System Modeling, Characterization, and Design Considerations for Generators in Commercial Watches With Application to Energy Harvesting for Wearables

This paper presents the characterization of the energy generators embedded in commercial watches with a focus on the Kinetron microgenerator system. These motion-powered watches are potential benchmarking subjects for any effort to develop wearable energy harvesters, and yet have not been systematically characterized. We have developed a system-level model including both the kinematics of the rotational proof mass and the dynamics of the electromechanical transducer for the energy generator based on a generalized rotational energy harvester model. Our experimental characterization includes both controlled bench-top swing arm tests as well as human subject tests. Multiaxial inertial inputs either constructed or obtained from real-world measurement serve as the inputs in the simulation. These characterization results not only serve as a means for model validation but also to provide insight into the state-of-the-art of commercially available wearable energy harvesting capabilities. The experimentally validated model allows us to perform numerical simulations to study scaling relationships and explore pathways to improved power output.