A study of closed loop control applicable to active technique with BVI detection method for helicopter noise reduction

摘要

This paper presents a research activity of a control law for helicopter BVI noise reduction utilizing the blade surface pressure as the reference signal. The required measurement item is effectively measured with sensors installed only on the helicopter blade. BVI noise is generated during the flight condition when a helicopter approaches to the landing area. Therefore it is very annoying in the residential area around heliports. BVI is generated by the aerodynamic interference between the tip vortex coming out of the preceding blade and the following blade, which causes abrupt change of the blade surface pressure, resulting in the impulsive noise. This study proposes a closed loop control law using Kalman filter with the blade surface pressure fluctuation as an index to represent the degree of BVI based on a mechanism of BVI mentioned above. This control law is evaluated by a wind tunnel test of a model rotor system. It is demonstrated by the wind tunnel test that the control law utilizing the blade surface pressure, which enables the control system to be made only by on-board sensors, successfully functioned to make use of the active technique capability to reduce BVI noise.