A method for online detecting the dynamic balance of the spindle of a numerically controlled machine tool and digital leveling

Abstract

A method for online detection of the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool. The spindle encoder pulse signal is collected by using a spindle encoder acquisition card, the spindle vibration signal is collected by using a vibration sensor built in the spindle, and the signal transmitted by the vibration sensor is collected by using a vibration signal acquisition card. The collected encoder pulse signal and vibration sensor signal are processed through an algorithm to obtain the mass and angle of the balancing nails for leveling the dynamic balance of the spindle. In the present invention, only one vibration sensor needs to be installed in the spindle to collect the vibration signal, and the encoder is used to collect the unbalance phase signal, so that the unbalance of the spindle can be quickly detected. Since no optical sensor is used, the time for installing the sensor is saved, and the sensor will not interfere with the workpiece, etc., and will not affect the normal machining of the machine tool. The dynamic balance change of the machine tool can be conveniently monitored, and the cost of adjusting the spindle unbalance is reduced.

Description

Technical Field

[0001] The present invention relates to the field of dynamic balance adjustment of machine tool spindles, and particularly to a method for on-line detection of the dynamic balance of a numerically controlled machine tool spindle and digital leveling. Background Art

[0002] For an electric spindle operating at high speed, due to design defects or rotor bending during operation, the central inertia axis of the electric spindle and the rotation axis do not coincide, resulting in an eccentricity, and the electric spindle has mass imbalance. The mass imbalance will generate an unbalanced force, causing internal stress in the spindle, and further causing vibration of the spindle and the machine tool. The greater the unbalance amount, the greater the vibration generated, which affects the surface quality of the machined workpiece. Therefore, currently, before fine machining, an MPM dynamic balance meter is usually used to adjust the dynamic balance of the spindle-tool holder system so that the vibration acceleration and unbalance amount of the spindle reach the allowable values. When the MPM dynamic balance meter detects the dynamic balance of the spindle, it is necessary to install a vibration sensor and a photoelectric sensor at the same time to obtain the amplitude and phase of the vibration acceleration of the spindle during rotation. Since the dynamic balance of the spindle-tool holder system will change at different speeds, different coordinates of the machine tool, and even different tool holders, it is necessary to adjust the unbalance amount of the spindle during each step of fine machining. However, because the photoelectric sensor of the MPM dynamic balance meter is very close to the spindle and cannot be detected during machining, it needs to be installed and removed frequently. The detection and adjustment will take a lot of working time and affect the continuity of machining. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for on-line detection of the dynamic balance of a numerically controlled machine tool spindle and digital leveling in view of the deficiencies in the above-mentioned prior art field, so that during the use of the machine tool, the dynamic balance state of the machine tool can be obtained in real time, and then corresponding adjustments can be made according to the processing requirements and the current dynamic balance state.

[0004] To achieve the above object, the technical solution adopted by the present invention includes the following steps:

[0005] Step 1: Let the spindle rotate at an arbitrarily specified speed r, use the spindle encoder acquisition card of the machine tool to collect the spindle encoder pulse signal, and at the same time use the vibration sensor to collect the spindle vibration signal, and use the vibration signal acquisition card to collect the signal transmitted from the vibration sensor;

[0006] Step 2: Sinusoidally process the spindle encoder pulse signal to obtain a set of sine signals, which is the time-domain signal of the spindle encoder pulse signal;

[0007] Step 3: Filter the spindle vibration signal to filter out the interference signal and only retain the vibration signal generated due to the imbalance of the spindle rotor;

[0008] Step 4: Calculate the phase difference between the spindle encoder pulse signal and the spindle vibration signal as the phase σ1 of the spindle unbalance amount.

[0009] Step 5: Perform Fourier transform on the spindle vibration signal ; where is the time-domain data, N = 8192, is the frequency, is the frequency-domain data; obtain the spectrogram of N spectral lines; assume the machine tool speed is S, then extract the larger amplitude of the two spectral lines closest to S / 60 in the spectrogram, and take the vibration amplitude at this frequency as the amplitude A1 of the vibration acceleration of the spindle unbalance amount before nailing. It forms the vector vibration acceleration before nailing with the phase σ1 of the spindle unbalance amount before nailing.

[0010] Step 6: Add a screw of known mass at a certain hole of the spindle screw hole, record this position and the mass of the added screw, and then repeat the processing procedures from Step 2) to Step 6) to calculate the vibration acceleration amplitude A2 and phase σ2 of the spindle after nailing, and obtain the vector vibration acceleration after nailing.

[0011] Step 7: Subtract the vector vibration acceleration before nailing from the vector vibration acceleration after nailing to obtain the vector difference of the vibration acceleration before and after nailing, with an amplitude of ΔA and a phase of Δσ. This vector difference of the vibration acceleration is the vibration acceleration caused by the unbalance amount generated during calibration by nailing.

[0012] Step 8: There is a proportional relationship between the amplitude of the vector difference of the vibration acceleration and the calibrated nailing mass. The amplitude of the vector difference of the vibration acceleration is ΔA, with the unit of mm / s 2 ; assume the calibrated nailing mass is m, with the unit of g; then their relationship is m = k * ΔA, where k is a constant. Therefore, after obtaining this functional relationship, the nailing mass required to level the spindle can be calculated through the vibration acceleration of the spindle before nailing.

[0013] Step 9: The phase of the vector difference of the vibration acceleration corresponds to the calibrated position on the spindle. Calculate the nailing angle through the phase of the spindle vibration acceleration before calibration and the phase of the vector difference of the vibration acceleration.

[0014] Step 10: Add the screw with the corresponding mass at the calculated nailing angle for leveling the spindle, and measure and calculate the unbalance amount and vibration acceleration of the spindle again. If the requirements are met, the leveling is completed; otherwise, calculate the nailing mass and angle and continue to adjust until the dynamic balance meets the requirements.

[0015] Further, in step 2), the method of sinusoidal processing is as follows: The original encoder pulse signal collected is a group of continuously changing pulse signals. For each revolution of the main shaft, the number of pulses is fixed. Therefore, one revolution of the main shaft can be regarded as a sine wave signal, and the pulse signal is sinusoidally processed to obtain a group of curves that change in a sine manner. This signal is recorded as the original time-domain data of the encoder pulse signal.

[0016] Further, in step 3), the method of filtering is as follows: The vibration acceleration data of the original vibration signal in the full frequency band is collected. Since unbalance only generates vibration amplitudes in a specific frequency band, the vibration acceleration data is further filtered to retain only the signals in the specific frequency band, obtaining the vibration acceleration time-domain data mainly caused by rotor unbalance, and its time-domain waveform is close to a sine wave.

[0017] Further, in step 4), the time-domain data of the vibration signal and the encoder pulse signal have the same period. The two signals are subjected to cross-correlation processing to obtain the phase difference between the two groups of signals. Since the phase of the time-domain data of the encoder pulse signal is fixed relative to the main shaft, the calculated phase difference can be used as the initial phase of the vibration acceleration.

[0018] Further, in step 5), since the unbalance of the main shaft rotor only causes vibration at the frequency corresponding to the rotational speed, where the frequency corresponding to the rotational speed is S / 60, S is the rotational speed of the main shaft, with the unit of rpm, the vibration signal in this frequency band is extracted as the amplitude of the vibration signal.

[0019] Further, in step 6), a screw with a known mass is added at a certain position on the main shaft, and the vibration signal and the encoder pulse signal after adding the screw are collected. The Fourier transform is used to extract the vibration amplitude A2 of the main shaft at a specific frequency, and the cross-correlation operation is used to obtain the phase difference σ2 between the vibration signal and the encoder pulse signal after adding the screw.

[0020] Further, the unbalance of the main shaft in step 8) cannot be directly measured, and only the vibration acceleration generated by the unbalance can be tested. There is a proportional relationship between the vibration acceleration amplitude A1 and the unbalance G, G = k2 * A1, where k2 is a constant. Correspondingly, there is also a proportional relationship between the mass m of the added screw required for balancing the dynamic balance of the main shaft and the vibration acceleration, m = k * A1, where k is a constant. Through calibration and corresponding calculations, m = k * ΔA, and ΔA = A2 - A1, then the value of the proportional relationship k can be calculated; since the amplitude and phase of the vibration acceleration before and after adding the screw have been calculated, A1, σ1, A2, σ2, which are the vector vibration accelerations before and after adding the screw. Subtracting the vector vibration acceleration before adding the screw from the vector vibration acceleration after adding the screw, the obtained vibration acceleration vector difference is the vibration acceleration vector difference caused by the unbalance generated by adding the screw during calibration, ΔA and Δσ. The proportional function relationship m = k * ΔA between this vibration acceleration vector difference and the mass of the added screw is the relationship between the vibration acceleration of the main shaft and the mass of the added screw under this specific condition.

[0021] Further, the calibration in step 10) can connect the phase of the main shaft with the phase of the vibration acceleration. The phase of the main shaft is the phase of the encoder pulse signal. Regarding the calibrated position as 0° for adding the screw, then the angle of adding the screw before calibration can be obtained using the formula 2π - σ1. According to this angle of adding the screw, the position of adding the screw for leveling the main shaft can be obtained. After adding the corresponding screw at this position, measure the vibration acceleration and unbalance again at this time. If the vibration acceleration and unbalance meet the corresponding requirements, the adjustment is completed. If not, repeat the above steps according to the vibration data and encoder data here to calculate the mass and angle of the screw added for leveling the main shaft at this time. Repeat this process until the vibration acceleration and unbalance of the main shaft meet the corresponding requirements.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] Advantage 1: The present invention only needs to install a vibration sensor in the main shaft to collect vibration signals and use an encoder to collect the phase signal of the unbalance, then it can quickly detect the unbalance of the main shaft. Since it does not use an optical sensor, it saves the time for installing the sensor, and the sensor will not interfere with the workpiece, etc., and will not affect the normal machining of the machine tool, and can conveniently monitor the change of the dynamic balance of the machine tool, reducing the cost of adjusting the unbalance of the main shaft.

[0024] Advantage 2: The present invention uses the acquisition card of the machine tool spindle encoder to collect the encoder pulse signal of the spindle, uses the vibration sensor built in the spindle to collect the vibration signal of the spindle, and uses the vibration signal acquisition card to collect the signal transmitted by the vibration sensor. The collected encoder pulse signal and vibration sensor signal are processed through an algorithm to obtain the mass and angle of the screw added for leveling the dynamic balance of the main shaft.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned by the practice of the present invention. Description of the Drawings

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 It is a flowchart for calculating the nailing quality of the present invention;

[0028] Figure 2 It is the original encoder pulse signal and the encoder pulse signal after sine processing of the present invention;

[0029] Figure 3 It is the vibration signal diagram before and after filtering of the present invention;

[0030] Figure 4 It is the time domain diagram of vibration acceleration before and after filtering of the present invention;

[0031] Figure 5 It is the cross-correlation diagram of the vibration signal and the encoder pulse signal of the present invention. Detailed Embodiments

[0032] The following will describe in more detail the exemplary embodiments disclosed by the present invention with reference to the drawings. These embodiments are for a more thorough understanding of the present invention and to be able to fully convey the scope of the present invention to those skilled in the art. Although the exemplary embodiments disclosed by the present invention are shown in the drawings, it should be understood that the present invention should not be limited by the embodiments set forth herein.

[0033] A method for on-line detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool includes the following steps:

[0034] Step 1: Let the spindle rotate at an arbitrarily specified speed r, use the spindle encoder acquisition card to collect the spindle encoder pulse signal, at the same time use the vibration sensor to collect the spindle vibration signal, and use the vibration signal acquisition card to collect the signal transmitted by the vibration sensor;

[0035] Step 2: Sinusoidally process the spindle encoder pulse signal to obtain a set of sine signals, which are the time domain signals of the spindle encoder pulse signal;

[0036] Step 3: Filter the spindle vibration signal to filter out the interference signal and only retain the vibration signal generated due to the imbalance of the spindle rotor;

[0037] Step 4: Calculate the phase difference between the spindle encoder pulse signal and the spindle vibration signal as the phase σ1 of the spindle unbalance amount.

[0038] Step 5: Perform Fourier transform on the spindle vibration signal ; where is the time-domain data, N = 8192, is the frequency, is the frequency-domain data; obtain the spectrogram of N spectral lines; assume the machine tool speed is S, then extract the larger amplitude among the two spectral lines closest to S / 60 in the spectrogram, and use the vibration amplitude at this frequency as the amplitude A1 of the vibration acceleration of the spindle unbalance amount before adding the screw. Its phase σ1 with the spindle unbalance amount before adding the screw forms the vector vibration acceleration before adding the screw.

[0039] For example: Assume the machine tool speed is S = 12000 rpm, then extract the larger amplitude among the two spectral lines closest to (S / 60) = 200 Hz in the spectrogram, and use the vibration amplitude at this frequency as the amplitude A1 of the vibration acceleration of the spindle unbalance amount before adding the screw. Its phase σ1 with the spindle unbalance amount before adding the screw forms the vector vibration acceleration before adding the screw.

[0040] Step 6: Add a screw with a known mass at a certain hole of the spindle screw hole, record this position and the mass of the added screw, and then repeat the processing procedures from step 2) to step 6) to calculate the vibration acceleration amplitude A2 and phase σ2 of the spindle after adding the screw, and the vector vibration acceleration after adding the screw can be obtained.

[0041] Step 7: Subtract the vector vibration acceleration before adding the screw from the vector vibration acceleration after adding the screw to obtain the vibration acceleration vector difference (amplitude is ΔA, phase is Δσ) before and after adding the screw. This vibration acceleration vector difference is the vibration acceleration caused by the unbalance amount generated by adding the screw during calibration.

[0042] Step 8: There is a proportional relationship between the amplitude of the vibration acceleration vector difference and the calibrated mass of the added screw (the amplitude of the vibration acceleration vector difference is ΔA, unit is mm / s 2 , assume the calibrated mass of the added screw is m, unit is g;, then their relationship is m = k * ΔA, k is a constant), so after obtaining this functional relationship, the mass of the screw needed to level the spindle can be calculated through the vibration acceleration of the spindle before adding the screw.

[0043] Step 9: The phase of the vibration acceleration vector difference corresponds to the calibrated position on the spindle. Calculate the screw addition angle through the phase of the spindle vibration acceleration before calibration and the phase of the vibration acceleration vector difference.

[0044] Step 10: Add corresponding mass screws at the calculated nail-adding angle for leveling the main shaft. Measure and calculate the unbalance and vibration acceleration of the main shaft again. If the requirements are met, the leveling is completed; otherwise, calculate the added nail mass and angle and continue to adjust until the dynamic balance meets the requirements.

[0045] Optimally, in step 2), the method of sine transformation is as follows: The original encoder pulse signal collected is a group of continuously changing pulse signals. The number of pulses is fixed when the main shaft rotates one circle. Therefore, one rotation of the main shaft can be regarded as a sine wave signal. The pulse signal is sine-transformed to obtain a group of curves that change in a sine manner. This signal is recorded as the time-domain original data of the encoder pulse signal.

[0046] Optimally, in step 3), the method of filtering is as follows: The vibration acceleration data of the original vibration signal in the full frequency band is collected. Since unbalance only generates vibration amplitudes in a specific frequency band, the original vibration acceleration data is further filtered to retain only the signals in the specific frequency band, obtaining the vibration acceleration time-domain data mainly caused by rotor unbalance, and its time-domain waveform is close to a sine wave.

[0047] Optimally, in step 4), the time-domain data of the vibration signal and the encoder pulse signal have the same period. The two signals are cross-correlated (obtain the phase difference when the product of the two sets of data is the largest) to obtain the phase difference between the two signals. Since the phase of the time-domain data of the encoder pulse signal is fixed relative to the main shaft, the calculated phase difference can be used as the initial phase of the vibration acceleration.

[0048] Optimally, in step 5), since the unbalance of the main shaft rotor only causes vibration at the frequency corresponding to the rotational speed, where the frequency corresponding to the rotational speed is S / 60, S is the rotational speed of the main shaft, with the unit of rpm, so the vibration signal in this frequency band is extracted as the amplitude of the vibration signal.

[0049] Optimally, in step 6), add a screw with a known mass (calibration) at a certain position on the main shaft. Collect the vibration signal and the encoder pulse signal after adding the nail. Use Fourier transform to extract the vibration amplitude A2 of the main shaft at a specific frequency (rotational speed (rpm) / 60Hz), and use cross-correlation operation to obtain the phase difference σ2 between the vibration signal and the encoder pulse signal after adding the nail.

[0050] Optimized. In step 8), the unbalance of the main shaft cannot be directly measured, and only the vibration acceleration generated by the unbalance can be tested. There is a proportional relationship between the vibration acceleration amplitude A1 and the unbalance G, G = k2 * A1, where k2 is a constant. Correspondingly, there is also a proportional relationship between the mass m of the added screw required to balance the dynamic balance of the main shaft and the vibration acceleration, m = k * A1, where k is a constant. Through calibration and corresponding calculations, m = k * ΔA, and ΔA = A2 - A1, then the value of the proportional relationship k between the two can be calculated. Since the amplitudes and phases of the vibration accelerations before and after adding the screw have been calculated, A1, σ1, A2, σ2, which are the vector vibration accelerations before and after adding the screw. Subtracting the vector vibration acceleration before adding the screw from the vector vibration acceleration after adding the screw, the resulting vibration acceleration vector difference is the vibration acceleration vector difference caused by the unbalance generated by adding the screw during calibration, ΔA and Δσ. The proportional function relationship m = k * ΔA between this vibration acceleration vector difference and the mass of the added screw is the relationship between the vibration acceleration of the main shaft and the mass of the added screw under this specific condition (speed, main shaft height).

[0051] Optimized. In step 10), calibration can relate the phase of the main shaft to the phase of the vibration acceleration. The phase of the main shaft is the phase of the encoder pulse signal. Taking the calibrated position as 0° for adding the screw, and then using the formula 2π - σ1, the angle of adding the screw before calibration can be obtained. According to this angle of adding the screw, the position of adding the screw to level the main shaft can be obtained. After adding the corresponding screw at this position, measure the vibration acceleration and unbalance at this time again. If the vibration acceleration and unbalance meet the corresponding requirements, the adjustment is completed. If not, repeat the above steps according to the vibration data and encoder data here to calculate the mass and angle of adding the screw to level the main shaft at this time (return to the first step, measure and calculate again the mass and angle of adding the screw to level the main shaft at this time), and repeat this process until the vibration acceleration and unbalance of the main shaft meet the corresponding requirements.

[0052] See Figure 1 , the implementation steps of the present invention are as follows:

[0053] As shown in Figure a, after sinusoidal processing of the encoder signal and filtering of the vibration signal, the vector vibration signal is obtained;

[0054] As shown in Figure b, using the vector vibration signals before and after adding the screw and the calibrated mass and angle for calculation, the functional relationship between the vibration signal and the mass of the added screw and the angle of adding the screw required to level the main shaft are obtained;

[0055] As shown in Figure c, using the functional relationship between the vibration signal and the mass of the added screw and the vector vibration signal before adding the screw, the mass of the added screw required to level the main shaft is obtained.

[0056] See Figure 2, in the present invention, the original encoder pulse signal collected and the encoder pulse signal after sine processing are provided. The original encoder pulse signal is a continuously increasing or decreasing pulse signal, and after processing, it becomes a sine signal.

[0057] See Figure 3 and Figure 4 , in the present invention, the vibration acceleration time-domain signal before and after filtering processing and the vibration acceleration frequency-domain signal before and after filtering processing are provided. The vibration velocity before filtering contains a lot of clutter of various frequencies, so the time-domain signal is relatively chaotic. After filtering, only the narrowband signal near the main frequency is retained, so the time-domain signal is very close to a sine wave.

[0058] See Figure 5 , in the present invention, the cross-correlation diagram of the vibration signal and the encoder pulse signal is provided. It can be seen that the vibration signal and the encoder pulse signal have the same period, but there is a phase difference, and this phase difference is the initial phase of the vibration velocity caused by the unbalance amount.

[0059] The present invention realizes the online high-efficiency detection and adjustment of the dynamic balance of the spindle-tool system well by means of a vibration sensor and a spindle encoder, ensuring that the dynamic balance during the finish machining process is in the optimal state, thereby improving the surface quality of the machined workpiece. Compared with the existing MPM dynamic balancer for measuring the dynamic balance of a machine tool, it does not require the installation of an optoelectronic sensor, saving the time for installing the sensor, and does not affect the normal machining of the machine tool. It can conveniently monitor the change of the dynamic balance of the machine tool and improve the machining continuity.

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention have been clearly and completely described above with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0061] Therefore, the above detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. An on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool, characterized in that, Including the following steps: Step 1: Let the main shaft rotate at an arbitrarily specified speed r. Use the machine tool spindle encoder acquisition card to collect the spindle encoder pulse signal, and at the same time use the vibration sensor to collect the spindle vibration signal, and use the vibration signal acquisition card to collect the signal transmitted from the vibration sensor; Step 2: Sinusoidally process the spindle encoder pulse signal to obtain a set of sine signals, which are the time-domain signals of the spindle encoder pulse signal; Step 3: Filter the spindle vibration signal to filter out the interference signal and only retain the vibration signal generated by the imbalance of the spindle rotor; Step 4: Calculate the phase difference between the spindle encoder pulse signal and the spindle vibration signal as the phase σ1 of the spindle unbalance; Step 5: Perform Fourier transform on the spindle vibration signal ; where is the time-domain data, N = 8192, is the frequency, is the frequency-domain data; obtain the spectrogram of N spectral lines; assume the machine tool speed is S, then extract the one with the larger amplitude among the two spectral lines closest to S / 60 in the spectrogram, and take the vibration amplitude at this frequency as the amplitude A1 of the vibration acceleration of the spindle unbalance before nailing. Its phase σ1 with the spindle unbalance before nailing constitutes the vector vibration acceleration before nailing; Step 6: Add a screw with a known mass at a certain hole of the spindle screw hole, record this position and the mass of the added screw, and then repeat the processing process from Step 2) to Step 6) to calculate the vibration acceleration amplitude A2 and phase σ2 of the spindle after adding the screw, and the vector vibration acceleration after adding the screw can be obtained; Step 7: Subtract the vector vibration acceleration before adding the screw from the vector vibration acceleration after adding the screw to obtain the vibration acceleration vector difference before and after adding the screw, with an amplitude of ΔA and a phase of Δσ. This vibration acceleration vector difference is the vibration acceleration caused by the unbalance generated by adding the screw during calibration; Step 8: There is a proportional relationship between the amplitude of the vibration acceleration vector difference and the calibrated mass of the added nails. The amplitude of the vibration acceleration vector difference is ΔA, with the unit of mm / s 2 ; Let the calibrated mass of the added nails be m, with the unit of g; then their relationship is m = k * ΔA, where k is a constant. Therefore, after obtaining this functional relationship, the mass of the added nails required to level the main shaft can be calculated through the vibration acceleration of the main shaft before adding the nails; Step 9: The phase of the vibration acceleration vector difference corresponds to the calibration position on the main shaft. Calculate the adding screw angle through the phase of the spindle vibration acceleration before calibration and the phase of the vibration acceleration vector difference; Step 10: Add a screw with the corresponding mass at the calculated adding screw angle for leveling the main shaft, and measure and calculate the unbalance and vibration acceleration of the main shaft again. If the requirements are met, the leveling is completed. Otherwise, calculate the adding screw mass and angle and continue to adjust until the dynamic balance meets the requirements.

2. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In the said Step 2), the method of sinusoidal processing is as follows: The original encoder pulse signal collected is a set of continuously changing pulse signals. The number of pulses is fixed when the main shaft rotates one circle. Therefore, one rotation of the main shaft can be regarded as a sine wave signal. Sinusoidally process the pulse signal to obtain a set of curves that change in a sine manner, and record this signal as the time-domain original data of the encoder pulse signal.

3. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In the said Step 3), the method of filtering is as follows: The vibration acceleration data of the original vibration signal in the full frequency band is collected. Since the imbalance only generates vibration amplitudes in a specific frequency band, the vibration acceleration data is further filtered to only retain the signal in the specific frequency band, and the time-domain data of the vibration acceleration mainly caused by the rotor imbalance is obtained, and its time-domain waveform is close to a sine wave.

4. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In the said Step 4), the time-domain data of the vibration signal and the encoder pulse signal have the same period. Cross-correlate the two signals to obtain the phase difference between the two sets of signals. Since the phase of the time-domain data of the encoder pulse signal is fixed relative to the main shaft, the calculated phase difference can be used as the initial phase of the vibration acceleration.

5. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In the said Step 5), since the imbalance of the spindle rotor only causes vibration at the frequency corresponding to the rotational speed, where the frequency corresponding to the rotational speed is S / 60, S is the spindle speed in rpm, so extract the vibration signal in this frequency band as the amplitude of the vibration signal.

6. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In step 6), a screw with a known mass is added at a certain position on the main shaft, and the vibration signal and encoder pulse signal after adding the screw are collected. The Fourier transform is used to extract the vibration amplitude A2 of the main shaft at a specific frequency, and the cross-correlation operation is used to obtain the phase difference σ2 between the vibration signal and the encoder pulse signal after adding the screw.

7. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In step 8), the unbalance of the main shaft cannot be directly measured, and only the vibration acceleration generated by the unbalance can be tested. There is a proportional relationship between the vibration acceleration amplitude A1 and the unbalance G, G = k2 * A1, where k2 is a constant. Correspondingly, there is also a proportional relationship between the mass m of the screw added to balance the dynamic balance of the main shaft and the vibration acceleration, m = k * A1, where k is a constant. Through calibration and corresponding calculations, m = k * ΔA, where ΔA = A2 - A1, and the value of the proportionality coefficient k can be calculated; since the amplitudes and phases of the vibration accelerations before and after adding the screw have been calculated, A1, σ1, A2, σ2, which are the vector vibration accelerations before and after adding the screw. Subtracting the vector vibration acceleration before adding the screw from the vector vibration acceleration after adding the screw, the resulting vibration acceleration vector difference is the vibration acceleration vector difference caused by the unbalance generated by adding the screw during calibration, ΔA and Δσ. The proportional function relationship m = k * ΔA between this vibration acceleration vector difference and the mass of the added screw is the relationship between the vibration acceleration of the main shaft and the mass of the added screw under this specific condition.

8. The on-line method for detecting the dynamic balance and digital leveling of the spindle of a numerically controlled machine tool according to claim 1, characterized in that, In step 10), calibration can relate the phase of the main shaft to the phase of the vibration acceleration. The phase of the main shaft is the phase of the encoder pulse signal. Taking the calibrated position as 0° for adding the screw, then using the formula 2π - σ1, the angle of adding the screw before calibration can be obtained. According to this angle of adding the screw, the position for adding the screw to level the main shaft can be obtained. After adding the corresponding screw at this position, the vibration acceleration and unbalance are measured again. If the vibration acceleration and unbalance meet the corresponding requirements, the adjustment is completed. If not, the mass and angle of the screw added to level the main shaft at this time are calculated by repeating the above steps based on the vibration data and encoder data here. Repeat this process until the vibration acceleration and unbalance of the main shaft meet the corresponding requirements.

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