Semi-enclosed soft gripper device with variable stiffness and method for adjusting thereof

Abstract

The application provides a semi-wrapping soft gripper device with variable rigidity and a regulating method thereof, which comprises a variable rigidity bag, a tendon, an alloy frame, a connecting seat assembly, a fixing seat and an air pump. The output end of the air pump is connected with the input end of the variable rigidity bag through an air pipe, the mounting end of the variable rigidity bag is fixedly connected with the third end of the alloy frame and the front end cover of the connecting seat, the first mounting end of the tendon is fixedly connected with the first retention hole of the variable rigidity bag, and the second mounting end of the tendon is fixedly connected with the second retention hole. The second mounting end of the first fixing seat is fixedly connected with the input end of the first transmission component, the first transmission component is engaged with the second transmission component, and the connecting seat threaded hole of the second fixing seat is fixedly connected with the built-in threaded hole of the connecting seat protrusion. The application drives the transmission component to drive the tendon to rotate uniformly and circumferentially without intersection, so that the variable rigidity bag is deformed to be concave, at the same time, the inside of the variable rigidity bag is in a negative pressure state, the grabbing assembly is attached to the surface of the grabbed object, and self-adaption and semi-covering grabbing are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft gripper, and particularly relates to a semi-wrapping soft gripper device with variable rigidity and a regulating method thereof. BACKGROUND

[0002] At present, most robot grippers are rigid, but the environmental adaptability of rigid hands is poor, and they lack compliance and are not suitable for grasping fragile, soft and special-shaped objects. In recent years, due to the good environmental adaptability, compliance and flexibility of soft robots, many materials can be used in the end effector of soft hands, so that objects of various shapes can be wrapped and grasped according to the change of their shapes. In order to improve the stability and load capacity of soft hands during grasping, the end effector based on the blocking variable rigidity method makes the variable rigidity soft gripper exhibit strong stability and high load capacity during grasping, but it lacks in grasping efficiency and scene adaptability.

[0003] Chinese patent CN111360856A discloses a wrapping soft gripper, which keeps open state during work, approaches the object from top to bottom, and realizes closed grasping of the object when the wrapping device completely wraps the object. Chinese patent CN113370241A discloses a transverse and longitudinal coupled pneumatic multi-finger soft manipulator, which completes a grasping process by driving the pneumatic fingers to contract the telescopic part transversely. The above two grasping modes belong to top-down full-wrapping grasping, and whether it is a bag-shaped wrapping device or a telescopic device at the bottom, the open range of the soft hand is limited due to its configuration in the full-wrapping mode, and the object needs to be completely wrapped before stable lifting during grasping, so it has certain difficulty in grasping special-shaped objects such as plate-shaped, bottle-shaped, rod-shaped or pipe-shaped objects.

[0004] At present, full-wrapping soft grippers account for the main part of soft hands, and mainly have problems such as insufficient adaptability and complicated control. The semi-wrapping soft gripper device with variable rigidity proposed in the present application can solve the problem of insufficient adaptability in grasping special-shaped objects, and the manipulator can be applied in fruit picking, object rapid transfer and other scenes. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a semi-wrapped soft gripper device with variable stiffness and an adjusting method thereof, which is driven by the meshing transmission of the first transmission component and the second transmission component, so that the tendon connected with the second retention hole in the second transmission component rotates uniformly along the circumference of the second transmission component without crossing, causing the variable stiffness bag to be deformed by concave from inside to outside, while the variable stiffness bag is under the pressure of the air pump, so that the inside of the variable stiffness bag is in a negative pressure state, and the gripping assembly is attached to the surface of the object to be gripped in a gripping state, achieving a self-adaptive and semi-coated gripping state, and the whole device has the advantages of simple structure, strong adaptability and large gripping range.

[0006] The present application provides a semi-wrapped soft gripper device with variable stiffness, which comprises a variable stiffness bag, a tendon, an alloy frame, a connecting seat assembly, a first fixed seat, a second fixed seat, an air pump and an air pipe. The connecting seat assembly comprises a connecting seat rear end cover, a connecting seat protrusion, a connecting seat front end cover, a first transmission component, a second transmission component, an internal thread hole, a gear key groove, a second retention hole and a pin hole, the first end of the connecting seat rear end cover is provided with a connecting seat protrusion, the connecting seat protrusion is provided with an internal thread hole, the mounting end of the connecting seat rear end cover is connected with the mounting end of the connecting seat front end cover, the mounting ends of the first transmission component and the second transmission component are connected with the first end and the second end of the connecting seat front end cover respectively, the circumference of the second transmission component is symmetrically provided with a gear key groove, the inside of the gear key groove is provided with a second retention hole, and one side of the mounting end of the second transmission component is provided with a pin hole. The inside of the variable stiffness bag is uniformly provided with a variable stiffness layer filler, the output end of the air pump is connected with the first end of the air pipe, the second end of the air pipe is connected with the input end of the variable stiffness bag, the first retention hole of the variable stiffness bag coincides with the first retention hole of the alloy frame, the sheet-shaped pin of the alloy frame is fixedly connected with the pin hole of the second transmission component, the first mounting end of the tendon is fixedly connected with the first retention hole, the second mounting end of the tendon is fixedly connected with the second retention hole, and the tendon is uniformly distributed in a clockwise non-crossing manner on the second transmission component and the variable stiffness bag. The first mounting end of the first fixed seat is provided with a flange, the second mounting end of the first fixed seat is fixedly connected with the input end of the first transmission component, the first transmission component is meshingly connected with the second transmission component, and the connecting seat threaded hole of the second fixed seat is fixedly connected with the internal thread hole of the connecting seat protrusion.

[0007] Preferably, the first transmission component and the second transmission component constitute a transmission assembly, the transmission assembly, the first fixed seat, the second fixed seat and the connecting seat assembly constitute a driving assembly, and the alloy frame, the tendon and the variable stiffness bag constitute a gripping assembly.

[0008] Preferably, the alloy frame comprises a short arc strip, a long arc strip, a connecting strip and a sheet-shaped pin, the short arc strip has a semi-optimal arc shape, the semi-optimal arc has a maximum radius smaller than a maximum radius of an outer tangent circle of a front end cover of a connecting seat connected to the short arc strip, and one end of the short arc strip is provided with a sheet-shaped pin; the long arc strip has a semi-poor arc shape, and a first reserved hole is uniformly distributed along an edge of an upper surface of the long arc strip.

[0009] Preferably, the number of the circular holes of the long arc strip, the number of the first reserved holes, the number of the second reserved holes and the number of the tendons are equal.

[0010] Preferably, the surface of the variable stiffness bag is concave from two sides to the inside, the variable stiffness layer filler adopts one or more variable stiffness layer fillers selected from a friction plate, a granular solid, a fiber, a foam and a debris, and the stiffness is adjusted by changing the air pressure in the variable stiffness bag.

[0011] Preferably, the mounting axis of the first fixing seat and the mounting axis of the second fixing seat are parallel, the mounting axis of the first fixing seat and the axis of the first transmission component are on the same straight line, and the mounting axis of the second fixing seat and the axis of the second transmission component are on the same straight line.

[0012] In another aspect of the present application, a regulating method using the aforementioned semi-wrapped soft gripper device with variable stiffness is provided, which comprises the following steps:

[0013] S1, in the initial state of grabbing, the grabbing assembly is in a relaxed state, the first transmission component connected to the motor through the first fixing seat is started, and the second transmission component is engaged and rotated under the driving of the first transmission component.

[0014] S2, the tendon connected to the second reserved hole on the second transmission component rotates uniformly in the circumferential direction without intersection, the alloy frame is deformed under the driving of the stretching of the tendon, so as to drive the variable stiffness bag to be concave inward.

[0015] S3, the air pump is started to perform air extraction on the inside of the variable stiffness bag through the air pipe, so that the variable stiffness bag is deformed in the whole shrinkage, so that the variable stiffness bag is attached to the surface of the grabbed object to realize semi-wrapped grabbing.

[0016] S4, after the grabbing is completed, the air pump is closed, and the first transmission component connected to the motor through the first fixing seat is rotated in the opposite direction to that in S1, and the tendon connected to the second reserved hole on the second transmission component rotates uniformly in the circumferential direction without intersection in the opposite direction to that in S1, so that the alloy frame returns to the state before deformation, so that the variable stiffness bag returns to the initial state.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] 1. The present application realizes the configuration of soft gripper by using motor, negative pressure assembly, tendon and variable stiffness layer. The motor drives the transmission mechanism to drive the tendon to rotate and form a palm shape with the variable stiffness bag. The palm part is shaped by the negative pressure assembly. It can grasp many irregular objects and quickly pick up long rod-shaped, plate-shaped and bottle-shaped target objects in a "side grip" manner. Under the influence of variable stiffness, it can realize the performance of controllable stiffness and flexibility, so as to improve the wrapping and adaptability during grasping.

[0019] 2. Compared with the full-wrapping and closed soft gripper, the present application realizes the damage-free grasping of objects in a side grip or grip manner, can stably grasp irregular objects such as plates, rods and bottles, and can realize the transfer actions such as holding, gripping or lifting after grasping. It has great application prospect in fruit picking, object rapid transfer and other occasions. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the overall structure diagram of the semi-wrapping soft gripper device with variable stiffness of the present application.

[0021] Figure 2 It is the structure diagram of the transmission assembly in the semi-wrapping soft gripper device with variable stiffness of the present application.

[0022] Figure 3 It is the overall sectional view of the semi-wrapping soft gripper device with variable stiffness of the present application.

[0023] Figure 4 It is the structure diagram of the variable stiffness layer in the semi-wrapping soft gripper device with variable stiffness of the present application.

[0024] Figure 5 It is the state diagram when the semi-wrapping soft gripper device with variable stiffness of the present application grasps objects.

[0025] Figure 6 It is the structure diagram of the alloy frame in the semi-wrapping soft gripper device with variable stiffness of the present application.

[0026] MAIN REFERENCE NUMBERS:

[0027] Variable stiffness bag 1, variable stiffness layer filler 11, tendon 2, alloy frame 3, first retaining hole 31, short circular arc strip 32, sheet-shaped pin 33, connecting strip 34, long circular arc strip 35, connecting seat assembly 4, connecting seat rear end cover 41, connecting seat protrusion 42, connecting seat front end cover 43, first transmission part 44, second transmission part 45, built-in threaded hole 46, gear key groove 47, second retaining hole 48, pin hole 49, first fixed seat 5, second fixed seat 6, connecting seat threaded hole 61, air pump 7, air pipe 8. DETAILED DESCRIPTION

[0028] In order to make the technical content, structural features, achieved purposes and effects of the present application clear, the following will be described in detail in combination with the drawings of the specification.

[0029] The semi-wrapped soft gripper device with variable stiffness can solve the problem of insufficient adaptability of full-wrapped grippers when grabbing special-shaped objects. The gripper is designed as a structure imitating the shape of a human palm, simulating the state of a human hand when grabbing objects, as shown in Figure 1 and Figure 3 , including a variable stiffness bag 1, a tendon 2, an alloy frame 3, a connecting seat assembly 4, a first fixed seat 5, a second fixed seat 6, an air pump 7 and an air pipe 8.

[0030] The variable stiffness bag 1 can be stitched from materials such as rubber or silicone with certain flexibility and good sealing to ensure the switching of the positive and negative pressure states inside the variable stiffness bag 1, and has gas holes on the side for gas exchange with the outside. The tendon 2 can be made of materials such as linear sensors and rubber with good toughness to ensure that it will not break or be damaged during work; the alloy frame 3 can be made of metal sheets with low strength, good toughness and elasticity to ensure that it will not be damaged during grabbing as the variable stiffness bag 1 deforms; the components of other grabbing assemblies and driving assemblies can be made by 3D printing.

[0031] The connecting seat assembly 4, as shown in Figure 1 , Figure 2 and Figure 3 , includes a connecting seat rear end cover 41, a connecting seat protrusion 42, a connecting seat front end cover 43, a first transmission component 44, a second transmission component 45, an internal thread hole 46, a gear key groove 47, a second retention hole 48 and a pin hole 49. The connecting seat front end cover 43 is in the shape of an inverted pear-shaped shell, the first end of the connecting seat rear end cover 41 is provided with the connecting seat protrusion 42, the side of the connecting seat protrusion 42 is uniformly distributed with multiple groups of equal number of internal thread holes 46 along the circumferential direction of the circular bottom surface at the end, the mounting end of the connecting seat rear end cover 41 is connected with the mounting end of the connecting seat front end cover 43, the mounting ends of the first transmission component 44 and the second transmission component 45 are connected with the first end and the second end of the connecting seat front end cover 43 respectively, the second transmission component 45 is symmetrically provided with the gear key groove 47 on the circumference, the inside of the gear key groove 47 is provided with the second retention hole 48, and one side of the mounting end of the second transmission component 45 is provided with the pin hole 49. Further, in order to realize the semi-wrapped state of the device, the number of gear key grooves 47 is preferably 4, and in the initial position, i.e. the non-working state, the gear key grooves 47 are uniformly arranged in the lower half of the second transmission component 45.

[0032] As shown in Figure 4As shown, the inside of the variable stiffness bag 1 is uniformly provided with a variable stiffness layer filler 11, the output end of the air pump 7 is connected with the first end of the air pipe 8, the second end of the air pipe 8 is connected with the input end of the variable stiffness bag 1, the interface part is stitched under the condition that the inside of the variable stiffness bag 1 is closed, the first retaining hole 31 of the variable stiffness bag 1 coincides with the first retaining hole 31 of the alloy rack 3, the fixed end of the variable stiffness bag 1 is stitched and connected with the long circular arc strip 35 of the alloy rack 3, the sheet-shaped pin 33 of the alloy rack 3 is fixedly connected with the pin hole 49 of the second transmission component 45, the first mounting end of the tendon 2 is in the form of needle threading, sequentially passes through the first retaining hole 31 of the alloy rack 3 and the variable stiffness bag 1, and the variable stiffness bag is attached to the surface of the alloy rack 3, the tendon 2 is knotted and fixed after the perforation, the second mounting end of the tendon 2 is fixedly connected with the second retaining hole 48, and the two are combined into one, and the whole is in the form of a half-wrapped palm, the tendon 2 is evenly distributed in the circumferential direction of the second transmission component 45 and the variable stiffness bag 1 in the form of clockwise non-crossing, and the tendon 2 rotates together with the second transmission component 45.

[0033] The first mounting end of the first fixed seat 5 is provided with a flange plate, a plurality of groups of equal number of threaded holes are uniformly distributed on the side surface of the flange plate, and the flange plate is used for being connected with a driving device and a mechanical arm end, the driving device can be selected from a small stepping motor or a servo motor, under the condition that the gripping force can be met, a lighter motor is selected, the second mounting end of the first fixed seat 5 is fixedly connected with the input end of the first transmission component 44, the first transmission component 44 is engagedly connected with the second transmission component 45, the threaded hole 61 of the connecting seat of the second fixed seat 6 is fixedly connected with the built-in threaded hole 46 of the connecting seat protrusion 42 through a screw, the first fixed seat 5 is fixedly and matchingly connected with the fixed end of the connecting seat rear end cover 41, and the built-in transmission assembly of the connecting seat assembly 4 leaves a certain gap with the connecting piece assembly 4.

[0034] In a preferred embodiment of the present application, the first transmission component 44 and the second transmission component 45 constitute a transmission assembly, the first transmission component 44 is driven by an external driving device to complete transmission movement, the internal transmission assembly can adopt belt transmission, gear transmission or chain transmission, and a circular hole is arranged on the built-in transmission assembly for being connected with the tendon 2. Further, the present application adopts gear transmission with a transmission ratio of two based on the purposes of stable gripping and high precision.

[0035] The transmission assembly, the first fixed seat 5, the second fixed seat 6 and the connecting seat assembly 4 constitute a driving assembly, the transmission mechanism is located in the inside of the connecting seat assembly 4, the driving assembly is located at the rear end of the whole device, the alloy rack 3, the tendon 2 and the variable stiffness bag 1 constitute a gripping assembly, and the gripping assembly is fixedly installed at the front end of the whole device.

[0036] The alloy rack 3 is in the form of a curved long strip and is welded by three metal strips, is attached and fixed on the surface of the variable stiffness bag 1, and is used for supporting the variable stiffness bag 1 and restraining the deformation thereof, likeFigure 6 As shown, it comprises a short circular arc strip 32, a long circular arc strip 35, a connecting strip 34 and a sheet-shaped pin 33, the outer shape of the short circular arc strip 32 is a semi-arc of maximum radius smaller than the maximum outer tangent circle radius of the connecting seat front end cover 43 connected thereto, and one end of the short circular arc strip 32 is provided with the sheet-shaped pin 33 connected with the transmission assembly. The outer shape of the long circular arc strip 35 is a semi-arc of maximum radius, and the upper surface of the long circular arc strip 35 is uniformly distributed with the first retaining holes 31 along the edge. Preferably, the number of the circular holes of the long circular arc strip 35, the number of the first retaining holes 31, the number of the second retaining holes 48 and the number of the tendons 2 are equal.

[0037] Specifically, the surface of the variable stiffness bag 1 is recessed from both sides to the inside, the variable stiffness layer filler 11 can adopt one or more interference modes such as layer interference, particle interference and fiber interference to realize stiffness adjustment, and therefore one or more variable stiffness layer fillers such as friction plate, granular solid, fiber, foam and debris can be adopted, the purpose being to improve the stability of the grabbing process and enhance the load capacity of the soft gripper when grabbing objects. The stiffness change is realized by means of negative pressure, and the switching of the negative pressure mode is realized by charging and discharging the variable stiffness bag 1 through the air pipe 8 connected with the air pump 7, the stiffness adjustment is realized by changing the internal air pressure of the variable stiffness bag 1, and when the variable stiffness bag 1 is in a negative pressure state, its shape is contracted to be flat, and is attached to the surface of the grabbed object to realize variable stiffness grabbing.

[0038] The mounting axis of the first fixed seat 5 and the mounting axis of the second fixed seat 6 are parallel, the mounting axis of the first fixed seat 5 and the axis of the first transmission component 44 are on the same straight line, and the mounting axis of the second fixed seat 6 and the axis of the second transmission component 45 are on the same straight line.

[0039] The variable stiffness semi-wrapping soft gripper device and the adjusting method thereof will be further described in combination with embodiments as follows:

[0040] The adjusting method of the variable stiffness semi-wrapping soft gripper device, comprising the following steps:

[0041] S1, in the initial state of grabbing, the grabbing assembly is in a relaxed state, the front end of the device is in an unfolded state like a human palm, the first transmission component 44 connected with the motor through the first fixed seat 5 is started, and the second transmission component 45 is driven to rotate.

[0042] S2, the tendons 2 connected with the second retaining holes 48 on the second transmission component 45 rotate uniformly without intersection in the circumferential direction, since the tendons 2 have elasticity and scalability, and are attached to the surface of the alloy frame 3, at the same time, the alloy frame 3 is deformed under the stretching of the tendons 2, the variable stiffness bag 1 gradually presents a human hand gripping state like a human palm, so as to drive the variable stiffness bag 1 to be recessed inward and be attached to the surface of the grabbed object.

[0043] S3, start the air pump 7 through the trachea 8 on the inside of the variable stiffness bag 1 row of suction, vacuum negative pressure state, so that the variable stiffness bag 1 overall shrinkage deformation, so that the variable stiffness bag 1 adhere to the surface of the object to be grabbed, solid particles in the variable stiffness bag 1 in the state of negative pressure, internal generate huge normal force, thus will produce friction will prevent the deformation of the blocking structure, eventually the variable stiffness bag 1 adhere to the surface of the object to be grabbed, realize the stable grasp of the object, such as Figure 5

[0044] In a preferred embodiment of the present application, the variable stiffness layer filler 11 is a solid particle, which is stitched in the variable stiffness bag 1. In a free state, the solid particles are irregularly arranged inside the variable stiffness bag 1 and can float freely. When the variable stiffness bag 1 is in a negative pressure or vacuum state, the gap between the solid particles is reduced, thereby generating friction between the solid particles to achieve the effect of variable stiffness.

[0045] S4, after the end of the grab, close the air pump 7, at the same time through the first fixed seat 5 connected to the motor of the first transmission component 44 in the opposite direction of rotation in S1 rotation, with the second transmission component 45 on the second retention hole 48 connected tendon 2 along the circumferential non-crossing uniform speed to the opposite direction of rotation in S1, make the alloy frame 3 restore the state before deformation, so that the variable stiffness bag 1 overall recovery to the initial state.

[0046] The above-described embodiments are only preferred embodiments of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.​

Claims

1. A semi-wrapped soft gripper device with variable stiffness, comprising a variable stiffness bag, a tendon, an alloy frame, a connecting seat assembly, a first fixed seat, a second fixed seat and a gas pump, characterized in that, the connecting seat assembly comprises a connecting seat rear end cover, a connecting seat protrusion, a connecting seat front end cover, a first transmission component, a second transmission component, an internal thread hole, a gear key groove, a second retention hole and a pin hole, the first end of the connecting seat rear end cover is provided with a connecting seat protrusion, the connecting seat protrusion is provided with an internal thread hole, the mounting end of the connecting seat rear end cover and the mounting end of the connecting seat front end cover are connected, the mounting ends of the first transmission component and the second transmission component are connected with the first end and the second end of the connecting seat front end cover respectively, the second transmission component is symmetrically provided with a gear key groove on the circumference, the inside of the gear key groove is provided with a second retention hole, and one side of the mounting end of the second transmission component is provided with a pin hole; the inside of the variable stiffness bag is uniformly provided with a variable stiffness layer filler, the output end of the gas pump is connected with a first end of a gas pipe, a second end of the gas pipe is connected with an input end of the variable stiffness bag, a first retention hole of the variable stiffness bag coincides with a first retention hole of the alloy frame, a sheet-shaped pin of the alloy frame is fixedly connected with the pin hole of the second transmission component, a first mounting end of the tendon is fixedly connected with the first retention hole, a second mounting end of the tendon is fixedly connected with the second retention hole, and the tendon is evenly distributed in a clockwise non-crossing manner on the second transmission component and the variable stiffness bag; the first mounting end of the first fixed seat is provided with a flange, the second mounting end of the first fixed seat is fixedly connected with the input end of the first transmission component, the first transmission component is engagedly connected with the second transmission component, and the connecting seat thread hole of the second fixed seat is fixedly connected with the internal thread hole of the connecting seat protrusion.

2. The semi-wrapped soft body gripper device with variable stiffness of claim 1, wherein, The first transmission component and the second transmission component constitute a transmission assembly, the transmission assembly, the first fixed seat, the second fixed seat and the connecting seat assembly constitute a driving assembly, and the alloy frame, the tendon and the variable stiffness bag constitute a gripping assembly.

3. The semi-wrapped soft body gripper device with variable stiffness of claim 1, wherein, The alloy frame comprises a short circular arc strip, a long circular arc strip, a connecting strip and a sheet-shaped pin, the outer shape of the short circular arc strip is a half superior arc, the maximum radius of the half superior arc is smaller than the maximum circumscribed circle radius of the connecting seat front end cover connected therewith, and one end of the short circular arc strip is provided with a sheet-shaped pin; the outer shape of the long circular arc strip is a half inferior arc, and the upper surface of the long circular arc strip is uniformly distributed with first retention holes along the edge.

4. The semi-wrapped soft body gripper device with variable stiffness of claim 3, wherein, The number of first retention holes of the variable stiffness bag, the number of first retention holes of the alloy frame, the number of second retention holes and the number of tendons are equal.

5. The semi-wrapped soft body gripper device with variable stiffness of claim 1, wherein, The surface of the variable stiffness bag is recessed from both sides to the inside, the variable stiffness layer filler adopts one or more variable stiffness layer fillers of a friction plate, a granular solid, a fiber, a foam and a debris, and the stiffness is adjusted by changing the air pressure in the variable stiffness bag.

6. The semi-wrapped soft body gripper device with variable stiffness of claim 1, wherein, The mounting axis of the first fixed seat and the mounting axis of the second fixed seat are parallel, the mounting axis of the first fixed seat and the axis of the first transmission component are on the same straight line, and the mounting axis of the second fixed seat and the axis of the second transmission component are on the same straight line.

7. A method of adjusting a semi-wrapped soft gripper device with variable stiffness according to claim 2, characterized in that, It comprises the following steps: S1, in the initial state of grabbing, the grabbing assembly is in a relaxed state, the first transmission component connected with the motor through the first fixed seat is started, and the second transmission component is engaged to rotate under the driving of the first transmission component; S2, the tendon connected with the second reserved hole on the second transmission component rotates uniformly and circumferentially without intersection, the alloy frame is deformed under the stretching of the tendon, so as to drive the variable stiffness bag to be concave inward; S3, the air pump is started to perform air extraction inside the variable stiffness bag through the air pipe, so that the variable stiffness bag is deformed to shrink as a whole, so that the variable stiffness bag is attached to the surface of the grabbed object to realize semi-enclosed grabbing; S4, after the grabbing is completed, the air pump is closed, the first transmission component connected with the motor through the first fixed seat is rotated in the opposite direction to that in S1, the tendon connected with the second reserved hole on the second transmission component rotates uniformly and circumferentially without intersection in the opposite direction to that in S1, the alloy frame returns to the state before deformation, so that the variable stiffness bag returns to the initial state as a whole.

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