A Novel Adaptive Structural Impedance Control Approach to Suppress Aircraft Vibration and Noise

Significant levels of undesired vibration and noise are inherent in transport and combat vehicles, particularly in helicopters and propeller aircraft. Therefore, it is important to investigate techniques that reduce vibration and noise in the cabin to improve habitability, effectiveness, and safety for passengers. In addition, continuous exposure may lead to long-term physiological effects. In contrast to passive approaches, active techniques have the potential to suppress low frequency vibration and noise over a broadband of frequencies. Various smart structure based techniques using active materials have been studied for vibration and noise suppression applications. These include active helicopters blades, variable twist propeller blades, adaptive damper, etc. Use of these techniques promises vast improvements in vibration and noise levels. However, full-scale implementations of these techniques have been hindered by electromechanical limitations of active materials. The Smart Spring is a novel approach to control combinations of impedance properties of a structure, such as stiffness, damping, and effective mass. It uses stacked piezoceramic actuators to adaptively vary structural impedance at strategic locations to suppress mechanical vibration. The Smart Spring is a versatile approach that can be implemented in a variety of applications. For example, an adaptive Smart Spring mount can be used to reduce vibration on vehicle seats, mitigate vibratory loads transmitted from engines, or suppress rotor vibration in helicopters. It is an unique concept that overcomes some of the difficulties encountered with other piezoceramic based vibration control approaches. Extensive experiments have demonstrated the ability of the Smart Spring to control structural impedance properties in an adaptive manner to suppress mechanical vibration. Wind tunnel tests have verified the ability of the Smart Spring to suppress both the vibratory displacement as well as the reaction force under unsteady excitation of a helicopter rotor blade.