The second Wind-tunnel test of DLR's multiple swashplate system

After proving its individual blade control (IBC) capabilities on a four-bladed rotor system in the wind tunnel, the DLR’s multiple swashplate system and its control software were developed further to allow IBC operation on a five-bladed rotor system. After preliminary tests in hover conditions, a second wind-tunnel test was performed in the DNW-LLF wind tunnel in late 2016. The goal of this test on a Mach-scaled model rotor was to reduce vibration, noise, and required rotor power in different flight conditions using proven IBC strategies as well as localized pitch control (LPC) on five blades. In descent flight condition, significant reductions of blade–vortex interaction noise relative to the baseline case were achieved on both sides of the rotor disk through the application of 2/rev higher harmonic control as well as using an LPC schedule. Through the application of 3/rev IBC as well as a vibration controller using a 4–6/rev multi-harmonic IBC Signal, 5/rev hub loads were reduced significantly and the 5/rev vertical vibrations were nearly eliminated. In addition, during simulated high-speed-level flight with a wind speed of 76 m/s, the required rotor power was successfully reduced using a 2/rev input with an amplitude of 1°

Application of the Multiple Swashplate System for Individual Blade Control of a 5-bladed Model Rotor in the DNW-LLF Wind Tunnel

After a successful wind tunnel test in the DNW in late 2015, where for the first time DLR’s patented multiple swashplate system (META) was used to demonstrate its full IBC capabilities on a Mach-scaled, 4-bladed model rotor, the META system as well as DLR’s rotor test rig were modified and upgraded extensively to allow IBC operation on a 5-bladed rotor system. After these system upgrades, a second wind tunnel test was performed in late 2016. The goal of this test was to reduce vibration, noise and required rotor power in different flight conditions on a 5-bladed model rotor using proven individual blade control (IBC) as well as localized pitch control (LPC) strategies. In the test the 5/rev hub vibration levels were reduced significantly both through the application of 3/rev higher harmonic control (HHC) and a vibration controller using a 4-6/rev multi-harmonic control signal. The highest reduction was achieved for the vertical 5/rev force, nearly eliminating this most prominent component of rotor hub vibrations. Additional highlights of the test were 2/rev HHC sweeps and the test of different LPC schedules for the reduction of noise and required rotor power. In descent flight condition, significant blade vortex interaction (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 LPC. In simulated high-speed flight, the required rotor power was successfully reduced using 2/rev HHC

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

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°. 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

The First Wind Tunnel Test of the Multiple Swashplate System: Test Procedure and Principal Results

In September 2015, the DLR completed the first wind tunnel test of its patented Multiple Swashplate System in the DNW's Large Low-Speed Facility in the Netherlands. During these tests, the potential of this new active rotor control system to effectively reduce noise, vibration, and power consumption using several individual blade control strategies, including 2/rev inputs, was successfully demonstrated on two different model rotors without using actuators in the rotating frame. For a Mach-scaled Bo105 model, rotor power reductions of up to 4% in level flight and reductions of the weighted 4/rev vibratory hub loads of up to 77% in a descent flight condition were measured, and BVI noise levels were reduced by up to 4.5 dB by the application of 3/rev higher harmonic control, confirming findings from the HART II test. For the second model rotor using a contemporary blade geometry, the maximum reductions were measured at 3%, 52%, and 3.9 dB for power, vibration, and BVI noise, respectively

The First Wind Tunnel Test of the DLR’s Multiple Swashplate System: Test Procedure and Preliminary Results

In September 2015 the DLR completed the first wind tunnel test of its patented Multiple Swashplate System (META) in the DNW’s Large Low-Speed Facility (LLF) in the Netherlands. During these tests, the potential of this new active rotor control system to effectively reduce noise, vibrations and power consumption using several individual blade control (IBC) strategies, including 2=rev inputs, was successfully demonstrated on two different model rotors without using actuators in the rotating frame. For a Mach-scaled Bo105 model rotor power reductions of up t

Testing Active Rotor Control Applications using DLR's Multiple Swashplate Control System in the LLF of DNW

In the context of the joint research project advanced swashplate concepts within the nationally funded aeronautical research programm LuFo V-1, DLR’s multiple swashplate control system has successfully completed its first wind tunnel tests in DNW’s large low-speed facility. The main goal of the wind tunnel tests was to examine the effectiveness of several individual blade control strategies regarding noise, vibration and power reduction at different wind speeds and flight attitudes using highly instrumented Bo105-type model rotor blades as well as a newly manufactured set of model rotor blades with a more modern blade planform and profiles. The results of these tests, which for the first time included 2/rev higher harmonic control and tip path plane splitting without using actuators in the rotating frame, are a valuable addition to the data gathered from the HART- and HART II campaigns and additionally provide the opportunity to directly compare the performance of two different generations of rotor blades under otherwise identical test conditions. This paper provides an initial overview over the test setup of the rotor test rig including the multiple swashplate control system, the different measurement systems used in the wind tunnel tests, the test procedures as well as the specific blade control strategies to reach the goals. Selected first results are presented to provide an initial overview over the measurements taken and an outlook on broader, more in-depth analyses available after further data evaluation