High resolution position measurement system

Abstract

A system for determining the cumulative position and periodic average velocity of a rotating body having an incremental encoder, operatively connected to the body, for generating a series of periodic signals indicative of rotation of the body. The system also includes a high frequency clock for generating clock pulses at a frequency greater than the maximum frequency of the encoder signal, and a timer for controlling the total time of a predetermined sample interval. Also included in the device is a counter for accumulating the number of integral encoder signal cycles that have been completed, an arithmetic logic unit for determining the size of a fractional portion of an encoder signal cycle that was completed between the last integral encoder cycle and the end of the sample interval. Subsequently, the number of integral encoder signal cycles is added to the fractional portion of an encoder cycle to determine the total number of encoder signal cycles completed, whereby the total is then multiplied by an encoder position conversion factor to determine the cumulative position of the rotating body or belt driven therefrom.