Comfortable helicopter flight via passive/active morphing

This article offers a new perspective in defining comfortable helicopter flight along with two solutions based on passive and active main rotor morphing. Constrained optimization design problems aimed at minimizing flight control energy while satisfying variance constraints on flight parameters that are considered important in passenger comfort and noise reduction are formulated and solved. Output variance constrained (OVC) control is used for control system design and simultaneous perturbation stochastic approximation (SPSA) is employed to solve the resulting constrained optimization problems. Details on the computation of the control energy are given. Closed-loop responses of designs that satisfy prescribed variance constraints with a very small margin on the achievable variance bounds are compared with responses of designs that satisfy such constraints with a larger margin both for passively and actively morphing helicopters.