Patent ID: 6144198
Filing Date: 2000-11-07
Classification: G01P,H02P

Abstract:
A system for determining rate of rotation, comprising:a brushless DC motor having a shaft driven to rotation and having windings disposed about said shaft wherein, when said shaft rotates, a back electromagnetic force (emf) is produced on each of said windings, said back-emf including information on rate of rotation of said shaft;a plurality of squaring circuits, each of said plurality of squaring circuits coupled directly to a corresponding one of said windings for squaring said back-emf associated therewith to produce a corresponding plurality of squared outputs;a combining circuit coupled to said plurality of squaring circuits for combining said plurality of squared outputs to produce a combined output; anda square root circuit coupled to said combining circuit for taking the square root of said combined output to produce a DC output proportional only to said rate of rotation of said shaft.