Axial variable stiffness soft body driver based on soft tooth structure meshing slippage

Abstract

The invention relates to an axial variable-stiffness soft driver based on soft tooth structure meshing slippage, and solves the problems that an existing soft driver lacks a resistance applying structure in the movement direction, the requirement for continuous adjustment of axial stiffness is difficult to meet, an external structure is difficult to assist in achieving resistance movement, and the requirement for small size and light weight is difficult to meet. The device comprises a driving core body and a soft damping body, the driving core body comprises an axial flexible pipe, a fabric wrapping layer, a thread rope winding layer, a flexible wrapping layer and a first pipeline, the axial flexible pipe is provided with an axial driving cavity, the fabric wrapping layer is provided with a thread rope winding layer, and the thread rope winding layer is provided with a thread rope winding layer; the soft damping body comprises a radial expansion cylinder, an outer cylinder, a second pipeline, a rear end cover and a front end cover, a plurality of inner-layer low-modulus soft teeth are arranged on the periphery of the radial expansion cylinder, and a plurality of outer-layer high-modulus soft teeth are arranged on the inner wall of the outer cylinder. The invention is widely applied to human motion driving and resistance application in the fields of medical rehabilitation, exoskeleton, interactive games, wearable equipment, soft robots and the like.

Description

Technical Field

[0001] The invention relates to the technical field of soft drive, and in particular to an axially variable stiffness soft drive based on meshing and sliding of a soft tooth structure. Background Art

[0002] In the fields of wearable devices, soft robots, and exoskeleton technology, soft actuators are key components. They are widely used because of their softness, comfort, safety, strong controllability, and low cost. In medical rehabilitation and interactive game scenarios, soft actuators can drive or hinder human limbs to complete a given movement, thereby achieving a given movement goal.

[0003] The working principle of soft actuators is mainly to achieve driving through bending, stretching, twisting and deformation. At present, according to the classification of driving and resisting methods along the axis direction, soft actuators mainly have the following driving and resisting methods:

[0004] (1) Axial drive is achieved through wire ropes, shape memory alloys or pneumatics. For the shape memory alloy drive method, please refer to the invention patent application with application publication number CN115352544A, and for the pneumatic method, please refer to the invention patent application with application publication number CN115817665A; however, these methods can generally only achieve axial drive or assistance for the driver, load and fixed non-powered external structure. Due to the lack of a resistance structure along the direction of movement, it is difficult to provide axial resistance for 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 is controlled by changing the blocking state of the internal unit to achieve external resistance. Specifically, the airbag is filled with particles, fibers or surface structures. When the airbag is evacuated and there is a certain vacuum inside, the particles, fibers and surface structures are compressed together to show a certain stiffness to the outside. However, this method is difficult to achieve continuous change of stiffness, and it is almost impossible to deform axially at high stiffness. Therefore, it is only suitable for axial deformation under low stiffness state and vertical load under high bending stiffness state, but not suitable for driving and resistance that require continuous adjustment of axial stiffness.

[0006] (3) Using the phase change of polymer or low-melting-point alloy materials to achieve stiffness control to achieve external resistance. This method can achieve axial drive and continuously variable stiffness resistance, but the temperature required for phase change is often higher than human body temperature and the adjustment time is long. In addition, the addition of flow channels and thermal insulation layers will increase the overall weight and volume. Therefore, the high temperature safety hazard and weight and volume issues make this method unsuitable for long-term safe and comfortable wearing.

[0007] (4) The axial stiffness is adjusted by using the principle of electrostatic adsorption to achieve external resistance. Specifically, the electrostatic adsorption between the electrode plates achieves attraction between the plates, which results in the movement of the structure in the length direction of the plates being restricted to a certain extent, thereby showing a certain stiffness to the outside. However, this method requires a very high voltage and the retractable axial distance is very small. It is not suitable for human limb movement driving scenarios with high safety requirements and a large deformation range.

[0008] (5) Combine mechanical components to complete partial or full axial locking to achieve stiffness control. However, this method cannot achieve full flexibility and cannot reduce weight due to the use of rigid components, which will reduce the interactive comfort of the soft drive.

[0009] At present, the driving and resistance control methods of soft actuators are mainly: directly controlling the rotation of the motor to drive the movement of the rope or mechanical components, directly controlling the phase change temperature of the shape memory alloy, and directly controlling the air pressure in the air cavity to achieve axial drive deformation. However, the actual degree of deformation is not detected and there is no feedback on the actual degree of deformation, resulting in the inability to achieve precise control and the low movement accuracy of the soft actuator. Summary of the invention

[0010] The present invention is to solve the technical problems that the existing soft drivers lack a resistance structure along the direction of movement, are difficult to meet the requirements of continuous adjustment of axial stiffness, are difficult to assist external structures to achieve resistance movement, are difficult to meet the requirements of small size and light weight, and the degree of deformation during movement is not detected, resulting in the inability to achieve precise control. The present invention provides an axial variable stiffness soft driver based on the meshing and sliding of a soft tooth structure, which has a resistance structure along the direction of movement, can achieve precise continuous adjustment of axial stiffness, can meet the requirements of small size and light weight, and can be precisely controlled.

[0011] The present invention provides an axial variable stiffness soft body driver based on the meshing and sliding of a soft tooth structure, comprising a driving core and a soft damping body, wherein the driving core comprises an axial flexible tube, a fabric wrapping layer, a cord wrapping layer, a flexible coating layer and a pipe, wherein the axial flexible tube is made of a flexible material and is provided with an axial driving cavity;

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

[0013] The cord wrapping layer is formed by spirally winding an inextensible cord around the fabric wrapping layer;

[0014] The flexible covering layer is formed by covering the cord winding layer with a flexible material;

[0015] The soft damping body includes a radial expansion tube, an outer tube, a second pipe, a rear end cover and a front end cover. The radial expansion tube and the outer tube are both made of flexible materials. A plurality of inner low modulus soft teeth are arranged on the periphery of the radial expansion tube. Each inner low modulus soft tooth is located in the radial direction of the radial expansion tube. The plurality of inner low modulus soft teeth are distributed along the axial direction of the radial expansion tube to form a corrugated shape. The rear end of the outer tube is fixedly connected to the rear end cover. The front end of the outer tube is open. A plurality of outer high modulus soft teeth are arranged on the inner wall of the outer tube. Each outer high modulus soft tooth is located in the radial direction of the outer tube. The radial expansion tube is located in the outer tube. The inner low modulus soft teeth correspond to the outer high modulus soft teeth. 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 tube is fixedly connected to the rear end cover. The second pipe is connected to the rear end cover. The second pipe passes 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 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, pipe one is connected to the rear end cover, pipe one passes through the rear end cover, and pipe one is connected to the axial driving cavity of the axial flexible tube; a radial expansion cavity is formed between the periphery of the driving core and the inner wall of the radial expansion cylinder, and pipe two is connected to the radial expansion cavity.

[0017] Preferably, pipeline one is a trachea and pipeline two is a trachea.

[0018] Preferably, 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 tube is silicone, natural rubber, latex or gel; the flexible material of the outer tube is silicone, natural rubber, latex or gel.

[0019] Preferably, the winding mode of the cord winding layer is left-handed and right-handed.

[0020] Preferably, the axial variable stiffness soft driver based on the meshing and sliding of the soft tooth structure further comprises a sensing component, the sensing component comprises an axial strain sensing unit, and the axial strain sensing unit 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, the axial stiffness sensing unit 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, and the axial stiffness sensing unit 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, an axial variable-rigidity soft driver based on the meshing and sliding of a 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 meshes with the outer layer of high-modulus soft teeth, 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 stiffness of the axial expansion and contraction.

[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 volume of the whole product can be made very small.

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

[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 an axial variable stiffness soft body actuator based on the meshing and sliding of a soft tooth structure;

[0034] Figure 2 It is a three-dimensional model diagram of an axial 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 driver 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 It is a cross-sectional view of an axial variable stiffness soft body actuator based on the meshing and slipping of a soft tooth structure;

[0039] Figure 7 yes Figure 6 Sectional view in the AA direction;

[0040] Figure 8 This is the state diagram when the inner layer low modulus soft teeth and the outer layer high modulus soft teeth are not meshing;

[0041] Fig. 9 This is a diagram of the state where the inner layer of low modulus soft teeth and the outer layer of high modulus soft teeth are meshed together;

[0042] Fig.10 It is a schematic diagram of the structure of a dielectric elastomer sensor used to make an axial strain sensing unit;

[0043] Fig.11 yes Fig.10 Dimensional diagram of the first electrode layer and the first silicone layer in the dielectric elastomer sensor shown;

[0044] Fig.12 It is a schematic diagram of the structure of a dielectric elastomer sensor used to make an axial stiffness sensing unit;

[0045] Fig.13 yes Fig.12 Dimensional diagram of the third electrode layer and the fourth silicone layer in the dielectric elastomer sensor shown;

[0046] Fig.14 is the relationship between the axial length of the axial flexible tube and the gas pressure in the axial drive chamber;

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

[0048] Fig.16 This is a relationship diagram of the axial drive control accuracy of the axial variable stiffness soft actuator based on the meshing slip of the soft tooth structure, wherein Figure (a) is the relationship between the air pressure in the axial flexible tube and the length of the entire axial variable stiffness soft actuator during open-loop control, and Figure (b) is the relationship between the air pressure in the axial flexible tube and the length of the entire axial variable stiffness soft actuator during closed-loop control;

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

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

[0051] Fig.19 It is an application diagram of an axial variable stiffness soft body actuator based on the meshing and sliding of a soft tooth structure;

[0052] Fig. 20 It is a schematic diagram of the structure of the axial variable stiffness soft actuator based on the meshing and sliding of the soft tooth structure during the movement process of the human elbow joint;

[0053] Fig.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 drive based on meshing and sliding 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 layer low modulus soft teeth, 12-2. outer cylinder, 123. outer layer 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 by way of 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 includes an axial flexible tube 111, a fabric wrapping layer 112, a cord wrapping layer 113, a flexible coating layer 114, and a pipe 115. The axial flexible tube 111 is made of a flexible material, and is provided with an axial driving cavity, and the pipe 115 is connected to the axial driving cavity. Inflating the axial driving cavity of the axial flexible tube 111 through the pipe 115 can make the axial flexible tube 111 extend in the axial direction, thereby extending the axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure; deflating the axial driving cavity of the axial flexible tube 111 through the pipe 115 can shorten the axial flexible tube 111 in the axial direction, thereby shortening the axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure.

[0062] The fabric wrapping layer 112 is made of an anisotropic fabric material, which is wrapped around the periphery of the axial flexible tube 111 to form the fabric wrapping layer 112; the anisotropic fabric material has high elasticity along the axial direction of the axial flexible tube 111, and has very low elasticity and is almost non-deformable along the direction perpendicular to the axial direction. When the axial drive cavity of the axial flexible tube 111 is inflated, the fabric wrapping layer 112 can limit the radial expansion of the axial drive cavity and increase the axial strain of the axial flexible tube 111.

[0063] The cord winding layer 113 is formed by spirally winding an inextensible polyethylene cord in a left-handed and right-handed manner on the fabric wrapping layer 112. On the one hand, the fabric wrapping layer 112 can be fixed in a binding manner; on the other hand, the radial expansion of the axial flexible tube 111 can be limited, because the anisotropic fabric is not absolutely non-deformable in the radial direction, and bundling with inextensible cords can limit the deformation of the anisotropic fabric in the radial direction.

[0064] The flexible covering layer 114 is made of a flexible material to cover the cord winding layer 113 , thereby protecting the cord and preventing the cord from moving.

[0065] like Figure 2 , 4As shown in FIGS. 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 high modulus soft teeth 123, and each outer 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 low modulus soft teeth 122 correspond to the outer 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, the pipe 12-3 is connected to the rear end cover 12-4, the pipe 12-3 passes through the rear end cover 12-4, and the pipe 12-3 is connected to the inner cavity of the radial expansion cylinder 12-1.

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

[0067] When air is ventilated to the radial expansion chamber 121 through the 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 (slippage between flexible materials). In the process of meshing and slipping, the normal force and the stick-slip friction force hinder the telescopic movement of the driving core 11. 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, and the resistance can be controlled by the air pressure in 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 meshed, when the radial expansion chamber 121 is exhausted outwardly through the 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 mesh. Figure 8 It shows that the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 are not meshing). 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] Fig. 9 It is shown that the inner layer low modulus soft teeth 122 and the outer layer high modulus soft teeth 123 are meshed together, and the meshing degree is relatively high. Fig. 9 The degree of meshing is higher than Figure 6 Displays the degree of meshing.

[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 driving core 11 (i.e., attached to the flexible coating layer 114) to detect the strain of the driving 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) to detect the strain of the outer high modulus soft teeth 123. 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 telescopic stiffness of the axial variable stiffness soft driver 1 based on the meshing slip of the soft tooth structure.

[0072] The axial strain sensing unit 131 uses a well-known dielectric elastomer sensor, such as Fig.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 a positive electrode layer and a 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. Fig.11As shown, a specific size of the first silicone layer 1311 is: 60mm long and 35mm wide, and the size of the first electrode layer 1312 is: 50mm long and 30mm wide. The dielectric elastomer sensor also includes a first copper foil and a second copper foil, the first copper foil is connected to the first electrode layer 1312, and the second copper foil is connected to the second electrode layer 1313. The first copper foil and the second copper foil are used as pins to be electrically connected to the measurement circuit. The first signal line is welded to the first copper foil, and the second signal line is welded to the second copper foil. The first signal line and the second signal line pass through the rear end cover 12-4 respectively, and the first signal line and the second signal line are electrically connected to the external measurement circuit respectively. The dielectric elastomer sensor detects the capacitance data as the strain information detected by the axial strain sensing unit 131, and the detection accuracy is high.

[0073] The axial stiffness sensing unit 132 uses a well-known dielectric elastomer sensor, such as Fig.12 As shown, the flattened dielectric elastomer sensor includes a fourth silicone layer 1321, a third electrode layer 1322, a fourth electrode layer 1323, a fifth silicone layer 1324, and a sixth silicone layer 1325 connected together, the fourth silicone layer 1321 serves as a dielectric layer, the third electrode layer 1322 and the fourth electrode layer 1323 serve as a positive electrode layer and a negative electrode layer of the fourth silicone layer 1321, respectively, and the fifth silicone layer 1324 and the sixth silicone layer 1325 serve as protective layers. Fig.13 As shown, a size of the fourth silicone layer 1321 is: 60 mm long and 79 mm wide, and a size of the third electrode layer 1322 is: 50 mm long and 74 mm wide. The dielectric elastomer sensor also includes a third copper foil and a fourth copper foil, the third copper foil is connected to the third electrode layer 1322, and the fourth copper foil is connected to the fourth electrode layer 1323. The third copper foil and the fourth copper foil are used as pins to be electrically connected to the measurement circuit. The dielectric elastomer sensor detects capacitance data as strain information detected by the axial stiffness sensing unit 132, and has high detection accuracy.

[0074] When the axial drive cavity of the axial flexible tube 111 is inflated or deflated, the entire axial variable stiffness soft drive 1 based on the meshing and sliding of the soft tooth structure can be extended or shortened. The relationship between the axial length of the entire axial variable stiffness soft drive and the air pressure in the axial drive cavity is as follows: Fig.14 As shown. Fig.14As shown, the horizontal axis is the air pressure value 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, that is, the driving 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 driver 1 based on the meshing and sliding of the soft tooth structure to extend, thereby driving an external object; similarly, deflating the axial drive cavity of the axial flexible tube 111 causes the entire axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure to shorten, thereby also driving an external object.

[0075] When the inner layer of low modulus soft teeth 122 and the outer layer of high modulus soft teeth 123 are in meshing state, the inner layer of low modulus soft teeth 122 and the outer layer of high modulus soft teeth 123 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 surface 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 meshing degree of the inner layer of low modulus soft teeth 122 and the outer layer of high modulus soft teeth 123. The meshing degree can be controlled by the air pressure of the radial expansion chamber 121, thereby controlling the resistance. Fig.15 As shown, 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 body driver 1 based on the meshing and sliding of the soft tooth structure increases accordingly. When the air pressure in the radial expansion chamber 121 is 0 kPa, the axial equivalent Young's modulus of the entire axial variable stiffness soft body driver is 266.2 kPa. When the air pressure in the radial expansion chamber 121 is 20 kPa, the axial equivalent Young's modulus of the entire axial variable stiffness soft body driver is 1923.9 kPa, which changes by 7.2 times. It can be seen that the higher the degree of meshing, the greater the resistance.

[0076] Under the closed-loop control using 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: Fig.16 Under the same experimental conditions, four 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 Fig.16 As shown in the middle 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 FIG. Fig.16As shown in the middle figure (b), the error is about 1 / 3 of the open-loop drive control error. It can be seen that the closed-loop drive control accuracy 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 accuracy of the axial variable stiffness soft drive 1 based on the meshing slip of the soft tooth structure is as follows: Fig.17 As shown, the ordinate of Figure (a) is the axial equivalent Young's modulus, the abscissa is the air pressure in the radial expansion chamber 121, and the ordinate of Figure (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 open-loop drive control using only the air pressure in the radial expansion chamber 121 is 3.74%, as shown in FIG. Fig.17 As shown in the middle figure (b), the relative error of the closed-loop drive control combined with the strain information of the axial stiffness sensing unit 132 is 1.20%, which is less than 1 / 3 of the open-loop drive control error.

[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 telescopic stiffness of the axial variable stiffness soft drive 1 based on the meshing slip of the soft tooth structure. A specific implementation method may be, referring to Fig.21 , the function is obtained by polynomial fitting method:

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

[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; z is the axial equivalent Young's modulus of the entire axial variable stiffness soft drive.

[0081] refer to Fig.18 The preparation process of the axial variable stiffness soft drive 1 based on the meshing and sliding of the soft tooth structure is as follows:

[0082] Step S01 , preparing the axial flexible tube 111 by a silicone casting process. It is a preferred solution to select silicone as the manufacturing material of the axial flexible tube 111 .

[0083] Step S02, anisotropic fabric is wrapped around the outside of the axial flexible tube 111 to form a fabric wrapping layer 112, polyethylene cord is wrapped around the outside of the fabric wrapping layer 112 in a bidirectional spiral winding manner to form a cord wrapping layer 113, and then silicone is coated on the outside of the cord wrapping layer 113 to form a flexible coating layer 114, thereby forming the driving core 11. Silicone is the preferred material for the flexible coating layer 114.

[0084] 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 coating layer 114 , thereby forming an axial strain sensing unit 131 .

[0085] Step S04, preparing the radial expansion tube 12-1 by a silicone casting process. The radial expansion tube 12-1 is integrally formed, and the manufactured radial expansion tube 12-1 has a plurality of inner low modulus soft teeth 122; using silicone as the manufacturing material of the radial expansion tube 12-1 is the preferred solution.

[0086] Step S05, preparing the outer cylinder 12-2 by a silicone casting process, the outer cylinder 12-2 is integrally formed, and the inner wall of the outer cylinder 12-2 has a plurality of outer high modulus soft teeth 123; using silicone as the material for making the outer cylinder 12-2 is a preferred solution.

[0087] Step S06, prepare pipe 1 115, pipe 2 12-3, and prepare a first mold and a second mold. The material of pipe 1 115 and pipe 2 12-3 is preferably a flexible material (such as silicone). In this case, pipe 1 115 and pipe 2 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 put them on the first mold, with the rear ends of the radial expansion cylinder 12-1 and the driving core 11 facing downward and standing up in the vertical direction; then put the pipe 1 115 and the pipe 2 12-3 in the holes on the first mold for positioning;

[0089] Step S08, pouring silicone into the first mold to form the rear end cover 12-4, the rear end of the radial expansion cylinder 12-1 is fixedly connected to the rear end cover 12-4, the rear end of the driving core 11 is fixedly connected to the rear end cover 12-4, pipe 1 115 and pipe 2 12-3 pass through the rear end cover 12-4, pipe 1 115 is connected to the axial driving cavity of the driving core 11, and pipe 2 12-3 is connected to the inner cavity of the radial expansion cylinder 12-1.

[0090] Step S09, removing 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 facing downward and standing up in the vertical direction; then pour silicone into the second mold to form a front end cover 12-5, and the front end of the radial expansion cylinder 12-1 is fixedly connected to the front end cover 12-5, and the front end of the driving core 11 is fixedly connected to the front end cover 12-5.

[0092] Step S11, removing the second mold.

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

[0094] Step S13, the outer tube 12-2 and the radial expansion tube 12-1 are sleeved together, and the rear end surface of the outer tube 12-2 is fixedly connected with the rear end cover 12-4 by using a silicone adhesive. At this time, the rear end of the outer tube 12-2 is closed, and the front end of the outer tube 12-2 is open (not closed).

[0095] It should be noted that, in addition to silicone, the material of the axial flexible tube 111 can also be other flexible materials such as natural rubber, latex or gel. In addition to silicone, the material of the flexible coating layer 114 can also be other flexible materials such as natural rubber, latex or gel; in addition to silicone, the material of the radial expansion tube 12-1 can also be other flexible materials such as natural rubber, latex or gel. In addition to silicone, the material of the outer tube 12-2 can also be other flexible materials such as natural rubber, latex or gel. It is a preferred option to use silicone as the material of the rear end cover 12-4 and the front end cover 12-5, and other flexible materials such as natural rubber, latex or gel can also be used.

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

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

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

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

[0100] As for the anisotropic fabric material, specifically polyester, nylon, spandex or cotton can be selected.

[0101] It should be noted that inflating the axial drive cavity of the axial flexible tube 111 is a preferred solution (in this case, the pipe 115 is the air pipe 1 for ventilation). The use of gas has some advantages, such as: convenient and fast inflation and exhaust operations, easy exhaust of the gas in 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 the medium.

[0102] Similarly, inflating and exhausting the radial expansion chamber 121 is also a preferred solution (in this case, the pipe 2 12-3 is the air pipe 2 used for ventilation). However, in addition to using gas, water or oil or other fluids can also be used as the medium.

[0103] The axial variable stiffness soft driver of the present invention can be very 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 drive core 11 can be 10 mm, the inner diameter of the axial drive 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 teeth can be 2 mm.

[0104] The following introduces an application scenario.

[0105] like Fig.19 As shown, the outer cylinder 12-2 is fixedly connected to the first external structure 100, and the front end of the radial expansion cylinder 12-1 is fixedly connected to the second external structure 200. Then, the first external structure 100 is fixed and the second external structure 200 is moved. During the movement of the second external structure 200, the resistance between the outer cylinder 12-2 and the radial expansion cylinder 12-1 needs to be overcome to achieve the resistance movement. Of course, the second external structure 200 can also be fixed while the first external structure 100 moves, and the resistance movement can also be achieved. That is to say, the first external structure 100 and the second external structure 200 move relative to each other, and the axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure is used to achieve the resistance movement, and the auxiliary external structure achieves the resistance movement.

[0106] The following introduces another application scenario.

[0107] In the field of muscle strength rehabilitation training, generally including passive training, power training, active training and resistance training. The present invention can be applied to resistance training to provide matching resistance for the rehabilitation limbs.

[0108] For human elbow joint movement, the outer tube 12-2 is connected to the forearm using Velcro or a string, such as Fig. 20As shown, Velcro or cord is used to connect the front end of the radial expansion tube 12-1 to the upper arm. When the axial drive chamber of the axial flexible tube 111 is inflated and the radial expansion chamber 121 is not inflated, the movement of the elbow joint drives the entire axial variable stiffness soft driver 1 based on the meshing and sliding of the soft tooth structure to axially extend and retract (at this time, there is no resistance between the outer tube 12-2 and the radial expansion tube 12-1), which can realize passive training or power training of the muscle group during the joint extension process. When the axial drive chamber of the axial flexible tube 111 is inflated (maintaining a certain air pressure), the radial expansion chamber 121 is also inflated (at this time, there is resistance between the outer tube 12-2 and the radial expansion tube 12-1), and the resistance that adapts to the needs is provided for the active extension process of the elbow joint to realize the resistance training of the muscle group.

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

Claims

1. An axial variable stiffness soft drive 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 comprises a radial expansion tube, an outer tube, a second pipe, a rear end cover and a front end cover. The radial expansion tube and the outer tube are both made of flexible materials. The outer periphery of the radial expansion tube is provided with a plurality of inner low modulus soft teeth, each of which is located in the radial direction of the radial expansion tube, and the plurality of inner low modulus soft teeth are distributed along the axial direction of the radial expansion tube to form a corrugated shape; the rear end of the outer tube is fixedly connected to the rear end cover, the front end of the outer tube is open, and the inner wall of the outer tube is provided with a plurality of outer high modulus soft teeth, each of which is located in the radial direction of the outer tube; the radial expansion tube is located in the outer tube, 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 tube 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 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 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 tube is silicone, natural rubber, latex or gel; the flexible material of the outer tube is silicone, natural rubber, latex or gel.

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

5. The axial 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 also includes a sensing component, and the sensing component includes an axial strain sensing unit, and the axial strain sensing unit is attached to the outer surface of the driving core.

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

7. The axial variable stiffness soft actuator based on the meshing and sliding of soft tooth structure according to claim 6, characterized in that: 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 is a dielectric elastomer sensor.

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

10. The axial variable stiffness soft actuator based on the meshing and sliding of soft tooth structure 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 are meshed, and the first external structure and the second external structure move relative to each other.

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