Design and experimental validation of an adaptive fast-finite-time observer on uncertain electro-hydraulic systems

This paper presents the design of an adaptive fast-finite-time extended state observer for electro-hydraulic actuator systems. First, the system model is divided into three parts, and fast-finite-time state observers are designed independently for each part. This guarantees the fast-finite-time uniform ultimate boundedness of the estimation errors. Then, based on the designed state observers and without neither any knowledge about the upper bounds of the uncertainties nor their derivative, supplementary observers are presented to estimate the unknown terms. Rigorous analyses of the proposed strategy are provided through the Lyapunov approach. The suggested adaptive framework can improve the convergence rate for zones both far from the equilibrium points and around them. The adaptive gains are computed based on the straightforward evaluation of the absolute value of the observation errors, thus their values are valid in real life applications, achieving finite-time estimate of both the full state variables as well as uncertainties. Comparative simulations are presented to analyze the effectiveness of the proposed observers with and without unknown measurement noise. Finally, the effectiveness of the proposed approach in real-life conditions is demonstrated through experimental studies.