Air floating bearing stiffness testing device and method

Abstract

The present application relates to air bearing test technical field, especially to a kind of air bearing stiffness testing device and method, including test table, air bearing installation mechanism, gas film gap adjusting mechanism, levelness adjusting mechanism and measurement system;Air bearing installation mechanism is invertedly installed on the top of test table, and gap detection assembly is provided on air bearing installation mechanism;Gas film gap adjusting mechanism is set in test table and is just for the below of air bearing installation mechanism;Levelness adjusting mechanism includes at least three flexible hinges, and flexible hinge is distributed between fixed seat and bearing platform in three-point support;Measurement system includes control unit, control unit is integrated with closed-loop control algorithm, and is connected with gap detection assembly, gas film gap adjusting mechanism communication respectively.The present application realizes micron gas film gap control by innovative gas film gap adjusting mode, levelness guarantee structure and air bearing installation mechanism inverted design, and significantly improves stiffness test precision.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of air floating bearing testing, in particular to an air floating bearing stiffness testing device and method. BACKGROUND

[0002] Air floating bearings are widely used in the fields of precision manufacturing and aerospace due to their cleanliness, non-contact and low friction. An air floating bearing is a non-contact bearing that usually utilizes high-pressure air to form a micron-level air film with certain load bearing and stiffness. Air film stiffness is a key performance indicator of air floating bearings, and it is necessary to test the stiffness of air floating bearings to ensure high precision and stability of movement.

[0003] For example, the patent for invention with publication number CN117490952A discloses an air floating bearing stiffness testing device, which mainly solves the problems of inaccurate load caused by ordinary cylinder skewing and deformation caused by rigid connection. The device applies axial load through a frictionless cylinder and ensures that the loading direction is parallel to the bearing axis through symmetrical transmission modules. A displacement sensor detects the change in air film thickness, thereby enabling the testing of air floating bearing axial stiffness. However, when testing the stiffness of the air film, the device sets a displacement sensor outside the air film to detect the change in air film thickness. Since the sensor is not in direct contact with the air film, it is easily affected by factors such as installation position deviation and environmental airflow disturbance, making it difficult to break through the micron level in air film gap measurement accuracy. Meanwhile, the device's air film gap adjustment mostly adopts manual or open-loop control methods, which makes it difficult to dynamically compensate for air film changes based on real-time monitoring data, resulting in the need for repeated start-stop adjustments during the testing process, low overall testing efficiency, and an inability to meet the rapid batch testing needs of high-precision air floating bearings.

[0004] The patent for invention with publication number CN119666364B discloses a high-precision gas bearing static characteristic testing table and its testing method, which actually solves the problems of poor self-adaptation caused by mechanical ball hinge friction, inaccurate air film thickness measurement, and precision affected by bearing plate deformation. The core is to achieve horizontal self-adaptation through air floating ball hinges and measure the air film thickness through a laser interference measurement assembly, with an angle adjustment mechanism assisting in leveling. However, in actual testing, the device's levelness is ensured through air floating ball hinges or symmetrical transmission structures, which not only have complex structures and high costs, but also do not specifically optimize the air film thickness difference caused by uneven air outlet from the air hole, easily causing bearing capacity measurement deviation.

[0005] In addition, the testing method of the air floating bearing static characteristic testing table is to pre-set the load or displacement, then adjust the air film gap manually or through open-loop control, measure the displacement value, and then calculate the stiffness through the ratio of the two. This testing method often requires manual intervention to adjust the air film gap, and cannot dynamically correct in real time during the testing process, resulting in lag in test data. SUMMARY

[0006] In order to solve the technical defects proposed in the background art, the purpose of the present application is to provide a kind of gas bearing stiffness testing device and method, to solve the problems such as low adjustment efficiency, insufficient precision, horizontality guarantee structure complex of gas bearing stiffness testing in prior art, to realize micron gas film gap control, and significantly improve the stiffness test precision.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] A kind of gas bearing stiffness testing device, comprising:

[0009] Test table;

[0010] Gas bearing mounting mechanism, for installing the gas bearing to be measured, the gas bearing mounting mechanism is installed upside down on the top of test table, gap detection component is provided on the gas bearing mounting mechanism, and the gap detection component is used to detect gas film gap value in real time;

[0011] Gas film gap adjustment mechanism, is set in test table and is just below gas bearing mounting mechanism;The gas film gap adjustment mechanism includes bearing table, coarse adjustment component and fine adjustment component, the bearing table is used to support gas bearing, and the bottom of bearing table is provided with fixed seat;One end of the coarse adjustment component is penetrated through test table and is drivingly connected with fixed seat, for driving the bearing table to quickly approach the gas bearing to be measured to reduce initial gap;The fine adjustment component is located between coarse adjustment component and fixed seat, for receiving the signal of gap detection component and then performing slight expansion and contraction;

[0012] Horizontality adjusting mechanism, including at least three flexible hinges, the flexible hinges are distributed between the fixed seat and the bearing table in three-point support, and the flexible hinges are used to automatically compensate the gas film thickness difference caused by installation error and gas hole gas unevenness, so that the installation surface of gas bearing and the bearing table are kept horizontal;

[0013] Measuring system, including control unit, the control unit is respectively connected with the gap detection component, gas film gap adjustment mechanism communication;The measuring system is used to control the start-stop and action amount adjustment of coarse adjustment component and fine adjustment component.

[0014] Preferably, the gap detection assembly comprises a force sensor, a plurality of laser displacement sensors and a plurality of mirrors, the force sensor is arranged between the air bearing mounting mechanism and the air bearing, and the force sensor is signal connected with the measurement system; the laser displacement sensors are uniformly distributed at the four corners of the bearing table surface, and are used for non-contact detection of the gas film gap; the mirrors are mounted on the air bearing mounting mechanism and correspond to the laser displacement sensors, and the mirrors are connected with the laser displacement sensors.

[0015] Preferably, the coarse adjustment assembly is a rodless cylinder, which drives the bearing table surface to move in the direction of approaching or moving away from the to-be-tested air bearing through air pressure control, and the rodless cylinder is communicatively connected with the measurement system.

[0016] Preferably, the fine adjustment assembly is a piezoelectric ceramic actuator, which is signal connected with the gap detection assembly and can dynamically compensate according to the real-time gas film gap value fed back by the gap detection assembly.

[0017] Preferably, the test bench comprises a frame and a mounting plate arranged equidistantly in the frame, a base is arranged at the bottom of the frame, and a vibration isolation assembly is arranged between the base and the ground, and the vibration isolation assembly is used for isolating ground vibration transmission.

[0018] Preferably, the vibration isolation assembly comprises at least four air springs, the air springs are arranged at the four bottom corners of the base respectively, and the internal pressure of the air springs can be independently controlled through the air pressure adjusting device.

[0019] Preferably, the measurement system further comprises a data acquisition card and a computer, the force sensor and the laser displacement sensor are communicatively connected with the computer through the data acquisition card; and the computer is used for data processing, display and generation of a stiffness test report.

[0020] A stiffness test method of an air bearing, comprising the following steps:

[0021] S1, installing a to-be-tested air bearing on an air bearing mounting mechanism, automatically leveling through a levelness adjusting mechanism, keeping the air bearing mounting surface and the bearing table surface horizontal, and clearing the measurement system;

[0022] S2, starting a gas film gap adjusting mechanism, controlling a coarse adjustment assembly to drive the bearing table surface and the fixed seat to quickly approach the to-be-tested air bearing, and reducing the gas film gap to a preset preliminary range;

[0023] S3, real-time detecting a current gas film gap value through a gap detection assembly, and transmitting data to a measurement system;

[0024] S4. The control unit controls the fine-tuning component to perform micron-level correction on the air film gap based on the detection data until the target gap value is reached.

[0025] S5. Collect the air film gap value and corresponding bearing capacity data through the measurement system, and calculate the stiffness of the air bearing according to the stiffness formula K=F / x, where K is the stiffness, F is the bearing capacity, and x is the change in air film gap.

[0026] S6. Process data using a computer to output stiffness curves and test reports.

[0027] Preferably, the initial air film gap values ​​at the four corners of the support platform are collected by the gap detection component and recorded as d1, d2, d3, and d4. The control unit drives the flexible hinge at the corresponding position to produce micro-deformation based on the difference of each initial air film gap value.

[0028] Preferably, before performing stiffness calculation in step S5, system deformation compensation needs to be performed on the bearing capacity data; the specific process is as follows:

[0029] When the load F is applied to the air bearing, the air film is compressed, and the load-bearing structure of the testing device undergoes elastic deformation δ due to the force. The displacement value measured by the laser displacement sensor is the sum of the air film gap variable x and the elastic deformation δ, i.e., (x + δ); the stiffness measurement value K is calculated from this. 测 = F / (x+δ), its value is less than the actual stiffness value K of the air bearing. 真 ;

[0030] The control unit of the measurement system uses the elastic deformation δ as a feedback signal to drive the piezoelectric ceramic actuator of the fine-tuning component to generate an active compensation displacement, adjusting and maintaining the air film gap at the target value x. At this time, the load detected by the force sensor is the true bearing capacity F of the air bearing. 真 .

[0031] In summary, the beneficial effects of the present invention are as follows:

[0032] 1. This invention, by inverting the air bearing mounting mechanism and installing it on the top of the test bench, together with the air film gap adjustment mechanism located below it, forms a corresponding and compact test layout. This design can effectively shorten the force transmission path and reduce the interference of the external environment on the test accuracy. At the same time, in terms of levelness adjustment, unlike the traditional complex air bearing ball hinge or symmetrical transmission structure, this invention achieves automatic compensation through a three-point supported flexible hinge, which can effectively cope with the differences in air film thickness caused by installation errors and uneven air outlet, ensuring that the air bearing mounting surface and the bearing platform always remain horizontal, providing stable reference conditions for subsequent stiffness testing.

[0033] 2. Relative to the conventional method of measuring the stiffness of an air bearing, the test method proposed by the application innovatively uses a hierarchical adjustment displacement, effectively solving the problems of low adjustment efficiency and poor dynamic response existing in the existing test method, and realizing automatic balancing of the air film gap through a levelness adjusting mechanism; at the same time, a closed-loop load active compensation scheme is adopted, first setting a test reference and a target air film gap, then taking the elastic deformation δ as a feedback signal by a control unit of the measurement system, driving a piezoelectric ceramic actuator of a fine adjustment assembly to generate an active compensation displacement, so as to accurately restore the air film gap to the target value x, at this time, the load detected by the force sensor is the real bearing capacity F of the air bearing 真 ; the entire test process forcibly maintains the air film gap constant, so that the influence of the device deformation δ is offset by the active displacement of the piezoelectric ceramic actuator, completely eliminating the displacement measurement error. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structural schematic diagram of the air bearing stiffness test device for static test in the application;

[0035] Figure 2 is a front view of the air bearing stiffness test device for static test in the application;

[0036] Figure 3 is Figure 2 a sectional view of A-A in

[0037] Figure 4 is an exploded view of the air film gap adjusting mechanism in the application;

[0038] Figure 5 is a work flow chart of the air bearing stiffness test device in the application.

[0039] Explanation of reference numerals in the drawings:

[0040] 1, test table; 11, frame; 12, mounting plate; 13, base; 2, air bearing mounting mechanism; 3, air film gap adjusting mechanism; 31, bearing table; 311, fixed seat; 32, coarse adjustment assembly; 33, fine adjustment assembly; 4, levelness adjusting mechanism; 5, gap detection assembly; 51, force sensor; 52, laser displacement sensor; 53, reflector; 6, vibration isolation assembly; 7, air bearing. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the application.

[0042] Those skilled in the art should understand that in the disclosure of the present application, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like in the drawings is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0043] In the description of the present application, if the word "several" or the like is described, it means one or more, the meaning of multiple is two and more, greater than, less than, more than, etc. are not included in the number, above, below, within, etc. are understood to include the number. If it is described as first, second, third, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0044] The following will be described in detail in combination with the accompanying drawings Figures 1-5 Further detailed description will be made on the embodiment of the air bearing stiffness testing device and method of the present application.

[0045] An air bearing 7 stiffness testing device, as shown in Figure 1 , 2 , includes a test table 1, an air bearing mounting mechanism 2, an air film gap adjusting mechanism 3, a level adjusting mechanism 4 and a measurement system.

[0046] The test table 1 includes a frame 11 and mounting plates 12 arranged equidistantly in the frame 11, the frame 11 is welded by No. 45 steel, and the surface is treated by aging to eliminate internal stress and ensure structural rigidity; the mounting plates 12 are made of aviation aluminum alloy and are fixedly connected with the frame 11 by bolts, and are used for mounting the air film gap adjusting mechanism 3 and related pipelines and cables.

[0047] Specifically, a base 13 is arranged at the bottom of the frame 11, and a vibration isolation assembly 6 is arranged between the base 13 and the ground, which is used to isolate the transmission of ground vibration. The vibration isolation assembly 6 includes at least four air springs, which are arranged at the four bottom corners of the base 13 respectively, and the internal pressure of the air springs can be independently controlled by air pressure adjusting devices. The carrying capacity of each air spring is 500 kg, and the natural frequency is 1.5-2.5 Hz. By adjusting the inflation pressure of each air spring, not only the horizontal attitude adjustment of the test table 1 can be realized, but also the ground vibration can be effectively attenuated, so as to avoid the interference of external vibration on precise measurement.

[0048] In the embodiment, as shown in Figure 2 and Figure 4As shown, the air bearing mounting mechanism 2 is used to mount the air bearing 7 to be tested, the air bearing mounting mechanism 2 is mounted upside down on the top of the test bench 1, and the gap detection assembly 5 is arranged on the air bearing mounting mechanism 2, which is used to detect the air film gap value in real time; the gap detection assembly 5 includes a force sensor 51, a plurality of laser displacement sensors 52 and a plurality of mirrors 53, the force sensor 51 is arranged between the air bearing mounting mechanism 2 and the air bearing 7, and the force sensor 51 is connected with the measurement system; the plurality of laser displacement sensors 52 are uniformly distributed at the four corners of the bearing table 31, which are used to detect the air film gap in a non-contact manner; the plurality of mirrors 53 are mounted on the air bearing mounting mechanism 2 and correspond to the laser displacement sensors 52, and the mirror 53 is connected with the laser displacement sensor 52 in cooperation.

[0049] Specifically, the laser displacement sensor 52 adopts a high-precision laser interferometer, which is uniformly distributed at the four corners of the bearing table 31 through an angle code support; at the same time, the emission end of the laser displacement sensor 52 is upward, opposite to the mirror 53 on the air bearing mounting mechanism 2. The force sensor 51 selects an S-shaped tension and compression force sensor, which can collect the bearing force data between the air bearing 7 and the bearing table 31 in real time, and convert the analog signal into a digital signal transmitted to the measurement system. The mirror 53 is made of quartz, which is fixed on the lower surface of the air bearing mounting mechanism 2 by vacuum adsorption, the center of the mirror 53 coincides with the axis of the air bearing 7, which ensures that the light beam emitted by the laser displacement sensor 52 is perpendicular to the surface of the mirror 53, reducing the detection error caused by the deviation of the light path. The laser displacement sensor 52 emits a laser beam to the mirror 53, receives the interference signal after reflection, calculates the air film gap value according to the optical path difference, and realizes non-contact and high-precision real-time monitoring.

[0050] It should be noted that the advantages of upside-down mounting are: the force sensor 51 directly contacts with the air bearing 7, compared with the conventional normal design, the measurement chain length is shortened, and the system stiffness loss is reduced by more than 60%; at the same time, the mirror 53 and the air bearing 7 are rigidly connected with the mounting reference surface, which ensures that the displacement signal detected by the laser displacement sensor 52 can truly reflect the change of the air film gap. The laser displacement sensor 52 can directly detect the air film gap, avoiding the influence of the deformation of the intermediate transmission component on the detection result, thereby effectively improving the detection accuracy.

[0051] In the embodiment, as Figures 2 to 4As shown, the gas film gap adjusting mechanism 3 is arranged in the test table 1 and is opposite to the lower side of the gas bearing mounting mechanism 2; the gas film gap adjusting mechanism 3 comprises a bearing table 31, a coarse adjusting assembly 32 and a fine adjusting assembly 33, the bearing table 31 is used for supporting the gas bearing 7, and the bottom of the bearing table 31 is provided with a fixing seat 311; one end of the coarse adjusting assembly 32 penetrates through the test table 1 and is in driving connection with the fixing seat 311, and is used for driving the bearing table 31 to quickly approach the gas bearing 7 to be tested to reduce the initial gap.

[0052] Specifically, the coarse adjusting assembly 32 in the gas film gap adjusting mechanism 3 is a rodless cylinder, the rodless cylinder drives the bearing table 31 to move along the direction of approaching or moving away from the gas bearing 7 to be tested through air pressure control, and the rodless cylinder is in communication connection with the measurement system. Wherein, the cylinder body of the rodless cylinder is fixed to the middle layer mounting plate 12 of the test table 1 through four groups of bolts, and the top end of the piston rod is connected with the fine adjusting assembly 33 through a floating joint; the air supply circuit of the rodless cylinder is additionally provided with a precision pressure reducing valve and an electromagnetic reversing valve, and the start-stop and speed of the cylinder are controlled through the control unit of the measurement system. In the initial stage, the rodless cylinder drives the bearing table 31 to quickly approach the gas bearing 7, and when the gap detection assembly 5 detects that the gas film gap is reduced to a preset preliminary range, the rodless cylinder automatically stops, and at this time, the gas film gap is usually controlled within the range of 0.1-0.3 mm, thereby providing a reasonable initial basis for the micron-level adjustment of the fine adjusting assembly 33.

[0053] In the embodiment, the fine adjusting assembly 33 is located between the coarse adjusting assembly 32 and the fixing seat 311, and adopts a piezoelectric ceramic actuator, the piezoelectric ceramic actuator is in signal connection with the gap detection assembly 5 and can perform dynamic compensation according to the real-time gas film gap value fed back by the gap detection assembly 5.

[0054] Specifically, the piezoelectric ceramic actuator is connected in series between the coarse adjusting assembly 32 and the fixing seat 311, and the power supply and control of the piezoelectric ceramic are realized through a controller, and the controller is in communication connection with the measurement system. When the coarse adjusting assembly 32 reduces the gas film gap to a preset preliminary range, the measurement system sends a control signal to the controller according to the real-time detection data of the laser displacement sensor 52, drives the piezoelectric ceramic actuator to perform a slight expansion and contraction, corrects the gas film gap to a target value, and the error is controlled within 0.1 μm, thereby performing micron-level correction on the gas film gap, and ensuring that the final gap value is accurately controlled within the target range. In addition, the piezoelectric ceramic driver can also be other structures for realizing micron-level distance adjustment, such as a wedge-shaped adjusting table and the like, which are well known in the prior art, and therefore will not be described in detail in the embodiment.

[0055] It should be noted that the advantage of hierarchical adjustment is that the rodless cylinder can complete a stroke of 500 mm within 10 s, solving the problem of small stroke and slow adjustment of existing piezoelectric ceramics. The micrometer-level fine adjustment of the piezoelectric ceramic actuator compensates for the low precision of the rodless cylinder. After the combination of the two, the adjustment efficiency of the gas film gap is improved by more than 3 times, and the adjustment precision reaches the level of 0.1 μm, meeting the stringent requirements of the gap control of the stiffness test of the air floating bearing 7.

[0056] In the present embodiment, as shown in Figure 4 The levelness adjusting mechanism 4 includes at least three flexible hinges, which are distributed in a three-point support manner between the fixed seat 311 and the load table 31, and are used to automatically compensate for the gas film thickness difference caused by installation errors and uneven gas outlet of the gas hole, so that the installation surface of the air floating bearing 7 and the load table 31 remain horizontal.

[0057] Specifically, the three flexible hinges are uniformly distributed at an angle of 120° along the center circumference of the load table 31, each flexible hinge adopts a cross-shaped structure design, and provides bending stiffness around the X and Y axes, and can compensate for a certain range of angular displacement. When the laser displacement sensor 52 detects that there is a difference in the gas film gap at the four corners of the load table 31, the control unit of the measurement system will calculate the required compensation angle of each flexible hinge according to the deviation of each gap value. Subsequently, the control unit of the measurement system will calculate the required compensation angle of each flexible hinge according to the deviation of each gap value, and control the micro piezoelectric ceramic piece integrated at the bottom of the flexible hinge to produce a slight deformation through the integrated drive circuit, so as to drive the load table 31 to adjust the posture, thereby ensuring that the installation surface of the air floating bearing 7 and the load table 31 remain on the same level. Compared with the traditional multi-point adjustment mode, the three-point support flexible hinge structure has higher dynamic response speed and structural stability, and can quickly complete the automatic compensation of the levelness, effectively avoiding the adjustment lag problem caused by the mechanical transmission gap.

[0058] In the present embodiment, the measurement system includes a control unit, which is in communication connection with the gap detection assembly 5 and the gas film gap adjusting mechanism 3 respectively; the measurement system is used to control the start-stop and action amount adjustment of the coarse adjustment assembly 32 and the fine adjustment assembly 33, and the measurement system further includes a data acquisition card and a computer, and the force sensor 51 and the laser displacement sensor 52 are in communication connection with the computer through the data acquisition card.

[0059] Specifically, the control unit adopts a microcontroller as the core processor, which can process 8 analog signals and 16 digital signals simultaneously. Among them, the data acquisition card selects a 16-bit high-precision AD conversion module, which can synchronously collect the bearing force signal of the force sensor 51 and the air film gap signal of the laser displacement sensor 52, and transmit the raw data to the computer through the Ethernet interface. The computer has a built-in test software developed by LabVIEW, which has functions of real-time data display, curve drawing, parameter setting and report generation. The software interface includes an air film gap dynamic monitoring window, a bearing force-displacement curve real-time drawing area, a temperature compensation parameter setting panel and a test report preview module. The operator can set test parameters such as target air film gap range, temperature compensation coefficient, sampling frequency, etc. through the software, and start the automatic test process with one key.

[0060] During the test, the control unit can compare the actual air film gap value fed back by the laser displacement sensor 52 with the set target value in real time. When the actual value deviates from the target value by more than 1 μm, the piezoelectric ceramic actuator is immediately driven to compensate and adjust, so as to ensure that the air film gap is always stable within the set range during the test. At the same time, the test software automatically records the timestamp, compensation amount and corresponding bearing force data of each adjustment, forming a complete test data log for subsequent data analysis and tracing.

[0061] After the test is completed, the computer automatically generates a report containing test conditions (environmental temperature, humidity, atmospheric pressure), equipment parameters (air bearing 7 model, number), raw data table, stiffness curve (horizontal axis is air film gap, vertical axis is stiffness value) and test conclusion according to the preset report template, and supports data export to Excel or Matlab format file for further data analysis and processing.

[0062] An air bearing stiffness test method, as shown in Figure 5 , comprising the following steps:

[0063] S1, install the air bearing 7 to be tested on the air bearing mounting mechanism 2, automatically level the air bearing 7 through the levelness adjusting mechanism 4, so that the mounting surface of the air bearing 7 and the bearing table surface 31 are kept horizontal, and the measuring system is cleared;

[0064] S2, start the air film gap adjusting mechanism 3, control the coarse adjustment assembly 32 to drive the bearing table surface 31 and the fixed seat 311 to quickly approach the air bearing 7 to be tested, and narrow the air film gap to a preset preliminary range;

[0065] S3, detect the current air film gap value in real time through the gap detection assembly 5, and transmit the data to the measuring system;

[0066] S4, the control unit controls the fine adjustment assembly 33 to act according to the detection data, and corrects the air film gap to micron level until the target gap value is reached.

[0067] S5, collecting the gas film gap value and the corresponding bearing capacity data by the measuring system, and calculating the gas bearing stiffness according to the stiffness formula K=F / x, wherein K is the stiffness, F is the bearing capacity, and x is the change amount of the gas film gap;

[0068] S6, processing the data by the computer, and outputting the stiffness curve and the test report.

[0069] Specifically, when the stiffness of the gas bearing 7 is tested, first, the gas bearing 7 to be tested is installed on the bottom of the gas bearing installation mechanism 2 through a special fixture, so as to ensure that the installation reference surface of the gas bearing 7 is closely attached to the force sensor 51; at the same time, the control unit drives the levelness adjusting mechanism 4 to automatically level, the initial gas film gap values at four corners of the bearing platform 31 are collected by the gap detection assembly 5, and are recorded as d1, d2, d3 and d4, and the control unit drives the flexible hinge at the corresponding position to produce a micro-deformation according to the difference between the gap values, so as to complete the levelness calibration.

[0070] Then, the gas film gap adjusting mechanism 3 is started, the bearing platform 31 is first driven by the coarse adjustment assembly 32 to quickly rise, and when the laser displacement sensor 52 detects that the gas film gap is reduced to a preset preliminary range, the coarse adjustment assembly 32 stops acting;

[0071] At this time, the force sensor 51 collects the current bearing capacity F, not only the gas film is compressed, but also the bearing structure of the whole test device will be elastically deformed δ due to the force. The displacement actually measured by the displacement sensor is (x+δ), and the stiffness measurement value K is obtained 测 =F / (x+δ) is less than the stiffness K 真 .

[0072] Subsequently, the control unit of the measuring system takes the elastic deformation δ as a feedback signal, drives the piezoelectric ceramic actuator of the fine adjustment assembly to produce an active compensation displacement, until the gas film gap is adjusted and maintained at the target value x, and at this time, the load detected by the force sensor is the real bearing capacity F of the gas bearing 真 .

[0073] After the test is completed, the computer automatically generates a test report containing the stiffness value, the gas film gap curve, the temperature compensation data and other information, so as to provide comprehensive data support for the performance evaluation of the gas bearing 7.

[0074] The closed-loop load active compensation scheme is adopted in the application, the test reference and the target gas film gap are set, the measuring system detects the distance as the set value x+gap offset δ after the gas bearing load is applied, the control system takes the deviation δ as a feedback signal, drives the piezoelectric ceramic actuator to actively compensate the offset, so that the gas film gap is accurately restored to x, and at this time, the force sensor measures the real bearing capacity F 真The whole test process forces to keep the air film gap constant, the influence of the device deformation delta is offset by the active displacement of the piezoelectric ceramic actuator, and the displacement measurement error is completely eliminated.

[0075] The working principle of the present application is as follows:

[0076] First, the air bearing 7 to be tested is installed on the bottom of the air bearing mounting mechanism 2 through a special fixture, ensuring that the working surface of the air bearing 7 faces downward and is in a preset initial alignment state with the bearing table 31.

[0077] Subsequently, the air supply system is started, and compressed air is supplied to the air bearing 7 to be tested, so that a stable air film is formed between the air bearing 7 and the bearing table 31. At the same time, the internal pressure of the air spring is adjusted to a preset value through the air pressure adjusting device, and the horizontal posture calibration and vibration isolation preparation of the test bench 1 are completed.

[0078] After the measurement system is initialized, the control unit drives the coarse adjustment assembly 32 to act, and the rodless cylinder pushes the bearing table 31 to rise quickly until the laser displacement sensor 52 detects that the air film gap enters the preset preliminary range, at which time the coarse adjustment assembly 32 stops acting.

[0079] Then, the fine adjustment assembly 33 dynamically compensates according to the real-time air film gap value fed back by the gap detection assembly 5, and adjusts the air film gap to the target value through nanoscale displacement adjustment. In this process, the flexible hinge of the levelness adjusting mechanism 4 compensates for the installation error and the air film thickness difference in real time, ensuring that the air bearing 7 mounting surface and the bearing table 31 always remain horizontal.

[0080] When the system reaches a stable state, the force sensor 51 collects the current bearing force data, and the laser displacement sensor 52 records the air film gap value. The data is transmitted to the computer through the data acquisition card, and the computer calculates the static stiffness according to the stiffness formula K=F / Δx.

[0081] In summary, the present embodiment optimizes the inverted layout of the air bearing mounting mechanism 2, shortens the force transmission path, and reduces the system stiffness loss. The levelness adjusting mechanism 4 uses a flexible hinge three-point support, which reduces the number of parts by 40% compared to the traditional air floating ball hinge structure, and shortens the leveling response time to within 2s. The air film gap adjusting mechanism 3 combines the coarse adjustment of the rodless cylinder and the fine adjustment of the piezoelectric ceramic actuator, realizing an efficient adjustment mode of fast positioning and precise correction, and reducing the adjustment time by 60% compared to a single adjustment method. The closed-loop control algorithm and high-precision sensor integrated in the measurement system make the air film gap control accuracy reach ±0.1μm, and the stiffness test repeatability error is less than 1%, which is significantly better than existing test devices. The device can be widely used in the static stiffness test of air bearings 7 in the fields of precision machine tools, aircraft engines, semiconductor lithography machines, etc., and provides a reliable performance detection means for the research and development and manufacturing of high-end equipment.

[0082] The embodiments of the present application are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, wherein the same parts are denoted by the same reference numerals. Therefore, any equivalent changes made on the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. An air-float bearing stiffness testing device, characterized by, The test bench comprises: a test bench; an air bearing mounting mechanism for mounting the air bearing to be tested, the air bearing mounting mechanism is mounted upside down on the top of the test bench, a gap detection assembly is arranged on the air bearing mounting mechanism, and the gap detection assembly is used for real-time detection of the air film gap value; an air film gap adjusting mechanism arranged in the test bench and opposite to the lower side of the air bearing mounting mechanism; the air film gap adjusting mechanism comprises a bearing table, a coarse adjustment assembly and a fine adjustment assembly, the bearing table is used for bearing and supporting the air bearing, and the bottom of the bearing table is provided with a fixed seat; one end of the coarse adjustment assembly penetrates through the test bench and is in transmission connection with the fixed seat, and is used for driving the bearing table to quickly approach the air bearing to be tested to reduce the initial gap; the fine adjustment assembly is located between the coarse adjustment assembly and the fixed seat, and is used for micro expansion and contraction after receiving the signal of the gap detection assembly; a levelness adjusting mechanism comprising at least three flexible hinges, the flexible hinges are distributed in three-point support between the fixed seat and the bearing table, and the flexible hinges are used for automatically compensating the air film thickness difference caused by installation error and uneven air outlet of the air hole, so that the mounting surface of the air bearing and the bearing table are kept horizontal; a measurement system comprising a control unit, the control unit is in communication connection with the gap detection assembly and the air film gap adjusting mechanism; the measurement system is used for controlling the start-stop and action amount adjustment of the coarse adjustment assembly and the fine adjustment assembly.

2. The air foil bearing stiffness test device of claim 1 wherein, The gap detection assembly comprises a force sensor, a plurality of laser displacement sensors and a plurality of mirrors, the force sensor is arranged between the air bearing mounting mechanism and the air bearing, and the force sensor is in signal connection with the measurement system; the laser displacement sensors are uniformly distributed at the four corners of the bearing table, and are used for non-contact detection of the air film gap; the mirrors are installed on the air bearing mounting mechanism and correspond to the laser displacement sensors, and the mirrors are in matched connection with the laser displacement sensors.

3. The air foil bearing stiffness test device of claim 1 wherein, The coarse adjustment assembly is a rodless air cylinder, the rodless air cylinder drives the bearing table to move along the direction of approaching or moving away from the air bearing to be tested through air pressure control, and the rodless air cylinder is in communication connection with the measurement system.

4. The air foil bearing stiffness test device of claim 1 wherein, The fine adjustment assembly is a piezoelectric ceramic actuator, the piezoelectric ceramic actuator is in signal connection with the gap detection assembly, and can dynamically compensate according to the real-time air film gap value fed back by the gap detection assembly.

5. The air foil bearing stiffness test device of claim 1 wherein, The test bench comprises a frame and a mounting plate arranged equidistantly in the frame, the bottom of the frame is provided with a base, a vibration isolation assembly is arranged between the base and the ground, and the vibration isolation assembly is used for isolating the transmission of ground vibration.

6. The air foil bearing stiffness test device of claim 5 wherein, The vibration isolation assembly comprises at least four air springs, the air springs are arranged at the four bottom corners of the base respectively, and the internal pressure of the air springs can be independently controlled through an air pressure adjusting device.

7. The air foil bearing stiffness test device of claim 2 wherein, The measurement system further comprises a data acquisition card and a computer, the force sensor and the laser displacement sensor are in communication connection with the computer through the data acquisition card; the computer is used for data processing, display and generation of stiffness test report.

8. An air-float bearing stiffness testing method based on the testing device according to any one of claims 1-7, characterized in that, The test method comprises the following steps: S1, install the to-be-tested air floating bearing on the air floating bearing mounting mechanism, automatically level by the levelness adjusting mechanism, keep the air floating bearing mounting surface and the bearing table surface horizontal, and clear the measurement system; S2, start the air film gap adjusting mechanism, control the coarse adjustment assembly to drive the bearing table surface and the fixed seat to quickly approach the to-be-tested air floating bearing, and reduce the air film gap to a preset preliminary range; S3, detect the current air film gap value in real time by the gap detection assembly, and transmit the data to the measurement system; S4, control the fine adjustment assembly to act according to the detection data, and correct the air film gap in the micron level until the target gap value is reached; S5, collect the air film gap value and the corresponding bearing force data by the measurement system, calculate the air floating bearing stiffness, wherein K=F / x, K is the stiffness, F is the bearing force, and x is the change amount of the air film gap; S6, process the data by the computer, and output the stiffness curve and the test report.

9. The air foil bearing stiffness test method of claim 8 wherein, The leveling process of the levelness adjusting mechanism in step S1 is as follows: collect the initial air film gap values of the four corners of the bearing table surface by the gap detection assembly, and record them as d1, d2, d3 and d4; and the control unit drives the flexible hinge at the corresponding position to produce a micro-deformation according to the difference between the initial air film gap values.

10. The method of air bearing stiffness testing of claim 8, wherein, Before the stiffness calculation in step S5, the bearing force data needs to be subjected to system deformation compensation; the specific process is as follows: When the load F is applied to the air bearing, the air film is compressed, and the load-bearing structure of the testing device undergoes elastic deformation δ due to the force. The displacement value measured by the laser displacement sensor is the sum of the change in the air film gap x and the elastic deformation δ, i.e., (x + δ); the stiffness measurement value K is calculated from this. 测 = F / (x+δ), its value is less than the actual stiffness value K of the air bearing. 真 ; The control unit of the measuring system takes the elastic deformation δ as a feedback signal, drives the piezoelectric ceramic actuator of the fine adjustment assembly to generate an active compensation displacement, adjusts and maintains the gas film gap at the target value x, and at this time the load detected by the force sensor is the real load bearing force F of the gas bearing 真 .

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