where t[n] is the time at n and t[n-1] is the time of the previous
sample, n-1. The speed data does not have a unity transfer
function to the torque as it is effected by the inertia and
viscous friction of the mechanical system of the motor. Again,
the magnitudes of the torque ripple at the 20th and 24th
harmonics are recorded for each step of the iterative algorithm.
For the third part of the experiment, a piece of air duct was
attached to the stator and the system adjusted to use data from
a microphone. The air duct was excited by the vibrations of the
torque ripple and the sound produced was sampled by the
microphone. The microphone used has a deviation of 1dB
from 5Hz to 7.5Hz and a deviation of 2dB from 3.5Hz to
10kHz. As with the first two parts of the experiment, the
magnitude of the torque ripple at the 20th and 24th harmonics
were recorded for each step of the iterative algorithm.