A laser measurement precision improvement method

Abstract

The application discloses a laser measurement precision improving method for improving the precision of measuring a complex surface of a non-cooperative target, and belongs to the field of space target measurement. The method comprises the following steps: S1, preliminarily setting the distance between a measured target and a sensor, and measuring a true value; S2, measuring the distance of the target by using the sensor to obtain the distance value under different gray scales; S3, determining an inflection point gray scale; S4, establishing an error compensation fitting polynomial; S5, repeating S1-S4 to obtain the error compensation fitting polynomial under different distance conditions between the measured target and the sensor; and S6, performing error compensation on the measurement result of the sensor by using the error compensation fitting polynomial.

Description

Technical Field

[0001] This invention relates to a method for improving the accuracy of laser measurement, belonging to the field of space target measurement. Background Technology

[0002] Relative position and attitude measurement of non-cooperative targets is a crucial supporting technology in on-orbit servicing and space manipulation. The measurement sensors used are primarily laser-based sensors based on the time-of-flight method. Non-cooperative targets have diverse surface materials and varying reflectivity. Furthermore, the measurement process is affected by factors such as the incident angle, reflectivity, and transmittance differences at various locations within the scene, leading to large fluctuations in echo intensity. Consequently, the measurement sensors exhibit varying measurement effects and accuracy for different target surface materials. In particular, when the echo intensity is oversaturated, the measurement accuracy drops sharply, significantly impacting the accuracy of measuring the relative position and attitude of non-cooperative targets. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and improve the accuracy of measuring complex surfaces of non-cooperative targets.

[0004] The objective of this invention is achieved through the following technical solutions: A method for improving the accuracy of laser measurement includes the following steps: S1. Initially set the distance between the target and the sensor, and measure the true value; S2. Use a sensor to measure the distance to the target and obtain the distance values ​​under different gray levels; S3. Determine the grayscale value at the inflection point; S4. Establish the error compensation fitting polynomial; S5. Repeat S1~S4 to obtain the error compensation fitting polynomial for different distances between the target and the sensor; S6. Use an error compensation fitting polynomial to compensate for the measurement results of the sensor.

[0005] In one embodiment of the present invention, in S1, multiple devices are used to measure the true distance value between the target and the sensor, i.e., the true value, denoted as L.

[0006] In one embodiment of the present invention, in S2, different gray levels are adjusted by adjusting different laser powers, target reflectivity, and one or more combinations of adjusting attenuators in the optical path.

[0007] In one embodiment of the present invention, in S2, it is assumed that the threshold gray level is... saturated grayscale is By adjusting different gray levels, the echo signal intensity value can be adjusted from... Gradually increase to Assume the grayscale value of the i-th point is The corresponding distance measurement value is , The difference between L and ( That is , It is an ordinal number.

[0008] In one embodiment of the present invention, determining the inflection point grayscale includes: the grayscale value at which a deviation begins to occur between the measured value and the true value is the inflection point grayscale, denoted as . ,Should The corresponding distance measurement value is For grayscale values ​​less than 100,000, the grayscale value is 100,000. The distance values ​​are distributed in On both sides, there exists a ratio Larger values ​​also exist than... Smaller values, while grayscale is greater than The distance values ​​are all higher than It should be small.

[0009] In one embodiment of the present invention, saturation is defined as the saturation at point j. , The value range is [0,1]; by The data is y, expressed in terms of saturation. For x, perform polynomial fitting to obtain... and The relationship between them is used to establish an error compensation fitting polynomial, denoted as... .

[0010] In one embodiment of the present invention, the polynomial fitting is greater than order 3.

[0011] In one embodiment of the present invention, The range of values ​​is arrive .

[0012] In one embodiment of the present invention, in S5, based on the error compensation fitting polynomials under different distance conditions, if a certain distance value A does not have an error compensation fitting polynomial obtained through S1~S4, a new error compensation fitting polynomial is obtained by finding the two error compensation fitting polynomials closest to the distance value A, taking the fitting parameters of the corresponding order and performing linear weighting respectively.

[0013] Compared with the prior art, the present invention has the following advantages: (1) This invention tests the influence of various factors on accuracy, and derives the relationship between accuracy and echo intensity based on data analysis, and then makes corrections. This method is highly versatile, feasible, and effective, and can significantly improve measurement accuracy. (2) The method of the present invention can effectively utilize saturation region data and effectively improve the dynamic range of the laser sensor.

[0014] (3) In the field of non-cooperative target measurement, the method of the present invention can further improve the measurement accuracy of the laser sensor when facing non-cooperative targets and other targets with complex reflection characteristics, and further improve the measurement accuracy of relative distance, position and attitude. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the laser measurement accuracy improvement method of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0017] A method for improving the accuracy of laser measurement, such as Figure 1 As shown, it includes: S1. Initially set the distance between the target and the sensor. Use multiple devices such as a total station and a theodolite to measure the true distance between the target and the sensor, which is denoted as L.

[0018] S2. By adjusting one or more combinations of different laser powers, target reflectivity, and attenuators in the optical path, a sensor is used to measure the distance to the target, obtaining ranging values ​​at different gray levels. Assume the threshold gray level is... saturated grayscale is By adjusting the signal strength through one or more of the above methods, the echo signal strength value is reduced from... Gradually increase to Assume the gray value of the i-th point is... The corresponding distance measurement value is The difference between it and L ( That is , It is an ordinal number, and its value is generally greater than 8.

[0019] In the unsaturated grayscale stage, the ranging values ​​corresponding to different grayscale values ​​are generally quite close, and the ranging value does not change much with different grayscale values. As the signal gradually saturates, the ranging values ​​corresponding to different grayscale values ​​decrease as the grayscale value increases.

[0020] S3. Determine the inflection point grayscale where the measured value and the true value begin to deviate, which is... ,Should Corresponding distance value The difference between L and L is denoted as .

[0021] in, The method for selecting points is as follows: for grayscale values ​​less than... The distance values ​​are distributed in On both sides, there exists a ratio Larger values ​​also exist than... Smaller values. And grayscale values ​​greater than The distance values ​​are all higher than It should be small.

[0022] S4. Define the concept of saturation, the saturation at point j. , The value range is [0,1].

[0023] by (The range of values ​​is) arrive The data is y, expressed in terms of saturation. For x, perform polynomial fitting (generally greater than order 3) to obtain... and The relationship between them is used to establish an error compensation fitting polynomial, denoted as... .

[0024] S5. Adjust the distance between the target and the sensor, and repeat steps S1 to S4 to obtain the error compensation fitting polynomials at different distances. Taking a fourth-order fitting polynomial as an example, the error compensation fitting polynomial for each distance yields five fitting parameters.

[0025] The fitted polynomials obtained above are weighted to obtain new fitted polynomials. Taking a fourth-order fitted polynomial as an example, for a measured distance value and gray value, the fitted polynomial closest to that distance value is found, and the fitted parameters of the corresponding orders are linearly weighted to obtain new fitted parameters, and thus a new fitted polynomial.

[0026] S6. In practical applications, error compensation is performed using a fitting polynomial to improve measurement accuracy. The compensated value is denoted as... , .

[0027] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0028] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for improving the accuracy of laser measurement, characterized in that, Includes the following steps: S1. Initially set the distance between the target and the sensor, and measure the true value; S2. Use a sensor to measure the distance to the target and obtain the distance values ​​under different gray levels; S3. Determine the grayscale value at the inflection point; S4. Establish the error compensation fitting polynomial; S5. Repeat S1~S4 to obtain the error compensation fitting polynomial for different distances between the target and the sensor; S6. Use an error compensation fitting polynomial to compensate for the measurement results of the sensor.

2. The laser measurement accuracy improvement method according to claim 1, characterized in that, In S1, multiple devices are used to measure the true distance between the target and the sensor, i.e., the true value, denoted as L.

3. The laser measurement accuracy improvement method according to claim 1, characterized in that, In S2, different gray levels can be adjusted by regulating different laser powers, target reflectivity, and one or more combinations of adjusting attenuators in the optical path.

4. The laser measurement accuracy improvement method according to claim 2, characterized in that, In S2, assuming the threshold gray level is saturated grayscale is By adjusting different gray levels, the echo signal intensity value can be adjusted from... Gradually increase to ; Assume the gray value of the i-th point is The corresponding distance measurement value is , The difference between L and ( That is , It is an ordinal number.

5. The laser measurement accuracy improvement method according to claim 4, characterized in that, Determining the inflection point grayscale includes: the grayscale value at which the measured value and the true value begin to deviate is the inflection point grayscale, denoted as . ,Should The corresponding distance measurement value is For grayscale values ​​less than 100,000, the grayscale value is 100,000. The distance values ​​are distributed in On both sides, there exists a ratio Larger values ​​also exist than... Smaller values, while grayscale is greater than The distance values ​​are all higher than It should be small.

6. The laser measurement accuracy improvement method according to claim 5, characterized in that, the definition is... Saturation, saturation at point j , The value range is [0,1]; by The data is y, expressed in terms of saturation. For x, perform polynomial fitting to obtain... and The relationship between them is used to establish an error compensation fitting polynomial, denoted as... .

7. The laser measurement accuracy improvement method according to claim 6, characterized in that, The polynomial fit is greater than order 3.

8. The laser measurement accuracy improvement method according to claim 6, characterized in that, The range of values ​​is arrive .

9. The method for improving laser measurement accuracy according to claim 1, characterized in that, In S5, based on the error compensation fitting polynomials under different distance conditions, if a certain distance value A does not have an error compensation fitting polynomial obtained through S1~S4, a new error compensation fitting polynomial is obtained by finding the two error compensation fitting polynomials closest to the distance value A, taking the fitting parameters of the corresponding order and performing linear weighting respectively.

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