Study On The Control Theory And Technology Of The Global Vision Guided AGV

AGV(Automatic Guided Vehicle) is a kind of transport car. The article has introduced the guided way and the characteristic of the AGVS first , there are two types: free route and fix route, according to having the fixed guiding line or not . There are other two types : vision navigation system and normal navigation system according to the different hardware system for the AGVS. Then the vision navigation system can be divide into global located system and local located system. This article will introduce the global located AGV system mostly.CCD (Charge Coupled Device) is independent from the car in the global located system, the control system on the car will communicate with the CCD system by the wireless communication system, the host controlling machine control the AGV according to the information collected by the CCD system , then send the control order to the car by the wireless communication system . The global located system has a lot of advantage points than the local located system: such as it needn't to set the mark on the ground in the global located system, it can control many AGV systems at the same time, it also can cut down the cost of product, and so on.A lot of AGVS adopt the independent wheel differential speed drive structure, this article have adopted the four wheel structure. The article have established the mathematic model for the steering system. When the AGV run on the curve route ,the guided precision will come down and the stability will become bad, because the rate of the close loop control method is restricted by the speed of the image processing, then analyses the reason for the precision falling in the curve route guiding. The present a novel approach to the steering problem under global vision guided mode, that is the open loop control method, and analyses the theory of the method deeply. The image processing system has establish the dummy coordinate system according to the environment of the AGVS, then a mark is set on the top of the car ,the image processing system can calculate the coordinate and direction of the car according to the mark. The control system was designed for the car based on the AT89C201, the PID speed controller was adopted for the drive motor . Article have done many experiments about the global vision guided AGV, the results of the experiment have proved that he global vision guided AGV have more route set flexible than the local vision guided AGV, when the AGV run on the curve route, the open loop control system need not the image process, this can reduce the demand of the image processing system, and the car can run stable on the curve route.In order to enlarge the range of the car ,the control system need more image and other information, the global located AGV system should develop on the multi-vision sensor guided AGVS. The global vision guided AGVS need not to set mark on the ground, then this kind of AGV need to design a perfect route plan system, all of these are the key research points for the global vision guided AGV in the future.