Method and system for controlling three-dimensional motion of magnetic micro-robot in water

Abstract

The invention belongs to the field of magnetic micro-nano robot preparation and control, and particularly relates to a three-dimensional motion control method and system of a magnetic micro-robot in water, and the method comprises the following steps: S1, obtaining a two-dimensional motion image of an underwater magnetic micro-spiral robot MMR in real time; s2, extracting feature parameters of the minimum enclosing rectangle of the MMR based on an image processing algorithm, establishing a mapping relation with the depth, pitch angle and course angle of the MMR according to the width, length and rotation angle of the minimum enclosing rectangle, and resolving three-dimensional pose information of the MMR in real time; and S3, generating a three-dimensional rotating magnetic field by using a five-coil electromagnetic driving device, and adjusting parameters of the three-dimensional rotating magnetic field through a control algorithm in combination with the three-dimensional pose information to realize three-dimensional motion control of the MMR in water. According to the method, real-time calculation of the depth, the pitch angle and the course angle is achieved based on the mapping relation between the minimum bounding rectangle parameter and the three-dimensional pose, the calculation precision is smaller than 8% of the body length of the robot, and the requirement for micro-nano scale operation is met.

Description

Technical Field

[0001] The present invention belongs to the field of preparation and control of magnetic micro-nano robots, and in particular relates to a method and system for controlling the three-dimensional motion of a magnetic micro-robot in water. Background Art

[0002] Magnetic microrobots (MMRs) have shown significant application prospects in biomedical fields, such as targeted drug delivery, minimally invasive surgery, and micro-nanomanipulation. To achieve precision medicine, MMRs require precise trajectory tracking and motion control within complex three-dimensional biological environments to reach the target area and complete treatment. Currently, a variety of advanced tracking and control methods have been developed for real-time state monitoring of MMRs (including X, Y, and Z spatial coordinates and parameters such as heading and pitch angles), enabling precise two-dimensional and three-dimensional motion control.

[0003] However, existing research is mostly limited to in vitro experimental environments, typically relying on side-mounted camera systems to obtain the MMR's pose information and Z-axis position. This configuration faces significant challenges in real-world in vivo applications: due to anatomical limitations and the requirement for minimally invasive procedures, it is impossible to deploy additional side-viewing imaging equipment within the organism, making traditional 3D pose detection methods difficult to directly apply in clinical settings. This technical bottleneck severely restricts the practical application of MMR in real-world medical scenarios. Therefore, how to accurately estimate the pose and depth information of MMR using monocular imaging remains an urgent problem. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for preparing and three-dimensional motion control of a magnetic micro-helical robot (MMR) based on monocular microscope imaging and five-coil electromagnetic system drive. The MMR is prepared by two-photon 3D printing and magnetron sputtering technology, and images are collected in real time using a monocular microscope. The robot's circumscribed rectangle parameters are extracted through algorithm processing and the three-dimensional posture information is solved. Finally, precise underwater motion control is achieved through electromagnetic drive, so that the precise posture information of the MMR can be obtained in real time and transmitted to the designed controller, thereby realizing precise control of the three-dimensional motion of the MMR in water.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned object is: a method for controlling the three-dimensional motion of a magnetic microrobot in water, comprising the following steps:

[0006] S1: Real-time acquisition of two-dimensional motion images of the underwater magnetic micro-helical robot (MMR) using a monocular micro-imaging system;

[0007] S2: Extract the minimum bounding rectangle feature parameters of the MMR based on an image processing algorithm, and establish a mapping relationship between the width, length, and rotation angle of the minimum bounding rectangle and the depth, pitch angle, and heading angle of the MMR to calculate the three-dimensional pose information of the MMR in real time;

[0008] S3: Generate a three-dimensional rotating magnetic field using a five-coil electromagnetic drive device, combine the three-dimensional posture information, and adjust the parameters of the three-dimensional rotating magnetic field through a control algorithm to achieve three-dimensional motion control of the MMR in water.

[0009] The preparation method of the MMR is specifically as follows:

[0010] S1-1: Using two-photon polymerization 3D printing technology, IP-Dip photoresist is used as the raw material to prepare a substrate with a micro-helical structure;

[0011] S1-2: Using magnetron sputtering technology, a nickel layer and a gold layer are sequentially sputtered on the surface of the micro-helical structure to make it magnetically responsive and biocompatible;

[0012] The total length of the micro-helical structure is 60-68 μm, the diameter is 10-15 μm, the pitch is 18-20 μm, and the head is provided with a hollow cylindrical structure to increase the magnetic attachment area;

[0013] The nickel sputtering rate is 5-10 nm / min, and the gold sputtering rate is 20-25 nm / min, so that the thickness of the sputtered nickel layer is 260-300 nm, and the thickness of the gold layer is 180-220 nm, so that the MMR has magnetic responsiveness and biocompatibility.

[0014] The image processing algorithm comprises:

[0015] S2-1: Using the CSRT tracking algorithm, the search area of ​​the current frame is predicted based on the MMR position in the previous frame image to locate the real-time area of ​​the MMR;

[0016] S2-2: extracting the outer contour of the MMR using a contour detection algorithm within the region;

[0017] S2-3: Based on the Scan algorithm, the convex hull of the contour point set of the outer contour is calculated to generate the minimum circumscribed rectangle of the MMR, and the center coordinates (X, Y), width W, length L and rotation angle θ of the rectangle are extracted as feature parameters.

[0018] The method for establishing the mapping relationship includes:

[0019] The minimum bounding rectangle parameters of the MMR at different depths and different pitch angles are collected by a control variable method;

[0020] A third-order polynomial fitting method is used to construct a quantitative relationship between the width and depth of the rectangle, the length and width of the rectangle, and the pitch angle;

[0021] Among them, the mapping relationship between the rectangle width W and the depth Z is:

[0022] Z = 3.447W-130.8, depth range 0-80μm;

[0023] The mapping relationship between the rectangle length L, width W and pitch angle α is:

[0024]

[0025] The control algorithm includes:

[0026] S3-1: Determine, based on the three-dimensional posture information, whether the motion state of the MMR is base motion, vertical motion, or suspended motion;

[0027] a. When the minimum bounding rectangle width is less than or equal to 38, it is determined to be base movement;

[0028] b. When the minimum bounding rectangle width is greater than 38 and |LW| is less than or equal to 5, it is determined to be vertical movement;

[0029] c. When the minimum bounding rectangle width is greater than 38 and |LW| is greater than 5, it is determined to be a suspended motion;

[0030] S3-2: Based on the motion state, select a corresponding compensation controller, namely:

[0031] S3-2-1: When the substrate is in motion, a PD controller is used to compensate for friction.

[0032] When the base moves, the magnetic intensity is kept constant at 6mT, and only the magnetic field frequency is changed in the range of 2-6Hz. The offset angle obtained by testing is:

[0033]

[0034] At the same time, the Euclidean distance between the robot's target point and the current position is used as the error, a PD controller is constructed, and the relationship between the error and the magnetic frequency is established, namely:

[0035] f=0.05error+0.7(error-pre_error)

[0036] S3-2-2: In vertical motion or suspended motion, establish a PD controller in the depth direction to overcome gravity and perform vertical upward motion. The magnetic intensity remains unchanged at 12mT, and the magnetic frequency is within the range of 12-18Hz.

[0037] The depth difference between the current point and the target point is the error, and its controller is:

[0038] f=5.4error+1.7(error-pre_error)

[0039] S3-2-3: Levitation motion: The initial pitch angle was set to 60°, the magnetic field frequency was 16 Hz, and the magnetic field strength was 12 mT. PD controllers were established in depth and in the two-dimensional plane to fine-tune the magnetic field frequency and pitch angle.

[0040] Among them, the PD controller in the depth direction is as follows:

[0041] depth_f=0.78Z_error+0.5(Z_error-Z_pre_error)+16sin(60°)

[0042] The PD controller for the two-dimensional plane is as follows:

[0043] plane_f=0.02error+0.5(error-pre_error)+16cos(60°).

[0044] The calculation accuracy of the three-dimensional posture information is less than 8% of the MMR body length.

[0045] A control system for a three-dimensional motion control method of a magnetic microrobot in water, comprising:

[0046] A monocular microscopic imaging system for acquiring real-time 2D motion images of underwater MMR;

[0047] An image processing module, connected to the monocular microscopic imaging system, is used to extract the minimum circumscribed rectangle feature parameters of the MMR through a target detection algorithm, including the rectangle center coordinates, width, length, and rotation angle;

[0048] A state determination module is connected to the image processing module and is used to calculate the three-dimensional posture information of the MMR in real time based on the minimum bounding rectangle parameters through a pre-established mapping relationship, including the X, Y, and Z axis coordinates and the pitch angle and heading angle α;

[0049] A five-coil electromagnetic drive device for generating a programmable three-dimensional rotating magnetic field;

[0050] A control module is connected to the state determination module and the five-coil electromagnetic drive device, and is used to adjust the frequency, direction and intensity of the three-dimensional rotating magnetic field according to the three-dimensional posture information to achieve precise three-dimensional motion control of the MMR.

[0051] The five-coil electromagnetic drive device comprises: three pairs of orthogonal Helmholtz coils;

[0052] In a two-dimensional plane, the X-axis and Y-axis coils are symmetrically distributed to generate a uniform magnetic field in any direction in the XOY plane. At the same time, a single vertical coil is nested with the origin as the center of the circle, wrapping the workspace to generate a uniform vertical magnetic field in the workspace.

[0053] By overcoupling the uniform magnetic fields in three directions, a rotating magnetic field in any direction is generated in the workspace.

[0054] The five-coil electromagnetic drive device generates a three-dimensional uniform rotating magnetic field with a frequency of 0-30 Hz, and controls the three-dimensional motion trajectory of the MMR by adjusting the direction and frequency of the magnetic field.

[0055] The present invention has the following beneficial effects and advantages:

[0056] 1. The present invention establishes a mapping relationship between the minimum bounding rectangle parameters of the MMR (rectangle width, rectangle length) and the MMR posture and depth. Under monocular imaging mode, the MMR's posture information is determined by the two-dimensional image of the MMR. The process is efficient and accurate, and the three-dimensional motion control of the MMR in water is realized.

[0057] 2. Based on the mapping relationship between the minimum circumscribed rectangle parameters (width, length, rotation angle) and the three-dimensional posture, the present invention realizes the real-time calculation of depth, pitch angle and heading angle. The calculation accuracy is less than 8% of the robot body length, meeting the needs of micro-nanoscale operations.

[0058] 3. The present invention dynamically switches the PD controller according to the robot's motion state (base, vertical, suspension), specifically compensates for friction or gravity, and significantly improves the stability and accuracy of motion control.

[0059] 4. The present invention uses two-photon 3D printing technology combined with magnetron sputtering coating to ensure high-precision molding and magnetic responsiveness of the micro-helical structure. At the same time, the biocompatibility of the gold layer expands the application potential of the robot in medical scenarios.

[0060] 5. The system of the present invention achieves closed-loop control through rapid image processing and magnetic field regulation, with a response speed of milliseconds; the proposed method can be adapted to microrobots of different sizes or structures and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a schematic diagram of the preparation principle of MMR prepared in the present invention;

[0062] Figure 2Schematic diagram of SEM images of the MMR prepared in the present invention; wherein, (a) is the SEM image of the magnetic micro-helical robot prepared in batches, and (b) is the SEM image of a single magnetic micro-helical robot;

[0063] Figure 3 Schematic diagram of the three-dimensional motion of the MMR based on monocular microscope imaging and a five-coil electromagnetic system drive according to the present invention;

[0064] Among them, 1 is the MMR, 2 is the five-coil electromagnetic drive device, and 3 is the monocular microscopic imaging system;

[0065] Figure 4 This is a flow chart of the method of the state determination module in the present invention;

[0066] Figure 5 The three-dimensional motion process of MMR in water under different motion states controlled by the method of the present invention. DETAILED DESCRIPTION

[0067] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0068] The present invention first uses two-photon polymerization 3D printing and magnetron sputtering technology to mass-produce magnetic microrobots with excellent magnetic response capabilities, namely MMR (hereinafter referred to as MMR). Subsequently, the real-time image obtained by the monocular microscope is processed by the target detection algorithm to obtain the relevant parameters of the minimum circumscribed rectangle of the MMR (rectangle center, rectangle width, rectangle length, rotation angle); and a mapping relationship between rectangle width-MMR depth, rectangle length and width-MMR pitch angle is established to achieve estimation of the MMR posture and depth, and pass the relevant posture information to the compensation-based control module to achieve three-dimensional motion control of the MMR in water. The specific steps are as follows:

[0069] like Figure 4 FIG. 1 is a flow chart of a state determination module in the present invention. The present invention provides a three-dimensional motion control method for a magnetic microrobot in water, comprising the following steps:

[0070] S1: Real-time acquisition of two-dimensional motion images of the underwater magnetic micro-helical robot (MMR) using a monocular micro-imaging system;

[0071] Among them, such as Figure 1 As shown in FIG, a schematic diagram of the preparation principle of MMR of the present invention is shown, and the preparation method of MMR of the present invention is specifically as follows:

[0072] S1-1: Using two-photon polymerization 3D printing technology, IP-Dip photoresist is used as the raw material to prepare a substrate with a micro-helical structure;

[0073] S1-2: Using magnetron sputtering technology, a nickel layer and a gold layer are sequentially sputtered on the surface of the micro-helical structure to make it magnetically responsive and biocompatible;

[0074] The total length of the micro-helical structure is 60-68 μm, the diameter is 10-15 μm, the pitch is 18-20 μm, and the head is provided with a hollow cylindrical structure to increase the magnetic attachment area;

[0075] The nickel sputtering rate is 5-10 nm / min, and the gold sputtering rate is 20-25 nm / min, so that the thickness of the sputtered nickel layer is 260-300 nm, and the thickness of the gold layer is 180-220 nm, so that the MMR has magnetic responsiveness and biocompatibility.

[0076] S2: Extract the minimum bounding rectangle feature parameters of the MMR based on the image processing algorithm, and establish a mapping relationship with the depth, pitch angle and heading angle of the MMR based on the width, length and rotation angle of the minimum bounding rectangle, and calculate the three-dimensional pose information of the MMR in real time;

[0077] The image processing algorithm performs the following steps:

[0078] S2-1: Using the CSRT tracking algorithm, the search area of ​​the current frame is predicted based on the MMR position in the previous frame image to locate the real-time area of ​​the MMR;

[0079] S2-2: extracting the outer contour of the MMR using a contour detection algorithm within the region;

[0080] S2-3: Based on the Scan algorithm, the convex hull of the contour point set of the outer contour is calculated to generate the minimum circumscribed rectangle of the MMR, and the center coordinates (X, Y), width W, length L and rotation angle θ of the rectangle are extracted as feature parameters.

[0081] In step S2, the method for establishing the mapping relationship includes:

[0082] The minimum bounding rectangle parameters of the MMR at different depths and different pitch angles are collected by a control variable method;

[0083] A third-order polynomial fitting method is used to construct a quantitative relationship between the width and depth of the rectangle, the length and width of the rectangle, and the pitch angle;

[0084] Among them, the mapping relationship between the rectangle width W and the depth Z is:

[0085] Z=3.447W-130.8, depth range is 0-80μm

[0086] The mapping relationship between the rectangle length L, width W and pitch angle α is:

[0087]

[0088] S3: Generate a three-dimensional rotating magnetic field using a five-coil electromagnetic drive device, combine the three-dimensional posture information, and adjust the parameters of the three-dimensional rotating magnetic field through a control algorithm to achieve three-dimensional motion control of the MMR in water.

[0089] The control algorithm is as follows:

[0090] S3-1: Determine, based on the three-dimensional posture information, whether the motion state of the MMR is base motion, vertical motion, or suspended motion;

[0091] a. When the minimum bounding rectangle width is less than or equal to 38, it is determined to be base movement;

[0092] b. When the minimum bounding rectangle width is greater than 38 and |LW| is less than or equal to 5, it is determined to be vertical movement;

[0093] c. When the minimum bounding rectangle width is greater than 38 and |LW| is greater than 5, it is determined to be a suspended motion;

[0094] S3-2: Based on the motion state, select a corresponding compensation controller, namely:

[0095] S3-2-1: When the substrate is in motion, a PD controller is used to compensate for friction.

[0096] When the base moves, the magnetic intensity is kept constant at 6mT, and only the magnetic field frequency is changed in the range of 2-6Hz. The offset angle obtained by testing is:

[0097]

[0098] At the same time, the Euclidean distance between the robot's target point and the current position is used as the error, a PD controller is constructed, and the relationship between the error and the magnetic frequency is established, namely:

[0099] f=0.05error+0.7(error-pre_error)

[0100] S3-2-2: In vertical motion or suspended motion, establish a PD controller in the depth direction to overcome gravity and perform vertical upward motion. The magnetic intensity remains unchanged at 12mT, and the magnetic frequency is within the range of 12-18Hz.

[0101] The depth difference between the current point and the target point is the error, and its controller is:

[0102] f=5.4error+1.7(error-pre_error)

[0103] S3-2-3: Levitation motion: The initial pitch angle was set to 60°, the magnetic field frequency was 16 Hz, and the magnetic field strength was 12 mT. PD controllers were established in depth and in the two-dimensional plane to fine-tune the magnetic field frequency and pitch angle.

[0104] Among them, the PD controller in the depth direction is as follows:

[0105] depth_f=0.78Z_error+0.5(Z_error-Z_pre_error)+16sin(60°)

[0106] The PD controller for the two-dimensional plane is as follows:

[0107] plane_f=0.02error+0.5(error-pre_error)+16cos(60°).

[0108] The calculation accuracy of the three-dimensional posture information is less than 8% of the MMR body length.

[0109] like Figure 4 As shown, in combination with the architecture of the present invention, the control system of the method for controlling the three-dimensional motion of a magnetic microrobot in water of the present invention includes:

[0110] The monocular microscopic imaging system 3 is a monocular microscopic camera used to obtain two-dimensional motion images of the underwater MMR1 in real time;

[0111] An image processing module, connected to the monocular microscopic imaging system, is used to extract the minimum bounding rectangle feature parameters of the MMR1 through a target detection algorithm, including: rectangle center coordinates, width, length and rotation angle;

[0112] A state determination module is connected to the image processing module and is used to calculate the three-dimensional posture information of the MMR1 in real time based on the minimum bounding rectangle parameters through a pre-established mapping relationship, including the X, Y, and Z axis coordinates and the pitch angle and heading angle α;

[0113] A five-coil electromagnetic drive device 2 for generating a programmable three-dimensional rotating magnetic field;

[0114] The control module is connected to the state determination module and the five-coil electromagnetic drive device 2, and is used to adjust the frequency, direction and intensity of the three-dimensional rotating magnetic field according to the three-dimensional posture information to achieve precise three-dimensional motion control of the MMR.

[0115] like Figure 3 As shown, it is a schematic diagram of the three-dimensional motion of the MMR based on monocular microscope imaging and five-coil electromagnetic system driving; the five-coil electromagnetic driving device 2 in the present invention is: three pairs of orthogonal Helmholtz coils;

[0116] In a two-dimensional plane, the X-axis and Y-axis coils are symmetrically distributed to generate a uniform magnetic field in any direction in the XOY plane. At the same time, a single vertical coil is nested with the origin as the center of the circle, wrapping the workspace to generate a uniform vertical magnetic field in the workspace.

[0117] By overcoupling the uniform magnetic fields in three directions, a rotating magnetic field in any direction is generated in the workspace.

[0118] The five-coil electromagnetic drive device 2 generates a three-dimensional uniform rotating magnetic field with a frequency of 0-30 Hz, and controls the three-dimensional motion trajectory of the MMR by adjusting the direction and frequency of the magnetic field.

[0119] Example:

[0120] Figure 1 This is a method for preparing MMR in large quantities at low cost. The preparation method of MMR1 is as follows: In this embodiment, a micro-helical structure is designed with a total length of 64μm, a diameter of 12μm, and a pitch of 19μm. A hollow cylindrical shape is designed at the head to increase the magnetic attachment area. It is prepared using IP-Dip photoresist using a two-photon printing device, and Ni and Au films are sputtered on the surface in succession. The sputtering times are 60min and 10min, respectively, to ensure that it has excellent magnetic response and biocompatibility.

[0121] Figure 2 (a) and (b) are the SEM images of batch-prepared MMR and the SEM images of a single MMR, respectively. It can be seen that the MMRs prepared in the same batch show good consistency in morphology and size; all MMR structures are intact and there are no preparation defects such as breakage or deformation; a single MMR presents a clear and regular three-dimensional spiral structure.

[0122] Figure 3 Schematic diagram of the three-dimensional motion of an MMR based on monocular microscope imaging and a five-coil electromagnetic system. 1 is the MMR driven by a three-dimensional rotating magnetic field, 2 is the five-coil electromagnetic drive device, and 3 is the monocular microscope imaging system 3. The five-coil electromagnetic drive device 2 can generate a uniform rotating magnetic field in any three-dimensional direction within the workspace, with a maximum rotation frequency of 30 Hz, controlling the MMR to move along a designed three-dimensional trajectory.

[0123] Figure 4This is the state determination module designed. Since the projection area formed by MMR1 at different depths is different under a monocular microscope, we use this principle to establish a mapping relationship between the parameters related to the minimum bounding rectangle of the MMR1 projection and the state information. First, the mapping relationship between the rectangle width and the depth of MMR1. When the depth is higher, the rectangle width is larger. We collected the minimum bounding rectangle width of MMR1 at different depths and established a mapping relationship between the two through polynomial fitting. Next, the relationship between the rectangle width, length and the pitch angle of MMR1 is established. Since the length of the rectangle is determined by the depth and pitch angle, we first infer the depth of MMR1 through the rectangle width, and then use the rectangle length to infer the pitch angle. Similar to the above acquisition method, a mapping relationship between the three is established.

[0124] Subsequently, since the MMR1 is subject to different forces in different states (for example, it is disturbed by surface friction when moving on the base, and it is disturbed by gravity when moving at a certain depth), we divide the robot states into three categories: base movement, vertical movement, and suspended movement. The estimated depth information is used to determine whether the robot is in the base movement state, and then the width and length of the minimum circumscribed rectangle of the MMR1 are compared to determine whether it is in the vertical movement state (in vertical movement, the width and length of the rectangle are similar). After determining the state of the MMR1, two different controllers will be used: a PD controller based on compensating friction and a PD controller based on compensating gravity, corresponding to base movement, vertical movement, and suspended movement, respectively.

[0125] Figure 5 The three-dimensional motion of MMR1 in water using the state determination module and control module proposed in the present invention is shown. The state determination module designed in different motion states can accurately estimate the position information of MMR1 in real time, and its control accuracy can be less than 8% of the body length.

[0126] In summary, combined with the embodiments of the present invention, this paper proposes an innovative method for fabricating and controlling the three-dimensional motion of a magnetic microrobot (MMR). This method uses a monocular microscopic imaging system to acquire two-dimensional images in real time. By mapping the minimum bounding rectangle feature parameters to the three-dimensional pose, high-precision depth and pose calculations are achieved. Furthermore, a five-coil electromagnetic drive system generates a programmable three-dimensional rotating magnetic field. The magnetic field parameters are dynamically adjusted using an adaptive control algorithm, ultimately achieving precise three-dimensional motion control of the MMR in water. Compared to existing technologies, this method overcomes imaging limitations in in vivo applications and reduces system complexity. Furthermore, by optimizing the fabrication process and control strategy, it significantly improves the robot's motion accuracy and clinical applicability. Experimental results demonstrate that the system's control accuracy can reach within 8% of its body length, providing reliable technical support for biomedical applications such as targeted drug delivery and minimally invasive surgery. The core innovation of this invention lies in the deep integration of monocular imaging and electromagnetic drive, combining efficiency, cost-effectiveness, and scalability, opening up new avenues for the practical medical application of microrobots.

[0127] Those skilled in the art will understand that the above description is only a preferred embodiment of the present invention, and the features described in the various embodiments and / or claims of the present disclosure may be combined or coupled in various ways, even if such a combination or coupling is not explicitly described in the present disclosure. It is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

[0128] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A method for controlling the three-dimensional motion of a magnetic microrobot in water, characterized in that: The following steps are involved: S1: Real-time acquisition of two-dimensional motion images of the underwater magnetic micro-helical robot (MMR) using a monocular micro-imaging system; S2: Extract the minimum bounding rectangle feature parameters of the MMR based on an image processing algorithm, and establish a mapping relationship between the width, length, and rotation angle of the minimum bounding rectangle and the depth, pitch angle, and heading angle of the MMR to calculate the three-dimensional pose information of the MMR in real time; S3: Generate a three-dimensional rotating magnetic field using a five-coil electromagnetic drive device, combine the three-dimensional posture information, and adjust the parameters of the three-dimensional rotating magnetic field through a control algorithm to achieve three-dimensional motion control of the MMR in water.

2. The method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 1, characterized in that: The preparation method of the MMR is specifically as follows: S1-1: Using two-photon polymerization 3D printing technology, IP-Dip photoresist is used as the raw material to prepare a substrate with a micro-helical structure; S1-2: A nickel layer and a gold layer are sequentially sputtered on the surface of the micro-helical structure by magnetron sputtering coating technology, so that the micro-helical structure has magnetic responsiveness and biocompatibility.

3. The method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 2, characterized in that: The total length of the micro-helical structure is 60-68 μm, the diameter is 10-15 μm, the pitch is 18-20 μm, and the head is provided with a hollow cylindrical structure to increase the magnetic attachment area; The nickel sputtering rate is 5-10 nm / min, and the gold sputtering rate is 20-25 nm / min, so that the thickness of the sputtered nickel layer is 260-300 nm, and the thickness of the gold layer is 180-220 nm, so that the MMR has magnetic responsiveness and biocompatibility.

4. The method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 1, characterized in that: The image processing algorithm comprises: S2-1: Using the CSRT tracking algorithm, the search area of ​​the current frame is predicted based on the MMR position in the previous frame image to locate the real-time area of ​​the MMR; S2-2: extracting the outer contour of the MMR using a contour detection algorithm within the region; S2-3: Based on the Scan algorithm, the convex hull of the contour point set of the outer contour is calculated to generate the minimum circumscribed rectangle of the MMR, and the center coordinates (X, Y), width W, length L and rotation angle θ of the rectangle are extracted as feature parameters.

5. The method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 1, characterized in that: The method for establishing the mapping relationship includes: The minimum bounding rectangle parameters of the MMR at different depths and different pitch angles are collected by a control variable method; A third-order polynomial fitting method is used to construct a quantitative relationship between the width and depth of the rectangle, the length and width of the rectangle, and the pitch angle; Among them, the mapping relationship between the rectangle width W and the depth Z is: Z = 3.447W-130.8, depth range 0-80μm; The mapping relationship between the rectangle length L, width W and pitch angle α is:

6. The method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 1, characterized in that: The control algorithm includes: S3-1: Determine, based on the three-dimensional posture information, whether the motion state of the MMR is base motion, vertical motion, or suspended motion; a. When the minimum bounding rectangle width is less than or equal to 38, it is determined to be base movement; b. When the minimum bounding rectangle width is greater than 38 and |LW| is less than or equal to 5, it is determined to be vertical movement; c. When the minimum bounding rectangle width is greater than 38 and |LW| is greater than 5, it is determined to be a suspended motion; S3-2: Based on the motion state, select a corresponding compensation controller, namely: S3-2-1: When the substrate is in motion, a PD controller is used to compensate for friction. When the base moves, the magnetic intensity is kept constant at 6mT, and only the magnetic field frequency is changed in the range of 2-6Hz. The offset angle obtained by testing is: At the same time, the Euclidean distance between the robot's target point and the current position is used as the error, a PD controller is constructed, and the relationship between the error and the magnetic frequency is established, namely: f=0.05error+0.7(error-pre_error) S3-2-2: In vertical motion or suspended motion, establish a PD controller in the depth direction to overcome gravity and perform vertical upward motion. The magnetic intensity remains unchanged at 12mT, and the magnetic frequency is within the range of 12-18Hz. The depth difference between the current point and the target point is the error, and its controller is: f=5.4error+1.7(error-pre_error) S3-2-3: Levitation motion: The initial pitch angle was set to 60°, the magnetic field frequency was 16 Hz, and the magnetic field strength was 12 mT. PD controllers were established in depth and in the two-dimensional plane to fine-tune the magnetic field frequency and pitch angle. Among them, the PD controller in the depth direction is as follows: depth_f=0.78Z_error+0.5(Z_error-Z_pre_error)+16sin(60°) The PD controller for the two-dimensional plane is as follows: plane_f=0.02error+0.5(error-pre_error)+16cos(60°).

7. The method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 1, characterized in that: The calculation accuracy of the three-dimensional posture information is less than 8% of the MMR body length.

8. The control system of the method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 1, characterized in that: include: A monocular microscopic imaging system for acquiring real-time 2D motion images of underwater MMR; An image processing module, connected to the monocular microscopic imaging system, is used to extract the minimum circumscribed rectangle feature parameters of the MMR through a target detection algorithm, including the rectangle center coordinates, width, length, and rotation angle; A state determination module is connected to the image processing module and is used to calculate the three-dimensional posture information of the MMR in real time based on the minimum bounding rectangle parameters through a pre-established mapping relationship, including the X, Y, and Z axis coordinates and the pitch angle and heading angle α; A five-coil electromagnetic drive device for generating a programmable three-dimensional rotating magnetic field; A control module is connected to the state determination module and the five-coil electromagnetic drive device, and is used to adjust the frequency, direction and intensity of the three-dimensional rotating magnetic field according to the three-dimensional posture information to achieve precise three-dimensional motion control of the MMR.

9. The control system of the method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 8, characterized in that: The five-coil electromagnetic drive device comprises: three pairs of orthogonal Helmholtz coils; In a two-dimensional plane, the X-axis and Y-axis coils are symmetrically distributed to generate a uniform magnetic field in any direction in the XOY plane. At the same time, a single vertical coil is nested with the origin as the center of the circle, wrapping the workspace to generate a uniform vertical magnetic field in the workspace. By overcoupling the uniform magnetic fields in three directions, a rotating magnetic field in any direction is generated in the workspace.

10. The control system of the method for controlling the three-dimensional motion of a magnetic microrobot in water according to claim 9, characterized in that: The five-coil electromagnetic drive device generates a three-dimensional uniform rotating magnetic field with a frequency of 0-30 Hz, and controls the three-dimensional motion trajectory of the MMR by adjusting the direction and frequency of the magnetic field.

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