New strategy for designing composite rotor blades with active flaps

This article presents the development of a mixed-variable optimization framework for the design of composite rotor blades with active flaps in order to maximize the control authority for vibration reduction. For the studies presented in this article, the amplitude of dynamic twist at the blade tip at 4/rev flap actuation frequency is used as the objective function, and it is shown that there is a direct correlation between the amplitude of dynamic twist and the vibration reduction authority of active flaps. The optimization framework developed includes Intelligent Cross-section Generator as the cross section and mesh generator, University of Michigan/Variational Asymptotic Beam Sectional Analysis for the cross-sectional analysis, and Rotorcraft Comprehensive Analysis System for the aeroelastic analysis of active rotor blades. The optimization problem is solved using a surrogate-based approach in combination with the efficient global optimization algorithm. The optimum results with both mixed and continuous design variables are obtained for three different spanwise locations of active flap.