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四轮转向系统(4WS)可根据前轮转向和车辆的状态通过后轮的转向提高车辆转弯能力,同样,利用这一转向系统可以改进车辆的横向稳定性和操纵性能.当前轮转向相同时四轮转向车辆的转弯半径大于两轮转向,而且普通的控制方法不考虑前轮转向的动态过程影响.本文利用分数阶导数理论提出一种新的四轮转向控制方法,其不仅考虑前轮转角和横摆角速度的大小,而且也考虑到转向角速度的影响.同时也给出控制方法的一些设计方法,数值计算结果验证了该控制方法的有效性.通过对两轮转向和四轮转向的转弯车辆的侧偏角、车辆绕质心的横摆角速度和转弯半径等动力学和运动学特性的计算结果比较,本文的控制方法对四轮转向车辆在转向过程中的瞬态响应有所改进,并减小了转弯半径。
Four-wheel steering system (4WS) can be based on the front wheel steering and the state of the vehicle through the rear wheel steering to improve the vehicle cornering ability, the same, the use of this steering system can improve the vehicle’s lateral stability and maneuverability.When the current steering the same time four The turning radius of the wheel-steering vehicle is greater than two-wheel steering, and the ordinary control method does not consider the influence of the dynamic process of the front-wheel steering.This paper proposes a new four-wheel steering control method based on fractional derivative theory, which not only considers the front wheel angle and But also take into account the influence of the steering angle velocity.At the same time, some design methods of the control method are also given.Numerical results show the effectiveness of the control method.According to the two-wheel steering and four-wheel steering turning vehicles Compared with the calculation results of the dynamic and kinematic characteristics such as yaw rate and turning radius of the vehicle around the center of mass, the control method of this paper improves the transient response of the four-wheel steering vehicle during steering and reduces Small turning radius.