Fuzzy logic control of an electrohydraulic valve for auto-steering off-road vehicles

Most off-road vehicles employ fluid power to actuate their steering system. Although the actual force that turns the wheels is exerted by hydraulic cylinders, the critical element of a steering control system is the directional control valve. Auto-steering control is typically achieved by sending electrical signals to the valve solenoid drivers. A fuzzy logic controller was designed to create such steering signals. The fuzzy control algorithm was implemented in a hardware-in-the-loop electrohydraulic steering simulator. A set of 25 logic rules was defined to represent the four types of valve characteristic curve observed in different steering operations. The performance of the steering system depended on both the steering signal characteristics and the controller functionalities. The results obtained from this research provided some fundamental information for designing high-performance electrohydraulic steering controllers for autonomous off-road vehicles.