Coordinated Motion Control For An AGV With Two Differential Driving Modules

Automated Guided Vehiche(AGV) is a transport equipment of high automation, operational flexibility and space utilization, used widely in advanced manufacture industries and modern warehouse industries. Modularized AGV containing several differential driving units is considered to be able to meet the requirements of load-carrying capacity and maneuverability for transporting large-scale assembly. It has a great theoretical significance and engineering value for launching a research on coordinated motion control of several diferential driving units.Firstly, coordinated motion control of an AGV with monocular vision guidance and two diferential driving units is investigated, in which a camera is placed on the AGV frame and located in the middle point of two driving units. A nonlinear kinematics model is established and then processed by the input-output linearization. The speed constraints of several driving units are analyzed for coordinated motion control, and a hybrid control law combining an evaluation function method of error intelligent-transformation with an approach of exponential stability control is proposed. The evaluation function method is used to compute the suitable control output intelligently for different error states so as to convert them into the applicable range of exponential stability control. Then the latter is used to eliminate posture angle error and distance error synchronously towards zero. Secondly, coordinated motion control of an AGV with binocular vision guidance and two diferential driving units is investigated, in which one camera is placed on each driving unit. Another hybrid control law combining a PID control and artifical an intelligent control based on error states is presented. A synchronous deviation-rectifying control algorithm for the third kind of error state is designed on the large error condition, and the PID control is used to handle other error states. Digital simulation based on Matlab software verifies the effectiveness of these above algorithms.On the basis of theoretical research, an on-board controller is developed for the AGV with two differential driving modules by using the embedded computer system, and many system operation tests and path tracking experiments are conducted on the AGV prototype. This AGV can track the guide paths of straight, arc and other complex-shaped lines precisely and steadily. The experiment results testify the effectiveness of the coordinated control technique proposed, which provides a solid technical foundation for developing modularized and configurable heavy-loading AGVs. Key words: Automated Guided Vehicle, Dual differential driving, Coordinated control, Path tracking,...