System and method for actively inhibiting thermal error of electric spindle of numerical control machine tool

Abstract

The invention provides a numerical control machine tool motorized spindle thermal error active suppression system, and the system comprises a temperature collection module which is used for collecting temperature data; the numerical control subsystem is used for receiving the temperature data, calculating the optimal analog quantity according to the temperature data and controlling the running speed of a water pump of the water cooling machine in real time according to the analog quantity; the water cooling machine module comprises a water pump and cooling water and is used for conveying the cooling water to the machine tool electric spindle so as to reduce the temperature of the machine tool electric spindle in real time. The temperature data of the motorized spindle and the environment are collected in real time and transmitted to the numerical control subsystem, the operation power of the motorized spindle water cooling machine is dynamically and accurately adjusted through the PID control module, temperature change fluctuation of the motorized spindle can be reduced, and thermal errors of a machine tool are restrained.

Description

Technical Field

[0001] The present application relates to the technical field of CNC machine tools, and in particular to a system and method for actively suppressing thermal errors of an electric spindle of a CNC machine tool. Background Art

[0002] In recent years, the aerospace and automotive equipment technologies have developed rapidly, and the requirements for the manufacturing accuracy and precision retention of CNC machining equipment have become increasingly higher. Many researchers have invested in the research of improving the precision of precision machine tools. Related studies have pointed out that factors such as machine tool assembly errors, errors caused by heat generation, and machine tool geometric errors are the main sources of errors affecting the machining accuracy of high-end precision machine tools. Among these types of errors, thermal factor errors caused by thermal deformation of machine tool parts caused by heat generated by machine tool operation are one of the main reasons affecting the production and machining accuracy of high-end precision CNC equipment. Studies have shown that in the CNC machining process, thermal error factors affect the machining accuracy of high-end precision machine tools by as much as 65%.

[0003] The electric spindle is mainly responsible for common processing types such as drilling, milling and grinding during the processing of CNC equipment. It is a key functional component of various high-end precision machine tools.

[0004] Traditionally, high-end precision machine tool electric spindles mainly use a constant-speed water-cooled machine to suppress thermal deformation. Its operating power has nothing to do with the working conditions of the machine tool, and its real-time performance is not high, making it difficult to meet the needs of high-speed and high-precision production. Summary of the invention

[0005] The embodiment of the present application provides a system for actively suppressing thermal errors of an electric spindle of a CNC machine tool, which can reduce temperature fluctuations of the electric spindle and suppress thermal errors of the machine tool.

[0006] To solve the above technical problems, the present application provides the following technical solutions: The present application provides a system for actively suppressing thermal errors of an electric spindle of a CNC machine tool, comprising: Temperature acquisition module, used to collect temperature data; A numerical control subsystem, used for receiving the temperature data, calculating the optimal analog value according to the temperature data, and controlling the running speed of the water pump of the water chiller in real time according to the analog value; The water cooling machine module includes a water pump and cooling water, and is used to deliver cooling water to the electric spindle of the machine tool to reduce the temperature of the electric spindle of the machine tool in real time.

[0007] As a further improvement of the present application, the above-mentioned CNC machine tool electric spindle thermal error active suppression system, wherein the temperature acquisition module includes a plurality of temperature sensors and a data processing module, and the plurality of temperature sensors are respectively connected to the data processing module; the data processing module includes a signal conditioning module, an analog-to-digital conversion module, a control module and a network communication module connected in sequence; The signal conditioning module is used to receive temperature data input by multiple temperature sensors, and filter, adjust the amplitude and impedance match the temperature data to obtain adjusted temperature data; The analog-to-digital conversion module is used to receive the adjusted temperature data and convert the adjusted temperature data into a digital temperature signal; The control module is used to receive and store the digital temperature signal; The network communication module is used to receive the stored digital temperature signal and send it to the numerical control subsystem.

[0008] As a further improvement of the present application, in the above-mentioned CNC machine tool electric spindle thermal error active suppression system, the water cooling machine module includes a variable frequency water cooling machine, a flow meter and a frequency converter; The frequency converter is used to receive the analog quantity output by the numerical control subsystem and control the water pump speed of the variable frequency water chiller; The flow meter is used to record the flow of cooling water.

[0009] As a further improvement of the present application, the above-mentioned CNC machine tool electric spindle thermal error active suppression system, wherein the CNC subsystem includes a PID control module, the PID control module is used to calculate the optimal PID parameters through a sparrow search algorithm, determine an analog quantity based on the optimal PID parameters, and control the water pump speed of the variable frequency water chiller through the analog quantity.

[0010] As a further improvement of the present application, the above-mentioned CNC machine tool electric spindle thermal error active suppression system, wherein the multiple temperature sensors are respectively installed on the machine tool cover, the electric spindle front bearing, the electric spindle rear bearing, the spindle housing, the spindle water inlet, the spindle water outlet, the water cooler water inlet and the water cooler water outlet.

[0011] The present application also provides a method for actively suppressing thermal errors of electric spindles of numerically controlled machine tools, which is applied to an active thermal error suppression system for electric spindles of numerically controlled machine tools. The active thermal error suppression system for electric spindles of numerically controlled machine tools includes a temperature acquisition module, a numerical control subsystem, and a water cooling machine module. The method includes: Collect temperature data; The optimal analog value is calculated based on the temperature data, and the water pump running speed of the chiller is controlled in real time according to the analog value to adjust the cooling water flow so as to reduce the temperature of the electric spindle of the machine tool in real time.

[0012] As a further improvement of the present application, the above-mentioned method for actively suppressing thermal errors of electric spindles of CNC machine tools, wherein the optimal analog value is calculated based on the temperature data, comprises: Construct a mathematical model of the cooling water pump; By changing the analog value, we can obtain multiple sets of temperature data of the heat-sensitive points of the electric spindle at different water pump speeds; Obtaining a temperature variation trend based on a plurality of groups of temperature data of thermally sensitive points of the electric spindle, and determining parameters in a mathematical model of the cooling water pump based on the temperature variation trend; Calculate the optimal PID parameters through the sparrow search algorithm; The analog quantity is determined based on the optimal PID parameter.

[0013] As a further improvement of the present application, in the above-mentioned method for actively suppressing thermal errors of the electric spindle of a CNC machine tool, the mathematical model of the cooling water pump is:

[0014] in, is an uncertain parameter, , is the inertia time constant of the cooling water system, is the lag time constant of the cooling water system.

[0015] As a further improvement of the present application, in the above-mentioned method for actively suppressing thermal errors of the electric spindle of a CNC machine tool, the control process of the water cooler includes water cooler operating temperature control and water cooler water pump speed control.

[0016] As a further improvement of the present application, the above-mentioned method for actively suppressing thermal errors of electric spindles of CNC machine tools, wherein, in the water cooler operating temperature control, the ambient temperature collected by the temperature sensor is compared with the water cooler operating temperature, and the operation of the water cooler compressor is dynamically controlled by the temperature regulator; In the water chiller water pump speed control, the inverter is controlled by the optimal PID parameters to adaptively adjust the cooling water pump speed.

[0017] Beneficial effects: The system and method for actively suppressing thermal errors of the electric spindle of a CNC machine tool provided in the present application can reduce the temperature fluctuations of the electric spindle and suppress thermal errors of the machine tool by collecting the electric spindle and ambient temperature data in real time and transmitting the data to the CNC subsystem, and dynamically and accurately adjusting the operating power of the electric spindle water cooler through the PID control module. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0019] Figure 1 A schematic diagram of the structure of a system for actively suppressing thermal errors of an electric spindle of a CNC machine tool provided in an embodiment of the present application.

[0020] Figure 2 A schematic diagram of the structure of another active thermal error suppression system for an electric spindle of a CNC machine tool provided in an embodiment of the present application.

[0021] Figure 3 A control flow chart of the water cooling module provided in an embodiment of the present application.

[0022] Figure 4 A flow chart of a method for actively suppressing thermal errors of an electric spindle of a CNC machine tool provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0024] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] The terms "first", "second", "third", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0026] The present application provides a system for actively suppressing thermal errors of an electric spindle of a CNC machine tool. Figure 1 A schematic diagram of the structure of a CNC machine tool electric spindle thermal error active suppression system provided in an embodiment of the present application is shown in FIG. Figure 1 As shown in the figure, the active thermal error suppression system of the CNC machine tool electric spindle includes a temperature acquisition module, a CNC subsystem and a water chiller module. The temperature acquisition module is used to collect temperature data; the CNC subsystem is used to receive temperature data and calculate the optimal analog value according to the temperature data, and control the running speed of the water pump of the water chiller in real time according to the analog value; the water chiller module includes a water pump and cooling water, which is used to transport cooling water to the machine tool electric spindle to reduce the temperature of the machine tool electric spindle in real time.

[0027] Figure 2 A schematic diagram of the structure of another CNC machine tool electric spindle thermal error active suppression system provided in an embodiment of the present application is shown in FIG. Figure 2As shown, the temperature acquisition module includes multiple temperature sensors and a data processing module, and the multiple temperature sensors are respectively connected to the data processing module; the data processing module includes a signal conditioning module, an analog-to-digital conversion module, a control module and a network communication module connected in sequence. The signal conditioning module is used to receive the temperature data input by multiple temperature sensors, and filter, adjust the amplitude and impedance match the temperature data to obtain the adjusted temperature data; the analog-to-digital conversion module is used to receive the adjusted temperature data and convert the adjusted temperature data into a digital temperature signal; the control module is used to receive and store the digital temperature signal; the network communication module is used to receive the stored digital temperature signal and send it to the numerical control subsystem.

[0028] As an example, the number of temperature sensors can be nine, and the nine temperature sensors are respectively installed on the machine tool cover, the front bearing of the electric spindle, the rear bearing of the electric spindle, the spindle housing, the spindle water inlet, the spindle water outlet, the water inlet of the water cooler and the water outlet of the water cooler, and are used to measure the ambient temperature, the temperature of the electric spindle, the water cooler and other parts.

[0029] In one embodiment, the numerical control subsystem includes a PID control module, which is used to calculate optimal PID parameters through a sparrow search algorithm, determine analog quantities according to the optimal PID parameters, and control the water pump speed of the variable frequency water chiller through the analog quantities.

[0030] In one embodiment, the water chiller module includes a variable frequency water chiller, a flow meter and a frequency converter. The frequency converter is used to receive the analog quantity output by the numerical control subsystem and control the water pump speed of the variable frequency water chiller; the flow meter is used to record the flow of cooling water.

[0031] The control of the water chiller module includes two aspects: 1) Water cooler operating temperature control: The ambient temperature is divided into intervals and sent directly to the water cooler control end, so as to achieve dynamic adjustment of the water cooler outlet water temperature and the ambient temperature.

[0032] 2) Water chiller water pump speed control: PID control module is used for digital-to-analog conversion, PID parameters adjust the frequency of the inverter, the inverter is used to control the water pump speed, and the flow meter is used to record the cooling water flow.

[0033] Figure 3 The control flow chart of the water cooling module provided in the embodiment of the present application is as follows: Figure 3 As shown, the entire control process includes two closed-loop control components. The first closed-loop control is the water-cooling machine operating temperature control, and the second closed-loop control is the water-cooling machine water pump speed control.

[0034] In the water-cooler operating temperature control, the ambient temperature collected by the temperature sensor is compared with the water-cooler operating temperature, and the operation of the water-cooler compressor is dynamically controlled by the temperature regulator.

[0035] In the water cooler pump speed control, the PID control module of the CNC subsystem aims to control the temperature of the heat-sensitive points of the electric spindle, outputs the PID parameters and transmits them to the I / O control board, controls the inverter to adaptively adjust the cooling water pump speed, performs heat exchange in real time to remove the heat of the heat-generating components, and ensures that the temperature of the heat-generating components is within the control range, so as to reduce the thermal error of the electric spindle.

[0036] The present application also provides a method for actively suppressing thermal errors of electric spindles of numerically controlled machine tools, which is applied to an active thermal error suppression system for electric spindles of numerically controlled machine tools. The active thermal error suppression system for electric spindles of numerically controlled machine tools includes a temperature acquisition module, a numerical control subsystem, and a water cooling machine module. Figure 4 The flowchart of the method for actively suppressing thermal errors of the electric spindle of a CNC machine tool provided in the embodiment of the present application is as follows: Figure 4 As shown, the active method for suppressing thermal errors of CNC machine tool electric spindles includes: S1, collect temperature data.

[0037] S2 calculates the optimal analog value based on the temperature data, controls the water pump speed of the chiller in real time according to the analog value, and adjusts the cooling water flow to reduce the temperature of the machine tool electric spindle in real time.

[0038] In one embodiment, step S2 comprises the following steps: S21, construct a mathematical model of the cooling water pump.

[0039] Specifically, the heat transfer of machine tools during the processing is complex and changeable, with large time lag, and the working environment is harsh, so it is difficult to establish an accurate model for it. Therefore, a second-order closed-loop system with time lag at the end of the air conditioner is used to simulate the mathematical model of the cooling water pump, and an intelligent optimization algorithm is used to optimize its PID parameters. The second-order closed-loop system model with time lag at the end of the air conditioner (that is, the mathematical model of the cold zone water pump) is:

[0040] in, is an uncertain parameter, , is the inertia time constant of the cooling water system, is the lag time constant of the cooling water system.

[0041] S22, changes the analog value to obtain multiple sets of temperature data of the thermal sensitive points of the electric spindle under different water pump speeds.

[0042] The above cooling water pump model has uncertain parameters, which need to be identified based on actual data. The experimental data method is used to identify the system parameters. The machine tool is started and the electric spindle is adjusted to 4000rpm until thermal equilibrium is reached. The analog output signal is given in the CNC PLC, and the temperature data of the thermal sensitive points of the electric spindle are tested at multiple groups of different water pump speeds.

[0043] The following are two of the experiments: (1) Open-loop experiment under 10V analog quantity Set the constant temperature workshop temperature to 16℃, the water cooling temperature to 16℃, output 10V analog quantity in the CNC PLC, and adjust the water pump speed by adjusting the inverter frequency.

[0044] (2) Open-loop experiment under 7V analog quantity Set the constant temperature workshop temperature to 16℃, the water cooling temperature to 16℃, output 7V analog quantity in the CNC PLC, control the inverter frequency through the 1073 module, and adjust the water pump speed.

[0045] S23, obtaining a temperature change trend based on multiple groups of temperature data of thermally sensitive points of the electric spindle, and determining parameters in a mathematical model of a cooling water pump based on the temperature change trend.

[0046] By changing the analog input to change the pump speed, the temperature change trend in the same time under different analog quantities was tested many times. The system identification tool in Matlab was used to identify the uncertain parameters of the system, and the corresponding delay time was set according to the response time.

[0047] S24, calculating the optimal PID parameters by using a sparrow search algorithm.

[0048] First, the population is initialized to set the cooling water pump model parameters, the parameter range that needs to be optimized, etc., and then the population is divided into three dimensions, namely: PID three parameters, the fitness value of PID acting on the cooling water pump model is calculated, and the population parameters are continuously updated until the maximum number of iterations is reached, and the optimal PID parameters are output.

[0049] S25, determining the analog quantity based on the optimal PID parameters.

[0050] Specifically, the optimal PID parameters are converted from digital to analog to obtain analog quantities.

[0051] The system and method for actively suppressing thermal errors of the electric spindle of a CNC machine tool provided in the present application can reduce the temperature fluctuations of the electric spindle and suppress thermal errors of the machine tool by collecting the electric spindle and ambient temperature data in real time and transmitting the data to the CNC subsystem, and dynamically and accurately adjusting the operating power of the electric spindle water cooler through the PID control module.

[0052] During specific implementation, the above modules and / or units can be implemented as independent entities, or can be arbitrarily combined to be implemented as the same or several entities. The specific implementation of the above modules and / or units can refer to the previous method embodiments, and the specific beneficial effects that can be achieved can also refer to the beneficial effects in the previous system embodiments, which will not be repeated here.

[0053] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are only regarded as exemplary, and the scope of the present disclosure is defined by the claims.

[0054] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A CNC machine tool electric spindle thermal error active suppression system, characterized in that: include: Temperature acquisition module, used to collect temperature data; A numerical control subsystem, used for receiving the temperature data, calculating the optimal analog value according to the temperature data, and controlling the running speed of the water pump of the water chiller in real time according to the analog value; The water cooling machine module includes a water pump and cooling water, and is used to deliver cooling water to the electric spindle of the machine tool to reduce the temperature of the electric spindle of the machine tool in real time.

2. The CNC machine tool electric spindle thermal error active suppression system according to claim 1 is characterized in that: The temperature acquisition module includes a plurality of temperature sensors and a data processing module, wherein the plurality of temperature sensors are respectively connected to the data processing module; the data processing module includes a signal conditioning module, an analog-to-digital conversion module, a control module and a network communication module which are connected in sequence; The signal conditioning module is used to receive temperature data input by multiple temperature sensors, and filter, adjust the amplitude and impedance match the temperature data to obtain adjusted temperature data; The analog-to-digital conversion module is used to receive the adjusted temperature data and convert the adjusted temperature data into a digital temperature signal; The control module is used to receive and store the digital temperature signal; The network communication module is used to receive the stored digital temperature signal and send it to the numerical control subsystem.

3. The CNC machine tool electric spindle thermal error active suppression system according to claim 1 is characterized in that: The water-cooling machine module includes a variable-frequency water-cooling machine, a flow meter and a frequency converter; The frequency converter is used to receive the analog quantity output by the numerical control subsystem and control the water pump speed of the variable frequency water chiller; The flow meter is used to record the flow of cooling water.

4. The CNC machine tool electric spindle thermal error active suppression system according to claim 3 is characterized in that: The numerical control subsystem includes a PID control module, which is used to calculate optimal PID parameters through a sparrow search algorithm, determine analog quantities according to the optimal PID parameters, and control the water pump speed of the variable frequency water chiller through the analog quantities.

5. The CNC machine tool electric spindle thermal error active suppression system according to claim 2 is characterized in that The multiple temperature sensors are respectively installed on the machine tool cover, the electric spindle front bearing, the electric spindle rear bearing, the spindle housing, the spindle water inlet, the spindle water outlet, the water inlet of the water cooler and the water outlet of the water cooler.

6. A method for actively suppressing thermal errors of electric spindles of CNC machine tools, characterized in that: Applied to the active thermal error suppression system of the electric spindle of a CNC machine tool, the active thermal error suppression system of the electric spindle of a CNC machine tool comprises a temperature acquisition module, a CNC subsystem and a water cooling machine module, and the method comprises: Collect temperature data; The optimal analog value is calculated based on the temperature data, and the water pump running speed of the chiller is controlled in real time according to the analog value to adjust the cooling water flow so as to reduce the temperature of the electric spindle of the machine tool in real time.

7. The method for actively suppressing thermal errors of electric spindles of CNC machine tools according to claim 5, characterized in that: The calculating the optimal analog value based on the temperature data comprises: Construct a mathematical model of the cooling water pump; By changing the analog value, we can obtain multiple sets of temperature data of the heat-sensitive points of the electric spindle at different water pump speeds; Obtaining a temperature variation trend based on a plurality of groups of temperature data of thermally sensitive points of the electric spindle, and determining parameters in a mathematical model of the cooling water pump based on the temperature variation trend; Calculate the optimal PID parameters through the sparrow search algorithm; The analog quantity is determined based on the optimal PID parameter.

8. The method for actively suppressing thermal errors of electric spindles of CNC machine tools according to claim 7, characterized in that: The cooling water pump mathematical model is: in, is an uncertain parameter, , is the inertia time constant of the cooling water system, is the lag time constant of the cooling water system.

9. The method for actively suppressing thermal errors of electric spindles of CNC machine tools according to claim 6, characterized in that: The control process of the water cooler includes water cooler operating temperature control and water cooler water pump speed control.

10. The method for actively suppressing thermal errors of an electric spindle of a CNC machine tool according to claim 9, characterized in that: In the water-cooler operating temperature control, the ambient temperature collected by the temperature sensor is compared with the water-cooler operating temperature, and the operation of the water-cooler compressor is dynamically controlled by the temperature regulator; In the water chiller water pump speed control, the inverter is controlled by the optimal PID parameters to adaptively adjust the cooling water pump speed.

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