A Novel Sliding Mode Control Strategy for an Electro-Hydrostatic Actuator Based on Singular Perturbation Theory

The Electro-Hydrostatic Actuator (EHA) is a high-order nonlinear system with notable parameter uncertainties and coupled electro-hydraulic dynamics. To achieve high-precision position control, this paper proposes a novel sliding mode control strategy based on singular perturbation theory (SPT-SMC). The singular perturbation theory is applied to achieve a rational order reduction of the EHA system, simplifying controller design while mitigating unmatched disturbances. A sliding mode controller incorporating a new reaching law is then designed based on the reduced-order system. Finally, simulations studies are executed to assess the SPT-SMC. The results demonstrate that, compared with widely used control strategies, the proposed approach achieves faster response while ensuring stability.