Aeroelastic vehicle optimal sensor placement for feedback control applications using mixed gain-phase stability

Optimal positions for aeroelastic vehicle feedback sensors, which meet design constraints and control requirements, are difficult to determine. A new systematic and optimal approach for choosing sensor locations based on root locus principles is presented. A steepest descent optimization method with constraints is used to minimize objective criteria, which are based on the departure angles as well as dipole magnitudes for each aeroelastic mode appearing in a traditional Evans diagram for a scalar control loop. Each departure angle and dipole term is multiplied by a weight parameter. Rigid-body augmentation characteristics are implicitly accounted for in the type of input-output pairs utilized and in predefined loop compensation structure. Constraints enforcing minimum phase zeros in the transfer function are also considered. A flexible aircraft structure is used as an example to demonstrate this procedure. Results indicate flight control and structural mode control characteristics can be effectively balanced.