FUZZY CONTROL OF ELECTROHYDRAULIC STEERING SYSTEMS FOR AGRICULTURAL VEHICLES

Abstract

This paper presents the development of a fuzzy steering controller for wheel–type agricultural vehicles with an electrohydraulic (E/H) steering system. The fuzzy controller,which consisted of a variable fuzzifier, an inference engine with a steering control rulebase, and a control signal defuzzifier, was developed based on a common–sense model of agricultural vehicle steering. The controller implemented steering corrections based upon the desired steering rate and the error between the desired and the actual wheel angles. Test results indicated that this controller could be used on vehicles with similar steering actuating mechanisms. Limited tuning on fuzzy membership functions was used to account for physical differences between vehicles. This fuzzy controller achieved prompt and accurate steering performance on both a hardware–in–the–loop electrohydraulic steering simulator and on an agricultural tractor. The adoption of this fuzzy controller can significantly reduce the time and costs in the design of steering controllers for agricultural vehicles.