Researches for improving the control performance of hydraulic systems in both control accuracy and energy efficiency have never stopped in aerospace and industrial applications. The existence of nonlinearities, uncertainties, and unknown terms in the system dynamics, however, significantly limits the desired performance. To realize improvements by dealing with these problems, an advanced position controller incorporated with effective disturbance observers (DOs) applied for a pump-controlled hydraulic system is proposed in this article. Here, uncertainties are considered as certainties (nominal terms) and their deviations. To eliminate certain nonlinearities in the system dynamics, the proposed controller is designed based on a simplified robust sliding-mode-backstepping scheme. The lumped unknown terms, which mainly degrade the performance of the controller, in pressure dynamics and force dynamics are expanded by using equivalent nonautonomous models. To effectively approximate the terms and to ensure usability of the estimated results inside the control framework, two different high-order DOs are developed. Asymptotic convergences of these observers are achieved by adopting nonlinear combinations of the estimation errors. Effectiveness and feasibility of the designed observers and the closed-loop system for an asymptotically tracking performance in the presence of bounded time-varying disturbances are then confirmed by Lyapunov-based proofs and extensive experiments.

中文翻译：

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基于有效扰动观测器的泵控制液压系统非线性控制器

在航空航天和工业应用中，从控制精度和能源效率两方面提高液压系统控制性能的研究从未停止。但是，系统动力学中非线性，不确定性和未知项的存在极大地限制了所需的性能。为了通过解决这些问题实现改进，本文提出了一种先进的位置控制器，该控制器结合了适用于泵控制液压系统的有效干扰观测器（DO）。在此，不确定性被视为确定性（名义项）及其偏差。为了消除系统动力学中的某些非线性，所提出的控制器是基于简化的鲁棒滑模反推方案设计的。混在一起的未知术语，使用等效的非自治模型扩展了压力动力学和力动力学，这主要降低了控制器的性能。为了有效地近似这些术语并确保控制框架内估计结果的可用性，开发了两个不同的高阶DO。这些观察者的渐近收敛是通过采用估计误差的非线性组合来实现的。然后，基于Lyapunov的证明和广泛的实验证实了设计的观测器和闭环系统在有界时变扰动情况下渐近跟踪性能的有效性和可行性。为了有效地近似这些术语并确保控制框架内估计结果的可用性，开发了两个不同的高阶DO。这些观察者的渐近收敛是通过采用估计误差的非线性组合来实现的。然后，基于Lyapunov的证明和广泛的实验证实了设计的观测器和闭环系统在有界时变扰动情况下渐近跟踪性能的有效性和可行性。为了有效地近似这些术语并确保控制框架内估计结果的可用性，开发了两个不同的高阶DO。这些观察者的渐近收敛是通过采用估计误差的非线性组合来实现的。然后，基于Lyapunov的证明和广泛的实验证实了设计的观测器和闭环系统在有界时变扰动情况下渐近跟踪性能的有效性和可行性。