A method of detecting measurement errors in a laser tracker

Abstract

The application relates to the technical field of instrument precision detection, and discloses a method for detecting measurement error of a laser tracker, which comprises the following steps: marking a projection point of a target ball on a measurement plane of the laser tracker; rotating the laser tracker around a rotation center to a measurement point; establishing a length measurement error detection model according to the positional relationship among the rotation center, the projection point, the measurement point and the target ball; and obtaining a length measurement error detection result according to the length measurement error detection model. A virtual projection point of the target ball on the measurement plane of the laser tracker is marked; the virtual projection point is a projection point of the simulated target ball on the measurement plane of the laser tracker after the target ball is rotated with the laser tracker; a length measurement error detection model is established according to the positional relationship among the projection point, the virtual projection point, the measurement point and the rotation center; and a length measurement error detection result is obtained according to the pitch axis angle of the laser tracker and the length measurement detection model. The application can simultaneously detect the length measurement error and the angle measurement error of the laser tracker with high precision.

Description

Technical Field

[0001] This invention relates to the field of instrument accuracy testing technology, and more specifically, to a method for detecting measurement errors in a laser tracker. Background Technology

[0002] Laser trackers are important benchmarks for large-scale spatial measurements, widely used in the geometric inspection, assembly, and intelligent manufacturing equipment of large-scale components. In the process of equipment / coordinate measuring machine (CMM) spatial accuracy inspection, the error of the laser tracker has a significant impact on the measurement results. Therefore, it is necessary to evaluate the accuracy of laser trackers to provide a reference for high-precision measurements.

[0003] In the testing of intelligent manufacturing equipment, the accuracy of laser trackers significantly impacts their spatial accuracy, especially angular accuracy. Therefore, on-site evaluation of laser tracker measurement accuracy is crucial during intelligent manufacturing equipment testing. Common methods for evaluating laser tracker accuracy primarily involve placing a high-precision standard ruler at different locations in space and measuring the lengths at both ends of the ruler using the tracker to comprehensively evaluate the tracker's performance. Alternatively, a laser interferometer can be used as a comparison benchmark to calibrate the length measurement error of the laser tracker. Another method involves calibrating the tracking measurement system using a coordinate measuring machine (CMM), which requires additional testing equipment and demands high precision from the CMM. All of these methods have limitations; they may not simultaneously evaluate length and angle measurement errors, or they may require large, high-precision equipment.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting measurement errors of a laser tracker, thereby solving the problem that existing technologies cannot simultaneously detect the length measurement error and angle measurement error of a laser tracker.

[0006] This invention is achieved through the following technical solution:

[0007] A method for detecting measurement errors of a laser tracker is provided, comprising: length measurement error detection and angle measurement error detection; the length measurement error detection includes: executing step A multiple times to obtain multiple length measurement error detection models; obtaining a length measurement error detection result based on the multiple length measurement error detection models; step A includes: marking the projection point of the target ball on the measurement plane of the laser tracker; rotating the laser tracker around the rotation center to the measurement point; establishing a length measurement error detection model based on the positional relationship between the rotation center, the projection point, the measurement point, and the target ball; the angle measurement error detection includes: after executing step A, executing step B to obtain the current angle measurement error; step B includes: marking the virtual projection point of the target ball on the measurement plane of the laser tracker; the virtual projection point is the projection point of the simulated target ball on the measurement plane of the laser tracker after it rotates with the laser tracker; establishing a length measurement error detection model based on the positional relationship between the projection point, the virtual projection point, the measurement point, and the rotation center; and obtaining a length measurement error detection result based on the pitch axis angle of the laser tracker and the length measurement detection model.

[0008] Furthermore, before performing step A, the following steps are included: fixing the laser tracker on the metering turntable; obtaining the eccentricity of the installation position of the laser tracker relative to the rotation center of the metering turntable; and installing the target ball to the target point.

[0009] Furthermore, before performing step A, the following steps are also included: placing the metering turntable on the marble vibration isolation platform; adjusting the detection environment temperature to between 19.5℃ and 20.5℃.

[0010] Furthermore, the installation of the target ball to the target position includes the following steps: installing the target ball on an adjustable target ball holder; adjusting the adjustable target ball holder so that the height of the center of the target ball is consistent with the height of the measurement center of the laser tracker.

[0011] Furthermore, the establishment of the length measurement error detection model includes the following steps: in the triangle formed by the measurement point, the projection point, and the rotation center, a first trigonometric function relationship model is established based on the law of cosines; in the right triangle formed by the measurement point, the target ball, and the projection point, a second trigonometric function relationship model is established; and the first trigonometric function relationship model and the second trigonometric function relationship model are combined to obtain the length measurement error detection model.

[0012] Furthermore, the expression for the first trigonometric function relationship model is: Where, θ iLet Φ represent the rotation angle of the metering turntable corresponding to the i-th rotation, Φ represent the eccentricity of the installation position of the laser tracker relative to the rotation center of the metering turntable, OA represent the side formed by connecting the rotation center and the measurement point, OC represent the side formed by connecting the rotation center and the projection point, and AC represent the side formed by connecting the measurement point and the projection point; the expression of the second trigonometric function relationship model is: Wherein, AB represents the edge connecting the measurement point and the target ball. d represents the angle formed by the side corresponding to AB and the side corresponding to AC after the i-th rotation of the measuring turntable; i This represents the length of the side corresponding to AB; the expression for the length measurement error detection module is: Among them, f i R represents the length measurement error value obtained by the laser tracker in a single measurement, and l represents the length of the side corresponding to OA.

[0013] Furthermore, obtaining the length measurement error detection result includes the following steps: transforming the length measurement error detection model to obtain a transformed length measurement error detection model; solving the transformed length measurement error detection model using an optimization iterative algorithm to obtain a solution result; and obtaining the residual of the solution result to obtain the length measurement error of the laser tracker.

[0014] Furthermore, the expression for the transformed length measurement error detection model is as follows: Where F represents the length measurement error value of the laser tracker.

[0015] Furthermore, the establishment of the angle measurement error detection model includes the following steps: in the triangle formed by the rotation center, the measurement point and the virtual projection point and the triangle formed by the rotation center, the measurement point and the projection point, a first geometric relationship model and a second geometric relationship model are established based on the geometric relationship between the interior angles and the exterior angles;

[0016] By combining the first set relation model and the second set relation model, the angle measurement error detection model is obtained.

[0017] 9. A method for detecting measurement errors in a laser tracker according to claim 8, characterized in that,

[0018] The first geometric relationship model is ∠C1A1C=∠C1A1M1+∠CA1M1; where ∠C1A1C represents the interior angle formed by sequentially connecting the virtual projection point, the rotation center, and the measurement point; ∠C1A1M1 represents the exterior angle formed by the extensions of side OC1 and side OA1; side OC1 is the side connecting the rotation center and the virtual projection point; side OA1 is the side connecting the rotation center and the measurement point; ∠CA1M1 represents the included angle formed by the extensions of side CA1 and side OA1; side CA1 is the side connecting the projection point and the measurement point; the second geometric relationship model is... Wherein, ∠C1OM1 represents the angle formed by the extensions of sides OC and OA1, side OC is the side connecting the projection point and the rotation center, ∠A1C1O represents the angle formed by sides A1C1 and OC1, side A1C1 is the side connecting the measurement point and the virtual projection point, ∠COM1 represents the angle formed by sides OC and OA1, and ∠A1CO represents the angle formed by sides CA1 and OC.

[0019] Furthermore, the length measurement error detection result is δ i =α i -β i ; where δ i Let α represent the angle measured by the laser tracker, where α i α represents the measurement increment angle of the laser tracker. i Let ∠C1A1C, δ i β represents the angular measurement error of the laser tracker. i This represents the i-th pitch axis angle of the laser tracker.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: by driving the laser tracker to rotate coaxially through the angle measurement turntable, the laser tracker tracks the target ball. Based on the geometric relationship between the laser tracker, the target ball, and the projection of the target ball on the measurement plane, the length measurement error and angle measurement error of the laser tracker can be detected simultaneously. Moreover, this method does not require large-scale high-precision equipment such as a coordinate measuring machine, and can meet the needs of high-precision detection of length and angle measurement errors of the laser tracker under laboratory conditions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the detection device structure provided in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram illustrating the principle of length measurement error detection provided in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram illustrating the principle of angle measurement error detection provided in an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the installation deviation of the laser tracker provided in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example

[0028] To address the problem that existing technologies cannot simultaneously detect the length measurement error and angle measurement error of a laser tracker, this embodiment provides a method for detecting the measurement error of a laser tracker, including the following steps:

[0029] Step 1: Install the testing equipment. The installed testing equipment should look like this: Figure 1 As shown. The specific installation steps are as follows:

[0030] Step 1.1: Place the metering turntable on the marble vibration isolation platform; adjust the ambient temperature of the testing environment to between 19.5℃ and 20.5℃.

[0031] Step 1.2: Fix the laser tracker on the metering turntable. The metering turntable has a spatial rectangular coordinate system with an angular position accuracy of 0.12″ (u=0.05″, k=2).

[0032] Step 1.3: Control the eccentricity of the installation position of the laser tracker relative to the rotation center of the metering turntable to less than 0.5mm.

[0033] Step 1.4: Install the target ball on the adjustable target ball holder and adjust the adjustable target ball holder so that the height of the target ball's center is consistent with the height of the laser tracker's measurement center.

[0034] Step 2: Use the installed testing equipment to detect length measurement errors. (Reference) Figure 2 Step 2 specifically includes:

[0035] Step 2.1: Execute step A multiple times to obtain multiple length measurement error detection models.

[0036] Step 2.2: Obtain the length measurement error detection results based on multiple length measurement error detection models.

[0037] Step A includes:

[0038] Step A1: Mark the target ball ( Figure 2 The projection point C of point B in the measurement plane of the laser tracker.

[0039] Step A2: Rotate the laser tracker around the rotation center O to the measurement point A; based on the positional relationship between the rotation center O, the projection point C, the measurement point A, and the target ball B, establish a length measurement error detection model.

[0040] Specifically, the method for establishing a length measurement error detection model is as follows:

[0041] Step A2.1: In triangle OAC, which is composed of measurement point A, projection point C and rotation center O, establish the first trigonometric function relationship model according to the law of cosines.

[0042] The expression for the first trigonometric function relationship model is: Where, θ i Let Φ represent the rotation angle of the metering turntable corresponding to the i-th rotation of the metering turntable, Φ represent the eccentricity of the installation position of the laser tracker relative to the rotation center O of the metering turntable, OA represent the side formed by connecting the rotation center O and the measurement point A, OC represent the side formed by connecting the rotation center O and the projection point C, and AC represent the side formed by connecting the measurement point A and the projection point C.

[0043] Step A2.2: In the right triangle ABC formed by measurement point A, target ball B, and projection point C, establish the second trigonometric function relationship model. The expression of the second trigonometric function relationship model is: Wherein, AB represents the edge formed by connecting measurement point A and target ball B. d represents the angle formed by side AB and side AC after the i-th rotation of the measuring turntable; i This represents the length of side AB.

[0044] Step A2.3: Simultaneously establish the first and second trigonometric function relationship models to obtain the length measurement error detection model. The expression for the length measurement error detection module is as follows: Among them, f i R represents the length measurement error value obtained by the laser tracker in a single measurement, and l represents the length of side OA.

[0045] Furthermore, in step 2.2, the length measurement error detection results are obtained, including:

[0046] Step 2.21: Transform the length measurement error detection model to obtain the transformed length measurement error detection model. The expression of the transformed length measurement error detection model is as follows: Where F represents the length measurement error value of the laser tracker.

[0047] Step 2.22: Solve the transformed length measurement error detection model using an optimization iterative algorithm to obtain the solution results.

[0048] Step 2.23: Obtain the residual of the solution result to get the length measurement error of the laser tracker.

[0049] Step 3: Use the installed testing equipment to detect length measurement errors. (Reference) Figure 3 After completing step A, the following steps are performed:

[0050] Step 3.1: Mark the virtual projection point C1 of the target ball B on the measurement plane of the laser tracker. This virtual projection point is the projection point of the simulated target ball on the measurement plane of the laser tracker after it rotates with the laser tracker.

[0051] Step 3.2: Based on the positional relationship between projection point C, virtual projection point C1, measurement point A1 and rotation center A, establish a length measurement error detection model. Figure 3 In the diagram, point A represents the initial position of the laser tracker.

[0052] The establishment of the angle measurement error detection model includes the following steps:

[0053] Step 3.21: In triangle OA1C1 formed by the rotation center O, measurement point A1 and virtual projection point C1 and triangle OA1C formed by the rotation center O, measurement point A1 and projection point C, establish the first geometric relationship model and the second geometric relationship model based on the geometric relationship between the interior angles and the exterior angles.

[0054] The first geometric relationship model is ∠C1A1C=∠C1A1M1+∠CA1M1(5); where ∠C1A1C represents the interior angle formed by connecting the virtual projection point C1, the rotation center O and the measurement point A1 in sequence, ∠C1A1M1 represents the exterior angle formed by the extension of side OC1 and side OA1, side OC1 is the side formed by connecting the rotation center O and the virtual projection point C1, side OA1 is the side formed by connecting the rotation center O and the measurement point A1, ∠CA1M1 represents the angle formed by the extension of side CA1 and side OA1, and side CA1 is the side formed by connecting the projection point and the measurement point.

[0055] The second geometric relationship model is: Wherein, ∠C1OM1 represents the angle formed by the extensions of sides OC and OA1, side OC is the side connecting the projection point C and the rotation center O, ∠A1C1O represents the angle formed by sides A1C1 and OC1, side A1C1 is the side connecting the measurement point A1 and the virtual projection point C1, ∠COM1 represents the angle formed by sides OC and OA1, and ∠A1CO represents the angle formed by sides CA1 and OC.

[0056] Step 3.22: Combine the first set relation model and the second set relation model to obtain the angle measurement error detection model.

[0057] Step 3.3: Based on the pitch axis angle of the laser tracker and the length measurement detection model, obtain the length measurement error detection result. The length measurement error detection result is δ. i =α i -β i (8); where δ i β represents the angular measurement error of the laser tracker. i Let α represent the i-th pitch axis angle of the laser tracker. i α represents the measurement increment angle of the laser tracker. i It is ∠C1A1C.

[0058] It should be noted that when the center of the laser tracker and the center of the turntable are not in the same quadrant, the signs in equations (6) and (7) will change.

[0059] The above method for detecting measurement errors in laser trackers was verified through experiments as follows:

[0060] An experiment was conducted at a temperature of 20±0.5℃ using a self-developed metrology turntable and a laser tracker. A simplified experimental diagram is shown below. Figure 4As shown. The target ball was fixed to the mounting base using an adjustable clamp, and the laser tracker was fixed to the metering turntable using a magnetic clamp. All tests were conducted on a marble vibration isolation platform. The laser tracker was adjusted so that its measurement center was coaxial with the rotation axis of the metering turntable, and its eccentricity was controlled to be below 0.5 mm. The adjustable target ball holder was adjusted so that the center of the target ball was approximately on the same plane as the measurement center of the laser tracker and the rotation plane of the metering turntable.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting measurement errors in a laser tracker, characterized in that, include: Length measurement error detection and angle measurement error detection; The length measurement error detection includes: executing step A multiple times to obtain multiple length measurement error detection models; and obtaining length measurement error detection results based on the multiple length measurement error detection models. Step A includes: marking the projection point of the target ball on the measurement plane of the laser tracker; rotating the laser tracker around the rotation center to the measurement point; and establishing a length measurement error detection model based on the positional relationship between the rotation center, the projection point, the measurement point, and the target ball. The angle measurement error detection includes: after performing step A, performing step B to obtain the current angle measurement error; Step B includes: marking a virtual projection point of the target ball on the measurement plane of the laser tracker; the virtual projection point is a simulated projection point of the target ball on the measurement plane of the laser tracker after it rotates with the laser tracker; establishing an angle measurement error detection model based on the positional relationship between the projection point, the virtual projection point, the measurement point, and the rotation center; and obtaining the angle measurement error detection result based on the pitch axis angle of the laser tracker and the angle measurement error detection model. The establishment of the angle measurement error detection model includes the following steps: in the triangle formed by the rotation center, the measurement point, and the virtual projection point, and the triangle formed by the rotation center, the measurement point, and the projection point, a first geometric relationship model and a second geometric relationship model are established based on the geometric relationship between the interior angles and the exterior angles; the first geometric relationship model and the second geometric relationship model are combined to obtain the angle measurement error detection model; The angle measurement error detection result is: ;in, This represents the measurement increment angle of the laser tracker, where the measurement increment angle is the interior angle formed by sequentially connecting the virtual projection point, the projection point, and the measurement point. This indicates the angle measurement error of the laser tracker. This represents the i-th pitch axis angle of the laser tracker.

2. The method for detecting measurement error of a laser tracker according to claim 1, characterized in that, Before performing step A, the following steps are included: The laser tracker is fixedly mounted on the metering turntable; Obtain the eccentricity of the installation position of the laser tracker relative to the rotation center of the metering turntable; Install the target ball to the target point.

3. The method for detecting measurement error of a laser tracker according to claim 2, characterized in that, Before performing step A, the following steps are also included: placing the metering turntable on the marble vibration isolation platform; adjusting the detection environment temperature to between 19.5℃ and 20.5℃; The installation of the target ball to the target point includes the following steps: installing the target ball on an adjustable target ball holder; adjusting the adjustable target ball holder so that the height of the center of the target ball is consistent with the height of the measurement center of the laser tracker.

4. A method for detecting measurement errors of a laser tracker according to claim 2 or 3, characterized in that, The establishment of the length measurement error detection model includes the following steps: In the triangle formed by the measurement point, the projection point, and the rotation center, a first trigonometric function relationship model is established according to the law of cosines; A second trigonometric function relationship model is established in the right triangle formed by the measurement point, the target ball, and the projection point; By combining the first trigonometric function relationship model and the second trigonometric function relationship model, the length measurement error detection model is obtained.

5. The method for detecting measurement error of a laser tracker according to claim 4, characterized in that, The expression for the first trigonometric function relationship model is: ; where θ i Φ represents the rotation angle of the metering turntable corresponding to the i-th rotation of the metering turntable, Φ represents the eccentricity of the installation position of the laser tracker relative to the rotation center of the metering turntable, OA represents the side formed by connecting the rotation center and the measurement point, OC represents the side formed by connecting the rotation center and the projection point, and AC represents the side formed by connecting the measurement point and the projection point. The expression for the second trigonometric function relationship model is: Wherein, AB represents the edge connecting the measurement point and the target ball. This represents the angle formed by the side corresponding to AB and the side corresponding to AC after the i-th rotation of the measuring turntable; This represents the length of the side corresponding to AB; The expression for the length measurement error detection module is: ;in, R represents the length measurement error value obtained by the laser tracker in a single measurement, and l represents the length of the side corresponding to OA.

6. The method for detecting measurement error of a laser tracker according to claim 5, characterized in that, The process of obtaining the length measurement error detection result includes the following steps: The length measurement error detection model is transformed to obtain the transformed length measurement error detection model; The transformed length measurement error detection model was solved using an optimization iterative algorithm, and the solution results were obtained. The residual of the solution result is obtained to obtain the length measurement error of the laser tracker.

7. The method for detecting measurement error of a laser tracker according to claim 6, characterized in that, The expression for the transformed length measurement error detection model is as follows: Where F represents the length measurement error value of the laser tracker.

8. The method for detecting measurement error of a laser tracker according to claim 1, characterized in that, The first geometric relationship model is ;in, This represents the interior angle formed by sequentially connecting the virtual projection point, the projection point, and the measurement point. This represents the exterior angle formed by the extensions of sides OC1 and OA1, where side OC1 is the side connecting the rotation center and the virtual projection point, and side OA1 is the side connecting the rotation center and the measurement point. This represents the angle formed by the extensions of side CA1 and side OA1, where side CA1 is the side connecting the projection point and the measurement point; The second geometric relationship model is ;in, This represents the angle formed by the extensions of side OC and side OA1, where side OC is the side connecting the projection point and the center of rotation. This represents the angle formed by sides A1C1 and OC1, where side A1C1 is the side connecting the measurement point and the virtual projection point. This represents the angle formed by side OC and side OA1. This represents the angle formed by side CA1 and side OC.

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