The resulting equation (2) contains two unknown values;
torque ripple harmonic (Tˆ(h) ) and the transfer function
between the torque and sensor input ( Hˆ (h) ). Both can be
estimated by solving (2) using the two sets of injected data
( ˆ ( )
1 C h and ˆ ( )
2 C h where ˆ ( )
1 C h = 0) and measured data sets
( ˆ ( )
1 M h and ˆ ( )
2 M h ). The effect of any noise in the system
can be reduced by taking data from multiple rotations of the
motor. Once the torque has been estimated, the inverse can
then be added to the constant set point as a new injected signal
( ˆ ( )
3 C h ). As long as the compensating harmonics are within
the bandwidth of the controller the result should be a reduction
in the torque ripple.