Harvesting energy from ambient vibration is a promising method for providing a continuous source of power for wireless sensor nodes. However, traditional energy harvesters are often derived from resonant linear oscillators which are capable of providing sufficient output power only if the dominant frequency of input vibrations closely matches the device resonant frequency. The limited scope of such devices has sparked an interest in the use of nonlinear oscillators as mechanisms for broadband energy harvesting. In this study, we investigate the harvesting performance of an electromagnetic harvester sustaining oscillations through the phenomena of magnetic levitation. The nonlinear behavior of the device is effectively modeled by Duffing’s equation, and direct numerical integration confirms the broadband frequency response of the nonlinear harvester. The nonlinear harvester’s power generation capabilities are directly compared to a linear electromagnetic harvester with similar dynamic parameters. Experimental testing shows that the presence of both high and low amplitude solutions for the nonlinear energy harvester results in a tendency for the oscillator to remain in a low energy state for non-harmonic vibration inputs, unless continuous energy impulses are provided. We conclude by considering future applications and improvements for such nonlinear devices.
With an emphasis on understanding fundamental concepts, students will learn to create and analyze mathematical models for mechanical and electromechanical systems that are changing in time. Equations of motion for 3D rigid bodies and systems will be derived using conservation of momentum and energy methods. Concepts involving equilibrium, linearization, and stability will be applied to study dynamic response in both the time and frequency domains through time-integration, transfer function, and state-space analysis. The idea of feedback control is introduced. Coursework and projects will involve examples such as robots, mechanisms, vehicles, and aircraft/spacecraft.