A comparison of three steering controllers for off-road vehicles

Many off-road vehicles use electrohydraulic (E/H) actuators for implementing steering controls. However, the high non-linearity of E/H steering systems often results in difficulties in achieving high performance in steering control, especially when it requires only some small steering corrections. Such features of E/H steering systems call for capable control methods to overcome the non-linearity problems in achieving a desirable level of steering performance. This paper presents a comparison of the performance of three commonly used controllers, namely a proportional-integral-derivative (PID) controller, a feedforward-plus-PID (FPID) controller, and a fuzzy controller, for an E/H steering system. To isolate environment influences on the investigation of the controller performance, the comparison tests were implemented on a validated hardware-in-the-loop (HIL) E/H steering system simulator. The results obtained confirmed that both the FPID and fuzzy controllers have superior performance in compensating for system deadband and could achieve more sensitive and accurate small steering corrections than a PID controller.