考虑万向轮扭转角扰动轮式移动机器人轨迹跟踪

为了研究轮式移动机器人运动过程中万向轮扭转的扰动对其轨迹跟踪的影响，提出了一种考虑前端万向轮摩擦扰动及其质心与几何中心不重合的轨迹跟踪控制方法。首先，建立了考虑万向轮扭转角扰动的轮式移动机器人动力学模型；其次，根据位姿误差模型，采用反步法设计虚拟速度控制器收敛系统位姿误差；然后，结合扰动观测器对机器人行进过程中万向轮扭转所带来的摩擦扰动进行估计，构造出一种基于积分滑模思想的力矩控制器以保证速度追踪；最后，利用Lyapunov稳定性理论对系统的稳定性和渐近收敛进行证明。仿真及实验结果表明，将万向轮摩擦所带来的扰动反馈给动力学控制器，可以减轻控制器的负载。与忽略万向轮扰动的控制方法相比，轮式移动机器人的位置误差最大值的均方根值降低了37.37%，提高了运动系统的稳定性。

Trajectory Tracking for Wheeled Mobile Robots Considering the Castor Wheel's Torsion Angle Disturbance

To study the influence of the disturbance of castor wheel's torsion on the trajectory tracking of wheeled mobile robots, a trajectory tracking control method considering the friction disturbance of the castor at the front of the robot and the noncoincidence between the centroid and the geometric center of the robot is proposed. First, the dynamic model of the wheeled mobile robot with castor wheel's disturbance is established. Then, according to the pose error model, the virtual velocity controller is designed by backstepping method to make the pose error converge. Next, combined with the disturbance observer, the friction disturbance caused by the torsion of the castor wheel during the robot's moving process is estimated. A torque controller based on the integral sliding mode idea is constructed to ensure the speed tracking. Finally, the stability and asymptotic convergence of the system are proved using the Lyapunov stability theory. Simulation and experimental results show that the load of the controller can be reduced when the disturbance caused by the castor wheel friction is fed back into the dynamic control controller. Compared with the control method which ignores the disturbance of the castor wheel, the root-mean-square of the maximum position error of the wheeled mobile robot is reduced by 37.37%, and the stability of the motion system can be improved.