A multi-station laser tracking system calibration device and measurement method

Abstract

The present invention discloses a multi-station laser tracking system calibration device and measurement method. The rotation plane of a high-precision turntable faces the multi-station laser tracker, and the high-precision turntable is controlled to drive the laser tracker target balls at both ends of the club to rotate. In vertical and horizontal postures, each laser tracker measures the absolute distance from the laser tracker target ball at each position to itself, and then combines the center distance of the two balls at both ends of the club to obtain the center coordinates of the laser tracker; the laser tracker target ball is placed at the measured position, and the absolute distance from each laser tracker to the laser tracker target ball is detected, and the coordinates of the measured position are obtained by combining the center coordinates of the laser tracker. The present invention effectively eliminates the pitch and horizontal movement rotation encoder errors in the laser tracker, and only uses the absolute high-precision interference ranging function of the laser tracker, thereby improving the measurement accuracy, having a simple structure, and being easy to operate.

Description

Technical Field

[0001] The invention relates to a detection device and a detection method, and in particular to a multi-station laser tracking system calibration device and a calibration measurement method. Background Art

[0002] With the development of measurement technology in intelligent manufacturing, the requirements for spatial coordinate measurement accuracy in large-scale measurement processes are becoming increasingly higher. In particular, coordinate measurement is a commonly used method for geometric dimension detection in robot positioning and large aircraft measurement.

[0003] Laser trackers are commonly used coordinate measuring instruments with large measurement ranges and high measurement accuracy. However, single-station laser tracking has difficulties measuring the blind area on the back of the sample, and the measurement process is affected by rotational encoding errors, making it difficult to achieve high-precision measurement requirements in some large-scale, high-precision measurement applications. Multi-station laser tracking measurement systems can effectively solve these problems by utilizing multiple-station laser trackers, and are therefore widely used in aerospace and precision large-scale measurement. Compared to single-station systems, multi-station systems can solve the measurement blind area problem caused by obstruction of the measured sample. However, the unification of coordinates and calibration of the overall measurement accuracy of multi-station laser tracking measurement systems have always been difficult to solve. Summary of the Invention

[0004] In order to solve the problems of spatial coordinate unification and precision calibration in a multi-station laser tracking measurement system, the present invention provides a multi-station laser tracking system calibration device and a calibration measurement method.

[0005] The technical solution adopted in the present invention is as follows:

[0006] 1. A multi-station laser tracking system calibration device:

[0007] The device includes a first laser tracker, a second laser tracker, a third laser tracker, a high-precision turntable, a bat, a first laser tracker target ball, a second laser tracker target ball, a fixture, and a turntable tripod. The first laser tracker, the second laser tracker, and the third laser tracker are arranged at intervals to form a multi-station laser tracker. The high-precision turntable and the multi-station laser tracker are arranged at intervals. The high-precision turntable is fixed on the turntable tripod. The rotation plane of the high-precision turntable is arranged vertically. The bat is fixedly installed on the rotation plane of the high-precision turntable by a fixture. The center of the bat passes through the rotation center of the rotation plane of the high-precision turntable. A laser tracker target ball is fixedly distributed at both ends of the bat.

[0008] The ball stick rotates along with the rotating plane of the high-precision turntable, driving the target balls of the laser trackers at both ends to move.

[0009] The rotating plane of the high-precision turntable only drives the bat to rotate in two directions: along the vertical direction of gravity and along the horizontal direction.

[0010] 2. A measurement method for a multi-station laser tracking system, the method comprising:

[0011] S1. The multi-station laser trackers are evenly distributed in the spatial area and fixed in position. A high-precision turntable tripod is arranged in front of the multi-station laser tracker. The high-precision turntable is stably fixed on the turntable tripod. The rotation plane of the high-precision turntable is roughly facing the multi-station laser tracker. A baseball bat is fixed on the rotation plane of the high-precision turntable by a clamp. The center of the baseball bat passes through the rotation center of the rotation plane of the high-precision turntable. A laser tracker target ball is fixed at both ends of the baseball bat. It is ensured that the target balls on the turntable bat can be connected to the multi-station tracker.

[0012] The two laser tracker targets at both ends of the bat do not have to be symmetrically distributed.

[0013] S2. Control the high-precision turntable to rotate the bat, rotating it to two positions: vertically and horizontally due to gravity. Each laser tracker measures the absolute distance between the two laser tracker targets at both ends of the bat and itself in each position for precise distance measurement. The laser tracker targets are in four different positions, obtaining a total of four absolute distances.

[0014] S3, using the four absolute distances combined with the previously obtained distance between the centers of the two laser tracker target balls at both ends of the club to obtain the center coordinates of the laser tracker;

[0015] S4. Place a laser tracker target ball at the measured position, use each laser tracker to measure a laser tracker target ball at any position in space, obtain the absolute distance between each laser tracker and the laser tracker target ball, and obtain a total of multiple absolute distances equal to the number of laser trackers. Then, use the multiple absolute distances combined with the center coordinates of each laser tracker to calculate and process to obtain the precise coordinates of any measured position in space.

[0016] The center distance between the two laser tracker target balls at both ends of the club is measured in advance by the fixed angle distance measurement function of the first laser tracker.

[0017] S3 specifically involves solving the following formula to obtain the center coordinates of the laser tracker:

[0018]

[0019] Where x1, y1, and z1 represent the three-dimensional center coordinates of the laser tracker. L1, L2, L3, and L4 represent the four absolute distances from the laser tracker target balls at four different positions measured by the laser tracker to the laser tracker. a represents the distance from the laser tracker target ball at one end of the bat to the center of the rotation axis of the high-precision turntable's rotation plane. b represents the distance from the laser tracker target ball at the other end of the bat to the center of the rotation axis of the high-precision turntable's rotation plane. L represents the distance between the centers of the two laser tracker target balls at both ends of the bat.

[0020] The number of laser trackers in the multi-station laser tracker is three, and the coordinates of the measured position in step S4 are obtained by solving the following formula:

[0021]

[0022] Among them, x p ,y p , z p Represents the three-dimensional coordinates of the measured position, L1′, L2′, and L3′ respectively represent the absolute distances between the three laser trackers measuring themselves and the laser trackers of the measured position, x1, y1, and z1 represent the three-dimensional center coordinates of the first laser tracker, x2, y2, and z2 represent the three-dimensional center coordinates of the second laser tracker, and x3, y3, and z3 represent the three-dimensional center coordinates of the third laser tracker.

[0023] During the measurement process, the present invention only uses the absolute distance measurement function of the laser tracker, and does not use the coordinate measurement function of the laser tracker.

[0024] The present invention calibrates the center coordinate values ​​of each laser tracker in space by moving the turntable at two vertical angles and using the calibrated standard ball center distance as calibration data, thereby unifying the coordinate values ​​of each station of the multi-station laser tracking measurement system and providing calibration data for large-scale measurement using the multi-station laser tracking measurement system.

[0025] The beneficial effects of the present invention are as follows:

[0026] Typically, the pitch and horizontal motion rotary encoders in laser trackers have rotational errors, resulting in errors in horizontal and pitch measurements, while absolute ranging functions are always accurate. The method of the present invention effectively eliminates these errors in the laser tracker's pitch and horizontal motion rotary encoders, utilizing only the laser tracker's absolute, high-precision interferometric ranging function. This overcomes the errors inherent in existing laser trackers and improves measurement accuracy.

[0027] The invention has a simple structure and is easy to operate, and can be used to calibrate the measurement capability of a multi-station laser tracking measurement system and is applicable to large-space precision measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the calibration of the multi-station laser tracking measurement system of the present invention.

[0029] Figure 2 This is a structural diagram of the turntable and target ball.

[0030] In the figure: 1. First laser tracker, 2. Second laser tracker, 3. Third laser tracker, 4. High-precision turntable, 5. Baseball bat, 6. Target ball for first laser tracker, 7. Target ball for second laser tracker, 8. Fixture, 9. Turntable tripod. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and examples.

[0032] like Figure 1 and Figure 2 As shown, the device specifically includes a first laser tracker 1, a second laser tracker 2, a third laser tracker 3, a high-precision turntable 4, a ball stick 5, a first laser tracker target ball 6, a second laser tracker target ball 7, a clamp 8 and a turntable tripod 9; the first laser tracker 1, the second laser tracker 2, and the third laser tracker 3 are arranged at intervals to form a multi-station laser tracker, the high-precision turntable 4 and the multi-station laser tracker are arranged at intervals, the high-precision turntable 4 is fixed on the turntable tripod 9, the rotation plane of the high-precision turntable 4 is arranged vertically, and the ball stick 5 is fixedly installed on the rotation plane of the high-precision turntable 4 by the clamp 8, the center of the ball stick 5 passes through the rotation center of the rotation plane of the high-precision turntable 4, and a laser tracker target ball is fixedly distributed at both ends of the ball stick 5, namely the first laser tracking target ball 6 and the second laser tracker target ball 7.

[0033] The bat 5 rotates along with the rotation plane of the high-precision turntable 4, driving the laser tracker target balls at both ends to move.

[0034] The rotation plane of the high-precision turntable 4 only drives the ball bat 5 to rotate in two directions: along the vertical direction of gravity and along the horizontal direction.

[0035] The high-precision turntable is a single-axis turntable that faces the multi-station laser tracker and can rotate 90 degrees at a fixed angle.

[0036] The high precision of the high-precision turntable 4 refers to a positioning accuracy higher than 1″.

[0037] Laser tracker targets are fixed at both ends of the bat. The laser tracker target ball rotates with the rotating screen of the high-precision turntable. The rotation process can be connected to multiple-station laser trackers.

[0038] The three laser trackers 1, 2, and 3 can effectively measure the absolute distance between the target balls at both ends of the club 5 and the club itself.

[0039] The high-precision turntable angle positioning accuracy is 1", and the positioning error of 1" for the target balls at both ends of the 1m ball stick is

[0040] tan(1″)×500mm≈0.002mm

[0041] The target ball positioning accuracy of 0.002mm meets the needs of multi-station spatial calibration.

[0042] In the specific implementation of the method of the present invention, the calibration process of multi-station laser tracking measurement is as follows:

[0043] Step 1:

[0044] The multi-station laser trackers are evenly distributed across the spatial area. A high-precision turntable 4 is designed on the front of the multi-station laser tracker. The high-precision turntable 4 is stably fixed to the turntable 9, with its rotation plane facing the multi-station laser tracker. The high-precision turntable 4 is mounted on the bat using a fixture. The two laser tracker targets at each end of the bat rotate 90° from an initial 0° horizontal position to a 90° vertical position along the rotation plane of the high-precision turntable 4. The multi-station laser tracker ensures tracking in both the 0° and 90° positions. The bat's orientation in both turntable rotation positions is defined as the x and y axes.

[0045] Step 2: Under the two postures of 0° and 90°, the first laser tracker 1 is used to precisely measure the absolute distance between the laser tracker target ball and itself at the four positions under the two postures.

[0046] Step 3:

[0047] Using the four absolute distances obtained and the center distances between the two laser tracker target balls at both ends of the club, the center coordinates of the first laser tracker 1 in the target ball coordinate system are obtained:

[0048] The laser tracker target balls are located at both ends of the club, and the length of the club is obtained by measuring the angle of the laser tracker and used as the ball center distance L.

[0049] The axial direction of the bat in the horizontal posture of 0° is set as the x-axis, the axial direction in the horizontal posture of 0° is set as the y-axis, and the center of the rotation axis of the rotation plane of the high-precision turntable 4 is set as the origin.

[0050] At a 0° horizontal position, the coordinates of the first laser tracker target sphere 6 are A(-a, 0), and the coordinates of the second laser tracker target sphere 7 are B(b, 0). At a 90° horizontal position, the coordinates of the first laser tracker target sphere 6 are A'(0, a), and the coordinates of the second laser tracker target sphere 7 are B'(0, -b). The laser trackers measure the absolute distances from A, B, A', and B' to themselves, respectively, as L1, L2, L3, and L4.

[0051] According to the above measurement results, the following formula is input to solve the center coordinates (x1, y1, z1) of the first laser tracker 1:

[0052]

[0053] Step 4:

[0054] The above method is used to measure the center coordinates of the remaining second laser tracker 2 and the third laser tracker 3 to obtain the center coordinates of the positions of all three laser trackers 1-3.

[0055] That is, according to the same method, the center coordinates (x2, y2, z2) of the second laser tracker 2 and the center coordinates (x3, y3, z3) of the third laser tracker 3 are obtained.

[0056] Step 5:

[0057] After obtaining the center coordinates of each laser tracker, the laser tracker target ball placed at any measured position in the space is measured, and the coordinate value of any measured position of the spatial point is obtained by calculation using the coordinates of the three-station laser tracker.

[0058] The measurement point P(x p ,y p , z p ), the absolute distances of the three laser trackers to the measuring point P are L1′, L2′, and L3′ respectively. Based on the three absolute distances, the following formula is used to solve the measurement point P (x p ,y p , z p )'s coordinates:

[0059]

[0060] This enables the calibration and measurement of multi-station laser trackers.

Claims

1. A measurement method for a multi-station laser tracking system, characterized in that: Methods include: S1, the multi-station laser trackers are evenly distributed in the spatial area and fixed in position, the rotation plane of the high-precision turntable (4) faces the multi-station laser trackers, the ball stick (5) is fixedly installed on the rotation plane of the high-precision turntable (4) through the clamp (8), the center of the ball stick (5) passes through the rotation center of the rotation plane of the high-precision turntable (4), and a laser tracker target ball is fixedly distributed at both ends of the ball stick (5); S2. Control the high-precision turntable (4) to drive the bat (5) to rotate, and rotate to two postures along the vertical direction of gravity and along the horizontal direction respectively. Each laser tracker measures the absolute distance between the two laser tracker target balls at both ends of the bat (5) and itself in each posture, and obtains four absolute distances in total; S3, using the four absolute distances combined with the center distance between the two laser tracker target balls at both ends of the stick (5) to obtain the center coordinates of the laser tracker; S4. Place a laser tracker target ball at the measured position, use each laser tracker to measure a laser tracker target ball at any position in space, obtain the absolute distance between each laser tracker and the laser tracker target ball, and obtain a total of multiple absolute distances equal to the number of laser trackers. Then, use the multiple absolute distances combined with the center coordinates of each laser tracker to calculate and process the coordinates of the measured position; The high precision of the high-precision turntable (4) refers to a positioning accuracy higher than 1″.

2. The measurement method of a multi-station laser tracking system according to claim 1, characterized in that: The center distance between the two laser tracker target balls at both ends of the ball stick (5) is measured in advance by the fixed angle distance measurement function of the first laser tracker (1).

3. The measurement method of a multi-station laser tracking system according to claim 1, characterized in that: S3 specifically involves solving the following formula to obtain the center coordinates of the laser tracker: Wherein, x1, y1, z1 represent the three-dimensional center coordinates of the laser tracker (1), L1, L2, L3, L4 represent four absolute distances respectively, a represents the distance between the laser tracker target ball at one end of the club (5) and the center of the rotation axis of the rotation plane of the high-precision turntable (4), b represents the distance between the laser tracker target ball at the other end of the club (5) and the center of the rotation axis of the rotation plane of the high-precision turntable (4), and L represents the distance between the centers of the two laser tracker target balls at both ends of the club (5).

4. The measurement method of a multi-station laser tracking system according to claim 1, characterized in that: The number of laser trackers in the multi-station laser tracker is three, and the coordinates of the measured position in step S4 are obtained by solving the following formula: Among them, x p ,y p ,z p represents the three-dimensional coordinates of the measured position, L1′, L2′, and L3′ respectively represent the absolute distances between the three laser trackers measuring themselves and the laser trackers of the measured position, x1, y1, and z1 represent the three-dimensional center coordinates of the first laser tracker, x2, y2, and z2 represent the three-dimensional center coordinates of the second laser tracker, and x3, y3, and z3 represent the three-dimensional center coordinates of the third laser tracker.

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