IR compensation is what provides the speed regulation of the control. When the load on a PMDC motor increases, the amount of current that the motor draws also increases. Per the performance characteristics of permanent magnet DC motors, an increase in load will cause a decrease in speed, because of the negative correlation between speed and torque (see speed-torque curve below). The IR compensation increases the voltage going to the motor, thus compensating for changes in the load, in order to maintain a constant speed at the end-user’s setting regardless of load variations.