Parallel linkage steering for an automated guided vehicle

The computer-aided design of suitable control strategies for parallel linkage steering of an experimental automated guided vehicle is described. The microprocessor-based steering control system is modeled, and stability characteristics using proportional control are investigated by means of describing functions. Although the approximation is coarse, the analysis indicates an upper bound for gain and suggests derivative action for improved control. For better accuracy, a flexible and fast simulation program that makes possible an efficient search for optimal control laws for operation of the vehicle under the constant speed mode and slow-down mode is developed. Time-independent control laws are investigated, and solutions are found that give tolerable tracking over 90 degrees arcs of 0.5 m radius. The simulation results show that time-dependent control laws are essential for improved, nonoscillatory tracking.< >