Design of modified backstepping attitude controller

In this paper, a three-axis nonlinear two step attitude controller design composed of control law module and control allocation module is presented for the attitude control of hypersonic vehicle in the re-entry phase. The modified backstepping control law integrated backstepping technique and extended state observers (ESOs). In order to facilitate the backstepping design, a command filter was introduced. To deal with the large and fast-varying uncertainties, linear extended state observers were designed to estimate and compensate for the uncertainties in real time. Simulations performed using six-degree-of-freedom nonlinear dynamics in MATLAB show that design using the proposed modified backstepping attitude controller has better tracking performance and is more robust to uncertainties with fewer control demands than traditional backstepping design.