A precise measuring device for complex columnar parts and its calibration method

Abstract

The present invention discloses a precise measurement device for complex columnar parts and its calibration method, belonging to the technical fields of intelligent manufacturing and precise measurement of columnar parts. The device consists of a motion drive and control unit, a composite clamping unit, a double probe unit and a frame. The composite clamping unit is designed with a replaceable clamping module and a new type of center, and has two clamping modes: double-center clamping and chuck-center clamping, which can meet the full-condition clamping of columnar parts. Secondly, the double probe unit can obtain the full-size information of the workpiece by using two line-structured light probes. And the motion drive and control unit adopts a differential gear train, and only a single motor is required to complete the clamping and measurement of the workpiece, further reducing costs and simplifying operations. In addition, the calibration method calibrates the probe pose in real time according to the combined features, ensuring the measurement accuracy. The present invention can achieve full-condition clamping and full-information measurement of complex columnar parts, with high precision and low cost, and has strong practicability and versatility.

Description

Technical Field

[0001] The present invention relates to a complex column component precision measuring device comprising a motion drive control unit, a composite clamping unit, a double probe unit and a frame and a calibration method thereof, belonging to the technical field of intelligent manufacturing and precision measurement of column components. Background Art

[0002] According to the "Global and China Shaft Parts Market Research Report" released by Yunshang Think Tank, the global shaft and column parts market size will reach US$687 billion. How to ensure the manufacturing quality of complex column parts, the first thing is to ensure that the key geometric dimension indicators of column parts meet the design requirements. Due to the widespread application of complexity, three-dimensional deformation, topology optimization, etc. in component design and production, the traditional contact measurement is incomplete, time-consuming, and labor-intensive in the clamping and inspection of complex column parts. It has become an industry consensus that the measurement items are incomplete, time-consuming, and labor-intensive, and there is a lack of precise measuring devices and accurate calibration methods. There is a large actual market demand for rapid detection of complex column parts. Traditional contact measurement methods have some problems in the clamping and inspection of complex column parts, such as incomplete measurement items, time-consuming and labor-intensive, lack of precise measuring devices and accurate calibration methods, etc. Therefore, in the rapid detection industry of complex column parts, traditional contact measurement methods can no longer meet the growing market demand.

[0003] At present, there are mainly two methods for the rapid detection of complex columnar parts: (1) In the contact measurement with measuring instruments, generally, a three-jaw chuck or bench vice is used to fix the columnar part to be measured, and then traditional measuring instruments such as micrometers and vernier calipers are used to obtain the dimensional parameters of the columnar part, and then the manufacturing accuracy and quality are evaluated. However, this method has problems such as low efficiency, being easily affected by random errors, poor repeatability, and being unable to capture all the dimensional information on the surface of the columnar part; (2) The measurement with a special non-contact device is to design a special structure and device to obtain the actual dimensional indexes of the columnar part in the form of complex trajectory tracking. Patent CN114192818A provides a method for clamping and measuring long-axis workpieces. This device uses a hydraulic chuck to clamp the workpiece to be measured and measures the length of the long-axis workpiece with an absolute encoder semi-closed loop. The device is easy to operate, but the disadvantage is that it can only measure the length and cannot capture all the dimensional information on the surface of the columnar part. Secondly, patent CN110044299A provides a non-contact detection device for columnar parts. Due to the horizontal clamping, micro-deformation will occur to the long-axis columnar part to be measured, and there is a lack of rotation of the axis of the part to be measured. If there is an installation error of the probe in the direction perpendicular to the axis of the part, it will affect the measurement accuracy and accuracy of the device. Furthermore, patent CN110095101B provides a device for measuring and calibrating the coordinate system of columnar parts with dot structured light. It can check whether the laser beam of the probe passes through the axis of the workpiece to be measured by adjusting the fine adjustment knob, but because it uses a manual adjustment method, it cannot calibrate the pose of the probe in real time, and the dynamic measurement accuracy cannot be guaranteed. In terms of the clamping of the columnar part to be measured, the above devices only support the chuck clamping mode, and the applicable working conditions are very limited, resulting in poor versatility of the device. Moreover, in terms of the clamping accuracy, stiffness, and disassembly and assembly speed, the performance of chuck clamping is inferior to that of center clamping. To sum up, the current columnar part detection devices have problems such as incomplete measurement dimension information, poor measurement repeatability, insufficient real-time dynamic measurement accuracy, and limited applicable working conditions of the clamping function, and there is an urgent need to develop a new generation of rapid measurement device for columnar parts integrating clamping and measurement.

[0004] To overcome the above problems, the present invention discloses a precision measurement device and its calibration method for complex columnar parts. Considering the deficiencies of the foregoing measurement devices and methods, in terms of the clamping of the part to be measured, a replaceable clamping module and a new type of center are designed, and double-center clamping or chuck-center clamping can be selected, covering the full working condition clamping modes of complex columnar parts; secondly, in terms of the calibration method and measurement, two mutually perpendicular line structured light probes are designed, and the pose of the probe is innovatively calibrated in real time according to the combined features, which can solve the core problem of precision measurement and ensure the dynamic measurement accuracy; and, in terms of transmission, a differential gear train is adopted, and only a single motor is required to drive to complete the two processes of clamping and measurement, reducing the production cost and operation difficulty of the device while realizing the required clamping and measurement functions. Summary of the Invention

[0005] The present invention is used to solve the problems of poor clamping versatility of existing columnar parts, incomplete acquisition of dimensional information during measurement, and poor measurement accuracy and inaccurate measurement results caused by calibration, and provides a clamping and measuring device for columnar parts.

[0006] In view of the problems existing in the existing measuring devices for columnar parts, the present invention makes a principle innovation. The basic idea is as follows: ① The switching between the chuck-center and the upper and lower double centers clamping modes is realized through the lead screw and the guide rail slider, so as to achieve full-condition clamping; and a new type of center is designed to realize over-constraint clamping of specific complex column parts and buffer force application to flexible slender columnar parts, reducing measurement damage to workpieces. ② In order to ensure the accuracy of measuring data of columnar parts, a real-time calibration method based on combined features is proposed, and a double-probe unit composed of two line-structured light probes installed perpendicular to each other is designed corresponding to this calibration method to ensure the measurement accuracy during the dynamic measurement process. ③ A differential gear train is adopted to enable one motor to perform two processes of clamping and measuring at the same time, and all dimensional information on the surface of the columnar part is captured by the line-structured light probe during the measuring process.

[0007] To achieve the above purposes and principles, the technical solution of the present invention is as follows:

[0008] A clamping and measuring device for columnar parts is composed of four parts: a motion drive and control unit 1, a composite clamping unit 2, a double-probe unit 3, and a frame 4;

[0009] The motion drive and control unit 1 can realize two processes of linear motion and rotational motion, and includes a linear motion motor 1.1, a differential gear train 1.2, a center worm 1.3, a center worm gear 1.4, a center lead screw 1.5, an upper center platform 1.6, an upper center 1.7, a reversing gear set 1.8, a probe worm 1.9, a probe worm gear 1.10, a probe lead screw 1.11, a rotational motion motor 1.12, a gear 1.13, a rotating table 1.14, a circular grating 1.15, and a grating scale 1.16;

[0010] The linear motion motor 1.1 is fixed on the frame 4 by bolts, and its output shaft is connected to the differential gear train 1.2 and drives it to rotate; the left output shaft of the differential gear train 1.2 is connected to the center worm 1.3 by a coupling; the center worm gear 1.4 is engaged with the center worm 1.3 and is connected to the center lead screw 1.5 by a flat key and drives it to rotate. The upper center platform 1.6 is connected to the center lead screw 1.5 by a thread, connected to the guide rail slider in the vertical direction by screws, and connected to the upper center 1.7 by a tapered roller bearing. It drives the upper center 1.7 to move in the vertical direction through screw drive combined with the guiding function of the guide rail, so as to clamp the columnar part; the worm and worm gear drive adopted can ensure the self-locking characteristic and self-adaptability of the clamping process;

[0011] While the differential gear train 1.2 drives the left upper center 1.7 to move in the vertical direction, it can make the double probe unit 3 on the right move linearly along the guide rail in the vertical direction; the output shaft at the right end of the differential gear train 1.2 is connected to the input shaft of the reversing gear set 1.8 through a coupling and drives it to rotate; the output shaft of the reversing gear set 1.8 is connected to the probe worm 1.9 through a coupling, and while the probe worm gear 1.10 meshes with the probe worm 1.9, it is connected to the probe lead screw 1.11 through a flat key to realize the rotation of the probe lead screw 1.11; the double probe unit 3 is connected to the probe lead screw 1.11 through a thread and is simultaneously connected to the guide rail slider in the vertical direction through a screw. The combination of screw drive and the guiding function of the guide rail can realize the linear movement of the double probe unit 3 in the vertical direction; the grating scale 1.16 is fixed on the inner wall of the frame 4 through a screw and can measure in real time the moving distance of the double probe unit 3 along the guide rail in the vertical direction, so as to realize the closed-loop control of the linear position of the double probe unit 3;

[0012] The described reversing gear set 1.8 is a commonly used manual shifting component on the market;

[0013] The rotating table 1.14 is of a hollow cylindrical structure, with a spline groove provided on the inner ring and teeth existing at the lower part of the outer ring; the gear 1.13 meshes with the teeth at the lower part of the rotating table 1.14, and the rotation of the gear 1.13 is controlled by the forward and reverse rotation of the rotation motion motor 1.12, so as to realize the rotation of the rotating table 1.14; the outer ring reading head of the circular grating 1.15 is fixed on the inner wall of the frame 4, and the inner ring is connected to the neck of the rotating table 1.14 through a screw to obtain the rotation angle of the rotating table 1.14 and realize the closed-loop control of the rotation angle of the rotating table 1.14;

[0014] The described composite clamping unit 2 includes a lower center motor 2.1, a lower center lead screw 2.2, a lower center platform 2.3, a guide rail slider 2.4, a lower center 2.5, and a three-jaw chuck 2.6;

[0015] The lower center lead screw 2.2 is connected to the output shaft of the lower center motor 2.1 through a coupling and is simultaneously connected to the lower center platform 2.3 through a thread. The lower center platform 2.3 is connected to the slider in the guide rail slider 2.4 through a screw, so that it can move linearly in the vertical direction under the screw drive; the lower center 2.5 is connected to the lower center platform 2.3 through a thrust bearing and is simultaneously connected to the inner ring of the rotating table 1.14 in the motion drive and control unit 1 through a spline, so that it can rotate synchronously with the rotating table 1.14; the three-jaw chuck 2.6 is fixed on the upper end face of the rotating table 1.14 and can rotate synchronously with the rotating table 1.14;

[0016] The lower center 2.5 and the upper center 1.7 have the same structure, including a top cover 2.7, a buffer spring 2.8, a push rod 2.9, a push head 2.10, a ball string 2.11, a ball spring 2.12, a bottom cover 2.13, and a center head 2.14;

[0017] The push head 2.10 is lapped on the bottom cover 2.13, and four groups of ball strings 2.11 and ball springs 2.12 are evenly distributed on its side. At the same time, the bottom is connected to the center head 2.14 by a thread; the bottom cover 2.13 is connected to the top cover 2.7 by a thread, and a push rod 2.9 and a buffer spring 2.8 are arranged in the cavity between the two. One end of the buffer spring 2.8 is fixed on the top cover 2.7, and the other end is fixed on the push rod 2.9. The buffer spring 2.8 is compressed by the movement of the push rod 2.9, so as to achieve the effect of buffering and applying force;

[0018] The ball string 2.11 is composed of two upper and lower balls connected by a connecting rod, and the upper ball can move slightly along the direction of the connecting rod; the lower ball in the ball string 2.11 extends into the complex cylindrical part, and the upper ball contacts the part end face. Under the extrusion of the part end face, the upper ball moves slightly along the chute away from the lower ball. When the upper ball moves to the limit distance allowed by the connecting rod, the upper ball begins to pull the lower ball through the connecting rod, so that the lower ball applies a force F2 to the inner wall of the part, restricting the radial and axial movements of the part. At the same time, the upper ball applies a force F1 to the part end face, restricting the radial and axial movements of the part; through the overconstraint of F1 and F2 in the radial and axial directions, the clamping stability of the complex cylindrical part is enhanced; after the part to be measured is clamped, it is judged whether the axis of the part coincides with the center axis by checking whether there is any looseness in the ball string 2.11;

[0019] According to the above structure, the composite clamping unit 2 can realize two clamping modes: chuck-center and double centers;

[0020] Chuck-center clamping mode: The lower center motor 2.1 drives the lower center 2.5 to descend into the rotary table 1.14. The three-jaw chuck 2.6 clamps the lower part of the cylindrical part to be measured based on the self-centering principle. The linear motion motor 1.1 drives the upper center 1.7 to descend and cooperate with the upper conical hole of the cylindrical part to complete the clamping of the part to be measured;

[0021] Double centers clamping mode: The jaws of the three-jaw chuck 2.6 open outwards. The lower center motor 2.1 drives the lower center 2.5 to rise above the rotary table 1.14. The linear motion motor 1.1 drives the upper center 1.7 to descend and cooperate with the lower center 2.5 to clamp the cylindrical part to be measured;

[0022] The two clamping modes enable the composite clamping unit 2 to meet the clamping requirements of different working conditions and cylindrical parts with different cross-sectional sizes, enhancing the versatility of the clamping function of the device;

[0023] The double probe unit 3 includes a z-axis moving stage 3.1, an x-axis motor 3.2, an x-axis motor bracket 3.3, an x-axis lead screw 3.4, an x-axis moving stage 3.5, an x-axis servo 3.6, an x-axis servo bracket 3.7, a pedestal bearing 3.8, an x-axis swing bracket 3.9, a y-axis servo 3.10, a y-axis swing bracket 3.11, a probe bracket 3.12, a first probe 3.13, and a second probe 3.14;

[0024] The first probe 3.13 is fixed to the y-axis swing bracket 3.11 by screws; the second probe 3.14 is fixed to the y-axis swing bracket 3.11 through the probe bracket 3.12, jointly forming a pair of mutually perpendicular double probes with the first probe 3.13; the x-axis servo 3.6 is fixed to the x-axis moving stage 3.5 through the x-axis servo bracket 3.7 and screws, and its output shaft is connected to the x-axis swing bracket 3.9 and drives it to rotate, realizing the free rotation of the double probes on the x-axis. To enhance stability, two pedestal bearings 3.8 are provided between the x-axis swing bracket 3.9 and the x-axis servo 3.6; the y-axis servo 3.10 is fixed to the side of the x-axis swing bracket 3.9 by screws, and its output shaft is connected to the y-axis swing bracket 3.11 through a coupling, realizing the free rotation of the double probes on the y-axis; the x-axis motor 3.2 is fixed to the z-axis moving stage 3.1 through the x-axis motor bracket 3.3 and screws, and at the same time its output shaft is connected to the x-axis lead screw 3.4 through a coupling; the x-axis moving stage 3.5 is threadedly connected to the x-axis lead screw 3.4 and is also connected to the guide rail slider in the x-axis direction by screws, driving the double probes to linearly move along the x-axis, so that the distance between the double probes and the surface of the to-be-measured cylindrical part in the x-axis direction can be adjusted in real time during the measurement process, enabling the to-be-measured cylindrical part to be in the best measurement range of the line structured light; the z-axis moving stage 3.1 is provided with threaded holes, is threadedly connected to the probe lead screw 1.11, and is connected to the guide rail slider in the z-axis direction by screws, thereby driving the double probes to linearly move along the z-axis, cooperating with the lower center 2.5 and the three-jaw chuck 2.6 to drive the to-be-measured cylindrical part to rotate to obtain the complete dimensional information of the surface of the cylindrical part;

[0025] The above is the technical solution of the precision measurement device for complex cylindrical parts of the present invention; due to manufacturing errors and installation errors in the system, there are deviations between the coordinate features collected by the probes and the actual situation. To ensure the accuracy of the measurement device and the stability of the measurement data of the parts, it is crucial to calibrate with a standard cylindrical calibration piece before formal measurement.

[0026] Based on the above precision measurement device for complex cylindrical parts, the present invention provides a corresponding calibration method, and the specific principle and process are as follows:

[0027] In the theoretical case, i.e., without errors, the combined features of the standard cylindrical calibration piece collected by the first probe 3.13 and the second probe 3.14 are a straight line and a perfect circle. However, due to manufacturing errors and installation errors in the system, the actual combined features presented by the first probe 3.13 and the second probe 3.14 are ellipses. Based on this principle, the calibration process is carried out as follows:

[0028] S1: The double probes are reset in the x-axis and z-axis directions, and the grating ruler is set to zero.

[0029] S2: Clamp the calibration piece.

[0030] S3: Adjust the position of the double probes in the x-axis direction.

[0031] The motor 3.2 adjusts the position of the double probes in the x-axis direction so that the calibration piece is within the optimal measurement range of the line structured light.

[0032] S4: Correct the angle error of the X-axis.

[0033] The x-axis servo 3.6 adjusts the attitude of the double probes so that they rotate around the x-axis until the coordinate feature presented by the first probe 3.13 is a straight line.

[0034] S5: Correct the angle error of the Y-axis.

[0035] The y-axis servo 3.10 adjusts the attitude of the double probes so that they rotate around the y-axis until the coordinate feature presented by the second probe 3.14 is a perfect circle.

[0036] At this point, the combined features presented by the double probes are a straight line and a perfect circle, and the measurement accuracy is within an acceptable range.

[0037] During the dynamic measurement process, the double probes adjust their own poses in real time according to the captured cylindrical features in combination with the above calibration steps S4 to S5 to ensure the dynamic measurement accuracy.

[0038] The beneficial effects of the present invention are as follows:

[0039] 1. The composite clamping unit in the device of the present invention realizes the switching between the chuck-center and the upper and lower double centers clamping modes through modular design, making the clamping process of the device applicable to various working conditions and enhancing the general effect of the clamping function.

[0040] 2. The new center in the present invention can perform radial and axial overconstraints on the part when clamping complex cylindrical parts, has better versatility and stability compared with ordinary centers, and its axial buffer force application function can avoid deformation of flexible slender cylindrical parts during clamping. When using this new center to clamp complex cylindrical parts, it can also detect whether the axis of the part coincides with the axis of the center, thereby ensuring the measurement accuracy of subsequent measurement processes.

[0041] 3. The present invention proposes a calibration method based on combined features, which can efficiently compensate for manufacturing errors and installation errors, and can calibrate the probe pose in real time during subsequent measurement processes to ensure dynamic measurement accuracy.

[0042] 4. In terms of transmission, the present invention adopts a differential gear train and a worm and worm gear scheme. Only one motor is required to perform two processes of clamping and measurement simultaneously, reducing the operation difficulty and production cost of the device. Moreover, the use of a worm and worm gear makes the clamping function of the device have self-locking and self-adaptability, further ensuring the clamping effect on the columnar part to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Overall view of a precision measurement device for complex columnar parts;

[0044] Figure 2 Cross-sectional view of the motion drive and control unit;

[0045] Figure 3 Axonometric view of the motion drive and control unit;

[0046] Figure 4 Cross-sectional view of the composite clamping unit;

[0047] Figure 5 Structural diagram of the rotary table in the motion drive and control unit;

[0048] Figure 6 Schematic diagram of the new center structure;

[0049] Figure 7 Cross-sectional view of the working principle when the center clamps a complex columnar part;

[0050] Figure 8 Axonometric view of the working principle when the center clamps a complex columnar part;

[0051] Figure 9 Schematic diagram of the principle for detecting whether the axis of the complex columnar part coincides with the axis of the center;

[0052] Figure 10 Structural diagram of the double probe unit 3;

[0053] Figure 11 Schematic diagram of the combined features presented by the double probes when there are errors;

[0054] Figure 12 Schematic diagram of the combined features presented by the double probes without errors under theoretical conditions;

[0055] Figure 13 Calibration and dynamic measurement flow chart.

[0056] The reference numerals in the figure are as follows: 1 - Motion drive and control unit, 2 - Composite clamping unit, 3 - Double probe unit, 4 - Machine frame, 1.1 - Linear motion motor, 1.2 - Differential gear train, 1.3 - Center worm, 1.4 - Center worm gear, 1.5 - Center lead screw, 1.6 - Upper center platform, 1.7 - Upper center, 1.8 - Reversing gear set, 1.9 - Probe worm, 1.10 - Probe worm gear, 1.11 - Probe lead screw, 1.12 - Rotary motion motor, 1.13 - Gear, 1.14 - Rotary table, 1.15 - Circular grating, 1.16 - Linear grating, 2.1 - Lower center motor, 2.2 - Lower center lead screw, 2.3 - Lower center platform, 2.4 - Guide rail slider, 2.5 - Lower center, 2.6 - Three-jaw chuck, 2.7 - Top cover, 2.8 - Buffer spring, 2.9 - Push rod, 2.10 - Pusher head, 2.11 - Ball string, 2.12 - Ball spring, 2.13 - Bottom cover, 2.14 - Center tip, 3.1 - Z-axis moving stage, 3.2 - X-axis motor, 3.3 - X-axis motor bracket, 3.4 - X-axis lead screw, 3.5 - X-axis moving stage, 3.6 - X-axis servo, 3.7 - X-axis servo bracket, 3.8 - Pillow block bearing, 3.9 - X-axis swing bracket, 3.10 - Y-axis servo, 3.11 - Y-axis swing bracket, 3.12 - Probe bracket, 3.13 - First probe, 3.14 - Second probe. Detailed implementation mode

[0057] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0058] As Figures 1-13 shown, a precision measuring device for complex cylindrical parts is composed of four parts: a motion drive and control unit 1, a composite clamping unit 2, a double probe unit 3, and a machine frame 4.

[0059] Embodiment 1: A cylindrical part made of aluminum alloy, with an outer diameter of 34 mm, an inner diameter of 20 mm, a height of 200 mm, and a shaft section with an outer diameter of 48 mm and a height of 60 mm in the middle is measured.

[0060] The first step: System calibration;

[0061] In theory, that is, without error, the combined features of the standard cylindrical calibration piece collected by the first probe 3.13 and the second probe 3.14 are a straight line and a perfect circle; however, due to manufacturing errors and installation errors in the system, the actual combined features presented by the first probe 3.13 and the second probe 3.14 are ellipses and ellipses. The calibration process is carried out according to this principle:

[0062] S1: The double probes are reset in the x-axis and z-axis directions, and the linear grating is zeroed;

[0063] S2: Clamp the calibration piece;

[0064] S3: Adjust the position of the double probe along the x-axis direction;

[0065] The motor 3.2 adjusts the position of the double probe in the x-axis direction so that the calibration part is within the optimal measurement range of the line structured light;

[0066] S4: Correct the x-axis angle error;

[0067] The x-axis servo 3.6 adjusts the attitude of the double probe so that it rotates around the x-axis until the coordinate feature presented by the first probe 3.13 is a straight line;

[0068] S5: Correct the y-axis angle error;

[0069] The y-axis servo 3.10 adjusts the attitude of the double probe so that it rotates around the y-axis until the coordinate feature presented by the second probe 3.14 is a perfect circle;

[0070] At this point, the combined features presented by the double probe are a straight line and a perfect circle, and the measurement accuracy is within an acceptable range.

[0071] During the dynamic measurement process, the double probe adjusts its own pose in real time according to the captured cylindrical features in combination with the above calibration steps S4 to S5 to ensure the dynamic measurement accuracy.

[0072] Second step: The motion drive and control unit 1 and the composite clamping unit 2 cooperate to clamp the part to be measured;

[0073] The motion drive and control unit 1 can realize two processes of linear motion and rotational motion, including a linear motion motor 1.1, a differential gear train 1.2, a top worm 1.3, a top worm gear 1.4, a top lead screw 1.5, an upper top platform 1.6, an upper top 1.7, a reversing gear set 1.8, a probe worm 1.9, a probe worm gear 1.10, a probe lead screw 1.11, a rotational motion motor 1.12, a gear 1.13, a rotating table 1.14, a circular grating 1.15, and a grating scale 1.16;

[0074] The linear motion motor 1.1 is fixed to the frame 4 by bolts, and its output shaft is connected to the differential gear train 1.2 and drives it to rotate; the left end output shaft of the differential gear train 1.2 is connected to the top worm 1.3 by a coupling; the top worm gear 1.4 is meshed with the top worm 1.3 and is connected to the top lead screw 1.5 by a flat key and drives it to rotate. The upper top platform 1.6 is connected to the top lead screw 1.5 by a thread, connected to the vertical guide rail slider by screws, and connected to the upper top 1.7 by a tapered roller bearing. It drives the upper top 1.7 to move vertically through screw drive combined with the guiding function of the guide rail, so that the cylindrical part can be clamped; the worm and worm gear drive adopted can ensure the self-locking characteristic and self-adaptability of the clamping process;

[0075] The described reversing gear set 1.8 is a commonly used manual shifting component on the market;

[0076] The described rotary table 1.14 is of a hollow cylindrical structure, with a spline groove provided on the inner ring and teeth existing at the lower part of the outer ring; The gear 1.13 meshes with the teeth at the lower part of the rotary table 1.14, and the rotation of the gear 1.13 is controlled by the forward and reverse rotation of the rotary motion motor 1.12, thereby realizing the rotation of the rotary table 1.14; The circular grating 1.15 is fixed on the inner wall of the frame 4 and is used to obtain the rotation angle of the rotary table 1.14, so as to realize the closed-loop control of the rotation angle of the rotary table 1.14;

[0077] The described composite clamping unit 2 includes a lower center motor 2.1, a lower center lead screw 2.2, a lower center platform 2.3, a guide rail slider 2.4, a lower center 2.5, and a three-jaw chuck 2.6;

[0078] The output shaft of the lower center motor 2.1 is connected to the lower center lead screw 2.2 through a coupling. The lower center platform 2.3 is provided with an internal threaded hole and is threadedly connected to the lower center lead screw 2.2; The lower center platform 2.3 is connected to the slider in the guide rail slider 2.4 through screws, so that it can move linearly in the vertical direction along the guide rail fixed on the inner wall of the frame 4; The lower center 2.5 is connected to the lower center platform 2.3 through a thrust bearing and is also connected to the inner ring of the rotary table 1.14 in the motion drive and control unit 1 through splines, so that the rotary table 1.14 can drive the lower center 2.5 to rotate synchronously; The three-jaw chuck 2.6 is fixed on the upper end face of the rotary table 1.14 and can rotate synchronously with the rotary table 1.14;

[0079] The described lower center 2.5 and the upper center 1.7 have the same structure, including a top cover 2.7, a buffer spring 2.8, a push rod 2.9, a push head 2.10, a ball string 2.11, a ball spring 2.12, a bottom cover 2.13, and a center head 2.14;

[0080] The push head 2.10 is lapped on the bottom cover 2.13, and four groups of ball strings 2.11 and ball springs 2.12 are evenly distributed on its side. At the same time, the bottom is threadedly connected to the center head 2.14; The bottom cover 2.13 is threadedly connected to the top cover 2.7, and a push rod 2.9 and a buffer spring 2.8 are arranged in the cavity between the two. One end of the buffer spring 2.8 is fixed on the top cover 2.7, and the other end is fixed on the push rod 2.9. The buffer spring 2.8 is compressed through the movement of the push rod 2.9, thereby realizing the effect of buffering and applying force;

[0081] The ball string 2.11 is composed of two upper and lower balls connected by a connecting rod. The upper ball can move slightly along the direction of the connecting rod. The lower ball in the ball string 2.11 extends into the interior of the complex cylindrical part, and the upper ball contacts the end face of the part. Under the extrusion of the part end face, the upper ball moves slightly along the chute away from the lower ball. When the upper ball moves to the limit distance allowed by the connecting rod, the upper ball starts to pull the lower ball through the connecting rod, so that the lower ball applies a force F2 to the inner wall of the part, restricting the radial and axial movements of the part. At the same time, the upper ball applies a force F1 to the part end face, restricting the radial and axial movements of the part. Through the over-constraint of F1 and F2 in the radial and axial directions, the clamping stability of the complex cylindrical part is enhanced. After the complex cylindrical part to be measured is clamped, it is judged whether the axis of the part coincides with the axis of the center point by checking whether the ball string 2.11 is loose. If the axis of the complex cylindrical part coincides with the axis of the center point, all four groups of ball strings 2.11 should be clamped tightly on the inner wall and end face of the hollow cylinder, (as Figure 8 shown). On the contrary, if any group of ball strings 2.11 is loose, it means that the axis of the part and the axis of the center point do not coincide (as Figure 9 shown). At this time, the part should be removed and re-clamped;

[0082] The described composite clamping unit 2 can achieve two clamping modes: chuck-center point and upper and lower center points;

[0083] Clamping mode 1: Chuck-center point clamping; When the diameter of the cylindrical part to be clamped is too large for the upper and lower center point clamping to meet the requirements, reverse the lower center point motor 2.1 to drive the lower center point 2.5 to descend into the rotary table 1.14. Then use a wrench to lock the three-jaw chuck 2.6 to perform a preliminary clamping on the cylindrical part to be measured. Start the linear motion motor 1.1 to drive the upper center point 1.7 to descend to further clamp the part, completing the clamping of the cylindrical part;

[0084] Clamping mode 2: Upper and lower center point clamping; When there are higher precision requirements for clamping or the part to be clamped has an irregular shape and cannot use a three-jaw chuck, use a wrench to open the jaws of the three-jaw chuck 2.6 outward. Forward the lower center point motor 2.1 to drive the lower center point 2.5 to rise above the rotary table 1.14. Then the lower center point 2.5 remains fixed. Start the linear motion motor 1.1 to drive the upper center point 1.7 to descend to cooperate with the lower center point 2.5 to clamp the cylindrical part to be measured. The center point head 2.14 can be replaced at any time according to the size of the part to be clamped during clamping;

[0085] The third step: The motion control unit 1 and the double probe unit 3 cooperate to reset the double probe along the x-axis and z-axis directions and zero the grating scale;

[0086] While the differential gear train 1.2 drives the left upper center 1.7 to move in the vertical direction, it enables the double probe unit 3 on the right side to perform a linear motion along the guide rail in the vertical direction; the output shaft at the right end of the differential gear train 1.2 is connected to the input shaft of the reversing gear set 1.8 through a coupling and drives it to rotate; the output shaft of the reversing gear set 1.8 is connected to the probe worm 1.9 through a coupling, and while the probe worm gear 1.10 meshes with the probe worm 1.9, it is connected to the probe lead screw 1.11 through a flat key to achieve the rotation of the probe lead screw 1.11; the double probe unit 3 is connected to the probe lead screw 1.11 through a thread and is simultaneously connected to the guide rail slider in the vertical direction through a screw. The combination of screw drive and the guiding function of the guide rail can achieve the linear movement of the double probe unit 3 in the vertical direction; the grating scale 1.16 is fixed to the inner wall of the frame 4 through a screw and can measure in real time the moving distance of the double probe unit 3 along the guide rail in the vertical direction, thereby achieving the closed-loop control of the linear position of the double probe unit 3;

[0087] The double probe unit 3 includes a z-axis moving table 3.1, an x-axis motor 3.2, an x-axis motor bracket 3.3, an x-axis lead screw 3.4, an x-axis moving table 3.5, an x-axis servo 3.6, an x-axis servo bracket 3.7, a pedestal bearing 3.8, an x-axis swing bracket 3.9, a y-axis servo 3.10, a y-axis swing bracket 3.11, a probe bracket 3.12, a first probe 3.13, and a second probe 3.14;

[0088] The first probe 3.13 is fixed on the y-axis swing bracket 3.11 by screws and emits line structured light in the vertical direction; the second probe 3.14 is connected to the probe bracket 3.12 by screws and is fixed perpendicular to the first probe 3.13 on the y-axis swing bracket 3.11, emitting line structured light in the horizontal direction; the x-axis servo 3.6 is fixed on the x-axis moving stage 3.5 by the x-axis servo bracket 3.7 and screws, and its output shaft is connected to the x-axis swing bracket 3.9 and drives it to rotate, realizing the rotation of the double probes on the x-axis. To ensure the stability of the probes during swinging, two pedestal bearings 3.8 are arranged between the x-axis swing bracket 3.9 and the x-axis servo 3.6; the y-axis servo 3.10 is fixed on the side of the x-axis swing bracket 3.9 by screws, and its output shaft is connected to the y-axis swing bracket 3.11 through a coupling, realizing the rotation of the double probes on the y-axis; the x-axis moving stage 3.5 is connected to the x-axis lead screw 3.4 by threads and is also connected to the guide rail slider in the x-axis direction by screws. The x-axis motor 3.2 is fixed on the z-axis moving stage 3.1 by the x-axis motor bracket 3.3 and screws, and at the same time its output shaft is connected to the x-axis lead screw 3.4 through a coupling. By driving the rotation of the lead screw 3.4, the x-axis moving stage 3.5 drives the double probes to linearly move along the x-axis, so that the distance between the double probes and the surface of the to-be-measured cylindrical part in the x-axis direction can be adjusted in real time during the measurement process, ensuring that the to-be-measured cylindrical part does not deviate from the optimal measurement range of the line structured light; the z-axis moving stage 3.1 is provided with threaded holes, which are connected to the probe lead screw 1.11 by threads and are also connected to the frame 4 through sliders and guide rails, so as to realize the linear movement of the z-axis moving stage 3.1 driving the double probes along the z-axis. Cooperating with the rotation movement of the lower center 2.5 and the three-jaw chuck 2.6 driving the to-be-measured cylindrical part, the complete dimensions of the surface of the cylindrical part can be obtained;

[0089] Step 4: The reversing gear set 1.8 is shifted to the upshift position, and the double-probe unit 3 rises along the z-axis to obtain the coordinate features of the single-sided surface of the part, and the probe pose is adjusted in real time;

[0090] The reversing gear set 1.8 is shifted to the upshift position, and the double probes rise along the z-axis and continuously capture the coordinate features of the part surface. At the same time, according to the measurement data of the cylindrical features, the self-pose is adjusted in real time based on the calibration from S4 to S5; the grating scale 1.16 records the displacement of the double probes in real time;

[0091] Step 5: The double probes move to the top of the part, the reversing gear set 1.8 is in neutral, and the double probes stop moving;

[0092] Step 6: The part rotates clockwise by 180°;

[0093] The rotary motion motor 1.12 drives the lower drive rotary table 1.14 to rotate, and controls the part to rotate 180° according to the reading of the circular grating 1.15;

[0094] Step 7: The reversing gear set 1.8 engages the lowering gear, and the double probes descend along the z-axis to obtain the coordinate features of the other side surface of the part, and the probe poses are adjusted in real time;

[0095] The reversing gear set 1.8 engages the lowering gear, and the double probes descend along the z-axis and continuously capture the coordinate features of the part surface. At the same time, according to the measurement data of the cylindrical feature, the self-pose is adjusted in real time based on the calibration from S4 to S5; the grating scale 1.16 records the displacement of the double probes in real time;

[0096] Step 8: The double probes move to the bottom end of the part, the reversing gear set 1.8 engages the neutral gear, and the double probes stop moving;

[0097] Step 9: The measurement is completed, and the report form is printed.

[0098] The detailed part measurement process is as Figure 13 shown.

[0099] All the coordinate features of the part surface dimensions are obtained through the reciprocating lifting motion of the double probes combined with the rotation of the part to be measured; the length dimension of the part is obtained through the grating scale; the dynamic measurement accuracy is guaranteed by adjusting the probe poses in real time.

[0100] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

Claims

1. A precise measurement device for complex column-like parts, characterized in that: It consists of four parts: a motion drive and control unit (1), a composite clamping unit (2), a double probe unit (3), and a frame (4). The composite clamping unit (2) includes a lower center motor (2.1), a lower center screw (2.2), a lower center platform (2.3), a guide rail slider (2.4), a lower center (2.5), and a three-jaw chuck (2.6). The lower center screw (2.2) is connected to the output shaft of the lower center motor (2.1) through a coupling and is also connected to the lower center platform (2.3) through a thread. The lower center platform (2.3) is connected to the slider in the guide rail slider (2.4) through screws. The lower center (2.5) is connected to the lower center platform (2.3) through a thrust bearing and is also connected to the inner ring of the rotary table (1.14) in the motion drive and control unit (1) through a spline. The three-jaw chuck (2.6) is fixed on the upper end face of the rotary table (1.14). The lower center (2.5) and the upper center (1.7) have the same structure, including a top cover (2.7), a buffer spring (2.8), a push rod (2.9), a push head (2.10), a ball string (2.11), a ball spring (2.12), a bottom cover (2.13), and a center head (2.14). The push head (2.10) is lapped on the bottom cover (2.13). Four groups of ball strings (2.11) and ball springs (2.12) are evenly distributed on its side. At the same time, the bottom is connected to the center head (2.14) through a thread. The bottom cover (2.13) is connected to the top cover (2.7) through a thread. A push rod (2.9) and a buffer spring (2.8) are arranged in the cavity between the two. One end of the buffer spring (2.8) is fixed on the top cover (2.7), and the other end is fixed on the push rod (2.9). The ball string (2.11) is composed of two balls connected by a connecting rod. The upper ball can move slightly along the direction of the connecting rod. The lower ball in the ball string (2.11) extends into the interior of the complex cylindrical part, and the upper ball contacts the part end face.

2. The precision measuring device for complex columnar parts according to claim 1, characterized in that: The motion drive and control unit (1) includes a linear motion motor (1.1), a differential gear train (1.2), a center worm (1.3), a center worm gear (1.4), a center screw (1.5), an upper center platform (1.6), an upper center (1.7), a reversing gear set (1.8), a probe worm (1.9), a probe worm gear (1.10), a probe screw (1.11), a rotary motion motor (1.12), a gear (1.13), a rotary table (1.14), a circular grating (1.15), and a grating scale (1.16). The linear motion motor (1.1) is fixed on the frame (4) through bolts, and its output shaft is connected to the differential gear train (1.2). The left output shaft of the differential gear train (1.2) is connected to the center worm (1.3). The center worm gear (1.4) is engaged with the center worm (1.3) and is also connected to the center screw (1.5) through a flat key. The upper center platform (1.6) is connected to the center screw (1.5) through a thread, is connected to the vertical guide rail slider through screws, and is connected to the upper center (1.7) through a tapered roller bearing. The output shaft at the right end of the differential gear train (1.2) is connected to the input shaft of the reversing gear set (1.8) through a coupling; the output shaft of the reversing gear set (1.8) is connected to the probe worm (1.9). The probe worm wheel (1.10) is meshed with the probe worm (1.9) and is connected to the probe lead screw (1.11) through a flat key. The double probe unit (3) is connected to the probe lead screw (1.11) through a thread and is also connected to the guide rail slider in the vertical direction through a screw; the grating scale (1.16) is fixed to the inner wall of the frame (4) through a screw. The rotary table (1.14) is a hollow cylindrical structure with a spline groove provided on the inner ring and teeth existing on the lower part of the outer ring; the gear (1.13) is meshed with the teeth on the lower part of the rotary table (1.14); the reading head on the outer ring of the circular grating (1.15) is fixed to the inner wall of the frame (4), and the inner ring is connected to the neck of the rotary table (1.14) through a screw.

3. The precision measuring device for complex column-like components according to claim 1, characterized in that: The double probe unit (3) includes a z-axis moving stage (3.1), an x-axis motor (3.2), an x-axis motor bracket (3.3), an x-axis lead screw (3.4), an x-axis moving stage (3.5), an x-axis servo (3.6), an x-axis servo bracket (3.7), a pedestal bearing (3.8), an x-axis swing bracket (3.9), a y-axis servo (3.10), a y-axis swing bracket (3.11), a probe bracket (3.12), a first probe (3.13), and a second probe (3.14). The first probe (3.13) is fixed to the y-axis swing bracket (3.11) through a screw; the second probe (3.14) is fixed to the y-axis swing bracket (3.11) through the probe bracket (3.12) and together with the first probe (3.13) forms a pair of mutually perpendicular double probes; the x-axis servo (3.6) is fixed to the x-axis moving stage (3.5) through the x-axis servo bracket (3.7) and a screw, and its output shaft is connected to the x-axis swing bracket (3.9). Two pedestal bearings (3.8) are provided between the x-axis swing bracket (3.9) and the x-axis servo (3.6); the y-axis servo (3.10) is fixed to the side of the x-axis swing bracket (3.9) through a screw, and its output shaft is connected to the y-axis swing bracket (3.11) through a coupling; the x-axis motor (3.2) is fixed to the z-axis moving stage (3.1) through the x-axis motor bracket (3.3) and a screw, and at the same time its output shaft is connected to the x-axis lead screw (3.4) through a coupling; the x-axis moving stage (3.5) is connected to the x-axis lead screw (3.4) through a thread and is also connected to the guide rail slider in the x-axis direction through a screw; the z-axis moving stage (3.1) is provided with a threaded hole and is connected to the probe lead screw (1.11) through a thread and is connected to the guide rail slider in the z-axis direction through a screw.

4. A calibration method, based on a precise measurement device for complex columnar parts as described in claim 1, characterized in that: The specific steps are as follows: S1: The double probes are reset in the x-axis and z-axis directions, and the grating scale is zeroed. S2: Clamp the calibration piece. S3: Adjust the position of the double probes in the x-axis direction. The motor adjusts the position of the double probes in the x-axis direction so that the calibration piece is within the optimal measurement range of the line structured light. S4: Correct the X-axis angle error. The x-axis servo adjusts the attitude of the double probe so that it rotates around the x-axis until the coordinate feature presented by the first probe is a straight line; S5: Correct the Y-axis angle error; The y-axis servo adjusts the attitude of the double probe so that it rotates around the y-axis until the coordinate feature presented by the second probe is a perfect circle; At this point, the combined features presented by the double probe are a straight line and a perfect circle, and the measurement accuracy is within the acceptable range.

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