Quaternion-based reusable launch vehicle composite attitude control via active disturbance rejection control andsliding modeapproach

9In this paper, a robust attitude controller for a Reusable Launch Vehicle (RLV) with large speed-range and high turning maneuver is proposed based on the combination of Active Disturbance Rejection Control (ADRC) and Sliding Mode Control (SMC). Quaternion is presented to derive the attitude kinematics model to avoid the singular problem under the traditional Euler angle definition. A MIMO tracking-differentiator is used twice to obtain the quaternion-based angular velocity and traditional Euler angular acceleration respectively. A composite controller is designed based on Sliding Mode Control (SMC) and Extended State Observer (ESO), where the SMC-based controller is used to drive the undisturbed quaternion-based angles to the expected values, and replace the nonlinear controller in ADRC to improve the convergence rate and stability of the designed control system. The ESO is employed to estimate and dynamically pre-compensate the lumped disturbances. Compared with traditional ADRC via computer simulations, the advantages of the designed composite control system is verified.