A modal testing method and testing system based on self-excitation of CNC machine tools

Abstract

The invention relates to a modal testing method and a testing system based on self-excitation of a numerical control machine tool, which belongs to the technical field of modal testing and solves the problems in the prior art that the modal testing is not comprehensive enough and the process is too complicated. The method comprises: step S0, constructing a modal testing system; step S1, pasting an acceleration sensor according to the type of a measurement object on the numerical control machine tool; step S2, setting a frequency sweep parameter in the modal testing system, starting the frequency sweep, and synchronously collecting a command speed signal of the frequency sweep and response acceleration data by the numerical control system; step S3, the modal testing system obtaining the command speed signal and response acceleration data of this frequency sweep, integrating the collected response acceleration data, and obtaining speed response data; and step S4, the modal testing system calculating the mutual power density spectrum and the self-power density spectrum according to the speed response data and the command speed signal, and drawing a Bode diagram of the measurement object to obtain the modal parameters of the measurement object.

Description

Technical Field

[0001] The present invention relates to the technical field of modal testing, and in particular to a modal testing method and a testing system based on self-excitation of a numerically controlled machine tool. Background Art

[0002] CNC machine tools are indispensable key equipment in modern manufacturing. Most aerospace parts need to be processed using CNC machine tools, and have very high precision and stability requirements. For aerospace CNC processing plants, modal testing is often an indispensable link. On the one hand, during the use of CNC machine tools, affected by the material and structure of the machine tools themselves, it is necessary to perform modal testing on the machine tools regularly, including the modal of the machine tool mechanical structure and the modal of the machine tool feed system. On the other hand, most of the parts processed by aerospace CNC processing plants are thin-walled parts of steel, aluminum and titanium alloys. In order to understand the vibration characteristics of thin-walled parts in order to continuously improve the design and processing technology, and to verify whether the parts processing results meet the design requirements, it is necessary to frequently perform modal testing on the parts.

[0003] The Chinese invention patent application, publication number CN109531270A, titled "Modal test method for CNC machine tool feed system based on built-in sensor", discloses a modal test method, in which a vibration exciter is provided to send a test signal to the machine tool. The vibration exciter is required to provide an exciting force to the machine tool, but the cost of the vibration exciter is high, and the equipment needs to be shut down during installation, affecting normal operation.

[0004] The Chinese utility model patent, publication number CN 202010918U, utility model name "A measurement device for torsional vibration modes of CNC machine tools", discloses a modal test device, which discloses the use of a high-resolution rotary encoder mounted on a ball screw to measure the rotational angular velocity of the ball screw. Therefore, only the modal parameters of the ball screw of the machine tool can be calculated.

[0005] Existing modal testing methods require the use of a vibration exciter, which is expensive, inconvenient to install, and requires the machine tool to be shut down for modal testing. In addition, using a vibration exciter as an excitation source increases the risk of external force damaging the machine tool.

[0006] Therefore, in the current precision and complex processing fields such as aerospace CNC machining, there is a demand for a simpler and lower-cost method that can test the machine tool mechanical structure mode, feed system mode and workpiece mode. Summary of the invention

[0007] In order to solve the above problems, the present invention proposes a modal testing method based on self-excitation of a CNC machine tool.

[0008] The present invention can use a unified testing method and data processing method to complete the testing of the machine tool mechanical structure mode, feed system mode and workpiece mode, avoid the use of expensive exciter equipment, reduce the requirements for technicians, and facilitate testing without stopping the machine tool during the testing process.

[0009] According to an embodiment of the present invention, a modal testing method based on self-excitation of a numerically controlled machine tool is provided, comprising the following steps:

[0010] Step S0, constructing a modal test system, the modal test system including an excitation signal selection module, a numerical control system communication interface module and a data analysis and processing module;

[0011] Step S1, planning the acceleration sensor pasting position according to the type of the measurement object on the CNC machine tool, pasting the acceleration sensor, and connecting the measurement signal of the acceleration sensor to the analog quantity acquisition module of the CNC system of the CNC machine tool, and the CNC system performs data acquisition on the measurement signal of the acceleration sensor;

[0012] Step S2: setting frequency sweep parameters in the modal test system, starting the frequency sweep, and synchronously collecting the command speed signal of the frequency sweep and the response acceleration data of all acceleration sensors by the numerical control system;

[0013] Step S3: the modal test system obtains the command speed signal and response acceleration data of this frequency sweep from the numerical control system, and integrates the response acceleration data to obtain speed response data;

[0014] In step S4, the modal test system calculates the cross-power density spectrum and the auto-power density spectrum according to the speed response data and the command speed signal, and calculates and draws the Bode diagram of the measurement object to obtain the modal parameters of the measurement object.

[0015] Optionally, the step S1 specifically includes the following steps:

[0016] Step S1.1, judging the type of the measurement object on the CNC machine tool, judging whether it belongs to the type of the machine tool feed system, the machine tool mechanical structure, or the workpiece, and obtaining the type of the measurement object as a judgment result;

[0017] Step S1.2, sticking the acceleration sensor according to the judgment result, wherein if the type of the measured object is a machine tool feed system, sticking the acceleration sensor to the workbench at the end of the machine tool feed system, if it is a machine tool mechanical structure, sticking the acceleration sensor to the surface of the machine tool mechanical structure, if it is a workpiece, sticking the acceleration sensor to the surface of the workpiece clamped on the machine tool;

[0018] Step S1.3, setting the attached acceleration sensor, connecting the measurement signal of the acceleration sensor to the analog quantity acquisition module in the numerical control system of the numerical control machine tool, and the analog quantity acquisition module performs data acquisition on the measurement signal of the acceleration sensor.

[0019] Optionally, the step S2 specifically includes the following steps:

[0020] Step S2.1, the excitation signal selection module of the modal test system selects a frequency sweep signal type from linear frequency sweep, step frequency sweep and logarithmic frequency sweep according to the signal type supported by the numerical control system of the numerical control machine tool, and sets the frequency sweep parameters including the frequency sweep rate and the frequency sweep range accordingly;

[0021] Step S2.2, the excitation signal selection module generates the G code required for the frequency sweep as an excitation instruction according to the set frequency sweep parameters and the signal type supported by the CNC system, and the CNC system communication interface module sends the G code as the excitation instruction to the CNC system;

[0022] Step S2.3, self-excitation frequency sweep, the CNC system generates a frequency sweep speed instruction according to the received G code, and drives the CNC machine tool to move and start the frequency sweep;

[0023] Step S2.4, the acceleration sensor senses and obtains the response acceleration data of the measurement object, the numerical control system obtains the response acceleration data from the acceleration sensor, and obtains the command speed signal according to the sweep speed command.

[0024] Optionally, the step S3 specifically includes the following steps:

[0025] Step S3.1, the numerical control system communication interface module of the modal test system obtains the command speed signal and response acceleration data of this frequency sweep from the numerical control system, and transmits them to the data analysis and processing module;

[0026] Step S3.2, dimensional unification processing, the data analysis and processing module integrates the received response acceleration data to obtain speed response data, thereby unifying the dimension with the command speed signal.

[0027] Optionally, the step S4 specifically includes the following steps:

[0028] Step S4.1, the data analysis and processing module of the modal test system processes the speed response data and the command speed signal, sets a window function, and calculates and obtains the cross-power density spectrum and the auto-power density spectrum of the speed response data and the command speed signal;

[0029] Step S4.2, the data analysis and processing module of the modal test system calculates the amplitude frequency and phase frequency of the Bode diagram by using the cross-power density spectrum and the auto-power density spectrum, and obtains the Bode diagram and modal parameters of the measured object.

[0030] According to another embodiment of the present invention, a test system for executing the modal test method based on self-excitation of a CNC machine tool includes: an excitation signal selection module, which selects a frequency sweep signal type and sets frequency sweep parameters according to the signal type supported by the CNC system of the CNC machine tool under test, and generates a G code required for the frequency sweep according to the set frequency sweep parameters and the signal type supported by the CNC system; a CNC system communication interface module, which establishes communication with the CNC system of the CNC machine tool, sends the G code required for the frequency sweep obtained from the excitation signal selection module to the CNC system, and collects the command speed signal and response acceleration data during the test from the CNC system; and a data analysis and processing module, which obtains the command speed signal and response acceleration data of the test from the CNC system communication interface module, and processes them to obtain the Bode diagram and modal parameters of the measured object.

[0031] Compared with the prior art, a modal testing method and a testing system based on self-excitation of a CNC machine tool provided according to an embodiment of the present invention have at least the following beneficial effects and advantages.

[0032] 1) According to the modal testing method based on self-excitation of CNC machine tools provided in an embodiment of the present invention, the modal of a workpiece is tested using a machine tool, including using the self-excitation of the machine tool to measure the modal of the workpiece, thereby avoiding the use of expensive exciter equipment to perform modal testing on the workpiece, reducing the testing cost, and also avoiding the possibility of the external force of the exciter causing damage to the machine tool due to the setting of the exciter; in addition, the machine tool does not need to be shut down during the test, thereby improving the detection and production efficiency.

[0033] 2) The modal testing system based on self-excitation of CNC machine tools provided in accordance with an embodiment of the present invention is applicable to complex processing technology fields such as aerospace CNC processing plants. By using a unified modal testing system, unified testing of the machine tool mechanical structure modal, feed system modal and workpiece modal can be completed, which is convenient and fast and reduces the operating requirements for technical personnel.

[0034] 3) According to the modal testing system based on CNC machine tool self-excitation provided by the embodiment of the present invention, the acceleration sensor is connected to the CNC system, and the CNC system performs unified data acquisition, which simplifies the data acquisition process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the drawings. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 According to an embodiment of the present invention, a working structure framework of a modal testing system based on self-excitation of a numerically controlled machine tool is provided.

[0037] Figure 2 A flowchart of a modal testing method based on self-excitation of a CNC machine tool is provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0040] A modal testing method and a testing system based on self-excitation of a numerically controlled machine tool according to an embodiment of the present invention are described in detail below with reference to the accompanying drawings.

[0041] The embodiment of the present invention provides a modal testing method based on self-excitation of CNC machine tools, and further designs a test system for executing the method, which can complete the testing of the machine tool mechanical structure modal, feed system modal and workpiece modal in a unified method. The self-excitation of CNC machine tools is used as the excitation source of modal testing to avoid the use of expensive exciter equipment. An acceleration sensor is used to collect vibration response signals, and the acceleration sensor is pasted on the surface of the tested component. The method of the present invention can uniformly complete the testing of the machine tool mechanical structure modal, feed system modal and workpiece modal. When measuring the machine tool mechanical structure modal, the acceleration sensor needs to be pasted on the test point of the tested mechanical structure; when measuring the machine tool feed system modal, the acceleration sensor needs to be pasted on the workbench of the tested feed shaft; when measuring the workpiece modal, the workpiece needs to be fixed on the workbench of a certain feed shaft using a fixture, and then the acceleration sensor is pasted on the test point of the workpiece.

[0042] refer to Figure 1, shows a working framework diagram of a modal testing system based on self-excitation of a CNC machine tool provided according to an embodiment of the present invention.

[0043] According to an embodiment of the present invention, a modal test system based on self-excitation of a numerical control machine tool is provided, which communicates data with the numerical control system of the numerical control machine tool to be tested, sends the G code required for frequency sweeping to the numerical control system, and collects the command speed signal and response acceleration data from the numerical control system. The numerical control system generates a command speed signal according to the frequency sweeping G code, and drives the numerical control machine tool to move, that is, self-excitation frequency sweeping. An acceleration sensor is pasted on the test point of the component to be tested, and the acceleration sensor can be pasted on the mechanical structure surface of the numerical control machine tool to measure the modality of the mechanical structure of the machine tool; for example, the acceleration sensor can be pasted on the workbench of the feed shaft to be tested to measure the modality of the machine tool feed system; the acceleration sensor can also be pasted on the workpiece, and the workpiece is clamped on the moving workbench of the numerical control machine tool to measure the modality of the workpiece. The acceleration sensor is connected to the analog quantity acquisition module of the numerical control system, and the numerical control system uniformly collects the acceleration sensor data. The modal test system analyzes and processes the command speed signal and response acceleration data collected during the test to obtain the Bode diagram of the measured object and complete the modal test.

[0044] The modal testing system based on self-excitation of a numerical control machine tool according to an embodiment of the present invention includes three modules: an excitation signal selection module, a numerical control system communication interface module, and a data analysis and processing module.

[0045] Excitation signal selection module: According to the signal type supported by the CNC system of the machine tool under test, a reasonable type is selected from linear frequency sweep, step frequency sweep, logarithmic frequency sweep and other types, and parameters such as frequency sweep rate and frequency sweep range are set; this module will generate the G code required for the frequency sweep based on the set parameters and the signal type supported by the CNC system, and the G code will be sent to the CNC system by the CNC system communication interface module.

[0046] CNC system communication interface module: establish communication with the CNC system of the CNC machine tool, send the G code required for frequency sweeping to the CNC system, and collect the command speed signal and response acceleration data from the CNC system during the test. This module needs to establish communication with the CNC system in a targeted manner according to the communication protocol supported by the CNC system of the machine tool under test to achieve the required functions.

[0047] Data analysis and processing module: This module will obtain the command speed signal and response acceleration data of the test from the CNC system communication interface module. The acceleration signal is low-pass filtered to remove the DC component and random noise, and then the response speed signal is obtained by integration. The window function is selected to calculate the cross-power density spectrum and auto-power density spectrum of the command speed signal and the integrated speed signal; the cross-power density spectrum and auto-power density spectrum are used to calculate the amplitude frequency and phase frequency of the Bode diagram to obtain the Bode diagram and modal parameters of the measured object.

[0048] like Figure 2 As shown, a modal testing method based on self-excitation of a CNC machine tool provided according to an embodiment of the present invention includes the following steps.

[0049] Step S0, constructing a modal test system, which includes an excitation signal selection module, a numerical control system communication interface module and a data analysis and processing module.

[0050] Step S1, according to the type of measurement object on the CNC machine tool, plan the acceleration sensor pasting position, paste the acceleration sensor, and connect the measurement signal of the acceleration sensor to the analog quantity acquisition module of the CNC system of the CNC machine tool, and the CNC system performs data acquisition on the measurement signal of the acceleration sensor.

[0051] The step S1 is specifically as follows: according to the measurement object, the acceleration sensor pasting position is planned, and the acceleration sensor is pasted, and the measurement signal of the acceleration sensor is connected to the analog quantity acquisition module of the numerical control system. In this embodiment, the optional measurement objects include: the machine tool feed system, the machine tool mechanical structure and the workpiece. For the modal test of the machine tool feed system, the acceleration sensor can be pasted on the workbench at the end of the machine tool feed system to measure the actual acceleration of the workbench during the frequency sweep of the feed axis; for the modal test of the machine tool mechanical structure, the acceleration sensor can be pasted on the surface of the structure to be measured, for example, the acceleration sensor is pasted on the surface of the X-axis structure to measure the acceleration data of each sensor during the X-axis frequency sweep; for the modal measurement of the workpiece, the part to be measured can be clamped on the moving workbench of the machine tool, the measurement points are divided on the surface of the part and the acceleration sensor is pasted, and the numerical control system is used to drive the workbench to perform frequency sweeping motion to obtain the acceleration data of each sensor on the surface of the part to be measured.

[0052] Step S1 specifically includes the following steps.

[0053] Step S1.1, judging the type of the measurement object on the CNC machine tool, judging whether it belongs to the type of the machine tool feed system, the machine tool mechanical structure, or the workpiece, and obtaining the type of the measurement object as a judgment result;

[0054] Step S1.2, the acceleration sensor is pasted according to the judgment result, wherein if the type of the measured object is a machine tool feed system, the acceleration sensor is pasted on the workbench at the end of the machine tool feed system, if it is a machine tool mechanical structure, the acceleration sensor is pasted on the surface of the machine tool mechanical structure, and if it is a workpiece, the acceleration sensor is pasted on the surface of the workpiece clamped on the machine tool. Pasting the acceleration sensor on the surface of the machine tool mechanical structure can be pasting the acceleration sensor on the X-axis structure surface of the machine tool mechanical structure, and measuring the acceleration data of each sensor when the X-axis is swept. In addition, optionally, before pasting the acceleration sensor on the surface of the workpiece clamped on the machine tool, the measurement points can be divided on the workpiece surface, and then the acceleration sensor is pasted according to the measurement points.

[0055] Step S1.3, setting the attached acceleration sensor, connecting the measurement signal of the acceleration sensor to the analog quantity acquisition module in the numerical control system of the numerical control machine tool, and the analog quantity acquisition module performs data acquisition on the measurement signal of the acceleration sensor.

[0056] Step S2: Set the frequency sweep parameters in the modal test system and start the frequency sweep. The modal test system will generate the G code required for the frequency sweep based on the frequency sweep parameters and the signal types supported by the CNC system, and send it to the CNC system. While the frequency sweep is in progress, the CNC system will synchronously collect the command speed signal of the frequency sweep and the response acceleration data of all acceleration sensors.

[0057] The step S2 is specifically to set the frequency sweep parameters in the modal test system, including the frequency sweep signal type, frequency sweep rate, frequency sweep range, etc. The system will generate the G code required for the frequency sweep according to the frequency sweep parameters and the signal type supported by the numerical control system, and send it to the numerical control system to start the frequency sweep. At the same time, the numerical control system collects the command speed signal of the frequency sweep and the response acceleration data of the acceleration sensor to achieve synchronous collection of the two types of signals.

[0058] Step S2 specifically includes the following steps.

[0059] Step S2.1, the excitation signal selection module of the modal test system selects a sweep signal type from linear sweep, step sweep, logarithmic sweep and other types according to the signal type that can be realized by the CNC system of the CNC machine tool, and sets the sweep parameters such as sweep rate and sweep range accordingly.

[0060] Step S2.2, the excitation signal selection module generates the G code required for the frequency sweep as an excitation instruction according to the set frequency sweep parameters and the signal type supported by the CNC system, and the CNC system communication interface module sends the G code as the excitation instruction to the CNC system.

[0061] Step S2.3, self-excitation frequency sweep, the CNC system generates a frequency sweep speed instruction according to the received G code, and drives the CNC machine tool to move and start the frequency sweep.

[0062] Step S2.4, the acceleration sensor senses and obtains the response acceleration data of the measurement object, the numerical control system obtains the response acceleration data from the acceleration sensor, and obtains the command speed signal according to the sweep speed command.

[0063] Step S3: The modal test system obtains the command speed signal and response acceleration data of this frequency sweep from the numerical control system, processes the obtained data, and integrates the collected response acceleration data to obtain speed response data.

[0064] The step S3 is specifically data processing. The modal test system will automatically obtain the command speed signal and response acceleration data of this frequency sweep from the numerical control system. Since the command speed signal is a speed signal value and the response acceleration data of the acceleration sensor is an acceleration value, the dimensions need to be unified. Considering that in many cases it is impossible to directly measure the response signal using a position sensor and a speed sensor, it is necessary to first use an acceleration sensor to measure the response acceleration data, and then integrate to obtain a speed response signal.

[0065] The step S3 specifically includes the following steps.

[0066] Step S3.1, the numerical control system communication interface module of the modal test system obtains the command speed signal and response acceleration data of this frequency sweep from the numerical control system, and transmits them to the data analysis and processing module.

[0067] Step S3.2, dimensional unification processing, the data analysis and processing module integrates the received response acceleration data to obtain speed response data, thereby unifying the dimension with the command speed signal.

[0068] Among them, the integration processing method can be selected as time domain integration or frequency domain integration. The time domain integration method can use the trapezoidal method and the Simpson method, thereby avoiding the energy leakage caused by the Fourier transform. However, it is necessary to consider the removal of the trend term generated by the integration. The frequency domain integration rule converts the signal into the frequency domain through the fast Fourier transform, performs corresponding processing in the frequency domain, and then converts it into the time domain through the inverse Fourier transform to obtain the speed response signal; the frequency domain integration method can avoid the generation of trend terms in the integration process.

[0069] Step S4, draw a Bode diagram to obtain the modal parameters of the measured object. The modal test system will calculate the cross-power density spectrum and the self-power density spectrum based on the velocity response data and the command velocity signal, and finally calculate the Bode diagram of the measured object to obtain the modal parameters of the measured object. The modal parameters of the measured object may include the natural frequency of the measured object.

[0070] The step S4 is specifically to draw a Bode diagram to obtain the modal parameters of the measured object. The modal test system will automatically select the window function, and the operator can also manually set the window function, and then calculate the cross-power density spectrum and the self-power density spectrum of the command speed signal and the speed response signal, and then calculate the amplitude-frequency curve of the Bode diagram, and further analyze and obtain the Bode diagram and modal parameters of the measured object.

[0071] Step S4 specifically includes the following steps.

[0072] Step S4.1, the data analysis and processing module of the modal test system processes the speed response data and the command speed signal, sets a window function, and calculates and obtains the cross-power density spectrum and the auto-power density spectrum of the speed response data and the command speed signal.

[0073] Step S4.2, the data analysis and processing module of the modal test system calculates the amplitude frequency and phase frequency of the Bode diagram by using the cross-power density spectrum and the auto-power density spectrum, and obtains the Bode diagram and modal parameters of the measured object.

[0074] The following describes an embodiment of a modal testing method and a testing system based on self-excitation of a numerically controlled machine tool provided by an embodiment of the present invention.

[0075] Reference Figure 1 In this embodiment, a BH-INC CNC machine tool is used to clamp the thin plate workpiece on the Y-axis workbench, and the method of the present invention is used to measure the thin plate mode.

[0076] Construction of modal test system: The excitation signal selection module and the CNC system communication interface module need to be specifically constructed according to the different CNC systems. The BH-INC CNC system supports the ADS communication protocol and the linear speed sweep function. Therefore, the CNC system communication interface module of the modal test system based on the ADS protocol can send the sweep G code to the CNC system and can synchronously collect the command speed signal and response acceleration data from the CNC system. In the excitation signal selection module, the selection of the linear speed sweep signal is added, and the starting frequency, end frequency, and sweep rate of the linear sweep can be set, and the G code of the linear speed sweep supported by the CNC system can be generated.

[0077] After completing the targeted construction of the modal test system, refer to Figure 2 , a modal testing method based on self-excitation of CNC machine tools includes the following steps:

[0078] Step S1, in this example, a square thin plate is selected as a modal test object, and a modal test is performed on it using the method of the present invention. First, the thin plate is vertically clamped on a horizontal workbench of a CNC machine tool, and the workbench is driven by the Y axis of the CNC machine tool; during clamping, only the bottom edge of the thin plate is fixed. An acceleration sensor is attached to the upper left vertex of the thin plate, and the acceleration sensor is connected to the analog data acquisition module of the CNC system.

[0079] Step S2, set the sweep frequency parameters in the modal test system. In this example, the sweep frequency signal is set to a linear speed sweep frequency signal, the sweep frequency rate is set to 10 Hz / s, the start frequency is 1 Hz, and the end frequency is 400 Hz. The system will generate the G code required for the sweep frequency and send it to the CNC system to start the sweep frequency. At the same time, the CNC system collects the command speed signal of the sweep frequency and the response acceleration data of the acceleration sensor to achieve synchronous collection of the two types of signals.

[0080] Step S3, data processing. The modal test system will automatically obtain the command speed signal and response acceleration data of this frequency sweep from the numerical control system. Since the command signal is a speed signal and the response signal is an acceleration signal, the dimensions need to be unified. Because in many cases it is not possible to directly measure the speed signal using a position sensor and a speed sensor, it is necessary to first use an acceleration sensor to measure the acceleration signal, and then integrate it to obtain the speed signal. During the integration process, additional processing is required to take into account the measurement error and the speed offset caused by low-frequency interference.

[0081] In this example, in the data analysis and processing module, the time domain integration method is used to integrate the acceleration signal. Since there are obvious DC components and random noise in the acceleration signal, the acceleration signal is first low-pass filtered. Then the response acceleration data is integrated using the time domain integration method to obtain the response speed signal. Since a trend term is generated in the integrated speed signal, the polynomial least squares method is used to remove the trend term in the signal.

[0082] Step S4, in the data analysis and processing module, after obtaining the response speed signal, select the window function to calculate the cross power density spectrum and the self power density spectrum of the command speed signal and the integrated speed signal. Use the cross power density spectrum and the self power density spectrum to calculate the amplitude frequency and phase frequency of the Bode diagram, and obtain the Bode diagram and modal parameters of the measured object. In this example, the vibration Bode diagram of the upper left vertex of the vertical thin plate calculated when the bottom edge is fixed, and further derive the 1st-5th order natural frequencies of the upper left vertex as: 16HZ, 44HZ, 105HZ, 144HZ, 160HZ.

[0083] All the above optional technical solutions can be arbitrarily combined to form optional embodiments of the present application, which will not be described one by one here.

[0084] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0085] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A modal testing method based on self-excitation of CNC machine tools, characterized in that: The following steps are involved: Step S0, constructing a modal test system, the modal test system including an excitation signal selection module, a numerical control system communication interface module and a data analysis and processing module; Step S1, planning the acceleration sensor pasting position according to the type of the measurement object on the CNC machine tool, pasting the acceleration sensor, and connecting the measurement signal of the acceleration sensor to the analog quantity acquisition module of the CNC system of the CNC machine tool, and the CNC system performs data acquisition on the measurement signal of the acceleration sensor; Step S2: setting frequency sweep parameters in the modal test system, starting the frequency sweep, and synchronously collecting the command speed signal of the frequency sweep and the response acceleration data of all acceleration sensors by the numerical control system; Step S3: the modal test system obtains the command speed signal and response acceleration data of this frequency sweep from the numerical control system, and integrates the response acceleration data to obtain speed response data; In step S4, the modal test system calculates the cross-power density spectrum and the auto-power density spectrum according to the speed response data and the command speed signal, and calculates and draws the Bode diagram of the measurement object to obtain the modal parameters of the measurement object.

2. The modal testing method based on self-excitation of CNC machine tools according to claim 1 is characterized in that: The step S1 specifically includes the following steps: Step S1.1, judging the type of the measurement object on the CNC machine tool, judging whether it belongs to the type of the machine tool feed system, the machine tool mechanical structure, or the workpiece, and obtaining the type of the measurement object as a judgment result; Step S1.2, sticking the acceleration sensor according to the judgment result, wherein if the type of the measured object is a machine tool feed system, sticking the acceleration sensor to the workbench at the end of the machine tool feed system, if it is a machine tool mechanical structure, sticking the acceleration sensor to the surface of the machine tool mechanical structure, if it is a workpiece, sticking the acceleration sensor to the surface of the workpiece clamped on the machine tool; Step S1.3, setting the attached acceleration sensor, connecting the measurement signal of the acceleration sensor to the analog quantity acquisition module in the numerical control system of the numerical control machine tool, and the analog quantity acquisition module performs data acquisition on the measurement signal of the acceleration sensor.

3. The modal testing method based on self-excitation of CNC machine tools according to claim 2 is characterized in that: The step S2 specifically includes the following steps: Step S2.1, the excitation signal selection module of the modal test system selects a frequency sweep signal type from linear frequency sweep, step frequency sweep and logarithmic frequency sweep according to the signal type supported by the numerical control system of the numerical control machine tool, and sets the frequency sweep parameters including the frequency sweep rate and the frequency sweep range accordingly; Step S2.2, the excitation signal selection module generates the G code required for the frequency sweep as an excitation instruction according to the set frequency sweep parameters and the signal type supported by the CNC system, and the CNC system communication interface module sends the G code as the excitation instruction to the CNC system; Step S2.3, self-excitation frequency sweep, the CNC system generates a frequency sweep speed instruction according to the received G code, and drives the CNC machine tool to move and start the frequency sweep; Step S2.4, the acceleration sensor senses and obtains the response acceleration data of the measurement object, the numerical control system obtains the response acceleration data from the acceleration sensor, and obtains the command speed signal according to the sweep speed command.

4. The modal testing method based on self-excitation of a CNC machine tool according to claim 3 is characterized in that: The step S3 specifically comprises the following steps: Step S3.1, the numerical control system communication interface module of the modal test system obtains the command speed signal and response acceleration data of this frequency sweep from the numerical control system, and transmits them to the data analysis and processing module; Step S3.2, dimensional unification processing, the data analysis and processing module integrates the received response acceleration data to obtain speed response data, thereby unifying the dimension with the command speed signal.

5. The modal testing method based on self-excitation of CNC machine tools according to claim 4 is characterized in that: The step S4 specifically comprises the following steps: Step S4.1, the data analysis and processing module of the modal test system processes the speed response data and the command speed signal, sets a window function, and calculates and obtains the cross-power density spectrum and the auto-power density spectrum of the speed response data and the command speed signal; Step S4.2, the data analysis and processing module of the modal test system calculates the amplitude frequency and phase frequency of the Bode diagram by using the cross-power density spectrum and the auto-power density spectrum, and obtains the Bode diagram and modal parameters of the measured object.

6. A test system for executing the modal test method based on self-excitation of a numerically controlled machine tool according to any one of claims 1 to 5, characterized in that: include: The excitation signal selection module selects the frequency sweep signal type and sets the frequency sweep parameters according to the signal type supported by the numerical control system of the CNC machine tool under test, and generates the G code required for the frequency sweep according to the set frequency sweep parameters and the signal type supported by the numerical control system; A numerical control system communication interface module establishes communication with the numerical control system of the numerical control machine tool, sends the G code required for the frequency sweep obtained from the excitation signal selection module to the numerical control system, and collects the command speed signal and response acceleration data during the test from the numerical control system; and The data analysis and processing module obtains the test command speed signal and response acceleration data from the CNC system communication interface module, and processes them to obtain the Bode diagram and modal parameters of the measured object.

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