Intelligent grinding wheel laser dressing system, and method

Abstract

An intelligent grinding wheel laser dressing system, which belongs to the field of grinding wheel dressing. The system comprises: an input end, a machining system and an output end, wherein grinding wheel data is inputted from the input end into the machining system; the machining system consists of a database, a CAM system and a monitoring system; and a product generated by the machining system is obtained from the output end. The grinding wheel laser dressing method comprises: 1, inputting grinding wheel data into a system; 2, a monitoring system automatically generating a tool setting point and margin information; 3, optimizing machining process parameters; 4, calculating a laser beam attitude adjustment manner and a laser energy compensation manner, and generating a trajectory plan; step 5, performing interpolation motion, and dressing a grinding wheel; step 6, monitoring a machining process, and observing a change in terms of margin; and step 7, after the margin is met, the monitoring system sending shutdown detection information. In the present invention, laser beam posture attitude and energy compensation can be performed on the basis of the outline size of a grinding wheel blank during drawing designing and dressing, so that autonomous iteration of a full process can be implemented.

Description

Intelligent system and method for laser dressing of grinding wheel

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present application claims priority to the Chinese patent application No. 202411314449.5, filed on September 20, 2024, entitled “Intelligent system and method for laser dressing of grinding wheel”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application belongs to the technical field of grinding wheel dressing, and specifically relates to an intelligent system and method for laser dressing of grinding wheel. BACKGROUND

[0004] Current laser dressing of grinding wheel highly depends on manual operation, and in many aspects such as laser parameter setting, grinding wheel material analysis, processing parameter determination, part of dressing steps (such as tool setting), dressing automation and completion determination, feeding and discharging, etc., manual operation is relied on.

[0005] Intelligent processing system focuses on manual replacement, including manual operation, process experience judgment, feeding and discharging, etc. The difference between this and traditional automation is that the automation of manual replacement mainly replaces manual operation, such as automatic tool feeding and automatic interpolation. Intelligentization is different, which uses database data analysis to form the selection of experience parameters. Visual, sound, heat, electromagnetic, force, etc. are used to judge the whole process of processing. CAM core algorithm is used to plan and customize the processing of grinding wheel. Therefore, intelligentization is not a simple upgrade of automation, but a comprehensive replacement of manual processing including automation.

[0006] The laser dressing system of formed grinding wheel is currently in the process of experiment, and has not formed an integrated, automated and intelligent processing system. SUMMARY

[0007] The purpose of the present application is to provide an intelligent system and method for laser dressing of grinding wheel, which can adjust the laser beam attitude and compensate the energy according to the profile requirements of the drawing design and the real-time changes of the shape and size of the grinding wheel blank during the dressing process, and can also realize self-iteration of the whole process and iterative upgrading of the whole processing system. The method realizes automatic generation of trajectory planning through dressing parameter determination, defocusing amount compensation and avoidance of laser interference.

[0008] The technical solution adopted by the present application is as follows:

[0009] An intelligent system for laser dressing of grinding wheel, comprising an input end, a processing system and an output end.

[0010] The input end inputs the grinding wheel data into the processing system according to product requirements, wherein the grinding wheel data includes the profile requirement parameters designed on the drawing, the model, and the material information and the outer shape size of the grinding wheel blank; the drawing is in a digital form, and the material information and the outer shape size of the grinding wheel blank are obtained by using various sensors, cameras and other hardware facilities on the machine tool.

[0011] The processing system is composed of a database, a CAM system and a monitoring system; the database can realize four functions of expert prediction, parameter optimization, digital twinning and machine learning; the CAM system receives the processing parameters from the database and performs two functions of laser beam posture adjustment and energy compensation based on the processing parameters; the functions of the monitoring system include the remaining amount judgment of the grinding wheel dressing, the identification of the tool point and the abnormal situation judgment; on the one hand, the monitoring system feeds back the real-time data of the processing to the database to help upgrade the database, and on the other hand, interacts with the CAM to output the real-time position and the remaining amount information required by the CAM system and accepts the following control of the CAM system; during the operation of the processing system, the whole process is realized to be iterated autonomously, and the whole processing system is iterated and upgraded;

[0012] The output end obtains the products generated by the processing system, including qualified grinding wheels and detection reports. The output qualified grinding wheels (customers), the processing detection results (customers) and the processing cost consumption (factory).

[0013] A method for laser intelligent dressing of grinding wheels, comprising the following steps:

[0014] Step 1: input the grinding wheel data into the grinding wheel laser dressing intelligent system through the input end;

[0015] Step 2: the monitoring system compares and analyzes the outer shape size of the grinding wheel blank and the profile requirement parameters of the drawing, and then automatically generates the tool point and the remaining amount information;

[0016] The monitoring system mainly analyzes the actual outer shape size of the blank, and then compares the two. It is equivalent to finding the difference by covering them together.

[0017] Step 3: compare the material information and the outer shape size of the grinding wheel blank with the pre-stored dressing cases in the database, find similar or consistent dressing cases, and then optimize the processing parameters by the functions of expert prediction and parameter optimization; if there is no similar case, machine learning is performed through the known cases to generate a set of processing parameters; the generated processing parameters are prepared for digital twinning;

[0018] Step 4: send the processing parameters generated by the database to the CAM system, and the CAM system calculates the laser beam posture adjustment mode and the laser energy compensation mode according to the profile requirement parameters and the processing parameters of the grinding wheel, and generates the trajectory planning of the laser processing process;

[0019] Step 5: The machine tool performs interpolation motion according to the trajectory planning generated by the CAM system, and starts dressing the grinding wheel;

[0020] Step 6: The monitoring system monitors the machining process after the interpolation motion starts, and observes the change of the blank in real time. Through template matching and target recognition, it sends real-time stock and grinding wheel blank position information to the CAM system and database;

[0021] The CAM system compensates for abnormal machining points using stock and blank position information, and the database uses real-time position and stock to perform digital twin performance;

[0022] Step 7: When the stock meets the machining requirements, the monitoring system sends information to stop and detect;

[0023] Step 8: Output the detection results. If the product is qualified, output the qualified product and detection report; if not, re-analyze the grinding wheel information and plan the next round of dressing;

[0024] Step 9: If the special grinding wheel is difficult to qualify after repeated dressing, use the system iteration function to optimize the system database and find more optimized parameters.

[0025] Further, in step 2, the monitoring system automatically generates tool setting points and stock information according to the following methods:

[0026] For grinding wheel blank judgment: judge the size of the blank machining stock through visual observation and inspection;

[0027] For tool point detection: use the trial burning method, and then judge the position of the molten pool and the laser tool tip according to visual observation; when using mechanical method, judge the tool setting depth and position through sound sensing and vision;

[0028] For monitoring of the machining process: judge whether the energy absorption of the machining point is uniform according to the energy of the laser optical spectrometer; compare the actual profile observed by vision with the profile required by the drawing, and judge whether the machining is complete according to the difference between the two; judge the roundness, runout, and profile accuracy of the finished product according to the visual observation and edge detection synthesis algorithm; judge the running state of the whole equipment according to the sound and current.

[0029] The monitoring system is a full-process monitoring system. According to different ways of vision, optics, and acoustics, it needs to be assembled by itself. Commonly used are direct visual observation with backlight source, optical spectrum detection, and sound vibration sensing detection for tool setting. It is used for grinding wheel blank stock judgment, tool setting point detection, abnormal machining point judgment, machining completion stop judgment, finished product detection, and whole equipment monitoring.

[0030] Further, in step 3, the processing parameters are optimized using a particle swarm optimization (PSO) algorithm, which includes the following steps:

[0031] S301, the position and velocity of the particle swarm are initialized in a random manner; including the individual particle historical optimal position and the group historical optimal position, the individual particle historical best fitness value and the group historical best fitness value;

[0032] S302, the position and velocity of the individual particle are updated using formulas (1) and (2):

[0033] The distance and direction of the next step of each particle in the PSO algorithm are a position vector, referred to as the next iteration speed, denoted as:

[0034] wherein, represents the position vector of the d-th dimension of the particle i in the k+1th iteration; represents the position vector of the d-th dimension of the particle i in the kth iteration; represents the velocity vector of the d-th dimension of the particle i in the k+1th iteration; represents the velocity vector of the d-th dimension of the particle i in the kth iteration; ω represents the inertia weight; c1, c2 represent the learning factor; r1, r2 represent two random numbers, the value range is 0-1; represents the historical optimal position of the d-th dimension of the particle i in the kth iteration, i.e., the optimal solution searched by the i-th particle (individual) in the d-th dimension after the kth iteration; represents the historical optimal position of the d-th dimension of the group (in the global) in the kth iteration, i.e., the optimal solution of the d-th dimension of the entire particle group after the kth iteration;

[0035] S303, the fitness value of the individual particle is calculated, which needs to meet the requirements of formula (3):

[0036] wherein, η m represents the fitness value of each particle; m represents the particle number; the fitness value represents the optimization target, and the fitness values of the particles together meet the tolerance requirements, so that the fitting result is considered to have better detection reliability;

[0037] S304, the historical best fitting value of the individual particle is updated;

[0038] S305, the historical best fitting value and position of the group are updated;

[0039] S306, the inertia weight and the iteration number are updated:

[0040] The inertia weight is updated as follows in formula (4) by using a linearly changing inertia weight strategy:

[0041] where ω max and ω min represent the maximum inertia weight and the minimum inertia weight, respectively; iter represents the current iteration number; iter max represents the maximum iteration number.

[0042] S307, when the terminal condition is met, output the final optimal solution, otherwise repeat steps S302-S306.

[0043] Further, in step 5, the CAM system generates a trajectory planning process, including the following steps:

[0044] The CAM trajectory planning system is used to plan the multi-channel optimization of laser trajectory in adjustment and finishing, real-time attitude adjustment, energy compensation, and abnormal processing point compensation. The system needs to be established by itself, because there is no CAM software, algorithm, and planning system for grinding wheel laser finishing on the market. These adjustments need to be based on the data provided by the database in the grinding wheel material processing process, such as single-channel ablation speed, inclination angle and forming angle relationship, grinding wheel diameter-laser original cutting depth-laser beam divergence angle corresponding relationship, and the influence of feed rate on single-channel ablation rate, and make trajectory planning based on this.

[0045] S501, the finishing parameter is determined:

[0046] In tangential finishing, the laser spot is irradiated to the grinding wheel surface by pulse mode, and the shape of the spot on the grinding wheel surface is approximately an ellipse; according to the literature and industry consensus, laser is used for tangential shaping and radial dressing when finishing the grinding wheel. Only tangential finishing is considered for precision and forming.

[0047] The spot overlap rate in the circumferential direction of the grinding wheel is defined as: the ratio of the overlapping area of the spot to the area of the spot under two pulses, denoted by Oc, and Oc is described as:

[0048] where S overlap represents the overlapping area of the spot; S ellipse represents the area of the spot; a e and b e represent the parameters of the ellipse; and l c represents the offset of the spot center in the circumferential direction.

[0049] The spot overlap rate needs to reach more than 85% to obtain a better grinding wheel surface quality; the grinding wheel speed when the spot overlap rate reaches 85% is given by formula (6):

[0050] Where D is the diameter of the grinding wheel; T represents the pulse period of the laser, which is the inverse of the repetition frequency;

[0051] The spot overlap ratio in the direction of the generatrix of the grinding wheel is defined as the ratio of the area of the overlapping part of the spots to the area of the spot, denoted by O A , O A is described as:

[0052] Where l A is the offset of the center of the spot on the generatrix;

[0053] Then, at the rotational speed n, the feed rate F of the grinding wheel is calculated by formula (8): F = nl A (8)

[0054] The dressing parameters can be determined by formula (5) to formula (8);

[0055] S502, defocus amount compensation:

[0056] The edge point of the grinding wheel is taken as the origin of the coordinates, the direction of the generatrix of the grinding wheel cylinder is taken as the X direction, the diameter direction is taken as the Y direction and the Z direction; before dressing, the surface cylindrical ring surface of the grinding wheel is described as:

[0057] The trajectory of the laser to be moved is described by formula (9) to construct a mathematical model of defocus amount compensation. In the formula, x, y and z are the positions of the three directions after the coordinate system is established, and the origin of the coordinates is at the edge of the grinding wheel; B is the thickness of the grinding wheel (equivalent to the length of the generatrix of the cylinder);

[0058] When the spot irradiates on the material surface, it is generally within the range of the Rayleigh length, at which time the laser beam can be considered as a cylinder. In the material removal process, the laser beam irradiated vertically needs to rotate around the laser beam focal point O in the X-O-Z plane, and the state of rotating by an angle a is described as:

[0059] Where r represents the radius of the laser beam at a certain position; h represents the length of the position from the laser focal point; r0 represents the radius of the spot at the laser focal point (h = 0 position), and the laser beam adopts a near-field cylindrical model r always remains consistent with r0; L ray represents the Rayleigh length of the laser beam, and e0 is the initial defocus amount in the vertical state of the laser beam.

[0060] For the laser irradiated vertically, the focal point is on the X-O-Y plane, and as the laser beam rotates, the intersection point (i.e., the actual irradiation position) P T of the laser beam and the grinding wheel changes, in order to maintain a stable defocus amount, compensation needs to be made in the X and Z directions, and the compensation amount is:

[0061] When the defocus amount is compensated, the focus is considered to be always kept on the X-O-Y plane.

[0062] S503, avoidance of laser interference:

[0063] When the action point of the laser beam on the material is beyond the Rayleigh length, the laser beam is considered to be a far-field laser composed of hyperbolic curves;

[0064] Under the far-field model, the radius value r of the beam direction at a certain height h is obtained by using the asymptote model b The approximate description is:

[0065] wherein, is the divergence angle of the laser beam; h b is the beam length;

[0066] In the vertical direction, the beam length h b satisfies the following geometric relationship between the height h and the beam length h: b h = h / cosα h (13)

[0067] wherein, α h represents the angle of rotation of the A-axis when the laser is blocked by half;

[0068] The shape profile of the wafer chamfering grinding wheel is described by using the following piecewise function (the profile shape of the wafer chamfering grinding wheel can be understood as a combined graph composed of straight lines and circular arcs):

[0069] wherein, K s represents the intercept of the hypotenuse straight line, (x r , y r ) represents the center coordinates of the circular arc, which varies with the serial number of the circular arc; θ represents the included angle between the profile line and the horizontal direction; y represents the coordinate system position;

[0070] In the process of grinding wheel ablation, the laser tip needs a certain depth of cut, and assuming that the depth of cut is fixed in the machining, the actual position of the laser and the grinding wheel will be raised due to the action of the circular grinding wheel, so the actual profile of the laser spot should be obtained by the deformation of the shaped profile (in the actual machining process, the laser spot is not absolutely tangent, but has a certain depth of cut. In the previous method, it is considered that the laser interpolation trajectory is the profile trajectory of the drawing. However, through theoretical calculation, it is found that the depth of cut causes the laser spot to be raised on the grinding wheel surface, causing the removal point trajectory to be deformed relative to the laser interpolation trajectory). The height Δh of the raised part is obtained by the following geometric relationship:

[0071] in 'a' represents the radius of the grinding wheel; 'a' represents the depth of cut of the laser cutting tip.

[0072] At a height of Δh, the shape profile y of the forming grinding wheel h Transformed into:

[0073] As the laser beam deflection angle (in this method, the deflection center, the A-axis rotation center, and the laser beam focal point coincide, so the rotation angle is consistent. With the laser head on the A-axis, the laser beam deflection angle is the same as the A-axis rotation angle) continues to increase, the laser beam will intersect with the outer circle of the grinding wheel, causing a light-blocking effect on the laser from the outer circle. The angle α at this point... h Calculate using the following formula:

[0074] In the formula, α h This represents the angle of rotation along the A-axis when half of the laser beam is blocked. Empirically, when half the laser beam is blocked, the energy is insufficient for further processing, and a complete blocking effect is considered to exist at this point. Therefore, αh can be considered the position of the beam centerline where the blocking effect occurs. t The width of the groove is represented by D, the diameter by x. l This indicates the distance from a certain position to the center of the groove, mainly for convenient mathematical calculations of the arc portion. It can also be changed to x-position; y is the y-axis position.

[0075] When the light-blocking effect occurs, the corresponding critical angle α2 is described as follows:

[0076] After the laser beam intersects with the outer circle of the grinding wheel, the laser beam cannot penetrate the grinding wheel material to continue irradiating the contour surface of the grinding wheel. Therefore, some of the laser energy is dispersed to the outer circle surface that should not be processed, resulting in the inability to replicate the shaped contour.

[0077] The critical angle α2 for laser beam blocking is a series of critical values ​​that vary with x. For any point on the forming profile of the grinding wheel (excluding the outer circular surface), there is always a critical angle α2 for laser beam blocking. When the angle of laser beam deflection is greater than this critical angle α2, the laser is blocked by the outer circular surface of the forming grinding wheel and cannot effectively remove the dressing allowance in the forming profile. Therefore, the condition for laser dressing of the forming grinding wheel without blocking is that the deflection angle of the laser at any point on the profile is less than the critical angle of blocking at that point, that is: α(x) < α2(x) (19)

[0078] In the range of alpha 2, because the laser is shielded, the laser power density drops sharply, and the material cannot be removed. Therefore, when the grinding wheel is profiled, different deflection angles alpha need to be used at different profiles.

[0079] It can be seen that different laser deflection angles correspond to different positions on the circular arc of the grinding wheel. In actual processing technology, the deflection resolution M required for processing the circular arc is calculated using the following formula:

[0080] Where K CW is a parameter, an integer; L g represents the length of the secant of the circular arc profile, L α is the length of the circular arc ablation corresponding to the critical angle of the hypotenuse ablation.

[0081] The beneficial effects of the present application are:

[0082] The grinding wheel laser dressing intelligent system of the present application can adjust the laser beam attitude and compensate for energy according to the profile requirements of the design drawings and the real-time changes in the shape and size of the grinding wheel blank during the dressing process. It can also achieve autonomous iteration of the entire process and upgrade the entire processing system. The method realizes automatic generation of trajectory planning through dressing parameter determination, defocusing amount compensation and laser interference avoidance. BRIEF DESCRIPTION OF DRAWINGS

[0083] Figure 1 is a schematic diagram of the overall technical scheme of the grinding wheel laser dressing intelligent system of the present application;

[0084] Figure 2 is a schematic diagram of the monitoring system monitoring the dressing process;

[0085] Figure 3 is a schematic diagram of the interference under the laser far-field model. DETAILED DESCRIPTION

[0086] As shown in Figure 1, a grinding wheel laser dressing intelligent system includes an input end, a processing system, and an output end;

[0087] The input end inputs the grinding wheel data into the processing system according to product requirements, the grinding wheel data includes the profile requirement parameters designed on the drawings, the model, and the material information and the shape and size of the grinding wheel blank; the drawings are in digital form, and the material information and the shape and size of the grinding wheel blank are obtained using various sensors, cameras, and other hardware facilities on the machine tool.

[0088] The processing system is composed of a database, a CAM system and a monitoring system; the database can realize four functions of expert prediction, parameter optimization, digital twin and machine learning; the CAM system receives the processing parameters from the database and performs two functions of laser beam posture adjustment and energy compensation based on the processing parameters; the functions of the monitoring system include judgment of the remaining amount of grinding wheel dressing, identification of tool point and abnormal situation, on the one hand, the monitoring system feeds back the real-time data of processing to the database to help upgrade the database, on the other hand, it interacts with the CAM to output the real-time position and the remaining amount information required by the CAM system, and accepts the following control of the CAM system; during the operation of the processing system, the whole process is iterated autonomously, and the whole processing system is iterated and upgraded;

[0089] The output end obtains the products generated by the processing system, including qualified grinding wheels and detection reports. The qualified grinding wheels (customers) and the processing detection results (customers) are output, and the processing cost consumption (factory) is output.

[0090] A method for laser intelligent dressing of grinding wheels, comprising the following steps:

[0091] Step 1: input the grinding wheel data into the grinding wheel laser dressing system through the input end;

[0092] Step 2: the monitoring system compares and analyzes the shape size of the grinding wheel blank and the contour requirement parameters of the drawing, and then automatically generates the tool setting point and the remaining amount information;

[0093] The monitoring system mainly analyzes the actual shape size of the blank, and compares the two after analysis. It is equivalent to finding the difference by covering together. Referring to FIG. 2. The monitoring system automatically generates the tool setting point and the remaining amount information according to the following mode:

[0094] For the judgment of the grinding wheel blank: judge the size of the remaining amount of the blank processing by visual observation and inspection of the remaining amount;

[0095] For tool point detection: adopt the trial burning method, and then judge the position of the molten pool and the laser tool tip according to visual observation; when the mechanical method is adopted, the tool setting depth and the tool setting position are judged by sound sensing and vision;

[0096] For monitoring of the processing process: according to the energy of the laser optical spectrometer, judge whether the energy absorption of the processing point is uniform; compare the actual contour observed by vision with the contour required by the drawing, and judge whether the processing is completed according to the difference between the two; according to the visual observation and edge detection synthesis algorithm, judge the roundness, runout and contour accuracy of the finished product; judge the running state of the whole equipment according to the sound and current.

[0097] The monitoring system is a whole-process monitoring system. According to different ways of vision, optics, acoustics and the like, it needs to be assembled by itself. Commonly, there is visual direct observation, using a backlight source mode. Optics such as spectrum detection, sound vibration sensing detection, tool setting and the like. It is used for judging the excess amount of the grinding wheel blank, detecting the tool setting point, judging the abnormal processing point, judging the stop of processing after completion, detecting the finished product, and monitoring the whole equipment.

[0098] Step 3: Comparing the material information and the size of the grinding wheel blank with the pre-stored trimming cases in the database, finding similar or consistent trimming cases, and then optimizing the processing parameters through expert prediction and parameter optimization functions; if there is no similar case, machine learning is carried out through the known cases to generate a set of processing parameters; the generated processing parameters are prepared for digital twinning;

[0099] The optimization of the processing parameters adopts the particle swarm PSO algorithm, which includes the following steps:

[0100] The database needs a large amount of grinding wheel trimming data for judging the grinding wheel trimming process parameters. The judgment method adopts a prediction system, parameter classification, parameter optimization, machine learning and the like to complete three tasks of laser parameter setting, grinding wheel material analysis and processing parameter determination. The laser parameter setting includes laser power (10-200W), repetition frequency (50-200kHz), pulse width (100fs-200ns), wavelength (100-1064nm) and the like, the grinding wheel material includes metal, resin, ceramic and the like and the composite binder, the heterogeneous material of diamond, CBN and the like abrasive particles, the processing technology includes galvanometer scanning, interpolation trimming, deflection laser, Deep-Cutting and the like pure laser method, electric spark, mixed powder electric spark, dry electric spark and the like pure electric spark method, and mechanical profiling, mechanical forming and the like mechanical method, and also includes the composite method of these processing technologies. All these processing parameters are used as the processing parameters.

[0101] The expert system based on the database belongs to an independent library established by itself. The induction and mining of data by the expert system need to be based on the particle swarm PSO algorithm, because the particle swarm PSO algorithm has fast convergence, which can meet the requirements of the trimming system for real-time low delay.

[0102] S301, the position and speed of the particle swarm are initialized in a random way; including the historical optimal position of a single particle and the historical optimal position of the group, the historical best fitness value of a single particle and the historical best fitness value of the group;

[0103] S302, the position and speed of the single particle are updated by using formulas (1) and (2):

[0104] The distance and direction of the next step of each particle in the PSO algorithm is a position vector, referred to as the speed of the next iteration, denoted as:

[0105] wherein, represents the position vector of the dth dimension of the particle i in the k+1th iteration; represents the position vector of the dth dimension of the particle i in the kth iteration; represents the speed vector of the dth dimension of the particle i in the k+1th iteration; represents the speed vector of the dth dimension of the particle i in the kth iteration; ω represents an inertia weight; c1 and c2 represent learning factors; r1 and r2 represent two random numbers, with a value range of 0-1; represents the historical optimal position of the dth dimension of the particle i in the kth iteration, i.e., the optimal solution searched by the ith particle (individual) in the dth dimension after the kth iteration; represents the historical optimal position of the dth dimension of the group (in the global) in the kth iteration, i.e., the optimal solution of the dth dimension of the entire particle group after the kth iteration;

[0106] S303, the fitness value of a single particle is calculated, which needs to meet the requirements of formula (3):

[0107] wherein, η m represents the fitness value of each particle; m represents the particle number; the fitness value represents the optimized target, and the fitness values of the particles together meet the tolerance requirements, so that the fitting result is considered to have better detection reliability;

[0108] S304, the historical best fitting value of a single particle is updated;

[0109] S305, the historical best fitting value and position of the group are updated;

[0110] S306, the inertia weight and the iteration number are updated:

[0111] The inertia weight is updated as formula (4) using a linearly changing inertia weight strategy:

[0112] wherein, ω max and ω min respectively represent the maximum inertia weight and the minimum inertia weight; iter represents the current iteration number; iter max represents the maximum iteration number;

[0113] S307, when the terminal condition is met, the final optimal solution is output, otherwise steps S302-S306 are repeated.

[0114] Step 4: The database generated processing parameters are sent to the CAM system, and the CAM system calculates the laser beam posture adjustment mode, laser energy compensation mode according to the profile requirements of the grinding wheel and the processing parameters, and generates the trajectory planning of the laser processing process;

[0115] Step 5: The machine tool performs interpolation motion according to the trajectory planning generated by the CAM system, and starts to dress the grinding wheel; The process of generating trajectory planning by the CAM system includes the following steps:

[0116] The CAM trajectory planning system is used to plan the multi-channel optimization of laser trajectory in dressing, real-time posture adjustment, energy compensation, and abnormal processing point compensation. The system needs to be established by itself, because there is no CAM software, algorithm, and planning system for laser dressing of grinding wheels on the market. These adjustments need to be based on the data provided by the database on the processing process of the grinding wheel material, such as single-channel ablation speed, inclination angle and forming angle relationship, grinding wheel diameter-laser original cutting depth-laser beam divergence angle correspondence, and the influence of feed rate on single-channel ablation rate, and make trajectory planning based on this.

[0117] S501, dressing parameter determination:

[0118] In tangential dressing, the laser spot is irradiated to the grinding wheel surface by pulse method, and the shape of the spot on the grinding wheel surface is approximately an ellipse; According to the literature and industry consensus, laser is used for tangential shaping and radial dressing when dressing the grinding wheel. Only tangential dressing is considered for precision and forming.

[0119] The spot overlap rate in the circumferential direction of the grinding wheel is defined as: the ratio of the overlapping area of the spot to the area of the spot under two pulses, denoted by Oc, which is described as:

[0120] Where, S overlap represents the overlapping area of the spot; S ellipse represents the area of the spot; a e and b e represent the parameters of the ellipse; l c represents the offset of the spot center in the circumferential direction;

[0121] The spot overlap rate needs to reach more than 85% to get a better grinding wheel surface quality; The grinding wheel speed when the spot overlap rate reaches 85% is given by formula (6):

[0122] Where, D is the diameter of the grinding wheel; T represents the pulse period of the laser, which is the inverse of the repetition frequency;

[0123] The spot overlap rate in the generatrix direction of the grinding wheel is defined as: the ratio of the overlapping area of the spot to the area of the spot, denoted by O Arepresents, O A is described as:

[0124] wherein, l A is the offset of the spot center on the generatrix;

[0125] Then, at the rotational speed n, the grinding wheel feed rate F is calculated by formula (8): F = nl A (8)

[0126] The dressing parameters can be determined by formula (5) to formula (8);

[0127] S502, defocus amount compensation:

[0128] The edge point of the grinding wheel is taken as the origin of the coordinates, the generatrix direction of the grinding wheel cylinder is taken as the X direction, the diameter direction is taken as the Y direction and the Z direction; before dressing, the surface cylindrical ring surface of the grinding wheel is described as:

[0129] The trajectory of the laser to be moved is described by formula (9) to construct a mathematical model of defocus amount compensation. In the formula, x, y and z are the positions of the three directions after the coordinate system is established, and the coordinate origin is at the edge of the grinding wheel; B is the thickness of the grinding wheel (equivalent to the length of the generatrix of the cylinder);

[0130] When the spot is irradiated on the material surface, it is generally within the range of the Rayleigh length, at which time the laser beam can be considered as a cylinder. In the material removal process, the laser beam vertically irradiated needs to rotate around the laser beam focal point O in the X-O-Z plane, and the state of rotating an angle α is described as:

[0131] Wherein, r represents the radius of the laser beam at a certain position; h represents the length of the position from the laser focal point; r0 represents the radius of the spot at the laser focal point (h = 0 position), and the laser beam adopts a near-field cylindrical model r always consistent with r0; L ray represents the Rayleigh length of the laser beam, and e0 is the initial defocus amount of the laser beam in the vertical state.

[0132] For the vertically irradiated laser, the focal point is on the X-O-Y plane, and as the laser beam rotates, the intersection point (i.e. the actual irradiation position) P T of the laser beam and the grinding wheel changes, in order to maintain a stable defocus amount, compensation needs to be made in the X and Z directions, and the compensation amount is:

[0133] When the defocus amount compensation is performed, it is considered that the focal point always remains on the X-O-Y plane.

[0134] S503, laser interference avoidance:

[0135] As shown in Fig. 3, when the action point of the laser beam on the material exceeds the Rayleigh length, the laser beam is considered to be a far-field laser beam composed of hyperbolas;

[0136] Under the far-field model, the radius value r b is approximately described as:

[0137] wherein, is the divergence angle of the laser beam; h b is the beam length;

[0138] In the vertical direction, the beam length h b satisfies the following geometric relationship between the height h b = h / cosα h (13)

[0139] wherein, α h represents the angle of rotation of the A-axis when the laser is blocked by half;

[0140] The shape profile of the wafer chamfering grinding wheel is described using the following piecewise function (the profile shape of the wafer chamfering grinding wheel can be understood as a combined graph composed of straight lines and circular arcs) :

[0141] wherein, K s represents the intercept of the hypotenuse straight line, (x r , y r ) represents the center coordinates of the circular arc, which varies with the serial number of the circular arc; θ represents the included angle between the profile line and the horizontal direction; y represents the coordinate system position;

[0142] In the grinding wheel ablation process, the laser tip needs a certain depth of cut, and assuming that the depth of cut is fixed in the machining, the actual position of the laser and the grinding wheel will be raised due to the action of the circular grinding wheel, so the actual profile of the laser spot should be obtained by the deformation of the shaped profile (in the actual machining process, the laser spot is not absolutely tangent, but has a certain depth of cut. In the previous method, it is considered that the laser interpolation trajectory is the profile trajectory of the drawing. However, through theoretical calculation, it is found that the depth of cut causes the laser spot to be raised on the grinding wheel surface, causing the removal point trajectory to be deformed relative to the laser interpolation trajectory). The height Δh of the raised part is obtained from the following geometric relationship:

[0143] wherein is the radius of the grinding wheel; a represents the depth of cut of the laser tip;

[0144] At the height of Δh, the shape profile yh Transformed as:

[0145] When the laser beam deflection angle (the deflection used in this method, the laser beam deflection center, the A-axis rotation center and the laser beam focal point are coincident, so the angle of rotation is consistent. The laser head is on the A-axis, and the laser beam deflection angle is the angle of rotation of the A-axis) continues to increase, the laser beam will intersect with the outer circle of the grinding wheel, and thus cause the outer circle to block the light of the laser. At this time, the angle α h The following formula is used to calculate:

[0146] In the formula, α h represents the angle of rotation of the A-axis when the laser is half blocked. Because in experience, when the laser beam is half blocked, the energy is not enough to continue processing, it is considered that there is a complete blocking effect at this time. Therefore, αh can be considered as the position of the beam center line in the position participating in the shielding effect. L t represents the width of the groove, D represents the diameter, x l represents the distance of a certain position from the center of the groove, mainly for mathematical calculation of the circular arc part. It can also be changed to x position; y is the y-axis position;

[0147] When the light blocking effect occurs, the corresponding critical angle α2 is described as:

[0148] After the laser beam intersects with the outer circle of the grinding wheel, the laser beam cannot penetrate the grinding wheel material to continue irradiating on the profile surface of the grinding wheel, so the energy of the laser is dispersed to the outer circle surface which should not be processed, and the formed profile cannot be copied.

[0149] The critical angle α2 of the grinding wheel light blocking is a series of critical values that change with x. For a point on the profile of the grinding wheel (except the outer circle surface), there is always a light blocking critical angle α2 of the laser, so that when the deflection angle of the laser beam is greater than the critical angle α2, the laser is blocked by the outer circle surface of the formed grinding wheel, and cannot effectively remove the trimming allowance in the formed profile; Therefore, the non-blocking condition of the laser trimming formed grinding wheel is: the deflection angle of the laser is less than the light blocking critical angle at a certain point on the profile, that is: α(x) < α2(x) (19)

[0150] Within the range of α2, because the laser is blocked, the laser power density decreases sharply and cannot remove the material. Therefore, when copying the grinding wheel, different deflection angles α need to be used at different profiles.

[0151] It can be seen that different laser deflection angles correspond to different positions that can be processed on the circular arc of the grinding wheel. In actual processing technology, the deflection resolution M required for processing the circular arc is calculated using the following formula:

[0152] wherein, K CW is a parameter, taking integer; L g represents the length of the secant of the circular arc profile, L α is the length of the circular arc ablation corresponding to the critical angle of bevel ablation.

[0153] Step 6: After the interpolation motion starts, the monitoring system monitors the machining process, and observes the change of the stock in real time, and then sends the real-time stock and the position information of the grinding wheel stock to the CAM system and the database through template matching and target recognition;

[0154] The CAM system compensates the abnormal machining points using the stock and the position information of the stock, and the database performs digital twin performance using the real-time position and the stock;

[0155] Step 7: After the stock meets the machining requirements, the monitoring system sends information to stop and detect;

[0156] Step 8: Output the detection result, if the product is qualified, output the qualified product and the detection report; if not, re-analyze the grinding wheel information and plan the next round of dressing;

[0157] Step 9: If the special grinding wheel is difficult to qualify after repeated dressing, use the system iteration function to optimize the system database to find more optimized parameters.

Claims

1. An intelligent system for laser dressing of a grinding wheel, characterized in that, It comprises an input end, a processing system and an output end; The input end inputs the grinding wheel data into the processing system according to product requirements, wherein the grinding wheel data comprises profile requirement parameters designed on a drawing, a model, and material information and an outer shape size of a grinding wheel blank; The processing system is composed of a database, a CAM system and a monitoring system; the database can realize four functions of expert prediction, parameter optimization, digital twinning and machine learning; the CAM system receives processing parameters from the database and performs two functions of laser beam posture adjustment and energy compensation based on the processing parameters; the functions of the monitoring system include judgment of the remaining amount of grinding wheel dressing, identification of tool points and abnormal condition judgment; on the one hand, the monitoring system feeds back real-time data of processing to the database to help upgrade the database; on the other hand, it interacts with the CAM to output real-time position and remaining amount information required by the CAM system and accepts the following control of the CAM system; during the operation of the processing system, the whole process is iterated autonomously, and the whole processing system is iterated and upgraded; The output end obtains products generated by the processing system, including qualified grinding wheels and detection reports.

2. A method of laser-intelligently dressing a grinding wheel, characterized by, It comprises the following steps: Step 1: input the grinding wheel data into the grinding wheel laser dressing intelligent system through the input end; Step 2: the monitoring system compares and analyzes the outer shape size of the grinding wheel blank and the profile requirement parameters of the drawing, and then automatically generates the tool setting point and the remaining amount information; Step 3: compare the material information and the outer shape size of the grinding wheel blank with the pre-stored dressing cases in the database, find similar or consistent dressing cases, and then optimize the processing parameters through the functions of expert prediction and parameter optimization; if there is no similar case, machine learning is performed through the known cases to generate a set of processing parameters; the generated processing parameters are prepared for digital twinning; Step 4: send the processing parameters generated by the database to the CAM system, and the CAM system calculates the laser beam posture adjustment mode and the laser energy compensation mode according to the profile requirement parameters and the processing parameters of the grinding wheel, and generates the trajectory planning of the laser processing process; Step 5: the machine tool performs interpolation motion according to the trajectory planning generated by the CAM system, and starts dressing the grinding wheel; Step 6: the monitoring system monitors the processing process after the interpolation motion starts, and observes the change of the remaining amount of the blank in real time, and then sends the real-time remaining amount and the position information of the grinding wheel blank to the CAM system and the database through template matching and target recognition; Step 7: after the remaining amount meets the processing requirements, the monitoring system sends information to stop and detect; Step 8: output the detection result, if the product is qualified, output the qualified product and the detection report; if not, re-analyze the grinding wheel information and plan the next round of dressing; Step 9: if the special grinding wheel is difficult to be qualified after repeated dressing, use the system iteration function to optimize the system database and find more optimized parameters.

3. A method of laser intelligent dressing of a grinding wheel as claimed in claim 2, wherein, In step 2, the monitoring system automatically generates the tool setting point and the remaining amount information according to the following methods: For grinding wheel blank judgment: judge the remaining amount of the blank by visual observation and inspection; For the detection of the laser tip: using the method of trial, and then according to the visual observation, the position of the molten pool and the laser tip is judged; when using the mechanical method, the depth and position of the tool are judged by sound sensing and vision; For the monitoring of the processing: according to the energy of the laser optical spectrometer, it is judged whether the energy absorption of the processing point is uniform; the actual profile observed by vision is compared with the profile required by the drawing, and whether the processing is completed is judged according to the difference between the two; the circumferential roundness, runout and profile accuracy of the finished product are judged according to the visual observation and the edge detection synthesis algorithm; the running state of the whole equipment is judged according to the sound and current.

4. The method for intelligent laser dressing of grinding wheels as described in claim 2, characterized in that, In step 3, the particle swarm optimization (PSO) algorithm is used to optimize the processing parameters, which includes the following steps: S301, the position and speed of the particle swarm are initialized in a random way: including the historical optimal position of a single particle and the historical optimal position of the group, the historical best fitness value of a single particle and the historical best fitness value of the group; S302, update the position and velocity of the single particle by using formulas (1) and (2): The distance and direction of each particle in the PSO algorithm for the next step is a position vector, referred to as the speed of the next iteration, denoted as: wherein represents the position vector of particle i in the dth dimension in the k+1th iteration; represents the position vector of particle i in the d-th dimension in the k-th iteration; Vid(k) represents the velocity vector of particle i in the d-th dimension in the k-th iteration; vi,d(k) represents the velocity vector of particle i in the dth dimension in the kth iteration; ω represents an inertial weight; c1, c2 represent learning factors; r1, r2 represent two random numbers, with a value range of 0-1; Xi(k) represents the historical optimal position of the particle i in the dth dimension in the kth iteration, that is, the optimal solution searched by the ith particle in the dth dimension after the kth iteration; Xk d represents the historical optimal position of the group in the dth dimension in the kth iteration, that is, after the kth iteration, the optimal solution of the entire particle group in the dth dimension; S303, the fitness value of the single particle is calculated, and the fitness value needs to meet the requirement of formula (3): wherein η m represents the fitness value of each particle; m represents the particle number; S304, update the historical best fitness value of a single particle; S305, update the historical best fitness value and position of the group; S306, update the inertia weight and the number of iterations: The inertia weight is updated according to the following equation (4) using a linearly varying inertia weight strategy: where ω max and ω min represent the maximum and minimum inertia weights, respectively; iter represents the current iteration number; iter max represents the maximum number of iterations. S307, when the terminal condition is met, output the final optimal solution, otherwise repeat steps S302-S306.

5. The method for intelligent laser dressing of grinding wheels as described in claim 2, characterized in that, In step 5, the process of generating trajectory planning by the CAM system includes the following steps: S501, trimming parameter determination: In the tangential dressing, the laser spot is irradiated to the surface of the grinding wheel in a pulse mode, and the shape of the spot on the surface of the grinding wheel is approximately an ellipse. The spot overlap ratio in the circumferential direction of the grinding wheel is defined as the ratio of the area of the overlapping part of the spot to the area of the spot in two pulses, and is denoted by Oc. Oc is described as: where S overlap represents the area of the light spot overlap portion; S ellipse represents the area of the light spot; a e and b e represent the parameters of the ellipse; l c represents the offset of the light spot center in the circumferential direction; The wheel speed at which the spot overlap reaches 85% is given by equation (6): In the formula, D is the diameter of the grinding wheel; T represents the pulse period of the laser, which is the reciprocal of the repetition frequency; The spot overlap ratio defining the direction of the generatrix of the grinding wheel is the ratio of the area of the overlapping part of the spots to the area of the spot, denoted by O A A is described as: ​ wherein, l A is the offset of the spot center on the busbar; Then, the grinding wheel feed rate F is calculated by formula (8) at the speed n: F = nl A (8) The trimming parameters can be determined by formula (5) to formula (8); S502, defocus amount compensation: The edge point of the grinding wheel is taken as the origin of coordinates, the generatrix direction of the grinding wheel cylinder is taken as the X direction, the diameter direction is taken as the Y direction and the Z direction; before dressing, the surface cylindrical ring surface of the grinding wheel is described as: In the formula, x, y, z are the positions of the three directions after the establishment of the coordinate system, and the coordinate origin is at the edge of the grinding wheel; B is the thickness of the grinding wheel; In the material removal process, the vertically irradiated laser beam needs to rotate in the X-O-Z plane with the laser beam focal point O as the center of rotation, and the state of rotating an angle a is described as: Wherein, r represents the radius size of the laser beam at a position; h represents the length of the position distance from the laser focus; r0represents the radius of the laser focus spot; L ray represents the Rayleigh length of the laser beam, e0is the initial defocusing amount of the laser beam in the vertical state; For the vertical irradiation of the laser, the focal point is on the X-O-Y plane, and as the laser beam rotates, the intersection P of the laser beam and the grinding wheel T Changes occur, and in order to maintain a stable defocus amount, compensation in the X and Z directions is required, with a compensation amount of: When the defocus amount compensation is performed, it is considered that the focal point always remains on the X-O-Y plane; S503, laser interference avoidance: When the interaction point of the laser beam with the material exceeds the Rayleigh length, the laser beam is considered to be a far-field laser composed of hyperbolas; under the far-field model, the radius value r at a certain height h of the beam direction is calculated using the asymptote model b The approximate description is: wherein, is the divergence angle of the laser beam; h b is the length of the light beam; In the vertical direction, the beam length h b The following geometrical relationship is satisfied between the height h and the beam length h: h b = h / cos a h (13) wherein a h represents the angle of rotation of the A-axis when the laser is half-occluded; The shape profile of the wafer bevel grinding wheel is described using a piecewise function as follows: wherein K s represents the intercept of the hypotenuse straight line, (x r , y r ) represents the center coordinates of the circular arc, which varies with the serial number of the circular arc; θ represents the included angle of the profile line with the horizontal direction; and y represents the coordinate system position. In the process of grinding wheel ablation, the laser tip needs a certain amount of cutting depth. Assuming that the cutting depth is fixed in the process, the actual position of the laser and the grinding wheel will be raised due to the circular action of the grinding wheel. The height Δh of the raised part is obtained from the following geometric relationship: wherein R is the radius of the grinding wheel; a represents the depth of the laser tip; At a height of Ah, the shape profile y of the profiled grinding wheel h is transformed into When the laser beam deflection angle continues to increase, the laser beam will intersect with the outer circle of the grinding wheel, and thus cause the outer circle to block the light of the laser. At this time, the angle α h The following formula is used for calculation: In the formula, α h represents the angle of rotation of the A-axis when the laser is blocked by half; L t represents the width of the groove, D represents the diameter, x l represents the distance of a certain position from the center of the groove; When the light blocking effect occurs, the corresponding critical angle a2 is described as: For a point on the profile of the grinding wheel, there is always a critical light blocking angle α2 of the laser, so that when the deflection angle of the laser beam is greater than the critical angle α2, the laser is blocked by the outer cylindrical surface of the formed grinding wheel and cannot effectively remove the trimming allowance in the profile; therefore, the non-light blocking condition for laser trimming of the formed grinding wheel is that the deflection angle of the laser is less than the critical light blocking angle at a certain point on the profile, that is: α(x) < α2(x) (19) In an actual machining process, the deflection resolution M required for machining a circular arc is calculated using the following equation: Wherein, K CW is a parameter, an integer; L g represents the length of the secant of the circular arc profile, L α is the length of the circular arc ablation corresponding to the critical angle of the bevel ablation.

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