Variable stiffness flexible gripper

Abstract

This invention provides a rope-driven variable stiffness flexible gripper, comprising a drive assembly, a connecting assembly, a variable stiffness gripping unit, a drive rope, and a sensor assembly. The variable stiffness gripping unit, shaped like a clamp, is fixed to the connecting assembly. The drive rope connects the variable stiffness gripping unit to the drive assembly. Under the pull of the drive rope, the variable stiffness gripping unit opens and closes. The stiffness of the variable stiffness gripping unit is adjusted according to the hardness properties of the object being gripped, as sensed by the sensor assembly, ultimately achieving object gripping. This invention features a simple structure and control, and the gripping unit can envelop and grip objects with a large contact area. Therefore, this flexible gripper has the characteristics of strong gripping adaptability and good gripping accuracy, and can be applied to the gripping of various objects.

Description

Technical Field

[0001] This invention relates to the field of robot end effector, specifically to a rope-driven variable stiffness flexible gripper. Background Technology

[0002] Currently, rigid robotic arms are mostly based on rigid grippers as their structural body. They are widely used in many industrial fields to achieve fast, accurate and stable work when grasping target objects. However, rigid robotic arms are usually designed for objects of specific shapes and sizes. For irregular, curved or irregularly shaped objects, rigid grippers cannot show sufficient adaptability and flexibility, resulting in poor grasping effect.

[0003] With the development of robotic arm technology, soft robotic arms, due to their flexibility and deformability, can better handle irregularly shaped objects and perform more complex grasping and manipulation tasks. This makes soft arms more flexible and adaptable in handling various tasks.

[0004] Furthermore, grasping and delivery are the primary methods by which robots perform human-robot interaction. When performing human-robot interaction tasks, grasping robots must not only execute different tasks but also prioritize human-robot collaboration safety. Compared to traditional rigid grasping robots, soft grasping robots offer the advantage of a higher safety index.

[0005] Chinese patent application CN107718021A discloses a pneumatic multi-finger soft manipulator. All three soft finger units can achieve a wide range of bending and deformation. However, due to its pneumatic drive and the lack of rigid support within the fingers, it suffers from insufficient envelopment of objects during grasping, resulting in unstable gripping. Chinese patent application CN113370241A discloses a mesh-structured multi-finger soft manipulator. This manipulator is driven by strings to open and close four soft fingers, offering a large grasping range. However, it still faces difficulties in grasping small rods and plates. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention aims to provide a rope-driven variable stiffness flexible gripper. This gripper uses a stepper motor to directly drive the rope pulling and gripping unit to open and close the soft hand. It determines the hardness attribute of the object based on the sensing signals collected by the sensor components, and finally achieves variable stiffness intelligent gripping of the object based on the determination result.

[0007] Specifically, the present invention provides a rope-driven variable stiffness flexible gripper, which includes a drive assembly, a connecting assembly, a variable stiffness gripping unit, a drive rope, and a sensor assembly.

[0008] The variable stiffness gripping unit is fixed to the connecting assembly in the shape of a clamp. The driving assembly is connected to the variable stiffness gripping unit by means of the driving rope. Under the pull of the driving rope, the variable stiffness gripping unit opens and closes. The sensor assembly is used to detect the hardness of the gripped object and adjust the stiffness of the variable stiffness gripping unit based on the detected hardness of the gripped object.

[0009] The drive assembly includes a drive motor and a boss disk. The drive motor drives the boss disk to rotate. The upper surface of the boss disk is circular and the lower part is inverted cone. Several circular threading holes of equal size are evenly arranged circumferentially at the edge of the circular disk. The drive rope passes through the threading holes on the disk in sequence.

[0010] The connecting assembly includes a flange, a protective cover, and a connecting seat. The flange is located at the top of the gripper. The upper end of the flange is used to connect with the remote operating arm. The lower end of the flange is connected to the protective cover. The protective cover is in the shape of a boss. The connecting seat is placed inside the protective cover and is used to connect the drive assembly and the variable stiffness gripping unit.

[0011] The variable stiffness gripping unit includes a variable stiffness sealing device and gripping units. Multiple gripping units are stacked together and sealed by the variable stiffness sealing device. The stiffness is dynamically adjusted by changing the internal air pressure of the variable stiffness gripping unit.

[0012] Multiple gripping units are shaped like clamps, with their open ends connected to the protective cover. The ends of the clamps have two rows of evenly spaced wire holes. The grippers on both sides of the gripping unit are the execution ends. The grippers have evenly distributed wire holes along their bottom on both sides. The drive rope passes through the wire holes in sequence and connects to the drive assembly.

[0013] The angle of bending when the variable stiffness gripper unit grips an object The angle between the tangent at the sensor's outermost point and the extension of the sensor's initial position is represented by X, where X represents the displacement value of the soft gripper's bending during grasping. Each bending angle corresponds to a displacement value X, i.e., the bending angle. It is a function that is positively correlated with X;

[0014] The real-time monitored pressure and curvature signals are processed and fused. During the object hardness identification process, the object's hardness is calculated and defined as H. The larger the H value, the greater the object's hardness. The formula for calculating the object's hardness H is:

[0015] ;

[0016] Where F is the contact pressure measured when grasping the object. The measured bending angle;

[0017] The air pressure inside the variable stiffness layer is adjusted based on the calculated object hardness. When the calculated object hardness H is greater than or equal to the hardness threshold H0, the variable stiffness gripping unit is inflated to reduce its stiffness, thereby controlling the robotic arm to stably grip the object.

[0018] Preferably, the bottom of the boss disk is provided with a cylindrical protruding short shaft, which is used to connect the boss disk and the connecting seat by clearance or interference fit with the bearing.

[0019] Preferably, the top of the boss disc has a pin groove for connecting with the motor shaft, and the shaft pin installed at the end of the motor shaft is inserted into the pin groove to drive the boss disc to rotate.

[0020] Preferably, the number of wire holes at the edge of the boss disk surface, the total number of wire holes in the two rows at the opening end of the variable stiffness gripping unit, and the total number of wire holes on both sides of the execution end of the variable stiffness gripping unit are equal.

[0021] Preferably, the drive rope includes a first drive rope and a second drive rope, which are respectively arranged on both sides of the variable stiffness gripping unit and threaded in a parallel or cross manner. The first drive rope or the second drive rope first passes through the side threading hole on the execution end side of the variable stiffness gripping unit, then passes through one row of threading holes at the opening end of the variable stiffness gripping unit, passes through a threading hole on the surface of the boss disk in the drive assembly, and then freely enters and exits the row of threading holes at the opening end of the variable stiffness gripping unit, and finally freely enters the threading hole at the execution end of the variable stiffness gripping unit.

[0022] Preferably, the sensor assembly includes a bending sensor and a thin-film pressure sensor;

[0023] The bending sensor includes a signal conversion unit and a bar-shaped sensing unit. The signal conversion unit is placed in the sensor limiting groove on the side of the protective cover, and the bar-shaped sensing unit is attached to the outer surface of the variable stiffness gripping unit to detect the bending angle when the variable stiffness gripping unit grips an object.

[0024] Preferably, the thin-film pressure sensor is attached to the inner surface of the variable stiffness gripping unit to detect the contact pressure when gripping an object.

[0025] Preferably, the strip sensing unit is a Flex bending sensor.

[0026] Preferably, the variable stiffness gripping unit has at least three layers.

[0027] Preferably, the variable stiffness sealing device is a sealing bag.

[0028] On the other hand, the present invention provides a gripping method for a rope-driven variable stiffness flexible gripper, which includes the following steps:

[0029] S1. In the initial state of the grasping task, the grasping part execution end is open and the drive rope is in a slack state.

[0030] S2. Place the object to be grabbed within the gripping range of the variable stiffness gripping unit, control the motor to rotate, and drive the boss disc to rotate synchronously with it. The drive rope attached to the boss disc passively changes from a slack to a taut state, pulling the grippers on both sides of the variable stiffness gripping unit to retract inward. When the grippers completely wrap around and adhere to the object, control the motor to stop.

[0031] S3. During the grasping process, the hardness attribute of the object is determined based on the sensing signals collected by the sensor components. The air pressure inside the variable stiffness layer is adjusted based on the hardness attribute of the object, thereby changing the stiffness of the variable stiffness grasping unit. Finally, the robot arm is controlled to stably grasp the object to be grasped.

[0032] S4. After the gripping is completed, restore the variable stiffness layer to the initial air pressure state, control the motor to reverse so that the boss disk rotates in the opposite direction, and then cause the drive rope to open the variable stiffness gripping unit outward to place the object. This completes one workflow.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) Since the gripping unit of the present invention is composed of a large-area sheet structure, it can envelop and grip the object with a large contact area when gripping the object, and has good gripping adaptability and gripping accuracy.

[0035] (2) This invention utilizes stepper motors, drive ropes, and other main components to realize the configuration of a soft gripper. The gripper structure and control are simple, and it is convenient and quick to use. The soft gripper uses a stepper motor to directly drive the rope to pull the gripping unit to realize the opening and closing of the soft hand. Based on the sensing signals collected by the sensor components, the hardness attribute of the object is determined, and finally, the object is grasped with variable stiffness intelligently based on the determination result.

[0036] (3) The present invention determines the hardness attribute of an object based on the sensor information collected by the sensor component, and performs variable stiffness intelligent grasping of the object based on the determination result. The stiffness is adjusted in real time according to the hardness of the object to meet the needs of various scenarios. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the three-dimensional structure of the rope-driven variable stiffness flexible gripper of the present invention;

[0038] Figure 2This is a schematic diagram of the overall cross-sectional structure of the rope-driven variable stiffness flexible gripper of the present invention.

[0039] Figure 3 This is a schematic diagram showing the connection between the driving part and the gripping part of the rope-driven variable stiffness flexible gripper of the present invention.

[0040] Figure 4 This is a schematic diagram of the three-dimensional structure of the boss disc of the rope-driven variable stiffness flexible gripper of the present invention.

[0041] Figure 5 This is a three-dimensional structural diagram of the flexible gripper variable stiffness grasping unit of the present invention;

[0042] Figure 6 This is a schematic diagram illustrating the bending angle principle of the Flex sensor of the present invention;

[0043] Figure 7 This is a schematic diagram of another threading mode for the rope-driven variable stiffness flexible gripper of the present invention.

[0044] Figure 8 This is a schematic diagram of the grasping state of the rope-driven variable stiffness flexible gripper of the present invention.

[0045] The main reference numerals in the attached drawings are as follows: 11 boss disc, 111 square pin groove, 112 boss disc wire hole, 113 cylindrical protruding short shaft, 12 drive motor, 121 motor shaft pin, 21 flange, 211 flange threaded hole, 22 protective cover, 221 sensor limiting groove, 23 connecting seat, 231 connecting seat threaded hole, 31 variable stiffness gripping unit execution end wire hole, 32 variable stiffness gripping unit opening end wire hole, 33 threaded hole connecting the variable stiffness gripping unit to the protective cover, 34 threaded hole connecting the variable stiffness gripping unit to the connecting seat, 35 bearing hole, 4 drive rope, 51 bending sensor, and 52 diaphragm pressure sensor. Detailed Implementation

[0046] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0047] like Figures 1-3 As shown, this invention discloses a rope-driven variable stiffness flexible gripper, comprising a drive assembly, a connecting assembly, at least three layers of variable stiffness gripping units 3, a drive rope 4, and a sensor assembly. The flexible variable stiffness gripping units 3 are fixed to the connecting assembly. The drive rope 4 connects the variable stiffness gripping units 3 to the drive assembly. Under the action of the drive rope 4, the flexible variable stiffness gripping units 3 can expand or close, and the stiffness of the variable stiffness gripping units 3 is adjusted in real time based on the object hardness information sensed by the sensor assembly, ultimately achieving real-time intelligent gripping of objects.

[0048] like Figures 3-5As shown, the drive assembly includes a boss disk 11 and a drive motor 12. The upper end of the boss disk 11 is circular, and the lower part is inverted conical. A square pin groove 111 is provided in the center of the disk. The square pin groove 111 cooperates with the motor shaft pin 121 to make the motor shaft drive the boss disk to rotate. The surface of the boss disk 11 is provided with circular wire holes 112 of equal size and evenly arranged in the circumferential direction. The wire holes are used to connect the drive rope 4 and the variable stiffness gripping unit 3. A cylindrical protruding short shaft 113 is provided at the bottom of the boss disk 11. The cylindrical protruding short shaft 113 is connected to the bearing by clearance or interference fit to realize the connection between the boss disk 11 and the connecting seat 23.

[0049] Furthermore, in order to better achieve gripping and palm-enveloping grasping, the number of circular threading holes 112 on the boss disc is preferably 12.

[0050] like Figure 1 and Figure 3 As shown, the connecting assembly includes a flange 21, a protective cover 22, and a connecting seat 23. The flange 21 is located at the top of the entire gripper and is connected to the operating arm by bolts. The bottom of the flange 21 has a threaded hole 211 for connecting the protective cover 22. In order to prevent fatigue damage to the drive unit during operation, the protective cover 22 is set to protect the drive assembly. The upper end of the protective cover 22 is connected to the flange 21, and the bottom end of the protective cover 22 has a protective cover threaded hole for connecting to the variable stiffness gripping unit 3. The connecting seat 23 is a flat plate shape and is engaged with the bottom end of the boss disc 11 by bearings. The surface of the connecting seat 23 has symmetrically distributed threaded holes 231, through which it is connected to the variable stiffness gripping unit 3.

[0051] Specifically, the schematic diagram of the angle of the Flex bending sensor used in this invention is shown below. Figure 6 As shown, this angle represents the angle between the tangent at the sensor's outermost point and the extension of the sensor's initial position. X represents the displacement value of the soft gripper's bending degree during grasping. Figure 6 It can be seen that each bending angle corresponds to an X displacement value, that is, the bending angle. It is a function that is positively correlated with X.

[0052] The real-time monitored pressure and curvature signals are processed and fused using an algorithm. In the process of object hardness identification, a ratio H is defined to represent the object's hardness. The larger the H value, the greater the object's hardness. Therefore:

[0053]

[0054] Where F represents the contact pressure measured when grasping the object. This represents the measured bending angle; under the same conditions, the smaller F is, the greater the bending angle. The larger the value, the smaller the H value; the greater the hardness of an object, the larger the F value. The smaller the value, the larger the calculated H. The hardness characteristic value H is extracted by using the ratio of the pressure applied by the gripper when pressing the object to the bending angle, effectively distinguishing the object's hardness index. Based on the calculated object hardness, the air pressure inside the variable stiffness layer is adjusted. When the calculated object hardness H is greater than or equal to the hardness threshold H0, the variable stiffness gripping unit is inflated to reduce its stiffness, controlling the robotic arm to stably grip the object.

[0055] like Figure 5 The diagram shows a three-dimensional structural schematic of the variable stiffness gripping unit 3. The soft hand variable stiffness gripping unit 3 of the present invention is made of thin sheet materials such as plastic sheet or alloy sheet with a thickness of 0.5-1.2mm. The material is bent into three parts, with the middle part serving as the open end and the two edge parts symmetrical about the middle to form the execution end of the gripper. When selecting the material of the variable stiffness gripping unit, it is required to have sufficient bending strength and load-bearing capacity, so that it does not lose its bending ability when bending and gripping objects, and can freely realize the opening and closing of the variable stiffness gripping unit.

[0056] Furthermore, in order to satisfy both gripping and palm-envelope grasping during grasping, this robot, based on the variable stiffness principle of sheet interference, uses no fewer than three thin sheets to form a variable stiffness grasping unit, such as... Figure 1 The image shows a variable stiffness gripping unit consisting of three thin sheets sealed using a variable stiffness sealing device.

[0057] In order to connect the variable stiffness gripping unit 3 with the boss disk 11, the protective cover 22 and the connecting seat 23, the variable stiffness gripping unit execution end through hole 31 is provided on both sides of the execution end of the variable stiffness gripping unit 3, and the variable stiffness gripping unit opening end through hole 32 is provided on the middle open end. The total number of through holes on the open end and the execution end is 12. In addition, the surface of the opening end of the variable stiffness gripping unit is provided from the inside to the outside with bearing hole 35, threaded hole 34 for connecting the variable stiffness gripping unit to the connecting seat and threaded hole 33 for connecting the variable stiffness gripping unit to the protective cover for their respective connections.

[0058] There are two drive ropes 4 in total, namely the first drive rope and the second drive rope. The two drive ropes pass through the variable stiffness gripping unit 3 and the boss disk 11 in a cross or parallel manner.

[0059] like Figure 3As shown, in this embodiment, the drive rope 4 is threaded in a parallel manner. The parallel winding process is as follows: First, thread one drive rope 4 into the threading hole 31 on either side of the execution end of the variable stiffness gripping unit. Then, thread the drive rope 4 into the threading hole 32 at the opening end of the variable stiffness gripping unit on the opposite side. Next, thread the drive rope 4 into one threading hole 112 of the boss disc. Then, thread the drive rope 4 into the adjacent threading hole 112 of the boss disc in a clockwise or counterclockwise direction. Next, thread the drive rope 4 into the threading hole 32 at the opening end of the variable stiffness gripping unit on the same side. Finally, thread the drive rope 4 into the threading hole 31 at the execution end of the variable stiffness gripping unit on the opposite side. This completes the first threading cycle. Repeating the cycle three times completes the threading work on one side of the gripper. Take another threading rope and repeat the above operation to complete the parallel threading work.

[0060] like Figure 7 As shown, in this embodiment, the drive rope 4 is threaded in a crisscross manner. The crisscross threading process is as follows: First, thread one drive rope 4 into the threading hole 31 on either side of the execution end of the variable stiffness gripping unit. Then, thread the drive rope 4 into a threading hole 32 at the opening end of the variable stiffness gripping unit on the opposite side. Next, thread the drive rope 4 into a threading hole 112 on the boss disc. Then, thread the drive rope 4 into the threading hole 112 adjacent to the boss disc. Next, thread the drive rope 4 into the adjacent threading hole 32 at the opening end of the variable stiffness gripping unit on the same side. Finally, thread the drive rope 4 into the adjacent threading hole 31 at the execution end of the variable stiffness gripping unit on the opposite side. This completes the first threading cycle. Repeating the cycle three times completes the threading work on one side of the gripper. Then, take another threading rope and repeat the above operation to complete the crisscross threading work.

[0061] In specific applications, the drive rope 4 can be a nylon rope or a steel wire rope. In a preferred embodiment of the present invention, a steel wire rope is preferred. The advantage of a steel wire rope is that it has a large load-bearing capacity, and tightening the drive rope can improve the stability and load-bearing capacity when gripping objects.

[0062] The sensor assembly includes a bending degree sensor 51 and a thin film pressure sensor 52. The signal conversion unit of the bending degree sensor 51 is placed in the sensor limiting groove 221 of the protective cover 22. The elongated sensing unit of the bending degree sensor 51 is attached to the outer surface of the variable stiffness gripping unit 3 and opens and closes synchronously with the variable stiffness gripping unit 3. The bending degree sensor is used to detect the bending angle when the variable stiffness gripping unit 3 grips an object.

[0063] The thin-film pressure sensor 52 is attached to the inner surface of the variable stiffness gripping unit 3. In order to better detect the contact pressure between the gripper and the object when gripping the object, we place the circular sensor detection unit at the bottom of the execution end of the variable stiffness gripping unit 3 to achieve better contact detection effect.

[0064] Furthermore, when grasping an object, the hardness attribute of the object is initially determined by the real-time detected bending angle and contact pressure information. The hardness of the variable stiffness grasping unit 3 is adjusted according to the determined hardness attribute of the grasped object, so as to achieve stable grasping of the object.

[0065] On the other hand, the present invention provides a gripping method for a rope-driven variable stiffness flexible gripper, which includes the following steps:

[0066] S1. In the initial state of the grasping task, the grasping part execution end is open and the drive rope is slack.

[0067] S2. Place the object to be grabbed within the gripping range of the variable stiffness gripping unit, control the motor to rotate, and the motor drives the boss disc to rotate synchronously with it. The drive rope attached to the boss disc passively changes from a slack to a taut state, pulling the grippers on both sides of the variable stiffness gripping unit to retract inward. When the grippers completely wrap around and adhere to the object, control the motor to stop.

[0068] S3. During the grasping process, the hardness attribute of the object is first determined based on the sensing signals collected by the sensor components. Then, the air pressure inside the variable stiffness layer is adjusted according to the hardness attribute of the object, thereby changing the stiffness of the variable stiffness grasping unit. Finally, the robotic arm is controlled to stably grasp the object to be grasped.

[0069] S4. After the gripping is completed, restore the variable stiffness layer to the initial air pressure state, control the motor to reverse so that the boss disk rotates in the opposite direction, and then cause the drive rope to open the variable stiffness gripping unit outward to place the object. This completes one workflow. Specific Implementation

[0070] This embodiment takes the grasping of a cylindrical object as an example. The rope-driven variable stiffness flexible gripper includes a drive assembly, a connecting assembly, at least three layers of variable stiffness grasping units 3, a drive rope 4, and a sensor assembly. The soft variable stiffness grasping unit 3 is fixed to the connecting assembly. The drive rope 4 connects the variable stiffness grasping unit 3 to the drive assembly. Under the action of the drive rope 4, the soft variable stiffness grasping unit 3 can unfold or close, and the stiffness of the variable stiffness grasping unit 3 is adjusted in real time according to the object hardness information sensed by the sensor assembly, realizing intelligent grasping of the object. The grasping state is as follows: Figure 8 As shown.

[0071] The drive assembly includes a boss disk 11 and a drive motor 12. The upper part of the boss disk 11 is circular, and the lower part is inverted conical. A square pin groove 111 is provided in the center of the disk. The square pin groove 111 cooperates with the motor shaft pin 121 to make the motor shaft drive the boss disk to rotate. The surface of the boss disk 11 is provided with circular wire holes 112 of equal size and evenly arranged in the circumferential direction. The wire holes are used to connect the drive rope 4 and the variable stiffness gripping unit 3. A cylindrical protruding short shaft is provided at the bottom of the boss disk 11. The cylindrical protruding short shaft and the bearing are connected to the boss disk 11 and the connecting seat 23 by clearance or interference fit.

[0072] The specific scraping process is as follows:

[0073] S1. In the initial state of the grasping task, the grasping part execution end is open and the drive rope is slack.

[0074] S2. Place the cylindrical object to be gripped within the gripping range of the variable stiffness gripping unit, control the motor to rotate, and the motor drives the boss disc to rotate synchronously with it. The drive rope attached to the boss disc passively changes from a slack state to a taut state, pulling the grippers on both sides of the variable stiffness gripping unit to retract inward. When the grippers completely wrap around and adhere to the object, control the motor to stop.

[0075] S3. During grasping, the hardness attribute of the object is first determined based on the sensing signals collected by the sensor components. Since the cylindrical object has a high hardness attribute, the packaging bag needs to be inflated first to adjust the air pressure inside the variable stiffness layer, reducing the stiffness of the variable stiffness grasping unit. This allows the robotic arm to stably grasp the object. The state of the grasped object is as follows: Figure 7 As shown.

[0076] S4. After the gripping is completed, restore the variable stiffness layer to the initial air pressure state, control the motor to reverse so that the boss disk rotates in the opposite direction, and then cause the drive rope to open the variable stiffness gripping unit outward to place the object. This completes one workflow.

[0077] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A rope-driven variable stiffness flexible gripper, characterized in that: It includes drive components, connection components, variable stiffness gripping units, drive ropes, and sensor components; The variable stiffness gripping unit is fixed to the connecting assembly in the shape of a clamp. The driving assembly is connected to the variable stiffness gripping unit by means of the driving rope. Under the pull of the driving rope, the variable stiffness gripping unit opens and closes. The sensor assembly is used to detect the hardness of the gripped object and adjust the stiffness of the variable stiffness gripping unit based on the detected hardness of the gripped object. The drive assembly includes a drive motor and a boss disk. The drive motor drives the boss disk to rotate. The upper surface of the boss disk is circular and the lower part is inverted cone shape. Several circular wire holes of equal size are evenly arranged circumferentially at the edge of the circular disk. The connecting assembly includes a flange, a protective cover, and a connecting seat. The flange is located at the top of the gripper. The upper end of the flange is used to connect with the remote operating arm. The lower end of the flange is connected to the protective cover. The protective cover is in the shape of a boss. The connecting seat is placed inside the protective cover and is used to connect the drive assembly and the variable stiffness gripping unit. The variable stiffness gripping unit includes a variable stiffness sealing device and gripping units. Multiple gripping units are stacked together and encapsulated by the variable stiffness sealing device. The stiffness is dynamically adjusted by changing the internal air pressure of the variable stiffness gripping unit. Multiple gripping units are shaped like clamps, with their open ends connected to a protective cover. The ends of the clamps have two rows of evenly spaced wire holes. The grippers on both sides of the gripping unit are the execution ends, and the grippers have evenly distributed wire holes along their bottom on both sides. The drive rope includes a first drive rope and a second drive rope, which are respectively arranged on both sides of the variable stiffness gripping unit and are threaded in a parallel or cross manner. Bending angle when a variable stiffness gripping unit grips an object θ The angle between the tangent at the sensor's outermost point and the extension of the sensor's initial position is represented by X. X represents the displacement value of the flexible gripper's bending during grasping; each bending angle corresponds to a displacement value X, i.e., the bending angle. θ It is a function that is positively correlated with X; The real-time monitored pressure and bending angle signals are processed and fused. During the object hardness identification process, the object's hardness is calculated and defined as H. The larger the H value, the greater the object's hardness. The formula for calculating the object's hardness H is: ； Where F is the contact pressure measured when grasping the object. θ The measured bending angle; The air pressure inside the variable stiffness gripping unit is adjusted based on the calculated object hardness. When the calculated object hardness H is greater than or equal to the hardness threshold H0, the variable stiffness gripping unit is inflated to reduce its stiffness, thereby controlling the flexible gripper to stably grip the object.

2. The rope-driven variable stiffness flexible gripper according to claim 1, characterized in that: The top of the boss disk is provided with a pin groove for connecting to the motor shaft of the drive motor. The end of the motor shaft is inserted into the pin groove by means of a shaft pin to drive the boss disk to rotate.

3. The rope-driven variable stiffness flexible gripper according to claim 2, characterized in that: The number of wire holes at the edge of the boss disk surface, the total number of wire holes in the two rows at the opening end of the variable stiffness gripping unit, and the total number of wire holes on both sides of the execution end of the variable stiffness gripping unit are equal.

4. The rope-driven variable stiffness flexible gripper according to claim 1, characterized in that: The sensor assembly includes a bending sensor and a thin-film pressure sensor; The bending sensor includes a signal conversion unit and a bar-shaped sensing unit. The signal conversion unit is placed in the sensor limiting groove on the side of the protective cover, and the bar-shaped sensing unit is attached to the outer surface of the variable stiffness gripping unit to detect the bending angle when the variable stiffness gripping unit grips an object.

5. The rope-driven variable stiffness flexible gripper according to claim 4, characterized in that: The thin-film pressure sensor is attached to the inner surface of the variable stiffness gripping unit and is used to detect the contact pressure when gripping an object.

6. The rope-driven variable stiffness flexible gripper according to claim 4, characterized in that: The strip sensing unit uses a Flex bending sensor.

7. The rope-driven variable stiffness flexible gripper according to claim 1, characterized in that: The variable stiffness gripping unit has at least three layers of gripping units.

8. The rope-driven variable stiffness flexible gripper according to claim 1, characterized in that: The variable stiffness sealing device is a sealing bag.

9. A gripping method based on the rope-driven variable stiffness flexible gripper of claim 1, characterized in that: It includes the following steps: S1. In the initial state of the grasping task, the grasping unit execution end is open and the drive rope is slack. S2. Place the object to be grabbed within the gripping range of the variable stiffness gripping unit, control the motor to rotate, and drive the boss disc to rotate synchronously with it. The drive rope attached to the boss disc passively changes from a slack state to a taut state, pulling the grippers on both sides of the variable stiffness gripping unit to retract inward. When the grippers completely wrap around and adhere to the object, control the motor to stop. S3. During the grasping process, the hardness attribute of the object is determined based on the sensing signal collected by the sensor component. Based on the hardness attribute of the object, the air pressure inside the variable stiffness grasping unit is adjusted, thereby changing the stiffness of the variable stiffness grasping unit. Finally, the flexible gripper is controlled to stably grasp the object to be grasped. S4. After the gripping is completed, restore the variable stiffness gripping unit to the initial air pressure state, control the motor to reverse so that the boss disc rotates in the opposite direction, and then cause the drive rope to open the variable stiffness gripping unit outward to place the object. This completes one workflow.

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