Application of the cascade control to the redesign of the attitude controller

This paper presents an effective method for the redesign of the M-V 3^rd stage attitude control algorithm. The objective of the redesign procedure is to introduce an integral term into the controller in order to reduce the steady state error due to the offset of the centre of gravity point of the vehicle and due to the thrust axis misalignment. The proposed method is based on the idea to use the existing controller as the inner (attitude angular velocity) controller of the cascade control. By adding the velocity-position integrator into the controller itself its desired integral characteristic is obtained. The dynamic characteristics and the robustness (by means of the gain and amplitude margins) are investigated for five controllers and corresponding nominal and deviated models.