Experimental implementation of an active synthesis of a gyroscopic-nonreciprocal acoustic metamaterial

Abstract

Experimental realization of a new class of active Nonreciprocal Gyroscopic Meta-Material (NGMM) is presented. The proposed active NGMM system consists of a one-dimensional acoustic cavity provided with piezoelectric boundaries that act as sensors and actuators. These active boundaries are integrated with linear dynamic control capabilities that virtually synthesize a gyroscopic control action in order to generate desirable non-reciprocal characteristics of tunable magnitude and phase shift. The dynamics of a prototype of the NGMM cell are identified experimentally and the theoretical characteristics of the virtual gyroscopic controller are predicted for various control gains for both forward and backward propagations. The theoretical predictions are validated experimentally using a dummy NGMM cell to act as a physical dynamic controller. Such a preferred arrangement is coupled with analog controllers in order to enable fast execution of the controller and, in turn, enhance the bandwidth of its operating frequency. The time and frequency response characteristics of the NGMM cell are measured for different control gain and the behavior is evaluated for both forward and backward propagations. The obtained experimental results are found to be in close agreement with the theoretical predictions. The presented concept, controller design, and implementation of the NGMM can be extended to various critical structures to achieve realistic acoustic diode configurations in a simple and programmable manner.