Design of Nonlinear Attitude Control System for Spaceplane Using Disturbance-Accommodating Control

In this paper, we describe a design of robust attitude controller for a spaceplanc based on feedback linearization. The feedback linearization method with a timescale separation concept has attracted research interest regarding the design of attitude control systems for aircrafts including spaceplanes. The features of this technique are the elimination of the need for any approximation in the linearization of the vehicle's dynamics and the coverage of a wider flight region. However. since this technique involves the cancellation of the nonlinear dynamics, the accuracy of the cancellation cannot be guaranteed in the presence of changes in aerodynamic and other uncertainties. Therefore, we propose the application of a nonlinear control law. which deals with the feedback linearization, using disturbance-accommodating control (DAC). Unmodeled phenomena are estimated as a new state variable by a DAC observer. Furthermore, the sensitivity function and the complementary sensitivity function in the frequency domain are shaped to design the DAC observer. Finally, Monte-Carlo simulations were performed to verify the effectiveness of the proposed attitude control law.