A method for suppressing vibration-type ripple errors in ultra-precision polishing of industrial robots

Abstract

A method for suppressing tremor-type ripple errors in ultra-precision polishing of industrial robots, comprising: firstly collecting and measuring the removal function of the tool to be used, then determining the processing path step according to the collected spectral characteristics of the removal function, then calculating the dwell time distribution according to the predetermined step path and the surface shape error of the component to be processed measured by the laser interferometer and generating a processing program file; then determining the tremor cycle according to the processing file and the path step, then interpolating the processing program according to the set tremor cycle and modifying the z value to realize tremor-type program generation; finally, using the program with periodic tremor to process the component to be processed. The present invention does not need to add additional modules such as force control to the traditional robot small tool processing equipment. It can suppress the generation of robot periodic ripple errors by only giving periodic vibration tremor to the dwell time distribution, and does not affect the low-frequency error and high-frequency error of the component, which is of great significance to the improvement of the accuracy and reduction of the cost of industrial robot polishing equipment.

Description

Technical Field

[0001] The invention belongs to the field of optical ultra-precision machining, and in particular relates to a method for suppressing vibration-type ripple errors in ultra-precision polishing of an industrial robot. Background Art

[0002] Synchrotron radiation sources, high-energy lasers, and extreme ultraviolet lithography systems are the crown jewels of today's science and industry, and the systems require large quantities of high-precision optical components. The current mainstream processing methods include: magnetorheological polishing, ion beam polishing, jet polishing, robot small tool polishing, and high-frequency vibration polishing. Among them, robot small tool polishing suitable for large-caliber, high-steepness special surfaces has outstanding advantages such as high efficiency, flexible processing trajectory, high precision, and low cost. It has great potential in the field of optical component manufacturing with growing demand. However, due to the dynamic characteristics of the robot itself, in the actual processing process, the multi-axis error amplification effect produces terminal corrugated motion, and eventually severe periodic intermediate frequency ripples will remain on the optical surface. In extreme optical systems, intermediate frequency errors will cause small-angle scattering of the incident light, resulting in a decrease in the peak intensity of the optical system, an increase in the spot size, affecting the imaging quality, and reducing the performance of the optical system, thereby limiting the further development of industrial robot processing equipment.

[0003] In recent years, the processing ripples introduced by the robot's own motion error have been mainly alleviated by measuring and compensating with a tracker before processing or adding a force-controlled end stabilizer. However, these methods require additional equipment, and the equipment cost is close to or even higher than the industrial robot itself, which undoubtedly greatly weakens the competitiveness of industrial robot processing equipment. If the bottleneck problem of the above-mentioned industrial robot's intermediate frequency ripple amplification can be avoided from the perspective of algorithm control, it will have a great driving value for the ultra-precision processing capabilities and wide applications of industrial robots. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned existing methods for suppressing intermediate frequency errors of the polishing head of a robot gadget, and to suppress the intermediate frequency ripple errors inherent in the robot gadget by adding periodic vibration tremors. The provided method solves the problem of inherent intermediate frequency errors caused by the vibration of the robot gadget polishing equipment itself by optimizing the processing program, does not require any modification of the robot or the polishing tool head, is applicable to all robot polishing equipment, greatly reduces costs, saves time, and has obvious intermediate frequency error suppression effects.

[0005] The technical solutions to achieve the purpose of the present invention are as follows:

[0006] A method for suppressing vibration-type ripple errors in ultra-precision polishing of an industrial robot is characterized in that it comprises the following steps:

[0007] Step S1. Generate a processing program file based on the surface error distribution E(x, y) of the component to be processed and the removal function TIF. The processing program file is a point set sequence. The coordinates of the i-th point are (x i ,y i ,z i ,rx i ,ry i ,v i ), where rx is the rotation angle relative to the x-axis, ry is the rotation angle relative to the y-axis, and v is the speed;

[0008] Step S2: Determine the tremor period t, the formula is as follows:

[0009]

[0010] In the formula, m is the attenuation constant, RMS(E(x,y)) is the surface error rm s value, is the value of the Fourier transform of the removal function at the corresponding frequency f; Mid-spatial frequency (MSF) represents the intermediate frequency error, and RMS (MSF) is the intermediate frequency error of the surface shape. rm s value;

[0011] Step S3. interpolating the processing program file according to the tremor cycle t, that is, encrypting the processing program file by linear interpolation method with half of the tremor cycle t as the actual point distance to obtain an encrypted point set sequence;

[0012] Step S4. Encrypt the point set sequence z i The value is adjusted for parity and evenness to generate a processing program file for periodic vibration. The formula is as follows:

[0013]

[0014] Where A is the vibration amplitude, which is 0.3 to 2 mm;

[0015] Step S5: Processing the component to be processed according to the processing program file of the periodic vibration.

[0016] Preferably, the step S1 generates a processing program file, specifically including:

[0017] S1.1 Collect and measure the removal function TIF of the tool to be used: Under the same conditions as the process parameters to be polished, collect the surface shape changes before and after processing at a fixed point, and extract the removal function through subtraction operation; or directly use the known removal function;

[0018] S1.2 Measure the surface error distribution of the component to be processed: Use the surface error detection equipment to detect the surface error of the component to be processed, and obtain the surface error distribution E(x, y);

[0019] S1.3 Determine the machining path step distance d according to the following formula:

[0020]

[0021] S1.4 calculates the machining removal distribution Z(x,y) based on the surface error distribution obtained in S1.2. The formula is as follows:

[0022] Z(x,y)=E(x,y)+3·RMS(E(x,y))+TIF*T min

[0023] Where, T min It refers to the minimum dwell time distribution corresponding to the maximum feed rate of the machine tool under the path spacing d;

[0024] S1.5 Calculate the residence time distribution: According to the machining removal amount distribution Z(x, y) and the step size d, use a deconvolution algorithm to calculate the residence time distribution and generate a machining program file.

[0025] Preferably, the attenuation constant m The value ranges from 1 to 10.

[0026] Preferably, the linear interpolation encryption in step S3 is specifically:

[0027] At the adjacent i-th point (x i ,y i ,z i ,rx i ,ry i ,v i ) and the i+1th point (x i+1 ,y i+1 ,z i+1 ,rx i+1 ,ry i+1 ,v i+1 ) between k points (x k ,y k ,z k ,rx k ,ry k ,v k ), the formula is as follows:

[0028]

[0029] Compared with the prior art, the technical effects of the present invention are as follows:

[0030] 1) The present invention determines the path period and the vibration period by removing the distribution of the removal amount of the function characteristics, rewrites the program interpolation points based on given parameters and generates new numerical control codes, and controls the robot polishing equipment to perform ultra-precision grinding and polishing according to the vibration processing program.

[0031] 2) The present invention does not need to add additional modules such as force control to traditional robot small tool processing equipment. It can suppress the generation of periodic ripple errors of the robot by only giving periodic vibration tremor to the residence time distribution, and does not affect the low-frequency error and high-frequency error of the components. This is of great significance to the improvement of accuracy and reduction of cost of industrial robot polishing equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the method for suppressing the vibration type ripple error of the ultra-precision polishing of the industrial robot of the present invention;

[0033] Figure 2 The initial surface shape of the component to be processed in Example 1;

[0034] Figure 3 The surface shape of the component to be processed in Example 1 after the robot gadget adopts the method of the present invention;

[0035] Figure 4 is the initial surface shape of the component to be processed in Example 2;

[0036] Figure 5 The robot gadget uses conventional polishing on the surface of the component to be processed in Example 2;

[0037] Figure 6 The surface shape of the component to be processed in Example 2 after conventional polishing is compared with the surface shape of the component after the method of the present invention is adopted. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention shall not be limited.

[0039] See also Figure 1 , Figure 1 The flowchart of the method for suppressing the vibration type ripple error of the ultra-precision polishing of the industrial robot of the present invention is shown in the figure. The method for suppressing the vibration type ripple error of the ultra-precision polishing of the industrial robot comprises the following steps:

[0040] 1) Collect and measure the removal function TIF of the tool to be used: Under the same conditions as the polishing process parameters, collect the surface shape changes before and after processing at a fixed point, and extract the removal function through subtraction operation; or directly use the known removal function;

[0041] 2) Measure the surface error of the component to be processed: Use the surface detection equipment to detect the surface error of the component to be processed and obtain the surface error distribution E(x, y);

[0042] 3) Determine the machining path step d according to the frequency spectrum characteristics of the removal function: Determine the path step according to the surface error distribution E(x, y) and the removal function TIF(x, y). The specific calculation method is obtained by solving the following formula:

[0043]

[0044] In the formula, RMS(E(x,y)) is the surface error rm s value, is the value of the Fourier transform of the removal function at the corresponding frequency f; Mid-spatial frequency (MSF) represents the intermediate frequency error, and RMS (MSF) is the intermediate frequency error of the surface shape. rm s value, m is the attenuation constant.

[0045] 4) Determine the machining removal amount distribution Z(x,y) based on the surface error distribution: Since the machining principle is subtractive machining, the overall removal amount can only be positive. The actual removal amount Z(x,y) is obtained by adding a constant to the surface error E(x,y). The specific calculation method is based on the following formula:

[0046] Z(x,y)=E(x,y)+3·RMS(E(x,y))+TIF*T min

[0047] Where, T min It refers to the minimum dwell time distribution corresponding to the maximum feed rate of the machine tool under the path spacing d;

[0048] 5) Calculating the dwell time to generate a processing program file: using the removal amount generated by the above parameters and the path condition of step distance d, the dwell time distribution is calculated based on the existing deconvolution algorithm and a processing program file is generated;

[0049] 6) Determine the chatter period t: Determine the chatter period t based on the surface error distribution E(x, y) and the removal function TIF(x, y), which can be determined by solving the following formula:

[0050]

[0051] 7) Determine the vibration amplitude A: The vibration amplitude setting is selected from the range of 0.3 to 2 mm. The purpose is to be larger than the robot motion error amplitude and to meet the robot motion dynamic performance response.

[0052] 8) Interpolate the machining program according to the set tremor cycle: The machining program is a point set sequence, and the machining program point set is encrypted with half of the tremor cycle t as the actual point distance. The specific value can be determined according to the following rules:

[0053] For two adjacent points (x i ,y i ,z i ,rx i ,ry i ,v i ) and (x i+1 ,y i+1 ,z i+1 ,rx i+1 ,ry i+1 ,v i+1 ), if there is a new point (x k ,y k ) needs to be inserted, then z k ,rx k ,ry k ,v k The three values ​​can be determined by the following formula:

[0054]

[0055]

[0056]

[0057] v k =v i

[0058] 9) Adjust the parity of the z value of the encrypted point set and generate a processing program to achieve trembling processing

[0059] Effect: The specific operation is as follows:

[0060]

[0061] 10) Finally, the component to be processed is processed using a program with periodic vibration.

[0062] Embodiment 1:

[0063] The component 1 to be processed is a zinc sulfide plane component of 80mm*80mm. The initial surface shape error of the optical component to be processed is measured by laser interferometer. Figure 2The machining adopts the self-rotation motion mode, the rotation speed is 260rpm, the diameter of the polishing disc is 30mm, the removal function is collected according to the above process method, and the surface error is calculated and analyzed. The path spacing is 1mm, and the vibration parameters of the vibration period t is 1mm are determined. The program with periodic vibration is used for polishing, and the polishing time is 20min. The surface error distribution after machining is measured by laser interferometer as shown in Figure 3 As shown, the processing results show that no intermediate frequency error is generated.

[0064] Embodiment 2:

[0065] The component 2 to be processed is a zinc sulfide plane component of 80mm*80mm. The initial surface shape error of the optical component to be processed is measured by laser interferometer. Figure 4 As shown, the processing adopts the self-rotation motion mode, the speed is 260rpm, and the diameter of the polishing disk is 30mm; the component 2 to be processed is polished by a conventional robot gadget, the polishing time is 20min, and the surface error distribution after processing is measured by a laser interferometer as shown in Figure 5 As shown, it can be clearly seen from the results that there is a periodic intermediate frequency ripple error on the surface of the component.

[0066] The component 2 to be processed is processed using the same process parameters as in Example 1 using a periodic tremor program. The surface error distribution after processing is as follows: Figure 6 As shown, compared Figure 5 and Figure 6 , it can be seen that periodic vibration processing has a good improvement effect on the intermediate frequency error.

[0067] The whole result proves that the robot gadget can suppress the generation of periodic ripple errors of the robot simply by giving periodic vibration tremor to the dwell time distribution, and it also improves the medium-frequency ripple without affecting the low-frequency and high-frequency errors of the components. This is of great significance to the improvement of the accuracy and reduction of the cost of industrial robot polishing equipment.

Claims

1. A method for suppressing vibration-type ripple errors in ultra-precision polishing of industrial robots, characterized in that: The following steps are involved: Step S1. Generate a processing program file based on the surface error distribution E(x, y) of the component to be processed and the removal function TIF. The processing program file is a point set sequence. The coordinates of the i-th point are (x i ,y i ,z i ,rx i ,ry i ,v i ), where rx is the rotation angle relative to the x-axis, ry is the rotation angle relative to the y-axis, and v is the speed; Step S2: Determine the tremor period t, the formula is as follows: In the formula, m is the attenuation constant, RMS(E(x,y)) is the surface error rms value, is the value of the Fourier transform of the removal function at the corresponding frequency f; Mid-spatial frequency (MSF) represents the intermediate frequency error, and RMS (MSF) is the intermediate frequency error of the surface shape. rms value; Step S3. interpolating the processing program file according to the tremor cycle t, that is, encrypting the processing program file by linear interpolation method with half of the tremor cycle t as the actual point distance to obtain an encrypted point set sequence; Step S4. Encrypt the point set sequence z i The value is adjusted for parity and evenness to generate a processing program file for periodic vibration. The formula is as follows: Where A is the vibration amplitude, which is 0.3 to 2 mm; Step S5: Processing the component to be processed according to the processing program file of the periodic vibration.

2. The method for suppressing vibration-type ripple errors in ultra-precision polishing of industrial robots according to claim 1, characterized in that: The step S1 generates a processing program file, specifically including: S1.1 Collect and measure the removal function TIF of the tool to be used: Under the same conditions as the process parameters to be polished, collect the surface shape changes before and after processing at a fixed point, and extract the removal function through subtraction operation; or directly use the known removal function; S1.2 Measure the surface error distribution of the component to be processed: Use the surface error detection equipment to detect the surface error of the component to be processed, and obtain the surface error distribution E(x, y); S1.3 Determine the machining path step distance d according to the following formula: S1.4 calculates the machining removal distribution Z(x,y) based on the surface error distribution obtained in S1.

2. The formula is as follows: Z(x,y)=E(x,y)+3·RMS(E(x,y))+TIF*T min Where, T min It refers to the minimum dwell time distribution corresponding to the maximum feed rate of the machine tool under the path spacing d; S1.5 Calculate the residence time distribution: According to the machining removal amount distribution Z(x, y) and the step size d, use a deconvolution algorithm to calculate the residence time distribution and generate a machining program file.

3. The method for suppressing vibration-type ripple errors in ultra-precision polishing of industrial robots according to claim 1, characterized in that: Decay Constant m The value ranges from 1 to 10.

4. The method for suppressing vibration-type ripple errors in ultra-precision polishing of an industrial robot according to claim 1, characterized in that: The linear interpolation encryption in step S3 is specifically: At the adjacent i-th point (x i ,y i ,z i ,rx i ,ry i ,v i ) and the i+1th point (x i+1 ,y i+1 ,z i+1 ,rx i+1 ,ry i+1 ,v i+1 ) between k points (x k ,y k ,z k ,rx k ,ry k ,v k ), the formula is as follows:

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