Integral control of a spinning drag-free satellite

The classical theory of integral control is extended to the reduction of errors in the presence of nonconstant forces that can be modelled by differential equations. The performance of systems with integral control and estimators to generate missing states is studied. A spinning body possesses symmetry that enables its behavior to be described by differential equations of lower order with explicit complex terms. The techniques of complex symmetry are applied to the synthesis of a control system for the spinning drag-free satellite. Classical synthesis and analysis techniques are extended to complex symmetric systems. These include the complex symmetric root locus, Bode plot, polar plot and Nyquist criterion, and root square locus for optimal control. The control system was mechanized on a laboratory simulator to demonstrate the performance of the system with integral control. The effects of parameter variation and system nonlinearities are reported.