System and method for determining rate of rotation using brushless DC motor
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsDavid E. Howard, Dennis A. Smith
Life of this patent
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Abstract
A system and method are provided for measuring rate of rotation. A brushless DC motor is rotated and produces a back electromagnetic force (emf) on each winding thereof. Each winding's back-emf is squared. The squared outputs associated with each winding are combined, with the square root being taken of such combination, to produce a DC output proportional only to the rate of rotation of the motor's shaft.
Claims8
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;
- and
- a 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.
A method of producing a DC output indicative of rate of rotation, comprising the steps of:
- providing a brushless DC motor having a shaft and windings disposed about said shaft;
- rotating said shaft wherein a back electromagnetic force (emf) is produced on each of said windings, said back-emf including information on rate of rotation of said shaft;
- squaring each said back-emf associated with each of said windings to produce a plurality of squared outputs;
- combining said plurality of squared outputs to produce a combined output;
- and
- obtaining the square root of said combined output to produce a DC output proportional only to said rate of rotation of said shaft.
Dependencies are inferred from the claim text.