Development of shaped PVDF sensors for the measurement of volume displacement

Abstract

To attenuate the sound radiated from a vibrating structure, active control can be implemented. When this radiated sound is in the lower frequencies, a reduction of the surface volume displacement of the vibrating structure is suitable for achieving attenuation within these lower frequencies. The sound power emitted from the surface is directly related to the surface volume displacement of the vibrating structure. Traditionally, measurement of the vibration of the structural surface is done using multiple point sensors. Previous work has shown that for a one-dimensional vibrating structure a single sensor made of polyvinylidene fluoride (PVDF) can be used in place of point sensors. Additionally, PVDF sensors have been developed to sense the surface volume displacement in a local area of interest by spanning only that area. However, it has been observed that at higher frequencies both the total and local sensors tend to exhibit reduced accuracy. Thus, a series of experiments was conducted to determine if the PVDF stress/charge coefficient varies as a function of frequency. Additionally, a simulation program was developed to predict sensor charge output for arbitrarily shaped sensors. This simulation, which allows us to develop sensor shapes and predict sensor placement errors, was verified experimentally.