Modeling the Effect of Orientation on Human-Powered Inertial Energy Harvesters

A fundamental challenge in realizing body-worn sensors is in providing an effective and long-lasting power supply. Issues regarding batteries have prompted researchers to investigate powering devices by extracting energy from the inertial movement of the human body. While previous studies have investigated the effect of generator location and wearer activity on harvestable power, they have not considered the orientation of the generator; this is the focus of this paper. Acceleration data collected across a sample population (10 participants) during different activities (walking and running) and generator location (five locations on the body) are presented. These data are processed to analyze the effect of orientation, and we find that it can significantly reduce the harvestable power. Subsequently, we propose and analyze how two degree-of-freedom generators can improve tolerance to rotation; results indicate that it can be improved by one order of magnitude.