Abstract: Taking a wheel loader steering by wire system as the object aiming at the features of the system,i.e., the big variation ranges of the steering resistance and the input flow, and its serious nonlinearity, the on-line self-tuning of the parameters of the PID controller was achieved for the different conditions of the systems by means of the fuzzy control theory. The structure of the steering by wire system, the mathematical model of the control system, the design process of the fuzzy controller and its control rules were introduced in detail. Both the simulated and tested results show that introduction of the fuzzy sell-tuning PID controller results in speeding up the system response, widening the frequency band, enhancing the antijamming ability, being able to satisfy the requirement of the actual steering systems.

Key words: special-use machinery and engineering, wheel loader, steer by wire, fuzzy control, self-tuning