High-precision rotation angular velocity and angular acceleration detection method based on laser tracker

Abstract

The invention relates to a high-precision rotation angular velocity and angular acceleration detection method based on a laser tracker, and relates to the technical field of optical detection.The detection method comprises the steps that the laser tracker is fixed to a supporting tripod, and an SCE cat eye target ball and a target seat are connected with a to-be-detected slewing mechanism; when the to-be-detected slewing mechanism moves, the laser tracker captures discrete track points of the whole stroke; the motion trails of an SCE cat eye target ball and a target seat are fitted according to the space sampling points, a rotation center is constructed, data are processed through Matlab, and the angular speed and the angular acceleration of a rotation mechanism are obtained. According to the detection method, the application range of the laser tracker is further expanded, and high-precision speed measurement of the low-speed swing mechanism is achieved. While the measurement precision is improved, the mechanism to be measured is not greatly modified, and a new and convenient angular velocity and angular acceleration measurement scheme is provided.

Description

Technical Field

[0001] The present invention relates to the field of optical detection technology, and in particular to a method for detecting high-precision rotational angular velocity and angular acceleration based on a laser tracker. Background Art

[0002] As a universal measuring device, laser trackers are increasingly used in various stages of scientific research, production and construction. Their non-contact measurement method not only improves the measurement accuracy, but also improves their environmental applicability. Usually, laser trackers are mostly used to detect mechanical tolerances such as geometric features and shape and position features of workpieces. During the measurement process, since the target ball adopts a corner reflector structure, its light receiving angle is limited, making it difficult to apply it to the measurement of rotational trajectories. With the continuous development of aviation and aerospace technology, the requirements for the motion accuracy of rotary mechanisms are getting higher and higher. Traditional speed measurement methods often use inertial gyroscopes or mechanical and electromagnetic induction sensors to achieve indirect measurement of angular velocity and angular acceleration with the help of Coriolis force in rotary motion.

[0003] The Chinese patent document with publication number 110736454A, publication date 2020.01.31, and titled "Device and measurement method suitable for angular velocity measurement" relies on a vibrating string-beam structure to construct a rotating structure, and a fixed frequency vibration is generated inside the structure through an exciter. When the rotating structure rotates at a certain angular velocity, the amplitude and vibration mode of the vibrating string-beam structure change under the action of the Coriolis force, and the angular velocity of the rotating structure is indirectly obtained by measuring this change. This method aims to use a vibrating string-beam structure to construct a resonant gyroscope, which can measure the angular velocity of the rotating mechanism, but it needs to be vibrated by an exciter inside, and the device is only applicable to the working condition where the mass body does not produce high-speed rotation and is initially fixedly connected to the rotating body to be detected. In addition, during the movement of the rotating mechanism to be measured, the error introduced by the disturbance generated by itself is difficult to eliminate by this device.

[0004] A Chinese patent document with the publication number 116500540A, publication date of July 28, 2023, and title of "An Angular Velocity Vector Measurement Device and Method with Super-Resolution" allows the rotation axis of the object to be measured to deviate from the center of the light source and there is external jitter. This method tracks the rotational motion of the mechanism to be measured by rotating the coherent structure of the light source. Based on the laser Doppler effect, a polarizer is used to directionally select vector light with a certain high-order polarization characteristic. When the rotating light source rotates in the same direction as the rotating mechanism to be measured, the light beam undergoes redshift; when they rotate in opposite directions, the light beam undergoes blueshift, so that the magnitude of the angular velocity can be determined simultaneously. With the polarization selection of polarizers with different polarization directions in two beams of light, the detection light generates a Doppler phase shift to determine the direction of motion, and then the direction of the angular velocity vector can be directly measured. This method has high measurement accuracy, and at the same time, by flexibly controlling the beat frequency of the detector, high-precision measurement in a large range from low speed to high speed is achieved, and the adaptability is better. However, the prerequisite for its measurement is that the center of the light source and the axis center of the rotating mechanism to be measured need to be mutually aligned. Within a certain limit, the greater the offset between the center of the light source and the axis of the target object, the more dispersed the Doppler frequency shift caused, and even submerged in noise, resulting in inability to measure. Summary of the Invention

[0005] The present invention aims to solve the technical problem of high-precision measurement of the angular velocity and angular acceleration of a rotating mechanism in the prior art, and provides a detection method for high-precision rotational angular velocity and angular acceleration based on a laser tracker.

[0006] To solve the above technical problems, the technical solution of the present invention is specifically as follows:

[0007] A detection method for high-precision rotational angular velocity and angular acceleration based on a laser tracker includes the following steps:

[0008] Step 1: The laser tracker is fixed on a support tripod, and the SCE cat's-eye target ball and target seat are connected to the rotating mechanism to be measured; the SCE cat's-eye target ball and target seat are used to receive the light beam of the laser tracker and reflect it back to the light receiving port of the laser tracker, so that the two light beams generate an interference effect;

[0009] Step 2: While the rotating mechanism to be measured is moving, the laser tracker captures discrete trajectory points for the full stroke;

[0010] Step 3: Fit the motion trajectory of the SCE cat's-eye target ball and target seat according to the spatial sampling points, construct the rotation center, and use Matlab to process the data to obtain the angular velocity and angular acceleration of the rotating mechanism to be measured.

[0011] In the above technical solution, step 2 is specifically:

[0012] When the rotary mechanism to be tested moves, the motion trajectory of the SCE cat's eye target ball and the target seat is a standard arc. By setting the time interval sampling, the laser tracker can capture the discrete trajectory points of the whole stroke and obtain the coordinates of several trajectory points in space.

[0013] In the above technical solution, the time interval set during sampling is 1 ms.

[0014] In the above technical solution, step 3 is specifically as follows:

[0015] The laser tracker is used to achieve precise measurement points. With its internal timing trigger function, the sampling time interval is set. During the movement of the rotary mechanism to be measured, continuous sampling is performed at the same time interval to measure the discrete motion trajectory.

[0016] According to the motion trajectory, the rotation center of the rotary mechanism to be tested is fitted;

[0017] Data processing: construct several vectors pointing from the center of rotation to the trajectory points, calculate the angular displacement per unit time through the normalized scalar product, and then obtain the magnitude of the angular velocity and angular acceleration.

[0018] In the above technical solution, the specific steps of data processing in step 3 are:

[0019] The rotary mechanism to be measured makes an angular displacement from trajectory point A to trajectory point B. After least square fitting, the centroid of several trajectory points is point O, and a measurement coordinate system is established with O as the origin of the coordinate system.

[0020] Construct a vector based on the coordinates of the center of mass O and the coordinates of points A and B Vector After unitization, use Get vector The cosine value of the angular displacement between time intervals is used to inversely solve the angular displacement using the arccosθ function, and the angular velocity at the time interval is obtained.

[0021] The direction of the velocity vector is determined based on the vector product of the two vectors; in the process of moving from trajectory point A to trajectory point B, the vector The direction of the vector product satisfies the right-hand rule. By determining the direction of the vector product, the direction of the velocity vector can be determined. By deriving the angular velocity formula, the angular acceleration can be solved.

[0022] In the above technical solution, in the SCE cat's eye target ball and the target holder, the SCE cat's eye target ball adopts a Luneburg lens structure.

[0023] The present invention has the following beneficial effects:

[0024] The high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker according to the present invention further expands the application range of the laser tracker and realizes high-precision speed measurement of a low-speed rotating mechanism. While improving the measurement accuracy, it does not require major modifications to the mechanism under test, providing a new and convenient angular velocity and angular acceleration measurement solution.

[0025] The measurement accuracy analysis when applying the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker according to the present invention is as follows: The dispersion accuracy RMS of the sampling point cloud of the laser tracker is 0.02, which is the measurement system error; the measurement accuracy is inversely proportional to the rotation diameter. Taking a sampling rate of 1 s as an example, the accuracy transfer function is When the rotation diameter is 100 mm, the measurement accuracy is 0.0229° / s. It should be noted that limited by the movement speed of the azimuth axis and elevation axis of the laser tracker (the fastest target displacement speed is 4 m / s), the method of the present invention is only applicable to high-precision speed measurement of low-speed rotating mechanisms. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0027] Figure 1 Schematic diagram of applying a laser tracker to measure the angular velocity and angular acceleration of a turntable by the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker according to the present invention.

[0028] Figure 2 Schematic diagram of applying a laser tracker to measure the angular velocity and angular acceleration of the blades of a low-speed rotating mechanism by the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker according to the present invention.

[0029] Figure 3 Schematic diagram of the measurement principle of the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker according to the present invention.

[0030] Figure 4 Schematic diagram of the data processing principle of the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker according to the present invention.

[0031] Figure 5 In (a) is the measured angular acceleration curve of the turntable; (b) is the measured angular velocity curve of the turntable.

[0032] The reference signs in the drawings are shown as:

[0033] 1 - Laser tracker, 2 - Support tripod; 3 - Rotary mechanism under test; 4 - Motion trajectory; 5 - Rotation center; 6 - SCE cat's eye target ball and target seat; 7 - Propeller. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The inventive concept of the present invention is as follows:

[0035] The measurement principle of the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker in the present invention is: measuring the motion trajectory points through a laser tracker, fitting the centroid according to the trajectory points, setting the same time interval for sampling by means of a timing function, and calculating the angular velocity and angular acceleration by the method of point sampling and timing.

[0036] The high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker in the present invention realizes the coordinate capture of the entire trajectory with the help of an SCE cat's eye target ball (luneberg lens) and a target seat, sets the sampling rate through the sampling interval, combines the operation and processing in the vector space, and calculates the instantaneous angular velocity and angular acceleration of the slewing mechanism by the method of point sampling and timing.

[0037] The high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker in the present invention provides a new non-contact measurement means without large-scale modification of the mechanism to be measured. Compared with the traditional measurement methods, the detection method of the present invention can make the laser tracker measurement have a higher sampling rate (the highest sampling trigger interval is 1 ms), a higher measurement point accuracy (the point cloud sampling accuracy RMS can reach 0.02 mm), and can provide a measurement range of 0 - 15 m according to the actual size of the structure to be measured, with higher applicability.

[0038] The following will describe the present invention in detail with reference to the accompanying drawings.

[0039] The measurement system applicable to the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker in the present invention, as Figure 1 shown, includes: a laser tracker 1, a supporting tripod 2, a slewing mechanism 3 to be measured, and an SCE cat's eye target ball and target seat 6. Figure 1 The slewing mechanism 3 to be measured shown is a turntable or a low-speed slewing mechanism.

[0040] The laser tracker 1 is fixed on the supporting tripod 2 through an adapter structure and can rotate in two degrees of freedom (the azimuth angle of the instrument is 0° to 360°; the elevation angle is ≥ 130°); the slewing mechanism 3 to be measured is placed within the measurement space range of the laser tracker 1; the SCE cat's eye target ball and target seat 6 are placed on the slewing mechanism 3 to be measured, and during the entire movement process of the slewing mechanism, it is necessary to always keep the measurement optical path unobstructed to ensure that the laser emitted by the laser tracker 1 can continuously irradiate the SCE cat's eye target ball and target seat 6.

[0041] See Figure 2, the SCE cat's-eye target ball and target seat 6 are used to receive the beam of the laser tracker 1 and reflect it back to the light-receiving port of the laser tracker 1, so that the two beams of light produce an interference effect. When the SCE cat's-eye target ball and target seat 6 are placed on the rotary mechanism 3 to be measured, they are fixed by means of dotting, and are pasted on the upper part of the propeller 7 to rotate with it, ensuring that during the movement of the rotary mechanism 3 to be measured, the SCE cat's-eye target ball and target seat 6 are not thrown off under the action of centrifugal force. When the trajectory measurement of the full stroke is realized through the SCE cat's-eye target ball and target seat 6, the motion trajectory 4 is a standard arc. By setting the sampling time interval to 1 ms, the sampling rate is maximally increased, and the coordinates of several trajectory points in space are obtained.

[0042] In addition, since the SCE cat's-eye target ball adopts a Luneburg lens structure, it can emit the incident light waves at various angles in parallel, and it is a wide-angle omnidirectional reflector with an extremely wide coverage angle of the secondary radiation direction. Due to the extremely wide secondary radiation angle, the SCE cat's-eye target ball can receive and reflect the beam at any position of the motion trajectory 4, that is, the light is continuously received throughout the full stroke.

[0043] The measurement principle of the high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker of the present invention is as follows:

[0044] Precise measurement points are realized through the laser tracker 1. With the internal timing trigger function, the sampling time interval is set to 1 ms. During the movement of the rotary mechanism 3 to be measured, continuous sampling is carried out at the same time interval, and the discretized motion trajectory 4 is measured. According to its motion trajectory 4, the rotation center 5 (center of mass) of the rotary mechanism 3 to be measured is fitted. With the help of the Matlab program, several vectors pointing from the rotation center 5 to the trajectory points are constructed, and the angular displacement per unit time is calculated through the normalized dot product, and then the magnitudes of the angular velocity and angular acceleration are obtained. For the direction discrimination of the velocity vector, the cross product of two adjacent vectors is used to construct the normal vector of the motion plane, and the direction of the velocity vector is judged through the direction of the normal vector.

[0045] The high-precision rotational angular velocity and angular acceleration detection method based on a laser tracker of the present invention includes the following steps:

[0046] The laser tracker 1 is fixed on the support tripod 2, and the SCE cat's-eye target ball and target seat 6 are connected to the rotary mechanism 3 to be measured;

[0047] While the rotary mechanism 3 to be measured is moving, the laser tracker 1 captures the discrete trajectory points of the full stroke;

[0048] According to the spatial sampling points, the motion trajectory 4 of the SCE cat's-eye target ball and target seat 6 is fitted, the rotation center 5 is constructed, and the Matlab is used to process the data to obtain the angular velocity and angular acceleration of the rotary mechanism 3 to be measured.

[0049] like Figure 3 As shown in the figure, when using Matlab to process data, the coordinates of the center of mass of the fitted trajectory and the coordinates of the trajectory points are used to construct several trajectory vectors pointing from the center of mass point to the capture point. After normalization, the cosine value of the angle between two adjacent trajectory points is obtained by the vector dot product, and then the angular displacement is obtained by the arccosine function. Combined with the sampling interval of 1ms, its instantaneous angular velocity and angular acceleration can be obtained. The turntable measured angular acceleration curve and the turntable measured angular velocity curve are shown in Figure 5 shown.

[0050] Specifically, the data processing method of the high-precision rotation angular velocity and angular acceleration detection method based on the laser tracker of the present invention is realized by the operation of the vector space. Figure 4 As shown in the figure, the rotary mechanism 3 to be measured makes an angular displacement from trajectory point A to trajectory point B. After least square fitting, the centroid of several trajectory points is point O, and a measurement coordinate system is established with O as the origin of the coordinates. The vector is constructed based on the coordinates of the centroid O and the coordinates of trajectory points A and B. Vector After unitization, The cosine value of the angular displacement between the two vectors is obtained, and the angular displacement is inversely solved by the arccosθ function to obtain the angular velocity at a 1ms interval; the direction of the velocity vector is determined based on the vector product of the two vectors, such as Figure 4 As shown in the figure, in the process of moving from trajectory point A to trajectory point B, the two vectors The direction of the vector product satisfies the right-hand rule. By determining the direction of the vector product, the direction of the velocity vector can be determined. By differentiating the angular velocity formula, the angular acceleration can be solved.

[0051] Experiments show that the detection method of the present invention is practical and effective.

[0052] The detection method of the present invention is used to measure the space XX target tracking and aiming system. The angular velocity and angular acceleration in different modes such as along the track and against the track are measured around the mechanism to be tested, and compared with the control input. The measurement results show that the angular velocity and angular acceleration curves are basically consistent with the input control end, and the control accuracy of the tracking and aiming system meets the index requirements.

[0053] The detection method of the present invention is used to measure the rotational angular velocity and angular acceleration of the turntable and the blade of the low-speed rotary mechanism. The results are consistent with the control input end data, indicating that the method is feasible.

[0054] The high-precision rotational angular velocity and angular acceleration detection method based on the laser tracker of the present invention further expands the application scope of the laser tracker and realizes high-precision speed measurement of low-speed rotary mechanisms. While improving the measurement accuracy, it does not require substantial modification of the mechanism to be measured, providing a new and convenient angular velocity and angular acceleration measurement solution.

[0055] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A detection method for high-precision rotational angular velocity and angular acceleration based on a laser tracker, characterized in that It includes the following steps: Step 1: The laser tracker (1) is fixed on the supporting tripod (2), and the SCE cat's-eye target ball and target seat (6) are connected to the rotary mechanism (3) to be measured; the SCE cat's-eye target ball and target seat (6) are used to receive the beam of the laser tracker (1) and reflect it back to the light receiving port of the laser tracker (1), so that the two beams produce an interference effect; Step 2: While the rotary mechanism (3) to be measured is moving, the laser tracker (1) captures discrete trajectory points over the full stroke; Step 3: Fit the motion trajectory (4) of the SCE cat's-eye target ball and target seat (6) based on the spatial sampling points, construct the rotation center (5), and use Matlab to process the data to obtain the angular velocity and angular acceleration of the rotary mechanism (3) to be measured.

2. The detection method of high-precision rotational angular velocity and angular acceleration based on a laser tracker according to claim 1, wherein Specifically, Step 2 is as follows: When the rotary mechanism (3) to be measured is moving, the motion trajectory (4) of the SCE cat's-eye target ball and target seat (6) is a standard arc. By setting a time interval for sampling, the laser tracker (1) captures discrete trajectory points over the full stroke and obtains the coordinates of several trajectory points in space.

3. The detection method of high-precision rotational angular velocity and angular acceleration based on a laser tracker according to claim 2, characterized in that, The set time interval for sampling is 1 ms.

4. The detection method of high-precision rotational angular velocity and angular acceleration based on a laser tracker according to claim 1, wherein Specifically, Step 3 is as follows: The laser tracker (1) is used to achieve precise measurement points, and with the internal timing trigger function, the sampling time interval is set. During the movement of the rotary mechanism (3) to be measured, continuous sampling is carried out at the same time interval to measure the discretized motion trajectory (4); Based on the motion trajectory (4), the rotation center (5) of the rotary mechanism (3) to be measured is fitted; Data processing; construct several vectors pointing from the rotation center (5) point to the trajectory points, and calculate the angular displacement per unit time through the normalized dot product, and then obtain the magnitudes of the angular velocity and angular acceleration.

5. The detection method of high-precision rotational angular velocity and angular acceleration based on a laser tracker according to claim 4, characterized in that, The specific steps of data processing in Step 3 are as follows: The rotary mechanism (3) to be measured makes an angular displacement from trajectory point A to trajectory point B. After least-squares fitting, the centroid of several trajectory points is point O, and a measurement coordinate system is established with O as the coordinate origin; Construct vectors based on the coordinates of the centroid O and the coordinates of points A and B For the vector After unitization, use to obtain the vector the cosine value of the angular displacement between them, and combine with the arccosθ function to inversely solve the angular displacement to obtain the angular velocity within the time interval; The direction judgment of the velocity vector is obtained based on the vector product of two vectors; during the movement from the trajectory point A to the trajectory point B, the direction of the vector product of the vector satisfies the right-hand rule, and the direction of the velocity vector is judged by judging the direction of the vector product; by differentiating the angular velocity formula, the angular acceleration is calculated.

6. The method for detecting high-precision rotational angular velocity and angular acceleration based on a laser tracker according to any one of claims 1-5, characterized in that, In the SCE cat's-eye target ball and target seat (6), the SCE cat's-eye target ball adopts a Luneburg lens structure.

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