基于速度调节与路径跟踪的差动机器人运动控制

Motion control of differential robot based on speed adjusting and path tracking

差动机器人是一种常见的移动机器人,在仓储、农业等行业的应用十分广泛.针对纵向速度接近最大值时差动机器人跟踪参考路径的能力与保持纵向速度的能力之间存在冲突的问题,从差动机器人纵向速度与转弯曲率之间的映射关系出发,提出了基于预瞄信息的速度调节控制器,并提出了配套的基于非线性模型预测控制的路径跟踪控制器,形成了基于速度调节与路径跟踪的差动机器人运动控制系统.仿真与实验结果表明,提出的运动控制系统可以在差动机器人的纵向速度设定值较高时主动调节纵向速度,保障较高的路径跟踪控制精确性,其中位移误差的绝对值不超过0.0499 m,航向误差的绝对值不超过0.0726 rad,相比无速度调节的运动控制系统,该系统可将位移误差和航向误差的最大绝对值分别减少达97.57%和45.04%.

A differential robot is a typical mobile robot widely used in storage,agriculture,and other industries.The motion control of differential robots,including longitudinal and lateral control,is a current research hotspot.To date,researchers have not paid much attention to the interaction between longitudinal and lateral control of differential robots.However,the conflict between the ability to track the reference path and maintain the longitudinal speed at its maximum value is a critical issue that limits the operational efficiency of the differential robot.To solve this problem,a mapping relationship between the longitudinal speed and the turning curvature is analyzed.The mapping relationship is established when the maximum value of the longitudinal speed is known,i.e.,the feasible upper limit of the longitudinal speed that can guarantee the steering ability of the differential robot is inversely proportional to the curvature of the trajectory.From this mapping relationship,a speed-adjusting method is proposed based on the preview information.This speed-adjusting method consists of two steps.First,the smaller value between the upper limit of the feasible longitudinal speed in a certain preview distance and the set value of the longitudinal speed are taken as the desired longitudinal speed.Second,a control law is established based on the deviation between this desired and current longitudinal speed.Additionally,a path-tracking method that cooperates with the above-mentioned speed-adjusting method is proposed.The theoretical basis of this path-tracking method is a nonlinear model predictive control.The prediction model used in this control method is derived from a kinematic model with longitudinal speed as a time-dependent parameter.Finally,a differential robot motion control system is formed based on speed adjusting and path tracking.The simulation and experimental results show that the proposed motion control system can actively adjust the longitudinal speed when the set value of the longitudinal speed of the differential robot is high and ensure high accuracy of path tracking control.Furthermore,the absolute value of the displacement and heading errors does not exceed 0.0499 m and 0.0726 rad,which are reduced by 97.57%and 45.04%compared with the motion control system without speed adjusting,respectively.