Robust gain-scheduled aircraft longitudinal controller design using an ℋ∞ approach

A robust gain-scheduled controller is designed for the longitudinal attitude control of a light commercial aircraft using an ℋ_∞ approach. Following a model reduction procedure that exploits the optimal controller structure, linear time-invariant controllers designed at the selected equilibrium points are reduced to second order controllers and realized in a feedback path configuration that is amenable to scheduling. A gain-scheduling law is developed and simulation results verify that the closed-loop performance specifications are met