CN114966626A

CN114966626A - Laser radar error correction method and device, electronic equipment and storage medium

Info

Publication number: CN114966626A
Application number: CN202210444843.5A
Authority: CN
Inventors: 秦禹康; 张勇; 徐跃明
Original assignee: Zhuhai Shixi Technology Co Ltd
Current assignee: Zhuhai Shixi Technology Co Ltd
Priority date: 2022-04-26
Filing date: 2022-04-26
Publication date: 2022-08-30
Anticipated expiration: 2042-04-26
Also published as: CN114966626B

Abstract

The application discloses a method and a device for laser radar error correction, electronic equipment and a storage medium, which are used for reducing errors of a laser radar in a using process and improving the accuracy of the laser radar. The method comprises the following steps: setting a first calibration target in the detection range of the laser radar; when the laser radar detects a first calibration target through a first mirror surface, acquiring a first angle and a first distance measurement value corresponding to the first mirror surface; when the laser radar detects the first calibration target through the second mirror surface, a second angle and a second distance measurement value corresponding to the second mirror surface are obtained; calculating a compensation angle according to the first angle and the second angle, and calculating a distance measurement difference value according to the first distance measurement value and the second distance measurement value; calculating a first compensation distance of the second mirror surface according to the compensation angle and the distance measurement difference value; when the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface; and correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value.

Description

Laser radar error correction method and device, electronic equipment and storage medium

Technical Field

The embodiment of the application relates to the field of laser radar ranging, in particular to a method and a device for laser radar error correction, an electronic device and a storage medium.

Background

Lidar (Lidar), an electronic system that utilizes a laser range sensor for environmental distance sensing. With the development of laser radar ranging technology, the laser radar is increasingly used for ranging in various fields, so that automatic obstacle avoidance and automatic operation of field operation machines are realized, and the degree of automation is improved. There are three general approaches used in the industry: mechanical rotation scheme, mixed solid state mode and all solid state mode.

The scheme is based on a mixed solid-state laser radar, and the design scheme is that the laser radar emits laser and captures echo, and a reflecting prism erected on a motor reflects the laser to change a deflection angle. The basic principle is that the laser radar calculates the distance between a target object and the ranging module by recording the time difference between the emission and the return of pulse waves. Laser is irradiated to a sector area through the rotation of the reflecting prism, the laser radar receives reflected light, point cloud information is generated according to the time difference between the emission and the receiving of the laser, and the distance of a target object in the sector area is determined from the point cloud information.

However, in the actual application of the laser radar, various errors exist, and the causes of the errors are different, such as assembly errors and track nonlinearity errors. When current laser radar is using when the object range finding of short distance, can ignore this type of error, but when using when the object range finding of long distance, then can arouse great error, lead to the precision decline of laser radar range finding.

Disclosure of Invention

The first aspect of the present application provides a method for laser radar error correction, which is characterized by comprising:

a first calibration target is arranged in the detection range of the laser radar, and the laser radar is provided with a reflecting prism which comprises at least two mirror surfaces;

when the laser radar detects a first calibration target through a first mirror surface, acquiring a first angle and a first distance measurement value corresponding to the first mirror surface;

when the laser radar detects the first calibration target through the second mirror surface, a second angle and a second distance measurement value corresponding to the second mirror surface are obtained;

calculating a compensation angle according to the first angle and the second angle, and calculating a distance measurement difference value according to the first distance measurement value and the second distance measurement value;

calculating a first compensation distance of the second mirror surface according to the compensation angle and the distance measurement difference value;

when the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface;

and correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value.

Optionally, after the assembly error of the third distance measurement value is corrected according to the first compensation distance to generate a first corrected distance value, the method further includes:

obtaining a measurement placing angle of a target object relative to a laser radar;

acquiring a track nonlinear error correction curve of the second mirror surface, wherein the track nonlinear error correction curve is a relation curve of a placing angle and a track nonlinear error compensation value;

determining a second compensation distance from the track nonlinear error correction curve according to the measurement placement angle;

and correcting the track nonlinear error of the first corrected distance value according to the second compensation distance to generate a second corrected distance value.

Optionally, before obtaining the measured placement angle of the target object relative to the lidar, the method further includes:

setting a second calibration target, so that the actual distance between the laser radar and the second calibration target is R;

acquiring the actual placement angle of the second calibration target relative to the laser radar;

acquiring a fourth distance measurement value of the second calibration target through a second mirror surface of the laser radar;

calculating a third compensation distance corresponding to the actual placement angle according to the fourth distance measurement value and the actual distance R;

and calculating compensation distances corresponding to at least two placing angles according to the steps, and fitting to generate a track nonlinear error correction curve related to the second mirror surface.

Optionally, after the track non-linear error is corrected for the first corrected distance value according to the second compensation distance to generate a second corrected distance value, the method further includes:

acquiring the actual rotation angular velocity of a reflecting prism in the laser radar;

acquiring an angular velocity error correction curve of the second mirror surface, wherein the angular velocity error correction curve is a relation curve of the second mirror surface and angular velocity compensation difference values under different rotation angular velocities;

determining a fourth compensation distance from the angular velocity error correction curve according to the actual rotation angular velocity;

and correcting the angular speed error of the second corrected distance value according to the fourth compensation distance to generate a third corrected distance value.

Optionally, before acquiring the actual rotational angular velocity of the reflecting prism in the laser radar, the method further includes:

setting a third calibration target in the detection range of the laser radar, wherein the actual distance value between the third calibration target and the laser radar is D;

rotating a reflecting prism of a laser radar at a preset angular speed;

measuring the distance of the third calibration target through a second mirror surface of the laser radar at a preset angular speed to generate a fifth distance measurement value;

the difference is obtained between the fifth distance measurement value and the actual distance value D, and an angular velocity compensation difference value is generated;

and calculating the angular velocity compensation difference corresponding to the at least two distance measurement values and the rotation angular velocity according to the steps to generate an angular velocity error correction curve related to the second mirror surface.

acquiring reflected light received by a laser radar;

measuring the propagation speed of the reflected light;

calculating a color error compensation value according to the propagation speed and the first correction distance value;

and compensating the first correction distance value according to the color error compensation value.

Optionally, measuring the propagation velocity of the reflected light comprises:

measuring the color type of the reflected light;

determining the refractive index of the reflected light according to the color type;

and determining the propagation speed of the reflected light in the current medium according to the refractive index.

The second aspect of the present application provides a laser radar error correction apparatus, which includes:

the laser radar detection device comprises a first setting unit, a second setting unit and a control unit, wherein the first setting unit is used for setting a first calibration target in a detection range of a laser radar, and the laser radar is provided with a reflecting prism which comprises at least two mirror surfaces;

the first acquisition unit is used for acquiring a first angle and a first distance measurement value corresponding to the first mirror surface when the laser radar detects the first calibration target through the first mirror surface;

the second acquisition unit is used for acquiring a second angle and a second distance measurement value corresponding to the second mirror surface when the laser radar detects the first calibration target through the second mirror surface;

the first calculating unit is used for calculating a compensation angle according to the first angle and the second angle and calculating a distance measuring difference value according to the first distance measuring value and the second distance measuring value;

the second calculating unit is used for calculating a first compensation distance of the second mirror surface according to the compensation angle and the distance measurement difference value;

the third acquisition unit is used for acquiring a third ranging value of the second mirror surface when the laser radar uses the second mirror surface to range the target object;

and the first correcting unit is used for correcting the assembly error of the third distance measuring value according to the first compensation distance to generate a first corrected distance value.

Optionally, the apparatus further comprises:

the fourth acquisition unit is used for acquiring the measurement placement angle of the target object relative to the laser radar;

a fifth obtaining unit, configured to obtain a trajectory nonlinear error correction curve of the second mirror, where the trajectory nonlinear error correction curve is a relation curve between the placement angle and a trajectory nonlinear error compensation value;

a first determining unit for determining a second compensation distance from the trajectory nonlinear error correction curve according to the measurement placement angle;

and the second correction unit is used for correcting the track nonlinear error of the first correction distance value according to the second compensation distance to generate a second correction distance value.

Optionally, the apparatus further comprises:

the second setting unit is used for setting a second calibration target, so that the actual distance between the laser radar and the second calibration target is R;

the sixth acquisition unit is used for acquiring the actual placement angle of the second calibration target relative to the laser radar;

the seventh obtaining unit is used for obtaining a fourth distance measurement value of the second calibration target through a second mirror surface of the laser radar;

the third calculating unit is used for calculating a third compensation distance corresponding to the actual placing angle according to the fourth distance measuring value and the actual distance R;

and the first generating unit is used for calculating the compensation distances corresponding to the at least two placing angles according to the steps and fitting to generate a track nonlinear error correction curve related to the second mirror surface.

Optionally, the apparatus further comprises:

an eighth acquiring unit, configured to acquire an actual rotational angular velocity of a reflecting prism in the laser radar;

a ninth acquiring unit, configured to acquire an angular velocity error correction curve of the second mirror surface, where the angular velocity error correction curve is a relation curve between the second mirror surface and the angular velocity compensation difference at different rotation angular velocities;

a second determination unit for determining a fourth compensation distance from the angular velocity error correction curve based on the actual rotational angular velocity;

and a third correcting unit configured to correct the angular velocity error of the second corrected distance value according to the fourth compensation distance, and generate a third corrected distance value.

Optionally, the apparatus further comprises:

the third setting unit is used for setting a third calibration target in the detection range of the laser radar, and the actual distance value between the third calibration target and the laser radar is D;

the rotating unit is used for rotating the reflecting prism of the laser radar at a preset angular speed;

the first measuring unit is used for measuring the distance of the third calibration target through a second mirror surface of the laser radar at a preset angular speed to generate a fifth distance measuring value;

the second generating unit is used for calculating the difference between the fifth distance measuring value and the actual distance value D to generate an angular velocity compensation difference value;

and a third generating unit for calculating the angular velocity compensation difference corresponding to the at least two distance measurement values and the rotation angular velocity according to the above steps, and generating an angular velocity error correction curve for the second mirror surface.

Optionally, the apparatus further comprises:

a tenth acquiring unit, configured to acquire reflected light received by the laser radar;

a second measuring unit for measuring a propagation speed of the reflected light;

a fourth calculation unit for calculating a color error compensation value based on the propagation velocity and the first corrected distance value;

and the fourth correcting unit is used for compensating the first correcting distance value according to the color error compensation value.

Optionally, the second measurement unit specifically includes:

measuring the color type of the reflected light;

A third aspect of the present application provides an electronic device, comprising:

the device comprises a processor, a memory, an input and output unit and a bus;

the processor is connected with the memory, the input and output unit and the bus;

the memory holds a program that is called by the processor to perform the method as described in the first aspect and any of the alternatives of the first aspect.

A fourth aspect of the present application provides a computer readable storage medium having a program stored thereon, the program, when executed on a computer, performing the method of the first aspect as well as any of the alternatives of the first aspect.

According to the technical scheme, the embodiment of the application has the following advantages:

in this application, set up first demarcation target in laser radar's detection range, wherein, be provided with reflection prism on the laser radar, reflection prism includes two at least mirror surfaces. When the laser radar sets one mirror as a reference mirror (first mirror), the rest mirrors are set as the mirrors to be calibrated (second mirrors). When the first calibration target is detected through the first mirror surface, a first angle corresponding to the current first mirror surface and a first distance measurement value of the first calibration target and the laser radar are read through equipment. And when the laser radar detects the first calibration target through the second mirror surface, reading a second angle corresponding to the current second mirror surface and a second distance measurement value of the first calibration target and the laser radar through equipment. A compensation angle is then calculated based on the first angle and the second angle, and a range difference is calculated based on the first range value and the second range value. And calculating a first compensation distance of the second mirror according to the compensation angle and the ranging difference. And when the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface. And correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value. The method comprises the steps of calculating a first compensation distance of a mirror surface to be calibrated by determining a reference mirror surface, taking a distance measurement value of the reference mirror surface as a standard distance value and taking an angle of the reference mirror surface as a standard angle, wherein the first compensation distance is a compensation value of an assembly error of a second mirror surface, and finally taking the first compensation distance as the assembly error compensation of the second mirror surface. When the laser radar is in the actual use process, as long as the distance value is measured through the second mirror surface, the error correction can be carried out by using the first compensation distance, the error of the laser radar in the use process is reduced, and the precision of the laser radar is improved.

Drawings

FIG. 1 is a schematic diagram of an embodiment of a laser radar error correction method according to the present application;

FIG. 2 is a schematic diagram of a quad-prism lidar ranging system according to the present application;

FIG. 3 is a schematic diagram of the four-prism assembly error of the present application;

FIG. 4 is a schematic diagram of a reference mirror measurement of a first calibration target for a quad-prism lidar according to the present application;

FIG. 5 is a schematic diagram of a mirror surface to be calibrated of the quad-prism lidar of the present application for measuring a first calibration target;

6-1, 6-2, 6-3, 6-4, and 6-5 are schematic diagrams of another embodiment of a method of lidar error correction of the present application;

FIG. 7 is a schematic diagram of the non-linear error of the quad-prism track of the present application;

FIG. 8 is a schematic diagram of a laser radar circular arc calibration plate according to the present application;

FIG. 9 is a schematic diagram of a distance measurement without track non-linearity error correction according to the present application;

FIG. 10 is a schematic diagram of a distance measurement for track non-linear error correction according to the present application;

FIG. 11 is a schematic diagram of an embodiment of an apparatus for lidar error correction according to the present application;

FIG. 12 is a schematic diagram of another embodiment of an apparatus for lidar error correction according to the present application;

fig. 13 is a schematic diagram of an embodiment of an electronic device according to the present application.

Detailed Description

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It should also be understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

As used in this specification and the appended claims, the term "if" may be interpreted contextually as "when", "upon" or "in response to" determining "or" in response to detecting ". Similarly, the phrase "if it is determined" or "if a [ described condition or event ] is detected" may be interpreted contextually to mean "upon determining" or "in response to determining" or "upon detecting [ described condition or event ]" or "in response to detecting [ described condition or event ]".

Furthermore, in the description of the present application and the appended claims, the terms "first," "second," "third," and the like are used for distinguishing between descriptions and not necessarily for describing or implying relative importance.

Reference throughout this specification to "one embodiment" or "some embodiments," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather "one or more but not all embodiments" unless specifically stated otherwise. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless expressly specified otherwise.

In the prior art, in the actual application of the laser radar, various errors exist, and the causes of the errors are different, such as assembly errors and track nonlinearity errors. When current laser radar is using when the object range finding of short distance, can ignore this type of error, but when using when the object range finding of long distance, then can arouse great error, lead to the precision decline of laser radar range finding.

Based on the above, the application discloses a method and a device for laser radar error correction, an electronic device and a storage medium, which are used for reducing the error of a laser radar in the using process and improving the accuracy of the laser radar.

The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The method of the present application may be applied to a server, a device, a terminal or other devices with logic processing capability, for example: the robot that sweeps floor, autopilot, automatic control survey appearance etc. equipment, to this, this application does not limit. For convenience of description, the following description will be given taking the execution body as an example.

Referring to fig. 1, the present application provides an embodiment of a method for laser radar error correction, including:

101. a first calibration target is arranged in the detection range of the laser radar, and the laser radar is provided with a reflecting prism which comprises at least two mirror surfaces;

the laser radar in the embodiment comprises a laser emitting module, a reflecting prism, a laser receiving module and a controller, wherein the laser emitting module, the laser receiving module and the controller are integrated into a ranging module. Wherein, traditional laser radar is through increasing the rotating electrical machines under the ranging module for laser can shine an about 360 circular region, but is used for the ranging module to need connect the power, and whole ranging module has characteristics bulky and that weight is big, has restricted the rotation speed, makes the timeliness of range finding descend. The lidar reflection prism that this embodiment used is through the laser of reflection lidar for laser can shine this circular region, and reflection prism only need set up the mirror surface, and can set up to cavity, makes weight reduction. The reflecting prism is a relatively independent module without being connected with other lines, so that the rotating speed of the reflecting prism can be set according to actual conditions, the reflecting prism is not limited by other lines, and the reflecting prism and the rotating motor of the reflecting prism only need to be periodically overhauled.

The reflection prism includes 2 mirror surfaces at least, and is rotatory through the motor for the laser of mirror surface continuous cycle reflection range finding module transmission, and the laser that the range finding module can accept each side to go up the reflection back, according to the speed range finding of laser propagation. Two square mirror surfaces are attached to each other through the back to form the reflecting prisms of two reflecting surfaces, the three square mirror surfaces are connected end to form the reflecting prism of which the appearance is a triangular prism, the four square mirror surfaces are connected end to form the reflecting prism of which the appearance is a quadrangular prism, and the like, and the reflecting prism can be formed by combining a plurality of mirror surfaces.

Referring to fig. 2, fig. 2 is a schematic diagram illustrating a principle of the quad-prism lidar ranging. Through rotating the four prisms, the ranging module can reflect the laser emitted from the fixed direction to different directions, and the ranging effect is achieved.

Referring to fig. 3, fig. 3 is a schematic diagram illustrating a principle of the quadrangular prism assembly error. In assembling the reflecting prism of the laser radar, an assembly error may occur in the quadrangular prism. For example: a regular quadrangular model is selected for use when the quadrangular prism is designed, the sizes and the shapes of four side faces of the quadrangular model are the same, two adjacent side faces are perpendicular to each other by 90 degrees, four mirror faces with the same size are arranged on the four side faces respectively, so that the two adjacent mirror faces are perpendicular to each other by 90 degrees, and the quadrangular prism is arranged. However, when the quadrangular prism is actually combined, because a standard quadrangular prism model is not used or the used quadrangular prism model has defects, certain assembly deviation is generated when four mirror surfaces are connected, two adjacent mirror surfaces are not perpendicular, the assembly error influences the angle information of the laser radar, the angle measurement of the laser radar leads to errors, and the final detection effect is influenced.

Referring to fig. 4, fig. 4 is a schematic diagram of a reference mirror surface of a four-prism laser radar to measure a first calibration target, first, after the position of the laser radar is set, a calibration target is set within the effective detection range of the laser radar in such a manner that a calibration target is set at the farthest range perpendicular to the incident light, and the width of the calibration target is the minimum resolution at the position of the laser radar.

Referring to fig. 5, fig. 5 is a schematic diagram of a four-prism laser radar to measure a first calibration target on a mirror surface to be calibrated.

102. When the laser radar detects a first calibration target through a first mirror surface, acquiring a first angle and a first distance measurement value corresponding to the first mirror surface;

the terminal selects one mirror surface of the reflecting prism as a reference mirror surface (a first mirror surface), the first mirror surface is rotated to a first angle, so that laser emitted by the distance measuring module is irradiated to a first calibration target through reflection of the first mirror surface, and the distance measuring module receives the laser reflected by the first calibration target. And calculating the distance according to the time interval of transmitting and receiving the laser to obtain a first ranging value. And the current angle of the first mirror is determined as a zero point angle (first angle).

103. When the laser radar detects the first calibration target through the second mirror surface, a second angle and a second distance measurement value corresponding to the second mirror surface are obtained;

the terminal takes any one of the mirror surfaces except the first mirror surface in the reflecting prism as a mirror surface to be calibrated (a second mirror surface), the second mirror surface is rotated to a second angle, so that laser emitted by the distance measuring module is irradiated to the first calibration target through reflection of the second mirror surface, and the distance measuring module receives the laser reflected by the first calibration target. And calculating the distance according to the time interval of transmitting and receiving the laser to obtain a second ranging value. And recording a current second angle of the second mirror.

104. Calculating a compensation angle according to the first angle and the second angle, and calculating a distance measurement difference value according to the first distance measurement value and the second distance measurement value;

105. calculating a first compensation distance of the second mirror surface according to the compensation angle and the distance measurement difference value;

the terminal carries out difference according to the first angle and the second angle so as to calculate a compensation angle, and calculates a distance measurement difference value according to the difference between the first distance measurement value and the second distance measurement value.

Then the terminal calculates a first compensation distance of the second mirror surface according to the compensation angle and the distance measurement difference value, and the formula is as follows:

Δ s1 is a first compensation distance, Δ dt is a distance measurement difference, θ is a rotation angle of the first mirror, and Δ θ is a compensation angle. The first compensation distance is the step value of the second mirror surface to the assembling error.

106. When the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface;

107. and correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value.

When the laser radar uses the second mirror surface to measure the distance of the target object, the terminal obtains a third distance measurement value of the second mirror surface, the terminal directly adds and calculates the third distance measurement value according to the first compensation distance, and then the assembly error can be corrected, and the generated first corrected distance value is the distance measurement value for eliminating the assembly error.

In the embodiment of the application, a first calibration target is arranged in the detection range of the laser radar, wherein the laser radar is provided with a reflecting prism, and the reflecting prism comprises at least two mirror surfaces. When the laser radar sets one mirror as a reference mirror (first mirror), the rest mirrors are set as the mirrors to be calibrated (second mirrors). When the first calibration target is detected through the first mirror surface, a first angle corresponding to the current first mirror surface and a first distance measurement value of the first calibration target and the laser radar are read through equipment. And when the laser radar detects the first calibration target through the second mirror surface, reading a second angle corresponding to the current second mirror surface and a second distance measurement value of the first calibration target and the laser radar through equipment. A compensation angle is then calculated based on the first angle and the second angle, and a range difference is calculated based on the first range value and the second range value. And calculating a first compensation distance of the second mirror according to the compensation angle and the ranging difference. And when the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface. And correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value. The method comprises the steps of calculating a first compensation distance of a mirror surface to be calibrated by determining a reference mirror surface, taking a distance measurement value of the reference mirror surface as a standard distance value and taking an angle of the reference mirror surface as a standard angle, wherein the first compensation distance is a compensation value of an assembly error of a second mirror surface, and finally taking the first compensation distance as the assembly error compensation of the second mirror surface. When the laser radar is in the actual use process, as long as the distance value is measured through the second mirror surface, the first compensation distance can be used for error correction, the error of the laser radar in the use process is reduced, and the precision of the laser radar is improved.

Referring to fig. 6-1, 6-2, 6-3, 6-4, and 6-5, the present application provides another embodiment of a method for lidar error correction, comprising:

601. setting a second calibration target, so that the actual distance between the laser radar and the second calibration target is R;

602. acquiring the actual placement angle of the second calibration target relative to the laser radar;

603. acquiring a fourth distance measurement value of the second calibration target through a second mirror surface of the laser radar;

604. calculating a third compensation distance corresponding to the actual placement angle according to the fourth distance measurement value and the actual distance R;

605. calculating compensation distances corresponding to at least two placing angles according to the steps, and fitting to generate a track nonlinear error correction curve related to the second mirror surface;

referring to fig. 7, fig. 7 is a schematic diagram illustrating a principle of the non-linearity error of the quadrangular prism track according to the present invention. In addition to assembly errors, lidar suffers from trajectory non-linearity errors. The track non-linear error is caused by the change of the light stroke caused by the movement of the reflecting point in the process of the movement of the four-prism.

The terminal sets the second calibration target in a certain angle direction of the laser radar, and the actual distance is R. And detecting the second calibration target through a second mirror surface of the laser radar to obtain a fourth distance measurement value. And calculating a third compensation distance corresponding to the actual placement angle according to the difference between the fourth distance measurement value and the actual distance R. And calculating the compensation distances corresponding to at least two placing angles according to the steps, and performing curve fitting calculation after data is obtained to generate a track nonlinear error correction curve related to the second mirror surface.

In addition, fitting of a track nonlinear error correction curve can be performed by means of the circular arc calibration plate.

Referring to fig. 8, fig. 8 is a schematic diagram of a circular arc calibration plate of a laser radar. And correcting the track nonlinear error of the laser radar, firstly, arranging a circular arc calibration plate with the radius of R on the terminal by taking the optical center of the laser radar as the center, and marking an angle numerical value on the circular arc calibration plate.

And the terminal sets a second calibration target at the edge of the circular arc calibration plate, so that the actual distance between the laser radar and the second calibration target is the radius R, and the actual placement angle of the second calibration target relative to the laser radar is obtained according to the circular arc calibration plate, namely the second calibration target is arranged at the position which is away from the laser radar by the distance R and the angle of which is known (actual placement angle).

At the moment, the terminal emits laser to the second mirror surface through the ranging module of the laser radar, the laser is projected onto the second calibration target, and the ranging module acquires a fourth ranging value of the second calibration target.

And the terminal calculates the difference between the fourth distance measurement value and the radius R to obtain a third compensation distance corresponding to the actual placement angle, and associates the third compensation distance with the actual placement angle.

And calculating compensation distances corresponding to at least two placing angles according to the steps, and fitting to generate a track nonlinear error correction curve related to the second mirror surface. After the plurality of groups of parameters of the compensation distances and the placing angles are calculated, fitting calculation can be performed according to the plurality of groups of parameters, a track nonlinear error correction curve is fitted in the rectangular coordinate system, and the horizontal and vertical coordinates of the track nonlinear error correction curve are the compensation distances of the placing angles and the track nonlinear errors respectively.

In the practical application of the laser radar, the terminal can obtain the compensation distance of the track nonlinear error from the track nonlinear error correction curve according to the placement angle of the object to be measured relative to the laser radar after the distance is measured, and corrects the track nonlinear error.

Referring to fig. 9 and 10, fig. 9 is a schematic diagram of a distance measurement without track nonlinear error correction, and fig. 10 is a schematic diagram of a distance measurement with track nonlinear error correction. It can be seen that when the track nonlinear error correction is not performed, the cloud point image has jitter, i.e., a large distance measurement error exists, and after the track nonlinear error correction is performed, the jitter is obviously reduced, and the distance measurement error is also reduced.

606. Setting a third calibration target in the detection range of the laser radar, wherein the actual distance value between the third calibration target and the laser radar is D;

607. rotating a reflecting prism of a laser radar at a preset angular speed;

608. measuring the distance of the third calibration target through a second mirror surface of the laser radar at a preset angular speed to generate a fifth distance measurement value;

609. the difference between the fifth distance measurement value and the actual distance value D is obtained, and an angular velocity compensation difference value is generated;

610. calculating angular velocity compensation difference values corresponding to at least two distance measurement values and the rotation angular velocity according to the steps, and generating an angular velocity error correction curve related to the second mirror surface;

the terminal has angular velocity errors in addition to assembly errors and trajectory non-linearity errors. The angular velocity error is caused by the fact that when the reflection prism rotates, the rotation speed needs to be increased or reduced according to actual conditions. When the rotation speed is fast, the reflecting prism will generate some slight displacement.

For example, when the angular velocity of the rectangular prism increases to a certain value, the rectangular prism itself generates a certain elastic movement due to the rotation, that is, the rectangular prism deviates slightly from the original displacement of the rectangular prism, so that the distance between the mirror surface of the rectangular prism and the distance measuring module changes.

For another example, the four-prism is adhered by a sticky substance at the joint, when the rotation angular velocity is large, elastic deformation is generated, the distance between the joint of two adjacent mirror surfaces is increased, so that the whole four-prism is slightly larger than that of the four-prism when standing, and the distance between the mirror surface of the four-prism and the ranging module can be changed.

In this embodiment, the terminal sets a third calibration target within the detection range of the laser radar, where an actual distance value between the third calibration target and the laser radar is D. And then the terminal rotates the reflecting prism of the laser radar at a preset angular speed. And under the preset angular speed, measuring the distance of the third calibration target through a second mirror surface of the laser radar, and generating a fifth distance measurement value. And the terminal calculates the difference between the fifth distance measurement value and the actual distance value D to generate an angular velocity compensation difference value, and finally, the angular velocity compensation difference values corresponding to at least two distance measurement values and the rotation angular velocity are calculated according to the steps and then are fitted to generate an angular velocity error correction curve related to the second mirror surface. In the practical application of the laser radar, the angular velocity compensation difference value can be determined from the angular velocity error correction curve according to the angular velocity of the current reflection prism, and finally the angular velocity error is corrected.

611. A first calibration target is arranged in the detection range of the laser radar, and the laser radar is provided with a reflecting prism which comprises at least two mirror surfaces;

612. when the laser radar detects a first calibration target through a first mirror surface, acquiring a first angle and a first distance measurement value corresponding to the first mirror surface;

613. when the laser radar detects the first calibration target through the second mirror surface, a second angle and a second distance measurement value corresponding to the second mirror surface are obtained;

614. calculating a compensation angle according to the first angle and the second angle, and calculating a distance measurement difference value according to the first distance measurement value and the second distance measurement value;

615. calculating a first compensation distance of the second mirror surface according to the compensation angle and the distance measurement difference value;

616. when the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface;

617. correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value;

steps 611 to 617 in this embodiment are similar to steps 101 to 107 in the previous embodiment, and are not described again here.

618. Acquiring reflected light received by a laser radar;

619. measuring the color type of the reflected light;

620. determining the refractive index of the reflected light according to the color type;

621. determining the propagation speed of the reflected light in the current medium according to the refractive index;

622. calculating a color error compensation value according to the propagation speed and the first correction distance value;

623. compensating the first correction distance value according to the color error compensation value;

the terminal can also correct the light color error after the assembly error correction, and the light color error is generated because the light speed is the same in vacuum due to the light with different colors, but the propagation speed is different in the medium due to the different refractive indexes (different frequencies of light) of the light with different colors. The laser emitted by the ranging module is known, the refractive index of the emitted laser can be accurately determined, and the speed is further known, but when the laser irradiates objects with different colors, the refractive index of the reflected light changes, and the light speed of the reflected light also changes, so that the calculation cannot be uniformly carried out according to the speed of the emitted laser.

After the terminal acquires the reflected light received by the laser radar, the color type of the reflected light needs to be measured, the refractive index of the reflected light is determined according to the color type, and then the propagation speed of the reflected light in the current medium is determined according to the refractive index. When the speed of emitting laser and the speed of received light are determined, a color error compensation value can be calculated according to the propagation speed and the first correction distance value, and finally the first correction distance value is compensated according to the color error compensation value.

624. Obtaining a measurement placing angle of a target object relative to a laser radar;

625. acquiring a track nonlinear error correction curve of the second mirror surface, wherein the track nonlinear error correction curve is a relation curve of a placing angle and a track nonlinear error compensation value;

626. determining a second compensation distance from the track nonlinear error correction curve according to the measurement placement angle;

627. correcting the track nonlinear error of the first corrected distance value according to the second compensation distance to generate a second corrected distance value;

when the terminal corrects the distance measurement value by the assembly error and the light color error, the track nonlinear error can be corrected. The terminal firstly obtains the measurement placement angle of the target object relative to the laser radar. And then acquiring a track nonlinear error correction curve of the second mirror surface, wherein the track nonlinear error correction curve is a relation curve of the placing angle and the track nonlinear error compensation value. A second compensation distance is then determined from the trajectory nonlinear error correction curve based on the measured placement angle. And finally, correcting the track nonlinear error of the first corrected distance value according to the second compensation distance to generate a second corrected distance value, thus finishing the track nonlinear error correction.

628. Acquiring the actual rotation angular velocity of a reflecting prism in the laser radar;

629. acquiring an angular velocity error correction curve of the second mirror surface, wherein the angular velocity error correction curve is a relation curve of the second mirror surface and angular velocity compensation difference values under different rotation angular velocities;

630. determining a fourth compensation distance from the angular velocity error correction curve according to the actual rotation angular velocity;

631. and correcting the angular speed error of the second corrected distance value according to the fourth compensation distance to generate a third corrected distance value.

When the terminal corrects the distance measurement value by assembly error, light color error and track nonlinear error, the angular speed error can be corrected. Firstly, the terminal acquires the actual rotation angular velocity of a reflecting prism in the laser radar. And the terminal acquires an angular velocity error correction curve of the second mirror surface, wherein the angular velocity error correction curve is a relation curve of the second mirror surface under different rotation angular velocities and angular velocity compensation difference values. The terminal then determines a fourth compensation distance from the angular velocity error correction curve based on the actual rotational angular velocity. And finally, the terminal corrects the angular speed error of the second corrected distance value according to the fourth compensation distance to generate a third corrected distance value. The correction of the angular velocity error can be completed.

In the embodiment of the present application, a trajectory nonlinear error correction curve is first calculated. Firstly, a terminal is provided with an arc calibration plate with the radius of R by taking the optical center of a laser radar as the center, and angle numerical values are marked on the arc calibration plate. And then, arranging a second calibration target at the edge of the circular arc calibration plate by the terminal, so that the actual distance between the laser radar and the second calibration target is the radius R. The terminal obtains the actual placement angle of the second calibration target relative to the laser radar according to the circular arc calibration plate, and then obtains a fourth distance measurement value of the second calibration target through a second mirror surface of the laser radar. And the terminal calculates a third compensation distance corresponding to the actual placement angle according to the fourth distance measurement value and the radius R. And the terminal calculates the compensation distances corresponding to the at least two placing angles according to the steps, and fits the compensation distances to generate a track nonlinear error correction curve related to the second mirror surface.

Then, an angular velocity error correction curve is calculated. Firstly, the terminal sets a third calibration target in the detection range of the laser radar, wherein the actual distance value between the third calibration target and the laser radar is D. And then the terminal rotates the reflecting prism of the laser radar at a preset angular speed. And measuring the distance of the third calibration target through a second mirror surface of the laser radar at a preset angular speed to generate a fifth distance measurement value. And the terminal calculates the difference between the fifth distance measurement value and the actual distance value D to generate an angular velocity compensation difference value, and finally, the angular velocity compensation difference values corresponding to at least two distance measurement values and the rotation angular velocity are calculated according to the steps and then are fitted to generate an angular velocity error correction curve related to the second mirror surface.

The method comprises the following steps of setting a first calibration target in a detection range of the laser radar, wherein the laser radar is provided with a reflecting prism, and the reflecting prism comprises at least two mirror surfaces. When the laser radar sets one mirror as a reference mirror (first mirror), the rest mirrors are set as the mirrors to be calibrated (second mirrors). When the first calibration target is detected through the first mirror surface, a first angle corresponding to the current first mirror surface and a first distance measurement value of the first calibration target and the laser radar are read through equipment. And when the laser radar detects the first calibration target through the second mirror surface, reading a second angle corresponding to the current second mirror surface and a second distance measurement value of the first calibration target and the laser radar through equipment. A compensation angle is then calculated based on the first angle and the second angle, and a range difference is calculated based on the first range value and the second range value. And calculating a first compensation distance of the second mirror according to the compensation angle and the ranging difference. And when the laser radar uses the second mirror surface to measure the distance of the target object, acquiring a third distance measurement value of the second mirror surface. And correcting the assembly error of the third distance measurement value according to the first compensation distance to generate a first corrected distance value. The method comprises the steps of calculating a first compensation distance of a mirror surface to be calibrated by determining a reference mirror surface, taking a distance measurement value of the reference mirror surface as a standard distance value and taking an angle of the reference mirror surface as a standard angle, wherein the first compensation distance is a compensation value of an assembly error of a second mirror surface, and finally taking the first compensation distance as the assembly error compensation of the second mirror surface.

When the terminal corrects the distance measurement value by the assembly error, the light color error and the track nonlinear error, the angular velocity error can be corrected. Firstly, the terminal acquires the actual rotation angular velocity of a reflecting prism in the laser radar. And the terminal acquires an angular velocity error correction curve of the second mirror surface, wherein the angular velocity error correction curve is a relation curve of the second mirror surface under different rotation angular velocities and angular velocity compensation difference values. The terminal then determines a fourth compensation distance from the angular velocity error correction curve based on the actual rotational angular velocity. And finally, the terminal corrects the angular speed error of the second corrected distance value according to the fourth compensation distance to generate a third corrected distance value. The correction of the angular velocity error can be completed.

When the laser radar is in the actual use process, as long as the distance value measured through the second mirror surface is obtained, the error correction can be carried out by using the first compensation distance, the assembly error of the laser radar in the use process is reduced, and the precision of the laser radar is improved.

Secondly, color errors caused by different propagation speeds of different color light rays in a medium are reduced by measuring the color types of the reflected light rays, determining the refractive indexes of the reflected light rays and compensating the color errors according to the refractive indexes.

Secondly, by calculating the track nonlinear error correction curve in advance, the measurement placement angle of the target object relative to the laser radar is only needed to be obtained, correction can be carried out according to the track nonlinear error correction curve, and the track nonlinear error is reduced.

Secondly, by calculating the angular velocity error correction curve in advance, correction can be performed according to the angular velocity error correction curve only by acquiring the rotation angular velocity of the target object relative to the reflection prism of the laser radar, so that the angular velocity error is reduced.

Referring to fig. 11, the present application provides an embodiment of an apparatus for laser radar error correction, including:

the first setting unit 1101 is configured to set a first calibration target in a detection range of a laser radar, where the laser radar is provided with a reflection prism, and the reflection prism includes at least two mirror surfaces;

the first obtaining unit 1102 is configured to obtain a first angle and a first distance measurement value corresponding to the first mirror when the laser radar detects the first calibration target through the first mirror;

a second obtaining unit 1103, configured to obtain a second angle and a second distance measurement value corresponding to the second mirror when the laser radar detects the first calibration target through the second mirror;

a first calculation unit 1104 for calculating a compensation angle based on the first angle and the second angle, and calculating a ranging difference based on the first ranging value and the second ranging value;

a second calculating unit 1105, configured to calculate a first compensation distance of the second mirror according to the compensation angle and the ranging difference;

a third obtaining unit 1106, configured to obtain a third ranging value of the second mirror when the laser radar uses the second mirror to range the target object;

a first correcting unit 1107 configured to correct the assembly error of the third distance measurement value according to the first compensation distance, and generate a first corrected distance value.

Referring to fig. 12, the present application provides another embodiment of an apparatus for laser radar error correction, including:

a second setting unit 1201, configured to set a second calibration target such that an actual distance between the laser radar and the second calibration target is R;

a sixth obtaining unit 1202, configured to obtain an actual placement angle of the second calibration target relative to the laser radar;

a seventh obtaining unit 1203, configured to obtain a fourth distance measurement value of the second calibration target through the second mirror of the laser radar;

a third calculating unit 1204, configured to calculate a third compensation distance corresponding to the actual placement angle according to the fourth distance measurement value and the actual distance R;

a first generating unit 1205, configured to calculate compensation distances corresponding to the at least two placement angles according to the above steps, and perform fitting to generate a trajectory nonlinear error correction curve about the second mirror surface;

a third setting unit 1206, configured to set a third calibration target within the detection range of the laser radar, where an actual distance value between the third calibration target and the laser radar is D;

a rotating unit 1207 configured to rotate the reflection prism of the laser radar at a preset angular velocity;

the first measuring unit 1208 is configured to measure the distance of the third calibration target through the second mirror of the laser radar at the preset angular velocity, and generate a fifth distance measurement value;

a second generating unit 1209, configured to perform a difference between the fifth distance measurement value and the actual distance value D to generate an angular velocity compensation difference value;

a third generating unit 1210 for calculating an angular velocity compensation difference corresponding to the at least two distance measurement values and the rotation angular velocity according to the above steps, and generating an angular velocity error correction curve for the second mirror surface;

a first setting unit 1211, configured to set a first calibration target in a detection range of a laser radar, where the laser radar is provided with a reflection prism, and the reflection prism includes at least two mirror surfaces;

the first obtaining unit 1212 is configured to obtain a first angle and a first distance measurement value corresponding to the first mirror when the laser radar detects the first calibration target through the first mirror;

a second obtaining unit 1213, configured to obtain a second angle and a second distance measurement value corresponding to the second mirror when the laser radar detects the first calibration target through the second mirror;

a first calculating unit 1214 for calculating a compensation angle according to the first angle and the second angle, and calculating a ranging difference value according to the first ranging value and the second ranging value;

a second calculation unit 1215 for calculating a first compensation distance of the second mirror according to the compensation angle and the ranging difference;

a third obtaining unit 1216, configured to obtain a third ranging value of the second mirror when the laser radar ranges the target object using the second mirror;

a first correcting unit 1217, configured to correct the assembly error of the third distance measurement value according to the first compensation distance, and generate a first corrected distance value;

a tenth acquiring unit 1218, configured to acquire reflected light received by the laser radar;

a second measurement unit 1219 for measuring the propagation velocity of the reflected light;

optionally, the second measurement unit 1219 specifically includes:

measuring the color type of the reflected light;

A fourth calculating unit 1220 for calculating a color error compensation value according to the propagation velocity and the first corrected distance value;

a fourth correcting unit 1221 configured to compensate the first corrected distance value according to the color error compensation value;

a fourth acquisition unit 1222 for acquiring a measured placement angle of the target object with respect to the laser radar;

a fifth obtaining unit 1223, configured to obtain a trajectory nonlinear error correction curve of the second mirror, where the trajectory nonlinear error correction curve is a relation curve between the placement angle and a trajectory nonlinear error compensation value;

a first determining unit 1224 for determining a second compensation distance from the trajectory nonlinear error correction curve according to the measured placement angle;

a second correcting unit 1225, configured to correct the track nonlinear error for the first corrected distance value according to the second compensation distance, and generate a second corrected distance value;

an eighth acquiring unit 1226 configured to acquire an actual rotational angular velocity of the reflection prism in the laser radar;

a ninth obtaining unit 1227, configured to obtain an angular velocity error correction curve of the second mirror, where the angular velocity error correction curve is a relation curve between the second mirror and the angular velocity compensation difference at different rotation angular velocities;

a second determining unit 1228 for determining a fourth compensation distance from the angular velocity error correction curve based on the actual rotational angular velocity;

a third correcting unit 1229, configured to correct the angular velocity error of the second corrected distance value according to the fourth compensation distance, and generate a third corrected distance value.

Referring to fig. 13, the present application provides an electronic device, including:

a processor 1301, a memory 1302, an input-output unit 1303, and a bus 1304.

The processor 1301 is connected to the memory 1302, the input-output unit 1303, and the bus 1304.

The memory 1301 holds a program, and the processor 1301 invokes the program to perform the methods as in fig. 1 to 6-1, 6-2, 6-3, 6-4, and 6-5.

The present application provides a computer readable storage medium having a program stored thereon, which when executed on a computer performs the method as in fig. 1-6-1, 6-2, 6-3, 6-4 and 6-5.

It can be clearly understood by those skilled in the art that, for convenience and simplicity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a read-only memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and the like.

Claims

1. A method of lidar error correction, comprising:

setting a first calibration target in a detection range of the laser radar, wherein the laser radar is provided with a reflecting prism, and the reflecting prism comprises at least two mirror surfaces;

when the laser radar detects the first calibration target through the first mirror surface, acquiring a first angle and a first distance measurement value corresponding to the first mirror surface;

when the laser radar detects the first calibration target through the second mirror surface, acquiring a second angle and a second distance measurement value corresponding to the second mirror surface;

when the laser radar uses the second mirror surface to measure the distance of a target object, acquiring a third distance measurement value of the second mirror surface;

2. The method of claim 1, wherein after the correcting for the assembly error of the third ranging value based on the first compensation distance to generate a first corrected distance value, the method further comprises:

acquiring a measurement placement angle of the target object relative to the laser radar;

determining a second compensation distance from the trajectory nonlinear error correction curve according to the measurement placement angle;

3. The method of claim 2, wherein prior to said obtaining a measured placement angle of said target object relative to said lidar, said method further comprises:

4. The method of claim 2, wherein after the correcting the trajectory non-linearity error for the first corrected distance value according to the second compensation distance to generate a second corrected distance value, the method further comprises:

acquiring an angular velocity error correction curve of the second mirror surface, wherein the angular velocity error correction curve is a relation curve of the second mirror surface under different rotation angular velocities and angular velocity compensation difference values;

5. The method of claim 4, wherein prior to said obtaining an actual rotational angular velocity of a reflecting prism in said lidar, said method further comprises:

rotating a reflecting prism of the laser radar at a preset angular speed;

measuring the distance of the third calibration target through a second mirror surface of the laser radar at the preset angular velocity to generate a fifth distance measurement value;

calculating the difference between the fifth distance measurement value and the actual distance value D to generate an angular velocity compensation difference value;

and calculating the angular velocity compensation difference corresponding to at least two distance measurement values and the rotation angular velocity according to the steps, and generating an angular velocity error correction curve related to the second mirror surface.

6. The method of any of claims 1 to 5, wherein after said correcting for assembly error of the third range values according to the first compensation distance, generating a first corrected distance value, the method further comprises:

acquiring reflected light received by the laser radar;

measuring the propagation speed of the reflected light;

7. The method of claim 6, wherein said measuring the propagation velocity of the reflected light comprises:

measuring the color type of the reflected light;

8. An apparatus for lidar error correction, comprising:

the laser radar detection device comprises a first setting unit, a second setting unit and a control unit, wherein the first setting unit is used for setting a first calibration target in a detection range of the laser radar, the laser radar is provided with a reflecting prism, and the reflecting prism comprises at least two mirror surfaces;

the first obtaining unit is used for obtaining a first angle and a first distance measurement value corresponding to the first mirror surface when the laser radar detects the first calibration target through the first mirror surface;

the second calculating unit is used for calculating a first compensation distance of the second mirror surface according to the compensation angle and the ranging difference value;

the third acquisition unit is used for acquiring a third ranging value of the second mirror when the laser radar uses the second mirror to range a target object;

9. An electronic device, comprising:

the device comprises a processor, a memory, an input and output unit and a bus;

the memory holds a program that the processor calls to perform the method of any one of claims 1 to 7.

10. A computer readable storage medium having a program stored thereon, the program, when executed on a computer, performing the method of any one of claims 1 to 7.