Axial stiffness variable soft actuator based on soft tooth structure engagement slip

Abstract

The present application relates to a kind of axial variable stiffness soft driver based on soft tooth structure engagement slip, it solves the technical problems that existing soft driver lacks resistance structure along the direction of movement, it is difficult to meet axial stiffness continuous adjustment, it is difficult to assist external structure to realize resistance movement, it is difficult to meet the requirements of small volume and light weight, deformation degree is not detected when moving, leading to unable to realize accurate control, it includes drive core body and soft damping body, drive core body includes axial flexible pipe, fabric wrapping layer, wire rope winding layer, flexible coating and pipeline one, axial flexible pipe is equipped with axial drive cavity, soft damping body includes radial expansion cylinder, outer cylinder, pipeline two, rear end cover and front end cover, the periphery of radial expansion cylinder is equipped with several inner layer low modulus soft teeth, the inner wall of outer cylinder is equipped with several outer layer high modulus soft teeth.The present application is widely applied to medical rehabilitation, exoskeleton, interactive game, wearable device, soft robot and other fields human motion driving, resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft actuator, in particular to an axial variable stiffness soft actuator based on soft tooth structure meshing slip. BACKGROUND

[0002] In the technical field of wearable devices, soft robots and exoskeletons, soft actuators are key components. Due to the advantages of soft actuators such as softness, comfort, safety, controllability, low cost and wide application, they are widely used. In medical rehabilitation and interactive game scenarios, soft actuators can drive or hinder human limbs to complete a predetermined movement, thereby achieving a predetermined movement goal.

[0003] The working principle of soft actuators is mainly achieved by bending, stretching, twisting and deforming. At present, according to the driving and resistance along the axial direction, the soft actuators mainly have the following driving and resistance modes:

[0004] (1) Axial driving is achieved by wire, shape memory alloy or pneumatic. The shape memory alloy driving mode can refer to the invention patent application with the application publication number CN115352544A, and the pneumatic mode can refer to the invention patent application with the application publication number CN115817665A. However, these modes can only achieve axial driving or assistance for the actuator, load and fixed non-powered external structure. Due to the lack of resistance structure along the movement direction, it is difficult to provide axial resistance to the powered external structure to hinder its axial movement, that is, it is difficult to assist the external structure to achieve resistance movement.

[0005] (2) The stiffness control is achieved by using the internal unit blockage state change to resist externally. Specifically, particles, fibers or planar structures are filled in the air bag. When the air bag is pumped out, the particles, fibers or planar structures are compressed together to exhibit a certain stiffness externally. However, this mode is difficult to achieve continuous stiffness change, and it is almost impossible to deform axially at high stiffness. Therefore, it is only suitable for axial deformation at low stiffness and vertical load at high bending stiffness, and is not suitable for driving and resistance with continuous axial stiffness adjustment.

[0006] (3) The stiffness control is achieved by using the phase change of polymer or low melting point alloy material to resist externally. This mode can achieve axial driving and continuous variable stiffness resistance, but the temperature required for phase change is often higher than the body temperature and the adjustment time is relatively long. In addition, the increase of flow channel and thermal insulation layer will increase the overall weight and volume. Therefore, the high-temperature safety hazard and the problems of weight and volume make this mode not suitable for long-term safe and comfortable wearing.

[0007] (4) Adjusting the axial stiffness by using the principle of electrostatic adsorption to realize external resistance, specifically, the electrostatic adsorption between the charged electrode plates realizes the attraction between the plates, which limits the movement of the structure in the plate length direction to a certain extent, thereby showing a certain stiffness to the outside, but this method requires a high voltage, and the extendable axial distance is small, which is not suitable for human body limb movement driving scenarios with high safety requirements and large deformation range.

[0008] (5) Combining mechanical components to complete partial or full locking in the axial direction to realize stiffness regulation, but this method cannot be fully flexible due to the use of rigid components, cannot reduce the weight, and will reduce the interaction comfort of the soft driver.

[0009] Currently, the driving and resistance control methods of the soft driver are mainly: directly controlling the rotation of the motor to drive the wire rope or mechanical component to move, directly controlling the phase change temperature of the shape memory alloy, and directly controlling the air pressure of the air cavity to realize axial driving deformation. However, the actual deformation degree is not detected, there is no feedback quantity of the actual deformation degree, which leads to the inability to achieve precise control, and the movement precision of the soft driver is low. SUMMARY

[0010] The present application is to solve the technical problems of the lack of resistance structure along the movement direction in the existing soft driver, the difficulty in meeting the continuous adjustment of axial stiffness, the difficulty in assisting the external structure to realize resistance movement, the difficulty in meeting the requirements of small size and light weight, and the inability to achieve precise control due to the lack of detection of deformation degree during movement. The present application provides an axial variable stiffness soft driver based on soft tooth structure meshing and slipping, which has a resistance structure along the movement direction, can realize precise continuous adjustment of axial stiffness, can meet the requirements of small size and light weight, and can be precisely controlled.

[0011] The present application provides an axial variable stiffness soft driver based on soft tooth structure meshing and slipping, which includes a driving core and a soft damping body. The driving core includes an axial flexible tube, a fabric wrapping layer, a wire rope winding layer, a flexible coating layer, and a pipeline one. The material of the axial flexible tube is flexible material, and the axial flexible tube is provided with an axial driving cavity.

[0012] The fabric wrapping layer is formed by wrapping an anisotropic fabric material around the periphery of the axial flexible tube;

[0013] The wire rope winding layer is formed by winding an inextensible wire rope on the fabric wrapping layer in a spiral manner;

[0014] The flexible coating layer is formed by coating the wire rope winding layer with flexible material;

[0015] The soft damping body comprises a radial expansion cylinder, an outer cylinder, a pipeline two, a rear end cover and a front end cover, the material of the radial expansion cylinder and the outer cylinder is flexible material, a plurality of inner layer low modulus soft teeth are arranged on the periphery of the radial expansion cylinder, each inner layer low modulus soft tooth is located in the radial direction of the radial expansion cylinder, and the plurality of inner layer low modulus soft teeth are distributed in the axial direction of the radial expansion cylinder to form a corrugated shape; the rear end of the outer cylinder is fixedly connected with the rear end cover, the front end of the outer cylinder is open, and the inner wall of the outer cylinder is provided with a plurality of outer layer high modulus soft teeth, each outer layer high modulus soft tooth is located in the radial direction of the outer cylinder; the radial expansion cylinder is located in the outer cylinder, the inner layer low modulus soft teeth correspond to the outer layer high modulus soft teeth, and the Young's modulus of the outer layer high modulus soft teeth is greater than that of the inner layer low modulus soft teeth; the rear end of the radial expansion cylinder is fixedly connected with the rear end cover; the pipeline two is connected with the rear end cover and penetrates through the rear end cover.

[0016] The driving core is located in the inner cavity of the radial expansion cylinder, the front end of the radial expansion cylinder is fixedly connected with the front end cover, the front end of the driving core is fixedly connected with the front end cover, the rear end of the driving core is fixedly connected with the rear end cover, the pipeline one is connected with the rear end cover and penetrates through the rear end cover, and the pipeline one is in communication with the axial driving cavity of the axial flexible pipe; the periphery of the driving core and the inner wall of the radial expansion cylinder form a radial expansion cavity, and the pipeline two is in communication with the radial expansion cavity.

[0017] Preferably, the pipeline one is a gas pipe, and the pipeline two is a gas pipe.

[0018] Preferably, the flexible material of the axial flexible pipe is silica gel, natural rubber, latex or gel; the flexible material of the flexible coating layer is silica gel, natural rubber, latex or gel; the flexible material of the radial expansion cylinder is silica gel, natural rubber, latex or gel; and the flexible material of the outer cylinder is silica gel, natural rubber, latex or gel.

[0019] Preferably, the winding mode of the wire rope winding layer is in accordance with the left-handed and right-handed mode.

[0020] Preferably, the axial variable stiffness soft driver based on the meshing and slipping of the soft tooth structure further comprises a sensing component, and the sensing component comprises an axial strain sensing unit, which is attached to the outer surface of the driving core.

[0021] Further preferably, the axial strain sensing unit is a dielectric elastomer sensor.

[0022] Further preferably, the sensing component further comprises an axial stiffness sensing unit, which is attached to the outer surface of the outer cylinder of the soft damping body, and the axial stiffness sensing unit is a dielectric elastomer sensor.

[0023] Further preferably, the sensing component further comprises an axial stiffness sensing unit, which is attached to the outer surface of the outer cylinder of the soft damping body.

[0024] Further preferably, the axial stiffness sensing unit is a dielectric elastomer sensor.

[0025] Preferably, the axial variable stiffness soft drive based on the meshing and sliding of the soft tooth structure is applied in the following manner: the outer cylinder is fixedly connected to the first external structure, the front end of the radial expansion cylinder is fixedly connected to the second external structure, and after the radial expansion cylinder expands, the inner layer of low modulus soft teeth and the outer layer of high modulus soft teeth engage with each other, and the first external structure and the second external structure move relative to each other.

[0026] The beneficial effects of the present invention are that it can realize axial variable stiffness, can accurately detect the axial stiffness, and can accurately and continuously adjust the axial telescopic stiffness.

[0027] The axial expansion and contraction process applies an adjustable resistance, which can accurately detect the axial stiffness and has high precision in axial resistance.

[0028] The control process is easy to operate and has strong controllability.

[0029] The entire product is made of fully soft materials, with large strain, large multiple axial variable stiffness and high precision.

[0030] The whole product is light in weight and small in size. The whole product can be made very small.

[0031] It can be applied to driving and resisting human motion in medical rehabilitation, exoskeletons, interactive games, wearable devices, soft robots and other fields.

[0032] Further features and aspects of the present invention will be clearly described in the following description of specific embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a physical picture of the axial variable stiffness soft actuator based on the meshing and sliding of the soft tooth structure;

[0034] Figure 2 This is a three-dimensional model diagram of an axially variable stiffness soft actuator based on the meshing and slipping of a soft tooth structure;

[0035] Figure 3 yes Figure 2 The three-dimensional model diagram of the driving core in the axial variable stiffness soft actuator shown;

[0036] Figure 4 yes Figure 2 The three-dimensional model diagram of the soft damping body in the axial variable stiffness soft body actuator shown;

[0037] Figure 5 yes Figure 2 The three-dimensional model diagram of the sensing component in the axial variable stiffness soft actuator shown;

[0038] Figure 6 is a cross-sectional view of an axial variable stiffness soft actuator based on meshing slip of soft tooth structure;

[0039] Figure 7 is Figure 6 is a cross-sectional view along A-A direction in

[0040] Figure 8 is a state diagram when the inner low modulus soft tooth and the outer high modulus soft tooth are not meshed together;

[0041] Figure 9 is a state diagram when the inner low modulus soft tooth and the outer high modulus soft tooth are meshed together;

[0042] Figure 10 is a structural schematic diagram of a dielectric elastomer sensor for making an axial strain sensing unit;

[0043] Figure 11 is Figure 10 is a size diagram of the first electrode layer and the first silica gel layer in the dielectric elastomer sensor shown in

[0044] Figure 12 is a structural schematic diagram of a dielectric elastomer sensor for making an axial stiffness sensing unit;

[0045] Figure 13 is Figure 12 is a size diagram of the third electrode layer and the fourth silica gel layer in the dielectric elastomer sensor shown in

[0046] Figure 14 is a relationship between the axial length of the axial flexible tube and the gas pressure in the axial driving cavity;

[0047] Figure 15 is a relationship between the axial equivalent Young's modulus of the axial variable stiffness soft actuator based on meshing slip of soft tooth structure and the gas pressure in the radial expansion cavity;

[0048] Figure 16 is a relationship diagram of the axial driving control precision of the axial variable stiffness soft actuator based on meshing slip of soft tooth structure, wherein figure (a) is a relationship between the gas pressure in the axial flexible tube and the length of the entire axial variable stiffness soft actuator when the open loop control is used, and figure (b) is a relationship between the gas pressure in the axial flexible tube and the length of the entire axial variable stiffness soft actuator when the closed loop control is used;

[0049] Figure 17 is a relationship between the axial equivalent Young's modulus of the axial variable stiffness soft actuator based on meshing slip of soft tooth structure and the gas pressure in the radial expansion cavity, wherein the ordinate of figure (a) is the axial equivalent Young's modulus, and the abscissa is the gas pressure value in the radial expansion cavity, wherein the ordinate of figure (b) is the error of the axial equivalent Young's modulus, and the abscissa is the gas pressure value in the radial expansion cavity.

[0050] Figure 18 This is a diagram showing the manufacturing process of an axially variable stiffness soft actuator based on the meshing and sliding of a soft tooth structure;

[0051] Figure 19 This is an application diagram of an axially variable stiffness soft actuator based on the meshing and sliding of a soft tooth structure;

[0052] Figure 20 This is a schematic diagram of the structure of an axial variable stiffness soft actuator based on the meshing and sliding of a soft tooth structure during the motion process of the human elbow joint.

[0053] Figure 21 The strain information of the axial stiffness sensing unit and the axial strain sensing unit is fitted into a function to reflect the relationship diagram of the axial telescopic stiffness of the entire axial variable stiffness soft actuator based on the meshing slip of the soft tooth structure.

[0054] Explanation of symbols in the figure:

[0055] 1. Axial variable stiffness soft actuator based on meshing and slipping of soft tooth structure, 11. Driving core, 111. Axial flexible tube, 112. Fabric wrapping layer, 113. Cord wrapping layer, 114. Flexible covering layer, 115. Pipeline 1;

[0056] 12. Soft damping body, 12-1. Radial expansion cylinder, 121. Radial expansion cavity, 122. Inner low-modulus soft teeth, 12-2. Outer cylinder, 123. Outer high-modulus soft teeth, 12-3. Pipeline II, 12-4. Rear end cover, 12-5. Front end cover;

[0057] 13. Sensing component, 131. Axial strain sensing unit, 1311. First silicone layer, 1312. First electrode layer, 1313. Second electrode layer, 1314. Second silicone layer, 1315. Third silicone layer, 132. Axial stiffness sensing unit, 1321. Fourth silicone layer, 1322. Third electrode layer, 1323. Fourth electrode layer, 1324. Fifth silicone layer, 1325. Sixth silicone layer;

[0058] 100. First external structure, 200. Second external structure. DETAILED DESCRIPTION

[0059] The present invention will be further described in detail below with reference to the accompanying drawings using specific embodiments.

[0060] like Figure 1-7 As shown, the axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure includes a driving core 11, a soft damping body 12 and a sensing component 13. The soft damping body 12 is connected to the driving core 11, and the sensing component 13 is connected to the driving core 11 and the soft damping body 12.

[0061] The driving core 11 comprises an axial flexible tube 111, a fabric wrapping layer 112, a wire rope winding layer 113, a flexible covering layer 114, and a pipeline 115. The axial flexible tube 111 is made of flexible material and is provided with an axial driving cavity. The pipeline 115 is in communication with the axial driving cavity. Inflation of the axial driving cavity of the axial flexible tube 111 through the pipeline 115 can make the axial flexible tube 111 elongate in the axial direction, so as to elongate the axial variable stiffness soft driver 1 based on the meshing and slipping of the soft tooth structure. Deflation of the axial driving cavity of the axial flexible tube 111 through the pipeline 115 can make the axial flexible tube 111 shorten in the axial direction, so as to shorten the axial variable stiffness soft driver 1 based on the meshing and slipping of the soft tooth structure.

[0062] The fabric wrapping layer 112 is made of anisotropic fabric material and is wrapped around the outer periphery of the axial flexible tube 111 to form the fabric wrapping layer 112. The anisotropic fabric material has high elasticity in the axial direction of the axial flexible tube 111 and has little elasticity or is almost invariable in the direction perpendicular to the axial direction. In the case that the axial driving cavity of the axial flexible tube 111 is inflated, the fabric wrapping layer 112 can limit the radial expansion of the axial driving cavity and increase the axial strain of the axial flexible tube 111.

[0063] The wire rope winding layer 113 is formed by spirally winding non-stretchable polyethylene wire ropes on the fabric wrapping layer 112 in the left-handed and right-handed ways. On the one hand, the wire rope winding layer 113 can fix the fabric wrapping layer 112 in a binding way; on the other hand, the wire rope winding layer 113 can limit the radial expansion of the axial flexible tube 111, because the anisotropic fabric is not absolutely invariable in the radial direction and the binding of the non-stretchable wire ropes can limit the deformation of the anisotropic fabric in the radial direction.

[0064] The flexible covering layer 114 is made of flexible material and covers the wire rope winding layer 113, so as to protect the wire ropes and prevent the wire ropes from moving.

[0065] As Figure 2 , 4As shown in Figures 6 and 7, the soft damping body 12 includes a radial expansion cylinder 12-1, an outer cylinder 12-2, a pipe 12-3, a rear end cover 12-4, and a front end cover 12-5. The radial expansion cylinder 12-1 and the outer cylinder 12-2 are made of flexible materials, the front end cover 12-5 is made of flexible materials, and the rear end cover 12-4 is made of flexible materials. The outer periphery of the radial expansion cylinder 12-1 is provided with a plurality of inner layer low modulus soft teeth 122, each inner layer low modulus soft tooth 122 is located in the radial direction of the radial expansion cylinder 12-1, and the plurality of inner layer low modulus soft teeth 122 are distributed along the axial direction of the radial expansion cylinder 12-1 to form a corrugated shape; the outer cylinder 12-2 The rear end is fixedly connected to the rear end cover 12-4, the front end of the outer cylinder 12-2 is open (not closed), and the inner wall of the outer cylinder 12-2 is provided with a plurality of outer layer high modulus soft teeth 123, each outer layer high modulus soft tooth 123 is located in the radial direction of the outer cylinder 12-2; the radial expansion cylinder 12-1 is located in the outer cylinder 12-2, and the inner layer low modulus soft teeth 122 correspond to the outer layer high modulus soft teeth 123; the rear end of the radial expansion cylinder 12-1 is fixedly connected to the rear end cover 12-4, pipe 2 12-3 is connected to the rear end cover 12-4, pipe 2 12-3 passes through the rear end cover 12-4, and pipe 2 12-3 is connected to the inner cavity of the radial expansion cylinder 12-1.

[0066] Drive core 11 is located within the inner cavity of radial expansion cylinder 12-1. The front end of radial expansion cylinder 12-1 is fixedly connected to front end cover 12-5. The front end of drive core 11 is fixedly connected to front end cover 12-5, and the rear end of drive core 11 is fixedly connected to rear end cover 12-4. Pipe 1 115 is connected to rear end cover 12-4 and passes through rear end cover 12-4. Pipe 1 115 communicates with the axial drive cavity of axial flexible tube 111. A radial expansion cavity 121 is formed between the periphery of drive core 11 and the inner wall of radial expansion cylinder 12-1. Pipe 2 12-3 communicates with radial expansion cavity 121.

[0067] When air is ventilated to the radial expansion chamber 121 through the second pipe 12-3, the radial expansion cylinder 12-1 expands, and the inner layer low modulus soft teeth 122 approach the outer layer high modulus soft teeth 123. When the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 approach to a certain extent, meshing occurs. Figure 6 As shown, the inner layer low modulus soft teeth and the outer layer high modulus soft teeth are in a meshing state (a state with a low degree of meshing). At this time, when the driving core 11 is extended or shortened, the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 slip (slip between flexible materials). In the process of meshing and sliding, accompanied by the obstruction of normal force and stick-slip friction, the telescopic movement of the driving core 11 will be affected by resistance, and the magnitude of the resistance is related to the meshing state of the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123. The magnitude of the resistance can be controlled by the air pressure of the radial expansion chamber 121.

[0068] When the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 are engaged, when the radial expansion chamber 121 is exhausted outwards through the second pipe 12-3, the radial expansion cylinder 12-1 will shrink, and the inner layer low modulus soft teeth 122 will move away from the outer layer high modulus soft teeth 123. When the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 move away from each other to a certain extent, they will no longer be engaged. Figure 8 It shows that the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 are not engaged). At this time, the driving core 11 performs telescopic movement, and there is no obstruction between the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123, and the telescopic movement of the driving core 11 is not affected by resistance.

[0069] Figure 9 It shows that the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 are meshed together, and the degree of meshing is relatively high. Figure 9 The degree of meshing is higher than Figure 6 Displays the degree of engagement.

[0070] The Young's modulus of the outer high modulus soft teeth 123 is greater than that of the inner low modulus soft teeth 122. In an optimized situation, the Young's modulus of the outer high modulus soft teeth 123 is 2000-3000 kPa, and the Young's modulus of the inner low modulus soft teeth 122 is 50-70 kPa.

[0071] The sensing component 13 includes an axial strain sensing unit 131 and an axial stiffness sensing unit 132. The axial strain sensing unit 131 is attached to the outer surface of the drive core 11 (i.e., attached to the flexible coating 114) and is used to detect the strain of the drive core 11. The axial stiffness sensing unit 132 is attached to the outer surface of the soft damping body 12 (i.e., attached to the outer surface of the outer cylinder 12-2) and is used to detect the strain of the outer high-modulus soft teeth 123. The detection results of the axial stiffness sensing unit 132, combined with the detection results of the axial strain sensing unit 131, can reflect the axial telescopic stiffness of the axial variable stiffness soft body actuator 1 based on the meshing slip of the soft tooth structure.

[0072] The axial strain sensing unit 131 adopts a well-known dielectric elastomer sensor, such as Figure 10 As shown, the flattened dielectric elastomer sensor includes a first silicone layer 1311, a first electrode layer 1312, a second electrode layer 1313, a second silicone layer 1314, and a third silicone layer 1315 connected together. The first silicone layer 1311 serves as a dielectric layer, the first electrode layer 1312 and the second electrode layer 1313 serve as the positive electrode layer and the negative electrode layer of the first silicone layer 1311, respectively, and the second silicone layer 1314 and the third silicone layer 1315 serve as protective layers. Figure 11As shown, one specific size of the first silica gel layer 1311 is: 60mm in length, 35mm in width, and the size of the first electrode layer 1312 is: 50mm in length, 30mm in width. The dielectric elastomer sensor further comprises a first copper foil and a second copper foil, the first copper foil is connected with the first electrode layer 1312, and the second copper foil is connected with the second electrode layer 1313, the first copper foil and the second copper foil are used as pins to be electrically connected with a measurement circuit. The first signal line is welded with the first copper foil, and the second signal line is welded with the second copper foil, the first signal line and the second signal line respectively pass through the rear end cover 12-4, and are respectively electrically connected with an external measurement circuit. The dielectric elastomer sensor detects the capacitance data as the strain information detected by the axial strain sensing unit 131, and has high detection accuracy.

[0073] The axial stiffness sensing unit 132 adopts a known dielectric elastomer sensor, such as Figure 12 As shown, the dielectric elastomer sensor in a flat state comprises a fourth silica gel layer 1321, a third electrode layer 1322, a fourth electrode layer 1323, a fifth silica gel layer 1324 and a sixth silica gel layer 1325 connected together, the fourth silica gel layer 1321 is used as a dielectric layer, the third electrode layer 1322 and the fourth electrode layer 1323 are respectively used as the positive electrode layer and the negative electrode layer of the fourth silica gel layer 1321, and the fifth silica gel layer 1324 and the sixth silica gel layer 1325 are used as protective layers. As shown Figure 13 As shown, one specific size of the fourth silica gel layer 1321 is: 60mm in length, 79mm in width, and the size of the third electrode layer 1322 is: 50mm in length, 74mm in width. The dielectric elastomer sensor further comprises a third copper foil and a fourth copper foil, the third copper foil is connected with the third electrode layer 1322, and the fourth copper foil is connected with the fourth electrode layer 1323, the third copper foil and the fourth copper foil are used as pins to be electrically connected with a measurement circuit. The dielectric elastomer sensor detects the capacitance data as the strain information detected by the axial stiffness sensing unit 132, and has high detection accuracy.

[0074] When the axial driving cavity of the axial flexible tube 111 is inflated or deflated, the elongation or shortening of the entire axial variable stiffness soft driver 1 based on the meshing slip of the soft tooth structure can be realized, and the relationship between the axial length of the entire axial variable stiffness soft driver and the air pressure in the axial driving cavity is as shown Figure 14 As shown Figure 14As shown, the horizontal axis represents the air pressure in the axial drive cavity. When the air pressure in the axial drive cavity increases, the length of the axial flexible tube 111 increases accordingly. When the air pressure in the axial drive cavity is 0 kPa, the original length of the axial flexible tube 111 is 90 mm. When the air pressure in the axial drive cavity is 120 kPa, the length of the axial flexible tube 111 is 141 mm, i.e., the driven length is 51 mm, and the length change rate is 56.7%. Therefore, inflating the axial drive cavity of the axial flexible tube 111 causes the entire axial variable stiffness soft actuator 1 based on the meshing and sliding of the soft tooth structure to extend, thereby enabling the actuator to drive an external object. Similarly, deflating the axial drive cavity of the axial flexible tube 111 causes the entire axial variable stiffness soft actuator 1 based on the meshing and sliding of the soft tooth structure to shorten, thereby also enabling the actuator to drive an external object.

[0075] When the inner low modulus soft teeth 122 and the outer high modulus soft teeth 123 are in meshing state, the inner low modulus soft teeth 122 and the outer high modulus soft teeth 123 will slip when the driving core 11 is extended or shortened. Since the microscopic surface of the soft material is very uneven and the material is deformable, stick-slip friction resistance is generated when the atoms on the surfaces are in close contact during the relative sliding of the soft material. This stick-slip friction force is much greater than the friction force under the contact of rigid materials. The resistance to the telescopic movement of the driving core 11 is related to the degree of meshing between the inner low modulus soft teeth 122 and the outer high modulus soft teeth 123. The degree of meshing, and thus the resistance, can be controlled by the air pressure in the radial expansion chamber 121. Figure 15 As shown in the figure, the horizontal axis is the air pressure value in the radial expansion chamber 121. When the air pressure in the radial expansion chamber 121 increases, the axial equivalent Young's modulus of the axial variable stiffness soft actuator 1 based on the meshing and slipping of the soft tooth structure increases accordingly. When the air pressure in the radial expansion chamber 121 is 0kPa, the axial equivalent Young's modulus of the entire axial variable stiffness soft actuator is 266.2kPa. When the air pressure in the radial expansion chamber 121 is 20kPa, the axial equivalent Young's modulus of the entire axial variable stiffness soft actuator is 1923.9kPa, a change of 7.2 times. It can be seen that the higher the degree of meshing, the greater the resistance.

[0076] Under the closed-loop control with the strain information of the axial strain sensing unit 131 as feedback, the axial drive control accuracy of the axial variable stiffness soft actuator 1 based on the meshing slip of the soft tooth structure is as follows: Figure 16 As shown. Under the same experimental conditions, 4 axial drive tests of the entire axial variable stiffness soft actuator were carried out. The relative error of open-loop drive control using only the air pressure in the axial flexible tube 111 was 5.90%, as shown in Figure 16 As shown in Figure (a); the relative error of the closed-loop drive control combined with the strain information of the axial strain sensing unit 131 is 2.02%, as shown in Figure 16As shown in FIG. 8(b), the error is about 1 / 3 of the open-loop driving control error. It can be seen that the closed-loop driving control precision combined with the strain information of the axial strain sensing unit 131 is very high.

[0077] Under the closed-loop control using the strain information of the axial stiffness sensing unit 132 as feedback, the axial stiffness control precision of the axial variable stiffness soft driver 1 based on the meshing and slippage of the soft tooth structure is as shown in FIG. 9, where the ordinate of FIG. 9(a) is the axial equivalent Young's modulus, and the abscissa is the air pressure in the radial expansion cavity 121. The ordinate of FIG. 9(b) is the error of the axial equivalent Young's modulus under open-loop and closed-loop control. Under the same experimental conditions, the relative error of the open-loop driving control using only the air pressure in the radial expansion cavity 121 is 3.74%, as shown in FIG. 8(a). Figure 17 Figure 17 As shown in FIG. 8(b), the error is about 1 / 3 of the open-loop driving control error. It can be seen that the closed-loop driving control precision combined with the strain information of the axial strain sensing unit 131 is very high.

[0078] The detection result of the axial stiffness sensing unit 132 combined with the detection result of the axial strain sensing unit 131 can reflect the axial expansion stiffness of the axial variable stiffness soft driver 1 based on the meshing and slippage of the soft tooth structure. A specific implementation manner can be that, referring to FIG. 10, a function is obtained by a polynomial fitting method: Figure 21

[0079] z = z0 + ax + by + cx + dy + fxy 2 2

[0080] In the above function, x represents the strain information detected by the axial strain sensing unit 131, y represents the strain information detected by the axial stiffness sensing unit 132, z0, a, b, c, d, and f are constants; and z is the axial equivalent Young's modulus of the entire axial variable stiffness soft driver.

[0081] Referring to FIG. 11, the preparation process of the above axial variable stiffness soft driver 1 based on the meshing and slippage of the soft tooth structure is as follows: Figure 18

[0082] In step S01, the axial flexible tube 111 is prepared by a silica gel casting process. It is a preferred scheme to select silica gel as the material for manufacturing the axial flexible tube 111.

[0083] In step S02, the anisotropic fabric is wrapped outside the axial flexible tube 111 to form a fabric wrapping layer 112. The polyethylene wire rope is wound outside the fabric wrapping layer 112 in a bidirectional spiral winding manner to form a wire rope winding layer 113. Then, the silica gel is coated outside the wire rope winding layer 113 to form a flexible coating layer 114, and then the driving core 11 is formed. It is a preferred scheme to select silica gel as the material of the flexible coating layer 114.​​​​​

[0084] Step S03, prepare the dielectric elastomer sensor in flat state, use the silicone adhesive to paste the dielectric elastomer sensor in flat state on the outside of the flexible cladding layer 114, so as to form the axial strain sensing unit 131.

[0085] Step S04, prepare the radial expansion cylinder 12-1 by silicone pouring process, the radial expansion cylinder 12-1 is integrally formed, and the radial expansion cylinder 12-1 produced has a plurality of inner layer low modulus soft teeth 122; it is a preferred scheme to select silicone as the material for making the radial expansion cylinder 12-1.

[0086] Step S05, prepare the outer cylinder 12-2 by silicone pouring process, the outer cylinder 12-2 is integrally formed, and the inner wall of the outer cylinder 12-2 produced has a plurality of outer layer high modulus soft teeth 123; it is a preferred scheme to select silicone as the material for making the outer cylinder 12-2.

[0087] Step S06, prepare the pipeline one 115, the pipeline two 12-3, and prepare the first mold and the second mold. The materials of the pipeline one 115 and the pipeline two 12-3 are preferably flexible materials (such as silicone), in which case the pipeline one 115 and the pipeline two 12-3 are soft, which is convenient for application in some scenarios.

[0088] Step S07, put the radial expansion cylinder 12-1 and the driving core 11 together, and then place them on the first mold, with the rear ends of the radial expansion cylinder 12-1 and the driving core 11 standing in the vertical direction; then position the pipeline one 115 and the pipeline two 12-3 in the holes on the first mold.

[0089] Step S08, pour silicone into the first mold, so as to form the rear end cover 12-4, the rear end of the radial expansion cylinder 12-1 is fixedly connected with the rear end cover 12-4, the rear end of the driving core 11 is fixedly connected with the rear end cover 12-4, the pipeline one 115 and the pipeline two 12-3 pass through the rear end cover 12-4, the pipeline one 115 communicates with the axial driving cavity of the driving core 11, and the pipeline two 12-3 communicates with the inner cavity of the radial expansion cylinder 12-1.

[0090] Step S09, remove the first mold.

[0091] Step S10, place the radial expansion cylinder 12-1 and the driving core 11 on the second mold, with the front ends of the radial expansion cylinder 12-1 and the driving core 11 standing in the vertical direction; then pour silicone into the second mold, so as to form the front end cover 12-5, the front end of the radial expansion cylinder 12-1 is fixedly connected with the front end cover 12-5, and the front end of the driving core 11 is fixedly connected with the front end cover 12-5.

[0092] Step S11, remove the second mold.

[0093] Step S12, prepare the dielectric elastomer sensor in flat state as the axial stiffness sensing unit 132, and use the silicone adhesive to paste the dielectric elastomer sensor on the outer surface of the outer cylinder 12-2 to form the axial stiffness sensing unit 132.

[0094] Step S13, put the outer cylinder 12-2 and the radial expansion cylinder 12-1 together, and use the silicone adhesive to fix the rear end surface of the outer cylinder 12-2 and the rear end cover 12-4. At this time, the rear end of the outer cylinder 12-2 is closed, and the front end of the outer cylinder 12-2 is in an open state (not closed).

[0095] It should be noted that the material of the axial flexible tube 111 can be selected from natural rubber, latex, or gel, in addition to silicone. The material of the flexible coating layer 114 can be selected from natural rubber, latex, or gel, in addition to silicone. The material of the radial expansion cylinder 12-1 can be selected from natural rubber, latex, or gel, in addition to silicone. The material of the outer cylinder 12-2 can be selected from natural rubber, latex, or gel, in addition to silicone. The materials of the rear end cover 12-4 and the front end cover 12-5 can be selected from natural rubber, latex, or gel, in addition to silicone.

[0096] It should be noted that the material of the axial flexible tube 111 is preferably a flexible material with an elongation greater than 500%.

[0097] It should be noted that the material of the flexible coating layer 114 is preferably a flexible material with an elongation greater than 500%.

[0098] It should be noted that the material of the radial expansion cylinder 12-1 is preferably a flexible material with an elongation greater than 300%.

[0099] It should be noted that the material of the outer cylinder 12-2 is preferably a flexible material with an elongation greater than 300%.

[0100] For anisotropic fabric materials, polyester, nylon, spandex, or cotton can be selected.

[0101] It should be noted that inflating the axial driving cavity of the axial flexible tube 111 is a preferred scheme (at this time, the pipeline 115 is the trachea for ventilation), and using gas has some advantages, such as: easy operation, fast speed, easy emptying of the cavity, and light weight of the entire product. However, in addition to using gas, water or oil or other fluids can also be used as a medium.

[0102] Similarly, it is also preferred to inflate and deflate the radial expansion cavity 121 (at this time, the pipeline two 12-3 is the air pipe two for ventilation), however, in addition to using gas, water or oil and other fluids can also be used as a medium.

[0103] The axial variable stiffness soft driver of the present application can be small in size to adapt to the required application scenarios. For example, the length of the axial variable stiffness soft driver can be 90 mm, the diameter can be 27 mm, the diameter of the driving core 11 can be 10 mm, the inner diameter of the axial driving cavity can be 5 mm, the diameter of the radial expansion cylinder 12-1 can be 13 mm, the thickness of the fabric wrapping layer 112 can be 0.2 mm, the thickness of the flexible coating layer 114 can be 0.4 mm, and the height of the soft tooth can be 2 mm.

[0104] The following describes an application scenario.

[0105] As shown in Figure 19 , the outer cylinder 12-2 is fixedly connected with the first external structure 100, the front end of the radial expansion cylinder 12-1 is fixedly connected with the second external structure 200, then the first external structure 100 is fixedly unmoved, and the second external structure 200 is moved, and the resistance between the outer cylinder 12-2 and the radial expansion cylinder 12-1 needs to be overcome during the movement of the second external structure 200, thereby realizing resistance movement. Of course, the second external structure 200 can also be fixedly unmoved and the first external structure 100 can be moved, and resistance movement can also be realized. That is, the first external structure 100 and the second external structure 200 move relatively, and the axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure is used to realize resistance movement, and the auxiliary external structure realizes resistance movement.

[0106] The following describes another application scenario.

[0107] In the field of muscle strength rehabilitation training, generally includes passive training, power-assisted training, active training and resistance training. The present application can be applied to resistance training to provide matched resistance for the rehabilitation limbs.

[0108] For human elbow joint movement, the outer cylinder 12-2 is connected with the forearm by using magic tape or string, as shown in Figure 20As shown, the front end of the radial expansion cylinder 12-1 is connected with the big arm using magic tape or string. In the case that the axial driving cavity of the axial flexible tube 111 is inflated, and the radial expansion cavity 121 is not inflated, the elbow joint movement drives the whole axial stiffness soft driver 1 based on soft tooth structure meshing slip to axially stretch and shrink (at this time, there is no resistance between the outer cylinder 12-2 and the radial expansion cylinder 12-1), which can realize passive training or power training of muscle groups in the process of joint stretching. In the case that the axial driving cavity of the axial flexible tube 111 is inflated (maintaining a certain air pressure), and the radial expansion cavity 121 is also inflated (at this time, there is resistance between the outer cylinder 12-2 and the radial expansion cylinder 12-1), resistance suitable for the needs of the elbow joint active stretching process is provided to realize resistance training of muscle groups.

[0109] The above description is only for the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the scope defined by the claims of the present application shall be within the protection scope of the present application.

Claims

1. An axial variable stiffness soft actuator based on meshing and sliding of soft tooth structure, characterized in that: It includes a driving core and a soft damping body; The driving core comprises an axial flexible tube, a fabric wrapping layer, a cord wrapping layer, a flexible coating layer and a pipe 1, wherein the axial flexible tube is made of a flexible material and is provided with an axial driving cavity; The fabric wrapping layer is formed by wrapping anisotropic fabric material around the periphery of the axial flexible tube; The cord winding layer is formed by spirally winding a non-retractable cord on the fabric wrapping layer; The flexible covering layer is formed by covering the cord winding layer with a flexible material; The soft damping body includes a radial expansion cylinder, an outer cylinder, a second pipe, a rear end cover and a front end cover. The radial expansion cylinder and the outer cylinder are both made of flexible materials. The outer periphery of the radial expansion cylinder is provided with a plurality of inner low-modulus soft teeth, each of which is located in the radial direction of the radial expansion cylinder, and the plurality of inner low-modulus soft teeth are distributed along the axial direction of the radial expansion cylinder to form a corrugated shape; the rear end of the outer cylinder is fixedly connected to the rear end cover, the front end of the outer cylinder is open, and the inner wall of the outer cylinder is provided with a plurality of outer high-modulus soft teeth, each of which is located in the radial direction of the outer cylinder; the radial expansion cylinder is located in the outer cylinder, the inner low-modulus soft teeth correspond to the outer high-modulus soft teeth, and the Young's modulus of the outer high-modulus soft teeth is greater than the Young's modulus of the inner low-modulus soft teeth; the rear end of the radial expansion cylinder is fixedly connected to the rear end cover; the second pipe is connected to the rear end cover, and the second pipe passes through the rear end cover; The driving core is located in the inner cavity of the radial expansion cylinder, the front end of the radial expansion cylinder is fixedly connected to the front end cover, the front end of the driving core is fixedly connected to the front end cover, the rear end of the driving core is fixedly connected to the rear end cover, the pipe 1 is connected to the rear end cover, the pipe 1 passes through the rear end cover, and the pipe 1 is connected to the axial driving cavity of the axial flexible tube; a radial expansion cavity is formed between the outer periphery of the driving core and the inner wall of the radial expansion cylinder, and the pipe 2 is connected to the radial expansion cavity.

2. The axial variable stiffness soft actuator based on the meshing and sliding of the soft tooth structure according to claim 1 is characterized in that: The first pipeline is a trachea, and the second pipeline is a trachea.

3. The axial variable stiffness soft actuator based on the meshing and sliding of the soft tooth structure according to claim 1 is characterized in that: The flexible material of the axial flexible tube is silicone, natural rubber, latex or gel; the flexible material of the flexible coating layer is silicone, natural rubber, latex or gel; the flexible material of the radial expansion cylinder is silicone, natural rubber, latex or gel; the flexible material of the outer cylinder is silicone, natural rubber, latex or gel.

4. The axial variable stiffness soft actuator based on the meshing and sliding of the soft tooth structure according to claim 1 is characterized in that: The winding mode of the cord winding layer is left-handed and right-handed.

5. The axially variable stiffness soft actuator based on the meshing and sliding of soft tooth structures according to claim 1, 2, 3 or 4, characterized in that: The axial variable stiffness soft driver based on the meshing and sliding of the soft tooth structure further includes a sensing component, which includes an axial strain sensing unit, and the axial strain sensing unit is attached to the outer surface of the driving core.

6. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 5 is characterized in that: The axial strain sensing unit is a dielectric elastomer sensor.

7. The axially variable stiffness soft actuator based on the meshing and sliding of the soft tooth structure according to claim 6 is characterized in that: The sensing component further includes an axial stiffness sensing unit, which is attached to the outer surface of the outer cylinder of the soft damping body and is a dielectric elastomer sensor.

8. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 5, characterized in that: The sensing component further comprises an axial stiffness sensing unit, and the axial stiffness sensing unit is attached to the outer surface of the outer cylinder of the soft damping body.

9. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 8, characterized in that: The axial stiffness sensing unit is a dielectric elastomer sensor.

10. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 1, characterized in that: The axial variable stiffness soft drive based on the meshing and sliding of the soft tooth structure is applied in the following manner: the outer cylinder is fixedly connected to the first external structure, the front end of the radial expansion cylinder is fixedly connected to the second external structure, and after the radial expansion cylinder expands, the inner layer of low modulus soft teeth and the outer layer of high modulus soft teeth engage with each other, and the first external structure and the second external structure move relative to each other.

11. The axially variable stiffness soft actuator based on the meshing and sliding of soft tooth structures according to claim 1, characterized in that: The Young's modulus of the outer layer high modulus soft teeth is 2000-3000 kPa, and the Young's modulus of the inner layer low modulus soft teeth is 50-70 kPa.

12. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 1, characterized in that: The elongation of the material of the axial flexible tube is greater than 500%, and the elongation of the material of the flexible coating layer is greater than 500%; the elongation of the material of the radial expansion cylinder is greater than 300%, and the elongation of the material of the outer cylinder is greater than 300%.

13. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 1 or 2, characterized in that: The first pipe is a soft trachea, and the second pipe is a soft trachea.

14. The axially variable stiffness soft actuator based on the meshing and sliding of soft tooth structures according to claim 1, 2, 3 or 4, characterized in that: The front end cover and / or the rear end cover are made of flexible material.

15. The axially variable stiffness soft actuator based on the meshing and sliding of soft tooth structures according to claim 7, characterized in that: The detection result of the axial stiffness sensing unit is combined with the detection result of the axial strain sensing unit to reflect the axial telescopic stiffness of the axial variable stiffness soft body actuator based on the meshing slip of the soft tooth structure.

16. The axially variable stiffness soft actuator based on meshing and sliding of soft tooth structures according to claim 7, characterized in that: The preparation process includes the following steps: Step S01, preparing an axially flexible tube by a silicone casting process; Step S02: Wrapping the outer side of the axial flexible tube with an anisotropic fabric to form a fabric wrapping layer, wrapping a polyethylene cord around the outer side of the fabric wrapping layer in a bidirectional spiral manner to form a cord wrapping layer, and then coating the outer side of the cord wrapping layer with silicone to form a flexible coating layer, thereby forming a driving core; Step S03: preparing a flat dielectric elastomer sensor, and using a silicone adhesive to adhere the flat dielectric elastomer sensor to the outside of the flexible covering layer, thereby forming an axial strain sensing unit; Step S04: preparing a radial expansion cylinder by a silicone casting process. The radial expansion cylinder is integrally formed and has a plurality of inner low-modulus soft teeth. Step S05: preparing the outer cylinder by a silicone casting process. The outer cylinder is formed in one piece, and the inner wall of the outer cylinder has a plurality of outer high modulus soft teeth; Step S06, preparing pipe 1, pipe 2, and preparing the first mold and the second mold; Step S07: The radial expansion cylinder and the driving core are sleeved together and then placed on the first mold, with the rear ends of the radial expansion cylinder and the driving core facing downward and standing vertically. Then, pipes 1 and 2 are placed in the holes of the first mold for positioning. Step S08: Pour silicone into the first mold to form a rear end cap. The rear end of the radial expansion cylinder is fixedly connected to the rear end cap, and the rear end of the drive core is fixedly connected to the rear end cap. Pipe 1 and Pipe 2 pass through the rear end cap. Pipe 1 communicates with the axial drive cavity of the drive core, and Pipe 2 communicates with the inner cavity of the radial expansion cylinder. Step S09, removing the first mold; Step S10: Place the radial expansion cylinder and the drive core on the second mold, with their front ends facing downward and standing vertically. Then, pour silicone into the second mold to form a front end cover. The front end of the radial expansion cylinder is fixedly connected to the front end cover, and the front end of the drive core is fixedly connected to the front end cover. Step S11, removing the second mold; Step S12: preparing a flat dielectric elastomer sensor as an axial stiffness sensing unit, and using a silicone adhesive to adhere the dielectric elastomer sensor to the outer surface of the outer cylinder to form the axial stiffness sensing unit; Step S13, the outer tube and the radial expansion tube are sleeved together, and the rear end surface of the outer tube is fixedly connected to the rear end cover with a silicone adhesive; at this time, the rear end of the outer tube is closed, and the front end of the outer tube is open.

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