SHAFT VELOCITY DETERMINED WITH BAR-CODE LABEL
Original Publication Date: 1992-Apr-30
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
It is commonly known to use a bar-coded label affixed to a moving element, to determine the movement of the element. Unfortunately, this technique has generally been limited to use in linear motion systems. The technique, while theoretically usable in the same manner as a disc encoder in a rotational motion system, has not been used in determining the velocity of a shaft, because of problems with accurately affixing the label on the shaft. These problems arise in affixing a precision label without a gap, overlap, or misalignment at the seam which would result in erroneous encoder output. Thus, minor variations in the shaft diameter, or the manner in which the label is affixed could easily result in the formation of a gap or overlap. As illustrated in Figure 1, shaft 12 has a label, 14, around its perimeter. However, the ends of label 14 do not meet, resulting in the formation of gap 16. Without accurate alignment of the ends of the label, there would be no way to use label 14 as an encoding means to determine the position and velocity of shaft 12, as there would be no encoder feedback over the gap region.