Problem Statement

Modern ASVs require 1–50W of continuous power for sensors and comms. While solar is powerful, it suffers from intermittency (night, clouds). Wind is consistent but low-density. Waves are the only energy source with 90% availability in open oceans.

However, the marine environment is hostile. Traditional harvesters with external moving parts succumb to biofouling and salt corrosion. The design requirement was clear: A fully enclosed, non-resonant system capable of harvesting ultra-low frequency (0.1–1.0 Hz) wave motion.

Ideation

Swinging

Spherical magnet array over copper coils

Rolling

Magnetic ball of magnets rolls over copper coils

Proof of Concept

I designed and fabricated simple testing rig constructed out of plywood with a magnet swinging over a stationary copper coil to demonstrate the effectiveness of this type of electromagnetic energy generator and to use as a benchmark for testing various coil configurations.

Dynamics & Lagrangian Mechanics

To optimize the system, I derived the nonlinear equations of motion using Lagrangian mechanics. The system couples the vessel's pitch angle $\alpha(t)$ with the ball's relative position $\beta(t)$.

Linearized Equation of Motion:

$$ \frac{7}{5}R\ddot{\beta} + \frac{(c_i + c_L)R}{m}\dot{\beta} + g\beta = -g\alpha - \kappa\ddot{\alpha} $$

This model revealed a critical "Null Point" at $d/R_i = 1.4$, where gravitational and inertial forces cancel out. Avoiding this geometric ratio was crucial for ensuring the ball actually moves under excitation.

Using MATLAB, we are bale to plot and visualize many properties of a system with a specific set of parameters

CAD

Design was completed using Onshape making use of Variable Studios to allow for configurability as parameters are changed and optimized.