Patent ID: 6958599

Claim:
An angular velocity sensor for detecting the an angular velocity of a rotor having an axis, the sensor comprising: at least two event generating means located at angularly spaced positions around the rotor; an angular position sensing means that is operative to produce a plurality of temporally spaced events as the rotor is rotated about its axis relative to said angular position sensing means, each event occurring as a respective event generating means passes said angular position sensing means, an event time measurement means that is operative to record the time at which said respective sensed temporally spaced events occur; an event position determining means including: a first means for determining an elapsed time taken for said rotor to complete a full revolution, a second means for determining the average velocity over said complete revolution from said elapsed time, a third means for determining the elapsed time between two events that occurred during said complete revolution, and a fourth means for determining the displacement of said rotor between said two events based upon said average velocity from said second means and said elapsed time from said third means; said event position determining means being operative to determine the angular position of the rotor at the time said events occur and to determine the relative angular position of said at least two event generating means from information previously obtained from said event time measurement means during at least one previous complete revolution of the rotor; and a velocity determining means that is operative to determine the average velocity of the rotor between two temporally spaced events based upon the measured times at which said events occur and the determined angular position of the rotor when said events occur, said velocity determining means further operative to determine a set of average velocity values with each of said average velocity values corresponding to a full revolution of the rotor and starting at the time of a different event with said event positioning means using said set of average velocity values to determine a relative position of those events that occur around half a revolution earlier in said corresponding full revolution.