Pneumatic flexible omnidirectional driver based on liquid metal phase change and control method thereof

Abstract

The invention discloses a pneumatic flexible omni-directional driver based on liquid metal phase change and a control method thereof.The driver comprises a phase change control module and a composite execution module controlled by the phase change control module, the composite execution module comprises a flexible base body, and a columnar hollow elastic cavity is formed in the middle of the flexible base body to serve as an air chamber; a fiber restraint layer is coated outside the flexible base body, a micro channel network is arranged inside the flexible base body, and a phase change material is injected into the micro channel network; the phase change control module comprises a control panel, the control panel is connected with a miniature refrigeration sheet, a sensor and an air pump through signal lines, the miniature refrigeration sheet is tightly attached to the network side of the miniature channel, and the phase change material is converted from a liquid state to a solid state through the miniature refrigeration sheet, so that the rigidity of the flexible substrate is adjusted; the output of the air pump communicates with the air chamber and is used for adjusting the air pressure of the air chamber, so that the air pump is matched with the miniature refrigeration piece to achieve posture adjustment of the flexible base body. The control is simple, the precision is high, and the dynamic adjustment of the rigidity of the driver can be realized.

Description

Technical Field

[0001] The present invention relates to the field of robot flexible actuator design, and particularly to a pneumatic flexible omnidirectional actuator based on liquid metal phase change and its control method. Background Art

[0002] In the field of search and rescue, the omnidirectional movement ability of the actuator enables rescue robots to move flexibly in complex environments such as ruins and rubble piles, without relying on specific paths or structures, and can quickly reach the location of trapped people. And during the rescue process, the robot may need to make contact and interact with trapped people or the surrounding environment. The flexibility of the actuator enables it to provide a gentle force when making contact, avoiding secondary injuries to trapped people, and at the same time can better adapt to soft or fragile objects in the environment. For example, when grasping fragile items or clearing obstacles in the ruins, it can automatically adjust the grasping force according to the shape and hardness of the object, realizing safe and effective operation. When the robot searches in complex ruins, the actuator senses its own pose in real time through resistance changes, and feeds back the position and attitude information to the control system. The control system corrects the movement trajectory of the robot according to this information to ensure that it explores efficiently according to the preset path and improves the rescue efficiency.

[0003] In the production field, the adjustable stiffness and omnidirectional movement ability of the actuator, supplemented by the feedback of sensors, enable it to adjust its own grasping posture and stiffness distribution in real time according to the shapes and sizes of different shaped parts, and realize stable grasping of complex-shaped parts. For example, in automotive manufacturing or aerospace component production, for irregularly shaped engine components, wings, etc., the robot can control the phase change of the liquid metal in the actuator to change the shape and stiffness of the fingers or fixtures, making them closely fit the surface of the part to complete precise grasping and placement. By precisely controlling the degree of phase change of the liquid metal, the precise adjustment of the grasping force can be realized, which can not only ensure firmly grasping the part, but also not damage the surface or structure of the part due to excessive force. This is particularly important for grasping some vulnerable and high-precision shaped parts, such as precision ceramic components and optical lenses in electronic devices, which can effectively improve production efficiency and product quality.

[0004] In the field of industrial inspection, the miniaturization and flexibility of the actuator enable it to enter narrow spaces or the interior of pipelines for inspection, such as chemical pipelines, gas pipelines, etc., to detect whether there are problems such as leaks, corrosion, and blockages inside. The robot can be equipped with various sensors, such as cameras, gas sensors, pressure sensors, etc., and can move flexibly inside the pipeline, transmitting detection data in real time, providing important basis for pipeline maintenance and safety assessment. In some dangerous environments such as high temperature, high pressure, strong radiation, toxic and harmful, etc., the actuator can be used to drive the inspection robot to replace manual inspection work to ensure personnel safety. For example, in scenarios such as the internal inspection of nuclear reactors and the inspection of chemical plant tanks, the robot can stably operate in complex and dangerous environments by using its flexible movement ability, obtain the operating state data of key equipment, and timely discover potential safety hazards. Its precise stiffness control and movement ability enable it to complete some high-precision operations and inspection tasks in industrial inspection, such as surface inspection and dimensional measurement of precision mechanical parts. The robot can achieve the detection and analysis of the micro-features of parts by precisely controlling the movement trajectory and contact force of the actuator, improving the accuracy and reliability of product quality inspection.

[0005] In the field of intelligent wearable exoskeleton technology, the integration of the actuator provides additional strength and endurance support for the human body. By adjusting the stiffness and assisting force in real time, it can assist the human body to complete various actions, reduce muscle burden, and improve exercise efficiency, enabling the wearer to perform long-term physical labor or exercise training more easily, such as helping the elderly and disabled walk more freely, or assisting soldiers, firefighters, etc. to enhance physical strength and mobility during task execution.

[0006] Currently, pneumatic soft actuators are mainly composed of chambers made of elastic materials and structures used to limit deformation. According to the different deformation-limiting structures, they can be divided into fiber-reinforced type and pneumatic tooth type, etc. Among them, the fiber-reinforced pneumatic soft actuator generally consists of a hollow elastic body chamber plus a fiber constraint layer. Under different fiber arrangement forms, by adjusting the magnitude / positive and negative of the input air pressure, the chamber inside the actuator can be expanded or contracted, thereby generating movements such as bending and stretching. However, only a single movement can be achieved with one fiber arrangement form. The pneumatic tooth soft actuator has a tooth-like shape, and each tooth-like structure is embedded with a chamber. The side wall of the chamber is often designed to be thin. After inflation, the side walls of the chambers expand, contact and squeeze each other, thereby generating bending curvature and clamping force. It is mainly applied to flexible grippers and can only generate movement in a single direction. Moreover, the actuator has non-linear characteristics such as hysteresis and creep during the inflation and deflation processes, making it difficult for traditional linear control methods to effectively control its precise movement. In summary, the following technical problems exist in both of them: Limited stiffness adjustment ability: The stiffness of ordinary fiber-reinforced actuators and pneumatic soft actuators is usually relatively fixed, which to a certain extent limits the flexibility and adaptability of the robot.

[0007] Low motion control accuracy: Due to the non-linear characteristics of ordinary fiber-reinforced actuators and pneumatic soft actuators, as well as problems such as model simplification, it is difficult to precisely control their motion states, and it is difficult to achieve high-precision trajectory tracking and attitude control.

[0008] Difficulty in achieving omnidirectional motion: Ordinary fiber-reinforced actuators and pneumatic soft actuators usually have difficulty achieving true omnidirectional motion in terms of structure and driving principle, and their motion directions and degrees of freedom are restricted to a certain extent.

[0009] Many air chambers and complex control: For some complex pneumatic soft actuators, in order to achieve multi-degree-of-freedom motion or more refined motion control, multiple air chambers often need to be designed. However, this will make the structure of the actuator more complex, and the control system also needs to precisely adjust the air pressure of multiple air chambers simultaneously, increasing the complexity and difficulty of control. Summary of the Invention

[0010] In order to solve the above technical problems existing in the prior art, the present invention proposes a pneumatic flexible omnidirectional actuator based on liquid metal phase change and its control method. The specific technical solutions are as follows: A pneumatic flexible omnidirectional actuator based on liquid metal phase change coupling, comprising a phase change control module and a composite execution module controlled and connected thereto. The composite execution module includes a flexible matrix, in the middle of which there is a columnar hollow elastic cavity as an air chamber, a fiber constraint layer is coated on the outside of the flexible matrix, a micro-channel network is arranged inside the flexible matrix body, and a phase change material is injected into the micro-channel network; the phase change control module includes a control board, which is controlled and connected to a micro-refrigerator, a sensor and an air pump through signal lines. The micro-refrigerator is closely attached to the side of the micro-channel network, and the phase change material is changed from a liquid state to a solid state through the micro-refrigerator, so as to adjust the stiffness of the flexible matrix; the output of the air pump is connected to the air chamber for adjusting the air pressure of the air chamber, so as to cooperate with the micro-refrigerator to realize the pose adjustment of the flexible matrix.

[0011] Further, the flexible matrix is made of silicone material.

[0012] Further, the phase change material is a liquid metal with a melting point lower than room temperature.

[0013] Further, the liquid metal is gallium indium alloy (EGaIn).

[0014] Further, the fiber constraint layer uses multiple groups or a group of fibers arranged on the flexible matrix by winding, and is integrated with the air chamber wall by casting and embedding.

[0015] Further, the fibers are wound clockwise and counterclockwise at a winding angle of 45°.

[0016] Further, the sensor includes a barometric pressure sensor and a temperature sensor, both of which are disposed in the air chamber, wherein the temperature sensor is closely attached to the side of the microchannel network.

[0017] A control method for a pneumatic flexible omnidirectional actuator based on liquid metal phase change coupling initializes the actuator control system and checks the actuator state to calibrate the temperature sensor and detect the initial state of the liquid metal. According to the state obtained by the external sensor, a target pose is given, and the required stiffness and movement direction are determined. Activate the phase change control module. According to the target pose, control the operation of the micro-refrigeration sheet to cause the liquid metal to undergo a phase change, thereby adjusting the stiffness of the flexible matrix and providing real-time feedback of temperature data. Start the air pump to adjust the air pressure in the air chamber, which cooperates with the phase change of the liquid metal to adjust the current pose of the flexible matrix and provide real-time feedback of air pressure data. Compare the current pose with the target pose. According to the preset allowable error range, keep the actuator in the current pose state or perform feedback control.

[0018] Further, after comparing the current pose with the target pose, if the error is within the allowable error range, keep the current pose state; otherwise, continue to control the air pump to adjust the air pressure and control the micro-refrigeration sheet to adjust the state of the liquid metal.

[0019] Further, the state obtained by the external sensor includes environmental state information and actuator body state information.

[0020] Advantages of the present invention: 1. By controlling the solid-liquid phase change of the liquid metal, the present invention can dynamically adjust the stiffness of the actuator, enabling the robot to better adapt to different environmental and task requirements, and solving the problem of limited stiffness adjustment ability of existing actuators.

[0021] 2. Using the resistance change of the liquid metal as a sensor to feedback the pose state of the actuator, the present invention can achieve closed-loop control, thereby significantly improving the accuracy and stability of motion control.

[0022] 3. By ingeniously designing the liquid metal microchannel network and the phase change control mechanism, the present invention can enable the actuator to generate multi-directional bending and deformation, thereby achieving omnidirectional motion, greatly expanding the motion ability and application scenarios of the robot.

[0023] 4. By using liquid metal phase change to achieve stiffness adjustment and motion control, the present invention does not require multiple independent air chambers, simplifies the structure and control method of the actuator, reduces the control complexity, and improves the reliability and maintainability of the overall actuator. Description of the Drawings

[0024] Figure 1 are the schematic diagrams of the component structures of the composite execution module of this embodiment; Figure 2 is the sectional view of the flexible matrix of this embodiment; Figure 3 is the schematic diagram of the overall structure of the composite execution module of this embodiment Figure 4 is the schematic diagram of the control circuit of a pneumatic flexible omnidirectional actuator based on liquid metal phase change coupling of this embodiment; Figure 5 is the flowchart of the control method of a pneumatic flexible omnidirectional actuator based on liquid metal phase change coupling of this embodiment; In the figure, 1 - liquid metal, 2 - flexible matrix, 3 - fiber constraint layer, 4 - microchannel network. Detailed implementation manners

[0025] In order to make the objectives, technical solutions and technical effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings of the specification and embodiments.

[0026] A pneumatic flexible omnidirectional actuator based on liquid metal phase change coupling of this embodiment includes a composite execution module and a phase change control module.

[0027] The composite execution module includes a flexible matrix 2. The flexible matrix 2 is a three-dimensional structure made of silicone material. A columnar hollow elastic body cavity is provided as an air chamber in the middle of the flexible matrix 2. A fiber constraint layer 3 is coated outside the flexible matrix 2. A microchannel network 4 is provided inside the flexible matrix 2 body, and a phase change material is injected into the microchannel network 4, such as Figures 1 to 3 shown. The phase change material is a liquid metal 1 with a melting point lower than room temperature, such as gallium indium alloy (EGaIn), whose melting point is about 15.5°C and is in a liquid state at room temperature. The fiber constraint layer 3 adopts an embedded fiber reinforcement structure. This structure uses multiple groups or a group of fibers arranged by winding and is embedded in the flexible air chamber wall of silicone through casting to become an integral body, making the overall structure more compact. The fiber structure is fixed by being embedded in the flexible matrix 2, so the fiber arrangement method is not restricted by the weaving form and has higher flexibility. In this embodiment, the fibers are wound clockwise and counterclockwise at a 45° winding angle.

[0028] Such as Figure 4As shown in the figure, in order to achieve the transformation of liquid metal 1 from liquid state to solid state, the phase change control module includes a power supply, a control board, a micro refrigeration chip, a temperature sensor and an air pump. The power supply supplies power to the air pump and the control board. The control board is connected to the micro refrigeration chip, the temperature sensor and the air pump through signal lines. The air pump is used to adjust the air pressure in the air chamber. The micro refrigeration chip works based on the thermoelectric effect. When current passes through the micro refrigeration chip, its working surface will produce the effect of temperature reduction. The micro refrigeration chip is closely attached to a specific area of the microchannel network 4 filled with liquid metal 1. When the phase change of liquid metal 1 is required, the micro refrigeration chip is started. The micro refrigeration chip absorbs heat from liquid metal 1, reducing the temperature of liquid metal 1 below its melting point, thereby achieving the transformation of liquid metal 1 from liquid state to solid state. In this process, by precisely controlling the working current and working time of the micro refrigeration chip through the control board control system, the cooling capacity can be adjusted, and further the precise control of the phase change process of liquid metal 1 can be achieved, ensuring that liquid metal 1 can complete the solid-liquid phase change at a predetermined time and area, providing a reliable guarantee for the stiffness adjustment of the actuator composite actuator structure. At the same time, in order to improve the efficiency and stability of phase change control, the phase change control module is also equipped with a temperature sensor for real-time monitoring of the temperature change of liquid metal 1 and feeding back the temperature data to the control board. The control system dynamically adjusts the working parameters of the micro refrigeration chip according to the feedback information, realizing the closed-loop control of the phase change process of liquid metal 1.

[0029] As Figure 5 shown in the figure is the specific control process for the actuator of this embodiment to achieve its omnidirectional movement through stiffness adjustment and air pressure adjustment.

[0030] In summary, through the ingenious design of the microchannel network 4 and the control of the solid-liquid phase change of liquid metal 1, the actuator of the present invention can cause the actuator to bend and deform in multiple directions and achieve the dynamic adjustment of the stiffness of the actuator, thereby realizing omnidirectional movement, enabling the robot to better adapt to different environmental and task requirements, and greatly expanding the movement ability and application scenarios of the robot. Moreover, using the resistance change of liquid metal 1 as a sensor to feedback the pose state of the actuator can achieve closed-loop control, thereby significantly improving the accuracy and stability of motion control. In addition, by using the phase change of liquid metal 1 to achieve stiffness adjustment and motion control, there is no need for multiple independent air chambers, simplifying the structure and control method of the actuator, reducing the complexity of the control system, and improving the reliability and maintainability of the overall drive system.

[0031] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions recorded in the foregoing examples or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A pneumatic flexible omnidirectional actuator based on liquid metal phase change, comprising a phase change control module and a composite execution module connected to the phase change control module, characterized in that: The composite execution module comprises a flexible substrate, a columnar hollow elastic cavity is arranged in the middle of the flexible substrate as an air chamber, a fiber constraint layer is coated outside the flexible substrate, a micro channel network is arranged inside the flexible substrate body, and a phase change material is injected into the micro channel network; The phase change control module includes a control board, which is connected to a micro-refrigeration sheet, a sensor and an air pump through signal line control. The micro-refrigeration sheet is tightly arranged on the side of the micro-channel network. The phase change material is transformed from liquid to solid through the micro-refrigeration sheet, thereby adjusting the stiffness of the flexible substrate; the air pump output is connected to the air chamber to adjust the air pressure in the air chamber, thereby cooperating with the micro-refrigeration sheet to realize the position adjustment of the flexible substrate.

2. The pneumatic flexible omnidirectional actuator according to claim 1, characterized in that: The flexible substrate is made of silica gel material.

3. The pneumatic flexible omnidirectional actuator according to claim 1, characterized in that: The phase change material is a liquid metal with a melting point lower than room temperature.

4. The pneumatic flexible omnidirectional actuator according to claim 3, characterized in that: The liquid metal is gallium-indium alloy (EGaIn).

5. The pneumatic flexible omnidirectional actuator according to claim 1, characterized in that: The fiber constraining layer uses a plurality of groups or a group of fibers arranged on the flexible substrate in a winding manner, and is embedded in the air chamber wall by casting to form a whole with the air chamber wall.

6. The pneumatic flexible omnidirectional actuator according to claim 5, characterized in that: The fiber was wound clockwise and counterclockwise at a winding angle of 45°.

7. The pneumatic flexible omnidirectional actuator according to claim 1, characterized in that: The sensors include an air pressure sensor and a temperature sensor, both of which are arranged in the air chamber, wherein the temperature sensor is closely arranged on the microchannel network side.

8. A control method using the pneumatic flexible omnidirectional actuator according to any one of claims 1 to 7, characterized in that: Initialize the drive control system and check the drive status to calibrate the temperature sensor and detect the initial state of the liquid metal; According to the status obtained by the external sensor, the target position is given and the required stiffness and movement direction are determined; Activate the phase change control module, control the micro-refrigeration sheet to work according to the target posture, make the liquid metal undergo phase change, thereby adjusting the stiffness of the flexible substrate, and provide real-time feedback of temperature data; start the air pump to adjust the air pressure in the air chamber, coordinate with the phase change of the liquid metal, thereby adjusting the current posture of the flexible substrate, and provide real-time feedback of air pressure data; Compare the current posture with the target posture, and according to the preset allowable error range, make the driver maintain the current posture state or perform feedback control.

9. The control method of the pneumatic flexible omnidirectional actuator according to claim 8, characterized in that: After comparing the current posture with the target posture, if the error is within the allowable error range, the current posture state is maintained. Otherwise, the air pump is continued to be controlled to adjust the air pressure, and the micro-refrigeration plate is controlled to adjust the liquid metal state.

10. The control method of the pneumatic flexible omnidirectional actuator according to claim 8, characterized in that: The status acquired by the external sensor includes environmental status information and driver body status information.

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