US 5,675,129 A · Initial track recovery in position-sensing systems that use windowing patterns

Abstract

To determine the track of an element in terms of the components of its displacement parallel to a predetermined axis, the element is arranged to be movable relative to a pattern having pattern features which considered in directions parallel to said predetermined axis form a series exhibiting a windowing property. By sensing the pattern features traversed by the element and comparing window-length portions of this succession of features with a stored representation of the overall series of features, it is possible eventually to detect an initial location of the element along this series. Further movement of the element can then be tracked incrementally; however, there will generally be a substantial initial track portion preceding the first location fix. By keeping a record of the pattern features sensed during this initial track, it is possible to carry out a backtracking process to seek to recover this initial track, this process involving working backwards away from the first location fix and using, for example, an incremental tracking technique with provision for reversal recovery.

Claims14

Dependent claims

A method of determining the track of an element in terms of the components of its displacement parallel to a predetermined axis, said element being movable relative to a pattern having pattern features which considered in directions parallel to said predetermined axis form a series exhibiting a windowing property, said method involving:

sensing a succession of pattern features of said series traversed by the element in moving relative to said pattern, and storing a representation of said succession of features,
determining an initial location for said element along said predetermined axis by comparing window-length portions of the stored representation of said succession of features with a stored representation of said series, the detection of a match at any particular position along the stored representation of said series serving to determine the location of said element along said series, and
following the determination of said initial location, carrying out a backtracking process to seek to recover an initial track of the element over at least the pattern features of said succession that precede those of the window-length portion used in determining the initial location of the element.

Dependencies are inferred from the claim text.

Initial track recovery in position-sensing systems that use windowing patterns

Life of this patent

Initial track recovery in position-sensing systems that use windowing patterns

Life of this patent

Abstract

Claims14