Sliding Mode Trajectory Tracking for Mars Atmospheric Entry based on Extended State Observer

In this paper, the finite-time trajectory tracking control problem for Mars landing with disturbances is addressed. To improve the accuracy of Mars landing, a new nonlinear entry guidance law for low lift landers has been developed. The sliding mode control (SMC) compound with extended state observer (ESO) for tracking a reference trajectory is proposed. The guidance method is based on SMC theory and ESO adapted to the problem of entry guidance. ESO are applied to estimate the disturbance, by which sliding mode controller is designed combining the two approaches respectively to force the state variables of the closed loop system to converge to the reference trajectory. Also, simulation results are presented to illustrate the effectiveness of the control strategy.