Common AGV Navigation Methods

Author: Neuvition, IncRelease time:2022-05-20 08:12:50

AGV is also called an automatic guided vehicle. The automatic guided vehicle can realize the process of autonomously planning the route and driving automatically mainly through electromagnetic, optical, or other automatic guidance devices. It is high-safety and can work with a variety of functions. Today, there are many common AGV navigation methods on the market, such as electromagnetic navigation, magnetic stripe navigation, QR code navigation, laser navigation, visual navigation, etc. So, what are the advantages and disadvantages of each of them?

AGV Navigation

AGV navigation based on electromagnetic field

Electromagnetic navigation is a traditional navigation method. By burying metal wires on the driving path of the AGV, and loading low-frequency and low-voltage currents, a magnetic field is generated around the wires. The induction coil on the AGV can identify and track the strength of the navigation magnetic field, to realize navigation.

The advantages of electromagnetic navigation: the guidewire is concealed, and not easy to be polluted and damaged. The AGV navigation principle is simple and reliable, easy to control communication, without interference to sound and light, and low investment cost.

Disadvantages of electromagnetic navigation: It is troublesome to change or expand the path, and it is difficult to lay the guidewire.

AGV navigation based on a magnetic stripe

The magnetic stripe navigation technology is similar to the AGV navigation based on the electromagnetic field. The difference is that the magnetic stripe is used on the ground surface instead of burying the metal wire under the ground. The navigation is realized by the magnetic stripe induction signal.

Advantages of AGV navigation based on magnetic stripe: AGV positioning is accurate, the laying, changing, or expansion of the path is easier than electromagnetic navigation, and the cost of the magnetic stripe is lower.

Disadvantages of AGV navigation based on magnetic stripe: The magnetic stripe is easily damaged and requires regular maintenance. The path change requires re-laying the tape. The AGV can only walk according to the magnetic stripe, and cannot achieve intelligent avoidance or real-time change of tasks through the control system.

There are also magnetic marker navigation and ribbon navigation that are similar to the principle of the navigation based on a magnetic stripe. Magnetic marker navigation is to lay magnetic markers on the ground. The advantages include good concealment, strong anti-interference, wear resistance, and acid and alkali resistance. The disadvantage is that it is easily affected by ferromagnetic substances, the amount of construction to change the path is large, and it is easy to cause damage to the ground. Generally, it is only used on the dock. Ribbon navigation is to paste the ribbon or paint on the ground, to realize the navigation through the image signal recognition collected by the on-board optical sensor. Because the ribbon is easily polluted and damaged, it has higher environmental requirements. At the same time, its low positioning accuracy limits its application.

AGV navigation based on two-dimensional code  

The principle of navigation based on two-dimensional code is to scan the two-dimensional code placed on the ground by the camera and obtain the current position information by analyzing the code information. The two-dimensional code navigation is usually combined with inertial navigation to achieve precise positioning. Inertial navigation is to obtain the position and attitude of the robot utilizing mobile robot sensors (photoelectric encoders, gyroscopes), usually serving as auxiliary positioning.

The advantage of the AGV navigation based on two-dimensional code is accurate positioning. It is small and flexible, easier to lay and change the path. It is convenient to manage and control information communication, and there is no interference with sound and light.

Disadvantages of the AGV navigation based on two-dimensional code: The path requires regular maintenance. If the site is not complex, the two-dimensional code needs to be replaced more frequently. The accuracy and service life of the gyroscope is strictly required. And there are certain requirements for the flatness of the site, and the price level is relatively high.

AGV navigation based on visual sensor

Visual navigation is a method of realizing navigation by acquiring image information around the operating area through the AGV on-board visual sensor. On the hardware, a down-view camera, fill light, and hood are required to support the realization of this navigation method. In this method, the ground texture is captured by the camera during the movement of the AGV to automatically build a map, and then the ground texture information obtained during operation is registered and compared with the texture image in the self-built map, to estimate the current pose of the AGV, to realize the positioning of the AGV.

Advantages of AGV navigation based on the visual sensor: low hardware cost and accurate positioning.

Disadvantages of AGV navigation based on the visual sensor: It has high requirements on the use environment (ground, light, etc.), and the running ground needs to have texture information. When the operating site area is large, the time for navigation mapping is longer than that of AGV navigation based on laser, and the visual navigation technology is not mature enough.

AGV navigation based on LiDAR laser

AGV navigation based on LiDAR laser

Laser reflector navigation is to install a precise reflector around the AGV’s driving path, and the laser scanner is installed on the AGV body. When the laser scanner emits a laser beam with the movement of the AGV, the emitted laser beam is directly reflected by the multiple groups of reflectors laid along the AGV driving path, triggering the controller to work and record and rotate the laser head’s angle when encountering various reflections. The controller needs to match the actual position information of the reflectors according to the angle values and calculate the absolute coordinates of the AGV. Based on this working principle, this method can realize precise navigation.

Advantages of AGV navigation based on laser: laser navigation enables AGV to flexibly plan the path and accurately locate, make the driving path flexible and changeable, and make the structure more convenient and adaptable.

Disadvantages of AGV navigation based on laser: high manufacturing cost, relatively high environmental requirements (external light, ground requirements, visibility, etc.).

At present, AGV navigation based on the laser is mainly divided into two technical routes, one with reflectors and the other one without reflectors (ie, laser SLAM). In AGV navigation based on the laser with reflectors,  LiDAR can obtain more accurate information and achieve more accurate AGV navigation and positioning. The accuracy of the AGV navigation based on the laser without reflectors is relatively weak, but the accuracy of LiDAR positioning and navigation can also be improved through algorithms.

The current LiDARs used in the AGV navigation are divided into 2D navigation LiDAR and 3D navigation LiDAR. The difference between the two is single-line LiDAR and multi-line LiDAR. 2D navigation LiDAR can only navigate in real time, and two-dimensional imaging lacks height information and cannot be imaged. 3D LiDAR can perform three-dimensional dynamic real-time imaging, real-time imaging, and can restore the shape and size of objects, and restore three-dimensional information in space.

Neuvition Titan S2 flash LiDAR

Titan S2 is the first flash LiDAR product in the Neuvition LiDAR family! S2 is specially designed for indoor close-range application scenarios mainly including logistics vehicles, supermarket flow statistics, privacy protection monitoring, security detection, indoor 3D imaging, volume measurement in trucks, industrial machine vision, AMR/AGV/RGV obstacle avoidance, etc.

Compared with traditional trucks, AGV navigation is flexible, high-efficiency, convenient in operation and maintenance, multifunctional, and strong-safety. During the handling process, the AGV does not need any fixing devices such as laying tracks or support frames during the operation. AGV can even be unaffected by the site and road. Therefore, in the automated logistics system, the flexibility and automation of AGV can fully help enterprises to carry out efficient and economical unmanned production in the true sense.