An application of a nonlinear Hybrid Rotary-Translational (HRT) generator is presented. An HRT generator differs from traditional energy harvesting devices in that it has the ability to harvest multi-axis base excitation. The device consists of a pendulum-like system whose rotations are caused by the base excitations. The swinging pendulum is coupled to a direct current micro generator to generate electricity.
The considered application is the energy harvesting from heartbeat induced vibrations. The motivation behind studying the effectiveness of this application comes from battery hindrance. The use of relatively large batteries to power pacemakers presents many medical problems, including increasing the size of the device to accommodate the battery causing surgery complications as well as needing periodic battery replacement. An energy harvesting device can eliminate the need for such a battery, relying instead on the power generated by the beating heart.
The nonlinearity of the device allows constant power to be generated across a wider range of frequencies (heartbeats per minute). The contractions of the heart are considered to be the base excitations of the device, causing the pendulum to swing. To validate and then optimize the design of the HRT system, the behavior and the power generation of the system will be studied under different parameters: size of generator, mass and length of pendulum components as well as frequency of heart beats (beats per minute). This presents an interesting design problem whose goal is to find the best HRT parameters that would result in generating the sufficient amounts of power required by pacemakers.
A method in approximating the nonlinear dynamics of the electro-mechanical energy harvesting system is also presented. By studying the analytical solutions to the nonlinear electromechanical system under a sine wave excitation, we can gain insight into the problem. The extent of this paper will only cover the analytical solution to the vertically excited pendulum. Perturbation methods, specifically the multiple scales method will be employed to study the effects of forcing amplitude and frequency on the system behavior and the energy harvesting system.