基座、臂杆全弹性空间机器人抗死区动态面控制

Anti-dead-zone control based on dynamic surface for space robot with flexible links and elastic base

为了抑制漂浮基空间机器人的弹性基座与柔性臂杆的振动及避免关节力矩输出死区的影响,探讨了基座、臂杆全弹性漂浮基空间机器人系统存在关节力矩输出死区时的轨迹跟踪及双重柔性抑振问题。将弹性基座与臂杆间的连接视为弹簧连接,结合假设模态法,推导出系统的动力学方程。应用奇异摄动方法,将系统分解慢变、快变子系统,分别表示刚性运动、基座弹性与双柔杆振动。对于慢变子系统,针对系统存在死区的情况,设计了基于自适应高斯基模糊的动态面控制器。动态面的引入避免了反演法引起的计算膨胀,减少了计算量;模糊逻辑函数逼近了含有死区误差和外部干扰在内的动力学不确定项;针对快变子系统,采用线性二次型最优控制以抑制基座与双杆的柔性振动并利用Matlab进行仿真验证。仿真结果表明:所设计的控制方案使得基座姿态与两臂杆相对转角收敛到期望角度,基座位移与臂杆的一、二阶振动模态收敛到零。

To suppress the vibration generated by the elastic base and flexible arms of a free-floating space robot and avoid being influenced by the joint-torque-output dead zone,in this paper,we discuss the trajectory tracking and double vibration suppression of the floating-space robot system with a joint-torque-output dead zone.By considering the elastic connection between the elastic base and the link as a linear spring and using the assumed mode method,we model the system dynamics.Next,using the singular perturbation theory,we obtain a slow subsystem that describes the rigid motion and a fast subsystem that corresponds to the vibration of an elastic base and two flexible links.For the slow subsystem,we design a dynamic surface control method based on an adaptive Gaussian fuzzy logic function for solving the dead-zone problem of the system.To reduce the amount of calculation required,we introduce a dynamic surface control scheme that avoids the calculation expansion associated with the backstepping method.We apply a fuzzy logic function to approximate the uncertainty term of the dynamic equation,including dead-zone errors and external disturbances.For the fast subsystem,we adopt an optimal linear quadratic controller to dampen any vibration of the two flexible links and elastic base.Using Matlab to perform the simulation,the results show that the designed control scheme makes the base attitude and relative angles of the two arms converge to the desired angles and the base displacement and the first-and second-order vibration modes of the arms converge to zero.