On the hierarchical control of the space station common module thermal system

Plots of singular values against frequency are used to design a controller for the proposed space station common module thermal system. Our main point is that these Bode plots yield useful design information regardless of the controller structure. Several controllers were designed using singular values, including a classical lead control loop with a multivariable disturbance input, and a multivariable output feedback controller. The singular value information allows one to design controllers with hierarchical and decoupled structure even though the plant may not be decoupled to the same extent. Our technique also allows the inclusion of desired additional dynamics such as compensators, and avoids the inclusion of undesired additional dynamics, such as Kalman filters. A technique is also suggested to avoid gain scheduling, or to minimize the number of scheduling points, for nonlinear systems by designing for robustness in plant parameter variations using singular value information.