Abstract Characterized by high power-to-weight ratio, modularity and energy efficiency, electro-hydrostatic actuators (EHAs) have been successfully applied to aircrafts and submarines, where high precision and repeatability are in high demand. The position tracking performance, however, can be inevitably affected by parametric uncertainties and uncertain nonlinearities. Model inaccuracy or system variations normally require a large loop gain to achieve robust performance, which leads to over-design. Leakage in the fluid power system decreases steady-state accuracy, and friction in the actuator degrades the transient performance or even causes stick-slip motion at low speeds. Furthermore, the system may exhibit limit cycle (or hunting) due to Stribeck friction and integral action. This paper proposes a robust high precision position control strategy incorporating leakage and friction compensation for EHAs. Quantitative feedback theory (QFT) is applied to design a robust controller that satisfies the prescribed performance specifications without over-design, considering model inaccuracy and system variations. The internal leakage is subsequently compensated based on experimental data instead of incorporating an integrator in the controller; hence, limit cycle is avoided, and response speed is improved. Friction in the actuator is identified based on the LuGre friction model and compensated through an observer in the loop. Friction variation and load fluctuation are considered to be output disturbances to be suppressed by the QFT controller. The QFT controller with leakage and friction compensation scheme is verified through experiments on a typical EHA. Both the steady-state and transient position tracking performances are greatly improved.

中文翻译：

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存在参数不确定性和不确定性非线性的情况下电动静液执行器的高精度位置控制

摘要 电液静力执行器（EHA）具有高功率重量比、模块化和能效等特点，已成功应用于对高精度和可重复性有很高要求的飞机和潜艇。然而，位置跟踪性能不可避免地受到参数不确定性和不确定非线性的影响。模型不准确或系统变化通常需要大的环路增益来实现稳健的性能，这会导致过度设计。流体动力系统中的泄漏会降低稳态精度，并且执行器中的摩擦会降低瞬态性能，甚至会导致低速下的粘滑运动。此外，由于 Stribeck 摩擦和积分作用，系统可能会出现极限循环（或振荡）。本文提出了一种鲁棒的高精度位置控制策略，结合了 EHA 的泄漏和摩擦补偿。考虑到模型不准确和系统变化，定量反馈理论 (QFT) 用于设计满足规定性能规格的鲁棒控制器，而不会过度设计。内部泄漏随后根据实验数据进行补偿，而不是在控制器中加入积分器；从而避免了极限环，提高了响应速度。执行器中的摩擦基于 LuGre 摩擦模型进行识别，并通过回路中的观察器进行补偿。摩擦变化和负载波动被认为是 QFT 控制器要抑制的输出干扰。通过对典型 EHA 的实验验证了具有泄漏和摩擦补偿方案的 QFT 控制器。稳态和瞬态位置跟踪性能都大大提高。