A six-dimensional tracking measurement system and method based on vision-based active tracking

Abstract

This disclosure relates to a six-dimensional tracking and measurement system and method based on visual active tracking. The measurement system includes a probe, a laser tracker, and a computing center. The probe includes: a target base, a target rotating seat rotatable along a first rotation direction, multiple feature marker structures disposed on the target rotating seat and capable of emitting or reflecting light beams, and a target disposed on the target rotating seat and rotatable along a second rotation direction. The laser tracker includes: a tracker base, a rotatable aiming unit that emits a laser beam, and an attitude camera linked to the aiming unit. The computing center is used to calculate the first attitude information of the target rotating seat relative to the attitude camera, and to calculate the target attitude information of the target base relative to the tracker base based on the first rotation angle, the third rotation angle, and the fourth rotation angle. Thus, the attitude information of the target rotating seat can be obtained through the attitude camera, thereby obtaining the attitude information of the target base.

Description

Technical Field

[0001] This disclosure relates to the field of intelligent manufacturing equipment industry, specifically to a six-dimensional tracking and measurement system and method. Background Technology

[0002] A laser tracker, also known as a coordinate measuring machine, works by placing a reflector at the point to be measured. The laser beam emitted by the laser tracking head (also called the aiming unit) travels along the measuring optical axis of the laser tracker to the reflector. The laser beam is then reflected back to the laser tracking head. The reflector can be mounted on a target such as a component or a robotic arm. As the reflector moves with the target, the laser tracking head can rotate to adjust the direction of the laser beam and aim at the reflector in real time.

[0003] After the laser beam of a laser tracker is aligned with the reflector, the laser tracker can calculate the three-dimensional coordinates of the target reflector through the rotation angle of the laser tracking head and the ranging unit, thereby obtaining the position information of the component or robotic arm. However, in some cases, it is necessary to obtain both the position and attitude information of the component or robotic arm simultaneously, and the original three-dimensional laser tracker is difficult to meet the measurement requirements. Summary of the Invention

[0004] This disclosure is made in view of the above circumstances, and its purpose is to provide a vision-based active tracking probe and a six-dimensional tracking measurement system capable of measuring attitude information.

[0005] To this end, the first aspect of this disclosure provides a six-dimensional tracking and measurement system based on visual active tracking, comprising a probe for receiving and reflecting a laser beam, a laser tracker for emitting the laser beam, and a computing center. The probe comprises: a target base; a target rotating seat rotatable along a first rotation direction; multiple feature marker structures disposed on the target rotating seat and capable of emitting or reflecting a laser beam; a target disposed on the target rotating seat and rotatable along a second rotation direction; a first rotation drive mechanism for driving the target rotating seat and the target to rotate and align with the laser tracker; and a first angle measurement mechanism for acquiring a first rotation angle of the target rotating seat in the first rotation direction. The laser tracker comprises: a tracker base; a rotatable aiming unit that emits a laser beam; a second rotation drive mechanism for driving the aiming unit to rotate and align with the probe; a second angle measurement mechanism for acquiring the rotation angle of the aiming unit; and an attitude camera linked to the aiming unit. The computing center is used to calculate first attitude information of the target rotating seat relative to the attitude camera, and to calculate target attitude information of the target base relative to the tracker base based on the first rotation angle, the third rotation angle, and the fourth rotation angle.

[0006] Therefore, by setting a target that can rotate in both a first and a second rotation direction, the probe achieves active reverse tracking and automatically aligns with the laser tracker. This breaks the angular constraint of the probe's laser beam reception, improves its flexibility, and allows targets such as fixed equipment parts or robotic arms to move more flexibly. Simultaneously, by setting multiple feature marker structures that present the attitude of the target's rotating base, the attitude information of the target's rotating base can be obtained visually, thereby enabling the calculation of the target base's attitude information and achieving attitude measurement.

[0007] Furthermore, in the six-dimensional tracking and measurement system disclosed in the first aspect of this invention, optionally, the number of feature marker structures is 6-12, and the multiple feature marker structures are arranged on different planes. This forms a three-dimensional feature marker structure array, effectively improving the stability of attitude recognition. Simultaneously, by reasonably arranging the distance between the various planes, it is possible to avoid the feature marker structures obstructing the corner prism at certain angles, and also to avoid the feature marker structures obstructing other feature marker structures at certain angles.

[0008] Furthermore, in the six-dimensional tracking and measurement system disclosed in the first aspect of this invention, optionally, the target rotation base includes a top, a middle, and a bottom of the rotation base that are fixedly connected in sequence, and the feature marker structure is provided on the top, the middle, and the bottom of the rotation base. Compared to a scheme that only centrally positions the feature marker structure at a certain location on the target rotation base, the scheme used in this example can distribute the feature marker structure more evenly around the target rotation base, thereby expanding the distribution range of the feature marker structure, improving the accuracy and stability of the attitude calculation model, and reducing the impact of feature marker structure occlusion.

[0009] Furthermore, in the six-dimensional tracking and measurement system disclosed in the first aspect of this invention, optionally, the middle portion of the rotating base includes a first support arm and a second support arm. The target is rotatably disposed between the first support arm and the second support arm, and the first support arm and the second support arm are respectively provided with protruding feature marking structures. The protruding feature marking structures help ensure that the feature marking structures are on a specific height plane, while preventing the light beams emitted or reflected by the feature marking structures from illuminating the housing of the target rotating base. In addition, the protruding feature marking structures allow for a smaller radius of the first and second support arms, thereby effectively reducing the weight and size of the housing and facilitating the carrying and installation of the probe.

[0010] Furthermore, in the six-dimensional tracking and measurement system disclosed in the first aspect of this invention, optionally, extended wings are provided on the left and right sides of the bottom of the rotating base, and the feature marker structures are respectively disposed on the extended wings on both sides of the bottom of the rotating base. The extended wings prevent the feature marker structures from being obscured, and simultaneously expand the layout space of the feature marker structures, improving the stability and robustness of the model, and thus the accuracy of attitude calculation. In addition, it can reduce the radius of the bottom of the rotating base, further reducing the size and weight of the equipment.

[0011] Furthermore, in the six-dimensional tracking and measurement system disclosed in the first aspect of this invention, the target includes a corner cube prism with a through-hole and a first position sensor disposed behind the corner cube prism. Whether the laser tracker is aligned with the target is determined by whether the laser beam forms a spot on the first position sensor. If the laser beam does not form a spot on the first position sensor, then at least a portion of the laser beam has passed through the through-hole, and it can be assumed that the laser beam was reflected back to the laser tracker by the corner cube prism, thus indicating whether the laser tracker is aligned with the target.

[0012] Furthermore, a second aspect of this disclosure provides a six-dimensional tracking measurement method based on visual active tracking. This method is used in conjunction with a probe and a laser tracker. The probe includes a target base, a target rotation seat that can be disposed on the target base and rotated on the target base along a first rotation direction, and a target disposed on the target rotation seat and rotated on the target rotation seat along a second rotation direction. The target rotation seat is provided with multiple feature marker structures for presenting the attitude of the target rotation seat. The laser tracker includes a tracker base, a rotatable aiming unit that emits a laser beam, and an attitude camera linked to the aiming unit. The six-dimensional tracking measurement method includes: adjusting the angle of the laser beam so that the laser beam is aligned with the probe; rotating the target along the first rotation direction and the second rotation direction and aligning it with the laser beam; recording the first rotation angle of the target in the first rotation direction and the rotation angle of the laser beam; capturing multiple feature marker structures through the attitude camera; calculating the first attitude information of the target rotation seat relative to the attitude camera; and calculating the target attitude information of the target base relative to the tracker base based on the first attitude information, the first rotation angle, and the rotation angle of the laser beam.

[0013] Furthermore, in the six-dimensional tracking and measurement method disclosed in the second aspect of this invention, optionally, second attitude information of the target rotator relative to the tracker base is obtained based on the first attitude information and the rotation angle of the laser beam. Target attitude information of the target base relative to the tracker base is obtained based on the second attitude information and the first rotation direction. Thus, according to the rotation angles of the rotatable target 21 and the rotatable aiming unit 11, each coordinate system can be sequentially associated, thereby realizing the transmission and measurement of attitude information.

[0014] Furthermore, in the six-dimensional tracking measurement method disclosed in the second aspect, optionally, a tracker coordinate system, a camera coordinate system, a target rotation coordinate system, and a target base coordinate system are created. The tracker coordinate system uses the laser beam emission direction as the X-axis, the vertically upward direction as the Z-axis, and obtains the Y-axis direction based on the right-hand rule. The camera coordinate system has an X-axis direction opposite to the Y-axis direction of the tracker coordinate system when the laser tracker is reset, and its Y-axis direction opposite to the Z-axis direction of the tracker coordinate system when the laser tracker is reset, while its Z-axis direction is the same as the X-axis direction of the tracker coordinate system when the laser tracker is reset. The target coordinate system uses the laser beam incident direction as the X-axis, the rotation axis of the second rotation direction as the Y-axis, and the rotation axis of the first rotation direction as the Z-axis. The coordinate axis directions of the target base coordinate system are the same as those of the target coordinate system when the target is reset.

[0015] Furthermore, the six-dimensional tracking and measurement method disclosed in the second aspect of this disclosure may optionally include a method for calculating auxiliary attitude information using a multi-sensor constraint method, and a method for calculating the attitude information of the target base based on the test environment. The multi-sensor constraint method includes setting multiple tilt sensors with different measurement directions on the laser tracker and the target base, and projecting the laser beam vector onto the world coordinate system using the tilt angles of the laser tracker base and the target base, respectively. This improves the stability of attitude information measurement.

[0016] According to this disclosure, a six-dimensional tracking measurement system and method based on visual active tracking that can realize attitude information measurement can be provided. Attached Figure Description

[0017] This disclosure will now be explained in further detail by way of example only with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram illustrating an application scenario of the six-dimensional tracking and measurement system involved in the example of this disclosure.

[0019] Figure 2 This is a three-dimensional schematic diagram of the probe involved in the example of this disclosure.

[0020] Figure 3 This is a schematic diagram showing the rotation direction of the probe involved in the example of this disclosure.

[0021] Figure 4 This is a front view of the probe involved in the example of this disclosure.

[0022] Figure 5 This is a side view of the probe involved in the example of this disclosure.

[0023] Figure 6 This is a schematic diagram illustrating the principle structure of the probe involved in the example of this disclosure.

[0024] Figure 7 This is a schematic diagram illustrating the principle structure of the target involved in the example of this disclosure.

[0025] Figure 8 This is a three-dimensional schematic diagram showing the aiming unit involved in the example of this disclosure.

[0026] Figure 9 This is a three-dimensional schematic diagram of the laser tracker involved in the example of this disclosure.

[0027] Figure 10 This is a flowchart illustrating the six-dimensional tracking measurement method involved in the example of this disclosure.

[0028] 1. Laser tracker; 2. Probe; 21. Target; 22. Target rotating base; 221. Top of rotating base; 222. Middle part of rotating base; 223. Bottom of rotating base; 23. Target base; 24. Feature marking structure; D1. First rotation direction; D2. Second rotation direction; A1. Rotation axis of the first rotation direction; A2. Rotation axis of the second rotation direction; S1. First plane; S2. Second plane; D3. Third rotation direction; D4. Fourth rotation direction; A3. Rotation axis of the third rotation direction; A4. Rotation axis of the fourth rotation direction; S3. Third plane; S4. Fourth plane; 2131. First position sensor; 2123. Filter; 213. Reference layer; 212. Intermediate layer; 211. Prism layer; 2111. Mirror; V. Vertex; Ao. Optical axis of the target; Sc. Cutting plane; Si. Incident plane; 11. Aiming unit; 13. Tracker rotating base; 12. Tracker base; 112. Attitude camera; 111. Window. Detailed Implementation Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same reference numerals are used for the same components, and repeated descriptions are omitted. Furthermore, the drawings are merely schematic diagrams, and the proportions of the components or the shapes of the components may differ from actual figures.

[0029] Furthermore, the subheadings and similar terms used in the following description of this disclosure are not intended to limit the content or scope of this disclosure; they are merely intended to serve as reading prompts. Such subheadings should not be construed as dividing the content of the article, nor should the content under a subheading be limited to the scope of that subheading.

[0030] This disclosure relates to a vision-based active tracking probe (also known as an auxiliary measurement device, 6D probe, 6D attitude probe, etc.) used to reflect a laser beam emitted by a laser tracker to determine the position and attitude information between the probe and the laser tracker. The probe can be configured with multiple feature marker structures to present and acquire attitude information, enabling attitude information to be determined simultaneously through the layout of these feature marker structures while performing reverse tracking. Therefore, reverse tracking expands the angular range of the laser beam received by the probe, improving its flexibility. Furthermore, attitude measurement can be achieved through multiple feature marker structures without using a gravity sensor, avoiding the instability of gravity sensors in some cases, thereby improving the accuracy of the probe's attitude measurement.

[0031] The visual active tracking described in this disclosure can refer to attitude measurement without relying on gravity / tilt sensors, but rather relying on vision. The solution disclosed in this disclosure can be used alone to achieve attitude measurement, but this disclosure is not limited to this. The solution disclosed in this disclosure can also be used in conjunction with gravity / tilt sensors. Higher accuracy and more stable attitude measurement can be achieved by switching attitude measurement methods (e.g., switching between attitude measurement achieved by vision and attitude measurement achieved by gravity / tilt sensors according to the test scenario) or by using multiple sensor constraints.

[0032] This disclosure also relates to a six-dimensional tracking and measurement system based on vision-based active tracking (hereinafter referred to as a measurement system, laser measurement system, laser tracking measurement system, etc.). The six dimensions refer to the target's three-dimensional position (which can be represented by three-dimensional coordinates) and spatial attitude (which can be represented by a rotation matrix or attitude angle). In other words, the six-dimensional tracking and measurement system can be used to measure the three-dimensional position and attitude information of targets such as equipment parts or robotic arms. The six-dimensional tracking and measurement system may include a laser tracker and a probe. When the laser tracker is aligned with the probe, the probe can actively track the laser tracker and acquire the target's three-dimensional position and attitude information at that time. The "vision" involved in this disclosure may refer to acquiring attitude information through an attitude camera.

[0033] In some examples, the alignment of a laser tracker (or aiming unit / laser beam / laser emitting unit) with a probe (or target / cornerstone prism) can be understood as follows: when the probe can receive the laser beam emitted by the laser tracker, and the laser beam reflected by the probe is received by the laser tracker, and the spot formed by the position sensor of the laser tracker is located at a preset position, then the laser tracker (or aiming unit / laser beam / laser emitting unit) can be considered aligned with the probe (or target / cornerstone prism). Alternatively, it can be understood as follows: when the laser beam is incident on the center of the cornerstone prism of the probe, then the laser tracker (or aiming unit / laser beam / laser emitting unit) can be considered aligned with the probe (or target / cornerstone prism).

[0034] In some examples, active tracking can refer to the probe (or target / cornerstone prism) actively tracking the laser tracker (or aiming unit / laser beam / laser emitting unit), and can also be called anti-tracking. In some examples, probe active tracking of the laser tracker can be understood as follows: the probe may include a target with a through-hole for reflecting the laser beam. When at least a portion of the laser beam emitted by the laser tracker passes through the through-hole and is parallel to the optical axis of the target, the target (or probe / cornerstone prism) can be considered aligned with the laser tracker (or aiming unit / laser beam / laser emitting unit). During target movement or changes in target attitude, by controlling the attitude of the target to keep the probe continuously aligned with the laser emitting unit, the probe (or target) can be considered to be actively tracking (i.e., the probe actively tracking the laser tracker).

[0035] In addition, this disclosure includes descriptions of orientation, such as "front" and "rear". For a laser tracker or other components or units disposed on the laser tracker (e.g., a laser emitting unit or light-emitting unit), "front" can refer to the direction from the laser tracker to the target when the laser tracker is aligned with the target; "rear" can refer to the direction from the target to the laser tracker when the laser tracker is aligned with the target. For a probe or other components disposed on the probe, "front" can refer to the direction from the target to the laser tracker when the target is aligned with the laser tracker; "rear" can refer to the direction from the laser tracker to the target when the laser tracker is aligned with the target.

[0036] Figure 1 This is a schematic diagram illustrating an application scenario of the six-dimensional tracking and measurement system involved in the example of this disclosure. Figure 2 This is a three-dimensional schematic diagram of the probe involved in the example of this disclosure. Figure 3 This is a schematic diagram showing the rotation direction of the probe involved in the example of this disclosure. Figure 4 This is a front view of the probe involved in the example of this disclosure. Figure 5 This is a side view of the probe involved in the example of this disclosure. Figure 6 This is a schematic diagram illustrating the principle structure of the probe involved in the example of this disclosure. Figure 7 This is a schematic diagram illustrating the principle structure of the target involved in the example of this disclosure.

[0037] In some examples, a six-dimensional tracking measurement system can be a measurement system used to track a target and obtain the target's position and orientation. In some examples, a six-dimensional tracking measurement system can include a laser tracker 1 and a probe 2 that works in conjunction with the laser tracker 1 to obtain the target's position and orientation.

[0038] In some examples, probe 2 can be mounted on a target. In some examples, when probe 2 is mounted on a target, at least a portion of probe 2 can remain relatively stationary with respect to the target. In some examples, probe 2 may include a target 21 and a target base 23 (described later) for mounting probe 2 on the target. In this case, the position and attitude of the target can be obtained by using probe 2 mounted on the target in conjunction with laser tracker 1.

[0039] In some examples, the target can be a workpiece or a robotic arm, or any object whose spatial position and / or spatial orientation needs to be measured.

[0040] See in some examples Figure 3 , Figure 4 and Figure 5 The probe 2 may include a target base 23 and a target 21. In this case, the probe 2 can be mounted on the target using the target base 23, and the target 21 can reflect the beam emitted by the laser tracker 1 (e.g., a laser beam and / or a scattered beam).

[0041] In some examples, probe 2 may include a target base 23, a target rotation seat 22 disposed on the target base 23 and capable of rotating on the target base 23 along a first rotation direction D1, and a target 21 disposed on the target rotation seat 22 and capable of rotating on the target rotation seat 22 along a second rotation direction D2. Thus, target 21 can rotate relative to target base 23 along the first rotation direction D1 and the second rotation direction D2. During measurement, target 21 can adjust its rotation direction according to the incident direction of the laser beam until target 21 is aligned with the laser beam. Due to the technical limitations of the collimating prism, the angle at which the probe receives the laser beam cannot exceed ±45 degrees in traditional probes. However, the probe of this disclosure, by setting a target capable of rotating in both the first and second rotation directions, achieves active reverse tracking of the probe and automatic alignment with the laser tracker, breaking the angle constraint of the probe's laser beam reception, improving the probe's flexibility, and allowing targets such as fixed equipment parts or robotic arms to move more flexibly.

[0042] In some examples, the first rotation direction D1 and the second rotation direction D2 can be any two different rotation directions. Preferably, the rotation axis A1 of the first rotation direction D1 and the rotation axis A2 of the second rotation direction D2 can be orthogonal. See [reference needed]. Figure 3 When probe 2 is placed horizontally, the first rotation direction D1 can refer to the direction of horizontal rotation, and the second rotation direction D2 can refer to the direction of pitch rotation.

[0043] In some examples, refer to Figure 3The rotation axis A1 of the first rotation direction D1 can be perpendicular to the first plane S1, and the rotation axis A2 of the second rotation direction D2 can be perpendicular to the second plane S2. In some examples, the rotation axis A1 of the first rotation direction D1 and the rotation axis A2 of the second rotation direction D2 can intersect at any angle. Preferably, the rotation axis A1 of the first rotation direction D1 and the rotation axis A2 of the second rotation direction D2 can be perpendicular to each other.

[0044] In some examples, the rotation axis A1 of the first rotation direction D1 can be located in the second plane S2, and the rotation axis A2 of the second rotation direction D2 can be located in the first plane S1. When the target 21 or probe 2 is in its reset state, the laser incident direction, the rotation axis A1 of the first rotation direction D1, and the rotation axis A2 of the second rotation direction D2 can be orthogonal to each other. Target 21 or probe 2 being reset can mean that the rotation angles of its first rotation direction D1 and second rotation direction D2 are 0.

[0045] In some examples, the probe 2 may also include multiple first angle measuring mechanisms, which respectively measure the rotation angle of the target 21 relative to the target base 23 in a first rotation direction D1 and a second rotation angle in a second rotation direction D2. In some examples, the first angle measuring mechanism may be a circular grating, a Hall sensor, or other sensors. In some examples, the target 21 may include a corner bevel prism with a through hole and a first position sensor 2131 disposed behind the corner bevel prism. The laser beam passes through the through hole and reaches the first position sensor 2131. Whether the laser beam forms a spot on the first position sensor 2131 is used to determine whether the laser tracker 1 is aligned with the target 21. If the laser beam does not form a spot on the first position sensor 2131, then at least a portion of the laser beam has passed through the through hole. It can be considered that the laser beam is reflected back to the laser tracker 1 by the corner bevel prism, and it can be considered that the laser tracker 1 is aligned with the target 21.

[0046] In some examples, the first position sensor 2131 may be a PSD position sensor.

[0047] In some examples, the target 21 may include a corner bevel prism with a through hole and a first position sensor 2131 disposed behind the corner bevel prism. The laser beam passes through the through hole and reaches the first position sensor 2131. The position of the laser beam spot formed by the first position sensor 2131 is used to determine whether the target 21 is aligned with the laser beam.

[0048] In some examples, the center of the cornerstone prism can be located at the intersection of the rotation axis A1 of the target 21 in the first rotation direction D1 and the rotation axis A2 of the target 21 in the second rotation direction D2. This facilitates subsequent attitude calculations.

[0049] In some examples, when the laser beam spot position of the first position sensor 2131 deviates from the first preset zero point, it can be determined that the target 21 or the probe 2 is not aligned with the laser beam. Based on the spot position of the laser beam formed by the first position sensor 2131 and the first preset zero point position, the rotation angle required for the target 21 in the first rotation direction D1 and / or the second rotation direction D2 can be calculated. At this time, the target 21 can be rotated along the first rotation direction D1 and / or the second rotation direction D2 until the target 21 is aligned with the laser beam.

[0050] In some examples, the structure of target 21 can be a symmetrical structure, for example, it can be about Figure 3 The second plane S2 in the diagram is symmetric.

[0051] In some examples, target 21 may have a multi-layered structure. For example, target 21 may include a three-layered structure. Specifically, target 21 may include a prism layer 211, an intermediate layer 212, and a reference layer 213 (see [link to documentation]). Figure 6 and Figure 7 In some examples, the intermediate layer 212 may be disposed between the prism layer 211 and the reference layer 213. In some examples, the target 21 may include the prism layer 211, the intermediate layer 212, and the reference layer 213 disposed from front to back.

[0052] See in some examples Figure 7 The prism layer 211 may be provided with a slit-shaped reflector 2111. For example, the slit-shaped reflector 2111 may be a solid pyramidal prism, a hollow pyramidal prism, or a hollow optical retroreflector. In this case, the laser beam can be returned to the laser tracker 1 in a direction opposite to the incident direction.

[0053] In some examples, the center of the pyramidal prism can refer to the vertex V of the reflector 2111 with the notch. For example, the vertex V of the reflector can refer to... Figure 7 The vertex V of the cornerstone prism. In some examples, the position coordinates of target 21 can refer to the position coordinates of the center of the cornerstone prism. In some examples, the through hole is located at vertex V.

[0054] In some examples, the diameter of the cut can be around 1.0 to 2.0 mm (e.g., the diameter of the cut can be 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2.0 mm), but this disclosure is not limited to this. The diameter of the cut can also be less than 1.0 mm or greater than 2.0 mm, and the diameter of the cut can also have higher or lower precision.

[0055] See in some examples Figure 7The notch plane Sc can be parallel to the incident plane Si. The notch plane Sc can refer to the cut surface that forms the notch, and the incident plane Si can refer to the plane on which the laser beam is incident on the reflector 2111 with the notch. In this case, at least a portion of the incident laser beam can be projected through the vertex V to the first position sensor 2131 behind it.

[0056] In some examples, the notched reflector 2111 can be a hollow corner prism. In this case, when the incident light beam enters the hollow corner prism, the reflection of the incident light beam through the plane can reduce the refraction of the beam and thus reduce the loss of light energy, and can reduce the complexity of the optical path caused by refraction, thereby reducing the computational complexity.

[0057] In some examples, a hollow pyramidal prism can be formed by three plane mirrors arranged perpendicularly in pairs. In this case, after the incident beam is reflected sequentially by the three plane mirrors, the direction of the outgoing beam can be parallel to the direction of the incident beam. However, this disclosure is not limited to this; the hollow pyramidal prism can also be any element capable of reflecting a beam in the opposite direction to the incident beam.

[0058] In some examples, the vertex V of the hollow pyramid prism can be located in the intermediate layer 212. In some examples, the body of the hollow pyramid prism can be located in the prism layer 211.

[0059] In some examples, the target 21 may include an intermediate layer 212 disposed behind the prism layer 211.

[0060] See in some examples Figure 7 The optical axis of the hollow corner prism can be made to be the optical axis Ao of the target 21. In some examples, the through hole can be located on the straight line where the optical axis Ao of the target 21 lies. In this case, when the laser beam emitted by the laser emitting unit is incident along the optical axis Ao of the hollow corner prism, that is, when the target 21 is aligned with the laser emitting unit, the laser beam can pass through the through hole and form a specific spot at a specific position behind the through hole (e.g., the first preset zero point described later). Thus, it is possible to determine whether the target 21 is aligned with the laser emitting unit based on whether there is a spot at the specific position behind the through hole.

[0061] In some examples, a perforated plate may be provided in the intermediate layer 212, and through holes may be provided in the perforated plate. In some examples, the through holes located in the perforated plate may also be located at the vertex V of the notched reflector 2111. In some examples, the through holes may be provided in the perforated plate and on the straight line where the optical axis Ao of the hollow corner prism lies, and the orientation of the through holes may be on the straight line where the optical axis Ao of the hollow corner prism lies.

[0062] In some examples, the pinhole plate can be an aluminum plate with through holes. However, this disclosure is not limited to this; the pinhole plate can also be made of metallic materials such as iron, copper, stainless steel, or tantalum, or non-metallic materials such as silicon, graphite, oxides, or carbides. In some examples, the pinhole plate can be a pinhole aperture.

[0063] In some examples, the shape of the through hole can be arbitrary; for example, the shape of the through hole can be any shape such as polygonal, elliptical, or circular. Preferably, the shape of the through hole can be circular.

[0064] In some examples, the size of the via can be smaller than the cross-sectional size of the laser beam. In this case, at least a portion of the laser beam can pass through the via and reach the reference layer 213 after the via to form a first spot.

[0065] See in some examples Figure 7 The target 21 may include a filter 2123. In some examples, the filter 2123 may be disposed between the pinhole plate and the first position sensor 2131; in other words, the filter 2123 may be disposed behind the pinhole plate. In this case, light outside a specific wavelength range (e.g., the wavelength of the laser beam formed by the laser emitting unit) can be filtered, so that the energy of the first light spot formed by the through-hole and the first position sensor 2131 comes from the laser beam formed by the laser emitting unit. This reduces the interference from ambient light or the light-emitting unit 14, thereby improving the detection accuracy of the laser beam orientation.

[0066] In some examples, the target 21 may include a reference layer 213 disposed behind the intermediate layer 212. In some examples, the reference layer 213 may be provided with a first position sensor 2131, which may be configured to receive a laser beam passing through a via.

[0067] In some examples, the first position sensor 2131 may have a photosensitive surface, which may be parallel to the notch plane Sc. In some examples, the photosensitive surface of the first position sensor 2131 may be parallel to the incident plane Si. In some examples, the photosensitive surface of the first position sensor 2131 may be perpendicular to the optical axis Ao of the target 21. However, this disclosure is not limited thereto, and the photosensitive surface of the first position sensor 2131 may also be non-parallel to the notch plane Sc.

[0068] In some examples, after the first position sensor 2131 receives the laser beam passing through the through hole, it can determine whether the target 21 is aligned with the laser emitting unit based on the first light spot formed by the laser beam on the photosensitive surface of the first position sensor 2131.

[0069] In some examples, the attitude adjustment method of the target 21 can be determined based on the relative position between the first light spot and the first preset zero point of the first position sensor 2131. The first preset zero point can be located at the position of the first light spot when the target 21 is aligned with the laser emitting unit.

[0070] In some examples, the first position sensor 2131 can acquire the position of the first light spot in real time. In other words, after the first position sensor 2131 forms the first light spot, it can continuously acquire the position of the first light spot. In this case, the attitude of the target 21 can be continuously determined, and thus the attitude adjustment method of the target 21 can be determined in real time, and the laser emitting unit can be aligned in real time.

[0071] In some examples, when the hollow corner prism does not receive a laser beam, it can be considered that the laser tracker 1 is not aligned with the target 21; when the hollow corner prism receives a laser beam, and the reflected laser beam forms a spot at the second position sensor located at the second preset zero point, it can be considered that the laser tracker 1 is aligned with the target 21; when the hollow corner prism receives a laser beam, and at least a portion of the laser beam passes through the through-hole and forms a spot at the first position sensor 2131, and the spot formed by at least a portion of the laser beam at the first position sensor 2131 is not located at the first preset zero point, it can be considered that the laser beam is not parallel to the optical axis Ao of the target 21, and the target 21 is not aligned with the laser tracker 1; when the hollow corner prism receives a laser beam, and at least a portion of the laser beam passes through the through-hole and forms a spot at the first position sensor 2131, and the spot formed by at least a portion of the laser beam at the first position sensor 2131 is located at the first preset zero point, it can be considered that the laser beam is parallel to the optical axis Ao of the target 21, and the target 21 is aligned with the laser tracker 1. In this case, it is possible to determine the stage of the six-dimensional laser tracking measurement system based on the relationship between the laser beam and probe 2.

[0072] In some examples, as described above, the probe 2 also includes a target rotator 22, which is provided with a plurality of feature marker structures 24. This allows the orientation of the target rotator 22 to be displayed through the feature marker structures 24.

[0073] In some examples, the number of feature marker structures 24 is no less than four, for example, six to twelve, preferably ten. In this case, a larger number of feature marker structures 24 can improve the accuracy of pose recognition. In some examples, multiple feature marker structures 24 are arranged on different planes, thereby forming a three-dimensional array of feature marker structures 24, which effectively improves the stability of pose recognition. At the same time, by reasonably arranging the distance between the planes, it is possible to avoid the feature marker structures 24 occluding the corner prism at certain angles, and also to avoid the feature marker structures 24 occluding other feature marker structures 24 at certain angles. In some examples, multiple feature marker structures 24 are symmetrically distributed (i.e., symmetrical about the first plane S1), which facilitates the rapid determination of the correspondence between the light spot position in the camera and the LED in subsequent calculations, reducing matching costs.

[0074] In some examples, the feature marker structure 24 can be an LED light source. This allows for the stable emission of a light beam, which is then received by the attitude camera 112 to obtain the position of the LED light source in the image. In some examples, the feature marker structure 24 is a red LED light source, which improves pitting resistance. In some examples, the feature marker structure 24 may include a light-transmitting sheet and the LED light source, with the light-transmitting sheet protecting the LED light source.

[0075] In some examples, the feature marker structure 24 can be a reflective label, such as a diffuse label, which, in conjunction with an illumination source located on the laser tracker 1, can reflect the illumination beam back to the attitude camera 112 to form a light spot.

[0076] In some examples, the feature marker structure 24 has the same size and orientation. This allows the feature marker structure 24 to form approximately the same spot shape in the attitude camera 112, improving measurement accuracy.

[0077] In some examples, the feature marker structure 24 is disposed on the housing of the target rotating seat 22, and the feature marker structure 24 may be protruding from the housing or flush with the housing surface. This prevents the feature marker structure 24 from reflecting or partially reflecting the light beam onto the housing, thus avoiding the formation of new light spots that could affect spot recognition.

[0078] In some examples, the target rotator 22 may include a top 221, a middle 222, and a bottom 223 of the rotator, which are fixedly connected in sequence. Feature marker structures 24 are provided on the top 221, the middle 222, and the bottom 223. Compared to a scheme where the feature marker structures 24 are concentrated in a certain part of the target rotator 22, the scheme used in this example can distribute the feature marker structures 24 more evenly and dispersedly around the target rotator 22, thereby expanding the distribution range of the feature marker structures 24, improving the accuracy and stability of the attitude calculation model, and reducing the impact of occlusion on the feature marker structures 24.

[0079] In some examples, the top 221, middle 222, and bottom 223 of the rotating seat can be fixedly connected. Therefore, the target rotating seat 22 can be considered as a rigid body, and the positional relationship between the feature marker structures 24 is fixed. The attitude information of the target rotating seat 22 can be determined by obtaining the two-dimensional position information of the feature marker structures 24 in the image captured by the attitude camera.

[0080] In some examples, the top 221 of the rotary seat may be located above the middle portion 222 of the rotary seat and has multiple feature marker structures 24, see [reference needed]. Figure 4 The top 221 of the rotating base may have two upward protrusions and one forward protrusion, and the ends of the protrusions are provided with feature marker structures 24, thereby forming a three-dimensional array of feature marker structures 24. The upward protrusions help to prevent the feature marker structures 24 from being obstructed, while the forward protrusions help to ensure that the feature marker structures 24 are on a specific height plane, and at the same time, prevent the light beams emitted or reflected by the feature marker structures 24 from shining on the housing of the target rotating base 22, thereby affecting the attitude measurement.

[0081] See in some examples Figure 5 Multiple feature marker structures 24 can be distributed in different height planes M1, M2, M3, and M4, respectively. Height plane M1 has 4 feature marker structures 24, height plane M2 has 2 feature marker structures 24, height plane M3 has 2 feature marker structures 24, and height plane M4 has 2 feature marker structures 24.

[0082] In some examples, the middle portion 222 of the rotating base includes a first support arm and a second support arm. The target 21 is rotatably positioned between the first and second support arms in a second rotation direction D2. The first and second support arms are each provided with a protruding feature marking structure 24. The protruding feature marking structure 24 helps to ensure that the feature marking structure 24 is in a specific height plane, while preventing the light beam emitted or reflected by the feature marking structure 24 from illuminating the housing of the target rotating base 22. In addition, the protruding feature marking structure 24 allows for a smaller radius of the first and second support arms, thereby effectively reducing the weight and size of the housing and facilitating the carrying and installation of the probe 2.

[0083] In some examples, bearings may be provided between the target 21 and the first support arm, and between the target 21 and the second support arm, thereby allowing the target 21 to be positioned between the first and second support arms in a manner that allows it to rotate in the second rotation direction D2.

[0084] In some examples, at least one first angle measuring mechanism may be provided inside the first support arm and / or the second support arm, thereby enabling the measurement of the rotation angle of the target 21 along the second rotation direction D2.

[0085] In some examples, at least one first rotary drive mechanism may be provided inside the first support arm and / or the second support arm, thereby driving the target 21 to rotate along the second rotation direction D2. The first rotary drive mechanism may be a drive motor.

[0086] In some examples, the bottom 223 of the rotating base can be located below the middle part 222 of the rotating base, and extended wings 2231 are provided on the left and right sides of the bottom 223 of the rotating base. Feature marker structures 24 are respectively provided on the extended wings 2231 on both sides of the bottom 223 of the rotating base. The extended wings 2231 can prevent the feature marker structures 24 from being obscured, and at the same time, it is beneficial to expand the layout space of the feature marker structures 24, improve the stability and robustness of the model, and thus improve the accuracy of attitude calculation. In addition, it can also reduce the radius of the bottom 223 of the rotating base, further reducing the size and weight of the device.

[0087] In some examples, the target rotator 22 can be mounted on the target base 23 via bearings, thereby enabling the target rotator 22 to rotate along a first rotation direction D1. In some examples, the target base 23 may be provided with at least one first angle measuring mechanism, thereby enabling the measurement of the rotation angle of the target 21 along the first rotation direction D1.

[0088] In some examples, the target base 23 may be provided with at least one first rotation drive mechanism, thereby enabling the target 21 to rotate along a first rotation direction D1.

[0089] In some examples, the target base 23 has mounting holes for securing the probe 2. This allows the target base 23 to be fixed to a device part or robotic arm using screws, thereby enabling the position and orientation of the device part or robotic arm to be determined based on the position and orientation of the target base 23.

[0090] Figure 8 This is a three-dimensional schematic diagram showing the aiming unit involved in the example of this disclosure. Figure 9 This is a three-dimensional schematic diagram of the laser tracker involved in the example of this disclosure.

[0091] In some examples, the laser tracker 1 may include: a tracker base 12, an aiming unit 11 mounted on the tracker base 12 and capable of rotating on the tracker base 12 along a third rotation direction D3 and a fourth rotation direction D4, and capable of emitting a laser beam, and an attitude camera 112 linked to the aiming unit 11. The tracker base 12 may be equipped with a tripod or casters, thereby facilitating the placement or movement of the laser tracker 1. The aiming unit 11 may include a housing and a cavity configured to accommodate components. In some examples, the cavity may be an internal chamber formed by the housing. In this case, the housing can be used to protect the components. In some examples, the components disposed in the internal chamber may include at least one of a laser emitting unit and a second position sensor. However, this disclosure is not limited to this; some components of the laser tracker 1 may also be connected via optical fibers or wires and disposed outside the housing.

[0092] In some examples, the laser tracker 1 may include a tracker rotating base 13, which is disposed on the tracker base 12 and is rotatable on the tracker base 12 in a third rotation direction D3. The tracker rotating base 13 includes a third support arm and a fourth support arm. The aiming unit 11 may be disposed between the third support arm and the fourth support arm and is rotatable in the fourth rotation direction D4.

[0093] In some examples, refer to Figure 8 The rotation axis A3 of the third rotation direction D3 can be perpendicular to the third plane S3, and the rotation axis A4 of the fourth rotation direction D4 can be perpendicular to the fourth plane S4. In some examples, the rotation axis A3 of the third rotation direction D3 and the rotation axis A4 of the fourth rotation direction D4 can intersect at any angle. Preferably, the rotation axis A3 of the third rotation direction D3 and the rotation axis A4 of the fourth rotation direction D4 can be perpendicular to each other.

[0094] In some examples, the rotation axis A3 of the third rotation direction D3 can be located in the fourth plane S4, and the rotation axis A4 of the fourth rotation direction D4 can be located in the third plane S3. When the aiming unit 11 or the laser tracker 1 is in the reset state, the laser emission direction, the rotation axis A3 of the third rotation direction D3, and the rotation axis A4 of the fourth rotation direction D4 can be orthogonal to each other.

[0095] The resetting of the aiming unit 11 or the laser tracker 1 can refer to the rotation angle of its third rotation direction D3 and fourth rotation direction D4 being 0.

[0096] It should be noted that, due to possible processing and assembly errors, the parallel, perpendicular, or intersecting positional relationships mentioned in this article do not mean that the two objects must be in a perfect parallel, perpendicular, or intersecting positional relationship without any errors. Rather, it means that within a certain error range, the two objects can be considered to be in a parallel, perpendicular, or intersecting positional relationship.

[0097] In some examples, the aiming unit 11 may be provided with components for emitting and receiving laser beams and / or scattered beams. See also [reference needed] for some examples. Figure 9 The housing of the aiming unit 11 may include a light-transmitting opening and a window 111 disposed in the light-transmitting opening. In some examples, the window 111 may be made of a light-transmitting material. In this case, laser beams can be emitted and received through the light-transmitting opening, thereby enabling the acquisition of the spatial position of the probe 2.

[0098] In some examples, the laser tracker 1 may include a laser emitting unit, which may be configured to emit a laser beam.

[0099] In some examples, the laser tracker 1 may have only one laser emitting unit. In this case, the internal structure of the laser tracker 1 can be effectively simplified, thereby reducing the manufacturing and design costs of the laser tracker 1.

[0100] In some examples, the laser tracker 1 may also include multiple laser emitting units. Specifically, the multiple laser emitting units may include a first laser emitting unit for absolute ranging and a second laser emitting unit for interferometric ranging. In other words, the laser tracker 1 may include an absolute ranging module and an interferometric ranging module. In this case, the position coordinates of the target 21 can be obtained by simultaneously using the absolute ranging module and the interferometric ranging module, improving the measurement accuracy. At the same time, compared to measuring distance using only the absolute ranging module, the interferometric ranging module has a faster ranging speed, thus also improving the measurement speed. In some examples, the distance from the mechanical zero point of the laser tracker 1 to the center of the corner cube prism can be obtained using the absolute ranging module and the interferometric ranging module, and then the position coordinates of the target can be calculated based on the rotation angle of the aiming unit 11. Here, the mechanical zero point can be any position of the laser tracker 1. For ease of calculation, the mechanical zero point can be set as the ideal intersection of the rotation axis A3 of the aiming unit 11 in the third rotation direction D3 and the rotation axis A4 of the aiming unit 11 in the fourth rotation direction D4.

[0101] In some examples, the absolute ranging module may include a first laser emitting unit, and the interferometric ranging module may include a second laser emitting unit. However, this disclosure is not limited thereto, and the second laser emitting unit may also be independent of the interferometric ranging module.

[0102] In some examples, the first laser emitting unit can be configured to emit a first laser beam, and the second laser emitting unit can be configured to emit a second laser beam. The optical paths of the first laser beam and the second laser beam can be coupled through a dichroic mirror.

[0103] In some examples, the laser emitting unit can be a helium-neon laser or a solid-state laser.

[0104] In some examples, the laser tracker 1 may also include a second position sensor, which may be a PSD position sensor. The second position sensor may be configured to receive the laser beam reflected by the probe 2 to determine whether the laser tracker 1 is misaligned with the probe 2. The rotation angle can then be calculated based on the position of the light spot on the second position sensor, thereby enabling the laser tracker 1 to continuously track the probe 2.

[0105] See in some examples Figure 9The laser tracker 1 also includes an attitude camera 112, which can be linked with the aiming unit 11, meaning the attitude camera 112 moves synchronously with the aiming unit 11. In some examples, the attitude camera 112 can be housed within the aiming unit 11. Thus, whenever the aiming unit 11 is rotated, the attitude camera 112 can move simultaneously in the same direction and at the same speed. In some examples, the attitude camera 112 can also be independently and detachably mounted outside the aiming unit 11, for example, above or to the left or right sides of the aiming unit 11, and the attitude camera 112 can be equipped with an independent drive device. In this case, the rotation of the aiming unit 11 and the attitude camera 112 can be synchronously controlled by the control system.

[0106] In some examples, the central optical axis of the attitude camera 112 is in the same direction as the optical axis of the laser beam, which simplifies the attitude calculation process.

[0107] In some examples, the laser tracker 1 also includes a second rotation drive mechanism that drives the aiming unit 11 to rotate in a third rotation direction D3 and a fourth rotation direction D4.

[0108] In some examples, the laser tracker 1 also includes a second angle measuring mechanism for obtaining the rotation angle of the aiming unit 11. In some instances, the second angle measuring mechanism may be a circular grating.

[0109] Figure 10 This is a flowchart illustrating the six-dimensional tracking measurement method involved in the example of this disclosure.

[0110] This disclosure also proposes a six-dimensional tracking and measurement system based on vision-based active tracking, including the probe 2 and laser tracker 1 described above. Furthermore, the six-dimensional tracking and measurement system also includes a computing center. In some examples, probe 2 may include: target base 23, target rotating seat 22 rotatable along a first rotation direction D1, multiple feature marker structures 24 disposed on the target rotating seat 22 and capable of emitting or reflecting a light beam, target 21 disposed on the target rotating seat 22 and rotatable along a second rotation direction D2, a first rotation drive mechanism for driving the target rotating seat 22 and target 1 to rotate to align with the laser tracker 1, and a first angle measuring mechanism for obtaining a first rotation angle of the target rotating seat in the first rotation direction.

[0111] In some examples, the laser tracker 1 may include: a tracker base, a rotatable aiming unit that emits a laser beam, a second rotation drive mechanism that drives the aiming unit to rotate to align with the probe 2, a second angle measuring mechanism that acquires the rotation angle of the aiming unit, and an attitude camera linked to the aiming unit.

[0112] In some examples, the computing center can be used to calculate the first attitude information of the target rotator 22 relative to the attitude camera, and to calculate the target attitude information of the target base 23 relative to the tracker base 23 based on the first attitude information, the first rotation angle, the third rotation angle, and the fourth rotation angle.

[0113] See in some examples Figure 10 The six-dimensional tracking and measurement system can measure position and attitude information in the following ways: Step S101: Adjust the angle of the laser beam so that the laser beam is aligned with the probe 2; Step S103: Rotate the target 21 along the first rotation direction D1 and the second rotation direction D2 and align it with the laser beam; Step S105: Record the first rotation angle of the target 21 in the first rotation direction D1 and the rotation angle of the laser beam; Step S107: Capture multiple feature marker structures with an attitude camera and calculate the first attitude information of the target rotating seat 22 relative to the attitude camera; Step S109: Calculate the target attitude information of the target base 23 relative to the tracker base based on the first rotation angle and the rotation angle of the laser beam. By acquiring the first attitude information through the attitude camera, the attitude of the target rotating seat 22 can be obtained quickly and stably, reducing the impact of the difficulty in stably measuring the tilt angle of the target base 23 using tilt sensors in some cases (e.g., the hysteresis of some tilt sensors, or their susceptibility to environmental influences, making it difficult to sensitively acquire the tilt angle of the target base 23). Using visual active tracking can effectively improve the stability and accuracy of the measurement data.

[0114] In step S101, it can be determined whether the laser beam is aligned with the probe 2 by using the first position sensor 2131 inside the probe 2 or the second position sensor inside the laser tracker 1. If the laser beam can form a spot in the first position sensor 2131 inside the probe 2, or if the spot formed by the laser beam reflected from the probe 2 at the second position sensor is located at the second preset zero point, it can be considered that the laser tracker 1 is aligned with the target 21. In addition, the required rotation angle of the laser beam can be calculated based on the spot formed by the laser beam at the second position sensor and the second preset zero point.

[0115] In step S103, after the laser beam is aligned with the probe 2, active tracking of the probe 2 can be performed. At this time, the required rotation angle of the target in the first rotation direction D1 and / or the second rotation direction D2 can be calculated based on the light spot formed by the laser beam in the first position sensor 2131 and the first preset zero point. The target 21 is adjusted based on the calculated rotation angle until the target 21 is aligned with the laser beam. At this time, the light spot formed by the laser beam in the first position sensor 2131 is located at the first preset zero point.

[0116] Step S105: After the target 21 is aligned with the laser beam, the first rotation angle of the target in the first rotation direction D1 can be obtained through the first angle measuring mechanism. Simultaneously, the third rotation angle of the laser beam (aiming unit) in the third rotation direction D3 and the fourth rotation angle of the laser beam (aiming unit) in the fourth rotation direction D4 can be obtained through the second angle measuring mechanism. Step S107: After the target 21 is aligned with the laser beam, multiple feature marker structures 24 can be captured by the attitude camera, and the first attitude information of the target rotation seat 22 relative to the attitude camera can be calculated. After the attitude camera captures the image, the position of the light spot formed by the feature marker structure 24 in the image can be obtained. After matching the light spot in the image with the feature marker structure on the probe 2 one by one, the position information of the target rotation seat 22 of the probe 2 relative to the attitude camera, that is, the first attitude information, can be calculated.

[0117] In some examples, after the attitude camera captures an image, preprocessing such as filtering and binarization can be performed, thereby improving computational accuracy.

[0118] Step S109: Calculate the target attitude information of the target base relative to the tracker base based on the first rotation angle and the rotation angle of the laser beam, thereby completing the calculation.

[0119] In step S109, coordinate systems can be created based on the various core components of the six-dimensional tracking and measurement system, including the tracker coordinate system, camera coordinate system, target rotation seat coordinate system, and target base coordinate system. The tracker coordinate system can be created based on the tracker base, with the laser beam emission direction as the X-axis, the vertically upward direction as the Z-axis, and the Y-axis direction obtained based on the right-hand rule.

[0120] The camera coordinate system can be created based on the attitude camera, and its transformation relationship with the tracker coordinate system changes as the attitude camera rotates. The X-axis direction of the camera coordinate system is opposite to the Y-axis direction of the tracker coordinate system when the laser tracker 1 is reset. The Y-axis direction is opposite to the Z-axis direction of the tracker coordinate system when the laser tracker 1 is reset. The Z-axis direction is the same as the X-axis direction of the tracker coordinate system when the laser tracker 1 is reset.

[0121] The target rotation coordinate system can be created based on the target rotation base 22. The target rotation coordinate system has the direction of laser beam incident as the X-axis, the direction of the rotation axis in the second rotation direction as the Y-axis, and the direction of the rotation axis in the first rotation direction as the Z-axis. In other words, the position information of the feature marker structure 24 in the target rotation coordinate system is a fixed value.

[0122] The target base coordinate system can be created based on the target base 23. The transformation relationship between the target rotation seat coordinate system and the target base coordinate system changes as the target rotation seat 22 rotates. The coordinate axis directions of the target base coordinate system are the same as those of the target coordinate system when the target 21 is reset. At the same time, the target base coordinate system is relatively stationary with respect to the target. Therefore, the attitude changes of the target can be determined by the relationship between the target coordinate system and the tracker coordinate system.

[0123] During the calculation process, the first attitude information can be associated with the camera coordinate system and the target rotation seat coordinate system. In other words, the first attitude information can characterize the attitude information of the target rotation seat 22 in the camera coordinate system.

[0124] In some instances, the transformation relationship between the camera coordinate system and the tracker coordinate system can be obtained based on the rotation angle of the laser beam. Since the rotation angle of the laser beam includes a third rotation angle and a fourth rotation angle, the transformation relationship between the camera coordinate system and the tracker coordinate system can be obtained based on the third rotation angle and the fourth rotation angle. Furthermore, the second attitude information of the target rotating seat 22 relative to the tracker base can be obtained based on the first attitude information and the rotation angle of the laser beam.

[0125] In some instances, the transformation relationship between the target rotation base coordinate system and the target base coordinate system can be obtained based on the rotation angle of the target rotation base 22. Since the rotation angle of the target rotation base 22 includes a first rotation angle, the transformation relationship between the target rotation base coordinate system and the target base coordinate system can be obtained based on the first rotation angle. Furthermore, the target attitude information of the target base 23 relative to the tracker base can be obtained based on the second attitude information and the first rotation direction. Thus, according to the rotation angles of the rotatable target 21 and the rotatable aiming unit 11, the various coordinate systems can be sequentially associated, thereby realizing the transmission and measurement of attitude information.

[0126] In the above method, the second rotation angle of the target 21 in the second rotation direction can be further obtained. Ideally, the target attitude information of the target base 23 relative to the tracker base can be uniquely calculated through the first rotation angle and the rotation angle of the laser beam. The second rotation angle can be used as an additional constraint to reduce the error introduced by the first attitude information, the first rotation angle and the rotation angle of the laser beam in the acquisition process, thereby obtaining more accurate attitude information.

[0127] In some examples, although the method described above for determining the attitude information of the target base 23 through the feature marker structure can be performed without using a gravity / tilt sensor, the six-dimensional tracking measurement method disclosed herein can also be used in conjunction with a gravity / tilt sensor. For example, the method for calculating attitude information can be switched based on the test conditions. When the test environment is bright or has interfering light sources, the attitude camera may have difficulty acquiring a clear and stable light spot formed by the feature marker structure. In such cases, the gravity / tilt sensor can be switched to calculate the attitude information of the target base 23. When the test environment is affected by factors such as vibration, temperature, and electromagnetic fields, the method of determining the attitude information of the target base 23 through the feature marker structure 24 can be used. This improves the stability of attitude information measurement.

[0128] The attitude information of the target base 23 can be obtained by using gravity / tilt sensors. Multiple gravity / tilt sensors with different measurement directions are set on the laser tracker base and the target base 23. The multiple gravity / tilt sensors on the same part have different directions. Preferably, two gravity / tilt sensors with orthogonal measurement directions are set on the laser tracker base and the target base 23 respectively. The laser beam vector is projected onto the world coordinate system using the tilt angles of the laser tracker base and the target base 23, respectively. The attitude information is then calculated using two expressions. Specifically, the expression for the laser beam in the tracker coordinate system is obtained by measuring the rotation angle of the laser beam. Multiple tilt angles are then obtained using the gravity / tilt sensor of the laser tracker base, leading to the first expression for the laser beam in the world coordinate system. Similarly, the expression for the laser beam in the target base coordinate system is obtained by measuring the rotation angle of the target 21. Multiple tilt angles are then obtained using the gravity / tilt sensor of the target base 23, leading to the second expression for the laser beam in the world coordinate system. Two Euler angles of the target base 23 are obtained based on the measured tilt angles. A third Euler angle of the target base 23 is calculated based on the first and second expressions, thus obtaining the three Euler angles of the target base 23 and achieving the attitude information measurement of the target base 23.

[0129] In some examples, the tilt angles of the target base 23 in multiple directions obtained by the gravity / tilt sensor can also be used as constraints to improve the stability and accuracy of the calculated attitude information of the target base 23.

[0130] While the present disclosure has been specifically described above in conjunction with the accompanying drawings and embodiments, it is to be understood that the above description does not limit the present disclosure in any way. Those skilled in the art can make modifications and variations to the present disclosure as needed without departing from its essential spirit and scope, and all such modifications and variations fall within the scope of the present disclosure.

Claims

1. A six-dimensional tracking and measurement system based on visual active tracking, comprising a probe for receiving and reflecting a laser beam, a laser tracker for emitting the laser beam, and a computing center, characterized in that, The probe includes: a target base, a target rotating seat that can rotate along a first rotation direction, multiple feature marker structures disposed on the target rotating seat and capable of emitting or reflecting a light beam, a target disposed on the target rotating seat and capable of rotating along a second rotation direction, a first rotation drive mechanism for driving the target rotating seat and the target to rotate to align with the laser tracker, and a first angle measurement mechanism for obtaining a first rotation angle of the target rotating seat in the first rotation direction; The laser tracker includes: a tracker base, a rotatable aiming unit that emits a laser beam, a second rotation drive mechanism that drives the aiming unit to rotate to align with the probe, a second angle measuring mechanism that acquires the rotation angle of the aiming unit, and an attitude camera linked to the aiming unit. The computing center is used to calculate the first attitude information of the target rotating base relative to the attitude camera, and to calculate the target attitude information of the target base relative to the tracker base based on the first rotation angle, the third rotation angle, and the fourth rotation angle.

2. The six-dimensional tracking and measurement system according to claim 1, characterized in that, The number of feature marker structures is 6-12, and the multiple feature marker structures are arranged on different planes.

3. The six-dimensional tracking and measurement system according to claim 1, characterized in that, The target rotating base includes a rotating base top, a rotating base middle part, and a rotating base bottom that are fixedly connected in sequence, and the feature mark structure is provided on the rotating base top, the rotating base middle part, and the rotating base bottom.

4. The six-dimensional tracking and measurement system according to claim 3, characterized in that, The middle part of the rotating seat includes a first support arm and a second support arm. The target is disposed between the first support arm and the second support arm in a manner that allows it to rotate along the second rotation direction. The first support arm and the second support arm are respectively provided with the protruding feature mark structure.

5. The six-dimensional tracking and measurement system according to claim 3, characterized in that, Extended wings are provided on the left and right sides of the bottom of the rotating base, and the feature marking structures are respectively provided on the extended wings on both sides of the bottom of the rotating base.

6. The six-dimensional tracking and measurement system according to claim 1, characterized in that, The target includes a corner bevel prism with a through hole and a first position sensor disposed behind the corner bevel prism.

7. A six-dimensional tracking measurement method based on visual active tracking, which is a six-dimensional tracking measurement method used in conjunction with a probe and a laser tracker. The probe includes a target base, a target rotation seat that can be disposed on the target base and rotated on the target base along a first rotation direction, and a target disposed on the target rotation seat and rotated on the target rotation seat along a second rotation direction. The target rotation seat is provided with multiple feature marker structures for presenting the attitude of the target rotation seat. The laser tracker includes a tracker base, a rotatable aiming unit that emits a laser beam, and an attitude camera linked to the aiming unit. The method is characterized in that... Six-dimensional tracking measurement methods include: Adjust the angle of the laser beam so that it is aligned with the probe; The target rotates along a first rotation direction and a second rotation direction and is aligned with the laser beam; Record the first rotation angle of the target in the first rotation direction and the rotation angle of the laser beam; The target rotation seat is photographed by the attitude camera to capture multiple feature marker structures, and the first attitude information of the target rotation seat relative to the attitude camera is calculated. Based on the first attitude information, the first rotation angle, and the rotation angle of the laser beam, the target attitude information of the target base relative to the tracker base is calculated.

8. The six-dimensional tracking measurement method according to claim 7, characterized in that, Based on the first attitude information and the rotation angle of the laser beam, the second attitude information of the target rotating seat relative to the tracker base is obtained.

9. The six-dimensional tracking measurement method according to claim 7, characterized in that, Based on the second attitude information and the first rotation direction, the target attitude information of the target base relative to the tracker base is obtained.

10. The six-dimensional tracking measurement method according to claim 7, characterized in that, It also includes methods for obtaining auxiliary attitude information through multi-sensor constraint methods, and methods for calculating attitude information based on replacing the target base in the test environment. The multi-sensor constraint method includes setting multiple tilt sensors with different measurement directions on the laser tracker and the target base, and projecting the laser beam vector onto the world coordinate system using the tilt angles of the laser tracker base and the target base, respectively.

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