Chattering Suppression Fast Terminal Sliding Mode Control for Aircraft EMA Braking System

The performance of the electromechanical actuator (EMA) in the aircraft braking system suffers from the system's nonlinear characteristics, whereas the robust control can contribute to the improvement of tracking precision in its servo system. In this article, a chattering suppression fast terminal sliding mode (FTSM) control strategy with an embedded nonlinear disturbance observer (NDO) is proposed for the EMA braking system, which can retain the fast convergence characteristic of the classical FTSM and guarantee the system converges to equilibrium point timely. Moreover, the singularity problem of the classical FTSM control is resolved through the well-designed sliding mode manifold. The NDO is designed to estimate the uncertain factors online, including time-varying parameters, external disturbance, and unmolded dynamics of the EMA system. By applying the compensation terms into the control law, the proposed control strategy can alleviate the chattering problem and improve system stability. To verify the performance of the proposed control strategy for EMA, wheel braking tests are conducted under various conditions regarding the type of runway and failure cases. The results indicate that the proposed control strategy can guarantee the servo performance, the control precision, and the response speed of the EMA servo system.