Wind-Tunnel Testing of Rotor with Individually Controlled Trailing-Edge Flaps for Vibration Reduction

A control method is proposed to reduce vibrations in helicopters using active trailing-edge flaps on the rotor blades. Each blade is controlled independently, taking into account possible blade dissimilarities. The method consists of performing simultaneous system identification and closed-loop control at each time step. For the system identification, different inputs are applied to each blade, and the relationship between the individual blade inputs and the resulting loads in the fixed frame is estimated on-line, assuming a linear-time-periodic model of the helicopter. Closed-loop tests are conducted using a four-bladed Mach-scaled rotor with piezobender trailing-edge flaps. The rotor model is fitted on a bearingless model-scale hub and tested in the Glenn L. Martin wind tunnel. These tests demonstrate the controller's ability to account for blade dissimilarities and generate different optimal inputs for each blade. The 1 and 4/rev components of fixed frame loads are reduced individually by 50 and 60%. Simultaneous reduction of 1 and 4/rev components is also demonstrated (43% reduction). However, vibration increases are noted for some nontarget hub loads.