Robust low order dynamic controller for flexible spacecraft

The design of an optimal low-order dynamic controller with a -shift (alpha-shift) for attitude control is attempted for a flexible satellite which is a solar electric propulsion spacecraft. The satellite consists of a central rigid body to which two flexible solar panels are attached. The design of a third-order dynamic controller is accomplished using modified linear quadratic Gaussian theory. The improvement in the satellite attitude response with a small uniform a-shift is demonstrated by numerical simulation. A novel concept of block-shift is introduced to move different sets of closed-loop eigenvalues by different amounts. The advantages of this type of block-shift in the design of the controller are shown by simulation. The robustness of the controller with respect to parameter variations is shown to be ample