Backstepping sliding mode control for Mars Entry with finite time convergence

There are usually large uncertainties in the aerodynamic parameters of Mars entry vehicles, which inevitably degrades the performance of entry guidance algorithms. The paper presents a backstepping sliding mode controller for drag tracking in Mars entry guidance, which can guarantee the tracking error with finite-time convergence. First, the drag can track the reference trajectory under the virtual control law by introducing a sliding manifold, and the extended state observer (ESO) is used to estimate and counteract the uncertainties. Then, the finite-time convergence of drag tracking error can be achieved under the proposed backstepping sliding mode guidance law. In addition, the rigorous proof of tracking error convergence is given. Finally, numerical simulation results are presented to demonstrate the effectiveness of the proposed guidance law.