A thermal characteristic test working condition reproduction variable temperature chamber and method of numerical control machine tool

Abstract

The present application belongs to the technical field of testing the thermal characteristics of numerical control machine tools, and specifically relates to a test working condition reproduction temperature variable cabin and method for testing the thermal characteristics of numerical control machine tools, aiming to solve the problem that when a numerical control machine tool to be tested is continuously running and generating dynamic thermal disturbance, the preset temperature change working condition is difficult to stabilize and repeatedly reproduce. The present application comprises a cabin body, a temperature detection unit, a working condition reproduction control unit, a temperature variable execution unit and an air flow organization unit. The expected influence of heat generation on the temperature in the cabin is determined according to the machine tool operation parameters, and the target temperature is corrected. The temperature variable control quantity is generated in combination with the actual temperature in the cabin. The present application can improve the stability of temperature change working condition reproduction, and the repeatability and comparability of thermal characteristic test results.

Description

Technical Field

[0001] This invention belongs to the field of CNC machine tool thermal characteristic testing technology, specifically relating to a variable temperature chamber and method for reproducing the working conditions of CNC machine tool thermal characteristic testing. Background Technology

[0002] During operation, CNC machine tools continuously generate heat from components such as the spindle, servo drive mechanism, and hydraulic system. This heat forms a complex temperature field inside the machine tool through conduction and convection, causing thermal deformation of the machine tool structure and affecting machining accuracy. Therefore, in the study of the thermal characteristics of CNC machine tools, it is necessary to conduct operational tests on the machine tool under set environmental temperature boundary conditions to obtain thermal characteristic data such as temperature changes and thermal deformation, providing a data foundation for thermal error analysis, modeling, and compensation. The accuracy and repeatability of thermal characteristic test results largely depend on the stability and controllability of the test environment temperature boundary conditions.

[0003] Currently, thermal characteristic testing of CNC machine tools is typically conducted in ordinary industrial environments or constant-temperature laboratory environments. In ordinary industrial environments, ambient temperature is easily affected by diurnal variations, seasonal changes, and the operating status of equipment in the workshop, making it difficult to maintain a consistent ambient temperature boundary during the testing process. This results in discrepancies in test data obtained at different times or locations. While constant-temperature laboratory environments can provide relatively stable ambient temperatures, they are primarily used to maintain constant temperature conditions. They cannot effectively reproduce time-varying temperature conditions in actual industrial environments, such as continuous heating, continuous cooling, step changes, or cyclic changes, following a predetermined temperature change process. Therefore, existing testing conditions are insufficient to provide a consistent time-varying ambient temperature boundary for thermal characteristic testing of different batches of CNC machine tools.

[0004] Furthermore, the CNC machine tool under test typically requires thermal characteristic testing while in operation. The heat generation status of internal heat sources such as the machine tool spindle, servo drive mechanism, and hydraulic system changes with the operating load. The heat generated by the machine tool, once released into the test environment, continuously and dynamically affects the actual temperature within the test space. When feedback adjustments are made solely based on the temperature deviation already generated within the test space, adjustments can only be made after the machine tool's heat generation has already manifested as a change in ambient temperature, thus easily leading to control lag. Especially when the machine tool's operating load changes, temperature disturbances caused by internal heat sources may cause the actual temperature of the test environment to deviate from the preset temperature change trajectory. Therefore, existing solutions struggle to simultaneously address the dynamic heat generation impact of the machine tool itself and the continuous tracking of preset temperature change conditions.

[0005] Therefore, existing CNC machine tool thermal characteristic testing technologies still face the problem of difficulty in establishing a controllable and repeatable environmental temperature boundary according to a preset temperature change curve under the condition of continuous operation and dynamic thermal disturbance of the CNC machine tool under test. This leads to the instability of temperature change condition reproduction and the repeatability and comparability of test results from different batches. Summary of the Invention

[0006] To address the problem in existing technologies that it is difficult to establish a controllable and repeatable ambient temperature boundary according to a preset temperature change curve under the condition of continuous operation and dynamic thermal disturbance of the CNC machine tool under test, which affects the stability of temperature change condition reproduction and the repeatability and comparability of test results from different batches, this invention provides a temperature-varying chamber for reproducing the thermal characteristics test conditions of CNC machine tools and a method for reproducing temperature change conditions.

[0007] In a first aspect, the present invention provides a variable temperature chamber for reproducing the working conditions of CNC machine tool thermal characteristic testing, comprising a chamber body, a temperature detection unit, a working condition reproduction control unit, a variable temperature execution unit, and an airflow organization unit.

[0008] The cabin forms a closed test space to accommodate the CNC machine tool to be tested.

[0009] The supply and return ends of the airflow organization unit are connected to the enclosed test space to form a circulating airflow path.

[0010] The temperature detection unit is located in a closed test space and is connected to the operating condition reproduction control unit via signal. The operating condition reproduction control unit is connected to the variable temperature actuator via control.

[0011] The operating condition reproduction control unit is used to acquire the target temperature change curve and the operating parameters characterizing the heat generation state of the CNC machine tool under test. It determines the target temperature based on the target temperature change curve, determines the expected impact of the heat generation of the CNC machine tool under test on the temperature inside the chamber based on the operating parameters, generates a compensation signal based on the expected impact, corrects the target temperature using the compensation signal, and generates a variable temperature control quantity based on the corrected target temperature and the actual temperature inside the chamber acquired by the temperature detection unit.

[0012] The variable temperature actuator is used to adjust the temperature of the circulating air in the circulating airflow path according to the variable temperature control value.

[0013] Furthermore, the operating parameters include spindle power, servo drive power, and hydraulic station power.

[0014] Furthermore, the operating condition reproduction control unit includes a temperature change curve setting unit, a feedforward compensator, a main PID controller, and a secondary PID controller.

[0015] The temperature change curve setting unit, feedforward compensator and main PID controller are connected in sequence. The main PID controller and temperature detection unit are respectively connected to the auxiliary PID controller. The auxiliary PID controller is connected to the temperature change execution unit for control.

[0016] The temperature change curve setting unit is used to determine the target temperature based on the target temperature change curve.

[0017] The feedforward compensator is used to determine the expected impact based on the preset transmission relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber, generate a compensation signal based on the expected impact, and use the compensation signal to correct the target temperature.

[0018] The main PID controller generates a first control quantity based on the corrected target temperature, and the secondary PID controller generates a variable temperature control quantity based on the first control quantity and the actual temperature inside the cabin.

[0019] Furthermore, the variable temperature actuator includes a main refrigeration circuit and a rapid refrigeration circuit, which are connected in parallel.

[0020] The rapid refrigeration circuit includes a compressor and a direct expansion evaporator. The compressor and the direct expansion evaporator are connected by a refrigerant line, and the direct expansion evaporator is located inside the compartment.

[0021] The main refrigeration circuit and the rapid refrigeration circuit are respectively connected to the operating condition reproduction control unit.

[0022] Furthermore, the variable temperature actuator includes a main heating component and a fine-tuning heating component.

[0023] The main heating assembly includes multiple heating elements, which are independently controlled and connected to the operating condition reproduction control unit.

[0024] The airflow organization unit includes an air supply duct that communicates with the enclosed test space, a fine-tuning heating component that is installed inside the air supply duct, and a control connection to the operating condition reproduction control unit.

[0025] Furthermore, the airflow organization unit includes a top perforated plate, a bottom return air inlet, and a recirculating fan.

[0026] The top perforated plate is located on the top of the cabin and is connected to the enclosed test space through air supply holes located on the top perforated plate.

[0027] The bottom return air vents are located on both sides of the bottom of the cabin and are connected to the enclosed test space.

[0028] A circulating airflow path is formed between the bottom return air vent and the top perforated plate. The circulating fan is installed in the circulating airflow path and is connected to the operating condition reproduction control unit.

[0029] Furthermore, the hull includes an enclosure structure and hatches mounted on the enclosure structure.

[0030] The enclosure structure includes two corrugated steel panels arranged opposite each other, a polyurethane insulation layer between the two corrugated steel panels, and a vapor barrier layer on the periphery of the enclosure structure.

[0031] The hatch includes a door frame, an insulating body that mates with the door frame, and an inflatable seal disposed between the door frame and the insulating body. The inflatable seal is connected to an inflation passage.

[0032] A heating element is installed inside the door frame, and the heating element is connected to the working condition reproduction control unit.

[0033] A second aspect of the present invention provides a method for reproducing temperature-changing operating conditions in the thermal characteristic testing of CNC machine tools, comprising: Obtain the target temperature change curve, and determine the target temperature corresponding to the current control moment based on the target temperature change curve; The system acquires operating parameters characterizing the heat generation state of the CNC machine tool under test, determines the expected impact of the heat generation of the CNC machine tool under test on the temperature inside the chamber based on the operating parameters, generates a compensation signal based on the expected impact, and uses the compensation signal to correct the target temperature. Obtain the actual temperature inside the cabin, and determine the temperature control quantity based on the corrected target temperature and the actual temperature inside the cabin. Adjust at least one of the following parameters based on the temperature control quantity: cooling capacity, heating capacity, and circulating airflow.

[0034] Furthermore, based on the operating parameters, the expected impact of heat generation from the CNC machine tool under test on the cabin temperature is determined, including: Based on the preset transmission relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber, as well as the operating parameters, the expected impact is determined.

[0035] The temperature control parameters are determined based on the revised target temperature and the actual temperature inside the cabin, including: The first stage of adjustment is performed based on the corrected target temperature to obtain the first control variable; The second-level adjustment is performed based on the first control value and the actual temperature inside the cabin to obtain the variable temperature control value.

[0036] Furthermore, the circulating airflow parameters include the circulating airflow rate and the circulating airflow path.

[0037] When the target temperature curve is in the cooling phase, increase the cooling capacity and circulating air flow rate, and adjust the flow path of the circulating air.

[0038] When the target temperature curve is in the heating phase, the heating amount and the circulating air flow rate are increased in stages to obtain the temperature difference between the surface temperature of the CNC machine tool under test and the actual temperature inside the chamber. The ratio of heating amount to circulating air flow rate is adjusted according to the temperature difference.

[0039] The beneficial effects of this invention are: This invention creates a closed testing space through a chamber and actively regulates the internal environment by combining a target temperature change curve, a temperature detection unit, a temperature-changing execution unit, and a circulating airflow path. This allows the testing environment temperature to be controlled according to a preset change pattern, rather than being entirely affected by fluctuations in the external factory environment temperature. Therefore, it is beneficial to establish a more consistent environmental temperature boundary in the thermal characteristic testing of CNC machine tools at different times and in different batches, improve the repeatability of testing conditions, and provide a relatively unified environmental basis for comparing different test results.

[0040] This invention acquires operating parameters that characterize the heat generation state of the CNC machine tool under test, such as spindle power, servo drive power, and hydraulic station power. It pre-determines the expected impact of machine tool heat generation on the chamber temperature and uses this expected impact to perform feedforward correction on the target temperature. Then, it combines this with the actual temperature inside the chamber for feedback adjustment. This allows temperature control to respond without waiting for significant temperature deviations caused by machine tool heat generation. Therefore, it helps reduce the impact of dynamic thermal disturbances caused by changes in machine tool operating load on the target temperature change curve tracking process and improves the timeliness of response and the stability of temperature tracking during the reproduction of temperature change conditions.

[0041] This invention utilizes a combination of a main refrigeration circuit and a rapid refrigeration circuit, a main heating component and a fine-tuning heating component, and a circulating airflow organization formed by a circulating fan, a top perforated plate, a bottom return air vent, and an air supply duct. This allows for adjustment of cooling capacity, heating capacity, and circulating airflow parameters according to different states such as temperature rise, temperature drop, and approaching the target temperature. Specifically, it enhances temperature change capability during periods of large temperature differences, and enables more precise temperature adjustment as the target temperature approaches. Simultaneously, the circulating airflow promotes heat exchange within the cabin and reduces temperature stratification, thus balancing temperature change response capability and cabin temperature field uniformity. Attached Figure Description

[0042] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the overall structure of a variable temperature chamber for reproducing the thermal characteristics testing conditions of a CNC machine tool according to the present invention. Figure 2 This is a schematic diagram of the cross-sectional structure of the enclosure structure of the present invention; Figure 3 This is a schematic diagram of the control principle of the working condition reproduction control unit of the present invention; Figure 4 This is a schematic diagram of the structure of the variable temperature execution unit and the airflow organization unit of the present invention; Figure 5 This is a flowchart illustrating a method for reproducing temperature-changing working conditions in CNC machine tool thermal characteristic testing according to the present invention.

[0043] In the diagram, 1. Cabin; 2. Temperature detection unit; 3. Operating condition reproduction control unit; 4. Variable temperature execution unit; 5. Airflow organization unit; 11. Enclosure structure; 12. Cabin door; 13. Color steel plate; 14. Polyurethane insulation layer; 15. Vapor barrier layer; 31. Temperature change curve setting unit; 32. Feedforward compensator; 33. Main PID controller; 34. Auxiliary PID controller; 41. Main refrigeration circuit; 42. Rapid refrigeration circuit; 421. Compressor; 422. Direct expansion evaporator; 43. Main heating component; 431. Heating unit; 44. Fine-tuning heating component; 51. Top perforated plate; 52. Bottom return air vent; 53. Circulating fan; 54. Air supply duct. Detailed Implementation

[0044] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] The first embodiment of this invention proposes a variable temperature chamber for reproducing the thermal characteristic testing conditions of CNC machine tools, see [link to relevant documentation]. Figure 1 It includes a cabin 1, a temperature detection unit 2, a working condition reproduction control unit 3, a temperature change execution unit 4, and an airflow organization unit 5.

[0047] The chamber 1 forms a closed test space for accommodating the CNC machine tool to be tested.

[0048] The supply and return air ends of the airflow organization unit 5 are connected to the enclosed test space to form a circulating airflow path.

[0049] Temperature detection unit 2 is set in a closed test space and is connected to the working condition reproduction control unit 3 by signal. The working condition reproduction control unit 3 is connected to the variable temperature execution unit 4 by control.

[0050] The working condition reproduction control unit 3 is used to acquire the target temperature change curve and the operating parameters characterizing the heat generation state of the CNC machine tool under test. It determines the target temperature based on the target temperature change curve, determines the expected impact of the heat generation of the CNC machine tool under test on the temperature inside the chamber based on the operating parameters, generates a compensation signal based on the expected impact, corrects the target temperature using the compensation signal, and generates a variable temperature control quantity based on the corrected target temperature and the actual temperature inside the chamber acquired by the temperature detection unit 2.

[0051] The variable temperature actuator 4 is used to adjust the temperature of the circulating air in the circulating airflow path according to the variable temperature control value.

[0052] In this embodiment, the chamber 1 constitutes a test area enclosed relative to the external environment. The CNC machine tool under test is entirely housed within this enclosed test space, allowing the environmental temperature boundary experienced by the machine tool during testing to be set and adjusted independently of the external factory environment. The temperature detection unit 2 continuously acquires the actual temperature inside the enclosed test space. In practice, the corresponding temperature acquisition positions can be set according to the internal space of the chamber 1 and the external position of the CNC machine tool under test to obtain temperature detection results that characterize the current test environment temperature state.

[0053] Before the test begins, input the target temperature change curve based on the actual environmental conditions to be reproduced. The target temperature change curve is used to characterize the relationship between ambient temperature and test time, and can be a linear heating curve, a linear cooling curve, a stepped temperature curve, a cyclic temperature curve, or a custom curve pre-established based on the actual ambient temperature change pattern.

[0054] In one specific implementation, after inputting the target temperature change curve, the curve is automatically parsed into a time-series temperature setpoint sequence arranged chronologically. The corresponding target temperature is then determined from this sequence based on the current control time, using the time-series temperature setpoint sequence as the target for temperature tracking control. This allows the ambient temperature to be changed sequentially according to a preset time relationship, simulating the environmental temperature changes experienced by CNC machine tools under conditions such as diurnal temperature variations, seasonal temperature changes, and the start / stop of workshop air conditioning.

[0055] The CNC machine tool under test is operated in a closed test space according to predetermined operating conditions. During the test, operating parameters that characterize the heat generation state of the CNC machine tool are acquired. Since the spindle, servo drive mechanism, and hydraulic system of the CNC machine tool continuously generate internal heat sources during operation, and the heat generation state of each internal heat source changes with the operating load, the expected impact of the heat generation of the CNC machine tool under test on the temperature inside the chamber is determined based on the current operating parameters, and a compensation signal is generated based on the expected impact.

[0056] The compensation signal is used to correct the current target temperature before the actual temperature inside the chamber fully responds to changes in the machine tool's heat generation. When the operating load of the CNC machine tool under test changes, the current temperature regulation requirement is adjusted accordingly based on the expected impact of the machine tool's heat generation on the chamber temperature. When the heat generation of the machine tool under test increases, the cooling requirement can be increased, the heating requirement reduced, or a corresponding temperature regulation correction can be made based on the relationship between the current target temperature and the actual temperature inside the chamber; when the heat generation of the machine tool under test decreases, compensation is performed in the opposite direction, thus enabling feedforward compensation to be applied to heating, cooling, and stable temperature tracking conditions.

[0057] After the target temperature correction is completed, a variable temperature control value is generated based on the corrected target temperature and the current actual temperature inside the cabin, and the temperature of the circulating air is adjusted according to the variable temperature control value. The circulating air that has completed heat exchange returns to the circulating airflow path, undergoes temperature adjustment again, and then re-enters the closed test space, thus forming a continuous cycle adjustment process.

[0058] As the test progresses, the target temperature corresponding to each control moment is determined sequentially according to the target temperature change curve. The process of acquiring operating parameters, determining the expected impact of heat generation, generating compensation signals, correcting the target temperature, acquiring the actual temperature inside the chamber, and determining the variable temperature control quantity is repeated to make the actual temperature inside the chamber change with the target temperature change curve.

[0059] Furthermore, independent dew point control is implemented during temperature control to reduce the possibility of condensation under low-temperature testing conditions. When it is necessary to increase the air humidity, electrode-type steam humidification is used; when it is necessary to reduce the air humidity, a two-stage dehumidification method combining refrigeration dehumidification and rotary dehumidification is used. Under normal operating conditions, a surface cooler is used for refrigeration dehumidification, and under low-temperature and low-humidity conditions, a silica gel moisture-absorbing rotary wheel is activated for further dehumidification, thereby adapting to the humidity control requirements in different temperature ranges.

[0060] Through the above settings, the time-varying and difficult-to-repeat temperature boundary in the actual industrial environment can be converted into a programmable and repeatable target temperature change curve. It can also compensate for the heat generation effect in advance when the CNC machine tool under test continuously generates internal heat, so that the tests conducted in different batches and locations have more consistent environmental boundary conditions, thereby improving the repeatability and comparability of thermal characteristic test data.

[0061] As a further explanation of the first embodiment of the present invention, the operating parameters include spindle power, servo drive power and hydraulic station power.

[0062] In this embodiment, the spindle power, servo drive power, and hydraulic station power are acquired in real time during the operation of the CNC machine tool under test according to the predetermined operating conditions. The spindle power is used to characterize the heat generation state generated during the spindle drive and spindle rotation process, the servo drive power is used to characterize the heat generation state generated during the drive of each feed axis, and the hydraulic station power is used to characterize the heat generation state generated during the continuous operation of the hydraulic system.

[0063] Furthermore, the opening and closing status of the hatch 12 is also acquired. When the hatch 12 is opened or closed, the air exchange state between the enclosed test space and the external environment changes. Therefore, the opening and closing status of the hatch 12 can reflect another type of thermal disturbance besides the heat generated by the CNC machine tool itself. The opening and closing status of the hatch 12, along with the spindle power, servo drive power, and hydraulic station power, are input into the feedforward compensation process to pre-compensate for temperature disturbances caused by changes in the internal heat source of the machine tool and changes in the hatch status.

[0064] In the specific implementation process, based on the spindle power, servo drive power, hydraulic station power, and the opening and closing status of the door 12, combined with the preset correspondence between machine tool heat generation and changes in cabin temperature, the expected impact of the current operating state on the cabin temperature is determined. When the spindle switches from a low-load state to a high-load state, the servo drive load increases, or the hydraulic station power changes, changes in the heat generation state can be identified in advance based on changes in operating parameters before the corresponding heat is completely transferred to the cabin air.

[0065] By using the real-time operating power of the CNC machine tool under test as the feedforward input, the ambient temperature control process does not have to wait for a significant change in the actual temperature inside the chamber before implementing the adjustment. This shortens the response time between changes in the internal heat source and the temperature adjustment action, and reduces the tracking deviation of the target temperature curve caused by changes in the machine tool's operating load.

[0066] As a further explanation of the first embodiment of the present invention, see [link to documentation]. Figure 3 The operating condition reproduction control unit 3 includes a temperature change curve setting unit 31, a feedforward compensator 32, a main PID controller 33, and a secondary PID controller 34.

[0067] The temperature change curve setting unit 31, the feedforward compensator 32 and the main PID controller 33 are connected in sequence. The main PID controller 33 and the temperature detection unit 2 are respectively connected to the auxiliary PID controller 34. The auxiliary PID controller 34 is connected to the temperature change execution unit 4 for control.

[0068] The temperature change curve setting unit 31 is used to determine the target temperature based on the target temperature change curve.

[0069] The feedforward compensator 32 is used to determine the expected impact based on the preset transmission relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber, generate a compensation signal based on the expected impact, and use the compensation signal to correct the target temperature.

[0070] The main PID controller 33 is used to generate a first control quantity based on the corrected target temperature, and the secondary PID controller 34 is used to generate a variable temperature control quantity based on the first control quantity and the actual temperature inside the cabin.

[0071] In this embodiment, the temperature change curve setting unit 31 parses the input target temperature change curve into a time-series temperature setpoint sequence and outputs the corresponding target temperature according to the current control time. For linear heating or linear cooling conditions, the target temperature is continuously changed according to the set temperature change law; for stepped temperature conditions, the corresponding target temperature is maintained in different time intervals, and the target value is changed between adjacent time intervals; for cyclic temperature conditions, the corresponding heating, holding, and cooling processes are repeated according to a predetermined cycle; for custom curves, a time-series temperature setpoint sequence is formed according to the pre-input time-temperature correspondence.

[0072] The feedforward compensator 32 uses a preset machine tool heat generation-temperature rise transfer function model. Based on the currently acquired spindle power, servo drive power, hydraulic station power, and the opening and closing status of the door 12, it calculates the expected impact of the heat generation of the CNC machine tool under test and external disturbances on the temperature field inside the cabin. Based on this expected impact, it generates a compensation signal in advance and superimposes the compensation signal onto the current temperature setpoint to form the target temperature after feedforward correction.

[0073] The machine tool heat generation-temperature rise transfer function model is used to characterize the dynamic correspondence between changes in input operating parameters and subsequent cabin temperature response. Its model parameters can be pre-calibrated and determined based on the operating parameters of the CNC machine tool under test and its corresponding cabin temperature response data before formal testing, thereby matching the transfer function model with the actual heat generation characteristics of the corresponding CNC machine tool under test.

[0074] The feedforward-corrected target temperature is input to the main PID controller 33, which is primarily responsible for rapid temperature regulation under conditions of large temperature differences. In one specific embodiment, the main PID controller 33 rapidly adjusts the cabin temperature to within ±5°C of the target temperature and generates the first control variable.

[0075] The first control quantity output by the main PID controller 33 and the actual cabin temperature obtained by the temperature detection unit 2 are input together into the secondary PID controller 34. The secondary PID controller 34 is used to further eliminate residual temperature deviation and suppress high-frequency temperature disturbances to obtain the final variable temperature control quantity.

[0076] In cooling mode, the final temperature control quantity can be allocated to the variable frequency fan and electronic expansion valve to change the cabin temperature by adjusting the circulating airflow and refrigerant flow. In heating mode, the heating output and circulating airflow are controlled according to the corresponding temperature regulation requirements.

[0077] Under conditions of strong internal heat sources, a control method combining machine tool heat generation feedforward compensation and cascade PID tracking can ensure that the actual temperature inside the chamber stably tracks the preset temperature change curve. In one specific implementation, the tracking deviation can be controlled within ±1℃, and the temperature control response corresponding to the heat generation change of the CNC machine tool under test can be shortened from minutes to tens of seconds.

[0078] By using the aforementioned feedforward compensation and cascade PID control method, the temperature regulation requirements can be corrected before the changes in the internal heat source are fully reflected in the actual temperature changes inside the cabin. Then, the remaining deviations can be eliminated step by step through the main PID control and the sub-PID control, thereby taking into account both the response speed under large temperature difference conditions and the tracking stability after approaching the target temperature.

[0079] As a further explanation of the first embodiment of the present invention, see [link to documentation]. Figure 4 The variable temperature actuator 4 includes a main refrigeration circuit 41 and a rapid refrigeration circuit 42, which are connected in parallel.

[0080] The rapid refrigeration circuit 42 includes a compressor 421 and a direct expansion evaporator 422. The compressor 421 and the direct expansion evaporator 422 are connected through a refrigerant pipeline. The direct expansion evaporator 422 is located inside the compartment 1.

[0081] The main cooling circuit 41 and the rapid cooling circuit 42 are respectively connected to the operating condition reproduction control unit 3.

[0082] In this embodiment, the main refrigeration circuit 41 adopts a single-stage compression cooling method to meet the refrigeration needs during routine cooling and stable temperature tracking. The main refrigeration circuit 41 is equipped with a variable frequency scroll compressor and an electronic expansion valve, and the refrigeration output is adjusted by the linkage between the variable frequency scroll compressor and the electronic expansion valve.

[0083] In one specific embodiment, the evaporation temperature of the main refrigeration circuit 41 is -10°C, and the variable frequency scroll compressor performs stepless adjustment within the frequency range of 20Hz to 120Hz, enabling the refrigeration capacity to be smoothly output within the range of 10% to 100%. The electronic expansion valve has a response time of less than 2 seconds and adjusts the refrigerant flow rate in real time according to the superheat of the evaporator outlet to match the current refrigeration demand.

[0084] The rapid cooling circuit 42 is used to improve cooling capacity during the rapid cooling phase of the target temperature curve. In one specific embodiment, the rapid cooling circuit 42 employs an independent direct expansion evaporator 422 and a large-capacity compressor 421. The rapid cooling circuit 42 is activated only during the rapid temperature change phase corresponding to the target temperature curve and operates in parallel with the main cooling circuit 41.

[0085] During rapid cooling, the main refrigeration circuit 41 and the rapid refrigeration circuit 42 operate simultaneously to increase the total cooling capacity acting on the cabin environment. The refrigerant directly evaporates and absorbs heat in the direct expansion evaporator 422, allowing the cooling capacity to act directly on the cabin air, reducing the intermediate heat exchange links formed by secondary heat exchange using a secondary refrigerant, thereby improving the temperature response speed during rapid cooling.

[0086] During rapid cooling, the operating frequency and airflow speed of the circulating fan 53 are increased, as well as the number of air exchanges, so that the cooling capacity generated by rapid cooling can be delivered to the area around the CNC machine tool under test more quickly. At the same time, the electric guide vane automatically adjusts its angle according to the temperature control process to change the flow path of the circulating airflow and optimize the airflow trajectory.

[0087] When the actual temperature inside the cabin gradually approaches the current target temperature, the cooling output of the rapid cooling circuit 42 is reduced or stopped, and the main cooling circuit 41 continues to perform temperature tracking and regulation.

[0088] By setting up a main cooling circuit 41 and a rapid cooling circuit 42 connected in parallel, the corresponding cooling capacity can be used for conventional temperature tracking and rapid cooling respectively. The cooling capacity is increased during the rapid cooling phase, while the rapid cooling output is reduced after approaching the target temperature, thus taking into account both rapid temperature change capability and stable temperature tracking capability.

[0089] As a further explanation of the first embodiment of the present invention, see [link to documentation]. Figure 4 The variable temperature execution unit 4 includes a main heating component 43 and a fine-tuning heating component 44.

[0090] The main heating assembly 43 includes multiple heating elements 431, which are independently controlled and connected to the working condition reproduction control unit 3.

[0091] The airflow organization unit 5 includes an air supply duct 54 that is connected to the closed test space. The fine-tuning heating component 44 is disposed in the air supply duct 54 and is controlled and connected to the working condition reproduction control unit 3.

[0092] In this embodiment, a two-stage layered heating method combining main heating and fine-tuning heating is adopted. The main heating component 43 is used to bear the main heating load when there is rapid temperature rise or when there is a large temperature difference between the actual temperature inside the cabin and the current target temperature, while the fine-tuning heating component 44 is used to implement fine temperature adjustment after the actual temperature inside the cabin approaches the current target temperature.

[0093] The main heating assembly 43 uses a stainless steel finned electric heater and is divided into twelve independently controlled heating sections 431. The total heating power of the main heating assembly 43 is changed by altering the number of heating sections 431 in operation.

[0094] When the target temperature curve enters the rapid heating stage, all electric heating power is put into operation according to the heating demand, and each heating unit 431 is put into operation in a grouped step-by-step switching method to avoid the simultaneous connection of all heating loads and the resulting large instantaneous current surge.

[0095] The fine-tuning heating component 44 employs a PTC ceramic heater and is housed within the air supply duct 54, allowing the heat it generates to directly act on the circulating air supplied to the enclosed test space. In one specific embodiment, the response time of the fine-tuning heating component 44 is less than 3 seconds. Once the actual temperature inside the chamber approaches the target temperature, fine-tuning of the temperature is achieved by adjusting the heating output of the fine-tuning heating component 44.

[0096] During rapid heating, the operating frequency and air delivery speed of the circulating fan 53 are increased simultaneously to enhance convective heat transfer between the circulating air and the surface of the CNC machine tool under test, as well as the cabin space. Simultaneously, the temperature difference between the surface of the CNC machine tool under test and the cabin air temperature is acquired, and the ratio between heating power and circulating air volume is dynamically adjusted based on this temperature difference to prevent excessively rapid temperature changes in localized areas from causing thermal stress concentration.

[0097] By adopting a two-level hierarchical control method of main heating and fine-tuning heating, the main heating component 43 can quickly provide a large heating capacity, and then the fine-tuning heating component 44 with a faster response speed can be used to implement fine adjustment after approaching the target temperature. Combined with the enhanced circulating airflow, the heat transfer speed in the cabin is improved, thus taking into account both rapid heating capacity and temperature tracking accuracy.

[0098] As a further explanation of the first embodiment of the present invention, see [link to documentation]. Figure 1 and Figure 4 The airflow organization unit 5 includes a top perforated plate 51, a bottom return air inlet 52, and a circulating fan 53.

[0099] The top perforated plate 51 is located on the top of the chamber 1 and is connected to the enclosed test space through the air supply holes provided on the top perforated plate 51.

[0100] Bottom return air vents 52 are located on both sides of the bottom of the cabin 1 and are connected to the enclosed test space.

[0101] A circulating airflow path is formed between the bottom return air inlet 52 and the top perforated plate 51. The circulating fan 53 is installed in the circulating airflow path and is controlled and connected to the working condition reproduction control unit 3.

[0102] In this embodiment, an airflow organization method is adopted, in which air is uniformly supplied through a top perforated plate and returned through both sides of the bottom. The temperature-regulated circulating air is delivered to the top of the chamber 1, and is uniformly and slowly delivered into the closed test space through the air supply holes on the top perforated plate 51, and flows slowly downward along the inner wall of the chamber 1 and the surface of the CNC machine tool under test.

[0103] As the circulating air flows downwards, it exchanges heat with the surface of the CNC machine tool under test and the air inside the chamber. After the heat exchange is completed, the air gathers at the bottom of the chamber 1 and is discharged from the bottom return air inlets 52 located on both sides of the bottom of the chamber 1. Then, under the action of the circulating fan 53, it re-enters the circulating airflow path to form a stable and orderly air circulation.

[0104] During the stable temperature tracking phase, the circulating fan 53 operates according to the operating conditions required to maintain air circulation in the chamber; during the rapid heating or rapid cooling phase, the operating frequency and air delivery speed of the circulating fan 53 are increased to increase the amount of circulating air participating in heat exchange per unit time.

[0105] By adopting the airflow organization method of uniform low-speed air supply from the top perforated plate 51 and return air from both sides of the bottom, the temperature-regulated circulating air can be uniformly introduced into the space around the CNC machine tool under test from the top of the chamber 1, and slowly sink along the surface of the machine tool and the wall of the chamber before being discharged from the bottom, thereby forming a stable air circulation and reducing the temperature stratification inside the chamber.

[0106] As a further explanation of the first embodiment of the present invention, the cabin 1 includes an enclosure structure 11 and a hatch 12 disposed on the enclosure structure 11.

[0107] See Figure 2 The enclosure structure 11 includes two corrugated steel plates 13 arranged opposite each other, a polyurethane insulation layer 14 disposed between the two corrugated steel plates 13, and a vapor barrier layer 15 disposed around the enclosure structure 11.

[0108] The hatch 12 includes a door frame, an insulating body that cooperates with the door frame, and an inflatable seal disposed between the door frame and the insulating body. The inflatable seal is connected to the inflation air passage.

[0109] A heating element is installed inside the door frame, and the heating element is connected to the working condition reproduction control unit 3.

[0110] In this embodiment, the enclosure structure 11 adopts a modular high-insulation warehouse structure, and the core insulation material of the walls and roof is a high-density rigid polyurethane foam sandwich panel, wherein the rigid polyurethane foam material forms a polyurethane insulation layer 14.

[0111] In one specific embodiment, the foaming density of the rigid polyurethane foam material is not less than 40 kg / m³, the thermal conductivity is not greater than 0.022 W / (m·K), and the heat transfer coefficient K value of the enclosure structure 11 is not greater than 0.25 W / (m²·K), so as to reduce the conduction heat transfer between the internal environment and the external environment of the cabin 1.

[0112] Color steel plates 13 are respectively installed on the inner and outer sides of the polyurethane insulation layer 14. The color steel plate 13 located on the inner side of the cabin 1 is made of high-strength anti-corrosion color steel plate, and the color steel plate 13 located on the outer side of the cabin 1 is made of weather-resistant color steel plate.

[0113] The enclosure structure 11 is formed by splicing multiple modular panels. Interlocking tongue-and-groove joints are provided between adjacent modular panels, and the panels are spliced ​​together by a mechanical locking structure using the tongue-and-groove joints. The joints between adjacent modular panels are sealed with double layers of high and low temperature resistant silicone airtight sealant to improve the airtightness of the splicing location.

[0114] An aluminum foil composite vapor barrier layer is installed around the perimeter of the enclosure structure 11 as a vapor barrier layer 15 to prevent water vapor in the external environment from penetrating into the low-temperature enclosure structure and reduce the possibility of condensation inside or on the surface of the enclosure structure during the low-temperature test.

[0115] The hatch 12 adopts an air-supported, fully sealed, flexible lifting structure. The door frame is a vertical thermally broken aluminum alloy frame, and the insulation body is a polyurethane insulation panel structure adapted to the thickness of the enclosure structure 11.

[0116] Three airtight hollow inflatable rubber sealing rings are installed around the door as inflatable seals. After the door 12 is closed, the pneumatic system inflates the inflatable seals through the inflation air passage, causing the inflatable seals to expand under pressure and fit tightly against the door frame, thus forming a circumferential airtight seal; when the door 12 needs to be opened, the inflation pressure in the inflatable seals is released.

[0117] A low-power electric heating wire is pre-embedded inside the door frame as a heating element. During low-temperature testing, the heating element is automatically activated according to the current test status to locally heat the door frame, thereby reducing the temperature difference between the inside and outside of the door frame, reducing cold bridge condensation, and preventing the inflatable seal from hardening in the low-temperature environment, which would lead to a decrease in sealing performance. After exiting the corresponding low-temperature test status, the heating element can be automatically turned off.

[0118] By adopting a highly insulated enclosure structure, modular airtight panel splicing, an outer vapor barrier, inflatable door sealing, and local heating of the door frame, the impact of external temperature and humidity changes on the enclosed test space can be reduced, and the sealing and anti-condensation capabilities of the door area 12 can be maintained under low temperature conditions, thereby providing a stable environmental boundary for the repeated reproduction of temperature change conditions.

[0119] See Figure 5 The second embodiment of the present invention proposes a method for reproducing temperature change conditions in CNC machine tool thermal characteristic testing, including: acquiring a target temperature change curve, and determining the target temperature corresponding to the current control moment based on the target temperature change curve.

[0120] The system acquires operating parameters characterizing the heat generation state of the CNC machine tool under test, determines the expected impact of the heat generation of the CNC machine tool under test on the temperature inside the chamber based on the operating parameters, generates a compensation signal based on the expected impact, and uses the compensation signal to correct the target temperature.

[0121] Obtain the actual temperature inside the cabin, and determine the temperature control quantity based on the corrected target temperature and the actual temperature inside the cabin.

[0122] Adjust at least one of the following parameters based on the temperature control quantity: cooling capacity, heating capacity, and circulating airflow.

[0123] In this embodiment, before starting the thermal characteristic test of the CNC machine tool, a target temperature change curve is determined based on the actual ambient temperature change relationship to be reproduced. The target temperature change curve can be a linear heating curve, a linear cooling curve, a stepped temperature curve, a cyclic temperature curve, or a custom temperature curve.

[0124] After inputting the target temperature change curve, the target temperature change curve is parsed into a time-series temperature setpoint sequence arranged in chronological order, and the current target temperature is determined from the time-series temperature setpoint sequence based on the current control time.

[0125] Subsequently, operating parameters characterizing the heat generation state of the CNC machine tool under test are acquired, including spindle power, servo drive power, and hydraulic station power, and the door opening and closing status is further acquired. Based on the operating parameters, door opening and closing status, and the preset transmission relationship between heat generation of the CNC machine tool under test and changes in cabin temperature, the expected impact of the current operating state on the cabin temperature is determined.

[0126] A compensation signal is generated based on the expected impact, and the compensation signal is superimposed on the current temperature setpoint to correct the current target temperature, so that the temperature impact caused by the heat generated by the CNC machine tool under test and the changes in the status of the cabin door can enter the temperature regulation process before it is fully reflected in the actual temperature inside the cabin.

[0127] After obtaining the current actual temperature inside the cabin, the variable temperature control quantity is determined based on the corrected target temperature and the actual temperature inside the cabin, and at least one of the cooling capacity, heating capacity and circulating airflow parameters is adjusted according to the variable temperature control quantity.

[0128] After completing the temperature adjustment at the current control moment, the system enters the next control moment, re-determines the new target temperature based on the time-series temperature setpoint sequence, and repeats the process of parameter acquisition, expected impact determination, compensation signal generation, target temperature correction, acquisition of actual cabin temperature, and determination of variable temperature control quantity until the entire test process corresponding to the target temperature change curve is completed.

[0129] During the testing process, dew point control was implemented independently based on the current temperature conditions. When humidification was needed, the air humidity was increased; when dehumidification was needed, cooling dehumidification was performed according to the environmental conditions; and under low temperature and low humidity conditions, adsorption-type rotary dehumidification was further implemented to reduce the possibility of condensation during temperature changes.

[0130] By using the above method, at each control moment, the current temperature change target, the internal heat generation state of the CNC machine tool under test, and the current actual temperature inside the chamber are all incorporated into the temperature control process, thereby forming a temperature change condition reproduction process that continuously connects target temperature determination, heat generation feedforward compensation, and actual temperature feedback, reducing the impact of the heat generation of the CNC machine tool under test on the preset temperature change trajectory.

[0131] As a further explanation of the second embodiment of the present invention, determining the expected impact of the heat generated by the CNC machine tool under test on the temperature inside the chamber based on the operating parameters includes: determining the expected impact based on the preset transmission relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber and the operating parameters.

[0132] The variable temperature control quantity is determined based on the corrected target temperature and the actual temperature inside the cabin, including: performing a first-stage adjustment based on the corrected target temperature to obtain the first control quantity.

[0133] The second-level adjustment is performed based on the first control value and the actual temperature inside the cabin to obtain the variable temperature control value.

[0134] In this embodiment, the pre-defined transfer relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber is characterized using a machine tool heat generation-temperature rise transfer function model. Based on the current spindle power, servo drive power, hydraulic station power, and corresponding disturbance states, the expected impact of the current operating state on the chamber temperature is determined, and a compensation signal is generated based on the expected impact. This compensation signal is then superimposed onto the current target temperature.

[0135] The first-stage adjustment is performed based on the feedforward-corrected target temperature. This first-stage adjustment is primarily responsible for rapid adjustment when there is a significant deviation between the current temperature and the target temperature. In one specific implementation, the first-stage adjustment employs PID control to quickly adjust the cabin temperature to within ±5°C of the target temperature, thus obtaining the first control variable.

[0136] A second-stage adjustment is performed based on the first control variable and the current actual temperature inside the cabin. In one specific embodiment, the second-stage adjustment employs PID control to further eliminate residual temperature deviations after the first-stage adjustment and suppress high-frequency temperature disturbances, thereby obtaining the final variable temperature control variable.

[0137] The final temperature control value is used to adjust the circulating airflow, refrigerant flow rate, or heating amount based on the current temperature state. During refrigeration regulation, the circulating air flow rate and refrigerant flow rate can be changed according to the temperature control value; during heating regulation, the heating amount and circulating air flow rate can be changed according to the temperature control value.

[0138] By combining machine tool heat generation feedforward compensation with two-stage PID regulation, the temperature regulation requirements can be corrected in advance before the changes in the internal heat source of the CNC machine tool under test are fully reflected in the actual temperature change inside the chamber. The two-stage regulation further eliminates the remaining deviation, improving the tracking accuracy and control response speed of the preset temperature change curve under strong internal heat source conditions.

[0139] As a further explanation of the second embodiment of the present invention, the circulating airflow parameters include the circulating airflow rate and the circulating airflow path.

[0140] When the target temperature curve is in the cooling phase, increase the cooling capacity and circulating air flow rate, and adjust the flow path of the circulating air.

[0141] When the target temperature curve is in the heating phase, the heating amount and the circulating air flow rate are increased in stages to obtain the temperature difference between the surface temperature of the CNC machine tool under test and the actual temperature inside the chamber. The ratio of heating amount to circulating air flow rate is adjusted according to the temperature difference.

[0142] In this embodiment, when the target temperature curve is in the rapid cooling phase, additional cooling capacity is added on the basis of conventional cooling, so that conventional cooling and rapid cooling work simultaneously, and the circulating air flow, air supply speed and air exchange frequency are increased to improve the speed at which cold energy is transferred to the cabin space.

[0143] During rapid cooling, additional cooling is achieved through direct refrigerant evaporation and heat absorption, reducing response delay caused by secondary heat exchange with the refrigerant. Simultaneously, the circulating airflow guide angle is automatically adjusted to alter the airflow path, optimizing the airflow trajectory during rapid cooling.

[0144] Once the actual temperature inside the cabin gradually approaches the current target temperature, the additional rapid cooling capacity is reduced or stopped, and the intensity of the circulating airflow is reduced, so that the temperature control switches from a rapid cooling state to a stable tracking state.

[0145] When the target temperature curve is in the rapid heating phase, all electric heating power is put into operation, and the heating amount is increased in a step-by-step manner in groups to reduce the instantaneous impact caused by the simultaneous input of heating load.

[0146] During rapid heating, the circulating air flow rate and velocity are increased simultaneously to enhance convective heat transfer. At the same time, the temperature difference between the surface temperature of the CNC machine tool under test and the actual temperature inside the chamber is acquired, and the ratio between the heating quantity and the circulating air flow rate is dynamically adjusted based on this temperature difference to reduce the possibility of thermal stress concentration caused by excessively rapid temperature changes in localized areas of the CNC machine tool under test.

[0147] By employing synergistic regulation of enhanced cooling and airflow in the cooling phase, and synergistic regulation of enhanced heat source and airflow in the heating phase, the actual ambient temperature can respond more quickly to changes in the target temperature curve, while also taking into account the air circulation state inside the chamber during the rapid temperature change phase and the temperature difference between the surface of the CNC machine tool under test and the surrounding air.

[0148] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0149] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0150] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A variable-temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools, characterized in that, It includes a cabin (1), a temperature detection unit (2), a working condition reproduction control unit (3), a temperature-changing execution unit (4), and an airflow organization unit (5). The cabin (1) forms a closed test space for accommodating the CNC machine tool to be tested; The air supply end and return end of the airflow organization unit (5) are respectively connected to the closed test space to form a circulating airflow path; The temperature detection unit (2) is located in the closed test space and is connected to the working condition reproduction control unit (3) by signal. The working condition reproduction control unit (3) is connected to the variable temperature execution unit (4) by control. The working condition reproduction control unit (3) is used to acquire the target temperature change curve and the operating parameters characterizing the heat generation state of the CNC machine tool under test, determine the target temperature according to the target temperature change curve, determine the expected impact of the heat generation of the CNC machine tool under test on the cabin temperature according to the operating parameters, generate a compensation signal according to the expected impact, correct the target temperature using the compensation signal, and generate a variable temperature control quantity according to the corrected target temperature and the actual cabin temperature acquired by the temperature detection unit (2). The variable temperature actuator (4) is used to adjust the temperature of the circulating air in the circulating airflow path according to the variable temperature control amount.

2. The variable temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools according to claim 1, characterized in that, The operating parameters include spindle power, servo drive power, and hydraulic station power.

3. The variable temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools according to claim 1, characterized in that, The operating condition reproduction control unit (3) includes a temperature change curve setting unit (31), a feedforward compensator (32), a main PID controller (33), and a secondary PID controller (34). The temperature curve setting unit (31), the feedforward compensator (32) and the main PID controller (33) are connected in sequence. The main PID controller (33) and the temperature detection unit (2) are respectively connected to the auxiliary PID controller (34). The auxiliary PID controller (34) is controlled by the temperature change execution unit (4). The temperature change curve setting unit (31) is used to determine the target temperature according to the target temperature change curve; The feedforward compensator (32) is used to determine the expected impact based on the preset transmission relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber, generate the compensation signal based on the expected impact, and use the compensation signal to correct the target temperature. The main PID controller (33) is used to generate a first control quantity based on the corrected target temperature, and the secondary PID controller (34) is used to generate the variable temperature control quantity based on the first control quantity and the actual temperature inside the cabin.

4. The variable temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools according to claim 1, characterized in that, The variable temperature actuator (4) includes a main refrigeration circuit (41) and a rapid refrigeration circuit (42), wherein the main refrigeration circuit (41) and the rapid refrigeration circuit (42) are connected in parallel. The rapid refrigeration circuit (42) includes a compressor (421) and a direct expansion evaporator (422). The compressor (421) and the direct expansion evaporator (422) are connected through a refrigerant pipeline. The direct expansion evaporator (422) is located inside the cabin (1). The main refrigeration circuit (41) and the rapid refrigeration circuit (42) are respectively connected to the operating condition reproduction control unit (3).

5. The variable temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools according to claim 1, characterized in that, The variable temperature actuator (4) includes a main heating component (43) and a fine-tuning heating component (44). The main heating assembly (43) includes multiple heating elements (431), which are independently controlled and connected to the working condition reproduction control unit (3). The airflow organization unit (5) includes an air supply duct (54) connected to the closed test space. The fine-tuning heating component (44) is disposed in the air supply duct (54) and is controlled and connected to the working condition reproduction control unit (3).

6. The variable temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools according to claim 1, characterized in that, The airflow organization unit (5) includes a top perforated plate (51), a bottom return air inlet (52), and a circulating fan (53); The top perforated plate (51) is disposed on the top of the cabin (1) and communicates with the closed test space through the air supply hole disposed on the top perforated plate (51); The bottom return air vent (52) is located on both sides of the bottom of the cabin (1) and is connected to the enclosed test space; The bottom return air inlet (52) and the top perforated plate (51) form the circulating airflow path, and the circulating fan (53) is installed in the circulating airflow path and is controlled and connected to the working condition reproduction control unit (3).

7. The variable temperature chamber for reproducing the thermal characteristics testing conditions of CNC machine tools according to claim 1, characterized in that, The cabin (1) includes an enclosure structure (11) and a hatch (12) disposed on the enclosure structure (11). The enclosure structure (11) includes a color steel plate (13) arranged opposite to each other, a polyurethane insulation layer (14) disposed between the two color steel plates (13), and a vapor barrier layer (15) disposed around the enclosure structure (11). The hatch (12) includes a door frame, an insulating body that cooperates with the door frame, and an inflatable sealing element disposed between the door frame and the insulating body, wherein the inflatable sealing element is connected to an inflatable air passage. A heating element is provided inside the door frame, and the heating element is controlled and connected to the working condition reproduction control unit (3).

8. A method for reproducing temperature-change operating conditions in thermal characteristic testing of CNC machine tools, characterized in that, include: Obtain the target temperature change curve, and determine the target temperature corresponding to the current control moment based on the target temperature change curve; The system acquires operating parameters characterizing the heat generation state of the CNC machine tool under test, determines the expected impact of the heat generation of the CNC machine tool under test on the cabin temperature based on the operating parameters, generates a compensation signal based on the expected impact, and uses the compensation signal to correct the target temperature. Obtain the actual temperature inside the cabin, and determine the temperature control amount based on the corrected target temperature and the actual temperature inside the cabin. Adjust at least one of the cooling capacity, heating capacity, and circulating airflow parameters according to the temperature control quantity.

9. The method for reproducing temperature change conditions in CNC machine tool thermal characteristic testing according to claim 8, characterized in that, Determine the expected impact of the heat generated by the CNC machine tool under test on the cabin temperature based on the operating parameters, including: The expected impact is determined based on the preset transmission relationship between the heat generated by the CNC machine tool under test and the temperature change inside the chamber, as well as the operating parameters. The temperature control quantity is determined based on the corrected target temperature and the actual temperature inside the cabin, including: The first stage of adjustment is performed based on the corrected target temperature to obtain the first control variable; The variable temperature control quantity is obtained by performing a second-level adjustment based on the first control quantity and the actual temperature inside the cabin.

10. The method for reproducing temperature change conditions in CNC machine tool thermal characteristic testing according to claim 8 or 9, characterized in that, The circulating airflow parameters include the circulating airflow rate and the circulating airflow path; When the target temperature curve is in the cooling range, increase the cooling capacity and the circulating air flow rate, and adjust the flow path of the circulating airflow. When the target temperature curve is in the heating phase, the heating amount and the circulating air flow rate are increased in stages to obtain the temperature difference between the surface temperature of the CNC machine tool under test and the actual temperature inside the chamber. The ratio of heating amount to circulating air flow rate is adjusted according to the temperature difference.

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