After 10 steps, the amplitude of the 20th harmonic has
been reduced to 2.1% of the initial value and the 24th to
2.1% as well. While the reduction in torque ripple when
using a torque sensor for feedback data is significant, in a
practical application this would mean adding an additional
and expensive sensor to your motor.
Part (b) of figure 3 shows the amplitude of the two
chosen critical harmonics for the first 10 steps of the
algorithm when the speed of the motor is used as feedback
data. The first two steps show a similar response to part (a).
At step 3, when the first estimate of the torque ripple is used
as compensation data, the amplitude of both harmonics are
reduced, however, to a lesser extent than part (a). In step 4,
the amplitudes reduce again as 3 sets of data are used to
estimate the torque ripple. For subsequent steps, more sets
of data are available and the amplitudes begin to converge
to their final values.