AGV Intelligent Solutions
Advantages: Inertial guidance is a mature and reliable guidance technology, which has the advantages of high reliability, high short-term accuracy and strong autonomy, but it has inevitable shortcomings.
Disadvantage: There are accumulated errors, resulting in insufficient long-term guidance accuracy. (Correction by other techniques. Vision guidance system, correcting the inertial navigation system for its accurate positioning)
Inertial navigation is to install a gyroscope on the AGV and install a positioning block on the ground in the driving area. The AGV can determine its own position and direction through the calculation of the gyroscope deviation signal and the acquisition of the ground positioning block signal, so as to achieve guidance.
This technology was used in the military earlier, and its main advantages are advanced technology, high positioning accuracy, strong flexibility, easy combination and compatibility, and a wide range of applications. It has been adopted by many foreign AGV manufacturers. The disadvantage is that the manufacturing cost is high, and the accuracy and reliability of the guidance are closely related to the manufacturing accuracy and service life of the gyroscope.
002------ Electromagnetic Navigation
Principle of electromagnetic navigation: Electromagnetic navigation is one of the more traditional navigation methods, which is still used by many systems. It embeds a metal wire on the driving path of the AGV, and loads the guide frequency on the metal wire. Identification to achieve AGV navigation.
Advantages of electromagnetic navigation: the guide wire is concealed, not easy to be polluted and damaged, the guiding principle is simple and reliable, easy to control communication, no interference to sound and light, and the investment cost is much lower than that of laser navigation;
Disadvantages of electromagnetic navigation: It is troublesome to change or expand the path, and it is relatively difficult to lay the guide wire.
Electromagnetic guidance is still used in many systems. It embeds metal wires on the driving path of agv, and loads the metal wire with a guiding frequency, and realizes the guidance of agv through the identification of the guiding frequency.
Its main advantages are that the lead wire is concealed, not easy to be polluted and damaged, the guiding principle is simple and reliable, easy to control and communicate, no interference to sound and light, and low manufacturing cost.
The disadvantage is that the path is difficult to change and expand, and it has great limitations on complex paths.
The principle of tape navigation: The tape navigation technology is similar to the electromagnetic navigation, the difference is that the tape is pasted on the road instead of burying the metal wire under the ground, and the guidance is realized by the tape induction signal.
Advantages of tape navigation: AGV positioning is accurate, the flexibility of tape navigation is better, it is easier to change or expand the path, the tape laying is relatively simple, the guiding principle is simple and reliable, easy to control communication, no interference to sound and light, and the investment cost is higher than that of laser navigation. much lower;
Disadvantages of tape navigation: The tape needs maintenance, and the severely damaged tape needs to be replaced in time, but the replacement of the tape is simple and convenient, and the cost is low. However, this guiding method is easily disturbed by metal substances around the loop, and is extremely sensitive to the mechanical damage of the magnetic tape, so the reliability of the guiding is greatly affected by the outside world.
Principle of visual navigation: Visual navigation is to paint paint with a large color contrast with the ground or paste a color tape with a large color contrast on the AGV's driving path. A photo sensor is installed on the AGV to compare the continuously captured pictures with the stored pictures. The offset signal is output to the drive control system, and the control system corrects the walking direction of the AGV through calculation to realize the navigation of the AGV.
Advantages of visual navigation: AGV positioning is accurate, the flexibility of visual navigation is better, it is easier to change or expand the path, the path laying is relatively simple, the guiding principle is also simple and reliable, easy to control communication, no interference to sound and light, and investment cost is relatively low. Laser navigation is also much lower, but slightly more expensive than tape navigation;
Disadvantages of visual navigation: The path also requires maintenance, but the maintenance is simpler and more convenient and the cost is lower. It is very sensitive to the contamination and mechanical wear of the ribbon, has high environmental requirements, poor guidance reliability, and is difficult to achieve precise positioning.
Principle of laser navigation: Laser navigation is to install a reflector with a precise position around the AGV's driving path. The AGV determines its current position and direction by emitting a laser beam and collecting the laser beam reflected by the reflector at the same time.
The initial position calculation of the AGV - the AGV car is stationary; the laser scanner can measure at least 4 beams, that is, at least "see" 4 reflectors; the precise positions (X, Y) of all reflectors are known;
Continuous position calculation of AGV - estimate the current position of the car according to the motion model, associate the reflector according to the estimated new position, correct its own position according to the associated reflector, and correct the next action of the AGV accordingly.
Advantages of laser navigation: AGV positioning is accurate, no other positioning facilities are required on the ground; the driving path can be flexibly changed;
Disadvantages of laser navigation: Due to the complex control and high investment cost of laser technology, there should be no obstacles between the reflective sheet and the AGV laser sensor, which is not suitable for occasions where there are logistics effects in the air.
006-----RFID Navigation (electronic label)
A low-frequency long-distance RFID card reader system is installed on the head of the AGV, and then an electronic tag is fixed at the track node, and each electronic tag is given an ID number and definition, so that the AGV can make corresponding actions according to the specific instructions of the ID number. .
The advantages are that there is no need to lay lines, the structure is simple, the cost is low, the flexibility is strong, the path can be changed at will, and it is easier to implement and can accurately locate. Disadvantages High requirements for RFID hardware.
Optical navigation paints or sticks ribbons on the driving path of the AGV, and realizes navigation by simply processing the ribbon image signals collected by the camera.
Advantages: The flexibility is relatively good, and the ground route setting is simple and easy.
Disadvantages: It is very sensitive to the contamination and mechanical wear of the ribbon, the environmental requirements are too high, the navigation reliability is poor, and it is difficult to achieve precise positioning.
008-----Direct Coordinate Guidance Technology
The AGV's driving area is divided into several small coordinate areas by the positioning block, and the guidance is realized by counting the small areas. Generally, there are photoelectric type (divide the small coordinate area into two colors and count by photoelectric devices) and electromagnetic type (the coordinate The small area is divided into metal blocks or magnetic blocks, and counted by electromagnetic induction devices. The disadvantage is that the ground measurement installation is complicated, the workload is large, the guidance accuracy and positioning accuracy are low, and it cannot meet the requirements of complex paths.
009----Image Recognition Guidance Technology
Image recognition of the environment in the driving area of AGV to realize intelligent driving Among them, there is no practical AGV using such technology yet.
It is conceivable that the combination of image recognition technology and laser guidance technology will provide unexpected possibilities for automation engineering, such as the accuracy and reliability of guidance, driving safety, and intelligent memory recognition will be more perfect. .
A simple comparison of several commonly used guidance methods is as follows:
The statistical results of the main guidance technologies adopted by 27 series of products of more than a dozen foreign AGV companies show that the proportions of electromagnetic induction, inertial navigation, optical detection, position setting, laser detection and image recognition are 32.3% and 27.8% respectively. , 16.9%, 13.8%, 7.69% and 1.54%. Among them, the application ratio of electromagnetic induction guidance technology is the highest, which shows that this technology is very mature. However, the application of machine vision-oriented technology is less, indicating that this technology still needs in-depth research and continuous improvement. In addition, autonomous navigation technology is still in the research stage, and there are still many technical problems to be solved.