A Simple Configuration of an Actively Synthesized Gyroscopic-Nonreciprocal Acoustic Metamaterial

Abstract

A simple configuration of an active nonreciprocal gyroscopic metamaterial (NGMM) is presented. In the proposed NGMM system, a one-dimensional acoustic cavity is provided with piezoelectric boundaries acting as a collocated pair of sensors and actuators. The active piezo-boundaries are controlled by a simple control algorithm that synthesizes a virtual gyroscopic control action to impart desirable nonreciprocal characteristics which are tunable both in magnitude and phase. The dynamic model of a prototype of the NGMM cell is experimentally identified in an attempt to provide means for predicting the characteristics of the virtual gyroscopic controller for various control gains during forward and backward propagations. The theoretical predictions are validated experimentally without the need for any physical dynamic controller which was provided, in earlier studies, by using a dummy NGMM cell. Such a simplified arrangement enables the fast execution of the controller with enhanced frequency bandwidth capabilities. The experimental and theoretical characteristics of the NGMM cell are monitored and predicted for different control gains in order to evaluate its behavior for both forward and backward propagations. The obtained experimental results are compared with the theoretical predictions and found to be in close agreement. The presented concepts provide the foundation necessary for the implementation of NGMM that can be employed in more complex 2D and 3D critical structures in order to achieve nonreciprocal behavior in a simple and programmable manner.