AGV indoor accurate positioning method

Abstract

The invention relates to an AGV indoor precise positioning method, and the method comprises the steps: installing a UWB tag at a P point at the center of the front end of an AGV, and installing a laser radar right above the P point; the positioning method comprises the steps that the stand columns are installed around a working area, numbering is conducted on the stand columns, UWB base station and label data are circularly collected through the industrial personal computer, and then position information of the stand columns is detected and extracted through the laser radar; then, finding out four upright posts closest to the point P, and respectively establishing four circles by taking each upright post as a circle center and taking the distance from the point P to each upright post as a radius; and finally, establishing an equation of the four circles, and calculating the coordinates of the P point through a least square method to finish accurate positioning of the AGV. According to the method, the problem that the AGV cannot be accurately positioned in a large-area open area or a non-static scene changing at any time can be solved through simple mathematical operation, the complex laser SLAM mapping process is omitted, and the operation efficiency and the positioning accuracy are improved.

Description

Technical Field

[0001] The present invention relates to a control method, in particular to a control method suitable for AGV, specifically to an indoor precise positioning method for AGV. Background Art

[0002] AGV (Automated Guided Vehicle) can undertake multiple tasks such as material handling, production line and assembly, inventory management, automatic sorting, etc., significantly improving work efficiency and accuracy. In factories, warehouses or logistics centers, AGVs can automatically transport goods, parts, raw materials, etc., and realize automatic transfer from warehouse to production line, from production line to warehouse, or from one area to another, thereby greatly improving the efficiency of logistics and production processes.

[0003] AGV needs to be positioned when it is running. At present, the main methods used for AGV indoor positioning include the following: 1) Laser positioning technology uses a laser scanner to scan the surrounding environment and calculate the distance and angle to the object to determine the robot's position. It has the characteristics of high precision and high reliability. However, in some special scenarios, such as large open areas and non-static scenes that change all the time, laser positioning will obviously reduce the accuracy or even fail to locate.

[0004] 2) Visual positioning technology uses cameras and image processing algorithms to identify and match feature points or landmarks in the environment. It has high flexibility and adaptability. However, this method is too dependent on light. If it is in a backlit or low-light environment, its working performance will be greatly reduced.

[0005] 3) Ultrasonic positioning technology uses ultrasonic sensors to emit and receive ultrasonic waves, and determines the position of the robot by calculating the ultrasonic propagation distance. It has the advantages of low cost and fast information collection rate. However, the accuracy of ultrasonic waves is poor and cannot meet the needs of AGV indoor positioning.

[0006] Therefore, it needs to be improved to better meet the usage requirements. Summary of the invention

[0007] The purpose of the present invention is to provide an AGV indoor precise positioning method in response to the difficulties encountered in the current AGV positioning, which can effectively solve the problem that the AGV cannot be accurately positioned using laser SLAM when it is in a large open area or a non-static scene that changes all the time, greatly improves the positioning accuracy and fully meets the needs of use.

[0008] The technical solution of the present invention is: A method for accurately positioning an AGV indoors, wherein a UWB tag is installed at a front center point P of the AGV, and a laser radar is installed directly above the point P; the positioning method comprises the following steps: 1) Initial positioning based on UWB system; 1.1) Determine the origin of the coordinate system xOy; 1.2) Install columns around the work area and number them; at the same time, use a total station to accurately determine the coordinates of each column relative to the origin; 1.3) Install UWB base stations on the top of each column; 1.4) The industrial computer collects the UWB base station and tag data cyclically, determines the distance from point P to each column, and converts it to the xOy plane to obtain the initial position relationship between point P and each column; 2) LiDAR-based column identification; 2.1) Scan the surrounding environment through the laser radar in a loop; when a pillar is detected, extract the distance and direction information from the pillar to the laser radar; 2.2) Match the information extracted in step 2.1) with the position information of all pillars in the UWB system according to the principle of minimum Euclidean distance, determine the current pillar number, and complete the pillar identity recognition; 3) Accurate positioning: 3.1) Find the four pillars closest to point P and measure the distance from point P to each pillar using LiDAR; 3.2) Create four circles with each column in step 3.1) as the center and the distance from P to each column as the radius. Then point P must be at the intersection of the four circles; 3.3) Establish the equations of the four circles in step 3.2) respectively, and then calculate the coordinates of point P by the least squares method, thus completing the precise positioning of the AGV.

[0009] Furthermore, in step 1.1), the origin of the coordinate system is located at the lower left corner.

[0010] Furthermore, in step 1.2), the pillars are circular, with a diameter ≥ 5 cm and a height ≥ the highest scanning line position of the laser radar, and the number and density of the pillars depend on the size of the AGV work site.

[0011] Furthermore, an IMU is installed on the AGV to more conveniently complete the identification of the column.

[0012] Beneficial effects of the present invention: The present invention has a reasonable design, a simple structure, and is easy to use. It can solve the problem that AGV cannot accurately locate in large open areas or non-static scenes that change all the time through simple mathematical operations, eliminating the complex laser SLAM mapping process and improving the operating efficiency and positioning accuracy. At the same time, the present invention can be implemented on a low-configuration embedded system, with low consumption of system hardware resources, which is conducive to promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the principle of the present invention.

[0014] The arrow represents the direction of travel of the AGV; the dotted circle is a circle with the column as the center and the distance from the column to point P as the radius. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] like Figure 1 shown.

[0017] The present invention provides an indoor precise positioning method for an AGV, comprising the following steps: wherein a UWB (Ultra Wide Band) tag is installed at a front center point P of the AGV, and a laser radar is installed directly above the point P.

[0018] 1) Initial positioning based on UWB system.

[0019] 1.1) Determine the origin of the coordinate system xOy. According to custom, the origin is usually selected in the lower left corner, so that the AGV working area is in the first quadrant.

[0020] 1.2) Install columns around the work area, and use a total station to accurately measure the coordinates of each column relative to the origin, and at the same time, digitally number each column. The columns are circular, with a diameter ≥ 5cm and a height ≥ the highest scanning line position of the laser radar. The number and density of the columns depend on the size of the AGV work area.

[0021] 1.3) Install UWB base station on the top of each column.

[0022] 1.4) The industrial computer cyclically collects the UWB base station and tag data, determines the distance from point P to each column, and converts it to the xOy plane to obtain the initial position relationship between point P and each column, that is, the low-precision position relationship.

[0023] 2) LiDAR-based column identification: 2.1) The laser radar scans the surrounding environment in a loop, and determines whether a pillar is detected in the laser radar return data based on the pillar's diameter, height and other dimensional information; if the laser radar detects a pillar, the distance and direction information from the pillar to the laser radar is extracted.

[0024] 2.2) According to the principle of minimum Euclidean distance, the above extracted information is matched with the orientation information of all pillars in the UWB system to determine the number of the current pillar and complete the identity recognition of the pillar. Preferably, the AGV is equipped with an IMU (Inertial Measurement Unit) to more conveniently complete the identity recognition of the pillar.

[0025] 3) Accurate positioning: 3.1) According to the detection results of the laser radar, find the four columns closest to point P in turn. The coordinates of the four columns have been measured in advance by the total station. At this time, the distance from point P to each column can be measured by the laser radar: R 1 , R 2 , R 3 and R 4 .

[0026] 3.2) Take each of the above columns as the center of the circle and R 1 , R 2 , R 3 and R 4 If four circles are established with radius , then point P must be at the intersection of the four circles.

[0027] 3.3) Establish the equations of the above four circles respectively, and then quickly calculate the coordinates of point P through the least squares method, thus completing the precise positioning of the AGV.

[0028] The operating principle of the present invention is: First, the UWB signals on each column are collected by the industrial computer to achieve the initial positioning of each column. Although the positioning accuracy of UWB is about 20cm, it is impossible to achieve precise positioning, but the relative position of each column and AGV can be determined through UWB.

[0029] Then, the pillars are detected by laser radar. Since laser radar can only return accurate distance and orientation information, it is impossible to determine the number of the measured object-the pillar, that is, it is impossible to determine the true coordinates of the pillar. Therefore, the orientation information of the pillar detected by the laser radar needs to be matched with the orientation information of all pillars in the UWB system according to the principle of minimum Euclidean distance, so as to determine the number of the current pillar and complete the pillar identification.

[0030] Finally, through mathematical calculations, the equations of the four circles are established, and the least squares method is used to quickly calculate the coordinates of point P on the AGV, thus completing the precise positioning of the AGV. The present invention can solve the problem that AGV cannot accurately locate in large open areas or non-static scenes that change all the time through simple mathematical operations, eliminating the complex laser SLAM mapping process and improving the operating efficiency and positioning accuracy. At the same time, the present invention can be implemented on low-configuration embedded systems, with low consumption of system hardware resources, which is conducive to promotion.

[0031] The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art.

Claims

1. A method for accurate indoor positioning of an AGV, characterized in that: A UWB tag is installed at the front center point P of the AGV, and a laser radar is installed directly above the point P; the positioning method includes the following steps: 1) Initial positioning based on UWB system; 1.1) Determine the origin of the coordinate system xOy; 1.2) Install columns around the work area and number them; at the same time, use a total station to accurately determine the coordinates of each column relative to the origin; 1.3) Install UWB base stations on the top of each column; 1.4) The industrial computer collects the UWB base station and tag data cyclically, determines the distance from point P to each column, and converts it to the xOy plane to obtain the initial position relationship between point P and each column; 2) LiDAR-based column identification; 2.1) Scan the surrounding environment through the laser radar in a loop; when a pillar is detected, extract the distance and direction information from the pillar to the laser radar; 2.2) Match the information extracted in step 2.1) with the position information of all pillars in the UWB system according to the principle of minimum Euclidean distance, determine the current pillar number, and complete the pillar identity recognition; 3) Accurate positioning: 3.1) Find the four pillars closest to point P and measure the distance from point P to each pillar using LiDAR; 3.2) Create four circles with each column in step 3.1) as the center and the distance from P to each column as the radius. Then, point P must be at the intersection of the four circles; 3.3) Establish the equations of the four circles in step 3.2) respectively, and then calculate the coordinates of point P by the least squares method, thus completing the precise positioning of the AGV.

2. The AGV indoor precise positioning method according to claim 1 is characterized in that: In the step 1.1), the origin of the coordinate system is located at the lower left corner.

3. The AGV indoor precise positioning method according to claim 1 is characterized in that: In the step 1.2), the pillars are circular, with a diameter ≥ 5 cm and a height ≥ the highest scanning line position of the laser radar. The number and density of the pillars depend on the size of the AGV work site.

4. The AGV indoor precise positioning method according to claim 1 is characterized in that: The AGV is equipped with an IMU to facilitate identification of the column.

Images