Measurement noise, parametric uncertainties, and external disturbances broadly exist in electro-hydraulic servo systems, which terribly deteriorate the system control performance. To figure out this problem, a novel finite-time output feedback controller with parameter adaptation is proposed for electro-hydraulic servo systems in this paper. First, to avoid using noise-polluted signals and attain active disturbance compensation, a finite-time state observer is adopted to estimate unknown system states and disturbances, which attenuates the impact of measurement noise and external disturbances on tracking performance. Second, by adopting a parameter adaptive law, the parametric uncertainties in the electro-hydraulic servo system can be much lessened, which is beneficial to averting the high-gain feedback in practice. Then, integrating the backstepping framework and the super-twisting sliding mode technique, a synthesized output feedback controller is constructed to achieve high-accuracy tracking performance for electro-hydraulic servo systems. Lyapunov stability analysis demonstrates that the proposed control scheme can acquire finite-time stability. The excellent tracking performance of the designed control law is verified by comparative simulation results.

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This article develops a high-precision tracking control without velocity measurement for electro-hydraulic actuators subject to mismatched and matched disturbances. Compared with previous studies, the presented control method is attractive from a practical point of view. First, velocity signal is often approximately derived by numerical differentiation on position signal, nevertheless, accompanied heavy noise will severely deteriorate tracking performance. Thus, to avert using noise-polluted velocity signal, a third-order super-twisting algorithm (STA) is developed to achieve velocity estimation. Second, the STA-based disturbance estimator is employed to estimate and compensate mismatched and matched disturbances in finite time. Then a composite STA-based control law is constructed to achieve a velocity-free high-performance tracking control, in which an employed modified STA only with an adjustable gain is easier to be performed for practical implementation. The stability analysis reveals the proposed controller is asymptotically stable while existing time-variant disturbances. Comparative experiment results validate the superiority of the presented method.

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