空间机械臂在轨插、拔孔操作基于力/位姿跟踪指数型阻抗控制

Exponential impedance control based on force/pose tracking for orbit insertion and extraction operation by space manipulator

  • 摘要: 讨论了空间机械臂在轨插、拔孔操作的阻抗控制问题。为此,结合系统动量守恒关系,空间机械臂替换部件末端输出插、拔孔主动力与孔内所受摩擦阻力作用关系,以及第二类拉格朗日方程,推导得到了载体位置、姿态均不受控制情况下,空间机械臂在轨插、拔孔操作过程系统动力学方程。同时,根据相关操作控制系统设计需要,利用系统位置几何关系分析、建立了空间机械臂替换部件末端相对基联坐标系的相对运动雅可比关系。之后,由空间机械臂替换部件末端位姿与末端输出插、拔孔主动力之间的动态关系并结合阻抗控制原理,建立了二阶线性阻抗模型。在上述工作基础上,针对空间机械臂在轨插、拔孔操作过程同时存在运动学与动力学不确定性的情况,设计了空间机械臂替换部件末端力/位姿跟踪指数型阻抗控制策略;并通过李雅普诺夫理论,证明了控制系统的稳定性。提到的控制策略具有结构简单、收敛速度快、稳定性好的特点。系统数值仿真,验证了上述控制策略的有效性。

     

    Abstract: With the developments in space technology and exploration, the space manipulator has become a better choice than astronauts for performing long-time and high-precision operation tasks, such as orbit assembly, orbit maintenance, and orbit refueling. In carrying out the above orbit service tasks, the space manipulator must perform insertion and extraction operations. By considering the impedance control, a dynamic relationship can be established between the pose and output force during insertion and extraction tasks. In this paper, the impedance control problems associated with the insertion and extraction operation of the space manipulator were discussed. By combining the conservation of the momentum of the system, relationship between the driving forces of insertion and extraction at the end of the replacement parts, friction resistance in the holes, and second Lagrange equation, we derived dynamic equations for the space manipulator during the orbit insertion and extraction operation when the position and attitude of the carrier were not controlled. In addition, based on the design requirements of the related operation and control systems, we established the Jacobian relation of the relative motion between the end of the replacement parts and the basic coordinate system by performing a geometric relation analysis of the system position. Then, we established a second-order linear impedance control model based on the dynamic relationship between the pose and driving force of the end of the replacement parts and the impedance control principle. Based on the above work, to address the uncertainty of the kinematics and dynamics of the orbit insertion and extraction operation, performed by the space manipulator, we designed an exponential impedance control strategy on the basis of force/pose tracking, and confirmed the stability of the control system based on the Lyapunov theory. The proposed control strategy has a simple structure, fast convergence speed, and good stability. As such, it is suitable for situations with limited computing and storage capacities, such as the space station computer. The numerical simulation results of this system verify the effectiveness of the proposed control strategy.

     

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