阅读说明：本技术 一种基于激光传感器的末端定位方法 (Terminal positioning method based on laser sensor ) 是由 刘胜明 周航 姜志英 司秀芬 于 2021-06-30 设计创作，主要内容包括：本发明公开了一种基于激光传感器的末端定位方法,包括：步骤1,检测目标类型；所述目标类型包括：目标的直线轮廓、固定在目标上的反光板或站板；步骤2,标定激光扫描仪的安装角度,标定激光传感器的坐标,计算车体相对于目标特征的位置和姿态角,实现对目标的定位。通过激光传感器进行末端定位,对激光扫描仪的安装角度和激光传感器的坐标进行标定,提高定位精度。(The invention discloses a terminal positioning method based on a laser sensor, which comprises the following steps: step 1, detecting a target type; the target types include: a linear profile of the target, a reflector or a stand plate fixed to the target; and 2, calibrating the installation angle of the laser scanner, calibrating the coordinates of the laser sensor, and calculating the position and attitude angle of the vehicle body relative to the target characteristics to realize the positioning of the target. The tail end is positioned through the laser sensor, the installation angle of the laser scanner and the coordinates of the laser sensor are calibrated, and the positioning precision is improved.)

1. A terminal positioning method based on a laser sensor is characterized by comprising the following steps:

step 1, detecting a target type; the target types include: a linear profile of the target, a reflector or a stand plate fixed to the target;

and 2, calibrating the installation angle of the laser scanner, calibrating the coordinates of the laser sensor, and calculating the position and attitude angle of the vehicle body relative to the target characteristics to realize the positioning of the target.

2. The laser-sensor-based tip location method according to claim 1,

for contour detection of a target, linear characteristics of the target need to be extracted, and the target is required to have a plane or cross beam structure in front of the fork teeth;

for the detection of the reflectors, two reflectors are required to be arranged on each target, the distance between the reflectors is the same, and the detection result of the reflectors is to determine the coordinates of the mass centers of the two reflectors and the azimuth angles of the straight lines of the connecting lines of the reflectors in a vehicle body coordinate system;

for the detection of the standing plate, one standing plate is required to be arranged on each target, and the posture of the standing plate relative to the target position is recorded, or two standing plates are required to be arranged on each target, and the distance between the two standing plates is the same.

3. The laser sensor-based tip location method of claim 2, wherein calibrating the installation angle of the laser scanner comprises:

s11, setting the default installation angle to 270 degrees and the installation radian toDenoted as angle _ low;

s12, pushing the vehicle to the plane target, making the fork teeth face the target, and confirming that the laser scanner can scan the target; measuring the distance a from the left fixed wheel to the plane target, the distance b from the right fixed wheel to the plane target and the distance d between the measuring points of the left fixed wheel and the right fixed wheel;

s13, calculating the azimuth angle of the straight line of the target plane in the vehicle body coordinate system as follows:

s14, calculating the arc value of the straight azimuth according to the AGV trolley system, and solving a difference d theta with the calculated azimuth;

s15, adding or subtracting the difference d theta to the default installation camber value angle _ low, and updating the value as a new angle _ low;

s16, repeating S14 and S15, and finishing calibration when the radian difference d theta is smaller than 0.01;

and S17, changing the posture of the vehicle body, repeating S12 to S14, verifying whether the difference d theta meets the requirement, and if not, finely adjusting the value of the angle _ low parameter.

4. The laser sensor-based tip location method of claim 3, wherein calibrating the coordinates of the laser sensor comprises:

s21, preliminarily estimating coordinates x _ low and y _ low of the laser sensor;

s22, calculating prior information of the target position, and measuring coordinate values x and y of the midpoint of the target under the vehicle body coordinate system;

s23, acquiring target information through a laser sensor, and calculating the coordinates of a target relative to a vehicle body according to the AGV trolley system;

s24, measuring coordinate values of the middle point of the target surface under the vehicle body coordinate system, accurately calibrating the position of the central axis of the vehicle body through a cross cursor when measuring the middle point of the front surface, and subtracting the position value of the middle point of the target to obtain deviation values dx and dy of x and y coordinates;

s25, subtracting or adding the deviation value dx and dy respectively by using the estimated coordinates x _ low and y _ low of the laser sensor, and updating the values as new coordinates x _ low and y _ low;

s26, repeating S23 to S25 until the coordinate of the target calculated by the AGV trolley system is close to the measurement result and the difference is within a preset range, and ending calibration;

and S27, when the vehicle is changed to a position after the calibration is finished, repeating the steps, verifying whether the end positioning result is consistent with the measured value, and determining whether the deviation meets the precision requirement.

5. The laser sensor-based tip location method of claim 4, further comprising: and when the installation angle of the laser scanner is changed, the coordinates of the laser sensor are calibrated again.

Technical Field

The invention belongs to the field of mobile robot navigation, and relates to a terminal positioning method based on a laser sensor.

Background

There are several major navigation/guidance techniques that can be used for AGVs: electromagnetic guidance, tape guidance, optical guidance, GPS navigation, inertial navigation, laser navigation, visual navigation. According to the traditional laser navigation, laser reflecting plates with accurate positions are installed around the traveling path of the AGV, the AGV emits laser beams through a laser scanner, meanwhile, the laser beams reflected by the reflecting plates are collected to determine the current position and the current course of the AGV, and the guidance of the AGV is realized through continuous triangular geometric operation. In recent years, a traditional laser navigation technology is gradually replaced by a reflector-free laser autonomous navigation technology, namely, a reflector is not required to be paved in the driving process of the AGV, autonomous navigation is realized through an SLAM technology, the method is less affected by a field, the cost is saved, and the method becomes a mainstream technology for factory transportation.

However, the positioning accuracy of the reflector-free laser autonomous navigation technology is relatively low, and the requirement of high-accuracy positioning in a specific environment cannot be met, so that the positioning accuracy needs to be improved through terminal positioning (secondary positioning). The common tail end positioning method comprises visual tail end positioning and laser tail end positioning, the visual tail end positioning is mostly used in clean occasions and is limited, the laser tail end positioning is widely applied, and if the installation error of the position and the angle of a laser sensor is large, certain influence can be generated on the positioning precision.

Disclosure of Invention

The invention aims to: the terminal positioning method based on the laser sensor is provided, and positioning accuracy is improved.

The technical scheme of the invention is as follows: a laser sensor based tip location method, comprising:

step 1, detecting a target type; the target types include: a linear profile of the target, a reflector or a stand plate fixed to the target;

and 2, calibrating the installation angle of the laser scanner, calibrating the coordinates of the laser sensor, and calculating the position and attitude angle of the vehicle body relative to the target characteristics to realize the positioning of the target.

The further technical scheme is as follows: for contour detection of a target, linear characteristics of the target need to be extracted, and the target is required to have a plane or cross beam structure in front of the fork teeth;

for the detection of the reflectors, two reflectors are required to be arranged on each target, the distance between the reflectors is the same, and the detection result of the reflectors is to determine the coordinates of the mass centers of the two reflectors and the azimuth angles of the straight lines of the connecting lines of the reflectors in a vehicle body coordinate system;

for the detection of the standing plate, one standing plate is required to be arranged on each target, and the posture of the standing plate relative to the target position is recorded, or two standing plates are required to be arranged on each target, and the distance between the two standing plates is the same.

The further technical scheme is as follows: the installation angle of calibration laser scanner includes:

s11, setting the default installation angle to 270 degrees and the installation radian toDenoted as angle _ low;

s12, pushing the vehicle to the plane target, making the fork teeth face the target, and confirming that the laser scanner can scan the target; measuring the distance a from the left fixed wheel to the plane target, the distance b from the right fixed wheel to the plane target and the distance d between the measuring points of the left fixed wheel and the right fixed wheel;

s13, calculating the azimuth angle of the straight line of the target plane in the vehicle body coordinate system as follows:

s14, calculating the arc value of the straight azimuth according to the AGV trolley system, and solving a difference d theta with the calculated azimuth;

s15, adding or subtracting the difference d theta to the default installation camber value angle _ low, and updating the value as a new angle _ low;

s16, repeating S14 and S15, and finishing calibration when the radian difference d theta is smaller than 0.01;

and S17, changing the posture of the vehicle body, repeating S12 to S14, verifying whether the difference d theta meets the requirement, and if not, finely adjusting the value of the angle _ low parameter.

The further technical scheme is as follows: the calibration of the coordinates of the laser sensor comprises the following steps:

s21, preliminarily estimating coordinates x _ low and y _ low of the laser sensor;

s22, calculating prior information of the target position, and measuring coordinate values x and y of the midpoint of the target under the vehicle body coordinate system;

s23, acquiring target information through a laser sensor, and calculating the coordinates of a target relative to a vehicle body according to the AGV trolley system;

s24, measuring coordinate values of the middle point of the target surface under the vehicle body coordinate system, accurately calibrating the position of the central axis of the vehicle body through a cross cursor when measuring the middle point of the front surface, and subtracting the position value of the middle point of the target to obtain deviation values dx and dy of x and y coordinates;

s25, subtracting or adding the deviation value dx and dy respectively by using the estimated coordinates x _ low and y _ low of the laser sensor, and updating the values as new coordinates x _ low and y _ low;

s26, repeating S23 to S25 until the coordinate of the target calculated by the AGV trolley system is close to the measurement result and the difference is within a preset range, and ending calibration;

and S27, when the vehicle is changed to a position after the calibration is finished, repeating the steps, verifying whether the end positioning result is consistent with the measured value, and determining whether the deviation meets the precision requirement.

The further technical scheme is as follows: further comprising: and when the installation angle of the laser scanner is changed, the coordinates of the laser sensor are calibrated again.

The invention has the advantages that:

the tail end is positioned through the laser sensor, the installation angle of the laser scanner and the coordinates of the laser sensor are calibrated, and the positioning precision is improved.

Drawings

The invention is further described with reference to the following figures and examples:

FIG. 1 is a flow chart of a laser sensor based tip location method provided herein;

FIG. 2 is an azimuthal schematic of a straight line segment provided herein;

FIG. 3 is a schematic view of the relative attitude of the vehicle body and the target at calibrating the mounting angle of the laser scanner provided herein;

fig. 4 is a schematic diagram of a relative posture of a vehicle body and a pickup target when coordinates of a laser sensor are calibrated.

Detailed Description

Example (b): the present application provides a laser sensor based tip location method, which may include the following steps, with reference to fig. 1 to 4 in combination.

Step 1, detecting the type of a target.

The types of targets that can be detected by the laser tip location method include: a linear profile of the target, a reflector or a standing plate fixed to the target.

For the contour detection of the target, only the linear characteristic is detected at present, the linear characteristic of the target needs to be extracted, and the target is required to have a plane or cross beam structure in front of the fork teeth, so that the linear characteristic can be conveniently extracted by laser detection. In addition, for the contour detection of the box body, the linear contours of the front plane and the side plane are required to be detected, and other target types only need to detect one linear feature.

Generally, the sizes of targets are required to be uniform, the calculation result of the AGV system itself is the azimuth angle of the straight line and the midpoint coordinate of the straight line in the vehicle body coordinate system, the azimuth angle of the straight line is shown in fig. 2, α in the figure is the azimuth angle, and it can be seen that the azimuth angle means the included angle between the normal (perpendicular line) of the straight line and the positive direction of the x axis, and the value range is [ -pi, pi ].

For the detection of the reflectors, two reflectors are required to be arranged on each target, the distance between the reflectors is the same, and the detection result of the reflectors is to determine the coordinates of the mass centers of the two reflectors and the azimuth angles of the straight lines of the connecting lines of the reflectors in the vehicle body coordinate system.

For the detection of the standing plate, one standing plate is required to be arranged on each target, and the posture of the standing plate relative to the target position is recorded, or two standing plates are required to be arranged on each target, and the distance between the two standing plates is the same.

And 2, calibrating the installation angle of the laser scanner, calibrating the coordinates of the laser sensor, and calculating the position and attitude angle of the vehicle body relative to the target characteristics to realize the positioning of the target.

The laser installation angle is the included angle between the x axis of the laser and the x axis of the vehicle body, for obstacle avoidance laser, the angle value is generally 135 degrees during installation, due to misoperation, the accurate value of the angle needs to be found out through calibration, and the error of changing the angle is generally required to be less than 0.5 degree, namelyThe radian, about 0.01 radian, is as precise as possible.

As shown in fig. 3, the vehicle is first pushed in front of a wall or flat cargo surface with the tines facing the target to ensure that the laser scanner can scan the target. Two points a and B in fig. 3 respectively represent the left and right fixed wheels of the forklift, a and B respectively represent the distances from the two fixed wheels to the wall, and d represents the distance between the measurement points of the left and right fixed wheels.

Demarcating the installation angle of the laser scanner includes:

s11, setting the default installation angle to 270 degrees and the installation radian toDenoted as angle _ low;

s12, pushing the vehicle to a plane target surface, placing the vehicle according to requirements, enabling the fork teeth to face the target, and confirming that the laser scanner can scan the target; measuring the distance a from the left fixed wheel to the plane target, the distance b from the right fixed wheel to the plane target and the distance d between the measuring points of the left fixed wheel and the right fixed wheel; for part of AGV robots, distance measuring photoelectricity are installed on two sides of a portal frame, and when the distance measuring photoelectricity is calibrated accurately, numerical values of a, b and d can be directly obtained through a distance measuring photoelectric sensor;

s13, calculating the azimuth angle of the straight line (wall straight line) of the target plane in the vehicle body coordinate system, and calculating the formula from the geometric relationship in the figure as follows:

s14, calculating the arc value of the straight line azimuth according to the AGV trolley system, and solving a difference d theta with the azimuth calculated in S13;

s15, adding or subtracting the difference d theta to the default installation camber value angle _ low, and updating the value as a new angle _ low, namely replacing the angle _ low with the value after adding or subtracting d theta;

s16, repeating S14 and S15, and finishing the calibration when the radian difference d theta is smaller than 0.01, namely the installation angle difference is smaller than 0.5 degrees; it should be noted that, because the laser measurement value fluctuates, the arc values of the straight azimuth calculated by the AGV itself system each time have slight differences, as long as the fluctuation difference is within the error requirement range;

and S17, changing the posture of the vehicle body, repeating S12 to S14, verifying whether the difference d theta meets the requirement, and if not, finely adjusting the value of the angle _ low parameter.

For the calibration of the coordinates of the laser sensor, the vehicle body is firstly placed, as shown in fig. 4, so that the central axis of the vehicle body is aligned to the midpoint of the front surface of the pickup target as much as possible, the vehicle body does not need to be aligned strictly when placed, the deviation is measured subsequently, and in order to ensure the measurement accuracy, the vehicle body needs to be close to the pickup target and is smaller than 5 meters as much as possible.

Calibrating the coordinates of the laser sensor, comprising:

s21, preliminarily estimating coordinates x _ low and y _ low of the laser sensor by a physical method (manual measurement), wherein the unit is meter, the two values are coordinates from a laser center to a vehicle body center, and the numerical values are different for different vehicle types and installation positions;

s22, calculating prior information of the target position, and roughly measuring coordinate values x and y of the midpoint of the box body or the goods taking target under a vehicle body coordinate system; it should be noted that if the x and y values and the actual placement deviation are large, the final calculation result will fail;

s23, acquiring information of the box or the goods taking target through a laser sensor, and calculating the coordinate of the target relative to the car body according to the AGV car system; if the central axis of the vehicle body is aligned with the midpoint of the goods-taking target, the y coordinate value is very close to zero (less than 1 cm);

s24, measuring coordinate values of the midpoint of the surface of the goods-taking target under the vehicle body coordinate system, accurately calibrating the position of the central axis of the vehicle body through a cross cursor when measuring the midpoint of the front surface, and subtracting the position value of the target midpoint to obtain deviation values dx and dy of x and y coordinates;

s25, subtracting or adding the deviation value dx, dy respectively by using the preliminarily estimated coordinates x _ low and y _ low of the laser sensor, and updating the values of the coordinates x _ low and y _ low as new values, namely replacing the coordinates x _ low and y _ low with the values after the deviation value dx, dy is added or subtracted;

s26, repeating S23 to S25 until the coordinate of the target calculated by the AGV trolley system is close to the measurement result and the difference is within a preset range (about plus or minus 1cm), and ending calibration; if the deviation is slightly large, the parameter values of x _ low and y _ low can be finely adjusted, and the adjustment amplitude is in the magnitude of millimeter;

and S27, when the vehicle is changed to a position after the calibration is finished, repeating the steps, verifying whether the end positioning result is consistent with the measured value, and determining whether the deviation meets the precision requirement.

It should be noted that: the calibration of the coordinates of the laser sensor is carried out on the premise that the angle is calibrated accurately, and when the installation angle of the laser scanner changes, namely the parameter angle _ low is changed, the coordinates of the laser sensor must be re-calibrated, namely the parameters x _ low and y _ low.

In summary, the terminal positioning method based on the laser sensor provided by the application performs terminal positioning through the laser sensor, calibrates the installation angle of the laser scanner and the coordinate of the laser sensor, and improves positioning accuracy.

The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying a number of the indicated technical features. Thus, a defined feature of "first", "second", may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

The above-mentioned serial numbers of the embodiments of the present application are merely for description and do not represent the merits of the embodiments.

It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk, an optical disk, or the like.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.