Dimension Y was initially fixed at 1mm and X was varied
between 1 and 3 mm. The optimum X dimension occurs
between 2 and 3 mm. Since, for a given volume, increasing
magnet width causes a reduction in the size of the proof mass,
dimension X was therefore limited to 2.5 mm. Given this value
for X, the subsequent simulations adjusted the Y dimension,
again between 1 and 3 mm. The simulation results again show
an improvement with an increase in magnet size. The optimum
practical dimension for Y was identified as 2 mm. The
optimum magnet size of 2.5x2x1.5mm produces 120 mVrms
compared to 52 mVrms for a generator with 1x1x1.5 mm size
magnets (see figure 3). This is a factor of improvement of 2.5
in the open circuit voltages (see figure 4) whilst maintaining the
volume of the cantilever generator within practical limits.