Abstract:
High-speed forward flight in helicopters causes high vibratory loads at the rotor hub, which are transmitted into the fuselage. This results in pilot fatigue and high maintenance requirements. Anti-vibration devices or vibration absorbers may be placed near the hub to reduce vibration transmission, while active vibration control systems may typically sense and reduce forces in specific areas of the fuselage. This paper focuses on developing strategies for optimal deployment (sizing, placement and control) of Circular Force Generators (CFGs) for vibration cancellation. Particle Swarm Optimization was used to carry out the optimization for two different load cases corresponding to different flight conditions. Converged solutions for CFG placement were obtained for: different individual load cases; multiple load cases; constrained and unconstrained actuator locations; and using different numbers of actuators. Two CFGs were found to be sufficient to cancel hub loads for a single load case. When two load cases are considered in multi-objective optimization, three actuators can substantially cancel the hub loads (to within 1%). And using four actuators can cancel the hub loads to within 0.1%. Finally, performance under actuator failure was considered as a way to distinguish among otherwise similarly-performing placement solutions.