基于滑模控制的半挂汽车倒车轨迹跟踪

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。 

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

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.