基于主动偏心轮的全方位移动机器人航位推算与跟踪控制

Dead Reckoning and Tracking Control of Omnidirectional Mobile Robots with Active Caster Wheels

针对基于主动偏心轮的全方位移动机器人系统,提出了一种基于冗余码盘的航位推算方法和一种具有饱和约束的轨迹跟踪控制器.具体而言,首先分析了车轮发生滑动的原因,考虑到机器人随动轮相对于主动轮不易打滑的特性,设计了具有冗余码盘的随动轮结构.基于该结构,将机器人航位推算转化为一个含约束的最小二乘问题.实验结果表明:与未考虑随动轮约束的传统方法相比,该方法降低了轮子打滑的影响,提高了航位推算的精度.考虑到实际机器人系统的速度控制量具有上限,基于李亚普诺夫方法设计了含饱和约束的轨迹跟踪控制器,并对其稳定性和有界性进行证明.仿真与实验结果表明本文提出的控制器具有良好的性能,同时能够满足控制量的饱和约束.

For an omnidirectional mobile robot with active caster wheels, a redundant encoders based dead reckoning method is proposed, and a trajectory tracking controller is further presented in the presence of velocity saturation constraints. Specifically, the reasons for wheel slipping are analyzed firstly, and then a passive caster wheel with redundant encoders are designed and equipped on the robot, inspired by the fact that the passive caster wheels present less slipping than the active casters. Subsequently, the dead reckoning problem is transformed into an equality-constrained linear least square problem. Experimental results show that, compared with the traditional dead reckoning method without redundant encoders, the proposed dead reckoning method alleviates the effects of the slipping on localization and improves the localization precision. Considering that the practical velocities are bounded for motors, a trajectory tracking controller is designed in the presence of such input saturation constraints, and the stability is proven by Lyapunov-based techniques while ensuring the velocity saturation constraints to be satisfied. Both simulation and experimental results demonstrate that the proposed controller presents superior performance, while satisfying the control saturation constraints.