Prescribed adaptive finite-time control of oil-immersed electro-hydrostatic actuators under wide temperature range

This work proposes a prescribed adaptive finite-time control approach that takes the impacts of oil temperature into account in order to address the problem of low tracking control accuracy in oil-immersed electro-hydrostatic actuators (OI-EHAs) under large temperature ranges. Firstly, a dynamic thermal coupling model is established to estimate the unmeasurable oil temperature in real-time, integrating temperature dynamics into the controller architecture to reduce system complexity. Secondly, a finite-time observer (FTO) is designed to effectively suppress composite disturbances arising from temperature prediction bias, parameter perturbations, and external disturbances. By feeding back the estimated disturbance values, the system error converges within a finite time. The tracking error and its dynamic properties are constrained by the introduction of a prescribed performance function (PPF), which guarantees that the error stays within specified bounds. Finally, the backstepping method is employed to integrate the FTO and the PPF, forming a composite controller with temperature-sensitive parameters and mechanisms for compensating uncertainty disturbances. This method ensures the stability of the closed-loop system. Experimental results demonstrate that the proposed controller exhibits excellent performance under various operating conditions.