基于有限时间收敛的双臂空间机器人捕获卫星主动对接力/位姿阻抗控制

ACTIVE DOCKING OPERATION OF DUAL-ARM SPACE ROBOT CAPTURE SATELLITE FORCE/POSTURE IMPEDANCE CONTROL BASED ON FINITE TIME CONVERGENT

针对双臂空间机器人捕获卫星主动对接力/位姿阻抗控制进行了研究.为防止捕获过程中机械臂末端执行器与卫星接触、碰撞时产生的冲击载荷对机器人关节造成冲击破坏,在各关节电机与机械臂之间加入了一种弹簧阻尼缓冲机构.该机构可通过弹簧实现冲击力矩的卸载,阻尼器则用于因弹簧引起的柔性振动的抑制.为解决捕获过程中的非完整动力学约束及捕获后混合体系统的协调控制问题,结合牛顿第三定律、捕获点的速度约束及闭链几何约束,获得捕获后混合体系统的动力学方程,且通过动量守恒关系计算碰撞冲击效应与碰撞冲击力.通过分析对接装置在载体坐标系下的运动学关系,建立对接装置相对载体的运动雅可比矩阵,并基于此建立基于力的二阶线性阻抗模型,实现对接装置输出力的精确控制.考虑到主动对接操作过程要求控制器具有收敛速度快,控制精度高的特点,通过结合终端滑模与超扭滑模的特点,提出一种非奇异快速终端滑模阻抗控制策略.该策略即能实现主动对接操作中位姿与输出力的快速响应,又能有效地抑制滑模的抖振以保证控制精度.通过Lyapunov定理证明系统的稳定性;利用数值模拟验证缓冲装置的抗冲击性能及所提阻抗控制策略的有效性.

The force and position impedance control of dual-arm space robot capture satellite active docking operation is studied. In order to prevent the joints of the space robot from being damaged by impact force generated when contact and impact between the end-effector of the manipulator and the satellite during the process of capture operation, a spring damping buffer device(SDBD) is added between each joint motor and manipulator. In order to solve the problems of nonholonomic dynamic constraints in the process of capture operation and the coordinated control of the closed-chain hybrid system after capture, combined with Newton’s third law, velocity constraints of captured points and closed-chain geometric constraints, the closed-chain dynamic model of hybrid system after capture operation is obtained, and the impact effect and impact force are calculated by the law of conservation of momentum. The Jacobian matrix between the docking device relative to the base of space robot is established by analyzing the kinematic relationship of the docking device in the base coordinate system. On this basis, a second-order linear impedance model based on force is established to achieve high precision output force control of the docking device. Considering that the active docking operation requires the controller to have the characteristics of fast convergence and high precision control of position and attitude, a nonsingular fast terminal sliding mode impedance control strategy which combining the advantages of terminal sliding mode and super-twisting sliding mode is proposed. This control strategy can not only realize the rapid response of position, attitude and output force in the process of active docking operation, but also effectively solve the chattering problem of sliding mode to ensure the position, attitude and output force high precision control. The stability of the closed-chain hybrid system is proved by Lyapunov theorem. The impact resistance of the buffer device and the effectiveness of the proposed impedance control strategy are verified by numerical simulation.