Static output-feedback control with selective pole constraints: Application to control of flexible aircrafts

A non-smooth optimization approach is considered for designing constant output-feedback controllers for linear time-invariant systems with lightly damped poles. The design requirements combine H_∞ performance requirements with regional pole constraints excluding high frequency lightly damped poles. In contrast to the usual (full) pole-placement (FPP) problem, the problem dealt here is one of Selective Pole Placement (SPP). The latter design problem is frequently encountered in the control of aircraft with non-negligible aeroelastic modes which are too fast to be handled by the control surface actuators. As in the FPP case, the pole constraints are embedded in the design criterion using a transformation on the system model which modifies the H _∞-norm of the closed-loop system via a barrier function that is related to the closed-loop poles damping. Dissimilar to the closed-loop solution that is designed for the FPP, in the SPP case, numerical calculations of the gradient of the cost function is needed. The proposed method is applied to a flight control example of a flexible aircraft.