Encoder signal analysis system for high-resolution position measurement

A method for identifying the position of a first member relative to a defined path;

• said path being defined by a second member;
• one of said first and second member providing a periodic field along at least a portion of said defined path, said method comprising the steps of:
• (a) providing an array of more than two spaced field sensors positioned at fixed locations with respect to the other of said first and second member not providing said periodic field and adjacent to at least a portion of said defined path, each of said field sensors sensing said portion of said periodic field at its fixed location and thereby generating a sensor signal in response thereto to provide a set of N sensor signals in a predetermined sequence associated with the position of said first member relative to said defined path, where N is greater than two;
• (b) providing a plurality of mathematically representative predetermined sensor signal models, each associated with a pre-identified position of said first member relative to said defined path;
• (c) comparing a mathematical representation of said set of N sensor signals to a first one of said plurality of mathematically representative predetermined sensor signal models associated with a first of said pre-identified positions to generate a correction signal;
• and
• (d) using said correction signal to generate an output position signal and to provide another one of said pre-identified positions associated with another one of said plurality of predetermined sensor signal models to be compared to said mathematical representation of said set of N sensor signals.

An apparatus for identifying the position of a first member relative to a defined path;

• said path being defined by a second member;
• one of said first and second member providing a periodic field along at least a portion of said defined path, said apparatus comprising:
• an array of spaced field sensors of number greater than two positioned at fixed locations with respect to the one of said first and second member not providing said periodic field and adjacent to at least a portion of said defined path, each of said field sensors sensing said portion of said periodic field at its fixed location and thereby generating a sensor signal in response thereto;
• a storage means comprising an addressable table comprising a plurality of mathematically representative predetermined sensor signal models, and a value for a pre-identified position associated with each predetermined sensor signal model;
• and
• a statistical interpolator comprising an error signal calculation module and an interpolation module;
• said error signal calculation module comprising a sensor signal processing circuit operably connected to said array for receiving said sensor signals, said sensor signal processing circuit generating a set of N sensor signals in a predetermined sequence associated with the position of said first member in response to said sensor signals, said error signal calculation module also operably connected to said storage means for selectively receiving said plurality of mathematically representative predetermined sensor signal models, said error signal calculation module further comprising a comparator for comparing a mathematical representation of said set of N sensor signals to at least one of said plurality of mathematically representative predetermined sensor signal models associated with one pre-identified position to generate a correction signal based on said set of N sensor signals, wherein said correction signal is determined by comparing said at least one of said plurality or mathematically representative predetermined signal models to said mathematical representation set of said set of N signals for every position of said first member relative to said defined path;
• and
• said interpolation module being operably connected to said error signal calculation module to receive said correction signal and to return an indexing signal associated with another pre-identified position to said error signal calculation module, said statistical interpolator programmed to use said correction signal to incrementally choose said another pre-identified position from said table as an approximation of the position of said first member in an iterative process to find the minimum correction signal and to thereby identify the position of said first member relative to said defined path.