基于滑模变结构控制的温室喷药移动机器人路径跟踪

为解决作物种植密集,地面障碍与空间障碍并存等非结构化环境因素对温室喷药移动机器人路径跟踪运动控制精度的影响,在建立移动机器人运动学模型的基础上,设计一种基于指数趋近律的滑模变结构控制方法以保证系统对不确定参数及外界干扰的鲁棒性。与此同时,为有效解决滑模控制固有的抖振问题,提出一种加权增益趋近律算法,在该趋近律的积分项中引入负的加权值,可有效避免当系统状态不在滑模切换时的切换增益的增大,使得控制器输出量平滑,并利用Lyapunov函数证明了其稳定性,并采用该文所设计的基于加权积分增益趋近律的滑模控制器对喷药移动机器人进行路径跟踪控制。试验结果表明,该算法可以顺利消除横向偏差,使实际运动轨迹平稳跟随理想作业路线,避免在作业区域产生较严重的重喷和漏喷现象,其研究成果为温室作物实施精准喷药提供了依据。

Path tracking of mobile robots for greenhouse spraying controlled by sliding mode variable structure

Abstract: In order to solve the bad effects of the complex unstructured environment of intensive planting, ground obstacles and spatial disorders on the trajectory tracking control precision of the spraying mobile robot working in greenhouse environment, a sliding mode control scheme was proposed to guarantee system robustness to uncertain parameters and external disturbances. Meanwhile, a novel weighed integral gain reaching law was introduced to solve the inherent chattering problem of sliding mode control, which can be freely controlled with the introduced law. Moreover, the asymptotical stability of the closed loop system was proved by Lyapunov function. The simulation and experimental results showed that adopting the proposed control method, the angular velocity of driving motor for mobile robot can reach the desired value in 0.015 s and the output signal of controller was smooth with the maximal amplitude of 0.02 V. Since the weighed integral gain reaching law included the absolute value of integral for switching function, when switching function approached zero, the gain of switching term converged to zero, while when the state of the system was not on the sliding mode surface, the integral weighted coefficient was negative which can effectively avoid switching gain increasing, smooth control was achieved. The straight-line walking test showed that the mobile robot can successfully eliminate lateral deviation, and can make the actual trajectory near to the desired route in the shortest time. So, it can avoid serious overlap and missing spraying phenomena in the work area. The research results provide a reference for precision spraying the greenhouse crops.