Individual Blade Control of a 5-bladed Rotor Using the Multiple Swashplate System

Abstract

After its first wind tunnel test in 2015, the multiple swashplate system (META) as well as the DLR's rotor test rig were modified and upgraded extensively to allow IBC operation on a five-bladed rotor system. In late 2016 a second wind tunnel test was performed on a Mach-scaled, five-bladed model rotor with the goal to reduce Vibration, noise and required rotor power on a five-bladed rotor in different flight conditions using proven IBC strategies. Highlights of the test matrix were 2/rev sweeps and the test of different localized pitch control (LPC) strategies for reduction of noise and required rotor power. In simulated high-speed flight, the required rotor power was successfully reduced using a 2/rev input with an amplitude of 1 deg. In descent flight condition, significant BVI noise reductions relative to the baseline case were achieved on both sides of the rotor disk through the application of 2/rev HHC as well as a localized pitch control (LPC) schedule. In addition the 5/rev hub vibration levels were reduced significantly both through the application of 3/rev IBC and a vibration controller using a 4-6/rev multi-harmonic IBC signal. The highest reduction was achieved for the vertical 5/rev force, nearby eliminating the most prominent component of rotor hub vibrations.