Four-point supporting three-point leveling mechanism and leveling method for precision measuring table

Abstract

The invention provides a four-point supporting three-point leveling mechanism and a leveling method for a precision measuring table, and belongs to the technical field of precision measuring table leveling. Four-point supporting is achieved through the two piezoelectric ceramic stacking micro-displacement mechanisms and the two air springs, stability is improved, communication of the two air springs is equivalent to single-point supporting, three-point leveling is achieved by controlling the two piezoelectric ceramic stacking micro-displacement mechanisms, and control precision is improved; a piezoelectric ceramic stack is adopted to push a top block, a leveling top ball and a wedge block to realize micro-displacement adjustment, and high-precision control and quick response are completed. The four-point supporting three-point leveling mechanism of the precision measuring table has good dynamic stability, the steady-state error reaches 10-5 degrees, friction lag and assembly stress caused by surface contact are avoided through single-point contact of the leveling top ball and the wedge-shaped block, and precision automatic leveling in the mandrel measuring process can be achieved.

Description

Technical Field

[0001] The invention relates to a four-point support and three-point leveling mechanism and a leveling method for a precision measuring platform, belonging to the technical field of leveling of precision measuring platforms. Background Art

[0002] With the advent of the artificial intelligence era, precision automatic leveling platforms have gradually become important devices in modern mechanical manufacturing and precision measurement. In the fields of precision measurement and manufacturing, the stability and accuracy of the worktable are extremely high. Any slight vibration and error may have a significant impact on measurement results and product quality.

[0003] High-precision automatic leveling platforms are a crucial component of precision measurement equipment, playing a vital role in fields such as precision manufacturing and measurement, microelectronics, aerospace, and bioengineering. In particular, in the field of precision and ultra-precision measurement, the demand for achievable accuracy is increasingly high, often reaching the micron or even nanometer level. For example, during operations such as machining and inspecting the surface of a Wolter-I mandrel, factors such as positional errors can significantly impact the assembly and adjustment process. This is especially true when multiple adjustments are required during the measurement process, which presents challenges such as human error and low efficiency. Therefore, precision automatic leveling platforms are particularly important in measurement and adjustment. Precision automatic leveling platforms monitor and adjust the platform's balance, eliminating or minimizing tilt caused by external interference or internal structural inhomogeneities. This not only improves work safety and reliability, but also enables high-precision measurement and increases assembly and adjustment efficiency.

[0004] At present, the research on precision automatic leveling platforms has made significant progress both at home and abroad. The roundness meter work platform developed by Taylor Hobson has an automatic leveling function. When the instrument is working, the pitch and azimuth angles of the workpiece coordinate system are obtained through the probe, and the offset of the workpiece center line relative to the rotation center line of the worktable is calculated. The offset on the leveling support is calculated through the leveling algorithm, and the center line of the workpiece and the center line of the platform are adjusted to be parallel, thereby achieving the leveling purpose. The leveling device for the leveling instrument tray invented by Zhejiang University adopts a three-point leveling method. The sliding wedge is driven by a bolt to move left and right, and the sliding wedge drives the moving wedge to move up and down, thereby achieving horizontal leveling. The Xi'an Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences has designed a wedge-type automatic leveling mechanism for use in theodolites. It converts its rotational motion into a small vertical movement of the lifting wedge through the transmission structure of the gear pair, worm gear pair, screw nut pair and wedge plane pair through the drive motor, thereby achieving the adjustment of the tilt angle of the vertical axis. The high-precision rapid leveling device developed by Shanghai Microelectronics Equipment Co., Ltd. adopts a three-point electric leveling method. During adjustment, the driving motor drives the cam to rotate, thereby achieving the leveling of the workbench. The leveling and centering workbench for high-precision cylindricimeters developed by the Beijing Institute of Aerospace Metrology and Testing Technology uses two sets of mutually orthogonal leveling and centering handwheels. After the centering feed end is decelerated by the worm gear box, the rotational motion of the handwheel is converted into the feed motion of the centering feed head, thereby achieving the adjustment of the platform. The platform can achieve high-precision adjustment, but the structure is complex and the manufacturing cost is relatively high. Fudan University invented a hollow centering and leveling mechanism based on a hinge structure, which is applied to the field of ultra-precision detection, measurement and processing technology. The base of the leveling device and the upper plate of the leveling device are connected through the upper shaft seat and the corresponding shaft. By rotating the hinge, two angles of rotation adjustment can be achieved, thereby realizing the leveling function, and it can be locked. Zhejiang University of Science and Technology has proposed a high-precision leveling work platform. The device adopts a three-point leveling method. Based on the piezoelectric ceramic self-sensing driver, an error leveling control method is proposed for the three legs. By adjusting the pressure exerted on each leg during the actual working process to the ideal pressure value, the work platform can be leveled.

[0005] Currently, automatic leveling systems at home and abroad are divided into three-point support leveling, four-point support leveling, and six-point support leveling according to the support structure. Existing precision leveling devices mostly use three-point support leveling and four-point support leveling. The three-point leveling method uses three support points to adjust and balance the level of the structure, forming a stable flat triangular structure. In theory, it can provide sufficient stability, and the leveling operation is relatively simple. Four-point support achieves this goal through four support points. Because it has more support points, it can increase the stability of the structure. Especially under unevenly distributed loads, four-point leveling can more accurately adjust the level of the platform, but the leveling process is relatively complicated.

[0006] In summary, existing precision adjustment mechanism workbenches mostly use traditional micro-motion mechanisms such as manual or motor-driven ones as transmission mechanisms. Prior to construction, these mechanisms suffer from friction creep and complex assembly and adjustment. When used on precision adjustment platforms, they place high demands on the manufacturing precision of transmission parts, resulting in complex structures and high manufacturing costs. Therefore, a four-point support and three-point leveling method for a precision measuring platform is proposed. Four-point support is achieved by using two sets of piezoelectric ceramic stack micro-feed mechanisms and two air springs to improve stability. The two air springs are connected to form a single-point support. Three-point leveling is achieved by controlling the micro-displacement of the two sets of piezoelectric ceramic stacks, improving control accuracy and simplifying the control process. This facilitates precise automatic leveling during Wolter-I mandrel measurement. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem in the above-mentioned prior art that the Wolter-Ⅰ type mandrel produces position error due to the platform inclination during the installation and adjustment process, which significantly affects the measurement accuracy during its precision measurement process, and thus provide a four-point support three-point leveling mechanism and leveling method for a precision measuring table.

[0008] The present invention uses two sets of piezoelectric ceramic stack micro-displacement mechanisms and two air springs to achieve four-point support to improve stability. The two air springs are connected to form a single-point support. By controlling the two sets of piezoelectric ceramic stack micro-displacement mechanisms, three-point leveling is achieved to improve control accuracy and simplify the control process. Simulation data shows that the leveling mechanism of the precision measuring platform designed according to the leveling method meets the predetermined requirements. The leveling system has good dynamic stability and a steady-state error of 10 -5 °, which enables precise automatic leveling during the spindle measurement process.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A precision measuring platform with a four-point support and three-point leveling mechanism includes: a platform, two air springs, a leveling lower plate, and two sets of piezoelectric ceramic stack micro-displacement mechanisms; the platform and the leveling lower plate are arranged in a corresponding upper and lower position, and the air springs and the two sets of piezoelectric ceramic stack micro-displacement mechanisms are fixedly arranged between the platform and the leveling lower plate;

[0011] The two air springs are air spring 1 and air spring 2; air spring 1 and air spring 2 are symmetrically distributed relative to the center of the platform and are positioned and fixed between the platform and the leveling lower plate. Air spring 1 and air spring 2 are respectively connected to the corresponding interfaces of the T-joint through pressure-resistant air pipes, and the bottom interface of the T-joint is connected to the solenoid valve through a connecting pipe;

[0012] Each set of piezoelectric ceramic stacked micro-displacement mechanisms includes: an upper wedge block, a lower wedge block, a leveling top ball and a piezoelectric telescopic ceramic actuator; the upper wedge block and the lower wedge block are stacked up and down, the upper wedge block is fixedly connected to the bottom end surface of the platform, the lower wedge block is fixedly connected to the upper end surface of the leveling lower plate, the leveling top ball is arranged in a V-shaped opening formed between the upper wedge block and the lower wedge block, and is in single-point contact with the inclined surfaces of the upper wedge block and the lower wedge block respectively, the piezoelectric telescopic ceramic actuator is arranged horizontally and connected to the leveling top ball, and the piezoelectric telescopic ceramic actuator is fixedly connected to the upper end surface of the leveling lower plate.

[0013] Preferably, the piezoelectric telescopic ceramic actuator includes: a top block, a piezoelectric ceramic stack and a pre-tightening mechanism; the top block and the piezoelectric ceramic stack are connected, the top block and the piezoelectric ceramic stack are slidably arranged in the piezoelectric ceramic actuator housing of the pre-tightening mechanism, and the top block is connected to the leveling top ball.

[0014] Preferably, the pre-tightening mechanism includes: a supporting elastic membrane, a top screw, a tightening nut, a locking nut, a pre-tightening bolt and a piezoelectric ceramic actuator housing; the front and rear ends of the piezoelectric ceramic actuator housing are both open, a supporting elastic membrane is fixedly installed in the piezoelectric ceramic actuator housing, the top block and the piezoelectric ceramic stack are slidingly arranged on the front side of the supporting elastic membrane in the piezoelectric ceramic actuator housing, the tightening nut is arranged in the piezoelectric ceramic actuator housing and is located on the rear side of the supporting elastic membrane, the tightening nut is fixedly connected to the piezoelectric ceramic actuator housing through the top screw, the pre-tightening bolt is threadedly connected to the tightening nut and the locking nut, the locking nut is located on the rear side of the tightening nut, and the piezoelectric ceramic actuator housing is fixed on the base.

[0015] Preferably, a convex column 1 is provided on the lower surface of the piezoelectric ceramic actuator housing, a groove 1 matching the convex column 1 is provided on the upper surface of the base, the convex column 1 is matched and arranged in the groove 1 and the two are fixedly connected by a lateral top screw, a convex column 2 is provided on the lower surface of the base, a groove 2 matching the convex column 2 is provided on the upper surface of the leveling lower plate, the convex column 2 is matched and arranged in the groove 2, and the pressure block presses the base while being fixedly connected to the leveling lower plate.

[0016] Preferably, a dust cover is provided between the platform and the leveling lower plate.

[0017] Preferably, the leveling lower plate is positioned and fixedly connected to the working surface of the precision measuring table.

[0018] Preferably, the wedge surface angles of the upper wedge block and the lower wedge block are consistent.

[0019] A leveling method based on a four-point support and three-point leveling mechanism of a precision measuring table comprises the following steps:

[0020] Step 1: Pre-calibrate the platform (1) of the four-point support and three-point leveling mechanism of the precision measuring table to eliminate the initial error. During the zeroing calibration process, the two sets of piezoelectric ceramic stack micro-displacement mechanisms are subjected to pre-tightening force through the pre-tightening mechanism;

[0021] Step 2: Subsequently, a Wolter-I type mandrel is placed on the platform (1) of the leveling mechanism, and the platform (1) of the leveling mechanism detects its inclination angle α in the x-axis direction and its inclination angle β in the y-axis direction in real time through a detection system;

[0022] Step 3: Based on the test results, select the equivalent point of air spring 1 (2-1) and air spring 2 (2-2) as the reference datum for posture adjustment, and drive the piezoelectric ceramic stack micro-displacement mechanism to fine-tune the platform (1) of the leveling mechanism;

[0023] Step 4: The platform (1) posture of the leveling mechanism is updated in real time through the detection system, and the tilt angle change is continuously monitored. The leveling process continues until the tilt angles in two directions meet the conditions of |α|, |β| < fixed threshold values. Then, the platform (1) meets the leveling requirements and the leveling process ends.

[0024] Preferably, the detection system in step 2 is a probe detection system, an optical detection system or a visual detection system.

[0025] Preferably, the step three specifically includes the following steps:

[0026] Step 31: The air spring 1 (2-1) and the air spring 2 (2-2) in the three-point leveling mechanism of the four-point support of the precision measuring platform and the two sets of piezoelectric ceramic stacked micro-displacement mechanisms are used as the four legs of the platform (1) of the leveling mechanism; wherein, the air spring 1 (2-1) and the air spring 2 (2-2) are used as the A leg and the B leg respectively, and the two sets of piezoelectric ceramic stacked micro-displacement mechanisms are used as the C leg and the D leg respectively; the four action points of the above four legs are distributed to form a rectangle ABCD, and the two action points AB are equivalent to the two force points in the leveling process as point H. The three-point leveling method is used to make the platform (1) equivalent to an isosceles triangle with three leveling support points as vertices, and the equivalent support point H is used as a fixed support point. The leveling purpose is achieved by adjusting the two movable support points CD.

[0027] Step 32: Take the equivalent leg H as the origin, the line connecting the A leg and the B leg as the y-axis, and a straight line perpendicular to the y-axis through the origin H as the x-axis to establish a spatial rectangular coordinate system. Assume that at any point P(x0, y0, z0) in space, when the platform (1) is in a non-horizontal state, the horizontal inclination angle of the platform (1) is divided into an inclination angle α in the x-axis direction and an inclination angle β in the y-axis direction;

[0028] Step 3: The point P(x0,y0,z0) on the platform (1) is first rotated by an angle α around the y-axis of the horizontal coordinate system to obtain the coordinates P'(x',y',z'), as shown in formula (1).

[0029] (1)

[0030] Step 3 and 4: Rotate the point around the x-axis by an angle β to obtain the coordinates P(x, y, z), as shown in formula (2). Substitute formula (1) into formula (2) to obtain the coordinates of point P in the non-horizontal state.

[0031] (2)

[0032] Step 35: Consider the two tilt angles α and β as , it is approximately considered that sinα=α, cosα=1, sinβ=β, cosβ=1, so formula (3) is simplified to formula (4);

[0033] (3)

[0034] (4)

[0035] Step 36: From the horizontal state modeling, we know that the coordinates of each support point in the horizontal coordinate system are: , , , the distance between any two adjacent legs is T, then:

[0036] (5)

[0037] Step 37: Substitute formula (5) into formula (4) to obtain the coordinates O of each leg after leveling, and then obtain the displacement required to adjust each leg as shown in formula (7);

[0038] (6)

[0039] (7)

[0040] Among them, z H is the displacement that needs to be adjusted for the fixed support point H on the z axis, C is the displacement of leg C that needs to be adjusted on the z axis, z D is the displacement of leg D that needs to be adjusted on the z-axis.

[0041] Preferably, the step 4 specifically includes the following steps:

[0042] Step 41: The detection system detects the tilt angle α of the Wolter-I mandrel in the x-axis direction and the tilt angle β in the y-axis direction of the platform;

[0043] Step 42: Based on the inclinations α and β, the piezoelectric ceramic stack micro-displacement mechanism (4) is controlled to adjust and update the posture of the platform (1) of the leveling mechanism in real time, and the changes in the inclinations α and β are continuously monitored. The leveling process continues until the inclination angles in the x and y directions meet the threshold conditions of |α| < 0.00001° and |β| < 0.00001°. Then, the platform (1) meets the leveling requirements and the leveling process ends.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention proposes a four-point support and three-point leveling mechanism and leveling method for a precision measuring table, which is used to achieve automatic leveling during the assembly and adjustment of a Wolter-I type mandrel during machining and testing, and has the following advantages:

[0046] (1) The present invention uses two connected air springs and two sets of piezoelectric ceramic stacked micro-displacement mechanisms to achieve four-point support, thereby improving the stability of the mechanism. At the same time, connecting the two air springs to form a single point reduces the complexity of leveling control.

[0047] (2) The present invention uses a stack of piezoelectric ceramics to push the top block, leveling ball, and wedge block to achieve micro-displacement adjustment, achieving high-precision control and rapid response. The single-point contact between the leveling ball and the wedge block avoids friction hysteresis and assembly stress caused by surface contact.

[0048] (3) The present invention shows through simulation analysis that the platform stability error reaches 10 in the leveling process of different tilt angles under the condition of bearing the core shaft. -5 °, effectively improving the platform leveling efficiency and leveling accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The figure is a structural schematic diagram of a four-point support and three-point leveling mechanism of a precision measuring platform of the present invention.

[0050] Figure 2 It is the four-point position distribution diagram of the present invention.

[0051] Figure 3 It is a schematic structural diagram of the air spring of the present invention.

[0052] Figure 4 It is a structural schematic diagram of the piezoelectric ceramic stack micro-displacement mechanism of the present invention.

[0053] Figure 5 It is a structural schematic diagram of the pre-tightening mechanism of the present invention.

[0054] Figure 6 It is a front view schematic diagram of the piezoelectric ceramic stack micro-displacement mechanism and the leveling lower plate installation structure of the present invention.

[0055] Figure 7 It is a side view schematic diagram of the piezoelectric ceramic stack micro-displacement mechanism and the leveling lower plate installation structure of the present invention.

[0056] Figure 8 It is a leveling flow chart of the present invention.

[0057] Figure 9 It is the mathematical inclination diagram under non-horizontal inclination of the present invention.

[0058] Figure 10 This is a schematic diagram of the force analysis of the four-point support and three-point leveling mechanism of the precision measuring platform of the present invention.

[0059] Figure 11 It is a schematic diagram of force analysis of the piezoelectric ceramic stack micro-displacement mechanism under horizontal thrust of the present invention.

[0060] Figure 12 This is the first set of platform inclination angle change trend diagram and error convergence diagram of the present invention; wherein:

[0061] Figure 12 (a) is a first set of platform inclination change trend diagrams of the present invention;

[0062] Figure 12 (b) is the first set of platform error convergence diagrams of the present invention.

[0063] Figure 13 This is the second set of platform inclination angle change trend diagram and error convergence diagram of the present invention; wherein:

[0064] Figure 13 (a) is a second set of platform inclination change trend diagrams of the present invention;

[0065] Figure 13 (b) is the second set of platform error convergence diagrams of the present invention.

[0066] Figure 14 This is the relationship diagram between the center of the cross-section circle and the inclination angle.

[0067] The reference numerals in the figure are: 1 for platform, 2 for air spring, 2-1 for air spring 1, 2-2 for air spring 2, 2-3 for pressure-resistant air pipe, 2-4 for T-joint, 3 for leveling lower plate, 4 for piezoelectric ceramic stack micro-displacement mechanism, 4-1 for upper wedge block, 4-2 for lower wedge block, 4-3 for leveling top ball, 4-4 for top block, 4-5 for piezoelectric ceramic stack, 4-6 for pre-tightening mechanism, 4-7 for supporting elastic membrane, 4-8 for top screw, 4-9 for clamping nut, 4-10 for locking nut, 4-11 for pre-tightening bolt, 4-12 for piezoelectric ceramic actuator housing, 4-13 for boss 1, 4-14 for base, 4-15 for boss 2, 4-16 for pressure block, and 4-17 for lateral top screw. DETAILED DESCRIPTION

[0068] The present invention will be further described in detail below with reference to the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method is given, but the protection scope of the present invention is not limited to the following embodiments. Specific implementation method one:

[0070] The four-point support and three-point leveling mechanism of the precision measuring platform consists of two sets of piezoelectric ceramic stacked micro-displacement mechanisms 4 and two interconnected air springs, such as Figure 1 As shown in the figure, a dust cover is installed between the platform 1 and the leveling lower plate 3 in the leveling mechanism to ensure waterproof and dustproof effects, improving the platform's reliability and service life. The leveling lower plate 3 is connected to the precision measuring table work surface with bolts and dowel pins, ensuring non-rotation and high repeatability.

[0071] The four parts of the leveling mechanism are supported by four points and are evenly distributed on the leveling base. The position distribution is as follows: Figure 2 As shown, two sets of piezoelectric ceramic stacked micro-displacement mechanisms 4 are located at points C and D, respectively. The connected air springs 1 2-1 and 2-2 are located at points A and B, respectively, to achieve four-point support, where L and W are the lengths of the two sides of the rectangle ABCD. After placing a Wolter-Ⅰ mandrel on the stage, the automatic balancing is equivalent to point H, which is the midpoint of AB. During the leveling process, a three-point leveling method is used, and the leveling purpose is achieved by adjusting points H, C, and D. Combining the simplicity of three-point leveling with the stability of four-point support, it can simplify the operation process while ensuring stability.

[0072] The air spring 1 2-1 and air spring 2-2 in the leveling mechanism are symmetrically distributed below the platform 1. They are connected to the platform 1 and the leveling lower plate 3 with bolts equipped with positioning pins. They have the advantages of controllable preload, limited anti-rotation and modular replacement. The bottom surface of the platform 1 is provided with a groove structure, which forms a constrained fit with the raised crown structure on the top of the air spring 2. The pressure-resistant air pipe 2-3 is connected to the left and right interfaces of the T-joint 2-4, and the air chamber inlets and outlets of the air spring 1 2-1 and the air spring 2 2-2 are connected. The bottom interface connecting pipe of the T-joint 2-4 is connected to the solenoid valve, which can realize active control of the support height of the air spring 2, such as Figure 3 When the Wolter-Ⅰ mandrel is placed on platform 1, the air pressure is automatically distributed between air spring 1 2-1 and air spring 2-2, achieving load balancing, which can be equivalent to a leveling point during leveling.

[0073] The piezoelectric ceramic stack micro-displacement mechanism 4 is composed of an upper wedge block 4-1, a lower wedge block 4-2, a leveling top ball 4-3, a top block 4-4, a piezoelectric ceramic stack 4-5 and a pre-tightening mechanism 4-6. Figure 4As shown. Countersunk holes are set at the corresponding positions of the upper wedge block 4-1 and the lower wedge block 4-2. The upper wedge block 4-1 and the lower wedge block 4-2 are fixedly connected to the platform 1 and the leveling lower plate 3 respectively by means of hexagon socket screws passing through the countersunk holes; and positioning pins are added to ensure that the angles of the wedge blocks are consistent during assembly, and the wedge surface angle is a fixed value of 22° with no rotation error. The leveling top ball 4-3 cooperates with the concave inclined surfaces of the upper wedge block 4-1 and the lower wedge block 4-2, and adopts single-point contact to avoid friction lag and assembly stress caused by surface contact. The piezoelectric ceramic stack micro-displacement mechanism 4 is fixed to the base by means of convex column positioning and side pressure block clamping, and the base is then installed on the leveling lower plate 3 by means of convex column positioning and pressure ring locking. This dual positioning method and clamping structure not only ensures the stability of the system, but also takes into account the leveling accuracy, structural rigidity and maintainability. A pre-tightening mechanism 4-6 is set inside the piezoelectric ceramic stack 4-5 to improve the connection reliability and transmission stability.

[0074] Piezoelectric ceramics are piezoelectric materials with both direct and inverse piezoelectric effects. In actual operation, a stacked structure is generally used to increase the expansion and contraction of piezoelectric ceramics, which is equivalent to mechanically connecting piezoelectric ceramic sheets in series. Based on the design of the piezoelectric ceramic stack leveling device assembly, the piezoelectric ceramic stack 4-5, the top block 4-4, and the preload mechanism 4-6 are combined into a piezoelectric telescopic ceramic actuator. The leveling top ball 4-3 is placed between the upper wedge block 4-1 and the lower wedge block 4-2, and the leveling top ball 4-3 is connected to the piezoelectric telescopic ceramic actuator. During operation, the piezoelectric ceramic stack 4-5 outputs a displacement acting on the top block 4-4, which pushes the leveling top ball 4-3. The leveling top ball 4-3 interacts with the upper wedge block 4-1 and the lower wedge block 4-2 to convert the horizontal displacement into the vertical displacement, thereby achieving the leveling purpose.

[0075] The piezoelectric telescopic ceramic actuator includes: a top block 4-4, a piezoelectric ceramic stack 4-5 and a pre-tightening mechanism 4-6; the top block 4-4 and the piezoelectric ceramic stack 4-5 are connected, and the top block 4-4 and the piezoelectric ceramic stack 4-5 are slidably arranged in the piezoelectric ceramic actuator housing 4-12 of the pre-tightening mechanism 4-6; the top block 4-4 is connected to the leveling top ball 4-3. Figure 5As shown, the pre-tightening mechanism 4-6 includes: a supporting elastic membrane 4-7, a top screw 4-8, a tightening nut 4-9, a locking nut 4-10, a pre-tightening bolt 4-11 and a piezoelectric ceramic actuator housing 4-12; the front and rear ends of the piezoelectric ceramic actuator housing 4-12 are both open, the supporting elastic membrane 4-7 is fixedly installed in the piezoelectric ceramic actuator housing 4-12, and the top block 4-4 and the piezoelectric ceramic stack 4-5 are slidably arranged in the piezoelectric ceramic actuator housing 4-12 On the front side of the supporting elastic membrane 4-7, the compression nut 4-9 is set in the piezoelectric ceramic actuator housing 4-12 and is located on the rear side of the supporting elastic membrane 4-7. The compression nut 4-9 is fixedly connected to the piezoelectric ceramic actuator housing 4-12 through the top screw 4-8. The pre-tightening bolt 4-11 is threadedly connected to the compression nut 4-9 and the locking nut 4-10. The locking nut 4-10 is located on the rear side of the compression nut 4-9. The piezoelectric ceramic actuator housing 4-12 is fixed to the base 4-14. The installation process is as follows: first, the compression nut 4-9 is screwed to the predetermined position and fixed with the top screw 4-8. Then, the pre-tightening bolt 4-11 is screwed into the compression nut 4-9 and the thread is rotated to cause the supporting elastic mold 4-7 to displace and deform, thereby applying a pre-tightening force to the piezoelectric ceramic stack 4-5. Finally, it is locked by the locking nut 4-10 to complete the pre-tightening.

[0076] like Figure 6 and Figure 7 As shown, the lower surface of the piezoelectric ceramic actuator housing 4-12 is provided with a boss 1 4-13, and the upper surface of the base 4-14 is provided with a groove 1 that matches the boss 1 4-13. The boss 1 4-13 is matched with the groove 1, and the two are fixedly connected by a lateral screw 4-17. The lower surface of the base 4-14 is provided with a boss 2 4-15, and the upper surface of the leveling lower plate 3 is provided with a groove 2 that matches the boss 2 4-15. The boss 2 4-15 is matched with the groove 2. The pressure block 4-16 presses the base 4-14 and is fixedly connected to the leveling lower plate 3 by bolts. The boss 1 4-13 and the boss 2 4-15 are preferably tapered columns.

[0077] The process of the four-point support and three-point leveling method of the precision measuring table is as follows Figure 8As shown in the figure, platform 1 undergoes pre-calibration to eliminate large initial errors. Because workpieces of varying weights placed on the measuring platform may slightly affect the air springs due to varying gravity, the platform requires pre-calibration before measurement. After pre-calibration, no z-axis adjustment is performed on the H fixed support point. During the zeroing calibration process, the two sets of piezoelectric ceramic stack micro-displacement mechanisms 4 apply a preload force through preload mechanisms 4-6, eliminating gaps between components and improving structural rigidity and positioning accuracy. Subsequently, a Wolter-I mandrel is placed on platform 1, and a detection probe measures its x-axis tilt angle α and y-axis tilt angle β in real time. Based on the detection results, two connected air spring equivalent points are selected as reference datums for posture adjustment, and the piezoelectric ceramic stack micro-displacement mechanism is driven to fine-tune platform 1. The detection system updates the posture of platform 1 in real time, continuously monitoring changes in tilt angle. The leveling process continues until the tilt angles in both directions meet the threshold conditions of |α| and |β|, indicating that platform 1 has met the leveling requirements and the leveling process ends. The detection system is a probe detection system, an optical detection system or a visual detection system, or other systems capable of detecting the tilt angle.

[0078] In this embodiment, the detection system preferably adopts a probe detection system. The probe is used to obtain cross-sectional circle data points at different positions on the surface of the Wolter-I mandrel. Then, the inclination α of the platform in the x-axis direction and the inclination β in the y-axis direction are calculated. The specific method is as follows:

[0079] 1) Surface profile measurement method: The cross-section method is selected as the surface profile data acquisition method for the Wolter-I mandrel.

[0080] 2) Inclination calculation method:

[0081] like Figure 14 As shown in the figure, the relationship between the center of the cross-section circle and the inclination angle, the centers of the two cross-section circles in the figure are O1 and O2 respectively, O1O2 is the axis of the workpiece in a non-horizontal state, and the inclination of the x-axis and y-axis can be calculated respectively, the formula is as follows:

[0082]

[0083] Where α represents the inclination of the x-axis; β represents the inclination of the y-axis; X1 represents the x-coordinate value of point O1; X2 represents the x-coordinate value of point O2; Y1 represents the y-coordinate value of point O1; Y2 represents the y-coordinate value of point O2; Z1 represents the z-coordinate value of point O1; and Z2 represents the z-coordinate value of point O2.

[0084] The piezoelectric ceramic actuator 4 is controlled according to the inclinations α and β, and the posture of the platform 1 of the leveling mechanism is adjusted and updated in real time. The changes in the inclinations α and β are continuously monitored. The leveling process continues until the inclination angles in the x and y directions meet the threshold conditions of |α|, |β|<0.00001°, and the specific threshold conditions are |α|<0.00001°, |β|<0.00001°. Then, the platform 1 meets the leveling requirements and the leveling process ends.

[0085] In the leveling method of the precision measuring platform, the leveling mechanism supports the platform 1 at four points ABCD. The two action points AB are two internally connected air springs. During the leveling process, the two force points are equivalent to point H. The three-point leveling method is used to make the platform 1 equivalent to an isosceles triangle with three leveling support points as vertices, as shown in the figure below. Figure 9 As shown in the figure, with the equivalent support point H as the fixed support point, leveling is achieved by adjusting the two movable support points CD. With the equivalent support leg H as the origin, the line connecting legs A and B as the y-axis, and a line perpendicular to the y-axis through the origin H as the x-axis, a spatial rectangular coordinate system is established. Assuming any point P(x0, y0, z0) in space, when platform 1 is in a non-horizontal state, the horizontal inclination angle of platform 1 can be divided into an inclination angle α along the x-axis and an inclination angle β along the y-axis.

[0086] Point P (x0, y0, z0) on platform 1 is first rotated by α around the y-axis of the horizontal coordinate system to obtain the coordinate P', as shown in formula (1), and then rotated by β around the x-axis to obtain the coordinate P, as shown in formula (2). Substituting formula (1) into formula (2) can obtain the coordinates of point P in the non-horizontal state.

[0087] Since the actual two tilt angles α and β after leveling are small, the two tilt angles α and β can be regarded as , it is approximately considered that sinα=α, cosα=1, sinβ=β, cosβ=1, so formula (3) can be simplified to formula (4).

[0088] (1)

[0089] (2)

[0090] (3)

[0091] (4)

[0092] From the horizontal state modeling, we know that the coordinates of each support point in the horizontal coordinate system are: , , , the distance between any two adjacent legs is T, then:

[0093] (5)

[0094] like Figure 2 As shown, the four supporting points ABCD are rectangles with two sides of L and W, respectively. This is a theoretically universal support point arrangement (applicable to various rectangular and circular platforms). Since the Wolter-I mandrel measuring platform is circular, the four supporting points ABCD are actually arranged in a square, that is, the distances between the four legs are equal, that is, L=W=T.

[0095] Substituting formula (5) into formula (4) yields the coordinates O of each leg after leveling, and then the displacement required to adjust each leg is obtained as shown in formula (7).

[0096] (6)

[0097] (7)

[0098] Among them, z H is the displacement that needs to be adjusted for the fixed support point H on the z axis, C is the displacement of leg C that needs to be adjusted on the z axis, z D The displacement of the support leg D on the z axis needs to be adjusted. Since the H fixed support point is not adjusted in the z direction after pre-calibration, z H This value is not actually adjusted, only the z value is adjusted through coordinate transformation. C and z D , after the platform is leveled, the Wolter-I mandrel measurement can be carried out. Specific implementation method 2:

[0100] This specific embodiment uses simulation analysis to determine the leveling performance of the three-point leveling method for a precision measuring platform with four-point support. During the simulation analysis, a Wolter-Ⅰ mandrel with a mass m of 11.765 kg is placed on the measuring platform 1. The changes in the extension and contraction amount of each leg during the leveling process are simulated and analyzed to determine the leveling performance.

[0101] For force analysis, when a Wolter-I mandrel with mass m is placed at the center of platform 1, gravity G is applied, see Figure 2 The H equivalent point is the midpoint between A and B, and its coordinates are , point C is located at , point D is located at , the total force balance of platform 1 is:

[0102] (8)

[0103] Among them F H 、F C and F Dare the forces at points H, C, and D, respectively. To prevent longitudinal tilt, the moments generated by the vertical distances of each point to point H need to be balanced, i.e.

[0104] (9)

[0105] To prevent lateral rotation, the moment balance in the horizontal direction is

[0106] (10)

[0107] Solving formulas (8), (9), and (10) yields

[0108] (11)

[0109] (12)

[0110] Based on the mechanical structure and kinematic characteristics of the platform leveling part, a three-dimensional model of the Wolter-Ⅰ mandrel measuring platform was established. Ansys Workbench software was used to simulate and analyze the stress conditions under the load of the measuring platform. Figure 10 As shown in the figure, the leveling platform is compressed downward in the vertical direction under the load, and the air spring also produces a certain amount of vertical displacement. The maximum total deformation of the platform under static load is 0.17166mm. When the deformation at the air spring support is between 0.09537mm and 0.06294mm, the deformation at the piezoelectric ceramic stack micro-feed mechanism support is less than 0.019074mm. The deformation value decreases evenly from the center to the edge, the gradient difference is stable, and the load distribution is uniform.

[0111] During the leveling operation, the piezoelectric ceramic stack micro-displacement mechanism applies force along the horizontal direction of the top block toward the center of the circle. The total deformation characteristics under the thrust of the two sets of micro-displacement mechanisms are systematically analyzed. The force analysis of the platform is as follows: Figure 11 As shown, the platform's maximum deformation is 0.03799mm, and the total deformation at the interface between the wedge and the top ball ranges from 0.0042211mm to 0.0084423mm, showing an overall decreasing gradient. This demonstrates the platform's ability to stably transfer loads to the support mechanism under thrust, while also enabling precise displacement control through the adjustable structure, demonstrating excellent horizontal stability and leveling accuracy. By fully accounting for factors such as friction and support angle, this structure effectively suppresses unexpected displacement or tilt, ensuring the reliability and responsiveness of the leveling platform when subjected to horizontal loads.

[0112] Perform leveling analysis and simulate the leveling process of the leveling platform with different tilt angles under the load-bearing core shaft. The trend diagram of α and β changes during the leveling process and the corresponding error convergence diagram are shown in Figure 2. Figure 12 、 13As shown, Figure 12 (a) is the first group of platform inclination change trend diagram; Figure 12 (b) is the first set of platform error convergence diagram; Figure 13 (a) is the second group of platform inclination change trend diagram; Figure 13 (b) is the second group of platform error convergence diagrams. The first group takes values ​​of α=0.005° and β=-0.003°, and the second group takes values ​​of α=-0.0005° and β=-0.001°. It can be seen that during the first leveling process of the platform, the inclination angle gradually converges to close to 0° over time, and there is no obvious oscillation within 10 seconds. The error convergence process shows an exponential decay trend, indicating that the leveling system has good dynamic stability. The inclination range of the second group is reduced, and the adjustment speed of the leveling platform is improved. A slight overshoot occurs in the early stage of the leveling process, and then gradually approaches zero. The system finally effectively suppresses the inclination fluctuation. The calculated values ​​of the steady-state error are shown in Table 1. Multiple groups of experiments show that the steady-state error magnitude reaches 10 -5 The platform's automatic leveling is achieved at a level of less than 10°, effectively eliminating the residual error caused by friction and backlash in traditional leveling systems. Leveling data at different inclination angles validates the platform's feasibility and demonstrates its advantages in automatic adjustment, such as fast response and low steady-state error.

[0113] Table 1 Steady-state error

[0114]

[0115] A four-point support and three-point leveling method for a precision measuring table is proposed to achieve automatic leveling of the Wolter-Ⅰ type mandrel during the assembly and adjustment process of machining and testing.

[0116] (1) Two connected air springs and two sets of piezoelectric ceramic stacked micro-displacement mechanisms are used to achieve four-point support, which improves the stability of the mechanism. At the same time, the two air springs are connected to form a single point to reduce the complexity of leveling control.

[0117] (2) The piezoelectric ceramic stack is used to push the top block, leveling top ball and wedge block to achieve micro-displacement adjustment, completing high-precision control and fast response. The single-point contact between the leveling top ball and the wedge block avoids the friction hysteresis and assembly stress caused by surface contact.

[0118] (3) Simulation analysis shows that the platform stability error reaches 10 during the leveling process at different tilt angles under the load-bearing core shaft. -5 °, effectively improving the platform leveling efficiency and leveling accuracy.

[0119] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A four-point support and three-point leveling mechanism for a precision measuring table, characterized in that: include: A platform (1), two air springs (2), a leveling lower plate (3), and two sets of piezoelectric ceramic stacked micro-displacement mechanisms (4); the platform (1) and the leveling lower plate (3) are arranged correspondingly up and down, and the air springs (2) and the two sets of piezoelectric ceramic stacked micro-displacement mechanisms (4) are fixedly arranged between the platform (1) and the leveling lower plate (3); The two air springs (2) are air spring 1 (2-1) and air spring 2 (2-2); air spring 1 (2-1) and air spring 2 (2-2) are symmetrically distributed relative to the center of the platform (1) and are positioned and fixed between the platform (1) and the leveling lower plate (3); air spring 1 (2-1) and air spring 2 (2-2) are respectively connected to the corresponding interfaces of the T-type joint (2-4) through the pressure-resistant air pipe (2-3); the bottom end interface of the T-type joint (2-4) is connected to the solenoid valve through a connecting pipe; Each set of piezoelectric ceramic stacked micro-displacement mechanisms (4) comprises: an upper wedge block (4-1), a lower wedge block (4-2), a leveling top ball (4-3) and a piezoelectric telescopic ceramic actuator; the upper wedge block (4-1) and the lower wedge block (4-2) are stacked up and down, the upper wedge block (4-1) is fixedly connected to the bottom end face of the platform (1), the lower wedge block (4-2) is fixedly connected to the upper end face of the leveling lower plate (3), the leveling top ball (4-3) is arranged in a V-shaped opening formed between the upper wedge block (4-1) and the lower wedge block (4-2), and is in single-point contact with the inclined surfaces of the upper wedge block (4-1) and the lower wedge block (4-2), respectively; the piezoelectric telescopic ceramic actuator is horizontally arranged and connected to the leveling top ball (4-3), and the piezoelectric telescopic ceramic actuator is fixedly connected to the upper end face of the leveling lower plate (3).

2. The four-point support and three-point leveling mechanism of a precision measuring platform according to claim 1 is characterized in that: The piezoelectric telescopic ceramic actuator comprises: a top block (4-4), a piezoelectric ceramic stack (4-5) and a pre-tightening mechanism (4-6); the top block (4-4) and the piezoelectric ceramic stack (4-5) are connected, the top block (4-4) and the piezoelectric ceramic stack (4-5) are slidably arranged in a piezoelectric ceramic actuator housing (4-12) of the pre-tightening mechanism (4-6), and the top block (4-4) is connected to a leveling top ball (4-3).

3. The four-point support and three-point leveling mechanism of a precision measuring platform according to claim 2 is characterized in that: The pre-tightening mechanism (4-6) comprises: a supporting elastic membrane (4-7), a top screw (4-8), a compression nut (4-9), a locking nut (4-10), a pre-tightening bolt (4-11) and a piezoelectric ceramic actuator housing (4-12); the front and rear ends of the piezoelectric ceramic actuator housing (4-12) are both open, the supporting elastic membrane (4-7) is fixedly installed in the piezoelectric ceramic actuator housing (4-12), and the top block (4-4) and the piezoelectric ceramic stack (4-5) are slidably arranged in the supporting space inside the piezoelectric ceramic actuator housing (4-12). The front side of the elastic membrane (4-7) is provided with a clamping nut (4-9) in the piezoelectric ceramic actuator housing (4-12) and is located at the rear side of the supporting elastic membrane (4-7). The clamping nut (4-9) is fixedly connected to the piezoelectric ceramic actuator housing (4-12) through a top screw (4-8). The pre-tightening bolt (4-11) is threadedly connected to the clamping nut (4-9) and the locking nut (4-10). The locking nut (4-10) is located at the rear side of the clamping nut (4-9). The piezoelectric ceramic actuator housing (4-12) is fixed on the base (4-14).

4. A four-point support and three-point leveling mechanism for a precision measuring platform according to claim 2 or 3, characterized in that: The lower surface of the piezoelectric ceramic actuator housing (4-12) is provided with a convex column (4-13), the upper surface of the base (4-14) is provided with a groove (1) that matches the convex column (4-13), the convex column (4-13) is matched and arranged in the groove (1) and the two are fixedly connected by a lateral top screw (4-17), the lower surface of the base (4-14) is provided with a convex column (4-15), the upper surface of the leveling lower plate (3) is provided with a groove (2) that matches the convex column (4-15), the convex column (4-15) is matched and arranged in the groove (2), and the pressure block (4-16) presses the base (4-14) and is fixedly connected to the leveling lower plate (3).

5. The four-point support and three-point leveling mechanism of a precision measuring platform according to claim 1 is characterized in that: A dust cover is provided between the platform (1) and the leveling lower plate (3).

6. The four-point support and three-point leveling mechanism of a precision measuring platform according to claim 1, characterized in that: The wedge-shaped surfaces of the upper wedge-shaped block (4-1) and the lower wedge-shaped block (4-2) have the same angle.

7. A leveling method based on the four-point support and three-point leveling mechanism of a precision measuring platform according to any one of claims 2 to 6, characterized in that: The following steps are involved: Step 1: Pre-calibrate the platform (1) of the four-point support and three-point leveling mechanism of the precision measuring table to eliminate the initial error. During the zeroing calibration process, the two sets of piezoelectric ceramic stack micro-displacement mechanisms are subjected to pre-tightening force through the pre-tightening mechanism; Step 2: Subsequently, a Wolter-I type mandrel is placed on the platform (1) of the leveling mechanism, and the platform (1) of the leveling mechanism detects its inclination angle α in the x-axis direction and its inclination angle β in the y-axis direction in real time through a detection system; Step 3: Based on the test results, select the equivalent point of air spring 1 (2-1) and air spring 2 (2-2) as the reference datum for posture adjustment, and drive the piezoelectric ceramic stack micro-displacement mechanism to fine-tune the platform (1) of the leveling mechanism; Step 4: The platform (1) posture of the leveling mechanism is updated in real time through the detection system, and the tilt angle change is continuously monitored. The leveling process continues until the tilt angles in two directions meet the conditions of |α|, |β| < fixed threshold values. Then, the platform (1) meets the leveling requirements and the leveling process ends.

8. The four-point support and three-point leveling method for a precision measuring platform according to claim 7, characterized in that: The detection system in step 2 is a probe detection system, an optical detection system or a visual detection system.

9. The four-point support and three-point leveling method for a precision measuring platform according to claim 7, characterized in that: The step three specifically includes the following steps: Step 31: The air spring 1 (2-1) and the air spring 2 (2-2) in the three-point leveling mechanism of the four-point support of the precision measuring platform and the two sets of piezoelectric ceramic stacked micro-displacement mechanisms are used as the four legs of the platform (1) of the leveling mechanism; wherein, the air spring 1 (2-1) and the air spring 2 (2-2) are used as the A leg and the B leg respectively, and the two sets of piezoelectric ceramic stacked micro-displacement mechanisms are used as the C leg and the D leg respectively; the four action points of the above four legs are distributed to form a rectangle ABCD, and the two action points AB are equivalent to the two force points in the leveling process as point H. The three-point leveling method is used to make the platform (1) equivalent to an isosceles triangle with three leveling support points as vertices, and the equivalent support point H is used as a fixed support point. The leveling purpose is achieved by adjusting the two movable support points CD. Step 32: Take the equivalent leg H as the origin, the line connecting the A leg and the B leg as the y-axis, and a straight line perpendicular to the y-axis through the origin H as the x-axis to establish a spatial rectangular coordinate system. Assume that at any point P(x0, y0, z0) in space, when the platform (1) is in a non-horizontal state, the horizontal inclination angle of the platform (1) is divided into an inclination angle α in the x-axis direction and an inclination angle β in the y-axis direction; Step 3: The point P(x0,y0,z0) on the platform (1) is first rotated by an angle α around the y-axis of the horizontal coordinate system to obtain the coordinates P'(x',y',z'), as shown in formula (1). （1） Step 3 and 4: Rotate the point around the x-axis by an angle β to obtain the coordinates P(x, y, z), as shown in formula (2). Substitute formula (1) into formula (2) to obtain the coordinates of point P in the non-horizontal state. （2） Step 35: Consider the two tilt angles α and β as , it is approximately considered that sinα=α, cosα=1, sinβ=β, cosβ=1, so formula (3) is simplified to formula (4); （3） （4） Step 36: From the horizontal state modeling, we know that the coordinates of each support point in the horizontal coordinate system are: , , , the distance between any two adjacent legs is T, then: （5） Step 37: Substitute formula (5) into formula (4) to obtain the coordinates O of each leg after leveling, and then obtain the displacement required to adjust each leg as shown in formula (7); （6） （7） Among them, z H is the displacement that needs to be adjusted for the fixed support point H on the z axis, C is the displacement of leg C that needs to be adjusted on the z axis, z D is the displacement of leg D that needs to be adjusted on the z-axis.

10. The four-point support and three-point leveling method for a precision measuring platform according to claim 9, characterized in that: The step 4 specifically includes the following steps: Step 41: The detection system detects the tilt angle α of the Wolter-I mandrel in the x-axis direction and the tilt angle β in the y-axis direction of the platform; Step 42: Based on the inclinations α and β, the piezoelectric ceramic stack micro-displacement mechanism (4) is controlled to adjust and update the posture of the platform (1) of the leveling mechanism in real time, and the changes in the inclinations α and β are continuously monitored. The leveling process continues until the inclination angles in the x and y directions meet the threshold conditions of |α| < 0.00001° and |β| < 0.00001°. Then, the platform (1) meets the leveling requirements and the leveling process ends.

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