An energy harvester for rotating environments using offset pendulum dynamics

We present an energy harvester for environments that rotate through the earth´s gravitational field. Example applications include shafts connected to motors, axles, propellers, fans, and wheels or tires. Our approach makes use of the unique dynamics of an offset pendulum along with a nonlinear bi-stable restoring spring to improve the operational bandwidth of the system. We apply our approach to a tire pressure monitoring system (TPMS) that is mounted on a car rim. Simulation and experimental test results show that the prototype generator is capable of directly powering an RF transmission every 60 seconds or less over a speed range of 6 to 95 mph.