On-Blade Control of Rotor Vibration, Noise, and Performance: Just Around the Corner? The 33rd Alexander Nikolsky Honorary Lecture

A concise review of the active control approaches for vibration reduction in rotorcraft is presented. Next, the evolution and status of higher harmonic control and pitch link actuated individual blade control is presented since these serve as the foundations of on blade control. Despite the success of these approaches, demonstrated by both full-scale wind tunnel and flight tests, higher harmonic control and pitch link actuated individual blade control have not managed to earn their way onto a production helicopter. An alternative, on blade control, is defined as a special implementation of individual blade control, where the control surfaces are located on the rotating blade and each blade has its own controller. A concise description of four on blade devices: (1) the actively controlled flap, (2) the active twist rotor, (3) the active tip rotor, and the (4) deployable Gurney flap, or microflap, is presented. An outline of an aeroelastic response modeling capability used to simulate active vibration and noise reduction using flaps or microflaps is presented. The simulation is a thread that links the various parts of the paper. Next, selected results from simulations and scale wind tunnel model tests on active flaps are used to provide insight on the operational and modeling aspects of these systems. Full-scale wind tunnel and flight tests are presented as culmination of the research effort invested in active flap rotors. Then, the evolution and application of the active twist rotor, and deployable Gurney flaps, or microflaps, is presented. The paper concludes with lessons learned and speculation about the potential implementation of on blade control on production rotorcraft.

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Higher Harmonic Control: A Historical Perspective

Journal of the American Helicopter Society ◽

10.4050/jahs.66.022001 ◽

2021 ◽

Author(s):

Charles E. Hammond

Keyword(s):

Wind Tunnel ◽

Ride Quality ◽

Flight Tests ◽

Flutter Suppression ◽

Harmonic Control ◽

Wing Flutter ◽

Higher Harmonic Control ◽

Higher Harmonic ◽

Langley Research Center ◽

Helicopter Vibration

Higher harmonic control (HHC) is an approach for achieving reduced helicopter vibration by controlling the vibratory rotor airloads in such a way that the fuselage excitation is minimized. This paper is a historical look at how a program aimed at helicopter vibration reduction started as an outgrowth of fixed wing flutter suppression at NASA Langley Research Center, proved the HHC concept on aeroelastically scaled wind tunnel models and went on to demonstrate viability in full-scale flight testing on the OH-6A helicopter in 1982. Following the OH-6A flight tests, the helicopter research community was stimulated to prove the effectiveness of HHC on different configurations through analysis, wind tunnel tests, and flight tests. All of these investigations have shown HHC to be effective in reducing vibration to levels not attainable with conventional vibration control methods and without any detrimental side effects. HHC development has progressed to the point that the technology provides one more option to address the ever-present vibration problem in helicopters. The literature demonstrates that helicopter ride quality equivalent to that of fixed wing aircraft is attainable with application of HHC.

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Higher Harmonic Control: Wind Tunnel Demonstration of Fully Effective Vibratory Hub Force Suppression

Journal of the American Helicopter Society ◽

10.4050/jahs.34.14 ◽

1989 ◽

Vol 34 (1) ◽

pp. 14-25 ◽

Cited By ~ 66

Author(s):

John Shaw ◽

Nicholas Albion ◽

Edward J. Hanker ◽

Richard S. Teal

Keyword(s):

Wind Tunnel ◽

Harmonic Control ◽

Higher Harmonic Control ◽

Higher Harmonic

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Full-Scale Demonstration of Higher Harmonic Control for Noise and Vibration Reduction on the XV-15 Rotor

Journal of the American Helicopter Society ◽

10.4050/jahs.46.182 ◽

2001 ◽

Vol 46 (3) ◽

pp. 182 ◽

Cited By ~ 20

Author(s):

Khanh Nguyen ◽

Mark Betzina ◽

Cahit Kitaplioglu

Keyword(s):

Vibration Reduction ◽

Full Scale ◽

Noise And Vibration ◽

Harmonic Control ◽

Higher Harmonic Control ◽

Higher Harmonic ◽

Noise And Vibration Reduction

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Active Twist Blades: Electromechanical Damping

Volume 2: Mechanics and Behavior of Active Materials; Integrated System Design and Implementation; Bio-Inspired Materials and Systems; Energy Harvesting ◽

10.1115/smasis2012-7980 ◽

2012 ◽

Author(s):

Johannes Riemenschneider ◽

Martin Schulz ◽

Martin Pohl

Keyword(s):

Piezoelectric Actuators ◽

Electrical Circuit ◽

Rotor Blades ◽

Single Frequency ◽

Electrical Networks ◽

Harmonic Control ◽

Rotating Blade ◽

Individual Blade Control ◽

Higher Harmonic Control ◽

Active Twist

Active Twist Rotor Blades for helicopter main rotors have been developed for the use in secondary control such as higher harmonic control (HHC) and individual blade control (IBC). The basic principle of such blades is the implementation of piezoelectric actuators into the blades causing the blades to twist. At the DLR such types of active twist blades have been designed for quite some years. Several model scale blades have been manufactured to demonstrate the feasibility of such systems. This paper presents a new set of rotor blades (4 m diameter) which is designed to go into a wind tunnel experiment within the “STAR” consortium. In this paper it is discussed, what kind of other applications for such blades — equipped with piezoceramic actuators — can be considered. Besides the capability to twist at frequencies of 1 through 6/rev, there is always the option of statically changing the pretwist of the blade, which will influence the figure of merrit. The idea is to use blade integrated actuators as part of electromechanical absorbers has been discussed recently. Using certain electrical networks, the structural behavior of the rotor blade can be significantly influenced. The effectiveness of such systems was experimentally investigated using a twist blade. In this paper results of a rotating blade with aerodynamic damping is shown for the first time. Different types of shunt networks have been investigated as presented in [1] before: At first an oscillating circuit was established coupling the capacitive piezoelectric actuators with an inductivity. If the setup is tuned right, this results in a significant decrease of the amplitues of a single frequency, e.g. torsional eigenfrequencies. In a next step a virtual “negative capacity” was used to dissipate the vibrating energy in the electrical circuit. Such an element shows the same amplitude response as the capacity, but the phase is shifted by 180 deg compared to a “regular capacity”. The advantage of this method is the effectiveness over a broad frequency range. That way several modes can be influenced at the same time. Finally, a first evaluation of the influence of these measures on the vibration level of a complete rotor was carried out.

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