A double helical fiber-reinforced sensor-actuator integrated artificial muscle

Abstract

The present invention relates to a double-helix fiber-reinforced inductive drive integrated artificial muscle, belonging to the field of soft robotics technology and inductive sensing technology design. The artificial muscle is seamlessly integrated with a hollow tubular body made of a rubber-like stretchable material and a double-helix conductive fiber coil. The artificial muscle is a fluid-driven elastic elongation unit. The double-helix conductive fiber coil wound on the hollow tubular body made of a rubber-like stretchable material limits the radial expansion of the tubular body, and can achieve elongation deformation under the drive of liquid or gas pressure. High-resolution length perception of the artificial muscle is achieved by detecting the inductance change of the double-helix fiber coil. The present invention realizes sub-millimeter (less than 0.01 mm) level length self-perception of artificial muscles. The length sensing based on self-perception can monitor the real length of the artificial muscle in real time, is not affected by the driving pressure of the artificial muscle and the external load, and can work stably for a long time.

Description

Technical Field

[0001] The invention belongs to the field of soft robot technology and inductive sensing technology design, and in particular relates to a double-helix fiber-reinforced sensor-drive integrated artificial muscle. Background Art

[0002] Artificial muscles based on fluid drive have the characteristics of fast response and strong load-bearing performance. Different from robots driven by rigid motors, they have better environmental adaptability, low manufacturing cost, and safety of human-machine interaction. They have great prospects in the development of new soft robots, underwater bionic operation robots, and bionic rigid-flexible hybrid robots. However, due to the complex viscoelastic effect of artificial muscle body materials and the body deformation introduced by external loads during the interaction between artificial muscles and the outside world, the prediction of muscle body shape changes based on kinematic models is inaccurate. Therefore, real-time proprioception (shape / posture perception) is crucial to achieve efficient closed-loop control of muscles and human-machine interaction.

[0003] In previous studies, many researchers have developed some self-sensing artificial muscles based on the principles of resistance, optics, magnetic field, and piezoresistance. However, although artificial muscles with perception capabilities have made some progress, many of these artificial muscles have complex structures and manufacturing schemes. On the one hand, some existing artificial muscles have hysteresis in the sensing mechanism or are easily affected by the environment, such as resistive and magnetic field sensing artificial muscles. On the other hand, connecting or embedding individual sensors into the robot body makes manufacturing difficult and long-term use will damage the driving performance of the sensor or robot. In addition, a large part of strain sensors are difficult to integrate well into artificial muscles. It can be seen that it is still a challenge to achieve self-sensing artificial muscles with simple structure, stable performance, strong reliability, and no hysteresis in perception. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a double helix fiber reinforced sensor-driven integrated artificial muscle, which realizes sub-millimeter (less than 0.01mm) level length perception of artificial muscle. The length sensing based on self-inductance can monitor the real length of artificial muscle in real time, which is not affected by artificial muscle driving pressure and external load. At the same time, the double helix coil enhances the mechanical properties of the muscle, so that it mainly shows axial elongation and can work stably for a long time. By measuring the inductance of the seamlessly integrated double helix coil, the real-time body length of the artificial muscle can be obtained. The double helix fiber reinforced self-sensing artificial muscle has good application prospects in the development of the next generation of bionic crawler robots, medical catheter robots, multi-degree-of-freedom soft grippers and other intelligent robot systems and human-computer interaction.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A double-helix fiber reinforced sensor-driven integrated artificial muscle, the sensor-driven integrated artificial muscle comprising a hollow tubular body made of a rubber-like stretchable material and a double-helix conductive fiber coil, wherein the hollow tubular body comprises a cavity and a tube wall of a preset thickness, the double-helix conductive fiber coil is completely embedded in the tube wall of the hollow tubular body, and the cavity receives pressure supply.

[0007] Furthermore, the axial cross-section of the sensor-drive integrated artificial muscle is tubular, and the inner and outer surfaces of the double-helix conductive fiber coil are completely encapsulated by rubber.

[0008] Furthermore, the pressure control unit is driven by either pneumatic drive or hydraulic drive.

[0009] Furthermore, the double helix conductive fiber coil is a solid conductor coil, a liquid metal coil or a composite material fiber coil.

[0010] Furthermore, the solid conductor coil is made of copper, aluminum or an alloy of any conductive metal, and the liquid metal is gallium indium tin or a covalent gallium-indium alloy.

[0011] Furthermore, the inductance of the double-helix conductive fiber coil is in an exponential monotonic function relationship with the length of the inductive-driven artificial muscle.

[0012] Furthermore, the pressure control module receives and executes instructions from the host computer, and transmits the driving pressure to the cavity through the pipeline. The double-helix conductive fiber coil is driven by the driving pressure to change shape and inductance following the hollow tubular body, and is connected to the inductance measurement circuit through a twisted pair of leads. The inductance measurement circuit transmits the measured inductance value to the host computer.

[0013] The beneficial effects of the present invention are:

[0014] The hollow tubular body composed of a double-helix conductive fiber coil and a rubber-like stretchable material is seamlessly integrated, which not only realizes the length perception of the artificial muscle, but also enhances the mechanical properties of the muscle; it has good versatility, simple structure, no hysteresis in length perception, low manufacturing cost, no need to establish a complex mathematical model, and long service life. The length of the artificial muscle can be obtained in real time by measuring the inductance of the conductive fiber coil; the size of the artificial muscle can be changed in time to meet the application in different scenarios. In addition, based on two or more single artificial muscles, a multi-degree-of-freedom soft robot can be realized, which has great scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of a double helical fiber reinforced sensor-actuator integrated artificial muscle structure of the present invention;

[0016] Figure 2This is a schematic diagram of a double-helix fiber-reinforced sensor-drive integrated artificial muscle drive and sensing measurement system of the present invention;

[0017] Figure 3 A schematic diagram of the driving principle of a double-helix fiber-reinforced sensor-drive integrated artificial muscle of the present invention;

[0018] Figure 4 A schematic diagram of the sensing principle of a double helical fiber reinforced sensor-drive integrated artificial muscle of the present invention;

[0019] Figure 5 This is a diagram showing the relationship between the driving pressure and length of a double helical fiber reinforced sensor-drive integrated artificial muscle of the present invention;

[0020] Figure 6 This is a graph showing the relationship between the inductance variation and length of a double helical fiber reinforced sensor-drive integrated artificial muscle of the present invention;

[0021] Figure 7 This is a diagram showing the changes in inductance and air pressure of a double-helix fiber-reinforced sensor-drive integrated artificial muscle under active air pressure drive;

[0022] Figure 8 The graph of the inductance and air pressure changes of a double-helix fiber-reinforced sensor-drive integrated artificial muscle of the present invention when driven without air pressure and loaded with weights of different weights;

[0023] Fig. 9 This is a graph of inductance variation of a double-helix fiber-reinforced sensor-drive integrated artificial muscle of the present invention during three cycles of pressurization and decompression under different driving pressures;

[0024] Fig.10 This is a step inductance variation diagram of a double helix fiber reinforced sensor-drive integrated artificial muscle of the present invention at an elongation step length of 0.5 mm;

[0025] Fig.11 This is a time diagram of the inductance response of a double-helix fiber-reinforced sensor-drive integrated artificial muscle of the present invention;

[0026] Fig.12 This is a graph showing the inductance variation of a double helical fiber reinforced sensor-actuator integrated artificial muscle of the present invention under more than 1000 cycles of pressurization and decompression;

[0027] Fig.13 This is a graph showing the inductance variation of a double helical fiber reinforced sensor-drive integrated artificial muscle under a tiny deformation of 0.075 mm according to the present invention;

[0028] Fig.14 This is a diagram showing the inductance variation of a double helical fiber reinforced sensor-drive integrated artificial muscle driven by water pressure in water;

[0029] Fig.15 A schematic diagram of a bidirectional bending artificial muscle and a multi-degree-of-freedom motion artificial muscle obtained by expanding a double-helix fiber-reinforced sensor-drive integrated artificial muscle according to the present invention;

[0030] Fig.16 It is a schematic diagram of the extended application scenario and multi-scenario intelligent operation system based on the present invention.

[0031] Reference numerals:

[0032] 1. Hollow tubular body; 2. Double helix conductive fiber coil; 3. Pressure control module; 4. Inductance measurement circuit; 5. Pipeline; 6. Twisted pair lead wire; 7. Host computer; 8. Cavity. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0034] The present invention proposes a sensor-driven integrated artificial muscle that realizes high-sensitivity length perception based on coil self-inductance by seamlessly integrating a double-helix conductive fiber coil 2 on a hollow tubular body 1 made of a rubber-like stretchable material. When the hollow tubular body 1 made of a rubber-like stretchable material is driven to stretch, the double-helix conductive fiber coil 2 follows the deformation in real time, the length of the double-helix conductive fiber coil 2 is stretched, and the total inductance of the double-helix conductive fiber coil 2 is reduced. The inductance of the double-helix conductive fiber coil 2 is determined only by its own geometric morphology, and has nothing to do with the driving pressure and external load, and can achieve micron-level length self-perception and can work stably for a long time.

[0035] According to an example of the present invention, Figure 1 As shown, a double-helix fiber-reinforced sensor-drive integrated artificial muscle based on the present invention is mainly composed of a hollow tubular body 1 made of a rubber-like stretchable material and a double-helix conductive fiber coil 2. The hollow tubular body 1 made of a rubber-like stretchable material is a hollow cylinder or a hollow tube, and its cylinder wall or tube wall has a certain thickness, such as a cylinder, a square cylinder or other irregular shapes. During the manufacturing process, a double-helix groove is pre-retained on the cylinder wall or the tube wall. After the double-helix conductive fiber coil 2 is wound along the groove on the hollow tubular body 1 made of a rubber-like stretchable material, it is brushed with liquid rubber and is packaged and fixed after solidification. That is, from the appearance, the hollow tubular body 1 and the double-helix conductive fiber coil 2 are integrated, and the cavity 8 in the middle of the hollow cylinder is used to receive the driving pressure.

[0036] According to an example of the present invention, Figure 2As shown, the hollow tubular body 1 made of rubber-like stretchable material is driven by the pressure control module 3 and stretches according to the driving pressure it receives. The driving pressure of the pressure control module 3 is delivered to the cavity 8 by the pipeline 5. The double helix conductive fiber coil 2 integrated on the hollow tubular body 1 changes shape with the hollow tubular body 1, and the inductance also changes accordingly, wherein the pressure control module 3 receives and executes the instructions of the host computer 7. The double helix conductive fiber coil 2 is connected to the inductance measurement circuit 4 through the twisted pair lead 6, and the inductance measurement circuit 4 transmits the measured inductance value to the host computer 7, which can read the inductance value of the double helix conductive fiber coil 2 in real time and obtain the corresponding length of the hollow tubular body 1 made of rubber-like stretchable material.

[0037] The inductance of the double helix conductive fiber coil 2 is directly related to its geometric shape. According to the Wheeler formula, the initial theoretical inductance of the three-dimensional solenoid coil is It can be calculated by the following formula:

[0038] (1)

[0039] In the above formula, N represents the number of turns of the double helix conductive fiber coil 2, represents the diameter of the double helix conductive fiber coil 2 in the initial state, represents the height of the double helix conductive fiber coil 2 in the initial state. and The unit of is mm and the unit of inductance is µH.

[0040] When the hollow tubular body 1 made of rubber-like stretchable material is driven to extend, the double helix conductive fiber coil 2 also extends. At the same time, according to the principle that the length of the conductive fiber is almost constant, the radial direction of the double helix conductive fiber coil 2 shrinks to a certain extent. The radial dimension of the conductive fiber when the hollow tubular body 1 made of rubber-like stretchable material is driven to extend to any length can be calculated by the following formula:

[0041] (2)

[0042] In the above formula, represents the diameter of the double helix conductive fiber coil 2 after extension, represents the length of the double helix conductive fiber coil 2 after extension. Substituting equation (2) into equation (1) yields the theoretical inductance of the double helix conductive fiber coil 2 at any extension length. :

[0043] (3)

[0044] like Figure 3As shown in FIG. 4 , when the air source supplies air pressure to the cavity 8 of the hollow tubular body 1 made of rubber-like stretchable material, the cavity of the hollow tubular body 1 made of rubber-like stretchable material of the artificial muscle expands, and the double helix conductive fiber coil 2 will restrain the radial expansion of the hollow tubular body 1. According to the principles of materials and mechanics, the hollow tubular body 1 will undergo axial elongation. When other fluids are used for pressure supply, similarly, the cavity expands, and the double helix conductive fiber coil 2 restrains the outer diameter expansion of the hollow tubular body 1, causing the hollow tubular body 1 to elongate axially. Experiments show that when the air pressure increases from 0 kPa to 45 kPa, the drive-sensing integrated artificial muscle elongates by 35 mm. In this state, since the double helix conductive fiber coil 2 deforms together with the hollow tubular body 1 and never separates, as shown in FIG. 4 , the double helix conductive fiber coil 2 is regarded as the sum of two single helix conductive fiber coils. When the length of the hollow tubular body 1 changes, the shape and size of the single helix conductive fiber coil also change, and the radial size decreases from 0 kPa to 45 kPa. Changes to , the overall length is extended, from Changes to The self-inductance of the single-helix conductive fiber coil decreases from high inductance to low inductance, thereby realizing the integration of drive and perception, and sensing the length change of the hollow tubular body 1 in real time without any hysteresis, that is, there is no hysteresis in sensing the length change of the artificial muscle.

[0045] The relationship between the driving pressure and the length of the hollow tubular body 1 made of rubber-like stretchable material of the artificial muscle is a relatively important mechanical characteristic, such as Figure 5 As shown in Figure 2, there is a large hysteresis between the driving pressure and length in a pressurization and depressurization cycle, which is 10.2%. This also shows that the prediction of artificial muscle deformation based on kinematics is inaccurate. Figure 6 As shown, the length perception of the hollow tubular body 1 made of rubber-like stretchable material of the artificial muscle based on the self-inductance effect of the double-helix conductive fiber coil 2 has no obvious hysteresis in a pressurization and decompression cycle. At the same time, it shows that the length of the hollow tubular body 1 made of rubber-like stretchable material of the artificial muscle and the inductance are in a monotonic function relationship. The fitting curve of the form of formula (4) can be obtained from the calibration data:

[0046] (4)

[0047] In the above formula, Indicates the length of the sensor-actuator artificial muscle. Indicates the real-time inductance value of the double helix conductive fiber coil 2, Represents the three constants obtained by fitting. According to this formula, the length of the sensor-actuated artificial muscle can be obtained in real time without hysteresis. Figure 7In the test, the air pressure is actively supplied to the sensor-driven artificial muscle from the outside. During the four pressurization and decompression cycles and the incremental pressurization and decompression tests, the sensor-driven artificial muscle can sense the changes in its length in real time.

[0048] According to an example of the present invention, Figure 8 This shows that under external load conditions, the sensor-driven artificial muscle can still sense its own length changes and is not affected by the size of the external load. When weights of different weights are added, the length of the sensor-driven artificial muscle will be lengthened due to the mechanical effect, and this deformation will be reflected in real time in the changes in the read inductance value.

[0049] According to an embodiment of the present invention, Fig. 9 As shown, the sensor-driven integrated artificial muscle was pressurized and released three times under four different driving air pressures. The sensor-driven integrated artificial muscle can work repeatedly under different deformations, and the corresponding inductance change has good repeatability. The length changes of the sensor-driven integrated artificial muscle under four different driving air pressures are 0.5 mm, 2.5 mm, 4.5 mm, and 7.5 mm, respectively.

[0050] According to an embodiment of the present invention, Fig.10 As shown in the figure, the sensor-actuated artificial muscle is driven by a small pressure to achieve incremental length changes with a step length of 0.5 mm. The corresponding inductance change steps of each step are clear and stable. It can be seen that the sensor-actuated artificial muscle can perform stable and accurate deformation movements.

[0051] According to an embodiment of the present invention, Fig.11 As shown, in order to measure the perception response time of the sensor-driven integrated artificial muscle, a switching pressure of 12.8 kPa is applied to the sensor-driven integrated artificial muscle through opening and closing of a high-speed solenoid valve. It can be obtained that the inductive response time of the sensor-driven integrated artificial muscle is only 40 ms, which shows that the sensor-driven integrated artificial muscle has an extremely fast response speed and the operating frequency can reach 11 Hz, which is comparable to the performance of human muscles.

[0052] According to an embodiment of the present invention, Fig.12 As shown in FIG. 1 , a cycle test was performed within the range of a driving pressure of 13 kPa. In the cycle test, a switch pressure was applied to the sensor-drive integrated artificial muscle of the present invention at a working frequency of 0.43 Hz, and the following results were obtained: Fig.11 From the curve shown, it can be seen that after more than 1000 cycles, the inductive response curve of the sensor-driven integrated artificial muscle is still the same as the initial response curve, which demonstrates the stability of the sensing work of the sensor-driven integrated artificial muscle.

[0053] According to an embodiment of the present invention, Fig.13As shown, in order to demonstrate the high resolution of length perception of the sensor-driven integrated artificial muscle of the present invention, the sensor-driven integrated artificial muscle is driven to undergo a tiny length deformation of 0.075 mm, and the inductive response is still clear and stable, much larger than the noise value, indicating that the sensor-driven integrated artificial muscle still has good perception performance under tiny deformation.

[0054] According to an embodiment of the present invention, Fig.14 As shown, in order to show that the sensing-driven integrated artificial muscle of the present invention can still work normally under the drive of water pressure in water, the sensing-driven integrated artificial muscle is vertically fixed in water, and the water pressure is used to drive the sensing-driven integrated artificial muscle to perform three pressurization and decompression cycles under different water pressures, and incremental water pressure pressurization and decompression are performed. The real-time length of the sensing-driven integrated artificial muscle can still be effectively obtained through the change of inductance, highlighting the advantages of the sensing-driven integrated artificial muscle in the development of the next generation of fluid drive and underwater bionic robots.

[0055] According to the examples of the present invention, based on two or more sensor-actuated artificial muscles of the present invention, a soft robot system (or actuator) with more modes can be realized, such as Fig.15 As shown, when two of the sensing-driven integrated artificial muscles of the present invention are bonded together to form an actuator, two working modes of bidirectional bending and elongation are realized. When the left sensing-driven integrated artificial muscle is pressurized, the actuator bends to the right, and vice versa. When both sensing-driven integrated artificial muscles are pressurized, the actuator will elongate. In addition, three of the sensing-driven integrated artificial muscles can be bonded together to form a soft robotic arm, and by controlling the driving pressure of the three sensing-driven integrated artificial muscles of the soft robotic arm, omnidirectional bending can be performed in 3D space. The good working performance and scalable combination of the sensing-driven integrated artificial muscle bring new ideas for the future development of more intelligent sports robots and soft robotic arms.

[0056] like Fig.16 As shown, based on the double-helix conductive fiber-reinforced sensor-driven integrated artificial muscle proposed in the present invention, an intelligent operation robot system can be realized in a variety of scenarios, such as an intelligent medical operation system. Sensor-driven integrated artificial muscles of different sizes are produced in different medical scenarios, and after expansion and combination, intelligent medical catheter robots and surgical robots are formed, thereby realizing an intelligent medical robot system. In addition, there is an intelligent sensing and grasping system. Based on the sensor-driven integrated artificial muscle, a high-performance intelligent gripper can be made, and combined with a robotic arm, intelligent grasping in complex environments can be achieved. In addition, there are bionic intelligent robots and underwater operation systems, such as bionic reptile robots, intelligent snake robots, and bionic underwater reptiles. According to different underwater operation environments, a continuous arm with scene adaptability can be customized to perform high-precision and high-efficiency automated underwater operations.

[0057] In summary, the present invention mainly provides a design idea of ​​a sensor-driven integrated artificial muscle based on double-helix conductive fiber reinforcement. Based on the self-inductance principle of the conductive fiber coil, on the one hand, the mechanical properties of the artificial muscle are structurally enhanced, and on the other hand, the non-hysteresis perception of the body deformation is realized. Simply measuring the inductance value of the double-helix conductive fiber coil 2 can obtain the real-time length of the sensor-driven integrated artificial muscle, and the proprioceptive performance is not affected by the driving pressure and external load. In addition, the sensor-driven integrated artificial muscle can be assembled into more and more complex systems, with the characteristics of high performance, easy implementation and modularity, which opens up many possibilities for its application in the fields of crawling robots, continuous soft robotic arms, soft grippers, and medical catheter robots.

[0058] Parts of the present invention that are not disclosed in detail belong to the common knowledge in the art.

[0059] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0060] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A double helical fiber reinforced sensor-actuator integrated artificial muscle, characterized in that: The sensor-driven integrated artificial muscle comprises a hollow tubular body made of a rubber-like stretchable material and a double-helix conductive fiber coil, wherein the hollow tubular body comprises a cavity and a tube wall of a preset thickness, the tube wall is pre-prepared with a double-helix groove, the double-helix conductive fiber coil is completely and seamlessly embedded in the tube wall of the hollow tubular body along the groove, the cavity receives pressure supply, and when the hollow tubular body is driven to stretch, the double-helix conductive fiber coil follows the deformation in real time; the length of the hollow tubular body and the inductance of the double-helix conductive fiber coil are in an exponential monotonic function relationship; The double-helix conductive fiber coil is composed of two single-helix conductive fiber coils that are completely symmetrically nested.

2. The double helical fiber reinforced sensor-actuator integrated artificial muscle according to claim 1, characterized in that: The axial cross-section of the sensor-drive integrated artificial muscle is tubular, and the inner and outer surfaces of the double-helix conductive fiber coil are completely encapsulated by rubber.

3. The double helical fiber reinforced sensor-actuator integrated artificial muscle according to claim 1, characterized in that: The pressure supply is provided by a pressure control module, and the pressure control module is driven by either air pressure or hydraulic pressure.

4. The double helical fiber reinforced sensor-actuator integrated artificial muscle according to claim 1, characterized in that: The double helix conductive fiber coil is a solid conductor coil, a liquid metal coil or a composite material fiber coil.

5. The double helical fiber reinforced sensor-actuator integrated artificial muscle according to claim 4, characterized in that: The solid conductor coil is made of copper, aluminum or any conductive metal alloy, and the liquid metal is gallium indium tin or covalent gallium-indium alloy.

6. The double helical fiber reinforced sensor-actuator integrated artificial muscle according to claim 1, characterized in that: The pressure control module receives and executes the instructions of the host computer, and transmits the driving pressure to the cavity through the pipeline. The double-helix conductive fiber coil is driven by the driving pressure to change shape and inductance following the hollow tubular body, and is connected to the inductance measurement circuit through a twisted pair of leads. The inductance measurement circuit transmits the measured inductance value to the host computer.

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