Magnetorheological polishing system and polishing method based on sensing of laser tracker

Abstract

The invention relates to the technical field of magneto-rheological polishing, in particular to a magneto-rheological polishing system and method based on sensing of a laser tracker, and the real-time change of the pose of the magneto-rheological polishing system in the machining process is measured through the laser tracker; and real-time constant control of the removal function is realized by adjusting the magnetic field intensity of the electromagnet or simultaneously adjusting the position of the polishing wheel and the magnetic field intensity of the electromagnet. According to the method, measurement equipment such as a force sensor does not need to be calibrated; the device is simple in structure, is not affected by the weight of the magneto-rheological polishing system, the operation precision, the operation speed, the posture and other factors, can measure the posture change of the magneto-rheological polishing system in the machining process in real time, visually reflects the posture error of the magneto-rheological polishing system, and has the advantages of being low in equipment cost and high in measurement precision.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetorheological finishing, and particularly to a magnetorheological finishing system and a finishing method based on laser tracker sensing. Background Art

[0002] Magnetorheological Finishing (MRF) is an advanced optical manufacturing technology developed in recent years. It has many advantages such as a stable removal function, controllable edge effect, small subsurface damage layer, no replication effect, strong shaping ability, and high processing accuracy. Therefore, magnetorheological finishing technology has received extensive attention in high-precision optical processing. The existing magnetorheological finishing machining centers mainly integrate the magnetorheological finishing module on a numerically controlled machine tool. However, there are some deficiencies in the numerically controlled machine tool (such as low degrees of freedom, large floor area, high cost, etc.), which limit the deviation of the aspherical surface and make it difficult to perform precise pose control along the surface normal. 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. Six-degree-of-freedom industrial robots have 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 finishing module on an industrial robot, in theory, high-precision machining of large-aperture complex surface optical elements can be achieved. However, due to the influence of factors such as machining, assembly, load, trajectory planning, and reduction ratio, the execution accuracy of the end of the industrial robot is relatively low, and the polishing gap changes greatly during the machining process. At the same time, magnetorheological finishing 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 numerically controlled machining center is within dozens of micrometers (PV < 0.1 mm), while the trajectory accuracy of common commercial industrial robots is generally in the sub-millimeter to millimeter range. This leads to a large change in the polishing gap during the machining process, reduces the certainty of the removal function, and affects 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 finishing technology for the change of the removal function during high-precision polishing.

[0003] In view of the problem of low motion accuracy of industrial robots, 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 industrial robot. First, gravity calibration is performed on the force sensor to ensure accurate measurement. The pose error is calculated by measuring the change in force, and then the pose error of the industrial robot is compensated by means of the industrial 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 equipment of large-size polishing wheels, and the weight of the magnetorheological processing module of large-size polishing wheels is generally over a hundred kilograms. However, for a magnetorheological processing module weighing over a hundred kilograms, the force change caused by the pose error of the industrial robot 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 equipment such as force sensors to reach one ten-thousandth, and the force sensor also needs to be in a state of 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

[0004] The purpose of the present invention is to provide a magnetorheological polishing system and polishing method based on laser tracker sensing to solve the problem that the use of high-precision force sensors will greatly increase the equipment cost.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows: A magnetorheological polishing system based on laser tracker sensing, comprising: A polishing platform, on which an element to be polished and a test polishing element are arranged; A polishing assembly, including an industrial robot and a magnetorheological polishing module. The industrial robot is used to drive the magnetorheological polishing module to move to the position where the test polishing element is located or the position where the element to be polished is located; the magnetorheological polishing module is used to process the element to be polished or the test polishing element. The magnetorheological polishing module includes a magnetorheological mounting frame, a polishing wheel, a nozzle, an electromagnet, a liquid pump, a position adjustment device, and a current intensity controller. The magnetorheological mounting frame is installed at the tool end of the industrial robot. The current intensity controller, the position adjustment device, the nozzle, and the electromagnet are respectively installed on the magnetorheological mounting frame. The liquid pump is arranged on the industrial robot or on one side of the industrial robot. The liquid pump is used to pump magnetorheological fluid into the nozzle. The nozzle is used to spray magnetorheological fluid onto the polishing wheel. The electromagnet is used to change the stiffness of the magnetorheological fluid. The position adjustment device is used to adjust the position of the polishing wheel. The polishing wheel is used to process the test polishing element or the element to be polished. The current intensity controller is used to control the energizing current of the electromagnet and adjust the magnetic field strength of the electromagnet; A laser tracker, whose target ball is installed at the tool end of an industrial robot. The laser tracker is used to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures, and convert the theoretical Z-axis spatial coordinate of the set working point of the polishing wheel into the theoretical Z-axis spatial coordinate of the target ball. A computer is used to calculate the distance error between the actual Z-axis spatial coordinate and the theoretical Z-axis spatial coordinate of the target ball at each polishing trajectory point. The computer is also used to adjust the electromagnetic field strength of the electromagnet according to the conversion relationship between the electromagnetic field strength of the electromagnet and the polishing gap or simultaneously adjust the position of the polishing wheel and the electromagnetic field strength of the electromagnet according to the conversion relationship between the position of the polishing wheel and the polishing gap when the distance error exceeds the set error range, so as to adjust the removal function and maintain the constancy of the removal function at each polishing trajectory point.

[0006] Furthermore, the position adjustment device includes a support fixing frame, a ball screw stepping motor and a connecting plate. The ball screw stepping motor is vertically installed on the magnetorheological mounting frame through the support fixing frame. The nut of the ball screw stepping motor is fixedly connected to the connecting plate, and the polishing wheel is connected to the connecting plate.

[0007] Furthermore, the magnetorheological polishing module further includes a polishing wheel driving device. The polishing wheel driving device includes a driving motor, a driving wheel, a driven wheel and a synchronous belt. The driving motor is installed on the magnetorheological mounting frame. A bearing seat is installed on the magnetorheological mounting frame, and a bearing is installed in the bearing seat. The bearing is connected to the polishing wheel. The driven wheel is sleeved on the bearing, and the driving wheel is sleeved on the output end of the driving motor. The synchronous belt is tensioned between the driven wheel and the driving wheel.

[0008] A magnetorheological polishing method based on the adjustment of the electromagnetic field strength of an electromagnet, which is realized by using the above-mentioned magnetorheological polishing system based on the perception of a laser tracker, includes the following steps: S1: Establish a measurement coordinate system of the laser tracker. Use the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures, and calculate the pose conversion relationship between the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball. According to the pose conversion relationship, convert the theoretical Z-axis spatial coordinate of the set working point of the polishing wheel into the theoretical Z-axis spatial coordinate of the target ball. S2: At different polishing gaps, by changing the electromagnetic field strength of the electromagnet, perform fixed-point machining on each machining point of the test polishing element, calculate the volume removal rate of the removal function at each machining point at different polishing gaps, and perform data fitting on the discrete volume removal rates of the removal functions and their corresponding electromagnetic field strengths at different polishing gaps to obtain the conversion relationship between the polishing gap and the electromagnetic field strength of the electromagnet. ; where represents the polishing gap corresponding to each volume removal rate of the removal function, represents the electromagnetic field strength of the electromagnet. Represents the conversion relationship between the polishing gap and the magnetic field strength of the electromagnet; S3: Use the magnetorheological polishing system to process the element to be polished. Real-time measure the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point through a laser tracker, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point; S4: Determine whether the distance error at each polishing trajectory point exceeds the set error range; if not, keep the magnetic field strength of the electromagnet at the current polishing trajectory point unchanged; if it exceeds, adjust the magnetic field strength of the electromagnet through a computer-controlled current intensity controller, change the removal function at the current polishing trajectory point, and finally maintain the constancy of the removal function at each polishing trajectory point.

[0009] Furthermore, the distance error , represents the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point, represents the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point; Set the maximum adjustment amount of the magnetic field strength of the electromagnet in the computer as , set the error range as , represents the maximum value of the distance error, then: When , keep the magnetic field strength of the electromagnet at the current polishing trajectory point unchanged; When and the magnetic field strength of the electromagnet at the current polishing trajectory point , adjust the magnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ; When and the magnetic field strength of the electromagnet at the current polishing trajectory point , adjust the magnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ; Among them, represents the set initial magnetic field strength of the electromagnet.

[0010] Furthermore, the process of establishing the measurement coordinate system of the laser tracker is as follows: Measure the coordinates of points on each axis when the industrial robot moves along the X-axis and Y-axis of the tool coordinate system using a laser tracker. The number of measured points on each axis is not less than 10. Use the line fitting function of the laser tracker to perform linear fitting on the measured points on each axis, and take the fitted line as the measurement coordinate system of the laser tracker, that is, the measurement coordinate system of the laser tracker is parallel to the tool coordinate system of the industrial robot.

[0011] Further, the process of using a laser tracker to measure the spatial coordinates of the polishing wheel working point and the spatial coordinates of the target ball when the industrial robot is in different postures is as follows: Set the tool end of the industrial robot to at least 12 postures, and use the industrial robot to drive the polishing wheel to at least 12 different poses; Use a laser tracker to measure the spatial coordinates of the polishing wheel working point and the spatial coordinates of the target ball when the industrial robot is in each pose; The measurement process of the spatial coordinates of the polishing wheel working point is as follows: Place the target ball at at least 10 different positions on the outer surface of the polishing wheel and measure its coordinates, and obtain the center point coordinates of the polishing wheel through the sphere fitting function of the laser tracker , and the straight line passing through the center point of the polishing wheel is: ; where a, b, and c are the normal vectors of the straight line, which are obtained through the teach pendant of the industrial robot; Solve for the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations and use them as the spatial coordinates of the polishing wheel working point : ; where R represents the radius of the polishing wheel.

[0012] A magnetorheological polishing method based on the simultaneous adjustment of the polishing wheel position and magnetic field strength is realized by using the above magnetorheological polishing system based on laser tracker perception, and includes the following steps: S1: Establish the measurement coordinate system of the laser tracker, use the laser tracker to measure the spatial coordinates of the polishing wheel working point and the spatial coordinates of the target ball when the industrial robot is in different postures, calculate the pose conversion relationship between the spatial coordinates of the polishing wheel working point and the spatial coordinates of the target ball, and convert the theoretical Z-axis spatial coordinate of the set polishing wheel working point into the theoretical Z-axis spatial coordinate of the target ball according to the pose conversion relationship; S2: At different polishing clearances, by changing the position of the polishing wheel, perform fixed-point machining on each machining point of the test polishing element, calculate the volume removal rate of the removal function at each machining point under different polishing clearances, and perform data fitting on the discrete volume removal rates of the removal function and their corresponding polishing wheel positions under different polishing clearances to obtain the conversion relationship between the polishing clearance and the polishing wheel position ; where represents the polishing clearance corresponding to each volume removal rate of the removal function, represents the position of the polishing wheel, represents the conversion relationship between the polishing clearance and the polishing wheel position; S3: Use the magnetorheological polishing system to machine the element to be polished, measure the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point in real time through a laser tracker, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point; S4: Determine whether the distance error at each polishing trajectory point exceeds the set error range; if not, keep the position of the polishing wheel and the magnetic field strength of the electromagnet unchanged at the current polishing trajectory point; if it exceeds, adjust the position of the polishing wheel through the computer-controlled position adjustment device, and at the same time control the current intensity controller to adjust the magnetic field strength of the electromagnet, change the removal function at the current polishing trajectory point, and finally maintain the constancy of the removal function at each polishing trajectory point.

[0013] Furthermore, the distance error , represents the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point, represents the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point; Set the maximum adjustment amount of the polishing wheel position in the computer to , and the maximum adjustment amount of the magnetic field strength of the electromagnet to , set the error range to , represents the maximum value of the distance error, then: When , keep the position of the polishing wheel and the magnetic field strength of the electromagnet unchanged; When and the position of the polishing wheel at the current polishing trajectory point and the magnetic field strength of the electromagnet at the current polishing trajectory point , adjust the position of the polishing wheel and the magnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ; ; Wherein, r represents the distance between the electromagnet and the polishing wheel, M represents the magnetic moment, and k is a proportionality coefficient; When and the position of the polishing wheel at the current polishing trajectory point and the magnetic field strength of the electromagnet at the current polishing trajectory point , the position of the polishing wheel at the current polishing trajectory point and the magnetic field strength of the electromagnet at the current polishing trajectory point are adjusted according to the following formula: ; ; Wherein, represents the set initial position of the polishing wheel, represents the set initial magnetic field strength of the electromagnet.

[0014] Furthermore, the process of establishing the measurement coordinate system of the laser tracker is as follows: Use the laser tracker to measure the coordinates of points on each axis when the industrial robot moves along the X-axis and Y-axis of the tool coordinate system respectively. The number of measured points on each axis is not less than 10. Use the line fitting function of the laser tracker to perform linear fitting on the measured points on each axis, and use the fitted line as the measurement coordinate system of the laser tracker, that is, the measurement coordinate system of the laser tracker is parallel to the tool coordinate system of the industrial robot.

[0015] Furthermore, the process of using the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures is as follows: Set the tool end of the industrial robot to at least 12 postures, and use the industrial robot to drive the polishing wheel to at least 12 different poses; Use the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in each pose; The measurement process of the spatial coordinates of the working point of the polishing wheel is as follows: Place the target ball at at least 10 different positions on the outer surface of the polishing wheel and measure its coordinates. The center point coordinates of the polishing wheel are obtained through the sphere fitting function of the laser tracker , and the straight line passing through the center point of the polishing wheel is: ; Wherein, a, b, and c are the normal vectors of the straight line, which are obtained through the teach pendant of the industrial robot; 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 spatial coordinates of the working point of the polishing wheel : ; wherein, R represents the radius of the polishing wheel.

[0016] Compared with the prior art, the present invention measures the real-time change of the pose of the magnetorheological polishing system during the polishing process through a laser tracker, and realizes the real-time constant control of the removal function by adjusting the magnetic field strength of the electromagnet or simultaneously adjusting the position of the polishing wheel and the magnetic field strength of the electromagnet. This method does not require calibration of measuring devices such as force sensors, and is not affected by factors such as the weight of the magnetorheological polishing system, the running accuracy of the equipment itself, the running speed, the posture, and other factors. During the optical polishing process, the pose change of the polishing system can be measured in real time, intuitively reflecting the pose error of the polishing system, and having the advantages of low equipment cost and high measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of the magnetorheological polishing system based on laser tracker sensing according to an embodiment of the present invention from one perspective; Figure 2 is a schematic structural diagram of the magnetorheological polishing system based on laser tracker sensing according to an embodiment of the present invention from another perspective; Figure 3 is a schematic structural diagram of the magnetorheological polishing module according to an embodiment of the present invention from one perspective; Figure 4 is a schematic structural diagram of the magnetorheological polishing module according to an embodiment of the present invention from another perspective; Figure 5 is a schematic structural diagram of the position adjustment device according to an embodiment of the present invention.

[0018] Reference numerals: polishing platform 1, element to be polished 101, test polishing element 102, industrial robot 201, magnetorheological mounting bracket 202, polishing wheel 203, electromagnet 204, nozzle 205, liquid pump 206, support fixing bracket 207, ball screw stepping motor 208, connecting plate 209, drive motor 210, driving wheel 211, driven wheel 212, synchronous belt 213, lead screw 214, guide rail 215, slider 216, nut 217, current intensity controller 218, mounting plate 219, laser tracker 3, target ball 301, computer 4. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to 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.

[0021] Aiming at the deficiencies existing in the force-position control method based on a force sensor, the present invention proposes a magnetorheological polishing system and a polishing method based on the perception of a laser tracker. By measuring the real-time changes in the pose of the polishing system during the polishing process with the laser tracker and using different control methods (adjusting the magnetic field strength of the electromagnet / adjusting the position of the polishing wheel and the magnetic field strength of the electromagnet simultaneously), the real-time constancy of the removal function is achieved. This method does not require calibration of measuring devices such as force sensors and is not affected by factors such as the weight of the magnetorheological processing module, the running accuracy of the equipment itself, the running speed, the posture, and other factors. During the optical polishing process, the pose changes of the polishing system can be measured in real time, intuitively reflecting the pose error of the polishing system, and having the advantage of high measurement accuracy.

[0022] The following will detail the maintenance of the constancy of the removal function with specific embodiments.

[0023] In the first aspect, this embodiment provides a magnetorheological polishing system based on the perception of a laser tracker. The structure of this device is as Figures 1-5 shown and includes: A polishing platform 1, on which a component to be polished 101 and a test polishing component 102 are provided; A polishing assembly, which includes an industrial robot 201 and a magnetorheological polishing module. The industrial robot 201 is used to drive the magnetorheological polishing module to move to the position where the test polishing element 102 is located or drive the magnetorheological polishing module to move to the position where the element to be polished 101 is located. The magnetorheological polishing module is used to process the element to be polished 101 or the test polishing element 102. The magnetorheological polishing module includes a magnetorheological mounting frame 202, a polishing wheel 203, an electromagnet 204, a nozzle 205, a liquid pump 206, a current intensity controller 218, a position adjustment device and a polishing wheel driving device. The magnetorheological mounting frame 202 is installed at the tool end of the industrial robot 201. The polishing wheel driving device is installed on the magnetorheological mounting frame 202 and is used to drive the polishing wheel 203 to rotate to process the element to be polished 101 or the test polishing element 102. The nozzle 205 is installed on the magnetorheological mounting frame 202 and is used to spray magnetorheological fluid onto the polishing wheel 203. The electromagnet 204 is installed on a mounting plate 219, near the working point of the polishing wheel 203 (the working point of the polishing wheel 203 is the closest point between the polishing wheel 203 and the surface of the element to be polished 101 along the normal direction of the surface of the element to be polished 101), and the mounting plate 219 is installed on the magnetorheological mounting frame 202 and is used to change the stiffness of the magnetorheological fluid. The current intensity controller 218 is installed on the magnetorheological mounting frame 202 and is used to control the energizing current of the electromagnet 204 and adjust the magnetic field intensity of the electromagnet 204. The current intensity controller 218 preferably uses the DA conversion module of the Smart200 series of Siemens. The liquid pump 206 is installed on the industrial robot 201 or arranged on one side of the industrial robot 201. The liquid pump 206 is connected to the nozzle 205 through a pipeline and is used to pump magnetorheological fluid into the nozzle 205. The liquid pump 206 selects the DFLD vertical multistage pump of Shanghai Dongfang Pump Industry Co., Ltd. The position adjustment device is installed on the magnetorheological mounting frame 202 and is used to adjust the position of the polishing wheel 203. A laser tracker 3, which is arranged on one side of the polishing platform 1 and is used in cooperation with a target ball 301. The target ball 301 is at the tool end of the industrial robot 201. The laser tracker 3 is used to measure the spatial coordinates of the working point of the polishing wheel (the working point of the polishing wheel refers to the lowest point of the polishing wheel when the magnetorheological polishing system is at zero) of the industrial robot 201 in different postures and the spatial coordinates of the target ball 301, and convert the theoretical Z-axis spatial coordinate of the set working point of the polishing wheel into the theoretical Z-axis spatial coordinate of the target ball 301. A computer 4 is used to calculate the distance error between the actual Z-axis spatial coordinate and the theoretical Z-axis spatial coordinate of the target ball 301 at each polishing track point. The computer 4 is also used to adjust the magnetic field intensity of the electromagnet 204 according to the conversion relationship between the magnetic field intensity of the electromagnet 204 and the polishing gap or simultaneously adjust the position of the polishing wheel 203 and the magnetic field intensity of the electromagnet 204 according to the conversion relationship between the position of the polishing wheel 203 and the polishing gap when the distance error exceeds the set error range, so as to adjust the removal function and maintain the constancy of the removal function at each polishing track point.

[0024] The position adjustment device includes a support fixing frame 207, a ball screw stepping motor 208, and a connecting plate 209. The ball screw stepping motor 208 is vertically installed on the magnetorheological mounting frame 202 through the support fixing frame 207. The nut 217 of the ball screw stepping motor 208 is fixedly connected to the connecting plate 209, and the polishing wheel 203 is connected to the connecting plate 209. The polishing wheel 203 is driven to move by the ball screw stepping motor 208 for position adjustment.

[0025] The polishing wheel driving device includes a driving motor 210, a driving wheel 211, a driven wheel 212, and a synchronous belt 213. The driving motor 210 is installed on the connecting plate 209. A bearing seat is installed on the connecting plate 209, and a bearing is installed in the bearing seat. The bearing is connected to the polishing wheel 203. The driven wheel 212 is sleeved on the bearing, the driving wheel 211 is sleeved on the output end of the driving motor 210, and the synchronous belt 213 is tensioned between the driven wheel 212 and the driving wheel 211. The polishing wheel 203 is driven to rotate by the driving motor 210. Reference can be made to the Chinese patent with the publication date of July 12, 2024 and the publication number of CN118322074A. The polishing wheel 203 is driven by the driving motor 210 to rotate at a high speed, and the magnetorheological fluid is brought into the magnetic field action area. The magnetorheological fluid flow forms a magnetorheological ribbon under the action of the magnetic field.

[0026] In the embodiment of the present invention, to ensure that the polishing wheel 203 and the electromagnet 204 can move stably along the screw rod 214 of the ball screw stepping motor 208, preferably, a guide rail 215 is installed on each side of the screw rod 214 on the support fixing frame 228, and the two guide rails 215 are parallel to the screw rod 214. A slider 216 is slidably connected to the two guide rails 215. At this time, the connecting plate 209 is fixedly connected to the nut 217 and the two sliders 216 at the same time. During polishing, the computer 5 sends a control signal to the ball screw stepping motor 208, and the ball screw stepping motor 208 drives the connecting plate 209 to move linearly under the sliding cooperation of the guide rail 215 and the slider 216.

[0027] It should be noted that there is a strong magnetic phenomenon in the working area where the magnetorheological polishing module is located. The connection of various circuits needs to avoid the working area to prevent the wires from being adsorbed onto the magnetorheological polishing module and affecting normal operation.

[0028] The working principle of the magnetorheological polishing system sensed by the laser tracker is as follows: First, use the laser tracker 3 to calibrate the pose conversion relationship between the target ball 301 and the lowest point of the polishing wheel 203; then set the operating control parameters of the magnetorheological polishing system; next, use the laser tracker 3 and the target ball 301 to measure the pose error of the magnetorheological polishing system in the moving state, compare the measured moving pose with the theoretical pose data to obtain the pose error information, calculate the change data of the polishing gap from the measured moving pose, and then obtain the change data of the removal function. Finally, adjust the magnetic field strength of the electromagnet 204 or simultaneously adjust the position of the polishing wheel 203 and the magnetic field strength of the electromagnet 204 to control the change of the removal function, achieve the desired control parameters, and ultimately achieve the purpose of keeping the removal function of each polishing point constant.

[0029] In the second aspect, the present embodiment further provides a magnetorheological polishing method based on the adjustment of the magnetic field strength of the electromagnet, which is implemented by using the above-mentioned magnetorheological polishing system sensed by the laser tracker, and includes the following steps: S1: Establish a measurement coordinate system of the laser tracker, use the laser tracker to measure the spatial coordinates of the working points of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures, calculate the pose conversion relationship between the spatial coordinates of the working points of the polishing wheel and the spatial coordinates of the target ball, and convert the theoretical Z-axis spatial coordinates of the set working points of the polishing wheel into the theoretical Z-axis spatial coordinates of the target ball according to the pose conversion relationship.

[0030] The process of establishing the measurement coordinate system of the laser tracker is as follows: Use the laser tracker to measure the coordinates of points on each axis when the industrial robot moves along the X-axis and Y-axis of the tool coordinate system respectively. The number of measured points on each axis shall not be less than 10. Use the line fitting function of the laser tracker (this function is a basic function of the laser tracker) to perform linear fitting on the measured points on each axis, and use the fitted line as the measurement coordinate system of the laser tracker, that is, the measurement coordinate system of the laser tracker is parallel to the tool coordinate system of the industrial robot.

[0031] The process of using the laser tracker to measure the spatial coordinates of the working points of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures is as follows: Set the tool end of the industrial robot to at least 12 postures, that is, drive the polishing wheel into at least 12 different poses by using the industrial robot. Use the laser tracker to measure the spatial coordinates of the working points of the polishing wheel and the spatial coordinates of the target ball in each pose.

[0032] The process of measuring the spatial coordinates of the target ball is as follows: when the tool end of the industrial robot is in different postures, measure the position coordinates of the target ball, and the spatial coordinates of the corresponding target ball measured at each posture are .

[0033] The process of measuring the spatial coordinates of the working point of the polishing wheel is as follows: place the target ball at at least 10 different positions on the outer surface of the polishing wheel and measure its coordinates. Through the sphere fitting function of the laser tracker (this function is the basic function of the laser tracker), obtain the center point coordinates (x2, y2, z2) of the polishing wheel. Through the teach pendant of the industrial robot, the posture information of the current tool end of the industrial robot can be known, and thus the straight line passing through the center point of the polishing wheel can be obtained: ; where a, b, and c are the normal vectors of this straight line and can be obtained through the teach pendant of the industrial robot.

[0034] Since the straight line passes through the working point of the polishing wheel, solving the following system of equations can obtain the spatial coordinates of the working point of the polishing wheel , and the spatial coordinates of the working point of the polishing wheel are the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the solution of the system of equations: ; where R is the radius of the polishing wheel.

[0035] Repeat the above measurement process when the tool end of the industrial robot is in different postures to obtain the spatial coordinates of the working point of the polishing wheel corresponding to each posture .

[0036] Calculate the pose transformation relationship T between the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball according to the following formula: .

[0037] After obtaining the pose transformation relationship T, the theoretical Z-axis spatial coordinate of the set working point of the polishing wheel can be converted into the theoretical Z-axis spatial coordinate of the target ball according to the pose transformation relationship T.

[0038] S2: At different polishing clearances, by changing the electromagnetic field strength of the electromagnet, perform fixed-point processing on each processing point of the test polishing element, calculate the volume removal rate of the removal function at each processing point under different polishing clearances, and perform data fitting on the discrete volume removal rates of the removal function and their corresponding electromagnetic field strengths under different polishing clearances to obtain the conversion relationship between the polishing clearance and the electromagnetic field strength ; where represents the polishing clearance corresponding to each volume removal rate of the removal function, Represents the magnetic field strength of the electromagnet, Represents the conversion relationship between the polishing gap and the magnetic field strength of the electromagnet.

[0039] In the present invention, the change adjustment of the removal function is achieved by adjusting the magnetic field strength of the electromagnet. The operation for determining the relationship between the magnetic field strength of the electromagnet and the change of the removal function is as follows: The industrial robot is used to drive the tool end to perform fixed-point machining for a period of time at different positions on the surface of the test polishing element with different polishing gaps. The magnetic field strength of the electromagnet at each machining point is different. Calculate the volume removal rate of the removal function at each machining point under different polishing gaps. Based on the discrete volume removal rates of the removal function and their corresponding magnetic field strengths of the electromagnet under different polishing gaps, use the Polyfit instruction of Matlab (this instruction is a basic general instruction of the Matlab software) to perform data fitting to obtain the conversion relationship between the polishing gap and the magnetic field strength of the electromagnet. This conversion relationship can be characterized as: .

[0040] The different polishing gaps refer to the situation where the relative distance between the polishing wheel and the magnet remains unchanged, and the distance between the entire magnetorheological polishing module and the element to be polished changes.

[0041] Since the discrete data volume corresponding to different polishing gaps obtained from the experiment is limited, the actual measured polishing gap during the machining process may not be equal to the polishing gap data value obtained from the experiment. The solution is to adopt the closest data, that is, the rounding principle. For example: The conversion relationship between the volume removal rate MRR of the removal function and the magnetic field strength B of the electromagnet corresponding to the polishing gaps of 1 mm and 2 mm is obtained from the experiment. However, the polishing gap during the machining process is 1.6 mm. At this time, the volume removal rate MRR of 2 mm is selected to calculate the conversion relationship between the polishing gap and the magnetic field strength B of the electromagnet.

[0042] S3: Use the magnetorheological polishing system to machine the element to be polished. Real-time measure the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point through a laser tracker, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point.

[0043] When polishing the element to be polished, continuously measure the spatial coordinates of the target ball, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point , , Represents the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point, Represents the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point, Represents the error range of the set distance error, Represents the maximum value of the distance error.

[0044] S4: Determine whether the distance error of each polishing trajectory point exceeds the set error range; if not, keep the electromagnetic field strength of the current polishing trajectory point unchanged; if it exceeds, adjust the electromagnetic field strength of the electromagnet through the computer-controlled current intensity controller to change the removal function of the current polishing trajectory point, and finally maintain the constancy of the removal function of each polishing trajectory point.

[0045] During the polishing process, the laser tracker continuously measures the spatial coordinates of the target ball. If the distance error is within the allowable change error range, that is , the trajectory error of the magnetorheological polishing equipment meets the requirements of high-precision machining, and the current electromagnetic field strength of the electromagnet remains unchanged; if , the trajectory error of the magnetorheological polishing system does not meet the requirements of high-precision machining. At this time, it is necessary to calculate the polishing gap of the current polishing trajectory point , represents the set initial polishing gap. According to the conversion relationship between the polishing gap of the current polishing trajectory point and the electromagnetic field strength of the electromagnet calculate the electromagnetic field strength of the electromagnet based on the volume removal rate of the set theoretical removal function, and send it to the current intensity controller through the computer. Finally, regulate the change of the removal function by adjusting the electromagnetic field strength of the electromagnet to achieve the regulation of the trajectory error of the magnetorheological polishing system.

[0046] Since the change amount of the operating pose error of the magnetorheological polishing system is small, the change of can be regarded as the change of the polishing gap.

[0047] To ensure processing safety and that the electromagnetic field strength of the electromagnet does not affect processing, set the maximum adjustment amount of the electromagnetic field strength of the electromagnet in the computer to , and the set error range is , represents the maximum value of the distance error, then: When , keep the electromagnetic field strength of the electromagnet at the current polishing trajectory point unchanged; When and the electromagnetic field strength of the current polishing trajectory point , adjust the electromagnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ; When and the electromagnetic field strength of the current polishing trajectory point , adjust the electromagnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ; Among them, represents the set initial magnetic field strength of the electromagnet.

[0048] Calculate the time required to control the magnetorheological processing module when the adjustment amount of the electromagnet magnetic field strength is at the maximum value : : ; Among them, is the highest adjustment rate of the magnetic field strength change. [[ID=E18]]

[0049] Statistically analyze b data measured by the laser tracker within a seconds to obtain the time for the laser tracker to measure a polishing trajectory point ; ; Calculate the minimum movement time between two adjacent polishing trajectory points of the magnetorheological processing module at the highest moving speed : : ; Among them, represents the distance between two adjacent polishing trajectory points.

[0050] When generating the processing control program, if [[ID=G43]]then the generated processing control program is appropriate; if it is necessary to increase the material removal thickness, extend the processing time, and regenerate the processing control program so that the processing dwell time of each polishing trajectory point .

[0051] During the entire processing process, the laser tracker and the target ball are used to continuously measure the pose error of the magnetorheological polishing system, and the running trajectory is adjusted in real time through the magnetorheological polishing system to achieve the desired control parameters, ensure the stability of the removal function during the processing process, and finally achieve the high-precision processing goal.

[0052] Compared with the current mainstream real-time control scheme based on force sensors, the present invention measures the real-time change of the pose of the magnetorheological polishing system during the polishing process through a laser tracker, and uses the adjustment of the electromagnet magnetic field strength to achieve real-time constant control of the removal function. This method does not require calibration of measurement devices such as force sensors, is not affected by factors such as the weight of the magnetorheological polishing system, the running accuracy of the equipment itself, the running speed, the posture, and other factors, can measure the pose change of the polishing system in real time during the optical polishing process, intuitively reflect the pose error of the polishing system, and has the advantages of low equipment cost and high measurement accuracy.

[0053] In a third aspect, the present embodiment further provides a magnetorheological polishing method based on the simultaneous adjustment of the position of the polishing wheel and the magnetic field strength, which is implemented by using the above-mentioned magnetorheological polishing system based on laser tracker sensing, and includes the following steps: S1: Establish a measurement coordinate system of the laser tracker. Use the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures, and calculate the pose transformation relationship between the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball. According to the pose transformation relationship, convert the theoretical Z-axis spatial coordinates of the set working point of the polishing wheel into the theoretical Z-axis spatial coordinates of the target ball.

[0054] The process of establishing the measurement coordinate system of the laser tracker is as follows: Use the laser tracker to measure the coordinates of points on each axis when the industrial robot moves along the X-axis and Y-axis of the tool coordinate system respectively. The number of measured points on each axis shall not be less than 10. Use the line fitting function of the laser tracker (this function is a basic function of the laser tracker) to perform linear fitting on the measured points on each axis, and use the fitted line as the measurement coordinate system of the laser tracker, that is, the measurement coordinate system of the laser tracker is parallel to the tool coordinate system of the industrial robot.

[0055] The process of using the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures is as follows: Set the tool end of the industrial robot to at least 12 postures, that is, drive the polishing wheel to at least 12 different poses by using the industrial robot. Use the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball in each pose.

[0056] The process of measuring the spatial coordinates of the target ball is: measure the position coordinates of the target ball when the tool end of the industrial robot is in different postures, and the spatial coordinates of the corresponding target ball measured in each posture are .

[0057] The process of measuring the spatial coordinates of the working point of the polishing wheel is: place the target ball at at least 10 different positions on the outer surface of the polishing wheel and measure its coordinates, and obtain the center point coordinates of the polishing wheel through the sphere fitting function of the laser tracker , and the straight line passing through the center point of the polishing wheel is: ; wherein, a, b, and c are the normal vectors of the straight line, which are obtained through the teach pendant of the industrial robot; Since the straight line passes through the working point of the polishing wheel, the spatial coordinates of the working point of the polishing wheel can be obtained by solving the following system of equations , the spatial coordinates of the working point of the polishing wheel is the spatial coordinate corresponding to the minimum value of the Z-axis coordinate in the solution of the system of equations: ; wherein, R is the radius of the polishing wheel.

[0058] When the tool end of the industrial robot is in different postures, repeat the above measurement process to obtain the spatial coordinates of the working point of the polishing wheel corresponding to each posture .

[0059] Calculate the spatial coordinates of the working point of the polishing wheel according to the following formula and the spatial coordinates of the target ball The pose transformation relationship T between them: .

[0060] After obtaining the pose transformation relationship T, the theoretical Z-axis spatial coordinates of the set working point of the polishing wheel can be converted into the theoretical Z-axis spatial coordinates of the target ball according to the pose transformation relationship T.

[0061] S2: At different polishing gaps, by changing the position of the polishing wheel, perform fixed-point machining on each machining point of the test polishing element, calculate the volume removal rate of the removal function at each machining point at different polishing gaps, and perform data fitting on the discrete volume removal rates of the removal function and their corresponding polishing wheel positions at different polishing gaps to obtain the conversion relationship between the polishing gap and the polishing wheel position ; wherein, represents the polishing gap corresponding to each volume removal rate of the removal function, represents the position of the polishing wheel, represents the conversion relationship between the polishing gap and the polishing wheel position.

[0062] The present invention realizes the adjustment of the change of the removal function by simultaneously adjusting the position of the polishing wheel and the magnetic field strength of the electromagnet. The operation for determining the relationship between the position of the polishing wheel and the change of the removal function is as follows: Use the industrial robot to drive the tool end to perform fixed-point machining for a period of time at different positions on the surface of the test polishing element at different polishing gaps. The positions of the polishing wheels at each machining point are different. Calculate the volume removal rate of the removal function at each machining point at different polishing gaps. Based on the discrete volume removal rates of the removal function and their corresponding polishing wheel positions at different polishing gaps, use the Polyfit instruction of Matlab (this instruction is a basic general instruction of the matlab software) to perform data fitting to obtain the conversion relationship between the polishing gap and the polishing wheel position. This conversion relationship can be characterized as: .

[0063] Different polishing gaps mean that the relative distance between the polishing wheel and the magnet remains unchanged, and the distance between the entire magnetorheological polishing module and the element to be polished changes. Changing the position of the polishing wheel alone is to change the position of the polishing wheel on the basis of each polishing gap.

[0064] For example, set the polishing gap to 1 mm and 2 mm. When collecting experimental data, first adjust the polishing gap to 1 mm, then separately change the position of the polishing wheel and collect data. After this set of experiments; adjust the polishing gap to 2 mm, then separately change the position of the polishing wheel and collect data.

[0065] Since the amount of discrete data corresponding to different polishing gaps obtained from the experiment is limited, the actual polishing gap measured during the processing may not be equal to the polishing gap data value obtained from the experiment. The solution is to adopt the closest data, that is, the rounding principle. For example: The conversion relationship between the volume removal rate MRR of the removal function and the position LW of the polishing wheel corresponding to the polishing gaps of 1 mm and 2 mm is obtained from the experiment, but the polishing gap during the processing is 1.6 mm. At this time, the volume removal rate MRR of 2 mm is selected to calculate the conversion relationship between the polishing gap and the position LW of the polishing wheel.

[0066] S3: Use the magnetorheological polishing system to process the element to be polished, and use a laser tracker to measure the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point in real time, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point.

[0067] During the polishing of the element to be polished, continuously measure the spatial coordinates of the target ball, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point , , represents the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point, represents the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point, represents the error range of the set distance error, represents the maximum value of the distance error.

[0068] S4: Determine whether the distance error at each polishing trajectory point exceeds the set error range; if not, keep the position of the polishing wheel and the magnetic field strength of the electromagnet unchanged at the current polishing trajectory point; if it exceeds, adjust the position of the polishing wheel through the computer-controlled position adjustment device, and at the same time control the current intensity controller to adjust the magnetic field strength of the electromagnet, change the removal function at the current polishing trajectory point, and finally maintain the constancy of the removal function at each polishing trajectory point.

[0069] Adjust the change of the removal function by simultaneously adjusting the position of the polishing wheel and the magnetic field strength of the electromagnet. During the polishing process of the element to be polished, the laser tracker continuously measures the spatial coordinates of the target ball. If the distance error is within the allowable change error range, that is Then the trajectory error of the magnetorheological polishing system meets the requirements of high-precision machining, and the current position of the polishing wheel and the magnetic field strength of the electromagnet remain unchanged; if , the trajectory error of the magnetorheological polishing system does not meet the requirements of high-precision machining. At this time, it is necessary to calculate the polishing gap at the current polishing trajectory point , represents the set initial polishing gap. According to the conversion relationship between the polishing gap at the current polishing trajectory point and the position of the polishing wheel and the set theoretical removal function volume removal rate, calculate the position of the polishing wheel and send it to the ball screw stepper motor through the computer to adjust the position of the polishing wheel. When the position of the polishing wheel changes, the relative distance between the polishing wheel and the electromagnet changes, resulting in a change in the magnetic field strength on the outer surface of the polishing wheel. At this time, it is necessary to change the magnetic field strength of the electromagnet to ensure that the magnetic field strength on the outer surface of the polishing wheel remains unchanged. Finally, through the simultaneous adjustment of the position of the polishing wheel and the magnetic field strength of the electromagnet, control the change of the removal function and realize the control of the trajectory error of the magnetorheological polishing system.

[0070] Since the change amount of the running pose error of the magnetorheological polishing system is small, the change can be regarded as the change of the polishing gap.

[0071] To ensure processing safety and that the position of the polishing wheel and the magnetic field strength do not affect processing, set the maximum adjustment amount of the polishing wheel position in the computer to , the maximum adjustment amount of the magnetic field strength of the electromagnet to , set the error range to , represents the maximum value of the distance error, then: When , keep the position of the polishing wheel and the magnetic field strength of the electromagnet at the current polishing trajectory point unchanged; When and the position of the polishing wheel at the current polishing trajectory point and the magnetic field strength of the electromagnet at the current polishing trajectory point, adjust the position of the polishing wheel at the current polishing trajectory point and the magnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ; ; Among them, r represents the distance between the electromagnet and the polishing wheel, M represents the magnetic moment, and k is the proportionality coefficient; When and the position of the polishing wheel at the current polishing trajectory point and the magnetic field strength of the electromagnet at the current polishing trajectory point At this time, the position of the polishing wheel at the current polishing trajectory point and the electromagnetic field strength of the electromagnet at the current polishing trajectory point are adjusted according to the following formula: ; ; wherein, represents the set initial position of the polishing wheel, represents the set initial electromagnetic field strength of the electromagnet.

[0072] Calculate the time required to control the magnetorheological processing module when the adjustment amount of the electromagnetic field strength is the maximum value : ; wherein, is the highest adjustment rate of the change in the magnetic field strength.

[0073] Calculate the time required to control the magnetorheological processing module when the adjustment amount of the polishing wheel position is the maximum value : ; wherein, is the highest moving speed of the position adjustment device.

[0074] Statistically analyze b data measured by the laser tracker within a seconds to obtain the time for the laser tracker to measure a polishing trajectory point: ; Calculate the minimum moving time max between two adjacent polishing trajectory points of the industrial robot at the highest moving speed V : ; wherein, represents the distance between two adjacent processing positions.

[0075] When generating the processing control program, if is satisfied, the generated processing control program is appropriate; if , it is necessary to increase the material removal thickness, extend the processing time, and regenerate the processing control program so that . represents and the maximum value in.

[0076] During the entire processing, a laser tracker and a target ball are used to continuously measure the pose error of the magnetorheological polishing system, and the running trajectory is adjusted in real time through the magnetorheological polishing system to achieve the desired control parameters, ensure the stability of the removal function during processing, and ultimately achieve the high-precision processing goal.

[0077] Compared with the current mainstream real-time control scheme based on force sensors, in this invention, the real-time changes in the pose of the magnetorheological polishing system during polishing are measured by a laser tracker, and the real-time constant control of the removal function is achieved by adjusting the magnetic field intensity of the electromagnet or simultaneously adjusting the position of the polishing wheel and the magnetic field intensity of the electromagnet. This method does not require calibration of measuring devices such as force sensors, and is not affected by factors such as the weight of the magnetorheological polishing system, the running accuracy of the equipment itself, the running speed, the posture, and other factors. During the optical polishing process, the pose changes of the polishing system can be measured in real time, intuitively reflecting the pose error of the polishing system, and having the advantages of low equipment cost and high measurement accuracy.

[0078] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the disclosure of this invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in this invention can be achieved, and no limitations are imposed herein.

[0079] The above specific embodiments do not constitute a limitation on the protection scope of this 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 principles of this invention shall be included within the protection scope of this invention.

Claims

1. A magnetorheological polishing system based on laser tracker sensing, characterized in that Including: A polishing platform, on which a component to be polished and a test polishing component are arranged; A polishing assembly, including an industrial robot and a magnetorheological polishing module. The industrial robot is used to drive the magnetorheological polishing module to move to the position where the test polishing component is located or the position where the component to be polished is located. The magnetorheological polishing module is used to process the component to be polished or the test polishing component. The magnetorheological polishing module includes a magnetorheological mounting frame, a polishing wheel, a nozzle, an electromagnet, a liquid pump, a position adjusting device and a current intensity controller. The magnetorheological mounting frame is mounted on the tool end of the industrial robot. The current intensity controller, the position adjusting device, the nozzle and the electromagnet are respectively mounted on the magnetorheological mounting frame. The liquid pump is arranged on the industrial robot or on one side of the industrial robot. The liquid pump is used to pump magnetorheological fluid into the nozzle. The nozzle is used to spray the magnetorheological fluid onto the polishing wheel. The electromagnet is used to change the stiffness of the magnetorheological fluid. The position adjusting device is used to adjust the position of the polishing wheel. The polishing wheel is used to process the test polishing component or the component to be polished. The current intensity controller is used to control the energizing current of the electromagnet and adjust the magnetic field intensity of the electromagnet; A laser tracker, the target ball of which is mounted on the tool end of the industrial robot. The laser tracker is used to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures, and convert the theoretical Z-axis spatial coordinates of the set working point of the polishing wheel into the theoretical Z-axis spatial coordinates of the target ball; A computer, which is used to calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing track point. The computer is also used to, when the distance error exceeds the set error range, adjust the magnetic field intensity of the electromagnet according to the conversion relationship between the magnetic field intensity of the electromagnet and the polishing gap or simultaneously adjust the position of the polishing wheel and the magnetic field intensity of the electromagnet according to the conversion relationship between the position of the polishing wheel and the polishing gap, so as to adjust the removal function and maintain the constancy of the removal function at each polishing track point.

2. The magnetorheological polishing system based on laser tracker sensing according to claim 1, characterized in that, The position adjusting device includes a support fixing frame, a ball screw stepping motor and a connecting plate. The ball screw stepping motor is vertically mounted on the magnetorheological mounting frame through the support fixing frame. The nut of the ball screw stepping motor is fixedly connected with the connecting plate. The polishing wheel is connected to the connecting plate.

3. The magnetorheological polishing system based on laser tracker sensing according to claim 1, characterized in that, The magnetorheological polishing module further includes a polishing wheel driving device. The polishing wheel driving device includes a driving motor, a driving wheel, a driven wheel and a synchronous belt. The driving motor is mounted on the magnetorheological mounting frame. A bearing seat is mounted on the magnetorheological mounting frame. A bearing is mounted in the bearing seat. The bearing is connected with the polishing wheel. The driven wheel is sleeved on the bearing. The driving wheel is sleeved on the output end of the driving motor. The synchronous belt is tensioned between the driven wheel and the driving wheel.

4. A magnetorheological polishing method based on the adjustment of the magnetic field strength of an electromagnet, which is realized by using the magnetorheological polishing system based on the perception of a laser tracker described in any one of claims 1 to 3, and is characterized in that Including the following steps: S1: Establish a measurement coordinate system of the laser tracker, use the laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures, calculate the pose conversion relationship between the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball, and convert the theoretical Z-axis spatial coordinates of the set working point of the polishing wheel into the theoretical Z-axis spatial coordinates of the target ball according to the pose conversion relationship; S2: At different polishing clearances, by changing the magnetic field intensity of the electromagnet, perform point-by-point machining on each machining point of the test polishing element, calculate the volume removal rate of the removal function for each machining point at different polishing clearances, and perform data fitting on the discrete volume removal rates of the removal function and their corresponding electromagnet magnetic field intensities at different polishing clearances to obtain the conversion relationship between the polishing clearance and the electromagnet magnetic field intensity ; among them, represents the polishing clearance corresponding to each volume removal rate of the removal function, represents the magnetic field intensity of the electromagnet, represents the conversion relationship between the polishing clearance and the magnetic field intensity of the electromagnet; S3: Use the magnetorheological polishing system to process the element to be polished. Measure the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point in real time through a laser tracker, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point. S4: Determine whether the distance error at each polishing trajectory point exceeds the set error range. If it does not exceed, keep the magnetic field strength of the electromagnet at the current polishing trajectory point unchanged. If it exceeds, adjust the magnetic field strength of the electromagnet by controlling the current intensity controller through the computer, change the removal function at the current polishing trajectory point, and finally maintain the constancy of the removal function at each polishing trajectory point.

5. The magnetorheological polishing method based on the adjustment of the magnetic field intensity of the electromagnet according to claim 4, characterized in that Distance error , represents the actual Z-axis spatial coordinate of the target ball at each polishing trajectory point, represents the theoretical Z-axis spatial coordinate of the target ball at each polishing trajectory point; Set the maximum adjustment amount of the electromagnetic field strength in the computer to be , and set the error range to be . represents the maximum value of the distance error, then: When the electromagnetic field intensity of the electromagnet at the current polishing trajectory point remains unchanged; When and the electromagnetic field intensity of the electromagnet at the current polishing trajectory point then, according to the following formula, adjust the electromagnetic field intensity of the electromagnet at the current polishing trajectory point as follows: ； When and the electromagnetic field intensity of the electromagnet at the current polishing trajectory point then, adjust the electromagnetic field intensity of the electromagnet at the current polishing trajectory point according to the following formula as follows: ； Among them, represents the set initial magnetic field strength of the electromagnet.

6. The magnetorheological polishing method based on the adjustment of the magnetic field strength of an electromagnet according to claim 4, characterized in that, The process of establishing the measurement coordinate system of the laser tracker is as follows: Use the laser tracker to measure the coordinates of points on each axis when the industrial robot moves along the X-axis and Y-axis of the tool coordinate system respectively. The number of measurement points on each axis is not less than 10. Use the line fitting function of the laser tracker to perform linear fitting on the measured points on each axis, and use the fitted line as the measurement coordinate system of the laser tracker, that is, the measurement coordinate system of the laser tracker is parallel to the tool coordinate system of the industrial robot.

7. The magnetorheological polishing method based on the adjustment of the magnetic field strength of an electromagnet according to claim 4, wherein The process of using the laser tracker to measure the spatial coordinates of the polishing wheel working point and the target ball when the industrial robot is in different postures is as follows: Set the tool end of the industrial robot to at least 12 postures, and use the industrial robot to drive the polishing wheel to at least 12 different poses. Use the laser tracker to measure the spatial coordinates of the polishing wheel working point and the target ball when the industrial robot is in each pose. The process of measuring the spatial coordinates of the polishing wheel working point is as follows: Place the target ball at at least 10 different positions on the outer surface of the polishing wheel and measure its coordinates. Obtain the coordinates of the center point of the polishing wheel through the sphere fitting function of the laser tracker. , and the straight line passing through the center point of the polishing wheel is: ； Among them, a, b, and c are the normal vectors of the straight line, which are obtained through the teach pendant of the industrial robot. 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 spatial coordinates of the working point of the polishing wheel : ； Among them, R represents the radius of the polishing wheel.

8. A magnetorheological polishing method based on simultaneous adjustment of the position of a polishing wheel and magnetic field strength, which is realized by using the magnetorheological polishing system based on laser tracker sensing described in any one of claims 1 to 3, and is characterized in that, It includes the following steps: S1: Establish the measurement coordinate system of the laser tracker, use the laser tracker to measure the spatial coordinates of the polishing wheel working point and the target ball when the industrial robot is in different postures, and calculate the pose conversion relationship between the spatial coordinates of the polishing wheel working point and the target ball. According to the pose conversion relationship, convert the theoretical Z-axis spatial coordinates of the set polishing wheel working point into the theoretical Z-axis spatial coordinates of the target ball. S2: At different polishing clearances, by changing the position of the polishing wheel, perform fixed-point machining on each machining point of the test polishing element, calculate the volume removal rate of the removal function at each machining point under different polishing clearances, and perform data fitting on the discrete volume removal rates of the removal function and their corresponding polishing wheel positions under different polishing clearances to obtain the conversion relationship between the polishing clearance and the polishing wheel position ; where represents the polishing clearance corresponding to each volume removal rate of the removal function, represents the position of the polishing wheel, represents the conversion relationship between the polishing clearance and the polishing wheel position; S3: Use the magnetorheological polishing system to process the element to be polished. Measure the actual Z-axis spatial coordinates of the target ball at each polishing trajectory point in real time through a laser tracker, and calculate the distance error between the actual Z-axis spatial coordinates and the theoretical Z-axis spatial coordinates of the target ball at each polishing trajectory point. S4: Determine whether the distance error at each polishing trajectory point exceeds the set error range. If it does not exceed, keep the position of the polishing wheel and the magnetic field strength of the electromagnet at the current polishing trajectory point unchanged. If it exceeds, adjust the position of the polishing wheel by controlling the position adjustment device through the computer, and at the same time control the current intensity controller to adjust the magnetic field strength of the electromagnet, change the removal function at the current polishing trajectory point, and finally maintain the constancy of the removal function at each polishing trajectory point.

9. The magnetorheological polishing method based on the simultaneous adjustment of the polishing wheel position and the magnetic field strength according to claim 8, characterized in that Distance error , represents the actual Z-axis spatial coordinate of the target ball at each polishing trajectory point, represents the theoretical Z-axis spatial coordinate of the target ball at each polishing trajectory point; The maximum adjustment amount for setting the position of the polishing wheel in the computer is , the maximum adjustment amount for the magnetic field strength of the electromagnet is , the set error range is , represents the maximum value of the distance error, then: When maintain the polishing wheel position of the current polishing trajectory point and the electromagnetic field strength of the electromagnet unchanged; When and the position of the polishing wheel at the current polishing trajectory point and the electromagnetic field strength of the electromagnet at the current polishing trajectory point meet the requirements, adjust the position of the polishing wheel at the current polishing trajectory point and the electromagnetic field strength of the electromagnet at the current polishing trajectory point according to the following formula: ； ； Among them, r represents the distance between the electromagnet and the polishing wheel, M represents the magnetic moment, and k is the proportionality coefficient. When and the polishing wheel position of the current polishing trajectory point and the electromagnetic field strength of the electromagnet at the current polishing trajectory point meet the requirements, the polishing wheel position of the current polishing trajectory point and the electromagnetic field strength of the electromagnet at the current polishing trajectory point shall be adjusted according to the following formula: ； ； Among them, represents the set initial position of the polishing wheel, represents the set initial magnetic field intensity of the electromagnet.

10. The magnetorheological polishing method based on simultaneous adjustment of the position of the polishing wheel and the magnetic field strength according to claim 8, wherein The process of establishing the measurement coordinate system of the laser tracker is as follows: Measure the coordinates of points on each axis when the industrial robot moves along the X-axis and Y-axis of the tool coordinate system using a laser tracker. The number of measured points on each axis is not less than 10. Use the line fitting function of the laser tracker to perform linear fitting on the measured points on each axis, and take the fitted line as the measurement coordinate system of the laser tracker, that is, the measurement coordinate system of the laser tracker is parallel to the tool coordinate system of the industrial robot.

11. The magnetorheological polishing method based on the simultaneous adjustment of the polishing wheel position and the magnetic field strength according to claim 8, wherein The process of measuring the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in different postures using a laser tracker is as follows: Set the tool end of the industrial robot to at least 12 postures, and use the industrial robot to drive the polishing wheel to at least 12 different poses; Use a laser tracker to measure the spatial coordinates of the working point of the polishing wheel and the spatial coordinates of the target ball when the industrial robot is in each pose; The measurement process of the spatial coordinates of the working point of the polishing wheel is as follows: Place the target ball at at least 10 different positions on the outer surface of the polishing wheel and measure its coordinates, and obtain the coordinates of the center point of the polishing wheel through the ball fitting function of the laser tracker. , and the straight line passing through the center point of the polishing wheel is: ； Among them, a, b, and c are the normal vectors of the straight line, which are obtained through the teach pendant of the industrial robot; By solving the spatial coordinates corresponding to the minimum value of the Z-axis coordinate in the following system of equations and using them as the spatial coordinates of the working point of the polishing wheel : ； Among them, R represents the radius of the polishing wheel.

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