Multi-mode gripper and gripping method

Abstract

The multi-mode gripper comprises a palm and at least two dexterous fingers connected with the palm, each dexterous finger comprises a swing unit and a bidirectional rigidity gripping unit, one end of each swing unit is connected with the palm, and the other end of each swing unit is connected with the bidirectional rigidity gripping unit; the swing unit comprises a center limiting layer and deformation layers which are connected to the two sides of the center limiting layer and are variable in size, the rigidity of the center limiting layer is larger than that of the deformation layers, and a plurality of oblique air cavities which are communicated and obliquely arranged are formed in the deformation layers; the bidirectional rigidity grabbing unit comprises an inner concave air cavity deformation layer, a limiting layer and a plurality of outer framework limiting blocks, wherein the inner concave air cavity deformation layer and the limiting layer are fixedly connected, and the outer framework limiting blocks are connected to the inner concave air cavity deformation layer. According to the two-way rigidity grasping unit, through the arrangement that the concave air cavities and the outer framework limiting blocks embedded into the concave air cavities are alternately arranged in a concave and convex mode, rigid-flexible coupling can be achieved, the pneumatic active grasping force and the bending deformation amount of the two-way rigidity grasping unit can be improved, and the fingertip force of the two-way rigidity grasping unit at the fingertip is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical grippers, and more particularly to a multi-modal gripper and a grasping method. Background Art

[0002] With the improvement of the technological level and the needs of production and life, compared with traditional rigid mechanical grippers, soft grippers have received extensive attention due to their excellent properties and potential scientific research and production value. As a cutting-edge design method, rigid-flexible coupling endows soft grippers with many excellent characteristics that break through their inherent disadvantages, providing a feasible solution for the multi-modal grasping and dexterous operation of soft grippers, and having great development prospects.

[0003] At the present stage, mechanical grippers can be mainly divided into three types: rigid, flexible, and rigid-flexible coupling structures. Traditional mechanical grippers are mainly rigid bodies, with a long development cycle, a wide working range, and excellent performance, accuracy, and maturity, which have long dominated industrial production. However, it has been noticed that rigid-body manipulators are difficult to meet the requirements of industrial and scientific research operations in the new stage, especially the safe interaction in unstructured environments, and have poor grasping ability for complex, irregular, and fragile objects, which are likely to cause damage to operators, the environment, and the objects to be operated. Compared with rigid-body manipulators, flexible manipulators show better environmental adaptability and wrapping properties in unstructured environment operations and the grasping of fragile and irregular objects, and have great application potential. However, flexible manipulators have low output power, limited working load, a short development cycle, and many limitations such as manufacturing materials and modeling theories. Especially for pneumatic soft hands, there are manufacturing problems such as difficult sealing and the defect that it is difficult to improve flexibility and grasping force simultaneously.

[0004] To solve the above problems of rigid and flexible manipulators, the design concept of rigid-flexible coupling has been proposed and shown great vitality, in order to integrate the advantages of large working load of rigid-body manipulators and compliant interaction of flexible manipulators. At the present stage, certain achievements have been made in rigid-flexible coupling manipulators, and it is considered a feasible research and design idea and has received extensive attention from researchers. However, through better coupling design, achieving the high working load and the ability of good environmental interaction and compliant multi-modal grasping of rigid-flexible coupling manipulators is still one of the most important difficulties.

[0005] In summary, there is still a lack of a gripper that can both exert the high working load capacity of a rigid manipulator and possess the advantages of good environmental interaction and flexible multi-modal non-destructive grasping of a flexible manipulator. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to provide a manipulator that can both have the high working load of a rigid manipulator and possess the advantages of good environmental interaction and flexible multi-modal non-destructive grasping of a flexible manipulator.

[0007] The present invention solves the above technical problems through the following technical means: A multi-modal gripper, including a palm and at least two dexterous fingers connected to the palm. The dexterous finger includes a swing unit and a bi-directional stiffness grasping unit. One end of the swing unit is connected to the palm, and the other end is connected to the bi-directional stiffness grasping unit. The swing unit includes a central limiting layer and deformable layers with variable volume connected to both sides of the central limiting layer. The stiffness of the central limiting layer is greater than that of the deformable layer. A plurality of inclined air cavities that are connected and inclined are formed in the deformable layer; the bi-directional stiffness grasping unit includes a concave air cavity deformable layer and a limiting layer fixedly connected, and a plurality of outer skeleton limiting blocks connected to the concave air cavity deformable layer. A plurality of concave air cavities with variable volume and spaced apart are formed on the concave air cavity deformable layer. The force vector synthesized by the restraint tension and air pressure of the concave air cavity points to the center line of the concave air cavity. One end of the outer skeleton limiting block is fixed in the concave air cavity, and the other end is provided with a limiting member. When the concave air cavity deformable layer is inflated and expanded, the shell-like structure can limit the circumferential expansion of the concave air cavity. When the bi-directional stiffness grasping unit does not actively inflate and bends outward, adjacent limiting members can bend a certain angle and cause form interference.

[0008] As a preferred technical solution, a depression is provided in the middle of the palm. The edge of the depression is covered with a skin. The skin and the depression enclose a sealed cavity structure. The cavity is filled with small balls. The cavity is also connected to the outside through a middle soft palm air passage and can form a negative pressure.

[0009] As a preferred technical solution, the swing unit is connected to the bi-directional stiffness grasping unit through a rotary connection structure and can rotate around the axis of the rotary connection structure. A limiting partition is provided in the rotary connection structure, and the limiting partition can cause form interference to the rotation of the bi-directional stiffness grasping unit relative to the swing unit.

[0010] As a preferred technical solution, the rotary connection structure includes a connecting member and a connecting housing. The connecting housing includes a first housing connected to the swing unit and a second housing. A rotating groove is provided in the second housing. One end of the connecting member extending into the rotating groove is fixedly connected with a limiting plate. A plurality of limiting holes adapted to the limiting partition are axially provided in the rotating groove. The other end of the connecting member is connected to the bi-directional stiffness grasping unit. Both ends of the swing unit are in interference fit with the first housing and the palm respectively.

[0011] As a preferred technical solution, a circumferentially wrapped housing is formed at the end of the outer skeleton limiting block extending out of the concave air cavity, and the limiting member is fixed on the housing. The limiting member includes a cylindrical column.

[0012] As a preferred technical solution, multiple inclined air cavities are arranged in a grid pattern, and the inclined air cavities of the two deformation layers are symmetric about the central limiting layer. The deformation layer includes a left inclined air cavity deformation layer and a right inclined air cavity deformation layer. The left inclined air cavity deformation layer is connected to a left inclined air cavity air path, and the right inclined air cavity deformation layer is connected to a right inclined air cavity air path. The inclined air cavities in the left inclined air cavity deformation layer and the right inclined air cavity deformation layer are respectively communicated with the left inclined air cavity air path and the right inclined air cavity air path.

[0013] As a preferred technical solution, the circumferential wall thickness of the inclined air cavity is thinner than the wall thickness of the front and rear air cavities.

[0014] As a preferred technical solution, the inflation deformation of the bidirectional stiffness grasping unit is concentrated on the inward envelope bending. The circumferential wall thickness of the concave air cavity deformation layer of the bidirectional stiffness grasping unit is thicker than the wall thickness of the concave air cavities on the front and rear sides.

[0015] As a preferred technical solution, a thin film pressure sensor is provided at one end of the skin facing the object to be operated. When the adaptive extrusion of the object to be operated detected by the thin film pressure sensor reaches the set pressure value, the air path of the middle soft palm unit is controlled to exhaust air to form a negative pressure, and the object to be operated is automatically wrapped.

[0016] As a preferred technical solution, by adjusting the pressure difference between the right inclined air cavity deformation layer and the left inclined air cavity deformation layer, the swinging unit can be controlled to swing left and right. Inflating the right inclined air cavity deformation layer and not inflating the left inclined air cavity deformation layer can control the swinging unit to swing left. Inflating the left inclined air cavity deformation layer and not inflating the right inclined air cavity deformation layer can control the swinging unit to swing right. Controlling the right inclined air cavity deformation layer and the left inclined air cavity deformation layer to be inflated simultaneously and having the same pressure difference can achieve the elongation of the swinging unit.

[0017] The present invention also provides a grasping method. When the angle formed by the bidirectional stiffness grasping unit and the horizontal plane is greater than the set angle, the gripper is in the active grasping mode, and the skeleton limiting block is driven to bend by inflating the bidirectional stiffness grasping unit. When the angle formed by the bidirectional stiffness grasping unit and the horizontal plane is less than the set angle, the gripper is in the self-locking grasping mode. When the mass of the object to be operated is large and exceeds the range of pneumatic active grasping, the object to be operated enters the wrapping space through the reverse bending of the bidirectional stiffness grasping unit and is limited. When the weight of the object exceeds the grasping ability of the pneumatic bending of the grasping unit, the bidirectional stiffness grasping unit bends reversely and abuts against the inner wall of the object to be operated to achieve grasping.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) In the present invention, through the arrangement of the concave air cavity and the outer skeleton limiting block embedded in the concave air cavity, which is an alternating arrangement of concave and convex, the rigid-flexible coupling can be realized, which can improve the pneumatic active grasping force and bending deformation of the bidirectional stiffness grasping unit, and increase the fingertip force of the bidirectional stiffness grasping unit at the fingertip. When grasping a flexible object, by inflating to drive the volume change of the concave air cavity, the bidirectional stiffness grasping unit can be driven to gently grasp light, fragile, and easily breakable objects such as tomatoes and tofu, effectively avoiding damage to the object surface. When facing an object with a large mass that is outside the pneumatic active grasping weight range, the gripper can switch the working mode, so that the object with a large mass can be grasped and lifted by the reverse form interference of the rigid interference block of the bidirectional stiffness grasping unit, increasing the stiffness. Thus, it has both the high working load of a rigid manipulator and the advantages of good environmental interaction and flexible multi-modal non-destructive grasping of a flexible manipulator; through the inclined air cavity, the air volume can be better converged, reducing redundant deformation to obtain better left and right swing performance, providing a better degree of freedom for left and right swing for the overall dexterous finger to facilitate the grasping of flexible and rigid objects.

[0020] (2) In the present invention, through the limiting partition, the angle of the bidirectional stiffness grasping unit relative to the swing unit can be adjusted, and the effective space where it is located can be adjusted to control the angle formed by the bidirectional stiffness grasping unit and the horizontal plane, so as to adapt to different characteristics and weights of the objects to be operated.

[0021] (3) In the present invention, the small ball is wrapped by the skin, and the cavity enclosed by the skin and the depression is evacuated by the air path of the middle soft palm, which can form a grasping force on the object to be wrapped. Compared with general rigid fixing frames and intermediate structures, the soft envelope palm based on the blocking principle improves the grasping ability and applicable scenarios of the multi-modal soft gripper to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the front view structural schematic diagram of the multi-modal gripper provided by the embodiment of the present invention;

[0023] Figure 2 is the cross-sectional view structural schematic diagram of the multi-modal gripper provided by the embodiment of the present invention;

[0024] Figure 3 is the structural schematic diagram of the dexterous finger provided by the embodiment of the present invention;

[0025] Figure 4 is the cross-sectional view structural schematic diagram of the bidirectional stiffness grasping part of the dexterous finger provided by the embodiment of the present invention;

[0026] Figure 5 is the cross-sectional view structural schematic diagram of the left and right swing part of the dexterous finger provided by the embodiment of the present invention;

[0027] Figure 6 Schematic cross-sectional structure diagram of the double-limiting connection device provided by the embodiment of the present invention;

[0028] Reference numerals in the drawings: 1. Air circuit of the middle soft palm unit; 2. Fixing device; 3. Middle soft palm unit; 4. Right inclined air cavity deformation layer; 5. Central limiting layer; 6. Air circuit of the grasping unit; 7. Concave air cavity deformation layer; 8. Third outer skeleton limiting block; 9. Limiting layer; 10. Connecting piece; 11. Limiting partition; 12. Bidirectional limiting connection device; 13. Second outer skeleton limiting block; 14. First outer skeleton limiting block; 15. Fourth outer skeleton limiting block; 16. Fifth outer skeleton limiting block; 17. Sixth outer skeleton limiting block; 18. Left inclined air cavity deformation layer; 19. Left inclined air cavity air circuit; 20. Right inclined air cavity air circuit. Specific embodiments

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Refer to Figure 1 , a multi-modal gripper includes dexterous fingers and a fixing device 2. The fixing device 2 forms the palm structure of the dexterous fingers. The fixing device 2 can be connected to carriers such as robotic arms, drones, and robots. Here, the carrier can be a mobile carrier or a fixed carrier. One end of the dexterous finger is connected to the fixing device 2. The dexterous finger includes a swinging unit and a bidirectional stiffness grasping unit. One end of the swinging unit of the dexterous finger is connected to the fixing device 2, and the other end is connected to the bidirectional stiffness grasping unit through a bidirectional limiting connection device 12. The swinging unit is fixedly connected to the fixing device 2. In this embodiment, an interference fit is taken as an example. The fixing device 2 is provided with an installation hole adapted to the swinging unit, and one end of the swinging unit is interference-fitted in the installation hole.

[0031] Refer to Figure 3 , Figure 5 , the swinging unit includes a central limiting layer 5 and deformation layers fixed on both sides of the central limiting layer 5. The two deformation layers have the same structure. The deformation layers are respectively a left inclined air cavity deformation layer 18 and a right inclined air cavity deformation layer 4. A plurality of inclined air cavities that are connected and inclined are provided in both the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4. The inclined air cavities are in a grid shape. An air path is left in the middle of the bottom side of each grid section. The front and rear wall thicknesses of the grid are relatively thin, and the circumferential wall thickness is relatively thick. When the air cavity is inflated and expanded, the inclined grid deforms greatly in the inclined direction and has a small circumferential expansion;

[0032] Both the central restraint layer 5 and the deformation layer are made of flexible materials. The stiffness of the central restraint layer 5 is greater than that of the deformation layer. In this embodiment, each deformation layer includes six semi-cylindrical hollow inclined air cavities with the same structure and inclined settings, and has a relatively small stiffness. The left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4 are symmetric about the central restraint layer 5. The central restraint layer 5 is adhesively fixed to the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4 respectively. The inclined air cavities in the central restraint layer 5, the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4 generally form a fishbone structure. The left inclined air cavity deformation layer 18 is connected with a left inclined air cavity air passage 19, and the right inclined air cavity deformation layer 4 is connected with a right inclined air cavity air passage 20;

[0033] When the left inclined air cavity air passage 19 is inflated, the left inclined air cavity deformation layer 18 expands and bends to the right, and the central restraint layer 5 with a greater stiffness also bends accordingly. By analogy, when one side of the inclined air cavity is inflated, the swinging unit shows a left or right deviation; when the left inclined air cavity air passage 19 and the right inclined air cavity air passage 20 are inflated simultaneously, the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4 show a slight elongation along the axial direction; when the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4 are inflated simultaneously, but there is a certain pressure difference, the swinging unit also shows a left or right deviation. However, compared with the situation where one side of the inclined air cavity is inflated and the other side is not inflated, the swinging mode with a pressure difference on both sides makes the stiffness of the deformation layers on both sides greater, and can provide a greater and more stable supporting force.

[0034] It should be noted that the circumferential wall thickness of the inclined air cavities of the right inclined air cavity deformation layer 4 and the left inclined air cavity deformation layer 18 is slightly thinner than the wall thickness of the front and rear air cavities, so as to facilitate the left and right swinging of the swinging unit. At the same time, the design of the inclined air cavity makes the resultant force vector formed by the expansion of the gas inside the air cavity have a certain inclination angle, which is more conducive to the left and right swinging of the swinging unit. Under the same air pressure, the left and right swinging amplitude of the swinging unit is greater.

[0035] Refer to Figure 5 , the inclined air cavities of the swinging unit adopt a thin-walled hollow structure. To make the left and right swinging effect better, the air cavity can be in the shape of an inclined semi-circular fan overall and the bottom port is sealed, with an air passage left in the center. During operation, the deformation layer is inflated through the air passage to make it expand and deform; due to the pressure difference, the air cavity structures are the same and symmetric about the central restraint layer 5, and the left and right deformation amounts of the left and right swinging units are not equal, and thus it is reflected as the left and right offsets in the overall form of the swinging unit; compared with the air cavity without an inclination angle, the air cavity with an inclination angle can provide a greater bending angle and output power for the swinging unit, further improving the bending effect of the flexible finger to increase its output force upper limit and dexterity.

[0036] When the dexterous fingers need to swing left and right, the swing unit realizes the left and right swing of the swing unit by inflating and deflating the oblique air chambers on the left and right sides; the adjacent dexterous fingers can grasp the object; when grasping the object, the bidirectional stiffness grasping unit has two working modes. When it is necessary to actively grasp an object with light weight, complex shape and moderate size, the bidirectional stiffness grasping unit realizes active grasping through pneumatic bending. When faced with an object with a large size and a weight that exceeds the grasping capacity of the pneumatic bending of the grasping unit, the bidirectional limit connection device 12 adjusts the angle between the bidirectional stiffness grasping unit and the horizontal plane to form a cage shape, and grasps the object through the sudden increase in stiffness brought about by the reverse geometric interference.

[0037] See also Figure 2 , Figure 6 The two-way limit connection device 12 includes a connection shell, a connection member 10, and a limit partition 11. The connection member 10 is generally a columnar structure. The connection shell is divided into an upper structure and a lower structure. The upper structure and the lower structure are respectively a first shell and a second shell. The first shell and the second shell are fixedly connected. The second shell and the first shell can also be an integrally formed structure. The upper structure is a columnar structure adapted to the swing unit. One end of the columnar structure that cooperates with the swing unit is provided with a docking groove adapted to the swing unit. The end of the swing unit away from the fixing device 2 is fixedly connected to the docking groove. In this embodiment, taking interference fit as an example, the lower structure is an annular shell, and a rotating groove that can accommodate the end of the connection member 10 is provided in the annular shell. The rotating groove is provided with an opening, and one end of the connection member 10 It extends into the rotating groove from the opening, and the rotating groove forms a covering on the end. One end of the connecting member 10 is rotatably connected in the rotating groove, and the end of the connecting member 10 extending into the rotating groove converges in a pagoda shape. The end of the connecting member 10 extending into the rotating groove is fixedly connected to the limiting plate. The connecting member 10 is fixedly connected to the bidirectional stiffness grasping unit of the smart finger, so that the angle adjustment of the bidirectional stiffness grasping unit relative to the swing unit can be achieved, so that it can rotate around the axis of the annular shell at a certain angle. The annular shell is circumferentially provided with limiting holes compatible with the limiting partition 11. The limiting holes can be equally divided or unequally divided. By inserting the limiting partition 11 into the limiting hole, the rotation of the limiting plate can be interfered with in shape and position, thereby limiting the entire bidirectional stiffness grasping unit.

[0038] See also Figure 4, the bidirectional stiffness grasping unit includes a concave air cavity deformation layer 7, a limiting layer 9 connected to the connecting member 10, and a plurality of outer skeleton limiting blocks connected to the concave air cavity deformation layer 7. An inflation cavity is arranged in the concave air cavity deformation layer 7. The vertical section of the outer skeleton limiting block is convex, and cooperates with the concave air cavity of the concave air cavity deformation layer 7. When the bidirectional stiffness grasping unit performs pneumatic active grasping, the concave air cavity inflates and expands, and its circumferential expansion is restricted by the extrusion of the rigid outer skeleton limiting block. This is a typical way to restrict the circumferential expansion of the soft pneumatic cavity by rigid-flexible coupling. This method improves the circumferential force and fingertip force of the bidirectional stiffness grasping unit, so that under the same air pressure, the bidirectional stiffness grasping unit has a higher output power compared with the ordinary pneumatic grid actuator.

[0039] The concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit is concave; the cross-sectional shape of the cavity is another key design factor to enhance the bending angle under the same pressure. The air cavity tension of the concave air cavity deformation layer 7 describes the elastic behavior. The force vector synthesized by the limiting tension and air pressure of the concave air cavity points to the center line of the air cavity. Therefore, less energy converges at the middle height of the air cavity, and the longitudinal strain of the deformation layer is larger; there are outer skeleton limiting blocks with a convex longitudinal section between the air cavities. The limiting blocks have a rigid structure. With the placement of the rigid structure, the damping ratio of the deformation layer is reduced, the force transmission rate is increased, and the grasping force and bending deformation of the bidirectional stiffness grasping unit are increased.

[0040] See Figure 3 , Figure 4 , one end of the outer skeleton limiting block extends into the concave air cavity, and a circumferentially wrapped shell-like structure, namely a shell, is formed at the other end of the concave air cavity. A cylindrical column-like body is fixed above the shell-like structure. When the concave air cavity deformation layer 7 inflates and expands, the circumferentially wrapped shell-like structure of the outer skeleton limiting block will restrict the circumferential expansion of the concave air cavity. Therefore, the inflation deformation of the bidirectional stiffness grasping unit is mainly concentrated on the inward enveloping bending. When the bidirectional stiffness grasping unit does not actively inflate and bends outward, the cylindrical column-like bodies on the outer skeleton limiting blocks will squeeze each other, resulting in geometric position interference. At this time, compared with the grasping force actively applied by the bidirectional stiffness grasping unit through pneumatic means, the bearing capacity of the outer skeleton limiting block due to position interference will be increased by more than 10 times, greatly improving the load capacity of the gripper.

[0041] In order to make better use of the air pressure in the air cavity, so that the internal gas energy can be better utilized in the deformation direction of the required phase change layer, and the gas energy utilization efficiency is higher. The circumferential wall thickness of the concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit is thicker than the wall thickness of the front and rear concave air cavities. When the concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit is inflated and expanded, the air cavity of the concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit is not prone to circumferential expansion, and it is easier to cause extrusion of the front and rear air cavities. Therefore, the concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit with unequal wall thicknesses can better generate bending strain, thereby improving the energy utilization efficiency.

[0042] Refer to Figure 4 , the bidirectional stiffness grasping unit further includes a grasping unit air passage 6. The grasping unit air passage 6 is communicated with the inflation cavity of the concave air cavity deformation layer 7 for inflating the concave air cavity deformation layer 7. There are six outer skeleton limiting blocks, and their sizes from small to large are the first outer skeleton limiting block 14, the second outer skeleton limiting block 13, the third outer skeleton limiting block 8, the fourth outer skeleton limiting block 15, the fifth outer skeleton limiting block 16, and the sixth outer skeleton limiting block 17, which are respectively fixed in the concave air cavity;

[0043] The concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit is cast from ultra-soft silicone ecoflex-0030; when preparing the silicone, pour the A glue and B glue into a paper cup in a ratio of 1:1, stir evenly, implant a vacuum pump, evacuate for 3 minutes, wait until the bubbles in the silicone in the paper cup are completely eliminated, then pour it into the mold, and then slowly close it. After standing for 20 hours until the silicone solidifies, demold.

[0044] The limiting layer 9 is prepared from Smooth-Sil 950 (silicone) with a stiffness of 60A; when preparing the silicone, pour the A glue and B glue into a paper cup in a ratio of 10:1, stir evenly, implant a vacuum pump, evacuate for 3 minutes, wait until the bubbles in the silicone in the paper cup are completely eliminated, and then pour it into the mold. After standing for 24 hours until the silicone solidifies, demold.

[0045] After the concave air cavity deformation layer 7 and the limiting layer 9 are bonded with Sil Poxy adhesive, the bidirectional stiffness grasping unit, the second outer skeleton limiting block 13, the first outer skeleton limiting block 14, the fourth outer skeleton limiting block 15, the fifth outer skeleton limiting block 16, the sixth outer skeleton limiting block 17, and the third outer skeleton limiting block 8 are manufactured by using the fused deposition manufacturing process. The shapes of the above six outer skeleton limiting blocks are all different. After manufacturing, the above six outer skeleton limiting blocks are fixedly bonded to the concave air cavity deformation layer 7 of the bidirectional stiffness grasping unit with G-998A silicone glue. Thus, the bidirectional stiffness grasping unit is manufactured.

[0046] When the bidirectional stiffness grasping unit performs pneumatic active inward bending and grasping, since the six outer skeleton limiting blocks of the cross-section convex bidirectional stiffness grasping unit and the concave air cavity deformation layer 7 of the cross-section concave bidirectional stiffness grasping unit are arranged in an alternating rigid-flexible coupling pattern. It should be noted here that the concave air cavity deformation layer 7 between adjacent concave air cavities is also convex. The outer skeleton limiting block is rigid relative to this convexity, and the convexity is flexible, so it is arranged in a rigid-flexible alternating coupling pattern.

[0047] Refer to Figure 2 , the fixing device 2 further includes a middle soft palm unit 3. In this embodiment, four flexible fingers are provided, so four mounting holes that are in interference fit with the swinging unit are formed on the fixing device 2. A conical depression is provided in the middle of the fixing device 2, and the internal filling is granular balls. The outside is covered with a soft and wear-resistant silicone skin. The internal granular balls fill the entire internal conical space and make the outer skin plump. The above-mentioned filler, skin and the middle soft palm unit air passage 1 left in the fixing device 2.

[0048] When the middle soft palm unit 3 finishes interacting with and squeezing the object to be operated, the middle soft palm unit 3 will undergo adaptive deformation according to the outer surface of the object to be operated and closely fit the object to be operated. After the middle soft palm unit 3 undergoes adaptive phase change and fits the object to be operated, the middle soft palm unit air passage 1 is evacuated to form a negative pressure; at this time, the internal filling particles undergo a blocking principle under the action of the negative pressure, squeeze each other, and the stiffness becomes larger, forming a certain grasping force on the object to be operated; cooperating with the dexterous fingers, the multi-modal soft gripper can better grasp the object to be operated.

[0049] At the same time, a thin-film pressure sensor can be placed on the outer skin of the middle soft palm unit 3. When the adaptive extrusion of the rest of the object to be operated reaches a certain pressure value, the middle soft palm unit air passage 1 is evacuated to form a negative pressure, and the automatic wrapping of the object to be operated is completed by using the blocking principle.

[0050] Usage method:

[0051] The dexterous finger composed of a swinging unit, a bidirectional stiffness grasping unit, and a double-limit connection device can have two degrees of freedom: left-right swinging and front-back bending. Through the superposition of these two degrees of freedom, the dexterous finger can complete various modal actions and operate on complex objects in an unstructured environment. It also has a double-limit connection device that can switch modes according to the characteristics of the object to be operated. When the angle between the bidirectional stiffness grasping unit and the horizontal plane is large, that is, when the dexterous finger is in an outward-opening state, the device is in the active grasping mode, and the bidirectional stiffness grasping unit of the dexterous finger can be bent by pneumatic drive. When the angle between the bidirectional stiffness grasping unit and the horizontal plane is small, the device is in the self-locking grasping mode. At this time, the bidirectional stiffness grasping unit has the freedom of reverse bending. For example, when the distance between the relatively arranged dexterous fingers is less than the circumferential size of the object to be grasped, the bidirectional stiffness grasping unit can bend outward at a certain angle in the reverse direction, so that the ends of the two relatively dexterous fingers extend below the plane where the bottom of the object to be grasped is located, thereby realizing the wrapping of the object to be grasped. The grasping principle of the four dexterous fingers is the same as above and will not be elaborated here. When the angle between the bidirectional stiffness grasping unit and the horizontal plane is small, the bidirectional stiffness grasping unit of the dexterous finger can also be directly driven to bend forward, so that the object to be operated is clamped by the four dexterous fingers or closely attached to the middle soft palm unit.

[0052] It should be noted that when the mass of the object to be operated is large and exceeds the range of pneumatic active grasping, since the main obstacle to the inward bending of the bidirectional stiffness grasping unit comes from the deformation layer 7 of the soft concave air cavity and the limiting layer 9, and the main obstacle to the outward bending comes from the form-position interference of the outer skeleton limiting block. Therefore, the object to be operated is easily inserted into the wrapping space. However, due to the reverse form-position interference of the outer skeleton limiting block, it is very difficult for the object to be operated to leave the wrapping space after entering it. Therefore, the gripper can complete the grasping of an object with a large mass by using the effect of the sudden increase in stiffness caused by the reverse interference of the bidirectional stiffness grasping unit.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-modal gripper, comprising a palm and at least two dexterous fingers connected to the palm, characterized in that, The dexterous finger includes a swinging unit and a two-way stiffness grasping unit. One end of the swinging unit is connected to the palm, and the other end is connected to the two-way stiffness grasping unit. The swinging unit includes a central limiting layer and deformable layers with variable volume connected to both sides of the central limiting layer. The stiffness of the central limiting layer is greater than that of the deformable layers. Multiple inclined air cavities that are connected and inclined are provided in the deformable layers; the two-way stiffness grasping unit includes a concave air cavity deformable layer and a limiting layer that are fixedly connected, and multiple outer skeleton limiting blocks connected to the concave air cavity deformable layer. Multiple concave air cavities with variable volume and distributed at intervals are formed on the concave air cavity deformable layer. The force vector synthesized by the restraint tension and air pressure of the concave air cavity points to the center line of the concave air cavity. One end of the outer skeleton limiting block is fixed in the concave air cavity, and the other end is provided with a limiting member. When the concave air cavity deformable layer is inflated and expands, the shell-like structure can limit the circumferential expansion of the concave air cavity. When the two-way stiffness grasping unit does not actively inflate and bends outward, adjacent limiting members can bend a certain angle and cause positional interference.

2. The multimodal gripper according to claim 1, wherein A depression is provided in the middle of the palm. The edge of the depression is covered with a skin. The skin and the depression enclose a sealed cavity structure. The cavity is filled with small balls. The cavity is also connected to the outside through a middle soft palm air passage and can form a negative pressure.

3. The multimodal gripper according to claim 1, characterized in that, The swinging unit is connected to the two-way stiffness grasping unit through a rotary connection structure and can rotate around the axis of the rotary connection structure. A limiting partition is provided in the rotary connection structure, and the limiting partition can cause positional interference to the rotation of the two-way stiffness grasping unit relative to the swinging unit.

4. The multimodal gripper according to claim 3, characterized in that, The rotary connection structure includes a connecting member and a connecting housing. The connecting housing includes a first housing connected to the swinging unit and a second housing. A rotating groove is provided in the second housing. One end of the connecting member extending into the rotating groove is fixedly connected with a limiting plate. Multiple limiting holes adapted to the limiting partition are axially provided in the rotating groove. The other end of the connecting member is connected to the two-way stiffness grasping unit. Both ends of the swinging unit are in interference fit with the first housing and the palm respectively.

5. A multimodal gripper according to claim 1, characterized in that, A circumferentially wrapped housing is formed at the end of the outer skeleton limiting block extending out of the concave air cavity. The limiting member is fixed on the housing. The limiting member includes a cylindrical column body.

6. The multi-modal gripper according to claim 1, wherein, Multiple inclined air cavities are arranged in a grid pattern, and the inclined air cavities of the two deformable layers are symmetric about the central limiting layer. The deformable layer includes a left inclined air cavity deformable layer and a right inclined air cavity deformable layer. The left inclined air cavity deformable layer is connected with a left inclined air cavity air passage, and the right inclined air cavity deformable layer is connected with a right inclined air cavity air passage. The inclined air cavities in the left inclined air cavity deformable layer and the right inclined air cavity deformable layer are respectively connected with the left inclined air cavity air passage and the right inclined air cavity air passage.

7. The multimodal gripper according to claim 1, wherein The circumferential wall thickness of the inclined air cavity is thinner than the wall thickness of the front and rear air cavities.

8. A multimodal gripper according to claim 1, wherein The inflation deformation of the two-way stiffness grasping unit is concentrated on the inward enveloping bend. The circumferential wall thickness of the concave air cavity deformable layer of the two-way stiffness grasping unit is thicker than the wall thickness of the concave air cavities on the front and rear sides.

9. The multi-modal gripper according to claim 2, characterized in that, A thin film pressure sensor is provided at one end of the skin facing the object to be operated. When the adaptive extrusion of the object to be operated detected by the thin film pressure sensor reaches the set pressure value, the air passage of the middle soft palm unit is controlled to pump air to form a negative pressure, and the object to be operated is automatically wrapped.

10. The grasping method of the multi-modal gripper according to any one of claims 1-9, characterized in that, When the angle formed by the bistiffness grasping unit and the horizontal plane is greater than the set angle, the gripper is in the active grasping mode, and the pneumatic drive skeleton limiting block is bent by inflating the bistiffness grasping unit; when the angle formed by the bistiffness grasping unit and the horizontal plane is less than the set angle, the gripper is in the self-locking grasping mode. When the mass of the object to be operated is large and exceeds the range of pneumatic active grasping, the object to be operated bends the bistiffness grasping unit in the opposite direction to make the object to be operated enter the wrapping space and limit the object to be operated; when the weight of the object exceeds the grasping ability of the pneumatic bending of the grasping unit, the bistiffness grasping unit bends in the opposite direction and abuts against the inner wall of the object to be operated to achieve grasping.

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