Output Approximate Loop Transfer Recovery For Fixed Order Dynamic Compensators

This paper extends the approximate loop transfer recovery method for fixed order dynamic compensators to the problem of robustness at the plant output Full state gains are first designed for the dual system, which is the equivalent of designing a full order observer. Then, the loop characteristics at the dual system input are approximated with an observer or controller canonical compensator. Finally, the optimal gains are implemented in the dual compensator to ensure robustness and tracking performance at the plant output. This paper also presents a theorem which further justifies the performance index used in the approximate loop transfer recovery formulation. In addition, an example demonstrates the robust compensator design and implementation. This design addresses the problem of helicopter longitudinal flight control.