关键词: 转向机构, 螺旋理论, 运动精度分析, 转向误差, 优化设计, 运动副间隙

Abstract:  To evaluate the influences of the joint clearances, including the joint radial clearances and the rack moving direction inclination to lateral direction of vehicle, on the steering errors of a rack and pinion steering mechanism, the joint radial clearances in the steering mechanisms were treated as joint clearance link or variable length link, and then the kinematic model of the spatial steering mechanisms with the joint clearances and the analytical relationship between the rotation angles of kingpin axis and steering wheel were deduced by using the screw theory. An optimization model for the steering mechanisms was established by aiming at minimizing steering errors and taking the maximum values of pressure angles and the minimum value of the maximum steering angle as the constrained conditions. The kinematic analysis of an example shows that the forward and the return steering processes of the steering mechanisms with joint clearances have different steering errors and the return steering errors are larger than that of the forward steering; the steering errors at the moment of revering operation increase sharply; the increase of the joint clearance or the inclination of the rack may increase the minimum steering radius of the vehicle. Steering accuracy of the steering mechanisms with joint clearances may be improved by the optimal design considering the joint clearances. 

Key words: steering mechanism, screw theory, kinematic accuracy analysis, steering error, optimization design, joint clearance