Ultrahigh-precision three-degree-of-freedom rotation angle measurement system and measurement method

Abstract

The invention relates to the field of rotation angle measurement, in particular to an ultrahigh-precision three-degree-of-freedom rotation angle measurement system and method, and the system comprises a first calibration device which is disposed on a moving platform of a parallel robot; the x / z-axis auto-collimation measurement device and the second calibration device are arranged on the two sides of the first calibration device in the y-axis direction; the x-axis laser interference measurement device is arranged on one side of the first calibration device along the x-axis direction; the y-axis auto-collimation measuring device and the third calibration device are arranged on the two sides of the first calibration device in the x-axis direction; the y-axis laser interference measurement device is arranged on one side of the first calibration device along the y-axis direction; and the z-axis laser interference measuring device is positioned on one side of the x / z-axis auto-collimation measuring device. According to the invention, measurement precision can be improved and corner coupling measurement can be realized.

Description

Technical Field

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

[0002] In the field of modern precision engineering and scientific research, accurate measurement of angles and coupled measurement of angles play a vital role in many high-end technologies and applications. For the measurement of angles (usually 1" or even smaller angles) in high-precision fields, due to its small measurement range, extremely high requirements are placed on the sensitivity, accuracy and anti-interference ability of the sensor. Accurate measurement of angles is particularly critical for robot motion control, aerospace equipment docking, optical alignment and other fields. At the same time, in parallel robots, flexible robotic arms and complex mechanical structures, the angle 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 method of coupled angles. Therefore, developing an angle measurement method that can achieve high precision and has the ability to measure angle coupling is a hot topic in current technical research.

[0003] The Chinese invention patent with publication number CN107101597A and publication date May 24, 2019, discloses an error calibration method for a rotation angle measurement system, which uses a laser autocollimator, a rotation angle measurement system and a laser autocollimator to synchronously measure the rotation angle of a surface reference part, firstly measures different rotation angles of the same surface group, and then measures all surface groups used in the rotation angle measurement system, and finally obtains an error calibration matrix based on different surface groups and different rotation angles, and provides compensation data for eliminating the rotation angle measurement error. When the rotation angle measurement system performs measurement work, the calibrated measurement error matrix is ​​used to compensate the measurement result in real time according to the selected 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 problem that the measurement accuracy of the laser autocollimator itself is not high, resulting in limited rotation angle measurement accuracy and the inability to measure angle coupling. Summary of the invention

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows: An ultra-high precision three-degree-of-freedom angle measurement system is 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; the ultra-high precision three-degree-of-freedom 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 parallel machine On the moving platform of the person, the x / z-axis autocollimation measuring device and the second calibration device are arranged on both sides of the first calibration device along the y-axis direction, and the x-axis laser interferometer measuring 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 measuring device and the third calibration device are arranged on both sides of the first calibration device along the x-axis direction, and the y-axis laser interferometer measuring 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 measuring device is located on one side of the x / z-axis autocollimation measuring device.

[0005] Furthermore, the first calibration device includes a T-shaped moving platform adapter plate, a cubic mirror, a first compound mirror, a second compound mirror and a reflective mirror. The cubic 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 reflective mirror are respectively arranged at the three free ends of the T-shaped moving platform adapter plate.

[0006] Furthermore, the second calibration device includes a first two-dimensional adjustment frame and a third compound mirror, wherein 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.

[0007] Furthermore, 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.

[0008] Furthermore, the x / z-axis autocollimation measuring device comprises a second lifting platform and an x / z-axis autocollimator, wherein 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.

[0009] Furthermore, the third calibration device includes a second two-dimensional adjustment frame and a fourth compound mirror, wherein 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.

[0010] Furthermore, 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.

[0011] Furthermore, 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.

[0012] Furthermore, the z-axis laser interferometer measurement device includes 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 reflector in the y-axis direction.

[0013] An ultra-high precision three-degree-of-freedom angle measurement method, using the above ultra-high precision three-degree-of-freedom angle measurement system to measure the angle of rotation of a 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'.

[0014] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention combines the advantages of an autocollimator and a laser interferometer, uses a laser interferometer to accurately measure the tiny displacement generated by the rotation of a parallel robot, uses an autocollimator to accurately measure the rotation angle of the parallel robot, and combines the precise data measured by the autocollimator and the laser interferometer to achieve ultra-high-precision angle measurement of three degrees of freedom, and also achieves ultra-high-precision 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 suitable for parallel robots and other high-precision measurement fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 It is a schematic diagram of the structure of the ultra-high precision three-degree-of-freedom angle measurement system according to an embodiment of the invention.

[0016] Figure 2 It is a schematic diagram of the structure of the parallel robot and the first calibration device described in an embodiment of the invention.

[0017] Figure 3 It is a partial schematic diagram of the ultra-high precision three-degree-of-freedom angle measurement system according to the embodiment of the invention measuring the angle of rotation of a parallel robot around the x-axis.

[0018] Figure 4 It is a schematic diagram of the principle of measuring the angle of the parallel robot when it rotates around the x-axis according to the ultra-high precision three-degree-of-freedom angle measurement system described in the embodiment of the invention.

[0019] Figure 5 It is a partial schematic diagram of the ultra-high precision three-degree-of-freedom angle measurement system according to the embodiment of the invention measuring the angle of rotation of a parallel robot around the y-axis.

[0020] Figure 6 It is a schematic diagram of the principle of measuring the angle of the parallel robot according to the embodiment of the invention when the ultra-high precision three-degree-of-freedom angle measurement system rotates around the y-axis.

[0021] Figure 7 It is a partial schematic diagram of the ultra-high precision three-degree-of-freedom angle measurement system according to the embodiment of the invention measuring the angle of rotation of a parallel robot around the z-axis.

[0022] Figure 8 It is a schematic diagram of the principle of measuring the angle of rotation by an ultra-high precision three-degree-of-freedom angle measurement system when the parallel robot rotates around the z-axis according to an embodiment of the invention.

[0023] Explanation of the accompanying drawings: parallel robot 1, moving platform 11, static platform 12, motion chain 13, optical platform 14, x / z-axis autocollimation measuring device 2, second lifting platform 21, x / z-axis autocollimator 22, y-axis autocollimation measuring device 3, fourth lifting platform 31, y-axis autocollimator 32, x-axis laser interferometer measuring device 4, first lifting platform 41, x-axis laser interferometer 42, interferometer 43, y-axis laser interferometer measuring device 5, third lifting platform 51, y-axis laser interferometer 52, interferometer 53, z-axis laser interferometer measuring device 6, fifth lifting platform 61, z-axis laser interferometer 62, interferometer 63, first calibration device 7, T-type moving platform adapter plate 71, cubic mirror 72, first compound mirror 73, second compound mirror 74, reflecting mirror 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 DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0025] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are 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, and therefore cannot be understood as a limitation on 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 indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0027] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0028] In view of the problem that the laser autocollimator itself has low measurement accuracy and cannot measure angle coupling, the present invention proposes an innovative angle measurement method, which is implemented by using an angle measurement system, combining the advantages of an autocollimator and a laser interferometer, overcoming the limitations of traditional measurement methods, thereby achieving angle measurement with higher accuracy and stability and a multi-angle coupling measurement method.

[0029] More specifically, the angle measurement method proposed in the present invention can overcome the problem of limited accuracy of traditional measuring tools by converting the measurement of angle into displacement measurement and combining it with a laser interferometer for precise measurement. The measurement accuracy of the autocollimator is ±0.2" within 20", and the error is ±0.3" within 600". The measurement accuracy is limited in high-precision measurement, while the laser interferometer can reach 0.1μm and has a high accuracy in measuring linear displacement. The present invention combines a laser interferometer with an autocollimator to achieve ultra-high-precision angle measurement.

[0030] The present invention combines the motion relationship of the laser interferometer with the parallel robot to reduce sensitivity to the environment. Especially in the case of a small turning angle, the influence of external factors on the turning angle measurement accuracy can be overcome by displacement measurement, thereby achieving more stable measurement.

[0031] The present invention can also realize the measurement of the angular coupling when the parallel robot performs multi-degree-of-freedom motion by combining the laser interferometer with the autocollimator.

[0032] The following will refer to Figure 1-Figure 8 The invention is described in detail with reference to the embodiments.

[0033] like Figure 1-8 As shown, the vertical movement direction of the parallel robot 1 is taken as the z-axis, the horizontal movement direction of the parallel robot 1 is taken as the x-axis and the y-axis, and the rotation of the parallel robot 1 around the x-axis, y-axis and z-axis are respectively referred to as three degrees of freedom. The ultra-high precision three-degree-of-freedom angle measurement system provided by the embodiment of the invention can measure the rotation angle of any one degree of freedom of the parallel robot 1 separately, and can also measure the rotation angle of the three degrees of freedom of the parallel robot 1 simultaneously.

[0034] The parallel robot 1 includes a moving platform 11 , a static platform 12 and a kinematic chain 13 . The static platform 12 is mounted on an optical platform 14 by means of a threaded connection. The kinematic chain 13 is connected between the static platform 12 and the moving platform 11 .

[0035] The ultra-high precision three-degree-of-freedom angle measurement system comprises an x / z-axis autocollimation measurement device 2, a y-axis autocollimation measurement device 3, an x-axis laser interferometer measurement device 4, a y-axis laser interferometer measurement device 5, a z-axis laser interferometer 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 a 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, the x-axis laser interferometer 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, the y-axis laser interferometer 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 interferometer measurement device 6 is located on one side of the x / z-axis autocollimation measurement device 2.

[0036] The first calibration device 7 includes a T-shaped moving platform adapter plate 71, a cubic mirror 72, a first compound mirror 73, a second compound mirror 74 and a reflector 75. The T-shaped moving platform adapter plate 71 is installed on the moving platform 11 by a threaded connection. The cubic 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, and the reflector 75 is arranged on 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 reflector 75 are respectively positioned by the bosses at the three free ends of the T-shaped moving platform adapter plate 71, and are glued to the T-shaped moving platform adapter plate 71.

[0037] 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 in a threaded connection manner.

[0038] 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 in a threaded connection manner.

[0039] 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 cubic mirror 72 in the y-axis direction. The surface of the cubic mirror 72 is the surface facing the x / z-axis autocollimator 22. The second lifting platform 21 is installed on the optical platform 14 in a threaded connection manner.

[0040] 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 cubic mirror 72 in the x-axis direction. This surface of the cubic mirror 72 is the surface facing the y-axis autocollimator 32. The fourth lifting platform 31 is installed on the optical platform 14 in a threaded connection manner.

[0041] 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 in a threaded connection manner.

[0042] The y-axis laser interferometer measuring device 5 includes a third lifting platform 51 and a y-axis laser interferometer 52. The y-axis laser interferometer 52 is arranged 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 installed on the optical platform 14 in a threaded connection manner.

[0043] The z-axis laser interferometer measuring device 6 includes a fifth lifting platform 61 and a z-axis laser interferometer 62. The z-axis laser interferometer 62 is arranged on the fifth lifting platform 61 and is coaxial with the reflector 75 in the y-axis direction. The fifth lifting platform 61 is installed on the optical platform 14 in a threaded connection manner.

[0044] For the measurement of the rotation angle of the parallel robot 1 around the x-axis, the basic measurement principle is: When the parallel robot 1 rotates around the x-axis, since the angle of rotation 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 accuracy and can measure this small displacement. By designing the length of the T-type moving platform adapter plate 71, a small angle of rotation can produce a larger displacement in the z-axis direction, thereby meeting the measurement accuracy of the laser interferometer. Since the T-type moving platform adapter plate 71 will cause certain errors during manufacturing and assembly, the actual length of the T-type moving platform adapter plate 71 may have a certain error from the ideal value of the design, which in turn causes an error in the corner radius, so the error can be calibrated by the x / z-axis autocollimator 22 and the cubic mirror 72. Although the autocollimator has a certain error in the accuracy of measuring the angle, by allowing the parallel robot 1 to rotate a relatively large angle around the x-axis, the value measured by the autocollimator when measuring a larger angle (greater than 10") is accurate (because the error is about 0.2" and can be ignored), thereby obtaining more accurate measurement data. In this process, a certain vertical displacement will be generated in the z-axis direction, and the vertical displacement (whose size is within the measurement accuracy of the laser interferometer) can be accurately measured by the x-axis laser interferometer 42. By combining the actual angle measured by the x / z-axis autocollimator 22 with the vertical displacement measured by the x-axis laser interferometer 42, the actual corner radius can be accurately calculated, and the difference between the actual corner radius and the ideal corner radius is the error value of the corner radius. When measuring the corner subsequently, the error value of the corner radius can be compensated in the actual angle to obtain the compensated corner value.

[0045] The principle of measuring the rotation angle of the parallel robot 1 around the y-axis and the z-axis is the same as the principle of measuring the rotation around the x-axis.

[0046] In order to make the technical solution, measurement principle and advantages of the present invention clearer, the detailed description of the technical solution of the present invention is introduced through the following content: 1. X-axis rotation angle measurement When the kinematic chain 13 drives the moving platform 11 to rotate around the x-axis, the angle measurement includes the following steps: S1a: Adjust the position of the third compound mirror 82 through the first two-dimensional adjustment frame 81, so that the third compound mirror 82 is 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, so that the interferometer 43 of the x-axis laser interferometer 42 is coaxial with the third compound mirror 82 in the x-axis direction, and adjust the height of the x / z-axis autocollimator 22 through the second lifting platform 21, so that the x / z-axis autocollimator 22 is adjusted to be coaxial with one surface of the cubic mirror 72 in the y-axis direction.

[0047] When the third compound mirror 82 is coaxial with the first compound mirror 73 in the z-axis direction and the interferometer 43 of the x-axis laser interferometer 42 is coaxial with the third compound mirror 82 in the x-axis direction, the line connecting the first compound mirror 73, the third compound mirror 82 and the interferometer 43 forms a right triangle.

[0048] S2a: The parallel robot 1 rotates around the x-axis, and the rotation angle α1 of the parallel robot is measured by the cooperation between the x / z-axis autocollimator 22 and the cubic mirror 72, where α1>10", and the displacement L2 of the parallel robot in the z-axis direction is measured by the cooperation between the x-axis laser interferometer 42 and the third compound mirror 82 and the first compound mirror 73.

[0049] 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.

[0050] S4a: The parallel robot 1 rotates around the x-axis, and the rotation angle α2 of the parallel robot is measured by the cooperation between the x / z-axis autocollimator 22 and the cubic mirror 72, α2<1", and the displacement L3 of the parallel robot in the z-axis direction is measured by the cooperation between the x-axis laser interferometer 42 and the third compound mirror 82 and the first compound mirror 73.

[0051] 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'.

[0052] The first composite mirror 73 is positioned by the boss of the T-shaped moving platform adapter plate 71. Figure 4 The 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 through the design dimensions of the T-shaped moving platform adapter plate 71. This distance is also the rotation radius L1 around the x-axis. However, this rotation radius is an ideal value. There must be errors in the installation and assembly process 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.

[0053] In order to calculate the error of the rotation radius, the present invention uses the x / z axis autocollimator 22 and the cubic mirror 72 to calibrate the error, and drives the moving platform 11 to rotate a relatively large angle around the x axis through the motion chain 13, so that its rotation angle is α1, thereby obtaining more accurate autocollimator measurement data. In this process, a certain displacement will occur in the z axis direction. Since the rotation angle is small (about 10"), the arc displacement can be mathematically approximated as a linear displacement AB, i.e., L2. The displacement L2 can be measured by the x-axis laser interferometer 42 (the displacement is within the measurement accuracy of the laser interferometer), and the value is also accurate. Substituting the displacement L2 and the rotation angle α1 into the formula L2=L1'×tanα1, the actual value L1' of the corner radius can be calculated. In this way, the error value ΔL1 of the corner radius can be calculated, i.e., ΔL1=L1-L1'. Then, the moving platform 11 is driven to rotate around the x-axis by a relatively small angle (i.e., the rotation angle before compensation) through the motion chain 13, and its rotation angle is α2. At this time, an arc displacement will be generated in the z-axis direction. , also because the rotation angle is small (less than 1"), the arc displacement It is approximately a linear displacement A'B', that is, L3. The displacement L3 can be measured by the x-axis laser interferometer 42, and the value is also accurate. The displacement L3, the ideal value L1 of the rotation radius, and the error value ΔL1 of the corner radius are substituted into the formula L3=(L1+ΔL1)×tanα2'. In this way, the size of the angle α2' can be calibrated, which is the value after compensation of the rotation angle around the x-axis. The compensation value is Δα1=α2-α2'.

[0054] (ii) Y-axis rotation angle measurement When the kinematic chain 13 drives the moving platform 11 to rotate around the y-axis, the angle measurement includes the following steps: 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, and adjust the height of the y-axis autocollimator 32 to be coaxial with the other surface of the cubic mirror 72 in the x-axis direction through the fourth lifting platform 31.

[0055] S2b: The parallel robot 1 rotates around the y-axis, and the rotation angle α3 of the parallel robot is measured by the cooperation between the y-axis autocollimator 32 and the cubic mirror 72, α3>10", and the displacement L5 of the parallel robot in the z-axis direction is measured by the cooperation between the y-axis laser interferometer 52 and the fourth compound mirror 92 and the second compound mirror 74.

[0056] 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.

[0057] S4b: The parallel robot 1 rotates around the y-axis, and the rotation angle α4 of the parallel robot is measured by the cooperation between the y-axis autocollimator 32 and the cubic mirror 72, α4 < 1", and the displacement L6 of the parallel robot in the z-axis direction is measured by the cooperation between the y-axis laser interferometer 52 and the fourth compound mirror 92 and the second compound mirror 74.

[0058] 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'.

[0059] The second composite mirror 74 is positioned 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 through the design dimensions of the T-shaped moving platform adapter plate 71. This distance is also the rotation radius L4 around the x-axis. However, this rotation radius is an ideal value. There must be errors in the installation and assembly process 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.

[0060] In order to calculate the error of the rotation radius, the present invention uses the y-axis autocollimator 32 and the cubic mirror 72 to calibrate the error, and drives the moving platform 11 to rotate around the y-axis by a relatively large angle through the kinematic chain 13, so that its rotation angle is α3, thereby obtaining more accurate autocollimator measurement data. In this process, a certain displacement will occur in the z-axis direction. Since the rotation angle is small (about 10"), the arc displacement can be mathematically approximated as a linear displacement EF, i.e., L5. The displacement L5 can be measured by the y-axis laser interferometer 52 (the displacement is within the measurement accuracy of the laser interferometer), and the value is also accurate. Substituting the displacement L5 and the rotation angle α3 into the formula L5=L4'×tanα3, the actual value L4' of the corner radius can be calculated. In this way, the error value ΔL2 of the corner radius can be calculated, i.e., ΔL2=L4-L4'. Then, the moving platform 11 is driven to rotate around the y-axis by a relatively small angle (i.e., the rotation angle before compensation) through the motion chain 13, and its rotation angle is α4. At this time, an arc displacement will be generated in the z-axis direction. , also because the rotation angle is small (less than 1"), the arc displacement It is approximately a linear displacement E'F', that is, L6. The displacement L6 can be measured by the y-axis laser interferometer 52, and the value is also accurate. The displacement L6, the ideal value of the rotation radius L4, and the error value of the corner radius ΔL2 are substituted into the formula L6=(L4+ΔL2)×tanα4'. In this way, the size of the angle α4' can be calibrated, which is the value after compensation of the rotation angle around the y-axis. The compensation value is Δα2=α4-α4'.

[0061] 3. Z-axis rotation angle measurement When the kinematic chain 13 drives the moving platform 11 to rotate around the z-axis, the angle measurement includes the following steps: S1c: The height of the z-axis laser interferometer 62 is adjusted to be coaxial with the reflection mirror 75 in the y-axis direction by the fifth lifting platform 61 .

[0062] S2c: The parallel robot 1 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 22 and the cubic mirror 72, α5>10", and the displacement L8 generated by the parallel robot in the y-axis direction is measured by the cooperation of the z-axis laser interferometer 62 and the reflector 75.

[0063] 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.

[0064] S4c: The parallel robot 1 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 22 and the cubic mirror 72, 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 62 and the reflector 75.

[0065] 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'.

[0066] The position of the reflector 75 is positioned by the boss of the T-shaped moving platform adapter plate 71. Figure 8 The distance between the center point C of the middle reflector 75 and the center point O of the T-shaped moving platform adapter plate 71 can be obtained through the design dimensions of the T-shaped moving platform adapter plate 71. This distance is also the rotation radius L7 around the z-axis. However, this rotation radius is an ideal value. There will definitely be errors during the installation and assembly process 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.

[0067] In order to calculate the error of the rotation radius, the present invention uses the x / z axis autocollimator 22 and the cubic mirror 72 to calibrate the error, and drives the moving platform 11 to rotate around the z axis by a relatively large angle through the motion chain 13, so that its rotation angle is α5, thereby obtaining more accurate autocollimator measurement data. In this process, a certain displacement will occur in the y-axis direction. Since the rotation angle is small (about 10"), the arc displacement can be mathematically approximated as a linear displacement CD, i.e., L8. The displacement L8 can be measured by the z-axis laser interferometer 62 (the displacement is within the measurement accuracy of the laser interferometer), and the value is also accurate. Substituting the displacement L8 and the rotation angle α5 into the formula L8=L7'×tanα5, the actual value L7' of the corner radius can be calculated. In this way, the error value ΔL3 of the corner radius can be calculated, i.e., ΔL3=L7-L7'. Then, the moving platform 11 is driven to rotate around the y-axis by a relatively small angle (i.e., the rotation angle before compensation) through the motion chain 13, and its rotation angle is set to α6. At this time, an arc displacement will be generated in the y-axis direction. , also because the rotation angle is small (less than 1"), the arc displacement It is approximately a linear displacement C'D', that is, L9. The displacement L9 can be measured by the z-axis laser interferometer 62, and the value is also accurate. The displacement L9, the ideal value of the rotation radius L7, and the error value of the corner radius ΔL3 are substituted into the formula L9=(L7+ΔL3)×tanα6'. In this way, the size of the angle α6' can be calibrated, which is the value after compensation of the rotation angle around the x-axis. The compensation value is Δα3=α6-α6'.

[0068] When the parallel robot 1 performs a single degree of freedom motion (rotates around any one of the x, y, and z axes), the present invention can measure the angle of the single degree of freedom motion of the parallel robot 1 separately. When the parallel robot 1 performs a coupled motion of multiple degrees of freedom (rotates around the x, y, and z axes at the same time), the present invention can simultaneously measure the angles of the three degrees of freedom motion, that is, realize angle coupling measurement.

[0069] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0070] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in 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 a 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.

2. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 1, characterized in that: The first calibration device includes a T-shaped moving platform adapter plate, a cubic mirror, a first compound mirror, a second compound mirror and a reflective mirror. The cubic 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 reflective mirror are respectively arranged at the three free ends of the T-shaped moving platform adapter plate.

3. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 2, characterized in that: 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.

4. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 3, 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.

5. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 4, 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.

6. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 5, 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.

7. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 6, 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.

8. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 7, 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.

9. The ultra-high precision three-degree-of-freedom angle measurement system according to claim 8, 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.

10. 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 9 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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