<title>Computational simulation of active piezoelectric coatings with sensors and actuators applied in underwater acoustics</title>

Abstract

Control of the sound reflection from an underwater object is a very important issue. Active piezoelectric layers properly coated on the external surface of the object can control the reflection of incident sound waves. In many active control systems, a sensing device must be employed for the detection of the incident sound. The detected signal is then fed to properly controlled actuators to produce a sound wave to cancel the sound reflection. Multi-layered active coatings are therefore employed, which includes layers of acoustic sensor, layers of actuators and layers of encapsulant. The paper addresses the applications of the active acoustic coating with piezoelectric sensors and actuators for the cancellation of underwater sound reflection and transmission in the frequency domain. Computational techniques are reviewed on analyzing multi-layered active coating systems and on calculating the voltages required for the piezoelectric layers to cancel underwater sound reflections and/or transmissions. Non-reflective piezoelectric coatings are discussed for a oblique and/or normal plane sound wave incidence. The formulations such as surface impedance tensor approach and transfer matrix approach are introduced. They account for the complex interaction between the sound waves and the submerged active coating. The design criterion of imbedded sensors in the multi-layered active non-reflective coating is considered.