Digital physical fusion machine tool precision retention accelerated test system and method

Abstract

The present application belongs to the field of numerical control machine tool performance testing, and discloses a kind of digital physical fusion's machine tool precision retention accelerated testing system and method.Testing system includes vibration stress loading system, temperature stress loading system, dynamic force in-machine loading system, digital twin system, machine tool state information monitoring system, machine tool precision testing system and the machine tool to be measured.Testing steps include: preparing the load spectrum and test program spectrum of the machine tool to be measured;The machine tool to be measured is installed in the accelerated testing system;Deploy the machine tool state information monitoring system;Establish the digital twin model of the machine tool to be measured;Precision testing and multi-stress loading test are carried out on the machine tool to be measured;Digital twin model simulation calculation of the precision degradation process of the machine tool to be measured;Evaluation of the precision retention capability of the machine tool to be measured and problem tracing.The testing system and method combine digital twin technology with accelerated testing technology, reduce the accelerated testing time, reduce energy consumption, greatly expand the data volume, and improve the testing efficiency of the machine tool precision retention.

Description

Technical Field

[0001] The present invention belongs to the technical field of CNC machine tool performance testing, and relates to a digital-physical fusion machine tool precision retention acceleration testing system and method. Background Art

[0002] Precision retention is one of the key performance indicators of CNC machine tools, describing the ability of a machine tool to maintain its original precision. During the long-term service of a machine tool, due to the effects of various loads such as cutting force, temperature, and vibration, the accuracy of the machine tool tends to gradually decline, resulting in deviations in the size and shape of machine-processed parts. Precision degradation has become a common and complex technical problem in the machine tool industry. Given the long-term and slow-changing characteristics of machine tool precision degradation, the on-site tracking test method in traditional service environments is too inefficient, and the test process can last for months or even years depending on the accuracy retention time, which seriously restricts the tracing of machine tool problems and iterative upgrades. Therefore, there is an urgent need to study efficient testing methods for machine tool precision retention, quickly obtain machine tool precision degradation data and potential weak links, and accelerate the iterative upgrades of machine tool products.

[0003] At present, preliminary explorations have been carried out at home and abroad on the precision retention test devices and methods of machine tools and functional components, and related technologies still need to be further optimized and improved. In 2018, Wang Liping et al. of Tsinghua University disclosed in patent CN201810317219.2 a non-contact force loading device that simulates three-axis CNC machine tool processing. Through the combination of a three-degree-of-freedom parallel mechanism and an electromagnetic loading disk, it is possible to apply forces of different frequencies to the machine tool. In 2023, Li Guofa et al. of Jilin University disclosed in patent CN202311566389.1 a dynamically loaded cradle-type pendulum reliability test device, which uses a hydraulic cylinder and a dynamometer to apply dynamic force and torque to the pendulum at any position. In 2023, Wang Yongqing and others from Dalian University of Technology disclosed in patent CN202311440828.4 a method and platform for accelerating the accuracy retention of CNC machine tools. By applying multiple stresses such as "force-heat-vibration-motion" to the machine tool, the actual service conditions of the machine tool are simulated to obtain the accuracy degradation data of the machine tool. In 2024, Liu Kuo and others from Dalian University of Technology disclosed in patent CN202410290290.1 ​​a platform and method for accelerating the accuracy retention of spindles based on multi-load loading. The platform uses a temperature load loading unit, a vibration load loading unit, and a simulated cutting load unit to load the spindle with multi-loads to accelerate the accuracy degradation of the spindle and shorten the test cycle.

[0004] Through research and analysis of existing precision retention testing devices and methods for machine tools and functional components, we found the following: 1. Machine tool precision retention testing devices should be capable of loading multiple stresses, including vibration, temperature, static and dynamic forces. Single force or torque loading cannot fully simulate the actual service conditions of machine tools. Currently available testing devices with multi-stress loading capabilities still have problems such as incompact structures and excessive floor space. 2. Currently available accelerated testing methods based on multi-stress loading are all fully physical tests, which have limitations such as limited data acquisition and long testing times. Summary of the Invention

[0005] The present invention provides a digital-physical fusion accelerated testing system and method for machine tool precision retention. By combining digital twin technology with accelerated testing technology, it reduces accelerated testing time, reduces energy consumption, greatly expands the amount of data, and further improves the testing efficiency of machine tool precision retention.

[0006] The technical solution of the present invention:

[0007] A digital-physical fusion machine tool precision retention acceleration test system mainly consists of a vibration stress loading system 1, a temperature stress loading system 2, a dynamic force on-machine loading system 3, a digital twin system 4, a machine tool status information monitoring system 5, a machine tool precision test system 6, and a machine tool under test 7;

[0008] The vibration stress loading system 1 mainly consists of an extended table 1-1, an auxiliary support structure 1-2 and a vibration generator 1-3; wherein the auxiliary support structure 1-2 is surrounded by columns, beams and webs, and the vibration generator 1-3 is arranged at the center of the auxiliary support structure 1-2. The vibration generator 1-3 and the auxiliary support structure 1-2 are both installed on the foundation and jointly support the extended table 1-1 located above;

[0009] The temperature stress loading system 2 is mainly composed of a top automatic hoisting mechanism 2-1, a temperature circulation unit 2-2 and an insulating warehouse body 2-3; wherein, the top automatic hoisting mechanism 2-1 is located above the insulating warehouse body 2-3, and the temperature circulation unit 2-2 is installed behind the insulating warehouse body 2-3; the top automatic hoisting mechanism 2-1 includes an up-and-down action cylinder 2-1-1, a left-and-right action cylinder 2-1-2, a movable sealing plate 2-1-3 and a movable sealing plate moving bracket 2-1-4; wherein, the left-and-right action cylinder 2-1-2 is fixed to the fixed frame and connected to the movable sealing plate moving bracket 2-1-4; the upper end of the up-and-down action cylinder 2-1-1 is connected to the movable sealing plate moving bracket 2-1-4, and the lower end is connected to the movable sealing plate 2-1-3, so as to realize the vertical and horizontal movement of the movable sealing plate 2-1-3;

[0010] The dynamic force loading system 3 is mainly composed of a machine tool spindle interface 3-1, a moving platform 3-2, three two-degree-of-freedom rigid hinges 3-3, three electric actuators 3-4, a fixed base 3-5 and an auxiliary support rib 3-6; wherein, the fixed base 3-5 is composed of two fixed bases with fixed plates vertically installed; the auxiliary support rib 3-6 is fixedly supported on the fixed base 3-5, and the three electric actuators 3-4 are evenly distributed at equal angles of 120° and are rigidly connected to the fixed plate of the fixed base 3-5 through a flange, one end of the two-degree-of-freedom rigid hinge 3-3 is rigidly connected to the output end of the electric actuator 3-4, and the other end is rigidly connected to the moving platform 3-2; the moving platform 3-2 is further rigidly connected to the machine tool spindle interface 3-1; the machine tool spindle interface 3-1 includes a simulated tool holder 3-1-1, a tool holder fixing cylinder 3-1-2, an anti-loosening end cover 3-1-3, a bearing 3-1-4, an interface base 3-1-5, a sealing end cover 3-16, a three-dimensional Force sensor 3-1-7 and sensor dust cover 3-1-8; Among them, the simulated tool handle 3-1-1 is installed in the center hole of the tool handle fixing cylinder 3-1-2, and is axially fixed by the anti-loosening end cover 3-1-3 and screws. The tool handle fixing cylinder 3-1-2 and the interface base 3-1-5 cooperate with the inner ring and outer ring of the bearing 3-1-4. The sealing end cover 3-1-6 is installed at the bottom of the interface base 3-1-5. The interface base 3-1-5, the sealing end cover 3-1-6 and the three-dimensional force sensor The sensor 3-1-7 is fixed by bolts, and the sensor dust cover 3-1-8 is outside the three-dimensional force sensor 3-1-7; the electric actuator 3-4 includes an electric cylinder 3-4-1, a guide rod 3-4-2, a hinge connection plate 3-4-3 and a fixed base connection plate 3-4-4; among which, the front end of the electric cylinder 3-4-1 is connected to the guide rod 3-4-2 through the fixed base connection plate 3-4-4, and the front end of the guide rod 3-4-2 is rigidly connected to the hinge connection plate 3-4-3;

[0011] The digital twin system 4 is mainly composed of a test scene digital twin construction module, a machine tool digital twin construction module, a data real-time mapping module, an offline test data injection module, a physical simulation module and a machine tool precision calculation module; the test scene digital twin construction module is used to construct the geometric model and motion model of the vibration stress loading system 1, the temperature stress loading system 2 and the dynamic force on-machine loading system 3; the machine tool digital twin construction module is used to construct the parameterized geometric model and motion model of the machine tool, and the parameterized geometric model adaptively updates the geometric structure according to the input parameters or physical simulation results; the data real-time mapping module is used to real-timely map the machine tool status information collected by the machine tool status information monitoring system 5, the vibration frequency and vibration amplitude of the vibration stress loading system 1, the temperature cycle information of the temperature stress loading system 2, and the loading force amplitude and frequency of the dynamic force on-machine loading system 3. Transmitted to the test scene digital twin and the machine tool digital twin and updated; the offline test data injection module is used to import the machine tool accuracy value and the linear feed axis shape curve obtained by the offline test of the machine tool accuracy test system 6 into the machine tool digital twin and update it; the physical simulation model embedded in the physical simulation module includes a dynamic joint surface wear model, a bolted joint surface loosening model and a base component stress evolution model. The physical simulation model represents the relationship between loading stress, action time and micro-deformation; the physical simulation module has the function of updating the parameters of the physical simulation model according to the actual test data and predicting the deformation caused by the wear, looseness and creep behavior of the machine tool 7 under test; the machine tool accuracy calculation module is used to calculate the geometric accuracy of each linear feed axis of the machine tool based on the deformation caused by the wear, looseness and creep behavior of the machine tool 7 under test predicted by the physical simulation module.

[0012] The machine tool status information monitoring system 5 is mainly composed of a CNC system communication gateway, a temperature sensor, a vibration sensor, a power sensor, an optical fiber strain sensor, a data acquisition card, and a signal conditioner;

[0013] The machine tool precision testing system 6 refers to a laser interferometer.

[0014] A method for accelerating the accuracy retention of machine tools using a digital-physical fusion accelerated accuracy retention test system includes the following steps:

[0015] Step 1: Prepare the load spectrum and program spectrum of the machine tool;

[0016] The vibration, temperature rise, feed speed and cutting force during the actual cutting process of the machine tool are collected to form the load spectrum of the machine tool's conventional cutting working conditions; according to the loading test process, the stress level is increased based on the machine tool's conventional cutting working conditions to form a program spectrum for the machine tool loading test.

[0017] Step 2: Install the machine tool 7 under test into the digital-physical fusion machine tool accuracy retention acceleration test system;

[0018] Lift the machine tool under test 7, open the automatic lifting mechanism 2-1 on the top of the temperature stress loading system 2, so that the lifting device carries the machine tool under test 7 into the heat-insulating chamber 2-3 of the temperature stress loading system 2, while avoiding interference between the lifting device and the automatic lifting mechanism 2-1 on the top of the temperature stress loading system 2, and then place the machine tool under test 7 on the extension table 1-1; adjust the machine tool under test 7 to a horizontal level, and fix the machine tool under test 7 to the extension table 1-1 through tooling such as a pressure plate to complete the installation and positioning of the machine tool under test 7.

[0019] Step 3: Deploy the machine tool status information monitoring system 5;

[0020] The numerical control system of the machine tool under test 7 is connected to the numerical control system communication gateway. Temperature sensors and vibration sensors are installed on the screw-nut pair, bearing seats at both ends of the screw, and linear feed shaft of the machine tool under test 7. An optical fiber strain sensor is installed on one side of the bed guide rail mounting surface of the machine tool under test 7. A power sensor is installed on the three-phase line of the motor driver of the machine tool under test 7 to collect the position information of the machine tool under test 7, the speed, vibration, temperature, strain and power of the linear feed shaft.

[0021] Step 4: Establish a digital twin of the machine tool under test 7;

[0022] The parametric geometric model and motion model of the machine tool under test 7 are established through the machine tool digital twin construction module of the digital twin system 4. The data real-time mapping module is connected to the machine tool status information collected in real time by the machine tool status information monitoring system 5, the vibration frequency and vibration amplitude of the vibration stress loading system 1, the temperature cycle information of the temperature stress loading system 2, and the loading force amplitude and frequency of the dynamic force on-machine loading system 3. By transmitting various data collected by the machine tool status information monitoring system 5, the vibration stress loading system 1, the temperature stress loading system 2 and the dynamic force on-machine loading system 3, the parametric geometric model and motion model of the machine tool under test 7 are driven to run synchronously with the physical entity.

[0023] Step 5: Performing accuracy test and multi-stress loading test on the machine tool 7 under test;

[0024] First, the positioning accuracy, straightness, angle and shape curve of each linear feed axis of the machine tool under test 7 are tested using the machine tool precision test system 6; then, according to the program spectrum of the machine tool loading test obtained in step 1, the machine tool under test 7 is subjected to a "vibration-temperature-speed-dynamic force" multi-stress loading test: the vibration stress loading system 1 and the temperature stress loading system 2 are used to synchronously load sinusoidal vibration stress and thermal cycle stress on the machine tool under test 7, and at the same time, the linear feed axis of the machine tool under test 7 is fed according to the set program; after the loading time reaches the set value, the pre-sequence loading is stopped, and the dynamic force on-machine loading system 3 is used to load the sinusoidal dynamic force on the machine tool under test 7 until the loading time reaches the set value; this loading process is a loading cycle. After completing a loading cycle, the accuracy of the machine tool under test 7 is retested, and the accuracy value obtained from the test and the shape curve of the linear feed axis are imported into the digital twin system 4 through the offline test data injection module; the loading, testing and data import are repeated until the specified number of loading cycles are completed.

[0025] Step 6: Simulation calculation of the accuracy degradation process of the machine tool 7 under test;

[0026] First, before the loading test in step five begins, the parametric geometric model of the machine tool under test 7 is updated based on the shape curve of the linear feed shaft obtained in the test; then, during the execution of step five, since the degradation process of the accuracy of the machine tool under test 7 is closely related to the casting and assembly process of the machine tool under test 7, the parametric geometric model of the machine tool under test 7 established in step four cannot reflect the differences in different machine tool manufacturing processes, which directly affects the accuracy of the physical simulation. Therefore, according to the machine tool status information collected in real time by the machine tool status information monitoring system 5 and the shape curve and loading stress of the linear feed shaft measured by the machine tool accuracy testing system 6, the parameters of the physical simulation model embedded in the physical simulation module are updated to form a physical simulation model that can reflect the manufacturing process of the machine tool under test 7. Then, after step five is completed, the accuracy change data of the machine tool under test 7 obtained in step five is used as prior information, and according to the load spectrum of the machine tool's conventional cutting working condition obtained in step one, the test scenario digital twin is run to simulate the loading test process. The deformation caused by the wear, loosening, and creep behavior of the machine tool under test 7 is simulated and calculated in real time through the physical simulation model, and the digital twin of the machine tool under test 7 updates the parametric geometric model of the machine tool under test 7 in real time; finally, the machine tool accuracy calculation module of the digital twin system 4 is used to calculate the geometric accuracy of each linear feed axis of the machine tool under test 7 in real time, and the iterative calculation is continued until the calculated accuracy of the machine tool under test 7 reaches the set failure threshold, and the simulation calculation is stopped.

[0027] Step 7: Evaluate the accuracy maintenance capability of the machine tool under test and trace the source of the problem.

[0028] Based on the geometric accuracy of each linear feed axis of the machine tool under test 7 calculated in real time in step 6, the accuracy degradation curve of the machine tool under test 7 is drawn to evaluate the accuracy maintenance ability of the machine tool under test 7; according to the simulation calculation results, the position where the deformation of the machine tool under test 7 accumulates the largest amount is the shortcoming of the accuracy maintenance of the machine tool under test 7, which needs to be the focus of subsequent machine tool optimization.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention provides a compact accelerated testing system for machine tool precision retention. Different from the overall mobile temperature stress loading system, this solution installs the machine tool under test by setting an automatic lifting mechanism on the top of the temperature stress loading system, thereby reducing the overall system footprint by 1 / 2. At the same time, the introduction of the digital twin system further enhances the intelligence level of the testing system.

[0031] 2. The present invention proposes a digital-physical fusion accelerated testing method for machine tool precision retention, which is dominated by physical loading tests and assisted by digital simulation tests. The differences between different machine tool manufacturing processes are characterized by the data measured through physical tests, and then the constraint parameters of the digital simulation model are adjusted based on the measured data. This can effectively avoid the problems of limited data acquisition and long testing time in pure physical tests, and the low calculation accuracy of pure digital tests and the difficulty in reflecting the differences in machine tool manufacturing processes, thereby further improving the testing efficiency of machine tool precision retention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the overall structure of the machine tool accuracy retention acceleration test system;

[0033] Figure 2 It is a structural diagram of the vibration stress loading system and the temperature stress loading system;

[0034] Figure 3 This is a structural diagram of the top automatic lifting mechanism of the temperature stress loading system;

[0035] Figure 4 It is a structural diagram of the dynamic force on-machine loading system;

[0036] Figure 5 It is a structural diagram of the machine tool spindle interface of the dynamic force on-machine loading system;

[0037] Figure 6 It is a structural diagram of the electric actuator of the dynamic force on-machine loading system;

[0038] Figure 7 It is a flow chart of the accelerated testing method for machine tool precision retention based on digital-physical fusion.

[0039] In the figure: 1 vibration stress loading system, 1-1 extension table, 1-2 auxiliary support structure, 1-3 vibration generator; 2 temperature stress loading system, 2-1 top automatic lifting mechanism, 2-2 temperature cycle unit, 2-3 insulation chamber, 2-1-1 up and down action cylinder, 2-1-2 left and right action cylinder, 2-1-3 movable sealing plate, 2-1-4 movable sealing plate movable bracket; 3 dynamic force on-machine loading system, 3-1 machine tool spindle interface, 3-2 dynamic platform, 3-3 two-degree-of-freedom rigid hinge, 3-4 electric actuator , 3-5 fixed base, 3-6 auxiliary support rib, 3-1-1 simulated tool holder, 3-1-2 tool holder fixing tube, 3-1-3 anti-loosening end cover, 3-1-4 bearing, 3-1-5 interface base, 3-1-6 sealing end cover, 3-1-7 three-dimensional force sensor, 3-1-8 sensor dust cover, 3-4-1 electric cylinder, 3-4-2 guide rod, 3-4-3 hinge connecting plate, 3-4-4 fixed base connecting plate; 4 digital twin system; 5 machine tool status information monitoring system; 6 machine tool precision testing system; 7 machine tool under test. DETAILED DESCRIPTION

[0040] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0041] Taking the accuracy retention acceleration test of a horizontal machining center as an example, the steps are as follows:

[0042] Step 1: Prepare the load spectrum and test program spectrum of the machine tool under test;

[0043] The vibration, temperature rise, feed speed and cutting force data of the horizontal machining center during the actual cutting process are collected to form the load spectrum of the conventional cutting working conditions of the horizontal machining center; according to the loading test process, the stress level is increased on the basis of the conventional working conditions to form the loading test program spectrum of the horizontal machining center.

[0044] Step 2: Install the machine tool under test into the digital-physical fusion machine tool accuracy retention acceleration test;

[0045] Lift the horizontal machining center, open the automatic lifting mechanism 2-1 on the top of the temperature stress loading system 2, so that the lifting device carries the horizontal machining center into the insulated warehouse 2-3 of the temperature stress loading system 2, and at the same time avoid interference between the lifting device and the automatic lifting mechanism 2-1 on the top of the temperature stress loading system 2, then place the horizontal machining center on the extended table 1-1, adjust the horizontal machining center to a horizontal level, and fix the horizontal machining center to the extended table 1-1 through tooling such as a pressure plate to complete the installation and positioning of the horizontal machining center to be tested.

[0046] Step 3: Deploy the machine tool status information monitoring system;

[0047] The CNC system of the horizontal machining center is connected to the gateway, and temperature sensors and vibration sensors are installed on the screw-nut pair, bearing seats at both ends of the screw, and linear feed axis motor of the horizontal machining center. A fiber optic strain sensor is installed on one side of the bed guide rail mounting surface of the horizontal machining center, and a power sensor is installed on the three-phase line of the motor driver of the horizontal machining center to collect the position information, feed axis speed, vibration, temperature, strain and power of the horizontal machining center.

[0048] Step 4: Establish a digital twin of the machine tool under test;

[0049] The parametric geometric model and motion model of the horizontal machining center are established through the machine tool digital twin construction module of the digital twin system 4. The data real-time mapping module is connected to the machine tool status information collected in real time by the machine tool status information monitoring system 5, the vibration frequency and vibration amplitude information of the vibration stress loading system 1, the temperature cycle information of the temperature stress loading system 2, and the loading force amplitude and frequency information of the dynamic force on-machine loading system 3. The digital twin model is driven by the multiple data transmitted from the machine tool status information monitoring system 5, the vibration stress loading system 1, the temperature stress loading system 2 and the dynamic force on-machine loading system 3 to run synchronously with the physical entity.

[0050] Step 5: Conduct accuracy test and multi-stress loading test on the machine tool under test;

[0051] The positioning accuracy, straightness, angle and shape curve of the X, Y and Z linear feed axes of the horizontal machining center are tested using the machine tool precision testing system 6; according to the acceleration test program spectrum compiled in step one, the horizontal machining center is subjected to a "vibration-temperature-speed-dynamic force" multi-stress loading test. The specific test process is as follows: the horizontal machining center is subjected to a frequency sweep test using the vibration stress loading system 1, and the three resonant frequencies of the horizontal machining center, 48Hz, 72Hz and 95Hz, are selected as the loading frequencies of the sinusoidal vibration stress. The three frequencies are vibrated continuously for 3 hours with an amplitude of 10μm at each frequency, for a total of 9 hours; while the sinusoidal vibration stress is being loaded, the temperature stress loading system 2 is used to perform a thermal cycle stress loading of 0~40℃ on the horizontal machining center; while the sinusoidal vibration stress and thermal cycle stress are being loaded, the X / Y / Z feed axes of the horizontal machining center are fed at a high speed of 40,000mm / min according to the set program. After the 12-hour "vibration-temperature-speed" loading is completed, the dynamic force on-machine loading system 3 is installed on the horizontal machining center: the fixed base 3-5 of the dynamic force on-machine loading system 3 is fixed to the workbench of the horizontal machining center through a pressure plate, and the machine tool spindle interface 3-1 is connected to the spindle of the horizontal machining center. The three two-degree-of-freedom rigid hinges 3-3 are driven by three electric actuators 3-4 to drive the dynamic platform 3-2 to synchronously apply X / Y / Z three-dimensional sinusoidal dynamic forces to the horizontal machining center. The amplitude of the force loading is 2000N, the frequency is 20Hz, and the duration is 9h. While the dynamic force is loading, the temperature of the temperature stress loading system 2 is always kept at 20°C. The above loading process constitutes a loading cycle. After completing one loading cycle, the temperature of the temperature stress loading system 2 is maintained at 20°C, and the positioning accuracy, straightness, angle, and shape curve of the X, Y, and Z linear feed axes of the horizontal machining center are retested. The accuracy values ​​and linear feed axis shape curves obtained from the test are imported into the digital twin system 4 through the offline test data injection module; the loading, testing, and data import are repeated until five loading cycles are completed.

[0052] Step 6: Simulation calculation of the accuracy degradation process of the machine tool under test;

[0053] First, before the start of the loading test in step five, the geometric model of the horizontal machining center is updated according to the linear feed axis shape curve obtained from the test; then, during the execution of step five, the parameters of the physical simulation model of the digital twin system 4 are updated according to the information obtained by the machine tool status information monitoring system 5, the linear feed axis shape curve and the loading stress information measured by the machine tool precision testing system 6, so as to form a special physical simulation model that can reflect the manufacturing process characteristics of the horizontal machining center; then, after the execution of step five, the precision change data of the horizontal machining center obtained in step five is used as prior information, and according to the normal working condition load spectrum of the machine tool compiled in step one, the digital twin of the test scenario is run to simulate the loading test process, and the deformation caused by the wear, looseness and creep behavior of the horizontal machining center is calculated in real time through the physical simulation model, and the geometric model of the digital twin of the horizontal machining center is updated in real time; finally, the geometric precision of the X / Y / Z feed axis of the machine tool is calculated in real time through the machine tool precision calculation module of the digital twin system 4, and the iterative calculation is continued until the calculated precision of the horizontal machining center reaches the set failure threshold, and the simulation calculation is stopped.

[0054] Step 7: Evaluate the accuracy maintenance capability of the machine tool under test and trace the source of the problem.

[0055] Based on the geometric accuracy of the X / Y / Z linear feed axes of the horizontal machining center calculated in real time in step six, the accuracy degradation curve of the horizontal machining center is drawn to evaluate the accuracy retention ability of the horizontal machining center; according to the simulation calculation results, the position with the largest accumulated deformation of the horizontal machining center is the shortcoming of the machine tool's accuracy retention and needs to be the focus of subsequent machine tool optimization.

[0056] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will appreciate that modifications may be made to the technical solutions described in the aforementioned embodiments, or that some of the technical features may be replaced with equivalents. Such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A digital-physical fusion machine tool precision retention acceleration test system, characterized by: The digital-physical fusion machine tool precision retention acceleration test system mainly consists of a vibration stress loading system (1), a temperature stress loading system (2), a dynamic force on-machine loading system (3), a digital twin system (4), a machine tool status information monitoring system (5), a machine tool precision test system (6) and a machine tool under test (7); The vibration stress loading system (1) mainly consists of an extended table (1-1), an auxiliary support structure (1-2) and a vibration generator (1-3); wherein the vibration generator (1-3) is arranged at the center of the auxiliary support structure (1-2); the vibration generator (1-3) and the auxiliary support structure (1-2) are both installed on the foundation to jointly support the extended table (1-1) located above; The temperature stress loading system (2) is mainly composed of a top automatic hoisting mechanism (2-1), a temperature circulation unit (2-2) and an insulation chamber (2-3); wherein the top automatic hoisting mechanism (2-1) is located above the insulation chamber (2-3), and the temperature circulation unit (2-2) is installed behind the insulation chamber (2-3); The dynamic force loading system (3) is mainly composed of a machine tool spindle interface (3-1), a moving platform (3-2), three two-degree-of-freedom rigid hinges (3-3), three electric actuators (3-4), a fixed base (3-5) and an auxiliary support rib (3-6); wherein, the fixed base (3-5) is composed of two fixed base plates vertically mounted with a fixed plate; the auxiliary support rib (3-6) is fixedly supported on the fixed base (3-5), and the three electric actuators (3-4) are evenly distributed at equal angles of 120 degrees and are rigidly connected to the fixed plate of the fixed base (3-5) through a flange; one end of the two-degree-of-freedom rigid hinge (3-3) is rigidly connected to the output end of the electric actuator (3-4), and the other end is rigidly connected to the moving platform (3-2); the moving platform (3-2) is further rigidly connected to the machine tool spindle interface (3-1); The digital twin system (4) is mainly composed of a test scene digital twin construction module, a machine tool digital twin construction module, a data real-time mapping module, an offline test data injection module, a physical simulation module and a machine tool precision calculation module; the test scene digital twin construction module is used to construct the geometric model and motion model of the vibration stress loading system (1), the temperature stress loading system (2) and the dynamic force on-machine loading system (3); the machine tool digital twin construction module is used to construct the parameterized geometric model and motion model of the machine tool, and the parameterized geometric model adaptively updates the geometric structure according to the input parameters or the physical simulation results; the data real-time mapping module is used to convert the machine tool status information collected by the machine tool status information monitoring system (5), the vibration frequency and vibration amplitude of the vibration stress loading system (1), the temperature cycle information of the temperature stress loading system (2), the loading force amplitude and frequency, and transmits it to the test scene digital twin and the machine tool digital twin in real time and updates them; the offline test data injection module is used to import the machine tool accuracy value and the linear feed axis shape curve obtained by the offline test of the machine tool accuracy test system (6) into the machine tool digital twin and update them; the physical simulation model embedded in the physical simulation module includes a dynamic joint surface wear model, a bolted joint surface loosening model and a basic component stress evolution model. The physical simulation model represents the relationship between loading stress, action time and micro-deformation; the physical simulation module has the function of updating the parameters of the physical simulation model according to the actual test data and predicting the deformation caused by the wear, looseness and creep behavior of the tested machine tool (7); the machine tool accuracy calculation module is used to calculate the geometric accuracy of each linear feed axis of the machine tool according to the deformation caused by the wear, looseness and creep behavior of the tested machine tool (7) predicted by the physical simulation module; The machine tool status information monitoring system (5) is mainly composed of a CNC system communication gateway, a temperature sensor, a vibration sensor, a power sensor, an optical fiber strain sensor, a data acquisition card, and a signal conditioner; The machine tool precision testing system (6) is a laser interferometer.

2. The digital-physical fusion machine tool precision retention acceleration test system according to claim 1 is characterized in that: The top automatic lifting mechanism (2-1) comprises an up-and-down action cylinder (2-1-1), a left-and-right action cylinder (2-1-2), a movable sealing plate (2-1-3) and a movable sealing plate moving bracket (2-1-4); wherein the left-and-right action cylinder (2-1-2) is fixed on a fixed frame and connected to the movable sealing plate moving bracket (2-1-4); the upper end of the up-and-down action cylinder (2-1-1) is connected to the movable sealing plate moving bracket (2-1-4), and the lower end is connected to the movable sealing plate (2-1-3), so as to realize the vertical and horizontal movement of the movable sealing plate (2-1-3).

3. The digital-physical fusion machine tool precision retention accelerated testing system according to claim 1 is characterized in that: The machine tool spindle interface (3-1) comprises a simulated tool holder (3-1-1), a tool holder fixing cylinder (3-1-2), an anti-loosening end cover (3-1-3), a bearing (3-1-4), an interface base (3-1-5), a sealing end cover (3-1-6), a three-dimensional force sensor (3-1-7) and a sensor dust cover (3-1-8); wherein the simulated tool holder (3-1-1) is installed in the center hole of the tool holder fixing cylinder (3-1-2) and is connected to the tool holder through the anti-loosening end cover (3-1 -3) and screws for axial fixation, the tool holder fixing cylinder (3-1-2) and the interface base (3-1-5) cooperate with the inner ring and outer ring of the bearing (3-1-4), the sealing end cover (3-1-6) is installed at the bottom of the interface base (3-1-5), the interface base (3-1-5), the sealing end cover (3-1-6) and the three-dimensional force sensor (3-1-7) are fixed by bolts, and the sensor dust cover (3-1-8) is outside the three-dimensional force sensor (3-1-7).

4. The digital-physical fusion machine tool precision retention acceleration test system according to claim 1 is characterized in that: The electric actuator (3-4) comprises an electric cylinder (3-4-1), a guide rod (3-4-2), a hinge connecting plate (3-4-3) and a fixed base connecting plate (3-4-4); wherein the front end of the electric cylinder (3-4-1) is connected to the guide rod (3-4-2) via the fixed base connecting plate (3-4-4), and the front end of the guide rod (3-4-2) is rigidly connected to the hinge connecting plate (3-4-3).

5. A method for accelerating the accuracy retention of machine tools using a digital-physical fusion accelerated testing system for machine tool accuracy retention, applied to a digital-physical fusion accelerated testing system for machine tool accuracy retention as described in any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Prepare the load spectrum and program spectrum of the machine tool; The vibration, temperature rise, feed speed and cutting force during the actual cutting process of the machine tool are collected to form the load spectrum of the machine tool's normal cutting working condition. According to the loading test process, the stress level is increased based on the normal cutting working condition of the machine tool to form the program spectrum of the machine tool loading test. Step 2: Install the machine tool under test (7) into the digital-physical fusion machine tool accuracy retention acceleration test system; Lift the machine tool under test (7), open the top automatic lifting mechanism (2-1) of the temperature stress loading system (2), so that the lifting device carries the machine tool under test (7) into the heat-insulating chamber (2-3) of the temperature stress loading system (2), and avoid interference between the lifting device and the top automatic lifting mechanism (2-1) of the temperature stress loading system (2), and then place the machine tool under test (7) on the extended table (1-1); adjust the machine tool under test (7) to a horizontal level, and fix the machine tool under test (7) to the extended table (1-1) by a pressure plate, thereby completing the installation and positioning of the machine tool under test (7); Step 3: Deploy the machine tool status information monitoring system (5); The numerical control system of the machine tool under test (7) is connected to the numerical control system communication gateway, and temperature sensors and vibration sensors are installed on the screw-nut pair, the bearing seats at both ends of the screw, and the linear feed shaft of the machine tool under test (7). An optical fiber strain sensor is installed on one side of the bed guide rail installation surface of the machine tool under test (7), and a power sensor is installed at the three-phase line of the motor driver of the machine tool under test (7) to collect the position information of the machine tool under test (7), the speed, vibration, temperature, strain and power of the linear feed shaft; Step 4: Create a digital twin of the machine tool under test (7); The parameterized geometric model and motion model of the machine tool under test (7) are established through the machine tool digital twin construction module of the digital twin system (4). The data real-time mapping module is connected to the machine tool status information collected in real time by the machine tool status information monitoring system (5), the vibration frequency and vibration amplitude of the vibration stress loading system (1), the temperature cycle information of the temperature stress loading system (2), and the loading force amplitude and frequency of the dynamic force on-machine loading system (3). By transmitting the various data collected by the machine tool status information monitoring system (5), the vibration stress loading system (1), the temperature stress loading system (2) and the dynamic force on-machine loading system (3), the parameterized geometric model and motion model of the machine tool under test (7) are driven to run synchronously with the physical entity. Step 5: Conducting precision testing and multi-stress loading tests on the machine tool under test (7); First, the positioning accuracy, straightness, angle and shape curve of each linear feed axis of the tested machine tool (7) are tested using the machine tool precision test system (6); then, according to the program spectrum of the machine tool loading test obtained in step 1, the tested machine tool (7) is subjected to a "vibration-temperature-speed-dynamic force" multi-stress loading test: the vibration stress loading system (1) and the temperature stress loading system (2) are used to synchronously load the tested machine tool (7) with sinusoidal vibration stress and thermal cycle stress, while the linear feed axis of the tested machine tool (7) is fed according to the set program; after the loading time reaches the set value, the pre-sequence loading is stopped, and the dynamic force on-machine loading system (3) is used to load the tested machine tool (7) with sinusoidal dynamic force until the loading time reaches the set value; this loading process is a loading cycle, and after completing a loading cycle, the accuracy of the tested machine tool (7) is retested, and the accuracy value obtained from the test and the shape curve of the linear feed axis are imported into the digital twin system (4) through the offline test data injection module; the loading, testing and data import are repeated in this way until the specified number of loading cycles are completed; Step 6: Simulation calculation of the accuracy degradation process of the machine tool under test (7); First, before the loading test in step five begins, the parametric geometric model of the machine tool under test (7) is updated based on the shape curve of the linear feed shaft obtained in the test; then, during the execution of step five, since the degradation process of the accuracy of the machine tool under test (7) is closely related to the casting and assembly process of the machine tool under test (7), the parametric geometric model of the machine tool under test (7) established in step four cannot reflect the differences in the manufacturing processes of different machine tools, which directly affects the accuracy of the physical simulation. Therefore, based on the machine tool status information collected in real time by the machine tool status information monitoring system (5), the shape curve of the linear feed shaft and the loading stress measured by the machine tool accuracy test system (6), the parameters of the physical simulation model embedded in the physical simulation module are updated to form a model that can reflect the manufacturing process of the machine tool under test (7). Then, after step five is completed, the accuracy change data of the machine tool under test (7) obtained in step five is used as prior information, and according to the load spectrum of the conventional cutting working condition of the machine tool obtained in step one, the test scenario digital twin is run to simulate the loading test process, and the deformation caused by the wear, looseness and creep behavior of the machine tool under test (7) is simulated and calculated in real time through the physical simulation model, and the digital twin of the machine tool under test (7) updates the parameterized geometric model of the machine tool under test (7) in real time; finally, the geometric accuracy of each linear feed axis of the machine tool under test (7) is calculated in real time through the machine tool accuracy calculation module of the digital twin system (4), and the iterative calculation is continued until the calculated accuracy of the machine tool under test (7) reaches the set failure threshold, and the simulation calculation is stopped; Step 7: Evaluate the accuracy maintenance capability of the machine tool under test and trace the source of the problem; According to the geometric accuracy of each linear feed axis of the machine tool under test (7) calculated in real time in step six, the accuracy degradation curve of the machine tool under test (7) is drawn to evaluate the accuracy retention capability of the machine tool under test (7); according to the simulation calculation results, the position where the deformation of the machine tool under test (7) accumulates the largest amount is the shortcoming of the accuracy retention of the machine tool under test (7), which needs to be the focus of subsequent machine tool optimization.

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