In this paper, the tracking control problem of underwater robot manipulators is investigated under the influence of the lumped disturbances, including unknown ocean current disturbances and parameter uncertainties. The proposed novel continuous nonsingular finite–time (CNFT) control method is twofold. Firstly, the modified adaptive super–twisting algorithm (ASTA) is proposed with a nonsingular fast terminal sliding mode (NFTSM) manifold to guarantee the finite–time convergence both in the sliding mode phase and the reaching phase. Secondly, a higher–order super–twisting disturbance observer (HOSTDO) is exploited to attenuate the effects of the lumped disturbances. Considering the time–varying gain matrix of the closed–loop control system, the bounded stability is strictly proved via the Lyapunov theory. Hence, the superiority of the proposed controller is singularity–free, fast convergence, chattering–free, high steady–state tracking performance, and good robustness by resorting to the methods of CNFT control and ASTA in combination with a disturbance observer. Finally, numerical simulations are conducted on a two degree–of–freedom (DOF) underwater robot manipulator to demonstrate the effectiveness and high tracking performance of the designed controller.

中文翻译：

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水下机器人操纵器的新型连续非奇异有限时间控制

本文研究了水下机器人操纵器在集中扰动影响下的跟踪控制问题，包括未知洋流扰动和参数不确定性。提出的新颖的连续非奇异有限时间（CNFT）控制方法是双重的。首先，提出了一种具有非奇异快速终端滑模（NFTSM）流形的改进型自适应超扭曲算法（ASTA），以确保滑模阶段和到达阶段的有限时间收敛性。其次，利用高阶超扭曲扰动观测器（HOSTDO）来减弱集总扰动的影响。考虑闭环控制系统的时变增益矩阵，通过李雅普诺夫理论严格证明了有界稳定性。因此，通过采用CNFT控制和ASTA与干扰观测器相结合的方法，所提出的控制器的优越性是无奇异性，快速收敛，无颤动，高稳态跟踪性能以及良好的鲁棒性。最后，在两自由度（DOF）水下机器人操纵器上进行了数值模拟，以证明所设计控制器的有效性和高跟踪性能。