Abstract

Apparatus for automatically tracking an endless belt or web of material in a stable, predetermined path of movement despite changes in the belt configuration due to differential belt stretching or the introduction into the machine of a new belt having a slightly different configuration. The apparatus includes a steering roller supported for rotational movement about the longitudinal central axis and tilting movement about an axis perpendicular to the longitudinal axis. In one embodiment, a steering roller control signal is produced by comparing the magnitude of the weighted sum of voltage signals representative of the lateral belt edge position and the tilted roller position with the magnitude of the integrated sum of the lateral belt edge position signal and a command signal representative of the desired lateral belt edge position. In a second embodiment, the steering roller control signal is produced by comparing the magnitude of the weighted sum of voltage signals representative of the lateral belt edge position and the instantaneous lateral belt deviation rate with the magnitude of the command signal representative of the desired lateral belt edge position.