Research On 4WS System Of Rear Wheel Control Independently

Four-wheel steering technology of car can significantly improve the operational stability at high speed, and can significantly reduce the turning radius and operational flexibility at low speed. Because of the front wheel steering vehicle large-scale used currently, this paper chooses four-wheel steering vehicle based on rear-wheel modified as the research object to study their properties in order to make these vehicles also have the advantages of four-wheel steering through a simple modification. The Major research results are:The rear wheels system was modified to make them achieve steering independence. The electric rear-wheel steering system, steering mechanism, brushless DC motor and its DSP-based controller, drive circuit and four-wheel steering control circuit were designed.The rear wheel steering characteristics of modified vehicle were studied. The high or low speed steering characteristics of the rear wheel steering system and ideal four-wheel steering system were analyzed. Besides, the tire wear caused by inconsistent steering center was focused on.Four wheels were chosen as the research object, and established 3-DOF vehicle model. The geometric relationship of previous wheel , the steady-state sideslip angle, and the three typical four-wheel steering center were elected as control objectives for the constraint. Meanwhile simulation model was established by MATLAB / SIMULINK, and the three typical patterns were also simulated comparison.Considered the nonlinear of actual wheel, the virtual prototype of modified four-wheel steering vehicle was established by ADAMS, including front / rear suspension model, front / rear steering system model, tire model and body model. Co-simulation was done combined with MATLAB, and the results are basically the same as that of the 3-DOF vehicle's SIMULINK simulation.By this study, the conclusion of appropriate control constraints can make the vehicle have four-wheel steering features basically was came to.