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

Abstract

A long-distance high-precision six-degree-of-freedom absolute pose calibration method and system, comprising: determining the absolute pose relationship between the LED active target, the first corner reflector, the relative measurement target device and the target platform; performing absolute pose measurement between the sensor platform coordinate system and the target platform coordinate system in the near distance; making the sensor platform and the target platform move relatively, and performing relative measurement of the six-degree-of-freedom pose change amount during the movement; calculating the absolute pose relationship of the sensor platform and the target platform coordinate system at a long distance; and solving the pose relationship between the sensors. The present application can realize high-precision calibration of the internal pose relationship of the sensors in the case of long-distance, high-precision absolute six-degree-of-freedom measurement of multiple sensor combinations, especially high-precision calibration of the optical coordinate systems of optical sensors.

Description

TECHNICAL FIELD

[0001] The application relates to a long-distance high-precision six-degree-of-freedom absolute pose calibration method and system, in particular to the application of fusion measurement of the six-degree-of-freedom (position and attitude) of a target by multiple sensors, and belongs to the technical field of pose measurement. BACKGROUND

[0002] Long-distance, high-precision, absolute measurement of the six-degree-of-freedom position and attitude of a target is widely required in the fields of industrial manufacturing, aerospace, robots and scientific research. However, in some special cases, considering the complexity of the measured target object, a single sensor or a single type of sensor gradually cannot meet the high-precision measurement requirements of the six-degree-of-freedom pose of the target in terms of measurement range, measurement accuracy and measurement efficiency. Therefore, combined measurement by multiple sensors is an effective way to solve this problem.

[0003] Generally, the purpose of multi-sensor measurement is to obtain the six-degree-of-freedom pose relationship between the sensor platform coordinate system and the target platform coordinate system through the fusion of the measurement results of multiple sensors. In order to realize the fusion of the measurement data of different types of sensors, the relative pose relationship between the different sensors used needs to be known, and this prior knowledge is obtained through a pre-calibration process. For a six-degree-of-freedom pose measurement device composed of a camera and a laser range finder, the camera coordinate system is a virtual point axis located at the camera optical center, and it is impossible to place a physical target for measurement. Moreover, the calibration error will be directly transmitted to the system error of the multi-sensor combined measurement device. Therefore, a long-distance, high-precision, absolute pose calibration method for the combined measurement device is crucial for achieving high-precision six-degree-of-freedom measurement.

[0004] Since there is no entity coordinate system for the camera and the laser in the combined measurement system, but the pose relationship between the two is needed as a known quantity for data fusion, and for a measurement range of tens to hundreds of meters, it is necessary to achieve micron-level displacement accuracy and angle-second-level attitude angle measurement accuracy. Currently, the three-coordinate machine method is mainly used to determine the pose relationship between the camera, the laser and multiple targets under short-distance application, which is low in efficiency, small in measurement range, and cannot locate the optical coordinate system of the camera and the laser, thus failing to meet the demand for large-range, high-precision six-degree-of-freedom absolute measurement.

[0005] Patent “Method and system for fusing point laser displacement sensor and binocular camera coordinate system” (CN112212784A) and patent “Fast calibration method and device for live-line work robot based on multiple sensors” (CN112223302A) propose corresponding solutions for the problem of cooperative pose measurement by multiple sensors under a specific scheme, but do not solve the calibration problem of multiple sensors without entity coordinate systems. SUMMARY

[0006] The technical solution of the present application is to overcome the shortcomings of the prior art and provide a long-distance high-precision six-degree-of-freedom absolute pose calibration method and system, which solves the technical problem of high-precision six-degree-of-freedom pose calibration of camera, laser and other optical sensor coordinate systems in a long distance, and realizes wide-range, high-precision and absolute six-degree-of-freedom pose measurement under the combination of camera and laser ranging sensor.

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

[0008] S0, a long-distance high-precision six-degree-of-freedom absolute pose calibration system is arranged in a site, comprising: a sensor platform, a target platform, and a laser tracker, the sensor platform and the target platform are 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 is moved according to the measurement requirement; the sensor platform is provided with a camera sensor, a laser range finder sensor, a relative six-degree-of-freedom measurement device, and three sensor platform positioning pin holes; the target platform is fixedly provided 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; four or more measurement positions are determined between the sensor platform and the target platform;

[0009] 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 range finder sensor and the positional relationship between the optical reference origin of the laser range finder sensor and the sensor platform are further determined by the laser tracker;

[0010] S2, the closest position to the sensor platform among the set measurement positions is defined as the initial measurement position, and the target platform is moved to the initial measurement position; the absolute pose relationship between the LED active target, the first corner reflector, the relative measurement target device and the target platform is determined by the laser tracker;

[0011] S3, the six-degree-of-freedom pose of the sensor platform and the target platform at the initial measurement position is determined while keeping the measurement position unchanged;

[0012] S4, the result of the relative six-degree-of-freedom measurement device is zeroed at the initial measurement position;

[0013] S5: move the target platform to the 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 six-degree-of-freedom relative change 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 degrees 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 range finder sensor and the first corner reflector;

[0016] S8: repeat the change of the target platform pose, solve the relationship between the camera sensor and the sensor platform, and complete the pose relationship calibration between the camera sensor and the laser range finder sensor.

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

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

[0019] The coordinate system of the relative measurement target device is defined as follows: the relative measurement target device coordinate system takes the center of the fourth corner reflector as the origin, the direction of the line connecting the second corner reflector and the center of the fourth corner reflector is the Y-axis direction, the normal direction of the plane passing through the centers of the second corner reflector, the third corner reflector and the fourth corner reflector 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 measurement device comprises a laser interferometer module and a collimator module, the laser interferometer module measures the relative distance, and the collimator module measures the relative angle;

[0021] When installed, the first corner reflector and the laser range finder sensor laser optical axis are collinear.

[0022] Preferably, 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 range finder sensor and the positional relationship between the optical reference origin of the laser range finder 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 of the three laser target balls in the reference coordinate system of the laser tracker S ic =(x Sic ,y Sic ,z Sic ), ic=1, 2, 3; the three target ball position coordinates determine the coordinate system of the sensor platform;

[0024] Let the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker be (x S1 ,y S1 ,z S1 ), then the unit vectors of the coordinate axes of the sensor platform coordinate system are:

[0025]

[0026] The subscript S represents a sensor platform coordinate system;

[0027] The position of the laser tracker is fixed, the first corner reflector of the target platform is moved to a plurality of different measurement positions along the laser axis of the laser range finder sensor, the three coordinate values (x Lj ,y Lj ,z Lj ) of the first corner reflector at different positions are measured by using the laser tracker, j = 1 ~ m represents the serial number of different measurement positions, and the ranging results d j of the laser range finder sensor are recorded simultaneously, j = 1 ~ m; the spatial straight line equation direction vector (l x ,l y ,l z ) in the reference coordinate system of the laser tracker is determined according to the three coordinate values of the points on the straight line:

[0028]

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

[0030]

[0031]

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

[0033] The reference origin of the laser range finder sensor is converted to the sensor platform coordinate system, so as to determine the position relationship between the optical reference origin of the laser range finder sensor and the sensor platform.

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

[0035] The target platform is moved to an initial measurement position, and three tracker target balls are respectively placed at three target platform positioning pin holes, and the coordinates T im =(x Tim ,y Tim ,z Tim of the three tracker target balls in the reference coordinate system of the laser tracker are measured.), im = 1, 2, 3; let the coordinates 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] Then, the LED lamps of the LED active target are removed, the target balls of the laser tracker are placed in the LED lamp holes in turn, the coordinate values are measured, and the relationship between the LED lamp holes and the target platform coordinate system is determined by conversion to the target platform coordinate system obtained above;

[0039] 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 are measured in turn using the laser tracker, the relationship between the first corner reflector and the target platform coordinate system is obtained, and finally the relationship between the relative measurement target device coordinate system and the target platform coordinate system is obtained according to the definition of the relative measurement target device coordinate system.

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

[0041] The initial measurement position of the target platform and the laser tracker is kept unchanged, the tracker target balls are placed at the positioning pin holes of the sensor platform, the coordinates of the three target balls in the tracker coordinate system are re-measured, and the coordinates (x S1 ,y S1 ,z S1 ) of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker are obtained and assigned;

[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, the six-degree-of-freedom pose between the sensor platform coordinate system and the target platform coordinate system at the initial measurement position is determined:

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

[0044]

[0045] Wherein: x T1 , yT1 z T1 These are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the laser tracker reference coordinate system; x S1 y S1 z S1 These 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; These 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; These 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, respectively. Let X be the angle between the X-axis direction of the sensor platform and the X-axis direction of the target platform at the initial position. Let Y be the angle between the Y-axis direction of the sensor platform and the Y-axis direction of the target platform at the initial position. Let be 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 step S5, the target platform is moved to a measurement position away from the sensor platform. During the movement, the measurement results relative to the six-degree-of-freedom measuring device are continuously measured and recorded, and the relative change of the six degrees of freedom of the target platform is solved. Specifically:

[0047] A fixed sensor platform is used, and the target platform is moved along a long guide rail to a distance. The maximum distance is determined based on 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 changes relative to the measuring target device during the target platform's motion. Based on the relationship between the relative measuring target device and the target platform coordinate system, the change Δx of the six-degree-of-freedom changes of the target platform coordinate system relative to the sensor platform is calculated. T Δy T Δz T , Δα T Δβ T Δγ T ,in:

[0049] Δx T Δy represents the change in the X-axis position component of the target platform coordinate system relative to the sensor platform coordinate system during motion. T Δz represents the change in the Y-axis position component of the target platform coordinate system relative to the sensor platform coordinate system. T Δα represents the change in the Z-axis position component of the target platform coordinate system relative to the sensor platform coordinate system. T Δβ represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the X-axis. TΔγ represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the Y-axis. T This represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the Z-axis.

[0050] Preferably, in S6, the six-degree-of-freedom pose of the target platform relative to the sensor platform when calculating the farthest measurement position is to be measured is as follows:

[0051] Based on the initial state relationship between the sensor platform coordinate system and the target platform coordinate system determined in step S3, and the six-degree-of-freedom relative changes of the target platform coordinate system in step 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.

[0052]

[0053] in, These are the three-axis position components between the sensor platform coordinate system and the target platform coordinate system at the furthest point to be measured; These represent the angles between the X, Y, and Z axes of the sensor platform coordinate system and the target platform coordinate system at the furthest point to be measured; x T1 y T1 z T1 These are the three-axis components of the coordinates of the target platform's coordinate system origin relative to the laser tracker's reference coordinate system at the initial position; x S1 y S1 z S1 These are the three-axis components of the coordinates of the sensor platform coordinate system origin relative to the laser tracker reference coordinate system at the initial position; Δx T Δy T Δz T These 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 as the target platform moves from its initial position to the furthest point to be measured. Δα represents the angles between the X, Y, and Z axes of the sensor platform and the X, Y, and Z axes of the target platform at the initial position, respectively. T Δβ T Δγ T These represent the changes in the angles between the target platform's coordinate system and the sensor platform's coordinate system along the X, Y, and Z axes, respectively, as the target platform moves from its initial position to the furthest point to be measured.

[0054] Preferably, in S7, 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 laser rangefinder sensor reference origin and the first corner reflector, are specifically calculated as follows:

[0055] The camera sensor is used to image the LED active target. The coordinates of each LED on the LED active target are solved in the optical coordinate system defined inside the camera sensor. Then, the relationship between the camera sensor and the target platform is determined 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 laser rangefinder sensor reference origin and the first corner reflector can be obtained directly.

[0057] Preferably, in S8, the target platform pose is repeatedly changed to solve the relationship between the camera sensor and the sensor platform, thus completing the pose relationship calibration between the camera sensor and the laser rangefinder sensor. Specifically:

[0058] The number of pose changes when altering the target platform is determined based on the number of sensors to be determined and the required accuracy specifications. A laser tracker is used to simultaneously measure the pose change of the target platform, while recording the measurement results from the camera sensor and laser rangefinder sensor. The relationship between the camera sensor and the sensor platform is then determined, thereby calibrating the pose relationship between the camera sensor and the laser rangefinder sensor. During the calculation process, homogeneous rotation and translation matrices are used to perform six-degree-of-freedom transformations.

[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 between the LED active target and the camera sensor is R2 and T2 respectively, the rotation matrix between the camera sensor and the sensor platform is R3 and T3 respectively, and the rotation matrix between the target platform coordinate system and the sensor platform coordinate system is R4 and T4 respectively.

[0060] Based on the above definition, we can obtain:

[0061] T4R4=T3R3T2R2T1R1

[0062] By repeatedly changing the pose of the target platform, multiple equations are obtained and solved to obtain the six-degree-of-freedom pose relationship between the target platform and the sensor platform. Using the positional relationship between the reference origin of the laser rangefinder sensor and the sensor platform, the positional relationship between the laser rangefinder sensor and the camera sensor is further obtained, thus realizing the pose calibration between the two sensors.

[0063] Secondly, a long-distance, high-precision six-degree-of-freedom absolute pose calibration system is provided, 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 can be moved according to the measurement needs to measure the absolute six degrees of freedom between the sensor platform coordinate system and the target platform coordinate system.

[0064] The sensor platform is fixedly mounted with a relative six degrees of freedom measurement device and multiple sensors that need to be calibrated for the pose between each pair. It is equipped with three sensor platform positioning pin holes. When installing each sensor and the relative six degrees of freedom measurement device, it is necessary to ensure that the optical path does not block each other. At the same time, each sensor should be as close as possible to ensure that the pose relationship between each sensor is not easily changed due to the deformation of the sensor platform after calibration.

[0065] The relative six-degree-of-freedom measurement device is designed based on the integration and modification of the principles of laser interferometer and autocollimator. It includes a laser interferometer module and an autocollimator module. The laser interferometer module measures relative distance, and the autocollimator module measures relative angle.

[0066] An LED active target, a first corner reflector, and a relative measurement target device are fixedly installed on the target platform; and three target platform positioning pin holes are provided.

[0067] The active LED target consists of multiple LEDs. To achieve the measurement function, at least four LEDs are required, and the spacing between the LEDs should be as large as possible. The LEDs are detachable, and their packaged external dimensions are consistent with the target sphere of the laser tracker to ensure that the position of the LED light spot is concentric with the center of the target sphere.

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

[0069] The relative measurement target device includes: a metal load-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 has the center of the fourth corner reflector as the origin, the direction of the line connecting the centers of the second and fourth corner reflectors is the Y-axis direction, the normal direction of the plane containing the centers of the second, third, and fourth corner reflectors 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 the pose between pairs of sensors are camera sensors and laser rangefinder sensors:

[0071] The camera sensor images an electrically powered LED active target and measures five degrees of freedom between itself and the LED active target, including two-dimensional displacement and three-axis rotation.

[0072] Laser rangefinder sensors use the reflected light from a first corner reflector to measure the absolute distance along the optical axis.

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

[0074] (1) This invention achieves high-precision absolute pose measurement over long distances by combining close-range high-precision absolute pose measurement with long-range relative pose measurement, thereby reducing the requirement for direct high-precision absolute six degrees of freedom measurement over long distances. At the same time, the pose calibration task of the "camera + laser" combined measurement device can be further realized by using the high-precision absolute six degrees of freedom measurement results over long distances.

[0075] (2) In the long-distance relative pose measurement method adopted in this invention, the combination of laser interferometry and laser collimation can achieve high-precision relative six degrees of freedom measurement, while having no requirements on the absolute relationship of the coordinate systems of the laser interferometry and laser collimation devices. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of the sensor platform and target platform corresponding to the method of the present invention;

[0077] Figure 2 This 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 flowchart illustrating the high-precision absolute pose measurement process over long distances according to the present invention.

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

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

[0081] Figure 6 This is a flowchart of the absolute pose calibration process of the present invention, taking "camera + laser" as an example;

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

[0083] Figure 8 This is a side view of the relative measurement target device of the present invention. Detailed Implementation

[0084] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0085] This invention proposes a long-distance, high-precision six-degree-of-freedom absolute pose calibration method, and uses the absolute pose calibration of a six-degree-of-freedom measurement device combining a camera and a laser as an example to introduce its specific implementation process. It can achieve high-precision pose calibration between multiple sensors. However, this invention is not limited to the "camera + laser" combined measurement device. Theoretically, the internal calibration of all six-degree-of-freedom measurement devices with multiple sensor combinations can be carried out using this method.

[0086] The first aspect of this invention proposes a method for achieving high-precision six-degree-of-freedom absolute pose measurement over long distances by combining "near-range absolute + long-distance relative" approaches, thereby enabling pose calibration within a "camera + laser" combined measurement device.

[0087] Different types of sensors (such as sensor 1, sensor 2, ... sensor n) are installed on sensor platform 1, and a sensor platform coordinate system is defined on sensor platform 1; the measurement targets of each sensor (target 1, target 2, ... target n) are installed on target platform 2, and a target platform coordinate system is defined on 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 positioning pin holes must be no less than 3. Figure 2 As shown, the center of the upper left corner positioning pin hole of sensor platform 1 is selected as the origin, the line connecting the center of the upper left corner positioning pin hole and the center of the upper right corner positioning pin hole is the X-axis direction, the normal direction of the plane where the centers of the three positioning 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 positioning pin holes 21 on the rigid body of the target platform 2. The number of positioning pin holes must be no less than 3. The center of the positioning pin hole at the upper left corner of the target platform 2 is selected as the origin. The line connecting the center of the positioning pin hole at the upper left corner and the center of the positioning pin hole at the upper right corner is the X-axis direction. The normal direction of the plane where the centers of the three positioning pin holes are located is the Z-axis direction. The Y-axis direction is determined according to the right-hand rule.

[0090] Figure 4 This is a long-distance, high-precision, six-DOF absolute pose calibration system, comprising: sensor platform 1, target platform 2, and 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 installed on the sensor platform 1. The installation positions of the camera sensor 12, laser rangefinder sensor 13, and relative six-degree-of-freedom measuring device 14 should ensure that the optical paths do not block each other.

[0092] The camera sensor 12 and the laser rangefinder sensor 13 are placed as close as possible to ensure that their pose relationship is not easily changed due to 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 installed on the target platform 2.

[0094] The LED active target 22 consists of multiple LEDs. To achieve the measurement function, at least four LEDs are required, and the spacing between the LEDs should be as large as possible. The LEDs are detachable, and their package dimensions are consistent with the target sphere of the laser tracker, ensuring that the position of the LED light spot is concentric with the center of the target sphere.

[0095] The first corner reflector 23 can be placed in the middle area of ​​multiple LEDs of the LED active target 22.

[0096] The relative six-degree-of-freedom measuring device 14 performs relative six-degree-of-freedom measurements on the relative measuring target device 24. The relative measuring target device 24 consists of 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.

[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 containing the centers of the second corner reflector 241, the third corner reflector 242, and the fourth corner reflector 243 is the Z-axis direction, and the X-axis direction is determined according to the right-hand rule.

[0098] During installation, the first corner reflector 23 and 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 as possible to the center of the field of view.

[0101] During installation, the laser interferometer module in the six-degree-of-freedom measuring device 14 emits five beams, with the beam axes of the emitted beams 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 beam, which 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, which are respectively 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. 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 load-bearing frame of the relative measuring target device 24, with the spacing between them as large as possible, for measuring displacement along the Z-axis and rotation angles 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 for measuring displacement changes along the Y-axis and rotation angle changes around the Z-axis. The sixth corner reflector 246 is mounted on the top surface of the metal frame for measuring displacement changes along the X-axis.

[0103] When the LED active target 22 is powered on, it emits light. The camera sensor 12 images the LED active target 22, thereby measuring the two-dimensional lateral displacement and three-axis rotation, which are five degrees of freedom between the camera sensor and the LED active target.

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

[0105] The relative six-degree-of-freedom measuring device 14 uses the relative measuring target device 24 to measure 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 measuring device 14 are all within their respective fields of view, whether at close range or at a distance.

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

[0108] The present invention proposes a method based on a combination of "near-range absolute + far-range relative" to achieve high-precision absolute pose measurement over long distances. The specific steps are as follows:

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

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

[0111] Step S103: Make the sensor platform move relative to the target platform, and measure the relative changes in pose of the six degrees of freedom during the movement;

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

[0113] Step S105: Solve for the pose relationship between the sensors (camera, laser rangefinder).

[0114] To determine the absolute pose relationship between the LED active target, the first corner reflector, the relative measurement target device, and the target platform, the LED lights can be removed. The coordinates of the mounting holes of each LED light can be measured sequentially using a laser tracker target ball. 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 positioning pin holes on the target platform can also be measured using a laser tracker. Based on the coordinate system definition, the absolute pose relationship between the coordinate system of the LED active target, the first corner reflector, the relative measurement target device, and the target platform can be determined.

[0115] The process involves relative motion between the sensor platform and the target platform, during which the relative measurement of six degrees of freedom pose changes is performed. Generally, the sensor platform is kept stationary while the target platform is moved from near to far. This 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] Solving the pose relationship between the sensors requires using the relationship between the sensor platform coordinate system and the target platform coordinate system obtained in the previous steps, as well as the absolute pose measurement results of the target by multiple sensors. This process involves solving in multiple different pose states and calculating the pose relationship between sensors 1, 2...n.

[0117] This invention proposes a long-distance, high-precision six-DOF absolute pose calibration method. This method obtains the absolute six-DOF pose information between a sensor platform and a target platform using a "near-range absolute + long-range relative" approach. Measurements are then taken using a camera and a laser rangefinder, and the relative pose relationship between the camera and the laser rangefinder is solved in reverse, thus achieving pose calibration between them. For ease of understanding, a specific implementation method for this measurement process is described below, such as... Figure 6 As shown.

[0118] Step S201: Determine 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 balls at the positioning pin hole 11 on the sensor platform 1, and measure the coordinates S of the three target balls in the tracker reference coordinate system (customized within the laser tracker device). ic =(x Sic ,y Sic ,z Sic (ic=1,2,3). The sensor platform coordinate system can be determined by the coordinates of these three target sphere positions, 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 If the coordinate axis X of the sensor platform coordinate system is... S Y S Z S The unit vector of the laser tracker in the reference coordinate system can be determined according to formula (1). S represents the sensor platform coordinate system.

[0120]

[0121] Then, keeping the laser tracker 3 stationary, the first corner reflector 23 is moved to multiple different positions along the laser optical axis of the laser rangefinder sensor 13 (e.g., Figure 4 At positions A, B, C, and D in the diagram, the three coordinate values ​​(e.g., x, y, y) of the first corner reflector 23 at different positions are measured using a laser tracker 3. Lj ,y Lj ,z Lj (j = 1 to m are the serial numbers of different measurement positions), and simultaneously record the ranging result d of the laser rangefinder sensor 13. j (j=1~m). The spatial line equation direction vector (l) in the reference coordinate system of the laser tracker can be determined from the three coordinate values ​​of the points on the line according to formula (2). x ,l y ,l z ).

[0122]

[0123] Next, based on the ranging result of the laser rangefinder sensor 13, the coordinates O of the laser point reference origin relative to the tracking system are uniquely determined. 1R (x O1R ,y O1R ,z O1R ), that is, the reference origin coordinates O of the laser rangefinder sensor 13. 1R (x O1R ,y O1R ,z O1R It satisfies both formula (2) and formula (3).

[0124]

[0125] Finally, the reference origin of the laser rangefinder sensor is converted to the coordinate system of the sensor platform, 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 pose 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 nearby (e.g., Figure 4 Position A): Place the tracker target ball at the positioning pin hole 21 on the target platform, and measure the coordinates T of the three target balls in the tracker reference coordinate system (customized within the laser tracker device). i =(x Tim ,y Tim ,z Tim (im=1,2,3). Let the coordinates of the origin of the target platform coordinate system relative to the laser tracker reference coordinate system be (x... T1 ,y T1 ,z T1 If the coordinate axis of the target platform coordinate system is x, then the coordinate axis of the target platform coordinate system is x. T y T z T The unit vector 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 lights from the LED active target 22, place the target ball of the laser tracker at the LED light hole positions in sequence, measure their coordinate values, and convert them to coordinates in the target platform coordinate system to determine the relationship between the LED light hole positions and the target platform coordinate system.

[0130] Then, 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 are measured sequentially using the laser tracker 3 to obtain the relationship between the first corner reflector 23 and the target platform coordinate system. Finally, according to the aforementioned definition of the coordinate system of the relative measurement target device 24, the relationship between the coordinate system of the relative measurement target device and the target platform coordinate system is obtained.

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

[0132] Specifically, keeping both the target platform 2 and the laser tracker 3 at the measurement position in step S202 unchanged, 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 measured again. 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 If the coordinate axis of the sensor platform coordinate system is x, then the coordinate axis of the sensor platform coordinate system is x. S y S z S The unit vector can be determined according to formula (1).

[0133] Using formula (5), the initial absolute position relationship between the sensor platform coordinate system and the target platform coordinate system is calculated as TL, and the attitude angle relationship is as follows: That is, the initial state (e.g.) can be determined Figure 4 Position 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 These are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the laser tracker reference coordinate system; x S1 y S1 z S1 These 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; These 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; These 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, respectively. Let X be the angle between the X-axis direction of the sensor platform and the X-axis direction of the target platform at the initial position. Let Y be the angle between the Y-axis direction of the sensor platform and the Y-axis direction of the target platform at the initial position. Let be 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 where 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 zeroed.

[0137] Specifically, the relative six degrees of freedom measurement device 14 is turned on, ensuring 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 degrees of freedom measurement device 14 in the initial state is zeroed.

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

[0139] Step S205: Move the target platform 2 to a distance, record the measurement results relative to the six-degree-of-freedom measuring device 14, and solve for the relative change of the six degrees of freedom of the target platform 2.

[0140] Specifically, the sensor platform 1 is fixed, and the target platform 2 is moved along the long guide rail to a distant location, such as position B, C, D, or other positions. The maximum distance is determined based on the range of the camera and laser rangefinder. The relative six-degree-of-freedom measuring device 14 continuously measures and records the six-degree-of-freedom changes relative to the measuring target device 24 during the movement of the target platform 2. Based on the relationship between the relative measuring 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 calculated. T Δy T Δz T , Δα T Δβ T Δγ T .

[0141] Where, Δx T Δy represents the change in the X-axis position component of the target platform coordinate system relative to the sensor platform coordinate system during motion. T Δz represents the change in the Y-axis position component of the target platform coordinate system relative to the sensor platform coordinate system. T Δα represents the change in the Z-axis position component of the target platform coordinate system relative to the sensor platform coordinate system. T Δβ represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the X-axis. T Δγ represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the Y-axis. TThis represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the Z-axis.

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

[0143] Specifically, based on 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 changes of the six degrees of freedom of the target platform coordinate system in step S205, the six-degree-of-freedom pose of the target platform coordinate system and the sensor platform coordinate system at a distance is obtained.

[0144]

[0145] in, These are the three-axis position components between the sensor platform coordinate system and the target platform coordinate system at the furthest point to be measured; These represent the angles between the X, Y, and Z axes of the sensor platform coordinate system and the target platform coordinate system at the furthest point to be measured; x T1 y T1 z T1 These are the three-axis components of the coordinates of the target platform's coordinate system origin relative to the laser tracker's reference coordinate system at the initial position; x S1 y S1 z S1 These are the three-axis components of the coordinates of the sensor platform coordinate system origin relative to the laser tracker reference coordinate system at the initial position; Δx T Δy T Δz T These 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 as the target platform moves from its initial position to the furthest point to be measured. Δα represents the angles between the X, Y, and Z axes of the sensor platform and the X, Y, and Z axes of the target platform at the initial position, respectively. T Δβ T Δγ T These represent the changes in the angles between the target platform's coordinate system and the sensor platform's coordinate system along the X, Y, and Z axes, respectively, as the target platform moves from its initial position to the furthest point to be measured.

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

[0147] Specifically, the camera sensor 12 is used to image the LED active target 22. Under the optical coordinate system defined inside the camera sensor, the coordinates of each LED of the LED active target 22 are solved. 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 laser rangefinder sensor reference origin and the first corner reflector 23, as determined in step S201, can be directly obtained.

[0149] Step S208: Change the pose of the target platform 2 multiple times, solve the relationship between the camera sensor 12 and the sensor platform 1, and complete the pose relationship calibration between the camera sensor 12 and the laser rangefinder sensor 13.

[0150] Specifically, since there are six unknowns in the six-degree-of-freedom relationship between the camera sensor and the sensor platform coordinate system, and one unknown between the camera sensor and the LED active target, determining these seven unknowns requires multiple changes to the target platform's pose. The laser tracker 3 must simultaneously measure the pose changes of the target platform 2, while recording the measurement results from the camera sensor and the laser rangefinder sensor. Figure 5 Using the coordinate system relationship shown, the relationship between the camera sensor and the sensor platform 1 is solved, and then the pose relationship between the camera sensor 12 and the laser rangefinder sensor 13 is calibrated.

[0151] The six-degree-of-freedom transformation can be calculated using homogeneous rotation and displacement matrices. For example, assuming 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 between the LED active target and the camera sensor is R2 and T2 respectively, the rotation matrix between the camera sensor and the sensor platform is R3 and T3 respectively, and the rotation matrix between the target platform coordinate system and the sensor platform coordinate system is R4 and T4 respectively, R4 and T4 can be obtained from the six-degree-of-freedom pose 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 pose 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 pose relationship between the target platform 2 and the sensor platform 1, the positional relationship between the laser rangefinder sensor 13 and the sensor platform 1 obtained in step S201 can be obtained, and the pose calibration between the two sensors can be realized.

[0152] T4R4=T3R3T2R2T1R1 (7)

[0153] Thus, the pose relationship between the optical coordinate system of the camera sensor 12 and the reference origin of the laser rangefinder sensor 13 can be obtained, which completes the internal pose relationship calibration of the combined six-degree-of-freedom measurement device "camera + laser".

[0154] This invention is particularly applicable to the internal calibration of multiple sensors requiring long-distance, high-precision measurement. The reason for using long-distance calibration in this case is that camera sensors are typically designed to perform measurements only within a specific distance range. Furthermore, since the measurement accuracy of a combined six-degree-of-freedom (6DOF) measurement device can reach 50 μm and 5", calibrating both typically requires a calibration method with at least three times the measurement accuracy. Currently, there are almost no absolute 6DOF pose measurement devices with such high precision. Therefore, this invention proposes using a relative 6DOF device for long-distance measurement, while using a high-precision laser tracker for close-range measurement. By employing a "close-range absolute + long-range relative" measurement method, the pose of the two measurement devices is calibrated, resulting in ultra-high precision absolute 6DOF information at long distances, thereby enabling the calibration of the pose relationships between multiple sensors.

[0155] In another aspect, the present invention provides a relative six-degree-of-freedom measuring device 14, which is based on the principle of laser interferometer and autocollimator. The laser interferometer realizes the relative distance measurement, and the autocollimator performs the relative angle measurement.

[0156] The laser interferometer employs the principle of dual-frequency laser heterodyne interference. Its output light contains two optical frequencies, f1 and f2, with similar frequencies and orthogonal polarizations. These are split by a polarizing beam splitter, allowing them to be incident on the reference mirror and the measuring mirror (i.e.,...) respectively. Figure 7 The light returned by the measuring mirror and the reference mirror is combined and then passes through a polarizer to generate heterodyne interference. The signal after low-pass filtering by the detector is shown in formula (8), where λ is the laser wavelength and Δ1-Δ2 is the optical path difference between the reference mirror and the measuring mirror. The displacement along the optical axis is obtained by the phase change of the interference signal during the target's motion.

[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 using a laser tracker or a coordinate measuring 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, Δz1 and Δz2, are measured using a laser interferometer. Therefore, the change in the rotation angle 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. 13The displacement changes of the two beams, Δz1 and Δz3, are measured using a laser interferometer. Therefore, the change in the rotation angle around the Y-axis is β=arcsin((Δz1-Δz3) / D 13 The rotation angle γ around the Z-axis is measured using a side plane mirror via laser autocollimation. The rotation angle is γ = arctan(δ / F) / 2, where δ is the distance between the two light spots on the reticle of the laser autocollimator in the Z-axis direction, and F is the focal length of the inner lens of the autocollimator. Displacement in the X-axis direction is measured using laser interferometry at the top. In summary, laser interferometry and laser autocollimation can be used to measure the six degrees of freedom variation between the relative six-degree-of-freedom measuring device 14 and the relative measuring target device 24.

[0159] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the disclosed methods and techniques without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall fall within the protection scope of the present invention. Where there is no conflict, the embodiments of this application and the technical features thereof can be combined with each other.

[0160] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A long-distance, high-precision six-DOF absolute pose calibration method, characterized in that... include: S0. A long-distance, high-precision six-degree-of-freedom absolute pose calibration system is set up in the field, including: 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. The laser tracker (3) is located outside the long guide rail and its position can be moved according to the measurement needs. A camera sensor (12), a laser rangefinder sensor (13), and a relative six-degree-of-freedom measuring device (14) are set on the sensor platform (1). An LED active target (22), a first corner reflector (23), and a relative measuring 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. Determine the coordinate system of the sensor platform under the reference coordinate system of the laser tracker, and further determine 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. Define the position closest to the sensor platform (1) in the set measurement position as the initial measurement position, and move the target platform (2) to the initial measurement position; determine the absolute pose relationship between the LED active target (22), the first corner reflector (23), the relative measurement target device (24) and the target platform (2) through the laser tracker (3); S3. Keep the measurement position unchanged and determine the six-degree-of-freedom pose of the sensor platform and the target platform at the initial measurement position; S4. At the initial measurement position, reset the result of the relative six-degree-of-freedom measuring device (14) to zero; S5: Move the target platform (2) to a measurement position away from the sensor platform (1), continuously measure and record the measurement results relative to the six-degree-of-freedom measuring device (14) during the movement, and solve for the six-degree-of-freedom relative change of the target platform (2); S6: Solve the six-degree-of-freedom pose of the target platform (2) relative to the sensor platform (1) at the farthest measurement position; S7: Solve for the five-degree-of-freedom measurement results of the camera sensor (12) relative to the target platform coordinate system, and the straight-line distance between the laser rangefinder sensor reference origin and the first corner reflector (23); S8: Repeatedly change the pose of the target platform (2), solve the relationship between the camera sensor (12) and the sensor platform (1), and complete the pose relationship calibration between the camera sensor (12) and the laser rangefinder sensor (13).

2. The long-distance, high-precision six-degree-of-freedom absolute pose calibration method according to claim 1, characterized in that: In the long-distance, high-precision six-DOF absolute pose calibration system: The relative measurement target device (24) includes: 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 measuring target device (24) is defined as follows: the coordinate system of the relative measuring 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 containing the centers of the second corner reflector (241), the third corner reflector (242), and the fourth corner reflector (243) is 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) 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. During installation, the laser optical axes of the first corner reflector (23) and the laser rangefinder sensor (13) are collinear.

3. The long-distance, high-precision six-degree-of-freedom absolute pose calibration method according to claim 1, characterized in that: In S1, the coordinate system of the sensor platform under the reference coordinate system of the laser tracker is determined. Further, 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 determined using 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 hole (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 coordinates of these three target ball positions determine the sensor platform coordinate system; Let the coordinates of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker be (x...). S1 ,y S1 ,z S1 If the coordinate axes of the sensor platform coordinate system are then defined as follows: The subscript S indicates the sensor platform coordinate system; With the laser tracker (3) fixed in place, the first corner reflector (23) of the target platform (2) is moved to multiple different measurement positions along the laser optical axis of the laser rangefinder sensor (13). The laser tracker (3) is used to measure the three coordinate values ​​(x, y, y) of the first corner reflector (23) at different positions. Lj ,y Lj ,z Lj ), j = 1 to m represent the serial numbers of different measurement positions, and the ranging results d of the laser rangefinder sensor (13) are recorded at the same time. j , j = 1 ~ m; Determine the direction vector (l) of the spatial straight line equation in the reference coordinate system of the laser tracker based on the three coordinate values ​​of the points on the straight line. x ,l y ,l z ): The coordinates of the reference origin O of the laser rangefinder sensor (13) 1R (x O1R ,y O1R ,z O1R Simultaneously satisfying the following two equations: Solving the system of equations simultaneously yields the coordinates O of the laser point reference origin relative to the tracking system. 1R (x O1R ,y O1R ,z O1R ); The reference origin of the laser rangefinder sensor is converted to the coordinate system of the sensor platform, thereby determining the positional relationship between the optical reference origin of the optical rangefinder sensor (13) and the sensor platform (1).

4. The long-distance, high-precision six-degree-of-freedom absolute pose calibration method according to claim 2, characterized in that: In S2, the absolute pose 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 the laser tracker (3), specifically as follows: 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 ball 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 coordinates of the origin of the target platform coordinate system relative to the laser tracker reference coordinate system be (x T1 ,y T1 ,z T1 If the coordinates of the target platform are such that the unit vector of the target platform coordinate system is: The subscript T indicates the target platform coordinate system; Next, remove the LED lights from the LED active target (22), place the laser tracker target ball at the LED light hole positions in sequence, measure its coordinate values, and convert them to the target platform coordinate system obtained above to determine the relationship between the LED light hole positions and the target platform coordinate system. The coordinate values ​​of the first corner reflector (23) and the second corner reflector (241), third corner reflector (242) and fourth corner reflector (243) on the relative measurement target device (24) are measured sequentially using a laser tracker (3) to obtain the relationship between the first corner reflector (23) and the target platform coordinate system. Finally, according to the definition of the coordinate system of the relative measurement target device (24), the relationship between the coordinate system of the relative measurement target device and the target platform coordinate system is obtained.

5. The long-distance, high-precision six-DOF absolute pose calibration method according to claim 1, characterized in that: S3 determines the six-degree-of-freedom poses of the sensor platform and the target platform at the initial measurement position, specifically as follows: The sensor platform (1) is provided with three sensor platform positioning pin holes (11); Keeping the target platform (2) and laser tracker (3) in their initial measurement positions unchanged, place the tracker target ball at the positioning pin hole (11) on the sensor platform, remeasure the coordinates of the three target balls in the tracker coordinate system, and obtain and assign the coordinates (x, y) of the origin of the sensor platform coordinate system relative to the reference coordinate system of the laser tracker. S1 ,y S1 ,z S1 ); Solve for the initial absolute position relationship between the sensor platform coordinate system and the target platform coordinate system, denoted as TL, and the attitude angle relationship as follows: That is, to 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 These are the three-axis components of the coordinates of the origin of the target platform coordinate system relative to the laser tracker reference coordinate system; x S1 y S1 z S1 These 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; These 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; These 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, respectively. Let X be the angle between the X-axis direction of the sensor platform and the X-axis direction of the target platform at the initial position. Let Y be the angle between the Y-axis direction of the sensor platform and the Y-axis direction of the target platform at the initial position. Let be 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. The long-distance, high-precision six-degree-of-freedom absolute pose 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). During the movement, the measurement results relative to the six-degree-of-freedom measuring device (14) are continuously measured and recorded. The relative change of the six degrees of freedom of the target platform (2) is solved, specifically: Fix the sensor platform (1), and move the target platform (2) along the long guide rail to a distance. The maximum 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 changes relative to the measuring target device (24) during the movement of the target platform (2), and solves for the six-degree-of-freedom changes Δx 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 Δy represents the change in the X-axis position component of the target platform coordinate system relative to the sensor platform coordinate system during motion. T Δz represents the change in the Y-axis position component of the target platform coordinate system relative to the sensor platform coordinate system. T Δα represents the change in the Z-axis position component of the target platform coordinate system relative to the sensor platform coordinate system. T Δβ represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the X-axis. T Δγ represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the Y-axis. T This represents the change in the angle between the target platform coordinate system and the sensor platform coordinate system along the Z-axis.

7. The long-distance, high-precision six-DOF absolute pose calibration method according to claim 1, characterized in that: In S6, the six-degree-of-freedom pose of the target platform (2) relative to the sensor platform (1) when the farthest measurement position to be measured is determined is as follows: Based on the six-DOF poses of the sensor platform coordinate system and the target platform in the initial state determined in S3, and the relative changes of the six-DOF of the target platform coordinate system in S5, the six-DOF poses of the target platform coordinate system and the sensor platform coordinate system at the farthest measurement position to be measured are obtained. in, These are the three-axis position components between the sensor platform coordinate system and the target platform coordinate system at the furthest point to be measured; These represent the angles between the X, Y, and Z axes of the sensor platform coordinate system and the target platform coordinate system at the furthest point to be measured; x T1 y T1 z T1 These are the three-axis components of the coordinates of the target platform's coordinate system origin relative to the laser tracker's reference coordinate system at the initial position; x S1 y S1 z S1 These are the three-axis components of the coordinates of the sensor platform coordinate system origin relative to the laser tracker reference coordinate system at the initial position; Δx T Δy T Δz T These 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 as the target platform moves from its initial position to the furthest point to be measured. Δα represents the angles between the X, Y, and Z axes of the sensor platform and the X, Y, and Z axes of the target platform at the initial position, respectively. T Δβ T Δγ T These represent the changes in the angles between the target platform's coordinate system and the sensor platform's coordinate system along the X, Y, and Z axes, respectively, as the target platform moves from its initial position to the furthest point to be measured.

8. The long-distance, high-precision six-degree-of-freedom absolute pose calibration method according to claim 1, characterized in that: In S7, the five-degree-of-freedom measurement results of the camera sensor (12) relative to the target platform coordinate system and the straight-line distance between the laser rangefinder sensor reference origin and the first corner reflector (23) are solved as follows: The camera sensor (12) is used to image the LED active target (22). Under the optical coordinate system defined inside the camera sensor, the coordinates of each LED on the LED active target (22) are solved. Then, based on the positional relationship between the LED active target (22) and the target platform coordinate system, the relationship between the camera sensor (12) and the target platform (2) is determined. Since the laser rangefinder sensor (13) is an absolute distance measuring instrument, the straight-line distance between the laser rangefinder sensor reference origin and the first corner reflector (23) can be obtained directly.

9. The long-distance, high-precision six-degree-of-freedom absolute pose calibration method according to claim 1, characterized in that: In S8, the pose of the target platform (2) is repeatedly changed to solve the relationship between the camera sensor (12) and the sensor platform (1), and the pose relationship calibration between the camera sensor (12) and the laser rangefinder sensor (13) is completed. Specifically: The number of changes when changing the pose of the target platform is determined based on the number of sensors to be determined and the required accuracy index; the pose change of the target platform (2) is measured synchronously using a laser tracker (3), 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 (1), and then the pose relationship calibration between the camera sensor (12) and the laser rangefinder sensor (13) is completed; in the calculation process, the six-degree-of-freedom transformation is calculated using homogeneous rotation matrix and 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 between the LED active target and the camera sensor is R2 and T2 respectively, the rotation matrix between the camera sensor and the sensor platform is R3 and T3 respectively, and the rotation matrix between the target platform coordinate system and the sensor platform coordinate system is R4 and T4 respectively. Based on the above definition, we can obtain: T4R4=T3R3T2R2T1R1 By changing the pose of the target platform (2) multiple times, multiple equations are obtained and solved to obtain the six-degree-of-freedom pose relationship of the target platform (2) relative to the sensor platform (1). Using the positional relationship between the reference origin of the laser rangefinder sensor (13) and the sensor platform (1), the positional relationship between the laser rangefinder sensor (13) and the camera sensor (12) is further obtained, thus realizing the pose calibration between the two sensors.

10. A long-distance, high-precision six-DOF absolute pose calibration system, characterized in that... include: Sensor platform (1), target platform (2), laser tracker (3). Sensor platform (1) and target platform (2) are both located on a long guide rail. Target platform (2) can move along the long guide rail. Laser tracker (3) is located outside the long guide rail. Its position can be moved according to measurement needs. The absolute six degrees of freedom between the coordinate system of sensor platform (1) and the coordinate system of target platform (2) are measured. A relative six-degree-of-freedom measuring device (14) and multiple sensors that need to be calibrated for the pose between each other are fixedly installed on the sensor platform (1). Three sensor platform positioning pin holes (11) are provided. When installing each sensor and the relative six-degree-of-freedom measuring device (14), it is necessary to ensure that the optical paths do not block each other. At the same time, each sensor should be as close as possible to ensure that the pose relationship between each sensor is not easily changed due to the deformation of the sensor platform after calibration. The relative six-degree-of-freedom measurement device (14) is designed based on the integration and modification of the principles of laser interferometer and autocollimator, including a laser interferometer module and an autocollimator module. The laser interferometer module measures the relative distance, and the autocollimator module measures the relative angle. 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); and three target platform positioning pin holes (21) are provided. Among them: the LED active target (22) is composed of multiple LEDs. To realize the measurement function, at least four LEDs are required. The spacing between LEDs should be as large as possible. The LEDs are detachable and their packaged appearance dimensions are consistent with the target ball of the laser tracker to ensure that the LED light spot position is concentric with the center of the target ball. The first corner reflector (23) is placed in the middle area of ​​multiple LED lights of the LED active target (22); The relative measurement target device (24) includes: 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 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 containing the centers of the second corner reflector (241), the third corner reflector (242), and the fourth corner reflector (243) 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 the pose between pairs of sensors are camera sensors and laser rangefinder sensors: The camera sensor images the active LED target (22) and measures its five degrees of freedom with respect to the active LED target, including two-dimensional displacement and three-axis rotation. The laser rangefinder sensor uses the reflected light from the first corner reflector (23) to measure the absolute distance along the optical axis.

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