Implementation Complexity Reduction of H-infinity-Optimal Controllers Using Model Matching and Parameter Optimization

The design study in "Hyde, The application of robust control to VSTOL aircraft", included an investigation of ways of scheduling controllers designed using H-infinity techniques. Scheduling was made possible by writing the H-infinity controllers obtained from the loop-shaping/robust stabilisation approach of "Glover and McFarlane, Robust stabilization of normalized coprime factor plant descriptions with H-infinity-bounded uncertainty" in an observer form. The approach was evaluated by application to the design of a flight control law for a Generic VSTOL Aircraft Model(GVAM). A major drawback of the approach was seen to be the number of parameters need to specify the observer matrices for each design point. The study here investigates the structure of the H-infinity controllers designed for the GVAM. The possibility of approximating the structure, and then using this approximation as the starting point of a parameter optimisation is considered