Research On Steering Control Strategy Of The Tractor’s Hydraulic Steering By-Wire System

Due to the poor working conditions and often traveling in rough land, the tractor’s steering mechanism has some requirements. Generally, the tractor’s steering system is full-hydraulic steering system, with the advantage of steering light and flexible, stable performance and convenient layout. However, the full hydraulic steering system often happens to be hard steering and failure steering. Steer-by-wire system completely gets rid of the various limitations of the traditional steering system because of the cancellation of a mechanical connection between steering wheel and vehicle steer wheel, and is easily integrated with other systems.This paper combined full hydraulic steering and steer-by-wire, and designed a new type of hydraulic steering by-wire system. The paper has done the following work.First, the paper accomplished the overall design of the hydraulic steering by-wire system. The steering wheel module, steering module and the ECU module of this system were designed, and also the composition of the three parts and the system’s working principles were presented in details. What’s more, the whole elements of the system were selected.Second, this paper designed angle transmission ratio of the hydraulic steering by-wire system. The steering characteristics of the system was analyzed in details and the variable gear ratio was designed according to the requirements of the tractor’s steering system. In addition, the structure of the tractor’s steering trapezoidal was analyzed in the paper, so as to obtain the relationship between the steering angle and steering cylinder’s displacement.Third, by comparing the advantages and disadvantages of various control strategies, the fuzzy control strategy was selected to realize the system’s steering function. Later, the fuzzy controller was designed and the fuzzy rules and membership functions were defined. The module of the mechanical, electrical and hydraulic of the steering system were simulated in Matlab/Simulink environment, and the contrast between fuzzy control and PID control were analyzed. In the end, the characteristics of the hydraulic steering by-wire system were realized, and the results showed that the fuzzy control had a good steering effect.Furthermore, the hydraulic steering by-wire system’s electronic control part was fulfilled in this paper, including circuit and software design of the control system, which was based on single chip microcontroller. The paper used C language to complete the programming of the entire system, including the main program, fuzzy algorithm, and display routines, etc. The controller realized signal acquisition of the steering wheel angle and cylinder displacement, the drive of electromagnetic proportional valve, and the display of the experimental results.Finally, the hydraulic steering by-wire system bench was designed and built, and the steering experimental test was done on it. The experimental results showed that this hydraulic steering by-wire system can achieve the tractor’s steering function very well.