Modeling and design considerations for a micro-hydraulic piezoelectric power generator

Abstract

Piezoelectric Micro-Hydraulic Transducers are compact high power density transducers, which can function bi-directionally as actuators/micropumps and/or power generators. They are designed to generate 0.5-1W power at frequencies of ~10-20kHz, resulting in high power densities approaching 500W/kg. These devices are comprised of a main chamber, two actively controlled valves, a low-pressure reservoir and a high-pressure reservoir. This thesis reports on modeling and design considerations for Micro-Hydraulic Piezoelectric Power Generators. Since these devices are complex fluid and structural systems, comprehensive simulation tools are needed for effective design. Operation of each subcomponent of the device is highly coupled and every design decision should be made with remaining components in mind. A system level simulation tool has been developed using Matlab/Simulink, by integrating models for different energy domains, namely fluids, structures, piezoelectrics and circuitry. The simulation architecture allows for integration of the elastic equations of structural members into the dynamic simulations as well as monitoring of important parameters such as chamber pressure, flowrate, and various structural component deflections and stresses. Using the simulation, the operation of the system is analyzed and important design considerations are evaluated. Fluidic oscillations within the system are analyzed and an optimization procedure for the membrane structure within the main chamber is presented. Parameter studies are performed for different piezoelectric materials, system compliances, and circuit topologies. Tradeoffs between operation conditions and their effect on the performance are discussed. A design procedure is developed. Results indicate that system efficiency is highly dependent on compliances within the device structure, the type of piezoelectric material used and rectifier circuit topology.