Adaptive attitude control with reduced number of estimated parameters for automatic landing system

The formulation of an adaptive attitude control law with reduced number of estimated parameters is introduced for the automatic landing system of a spaceplane. Adaptive attitude control systems have been designed to obtain the control law by estimating the parameters that describe the dynamics of the vehicle and actuator. Despite the fact that the vehicle was well controlled so as to track a reference trajectory, the estimated parameters did not agree with actual values because the number of estimated parameters was redundant for the controller. Therefore, the controller using the estimated parameters does not always show good performance during vehicle landing. In this study, we attempt to design an adaptive attitude controller by reducing number of estimated parameters for the automatic landing flight experiment (ALFLEX) vehicle. Assuming that the dynamics of the actuator is known, such model reduction is realized by decreasing the number of estimated parameters. The validity of the proposed method is verified and the effect of the dispersion of the actuator's dynamics on the control system is also investigated by numerical simulation.