Fuzzy speed and steering control of an AGV

Abstract

The development of techniques for lateral and longitudinal control of vehicles has become an important and active research topic in the face of emerging markets for advanced autonomous guided vehicles (AGVs) and mobile robots. In this respect, there has been much literature published, although not so much on the actual performance of such controllers in a practical setting. The primary focus in this paper is on the development and actual implementation of intelligent and stable fuzzy proportional derivative-proportional integral (PD-PI) controllers for steering and speed control of an AGV. The AGV used in this study is an electrically powered golf car, suitably modified for autonomous navigation and control. The use of fuzzy logic for control law synthesis, among other things, facilitates the incorporation of control heuristics, while guaranteeing stability, uncoupling steering control from speed control and providing for easy incorporation of a braking controller. Through experimentation, the designed controllers are demonstrated to be insensitive to parametric uncertainty, load and parameter fluctuations and, most importantly, amenable to real-time implementation. The performance of the proposed uncoupled direct fuzzy PD/PI control schemes for this particular outdoor AGV is also compared against conventional proportional-integral-derivative (PID) controllers. Experimental results demonstrate that the proposed fuzzy logic controllers, which are synthesized from a variable structure systems viewpoint, also outperform conventional PID schemes, particularly in tracking accuracy, steady-state error, control chatter and robustness.