Abstract

A method for controlling lateral positioning of a longitudinally moving endless belt having at least two targets aligned with tolerances on a longitudinal fixed reference line, in which belt displacement from the fixed reference line is measured at least two times during each revolution of belt movement to provide a current value of measured displacement and at least one prior value of measured. The current value of measured displacement and the at least one prior value of measured displacement are averaged to provide a current average value of measured displacement and a current average value of measured displacement is calculated for each successive current value of measured displacement to provide a belt steering correction factor used to steer the belt as necessary to reduce the current average value of measured displacement to zero. Each of the targets is preferably an apertured pattern of N-shaped configuration formed in the belt. Apparatus for carrying out the method includes a steering roller about which a portion of said belt is trained, a yoke for supporting said steering roller for angular movement about a longitudinal axis, and a stepping motor/cam device for adjusting the angular position of said steering roller about said longitudinal axis.