A multimodal gripper and gripping method

Abstract

This invention discloses a multimodal gripper and gripping method, including a palm and at least two dexterous fingers connected to the palm. Each dexterous finger includes a swing unit and a bidirectional stiffness gripping unit. One end of the swing unit is connected to the palm, and the other end is connected to the bidirectional stiffness gripping unit. The swing unit includes a central limiting layer and a variable-volume deformation layer connected to both sides of the central limiting layer. The central limiting layer has a higher stiffness than the deformation layer. Multiple interconnected and inclined air cavities are formed within the deformation layer. The bidirectional stiffness gripping unit includes a fixedly connected concave air cavity deformation layer and a limiting layer, as well as multiple external skeleton limiting blocks connected to the concave air cavity deformation layer. In this invention, the alternating arrangement of concave and convex concave air cavities and the external skeleton limiting blocks embedded in the concave air cavities achieves rigid-flexible coupling, which can improve the pneumatic active gripping force and bending deformation of the bidirectional stiffness gripping unit, and increase the fingertip force of the bidirectional stiffness gripping unit.

Description

Technical Field

[0001] This invention relates to the field of mechanical gripper technology, and more specifically to a multimodal gripper and gripping method. Background Technology

[0002] With the advancement of technology and the needs of production and daily life, soft grippers have gained widespread attention due to their superior properties and potential scientific research and production value compared to traditional rigid mechanical grippers. As a cutting-edge design approach, rigid-flexible coupling endows soft grippers with many excellent characteristics that overcome their inherent disadvantages, providing a feasible solution for multimodal gripping and dexterous operation of soft grippers, and has great development prospects.

[0003] Currently, mechanical grippers can be mainly divided into three types: rigid, flexible, and rigid-flexible coupled structures. Traditional mechanical grippers are mainly rigid, with a long development cycle, wide working range, and have long dominated industrial production due to their excellent performance, precision, and maturity. However, it has been noted that rigid manipulators are difficult to adapt to the needs of new-stage industrial and scientific research operations, especially in safe interaction in unstructured environments. They also have poor grasping ability when dealing with complex, irregular, and fragile objects, which can easily cause damage to the operator, the environment, and the manipulated object. Compared to rigid manipulators, flexible manipulators show better environmental adaptability and coverage in unstructured environments and in grasping fragile and irregular objects, and have great application potential. However, flexible manipulators have low output power, limited workload, and a shorter development cycle. They also have many limitations, such as manufacturing materials and modeling theories. In particular, pneumatic soft manipulators have difficulties in sealing during manufacturing and the inability to simultaneously improve flexibility and grasping force.

[0004] To address the aforementioned issues of rigid and flexible manipulators, the rigid-flexible coupling design concept has been proposed and shown great promise, combining the advantages of rigid manipulators (high workload) and flexible manipulators (compliant interaction). Rigid-flexible coupling manipulators have achieved some success and are considered a feasible research and design approach, attracting widespread attention from researchers. However, achieving high workload, good environmental interaction, and compliant multimodal grasping capabilities through effective coupling design remains one of the most significant challenges.

[0005] In summary, there is still a lack of a gripper that can leverage the high workload capacity of rigid manipulators while also possessing the advantages of flexible manipulators in environmental interaction and flexible multimodal non-destructive grasping. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to provide a robot that can combine the high workload of a rigid robot with the advantages of a flexible robot in terms of good environmental interaction and flexible multimodal non-destructive grasping.

[0007] This invention solves the above-mentioned technical problems through the following technical means: a multimodal gripper, including a palm and at least two dexterous fingers connected to the palm. Each dexterous finger includes a swing unit and a bidirectional stiffness gripping unit. One end of the swing unit is connected to the palm, and the other end is connected to the bidirectional stiffness gripping unit. The swing unit includes a central confinement layer and a deformable layer connected to both sides of the central confinement layer. The stiffness of the central confinement layer is greater than that of the deformable layer. Multiple interconnected and inclined air cavities are formed within the deformable layer. The bidirectional stiffness gripping unit includes fixedly connected concave air cavities. The system consists of a variable layer, a limiting layer, and multiple exoskeleton limiting blocks connected to the concave air cavity deformation layer. Multiple spaced and variable-volume concave air cavities are formed on the concave air cavity deformation layer. The force vector resulting from the limiting tension and air pressure of the concave air cavity points towards the center line of the concave air cavity. One end of the exoskeleton limiting block is fixed inside the concave air cavity, and the other end is provided with a limiting member. When the concave air cavity deformation layer is inflated, the shell structure can limit the circumferential expansion of the concave air cavity. When the bidirectional stiffness gripping unit is not actively inflated and bends outward, the adjacent limiting members can bend at a certain angle and form and position interference occurs.

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

[0009] As a preferred technical solution, the swing unit is connected to the bidirectional stiffness gripping unit through a rotary connection structure and can rotate about the axis of the rotary connection structure. The rotary connection structure is provided with a limiting partition, which can form a form and position interference on the rotation of the bidirectional stiffness gripping unit relative to the swing unit.

[0010] As a preferred technical solution, the rotary connection structure includes a connector and a connecting housing. The connecting housing includes a first housing connected to the swing unit and a second housing. A rotary groove is provided in the second housing. One end of the connector extending into the rotary groove is fixedly connected to a limiting plate. The rotary groove is provided with multiple limiting holes that are adapted to the limiting plate in the axial direction. The other end of the connector is connected to a bidirectional rigidity gripping unit. Both ends of the swing unit are respectively interference-fitted with the first housing and the palm.

[0011] As a preferred technical solution, the end of the outer skeleton limiting block extending out of the concave air cavity is formed with a circumferentially covered shell, and the limiting member is fixed on the shell, the limiting member including a cylindrical column.

[0012] As a preferred technical solution, multiple oblique air chambers are arranged in a grid pattern, and the oblique air chambers of the two deformation layers are symmetrical about the central confinement layer. The deformation layer includes a left oblique air chamber deformation layer and a right oblique air chamber deformation layer. The left oblique air chamber deformation layer is connected to the left oblique air chamber air passage, and the right oblique air chamber deformation layer is connected to the right oblique air chamber air passage. The oblique air chambers in the left oblique air chamber deformation layer and the right oblique air chamber deformation layer are respectively connected to the left oblique air chamber air passage and the right oblique air chamber air passage.

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

[0014] As a preferred technical solution, the inflation deformation of the bidirectional stiffness gripping unit is concentrated on the inward envelope bending, and the circumferential wall thickness of the deformation layer of the concave air cavity in the bidirectional stiffness gripping 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 the end of the skin facing the object being operated. When the thin-film pressure sensor detects that the adaptive compression of the object being operated reaches the set pressure value, it controls the air path of the central soft hand unit to draw air to form a negative pressure, which automatically covers the object being operated.

[0016] As a preferred technical solution, adjusting the pressure difference between the right oblique air cavity deformation layer and the left oblique air cavity deformation layer can control the swing unit to swing left and right. When the right oblique air cavity deformation layer is filled with air and the left oblique air cavity deformation layer is not filled with air, the swing unit can be controlled to swing to the left. When the left oblique air cavity deformation layer is filled with air and the right oblique air cavity deformation layer is not filled with air, the swing unit can be controlled to swing to the right. When the right oblique air cavity deformation layer and the left oblique air cavity deformation layer are filled with air at the same time and the pressure difference is the same, the extension of the swing unit can be achieved.

[0017] This invention also provides a gripping method. When the angle between the bidirectional stiffness gripping unit and the horizontal plane is greater than a set angle, the gripper is in an active gripping mode, and the frame limiting block is bent by inflating the bidirectional stiffness gripping unit. When the angle between the bidirectional stiffness gripping unit and the horizontal plane is less than a set angle, the gripper is in a self-locking gripping mode. When the mass of the object being manipulated is too large and exceeds the range of pneumatic active gripping, the object being manipulated is bent in the opposite direction by the bidirectional stiffness gripping unit to enter the enclosed space and limit the object being manipulated. When the weight of the object exceeds the gripping capacity of the gripping unit's pneumatic bending, the bidirectional stiffness gripping unit bends in the opposite direction and presses against the inner wall of the object being manipulated to achieve gripping.

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

[0019] (1) In this invention, the alternating arrangement of concave and convex concave air cavities and the outer skeleton limiting block embedded in the concave air cavities enables rigid-flexible coupling, which can improve the pneumatic active gripping force and bending deformation of the bidirectional rigidity gripping unit, and increase the fingertip force of the bidirectional rigidity gripping unit. When gripping flexible objects, the volume change of the concave air cavity driven by inflation can drive the bidirectional rigidity gripping unit to gently grip lightweight, fragile, and easily broken objects such as tomatoes and tofu, effectively avoiding damage to the surface of the object. When facing larger masses, the pneumatic active gripping weight... When handling objects outside the range, the gripper can switch working modes, allowing heavier objects to be gripped and lifted through the reverse form-position interference of the rigid interference blocks of the bidirectional stiffness gripping unit. This increases stiffness, combining the high workload of a rigid manipulator with the advantages of a flexible manipulator in terms of good environmental interaction and flexible multimodal non-destructive gripping. The inclined air chamber can better concentrate air volume, reduce redundant deformation, and obtain better left-right swing performance, providing the dexterous finger as a whole with a better degree of freedom for left-right swinging to facilitate the gripping of both flexible and rigid objects.

[0020] (2) In this invention, the angle between the bidirectional stiffness gripping unit and the swinging unit can be adjusted by the limiting partition, and the effective space in which it is located can be adjusted to control the angle formed between the bidirectional stiffness gripping unit and the horizontal plane, so as to adapt to the operated objects with different characteristics and weights.

[0021] (3) In this invention, the ball is covered by a skin, and negative pressure is drawn on the cavity enclosed by the skin and the recess through the air passage of the soft palm in the middle, which can form a gripping force on the covered object. Compared with the general rigid frame and intermediate structure, the soft enveloping palm based on the blocking principle improves the gripping ability and adaptability of the multimodal soft gripper to a certain extent. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the front view structure of the multimodal gripper provided in an embodiment of the present invention;

[0023] Figure 2 This is a cross-sectional view of the multimodal gripper provided in an embodiment of the present invention.

[0024] Figure 3 A schematic diagram of a dexterous finger structure provided in an embodiment of the present invention;

[0025] Figure 4 A schematic cross-sectional structure of a bidirectional stiffness gripping part of a dexterous finger provided in an embodiment of the present invention;

[0026] Figure 5 A schematic cross-sectional view of the left-right swinging portion of a dexterous finger provided in an embodiment of the present invention;

[0027] Figure 6 This is a schematic cross-sectional view of the dual-limiting connection device provided in an embodiment of the present invention;

[0028] Reference numerals: 1. Air path of the central soft hand unit; 2. Fixing device; 3. Central soft hand unit; 4. Right oblique air cavity deformation layer; 5. Central restriction layer; 6. Grip unit air path; 7. Concave air cavity deformation layer; 8. Third outer skeleton restriction block; 9. Restriction layer; 10. Connector; 11. Limiting partition; 12. Bidirectional limiting connection device; 13. Second outer skeleton restriction block; 14. First outer skeleton restriction block; 15. Fourth outer skeleton restriction block; 16. Fifth outer skeleton restriction block; 17. Sixth outer skeleton restriction block; 18. Left oblique air cavity deformation layer; 19. Left oblique air cavity air path; 20. Right oblique air cavity air path. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] See Figure 1 A multimodal gripper includes a dexterous finger and a fixing device 2. The fixing device 2 forms the palm structure of the dexterous finger. The fixing device 2 can be connected to a carrier such as a robotic arm, drone, or robot. 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 swing unit and a bidirectional stiffness gripping unit. One end of the swing unit of the dexterous finger is connected to the fixing device 2, and the other end is connected to the bidirectional stiffness gripping unit through a bidirectional limiting connection device 12. The swing unit is fixedly connected to the fixing device 2. In this embodiment, an interference fit is used as an example. The fixing device 2 has a mounting hole adapted to the swing unit, and one end of the swing unit is interference fitted into the mounting hole.

[0031] See Figure 3 , Figure 5 The swing 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 the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4. Both the left inclined air cavity deformation layer 18 and the right inclined air cavity deformation layer 4 are provided with multiple connected inclined air cavities. The inclined air cavities are grid-shaped. Each grid has an air passage at the center of the bottom side of the cross section. The front and rear walls of the grid are thinner, and the circumferential walls are thicker. When the air cavity is filled with air and expands, the inclined grid deforms more along the inclined direction and expands less circumferentially.

[0032] Both the central confinement layer 5 and the deformation layer are flexible materials. The stiffness of the central confinement layer 5 is greater than that of the deformation layer. In this embodiment, each deformation layer includes six identical semi-cylindrical hollow oblique air cavities arranged at an angle. The stiffness is relatively small. The left oblique air cavity deformation layer 18 and the right oblique air cavity deformation layer 4 are symmetrical about the central confinement layer 5. The central confinement layer 5 is bonded and fixed to the left oblique air cavity deformation layer 18 and the right oblique air cavity deformation layer 4, respectively. The central confinement layer 5 and the oblique air cavities in the left oblique air cavity deformation layer 18 and the right oblique air cavity deformation layer 4 generally form a fishbone-like structure. The left oblique air cavity deformation layer 18 is connected to the left oblique air cavity air passage 19, and the right oblique air cavity deformation layer 4 is connected to the right oblique air cavity air passage 20.

[0033] When the left oblique air chamber air passage 19 is inflated, the left oblique air chamber deformation layer 18 expands and bends to the right, and the stiffer central confinement layer 5 also bends accordingly; similarly, when one oblique air chamber is inflated, the oscillating unit exhibits left or right deviation; when the left oblique air chamber air passage 19 and the right oblique air chamber air passage 20 are inflated simultaneously, the left oblique air chamber deformation layer 18 and the right oblique air chamber deformation layer 4 exhibit slight elongation along the axial direction; when the left oblique air chamber deformation layer 18 and the right oblique air chamber deformation layer 4 are inflated simultaneously, but there is a certain pressure difference, the oscillating unit also exhibits left or right deviation, but compared to the case where one oblique air chamber is inflated while the other side is not inflated, the pressure difference-type oscillation mode on both sides makes the deformation layers on both sides stiffer, which can provide greater and more stable support force.

[0034] It should be noted that the circumferential wall thickness of the inclined air chambers of the right inclined air chamber deformation layer 4 and the left inclined air chamber deformation layer 18 is slightly thinner than that of the front and rear air chambers, which facilitates the left and right swing of the swing unit. At the same time, the design of the inclined air chamber makes the resultant force vector formed by the expansion of the gas inside the air chamber have a certain tilt angle, which is more conducive to the left and right swing of the swing unit. Under the same air pressure, the left and right swing amplitude of the swing unit is larger.

[0035] See Figure 5 The inclined air chamber of the swing unit adopts a thin-walled hollow structure. To improve the left and right swing effect, the air chamber can be in the shape of an inclined semi-circular fan and the bottom port is sealed. An air passage is left in the center. During operation, air is injected into the deformation layer through the air passage, causing it to expand and deform. Due to the pressure difference, the air chamber structures are the same and symmetrical about the central limiting layer 5. The deformation of the left and right sides of the left and right swing units is not equal, which is reflected in the left and right offset of the overall shape of the swing unit. Compared with the air chamber without an inclined angle, the inclined air chamber can provide the swing unit with a larger bending angle and output power, further improving the bending effect of the dexterous finger, thereby increasing its upper limit of output force and dexterity.

[0036] When the dexterous fingers need to swing left and right, the swing unit swings left and right by inflating and deflating the inclined air chambers on the left and right sides; it can enable adjacent dexterous fingers to grasp objects; when performing a grasping operation on an object, the bidirectional stiffness gripping unit has two working modes. When it is necessary to actively grasp objects that are not heavy, have complex shapes, and are of moderate size, the bidirectional stiffness gripping unit achieves active grasping through pneumatic bending. When facing objects that are large in size and whose weight exceeds the grasping capacity of the gripping unit's pneumatic bending, the bidirectional limiting connection device 12 adjusts the angle between the bidirectional stiffness gripping unit and the horizontal plane to form a cage shape. Through the sudden increase in stiffness brought about by the reverse geometric position interference, the object can be grasped.

[0037] See Figure 2 , Figure 6 The bidirectional limiting connection device 12 includes a connecting shell, a connector 10, and a limiting partition 11. The connector 10 is generally columnar. The connecting shell is divided into an upper structure and a lower structure, which 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 integrally formed. The upper structure is a columnar structure adapted to the swing unit. One end of the columnar structure that mates with the swing unit has a mating groove adapted to the swing unit. The end of the swing unit away from the fixing device 2 is fixedly connected to the mating groove. In this embodiment, taking an interference fit as an example, the lower structure is an annular shell. The annular shell has a rotating groove that can accommodate the end of the connector 10. The rotating groove has an opening. One end of the connector 10 The connector 10 extends into the rotating groove from the opening, and the rotating groove covers the end of the connector 10. One end of the connector 10 is rotatably connected to the rotating groove. The end of the connector 10 extending into the rotating groove converges in a pagoda shape. The end of the connector 10 extending into the rotating groove is fixedly connected to a limiting plate. The connector 10 is fixedly connected to the bidirectional rigidity gripping unit of the flexible finger, thereby enabling the bidirectional rigidity gripping unit to adjust its angle relative to the swing unit, allowing it to rotate around the axis of the annular shell at a certain angle. The annular shell has a limiting hole that matches the limiting partition 11 in the circumferential direction. The limiting hole 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 subjected to form and position interference, thereby limiting the entire bidirectional rigidity gripping unit.

[0038] See Figure 4The bidirectional stiffness gripping unit includes a concave air cavity deformation layer 7 and a limiting layer 9 connected to the connector 10, as well as multiple outer skeleton limiting blocks connected to the concave air cavity deformation layer 7. The concave air cavity deformation layer 7 is provided with an inflation cavity. The vertical section of the outer skeleton limiting blocks is convex and cooperates with the concave air cavity of the concave air cavity deformation layer 7. When the bidirectional stiffness gripping unit performs pneumatic active gripping, the concave air cavity is inflated and expanded. Its circumferential expansion is squeezed and limited by the rigid outer skeleton limiting blocks. This is a typical rigid-flexible coupling method to limit the circumferential expansion of the soft air cavity. This method improves the hugging force and fingertip force of the bidirectional stiffness gripping unit, so that under the same air pressure, the bidirectional stiffness gripping unit has a higher output power than the ordinary starting grid actuator.

[0039] The concave air cavity deformation layer 7 of the bidirectional stiffness gripping unit is concave. The cross-sectional shape of the cavity is another key design factor that enhances 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 is concentrated in the middle height of the air cavity, and the longitudinal strain of the deformation layer is greater. There are external skeleton limiting blocks with convex longitudinal cross-sections between the air cavities. The limiting blocks are rigid structures. The deformation layer reduces the damping ratio with the placement of the rigid structure, improves the force transmission rate, and increases the gripping force and bending deformation of the bidirectional stiffness gripping unit.

[0040] See Figure 3 , Figure 4 One end of the outer skeleton limiting block extends into the concave air cavity, and the other end of the concave air cavity is formed with a circumferentially enveloping shell-like structure, i.e., a shell. A quasi-cylindrical column is fixed on top of the shell-like structure. When the concave air cavity deformation layer 7 is inflated, the 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 gripping unit is mainly concentrated on the inward enveloping bending. When the bidirectional stiffness gripping unit is not actively inflated and bends outward, the quasi-cylindrical columns on the outer skeleton limiting block will squeeze each other, resulting in geometric form and position interference. At this time, compared with the gripping force actively applied by the bidirectional stiffness gripping unit through pneumatics, the load-bearing capacity due to the form and position interference of the outer skeleton limiting block will be increased to more than 10 times, which greatly improves the load capacity of the gripper.

[0041] To better utilize the air pressure within the air cavity and ensure that the internal gas energy is utilized more effectively in the desired deformation direction of the phase change layer, thereby increasing the gas energy utilization efficiency, the circumferential wall thickness of the concave air cavity deformation layer 7 in the bidirectional stiffness gripping unit is thicker than the wall thickness of the concave air cavities on the front and rear sides. When the concave air cavity deformation layer 7 in the bidirectional stiffness gripping unit is inflated, the air cavity of the concave air cavity deformation layer 7 is less likely to undergo circumferential expansion and is more likely to undergo compression of the front and rear air cavities. Therefore, the concave air cavity deformation layer 7 in the bidirectional stiffness gripping unit with unequal wall thickness can better undergo bending strain, thereby improving the energy utilization efficiency.

[0042] See Figure 4 The bidirectional stiffness gripping unit also includes a gripping unit air passage 6, which is connected to the inflation chamber of the concave air cavity deformation layer 7 and is used to inflate the concave air cavity deformation layer 7. There are six outer skeleton limiting blocks, which are arranged from smallest to largest as 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 fixed in the concave air cavity respectively.

[0043] The concave air cavity deformation layer 7 of the bidirectional stiffness gripping unit is cast from ultra-soft silicone ecoflex-0030. When mixing the silicone, pour A and B into a paper cup in a 1:1 ratio, stir evenly, insert a vacuum pump, and evacuate for 3 minutes. After the air bubbles in the silicone in the paper cup are completely eliminated, pour it into the mold, then slowly cover it, and let it stand for 20 hours until the silicone solidifies before demolding.

[0044] The limiting layer 9 is made of Smooth-Sil 950 (silicone) with a stiffness of 60A. When preparing the silicone, pour the A and B adhesives into a paper cup at a ratio of 10:1, stir evenly, insert a vacuum pump, and evacuate for 3 minutes. After the air bubbles in the silicone in the paper cup are completely eliminated, pour it into the mold. Let it stand for 24 hours to allow the silicone to solidify before demolding.

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

[0046] When the bidirectional stiffness gripping unit actively bends inward to grip, the six outer skeleton limiting blocks of the bidirectional stiffness gripping unit with an outward convex cross section and the inner concave air cavity deformation layer 7 of the bidirectional stiffness gripping unit with an inward concave cross section are arranged in an alternating rigid-flexible coupling. It should be noted that the inner concave air cavity deformation layer 7 between adjacent inner concave air cavities is also convex. The outer skeleton limiting blocks are rigid relative to the convexity, while the convexity is flexible, so they are arranged in a rigid-flexible coupling.

[0047] See Figure 2 The fixing device 2 also includes a central soft hand unit 3. In this embodiment, four flexible fingers are provided. The fixing device 2 is formed with four mounting holes that are interference fit with the swing unit. The fixing device 2 has a conical recess in the middle, which is filled with granular small balls. It is covered by a soft and wear-resistant silicone skin on the outside. The granular small balls fill the entire internal conical space and make the outer skin full. The above-mentioned filling material, skin and the central soft hand unit air passage 1 left in the middle of the fixing device 2.

[0048] When the central soft hand unit 3 and the object being manipulated come into contact and press against each other, the central soft hand unit 3 will adaptively deform according to the outer surface of the object being manipulated, closely fitting the object being manipulated. After the central soft hand unit 3 undergoes an adaptive phase change and fits the object being manipulated, the air passage 1 of the central soft hand unit is evacuated, forming a negative pressure. At this time, the internal filling particles are blocked under the action of negative pressure, compressing against each other, increasing stiffness, and forming a certain grasping force on the object being manipulated. Combined with the dexterous fingers, the multimodal soft gripper can better grasp the object being manipulated.

[0049] Meanwhile, a thin-film pressure sensor can be placed on the outer surface skin of the central soft hand unit 3. When the adaptive compression of the other operated objects reaches a certain pressure value, the air passage 1 of the central soft hand unit is controlled to draw air to form a negative pressure, and the automatic wrapping of the operated objects is completed by using the blocking principle.

[0050] Directions:

[0051] The dexterous finger, composed of a swinging unit, a bidirectional stiffness gripping unit, and a dual-limiting connection device, possesses two degrees of freedom: left-right swinging and forward-backward bending. Through the superposition of these two degrees of freedom, the dexterous finger can perform multiple modal movements, manipulating complex objects in unstructured environments. Furthermore, it features a dual-limiting connection device capable of modal switching based on the characteristics of the manipulated object. When the bidirectional stiffness gripping unit forms a large angle with the horizontal plane (i.e., the dexterous finger is outward-spreading), the device is in active gripping mode, and the bidirectional stiffness gripping unit of the dexterous finger can be pneumatically driven to bend. When the bidirectional stiffness gripping unit forms a small angle with the horizontal plane, the device... When in self-locking gripping mode, the bidirectional rigid gripping unit has the freedom to bend in the opposite direction. If the distance between the relatively set flexible fingers is less than the circumferential dimension of the object to be gripped, the bidirectional rigid gripping unit can bend outward by a certain angle, so that the ends of the two relatively flexible fingers extend into the plane below the bottom of the object to be gripped, thereby covering the object. The gripping principle of the four flexible fingers is the same as above, and will not be repeated here. When the angle between the bidirectional rigid gripping unit and the horizontal plane is small, the bidirectional rigid gripping unit of the flexible fingers can also be directly driven to bend in the forward direction, so that the object being operated is clamped by the four flexible fingers or closely attached to the central soft palm unit.

[0052] It should be noted that when the mass of the object being manipulated is large and exceeds the range of pneumatic active grasping, the main obstacles to the inward bending of the bidirectional stiffness gripping unit come from the deformation layer 7 and the limiting layer 9 of the soft concave air cavity, while the main obstacles to the outward bending come from the shape and position interference of the outer skeleton limiting block. Therefore, the object being manipulated can easily enter the encapsulation space. However, due to the reverse shape and position interference of the outer skeleton limiting block, the object being manipulated is difficult to leave after entering the encapsulation space. Therefore, the gripper can use the effect of the sudden increase in stiffness brought about by the reverse interference of the bidirectional stiffness gripping unit to complete the grasping of large-mass objects.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multimodal gripper, comprising a palm and at least two dexterous fingers connected to the palm, characterized in that, The dexterous finger includes a swing unit and a bidirectional stiffness gripping unit. One end of the swing unit is connected to the palm, and the other end is connected to the bidirectional stiffness gripping unit. The swing unit includes a central limiting layer and a deformable layer connected to both sides of the central limiting layer. The central limiting layer has greater stiffness than the deformable layer. Multiple interconnected and inclined air cavities are formed within the deformable layer. The bidirectional stiffness gripping unit includes a fixedly connected concave air cavity deformable layer and limiting layer, as well as multiple external skeleton limiting blocks connected to the concave air cavity deformable layer. Multiple spacers are formed on the concave air cavity deformable layer. The concave air cavities are distributed and have variable volumes. The force vector formed by the limiting tension and air pressure of the concave air cavities points to the center line of the concave air cavities. One end of the outer skeleton limiting block is fixed inside the concave air cavity, and the other end is provided with a limiting member. The end of the outer skeleton limiting block that extends out of the concave air cavity is formed with a circumferentially covering shell. The limiting member is fixed on the shell. When the deformation layer of the concave air cavity is inflated, the shell can limit the circumferential expansion of the concave air cavity. When the bidirectional stiffness gripping unit is not actively inflated and bends outward, the adjacent limiting members can bend at a certain angle and form and position interference occurs.

2. The multimodal gripper according to claim 1, characterized in that, The palm has a depression in the middle, and the edge of the depression is covered with skin. The skin and the depression form a closed cavity structure. The cavity is filled with small balls. The cavity is also connected to the outside through the air passage of the soft palm unit in the middle and can form negative pressure.

3. A multimodal gripper according to claim 1, characterized in that, The swing unit is connected to the bidirectional stiffness gripping unit through a rotary connection structure and can rotate about the axis of the rotary connection structure. The rotary connection structure is equipped with a limiting partition, which can form and position interference with the rotation of the bidirectional stiffness gripping unit relative to the swing unit.

4. A multimodal gripper according to claim 3, characterized in that, The rotary connection structure includes a connector 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 connector, which extends into the rotating groove, is fixedly connected to a limiting plate. The rotating groove is provided with multiple limiting holes that are adapted to the limiting plate in the axial direction. The other end of the connector is connected to a bidirectional rigidity gripping unit. Both ends of the swing unit are respectively interference-fitted with the first housing and the palm.

5. A multimodal gripper according to claim 1, characterized in that, The limiting component includes a cylindrical body.

6. A multimodal gripper according to claim 1, characterized in that, Multiple oblique air chambers are arranged in a grid pattern, and the oblique air chambers of the two deformation layers are symmetrical about the central confinement layer. The deformation layer includes a left oblique air chamber deformation layer and a right oblique air chamber deformation layer. The left oblique air chamber deformation layer is connected to the left oblique air chamber air passage, and the right oblique air chamber deformation layer is connected to the right oblique air chamber air passage. The oblique air chambers in the left oblique air chamber deformation layer and the right oblique air chamber deformation layer are respectively connected to the left oblique air chamber air passage and the right oblique air chamber air passage.

7. A multimodal gripper according to claim 1, characterized in that, The circumferential wall thickness of the oblique air chamber is thinner than the wall thickness of the front and rear air chambers.

8. A multimodal gripper according to claim 1, characterized in that, The inflation deformation of the bidirectional stiffness gripping unit is concentrated on the inward envelope bending, and the circumferential wall thickness of the deformation layer of the concave air cavity in the bidirectional stiffness gripping unit is thicker than the wall thickness of the concave air cavities on the front and rear sides.

9. A multimodal gripper according to claim 2, characterized in that, A thin-film pressure sensor is provided at the end of the skin facing the object being operated. When the thin-film pressure sensor detects that the adaptive compression of the object being operated reaches the set pressure value, it controls the air path of the central soft hand unit to draw air to form a negative pressure, which automatically covers the object being operated.

10. The grasping method of the multimodal gripper according to any one of claims 1-9, characterized in that, When the angle between the bidirectional stiffness gripping unit and the horizontal plane is greater than a set angle, the gripper is in pneumatic active gripping mode, and the frame limiting block is bent by inflating the bidirectional stiffness gripping unit. When the angle between the bidirectional stiffness gripping unit and the horizontal plane is less than a set angle, the gripper is in self-locking gripping mode. When the mass of the object being manipulated exceeds the range of pneumatic active gripping, the object being manipulated is bent in the opposite direction by the bidirectional stiffness gripping unit to enter the enclosed space and limit the object being manipulated. When the weight of the object exceeds the gripping capacity of the bidirectional stiffness gripping unit in pneumatic active gripping mode, the bidirectional stiffness gripping unit bends in the opposite direction and presses against the inner wall of the object being manipulated to achieve gripping.

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