Independent control method and system of magnetic drive film type soft robot

Abstract

The invention belongs to the technical field of magnetically-driven miniature soft robot control, and particularly relates to an independent control method and system for magnetically-driven thin film type soft robots, and the method comprises the steps: placing two magnetically-driven thin film type soft robots with the same geometrical shape and magnetization curve in a magnetic field space generated by a three-dimensional Helmholtz coil system; magnetic field parameters are adjusted through the magnetic field driving system to generate different magnetic field intensities and magnetic field angles, so that one robot generates crawling motion, and meanwhile, the other robot is kept in situ; position and attitude information of the two robots is acquired through the visual acquisition system and fed back to the magnetic field driving system, and closed-loop control is performed by adjusting magnetic field intensity and magnetic field angle to change motion forms of the robots, so that path tracking control of the robots is realized. According to the independent control method provided by the invention, the robot can better deal with various uncertain factors and keep stable path tracking capability in a dynamic environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetically driven micro soft robot control, and in particular relates to an independent control method and system for a magnetically driven thin-film soft robot. Background Art

[0002] Magnetic-driven micro soft robots have the unique advantage of performing complex tasks in narrow and closed environments due to their flexibility, miniaturization and cable-free drive. These robots can complete tasks such as micro-object transportation, micro-manipulation and targeted treatment in the human body in extremely confined spaces, and have broad application prospects.

[0003] The cooperation between multiple micro-robots can greatly improve the overall work efficiency. This cooperation can not only enable each robot to share tasks and reduce the workload of a single robot, but also coordinate in real time to optimize the workflow and path selection, and reduce the probability of duplication of work and errors. More importantly, this multi-robot system can cope with complex and diverse tasks through teamwork. This approach provides a new idea and solution for solving complex problems that are difficult to deal with with traditional methods, and shows the broad prospects for the future development of robotics technology.

[0004] However, although there have been some studies on robot motion modes and path tracking control, the independent control method between multiple micro-robots is still in the initial exploration stage. Therefore, a method for independent control of magnetically driven thin-film soft robots is needed. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to address the deficiencies in the prior art and to provide an independent control method and system for a magnetically driven thin-film soft robot, which can achieve path tracking of the robot through independent control and can accurately adjust its motion trajectory when the robot performs a task, so that it can still move along a predetermined path in different complex environments; this not only improves the flexibility and adaptability of the robot, but also ensures its high-precision operation in complex tasks. This independent control method enables the robot to better cope with various uncertain factors and maintain a stable path tracking capability in a dynamic environment.

[0006] Technical solution: The independent control method of the magnetically driven thin-film soft robot of the present invention comprises the following steps: Two magnetically driven thin-film soft robots with the same geometric shape and magnetization curve are placed in the magnetic field space generated by a three-dimensional Helmholtz coil system; The magnetic field parameters are adjusted by the magnetic field driving system to generate different magnetic field strengths and magnetic field angles, so that one of the robots generates a crawling motion while the other robot remains in place; Acquire the position and posture information of the two robots through a visual acquisition system; The extracted position information and posture are fed back to the magnetic field drive system, and the robot's motion form is changed by adjusting the magnetic field strength and magnetic field angle to perform closed-loop control to achieve path tracking control of the robot.

[0007] To further improve the above technical solution, the magnetic field space is a three-dimensional magnetic field coordinate system xyz constructed based on a three-dimensional Helmholtz coil system; The two robots are placed on the xy plane of the three-dimensional magnetic field coordinate system, and the magnetic field angle includes the angle between the magnetic field intensity B and the xy plane. and the angle between the magnetic field intensity B and the xz plane ,in, and Counterclockwise is positive.

[0008] Furthermore, the crawling movement includes two stages: contraction and extension, wherein: Contraction phase: Set it to a positive value, and gradually increase the magnetic field strength B from 0 to the preset value, so that the robot gradually shrinks upward; Stretching phase: Set it to a negative value and gradually reduce the magnetic field strength B from the preset value to 0, so that the robot gradually extends downward.

[0009] Furthermore, the image processing step of the visual feedback system includes: Get two images of the robot, one is the image of the test bench without the robot, and the other is the image after the robot is placed on the test bench; Image subtraction is used to extract the changed area or difference information between two images; Perform median filtering on the extracted image; Use the Blob Analysis module in Simulink to extract the robot's current position and posture information; The acquired position and attitude information is fed back to the magnetic field drive system.

[0010] Furthermore, by adjusting the magnetic field strength B and the magnetic field angle, the head and tail magnetic moments acting on a robot are generated. , and the head and tail magnetic moments acting on the other robot , , in order to realize the control of the bending and stretching of the two robots in the magnetic field; When controlling the robot: In each crawling cycle, the magnetic field strength B and the angle are set , causing one of the robots to crawl; at the same time, the other robot only changes its shape, and its center of mass position remains unchanged.

[0011] Furthermore, when the robot control target needs to be switched: the magnetic field strength B is rotated 180° around the y-axis; the robot whose original center of mass position remains unchanged starts to move, and the robot that originally generates crawling motion maintains the center of mass position unchanged.

[0012] Furthermore, assuming that the two robots are R1 and R2, the robot R1 is made to crawl by adjusting the magnetic field strength B and the magnetic field angle, while the center of mass position of the robot R2 remains unchanged. The magnetic moment of robot R2 is as follows: in, is the angle between the magnetization direction of the robot R2 head and the magnetic field direction, represents the angle of the tail, , is the magnetization intensity of the head and tail, V refers to the volume of the robot; During the contraction of robot R1, the moment balance equation of robot R2 relative to the center of mass point c is: Among them, G3 and G4 represent the gravity acting on the two ends of the robot R2, and They represent the angles between the two ends of the robot and the ground, and L refers to the length of the robot.

[0013] Furthermore, the method further includes a path tracking control step: Pre-set target locations and waypoints; Obtain robot position in real time through visual feedback system; The magnetic field strength and angle are dynamically adjusted according to the deviation between the actual position and the path point.

[0014] A system for implementing the above-mentioned independent control method of the magnetically driven thin-film soft robot comprises: A three-dimensional Helmholtz coil system for generating a controllable magnetic field in a three-dimensional magnetic field space; Two magnetically driven thin-film soft robots with the same geometric shape and magnetization curve are arranged in the magnetic field space and can perform contraction and extension actions under the drive of the magnetic field to achieve crawling motion; The visual acquisition system is used to collect images of the two robots in the magnetic field space and obtain the position and posture information of the robots through image processing; The magnetic field driving system receives the position and posture information output by the image processing module, calculates the required magnetic field parameters according to a preset control strategy, and outputs control signals to adjust the magnetic field parameters of the three-dimensional Helmholtz coil system to generate different magnetic field intensities and magnetic field angles, so that the two robots can crawl along the set path.

[0015] Beneficial effects: Compared with the prior art, the advantages of the present invention are: the present invention generates a uniform and adjustable magnetic field through a three-dimensional Helmholtz coil system, thereby realizing complex motion modes such as crawling, contraction, and extension of the robot in three-dimensional space; in the same magnetic field environment, multiple robots can be independently controlled to avoid mutual interference, which greatly improves the system's task execution capability and application flexibility.

[0016] Through precise control of magnetic field strength and direction, multiple robots can complete tasks independently or collaboratively, significantly improving task efficiency and adaptability; by sharing task loads and optimizing workflows, the system achieves higher task execution efficiency in complex environments and is suitable for applications in multiple fields such as medical and industrial.

[0017] By adjusting the magnetic field parameters, the robot can flexibly respond to changes in a dynamic environment, such as obstacle avoidance, trajectory changes, etc., to ensure the stability and continuity of task execution; the robot performs high-precision movement in a confined space through magnetic field control, demonstrating superior adaptability and technical advantages.

[0018] By using an external magnetic field to drive the robot, the need for complex internal structures and energy carriers is reduced, the system energy consumption is reduced, and the working time is extended. By optimizing the magnetic field control and robot motion modes, the complexity and response time of the control system are reduced, achieving efficient and stable task execution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of independent path tracking control of two robots under the same magnetic field in the present invention; Figure 2 It is a schematic diagram of the three-dimensional magnetic field coordinate system in the present invention; Figure 3 is a force analysis diagram of a single robot in the present invention; Figure 4 It is the magnetic field setting when a single robot crawls in the present invention; Figure 5 It is a complete crawling schematic diagram in the present invention; Figure 6 is a schematic diagram of the initial placement positions of the two robots in the present invention; Figure 7 It is a schematic diagram of the force analysis of the two robots; Figure 8It is a schematic diagram of the state transformation of two robots in the present invention; Fig. 9 This is a schematic diagram of the magnetic field when the robot is crawling; Fig.10 It is the motion trajectory diagram of the two robots during the independent path tracking control process passing through two target points; Fig.11 It is the motion trajectory diagram of two robots at different time stages in an independent control task. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0021] Embodiment 1: The present invention proposes a new independent control method for a magnetically driven thin-film soft robot, which enables two robots with exactly the same properties to exhibit different motion states under the same magnetic field. The method mainly includes: (1) accurately obtaining the position and posture information of the micro-robot through visual feedback and image processing technology; (2) proposing and verifying an independent control strategy, which can realize independent control of two robots with similar properties, such as Figure 1 shown.

[0022] The magnetic soft crawling robot is driven by an external magnetic field to achieve complex crawling movements. The magnetic field that drives its movement is generated by a three-dimensional Helmholtz coil system, which can accurately control the direction and intensity of the magnetic field in three-dimensional space, so that the robot can crawl along the set path. The three-dimensional Helmholtz coil controls the magnetic field components in each direction by adjusting the current in three orthogonal directions to form a uniform and stable magnetic field environment. By adjusting the magnetic field parameters, the micro robot can crawl within the magnetic field space.

[0023] 1. Magnetic field setting The micro robot crawls under the three-dimensional magnetic field and establishes a spatial magnetic field coordinate system, such as Figure 2 As shown, the micro robot is placed on the xy plane of the magnetic field coordinate system. Where B is the magnetic induction intensity of the external magnetic field, is the angle between B and the xy plane, is the angle between B and the xz plane, where and Counterclockwise is positive, The function is to adjust the robot's steering, which is also the robot's steering angle. The initial value is set to 0 degrees and will be adjusted continuously with the target path. size to realize the path tracking control of the robot.

[0024] 2. Image processing The image processing process was completed in Matlab / Simulink. First, two images of the robot were obtained. One was an image before the experiment started, when there was no robot on the experimental table; the other was an image after the robot was placed on the experimental table at the beginning of the experiment. The difference between the two images is that the robot appears in the second image. Therefore, the image subtraction method can be used to find the position where the robot appears, and the current position information of the robot can be obtained. Image subtraction is a basic and effective image processing method. By performing a difference operation on the corresponding pixel values ​​of the two images, the change area or difference information is extracted, and the image of the approximate area of ​​the robot is obtained. Subsequently, the extracted image is subjected to median filtering to eliminate noise and obtain a clearer image effect. Next, the Blob Analysis module in Simulink is used to extract the current position and posture information of the robot. Finally, the acquired position and posture are fed back to the magnetic field drive system, and the robot's motion form is changed by adjusting the size and direction of the magnetic field to achieve closed-loop control.

[0025] 3. The crawling process of a single robot The magnetic micro robot can crawl under the action of a magnetic field. Figure 3 Shown: Among them , are the magnetic moments of the head and tail, M1 and M2 are the magnetization intensities, B is the magnetic induction intensity of the external magnetic field space, G is the gravity of the robot, N1, N2, f1, and f2 are the support force and friction force of the head and tail respectively. Under the action of two opposite magnetic moments, the head and tail of the robot rotate in different directions, and the whole robot arches upward.

[0026] By using Ansys software for simulation and combining it with actual experiments, the following phenomena can be observed: (1) When , and When the magnitudes of B are equal but the directions are opposite, the robot is in a symmetrical state. In addition, as B increases, the bending degree of the robot also gradually increases.

[0027] (2) When and When fixed, the robot is in an asymmetric state. , then N1≥N2, as B increases, N1 gradually increases, and N2 gradually decreases. When B reaches a certain critical value, N1 = 2G, N2 = 0. At this time, point b is in a suspended state. The movement of the robot is that point a remains relatively still relative to the bottom surface, while point b slides relatively.

[0028] (3) When As B decreases, the behavior of N1 and N2 is opposite to that described in (2). N1 gradually decreases, while N2 gradually increases. When B drops to 0, the robot lies completely flat on the ground. During the whole process, point b remains stationary relative to the ground, while point a slides relatively.

[0029] Based on the above observations, Figure 4 The magnetic field configuration shown sets the B and The value of realizes the robot's crawling. Figure 5 As shown in Figure 1, a complete crawling process consists of two parts: contraction and extension. The specific implementation steps are as follows: Step 1: Set it to 20°, gradually increase the strength of B from 0 to 100Gs, and the robot begins to gradually retract upwards.

[0030] Step 2: When B reaches 100 Gs, the robot reaches its maximum bending state and completes the contraction action.

[0031] Step 3: Set to -20°, gradually reduce the strength of B from 100Gs to 0, and the robot begins to gradually stretch downward.

[0032] Step 4: When B decreases to 0Gs, the robot is completely flat and the stretching action is completed.

[0033] This complete contraction and extension process realizes the crawling motion function of the microrobot.

[0034] 4. Independently control two robots to crawl After implementing path-following control for a single robot, we turned to implementing independent path-following control for two robots. Two robots with the same geometry and magnetization curve were used. However, at the initial moment, the two robots were stationary in the environment with different orientations, such as Figure 6 As shown. In the previous part, the contraction and extension of robot R1 were achieved by controlling the magnetic field B, so that it could crawl. Next, the characteristics of robot R2 under the same magnetic field are analyzed. The following formula only explains that when R1 is crawling normally, R2 does not crawl, and how R1 is controlled is the same as the crawling process of a single robot in the specific implementation method. In the independent control process, the control of R1 is equivalent to controlling a single robot to crawl.

[0035] Given a magnetic field B in the xz plane, the force analysis of the two microrobots is as follows: Figure 7 As shown in the figure, M1, M2, M3, and M4 represent the magnetization directions of the two robots respectively. , , , Represents the magnetic moments of the head and tail of the two robots.

[0036] The magnetic moment of robot R2 is as follows: in, is the angle between the magnetization direction of the robot R2 head and the magnetic field direction, represents the angle of the tail, , is the magnetization intensity of the head and tail, and V refers to the volume of the robot.

[0037] During the contraction of R1, the torque balance equation of robot R2 relative to point c is: Among them, G3 and G4 represent the gravity acting on the two ends of the robot R2, and The two ends of the robot are angled relative to the ground, and L is the length of the robot. The magnetic torque acting on the robot will align its magnetization direction with the magnetic field. Therefore, under the action of the magnetic field, the two ends of R2 are aligned with the magnetic torque. and In this process, R2 only changes in shape, and the position of its center of mass point c remains unchanged.

[0038] During the extension phase of R1, as the magnetic field strength B gradually weakens, and As a result, the size of R2 decreases, which leads to a reduction in the deformation of R2. Therefore, R2 gradually transitions from a curved shape to a completely flat shape.

[0039] Figure 8(a) shows the above phenomenon and illustrates the change of the state of R2 during the contraction and extension of R1. Figure 8 (b) Depicts the situation where the two robots swap roles when the magnetic field B rotates 180° around the y-axis. The two crawling robots in this paper have the following two characteristics: first, they can maintain a stable gait; second, when one robot performs a task, the movement speed of the other robot is close to zero. Based on these characteristics, the following independent control strategies for the two crawling robots are designed: (1) The task is performed by robot R1: In each crawling cycle, the magnetic field strength B and γ are set as follows Figure 4 As shown, the robot R1 can move while the robot R2 stays in place.

[0040] (2) The task is performed by robot R2: In each crawling cycle, the magnetic field strength B and γ are set as follows Fig. 9 As shown, the robot R2 can move while the robot R1 stays in place.

[0041] 5. Experimental results The two micro-robots are independently controlled and guided to move to the corresponding desired target positions and complete the corresponding tasks through visual feedback. During the process, the Pure Pursuit algorithm is used to adjust the steering angle of the robot according to the deviation between the current position and the target position. , thus achieving path tracking control.

[0042] Independent path tracking control of two robots passing through two target points, Fig.10 is the motion trajectory of robots R1 and R2, Fig.11 To independently control the trajectory of the robot at different stages of the task.

[0043] In the experiment, robot R1 is placed at point A and robot R2 is placed at point D. R1 passes through points B and C in turn, while R2 remains stationary at the starting point D. When R1 returns to point A, R2 starts to move, passing through points E and F in turn. During the whole process, R1 always remains near the starting point A. When R2 returns to point D, the experimental task ends.

[0044] According to the experimental results, it is found that the gap between the actual path of the robot and the expected trajectory is small, which shows that the effect of independent path tracking control is ideal.

[0045] 6. Conclusion The present invention uses a pair of magnetically driven thin-film robots with similar properties and proposes an independent control method. First, the crawling motion of a single robot is controlled and an independent control strategy for multiple robots is designed. Then, a group of robots with similar characteristics are used for independent control, and the position control and path tracking control of the two robots are successfully realized, so that the two robots can independently complete their respective tasks under the action of the same magnetic field.

[0046] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. An independent control method for a magnetically driven thin-film soft robot, characterized in that: The following steps are involved: Two magnetically driven thin-film soft robots with the same geometric shape and magnetization curve are placed in the magnetic field space generated by a three-dimensional Helmholtz coil system; The magnetic field parameters are adjusted by the magnetic field driving system to generate different magnetic field strengths and magnetic field angles, so that one of the robots generates a crawling motion while the other robot remains in place; Acquire the position and posture information of the two robots through a visual acquisition system; The extracted position information and posture are fed back to the magnetic field drive system, and the robot's motion form is changed by adjusting the magnetic field strength and magnetic field angle to perform closed-loop control to achieve path tracking control of the robot.

2. The independent control method of the magnetically driven thin film soft robot according to claim 1, characterized in that: The magnetic field space is a three-dimensional magnetic field coordinate system xyz constructed based on a three-dimensional Helmholtz coil system; The two robots are placed on the xy plane of the three-dimensional magnetic field coordinate system, and the magnetic field angle includes the angle between the magnetic field intensity B and the xy plane. and the angle between the magnetic field intensity B and the xz plane ,in, and Counterclockwise is positive.

3. The independent control method of the magnetically driven thin film soft robot according to claim 2, characterized in that: The crawling movement includes two stages: contraction and extension, wherein: Contraction phase: Set it to a positive value, and gradually increase the magnetic field strength B from 0 to the preset value, so that the robot gradually shrinks upward; Stretching phase: Set it to a negative value and gradually reduce the magnetic field strength B from the preset value to 0, so that the robot gradually extends downward.

4. The independent control method of the magnetically driven thin film soft robot according to claim 1, characterized in that: The image processing step of the visual feedback system includes: Get two images of the robot, one is the image of the test bench without the robot, and the other is the image after the robot is placed on the test bench; Image subtraction is used to extract the changed area or difference information between two images; Perform median filtering on the extracted image; Use the Blob Analysis module in Simulink to extract the robot's current position and posture information; The acquired position and attitude information is fed back to the magnetic field drive system.

5. The independent control method of the magnetically driven thin film soft robot according to claim 3, characterized in that: The head and tail magnetic moments acting on a robot are generated by adjusting the magnetic field strength B and the magnetic field angle , and the head and tail magnetic moments acting on the other robot , , in order to realize the control of the bending and stretching of the two robots in the magnetic field; When controlling the robot: In each crawling cycle, the magnetic field strength B and the angle are set , causing one of the robots to crawl; at the same time, the other robot only changes its shape, and its center of mass position remains unchanged.

6. The independent control method of the magnetically driven thin film soft robot according to claim 5, characterized in that: When the robot control target needs to be switched: the magnetic field strength B is rotated 180° around the y-axis; the robot whose original center of mass position remains unchanged starts to move, and the robot that originally produces crawling motion keeps the center of mass position unchanged.

7. The independent control method of the magnetically driven thin film soft robot according to claim 5, characterized in that: Assume that the two robots are R1 and R2. By adjusting the magnetic field strength B and the magnetic field angle, the robot R1 will crawl, and the center of mass position of the robot R2 will remain unchanged. The magnetic moment of robot R2 is as follows: in, is the angle between the magnetization direction of the robot R2 head and the magnetic field direction, represents the angle of the tail, , is the magnetization intensity of the head and tail, V refers to the volume of the robot; During the contraction of robot R1, the moment balance equation of robot R2 relative to the center of mass point c is: Among them, G3 and G4 represent the gravity acting on the two ends of the robot R2, and They represent the angles between the two ends of the robot and the ground, and L refers to the length of the robot.

8. The independent control method of the magnetically driven thin film soft robot according to claim 1, characterized in that: Also includes the path tracking control steps: Pre-set target locations and waypoints; Obtain robot position in real time through visual feedback system; The magnetic field strength and angle are dynamically adjusted according to the deviation between the actual position and the path point.

9. A system for implementing the independent control method of the magnetically driven thin-film soft robot according to claim 1, characterized in that: include: A three-dimensional Helmholtz coil system for generating a controllable magnetic field in a three-dimensional magnetic field space; Two magnetically driven thin-film soft robots with the same geometric shape and magnetization curve are arranged in the magnetic field space and can perform contraction and extension actions under the drive of the magnetic field to achieve crawling motion; The visual acquisition system is used to collect images of the two robots in the magnetic field space and obtain the position and posture information of the robots through image processing; The magnetic field driving system receives the position and posture information output by the image processing module, calculates the required magnetic field parameters according to a preset control strategy, and outputs control signals to adjust the magnetic field parameters of the three-dimensional Helmholtz coil system to generate different magnetic field intensities and magnetic field angles, so that the two robots can crawl along the set path.

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