A Mechanical Wave Diode: Using Feedforward Control for One-Way Transmission of Elastic Extensional Waves

This paper concerns the design and analysis of an active device capable of controlling mechanical waves. Its functionality is similar to that of a diode in an electrical network and, therefore, it is referred to as a mechanical wave diode. The aim is to block waves in one direction in a mechanical structure, while not affecting waves travelling in the opposite direction. The device is based on feedforward control and its design is proposed on the basis of equations that describe elastic extensional waves in bars. We present an ideal feedforward design which performs perfectly in the noise-free case. However, it has poor noise properties and is modified to be useful when measurement noise is present. Theoretical analysis and computer simulations show that the modified design is significantly less sensitive to such noise.