ACTIVE NOISE AND VIBRATION CONTROL LITERATURE SURVEY: Sensors and Actuators

This study arose from the need to control noise in naval vessels to reduce their detectability and hence vulnerability to enemy attack. In this report a detailed review of sensor and actuator technologies that could be used for active noise and vibration control in ship structures has been provided. The review focused on a wide range of sensor and actuator materials, such as piezoelectric and electrostrictive materials; magnetostrictive materials; shape memory alloys (SMAs); optical fibers; electrorheological and magnetoeheological fluids, microphones; loudspeakers; electrodynamic actuators; and hydraulic and pneumatic actuators. The diesel engine noise problem was the focus of the study, and consideration was given to the noise transmission paths, namely, the engine mounting system; the exhaust stacks and piping systems; the drive shafts and mechanical couplings; and the air borne radiated noise. Sensor and actuator technologies that are suitable for active control of noise through these paths (or similar structural systems) were reviewed. Based on factors, such as cost, frequency of the disturbance, the operating (marine) environment, experience in other applications, ease of implementation, and the expected performance, detailed recommendations on sensors and actuators for the paths were provided. For the engine mounting system and the drive shafts and mechanical couplings, sensors and actuators, such as accelerometers, force transducers, hydraulic actuators, piezoelectric materials, and electrodynamic actuators, were recommended. On the other hand, acoustic sensors and actuators, such as microphones and loudspeakers, were recommended for the exhaust stacks and piping systems, and the air borne noise. It was also recommended that the active control strategies be combined with passive treatments when ever possible, to increase the robustness of the control system and to provide a fail-safe design. A systematic and pragmatic program, based on combined experimental and numerical investigations, was suggested in order to implement the sensor and actuator technologies recommendations made in the study.