基于滑模控制的半挂汽车倒车轨迹跟踪

Backward Path Tracking for Tractor-Semitrailer System Based on Sliding Model Control

针对半挂汽车自动倒车时的轨迹跟踪问题,建立了铰接式半挂汽车在极坐标系下的车辆非线性运动学模型。为简化求解过程,以半挂车期望路径的弧长作为新的时间量标,通过准确线性变换方法对建立的系统模型进行线性化,设计了滑模变结构控制器。为保证半挂车快速趋近期望路径同时削弱抖振,采用指数趋近律的方法和准滑动模态控制,采用极点配置法选取控制参数,最后对曲线轨迹的倒车路线跟踪控制进行了仿真分析。仿真结果表明,设计的反馈控制器能改善半挂汽车对行驶路径的跟踪能力,使偏离的挂车快速返回到期望的稳态轨迹上。

A backward path tracking control of a tractor-semitrailer system was presented. The kinematic nonlinear model of a tractor-semitrailer system was developed in polar coordinate system. To simplify process of solving,reference path’s arc length of semitrailer was taken as argument. Since tractor-semitrailer system was a nonlinear multi-input and multi-output model with strong couplings,accurate linearization algorithm was employed to overcome unknown nonlinearities and uncertain parameters.Sliding mode variable structure control was employed for linearized tractor-semitrailer system. In order to ensure that semitrailer approached desired path quickly and reduce chattering,exponential approach law and the quasi-sliding mode control were adopted. To determine poles to obtain transition performances preserving system stability,pole placement algorithm was used to design control law. Finally,backward path tracking algorithm controlled the system to follow a circle path in real time. The results suggested that simulated tractor-semitrailer system’s tracking path was smooth and almost identical to reference path.