Encoder eccentricity correction for motion control systems

A method of correcting encoder eccentricity in an image forming device that uses feedback signals from a rotary encoder to control speed and position of the rotary encoder, the method comprising:

• positioning a first encoder sensor and a second encoder sensor at different positions about an encoder wheel;
• determining a first speed count and a second speed count by counting a number of clock cycles that elapse per cycle of a pulse train received from the first encoder sensor and the second encoder sensor, respectively;
• determining a first position count by counting a number of clock cycles that elapse between a periodic command pulse and a transition of the pulse train received from the first encoder sensor;
• calculating a corrected speed count based upon an average of the first speed count and the second speed count;
• calculating a corrected position count based at least partly on the first position count;
• and
• maintaining a substantially constant value for the corrected speed count and for the corrected position count by adjusting the speed of the rotary encoder to effect speed and position control of the encoder wheel.

A method of correcting encoder eccentricity in an image forming device that uses encoder feedback signals to generate speed and position counts to control the speed and position of a rotary encoder, the method comprising:

• receiving a plurality of pulse trains indicative of the speed of the rotary encoder;
• receiving a clocking signal having a frequency greater than the pulse trains;
• generating a series of periodic sampling points;
• calculating a corrected speed count by averaging a first speed count and a second speed count, the first speed count and the second speed count determined by counting a number of cycles of the clocking signal that elapse per cycle of pulse trains received from rotary encoder sensors that are disposed about an encoder disc, substantially 180 rotary degrees apart from one another, respectively;
• and
• adjusting the speed of the rotary encoder and maintaining a substantially constant value for the corrected speed count to effect speed control.