双差速驱动移动机器人路径跟踪混合控制律研究

Hybrid Control Law for Path Tracking of Dual-differential-driven Mobile Robot

针对双差速驱动移动机器人的路径跟踪问题,建立了双输入-双输出的非线性运动学模型并进行了输入-输出线性化,分析了冗余运动约束的速度协同条件,提出了一种融合偏差智能转化评价函数法和指数稳定控制的混合控制律。评价函数法可针对不同的偏差状态智能选择合适的控制量以将其转化到指数稳定控制的适用范围,再通过指数稳定控制实现姿态角偏差和距离偏差向零的同步收敛。数字仿真和实验测试结果表明,该混合控制律可平滑转化偏差状态、同步消除位姿偏差,使移动机器人精确、稳定地跟踪直线和圆弧导引路径。

A dual-differential-driven mobile robot is consisted of two differential driving modules equipped with normal-shape wheels, suffering from constraints of nonholonomic and redundancy in motion. A two-input-two-output nonlinear kinematics model was established for path tracking of the proposed mobile robot and then linearized by the approach of input-output linearization. The need for coordinating the speeds of two driving modules was analyzed when considering the redundancy in motion, and a hybrid control law combining an evaluation function method of error intelligent-transformation with an approach of exponential stability control was proposed. The evaluation function method was used to compute the suitable control output intelligently for different error states so as to convert them into the applicable range of exponential stability control. Then the latter was used to eliminate posture angle error and distance error synchronously towards zero. The results of digital simulation and experiment test showed that the hybrid control law could transform error states smoothly and eliminate two pose errors synchronously, and the mobile robot could track the linear and circular guide paths accurately and steadily.