Near optimal control for flexible expendable launch vehicles

Based on a general review of the dynamics and control as well as relevant references for launch vehicle systems, a simplified mathematical model suitable for subsequent control design has been established. The model considers the attitude, lateral transverse motions coupled with flexible bending modes, the sensor and actuator dynamics and the wind gust loads. Originally there are three gyros in the system as sensors, one is for rotational position, the other two are for rotational rate. It was suggested by the user that an accelerometer collocated with the position sensor might be added to the system as an additional sensor. With the accelerometer the near optimal control logic can be applied to the system to achieve better performance than with the classical PID control. The accelerometer measurement equation is given in this paper. Numerical results for comparison of classical PID control systems and near optimal control systems for a class of representative flexible expendable launch vehicle systems are presented and illustrate the possibility of an alternative controller for flexible expendable launch vehicles.