Reducing aerodynamic vibration of rigid rotors with retreating side active control avoidance

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This paper proposes a new approach to eliminate aerodynamic lift oscillation, called the Dominant Sector Individual Blade Control (DS-IBC) method for rigid rotor helicopters. An Advancing Blade Concept (ABC) rotor model for aerodynamic analysis based on the free-wake method is applied. DS-IBC avoids applying active control on the rotor’s retreating side by employing and restricting active control inputs to a sector area of the rotor disc. Outside this sector, only primary collective and cyclic pitch control are used. Each blade takes turns entering the sector, creating a “relay” active control form to ensure continuous control inputs. The method also includes outer-trim and inner-trim iteration modules. Results show that DS-IBC can eliminate aerodynamic lift oscillation using much smaller control inputs than the sine-trim method. By focusing active control on the rotor’s advancing side, DS-IBC improves the effective lift-to-drag ratio and reduces the implementation difficulty of active rotor control for aerodynamic oscillation elimination, especially at a large lift-offset.