Disturbance observer based exponential time-varying sliding mode for re-entry attitude control

For re-entry vehicle attitude control problem, a disturbance observer-based exponential time-varying sliding mode attitude controller was designed to achieve precise attitude control when the matched parametric uncertainties and external disturbances occured. Firstly, feedback linearization method was applied to the nonlinear model of re-entry vehicle, which decomposed the pitch, roll and yaw channel decomposed into three independent second-order system. Then, as an example, an exponential time-varying sliding mode controller (ETVSMC) was designed for the pitch channel. Furthermore, to reduce the static error caused by boundary layer solution which was used to soften the chattering, a disturbance observer based exponential time-varying sliding mode control (DOETVSMC) method was presented. Finally, a six degree-of-freedom simulation mode was established for a re-entry vehicle considering the atmospheric density, inertial uncertainties and external high-frequency perturbations, to demonstrate the improved performance of DOETVSMC with ETVSMC.