H∞ loop shaping design for a spin stabilized seeker

In this paper the new one-degree and two-degree of freedom H_∞ loop shaping robust controllers are designed for a seeker scan loop, which has model uncertainty and subjects to external & internal disturbances. Both one-degree and two-degree of freedom H_∞ loop shaping are constructed of two main stages; first, the nominal plant is dynamically diagonalized and shaped by pre- and post-compensators to give a desired shape to the singular values of the open loop frequency response and then shaped plant robustly stabilized with respect to coprime factor uncertainty using simple H_∞ optimization and γ-iteration for one-degree of freedom H_∞ loop shaping and two-degree of freedom H_∞ loop shaping respectively. Finally, designed controllers are applied to the plant and simulation results in time and frequency domains such as step response, external and process disturbances rejection, robust performance and scan performance are shown and compared for these controllers and some other works.