基于相位补偿的电动助力转向系统控制方法

采用动力学与控制理论,研究了具有3个集中质量的电动助力转向系统的物理和数学模型,建立了总体结构图,在对外环特性进行分析的基础上,对总体结构图进行等效变换,根据系统要求对控制系统进行了设计,研究了控制对象的传递函数、控制系统的结构图、开环系统的Bode图、Nyquist图以及系统的稳定性,并进行了台架试验。研究发现控制系统的结构图可以表示为内、外两环结构,内环包含了反电动势的反馈通道,采用快速比例积分(PI)控制的内环,可以忽略反电动势,没有进行相位补偿的系统幅值裕度和相位裕度约为负值,稳定性较差,而进行相位补偿后系统的稳定性较好。结果表明在系统低频共振频率范围内采用超前校正,提供相位补偿是解决电动助力转向系统振动和稳定性的有效方法。

Control method of electric power steering system based on phase compensation

The physical and mathematic model of electric power steering system with three lumped masses was studied by dynamics analysis and control theory, and the general block-diagram of the system was established; the outer loop property of the system was analyzed, then the general block-diagram was transformed into its equivalent counterpart, and steering control system was designed according to the system requirement; the transfer function of controlled plant, the block-eiagraph, Bode plot and Nyquist plot of the open loop system and the stability of the system were studied, and the testbed test of the system was carried out. It is pointed that the block-diagraph may be expressed by a two-loop diagraph with an inner loop including a feedback channel of back electromotive force and an outer one, back electromotive force may be ignored when a fast proportional-integral(PI) controller in inner loop was used, the gain and phase margin of the system are negative without phase compensation, the system is unstable, while phase compensation may stabilize the system. Analysis result indicates that a lead corrector with phase compensation around low frequency resonance is an effective method to stabilize the system and restrain the system vibration. 1 tab, 13 figs, 10 refs.