Intellectual Merit: Vibrations are ubiquitous in many wireless sensor application spaces, and have been widely proposed as a potential source of power. A continuing issue with vibration energy harvesters is the very tight linkage between the specific parameters of the vibration environment and the structural parameters of the harvester necessary for efficient power generation. In reality, most vibration sources change with time, and therefore a harvester that adapts to its vibration environment could potentially operate much more efficiently and provide a stable source of power over a broad range of operating environments as does a battery. This BRIGE project proposes a new method of providing such adaptability through control of the nonlinear stiffness function of duffing oscillators. The research seeks to address the following questions: under what circumstances is closed loop control beneficial, and under what circumstances will active tuning of a nonlinear harvester outperform active tuning of a linear harvester? Understanding the conditions under which closed loop control can provide a net increase in power and the relationship between the characteristics of input vibrations and the optimal type of structure to control will lay the groundwork for efficient adaptable vibration energy harvesters. The models and data generated by this research will lead to further work on optimal control techniques for nonlinear harvesters.
Broader Impacts: The field of energy harvesting for wireless sensors is accessible to and has wide appeal across age groups and levels of technological sophistication. Leveraging that interest, this project will integrate two outreach activities with the express goal of broadening participation and interest in engineering careers among high school aged female students. The College of Engineering sponsors an annual summer camp designed to expose young women to a variety of engineering careers with hands-on experiential learning. A module will be developed for use in this camp in which students design, build, and test a simple piezoelectric accelerometer and energy harvester. The second activity is to sponsor interactive kinetic energy harvesting sculpture design projects for both undergraduate students and students at a local high school. During the first year of this grant, the principle investigator will supervise the sculpture project as part of the senior design course, and the following year he will sponsor the project at a local high school as a joint engineering / art class project. The sculpture design has the potential to engage artistically minded students who may not otherwise be interested in careers in engineering and science.
