Control of flexible space vehicles using an adjustable model and alternate control laws

The problem of model uncertainty is discussed and an attitude control system is proposed utilising a new onboard identification algorithm updating an adjustable model whose state estimate feeds two control laws, one for active flexure mode damping and the other for basic orientation. An onboard expert monitors the state estimate and automatically switches between the two alternate control laws according to the relative degrees of excitation of the rigid body and flexure modes. The present study is restricted to single-axis control and would be applicable for three-axis control in cases where the inter-axis coupling is negligible. The effectiveness of the control system is demonstrated by means of computer simulations.