Piezoelectric energy reclamation based on frequency up-conversion technique for digital actuator autonomous additional functions

Abstract

A piezoelectric vibration energy harvester aiming at collecting energy from the operation of an electromagnetic digital actuator is presented. It is based on the frequency up-conversion and can simultaneously obtain the information of discrete position location. The objective is an improved reliability of such digital actuators ensuring sample controls of the actuator positions. The considered electromagnetic digital actuator is capable of achieving two-dimensional in-plane movements by switching a mobile permanent magnet among four discrete positions. The demonstration of a first step toward integrated additional autonomous functions scavenging a part of the mechanical energy of the mobile permanent magnet is achieved. The vibration energy harvester consists of a piezoelectric cantilever beam magnetically attached to the mobile permanent magnet. The limited magnetic interaction force allows a frequency up-conversion strategy to be set. The frequency up-conversion technique that is used here consists of a “low frequency” excitation that drives a much higher natural frequency oscillator. Indeed, once the energy harvester separates from the mobile permanent magnet, a free oscillation occurs and the induced mechanical energy is harvested. This design concept is numerically analyzed and experimentally validated. Harvested energy of 4.7 µJ is obtained from preliminary experiments using a simple out-of-plane cantilever beam with 9 N/m stiffness and 16 mN magnetic attraction between the vibration energy harvester and the mobile permanent magnet when they contact each other. This energy is in accordance with the requirements for wireless communication of simple information. Finally, an L-shaped cantilever beam optimized design is proposed for future in-plane integration.