Magnetorheological polishing equipment and method for adjusting electromagnet based on sensor

Abstract

The invention relates to the technical field of optical machining, in particular to magneto-rheological polishing equipment and method based on a sensor adjusting electromagnet, and the equipment comprises a laser tracker, a control unit, a robot, a magneto-rheological machining module and a sensor module; the magneto-rheological machining module is arranged at the tail end of the robot, and the robot drives the magneto-rheological machining module to machine the optical element; the sensor module is arranged on the magneto-rheological processing module; the laser tracker is matched with the target ball to measure space coordinates of working points of polishing wheels in the sensor module and the magneto-rheological machining module; according to the method, a laser tracker and a sensor module are matched to measure real-time changes of the pose of a robot and the position of a magneto-rheological machining module in the machining process, the position or magnetic field intensity of an electromagnet in the magneto-rheological machining module is regulated and controlled in real time, and then real-time constant control over the removal function of the optical element is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical processing, and particularly relates to a magnetorheological polishing device and method for adjusting an electromagnet based on a sensor. Background Art

[0002] Magnetorheological Finishing (MRF) is an advanced optical manufacturing technology developed in recent years, which has many advantages such as a stable removal function, controllable edge effect, small damage layer on the lower surface, no replication effect, strong shaping ability, and high processing accuracy. Therefore, the magnetorheological polishing technology has received extensive attention in high-precision optical processing. The existing magnetorheological polishing mainly integrates the magnetorheological polishing module on a numerically controlled machine tool. However, the numerically controlled machine tool has some deficiencies (such as low degrees of freedom, large floor area, high cost, etc.), which lead to problems such as restricting the deviation of aspheric surfaces and making it difficult to perform precise pose control along the surface normal.

[0003] In view of these deficiencies of the numerically controlled machine tool, researchers have introduced six-degree-of-freedom industrial robots into the field of optical processing in recent years. The six-degree-of-freedom industrial robot has the advantages of high degrees of freedom, small floor area, large processing range, low cost, etc., making up for the deficiencies of the numerically controlled machine tool. Therefore, when integrating the magnetorheological polishing module into an industrial robot, it is theoretically possible to achieve high-precision processing of large-aperture complex-surface optical elements. However, due to the influence of factors such as processing, assembly, load, trajectory planning, and reduction ratio generated during the combination of the robot and the magnetorheological polishing module, the end-effector accuracy of the robot is relatively low, and the polishing gap changes greatly during the processing. At the same time, the magnetorheological polishing technology is an optical processing technology with a high degree of certainty of the removal function, and has high requirements for the change of the polishing gap during the polishing process. Generally, the change of the polishing gap in a magnetorheological numerical control processing center is in the order of dozens of micrometers (PV < 0.1 mm), while the trajectory accuracy of common commercial robots is generally in the sub-millimeter to millimeter range, which leads to a large change in the polishing gap during the processing. The large change in the polishing gap will result in a decrease in the certainty of the removal function and affect the final processing accuracy. Therefore, the motion accuracy of current commercial large six-degree-of-freedom industrial robots often fails to meet the requirements of the magnetorheological polishing technology for the change of the removal function during high-precision polishing.

[0004] In view of the problem of low robot motion accuracy, the current real-time control scheme based on constant-force grinding and polishing has become a research hotspot, and the force-position control method has become a common robot constant-force regulation grinding and polishing control method. A common application method is to place a force sensor between the processing tool and the robot. First, the gravity calibration of the force sensor is carried out to ensure the accurate determination of the measurement. The pose error is calculated by measuring the change of the force, and then the robot pose error is compensated by means of the robot body or other motion compensation mechanisms to achieve constant-force control. The high-efficiency processing of large-aperture optical elements relies on the magnetorheological processing module of a large-size polishing wheel, and the weight of the magnetorheological processing module of a large-size polishing wheel is generally over a hundred kilograms. However, for a magnetorheological processing module weighing over a hundred kilograms, the force change caused by the robot pose error is only a few tens of Newtons. When performing high-precision processing, the force needs to be constant at a few Newtons or even a fraction of a Newton, which requires the absolute measurement accuracy of measurement devices such as force sensors to reach one ten-thousandth, and the force sensor also needs to be in variable-speed and variable-pose motion. Force sensors that meet these requirements are often extremely expensive, greatly increasing the cost of the equipment. Summary of the Invention

[0005] In view of this, the present invention aims to provide a magnetorheological polishing device and method based on a sensor to adjust an electromagnet, which cooperates with a laser tracker and a sensor module to measure the real-time changes of the pose of the robot and the position of the magnetorheological processing module during the processing, and to adjust the position or magnetic field intensity of the electromagnet in the magnetorheological processing module in real time, so as to realize the real-time constant control of the removal function of the optical element to be processed.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows: A magnetorheological polishing device based on a sensor to adjust an electromagnet includes a laser tracker, a control unit, a robot, a magnetorheological processing module, and a sensor module; the magnetorheological processing module is arranged at the free end of the robot, and the robot drives the magnetorheological processing module to process the optical element; the sensor module is arranged on the magnetorheological processing module; the laser tracker cooperates with a target ball arranged on the magnetorheological processing module to measure the spatial coordinates of the sensor module and the working point of the polishing wheel in the magnetorheological processing module; The interior of the control unit includes: A coordinate relationship module, which integrates and calculates the spatial coordinates collected by the laser tracker and the position information collected by the sensor module, and outputs the integrated position information; A conversion relationship module, which fits the magnetic field intensity of the electromagnet in the magnetorheological processing module with the polishing gap of the polishing wheel to obtain a first conversion relationship, and fits the electromagnet position of the electromagnet with the polishing gap to obtain a second conversion relationship; The real-time control module adjusts the magnetic field strength according to the integrated position information and the first conversion relationship, and / or adjusts the position of the electromagnet according to the integrated position information and the second conversion relationship, so as to keep the removal function stable during the processing of the optical element.

[0007] Furthermore, the magnetorheological processing module further includes a conveyor belt, a polishing motor, a nozzle, a supply system, a real-time adjustment device, and a magnetorheological mounting bracket; wherein, the magnetorheological mounting bracket is arranged on the free end of the robot, the polishing wheel and the real-time adjustment device are arranged on the magnetorheological mounting bracket, and the real-time adjustment device is connected to the polishing wheel, so that the real-time adjustment device adjusts the position of the polishing wheel, thereby changing the polishing gap of the polishing wheel; the polishing motor is arranged on the magnetorheological mounting bracket and is connected to the polishing wheel through the conveyor belt, so that the polishing motor controls the rotation of the polishing wheel, thereby enabling the polishing wheel to process the optical element; the nozzle is arranged on the magnetorheological mounting bracket, and the nozzle direction of the nozzle is consistent with the rotation direction of the polishing wheel; the supply system is connected to the nozzle through a pipeline, and the supply system conveys the magnetorheological fluid to the nozzle, so that the polishing wheel processes the optical element with the magnetorheological fluid as the medium; the electromagnet is connected to the real-time adjustment device, and the electromagnet is close to the working point of the polishing wheel, so that the magnetorheological fluid changes its stiffness under the influence of the magnetic field strength of the electromagnet; at the same time, the real-time adjustment device adjusts the magnetic field strength and the distance between the electromagnet and the polishing wheel; the sensor module is arranged on the magnetorheological mounting bracket, and the laser tracker measures the spatial coordinates of the sensor module through the target ball.

[0008] Furthermore, the sensor module includes an acceleration sensor; the laser tracker, the sensor module, the robot, and the real-time adjustment device are respectively connected to the control unit to form their respective communication lines, so that the control unit receives and sends signals through the corresponding communication lines.

[0009] Furthermore, the real-time adjustment device includes a displacement output motor, a lead screw, a support fixing frame, and a current intensity controller; wherein, the support fixing frame is arranged on the magnetorheological mounting bracket, the displacement output motor is arranged on the support fixing frame, and the displacement output motor is connected to the lead screw arranged on the support fixing frame; the electromagnet or the polishing wheel is simultaneously connected to the nut on the lead screw, so that the lead screw drives the electromagnet or the polishing wheel to move; the current intensity controller is connected to the electromagnet through a wire to energize the electromagnet, so that the electromagnet generates a magnetic field; the current intensity controller is communicatively connected to the control unit, and the control unit sends a control signal to the current intensity controller, and the current intensity controller adjusts the current transmitted to the electromagnet according to the control signal, thereby changing the magnetic field strength of the electromagnet.

[0010] A magnetorheological polishing method based on magnetic field strength, based on the magnetorheological polishing equipment for adjusting an electromagnet based on a sensor provided by the present invention, includes the following steps: A1: Obtain the first coordinates of the sensor module and the second coordinates of the working point of the polishing wheel using a laser tracker; based on these two sets of coordinates, calculate the coordinate transformation relationship using the coordinate relationship module. A2: Using the coordinate relationship module, based on the coordinate transformation relationship, convert the first theoretical coordinates of the working point of the polishing wheel at different polishing trajectory points into the second theoretical coordinates of the sensor module, and obtain the theoretical straight-line distance based on the current second theoretical coordinates and the previous second theoretical coordinates. A3: Use the coordinate relationship module to record the measurement results of the sensor module to obtain the actual straight-line distance; calculate the distance error between the actual straight-line distance and the theoretical straight-line distance through the coordinate relationship module. A4: Control the magnetorheological machining module to perform fixed-point machining on the test optical element, and obtain the first conversion relationship through the conversion relationship module. A5: Set the distance error threshold, regulation maximum value, and maximum magnetic field strength; determine the machining conditions based on the distance error, distance gap threshold, and regulation maximum value; based on the machining conditions, combine the first conversion relationship and the maximum magnetic field strength to machine the optical element to be processed, and during the machining process, use the real-time regulation module to perform real-time regulation on the magnetic field strength of the electromagnet.

[0011] Further, in step A1, the laser tracker obtains the coordinates of no less than 4 positions on the sensor module through the target ball, and calculates the first coordinates (x1, y1, z1). The laser tracker obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel through the target ball, and then calculates the center point coordinates (x2, y2, z2) of the polishing wheel. The straight line passing through the center point coordinates is: ; where (a, b, c) represents the normal vector of the straight line of the center point coordinates. By solving the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations and taking them as the second coordinates (x, y, z): ; where R represents the radius of the polishing wheel. Obtain the coordinate transformation relationship from the second coordinates and the first coordinates: ; where T represents the coordinate transformation relationship.

[0012] Further, in step A2, obtain the theoretical straight-line distance through the following formula: ; where represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point. represents the Z coordinate in the current second theoretical coordinate, and represents the Z coordinate in the previous second theoretical coordinate.

[0013] Furthermore, in step A3, the actual linear distance is obtained by the following formula: ; where d ri represents the actual linear distance between the current polishing trajectory point and the previous polishing trajectory point; a i-1 represents the acceleration measured by the sensor module at the previous polishing trajectory point, v i-1 represents the velocity measured by the sensor module at the previous polishing trajectory point, and t represents the measurement time of the sensor module; furthermore, the distance error is obtained by the following formula : .

[0014] Furthermore, step A4 specifically includes the following steps: A41: Under different polishing gaps, the magnetic field intensity is separately changed, and machining is performed at different positions of the test optical element, and the volume removal rate of the removal function of each polishing trajectory point is calculated to obtain the third conversion relationship between the volume removal rate of the removal function and the magnetic field intensity: B = F bm (MRR); where B represents the magnetic field intensity, MRR represents the volume removal rate of the removal function, and F bm represents the third conversion relationship; A42: Control the polishing wheel to perform fixed-point machining for a period of time at different positions of the test optical element with different polishing gaps, and calculate the volume removal rate of the removal function of each polishing trajectory point to obtain the fourth conversion relationship between the volume removal rate of the removal function and the polishing gap: MRR = F mg (gap); where gap represents the polishing gap, and F mg represents the fourth conversion relationship; A43: According to the third conversion relationship and the fourth conversion relationship, obtain the first conversion relationship: B = F bg (gap) = F bm (F mg (gap)); where F bg represents the first conversion relationship.

[0015] Furthermore, in step A5, when the polishing wheel is located at the i-th polishing trajectory point, for the distance error and the distance gap threshold Comparison: If , then the current magnetic field strength B i is not regulated; If , then the current magnetic field strength B i is regulated as follows: If the current magnetic field strength B i is less than the maximum magnetic field strength |B max |, the real-time regulation module adjusts the current magnetic field strength B bg according to the first conversion relationship F i ; ; If the current magnetic field strength B i is greater than or equal to the maximum magnetic field strength |B max |, the current magnetic field strength B i is adjusted to ±|B max |.

[0016] A magnetorheological polishing method based on the position adjustment of an electromagnet, based on the magnetorheological polishing equipment for adjusting an electromagnet based on a sensor provided by the present invention, includes the following steps: B1: Obtain the first coordinates of the sensor module and the second coordinates of the working point of the polishing wheel using a laser tracker; through the two coordinates, calculate the coordinate conversion relationship using the coordinate relationship module; B2: Using the coordinate relationship module, through the coordinate conversion relationship, convert the first theoretical coordinates of the working point of the polishing wheel at different polishing trajectory points into the second theoretical coordinates of the sensor module, and obtain the theoretical straight-line distance based on the current second theoretical coordinates and the previous second theoretical coordinates; B3: Use the coordinate relationship module to record the measurement results of the sensor module to obtain the actual straight-line distance; calculate the distance error between the actual straight-line distance and the theoretical straight-line distance through the coordinate relationship module; B4: Control the magnetorheological processing module to perform fixed-point processing on the test optical element, and obtain the second conversion relationship through the conversion relationship module; B5: Set the distance error threshold, regulation maximum value, and maximum electromagnet position; determine the processing conditions based on the distance error, distance gap threshold, and regulation maximum value; based on the processing conditions, combine the second conversion relationship and the maximum electromagnet position to process the optical element to be processed, and perform real-time regulation on the magnetorheological processing module through the real-time regulation module during the processing.

[0017] Further, in step B1, the laser tracker obtains the coordinates of not less than 4 positions on the sensor module through a target ball, and calculates the first coordinates (x1, y1, z1); The laser tracker obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel through the target ball, and then calculates the center point coordinates (x2, y2, z2) of the polishing wheel. The straight line passing through the center point coordinates is: ; where (a, b, c) represents the normal vector of the straight line of the center point coordinates; By solving the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations and taking them as the second coordinates (x, y, z): ; where R represents the radius of the polishing wheel; The coordinate conversion relationship is obtained through the second coordinates and the first coordinates

[0018] ; where T represents the coordinate conversion relationship.

[0019] Furthermore, in step B2, the theoretical straight-line distance is obtained through the following formula: ; where d i represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinates, represents the Z coordinate in the previous second theoretical coordinates.

[0020] Furthermore, in step B3, the actual straight-line distance is obtained through the following formula: ; where d ri represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; a i-1 represents the acceleration measured by the sensor module at the previous polishing trajectory point, and v i-1 represents the velocity measured by the sensor module at the previous polishing trajectory point, represents the measurement time of the sensor module; and then the distance error is obtained through the following formula : .

[0021] Furthermore, step B4 includes the following steps: B41: At different polishing clearances, the position of the electromagnet is changed separately, and the test optical element is subjected to fixed-point processing for a period of time at different polishing clearances, and the volume removal rate of the removal function of each polishing trajectory point is calculated to obtain the fifth conversion relationship between the volume removal rate of the removal function and the position of the electromagnet: LT = F tm (MRR); Wherein, LT represents the position of the electromagnet, MRR represents the volume removal rate of the removal function, and F tm represents the fifth conversion relationship; B42: Keep the distance between the polishing wheel and the electromagnet unchanged, control the robot to drive the polishing wheel to process at different positions of the test optical element with different polishing gaps, and calculate the volume removal rate of the removal function at each polishing trajectory point to obtain the sixth conversion relationship between the volume removal rate of the removal function and the polishing gap: MRR = F mg (gap); Wherein, gap represents the polishing gap, and F mg represents the sixth conversion relationship; B43: Obtain the second conversion relationship according to the fifth conversion relationship and the sixth conversion relationship, that is: LT = F tg (gap) = F tm (F mg (gap)); Wherein, F tg represents the second conversion relationship.

[0022] Furthermore, in step B5, when the polishing wheel is at the i-th polishing trajectory point, compare the distance error with the distance gap threshold : If , then do not adjust the current electromagnet position LT i : If , then adjust the current electromagnet position LT i : If the current electromagnet position LT i is less than the maximum electromagnet position |LT max |, the current electromagnet position LT i is regulated according to the following formula: ; If the current electromagnet position LT i is greater than the maximum electromagnet position |LT max |, the current electromagnet position LT i is adjusted to ±|LT max |.

[0023] A magnetorheological polishing method based on magnetic field strength and polishing wheel movement is based on the magnetorheological polishing equipment for adjusting an electromagnet based on a sensor provided by the present invention, including the following steps: C1: Obtain the first coordinates of the sensor module and the second coordinates of the working point of the polishing wheel using a laser tracker; based on the two sets of coordinates, calculate the coordinate transformation relationship using a coordinate relationship module. C2: Using the coordinate relationship module, based on the coordinate transformation relationship, transform the first theoretical coordinates of the working point of the polishing wheel at different polishing trajectory points into the second theoretical coordinates of the sensor module, and obtain the theoretical straight-line distance based on the current second theoretical coordinates and the previous second theoretical coordinates. C3: Use the coordinate relationship module to record the measurement results of the sensor module to obtain the actual straight-line distance; calculate the distance error between the actual straight-line distance and the theoretical straight-line distance using the coordinate relationship module. C4: Set the distance error threshold, regulation maximum value, maximum electromagnet position, maximum magnetic field strength, and maximum polishing gap; determine the processing conditions based on the distance error, distance difference threshold, and regulation maximum value; based on the processing conditions, combine the maximum magnetic field strength and maximum polishing gap to process the optical element to be processed, and perform real-time regulation on the magnetorheological processing module through a real-time regulation module during the processing.

[0024] Furthermore, in step C1, the laser tracker obtains the coordinates of no less than 4 positions on the sensor module through a target ball, and calculates the first coordinates (x1, y1, z1). The laser tracker obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel through a target ball, and then calculates the center point coordinates (x2, y2, z2) of the polishing wheel. The straight line passing through the center point coordinates is: ; where (a, b, c) represents the normal vector of the straight line of the center point coordinates. Solve for the spatial coordinates corresponding to the minimum Z-axis coordinate in the following system of equations and use them as the second coordinates (x, y, z): ; where R represents the radius of the polishing wheel. Obtain the coordinate transformation relationship from the second coordinates and the first coordinates: ; where T represents the coordinate transformation relationship.

[0025] Furthermore, in step C2, obtain the theoretical straight-line distance through the following formula: ; where represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinates, Represents the Z coordinate in the previous second theoretical coordinate.

[0026] Further, in step C3, the actual straight-line distance is obtained by the following formula: ; where d ri represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; a i-1 represents the acceleration measured by the sensor module at the previous polishing trajectory point, v i-1 represents the velocity measured by the sensor module at the previous polishing trajectory point, and t represents the measurement time of the sensor module; and then the distance error is obtained by the following formula : .

[0027] Further, in step C4, when the polishing wheel is at the i-th polishing trajectory point, the distance error is compared with the distance gap threshold : If , then the current magnetic field strength and the current polishing gap are not adjusted; If , then the current magnetic field strength and the current polishing gap are adjusted: If the current magnetic field strength B i is less than the maximum magnetic field strength |B max |, and the current polishing gap gap i is less than the maximum polishing gap |gap max |, the current magnetic field strength B i and the current polishing gap gap i are adjusted respectively according to the following formulas: ; where gap0 is the initial polishing gap of the polishing wheel, r represents the distance between the lowest point of the polishing wheel and the electromagnet, M represents the magnetic moment, and k is a proportionality coefficient; If the current magnetic field strength B i is greater than or equal to the maximum magnetic field strength |B max |, and the current polishing gap gap i is greater than or equal to the maximum polishing gap |gap max |, the current magnetic field strength B i is adjusted to ±|B max |, and the current polishing gap gap i is adjusted to ±|gap max |.

[0028] Compared with the prior art, the present invention can achieve the following beneficial effects: In the magnetorheological polishing equipment and method for adjusting an electromagnet based on sensors of the present invention, the six-dimensional pose information of the robot during the machining process is measured in real time through the cooperation of a laser tracker and a sensor module, and the position or magnetic field strength of the electromagnet in the magnetorheological machining module is adjusted in real time, so as to realize the real-time constant control of the change of the removal function under the coupling of multiple factors during the machining process of the optical element; at the same time, the acquisition of the pose information does not need to rely on the actual machining process, and the pose error information of the machining equipment can be obtained during the trial operation link of the machining (no magnetorheological fluid is introduced in this link and no machining effect is generated), and it is not necessary to place the measuring equipment at the lowest point of the polishing wheel, which will not affect the actual machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention, and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 FIG. is a schematic structural diagram of the magnetorheological polishing equipment for adjusting an electromagnet based on sensors according to an embodiment of the present invention from one perspective; Figure 2 FIG. is a schematic structural diagram of the magnetorheological polishing equipment for adjusting an electromagnet based on sensors according to an embodiment of the present invention from another perspective; Figure 3 FIG. is a schematic structural diagram of the magnetorheological machining module according to an embodiment of the present invention, Figure 3 wherein (a) is a schematic structural diagram of the magnetorheological machining module from one perspective, Figure 3 and (b) is a schematic structural diagram of the magnetorheological machining module from another perspective; Figure 4 FIG. is a schematic structural diagram of the real-time adjustment device according to an embodiment of the present invention.

[0030] DESCRIPTION OF THE REFERENCE NUMERALS 1. Robot; 2. Sensor module; 3. Laser tracker; 4. Control unit; 5. Test bench; 6. Optical element to be machined; 7. Test optical element; 8. Target ball; 9. Polishing wheel; 10. Electromagnet; 11. Transmission belt; 12. Polishing motor; 13. Nozzle; 14. Real-time adjustment device; 15. Magnetorheological mounting bracket; 16. Displacement output motor; 17. Guide rail; 18. Slide block; 19. Lead screw; 20. Nut; 21. Support fixing bracket; 22. Connecting plate; 23. Current intensity controller. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0032] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0033] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0034] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0035] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0036] As Figures 1 to 4As shown in the figure, the magnetorheological polishing equipment based on a sensor for adjusting an electromagnet according to an embodiment of the present invention includes a robot 1, a magnetorheological processing module, a sensor module 2, a laser tracker 3, and a control unit 4. The magnetorheological processing module is disposed at the free end of the robot 1, and the robot 1 drives the magnetorheological processing module to process a to-be-processed optical element 6 and a test optical element 7 placed on a test bench 5. The sensor module 2 is disposed on the magnetorheological processing module. The laser tracker 3 cooperates with a target ball 8 disposed on the magnetorheological processing module to measure the spatial coordinates of the working point of the sensor module 2 and a polishing wheel 9 in the magnetorheological processing module. In an embodiment of the present invention, the laser tracker 3 is mounted on one side of the test bench 5, and the position of the target ball 8 is adjusted according to the needs of the measurement object. For example, when the spatial coordinates of the sensor module 2 need to be measured, the target ball 8 is mounted at a corresponding position of the sensor module 2; when the polishing wheel 9 needs to be measured, the target ball 8 is mounted at a corresponding position of the polishing wheel 9.

[0037] The interior of the control unit 4 includes a coordinate relationship module, a conversion relationship module, and a real-time regulation module. Among them, the coordinate relationship module integrates and calculates the spatial coordinates collected by the laser tracker 3 and the position information collected by the sensor module 2, and outputs integrated position information. The conversion relationship module fits the magnetic field strength of an electromagnet 10 in the magnetorheological processing module and the polishing gap of the polishing wheel 9 to obtain a first conversion relationship, and fits the electromagnet position of the electromagnet 10 and the polishing gap of the polishing wheel 9 to obtain a second conversion relationship. In an embodiment of the present invention, the electromagnet position is defined as the distance between the electromagnet 10 and the to-be-processed optical element 6 or the test optical element 7. The real-time regulation module adjusts the magnetic field strength of the electromagnet 10 according to the integrated position information and the first conversion relationship, and / or adjusts the position of the electromagnet 10 according to the integrated position information and the second conversion relationship, so as to keep the removal function stable when processing the to-be-processed optical element 6.

[0038] Figure 3 In (a) and (b) respectively show schematic structural diagrams of the magnetorheological processing module from two different perspectives. As Figure 3As shown in the figure, the magnetorheological processing module further includes a conveyor belt 11, a polishing motor 12, a nozzle 13, a supply system, a real-time adjustment device 14, and a magnetorheological mounting bracket 15. The magnetorheological mounting bracket 15 is installed on the free end of the robot 1. The polishing wheel 9 and the real-time adjustment device 14 are installed on the magnetorheological mounting bracket 15, and the real-time adjustment device 14 is connected to the polishing wheel 9 through a connecting plate 22. Specifically, the head end of the connecting plate 22 is installed on the real-time adjustment device 14, and the polishing wheel 9 is installed at the end of the connecting plate 22, so that the real-time adjustment device 14 adjusts the position of the polishing wheel 9, thereby changing the polishing gap of the polishing wheel 9. The polishing motor 12 is mounted on the magnetorheological mounting bracket 15, and the output end of the polishing motor 12 passes through the end of the connecting plate 22, so that the output end of the polishing motor 12 is connected to the bearing of the polishing wheel 9 through the conveyor belt 11, so that the polishing motor 12 controls the polishing wheel 9 to rotate, and then the polishing wheel 9 processes the optical element 6 to be processed or the test optical element 7. In the embodiment of the present invention, the manner in which the polishing motor 12 drives the polishing wheel 9 to rotate can refer to the invention patent application with the Chinese patent publication number CN118322074A, the publication date of July 12, 2024, and the patent name of "Self-rotating polishing module processing system". The nozzle 13 is arranged on the magnetorheological mounting bracket 15 along the rotation direction of the polishing wheel 9. The supply system conveys the magnetorheological fluid to the nozzle 13, and the nozzle 13 sprays the magnetorheological fluid to the working point of the polishing wheel 9, so that the polishing wheel 9 processes the optical element 6 to be processed or the test optical element 7 with the magnetorheological fluid as the medium. In the embodiment of the present invention, it is stipulated that the working point of the polishing wheel 9 is the point closest to the surface of the optical element along the normal direction of the surface of the optical element 6 to be processed or the test optical element 7. The electromagnet 10 is connected to the real-time adjustment device 14 through the connecting plate 22 and is close to the working point of the polishing wheel 9. Specifically, one end of the connecting plate 22 is installed on the real-time adjustment device 14, and the electromagnet 10 is installed at the other end of the connecting plate 22, so that the magnetorheological fluid changes the stiffness of the magnetorheological fluid under the influence of the magnetic field intensity of the electromagnet 10, and the polishing wheel 9 processes the optical element 6 to be processed or the test optical element 7 with the magnetorheological fluid with a certain stiffness as the medium. At the same time, the real-time adjustment device 14 adjusts the magnetic field intensity and the distance between the electromagnet 10 and the polishing wheel 9. The sensor module 2 is placed on the magnetorheological mounting bracket 15, and the laser tracker 3 measures the spatial coordinates of the sensor module 2 through the target ball 8.

[0039] In the embodiment of the present invention, the structure of the real-time adjustment device 14 that controls the electromagnet 10 and the polishing wheel 9 is as Figure 2 and Figure 4As shown in the figure, it includes a displacement output motor 16, a lead screw 19, a support fixing frame 21, and a current intensity controller 23. Among them, the lead screw 19 and the nut 20 with balls thereon together form a ball screw. The support fixing frame 21 is installed on the magnetorheological mounting frame 15, the displacement output motor 16 is installed on the top of the support fixing frame 21, and the displacement output motor 16 is connected to the lead screw 19 installed on the support fixing frame 21. The electromagnet 10 and the polishing wheel 9 are both connected to the nut 20. In the embodiment of the present invention, the electromagnet 10 and the polishing wheel 9 are connected to the nut 20 through a connecting plate 22, so that the lead screw 19 drives the electromagnet 10 and the polishing wheel 9 to move along the lead screw 19. In the embodiment of the present invention, in order to ensure the stable movement of the electromagnet 10 and the polishing wheel 9, two guide rails 17 parallel to the lead screw 19 are also provided on the support fixing frame 21, and the two guide rails 17 are respectively located on both sides of the lead screw 19. At this time, the connecting plate 22 is fixedly connected to the sliders 18 on the two guide rails 17 and the nut 20 at the same time. During the processing, the control unit 4 sends a control signal to the displacement output motor 16. When the displacement output motor 16 drives the lead screw 19 to rotate, the lead screw 19 and the two guide rails 17 cooperate to jointly pull the connecting plate 22, thereby driving the electromagnet 10 or the polishing wheel 9 to move along the lead screw 19. The current intensity controller 23 is connected to the electromagnet 10 through a wire and is used to energize the electromagnet 10 to generate a magnetic field. At the same time, the current intensity controller 23 is communicatively connected to the control unit 4. The control unit 4 sends a control signal to the current intensity controller 23, and the current intensity controller 23 adjusts the current transmitted to the electromagnet 10 according to the control signal, thereby changing the magnetic field intensity of the electromagnet 10. In the embodiment of the present invention, the current intensity controller 23 preferably uses the DA conversion module of the Smart200 series of Siemens Corporation.

[0040] In the embodiment of the present invention, the sensor module 2 includes an acceleration sensor. The robot 1, the sensor module 2, the laser tracker 3, and the real-time adjustment device 14 are respectively connected to the control unit 4 to form their respective communication lines, so that the control unit 4 receives and sends signals through the corresponding communication lines. Specifically, the control unit 4 receives signals from the sensor module 2 and the laser tracker 3 through the communication line. The control unit 4 sends a control signal for changing the position of the electromagnet 10 or the polishing wheel 9 to the displacement output motor 16 in the real-time adjustment device 14 through the communication line. The control unit 4 sends a control signal for changing the magnetic field intensity of the electromagnet 10 to the current intensity controller 23 in the real-time adjustment device 14 through the communication line. Since a strong magnetic region is generated around the polishing wheel 9 during the polishing operation, the communication line avoids the strong magnetic region.

[0041] Based on the magnetorheological polishing equipment for adjusting an electromagnet based on sensors described in the embodiments of the present invention, the embodiments of the present invention also provide a magnetorheological polishing method for adjusting an electromagnet based on sensors, including a magnetorheological polishing method based on magnetic field strength, a magnetorheological polishing method based on adjusting the position of the electromagnet, and a magnetorheological polishing method based on magnetic field strength and the movement of the polishing wheel.

[0042] Specific Embodiment 1: The magnetorheological polishing method based on magnetic field strength provided in this specific embodiment, based on the magnetorheological polishing equipment for adjusting an electromagnet based on sensors in the embodiments of the present invention, in combination with Figures 1 to 4 , includes the following steps: A1: Use a laser tracker 3 to obtain the first coordinate of the sensor module 2 and the second coordinate of the working point of the polishing wheel 9. Through the two coordinates, use the coordinate relationship module to calculate the coordinate conversion relationship.

[0043] In step A1, this specific embodiment uses a cylindrical or cuboid acceleration sensor as the sensor module 2, and obtains the coordinates of no less than 4 positions on the sensor module 2 through the cooperation of the laser tracker 3 and the target ball 8, and calculates the first coordinate through calculation .

[0044] Specifically, for the cylindrical acceleration sensor, place the target ball 8 at at least 3 different positions on the cylindrical bottom of the cylindrical acceleration sensor, and use the laser tracker 3 to measure the spatial coordinates of the target ball 8. Use the circle fitting function of the laser tracker 3 (this function is a basic function of the laser tracker 3) to obtain the X-Y coordinates of the cylindrical acceleration sensor , based on the Z-axis coordinates of the target ball 8 at different positions calculate the Z-axis coordinate where the bottom surface of the cylindrical acceleration sensor is located , where k represents the number of measurement points. Place the target ball 8 at at least 3 different positions on the top of the cylindrical acceleration sensor and use the laser tracker 3 to measure its spatial coordinates. Based on the Z-axis coordinates of the target ball 8 at different positions calculate the Z-axis coordinate where the top surface of the cylindrical acceleration sensor is located, , where j represents the number of measurement points, and the first coordinate of the cylindrical acceleration sensor is , and r is the radius of the target ball 8. In this specific embodiment, for the cylindrical acceleration sensor, 10 different positions are selected at its bottom and top respectively.

[0045] For the cuboid acceleration sensor, place the target ball 8 at the bottom of the four sides of the cuboid acceleration sensor respectively and use the laser tracker 3 to measure its spatial coordinates. Measure the coordinates of one target ball 8 point at the bottom of each side, and obtain the bottom coordinates of the four sides of the cuboid acceleration sensor as , , , , solve for the X - Y axis coordinates of the cuboid acceleration sensor to be , based on the Z - axis coordinates of the target ball 8 at different positions Calculate the Z - axis coordinate where the bottom surface of the cuboid acceleration sensor is located, and obtain ; Place the target ball 8 on top of the cuboid acceleration sensor at at least 3 different positions and use the laser tracker 3 to measure its spatial coordinates. Based on the Z - axis coordinates of the target ball 8 at different positions Calculate the Z - axis coordinate where the top surface of the cuboid acceleration sensor is located, , the first coordinate of the cuboid acceleration sensor is . In this specific embodiment, for the cuboid acceleration sensor, 10 different positions are selected on its top.

[0046] The laser tracker 3 obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel 9 through the target ball 8 (obtains the coordinates of 10 different positions in this specific embodiment). Through the coordinate calculation function of the laser tracker 3 itself, the center point coordinates of the polishing wheel 9 can be obtained , and the straight line passing through the center point coordinates is obtained through the teach pendant of the robot 1 as: ; Among them, represents the normal vector of the straight line indicating the center point coordinates; By solving the spatial coordinates corresponding to the minimum value of the Z - axis coordinate in the following system of equations and taking it as the second coordinate : ; Among them, represents the radius of the polishing wheel 9.

[0047] Obtain the coordinate conversion relationship through the second coordinate and the first coordinate: ; Among them, represents the coordinate conversion relationship.

[0048] A2: Use the coordinate relationship module to convert the first theoretical coordinates of the working points of the polishing wheel 9 at different polishing trajectory points into the second theoretical coordinates of the sensor module 2 through the coordinate conversion relationship, and obtain the theoretical straight - line distance according to the current second theoretical coordinate and the previous second theoretical coordinate. In this specific embodiment, the theoretical straight - line distance is the distance in the Z - axis direction.

[0049] In step A2, the theoretical straight - line distance is obtained through the following formula: ; Among them, represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinate, represents the Z coordinate in the previous second theoretical coordinate.

[0050] A3: Use the coordinate relationship module to record the measurement results of the sensor module 2 to obtain the actual straight-line distance; the distance error is calculated through the coordinate relationship module between the actual straight-line distance and the theoretical straight-line distance. In this specific embodiment, the actual straight-line distance is the distance in the Z-axis direction.

[0051] In step A3, the actual straight-line distance is obtained through the following formula: ; Among them, represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; represents the acceleration measured by the sensor module 2 at the previous polishing trajectory point, represents the velocity measured by the sensor module 2 at the previous polishing trajectory point, represents the measurement time of the sensor module 2. Furthermore, the distance error is obtained through the following formula : .

[0052] A4: Control the magnetorheological machining module to perform fixed-point machining on the test optical element 7, and obtain the first conversion relationship through the conversion relationship module. Step A4 specifically includes the following steps: A41: Under different polishing gaps, separately change the magnetic field intensity, perform machining at different positions on the test optical element 7, and calculate the volume removal rate of the removal function for each polishing trajectory point to obtain the third conversion relationship between the volume removal rate of the removal function and the magnetic field intensity: ; Among them, represents the magnetic field intensity, represents the volume removal rate of the removal function, represents the third conversion relationship. In this specific embodiment, it specifically means performing fixed-point machining at different positions on the test optical element 7 for a period of time with different magnetic field intensities.

[0053] A42: Control the polishing wheel 9 to perform fixed-point machining at different positions on the test optical element 7 with different polishing gaps for a period of time, and calculate the volume removal rate of the removal function for each polishing trajectory point to obtain the fourth conversion relationship between the volume removal rate of the removal function and the polishing gap: ; Among them, represents the polishing gap represents the fourth conversion relationship. In this specific embodiment, it specifically controls the polishing wheel 9 to perform fixed-point machining at different positions of the test optical element 7 for a period of time with different polishing gaps.

[0054] A43: According to the third conversion relationship and the fourth conversion relationship, obtain the first conversion relationship: ; wherein, represents the first conversion relationship.

[0055] A5: Set the distance error threshold, regulation maximum value, and maximum magnetic field strength; determine the machining conditions according to the distance error, distance gap threshold, and regulation maximum value; based on the machining conditions, combine the first conversion relationship and the maximum magnetic field strength to machine the optical element 6 to be machined, and during the machining process, the magnetic field strength of the electromagnet 10 is regulated in real time through the real-time regulation module. The distance error threshold, regulation maximum value, and maximum magnetic field strength are adaptively set according to the actual situation, and this specific embodiment does not limit this.

[0056] When the polishing wheel 9 is located at the th polishing trajectory point, compare the distance error with the distance gap threshold : If , then do not regulate the current magnetic field strength ; If , then regulate the current magnetic field strength : If the current magnetic field strength is less than the maximum magnetic field strength , that is, , the real-time regulation module adjusts the current magnetic field strength according to the first conversion relationship ; ; If the current magnetic field strength is greater than or equal to the maximum magnetic field strength , that is, , the current magnetic field strength is adjusted to .

[0057] In this specific embodiment, the discrete data volume corresponding to different polishing gaps obtained through experiments is limited. The actually measured polishing gap during the processing may not be equal to the polishing gap data value obtained through experiments. The solution is to adopt the closest data, that is, the rounding principle. For example: The fourth conversion relationship between the volume removal rate MRR of the removal function and the magnetic field strength corresponding to the polishing gaps of 1 mm and 2 mm is obtained through experiments, and then the corresponding first conversion relationship is obtained. However, the polishing gap during the processing is 1.6 mm. At this time, the volume removal rate MRR of 2 mm is calculated using the fourth conversion relationship. Between, and then obtain the corresponding first conversion relationship. However, the polishing gap during the processing is 1.6 mm. At this time, the volume removal rate MRR of 2 mm is calculated using the fourth conversion relationship.

[0058] Specific embodiment 2: The magnetorheological polishing method based on the adjustment of the electromagnet position provided in this specific embodiment, based on the magnetorheological polishing equipment for adjusting the electromagnet based on the sensor in the embodiment of the present invention, combined with Figures 1 to 4 , includes the following steps: B1: Use the laser tracker 3 to obtain the first coordinate of the sensor module 2 and the second coordinate of the working point of the polishing wheel 9; through the two coordinates, calculate the coordinate conversion relationship using the coordinate relationship module.

[0059] In step B1, in this specific embodiment, a cylindrical or cuboid acceleration sensor is used as the sensor module 2, and the coordinates of no less than 4 positions on the sensor module 2 are obtained through the cooperation of the laser tracker 3 and the target ball 8, and the first coordinate is obtained through calculation .

[0060] Specifically, for the cylindrical acceleration sensor, place the target ball 8 at at least 3 different positions on the cylindrical bottom of the cylindrical acceleration sensor and measure its spatial coordinates using the laser tracker 3. Use the circle fitting function of the laser tracker 3 (this function is the basic function of the laser tracker 3) to obtain the X-Y coordinates of the cylindrical acceleration sensor , based on the Z-axis coordinates of the target ball 8 at different positions Calculate the Z-axis coordinate where the bottom surface of the cylindrical acceleration sensor is located, , where k represents the number of measurement points. Place the target ball 8 at at least 3 different positions on the top of the cylindrical acceleration sensor and measure its spatial coordinates using the laser tracker 3. Based on the Z-axis coordinates of the target ball 8 at different positions Calculate the Z-axis coordinate where the top surface of the cylindrical acceleration sensor is located, , where j represents the number of measurement points. The first coordinate of the cylindrical acceleration sensor is , and r is the radius of the target ball 8. In this specific embodiment, for the cylindrical acceleration sensor, 10 different positions are selected at its bottom and top respectively.

[0061] For the cuboid acceleration sensor, the target ball 8 is placed at the bottom of each of the four side faces of the cuboid acceleration sensor, and the laser tracker 3 is used to measure its spatial coordinates. The coordinates of one point of the target ball 8 are measured at the bottom of each side face, and the bottom coordinates of the four side faces of the cuboid acceleration sensor are obtained as , , , . The X-Y axis coordinates of the cuboid acceleration sensor are solved as . Based on the Z-axis coordinates of the target ball 8 at different positions, the Z-axis coordinate where the bottom surface of the cuboid acceleration sensor is located is calculated to obtain ; The target ball 8 is placed at at least 3 different positions on the top of the cuboid acceleration sensor, and the laser tracker 3 is used to measure its spatial coordinates. Based on the Z-axis coordinates of the target ball 8 at different positions, the Z-axis coordinate where the top surface of the cuboid acceleration sensor is located is calculated as . The first coordinate of the cuboid acceleration sensor is . In this specific embodiment, for the cuboid acceleration sensor, 10 different positions are selected on its top.

[0062] The laser tracker 3 obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel 9 through the target ball 8 (10 different positions of coordinates are obtained in this specific embodiment). The center point coordinates of the polishing wheel 9 can be obtained through the coordinate calculation function of the laser tracker 3 itself , and the straight line passing through the center point coordinates is obtained through the teach pendant of the robot 1 as: ; Among them, represents the normal vector of the straight line of the center point coordinates; The spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations are solved and used as the second coordinate : ; Among them, represents the radius of the polishing wheel 9.

[0063] The coordinate transformation relationship is obtained from the second coordinate and the first coordinate: ; Among them, represents the coordinate transformation relationship.

[0064] B2: Using the coordinate relationship module, through the coordinate conversion relationship, the first theoretical coordinates of the working point of the polishing wheel 9 at different polishing trajectory points are converted into the second theoretical coordinates of the sensor module 2, and the theoretical straight-line distance is obtained based on the current second theoretical coordinates and the previous second theoretical coordinates. In this specific embodiment, the theoretical straight-line distance is the distance in the Z-axis direction.

[0065] In step B2, the theoretical straight-line distance is obtained through the following formula: ; where, represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinates, represents the Z coordinate in the previous second theoretical coordinates.

[0066] B3: Using the coordinate relationship module to record the measurement results of the sensor module 2 to obtain the actual straight-line distance; the distance error is calculated through the coordinate relationship module between the actual straight-line distance and the theoretical straight-line distance. In this specific embodiment, the actual straight-line distance is the distance in the Z-axis direction.

[0067] In step B3, the actual straight-line distance is obtained through the following formula: ; where, represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; represents the acceleration measured by the sensor module 2 at the previous polishing trajectory point, represents the velocity measured by the sensor module 2 at the previous polishing trajectory point, represents the measurement time; the distance error is obtained through the following formula : .

[0068] B4: Control the magnetorheological machining module to perform fixed-point machining on the test optical element 7, and obtain the second conversion relationship through the conversion relationship module, specifically: B41: At different polishing gaps, change the electromagnet position alone, machine the test optical element 7 at different polishing gaps, and calculate the volume removal rate of the removal function for each polishing trajectory point to obtain the fifth conversion relationship between the volume removal rate of the removal function and the electromagnet position: ; where, represents the electromagnet position, represents the volume removal rate of the removal function, Represents the fifth conversion relationship; in this specific embodiment, specifically, fixed-point machining is performed on the test optical element 7 for a period of time with different polishing gaps; B42: Keep the distance between the polishing wheel 9 and the electromagnet 10 unchanged, control the robot 1 to drive the polishing wheel 9 to perform machining at different positions of the test optical element 7 with different polishing gaps, and calculate the volume removal rate of the removal function for each polishing trajectory point to obtain the sixth conversion relationship between the volume removal rate of the removal function and the polishing gap: ; Among them, represents the polishing gap, represents the sixth conversion relationship; in this specific embodiment, specifically, fixed-point machining is performed for a period of time at different positions of the test optical element 7 with different polishing gaps ; B44: Obtain the second conversion relationship according to the fifth conversion relationship and the sixth conversion relationship, that is: ; Among them, represents the second conversion relationship.

[0069] B5: Set the distance error threshold, regulation maximum value, and maximum electromagnet position; determine the machining conditions according to the distance error, distance gap threshold, and regulation maximum value; based on the machining conditions, combine the second conversion relationship and the maximum electromagnet position to machine the optical element 6 to be machined, and perform real-time regulation on the magnetorheological machining module through the real-time regulation module during the machining process. The distance error threshold, regulation maximum value, and maximum electromagnet position are adaptively set according to the actual situation, and this specific embodiment does not limit this.

[0070] Further, in step B5, when the polishing wheel 9 is located at the th polishing trajectory point, compare the distance error with the distance gap threshold : If , then do not adjust the current electromagnet position : If , then adjust the current electromagnet position : If the current electromagnet position is less than the maximum electromagnet position , that is, , the current electromagnet position is regulated according to the following formula: ; If the current electromagnet position Greater than or equal to the maximum electromagnet position When it is the current electromagnet position is adjusted to .

[0071] In this specific embodiment, the amount of discrete data corresponding to different polishing gaps obtained through experiments is limited. During the machining process, the actually measured polishing gap may not be equal to the polishing gap data value obtained through experiments. The solution is to use the closest data, that is, the rounding principle. For example: The fifth conversion relationship between the volume removal rate MRR of the removal function and the electromagnet position corresponding to the polishing gaps of 1 mm and 2 mm is obtained through experiments, and then the corresponding second conversion relationship is obtained. However, the polishing gap during the machining process is 1.6 mm. At this time, the fifth conversion relationship is used to calculate the volume removal rate MRR of 2 mm of the removal function. between them

[0072] Specific Embodiment 3: The magnetorheological polishing method based on magnetic field intensity and polishing wheel movement provided in this specific embodiment, based on the magnetorheological polishing equipment for adjusting an electromagnet based on a sensor in the embodiment of the present invention, in combination with Figures 1 to 4 includes the following steps: C1: Use the laser tracker 3 to obtain the first coordinate of the sensor module 2 and the second coordinate of the working point of the polishing wheel 9; through the two coordinates, use the coordinate relationship module to calculate the coordinate conversion relationship.

[0073] In step C1, in this specific embodiment, a cylindrical or cuboid acceleration sensor is used as the sensor module 2, and the coordinates of no less than 4 positions on the sensor module 2 are obtained through the cooperation of the laser tracker 3 and the target ball 8, and the first coordinate is obtained through calculation .

[0074] For the cylindrical acceleration sensor, place the target ball 8 at at least 3 different positions on the cylindrical bottom of the cylindrical acceleration sensor and use the laser tracker 3 to measure its spatial coordinates. Use the circle fitting function of the laser tracker 3 (this function is the basic function of the laser tracker) to obtain the X-Y coordinates of the cylindrical acceleration sensor , based on the Z-axis coordinates of the target ball 8 at different positions calculate the Z-axis coordinate of the bottom surface of the cylindrical acceleration sensor, where k represents the number of measurement points. Place the target ball 8 at at least 3 different positions on the top of the cylindrical acceleration sensor and use the laser tracker 3 to measure its spatial coordinates. Based on the Z-axis coordinates of the target ball 8 at different positions , r is the radius of the target ball 8. In this specific embodiment, for the cylindrical acceleration sensor, 10 different positions are selected at the bottom and top thereof.

[0075] For the cuboid acceleration sensor, the target ball 8 is respectively placed at the bottom of the four side surfaces of the cuboid acceleration sensor, and the laser tracker 3 is used to measure its spatial coordinates. The coordinates of one point of the target ball 8 are measured at the bottom of each side surface, and the bottom coordinates of the four side surfaces of the cuboid acceleration sensor are respectively obtained as , , , , and the X-Y axis coordinates of the cuboid acceleration sensor are solved as . Based on the Z-axis coordinates of the target ball 8 at different positions, calculate the Z-axis coordinate where the bottom surface of the cuboid acceleration sensor is located, and obtain ; place the target ball 8 at at least 3 different positions on the top of the cuboid acceleration sensor and use the laser tracker 3 to measure its spatial coordinates. Based on the Z-axis coordinates of the target ball 8 at different positions, calculate the Z-axis coordinate where the top surface of the cuboid acceleration sensor is located. The first coordinate of the cuboid acceleration sensor is

[0076] The laser tracker 3 obtains the coordinates of not less than 10 different positions on the outer surface of the polishing wheel 9 through the target ball 8 (10 different positions of coordinates are obtained in this specific embodiment). The center point coordinates of the polishing wheel 9 can be obtained through the coordinate calculation function of the laser tracker 3 itself , and the straight line passing through the center point coordinates is obtained through the teach pendant of the robot 1 as: ; where, represents the normal vector of the straight line of the center point coordinates; By solving the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations and using it as the second coordinate : ; where, represents the radius of the polishing wheel 9.

[0077] The coordinate conversion relationship is obtained from the second coordinate and the first coordinate: ; where, represents the coordinate conversion relationship.

[0078] C2: Using the coordinate relationship module, through the coordinate conversion relationship, convert the first theoretical coordinates of the working point of the polishing wheel 9 at different polishing trajectory points into the second theoretical coordinates of the sensor module 2, and obtain the theoretical straight-line distance based on the current second theoretical coordinates and the previous second theoretical coordinates. In this specific embodiment, the theoretical straight-line distance is the distance in the Z-axis direction.

[0079] In step C2, the theoretical straight-line distance is obtained through the following formula for the theoretical straight-line distance: ; where, represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinates, represents the Z coordinate in the previous second theoretical coordinates.

[0080] C3: Use the coordinate relationship module to record the measurement results of the sensor module 2 to obtain the actual straight-line distance; the actual straight-line distance and the theoretical straight-line distance are used by the coordinate relationship module to calculate the distance error. In this specific embodiment, the actual straight-line distance is the distance in the Z-axis direction.

[0081] In step C3, the actual straight-line distance is obtained through the following formula : ; where, represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; represents the acceleration measured by the sensor module 2 at the previous polishing trajectory point, represents the velocity measured by the sensor module 2 at the previous polishing trajectory point, represents the measurement time of the sensor module 2. Furthermore, the distance error is obtained through the following formula : .

[0082] C4: Set the distance error threshold, regulation maximum value, maximum electromagnet position, maximum magnetic field strength, and maximum polishing gap; determine the processing conditions based on the distance error, distance gap threshold, and regulation maximum value; based on the processing conditions, combine the maximum magnetic field strength and maximum polishing gap to process the optical element 6 to be processed, and perform real-time regulation on the magnetorheological processing module through the real-time regulation module during the processing. The distance error threshold, regulation maximum value, maximum electromagnet position, maximum magnetic field strength, and maximum polishing gap are adaptively set according to the actual situation, and this specific embodiment does not limit this.

[0083] In step C4, when the polishing wheel 9 is at the When there are a certain number of polishing trajectory points, for the distance error is compared with the distance gap threshold as follows: If , then the current magnetic field strength and the current polishing gap are not adjusted; If , then the current magnetic field strength and the current polishing gap are adjusted as follows: If the current magnetic field strength is less than the maximum magnetic field strength , that is , and the current polishing gap is less than the maximum polishing gap , that is , then the current magnetic field strength and the current polishing gap are adjusted respectively according to the following formulas: ; ; Wherein, is the initial polishing gap of the polishing wheel 9, represents the distance between the lowest point of the polishing wheel and the electromagnet, specifically the distance between the electromagnet 10 and the lowest point of the polishing wheel 9, represents the magnetic moment, is the proportionality coefficient.

[0084] If the current magnetic field strength is greater than or equal to the maximum magnetic field strength , that is , and the current polishing gap is greater than or equal to the maximum polishing gap , that is , then the current magnetic field strength is adjusted to , and the current polishing gap is adjusted to .

[0085] It should be noted that since the changes in the magnetic field strength and the polishing gap are consistent, in the actual processing process, there will be no situation where the comparison of the current magnetic field strength with the maximum magnetic field strength is opposite to the comparison of the current polishing gap with the maximum polishing gap, that is, there will be no situation where the current magnetic field strength is greater than or equal to the maximum magnetic field strength while the current polishing gap is less than the maximum polishing gap , and there will be no situation where the current magnetic field strength is less than the maximum magnetic field strength while the current polishing gap is greater than or equal to the maximum polishing gap The situation occurs.

[0086] The fitting process in the above specific embodiments includes but is not limited to importing discrete data into Matlab software, completing data fitting with the polyfit fitting instruction of Matlab software, and solving their respective conversion relationships; the Polyfit fitting instruction is a basic general instruction of Matlab software. In this way, the corresponding relationship and the corresponding function curve can be more intuitively seen.

[0087] It should be understood that various forms of processes shown above can be used, steps can be reordered, added or deleted. For example, the steps recited in the disclosure of the present invention can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is imposed herein.

[0088] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A magnetorheological polishing device for adjusting an electromagnet based on a sensor, characterized in that: It includes a laser tracker, a control unit, a robot, a magnetorheological machining module and a sensor module; the magnetorheological machining module is arranged at the free end of the robot, and the robot drives the magnetorheological machining module to machine an optical element; the sensor module is arranged on the magnetorheological machining module; the laser tracker cooperates with a target ball arranged on the magnetorheological machining module to measure the spatial coordinates of the working point of the polishing wheel in the sensor module and the magnetorheological machining module. The interior of the control unit includes: A coordinate relationship module, which integrates and calculates the spatial coordinates collected by the laser tracker and the position information collected by the sensor module, and outputs integrated position information. A conversion relationship module, which fits the magnetic field strength of the electromagnet in the magnetorheological machining module and the polishing gap of the polishing wheel to obtain a first conversion relationship, and fits the electromagnet position of the electromagnet and the polishing gap to obtain a second conversion relationship. A real-time regulation module, which adjusts the magnetic field strength according to the integrated position information and the first conversion relationship, and / or adjusts the position of the electromagnet according to the integrated position information and the second conversion relationship, so as to keep the removal function stable when machining the optical element.

2. The magnetorheological polishing equipment for adjusting an electromagnet based on a sensor according to claim 1, characterized in that: The magnetorheological machining module further includes a transmission belt, a polishing motor, a nozzle, a supply system, a real-time adjustment device and a magnetorheological mounting bracket; among them, The magnetorheological mounting bracket is arranged at the free end of the robot, the polishing wheel and the real-time adjustment device are arranged on the magnetorheological mounting bracket, and the real-time adjustment device is connected to the polishing wheel, so that the real-time adjustment device adjusts the position of the polishing wheel, thereby changing the polishing gap of the polishing wheel. The polishing motor is connected to the polishing wheel through the transmission belt, so that the polishing motor controls the polishing wheel to rotate, and further the polishing wheel machines the optical element. The nozzle is arranged on the magnetorheological mounting bracket, and the nozzle direction of the nozzle is consistent with the rotation direction of the polishing wheel. The supply system is connected to the nozzle through a pipeline, and the supply system conveys the magnetorheological fluid to the nozzle, so that the polishing wheel machines the optical element with the magnetorheological fluid as the medium. The electromagnet is connected to the real-time adjustment device and is close to the working point of the polishing wheel, so that the magnetorheological fluid changes the stiffness of the magnetorheological fluid under the influence of the magnetic field strength of the electromagnet; at the same time, the real-time adjustment device adjusts the magnetic field strength and the distance between the electromagnet and the polishing wheel. The sensor module is arranged on the magnetorheological mounting bracket, and the laser tracker measures the spatial coordinates of the sensor module through the target ball.

3. The magnetorheological polishing apparatus for adjusting an electromagnet based on a sensor according to claim 2, wherein: The sensor module includes an acceleration sensor; the laser tracker, the sensor module, the robot and the real-time adjustment device are respectively connected to the control unit to form their respective communication lines, so that the control unit receives and sends signals through the corresponding communication lines.

4. The magnetorheological polishing apparatus for adjusting an electromagnet based on a sensor according to claim 3, wherein: The real-time adjustment device includes a displacement output motor, a lead screw, a support fixing frame, and a current intensity controller. Among them, the support fixing frame is arranged on the magnetorheological mounting frame, the displacement output motor is arranged on the support fixing frame, and the displacement output motor is connected to the lead screw arranged on the support fixing frame. The electromagnet or the polishing wheel is connected to the nut on the lead screw, so that the lead screw drives the electromagnet or the polishing wheel to move. The current intensity controller is connected to the electromagnet through a wire to supply power to the electromagnet, so that the electromagnet generates a magnetic field. The current intensity controller is communicatively connected to the control unit, the control unit sends a control signal to the current intensity controller, and the current intensity controller adjusts the current transmitted to the electromagnet according to the control signal, thereby changing the magnetic field intensity of the electromagnet.

5. A magnetorheological polishing method based on magnetic field strength, based on the magnetorheological polishing equipment for adjusting an electromagnet based on a sensor according to any one of claims 1 to 4, characterized in that: It includes the following steps: A1: Use the laser tracker to obtain the first coordinates of the sensor module and the second coordinates of the working point of the polishing wheel; through the two coordinates, use the coordinate relationship module to calculate the coordinate conversion relationship. A2: Use the coordinate relationship module to convert the first theoretical coordinates of the working point of the polishing wheel at different polishing trajectory points into the second theoretical coordinates of the sensor module through the coordinate conversion relationship, and obtain the theoretical straight-line distance according to the current second theoretical coordinates and the previous second theoretical coordinates. A3: Use the coordinate relationship module to record the measurement results of the sensor module to obtain the actual straight-line distance; the distance error is calculated through the coordinate relationship module from the actual straight-line distance and the theoretical straight-line distance. A4: Control the magnetorheological processing module to perform fixed-point processing on the test optical element, and obtain the first conversion relationship through the conversion relationship module. A5: Set the distance error threshold, regulation maximum value, and maximum magnetic field intensity; determine the processing conditions according to the distance error, distance gap threshold, and regulation maximum value; based on the processing conditions, combine the first conversion relationship and the maximum magnetic field intensity to process the optical element to be processed, and in the processing process, the magnetic field intensity of the electromagnet is adjusted in real time through the real-time regulation module.

6. The magnetorheological polishing method based on magnetic field strength according to claim 5, wherein: In step A1, the laser tracker obtains the coordinates of no less than 4 positions on the sensor module through the target ball, and calculates the first coordinates (x1, y1, z1). The laser tracker obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel through the target ball, and then calculates the center point coordinates (x2, y2, z2) of the polishing wheel. The straight line passing through the center point coordinates is: ； Among them, (a, b, c) represents the normal vector of the straight line. Solve the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations and use them as the second coordinates (x, y, z): ； Among them, R represents the radius of the polishing wheel. Obtain the coordinate conversion relationship from the second coordinates and the first coordinates: ； Among them, T represents the coordinate conversion relationship.

7. The magnetorheological polishing method based on magnetic field strength according to claim 6, wherein: In step A2, the theoretical straight-line distance is obtained through the following formula: ； Among them, represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinate, represents the Z coordinate in the previous second theoretical coordinate.

8. The magnetorheological polishing method based on magnetic field strength according to claim 7, wherein: In step A3, the actual linear distance is obtained by the following formula: ； where d ri represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; a i-1 represents the acceleration measured by the sensor module at the previous polishing trajectory point, v i-1 represents the velocity measured by the sensor module at the previous polishing trajectory point, and t represents the measurement time of the sensor module; and then the distance error is obtained through the following formula : 。 9. The magnetorheological polishing method based on magnetic field strength according to claim 8, characterized in that: Step A4 specifically includes the following steps: A41: Under different polishing clearances, the magnetic field intensity is separately changed, machining is performed at different positions of the test optical element, and the volume removal rate of the removal function at each polishing trajectory point is calculated to obtain the third conversion relationship between the volume removal rate of the removal function and the magnetic field intensity: B = F bm (MRR); Wherein, B represents the magnetic field strength, MRR represents the volume removal rate of the removal function, and F bm represents the third conversion relationship; A42: Control the polishing wheel to perform machining at different positions of the test optical element with different polishing clearances, and calculate the volume removal rate of the removal function at each polishing trajectory point to obtain the fourth conversion relationship between the volume removal rate of the removal function and the polishing clearance: MRR=F mg (gap); where gap represents the polishing gap, and F mg represents the fourth conversion relationship; A43: According to the third conversion relationship and the fourth conversion relationship, the first conversion relationship is obtained: B = F bg (gap) = F bm (F mg (gap)); Among them, F bg represents the first conversion relationship.

10. The magnetorheological polishing method based on magnetic field strength according to claim 9, characterized in that: In step A5, when the polishing wheel is located at the i-th polishing track point, the distance error is compared with the distance gap threshold as follows: If , the current magnetic field strength B i is not regulated; If , then adjust the current magnetic field strength B i : If the current magnetic field strength B i is less than the maximum magnetic field strength |B max |, the real-time regulation module adjusts the current magnetic field strength B bg according to the first conversion relationship F i ; ； If the current magnetic field strength B i is greater than or equal to the maximum magnetic field strength |B max |, the current magnetic field strength B i is adjusted to ±|B max |.

11. A magnetorheological polishing method based on the position adjustment of an electromagnet, based on the magnetorheological polishing equipment for adjusting the electromagnet based on a sensor according to any one of claims 1 to 4, characterized in that: including the following steps: B1: Use the laser tracker to obtain the first coordinates of the sensor module and the second coordinates of the working point of the polishing wheel; through the two coordinates, use the coordinate relationship module to calculate the coordinate conversion relationship; B2: Use the coordinate relationship module, through the coordinate conversion relationship, convert the first theoretical coordinates of the working point of the polishing wheel at different polishing trajectory points into the second theoretical coordinates of the sensor module, and obtain the theoretical linear distance according to the current second theoretical coordinates and the previous second theoretical coordinates; B3: Use the coordinate relationship module to record the measurement results of the sensor module to obtain the actual linear distance; the distance error is calculated through the coordinate relationship module between the actual linear distance and the theoretical linear distance; B4: Control the magnetorheological machining module to perform fixed-point machining on the test optical element, and obtain the second conversion relationship through the conversion relationship module; B5: Set the distance error threshold, regulation maximum value, and maximum electromagnet position; determine the machining conditions according to the distance error, distance gap threshold, and regulation maximum value; based on the machining conditions, combine the second conversion relationship and the maximum electromagnet position to machine the optical element to be machined, and perform real-time regulation on the magnetorheological machining module through the real-time regulation module during the machining process.

12. The magnetorheological polishing method based on the position adjustment of the electromagnet according to claim 11, wherein: In step B1, the laser tracker obtains the coordinates of no less than 4 positions on the sensor module through the target ball, and calculates the first coordinates (x1, y1, z1); The laser tracker obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel through the target ball, and then calculates the center point coordinates (x2, y2, z2) of the polishing wheel. The straight line passing through the center point coordinates is: ； where (a, b, c) represents the normal vector of the straight line of the center point coordinates; Solve the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following equations and use them as the second coordinates (x, y, z): ； where R represents the radius of the polishing wheel; Obtain the coordinate conversion relationship through the second coordinates and the first coordinates: ； where T represents the coordinate conversion relationship.

13. The magnetorheological polishing method based on the position adjustment of the electromagnet according to claim 12, wherein: In step B2, the theoretical linear distance is obtained by the following formula: ； Among them, represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinate, represents the Z coordinate in the previous second theoretical coordinate.

14. The magnetorheological polishing method based on the position adjustment of the electromagnet according to claim 13, characterized in that: In step B3, the actual linear distance is obtained by the following formula: ； where d ri represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; a i-1 represents the acceleration measured by the sensor module at the previous polishing trajectory point, and v i-1 represents the velocity measured by the sensor module at the previous polishing trajectory point, represents the measurement time of the sensor module; the distance error is obtained by the following formula : 。 15. The magnetorheological polishing method based on the position adjustment of the electromagnet according to claim 14, characterized in that: Step B4 includes the following steps: B41: At different polishing clearances, separately change the position of the electromagnet, process the test optical element at different polishing clearances, and calculate the volume removal rate of the removal function for each polishing trajectory point to obtain the fifth conversion relationship between the volume removal rate of the removal function and the position of the electromagnet: LT=F tm (MRR); Among them, LT represents the position of the electromagnet, MRR represents the volume removal rate of the removal function, and F tm represents the fifth conversion relationship; B42: Control the robot to drive the polishing wheel to process at different positions of the test optical element with different polishing clearances, and calculate the volume removal rate of the removal function for each polishing trajectory point to obtain the sixth conversion relationship between the volume removal rate of the removal function and the polishing clearance: MRR = F mg (gap); where gap represents the polishing gap, and F mg represents the sixth conversion relationship; B43: Obtain the second conversion relationship according to the fifth conversion relationship and the sixth conversion relationship, that is: LT=F tg (gap)=F tm (F mg (gap)); Among them, F tg represents the second conversion relationship.

16. The magnetorheological polishing method based on the position adjustment of the electromagnet according to claim 15, wherein: In step B5, When the polishing wheel is located at the i-th polishing track point, compare the distance error with the distance gap threshold as follows: If , then the current electromagnet position LT i is not adjusted: If , then adjust the current electromagnet position LT i as follows: If the current electromagnet position LT i is less than the maximum electromagnet position |LT max |, the current electromagnet position LT i is regulated according to the following formula: ； If the current electromagnet position LT i is greater than or equal to the maximum electromagnet position |LT max |, the current electromagnet position LT i is adjusted to ±|LT max |.

17. A magnetorheological polishing method based on magnetic field intensity and the movement of a polishing wheel, based on the magnetorheological polishing equipment for adjusting an electromagnet based on a sensor according to any one of claims 1 to 4, characterized in that: it includes the following steps: C1: Use the laser tracker to obtain the first coordinates of the sensor module and the second coordinates of the working point of the polishing wheel; through the two coordinates, use the coordinate relationship module to calculate the coordinate conversion relationship; C2: Use the coordinate relationship module, through the coordinate conversion relationship, convert the first theoretical coordinates of the working point of the polishing wheel at different polishing trajectory points into the second theoretical coordinates of the sensor module, and obtain the theoretical straight-line distance according to the current second theoretical coordinates and the previous second theoretical coordinates; C3: Use the coordinate relationship module to record the measurement results of the sensor module to obtain the actual straight-line distance; the distance error is calculated through the coordinate relationship module from the actual straight-line distance and the theoretical straight-line distance; C4: Set the distance error threshold, regulation maximum value, maximum electromagnet position, maximum magnetic field strength, and maximum polishing clearance; determine the processing conditions according to the distance error, distance gap threshold, and regulation maximum value; based on the processing conditions, combine the maximum magnetic field strength and the maximum polishing clearance to process the optical element to be processed, and perform real-time regulation on the magnetorheological processing module through the real-time regulation module during the processing.

18. The magnetorheological polishing method based on magnetic field strength and polishing wheel movement according to claim 17, wherein: In step C1, the laser tracker obtains the coordinates of no less than 4 positions on the sensor module through the target ball, and calculates the first coordinates (x1, y1, z1) through calculation; The laser tracker obtains the coordinates of no less than 10 different positions on the outer surface of the polishing wheel through the target ball, and then calculates the center point coordinates (x2, y2, z2) of the polishing wheel. The straight line passing through the center point coordinates is: ； where (a, b, c) represents the normal vector of the straight line of the center point coordinates; Solve the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following equations and use them as the second coordinates (x, y, z): ； where R represents the radius of the polishing wheel; Obtain the coordinate conversion relationship through the second coordinates and the first coordinates: ； where T represents the coordinate conversion relationship.

19. The magnetorheological polishing method based on magnetic field strength and polishing wheel movement according to claim 18, characterized in that: In step C2, obtain the theoretical straight-line distance through the following formula: ； Among them, represents the theoretical straight-line distance between the current polishing trajectory point and the previous polishing trajectory point, represents the Z coordinate in the current second theoretical coordinate, represents the Z coordinate in the previous second theoretical coordinate.

20. The magnetorheological polishing method based on magnetic field strength and polishing wheel movement according to claim 19, wherein: In step C3, obtain the actual straight-line distance through the following formula: ； Among them, d ri represents the actual straight-line distance between the current polishing trajectory point and the previous polishing trajectory point; a i-1 represents the acceleration measured by the sensor module at the previous polishing trajectory point, v i-1 represents the velocity measured by the sensor module at the previous polishing trajectory point, and t represents the measurement time of the sensor module; the distance error is obtained by the following formula : 。 21. The magnetorheological polishing method based on magnetic field strength and polishing wheel movement according to claim 20, wherein: In step C4, when the polishing wheel is at the i-th polishing track point, compare the distance error with the distance gap threshold as follows: If , then the current magnetic field strength and the current polishing gap are not adjusted; If , then adjust the current magnetic field strength and the current polishing gap: If the current magnetic field strength B i is less than the maximum magnetic field strength |B max |, and the current polishing gap gap i is less than the maximum polishing gap |gap max |, the current magnetic field strength B i and the current polishing gap gap i are respectively regulated according to the following formulas: ； Among them, gap0 is the initial polishing gap of the polishing wheel, r represents the distance between the lowest point of the polishing wheel and the electromagnet, M represents the magnetic moment, and k is the proportionality coefficient; If the current magnetic field strength B i is greater than or equal to the maximum magnetic field strength |B max |, and the current polishing gap gap i is greater than or equal to the maximum polishing gap |gap max |, the current magnetic field strength B i is adjusted to ±|B max |, and the current polishing gap gap i is adjusted to ±|gap max |.

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