Long-distance high-precision six-degree-of-freedom absolute pose calibration method and system

Abstract

The invention discloses a long-distance high-precision six-degree-of-freedom absolute pose calibration method and system. The method comprises the steps that the absolute pose relation among an LED active target, a first corner reflector, a relative measurement target device and a target platform is determined; absolute pose measurement between the coordinate system of the sensor platform and the coordinate system of the target platform is carried out nearby; enabling the sensor platform and the target platform to perform relative motion, and performing relative measurement of the six-degree-of-freedom pose variation in the motion process; calculating an absolute pose relationship between the sensor platform and the coordinate system of the target platform at a long distance; and solving the pose relation between the sensors. According to the invention, under the condition of long-distance and high-precision absolute six-degree-of-freedom measurement of a multi-sensor combination, high-precision calibration of the internal pose relation of the sensor, especially high-precision calibration between optical coordinate systems of optical sensors, can be realized.

Description

Technical Field

[0001] The present invention relates to a long-distance high-precision six-degree-of-freedom absolute position and posture calibration method and system, and in particular to an application of using multiple sensors to perform fusion measurement of the six degrees of freedom (position and posture) of a target, belonging to the technical field of position and posture measurement. Background Art

[0002] Long-distance, high-precision, absolute measurement of the six-degree-of-freedom position and posture of a target is widely needed in the fields of industrial manufacturing, aerospace, robotics, scientific research, etc. However, in some special occasions, considering the complexity of the target object, a single sensor or a single type of sensor is gradually unable to meet the high-precision measurement requirements of the six-degree-of-freedom position and posture of the target in terms of measurement range, measurement accuracy, measurement efficiency, etc. Using multiple or multiple sensors for combined measurement is an effective way to solve this problem.

[0003] Usually, the purpose of multi-sensor measurement is to obtain the six-degree-of-freedom posture relationship between the sensor platform coordinate system and the target platform coordinate system by fusing the measurement results of multiple sensors. In order to achieve the fusion of measurement data between different types of sensors, it is necessary to know the relative posture relationship between the different sensors used. This prior knowledge is obtained through a pre-calibration process. For a six-degree-of-freedom posture measurement device composed of camera photogrammetry and laser ranging, since the camera coordinate system is a virtual point axis located at the optical center of the camera, it is impossible to place a physical target for measurement, and since the calibration error will be directly transmitted to the system error of the multi-sensor combined measurement device, a long-distance, high-precision, absolute posture calibration method for the combined measurement device is crucial to achieve high-precision six-degree-of-freedom measurement.

[0004] Since there is no physical coordinate system for the camera and laser in the combined measurement system, but data fusion requires the posture relationship between the two as a known quantity, and for the measurement range of tens of meters to hundreds of meters, micron-level displacement accuracy and arc-second-level attitude angle measurement accuracy are achieved, the current three-coordinate machine method is mainly used to determine the posture relationship between the camera, laser and multiple targets for short-distance applications. It has low efficiency, small measurement range, and cannot be located in the optical coordinate system of the camera and laser, and cannot meet the large-scale, high-precision six-degree-of-freedom absolute measurement needs.

[0005] The patent "A method and system for fusing a point laser displacement sensor with a binocular camera coordinate system" (CN112212784A) and the patent "A method and device for rapid calibration of a live working robot based on multiple sensors" (CN112223302A) propose corresponding solutions to the problem of using multiple sensors for collaborative posture measurement under specific scenarios, but do not solve the problem of calibrating multiple sensors in the absence of a physical coordinate system. Summary of the invention

[0006] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a long-distance high-precision six-degree-of-freedom absolute posture calibration method and system, to solve the technical problem of high-precision six-degree-of-freedom posture calibration of the coordinate system of optical sensors such as cameras and lasers at a long distance, and to realize large-range, high-precision, absolute six-degree-of-freedom posture measurement under the combination of camera and laser ranging sensor.

[0007] The technical solution of the present invention is: a long-distance high-precision six-degree-of-freedom absolute posture calibration method, wherein:

[0008] S0. Arrange a long-distance, high-precision, six-degree-of-freedom absolute position calibration system in the field, including: a sensor platform, a target platform, and a laser tracker. The sensor platform and the target platform are both located on a long guide rail. The target platform can move along the long guide rail. The laser tracker is located outside the long guide rail, and its position moves according to measurement needs; the sensor platform is provided with a camera sensor, a laser rangefinder sensor, a relative six-degree-of-freedom measurement device, and three sensor platform positioning pin holes; the target platform is fixedly installed with an LED active target, a first corner reflector, and a relative measurement target device, and three target platform positioning pin holes; determine four or more measurement positions between the sensor platform and the target platform;

[0009] S1. Determine the coordinate system of the sensor platform in the reference coordinate system of the laser tracker, and further determine the optical reference origin of the laser rangefinder sensor and the positional relationship between the optical reference origin of the laser rangefinder sensor and the sensor platform through the laser tracker;

[0010] S2. Define the position closest to the sensor platform among the set measurement positions as the initial measurement position, move the target platform to the initial measurement position; determine the absolute position relationship between the LED active target, the first corner reflector, the relative measurement target device and the target platform through a laser tracker;

[0011] S3, keeping the measurement position unchanged, determining the six-degree-of-freedom posture of the sensor platform and the target platform at the initial measurement position;

[0012] S4. At the initial measurement position, the result of the relative six-degree-of-freedom measurement device is reset to zero;

[0013] S5: Move the target platform to a measurement position away from the sensor platform, continuously measure and record the measurement results of the relative six-degree-of-freedom measurement device during the movement, and solve the relative change of the six degrees of freedom of the target platform;

[0014] S6: Solve the six-degree-of-freedom pose of the target platform relative to the sensor platform at the farthest measurement position to be measured;

[0015] S7: Solve the five-degree-of-freedom measurement results of the camera sensor relative to the target platform coordinate system, and the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector;

[0016] S8: Repeatedly change the target platform posture, solve the relationship between the camera sensor and the sensor platform, and complete the posture relationship calibration between the camera sensor and the laser rangefinder sensor.

[0017] Preferably, in the long-distance high-precision six-degree-of-freedom absolute position and posture calibration system arranged:

[0018] The relative measurement target device comprises: a metal bearing frame, a second corner reflector, a third corner reflector, a fourth corner reflector, a fifth corner reflector, a measuring plane mirror and a sixth corner reflector;

[0019] The coordinate system of the relative measurement target device is defined as follows: the coordinate system of the relative measurement target device takes the center of the fourth corner reflector as the origin, the direction of the line connecting the center of the second corner reflector and the center of the fourth corner reflector is the Y-axis direction, the normal direction of the plane where the centers of the second corner reflector, the third corner reflector and the fourth corner reflector are located is the Z-axis direction, and the X-axis direction is determined according to the right-hand rule;

[0020] The relative six-degree-of-freedom measuring device comprises a laser interferometer module and an autocollimator module, wherein the laser interferometer module measures relative distances and the autocollimator module measures relative angles;

[0021] During installation, the first corner reflector and the laser optical axis of the laser rangefinder sensor are collinear.

[0022] Preferably, in S1, the coordinate system of the sensor platform in the reference coordinate system of the laser tracker is determined, and the optical reference origin of the laser rangefinder sensor and the positional relationship between the optical reference origin of the laser rangefinder sensor and the sensor platform are further determined by the laser tracker, specifically:

[0023] Turn on the laser tracker, place three laser tracker target balls at the positioning pin holes of the sensor platform, and measure the coordinates S of the three laser target balls in the reference coordinate system of the laser tracker. ic =(x Sic ,y Sic ,z Sic ), ic=1,2,3; the sensor platform coordinate system is determined by the three target ball position coordinates;

[0024] Assume that the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker are (x S1 ,y S1 ,z S1 ), then the unit vector of the sensor platform coordinate system axis is:

[0025]

[0026] The subscript S indicates the sensor platform coordinate system;

[0027] The laser tracker is fixed in position, and the first corner reflector of the target platform is moved to multiple different measurement positions along the laser optical axis direction of the laser rangefinder sensor. The laser tracker is used to measure the three coordinate values ​​(x Lj ,y Lj ,z Lj ), j = 1 ~ m represents the serial number of different measurement positions, and at the same time records the distance measurement result d of the laser rangefinder sensor j , j = 1 ~ m; determine the direction vector (l x ,l y ,l z ):

[0028]

[0029] The reference origin coordinates O of the laser rangefinder sensor 1R (x O1R ,y O1R ,z O1R ) satisfies the following two equations:

[0030]

[0031]

[0032] The coordinates O of the laser point reference origin relative to the tracker system are obtained by simultaneous solution. 1R (x O1R ,y O1R ,z O1R );

[0033] The reference origin of the laser rangefinder sensor is converted to the sensor platform coordinate system, thereby determining the positional relationship between the optical reference origin of the optical rangefinder sensor and the sensor platform.

[0034] Preferably, in S2, the absolute position relationship between the LED active target, the first corner reflector, the relative measurement target device and the target platform is determined by a laser tracker, specifically:

[0035] Move the target platform to the initial measurement position, place the tracker target balls at the three target platform positioning pin holes, and measure the coordinates T of the three tracker target balls in the laser tracker reference coordinate system. im =(x Tim ,y Tim ,z Tim), im=1,2,3; let the coordinate of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker be (x T1 ,y T1 ,z T1 ), then the unit vector of the target platform coordinate system is:

[0036]

[0037] The subscript T represents the target platform coordinate system;

[0038] Next, remove the LED lamp of the LED active target, place the laser tracker target ball at the LED lamp hole position in turn, measure its coordinate value, and convert it to the target platform coordinate system obtained above to determine the relationship between the LED lamp hole position and the target platform coordinate system;

[0039] A laser tracker is used to measure the coordinate values ​​of the first corner reflector and the second corner reflector, the third corner reflector, and the fourth corner reflector on the relative measurement target device in turn to obtain the relationship between the first corner reflector and the target platform coordinate system. Finally, according to the definition of the coordinate system of the relative measurement target device, the relationship between the relative measurement target device coordinate system and the target platform coordinate system is obtained.

[0040] Preferably, in S3, the six-degree-of-freedom posture of the sensor platform and the target platform at the initial measurement position is determined as follows:

[0041] Keep the target platform and laser tracker at the initial measurement position unchanged, place the tracker target ball at the positioning pin hole of the sensor platform, re-measure the coordinates of the three target balls in the tracker coordinate system, and obtain and assign the coordinates (x S1 ,y S1 ,z S1 );

[0042] The initial absolute position relationship between the sensor platform coordinate system and the target platform coordinate system is TL, and the attitude angle relationship is That is, determine the six-degree-of-freedom pose between the sensor platform coordinate system and the target platform coordinate system at the initial measurement position:

[0043] TL=[x T1 -x S1 y T1 -y S1 z T1 -z S1 ] T

[0044]

[0045] Where: x T1 ,yT1 、z T1 are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker; S1 ,y S1 、z S1 They are the three-axis components of the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker; They are the unit vectors of the X, Y, and Z axes of the target platform coordinate system relative to the laser tracker reference coordinate system; They are the unit vectors of the X, Y, and Z axes of the sensor platform coordinate system relative to the laser tracker reference coordinate system; is the angle between the X-axis direction of the sensor platform and the X-axis direction of the target platform at the initial position; is the angle between the Y-axis direction of the sensor platform and the Y-axis direction of the target platform at the initial position; is the angle between the Z-axis direction of the sensor platform and the Z-axis direction of the target platform at the initial position.

[0046] Preferably, in S5, the target platform is moved to a measurement position away from the sensor platform, and the measurement results of the relative six-degree-of-freedom measurement device are continuously measured and recorded during the movement to solve the relative change of the six degrees of freedom of the target platform, specifically:

[0047] Fix the sensor platform and move the target platform along the long guide rail to a far distance. The maximum distance is determined according to the range of the camera and laser rangefinder.

[0048] The relative six-degree-of-freedom measuring device continuously measures and records the six-degree-of-freedom change of the relative measuring target device during the movement of the target platform, and solves the six-degree-of-freedom change Δx of the target platform coordinate system relative to the sensor platform according to the relationship between the relative measuring target device and the target platform coordinate system. T , Δy T , Δz T , Δα T , Δβ T , Δγ T ,in:

[0049] Δx T Indicates the change in the X-axis position component of the target platform coordinate system relative to the sensor platform coordinate system during the motion process; Δy T Indicates the change in the Y-axis position component of the target platform coordinate system relative to the sensor platform coordinate system; Δz T Indicates the change in the Z-axis position component of the target platform coordinate system relative to the sensor platform coordinate system; Δα T Indicates the change in the angle between the target platform coordinate system and the sensor platform coordinate system in the X-axis direction; Δβ TIndicates the change in the Y-axis angle between the target platform coordinate system and the sensor platform coordinate system; Δγ T Indicates the change in the Z-axis angle between the target platform coordinate system and the sensor platform coordinate system.

[0050] Preferably, the six-degree-of-freedom posture of the target platform relative to the sensor platform when the farthest measurement position to be measured is solved in S6, specifically:

[0051] According to the relationship between the sensor platform coordinate system and the target platform coordinate system in the initial state determined in step S3, and the relative change of the six degrees of freedom of the target platform coordinate system in step S5, the six degrees of freedom pose of the target platform coordinate system and the sensor platform coordinate system at the farthest measurement position to be measured is obtained.

[0052]

[0053] in, They are the three-axis position components between the coordinate system of the farthest sensor platform to be measured and the coordinate system of the target platform; are the angles between the X, Y, and Z axes of the sensor platform coordinate system at the farthest point to be measured and the target platform coordinate system; T1 ,y T1 、z T1 are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker at the initial position; S1 ,y S1 、z S1 are the three-axis components of the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker at the initial position; Δx T , Δy T , Δz T They respectively represent the changes in the X, Y, and Z axis position components of the target platform coordinate system relative to the sensor platform coordinate system during the process of the target platform moving from the initial position to the farthest point to be measured; Respectively represent the angles between the sensor platform X, Y, Z axis and the target platform X, Y, Z axis at the initial position; Δα T , Δβ T , Δγ T They respectively represent the changes in the angles of the target platform coordinate system relative to the sensor platform coordinate system in the X, Y, and Z axis directions when the target platform moves from the initial position to the farthest point to be measured.

[0054] Preferably, in S7, the five-degree-of-freedom measurement result of the camera sensor relative to the target platform coordinate system and the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector are solved as follows:

[0055] Use the camera sensor to image the LED active target, solve the coordinates of each LED light on the LED active target in the optical coordinate system defined inside the camera sensor, and then determine the relationship between the camera sensor and the target platform based on the positional relationship between the LED active target and the target platform coordinate system;

[0056] Since the laser rangefinder sensor is an absolute distance measuring instrument, the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector is directly obtained.

[0057] Preferably, in S8, the target platform posture is repeatedly changed to solve the relationship between the camera sensor and the sensor platform, and the posture relationship calibration between the camera sensor and the laser rangefinder sensor is completed, specifically:

[0058] The number of changes when changing the target platform's posture is determined according to the number of sensors to be determined and the required accuracy index; the laser tracker is used to synchronously measure the change in the target platform's posture, and the measurement results of the camera sensor and the laser rangefinder sensor are recorded at the same time to solve the relationship between the camera sensor and the sensor platform, and then complete the posture relationship calibration between the camera sensor and the laser rangefinder sensor; in the calculation process, the homogeneous rotation matrix and the homogeneous displacement matrix are used to calculate the six-degree-of-freedom transformation:

[0059] Assume that the rotation matrix between the target platform coordinate system and the LED active target is R1, and the displacement matrix is ​​T1, the rotation matrix and displacement matrix between the LED active target and the camera sensor are R2 and T2 respectively, the rotation matrix and displacement matrix between the camera sensor and the sensor platform are R3 and T3 respectively, and the rotation matrix and displacement matrix between the target platform coordinate system and the sensor platform coordinate system are R4 and T4 respectively;

[0060] According to the above definition, we can get:

[0061] T4R4=T3R3T2R2T1R1

[0062] By changing the pose of the target platform multiple times, multiple equations are obtained and then solved to obtain the six-degree-of-freedom pose relationship of the target platform relative to the sensor platform. By using the position relationship between the reference origin of the laser rangefinder sensor and the sensor platform, the position relationship of the laser rangefinder sensor relative to the camera sensor is further obtained to achieve pose calibration between the two sensors.

[0063] In a second aspect, a long-distance, high-precision, six-degree-of-freedom absolute position and posture calibration system is provided, including: a sensor platform, a target platform, and a laser tracker, wherein the sensor platform and the target platform are both located on a long guide rail, the target platform can move along the long guide rail, and the laser tracker is located outside the long guide rail, and its position moves according to measurement needs, so as to measure the absolute six degrees of freedom between the sensor platform coordinate system and the target platform coordinate system;

[0064] The relative six-degree-of-freedom measuring device and multiple sensors that need to be calibrated for posture between each other are fixedly installed on the sensor platform, and three sensor platform positioning pin holes are provided. When installing each sensor and the relative six-degree-of-freedom measuring device, it is necessary to ensure that the optical paths do not block each other; at the same time, each sensor is as close as possible to ensure that the posture relationship between each sensor is not easily changed due to the deformation of the sensor platform after the calibration is completed;

[0065] The relative six-degree-of-freedom measuring device is designed based on the integration and transformation of the laser interferometer and autocollimator principles, including a laser interferometer module and an autocollimator module. The laser interferometer module measures relative distances, and the autocollimator module measures relative angles.

[0066] The target platform is fixedly installed with an LED active target, a first corner reflector, and a relative measurement target device; and is provided with three target platform positioning pin holes;

[0067] Wherein: the LED active target is composed of multiple LED lights, and at least four LED lights are required to realize the measurement function, and the distance between the LED lights should be as large as possible; the LED lights can be disassembled, and the package appearance size is consistent with the target ball of the laser tracker, ensuring that the position of the LED light point is concentric with the center of the target ball;

[0068] The first corner reflector is placed in the middle area of ​​the multiple LED lights of the LED active target;

[0069] The relative measurement target device comprises: a metal bearing frame, a second corner reflector, a third corner reflector, a fourth corner reflector, a fifth corner reflector, a measuring plane mirror and a sixth corner reflector; the coordinate system of the relative measurement target device takes the center of the fourth corner reflector as the origin, the direction of the line connecting the centers of the second corner reflector and the fourth corner reflector as the Y-axis direction, the normal direction of the plane where the centers of the second corner reflector, the third corner reflector and the fourth corner reflector are located is the Z-axis direction, and the X-axis direction is determined according to the right-hand rule;

[0070] When the sensors that need to calibrate their poses are camera sensors and laser rangefinder sensors:

[0071] The camera sensor images the LED active target when it is powered on and emits light, and measures the five degrees of freedom between it and the LED active target, including two-dimensional displacement and three-axis rotation angle;

[0072] The laser rangefinder sensor uses the return light from the first corner reflector to measure the absolute distance in the direction of the optical axis.

[0073] Compared with the prior art, the present invention has the following advantages:

[0074] (1) The present invention achieves high-precision absolute posture measurement at a long distance by combining short-distance high-precision absolute posture measurement with long-distance relative posture measurement, thereby reducing the requirement for high-precision absolute six-degree-of-freedom measurement at a long distance. At the same time, the posture calibration task of the "camera + laser" combined measurement device can be further achieved by using the high-precision absolute six-degree-of-freedom measurement results at a long distance.

[0075] (2) In the long-distance relative posture measurement combined with the method adopted by the present invention, high-precision relative six-degree-of-freedom measurement can be achieved by combining laser interferometry and laser collimation, and there is no requirement for the absolute relationship between the coordinate systems of the laser interferometry and laser collimation equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 Schematic diagram of the sensor platform and target platform corresponding to the method of the present invention;

[0077] Figure 2 It is a schematic diagram of the positioning pin holes of the sensor platform and the target platform of the present invention;

[0078] Figure 3 This is a flow chart of high-precision absolute posture measurement over long distances according to the present invention;

[0079] Figure 4 This is a composition diagram of a measurement system for internal calibration of a combined measurement device using "camera + laser" as an example in the present invention;

[0080] Figure 5 This is a coordinate system relationship diagram of the combined measurement device of the present invention taking "camera + laser" as an example;

[0081] Figure 6 This is the absolute posture calibration flow chart of the present invention taking "camera + laser" as an example;

[0082] Figure 7 It is a front view of the relative measurement target device of the present invention;

[0083] Figure 8 It is a side view of the relative measurement target device of the present invention. DETAILED DESCRIPTION

[0084] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0085] The present invention proposes a long-distance, high-precision six-degree-of-freedom absolute pose calibration method, and introduces its specific implementation process by taking the absolute pose calibration of a six-degree-of-freedom measuring device composed of a camera and a laser as an example. It can realize high-precision pose calibration between multiple sensors. However, the present invention is not limited to the combined measurement device of "camera + laser". In theory, this method can be used for the internal calibration of all six-degree-of-freedom measuring devices in the form of multi-sensor combinations.

[0086] The first aspect of the present invention proposes a method based on the combination of "absolute at close range + relative at long distance" to achieve high-precision six-degree-of-freedom absolute posture measurement at long distances, thereby realizing the posture calibration task in a "camera + laser" combined measurement device.

[0087] Different types of sensors (such as sensor 1, sensor 2, ... sensor n) are installed on a sensor platform 1, and a sensor platform coordinate system is defined on the sensor platform 1; the measurement targets of the sensors (target 1, target 2, ... target n) are installed on a target platform 2, and a target platform coordinate system is defined on the target platform 2.

[0088] The sensor platform coordinate system is defined by setting sensor platform positioning pin holes 11 on the rigid body of the sensor platform 1. The number of the positioning pin holes must be no less than 3. Figure 2 As shown, the center of the upper left locating pin hole of sensor platform 1 is selected as the origin, the line connecting the center of the upper left locating pin hole and the center of the upper right locating pin hole is the X-axis direction, the normal direction of the plane where the centers of the three locating pin holes are located is the Z-axis direction, and the Y-axis direction is determined according to the right-hand rule.

[0089] The target platform coordinate system is defined by setting target platform locating pin holes 21 on the target platform 2 rigid body. The number of locating pin holes must be no less than 3. The center of the locating pin hole in the upper left corner of the target platform 2 is selected as the origin. The line connecting the centers of the locating pin hole in the upper left corner and the locating pin hole in the upper right corner is the X-axis direction. The normal direction of the plane where the centers of the three locating pin holes are located is the Z-axis direction. The Y-axis direction is determined according to the right-hand rule.

[0090] Figure 4 The invention is a long-distance high-precision six-degree-of-freedom absolute position and posture calibration system, comprising: a sensor platform 1, a target platform 2, and a laser tracker 3.

[0091] A camera sensor 12, a laser rangefinder sensor 13, and a relative six-degree-of-freedom measuring device 14 are fixedly mounted on the sensor platform 1. The camera sensor 12, the laser rangefinder sensor 13, and the relative six-degree-of-freedom measuring device 14 are mounted at positions that ensure that their optical paths do not block each other.

[0092] The camera sensor 12 and the laser rangefinder sensor 13 are as close as possible to ensure that the posture relationship between the two is not easily changed due to the deformation of the sensor platform after calibration.

[0093] An LED active target 22 , a first corner reflector 23 , and a relative measurement target device 24 are fixedly mounted on the target platform 2 .

[0094] The LED active target 22 is composed of multiple LED lights. At least 4 LED lights are required to realize the measurement function. The distance between the LED lights should be as large as possible. The LED lights are detachable, and their package appearance dimensions are consistent with the target ball of the laser tracker, which can ensure that the position of the LED light point is concentric with the center of the target ball.

[0095] The first corner reflector 23 may be placed in the middle area of ​​the plurality of LED lamps of the LED active target 22 .

[0096] The relative six-degree-of-freedom measuring device 14 performs relative six-degree-of-freedom measurement on the relative measurement target device 24. The relative measurement target device 24 consists of a metal load-bearing frame and a second corner reflector 241, a third corner reflector 242, a fourth corner reflector 243, a fifth corner reflector 244, a measuring plane mirror 245, and a sixth corner reflector 246.

[0097] The coordinate system of the relative measurement target device takes the center of the fourth corner reflector 243 as the origin, the direction of the line connecting the centers of the second corner reflector 241 and the fourth corner reflector 243 is the Y-axis direction, the normal direction of the plane where the centers of the second corner reflector 241, the third corner reflector 242 and the fourth corner reflector 243 are located is the Z-axis direction, and the X-axis direction is determined according to the right-hand rule.

[0098] When installed, the first corner reflector 23 and the laser optical axis of the laser rangefinder sensor 13 are collinear.

[0099] The relative six-degree-of-freedom measuring device 14 includes a laser interferometer module and an autocollimator module, the laser interferometer module measures the relative distance, and the autocollimator module measures the relative angle;

[0100] During installation, ensure that the LED active target 22 is always within the field of view of the camera sensor 12 and as close to the center of the field of view as possible.

[0101] During installation, the laser interferometer module in the six-degree-of-freedom measuring device 14 emits five light beams, and the optical axis directions of the emitted light beams are collinear with the second corner reflector 241, the third corner reflector 242, the fourth corner reflector 243, the fifth corner reflector 244, and the sixth corner reflector 246, respectively; the autocollimator module emits one light beam, and can always be incident on the measuring plane mirror 245 during the movement of the target platform.

[0102] The relative six-degree-of-freedom measuring device 14 emits six beams of light that are incident on the second corner reflector 241, the third corner reflector 242, the fourth corner reflector 243, the fifth corner reflector 244, the measuring plane mirror 245, and the sixth corner reflector 246 respectively. The second corner reflector 241, the third corner reflector 242, and the fourth corner reflector 243 are fixedly mounted on the front of the metal bearing frame of the relative measurement target device 24, and the distance between the three is as large as possible, and are used for displacement measurement along the Z axis direction and measurement of the rotation angle around the X and Y axes. The fifth corner reflector 244 and the measuring plane mirror 245 are mounted on one side of the metal frame, and are used to measure the displacement change along the Y axis direction and the angle change around the Z axis. The sixth corner reflector 246 is mounted on the top surface of the metal frame, and is used to measure the displacement change along the X direction.

[0103] The LED active target 22 is powered on to emit light, and the camera sensor 12 images the LED active target 22 to achieve measurement of the two-dimensional lateral displacement and three-axis rotation angle between the camera sensor and the LED active target in five degrees of freedom.

[0104] The laser rangefinder sensor 13 uses the return light of the first corner reflector 23 to measure the absolute distance in the optical axis direction.

[0105] The relative six-degree-of-freedom measuring device 14 utilizes the measurement of the relative measurement target device 24 to achieve the measurement of the relative six-degree-of-freedom change between the two.

[0106] The target platform 2 is mounted on a one-dimensional motion long guide rail to ensure that the measurement targets of the camera sensor 12, the laser rangefinder sensor 13, and the relative six-degree-of-freedom measurement device 14 are all within their respective fields of view in both near and far situations.

[0107] The laser tracker 3 is placed near the long moving guide rail, and its position can be moved according to the measurement needs. The laser tracker 3 is used to measure the absolute six degrees of freedom between the sensor platform coordinate system and the target platform coordinate system at a close distance, determine the relationship between the LED active target 22, the first corner reflector 23, the relative measurement target device 24 and the target platform coordinate system on the target platform 2, and perform six degrees of freedom measurement in multiple posture states when the target platform 2 moves to the far end.

[0108] The present invention proposes a method based on the combination of "absolute at close range + relative at long distance" to achieve high-precision absolute posture measurement at long distances. The specific steps are as follows:

[0109] Step S101: determining the absolute position relationship between the LED active target, the first corner reflector, the relative measurement target device and the target platform;

[0110] Step S102: performing absolute pose measurement between the sensor platform coordinate system and the target platform coordinate system at a close distance;

[0111] Step S103: making the sensor platform and the target platform move relative to each other, and performing relative measurement of the six-degree-of-freedom posture change during the movement;

[0112] Step S104: Calculating the absolute position and posture relationship between the sensor platform and the target platform coordinate system at a long distance;

[0113] Step S105: Solve the position and posture relationship between sensors (camera, laser rangefinder).

[0114] To determine the absolute position and posture relationship between the LED active target, the first corner reflector, the relative measurement target device and the target platform, the LED lamp can be removed, and the coordinates of each LED lamp installation hole can be measured in turn using a laser tracker target ball. The laser tracker can also be used to measure the coordinates of the first corner reflector, the second corner reflector, the third corner reflector, the fourth corner reflector on the relative measurement target device, and the locating pin hole of the target platform. The absolute position and posture relationship between the LED active target, the first corner reflector, the relative measurement target device coordinate system and the target platform can be determined according to the coordinate system definition.

[0115] The sensor platform and the target platform are made to move relative to each other, and the relative measurement of the six-degree-of-freedom posture change is performed during the movement. Generally, the sensor platform is fixed and the target platform is moved from near to far. It can be a single-degree-of-freedom linear motion or a multi-degree-of-freedom motion, but it should be ensured that the cooperative targets of each sensor are within its spatial detection range.

[0116] To solve the posture relationship between sensors, it is necessary to use the relationship between the sensor platform coordinate system and the target platform coordinate system obtained in the previous steps, as well as the absolute posture measurement results of multiple sensors on the target. This process involves solving in multiple different posture states and calculating the posture relationship between sensors 1, 2...n.

[0117] The present invention proposes a long-distance high-precision six-degree-of-freedom absolute posture calibration method, which obtains the absolute six-degree-of-freedom posture information between the sensor platform and the target platform through the "near absolute + long-distance relative" method, and uses the camera and laser rangefinder to measure and obtain the measurement results respectively, and reversely solves the relative posture relationship between the camera and the laser rangefinder to achieve the posture calibration between the camera and the laser rangefinder. For ease of understanding, the specific implementation method of the measurement process is introduced, such as Figure 6 shown.

[0118] Step S201 : determining the positional relationship between the optical reference origin of the laser rangefinder sensor 13 and the sensor platform 1 .

[0119] Specifically, first, turn on the laser tracker 3, place the tracker target ball at the positioning pin hole 11 of the sensor platform 1, and measure the coordinates S of the three target balls in the tracker reference coordinate system (customized inside the laser tracker device) ic =(x Sic ,y Sic ,z Sic The sensor platform coordinate system can be determined by the three target ball position coordinates, and the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker are set as (x S1 ,y S1 ,z S1 ), then the coordinate axis X of the sensor platform coordinate system S , Y S , Z S The unit vector of in the reference coordinate system of the laser tracker can be determined according to formula (1). S represents the sensor platform coordinate system.

[0120]

[0121] Then, the laser tracker 3 is fixed in position, and the first corner reflector 23 is moved to a plurality of different positions (such as Figure 4 A, B, C, and D positions in the figure), the laser tracker 3 is used to measure the three coordinate values ​​of the first corner reflector 23 at different positions (such as (x Lj ,y Lj ,z Lj ), j=1~m is the serial number of different measurement positions), and at the same time records the distance measurement result d of the laser rangefinder sensor 13 j (j = 1 ~ m). Based on the three coordinates of the point on the straight line, the direction vector (l x ,l y ,l z ).

[0122]

[0123] Then, the coordinates of the laser point reference origin relative to the tracker system are uniquely determined based on the distance measurement result of the laser rangefinder sensor 13. 1R (x O1R ,y O1R ,z O1R ), namely the reference origin coordinate O of the laser rangefinder sensor 13 1R (x O1R ,y O1R ,z O1R ) satisfies both formula (2) and formula (3).

[0124]

[0125] Finally, the reference origin of the laser rangefinder sensor is converted to the sensor platform coordinate system, thereby determining the positional relationship between the optical reference origin of the optical rangefinder sensor 13 and the sensor platform 1 .

[0126] Step S202: Determine the absolute position relationship between the LED active target 22, the first corner reflector 23, the relative measurement target device 24 and the target platform 2.

[0127] Specifically, the initial measurement position of the target platform 2 is set at a nearby location (such as Figure 4 Position A), place the tracker target ball at the positioning pin hole 21 of the target platform, and measure the coordinates T of the three target balls in the tracker reference coordinate system (customized inside the laser tracker device) i =(x Tim ,y Tim ,z Tim )(im=1,2,3). Assume that the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker are (x T1 ,y T1 ,z T1 ), then the coordinate axis x of the target platform coordinate system T ,y T 、z T The unit vector of can be determined according to formula (4). T represents the target platform coordinate system. The unit vector of the target platform coordinate system in the laser tracker reference coordinate system is:

[0128]

[0129] Next, remove the LED lamp of the LED active target 22, use the laser tracker target ball to place it at the LED lamp hole position in turn, measure its coordinate value, and convert it to the coordinate of the target platform coordinate system to determine the relationship between the LED lamp hole position and the target platform coordinate system.

[0130] Then, the laser tracker 3 is used to measure the coordinate values ​​of the first corner reflector 23 and the second corner reflector 241, the third corner reflector 242, and the fourth corner reflector 243 on the relative measurement target device 24 in turn, and the relationship between the first corner reflector 23 and the target platform coordinate system is obtained. Finally, according to the definition of the coordinate system of the relative measurement target device 24, the relationship between the relative measurement target device coordinate system and the target platform coordinate system is obtained.

[0131] Step S203: Determine the six-degree-of-freedom posture of the sensor platform and the target platform at the initial measurement position.

[0132] Specifically, the target platform 2 and the laser tracker 3 are kept at the measurement position in step S202, and the tracker target ball is placed at the positioning pin hole 11 of the sensor platform 1, and the coordinates of the three target balls in the tracker coordinate system are remeasured, and the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker are set to (x S1 ,y S1 ,z S1 ), then the coordinate axis x of the sensor platform coordinate system S ,y S 、z S The unit vector of can be determined according to formula (1).

[0133] Formula (5) is used to calculate the initial absolute position relationship between the sensor platform coordinate system and the target platform coordinate system as TL, and the attitude angle relationship is It can be determined that the initial state (such as Figure 4 A) Absolute six-degree-of-freedom pose between the sensor platform coordinate system and the target platform coordinate system.

[0134]

[0135] Where: x T1 ,y T1 、z T1 are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker; S1 ,y S1 、z S1 They are the three-axis components of the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker; They are the unit vectors of the X, Y, and Z axes of the target platform coordinate system relative to the laser tracker reference coordinate system; They are the unit vectors of the X, Y, and Z axes of the sensor platform coordinate system relative to the laser tracker reference coordinate system; is the angle between the X-axis direction of the sensor platform and the X-axis direction of the target platform at the initial position; is the angle between the Y-axis direction of the sensor platform and the Y-axis direction of the target platform at the initial position; is the angle between the Z-axis direction of the sensor platform and the Z-axis direction of the target platform at the initial position.

[0136] Step S204: at the initial measurement position (the position at which the relative relationship between the target platform 2 and the laser tracker 3 is measured in step S203), the result of the relative six-degree-of-freedom measurement device 14 is reset to zero.

[0137] Specifically, the relative six-degree-of-freedom measuring device 14 is turned on to ensure that the positions of the sensor platform 1 and the target platform 2 remain unchanged in the above steps, so that the measurement result of the relative six-degree-of-freedom measuring device 14 in the initial state is reset to zero.

[0138] The current six-degree-of-freedom measurement result relative to the six-degree-of-freedom measurement device 14 can be recorded and used as a calibration constant value to be subtracted in subsequent measurements.

[0139] Step S205 : the target platform 2 moves to a far distance, and the measurement result of the relative six-degree-of-freedom measuring device 14 is recorded to solve the relative change of the six-degree-of-freedom of the target platform 2 .

[0140] Specifically, the sensor platform 1 is fixed, and the target platform 2 is moved to a distant position along the long guide rail, such as position B, C, D or other positions, and the farthest distance is determined according to the range of the camera and the laser rangefinder. The relative six-degree-of-freedom measuring device 14 continuously measures and records the six-degree-of-freedom change of the relative measurement target device 24 during the movement of the target platform 2, and according to the relationship between the relative measurement target device 24 and the target platform coordinate system in step S202, the six-degree-of-freedom change Δx of the target platform coordinate system relative to the sensor platform 1 can be solved. T , Δy T , Δz T , Δα T , Δβ T , Δγ T .

[0141] Where Δx T Indicates the change in the X-axis position component of the target platform coordinate system relative to the sensor platform coordinate system during the motion process; Δy T Indicates the change in the Y-axis position component of the target platform coordinate system relative to the sensor platform coordinate system; Δz T Indicates the change in the Z-axis position component of the target platform coordinate system relative to the sensor platform coordinate system; Δα T Indicates the change in the angle between the target platform coordinate system and the sensor platform coordinate system in the X-axis direction; Δβ T Indicates the change in the Y-axis angle between the target platform coordinate system and the sensor platform coordinate system; Δγ TIndicates the change in the Z-axis angle between the target platform coordinate system and the sensor platform coordinate system.

[0142] Step S206: Solve the six-degree-of-freedom position of the distant lower target platform 2 relative to the sensor platform 1.

[0143] Specifically, according to the relationship between the sensor platform coordinate system and the target platform coordinate system in the initial state determined in step S203, and the relative change of the six degrees of freedom of the target platform coordinate system in step S205, the six degrees of freedom pose of the target platform coordinate system and the sensor platform coordinate system at a distance is obtained.

[0144]

[0145] in, They are the three-axis position components between the coordinate system of the farthest sensor platform to be measured and the coordinate system of the target platform; are the angles between the X, Y, and Z axes of the sensor platform coordinate system at the farthest point to be measured and the target platform coordinate system; T1 ,y T1 、z T1 are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker at the initial position; S1 ,y S1 、z S1 are the three-axis components of the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker at the initial position; Δx T , Δy T , Δz T They respectively represent the changes in the X, Y, and Z axis position components of the target platform coordinate system relative to the sensor platform coordinate system during the process of the target platform moving from the initial position to the farthest point to be measured; Respectively represent the angles between the sensor platform X, Y, Z axis and the target platform X, Y, Z axis at the initial position; Δα T , Δβ T , Δγ T They respectively represent the changes in the angles of the target platform coordinate system relative to the sensor platform coordinate system in the X, Y, and Z axis directions when the target platform moves from the initial position to the farthest point to be measured.

[0146] Step S207 : solving the five-degree-of-freedom measurement result of the camera sensor 12 relative to the target platform coordinate system, and the one-dimensional absolute distance measurement result of the laser rangefinder sensor 13 to the first corner reflector 23 .

[0147] Specifically, the camera sensor 12 is used to image the LED active target 22, and the coordinates of each LED light of the LED active target 22 are solved in the optical coordinate system defined inside the camera sensor. Then, based on the positional relationship between the LED active target and the target platform coordinate system obtained in step S202, the relationship between the camera sensor 12 and the target platform 2 is determined.

[0148] Since the laser rangefinder sensor 13 is an absolute distance measuring instrument, the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector 23 determined in step S201 can be directly obtained.

[0149] Step S208: The position and posture of the target platform 2 is changed multiple times to solve the relationship between the camera sensor 12 and the sensor platform 1, and the position and posture relationship calibration between the camera sensor 12 and the laser rangefinder sensor 13 is completed.

[0150] Specifically, since the six-degree-of-freedom relationship between the camera sensor and the sensor platform coordinate system is 6 unknowns, and there is 1 unknown between the camera sensor and the LED active target, to determine these 7 unknowns, it is necessary to change the target platform posture multiple times, and use the laser tracker 3 to synchronously measure the change in the target platform 2 posture, and record the measurement results of the camera sensor and the laser rangefinder sensor at the same time, using Figure 5 The coordinate system relationship shown is used to solve the relationship between the camera sensor and the sensor platform 1, and then the position and posture relationship calibration between the camera sensor 12 and the laser rangefinder sensor 13 is completed.

[0151] Homogeneous rotation matrix and homogeneous displacement matrix can be used to calculate the six-degree-of-freedom conversion. For example, assuming that the rotation matrix between the target platform coordinate system and the LED active target is R1 and the displacement matrix is ​​T1, the rotation matrix and displacement matrix between the LED active target and the camera sensor are R2 and T2 respectively, the rotation matrix and displacement matrix between the camera sensor and the sensor platform are R3 and T3 respectively, and the rotation matrix and displacement matrix between the target platform coordinate system and the sensor platform coordinate system are R4 and T4 respectively, and R4 and T4 can be obtained according to the six-degree-of-freedom posture of the target platform 2 relative to the sensor platform 1 determined by the method in step S206. Based on the above assumptions, formula (7) can be obtained. By changing the posture of the target platform 2 multiple times, multiple equations can be obtained, and the unknowns can be solved. After obtaining the six-degree-of-freedom posture relationship of the target platform 2 relative to the sensor platform 1, the position relationship between the reference origin of the laser rangefinder sensor 13 and the sensor platform 1 obtained in step S201 can be used to obtain the position relationship of the laser rangefinder sensor 13 relative to the camera sensor 12, and realize the posture calibration between the two sensors.

[0152] T4R4=T3R3T2R2T1R1 (7)

[0153] At this point, the position and posture relationship between the optical coordinate system of the camera sensor 12 and the reference origin of the laser rangefinder sensor 13 can be obtained, that is, the internal position and posture relationship calibration of the combined six-degree-of-freedom measurement device "camera+laser" is completed.

[0154] The present invention is particularly suitable for the problem of multi-sensor internal calibration that needs to achieve long-distance high-precision measurement tasks. The reason for using long-distance calibration in this case is that camera sensors are usually designed to only achieve measurement within a specific distance range according to their uses, and because the measurement accuracy of the combined six-degree-of-freedom measurement device can reach 50μm, 5", to achieve calibration of the two, a calibration method with a measurement accuracy at least 3 times higher is usually required, and there is currently almost no such high-precision absolute six-degree-of-freedom posture measurement device. Therefore, the present invention proposes to use a relative six-degree-of-freedom device for long-distance measurement, and a laser tracker with higher accuracy for close measurement. The posture calibration between the two measuring devices is achieved through the "absolute near + relative far" measurement method, and ultra-high-precision absolute six-degree-of-freedom information can be obtained at a long distance, thereby achieving the calibration of the posture relationship between multiple sensors.

[0155] On the other hand, the present invention provides a relative six-degree-of-freedom measuring device 14, which is designed based on the principles of laser interferometer and autocollimator. The laser interferometer realizes relative distance measurement, and the autocollimator performs relative angle measurement.

[0156] The laser interferometer uses the principle of dual-frequency laser heterodyne interference. Its output light contains two optical frequencies f1 and f2 with close frequencies and orthogonal polarizations. The light is split by a polarization splitter prism and enters the reference mirror and the measuring mirror (i.e. Figure 7 The light returned by the measuring mirror and the reference mirror generates heterodyne interference after being combined and passed through a polarizer. The signal after low-pass filtering of the detector is shown in formula (8), where λ is the laser wavelength, Δ1-Δ2 is the optical path difference between the reference mirror and the measuring mirror, and the displacement along the optical axis direction is obtained through the phase change of the interference signal during the target movement.

[0157]

[0158] The distances between the second corner reflector 241, the third corner reflector 242, and the fourth corner reflector 243 are determined in advance by a laser tracker or a three-coordinate machine. For example, the distance between the second corner reflector 241 and the third corner reflector 242 is D 12 , the displacement changes of the two beams measured by laser interferometer are Δz1 and Δz2 respectively, and the rotation angle change around the X axis is α = arcsin ((Δz1-Δz2) / D 12 ), the distance between the second corner reflector 241 and the fourth corner reflector 243 is D 13, the displacement changes of the two beams measured by laser interferometer are Δz1 and Δz3 respectively, then the rotation angle change around the Y axis is β = arcsin ((Δz1-Δz3) / D 13 ). The side plane mirror is used to perform laser autocollimation measurement of the rotation angle γ around the Z axis, and the rotation angle is γ = arctan (δ / F) / 2, where δ is the distance between two light spots on the graticule of the laser autocollimator in the Z axis direction, and F is the focal length of the inner lens of the autocollimator. The top is measured by laser interference in the X axis direction. In summary, the laser interferometry method and the laser autocollimation method can be used to measure the six-degree-of-freedom change between the relative six-degree-of-freedom measuring device 14 and the relative measurement target device 24.

[0159] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall belong to the protection scope of the technical solution of the present invention. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0160] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in this field.

Claims

1. A long-distance high-precision six-degree-of-freedom absolute posture calibration method, characterized in that include: S0. Arrange a long-distance, high-precision, six-degree-of-freedom absolute position calibration system in a field, comprising: a sensor platform (1), a target platform (2), and a laser tracker (3); the sensor platform (1) and the target platform (2) are both located on a long guide rail, the target platform (2) can move along the long guide rail, and the laser tracker (3) is located outside the long guide rail, and its position is moved according to measurement needs; the sensor platform (1) is provided with a camera sensor (12), a laser rangefinder sensor (13), and a relative six-degree-of-freedom measurement device (14); an LED active target (22), a first corner reflector (23), and a relative measurement target device (24) are fixedly installed on the target platform (2); four or more measurement positions are determined between the sensor platform (1) and the target platform (2); S1, determining the coordinate system of the sensor platform in the reference coordinate system of the laser tracker, and further determining the optical reference origin of the laser rangefinder sensor (13) and the positional relationship between the optical reference origin of the laser rangefinder sensor (13) and the sensor platform (1) through the laser tracker (3); S2, defining the position closest to the sensor platform (1) among the set measurement positions as the initial measurement position, and moving the target platform (2) to the initial measurement position; determining the absolute position relationship between the LED active target (22), the first corner reflector (23), the relative measurement target device (24) and the target platform (2) by means of a laser tracker (3); S3, keeping the measurement position unchanged, determining the six-degree-of-freedom posture of the sensor platform and the target platform at the initial measurement position; S4, at the initial measurement position, returning the result of the relative six-degree-of-freedom measuring device (14) to zero; S5: moving the target platform (2) to a measurement position away from the sensor platform (1), continuously measuring and recording the measurement results of the relative six-degree-of-freedom measuring device (14) during the movement, and solving the relative change of the six degrees of freedom of the target platform (2); S6: solving the six-degree-of-freedom posture of the target platform (2) relative to the sensor platform (1) at the farthest measurement position to be measured; S7: solving the five-degree-of-freedom measurement result of the camera sensor (12) relative to the target platform coordinate system, and the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector (23); S8: Repeatedly change the position and posture of the target platform (2), solve the relationship between the camera sensor (12) and the sensor platform (1), and complete the calibration of the position and posture relationship between the camera sensor (12) and the laser rangefinder sensor (13).

2. A long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 1, characterized in that: In the long-distance high-precision six-degree-of-freedom absolute posture calibration system: The relative measurement target device (24) comprises: a metal load-bearing frame, a second corner reflector (241), a third corner reflector (242), a fourth corner reflector (243), a fifth corner reflector (244), a measuring plane mirror (245), and a sixth corner reflector (246); The coordinate system of the relative measurement target device (24) is defined as follows: the coordinate system of the relative measurement target device takes the center of the fourth corner reflector (243) as the origin, the direction of the line connecting the centers of the second corner reflector (241) and the fourth corner reflector (243) as the Y-axis direction, the normal direction of the plane where the centers of the second corner reflector (241), the third corner reflector (242) and the fourth corner reflector (243) are located as the Z-axis direction, and the X-axis direction is determined according to the right-hand rule; The relative six-degree-of-freedom measuring device (14) comprises a laser interferometer module and an autocollimator module, wherein the laser interferometer module measures relative distances and the autocollimator module measures relative angles; During installation, the first corner reflector (23) and the laser optical axis of the laser rangefinder sensor (13) are collinear.

3. A long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 1, characterized in that: In S1, the coordinate system of the sensor platform in the laser tracker reference coordinate system is determined, and the optical reference origin of the laser rangefinder sensor (13) and the positional relationship between the optical reference origin of the laser rangefinder sensor (13) and the sensor platform (1) are further determined by the laser tracker (3), specifically: The sensor platform (1) is provided with three sensor platform positioning pin holes (11); Turn on the laser tracker (3), place three laser tracker target balls at the positioning pin holes (11) of the sensor platform, and measure the coordinates S of the three laser target balls in the reference coordinate system of the laser tracker. ic =(x Sic ,y Sic ,z Sic ), ic=1,2,3; the sensor platform coordinate system is determined by the three target ball position coordinates; Assume that the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker are (x S1 ,y S1 ,z S1 ), then the unit vector of the sensor platform coordinate system axis is: The subscript S indicates the sensor platform coordinate system; The laser tracker (3) is fixed at a fixed position, and the first corner reflector (23) of the target platform (2) is moved to a plurality of different measuring positions along the laser optical axis direction of the laser rangefinder sensor (13), and the three coordinate values ​​(x Lj ,y Lj ,z Lj ), j=1~m represents the serial number of different measurement positions, and simultaneously records the distance measurement result d of the laser rangefinder sensor (13) j , j = 1 ~ m; determine the direction vector (l x ,l y ,l z ): The reference origin coordinate O of the laser rangefinder sensor (13) 1R (x O1R ,y O1R ,z O1R ) satisfies the following two equations: The coordinates O of the laser point reference origin relative to the tracker system are obtained by simultaneous solution. 1R (x O1R ,y O1R ,z O1R ); The reference origin of the laser rangefinder sensor is converted to the sensor platform coordinate system, thereby determining the positional relationship between the optical reference origin of the optical rangefinder sensor (13) and the sensor platform (1).

4. A long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 2, characterized in that: In S2, the absolute position relationship between the LED active target (22), the first corner reflector (23), the relative measurement target device (24) and the target platform (2) is determined by a laser tracker (3), specifically: The target platform (2) is provided with three target platform positioning pin holes (21); Move the target platform (2) to the initial measurement position, place the tracker target balls at the three target platform positioning pin holes (21), and measure the coordinates T of the three tracker target balls in the laser tracker reference coordinate system. im =(x Tim ,y Tim ,z Tim ), im=1,2,3; let the coordinate of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker be (x T1 ,y T1 ,z T1 ), then the unit vector of the target platform coordinate system is: The subscript T represents the target platform coordinate system; Next, the LED lamp of the LED active target (22) is removed, and the target ball of the laser tracker is placed at the position of the LED lamp hole in sequence, and its coordinate value is measured and converted to the target platform coordinate system obtained above, so as to determine the relationship between the LED lamp hole position and the target platform coordinate system; The laser tracker (3) is used to sequentially measure the coordinate values ​​of the first corner reflector (23) and the second corner reflector (241), the third corner reflector (242), and the fourth corner reflector (243) on the relative measurement target device (24), to obtain the relationship between the first corner reflector (23) and the target platform coordinate system, and finally, according to the definition of the coordinate system of the relative measurement target device (24), the relationship between the relative measurement target device coordinate system and the target platform coordinate system is obtained.

5. The long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 1, characterized in that: In S3, the six-degree-of-freedom pose of the sensor platform and the target platform at the initial measurement position is determined, specifically: The sensor platform (1) is provided with three sensor platform positioning pin holes (11); The target platform (2) and the laser tracker (3) are kept at the initial measurement positions unchanged, a tracker target ball is placed at the sensor platform positioning pin hole (11), the coordinates of the three target balls in the tracker coordinate system are remeasured, and the coordinates (x S1 ,y S1 ,z S1 ); The initial absolute position relationship between the sensor platform coordinate system and the target platform coordinate system is TL, and the attitude angle relationship is That is, determine the six-degree-of-freedom pose between the sensor platform coordinate system and the target platform coordinate system at the initial measurement position: Where: x T1 ,y T1 、z T1 are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker; S1 ,y S1 、z S1 They are the three-axis components of the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker; They are the unit vectors of the X, Y, and Z axes of the target platform coordinate system relative to the laser tracker reference coordinate system; They are the unit vectors of the X, Y, and Z axes of the sensor platform coordinate system relative to the laser tracker reference coordinate system; is the angle between the X-axis direction of the sensor platform and the X-axis direction of the target platform at the initial position; is the angle between the Y-axis direction of the sensor platform and the Y-axis direction of the target platform at the initial position; is the angle between the Z-axis direction of the sensor platform and the Z-axis direction of the target platform at the initial position.

6. A long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 2, characterized in that: In S5, the target platform (2) is moved to a measurement position away from the sensor platform (1), and the measurement results of the relative six-degree-of-freedom measuring device (14) are continuously measured and recorded during the movement, and the relative change of the six degrees of freedom of the target platform (2) is solved, which is specifically: The sensor platform (1) is fixed, and the target platform (2) is moved to a far distance along the long guide rail, wherein the farthest distance is determined according to the range of the camera and the laser rangefinder; The relative six-degree-of-freedom measuring device (14) continuously measures and records the six-degree-of-freedom variation of the relative measuring target device (24) during the movement of the target platform (2), and solves the variation Δx of the six-degree-of-freedom of the target platform coordinate system relative to the sensor platform (1) based on the relationship between the relative measuring target device (24) and the target platform coordinate system. T , Δy T , Δz T , Δα T , Δβ T , Δγ T ,in: Δx T Indicates the change in the X-axis position component of the target platform coordinate system relative to the sensor platform coordinate system during the motion process; Δy T Indicates the change in the Y-axis position component of the target platform coordinate system relative to the sensor platform coordinate system; Δz T Indicates the change in the Z-axis position component of the target platform coordinate system relative to the sensor platform coordinate system; Δα T Indicates the change in the angle between the target platform coordinate system and the sensor platform coordinate system in the X-axis direction; Δβ T Indicates the change in the Y-axis angle between the target platform coordinate system and the sensor platform coordinate system; Δγ T Indicates the change in the Z-axis angle between the target platform coordinate system and the sensor platform coordinate system.

7. The long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 1, characterized in that: In S6, the six-degree-of-freedom posture of the target platform (2) relative to the sensor platform (1) at the farthest measurement position to be measured is solved, specifically: According to the six-degree-of-freedom pose of the sensor platform coordinate system and the target platform in the initial state determined in S3, and the six-degree-of-freedom relative change of the target platform coordinate system in S5, the six-degree-of-freedom pose of the target platform coordinate system and the sensor platform coordinate system at the farthest measurement position to be measured is obtained. in, They are the three-axis position components between the coordinate system of the farthest sensor platform to be measured and the coordinate system of the target platform; are the angles between the X, Y, and Z axes of the sensor platform coordinate system at the farthest point to be measured and the target platform coordinate system; T1 ,y T1 、z T1 are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the reference coordinate system of the laser tracker at the initial position; S1 ,y S1 、z S1 are the three-axis components of the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker at the initial position; Δx T , Δy T , Δz T They respectively represent the changes in the X, Y, and Z axis position components of the target platform coordinate system relative to the sensor platform coordinate system during the process of the target platform moving from the initial position to the farthest point to be measured; Respectively represent the angles between the sensor platform X, Y, Z axis and the target platform X, Y, Z axis at the initial position; Δα T , Δβ T , Δγ T They respectively represent the changes in the angles of the target platform coordinate system relative to the sensor platform coordinate system in the X, Y, and Z axis directions when the target platform moves from the initial position to the farthest point to be measured.

8. The long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 1, characterized in that: In S7, the five-degree-of-freedom measurement result of the camera sensor (12) relative to the target platform coordinate system and the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector (23) are solved, specifically: Using a camera sensor (12) to image the LED active target (22), solving the coordinates of each LED light on the LED active target (22) in an optical coordinate system defined inside the camera sensor, and then determining the relationship between the camera sensor (12) and the target platform (2) based on the positional relationship between the LED active target (22) and the target platform coordinate system; Since the laser rangefinder sensor (13) is an absolute distance measuring instrument, the straight-line distance between the reference origin of the laser rangefinder sensor and the first corner reflector (23) is directly obtained.

9. The long-distance high-precision six-degree-of-freedom absolute position and posture calibration method according to claim 1, characterized in that: In S8, the position and posture of the target platform (2) are repeatedly changed to solve the relationship between the camera sensor (12) and the sensor platform (1), and the position and posture relationship calibration between the camera sensor (12) and the laser rangefinder sensor (13) is completed, specifically: The number of changes when changing the position and posture of the target platform is determined according to the number of sensors to be determined and the required accuracy index; the position and posture change of the target platform (2) is synchronously measured by a laser tracker (3), and the measurement results of the camera sensor and the laser rangefinder sensor are recorded at the same time, and the relationship between the camera sensor and the sensor platform (1) is solved, and then the position and posture relationship calibration between the camera sensor (12) and the laser rangefinder sensor (13) is completed; in the calculation process, the six-degree-of-freedom conversion is calculated by using a homogeneous rotation matrix and a homogeneous displacement matrix: Assume that the rotation matrix between the target platform coordinate system and the LED active target is R1, and the displacement matrix is ​​T1, the rotation matrix and displacement matrix between the LED active target and the camera sensor are R2 and T2 respectively, the rotation matrix and displacement matrix between the camera sensor and the sensor platform are R3 and T3 respectively, and the rotation matrix and displacement matrix between the target platform coordinate system and the sensor platform coordinate system are R4 and T4 respectively; According to the above definition, we can get: T4R4=T3R3T2R2T1R1 By changing the position and posture of the target platform (2) multiple times, multiple equations are obtained and then solved to obtain the six-degree-of-freedom position and posture relationship of the target platform (2) relative to the sensor platform (1). By using the position relationship between the reference origin of the laser rangefinder sensor (13) and the sensor platform (1), the position relationship of the laser rangefinder sensor (13) relative to the camera sensor (12) is further obtained to achieve position and posture calibration between the two sensors.

10. A long-distance, high-precision, six-degree-of-freedom absolute position and posture calibration system, characterized in that include: A sensor platform (1), a target platform (2), and a laser tracker (3), wherein the sensor platform (1) and the target platform (2) are both located on a long guide rail, the target platform (2) can move along the long guide rail, and the laser tracker (3) is located outside the long guide rail, and its position is moved according to measurement needs, so as to measure the absolute six degrees of freedom between the coordinate system of the sensor platform (1) and the coordinate system of the target platform (2); A relative six-degree-of-freedom measuring device (14) and a plurality of sensors whose postures need to be calibrated between each other are fixedly mounted on the sensor platform (1), and three sensor platform positioning pin holes (11) are provided. When the sensors and the relative six-degree-of-freedom measuring device (14) are installed, it is necessary to ensure that the optical paths do not block each other; at the same time, the sensors are as close as possible to ensure that the posture relationship between the sensors is not easily changed due to deformation of the sensor platform after the calibration is completed; The relative six-degree-of-freedom measuring device (14) is designed based on the integration and transformation of the laser interferometer and the autocollimator principle, and comprises a laser interferometer module and an autocollimator module, wherein the laser interferometer module measures relative distances and the autocollimator module measures relative angles; An LED active target (22), a first corner reflector (23), and a relative measurement target device (24) are fixedly mounted on the target platform (2); and three target platform positioning pin holes (21) are provided; Wherein: the LED active target (22) is composed of a plurality of LED lamps, and at least four LED lamps are required to realize the measurement function, and the distance between the LED lamps should be as large as possible; the LED lamp can be disassembled, and its package appearance size is consistent with the target ball of the laser tracker, ensuring that the position of the LED light point is concentric with the center of the target ball; The first corner reflector (23) is placed in the middle area of ​​the multiple LED lights of the LED active target (22); The relative measurement target device (24) comprises: a metal bearing frame, a second corner reflector (241), a third corner reflector (242), a fourth corner reflector (243), a fifth corner reflector (244), a measuring plane mirror (245) and a sixth corner reflector (246); the relative measurement target device coordinate system takes the center of the fourth corner reflector (243) as the origin, the direction of the line connecting the centers of the second corner reflector (241) and the fourth corner reflector (243) as the Y-axis direction, the normal direction of the plane where the centers of the second corner reflector (241), the third corner reflector (242) and the fourth corner reflector (243) are located is the Z-axis direction, and the X-axis direction is determined according to the right-hand rule; When the sensors that need to calibrate their poses are camera sensors and laser rangefinder sensors: The camera sensor measures five degrees of freedom between the camera sensor and the LED active target (22), including two-dimensional displacement and three-axis rotation angle, by imaging the LED active target (22) that is powered on and emits light; The laser rangefinder sensor uses the return light of the first corner reflector (23) to measure the absolute distance in the direction of the optical axis.

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