Path tracking control of crawler mobile platform based on bang-bang control with boundary layer
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摘要: 为实现无法闭环调速的开关阀控履带移动平台路径跟踪,考虑到平台速度低且可原地转向的特点,基于纯追踪算法,提出不需要底层轮速控制的带边界层bang-bang路径跟踪控制算法。根据几何及运动学关系,建立履带移动平台目标点追踪模型;以航向角偏差作为切换函数,通过bang-bang算法控制两侧履带正反转,引入边界层厚度参数,以减小电磁阀开关频率;根据李雅普诺夫稳定性理论,证明了边界层外系统各状态均是稳定的,但边界层内航向角偏差在原点处是不稳定的,且前视距离越小,航向角偏差发散越快。基于Matlab/Simulink和Recurdyn联合仿真平台,选择矩形目标路径,仿真验证了不同前视距离下bang-bang算法的路径跟踪效果,并与闭环调速的纯追踪算法进行对比。搭建样机试验平台,对bang-bang路径跟踪控制算法进行地面试验。仿真和试验结果表明,bang-bang路径跟踪控制算法可控制开关阀控履带移动平台实现对直线或折线路径的跟踪,且算法在转角处跟踪精度高于闭环调速的纯追踪算法路径,稳态误差小于9 cm,满足煤矿机器人自主导航行走要求。Abstract: In order to realize the path tracking of the on-off valve-controlled crawler mobile platform that cannot be closed-loop speed regulated, considering the low speed of the platform and the ability to turn in place, a bang-bang path tracking control algorithm with a boundary layer without the bottom wheel speed control is proposed based on pure pursuit algorithm. Based on the geometric and kinematic relations, a target point tracking model of crawler mobile platform is established. Taking the heading angle deviation as the switching function, the method controls the forward and reverse rotation of the crawlers on both sides through the bang-bang algorithm, and introduces the boundary layer thickness parameter to reduce the switching frequency of the solenoid valve. According to the Lyapunov stability theory, it is proved that all states of the system outside the boundary layer are stable, but the heading angle deviation inside the boundary layer is unstable at the origin. Moreover, the smaller the look ahead distance is, the faster the heading angle deviation diverges. Based on the Matlab/Simulink and Recurdyn joint simulation platform, the rectangular target path is selected, and the simulation verifies the path pursuit effect of the bang-bang algorithm with different look ahead distances, and compares it with the pure pursuit algorithm of closed-loop speed regulation. A prototype test platform is built to conduct ground tests on the bang-bang path tracking control algorithm. The simulation and test results show that the bang-bang path tracking control algorithm can control the on-off valve-controlled crawler mobile platform to track straight or broken-line paths. Moreover, the tracking accuracy of the algorithm at corners is higher than that of the pure pursuit algorithm path of closed-loop speed regulation. The steady-state error is less than 9 cm, which meets the requirements of autonomous navigation walking of coal mine robots.
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Key words:
- coal mine robot /
- crawler mobile platform /
- path tracking /
- bang-bang control /
- pure pursuit algorithm /
- boundary layer
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