漂浮基空间机器人固定时间收敛主动容错控制

针对载体位置不控、姿态受控的空间机器人存在执行机构存在失效及偏置故障的轨迹跟踪问题，设计了基于固定时间收敛的主动容错滑模控制算法。首先结合拉格朗日法推导出了包含力矩偏置及力矩失效故障的空间机器人系统动力学方程；其次，为消除故障对系统稳定性的影响，引入扩张状态观测器，以实现对故障的动态观测，并在此基础上设计基于固定时间收敛滑模控制器以实现主动容错控制。所提方法具备收敛时间与系统初始状态无关，仅需调节控制参数即可保证系统轨迹在固定时间内收敛的优点。最后通过仿真验算，仿真结果表明所提算法能对故障进行精确观测并在失效故障和偏置故障发生条件下保证系统轨迹精确跟踪及稳定控制，同时相较于其他算法所提算法收敛时间更短，稳态误差更小以及拥有出色的故障观测能力和更强的容错控制能力。

Active fault tolerant control for free-floating space robots with fixed time convergence

An active fault tolerant control algorithm with fixed time convergence was proposed for a free-floating space robot with loss-of-effectiveness fault and bias fault. First the dynamic equation of the space robot with both faults were derived using Lagrange equation. Next, in order to eliminate the influence of fault on the system, an extended state observer was used to estimate the fault of the robot, and further more a fixed time sliding mode controller was designed to realize active fault tolerant control for the system. The convergence time is independent of the initial state of the system, and it can be adjusted by the parameters of the controller. Finally, the simulation results demonstrate that the proposed strategy can observe the faults accurately and guarantee the tracking precision and control stability of the system with the occurrence of the loss-of-effectiveness fault and bias fault, and at the same time, the proposed algorithm has the advantage of less convergence time, smaller error, excellent fault observation ability and stronger fault tolerance.