Radial actuator for peristaltic soft robot

Abstract

The radial actuator is internally provided with an air cavity, a micro-channel and a cylindrical cavity, the cylindrical cavity is arranged along the central axis of the radial actuator, the air cavity is in a circular ring shape and is arranged along the inner wall of the radial actuator, and a first preset distance is kept between the air cavity and the radial actuator; the microchannel is arranged between the air cavity and the inner wall of the radial actuator, the air cavity surrounds the cylindrical cavity, a second preset distance is kept between the inner wall of the air cavity and the outer wall of the cylindrical cavity, and the air pressure in the air cavity can be increased or decreased; the liquid metal is arranged in the microchannel, when the air pressure in the increased air cavity changes, the radial actuator deforms to cause deformation of the microchannel, then the resistance of the liquid metal changes, and the expansion deformation condition of the radial actuator is judged according to the resistance change of the liquid metal. According to the invention, the expansion deformation performance of the radial actuator is improved, so that the radial actuator can move more quickly and fixedly, and the movement efficiency of the peristaltic soft robot is improved.

Description

Technical Field

[0001] The invention relates to the technical field of radial actuator design for soft robots, and in particular to a radial actuator for a creeping soft robot. Background Art

[0002] In recent years, the field of soft robots has attracted widespread attention at home and abroad. Among them, peristaltic soft robots have high adaptability in unstructured environments and can be widely used in various scenarios such as pipeline inspection and searching in confined spaces. As an important factor in determining motion efficiency, the radial actuator of peristaltic soft robots faces great challenges in control and motion performance.

[0003] There are two main problems in the mechanical design of peristaltic soft robots. The first is that the amount of gas input is too large, making the control of the robot challenging. The second problem is that the robot performance is low and cannot achieve the movement speed required for the robot's detection function.

[0004] In terms of control, soft robots have the development direction of integrated intelligent design and cutting-edge sensing technology. Wang combined the electrically driven soft robot with intelligent materials through structural design, and realized the multimodal function of the robot through shape reconstruction under external stimulation. Xu used a high-density dielectric elastomer actuator array as a soft peristaltic pump for the control and power source of fluid robots. However, peristaltic soft robots still rely on external sensor elements when feeding back motion data, such as pressure sensors placed near the air source rather than the soft robot body. Although this semi-closed-loop control method is simple, external interference has a greater impact on sensor data, especially in complex environments. External sensors cannot provide accurate data feedback, and have less sensitivity to the deformation of the actuator, which is not conducive to the control of the soft robot's flexible materials.

[0005] In terms of the motion performance of creeping soft robots, some scholars have also conducted research on this. Xiong proposed a multi-material hybrid actuator, called MASH actuator, which combines electrostatic adhesion (EA) with gas drive and introduces an adaptive deformation restriction layer inspired by the longitudinal muscles of earthworms. The length, stiffness and position of the actuator can be changed, which enhances the function of the robot, but different driving methods also increase the complexity of control. Jiang proposed the design and manufacture of a worm-like soft robot, which is designed to operate in a pipe. It uses pneumatic actuators and origami-fabric composite materials. Paper is used as the skeleton of the robot and fabric is used as the skin of the robot. The origami structural design makes the robot's soft actuator have stronger mechanical properties. However, the fusion of origami-fabric composite materials and liquid conductive materials is poor, which is not conducive to achieving the integrated design effect of the actuator. Liu proposed a modular bionic soft robot that can crawl and cross obstacles. The robot consists of multiple soft modules, each of which contains two parallel soft actuators. The gait of the bionic soft robot is changed by controlling the morphology of the two soft actuators, but it does not change the deformation time ratio of the soft actuator, and the improvement of the robot's movement efficiency is relatively limited.

[0006] Soft robots are composed of actuators, which are driven in various ways, such as by electricity, chemistry, magnetism, heat and fluid. The most common method is to use gas pressurization in different cavities to achieve the robot's expansion, contraction, twisting or bending movements. This versatility makes soft robots widely used in many fields. The radial actuator of the peristaltic soft robot is an important factor in determining its overall motion efficiency and control performance. However, the design of the radial actuator of the peristaltic soft robot has not been very effective and needs to be improved urgently. Summary of the invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the design of the radial actuator of the creeping soft robot in the prior art has not been very effective.

[0008] In order to solve the above technical problems, the present invention provides a radial actuator for a peristaltic soft robot, wherein an air cavity, a microchannel and a cylindrical cavity are arranged in the radial actuator, wherein:

[0009] The cylindrical cavity is arranged along the central axis of the radial actuator, the air cavity is annular and arranged along the inner wall of the radial actuator and keeps a first preset distance from the radial actuator, the microchannel is arranged between the air cavity and the inner wall of the radial actuator, the air cavity surrounds the cylindrical cavity, and the inner wall of the air cavity keeps a second preset distance from the outer wall of the cylindrical cavity, wherein,

[0010] The air cavity is used to communicate with the air pipe from the outside of the radial actuator, and the air pressure inside the air cavity is increased or decreased through the air pipe outside the radial actuator; the cylindrical cavity is used to store the air pipe connected to the air cavity of other radial actuators or axial actuators of the soft robot;

[0011] The microchannel contains liquid metal. When the air pressure in the air cavity changes, the radial actuator deforms, causing the microchannel to deform. The deformation of the microchannel causes the resistance of the liquid metal to change. The expansion deformation of the radial actuator is determined based on the change in the resistance of the liquid metal.

[0012] In one embodiment of the present invention, the major axis length of the cross section of the microchannel is , the minor axis length is ,and , where the major axis length of the cross section is and minor axis length The ratio increases as the pressure in the air cavity increases.

[0013] In one embodiment of the present invention, the cross-section of the microchannel includes a circular shape and an elliptical shape. Under the same gas pressure of the radial actuator, the microchannel with an elliptical cross-section has a greater expansion deformation than the microchannel with a circular cross-section.

[0014] In one embodiment of the present invention, the radial actuator is under the same gas pressure, when the major axis length of the microchannel is With minor axis length When the ratio is within the preset range, if the major axis length With minor axis length The larger the ratio is, the higher the deformation degree of the microchannel is, and the greater the expansion deformation of the side wall of the radial actuator is.

[0015] In one embodiment of the present invention, when the major axis length of the microchannel cross section is Equal to the minor axis length When the gas pressure is 0-225 kPa, the resistance of the liquid metal in the microchannel increases with the increase of the gas pressure and the growth rate is When the air pressure is 225-300 kPa, the resistance of the liquid metal in the microchannel increases with the increase of air pressure and the growth rate is ,in, ;

[0016] When the major axis length of the microchannel cross section Greater than the minor axis length When the gas pressure is 0-225 kPa, the resistance of the liquid metal in the microchannel increases with the increase of the gas pressure and the growth rate is When the air pressure is 225-300 kPa, the resistance of the liquid metal in the microchannel increases with the increase of air pressure and the growth rate is ,in, ,and .

[0017] In one embodiment of the present invention, the radial actuator is set at the same gas pressure, and the major axis length of the microchannel cross section is Equal to the minor axis length The first sensitivity of the microchannel is GF1, and the major axis length of the microchannel cross section is Greater than the minor axis length The second sensitivity of the microchannel is GF2, and the second sensitivity GF2 is greater than the first sensitivity GF1, wherein the sensitivity is used to reflect the radial expansion of the microchannel, and the formula is:

[0018] ;

[0019] in, is the sensitivity, represents the resistance of the microchannel when stretched, represents the resistance change, is the applied strain.

[0020] In one embodiment of the present invention, under the same air pressure, if other parameters of the radial actuator are the same, the thicker the thickness of the annular air cavity is, the greater the radial expansion deformation of the radial actuator is.

[0021] In one embodiment of the present invention, during the deformation of the radial actuator, it is assumed that the pressure is The tension on the side wall of the air cavity is The tensions borne by the upper and lower walls of the air cavity are , the constraint force generated by the fixed interfaces at both ends of the radial actuator is The side wall of the central cylindrical cavity is subject to a constraint force of , then it satisfies:

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] in, is the radius of the circular cross section of the radial actuator, is the distance between the air cavity and the inner wall of the radial actuator, is the thickness of the air cavity, is the height of the air cavity.

[0027] In one embodiment of the present invention, the radial actuator is made of silicone.

[0028] The above technical solution of the present invention has the following advantages compared with the prior art:

[0029] The radial actuator constructed in the present invention reduces the constraint force on the expansion and deformation of the radial actuator in structure, improves the expansion and deformation performance of the radial actuator, enables the actuator to fix the displacement faster under the same air pressure, shortens the transition time of the periodic motion of the peristaltic soft robot, improves the motion efficiency of the peristaltic soft robot, and can change the output resistance after the peristaltic soft robot itself expands and deforms, thereby realizing a fully flexible strain sensing function, which is beneficial to the precise control of the motion of the peristaltic soft robot;

[0030] The present invention mainly designs a cylindrical cavity in the radial actuator so that the contraction of the radial actuator can better fix the body of the peristaltic soft robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0032] Figure 1 Schematic diagram of the design of the radial actuator microchannel in an embodiment of the present invention;

[0033] Figure 2 Schematic diagram of preliminary setting of structural parameters of radial actuator in an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of the final setting of the structural parameters of the radial actuator in an embodiment of the present invention;

[0035] Figure 4 Schematic diagram of expansion deformation of two different radial actuator structures in an embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of a cross section and mesh division of a finite element model of a radial actuator in an embodiment of the present invention;

[0037] FIG6 (a) is a cloud diagram of radial deformation displacement of a radial actuator at a pressure of 100 kPa when the microchannel parameter a=b=0.4 in an embodiment of the present invention;

[0038] FIG6 (b) is a cloud diagram of radial deformation displacement of the radial actuator at a pressure of 200 kPa when the microchannel parameter a=b=0.4 in an embodiment of the present invention;

[0039] FIG6 (c) is a cloud diagram of radial deformation displacement of the radial actuator at a pressure of 300 kPa when the microchannel parameter a=b=0.4 in an embodiment of the present invention;

[0040] Figure 7 is a radial deformation displacement cloud diagram of the radial actuator at a pressure of 300 kPa when the microchannel parameters a=0.5 and b=1 in an embodiment of the present invention;

[0041] Figure 8 is a graph showing the relationship between the resistance and the gas pressure of microchannels with different structural parameters in an embodiment of the present invention;

[0042] Fig. 9 is a schematic diagram of a cross section and mesh division of a finite element model of a radial actuator with a changed base structure in an embodiment of the present invention;

[0043] FIG. 10 ( a ) is a cloud diagram of radial deformation displacement of the radial actuator in an embodiment of the present invention when the air cavity parameter d2 = 3 mm;

[0044] FIG. 10 ( b ) is a cloud diagram of radial deformation displacement of the radial actuator in an embodiment of the present invention when the air cavity parameter d2=3 mm;

[0045] FIG. 10 ( c ) is a cloud diagram of radial deformation displacement of the radial actuator in an embodiment of the present invention when the air cavity parameter d2 = 3 mm;

[0046] Fig.11 3 is a schematic diagram of a cross section and mesh division of a finite element model of a radial actuator obtained according to the structural parameters in Table 3 in an embodiment of the present invention;

[0047] FIG. 12 ( a ) is a deformation displacement cloud diagram of a radial actuator with a circular air cavity in an embodiment of the present invention;

[0048] FIG12( b ) is a deformation displacement cloud diagram of a radial actuator of a common air cavity in an embodiment of the present invention;

[0049] Fig.13 is a relationship diagram between the maximum displacement of the side wall and the gas pressure of the two structures of the radial actuator in the embodiment of the present invention;

[0050] Fig.14 4 is a graph showing the relationship between the output resistance and the expansion deformation of the radial actuator in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0052] Embodiment 1

[0053] Reference Figure 1-Figure 3As shown, the present invention relates to a radial actuator for a peristaltic soft robot, wherein an air cavity 1, a microchannel 2 and a cylindrical cavity 3 are arranged in the radial actuator, wherein:

[0054] The cylindrical cavity 3 is arranged along the central axis of the radial actuator, the air cavity 1 is annular and arranged along the inner wall of the radial actuator and maintains a first preset distance with the radial actuator (the first preset distance can be used to place the microchannel 2) to form a first gap (the first gap is consistent with the matrix material of the radial actuator, that is, filled with silicone), the microchannel 2 is arranged between the air cavity 1 and the inner wall of the radial actuator, the air cavity 1 surrounds the cylindrical cavity 3 and the inner wall of the air cavity 1 maintains a second preset distance with the outer wall of the cylindrical cavity 3 (the second preset distance is actually set to avoid the air cavity 1 from affecting the cylindrical cavity 3) to form a second gap (the second gap is consistent with the matrix material of the radial actuator, that is, filled with silicone).

[0055] The air cavity 1 is used to communicate with the air pipe from the outside of the radial actuator, and the air pressure inside the air cavity 1 is increased or decreased through the air pipe outside the radial actuator; the cylindrical cavity 3 is used to store the air pipe connected to the air cavity of other radial actuators or axial actuators of the soft robot;

[0056] The microchannel 2 contains liquid metal. When the air pressure in the enlarged air cavity 1 changes (increases or decreases), the radial actuator deforms (radially expands or contracts), causing the microchannel 2 to deform. The deformation of the microchannel 2 causes the resistance of the liquid metal to change. The expansion deformation of the radial actuator is determined based on the change in the resistance of the liquid metal.

[0057] It should be noted that the air cavity 1 and the cylindrical cavity 3 of the present embodiment are actually connected to the radial actuator substrate. The air cavity 1 and the cylindrical cavity 3 are both opened in the radial actuator substrate, that is, the gap corresponding to the first preset distance and the second preset distance is filled with silicone of the same material as the radial actuator substrate.

[0058] Further, assuming that the major axis length of the cross section of the microchannel 2 is , the minor axis length is ,and , where the major axis length of the cross section is and minor axis length The ratio increases as the pressure in the air cavity 1 increases.

[0059] Furthermore, the cross-section of the microchannel 2 includes a circular shape and an elliptical shape. Under the same air pressure of the radial actuator, the expansion deformation amount of the microchannel 2 with an elliptical cross-section is greater than that of the microchannel 2 with a circular cross-section.

[0060] Furthermore, when the radial actuator is under the same gas pressure, the major axis length of the microchannel 2 is With minor axis length When the ratio is within the preset range, if the major axis length With minor axis length The larger the ratio is, the higher the deformation degree of the microchannel 2 is, and the greater the expansion deformation of the side wall of the radial actuator is.

[0061] Furthermore, when the major axis length of the cross section of the microchannel 2 is Equal to the minor axis length When the gas pressure is 0-225 kPa, the resistance of the liquid metal in the microchannel 2 increases with the increase of the gas pressure and the growth rate is When the air pressure is 225-300 kPa, the resistance of the liquid metal in the microchannel 2 increases with the increase of the air pressure and the growth rate is ,in, ;

[0062] When the major axis length of the cross section of the microchannel 2 Greater than the minor axis length When the gas pressure is 0-225 kPa, the resistance of the liquid metal in the microchannel 2 increases with the increase of the gas pressure and the growth rate is When the air pressure is 225-300 kPa, the resistance of the liquid metal in the microchannel 2 increases with the increase of the air pressure and the growth rate is ,in, ,and .

[0063] Furthermore, the radial actuator is under the same air pressure, and the major axis length of the cross section of the microchannel 2 is Equal to the minor axis length The first sensitivity of microchannel 2 is GF1, and the major axis length of the cross section of microchannel 2 is Greater than the minor axis length The second sensitivity of the microchannel 2 is GF2, and the second sensitivity GF2 is greater than the first sensitivity GF1, wherein the sensitivity is used to reflect the radial expansion of the microchannel 2, and the formula is:

[0064]

[0065] in, is the sensitivity, represents the resistance of the microchannel when stretched, represents the resistance change, is the applied strain.

[0066] Furthermore, under the same air pressure, if other parameters of the radial actuator are the same, the thicker the annular air cavity 1 is, the greater the radial expansion deformation of the radial actuator is.

[0067] The following is a detailed introduction to this embodiment:

[0068] The peristaltic soft robot is mainly composed of a radial actuator, an axial actuator, a trachea, and a fiber-reinforced wire or spiral tube wound on the surface of the axial actuator. The radial actuator body is based on an annelid as a prototype, and its mechanical design is inspired by the symmetrical cylindrical part in the annelid body cavity. The radial actuator is made of superelastic silicone and can expand radially under the action of air pressure. When it expands to the inner wall of the pipe, it can fix the soft robot. This embodiment introduces a sensing layer (i.e., microchannel 2) and injects liquid metal, so that the radial actuator has a strain sensing function and maintains its overall flexibility. The radial actuator microchannel 2 is designed as follows: Figure 1 As shown, the microchannel 2 is also provided with a positive electrode and a negative electrode connection. Both the positive and negative electrodes extend from between the inner wall of the radial actuator and the outer wall of the air cavity 1 to the outside of the radial actuator, and are connected to a controller outside the axial actuator for detecting the resistance of the liquid metal in the microchannel 2.

[0069] When the air pressure in the radial actuator air cavity 1 is increased, the actuator expands radially, and the microchannel 2 is also stretched and deformed. Due to the incompressibility of the liquid, the shape of the liquid metal in the microchannel 2 will change accordingly, and the resistance of the liquid metal will also change with the change of shape. The structural parameters of the radial actuator are preliminarily set as follows: Figure 2 As shown, and are the minor axis length and major axis length of the cross section of microchannel 2, is the distance between the outer wall of the air cavity 1 and the inner wall of the radial actuator, is the thickness of the air cavity 1, is the height of air cavity 1, is the length of microchannel 2, is the length of the radial actuator, is the radius of the circular cross section of the radial actuator.

[0070] Resistance change of the microchannel 2 of the radial actuator of this embodiment The theoretical relationship with its deformation is as follows:

[0071] (1)

[0072] In the formula, and are the resistance of the radial actuator’s microchannel when stretched and undeformed, is the resistivity of the liquid metal, is the original length of the microchannel, is the applied strain, and are the minor axis length and major axis length of the microchannel cross section, are the deformation of the short axis and the long axis respectively. From formula (1), it can be seen that when the material of microchannel 2 is given, the resistance value of microchannel 2 is completely dependent on the original length of microchannel 2. , the minor axis length of the cross section of microchannel 2 and the major axis length When the radial actuator expands, the length of microchannel 2 increases, the cross-sectional area decreases, and the resistance of the liquid metal in microchannel 2 increases accordingly. After the radial actuator is released, microchannel 2 returns to its original geometric shape, elastically pushing the liquid back, resulting in a decrease in the resistance of the liquid metal. Therefore, the expansion deformation of the radial actuator can be judged by the change in the resistance of the microchannel 2 of the radial actuator.

[0073] The peristaltic soft robot needs to be driven by gas pressurization, and the control of different gait states requires adjusting the pressure in each air cavity separately. Therefore, the connection interface between the radial actuator and the trachea, axial actuator and other components is made of rubber with low elasticity and good air tightness, which can reduce the impact of the deformation of the superelastic actuator on the trachea. But at the same time, the top and bottom of the radial actuator are constrained by different interfaces respectively, resulting in stress concentration in the middle of the radial actuator, making the strain in the middle of the actuator greater than the strain at both ends of the actuator. The deformation performance of the middle of the radial actuator becomes the main factor affecting the effect of the actuator being fixed to the inner wall of the pipe after radial expansion.

[0074] In order to improve the deformation performance of the radial actuator, the complete structure of the radial actuator is designed in combination with the above-mentioned microchannel 2. Figure 3 As shown, the air cavity 1 is in a circular shape along the inner wall of the radial actuator, so that it surrounds the central cylindrical cavity 3. The central cylindrical cavity 3 and the connecting interface are combined into one and use the same material. The air pipe is fixed inside the cylindrical cavity 3 through the connecting interface and the gas is diverted at the same time, thereby reducing the range of the fixed interface at both axial ends of the radial actuator.

[0075] Figure 4 The expansion deformation principles of two radial actuator structures are compared, among which, Figure 4 (a) is a schematic diagram of the expansion deformation of a radial actuator with a common air cavity. Figure 4 (b) is a schematic diagram of the expansion deformation of a radial actuator with an outer ring air cavity.

[0076] exist Figure 4 During the deformation of the radial actuator shown in (a), the pressure is assumed to be , the tension on the side wall of the air cavity is The tensions borne by the upper and lower walls of the air cavity are , the constraint force generated by the fixed interfaces at both ends of the radial actuator is , the constraint forces on the radial actuator sidewalls at both ends are Pressurizing the air chamber of the radial actuator yields the force balance relationship:

[0077] (2)

[0078] (3)

[0079] (4)

[0080] (5)

[0081] From formulas (2)-(5), we can find that as the air pressure increases, and will increase in order to maintain balance. , Also increases, at this time the radial actuator does not undergo material deformation, and when , After increasing to the upper limit of the corresponding constraint force, only tension and Continue to increase with the increase of air pressure. , , the side wall of the actuator begins to extend axially and tends to expand under the action of pressure, and the degree of expansion increases with and The difference between them increases.

[0082] Therefore, under the same material parameters and air pressure conditions, reducing the constraint force Upper limit or increase tension The radial expansion deformation performance of the radial actuator can be enhanced and its deformation efficiency can be improved.

[0083] exist Figure 4 During the deformation of the radial actuator shown in (b), the pressure is assumed to be , the tension on the side wall of the air cavity 1 is The tensions borne by the upper and lower walls of the air cavity 1 are , the constraint force generated by the fixed interfaces at both ends of the radial actuator is ,and Figure 4 Compared with (a), the range of the restraining force is concentrated on the axial ends of the radial actuator. Figure 4The range of the restraining force in (b) is reduced as the range of the fixed interface is reduced, and is concentrated at the axial ends of the central cylindrical cavity 3, so that the side wall of the radial actuator is no longer subject to the restraining force at both ends, while the side wall of the central cylindrical cavity 3 is subject to the restraining force of , because the cylindrical cavity 3 in the center is made of the same material as the connection interface, which is a rubber material with low elasticity and good air tightness. Pressurizing the annular air cavity 1 of the radial actuator, the force balance relationship is obtained:

[0084] (6)

[0085] (7)

[0086] (8)

[0087] (9)

[0088] in, is the radius of the circular cross section of the radial actuator, is the distance between the air cavity and the inner wall of the radial actuator, is the thickness of the air cavity, is the height of the air cavity. From formulas (6)-(9), it is found that when and As the air pressure increases, in order to maintain balance, , It also increases with Figure 4 (a) The difference is that Figure 4 (b) The restraint force of the interfaces at both ends of the radial actuator on its side wall The action range is transferred to the side wall of the cylindrical cavity 3 in the center, which greatly reduces the resistance of the radial actuator side wall during deformation and improves the radial expansion deformation performance of the actuator. The side wall of the cylindrical cavity 3 in the center is fixed to the connection interface 4 at both ends and the material elasticity is small, so the constraint force The upper limit is high, and the side wall of the cylindrical cavity 3 in the center does not deform with the increase of gas pressure. Because the force balance process of the radial actuator side wall before material deformation is shortened, the radial actuator side wall is deformed with the tension. The increase ratio Figure 4 (a) reaches the deformation state faster, which improves the expansion deformation efficiency of the radial actuator.

[0089] The experimental analysis is as follows:

[0090] This embodiment uses COMSOL finite element simulation software to analyze the influence of different structural parameters on the strain sensing effect of the radial actuator microchannel 2 and the expansion deformation performance of the radial actuator. In order to facilitate simulation, the details of the electrode, air pipe and interface are simplified, and the material parameters are set. The density of the radial actuator silicone matrix is ​​2400kg / m 3 , elastic modulus is 1.8MPa, and the density of liquid metal is 6280kg / m 3 , dynamic viscosity is 0.002Pa·s, resistivity is 2.94×10 -7 Ω / m, after setting different structural parameters, the deformation of the actuator's radial expansion and the state of the microchannel cross section are obtained by multi-physics field simulation of fluid-solid coupling. The simulation results are compared and analyzed to optimize the design parameters.

[0091] Set the structural parameters H=12mm, h=10mm, R=7.5mm, r=6.5mm, L=7π, and change the cross-sectional parameters of microchannel 2 respectively. Microchannel cross-sectional parameters The finite element model of the radial actuator containing microchannel 2 is initially established and meshed. Figure 5 The current terminal and the ground are respectively set at the boundary sections at both ends of the microchannel 2, and the voltage is set to 1V. The sensing performance of the microchannel 2 with different cross-sectional parameters to the radial expansion strain of the actuator is studied.

[0092] Finite element simulation is performed on the radial actuator microchannel 2 with different structures. Figure 6 is the radial deformation displacement cloud diagram of the radial actuator under different pressures when the parameter a=b=0.4mm. From the comparison of Figure 6(a), Figure 6(b) and Figure 6(c), it can be seen that the expansion deformation of the actuator side wall increases with the increase of gas pressure, and the cross-sectional state of the microchannel 2 also changes with the pressure change. In the radial direction, as the pressure increases, the cross-section of the microchannel 2 is squeezed, thereby reducing the short axis length, while in the axial direction, as the pressure increases, the cross-section of the microchannel 2 increases the long axis length due to the stretching of the radial actuator side wall. Figure 7 When a=0.5 and b=1, the deformation cloud diagram of microchannel 2 at P=300kPa is compared with Figure 6(c). Figure 7 The compression and stretching deformation of microchannel 2 is higher, and the expansion deformation of the actuator side wall is also greater.

[0093] Figure 8It is a relationship diagram showing that the resistance of the microchannel 2 with different structures changes as the air pressure increases. In the figure, the resistance value of the microchannel 2 increases non-linearly with the increase of the pressure. Within a certain pressure range, the resistance value increases slowly. However, when the pressure increases beyond a certain range, the cross-section of the microchannel 2 will undergo obvious deformation, and when the length of the major axis of the cross-section of the microchannel 2 is greater than the length of the minor axis, the degree of deformation is higher and the influence on the resistance is greater. That is, when a < b, the non-linear relationship between the resistance value and the pressure is more obvious, and the resistance increase amplitude is greater under the same pressure.

[0094] In this embodiment, the radial expansion strain sensing performance of the actuator microchannel 2 is analyzed through the sensitivity (GF). The GF of the microchannel 2 can be calculated according to Equation (10):

[0095] (10)

[0096] In Equation (10), represents the resistance when the microchannel is stretched, represents the change amount of the resistance. The higher the GF value, the more sensitive the microchannel 2 is to the expansion strain. The relevant data of the microchannels 2 with different structures undergoing strain under the action of the same air pressure are shown in Table 1.

[0097] In Table 1, the lengths of the minor axes of the cross-sections of the first group, the second group, the third group, the fourth group, and the fifth group are all equal to the lengths of the major axes of the cross-sections. By comparing them with each other, it is found that when a = b, the deformation amount and sensitivity of the microchannel 2 do not change significantly due to different cross-section lengths. The lengths of the major axes of the cross-sections of the sixth group and the seventh group are both greater than the lengths of the minor axes of the cross-sections, and the sensitivity is significantly improved compared with the first five groups. This shows that the cross-section shape of the microchannel has a great influence on the sensing performance of the actuator microchannel 2. When the length of the major axis of the cross-section is greater than the length of the minor axis of the cross-section and the cross-section shape ratio is appropriate, the sensing performance of the radial actuator microchannel 2 can be improved to a certain extent. Therefore, the parameter data of the sixth group with the highest sensitivity are selected.

[0098] Table 1 Strain data of microchannels with different structures under the action of the same air pressure

[0099]

[0100] Set the structural parameters H = 12 mm, h = 10 mm, R = 7.5 mm, L = 7π, a = b = 0.4 mm, = 1 mm, change the radius of the central cylindrical cavity 3, that is, change the parameter , establish a finite element model of the radial actuator and perform mesh division as Fig. 9 shown. Set the current terminal and the ground at the boundary cross-sections at both ends of the microchannel 2 respectively, set the voltage to 1 V, and study the influence of different matrix structures on the radial expansion deformation performance of the actuator.

[0101] Figure 10 shows the case where only the parameters are changed under the same pressure. The displacement cloud diagram of the radial actuator substrate is obtained when the pressure is the same. The deformation and strain results of the radial actuator in the figure are shown in Table 2. By comparing Figure 10 with Figure 6(c) with the same pressure and the same structural parameters of the radial actuator microchannel 2, it is found that the expansion deformation of the radial actuator in Figure 10 is greater than the expansion deformation in Figure 6(c). By comparing the three groups of data in Table 2 with the third group of data in Table 1, it is found that when the overall size of the actuator and the structure of the microchannel 2 are the same, the radial actuator with an annular air cavity 1 has a larger strain than the ordinary radial actuator. The annular air cavity 1 can improve the deformation performance of the radial actuator substrate. In Table 2, the strain of radial actuators with different structures increases as the radius of the central cylindrical cavity 3 decreases, indicating that under the same conditions, the constraint force decreases as the radius of the central cylindrical cavity 3 decreases, which enhances the radial expansion deformation performance of the radial actuator substrate. Therefore, the parameters are selected. =5mm radial actuator base structure.

[0102] Table 2 Deformation results of radial actuators with different substrate structures

[0103]

[0104] According to the above content, this embodiment finally selects the structural parameters of the radial actuator shown in Table 3 to establish the final design model and divide the grid as follows: Fig.11 As shown, the expansion deformation effects of a radial actuator of a common structure and a radial actuator designed in this embodiment under the same material are compared and analyzed through finite element simulation.

[0105] Table 3 Structural parameters of radial actuator (unit: mm)

[0106]

[0107] Figure 12 is a deformation displacement cloud diagram of the radial actuators of the two structures when P = 300 kPa. The maximum displacement of the radial actuator side wall with the annular air cavity 1 is 2.18 mm, and the strain is 29.1%. The maximum displacement of the radial actuator side wall with the ordinary air cavity is 1.67 mm, and the strain is 22.3%. The relationship between the maximum displacement of the radial actuator side wall of the two structures and the air pressure is shown in Figure 12. Fig.13 As shown in the figure, it can be seen that under the same air pressure, the expansion deformation performance of the radial actuator with an annular air cavity 1 is significantly higher than that of the radial actuator with an ordinary air cavity, and the difference increases with the increase of air pressure. At the same time, the design of adding microchannel 2 makes the radial actuator not have to rely on external sensors to feedback the deformation state of the actuator. The relationship between the output resistance of the radial actuator and the expansion deformation is shown in Fig.14 As shown, full flexible sensing of the expansion and deformation process of the radial actuator can be achieved.

[0108] The radial actuator constructed in the present invention structurally reduces the constraint force on the expansion and deformation of the radial actuator, improves the expansion and deformation performance of the radial actuator, enables it to fix the displacement more quickly under the same air pressure, shortens the transition time of the periodic motion of the peristaltic soft robot, improves the motion efficiency of the peristaltic soft robot, and can change the output resistance after its own expansion and deformation, thereby realizing a fully flexible strain sensing function, which is beneficial to the precise control of the motion of the peristaltic soft robot.

[0109] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0110] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A radial actuator for a peristaltic soft robot, characterized in that: An air cavity (1), a microchannel (2) and a cylindrical cavity (3) are provided in the radial actuator, wherein: The cylindrical cavity (3) is arranged along the central axis of the radial actuator, the air cavity (1) is annular and arranged along the inner wall of the radial actuator and maintains a first preset distance from the radial actuator, the microchannel (2) is arranged between the air cavity (1) and the inner wall of the radial actuator, the air cavity (1) surrounds the cylindrical cavity (3), and the inner wall of the air cavity (1) and the outer wall of the cylindrical cavity (3) maintain a second preset distance, wherein: The air cavity (1) is used to communicate with an air pipe from outside the radial actuator, and the air pressure inside the air cavity (1) is increased or decreased through the air pipe outside the radial actuator; the cylindrical cavity (3) is used to store the air pipe that is connected to the air cavity of other radial actuators or axial actuators of the soft robot; The microchannel (2) contains liquid metal. When the air pressure in the enlarged air cavity (1) changes, the radial actuator deforms, causing the microchannel (2) to deform. The deformation of the microchannel (2) causes the resistance of the liquid metal to change. The expansion deformation of the radial actuator is determined based on the change in the resistance of the liquid metal.

2. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: Assume that the major axis length of the cross section of the microchannel (2) is , the minor axis length is ,and , where the major axis length of the cross section is and minor axis length The ratio increases as the pressure in the air cavity (1) increases.

3. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: The cross-section of the microchannel (2) includes a circular shape and an elliptical shape. Under the same air pressure, the radial actuator has a larger expansion deformation amount for a microchannel (2) with an elliptical cross-section than for a microchannel (2) with a circular cross-section.

4. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: When the radial actuator is under the same gas pressure, the major axis length of the microchannel (2) With minor axis length When the ratio is within the preset range, if the major axis length With minor axis length The larger the ratio, the higher the degree of deformation of the microchannel (2), and the greater the expansion deformation of the side wall of the radial actuator.

5. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: When the major axis length of the cross section of the microchannel (2) Equal to the minor axis length When the gas pressure is 0-225 kPa, the resistance of the liquid metal in the microchannel (2) increases with the increase of the gas pressure and the growth rate is When the gas pressure is 225-300 kPa, the resistance of the liquid metal in the microchannel (2) increases with the increase of the gas pressure and the growth rate is ,in, ; When the major axis length of the cross section of the microchannel (2) Greater than the minor axis length When the gas pressure is 0-225 kPa, the resistance of the liquid metal in the microchannel (2) increases with the increase of the gas pressure and the growth rate is When the gas pressure is 225-300 kPa, the resistance of the liquid metal in the microchannel (2) increases with the increase of the gas pressure and the growth rate is ,in, ,and .

6. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: The radial actuator is under the same gas pressure, and the major axis length of the cross section of the microchannel (2) is Equal to the minor axis length When the first sensitivity of the microchannel (2) is GF1, the length of the major axis of the cross section of the microchannel (2) is Greater than the minor axis length The second sensitivity of the microchannel (2) is GF2, and the second sensitivity GF2 is greater than the first sensitivity GF1, wherein the sensitivity is used to reflect the radial expansion of the microchannel (2), and the formula is: ； in, is the sensitivity, represents the resistance of the microchannel when stretched, represents the resistance change, is the applied strain.

7. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: Under the same air pressure, if other parameters of the radial actuator are the same, the thicker the thickness of the annular air cavity (1), the greater the radial expansion deformation of the radial actuator.

8. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: During the deformation of the radial actuator, the pressure is assumed to be The tension on the side wall of the air cavity is The tensions borne by the upper and lower walls of the air cavity are , the constraint force generated by the fixed interfaces at both ends of the radial actuator is The side wall of the central cylindrical cavity is subject to a constraint force of , then it satisfies: ； ； ； ； in, is the radius of the circular cross section of the radial actuator, is the distance between the air cavity and the inner wall of the radial actuator, is the thickness of the air cavity, is the height of the air cavity.

9. The radial actuator for a peristaltic soft robot according to claim 1, characterized in that: The radial actuator is made of silicone.

Images