A seven-point high-speed electric spindle rotary accuracy measurement system and measurement method

Abstract

The present invention discloses a seven-point high-speed electric spindle rotary accuracy measurement system and a measurement method, including: an electric spindle fixing module, an encoder fixing and fine-tuning module, a standard inspection rod, a radial laser displacement sensor fixing and fine-tuning module, and an axial laser displacement sensor fixing and fine-tuning module; a temperature sensor is provided on the electric spindle, and a total of seven displacement sensors are provided in the radial laser displacement sensor fixing and fine-tuning module and the axial laser displacement sensor fixing and fine-tuning module; after the temperature sensor determines that the spindle reaches the thermal stable state, data acquisition is started. The seven laser displacement sensors perform data acquisition on the electric spindle under the high-speed rotation state under the signal of the encoder, and the data is transmitted to the PC through a high-speed acquisition card. After the PC analyzes and calculates the data, the measurement result of the high-speed electric spindle rotary accuracy is obtained. The present invention can improve the test accuracy of the rotary error and overcome the shortcoming of the prior art that can only measure the rotary accuracy of the spindle at low speeds.

Description

Technical Field

[0001] The invention belongs to the field of machine tool testing, and particularly relates to a seven-point type high-speed electric spindle rotary accuracy measurement system and a measurement method. Background Art

[0002] Machine tools are the core production basis of the entire equipment manufacturing industry. Especially for top machine tools such as ultra-high precision machine tools and five-axis linkage high-grade CNC machine tools, their technical levels directly reflect the overall competitiveness of the manufacturing industry. The high-speed electric spindle is the core component of precision machining machine tools, and the accuracy of the high-speed electric spindle determines the machining accuracy of the machine tool.

[0003] In existing research, it is found that about 30%-70% of the machining errors of machine tools are caused by the rotational errors of the spindle. Moreover, with the development of high-speed electric spindle technology, this proportion increases with the increase of the spindle speed.

[0004] At present, the specifications for the performance of the spindle in China only include the evaluation indexes and detection methods for static performance. Among the detection methods for the spindle rotary accuracy, the standard recommended and commonly used is the dial indicator contact detection method, which can only detect the rotary accuracy of the spindle in a static state, and the detection accuracy is not high, and it has been unable to adapt to the detection of existing high-precision high-speed spindles. The remaining detection methods include two-point method, three-point method, five-point method, etc. The five-point method is developed on the basis of the two-point method, and both of them cannot separate the roundness error of the standard bar, and have relatively high requirements for the accuracy of the standard bar, with relatively low overall detection accuracy, and are limited by system errors and can only measure spindles with low rotational speeds; the three-point method is a method commonly used in radial errors at present, which can separate the roundness error, but can only detect the radial error of the spindle, and usually uses a capacitive sensor, and is limited by the sensor sampling frequency and can only detect spindles rotating at low speeds. For example, Chinese patent document with publication number CN102501137A discloses an on-line monitoring device for the radial rotary accuracy of the spindle. A monitoring ring is installed at the radial measurement position of the spindle, and 3 eddy current displacement sensors are installed on the monitoring ring. The three-point method error separation technology is used to separate the roundness error of the spindle to obtain the rotary error of the spindle, and finally the analysis result of the spindle rotary accuracy is displayed.

[0005] In the above detection methods, the sensors need to be arranged around the circumference of the electric spindle, and the sensors need to be located in the same circumferential plane. Therefore, in actual operation, the fixation, fine-tuning, and calibration of the sensors will take a lot of time, reducing the detection efficiency of the electric spindle.

[0006] Meanwhile, in the detection of the motorized spindle, the influence of temperature cannot be ignored. Temperature will affect the detection accuracy and consistency. Therefore, it is necessary to wait until the motorized spindle reaches thermal stability before measurement. The common practice is to preheat and rotate the motorized spindle according to the user manual until it reaches the thermal stability state. However, for different motorized spindles, due to their different sizes and materials, the preheating time is also different, and it is necessary to formulate the preheating time according to the user manual of the motorized spindle, which is a rather cumbersome process.

[0007] Therefore, to solve the above technical problems, it is indeed necessary to develop a measurement system for the rotational accuracy of a high-speed motorized spindle to overcome the problems in the prior art. Summary of the Invention

[0008] The present invention discloses a seven-point measurement system and method for the rotational accuracy of a high-speed motorized spindle, which can improve the test accuracy of the rotational error and overcome the disadvantage that the prior art can only measure the rotational accuracy of the spindle at low speeds.

[0009] A seven-point measurement system for the rotational accuracy of a high-speed motorized spindle includes: a motorized spindle fixing module for fixing the high-speed motorized spindle, an encoder fixing and fine-tuning module for fixing the encoder head, a standard inspection bar, a radial laser displacement sensor fixing and fine-tuning module, and an axial laser displacement sensor fixing and fine-tuning module.

[0010] A temperature sensor is provided on the high-speed motorized spindle; the radial laser displacement sensor fixing and fine-tuning module and the axial laser displacement sensor fixing and fine-tuning module are provided with a total of six axial laser displacement sensors and one radial displacement sensor; the seven laser displacement sensors are connected to a high-speed signal acquisition card through a laser displacement sensor controller.

[0011] The encoder fixing and fine-tuning module, the radial laser displacement sensor fixing and fine-tuning module, and the axial laser displacement sensor fixing and fine-tuning module are all fixed on the T-slot bottom plate, and their arrangement positions are matched with the standard inspection bar.

[0012] After the temperature sensor determines that the high-speed motorized spindle reaches the thermal stability state, it starts to collect temperature data. The seven laser displacement sensors collect the displacement data of the high-speed motorized spindle in the high-speed rotation state under the signal of the encoder. The temperature data and displacement data are transmitted to an industrial PC through the high-speed signal acquisition card, and the industrial PC analyzes and calculates the data to obtain the measurement result of the rotational accuracy of the high-speed motorized spindle.

[0013] The present invention can solve the problems in the prior art such as inaccurate measurement of the spindle rotational accuracy, small detection spindle speed range, inconsistent judgment criteria for spindle thermal stability, and difficult sensor fine-tuning, and realize the accurate measurement of the rotational accuracy of the motorized spindle during high-speed rotation.

[0014] The described electric spindle fixing module includes a T-slot cast iron plate, an electric spindle clamp, and a conversion adjustment plate. Among them, the high-speed electric spindle is fixed on the electric spindle clamp, the electric spindle clamp is fixed on the conversion adjustment plate by bolts, and the conversion adjustment plate is fixed on the T-slot cast iron plate by T-slot special nuts and bolts.

[0015] The number of the described temperature sensors is three, which are fixed on the front bearing, rear bearing, and rotor housing of the high-speed electric spindle by magnetic attraction, and their signals are connected to the high-speed acquisition card through cables.

[0016] The described encoder fixing and fine-tuning module includes an encoder head support plate, an encoder XY-axis displacement platform, an encoder head mounting connection plate, an encoder head, and an encoder magnetic ring.

[0017] The encoder magnetic ring is fixed at the bottom end of the standard inspection rod by interference fit connection; the encoder head is fixed on the encoder head mounting connection plate by bolts; the encoder head mounting connection plate is connected to the encoder XY-axis displacement platform by bolts; the encoder XY displacement platform is connected to the encoder head support plate by bolts; the encoder head support plate is fixed on the T-slot bottom plate by nuts and bolts.

[0018] The described radial laser displacement sensor fixing and fine-tuning module includes two sets of modules with the same structure. Each set includes a radial sensor support plate, a fixed guide ring fixed on the radial sensor support plate by bolts, and three radial laser displacement sensor modules installed on the fixed guide ring. The fixed guide ring is provided with a circular angle scale.

[0019] Among them, the described radial laser displacement sensor module includes a radial laser displacement sensor, a radial sensor mounting connection plate, a radial sensor XY-axis displacement platform, a circular fixed upper block, a conversion connection plate, and a circular fixed lower block. The radial laser displacement sensor is fixed on the radial sensor mounting connection plate by bolts, the radial sensor mounting connection plate is connected to the radial sensor XY-axis displacement platform by bolts, the radial sensor XY-axis displacement platform is connected to the circular fixed lower block by bolts, the circular fixed upper block and the circular fixed lower block are matched by long fixing bolts, and a fit is formed with the fixed guide ring through the intermediate groove formed by their connection, and the fixing and clamping with the fixed guide ring are realized by tightening the bolts.

[0020] The described axial displacement sensor fixing and fine-tuning module includes an axial sensor support plate, an axial sensor XY-axis displacement platform, an axial sensor mounting connection plate, and an axial laser displacement sensor.

[0021] The axial laser displacement sensor is fixed to the axial sensor mounting connecting plate by bolts. The axial sensor mounting connecting plate is connected to the axial sensor XY-axis displacement platform by bolts, and the axial sensor XY-axis displacement platform is connected to the axial sensor support plate by bolts. The laser beam of the axial laser displacement sensor is directed at the end face of the standard inspection rod.

[0022] In the present invention, the laser displacement sensor controller, the high-speed signal acquisition card, and the supporting PC form a signal acquisition module. The laser displacement sensor controller is connected to the laser displacement sensor through a cable, controls the laser displacement sensor to collect data and obtains the data. The output end of the controller is connected to the high-speed signal acquisition card through a cable. The DI port of the high-speed signal acquisition card is connected to the encoder head through a cable, and the AI port is connected to the output end of the controller. The signal of the controller is read according to the signal of the encoder head, and the analog signal collected from the controller is converted into a digital signal, and then the signal is transmitted to the PC through a cable.

[0023] The supporting data acquisition and analysis software is installed on the PC. Its functions include displaying, saving, and analyzing the data of the laser displacement sensor and the temperature sensor collected by the high-speed acquisition card, calculating the radial error, tilt error, and axial error, displaying and outputting the polar coordinate curves of the radial error, tilt error, and axial error, and generating a test report.

[0024] The said standard inspection rod is a standard part. One end is a high-precision cylinder, and its precision requirement is controlled within 0.001 mm. The other end is a tool head that fits with the measured high-speed electric spindle, and it is connected to the electric spindle through the tool head.

[0025] A method for measuring the rotational accuracy of a seven-point high-speed electric spindle uses the above-mentioned seven-point high-speed electric spindle rotational accuracy measurement system, and specifically includes the following steps:

[0026] 1) Start six radial laser displacement sensors and one axial laser displacement sensor for sensor preheating;

[0027] 2) Fine-tune all laser displacement sensors to calibrate the sensors;

[0028] 3) Record the included angles and distances between the sensors;

[0029] 4) Start the measured electric spindle;

[0030] 5) The electric spindle starts to rotate at the test speed;

[0031] 6) Collect temperature data, observe the readings, and wait for the electric spindle to reach thermal stability;

[0032] 7) Start the data acquisition device, and the acquisition card collects data according to the encoder signal;

[0033] 8) Calculate the radial error of the high-speed motorized spindle at the test speed;

[0034] 9) Calculate the tilt error of the high-speed motorized spindle at the test speed.

[0035] 10) Calculate the axial error of the high-speed motorized spindle at the test speed.

[0036] 11) Display the polar coordinate curve graphs of the radial error, tilt error, and axial error, and generate a test report;

[0037] 12) Determine whether to conduct tests at different speeds. If so, return to step 5 to adjust the spindle speed. If not, proceed to the next step;

[0038] 13) Stop the spindle rotation and turn off the sensors.

[0039] In step 1), the preheating of the sensor is to turn on the sensor power supply, adjust the laser to the on mode, and enable the sensor to emit laser light and operate normally for 30 minutes.

[0040] In step 2), the specific steps for fine-tuning and calibrating the radial sensor are as follows:

[0041] 2-1) Adjust the X-axis direction knob of the XY-axis displacement platform of the radial sensor, and at the same time observe the change in the reading on the displacement sensor controller. Adjust to the position where the reading is the smallest, and lock the X-axis locking screw.

[0042] 2-2) Adjust the Y-axis direction knob of the XY-axis displacement platform of the radial sensor, and at the same time observe the change in the reading on the displacement sensor controller and the change in the sensor indicator light. Adjust until the first two digits of the reading display the standard measurement distance value of the sensor, and the sensor indicator light turns green. Then lock the Y-axis locking screw.

[0043] The specific steps for fine-tuning and calibrating the axial sensor are as follows:

[0044] 2-3) Adjust the X-axis direction knob of the XY-axis displacement platform of the axial sensor to adjust the laser beam of the sensor to align with the center of the end face of the standard inspection rod, and lock the X-axis locking screw.

[0045] 2-4) Adjust the Y-axis direction knob of the XY-axis displacement platform of the axial sensor, and at the same time observe the change in the reading on the displacement sensor controller and the change in the sensor indicator light. Adjust until the first two digits of the reading display the standard measurement distance value of the sensor, and the sensor indicator light turns green. Then lock the Y-axis locking screw.

[0046] In step 3), the specific method for recording the included angles between sensors is as follows: First, record the scale readings of the six sensor modules on the circular protractor, and then perform subtraction. α1 and β1 are the included angles between sensors A1 and A2, B1 and B2, and α2 and β2 are the included angles between sensors A1 and A3, B1 and B3.

[0047] The specific method for recording the distance between sensors is as follows: First, determine two measurement planes according to the two sets of radial sensor lasers, and then use a scale to measure the vertical distance between the two planes and record it as l.

[0048] In step 6), waiting for the electric spindle to reach thermal stability specifically means observing the readings of the temperature sensors. If the readings of the three temperature sensors remain within 0.5 °C within 5 minutes, it is determined that the electric spindle has reached the thermal stability state.

[0049] In step 7), the specific process of data acquisition is as follows: The encoder magnetic ring is evenly distributed around the circumference with 1024 magnetic poles. When each magnetic pole passes through the encoder head, the encoder head will generate a low level and send out a signal. The signal is transmitted through a cable to the DI port of the high-speed acquisition card. Each time the acquisition card receives a signal from the encoder, it starts an acquisition signal program to acquire the signal of the laser displacement sensor once.

[0050] The specific process of step 8) is as follows:

[0051] 8-1) Read the data a1(i), a2(i), a3(i) collected by the three radial laser displacement sensors A1, A2, A3 on the A-group radial laser displacement sensor fixing and fine-tuning module

[0052] 8-2) Calculate the number of sampling points at sensor intervals: where N is the number of magnetic poles of the encoder magnetic ring, that is, the number of sensor samplings per revolution of the spindle;

[0053] 8-3) Construct a signal expression matrix: S = Ae, where S = [a1(i), a2(i), a3(i)] T , which is a column vector composed of the outputs a1(i), a2(i), a3(i) of sensors A1, A2, A3; e = [r(i), r(i + m1), r(i + m2), x(i), y(i)] T , which is a column vector composed of the original profile shape error and rotational error motion of the measured cross-section; is the output coefficient matrix of the measurement sensor;

[0054] 8 - 4) Introduce the weight coefficient row vector C = (c1, c2, c3), left - multiply the signal expression matrix, we get: CS = CAe, and expand it to construct the combined signal: S(i) = c1a1(i)+c2a2(i)+c3a3(i) = c1r(i)+c2r(i + m1)+c3r(i + m2)+(c1 + c2cosα1 + c3cosα2)x(i)+(c2sinα1 + c3sinα2)y(i)

[0055] 8 - 5) Take c1 = 1, and make the coefficients of x(i) and y(i) equal to 0, we get:

[0056] 8 - 6) Substitute c1, c2, and c3 into the combined signal, we get:

[0057] 8 - 7) Do Fourier transform on both ends and simplify to get: Denote Then

[0058] 8 - 8) Do inverse Fourier transform to get: r(i) = idft(R(t))

[0059] 8 - 9) Calculate the radial run - out motions in the x and y directions respectively as: x(i) = a1(i)-r(i), The total radial run - out motion function is:

[0060] 8 - 10) Calculate the radial run - out value: ε rad = δ(i) max -δ(i) min , where δ(i) max is the maximum value of the spindle radial run - out motion, and δ(i) min is the minimum value of the spindle radial run - out motion.

[0061] The specific process of step 9) is as follows:

[0062] 9 - 1) Use the data a1(i), a2(i), a3(i) and b1(i), b2(i), b c (i) collected by the radial laser displacement sensors A1, A2, A3 and B1, B2, B3 on the two - group radial laser displacement sensor fixing and fine - tuning modules, and calculate the total radial run - out motion functions δ A (i) and δ B (i) of group A and group B through the same steps as in step 8);

[0063] 9-2) Calculate the tilt error motion function: where l is the vertical distance between the measurement planes of two sets of radial sensors;

[0064] 9-3) Calculate the tilt error value: γ tilt = max(γ(i)).

[0065] The specific process of step 10) is as follows:

[0066] 10-1) Read the data c(i) collected by the axial laser displacement sensor A;

[0067] 10-2) Calculate the axial error motion function: ζ(i) = c(i);

[0068] 10-3) Calculate the axial error value: Calculate the radial runout error value: ε axi = ζ(i) max - ζ(i) min where ζ(i) max is the maximum value of the spindle axial runout error motion, and ζ(i) min is the minimum value of the spindle axial runout error motion.

[0069] In step 11), the polar coordinate curve of the radial error in the polar coordinate curve graph is drawn according to the radial runout error motion function (i.e., ); the polar coordinate curve of the tilt error is drawn according to the tilt error motion function (i.e., ); the polar coordinate curve of the axial error is drawn according to the axial error motion function (i.e., ζ(i) = c(i)).

[0070] The present invention uses high-precision, high-sampling-frequency high-performance laser displacement sensors, temperature sensors, high-precision standard inspection rods, and high-performance data acquisition cards to achieve accurate measurement of the rotational accuracy of high-speed motor spindles.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] 1. The present invention uses high-performance laser displacement sensors in the field of measuring the rotational accuracy of motor spindles, improving the test accuracy and overcoming the drawback of the prior art that can only measure the rotational accuracy of spindles at low speeds. It can measure the rotational accuracy of high-speed motor spindles at speeds above 10,000 r / min.

[0073] 2. The present invention uses the 7-point method to measure the rotational accuracy. Compared with the prior art, it can measure the radial error, tilt error, and axial error of the high-speed electric spindle simultaneously through one measurement. Moreover, it can separate the roundness error and eccentricity error of the standard test bar during the measurement, improving the test accuracy of the rotational error.

[0074] 3. The present invention adopts a fixture with an annular guide rail shape. Compared with the traditional three-point method fixture, it can better ensure that the three sensors in the same group are in the same plane and the same circumference, and it is more convenient to adjust the angles and positions between the sensors.

[0075] 4. The test module and the spindle installation and fixation module of the present invention are independent of each other. The test module can be conveniently transferred to any other electric spindle test bench or machine tool for testing the electric spindle, enabling in-machine testing of the electric spindle.

[0076] 5. The present invention uses a temperature sensor to collect data to determine whether the spindle reaches the thermal stability state, unifying the discrimination criteria for the thermal stability state of different spindles and improving the detection efficiency.

[0077] 6. The present invention has developed a set of related data acquisition and data analysis software, which can more conveniently perform operations such as test data acquisition and data analysis. The test results are presented in the form of a polar coordinate curve graph, which is more intuitive. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 is the overall structural schematic diagram of a seven-point type high-speed electric spindle rotational accuracy measurement system of the present invention;

[0079] Figure 2 is the schematic diagram of the electric spindle fixation module and the temperature sensor in the present invention;

[0080] Figure 3 is the overall installation and cooperation schematic diagram of the laser displacement sensor fixation and fine-tuning module and the encoder fixation and fine-tuning module in the present invention;

[0081] Figure 4 is the schematic diagram of the encoder fixation and fine-tuning module in the present invention;

[0082] Figure 5 is the schematic diagram of a set of radial laser displacement sensor fixation and fine-tuning modules in the present invention;

[0083] Figure 6 is the installation and cooperation schematic diagram of a single laser displacement sensor in the radial laser displacement sensor fixation and fine-tuning module of the present invention;

[0084] Figure 7 is the schematic diagram of the axial laser displacement sensor fixation and fine-tuning module in the present invention;

[0085] Figure 8 This is a flowchart of a method for measuring the rotational accuracy of a seven - point high - speed motorized spindle according to the present invention;

[0086] Figure 9 This is a schematic diagram of the included angle of the measurement sensors in step 3) of the present invention;

[0087] Figure 10 This is a schematic diagram of the thermal stability judgment and displacement signal acquisition window of the supporting software in the present invention;

[0088] Figure 11 This is a schematic diagram of the test result window of the supporting software in the present invention. Detailed implementation manners

[0089] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0090] As Figure 1 shown, a seven - point high - speed motorized spindle rotational accuracy measurement system includes a motorized spindle fixing module 1, an encoder fixing and fine - tuning module 2, a standard inspection bar 3, a radial laser displacement sensor and fine - tuning module 4, an axial laser displacement sensor fixing and fine - tuning module 5, a T - slot bottom plate 6, a marble platform 7, a laser displacement sensor controller 8, a high - speed signal acquisition card 9, and an industrial PC 10.

[0091] The motorized spindle fixing module 1 and the T - slot bottom plate 6 are fixed on the marble platform 7 with threaded holes by bolts. The laser displacement sensor controller 8 is connected to seven laser displacement sensors through cables. The laser displacement sensors and the encoder read head are connected to the high - speed signal acquisition card 9 through cables, and the high - speed signal acquisition card 9 is connected to the industrial PC 10 through cables.

[0092] The industrial PC 10 is installed with signal acquisition software supporting the high - speed acquisition card 9. This software can realize a series of functions such as data acquisition, processing, analysis, and display, and can control various parameters of data acquisition and start / stop.

[0093] As Figure 2As shown in the figure, the electric spindle fixing module 1 of the present invention is used to fix the high-speed electric spindle 101, and specifically includes: an electric spindle fixing clamp seat 103, a conversion and adjustment plate 106, and a fixed T-slot cast iron plate 107. The conversion and adjustment plate 103 is fixed on the fixed T-slot cast iron plate 104 through T-slot special nuts and bolts. The electric spindle fixing clamp seat 102 is fixed on the conversion and adjustment plate 103 through bolts. The high-speed electric spindle 101 is fixed on the electric spindle clamp seat 102 and is clamped and fixed through the fastening bolts on the electric spindle clamp seat 102. At the tail of the standard inspection rod 3, there is a standard tool holder matching the electric spindle, which is clamped and fixed with the tapered hole of the high-speed electric spindle 101.

[0094] The three temperature sensors of the present invention are fixed on the high-speed electric spindle 101 by magnetic attraction. The temperature sensor 102 is fixed at the rear bearing of the electric spindle, the temperature sensor 104 is fixed at the rotor of the electric spindle, and the temperature sensor 105 is fixed at the front bearing of the electric spindle.

[0095] As Figure 3 shown in the figure, the encoder fixing and fine-tuning module 2, the radial laser displacement sensor fixing and fine-tuning module 4 (including two groups of 4A and 4B), and the axial laser displacement sensor fixing and fine-tuning module 5 are fixed on the T-slot bottom plate 6 through T-slot special nuts and bolts, and the arrangement positions are matched with the standard inspection rod 3.

[0096] As Figure 4 shown in the figure, the encoder fixing and fine-tuning module 2 includes an encoder head support plate 201, an encoder XY-axis displacement platform 202, an encoder head mounting connecting plate 203, an encoder head 204, and an encoder magnetic ring 205. The encoder magnetic ring 205 is fixed at the bottom end of the standard inspection rod 3 and is connected by interference fit. The encoder head 204 is fixed on the encoder head mounting connecting plate 203 through bolts; the encoder head mounting connecting plate 203 is connected to the encoder XY-axis displacement platform 202 through bolts; the encoder XY-axis displacement platform 202 is also connected to the encoder head support plate 201 through bolts.

[0097] As Figure 3 shown in the figure, the radial laser displacement sensor fixing and fine-tuning module 4 is composed of two groups of 4A and 4B, and the composition and structure of the two groups are the same. As Figure 5 shown in the figure, a group of radial laser displacement sensor fixing and fine-tuning modules includes a radial sensor support plate 401, a fixed guide ring 402, an annular angle scale 403, a radial laser displacement sensor module 404, a radial laser displacement sensor module 405, and a radial laser displacement sensor module 406. The composition and structure of the three radial laser displacement sensor modules are the same, and they are installed on the fixed guide ring 402 through fixing devices; the fixed guide ring 402 is fixed on the radial sensor support plate 401 through bolts.

[0098] AsFigure 6 As shown in the figure, a radial laser displacement sensor module includes a radial laser displacement sensor 4061, a radial sensor mounting connecting plate 4062, a radial sensor XY-axis displacement platform 4063, fixing bolts 4064, fixing bolts 4065, an annular fixing upper block 4066, a conversion connecting plate 4067, and an annular fixing lower block 4068. The radial laser displacement sensor 4061 is fixed to the radial sensor mounting connecting plate 4062 by bolts, the radial sensor mounting connecting plate 4062 is connected to the radial sensor XY-axis displacement platform 4063 by bolts, the radial sensor XY-axis displacement platform 4063 is connected to the annular fixing lower block 4068 by bolts, and the annular fixing upper block 4066 and the annular fixing lower block 4068 are matched by the fixing bolts 4064 and fixing bolts 4065. A mating is formed with the fixed guide ring 402 through the intermediate groove formed by their connection, and the fixing and clamping with the fixed guide ring are achieved by tightening the bolts.

[0099] As Figure 7 shown in the figure, the axial displacement sensor fixing and fine-tuning module 5 includes an axial sensor support plate 501, an axial sensor XY-axis displacement platform 502, an axial sensor mounting connecting plate 503, and an axial laser displacement sensor 504. The axial laser displacement sensor 504 is fixed to the axial sensor mounting connecting plate 503 by bolts, the axial sensor mounting connecting plate 503 is connected to the axial sensor XY-axis displacement platform 502 by bolts, and the axial sensor XY-axis displacement platform 502 is connected to the axial sensor support plate 501 by bolts. The laser beam of the laser displacement sensor can be directed at the end face of the standard inspection rod 3.

[0100] As Figure 8 shown in the figure, a seven-point high-speed electric spindle rotational accuracy measurement method includes the following steps:

[0101] S01, Start the laser displacement sensor and perform sensor preheating. The sensor preheating is to turn on the sensor power supply, adjust the laser to the on mode, and enable the sensor to emit laser and operate normally for 30 minutes.

[0102] S02, Fine-tune and calibrate the sensor. The fine-tuning and calibration of the sensor include fine-tuning and calibrating 7 radial sensors and 1 axial sensor.

[0103] The specific steps for fine-tuning and calibrating the radial sensor are as follows:

[0104] (1) Adjust the X-axis direction knob of the radial sensor XY-axis displacement platform, and at the same time observe the change in the reading on the displacement sensor controller. Adjust to the position with the minimum reading and lock the X-axis locking screw.

[0105] (2) Adjust the Y-axis direction knob of the radial sensor XY-axis displacement platform, and at the same time observe the readings on the displacement sensor controller and the changes in the sensor indicator lights. Adjust until the first two digits of the reading display the standard measurement distance value of the sensor, and the sensor indicator light turns green, then lock the Y-axis locking screw.

[0106] The specific steps for the fine-tuning and calibration of the axial sensor are as follows:

[0107] (1) Adjust the X-axis direction knob of the axial sensor XY-axis displacement platform until the laser beam of the sensor is aligned with the center of the end face of the standard inspection rod, and then lock the X-axis locking screw.

[0108] (2) Adjust the Y-axis direction knob of the axial sensor XY-axis displacement platform, and at the same time observe the readings on the displacement sensor controller and the changes in the sensor indicator lights. Adjust until the first two digits of the reading display the standard measurement distance value of the sensor, and the sensor indicator light turns green, then lock the Y-axis locking screw.

[0109] S03. Record the included angle and distance between the sensors.

[0110] Specifically, to record the included angle between the sensors: First, record the scale readings of the six sensor modules on the circular angle scale, and then subtract them.

[0111] As Figure 9 shown, α1 is the included angle between sensors A1 and A2, and α2 is the included angle between sensors A1 and A3; similarly, β1 is the included angle between sensors B1 and B2, and β2 is the included angle between sensors B1 and B3.

[0112] Specifically, to record the distance between the sensors: First, determine two measurement planes according to the lasers of the two groups of radial sensors, and then use a scale to measure the vertical distance between the two planes and record it as l.

[0113] S04. Start the spindle to be measured.

[0114] S05. The spindle rotates at the test speed.

[0115] S06. Collect temperature data and observe the readings, waiting for the spindle to reach thermal stability. Specifically, observe the readings of the temperature sensors. If the readings of the three temperature sensors remain within 0.5 °C within 5 minutes, it is determined that the spindle has reached the thermal stability state.

[0116] S07. Start the data acquisition device, and the acquisition card collects data according to the encoder signal.

[0117] Specifically: The encoder magnetic ring is evenly distributed with 1024 magnetic poles around the circumference. When each magnetic pole passes through the encoder head, the encoder head will generate a low level and send out a signal. The signal is transmitted through the cable to the DI port of the high-speed acquisition card. Each time the acquisition card receives a signal from the encoder, it starts an acquisition signal program to acquire the signal of the laser displacement sensor once.

[0118] S08, calculate the radial error of the high-speed electric spindle at the test speed. The specific steps are as follows:

[0119] (1) Read the data a1(i), a2(i), a3(i) collected by the radial laser displacement sensors A1, A2, A3

[0120] (2) Calculate the number of points sampled at intervals of the sensors: where N is the number of magnetic poles of the encoder magnetic ring, that is, the number of samples taken by the sensor per revolution of the spindle

[0121] (3) Construct the signal expression matrix: S = Ae, where S = [a1(i), a2(i), a3(i)] T , which is the column vector composed of the outputs a1(i), a2(i), a3(i) of the sensors A1, A2, A3; e = [r(i), r(i + m1), r(i + m2), x(i), y(i)] T , which is the column vector composed of the original profile shape error and the rotational error motion of the measured cross-section; is the output coefficient matrix of the measurement sensor.

[0122] (4) Introduce the weight coefficient row vector C = (c1, c2, c3), and left multiply the signal expression matrix to get: CS = CAe, and expand it to construct the combined signal: S(i) = c1a1(i) + c2a2(i) + c3a3(i) = c1r(i) + c2r(i + m1) + c3r(i + m2) + (c1 + c2cosα1 + c3cosα2)x(i) + (c2sinα1 + c3sinα2)y(i)

[0123] (5) Take c1 = 1, and make the coefficients of x(i) and y(i) equal to 0, we can get:

[0124] (6) Substitute c1, c2, c3 into the combined signal, we can get:

[0125] (7) Perform Fourier transform on both ends and simplify to get: Denote Then

[0126] (8) Perform the inverse Fourier transform to obtain: r(i) = idft(R(t))

[0127] (9) Calculate the radial runout error motions in the x and y directions respectively as: x(i) = a1(i) - r(i), The total radial runout error motion function is:

[0128] (10) Calculate the radial runout error value: ε rad = δ(i) max - δ(i) min , where δ(i) max is the maximum value of the spindle radial runout error motion, and δ(i) min is the minimum value of the spindle radial runout error motion

[0129] S09. Calculate the tilt error of the high-speed motorized spindle at the test speed. The specific steps are as follows:

[0130] (1) The data a1(i), a2(i), a3(i) and b1(i), b2(i), b3(i) collected by using the radial laser displacement sensors A1, A2, A3 and B1, B2, B3 are used to calculate the total radial runout error motion functions δ A (i) and δ B (i)

[0131] (2) Calculate the tilt error motion function: where l is the vertical distance between the measurement planes of the two groups of radial sensors

[0132] (3) Calculate the tilt error value: γ tilt = max(γ(i))

[0133] S10. Calculate the axial error of the high-speed motorized spindle at the test speed. The specific steps are as follows:

[0134] (1) Read the data c(i) collected by the axial laser displacement sensor A

[0135] (2) Calculate the axial error motion function: ζ(i) = c(i)

[0136] (3) Calculate the axial error value: Calculate the radial runout error value: ε axi = ζ(i) max - ζ(i) min , where ζ(i) max is the maximum value of the spindle axial runout error motion, and ζ(i) minIt is the minimum value of the axial rotational error motion of the main shaft

[0137] S11. Display and output the polar coordinate curves of the radial error, tilt error, and axial error, and generate a test report.

[0138] Among them, the polar coordinate curve of the radial error is drawn according to the radial rotational error motion function (i.e., ); among them, the polar coordinate curve of the tilt error is drawn according to the tilt error motion function (i.e., ); among them, the polar coordinate curve of the axial error is drawn according to the axial error motion function (i.e., ζ(i) = c(i)).

[0139] S12. Determine whether to perform tests at different rotational speeds. If so, return to step 5 to adjust the rotational speed of the main shaft; if not, proceed to the next step.

[0140] S13. Stop the rotation of the main shaft and turn off the sensor.

[0141] As Figure 10 shown, the operation of the thermal stability judgment software is to click the "Start Detection" button, and the temperature sensor readings will be displayed in real time in the left window. When the "Thermal Stability Status Indicator" turns green, it indicates that the motorized spindle has reached the thermal stability state.

[0142] As Figure 10 shown, the operation of the displacement signal acquisition software is to first click on the physical channel, numerical range, sampling frequency setting, number of samples per channel, and file save location to set the required parameters, and then click the "Start Acquisition" button. The readings of the 7 displacement sensors will be displayed in real time in the left window, and the acquired data will be saved in real time to the set location; click the "Stop Acquisition" button to stop the program.

[0143] As Figure 11 shown, the operation of the software for saving test results is to first click on the file save location to set the file save location, and then click the "Save File" button to save the displayed radial error, tilt error, and axial error to the set location.

[0144] The above-described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements, and equivalent replacements made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the rotational accuracy of a seven-point high-speed motorized spindle, which uses a seven-point high-speed motorized spindle rotational accuracy measurement system, characterized in that, The described seven-point high-speed electric spindle rotation accuracy measurement system includes: an electric spindle fixing module (1) for fixing the high-speed electric spindle (101), an encoder fixing and fine-tuning module (2) for fixing the encoder head, a standard inspection rod (3), a radial laser displacement sensor fixing and fine-tuning module (4), and an axial laser displacement sensor fixing and fine-tuning module (5); A temperature sensor is provided on the high-speed electric spindle (101); the radial laser displacement sensor fixing and fine-tuning module (4) and the axial laser displacement sensor fixing and fine-tuning module (5) are provided with a total of six radial laser displacement sensors and one axial laser displacement sensor; the seven laser displacement sensors are connected to a high-speed signal acquisition card (9) through a laser displacement sensor controller (8); The encoder fixing and fine-tuning module (2), the radial laser displacement sensor fixing and fine-tuning module (4), and the axial laser displacement sensor fixing and fine-tuning module (5) are all fixed on the T-slot bottom plate (6), and the arrangement positions are matched with the standard inspection rod (3); After the temperature sensor determines that the high-speed electric spindle reaches the thermal stable state, it starts to collect temperature data. The seven laser displacement sensors collect displacement data of the high-speed electric spindle in the high-speed rotation state under the signal of the encoder. The temperature data and displacement data are transmitted to the industrial PC (10) through the high-speed signal acquisition card (9). The industrial PC (10) analyzes and calculates the data to obtain the high-speed electric spindle rotation accuracy measurement result; The described seven-point high-speed electric spindle rotation accuracy measurement method includes the following steps: 1) Start six radial laser displacement sensors and one axial laser displacement sensor for sensor preheating; 2) Fine-tune all laser displacement sensors to calibrate the sensors; 3) Record the included angles and distances between the sensors; 4) Start the electric spindle to be measured; 5) The electric spindle starts to rotate at the test speed; 6) Collect temperature data, observe the readings, and wait for the electric spindle to reach thermal stability; 7) Start the data acquisition device, and the acquisition card performs data acquisition according to the encoder signal; 8) Calculate the radial error of the high-speed electric spindle at the test speed; the specific process is as follows: 8-1) Read the data a1(i), a2(i), a3(i) collected by the three radial laser displacement sensors A1, A2, A3 on the A group of radial laser displacement sensor fixing and fine-tuning modules; 8-2) Calculate the number of points for sensor interval sampling: where N is the number of magnetic poles of the encoder magnetic ring, which is also the number of sensor samplings per revolution of the main shaft; (8-3) Construct the signal expression matrix: S = Ae, where S = [a1(i), a2(i), a3(i)] T , which is a column vector composed of the outputs a1(i), a2(i), and a3(i) of sensors A1, A2, and A3; e = [r(i), r(i + m1), r(i + m2), x(i), y(i)] T , which is a column vector composed of the original profile shape error and rotational error motion of the measured cross-section; is the output coefficient matrix of the measurement sensor; 8-4) Introduce the weight coefficient row vector C=(c1, c2, c3), left multiply the signal expression matrix, and get: CS = CAe, and expand to construct the combined signal: S(i)=c1a1(i)+c2a2(i)+c3a3(i)=c1r(i)+c2r(i + m1)+c3r(i + m2)+(c1 + c2cosα1 + c3cosα2)x(i)+(c2sinα1 + c3sinα2)y(i); 8 - 5) Take c1 = 1, set the coefficients of x(i) and y(i) to 0, and obtain: (8-6) Substitute c1, c2, and c3 into the combined signal to obtain: Perform Fourier transforms on both ends and simplify to obtain: Record Then 8-8) Perform the inverse Fourier transform to get: r(i)=idft(R(t)); 8 - 9) Calculate the radial runout error motions in the x and y directions respectively as: x(i) = a1(i) - r(i), The total radial runout error motion function is: (8 - 10) Calculate the radial runout error value: ε rad = δ(i) max - δ(i) min , where δ(i) max is the maximum value of the spindle radial runout motion, and δ(i) min is the minimum value of the spindle radial runout motion; 9) Calculate the tilt error of the high-speed electric spindle at the test speed; 10) Calculate the axial error of the high-speed electric spindle at the test speed; 11) Display a polar coordinate curve graph showing the radial error, tilt error, and axial error, and generate a test report; 12) Determine whether to conduct tests at different rotational speeds. If so, return to step 5 to adjust the spindle speed. If not, proceed to the next step; 13) Stop the spindle rotation and turn off the sensor.

2. The method for measuring the rotational accuracy of the seven-point high-speed electric spindle according to claim 1, characterized in that The electric spindle fixing module (1) includes a T-slot cast iron plate (107), an electric spindle clamp (103), and a conversion and adjustment plate (106). Among them, the high-speed electric spindle (101) is fixed on the electric spindle clamp (103), the electric spindle clamp (103) is fixed on the conversion and adjustment plate (106) by bolts, and the conversion and adjustment plate (106) is fixed on the T-slot cast iron plate (107) by T-slot special nuts and bolts.

3. The seven-point high-speed electric spindle rotation accuracy measurement method according to claim 1, characterized in that, The number of the temperature sensors is three, and they are fixed on the front bearing, rear bearing, and rotor housing of the high-speed electric spindle (101) by magnetic attraction. Their signals are connected to a high-speed acquisition card through cables.

4. The method for measuring the rotational accuracy of a seven-point high-speed electric spindle according to claim 1, characterized in that The encoder fixing and fine-tuning module (2) includes an encoder head support plate (201), an encoder XY-axis displacement platform (202), an encoder head mounting connecting plate (203), an encoder head (204), and an encoder magnetic ring (205); The encoder magnetic ring (205) is fixed at the bottom end of the standard inspection rod (3) by interference fit connection; the encoder head (204) is fixed on the encoder head mounting connecting plate (203) by bolts; the encoder head mounting connecting plate (203) is connected to the encoder XY-axis displacement platform (202) by bolts; the encoder XY-axis displacement platform (202) is connected to the encoder head support plate (201) by bolts; the encoder head support plate (201) is fixed on the T-slot bottom plate (6) by nuts and bolts.

5. The method for measuring the rotational accuracy of a seven-point high-speed electric spindle according to claim 1, characterized in that The radial laser displacement sensor fixing and fine-tuning module (4) contains two sets of modules with the same structure. Each set includes a radial sensor support plate (401), a fixed guide ring (402) fixed on the radial sensor support plate (401) by bolts, and three radial laser displacement sensor modules installed on the fixed guide ring (402); a circular angle scale (403) is provided on the fixed guide ring (402); Among them, the radial laser displacement sensor module includes a radial laser displacement sensor (4061), a radial sensor mounting connecting plate (4062), a radial sensor XY-axis displacement platform (4063), an annular fixed upper block (4066), a conversion connecting plate (4067), and an annular fixed lower block (4068); the radial laser displacement sensor (4061) is fixed on the radial sensor mounting connecting plate (4062) by bolts, the radial sensor mounting connecting plate (4062) is connected to the radial sensor XY-axis displacement platform (4063) by bolts, the radial sensor XY-axis displacement platform (4063) is connected to the annular fixed lower block (4068) by bolts, the annular fixed upper block (4066) and the annular fixed lower block (4068) are matched by long fixing bolts, and the intermediate groove formed by their connection is matched with the fixed guide ring (402), and the fixing and clamping with the fixed guide ring (402) is realized by tightening the bolts.

6. The method for measuring the rotational accuracy of the seven-point high-speed electric spindle according to claim 1, characterized in that, The axial laser displacement sensor fixing and fine-tuning module (5) includes an axial sensor support plate (501), an axial sensor XY-axis displacement platform (502), an axial sensor mounting connecting plate (503), and an axial laser displacement sensor (504); The axial laser displacement sensor (504) is fixed on the axial sensor mounting connecting plate (503) by bolts, the axial sensor mounting connecting plate (503) is connected to the axial sensor XY-axis displacement platform (502) by bolts, and the axial sensor XY-axis displacement platform (502) is connected to the axial sensor support plate (501) by bolts; the laser beam of the axial laser displacement sensor (504) is directly opposite to the end face of the standard inspection rod (3).

7. The method for measuring the rotational accuracy of the seven-point high-speed electric spindle according to claim 1, characterized in that The specific process of step 9) is as follows: 9-1) Use two sets of radial laser displacement sensors to fix and fine-tune the data a1(i), a2(i), a3(i) and b1(i), b2(i), b3(i) collected by the radial laser displacement sensors A1, A2, A3 and B1, B2, B3 on the module, and calculate the total radial runout error motion functions δ A (i) and δ B (i); 9-2) Calculate the tilt error motion function: where l is the vertical distance between the measurement planes of two sets of radial sensors; 9-3) Calculate the tilt error value: γ tilt = max(γ(i)).

8. The method for measuring the rotational accuracy of the seven-point high-speed electric spindle according to claim 1, characterized in that, The specific process of step 10) is as follows: 10-1) Read the data c(i) collected by the axial laser displacement sensor A; 10-2) Calculate the axial error motion function: ζ(i) = c(i); 10 - 3) Calculate the axial error value: Calculate the radial runout error value: ε axi = ζ(i) max - ζ(i) min , where ζ(i) max is the maximum value of the spindle axial runout error motion, and ζ(i) min is the minimum value of the spindle axial runout error motion.

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