Blade pitch

About: Blade pitch is a research topic. Over the lifetime, 5321 publications have been published within this topic receiving 63134 citations.

Analysis of a higher harmonic control test to reduce blade vortex interaction noise

Abstract: A noise study using an aeroelastically scaled BO-105 rotor was conducted in the German-Dutch Wind Tunnel to examine the use of higher harmonic control (HHC) of blade pitch to reduce impulsive blade-vortex interaction (BVI) noise. The noise directivity was measured over a large plane underneath the rotor using a traversing inflow microphone array. Noise and vibration measurements were made for a range of matched rotor operating conditions where prescribed (or open loop) HHC pitch, at various amplitudes and phases, was superimposed on normal (baseline) collective and cyclic trim pitch. Acoustic data are presented for 3, 4, and 5P HHC applied to a typical landing approach rotor operating condition where BVI noise is normally intense. Noise reductions of up to 6 dB were found for the advancing side BVI noise radiating upstream of the rotor, and also for the retreating side BVI noise radiating below and downstream of the rotor. The relative levels between the sides were modified by HHC control phase. To help give insight to the physics of the HHC/BVI noise problem, highresolution loading and noise prediction results are presented for comparison to the data. The predictions are based on a new high-resolution version of the CAMRAD rotor performance program under development at Langley, called HIRES.

Predictive pitch control of an electro-hydraulic digital pitch system for wind turbines based on the extreme learning machine:

Abstract: An electro-hydraulic digital pitch system is proposed in this paper to regulate output power and drive-train torque for wind turbines. This pitch system is driven by an electro-hydraulic digital se...

A Theoretical Technique for Analyzing Aeroelastic Stability of Bearingless Rotors

Abstract: A technique is introduced for aeroelastic stability analysis of certain hingeless helicopter rotors termed bearingless because of their lack of a pitch-change bearing. The rotor is modeled as three or more rigid blades, each joined to the hub by means of a flexible appendage known as the flexbeam or strap. The pitch-control system twists the flexbeam to provide blade pitch change. The analysis is capable of treating effects of several different pitch-control configurations, geometic nonlinearities associated with the equilibrium deflected shape of the flexbeam, and the built-in angular offsets of the flexbeam and blade. Numerical results are presented for a variety of system parameters. The stability of the system in both hub-fixed motion and coupled rotor-body motion is considered. System parameters can be chosen to stabilize most soft in-plane configurations for the hub-fixed case. The same parameters will also, under certain conditions, stabilize the coupled rotor-body system in hovering flight (air resonance). When the rotorcraft is in ground contact, however, at zero thrust, it appears that these parameters are not as effective in stabilizing the system (ground resonance).

Swashplateless helicopter blade actuation system

Abstract: A blade actuation system comprises at least one motor coupled to a rotor blade for changing the pitch angle of the rotor blade. The motor is configured to wirelessly communicate with at least one flight control computer to modulate the pitch angle. At least one generator may be mounted on a rotor shaft to generate power during rotation of the rotor shaft. The generator may provide power to the motor. The flight control computer is operative to provide control signals to at least one of the generators and motors for regulation thereof. The flight control computer, motor and generator may be configured to wirelessly communicate with one another.