Broad Frequency Vibration Energy Harvesting Control Approach Based on the Maximum Power Transfer Theorem

A control law for an electromagnetic vibration energy harvester is derived using the maximum power transfer theorem. Using regenerative electronics, the controller cancels the reactive portion of the harvester’s impedance by eliminating the effect of mechanical inertia and stiffness elements, and the coil’s electrical inductive element. The result is an energy harvester approach that captures more vibrational energy than a passive tuned harvester. It is shown that the controlled system acts like an infinite series of passive harvesters tuned to all frequency components within a certain frequency range. The control approach also avoids the delay and computational overhead of a Fast Fourier Transform as it does not require the explicit calculation of the excitation frequency. An experimental prototype harvester was built and characterized. The prototype’s multi-domain dynamics were modeled using bond-graph techniques, and its behavior as a passive harvester was experimentally validated. The prototype’s behavior under the proposed control method is simulated and compared to the passive case. It is shown that the proposed control method harvests more power for a range of excitation frequencies than the passive harvester.