Ultra-high-precision three-degree-of-freedom angle measurement system and measurement method

Abstract

The present invention relates to the field of angular measurement, and particularly to an ultra-high-precision three-degree-of-freedom angular measurement system and a measurement method. The measurement system includes a first calibration device, which is arranged on the moving platform of a parallel robot; an x / z-axis autocollimation measurement device and a second calibration device, which are arranged on both sides of the first calibration device along the y-axis direction; an x-axis laser interferometer measurement device, which is arranged on one side of the first calibration device along the x-axis direction; a y-axis autocollimation measurement device and a third calibration device, which are arranged on both sides of the first calibration device along the x-axis direction; a y-axis laser interferometer measurement device is arranged on one side of the first calibration device along the y-axis direction; and a z-axis laser interferometer measurement device is located on one side of the x / z-axis autocollimation measurement device. The present invention can improve the measurement accuracy and realize the angular coupling measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of angular measurement, and particularly relates to an ultra-high-precision three-degree-of-freedom angular measurement system and a measurement method. Background Art

[0002] In the fields of modern precision engineering and scientific research, the accurate measurement of angles and the coupled measurement of angles play crucial roles in multiple high-end technologies and applications. For the measurement of angles in high-precision fields (usually referring to angles of 1" or even smaller), due to the small measurement range, extremely high requirements are imposed on the sensitivity, accuracy, and anti-interference ability of sensors. The accurate measurement of angles is particularly critical in fields such as robot motion control, aerospace equipment docking, and optical alignment. At the same time, in parallel robots, flexible robotic arms, and complex mechanical structures, the angular changes of multiple degrees of freedom are often coupled. In order to achieve accurate description and control of complex motions, it is necessary to study the measurement methods of coupled angles. Therefore, developing an angular measurement method that can achieve both high precision and the ability to measure angular coupling is a current research hotspot in technology.

[0003] The Chinese invention patent with the publication number CN107101597A and the publication date of May 24, 2019, discloses an error calibration method for a rotation angle measurement system. This method uses a laser autocollimator, and synchronously measures the rotation angle of a curved surface reference piece using the rotation angle measurement system and the laser autocollimator. First, it measures different rotation angles of the same curved surface group, and then measures all the curved surface groups used in the rotation angle measurement system. Finally, an error calibration matrix based on different curved surface groups and different rotation angles is obtained, providing compensation data for eliminating rotation angle measurement errors. When the rotation angle measurement system is performing measurement work, the calibrated measurement error matrix is used to compensate the measurement results in real time according to the selected curved surface group number and the current measurement angle, so as to reduce the rotation angle measurement error and improve the measurement accuracy of the rotation angle measurement system. However, this method does not solve the problems that the measurement accuracy of the laser autocollimator itself is not high, resulting in limited rotation angle measurement accuracy, and the inability to measure angular coupling. Summary of the Invention

[0004] To achieve the above object, the technical solution of the present invention is realized as follows:

[0005] A super-high-precision three-degree-of-freedom rotation angle measurement system is used to measure the rotation angles of a parallel robot around the x, y, and z axes. The vertical movement direction of the parallel robot is taken as the z axis, and the horizontal movement directions of the parallel robot are taken as the x axis and the y axis. The super-high-precision three-degree-of-freedom rotation angle measurement system includes an x / z-axis autocollimation measurement device, a y-axis autocollimation measurement device, an x-axis laser interferometer measurement device, a y-axis laser interferometer measurement device, a z-axis laser interferometer measurement device, a first calibration device, a second calibration device, and a third calibration device. The first calibration device is arranged on the moving platform of the parallel robot. The x / z-axis autocollimation measurement device and the second calibration device are arranged on both sides of the first calibration device along the y-axis direction. The x-axis laser interferometer measurement device is arranged on one side of the first calibration device along the x-axis direction and corresponds to the position of the second calibration device. The y-axis autocollimation measurement device and the third calibration device are arranged on both sides of the first calibration device along the x-axis direction. The y-axis laser interferometer measurement device is arranged on one side of the first calibration device along the y-axis direction and corresponds to the position of the third calibration device. The z-axis laser interferometer measurement device is located on one side of the x / z-axis autocollimation measurement device.

[0006] Further, the first calibration device includes a T-shaped moving platform adapter plate, a cube mirror, a first compound mirror, a second compound mirror, and a reflector. The cube mirror is arranged at the intersection position of the T-shaped moving platform adapter plate, and the first compound mirror, the second compound mirror, and the reflector are respectively arranged at the three free ends of the T-shaped moving platform adapter plate.

[0007] Further, the second calibration device includes a first two-dimensional adjustment frame and a third compound mirror. The third compound mirror is arranged on the first two-dimensional adjustment frame and is coaxial with the first compound mirror in the z-axis direction.

[0008] Further, the x-axis laser interferometer measurement device includes a first lifting platform and an x-axis laser interferometer. The x-axis laser interferometer is arranged on the first lifting platform and is coaxial with the third compound mirror in the x-axis direction.

[0009] Further, the x / z-axis autocollimation measurement device includes a second lifting platform and an x / z-axis autocollimator. The x / z-axis autocollimator is arranged on the second lifting platform and is coaxial with one surface of the cube mirror in the y-axis direction.

[0010] Further, the third calibration device includes a second two-dimensional adjustment frame and a fourth compound mirror. The fourth compound mirror is arranged on the second two-dimensional adjustment frame and is coaxial with the second compound mirror in the z-axis direction.

[0011] Further, the y-axis laser interferometer measurement device includes a third lifting platform and a y-axis laser interferometer. The y-axis laser interferometer is arranged on the third lifting platform and is coaxial with the fourth compound mirror in the y-axis direction.

[0012] Further, the y-axis autocollimation measuring device includes a fourth lifting table and a y-axis autocollimator. The y-axis autocollimator is arranged on the fourth lifting table and is coaxial with the other surface of the cube mirror in the x-axis direction.

[0013] Further, the z-axis laser interferometry measuring device includes a fifth lifting table and a z-axis laser interferometer. The z-axis laser interferometer is arranged on the fifth lifting table and is coaxial with the mirror in the y-axis direction.

[0014] An ultra-high-precision three-degree-of-freedom rotation angle measurement method uses the above ultra-high-precision three-degree-of-freedom rotation angle measurement system to measure the rotation angles of the parallel robot around the x, y, and z axes;

[0015] When measuring the rotation angle around the x-axis, the following steps are included:

[0016] S1a: Adjust the third compound mirror to be coaxial with the first compound mirror in the z-axis direction through the first two-dimensional adjustment frame, adjust the height of the x-axis laser interferometer to be coaxial with the third compound mirror in the x-axis direction through the first lifting table, and adjust the height of the x / z-axis autocollimator to be coaxial with one surface of the cube mirror in the y-axis direction through the second lifting table;

[0017] S2a: The parallel robot rotates around the x-axis. Measure the rotation angle α1 of the parallel robot through the cooperation of the x / z-axis autocollimator and the cube mirror, where α1 > 10", and measure the displacement L2 generated by the parallel robot in the z-axis direction through the cooperation of the x-axis laser interferometer, the third compound mirror, and the first compound mirror;

[0018] S3a: Substitute the angle α1 and the displacement L2 into the tangent function formula to calculate the actual value L1' of the rotation radius, subtract it from the ideal value L1 of the rotation radius, and calculate the error value ΔL1 of the rotation radius;

[0019] S4a: The parallel robot rotates around the x-axis. Measure the rotation angle α2 of the parallel robot through the cooperation of the x / z-axis autocollimator and the cube mirror, where α2 < 1", and measure the displacement L3 generated by the parallel robot in the z-axis direction through the cooperation of the x-axis laser interferometer, the third compound mirror, and the first compound mirror;

[0020] S5a: Substitute the ideal value L1 of the rotation radius, the error value ΔL1 of the rotation radius, and the displacement L3 into the tangent function formula to calculate the compensated rotation angle α2';

[0021] When measuring the rotation angle around the y-axis, the following steps are included:

[0022] S1b: Adjust the fourth compound mirror to be coaxial with the second compound mirror in the z-axis direction through the second two-dimensional adjustment bracket, adjust the height of the y-axis laser interferometer to be coaxial with the fourth compound mirror in the y-axis direction through the third lifting platform, and adjust the height of the y-axis autocollimator to be coaxial with the other surface of the cube mirror in the x-axis direction through the fourth lifting platform;

[0023] S2b: The parallel robot rotates around the y-axis. Measure the rotation angle α3 of the parallel robot through the cooperation of the y-axis autocollimator and the cube mirror, where α3 > 10", and measure the displacement L5 generated by the parallel robot in the z-axis direction through the cooperation of the y-axis laser interferometer, the fourth compound mirror, and the second compound mirror;

[0024] S3b: Substitute the angle α3 and the displacement L5 into the tangent function formula to calculate the actual value L4' of the turning radius. Subtract it from the ideal value L4 of the turning radius to calculate the error value ΔL2 of the turning radius;

[0025] S4b: The parallel robot rotates around the y-axis. Measure the rotation angle α4 of the parallel robot through the cooperation of the y-axis autocollimator and the cube mirror, where α4 < 1", and measure the displacement L6 generated by the parallel robot in the z-axis direction through the cooperation of the y-axis laser interferometer, the fourth compound mirror, and the second compound mirror;

[0026] S5b: Substitute the ideal value L4 of the turning radius, the error value ΔL2 of the turning radius, and the displacement L6 into the tangent function formula to calculate the compensated rotation angle α4';

[0027] When measuring the rotation angle around the z-axis, the following steps are included:

[0028] S1c: Adjust the height of the z-axis laser interferometer to be coaxial with the reflector in the y-axis direction through the fifth lifting platform, and adjust the height of the x / z-axis autocollimator to be coaxial with one surface of the cube mirror in the y-axis direction through the second lifting platform;

[0029] S2c: The parallel robot rotates around the z-axis. Measure the rotation angle α5 of the parallel robot through the cooperation of the x / z-axis autocollimator and the cube mirror, where α5 > 10", and measure the displacement L8 generated by the parallel robot in the y-axis direction through the cooperation of the z-axis laser interferometer and the reflector;

[0030] S3c: Substitute the angle α5 and the displacement L8 into the tangent function formula to calculate the actual value L7' of the turning radius. Subtract it from the ideal value L7 of the turning radius to calculate the error value ΔL3 of the turning radius;

[0031] S4c: The parallel robot rotates around the z-axis. The rotation angle α6 of the parallel robot is measured by the cooperation of the x / z-axis autocollimator and the cube mirror, where α6 < 1", and the displacement L9 generated by the parallel robot in the y-axis direction is measured by the cooperation of the z-axis laser interferometer and the mirror.

[0032] S5c: Substitute the ideal value L7 of the rotation radius, the error value ΔL3 of the rotation radius, and the displacement L9 into the tangent function formula to calculate the compensated rotation angle α6'.

[0033] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0034] The present invention combines the advantages of the autocollimator and the laser interferometer. It uses the laser interferometer to accurately measure the tiny displacement generated by the rotation of the parallel robot, and uses the autocollimator to accurately measure the rotation angle of the parallel robot. The accurate data measured by the autocollimator and the laser interferometer can achieve ultra-high-precision rotation angle measurement of three degrees of freedom, and at the same time can also achieve ultra-high-precision rotation angle coupling measurement of the three degrees of freedom of the parallel robot. This method can effectively improve the measurement accuracy and ensure high stability in different measurement directions, and is applicable to parallel robots and other high-precision measurement fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0036] Figure 1 is a schematic structural diagram of the ultra-high-precision three-degree-of-freedom rotation angle measurement system according to the embodiment of the present invention.

[0037] Figure 2 is a schematic structural diagram of the parallel robot and the first calibration device according to the embodiment of the present invention.

[0038] Figure 3 is a partial schematic diagram of the ultra-high-precision three-degree-of-freedom rotation angle measurement system for measuring the rotation angle of the parallel robot around the x-axis according to the embodiment of the present invention.

[0039] Figure 4 is a schematic principle diagram of the ultra-high-precision three-degree-of-freedom rotation angle measurement system for measuring the rotation angle when the parallel robot rotates around the x-axis according to the embodiment of the present invention.

[0040] Figure 5 is a partial schematic diagram of the ultra-high-precision three-degree-of-freedom rotation angle measurement system for measuring the rotation angle of the parallel robot around the y-axis according to the embodiment of the present invention.

[0041] Figure 6 It is a schematic diagram of the principle for measuring the rotation angle by the ultra-high-precision three-degree-of-freedom rotation angle measurement system when the parallel robot rotates around the y-axis according to the embodiments of the present invention.

[0042] Figure 7 It is a partial schematic diagram of the ultra-high-precision three-degree-of-freedom rotation angle measurement system for measuring the rotation angle of the parallel robot when it rotates around the z-axis according to the embodiments of the present invention.

[0043] Figure 8 It is a schematic diagram of the principle for measuring the rotation angle by the ultra-high-precision three-degree-of-freedom rotation angle measurement system when the parallel robot rotates around the z-axis according to the embodiments of the present invention.

[0044] Explanation of reference numerals: Parallel robot 1, moving platform 11, static platform 12, kinematic chain 13, optical platform 14, x / z-axis autocollimation measurement device 2, second lifting platform 21, x / z-axis autocollimator 22, y-axis autocollimation measurement device 3, fourth lifting platform 31, y-axis autocollimator 32, x-axis laser interferometer measurement device 4, first lifting platform 41, x-axis laser interferometer 42, interference mirror 43, y-axis laser interferometer measurement device 5, third lifting platform 51, y-axis laser interferometer 52, interference mirror 53, z-axis laser interferometer measurement device 6, fifth lifting platform 61, z-axis laser interferometer 62, interference mirror 63, first calibration device 7, T-shaped moving platform adapter plate 71, cube mirror 72, first compound mirror 73, second compound mirror 74, reflector 75, second calibration device 8, first two-dimensional adjustment frame 81, third compound mirror 82, third calibration device 9, second two-dimensional adjustment frame 91, fourth compound mirror 92. Detailed implementation manners

[0045] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention.

[0046] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0047] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0048] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0049] Aiming at the problems of low measurement accuracy of the laser autocollimator itself and inability to measure angular coupling, the present invention proposes an innovative angular measurement method, which is realized by using an angular measurement system, combines the advantages of the autocollimator and the laser interferometer, overcomes the limitations in traditional measurement methods, and thus realizes a more accurate and stable angular measurement and a multi-angle coupling measurement method.

[0050] More specifically, the angular measurement method proposed by the present invention can convert the measurement of the angle into the measurement of displacement and combine with the laser interferometer for accurate measurement, which can break through the problem of limited accuracy of traditional measurement tools. The measurement accuracy of the autocollimator has an error of ±0.2" within 20", and an error of ±0.3" within 600". The measurement accuracy is limited during high-precision measurement, while the order of magnitude of the laser interferometer can reach 0.1μm, and the measurement accuracy of linear displacement is relatively high. The present invention combines the laser interferometer with the autocollimator to achieve ultra-high-precision angular measurement.

[0051] The present invention combines the motion relationship of the laser interferometer with that of the parallel robot, reduces the sensitivity to the environment. Especially when the angle is small, the influence of external factors on the angular measurement accuracy can be overcome through displacement measurement, thus realizing a more stable measurement.

[0052] Through the combination of a laser interferometer and an autocollimator, the present invention can also measure the angular coupling during the multi-degree-of-freedom motion of a parallel robot.

[0053] The following will refer to Figures 1-8 and in combination with embodiments to elaborate on the present invention.

[0054] As Figures 1-8 shown, taking the vertical motion direction of the parallel robot 1 as the z-axis, the horizontal motion directions of the parallel robot 1 as the x-axis and the y-axis, the rotations of the parallel robot 1 around the x, y, and z axes are called three degrees of freedom. Then, the ultra-high-precision three-degree-of-freedom angular measurement system provided by the embodiment of the present invention can separately measure the rotation angles of any one degree of freedom of the parallel robot 1, or simultaneously measure the rotation angles of the three degrees of freedom of the parallel robot 1.

[0055] The parallel robot 1 includes a moving platform 11, a stationary platform 12, and a kinematic chain 13. The stationary platform 12 is installed on the optical platform 14 by means of a threaded connection, and the kinematic chain 13 is connected between the stationary platform 12 and the moving platform 11.

[0056] The ultra-high-precision three-degree-of-freedom angular measurement system includes an x / z-axis autocollimation measurement device 2, a y-axis autocollimation measurement device 3, an x-axis laser interferometry measurement device 4, a y-axis laser interferometry measurement device 5, a z-axis laser interferometry measurement device 6, a first calibration device 7, a second calibration device 8, and a third calibration device 9; the first calibration device 7 is arranged on the moving platform 11 of the parallel robot 1, the x / z-axis autocollimation measurement device 2 and the second calibration device 8 are arranged on both sides of the first calibration device 7 along the y-axis direction, and the x-axis laser interferometry measurement device 4 is arranged on one side of the first calibration device 7 along the x-axis direction and corresponds to the position of the second calibration device 8; the y-axis autocollimation measurement device 3 and the third calibration device 9 are arranged on both sides of the first calibration device 7 along the x-axis direction, and the y-axis laser interferometry measurement device 5 is arranged on one side of the first calibration device 7 along the y-axis direction and corresponds to the position of the third calibration device 9; the z-axis laser interferometry measurement device 6 is located on one side of the x / z-axis autocollimation measurement device 2.

[0057] The first calibration device 7 includes a T-shaped moving platform adapter plate 71, a cube mirror 72, a first compound mirror 73, a second compound mirror 74, and a reflecting mirror 75. The T-shaped moving platform adapter plate 71 is installed on the moving platform 11 by means of threaded connection. The cube mirror 72 is arranged at the intersection position of the T-shaped moving platform adapter plate 71, that is, the center point position of the T-shaped moving platform adapter plate 71. The first compound mirror 73 is arranged at the free end of the T-shaped moving platform adapter plate 71 along the y-axis direction. The second compound mirror 74 is arranged at a free end of the T-shaped moving platform adapter plate 71 along the x-axis direction. The reflecting mirror 75 is arranged at the other free end of the T-shaped moving platform adapter plate 71 along the x-axis direction. The first compound mirror 73, the second compound mirror 74, and the reflecting mirror 75 are respectively positioned by the bosses at the three free ends of the T-shaped moving platform adapter plate 71 and are adhesively bonded to the T-shaped moving platform adapter plate 71.

[0058] The second calibration device 8 includes a first two-dimensional adjustment frame 81 and a third compound mirror 82. The third compound mirror 82 is arranged on the first two-dimensional adjustment frame 81 and is coaxial with the first compound mirror 73 in the z-axis direction. The first two-dimensional adjustment frame 81 is installed on the optical platform 14 by means of threaded connection.

[0059] The third calibration device 9 includes a second two-dimensional adjustment frame 91 and a fourth compound mirror 92. The fourth compound mirror 92 is arranged on the second two-dimensional adjustment frame 91 and is coaxial with the second compound mirror 74 in the z-axis direction. The second two-dimensional adjustment frame 91 is installed on the optical platform 14 by means of threaded connection.

[0060] The x / z-axis autocollimation measuring device 2 includes a second lifting platform 21 and an x / z-axis autocollimator 22. The x / z-axis autocollimator 22 is arranged on the second lifting platform 21 and is coaxial with one surface of the cube mirror 72 in the y-axis direction. This surface of the cube mirror 72 is the surface facing the x / z-axis autocollimator 22. The second lifting platform 21 is installed on the optical platform 14 by means of threaded connection.

[0061] The y-axis autocollimation measuring device 3 includes a fourth lifting platform 31 and a y-axis autocollimator 32. The y-axis autocollimator 32 is arranged on the fourth lifting platform 31 and is coaxial with the other surface of the cube mirror 72 in the x-axis direction. This surface of the cube mirror 72 is the surface facing the y-axis autocollimator 32. The fourth lifting platform 31 is installed on the optical platform 14 by means of threaded connection.

[0062] The x-axis laser interferometer measuring device 4 includes a first lifting platform 41 and an x-axis laser interferometer 42. The x-axis laser interferometer 42 is arranged on the first lifting platform 41 and is coaxial with the third compound mirror 82 in the x-axis direction. The first lifting platform 41 is installed on the optical platform 14 by means of threaded connection.

[0063] The y-axis laser interferometry device 5 includes a third lifting platform 51 and a y-axis laser interferometer 52. The y-axis laser interferometer 52 is disposed on the third lifting platform 51 and is coaxial with the fourth compound mirror 92 in the y-axis direction. The third lifting platform 51 is mounted onto the optical platform 14 in a threaded connection manner.

[0064] The z-axis laser interferometry device 6 includes a fifth lifting platform 61 and a z-axis laser interferometer 62. The z-axis laser interferometer 62 is disposed on the fifth lifting platform 61 and is coaxial with the reflecting mirror 75 in the y-axis direction. The fifth lifting platform 61 is mounted onto the optical platform 14 in a threaded connection manner.

[0065] For the measurement of the rotation angle of the parallel robot 1 about the x-axis, the basic measurement principle is as follows:

[0066] When the parallel robot 1 rotates about the x-axis, since the rotation angle is very small, it can be approximately considered that a small vertical displacement is generated in the z-axis direction. The x-axis laser interferometer 42 has extremely high precision and can measure this small displacement. By designing the length of the T-shaped moving platform adapter plate 71, a small rotation angle can generate a larger displacement in the z-axis direction, thereby meeting the measurement precision of the laser interferometer. Since certain errors will be caused during the manufacturing and assembly of the T-shaped moving platform adapter plate 71, the actual length of the T-shaped moving platform adapter plate 71 may have a certain error from the designed ideal value, which will further lead to an error in the rotation radius. Therefore, the error can be calibrated by the x / z-axis autocollimator 22 and the cube mirror 72. Although there is a certain error in the precision of the autocollimator when measuring the rotation angle, by rotating the parallel robot 1 about the x-axis by a relatively large angle, the measured value of the autocollimator when measuring a relatively large rotation angle (greater than 10") is accurate (because the error is about 0.2" and can be ignored), so as to obtain relatively accurate measurement data. During this process, a certain vertical displacement will be generated in the z-axis direction, and this vertical displacement (the magnitude of which is within the measurement precision of the laser interferometer) can be accurately measured by the x-axis laser interferometer 42. By combining the actual rotation angle measured by the x / z-axis autocollimator 22 with the vertical displacement measured by the x-axis laser interferometer 42, the actual rotation radius can be accurately calculated, and the difference between the actual rotation radius and the ideal rotation radius is the error value of the rotation radius. The error value of the rotation radius can be compensated in the actual rotation angle during subsequent rotation angle measurement to obtain the compensated rotation angle value.

[0067] The measurement principle for the rotation angles of the parallel robot 1 about the y-axis and z-axis is the same as that for the rotation about the x-axis.

[0068] To make the technical solution, measurement principle part, and advantages of the present invention clearer, the following content introduces the detailed elaboration of the technical solution of the present invention:

[0069] (I) Measurement of the rotation angle about the x-axis

[0070] When the motion chain 13 drives the moving platform 11 to rotate about the x-axis, the angle measurement includes the following steps:

[0071] S1a: Adjust the position of the third compound mirror 82 through the first two-dimensional adjustment frame 81 to make the third compound mirror 82 coaxial with the first compound mirror 73 in the z-axis direction. Adjust the height of the x-axis laser interferometer 42 through the first lifting platform 41 to make the interferometer mirror 43 of the x-axis laser interferometer 42 coaxial with the third compound mirror 82 in the x-axis direction. Adjust the height of the x / z-axis autocollimator 22 through the second lifting platform 21 to make the x / z-axis autocollimator 22 coaxial with one surface of the cube mirror 72 in the y-axis direction.

[0072] When the third compound mirror 82 is coaxial with the first compound mirror 73 in the z-axis direction and the interferometer mirror 43 of the x-axis laser interferometer 42 is coaxial with the third compound mirror 82 in the x-axis direction, the connecting lines of the first compound mirror 73, the third compound mirror 82 and the interferometer mirror 43 form a right triangle.

[0073] S2a: The parallel robot 1 rotates about the x-axis. Measure the rotation angle α1 of the parallel robot through the cooperation of the x / z-axis autocollimator 22 and the cube mirror 72, where α1 > 10", and measure the displacement L2 generated by the parallel robot in the z-axis direction through the cooperation of the x-axis laser interferometer 42 and the third compound mirror 82 and the first compound mirror 73.

[0074] S3a: Substitute the angle α1 and the displacement L2 into the tangent function formula to calculate the actual value L1' of the rotation angle radius. Subtract it from the ideal value L1 of the rotation angle radius to calculate the error value ΔL1 of the rotation angle radius.

[0075] S4a: The parallel robot 1 rotates about the x-axis. Measure the rotation angle α2 of the parallel robot through the cooperation of the x / z-axis autocollimator 22 and the cube mirror 72, where α2 < 1", and measure the displacement L3 generated by the parallel robot in the z-axis direction through the cooperation of the x-axis laser interferometer 42 and the third compound mirror 82 and the first compound mirror 73.

[0076] S5a: Substitute the ideal value L1 of the rotation angle radius, the error value ΔL1 of the rotation angle radius, and the displacement L3 into the tangent function formula to calculate the compensated rotation angle α2'.

[0077] Position the first compound mirror 73 through the boss of the T-shaped moving platform adapter plate 71. Figure 4The distance between the center point B of the first compound mirror 73 and the center point O of the T-shaped moving platform adapter plate 71 can be obtained from the design dimensions of the T-shaped moving platform adapter plate 71. This distance is also the rotation radius L1 about the x-axis. However, this rotation radius is an ideal value, and there will definitely be errors during the installation and assembly of the first calibration device 7, resulting in the actual value of the rotation radius being different from the ideal value, that is, there is an error in the rotation radius.

[0078] To calculate the error of the rotation radius, the present invention uses the x / z-axis autocollimator 22 and the cube mirror 72 for error calibration. The moving platform 11 is driven by the motion chain 13 to rotate about the x-axis by a relatively large angle, and its rotation angle is α1, so as to obtain relatively accurate autocollimator measurement data. During this process, there will be a certain displacement in the z-axis direction. Since the rotation angle is relatively small (about 10"), mathematically, this arc-shaped displacement can be approximated as a linear displacement AB, that is, L2. This displacement L2 can be measured by the x-axis laser interferometer 42 (the magnitude of this displacement is within the measurement accuracy of the laser interferometer), and this value is also accurate. Substitute the displacement L2 and the rotation angle α1 into the formula L2 = L1’×tanα1 to calculate the actual value L1’ of the rotation angle radius. In this way, the error value ΔL1 of the rotation angle radius can be calculated, that is, ΔL1 = L1 - L1’. Then, the moving platform 11 is driven by the motion chain 13 to rotate about the x-axis by a relatively small angle (that is, the angle of rotation before compensation), and its rotation angle is α2. At this time, there will be an arc-shaped displacement in the z-axis direction. Similarly, since the rotation angle is relatively small (less than 1"), this arc-shaped displacement can also be approximated as a linear displacement A’B’, that is, L3. This displacement L3 can be measured by the x-axis laser interferometer 42, and this value is also accurate. Substitute the displacement L3, the ideal value L1 of the rotation radius, and the error value ΔL1 of the rotation angle radius into the formula L3 = (L1 + ΔL1)×tanα2’, so as to calibrate the magnitude of the rotation angle α2’, that is, the value of the rotation angle about the x-axis after compensation. The compensation value is Δα1 = α2 - α2’.

[0079] (2) Measurement of the rotation angle about the y-axis

[0080] When the motion chain 13 drives the moving platform 11 to rotate about the y-axis, the rotation angle measurement includes the following steps:

[0081] S1b: Adjust the fourth compound mirror 92 to be coaxial with the second compound mirror 74 in the z-axis direction through the second two-dimensional adjustment frame 91. Adjust the height of the y-axis laser interferometer 52 to be coaxial with the second compound mirror 74 in the y-axis direction through the third lifting platform 51. Adjust the height of the y-axis autocollimator 32 to be coaxial with the other surface of the cube mirror 72 in the x-axis direction through the fourth lifting platform 31.

[0082] S2b: The parallel robot 1 rotates about the y-axis. The rotation angle α3 of the parallel robot is measured through the cooperation of the y-axis autocollimator 32 and the cube mirror 72, where α3 > 10", and the displacement L5 generated by the parallel robot in the z-axis direction is measured through the cooperation of the y-axis laser interferometer 52 and the fourth compound mirror 92 and the second compound mirror 74.

[0083] S3b: Substitute the angle α3 and the displacement L5 into the tangent function formula to calculate the actual value L4' of the rotation radius. Subtract it from the ideal value L4 of the rotation radius to calculate the error value ΔL2 of the rotation radius.

[0084] S4b: The parallel robot 1 rotates about the y-axis. The rotation angle α4 of the parallel robot is measured through the cooperation of the y-axis autocollimator 32 and the cube mirror 72, where α4 < 1", and the displacement L6 generated by the parallel robot in the z-axis direction is measured through the cooperation of the y-axis laser interferometer 52 and the fourth compound mirror 92 and the second compound mirror 74.

[0085] S5b: Substitute the ideal value L4 of the rotation radius, the error value ΔL2 of the rotation radius, and the displacement L6 into the tangent function formula to calculate the compensated rotation angle α4'.

[0086] The position of the second compound mirror 74 is located by the boss of the T-shaped moving platform adapter plate 71. Figure 6 The distance between the center point F of the second compound mirror 74 and the center point O of the T-shaped moving platform adapter plate 71 can be obtained from the design dimensions of the T-shaped moving platform adapter plate 71. This distance is the rotation radius L4 for rotation about the x-axis, but this rotation radius is an ideal value. There must be errors during the installation and assembly of the first calibration device 7, resulting in the actual value of the rotation radius being different from the ideal value, that is, there is an error in the rotation radius.

[0087] To calculate the error of the rotation radius, the present invention uses the y-axis autocollimator 32 and the cube mirror 72 for error calibration. The moving platform 11 is driven by the motion chain 13 to rotate about the y-axis by a relatively large angle, making its rotation angle α3, so as to obtain relatively accurate autocollimator measurement data. During this process, a certain displacement will be generated in the z-axis direction. , since the rotation angle is relatively small (about 10"), mathematically, the arc-shaped displacement can be approximated as a linear displacement EF, i.e., L5. This displacement L5 can be measured by the y-axis laser interferometer 52 (the magnitude of this displacement is within the measurement accuracy of the laser interferometer), and this value is also accurate. Substitute the displacement L5 and the rotation angle α3 into the formula L5 = L4’×tanα3 to calculate the actual value L4’ of the rotation radius. In this way, the error value ΔL2 of the rotation radius can be calculated, i.e., ΔL2 = L4 - L4’. Then, drive the moving platform 11 to rotate around the y-axis by a relatively small angle (i.e., the angle of rotation before compensation) through the kinematic chain 13, and let its rotation angle be α4. At this time, an arc-shaped displacement will be generated in the z-axis direction. , also because the rotation angle is relatively small (less than 1"), the arc-shaped displacement can also be approximated as a linear displacement E’F’, i.e., L6. This displacement L6 can be measured by the y-axis laser interferometer 52, and this value is also accurate. Substitute the displacement L6, the ideal value L4 of the rotation radius, and the error value ΔL2 of the rotation radius into the formula L6 = (L4 + ΔL2)×tanα4’ to calibrate the magnitude of the rotation angle α4’, which is also the value after the rotation angle compensation around the y-axis. The compensation value is Δα2 = α4 - α4’.

[0088] (3) Measurement of the rotation angle around the z-axis

[0089] When the kinematic chain 13 drives the moving platform 11 to rotate around the z-axis, the rotation angle measurement includes the following steps:

[0090] S1c: Adjust the height of the z-axis laser interferometer 62 to be coaxial with the mirror 75 in the y-axis direction through the fifth lifting platform 61.

[0091] S2c: The parallel robot 1 rotates around the z-axis. Measure the rotation angle α5 of the parallel robot through the cooperation of the x / z-axis autocollimator 22 and the cube mirror 72, where α5 > 10", and measure the displacement L8 generated by the parallel robot in the y-axis direction through the cooperation of the z-axis laser interferometer 62 and the mirror 75.

[0092] S3c: Substitute the angle α5 and the displacement L8 into the tangent function formula to calculate the actual value L7’ of the rotation radius. Subtract it from the ideal value L7 of the rotation radius to calculate the error value ΔL3 of the rotation radius.

[0093] S4c: The parallel robot 1 rotates around the z-axis. Measure the rotation angle α6 of the parallel robot through the cooperation of the x / z-axis autocollimator 22 and the cube mirror 72, where α6 < 1", and measure the displacement L9 generated by the parallel robot in the y-axis direction through the cooperation of the z-axis laser interferometer 62 and the mirror 75.

[0094] S5c: Substitute the ideal value L7 of the corner radius, the error value ΔL3 of the corner radius, and the displacement L9 into the tangent function formula to calculate the compensated corner α6'.

[0095] Position the reflecting mirror 75 through the boss of the T-shaped moving platform adapter plate 71. Figure 8 The distance between the center point C of the middle reflecting mirror 75 and the center point O of the T-shaped moving platform adapter plate 71 can be obtained from the design dimensions of the T-shaped moving platform adapter plate 71. This distance is the radius of rotation L7 about the z-axis, but this radius of rotation is the ideal value. During the installation and assembly of the first calibration device 7, there will definitely be errors, resulting in the actual value of the radius of rotation being different from the ideal value, that is, there is an error in the radius of rotation.

[0096] To calculate the error of the radius of rotation, the present invention uses the x / z-axis autocollimator 22 and the cube mirror 72 to calibrate the error. Drive the moving platform 11 to rotate about the z-axis by a relatively large angle through the motion chain 13, and make its rotation angle be α5, so as to obtain relatively accurate autocollimator measurement data. During this process, a certain displacement will be generated in the y-axis direction. , because the rotation angle is small (about 10"), mathematically, this arc-shaped displacement can be approximated as a linear displacement CD, that is, L8. This displacement L8 can be measured by the z-axis laser interferometer 62 (the magnitude of this displacement is within the measurement accuracy of the laser interferometer), and this value is also accurate. Substitute the displacement L8 and the rotation angle α5 into the formula L8 = L7'×tanα5 to calculate the actual value L7' of the corner radius. In this way, the error value ΔL3 of the corner radius can be calculated, that is, ΔL3 = L7 - L7'. Then drive the moving platform 11 to rotate about the y-axis by a relatively small angle (i.e., the rotation angle before compensation) through the motion chain 13, and make its rotation angle be α6. At this time, an arc-shaped displacement will be generated in the y-axis direction. , similarly, because the rotation angle is small (less than 1"), this arc-shaped displacement can also be approximated as a linear displacement C'D', that is, L9. This displacement L9 can be measured by the z-axis laser interferometer 62, and this value is also accurate. Substitute the displacement L9, the ideal value L7 of the corner radius, and the error value ΔL3 of the corner radius into the formula L9 = (L7 + ΔL3)×tanα6', so as to calibrate the magnitude of the corner α6', that is, the value after compensation of the rotation angle about the x-axis, and the compensation value is Δα3 = α6 - α6'.

[0097] When the parallel robot 1 performs a single-degree-of-freedom motion (rotation about any one of the x, y, and z axes), the present invention can separately measure the rotation angle of the single-degree-of-freedom motion of the parallel robot 1. When the parallel robot 1 performs a coupled motion of multiple degrees of freedom (rotation about the x, y, and z axes simultaneously), the present invention can simultaneously measure the rotation angles of the three-degree-of-freedom motion, that is, realize the coupled measurement of the rotation angles.

[0098] It should be understood that the various forms of the process shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is imposed herein.

[0099] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An ultra-high precision three-degree-of-freedom angle measurement system, used to measure the angle of rotation of a parallel robot around the x, y, and z axes, with the vertical movement direction of the parallel robot as the z axis and the horizontal movement direction of the parallel robot as the x axis and the y axis; characterized in that: The ultra-high precision three-degree-of-freedom angle measurement system comprises an x / z-axis autocollimation measurement device, a y-axis autocollimation measurement device, an x-axis laser interferometer measurement device, a y-axis laser interferometer measurement device, a z-axis laser interferometer measurement device, a first calibration device, a second calibration device and a third calibration device; the first calibration device is arranged on a moving platform of the parallel robot, the x / z-axis autocollimation measurement device and the second calibration device are arranged on both sides of the first calibration device along the y-axis direction, the x-axis laser interferometer measurement device is arranged on one side of the first calibration device along the x-axis direction and corresponds to the position of the second calibration device; the y-axis autocollimation measurement device and the third calibration device are arranged on the first calibration device along the x-axis direction The y-axis laser interferometer measuring device is arranged on both sides of the first calibration device along the y-axis direction and corresponds to the position of the third calibration device; the z-axis laser interferometer measuring device is located on one side of the x / z-axis self-collimation measuring device; the first calibration device includes a T-type moving platform adapter plate, a cubic mirror, a first compound mirror, a second compound mirror and a reflecting mirror, the cubic mirror is arranged at the intersection position of the T-type moving platform adapter plate, the first compound mirror, the second compound mirror and the reflecting mirror are respectively arranged at the three free ends of the T-type moving platform adapter plate; the second calibration device includes a first two-dimensional adjustment frame and a third compound mirror, the third compound mirror is arranged on the first two-dimensional adjustment frame and is coaxial with the first compound mirror in the z-axis direction.

2. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 1, characterized in that: The x-axis laser interferometer measurement device comprises a first lifting platform and an x-axis laser interferometer. The x-axis laser interferometer is arranged on the first lifting platform and is coaxial with the third compound mirror in the x-axis direction.

3. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 2, characterized in that: The x / z axis autocollimation measuring device comprises a second lifting platform and an x / z axis autocollimator. The x / z axis autocollimator is arranged on the second lifting platform and is coaxial with one surface of the cubic mirror in the y axis direction.

4. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 3, characterized in that: The third calibration device includes a second two-dimensional adjustment frame and a fourth compound mirror. The fourth compound mirror is arranged on the second two-dimensional adjustment frame and is coaxial with the second compound mirror in the z-axis direction.

5. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 4, characterized in that: The y-axis laser interferometer measurement device comprises a third lifting platform and a y-axis laser interferometer. The y-axis laser interferometer is arranged on the third lifting platform and is coaxial with the fourth compound mirror in the y-axis direction.

6. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 5, characterized in that: The y-axis autocollimation measuring device comprises a fourth lifting platform and a y-axis autocollimator. The y-axis autocollimator is arranged on the fourth lifting platform and is coaxial with the other surface of the cubic mirror in the x-axis direction.

7. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 6, characterized in that: The z-axis laser interferometer measurement device comprises a fifth lifting platform and a z-axis laser interferometer. The z-axis laser interferometer is arranged on the fifth lifting platform and is coaxial with the reflecting mirror in the y-axis direction.

8. An ultra-high precision three-degree-of-freedom angle measurement method, characterized in that: The ultra-high precision three-degree-of-freedom angle measurement system of claim 7 is used to measure the angle of rotation of the parallel robot around the x, y, and z axes; When measuring the rotation angle around the x-axis, the following steps are included: S1a: adjusting the third compound mirror to be coaxial with the first compound mirror in the z-axis direction through the first two-dimensional adjustment frame, adjusting the height of the x-axis laser interferometer to be coaxial with the third compound mirror in the x-axis direction through the first lifting platform, and adjusting the height of the x / z-axis autocollimator to be coaxial with one surface of the cubic mirror in the y-axis direction through the second lifting platform; S2a: The parallel robot rotates around the x-axis, and the rotation angle α1 of the parallel robot is measured by the cooperation of the x / z-axis autocollimator and the cubic mirror, α1>10", and the displacement L2 of the parallel robot in the z-axis direction is measured by the cooperation of the x-axis laser interferometer, the third compound mirror and the first compound mirror; S3a: Substitute the angle α1 and the displacement L2 into the tangent function formula to calculate the actual value L1' of the corner radius, and subtract it from the ideal value L1 of the corner radius to calculate the error value ΔL1 of the corner radius; S4a: The parallel robot rotates around the x-axis, and the rotation angle α2 of the parallel robot is measured by the cooperation of the x / z-axis autocollimator and the cubic mirror, α2 < 1", and the displacement L3 of the parallel robot in the z-axis direction is measured by the cooperation of the x-axis laser interferometer, the third compound mirror and the first compound mirror; S5a: Substitute the ideal value L1 of the corner radius, the error value ΔL1 of the corner radius, and the displacement L3 into the tangent function formula to calculate the compensated corner α2'; When measuring the rotation angle around the y-axis, the following steps are included: S1b: adjusting the fourth compound mirror to be coaxial with the second compound mirror in the z-axis direction through the second two-dimensional adjustment frame, adjusting the height of the y-axis laser interferometer to be coaxial with the fourth compound mirror in the y-axis direction through the third lifting platform, and adjusting the height of the y-axis autocollimator to be coaxial with the other surface of the cubic mirror in the x-axis direction through the fourth lifting platform; S2b: The parallel robot rotates around the y-axis, and the rotation angle α3 of the parallel robot is measured by the cooperation of the y-axis autocollimator and the cubic mirror, α3>10", and the displacement L5 of the parallel robot in the z-axis direction is measured by the cooperation of the y-axis laser interferometer, the fourth compound mirror and the second compound mirror; S3b: Substitute the angle α3 and the displacement L5 into the tangent function formula to calculate the actual value L4' of the corner radius, and subtract it from the ideal value L4 of the corner radius to calculate the error value ΔL2 of the corner radius; S4b: The parallel robot rotates around the y-axis, and the rotation angle α4 of the parallel robot is measured by the cooperation of the y-axis autocollimator and the cubic mirror, α4 < 1", and the displacement L6 of the parallel robot in the z-axis direction is measured by the cooperation of the y-axis laser interferometer, the fourth compound mirror and the second compound mirror; S5b: Substitute the ideal value L4 of the corner radius, the error value ΔL2 of the corner radius, and the displacement L6 into the tangent function formula to calculate the compensated corner α4'; When measuring the rotation angle around the z-axis, the following steps are included: S1c: adjusting the height of the z-axis laser interferometer to be coaxial with the reflector in the y-axis direction through the fifth lifting platform, and adjusting the height of the x / z-axis autocollimator to be coaxial with one surface of the cubic mirror in the y-axis direction through the second lifting platform; S2c: The parallel robot rotates around the z-axis, and the rotation angle α5 of the parallel robot is measured by the cooperation of the x / z-axis autocollimator and the cubic mirror, α5>10", and the displacement L8 of the parallel robot in the y-axis direction is measured by the cooperation of the z-axis laser interferometer and the reflector; S3c: Substitute the angle α5 and the displacement L8 into the tangent function formula to calculate the actual value L7' of the corner radius, and subtract it from the ideal value L7 of the corner radius to calculate the error value ΔL3 of the corner radius; S4c: The parallel robot rotates around the z-axis, and the rotation angle α6 of the parallel robot is measured by the cooperation of the x / z-axis autocollimator and the cubic mirror, α6 < 1", and the displacement L9 generated by the parallel robot in the y-axis direction is measured by the cooperation of the z-axis laser interferometer and the reflector; S5c: Substitute the ideal value L7 of the corner radius, the error value ΔL3 of the corner radius, and the displacement L9 into the tangent function formula to calculate the compensated corner α6'.

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