Patent ID: 7251444

Claim:
An apparatus for controlling a driving motor that drives a driving roller based on an output signal from an encoder attached to a driven roller, the apparatus comprising: an endless belt that is driven by the driving roller, the endless belt bearing a mark indicating a reference position and having a thickness of which variation is represented by a function of a phase, a maximum amplitude, and a period; a reference-position detector that detects the reference position by detecting the mark; a nonvolatile memory that stores the phase at the reference position, the maximum amplitude, and the period; a correction-value calculating unit that calculates a correction value for a position on the endless belt based on a thickness of the endless belt at the position, the thickness being determined by the phase, the maximum amplitude, and the period; a volatile memory that stores the correction value calculated; and a target-value calculating unit that reads out the correction value for the current position from the volatile memory based on a distance from the reference position to the current position, and adjusts a target value for controlling the driving motor based on the correction value to compensate for a variation in the output signal from the encoder due to the variation in the thickness of the endless belt.