preferred material with more passive suction force compared to EF30;

[0025] FIG. 18 shows an exemplary FEA validation for pre-bent bellows actuator;

[0026] FIG. 19A shows the steps of PB A Fabrication: (i) The Pre -bent Bellows section was cast in an open state with SmoothSil-960 using a three-piece press mold, (ii) The flat closing section of PB A was cast with SmoothSil-960 using a two-piece press mold, (iii) For PB A, the open bellows and flat sections were meticulously aligned and bonded together using uncured SmoothSil-960 paste as an adhesive;

[0027] FIG. 19B shows the steps of Flat Ray Fabrication: (i) The first ray layer with a network of vacuum channels, was cast with Dragon Skin 30 using a two-piece press mold, (ii) The second ray layer with projections connecting the vacuum network of the first ray layer to the stems of the passive suction cups, was cast similarly with Dragon Skin 30 using a two-piece press mold and stuck with the first layer after alignment with uncured Dragon Skin 30;

[0028] FIG. 19C shows the steps of Passive Suction Cup Fabrication: (i) The suction cups were cast with SmoothSil 960 for the cup sections and with Dragon Skin 30 for stems of the suction cups using a three-piece mold, (ii) A 1mm thick flat passive film of uncured Eco Flex 10 was generated using an in-house Direct Ink Writing apparatus, (iii) The suction cups were carefully placed atop uncured Eco Flex 10. (iv) After curing, the excess layer of Eco Flex 10 was removed by tracing the rim of the suction cup with a blade cutter, yielding a passive suction cup;

[0029] FIG. 19D shows a vacuum-actuated opened state of the scooping soft gripper ray assembled by combining PBA, flat ray, and passive suction cups using respective uncured silicones;

[0030] FIG. 19E shows a vacuum-actuated passive suction cups of the scooping soft gripper ray;

[0031] FIG. 19F shows the scooping soft gripper ray in unactuated pre-bent state holding a mushroom using passive suction;

[0032] FIG. 19G shows a fully assembled scooping soft gripper ray in the opened state combining cast rays and FDM-printed ASA parts for modular interfaces along with a gripper holder or gripper base;

[0033] FIG. 20A shows the scooping soft gripper grasping a half capsicum (due to payload capacity of 250 grams): grams): (i) Opened state of the scooping soft gripper holding half-cut capsicum, (ii) Closed / curved state of the scooping soft gripper grasping half-cut capsicum.

[0034] FIG. 20B shows the scooping soft gripper grasping individual shimeji mushrooms:(i) Opened state of the scooping soft gripper holding individual shimeji mushrooms, (ii) Closed / curved state of the scooping soft gripper grasping shimeji mushrooms cluster;

[0035] FIG. 20C shows the scooping soft gripper grasping of cherry tomatoes: (i) Opened state of the scooping soft gripper holding individual cherry tomatoes, (ii) Closed / curved state of the scooping soft gripper grasping cherry tomatoes cluster.

[0036] FIG. 20D shows the scooping soft gripper grasping of tangerines: (i) Opened state of the scooping soft gripper holding tangerines, (ii) Closed / curved state of the scooping soft gripper grasping tangerines;

[0037] FIG. 21 A shows the scooping soft gripper grasping Xiao Bai Cai despite suction limitation due to uneven leafy surfaces of Xiao Bai Cai;

[0038] FIG. 21B shows the scooping soft gripper grasping big mushrooms despite suction limitation due to slippery porous surfaces of big mushrooms; and

[0039] FIG. 21C shows the scooping soft gripper grasping shimeji mushrooms despite suction limitation due to the highly uneven surface of a heavy cluster of shimeji mushrooms.DETAILED DESCRIPTION

[0040] The following detailed description is made with reference to the accompanying drawings, showing details and embodiments of the present disclosure for the purposes ofillustration. 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.

[0041] Tn 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.

[0042] 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.

[0043] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0044] The term “pose” may include a position and an orientation of an object or part of an object. The term “position” may refer to a location or coordinate (for example, X-coordinatc, Y coordinate, Z coordinate) of an object or part of an object in a space or a frame. The term “orientation” may refer to a facing or angle (for example, an X-direction vector, a Y-direction vector, a Z-direction vector) of an object or part of an object in a space or a frame.

[0045] The term “negative pressure” may refer to a fluid pressure in a pneumatic line or channel which is lower than the atmospheric pressure, i.e. 0.5 bar. The term “negative pressure” may also refer to a negative differential pressure between an environment and the pneumatic line, wherein the pressure in the pneumatic line is lower than a pressure in the environment. Tn an example, a negative pressure may be near or substantially close to absolute zero pressure.

[0046] The term “positive pressure” may refer to a fluid pressure in a pneumatic line or channel which is higher than the atmospheric pressure, i.e. 1.5 bar. The term “positive pressure”may also refer to a positive differential pressure between an environment and the pneumatic line, wherein the pressure in the pneumatic line is higher than a pressure in the environment.

[0047] The term “crops”, “plants”, “grains” may be used interchangeably to refer to one or an aggregate of a harvest, such as a cereal, a fruit or vegetable.

[0048] For tasks such as handling crops, one of the challenges faced by robotic end-effectors is in minimizing fruit damages during harvesting. Tn addition, as crops and fruits are typically granular and of irregular shape, this presents challenges to conventional robotic grippers or robotic end effectors due to the need for precise force control, complex grasping techniques, and customization for conventional robotic grippers, often resulting in bulky and inefficient solutions.

[0049] Tn view of the above inexhaustive limitations, a different approach was taken towards accomplishing the challenge of handling crops. In place of a complex operation, proposed herein is a soft gripper and a soft gripper system actuatable by negative pressure for handling crops and fruits. The proposed soft gripper may be a rcconfigurablc gripper switchable between different states in assuming different modes of object handling. In some embodiments, the proposed soft gripper may switch or be reconfigured between a scooping / grasping state, a suction state, or a combination thereof. The reconfigurability of the soft gripper allows customization on the fly as well as the soft gripper assuming different operating modes in the course of a single picking / handling operation.

[0050] In various embodiments, one or more gripper fingers of the soft gripper may be biased towards a curved state or a curved contour, defining an at least a partially closed volume. This is analogous to wrapping fingers around one or more objects. The at least partially closed volume may include a fully closed volume or a partially closed volume, which is operable to hold or grasp the one or more objects. Generally, the curved state corresponds to one or more supporting surfaces to hold or grasps one or more objects against gravity. In an exemplaryembodiment, a single gripper finger in the curved state may also define a partially closed volume by assuming the shape of a scoop or a spoon.

[0051] In addition, the one or more gripper fingers of the soft gripper may be actuatable to displace to an opened state, diminishing the closed / partially closed volume. This is analogous to opening the fingers to release the object. Generally, the opened state corresponds to the diminishing of supporting surface(s) for holding one or more objects against gravity.

[0052] In the opened state, each of the gripper fingers may provide a suction pressure or suction force controllably and / or selectively. In various embodiments, each of the gripper fingers may also provide a suction pressure or suction force controllably and / or selectively in the curved state.

[0053] In various embodiments, actuating the gripper fingers from the curved state to the opened state may be enabled by providing a negative pressure or a pressure below atmospheric pressure from a vacuum pump. In addition, the suction pressure provided by the gripper fingers may also be provided the vacuum pump. Further, a single vacuum pump may be used for actuating and providing suction to all the gripper fingers concurrently via respective pneumatic valves. This allows a single pneumatic source to be used for the soft gripper, reducing the complexity of the soft gripper system and simplifying the hardware configurations.

[0054] FIG. 1 illustrates a schematic diagram of a soft gripper system 50 for handling crops 80 according to various embodiments of the disclosure. The soft gripper system 50 may include a soft gripper 100 coupled to a robotic arm 60. The robotic arm 60 may controllably displace a pose (including a position and an orientation) of the soft gripper 100. In addition, the soft gripper 100 may be connected to a pneumatic pressure source 70, such as a vacuum pump. In various embodiments, the soft gripper 100 may be actuated by reducing a pneumatic pressure in the various pneumatic lines or channels of the soft gripper 100. As such, it may be said that the soft gripper 100 is actuatable by one or more negative pressures.[0055 J In various embodiments, the soft gripper 100 may include a gripper base 110 and one or more gripper fingers 200 coupled to the gripper base 110. In various embodiments, the gripper base 110 may be coupleable to the robotic arm 60. The gripper base 110 may act as a reference body or a reference point for controlling the robotic arm 60.

[0056] In some examples as shown in FIG. 1, the soft gripper 100 may include a pair of opposing gripper fingers 200. In other examples, the soft gripper 100 may include four gripper fingers 200 or two pairs of opposing gripper fingers 200. In yet other examples, the soft gripper 100 may include a single gripper finger 200. Each of the gripper fingers 200 may be in a controllable fluid communication with a single pneumatic pressure source 70. Therefore, each of the gripper fingers 200 may be actuatable by the single pneumatic pressure source 70.

[0057] In various embodiments, each gripper finger 200 may include a finger base 210 defining generally the shape and form of the gripper finger 200. The finger base 210 may be generally planar and bendable. In various embodiments, the finger base 210 may be in a generally triangular form shape or at least comprises a generally triangular tip, but not limited thereto. This allows the gripper fingers 200 to form a closed volume and / or a partially closed volume without overlapping one another. In some examples, the finger base 210 may be shaped similar to a ray or an arm of a starfish. In other examples, the finger base 210 may be in a leaf shape. In yet other examples, the finger base 210 may be in a quadrilateral shape such as a diamond shape. In various embodiments, the finger base 210 may be generally planar. In other embodiments, the finger base 210 may be formed in a curved shape.

[0058] In various embodiments, the finger base 210 may be biased to a curved shape. In other words, the finger base 210 may be curved in an unactuated state. In various embodiments, each gripper finger 200 may further include an actuator 230 coupled to a first surface of the finger base 210, and a plurality of suction members 250 coupled to an opposing second surface of the finger base 210. The actuator 230 may be formed and / or coupled to the finger base 210such that the actuator 230 biases the finger base 210 to the curved state with a curved contour.The curved state corresponds to an unactuated state of the finger base 210. In an exemplary embodiment, the actuator 230 may be formed as curved member such that the finger base 210 conforming to the actuator 230 also assumes a curved contour.

[0059] In other embodiments, the finger base 210 may be formed as a curved member. As such, the finger base 210 may be biased to the curved state without the assi stance of the actuator 230. In some embodiments, the finger base 210 may be biased to the curved state with the assistance of the actuator 230 which is also a curved member.

[0060] Responsive to a first negative pressure provided or caused by the pneumatic pressure source 70, the actuator 230 may be actuatable to displace the finger base 210 away from the curved state, as shown by the dashed arrows in FIG. 1 . In addition, each of the plurality of suction members 250 may provide a respective suction pressure responsive to a second negative pressure provided or caused by the pneumatic pressure source 70. It may be noted that the first negative pressure and the second negative pressure may be controllably and independently provided to each of the actuator 230 and the plurality of suction members 250.

[0061] FIGs. 2 to 5 illustrate various embodiments of a soft gripper 100 for handling crops 80 of the present disclosure. The soft gripper 100 comprises a plurality of gripper fingers 200, for example two gripper fingers 200. Each of the gripper fingers 200 comprises a finger base 210 defining a center plane 211. The finger base 210 may further define a posterior end 202 of the finger base 210 to an anterior end 204 of the finger base. The finger base 210 may be formed with or define a network of pneumatic channels 212.

[0062] Referring to FIG. 4, in various embodiments, the network of pneumatic channels 212 may extend from the posterior end 202 to the anterior end 204. In addition, the network of pneumatic channels may be arranged along a lateral axis 213 generally transverse to the center plane 211. In some embodiments, the network of pneumatic channels 212 may comprise aplurality of parallel branches in fluid communication with a common inlet 215 disposed on or coupled to the finger base 210. In other embodiments, the network of pneumatic channels 212 may define multiple independent and fluidly insulated pneumatic zones, with each of the pneumatic zones in fluid communication with a respective inlet.

[0063] In various embodiments, the finger base 210 may be formed from an elastic material thus enabling the finger base 210 to bend about the lateral axis 213. In various embodiments, the finger base 210 may be generally planar in form, and further defines a first surface 214 and a second surface 216 opposing the first surface 214. Therefore, the first surface 214 and the second surface 216 may generally be transverse to the center plane 211.

[0064] In exemplary embodiments, the network of pneumatic channels 212 may be disposed or formed between the first surface 214 and the second surface 216. In other words, the network of pneumatic channels may be embedded within the finger base 210. In other embodiments, the network of pneumatic channels 212 may be formed on a surface of the finger base 210, such as the second surface 216.

[0065] In various embodiments, each of the gripper finger 200 may further comprise an actuator 230 coupled to the first surface 214 of the finger base 210. The actuator 230 may be a pneumatic actuator comprising one or more internal pneumatic chambers. In various embodiments, the actuator 230 may be formed from an elastic material. The actuator 230 may include a plurality of bellows 231 and a pneumatic actuator channel 232 in fluid communication with each of the plurality of bellows 231. Referring to FIG. 5, the plurality of bellow s 231 may be aligned along the center plane 21 1 of the finger base 210. The pneumatic actuator channel 232 may allow fluid communication between each of the plurality of bellows 231, terminating at an inlet 235. This enables the pressure in each of the plurality of bellows 231 to be controlled or varied collectively or concurrently.

[0066] In various embodiments, the actuator 230 may be formed with a curved contour. In various embodiments, the actuator 230 and / or the plurality of bellows 231 may have a higher stiffness than the finger base 210. Therefore, by coupling the actuator 230 to the finger base 210, the actuator 230 biases the finger base 210 to a curved state or unactuated state, as illustrated in FIG. 2.

[0067] In various embodiments, each of the gripper finger 200 may further comprise a plurality of suction members 250 coupled to the second surface 216. The plurality of suction members 250 may be configured in the form of a plurality of suction cups 250. The plurality of suction members 250 may be in fluid communication with the network of pneumatic channels 212.

[0068] Referring to FIG. 2, in various embodiments, the finger base 210 in the curved state corresponds to an at least partially closed volume 90 defined by the plurality of gripper fingers 200. The at least partially closed volume 90 may include a fully closed volume or a partially closed volume (as shown in FIG. 2), which is operable to hold or grasp crops 80. Generally, the curved state corresponds to one or more supporting surfaces to hold the crops 80 against gravity. In various embodiments, for handling small granular crops, the plurality of suction members 250 may define a scooping surface responsive to the finger base 210 being in the curved state.

[0069] In various embodiments, the actuator 230 may be actuatable to displace the finger base 210 away from the curved state towards an opened state, responsive to a first negative pressure in the pneumatic actuator channel 232. Concurrently or independently, each of the plurality of suction members 250 may provide a respective suction pressure responsive to a second negative pressure in the network of pneumatic channels 212.

[0070] Referring to FIG. 3, responsive to the first negative pressure in the pneumatic actuator channel 232, the pressure in the plurality of bellows 231 is lower than the environment forming a negative pressure differential. As such, the plurality of bellows 231 deforms orcollapses under the pressure differential to bend or displace the finger base 210 towards the opened state. Conversely, with the lack of first negative pressure in the pneumatic channel, i.e. the pressure in the pneumatic actuator channel 232 is equal to or higher than the environmental pressure, the plurality of bellows 231 bend the finger base 210 to bias the finger base 210 back to the curved state. In some embodiments, a small positive pressure in the pneumatic channel may aid in displacing the finger base 210 back to the curved state. In some embodiments, the small positive pressure may help to reduce one or more gaps / spacings formed between adjacent gripper fingers 200.

[0071] Referring to FIG. 3, as an example, the opened state of the finger base 210 may include the finger base 210 or the gripper finger 200 assuming a generally planar form. As shown in FIG. 3, the partially closed volume formed by the plurality of gripper fingers 200 diminishes with the actuation of the finger base 210 towards the opened state. In the opened state, the plurality of gripper fingers 200 are generally spaced apart and spread out relative to one another. Hence, when the finger base 210 is in the opened state, the second negative pressure forms a respective suction from each of the plurality of suction members 250, allowing the plurality of gripper fingers 200 to pick-up crops 80 or objects via the suction. This allows crops to be handled via a suction pressure, thus avoiding applying excessive grasping force on the crops 80 during handling. In addition, by using suction, irregular shaped crops may be handled without specific requirements and / or customization to the shape and form of the gripper.

[0072] In various embodiments as shown in FIG. 4, the network of pneumatic channels 212 may comprise a plurality of connecting nodes 217. Each of the plurality of connecting nodes 217 may be fluid communication with a respective one of the plurality of suction members 250. In various embodiments, the plurality of suction members 250 may be uniformly distributed on the second surface 216. This maximizes the reach of the suction members 250 when picking upthe crops 80. In various embodiments, the plurality of suction members 250 may be symmetrically disposed about the center plane 211 thus allowing a symmetrical suction force to be applied to a relatively larger crop.

[0073] In various embodiments as shown in FIG. 5, each of the plurality of bellows 231 define a respective bellow width (BW). Each of the bellow width (BW) may be configured parallel to the lateral axis 213. In various embodiments, wherein the respective bellow width BW of the plurality of bellows 231 may vary along the center plane 211. In various embodiments, the respective bellow width (BW) of the plurality of bellows 231 reduces from the posterior end 202 to the anterior end 204. As such, a large bellow 231 is disposed at the posterior end 202 while a smaller bellow 231 is arranged at the anterior end 204. This enables a large bending of the finger base 210 at the posterior end 202, facilitating a faster and more effective bending of the finger base 210 away from the curved state.

[0074] Referring to FIG. 6, in various embodiments of the soft gripper system 50 and the soft gripper 100, a common or single pneumatic pressure source 70 may be fluidly coupled or connected to each of the plurality of gripper fingers 200a / ... / 200n. In addition, the single pneumatic pressure source 70 may be in fluid communication with the respective network of pneumatic channels 212a / . , . / 212n as well as the respective pneumatic channels 232a / ... / 232n of the plurality of gripper fingers 200a / . ,. / 200n. In addition, a first valve 72a / ... / 72n may be connected between the single pneumatic pressure source 70 and the respective network of pneumatic channels 212a / 212n. Similarly, a second valve 74a / ... / 74n may be connected between the single pneumatic pressure source 70 and the respective pneumatic channels 232a / . . , / 232n. Hence, by controlling each of the first valves 72a / ... / 72n, the suction pressure / suction force from each of the gripper fingers 200a / . . . / 200n may be controlled. In addition, by controlling each of the second valves 74a / ... / 74n, a state (curved state or opened state) of each of the gripper fingers 200a / . . , / 200n may also be controlled. This enables a simplepneumatic configuration whereby a single pneumatic pressure source 70 is used for a soft gripper.

[0075] Referring now to FIGs. 7 and 8, in various embodiments of the disclosure, each of the plurality of suction members 250 may comprise a suction cup 252, a stem 254 coupled between the second surface 216 and the suction cup 252. The stem 252 may have a lower stiffness or modulus of elasticity than the suction cup 252. This allows the stem to deform 252 according to a contour of the crop 80. In various embodiments, the stem 254 and the suction cup 252 may define an interior space 251. The interior space 251 may be in fluid communication with the network of pneumatic channels 212 via the respective connecting nodes 217. Therefore, the interior space 251 may act as part of a fluid path for generating the suction force on the crops 80.

[0076] In various embodiments, the interior space 251 may terminate at an opening 255 of the suction cup 252. A film 256 may be disposed covering the opening 255 of the suction cup 252. The film 256 may have a lower stiffness or modulus of elasticity than the suction cup 252. Therefore, the film 256 is more deformable than the suction cup 252. Referring to FIG. 8, the film 256 may act as a seal with the crop 80 deforming to conform to the crop 80, thus improving a sealing contact between the suction cup 252 and the crop 80. In addition, the film 256 increases the area of contact with the crop 80, thus minimizing potential damages to the crop 80 due to the suction. In some embodiments, the film 256 may also have a lower stiffness or modulus of elasticity than the stem 254. Therefore, when in contact with the crop 80, the film 256 deforms first to conform with the crop 80 prior to deforming of the stem 254. The film 256 may also act to enable concurrent activation of all the suction cups 252 based on a common network of pneumatic channels. As it is often a challenge to ensure or determine whether all the suction cups are in contact with the crop 80, the film 256 helps to avoid the pneumatic channels from being exposed to the atmosphere, thus helping to avoid the failure or reductionof suction pressure. As an example, if there are no film present, the suction cup(s) not in contact with crops may cause a reduction in the overall suction force as each of the suction cups 252 are connected to a single common network of pneumatic channels.

[0077] Referring to FIGs. 9A and 9B, in various embodiments, the gripper base 110 may be coupleable or coupled to a robotic aim (not shown) along a gripper axis 112 (out of plane). In the exemplary embodiments as shown, the gripper base 1 10 may be coupled to a plurality of gripper fingers 200, such as three gripper fingers 200 (FIG. 9a) and four gripper fingers 200 (FIG. 9B). In various embodiments, the plurality of gripper fingers 200 may be disposed in a radial symmetry about the gripper axis 112. This enables the plurality of gripper fingers 200 to form a closed volume therebetween.

[0078] FIGs. 10A to 10D illustrate a series of operations of the soft gripper system 50 and the soft gripper 100 handling an object 80 according to various embodiments of the disclosure. The object 80 may be a crop or a fruit. The soft gripper 100 may comprise a pair of gripper fingers 200. The soft gripper 100 may be in fluid connection with a common or single pneumatic pressure source 70. As such, the common pneumatic pressure source 70 is configured to control each of the gripper finger 200.

[0079] Referring to FIG. 10A, the soft gripper 100 begins with each gripper finger 200 being in an initial and unactuated state, corresponding to the finger base 210 of the gripper finger 200 being in the curved state. The finger base 210 in the curved state corresponds generally to the gripper finger 200 assuming a curved shape. In the curved state or curved shape, a first negative pressure 76 is provided to the actuator 230 of the gripper finger 200 to actuate and displace the finger base 210 away from the curved state. As such, the finger base 210 or gripper finger 200 is actuated towards an opened state (as shown in FIG. 10B).

[0080] Referring to FIG. 10B, with the gripper finger 200 in the opened state, the robotic aim 60 may move the soft gripper 200 towaids the objects 80. When the soft gripper 200 isadjacent to the objects 80, the pneumatic pressure source 70 provides a second negative pressure 78 to the plurality of suction members 250, such that each of the plurality of suction members 250 provides a respective suction pressure. The suction pressure allows adjacent ones of the plurality of suction members 250 to hold the objects 80 via the suction pressure. This minimizes potential damages to the objects 80 as contact forces on the objects 80 are minimal.

[0081] Further referring to FIG. 10C, the first negative pressure 76 from the pneumatic pressure source 70 ceases such that the finger base 210 returns to the curved state, and hence the gripper finger 200 returns to the curved shape. While the finger base 210 returns to the curved state, the second negative pressure 78 provided to the plurality of suction members 250 is maintained to hold onto the objects 80 via the suction pressure. This enables the soft gripper 100 to grasp the objects 80 within the partially closed volume formed by the gripper fingers 200.

[0082] Referring next to FIG. 10D, when the objects 80 are robustly or firmly held by the soft gripper 100, the second negative pressure 78 ceases such that the objects 80 arc held solely by the scooping surfaces formed by the plurality of suction members 250 without the suction pressure.

[0083] In alternative embodiments, the operations in FIGs. 10A and 10B are performed in similar fashion as previously described. However, departing from the operations previously described, a positive pressure is provided to the finger base 210 such that a more robust grasp may be applied to the objects 80. Referring again to FIG. 10C, to facilitate the finger base 210 returning to the curved state, a small positive pressure 79 may be provided to the actuator 230 such that the gripper finger 200 exerts a higher grasping force on the objects 80 to hold the objects 80 firmly. Similarly, referring again to FIG. 10D, with the ceasing of the second negative pressure 78, the small positive pressure 79 is maintained to remain the higher grasping force on the objects 80 for a more robust grasp.

[0084] Exemplary embodiment

[0085] Referring to FIG. 11 to 21C, proposed herein an exemplary embodiment of a scooping soft gripper. The scooping soft gripper may be configured to grasp granular and / or irregular objects. The scooping soft gripper comprises: (1) an array of suction cups with compliant stems designed to conform to various surface shapes, and (2) a scooping mechanism for enclosing a cluster of items after initial grasping using suction.

[0086] Passive Suction Cup

[0087] A flat suction cup shape was chosen for the study due to its reliable performance with a wide range of flat or slightly curved objects. However, other suction cup shapes, such as bellows suction cups or oval suction cups may also be used. The decision to use the flat shape was driven by its simplicity. In most active suction-based automation solutions, a single suction cup is used instead of an array of suction cups involving fully connected open circuits driven by a single vacuum source. This is due to the inherent challenges of ensuring consistent sealing of all suction cups in an array, par ticularly in unstructured environments like agricultural setups. Failure to maintain a seal could lead to leakage and overall suction failure. Alternatively employing separate vacuum sources for individual suction cups is impractical. To overcome this challenge and enable the use of an array of suction cups in the scooping soft gripper, the concept of passive suction was implemented. As depicted in FIG. 13, a thin film was added to each suction cup in the array, with the entire network powered by a single vacuum source (refer to FIG. 14), facilitating passive suction actuation at the interface between the suction cup and the object, enabling constant sealing for all suction cups. The passive suction cups may be evenly distributed across the four finger bases or rays of the scooping soft gripper.

[0088] Prc-bcnt Bellows Actuator

[0089] In the exemplary embodiment, the choice of a starfish-shaped base with four finger bases / rays was to achieve an overall radially symmetric scoop shape when folding the finger bases / rays. A vacuum actuated bellows was used to actuate each of the scooping soft gripperrays. Conventional grippers with actuatable finger bases / rays, typically employ both vacuum and positive pressure (two distinct modes of actuation) for forward and backward finger base / ray bending thus necessitating complex control. The bellows actuators were integrated on the gripper rays’ top surfaces as the bottom surfaces were occupied by passive suction cups. This meant that a large positive pressure within the bellows was needed for actuation from an initially flat position (FIG. 1 1 ) to achieve complete encapsulation once the cluster adhered to the suction cups. However, relying solely on large positive pressures to achieve forward curling to form a closed scoop increased the risks of leaks and ruptures. As a safer and more durable alternative, a novel approach involving pre-bent bellows (see FIG. 13) was adopted. In this configuration, the scooping soft gripper in an unactuated state inherently forms an almost closed scoop shape, with vacuum exclusively employed to transition to a flat state or to even curl the ray backwards when necessary. This approach requires minimal to no positive pressure for complete scoop closure (see FIG. 12), enhancing safety and durability while minimizing the risk of leaks and ruptures.

[0090] To achieve the desired outcomes, optimization of two crucial gripper components: (1) Passive suction cups, and (2) Pre-bent Bellows Actuator (PBA), was performed. Referring to FIG. 13, the passive suction cup has three distinct features: i) a compliant suction cup stem facilitating independent movement for enhanced surface conformance; ii) a stiff suction cup providing sturdiness to prevent vacuum failure; and iii) a passive film affixed to the suction cup rim for providing secure sealing to improve the effectiveness of passive suction. The PBA design enables robust bending of an entire finger base / ray from a pre -bent scooping configuration to a flat or even a backwards curling configuration, for accessing confined spaces.

[0091] To estimate the curvature of the PBA, four finger bases / rays (with approximate shape) were visualized in a flat or planar setting. The finger bases / rays were flexed in thevisualization to form an almost fully closed or sealed scoop with minimal gaps. The remaining gaps, if any, were to be closed with a small positive pressure.

[0092] Components of the scooping soft gripper soft were fabricated using platinum- catalyzed room temperature vulcanized (RTV) silicones. The initial candidate materials before were: Ecoflex 00-10 (EF10), EcoFlex 00-30 (EF30). Dragon Skin 30 (DS30), and SmoothSil 960 (SS960). Table 1 presents a compilation of the material properties of the materials used. Tt is worth noting that the mechanical traits of RTV silicones can substantially deviate from published technical data due to variations stemming from manufacturing processes, material compositions, curing techniques, or testing parameters such as traction speed. Consequently, to improve representation, parameters utilized in 5 hyperelastic models (specifically, Yeoh and Ogden models) were ascertained through a fitting process involving experimental data, which were subsequently incorporated into the FEA simulations.

[0093] Material Optimization for Passive Suction Cup

[0094] To select the materials for the stem of the suction cup, the suction cup itself, and the passive film, two sets of tests were conducted. A force-displacement measurement system, consisting of an Tmada ZTA-DPU-500N force gauge and an EMX-1000N-L-FA motorized test stand, were used to measure the suction cup adhesion forces to a test surface (see FIG. 15). The test surface, which comprises an ASA base with a glass top layer for smoothness, was affixed to the base of the test stand. A smooth surface was chosen to remove the effects of surface texture on suction force as the aim of the experiment was to select the optimum material combination for compliance of the stem along with sufficient passive suction force. The test surface was adjusted to various angles to evaluate the suction cup’s adaptability to object orientation. Each test suction cup underwent preloading compression onto the test base of 1 ± 0.001 mm before testing. Subsequently, a vacuum of -80 kPa was applied before detaching the suction cup using a pulling speed of 0.2 mm / s.

[0095] The first set of tests were to identify optimal materials for both the suction cup and its stem, without yet employing a passive film. The second set of tests involved utilizing the best-performing suction cup-stem combination from the first set and attaching passive films of different materials to determine the optimal combination. FIGs. 16 and 17 provide an overview of the different par ameter combinations used in both test sets, alongside the respective measured suction forces, averaged over four measurements. The material combination of SS960 for the suction cup and DS30 for its stem yielded the highest suction force for all base angles, with a value of 4N for a horizontal base, highlighting the advantages of employing a dual-material suction cup, featuring a sturdier base and a more pliable stem, for enhanced suction force and adaptability, respectively. In addition, EF10 was determined as the preferred material for the passive film, as it yielded the maximum suction force.

[0096] FEA Validation for Pre-bent Bellows Actuator

[0097] SmoothSil 960 was identified as the optimal material for the PBA bellows. A softer material Dragon Skin 30 was chosen for the closing section of the PBA which would be the same material as the scooping soft gripper finger base / ray. Estimation of the unactuated curvature of the PBA relied on the configuration of the scooping soft gripper finger base / ray in its steady-state position. Assuming each bellow offered a consistent bending angle, an initial PBA design with seven bellows was considered for simulation, with the width of the first four bellows set at 28 mm and the last three at 24 mm while the bellow wall thickness was kept constant at 1 mm. The reduction in bellow width ensured the accommodation of all bellows within the ray’s diminishing width from base to tip. The PBA design with these specifications, the amount of bending, and the material combination were validated through an FEA study employing ABAQUS by Dassault Systems.

[0098] Hyperelastic Yeoh and Ogden constitutive models were used for SmoothSil 960 and Dragon Skin 30 respectively in the FEA simulations (Table 1). Referring to FIG. 18, the PBAwas modelled as a 3D deformable body. The first bellow’s wall was constrained using the ENCASTRE boundary condition, and a uniform negative pressure load of -80 KPa was applied to the internal walls in a static step to replicate vacuum actuation. Tetrahedral elements (C3D10H), featuring a hybrid formulation, were employed, along with standard contact controls encompassing non-elastic normal contact and frictionless tangential contact. The simulation confirmed that the chosen design parameters ensured sufficient unwrapping of the ray from a pre-bent position to a flat orientation under vacuum.Table 1. Mechanical properties and material models of all materials used.*Modulus measured at 100% strain.

[0099] Fabrication of the scooping soft gripper

[0100] In preparation for the fabrication process, Part A and Part B of the respective silicones were weighed according to the ratios provided by the supplier (1: 1 weight ratio for EF10 and DS30; 10:1 weight ratio for SS960). These material parts were then mixed at 2,000 rpm for 1 minute and subsequently subjected to a 2-minute defoaming process at 2,200 rpm, utilizing an ARE-310 Thinky Mixer. For components fabricated through press molding, a small amount of ThiVcx (Smooth-On) was added into the mixed silicone (1% by weight of B) to increase material viscosity. In contrast, for components fabricated via material injection into molds, Silicone Thinner (Smooth-On) was added into the mixed silicone (5% by weight of A+B) to reduce viscosity, facilitating smoother flow through fine features. The mixture, nowmodified for viscosity, was then placed within a degassing chamber for 5 minutes before being utilized for molding.

[0101] Molds employed in the fabrication process were printed via Fused Deposition Modeling (FDM) using Acrylonitrile Styrene Acrylate (ASA). Following the application of a light even coating of Ease Release™ 200 (Smooth-On) by spraying onto the mold surfaces, the prepared silicone material was either manually applied to press molds or injected into molds using an air pressure-driven dispensing syringe. Subsequently, the Tilled molds were subjected to a curing process at 60°C for 3 hours, after which the components were demolded. The four rays of the scooping soft gripper were fabricated in a flat position which would later assume the shape of the PBAs. To determine the shape of the ray, a scoop volume was visualized. This volume was cut by two perpendicular planes to obtain 4 quadrants of scoop volume representing the 4 rays of the scooping soft gripper arranged radially. A surface flattening operation of one quadrant scoop volume provided the final shape of the flat ray. The overall Scooping soft gripper fabrication process involved three primary components: the PBA, the flat ray, and the passive suction cups.

[0102] Fabricating the Pre -bent Bellows Actuator (PBA)

[0103] The PBA was cast in an opened state by applying a viscous layer of SmoothSil-960 within a three-piece press mold (FIG. 19 A(i) ). Separately, the flat closing section of the actuator was cast using a two-piece press mold (FIG. 19A(ii)). After curing, both the bellows and flat sections were meticulously aligned and bonded together using uncured SmoothSil-960 paste as an adhesive, resulting in the PBA (FIG. 19A(iii)). Subsequently, the actuator’s bending capability was tested using an external vacuum pump, applying a pressure of -80 kPa after inserting a silicone tube into the actuator inlet, which was securely bonded with uncured SmoothSil-960 paste.

[0104] Fabricating the flat finger base / rav[00105 J Dragon Skin 30 was selected as the material for the Scooping soft gripper’s rays, owing to its softer properties compared to SmoothSil 960. This choice was driven by the need for each ray to maintain a minimum thickness of 5 mm, accommodating the stems of the passive suction cups and an embedded network of vacuum channels connecting all the passive suction cups to a single vacuum inlet. A thick layer of stiffer material could potentially impede the bending of the ray from a pre-bent position to a flat one. Consequently, the softer material was favored, allowing the complete casting of the ray in a flat configuration, which would later conform to the stiffer PBA once bonded. Each ray was cast as two distinct layers. The first layer, featuring a network of vacuum channels, was cast by applying a viscous layer of Dragon Skin 30 within a two-piece press mold (FIG. 19B(i)). The second layer, with projections connecting the vacuum network to the stems of the passive suction cups, underwent a similar casting process using another set of two-piece press molds (FIG. 19B(ii)). Once both layers were cured, they were carefully aligned and bonded using a very thin coating of uncured Dragon Skin 30 as an adhesive, resulting in an assembled ray. The ray was then affixed to the PBA, held in place by a mold fixture, and bonded using uncured Dragon Skin 30 as an adhesive. The assembled ray’s bending capability was subsequently assessed by applying a vacuum through the PBA inlet.

[0106] Fabricating the passive suction cup[00107J The passive suction cups were casted using a three-piece mold. Initially, the bottom two mold sections were aligned, and SmoothSil 960 with added silicone thinner was injected into the mold. This process continued until the material filled the mold up to the level where the suction cup’s stem commenced. Additional silicone thinner-infused Dragon Skin 30 was then injected until the mold’s brim was reached (FIG. 19C(i)) followed by closing the mold with the third piece. The suction cups once cured, were placed atop a 1mm thick flat passive film of uncured Eco Flex 10, generated using an in-house Direct Ink Writing apparatus (FIGs.19C(ii) and 19C(iii)). After curing, any excess layer of Eco Flex 10 was meticulously removed by tracing the rim of the suction cup with a blade cutter, yielding a passive suction cup (FIG. 19C(iv)). The inner diameter of the passive suction cup’s stem matched the outer diameter of the projection extending from the ray, connecting the passive suction cup to one of the vacuum network channels inside the ray. Once all passive suction cups were cast, they were bonded to the ray using uncured Dragon Skin 30 as an adhesive, with the protruding projections inserted into the stem cavities of the passive suction cups. This process resulted in the completion of a ray of the Scooping soft gripper, combined with passive suction cups (FIGs. 19D, 19E, and 19F). Passive suction within the ray was subsequently evaluated by applying a vacuum to the ray’s inlet. The rays, once cast, were assembled using FDM printed ASA parts for modular interfaces and a gripper holder or gripper base to complete the scooping soft gripper (FIG. 19G).

[0108] Grasping operation of the scooping soft gripper

[0109] Mounted on a Ufactory xArm 7 robotic arm, the scooping soft gripper grasping capabilities were tested on a diverse array of items. The grasping approach commenced with the gripper in an opened state (actuated PBAs). The passive suction cups of the open rays were pre-loaded against the test samples to ensure an adequate seal at the surface interface. Subsequently, the vacuum was activated to initiate passive suction. As the seal remained effective for items in proper contact with the passive suction cups, the gripper was raised to a certain height, and with the items stuck to the passive suction cups, a vacuum of -80 kPa within the PBA was switched to a positive pressure of 60 kPa, transitioning the gripper into scooping mode. The vacuum responsible for passive suction was then switched off since the closed scooping state proved sufficient to securely hold the cluster intact without the need for continuous suction (see FIGs. 20A to 20D).

[0110] The scooping soft gripper presents two noteworthy advantages when compared to conventional finger-based soft grippers. Firstly, the scooping ability enables the immediatedeactivation of suction after closing the rays (until picking is done), distinguishing it from other suction-based solutions that necessitate the continuous use of suction until the entire grasping process (complete picking and placing) concludes. In scenarios consisting of lengthy robotic arm trajectories after picking operation before placing in the bin, the benefit of suction deactivation immediately after closing of rays would be realized in terms of energy savings. Secondly, it addresses a key challenge inherent in robotic arm operations - preventing slippage over the entire trajectory, which may vary in length depending on the specific task. Vibrations and sudden jerks due to acceleration pose a risk of slippage, particularly in cases involving suction-based grasping.

[0111] The scooping mode empowers the cluster to be moved at higher speeds and accelerations, a feat not achievable with suction alone. This becomes particularly evident when dealing with multiple items in a cluster, a scenario that the scooping soft gripper adeptly handles.

[0112] The proposed scooping soft gripper may be utilized for cluster grasping within agricultural automation setups. The proposed gripper, harnessing the combined functionalities of passive suction and scooping, significantly enhances grasping productivity. Notably, it outperforms traditional finger-based soft grippers by allowing the grasping of multiple items (for e.g., averaging approximately 3-4 mushrooms per grasp) as opposed to the one-item-per- grasp limitation typical of its counterparts. By introducing a dual material configuration to enhance the compliance of the suction cup, an increase of 116% in suction force is achieved (compared to the suction cup from a single material of SS960), with a further 6% increase facilitated by employing a softer EF10 passive film compared to EF30 film. In addition, despite the various suction limitation due to surface of the different crops, the proposed scooping gripper may be used to handle big mushrooms or uneven leafy surfaces of Xiao Bai Cai (Brasica rapa var chinensis) as shown in FIGs. 21A to 21C.

[0113] These parameters relating to the type of suction cup, effective suction area, cup density and arrangement, passive film meniscus angle, suction cup shape, cup orientation, and the integration of additional features like lips or supporting ribs are exemplary and inexhaustive in the present disclosure. In addition, parameters related to the pre-bent bellows actuator, such as material combinations, bellow wall thickness, and bellow size, may be subject to optimization aimed at enhancing the scooping force and the conformity of the ray to uneven cluster surfaces, are exemplary in this disclosure and inexhaustive.

[0114] All examples described herein, whether of 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

CLAIMS1. A soft gripper, comprising: a plurality of gripper fingers, each of the plurality of gripper fingers comprising: a finger base defining a first surface and a second surface opposing the first surface, the finger base defining a network of pneumatic channels; an actuator coupled to the first surface, the actuator defining a pneumatic channel; a plurality of suction members coupled to the second surface, the plurality of suction members in fluid communication with the network of pneumatic lines, wherein the finger base is biased to a curved state, wherein the actuator is actuatable to displace the finger base away from the curved state responsive to a first negative pressure in the pneumatic channel, wherein each of the plurality of suction members provides a respective suction pressure responsive to a second negative pressure in the network of pneumatic lines.

2. The soft gripper as recited in claim 1, wherein the finger base in the curved state corresponds to an at least partially closed volume defined by the plurality of gripper fingers.

3. The soft gripper as recited in any of the above claims, wherein the finger base is biased to the curved state by the actuator.

4. The soft gripper as recited in any of the above claims, wherein the network of pneumatic channels is disposed between the first surface and the second surface.

5. The soft gripper as recited in any of the above claims, wherein the network of pneumatic channels comprises a plurality of parallel branches in fluid communication with a common inlet disposed on the finger base.

6. The soft gripper as recited in any of the above claims, wherein the network of pneumatic channels comprises a plurality of connecting nodes, each of the plurality of connecting nodes in fluid communication with a respective one of the plurality of suction members.

7. The soft gripper as recited in any one of the above claims, each of the plurality of suction members further comprising: a suction cup; a stem coupled between the second surface and the suction cup; and a film covering an opening of the suction cup.

8. The soft gripper as recited in claim 7, wherein the stem has a lower stiffness than the suction cup.

9. The soft gripper as recited in claim 8, wherein the film has a lower stiffness than both the suction cup and the stem.

10. The soft gripper as recited in any one of the above claims, wherein the actuator comprises a plurality of bellows aligned along a center plane of the finger base, the plurality of bellows being in fluid communication with the pneumatic channel.

11. The soft gripper as recited in claim 10, wherein the plurality of bellows is configured to bend the finger base about a lateral axis to bias the finger base to the curved state responsive to a lack of first negative pressure in the pneumatic channel, wherein the lateral axis is transverse to the center plane.

12. The soft gripper as recited in claim 1 1 , wherein each of the plurality of bellows define a respective bellow width parallel to the lateral axis, wherein the respective bellow width of the plurality of bellows varies along the center plane.

13. The soft gripper as recited in claim 12, wherein the respective bellow width of the plurality of bellows reduces from a posterior end of the finger base to an anterior end of the finger base.

14. The soft gripper as recited in any one of claims 10 to 13, wherein, the plurality of bellows has a higher stiffness than the finger base.

15. The soft gripper as recited in any one of claims 10 to 14, wherein the plurality of suction members are symmetrically disposed about the center plane.

16. The soft gripper as recited in any one of the above claims, wherein the pneumatic channel and the network of pneumatic channels are fluidly coupleable to a single pneumatic pressure source.

17. The soft gripper as recited in any one of the above claims, wherein the plurality of suction members define a scooping surface responsive to the finger base being in the curved state.

18. The soft gripper as recited in any one of the above claims, wherein the plurality of suction members are uniformly distributed on the second surface.

19. The soft gripper as recited in claim 18, further comprising a gripper base coupled to the plurality of gripper fingers, the gripper base coupleable to a robotic arm along a gripper axis.

20. The soft gripper as recited in claim 19, wherein the plurality of gripper fingers are disposed in a radial symmetry about the gripper axis.

21. A soft gripper system, comprising: the soft gripper as recited in any one of the above claims; and a pneumatic pressure source in a controllable fluid communication with each of the at least one gripper finger.

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