Robust controllers for the Middeck Active Control Experiment using Popov controller synthesis

Abstruct-The purpose of this paper is to demonstrate robust compensators designed using Popov controller synthesis on the Middeck Active Control Experiment (MACE): a Shuttle program scheduled for flight in January, 1995. The experiment has been designed to investigate the extent to which the on-orbit behavior of a precision-controlled spacecraft can be predicted and controlled using analysis and ground testing prior to launch. Previous flight experiments indicate that, on-orbit, the structural dynamics can change significantly, and that these changes are very difficult to predict. Thus the need arises for robust control techniques that can guarantee on-orbit performance for flexible spacecraft even though the models have large parameter uncertainties. Such a technique is developed in this paper using the Popov stability criterion from absolute stability theory. A state space representation of the stability analysis test is combined with an 7-12 performance objective to provide a powerful technique for robust controller synthesis. A numerical algorithm for optimizing the controller gains and stability multipliers is discussed. Several experimental results on MACE are used to demonstrate that Popov controller synthesis guarantees robustness to d parameter variations and yields good performance with respect to the reference LQG designs.