Patent ID: 8653773

Claim:
In an imaging apparatus having a toner container, a method of adjusting a back EMF constant Ke used in a speed control system for a DC motor connected via a gear train to a rotatable toner metering device, the method comprising: storing an initial value for Ke; and during a motor calibration cycle: measuring a time of at least one rotation of the toner metering device; making a plurality of back EMF measurements of the DC motor; averaging the plurality of back EMF measurements; calculating an estimated speed of the DC motor using the initial value of Ke and the average value of the plurality of back EMF measurements; calculating an actual speed of the DC motor using the time of at least one rotation and a gear ratio of the connecting gear train; adjusting the stored value of Ke by multiplying the stored value of Ke by the ratio of the estimated speed to the actual speed; and storing the adjusted value of Ke in place of the previously stored value for Ke for the use in a next motor calibration cycle.