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Electronic Resonant Frequency Tuning of a Marine Energy Harvester

Recently we have reported a new technique for electronic tuning of inertial energy harvesters. An Hbridge power electronic interface is used to apply a variable complex load impedance to the transducer, allowing control over both the transfer of real power to a battery and the mechanical resonant frequency of the system. In this paper we demonstrate the application of this method to two types of resonant inertial harvester designed for marine applications. The first is a pendulum-based device in which the restoring force is provided by gravity, and the second is a rotational device with a torsion spring. Electronic tuning is demonstrated for both devices on a shaker table, and preliminary data is presented from a field trial of the pendulum harvester in a small unmanned surface vehicle (USV).