Position detecting apparatus using multiple magnetic sensors for determining relative and absolute angular position

A position detecting apparatus, comprising:

• first magnetic sensing means for accurately determining the angular position of a rotor fixedly mounted on a shaft for rotation therewith, said first magnetic sensing means including first target means having repetitive incremental variations in the periphery thereof fixedly mounted on said shaft so as to be operatively associated with said rotor so as to rotate with said shaft and said rotor, first sensor means fixedly mounted in spaced relation to said first target means and disposed at a fixed distance from the peripheral variations independent of the absolute angular position of said rotor to define a first air gap therebetween, and first magnet means fixedly mounted in proximity to said first target means and said first sensor means to create a first magnetic field in said first air gap, said first sensor means cooperating with said first target means to accurately determine the relative angular position of said rotor by detecting repetitive incremental variations in said first magnetic field in said first air gap produced by said first target means as it rotates with said shaft;
• second magnetic sensing means for absolutely determining the angular position of said rotor, said second magnetic sensing means including second target means having a smooth continuous variation in the periphery thereof fixedly mounted on said shaft so as to be operatively associated with said rotor so as to rotate with said shaft and said rotor, second sensor means fixedly mounted in spaced relation to said second target means and disposed at a variable distance from the periphery thereof dependent upon the absolute angular position of said rotor to define a second air gap therebetween, and second magnet means fixedly mounted in proximity to said second target means and said second sensor means to create a second magnetic field in said second air gap, said second sensor means cooperating with said second target means to absolutely determine the angular position of said rotor by detecting smooth, uninterrupted continuous variations in said second magnetic field in said second air gap produced by said second target means as it rotates with said shaft;
• third magnetic sensing means for compensating for inaccuracies in the absolute angular position of said rotor as determined by said second magnetic sensing means, said third magnetic sensing means including third target means fixedly mounted on said shaft so as to be operatively associated with said rotor so as to rotate with said shaft and said rotor, third sensor means fixedly mounted in spaced relation to said third target means at a fixed distance therefrom independent of the absolute angular position of said rotor to define a third air gap therebetween, and third magnet means fixedly mounted in spaced relation to said third target means so as to be disposed in proximity to said third target means and said third sensor means to create a third magnetic field in said third air gap, said third sensor means cooperating with said third target means to compensate for inaccuracies in the absolute angular position of said rotor by detecting variations from a reference level for said third magnetic field in said third air gap;
• and
• means for monitoring output signals from each of said first, second and third sensor means, said output signals being proportional to variations in magnetic field strengths so as to be indicative of said first, second and third magnetic fields, said first sensor means producing an output signal for accurately determining each of a specific discrete plurality of accurate relative angular positions of said rotor, said second sensor means producing an output signal for approximately determining the approximate angular position of said rotor, said third sensor means producing an output signal for comparison with a signal representative of a reference level to detect variations therebetween, said monitoring means determining the accurate and absolute angular position of said rotor by combining all of said output signals.

A position detecting apparatus, comprising:

• first magnetic sensing means for accurately determining the angular position of a rotor fixedly mounted on a shaft for rotation therewith, said first magnetic sensing means including first target means having repetitive incremental variations in the periphery thereof fixedly mounted on said shaft so as to be operatively associated with said rotor so as to rotate with said shaft and said rotor, first sensor means fixedly mounted in spaced relation to said first target means and disposed at a fixed distance from the peripheral variations thereof independent of the absolute angular position of said rotor to define a first air gap therebetween, and first magnet means fixedly mounted in proximity to said first target means and said first sensor means to create a first magnetic field in said first air gap, said first sensor means cooperating with said first target means to accurately determine the relative angular position of said rotor by detecting repetitive incremental variations in said first magnetic field in said first air gap produced by said first target means as it rotates with said shaft;
• second magnetic sensing means for absolutely determining the angular position of said rotor, said second magnetic sensing means including second target means having a smooth continuous variation in the periphery thereof fixedly mounted on said shaft so as to be operatively associated with said rotor so as to rotate with said shaft and said rotor, second sensor means fixedly mounted in spaced relation to said second target means and disposed at a variable distance from the periphery thereof dependent upon the absolute angular position of said rotor to define a second air gap therebetween, and second magnet means fixedly mounted in proximity to said second target means and said second sensor means to create a second magnetic field in said second air gap, said second sensor means cooperating with said second target means to absolutely determine the angular position of said rotor by detecting smooth, uninterrupted continuous variations in said second magnetic field in said second air gap produced by said second target means as it rotates with said shaft;
• third magnetic sensing means for compensating for inaccuracies in the absolute angular position of said rotor as determined by said second magnetic sensing means, said third magnetic sensing means including third target means fixedly mounted on said shaft so as to be operatively associated with said rotor so as to rotate with said shaft and said rotor, third sensor means fixedly mounted in spaced relation to said third target means and disposed at a fixed distance therefrom independent of the absolute angular position of said rotor to define a third air gap therebetween, and third magnet means fixedly mounted in spaced relation to said third target means so as to be disposed in proximity to said third target means and said third sensor means to create a third magnetic field in said third air gap, said third sensor means cooperating with said third target means to compensate for inaccuracies in the absolute angular position of said rotor by detecting variations from a reference level for said third magnetic field in said third air gap;
• said first, second and third sensor means each producing output signals indicative of said first, second and third magnetic fields;
• and
• means for monitoring said output signals from each of said first, second and third sensor means, said monitoring means combining said output signals from said second and third sensor means to determine the absolute angular position of said rotor when stationary, said output signal from said second sensor means being indicative of an approximate angular position, said output signal from said third sensor means being comparable with a signal representative of said reference level for said third magnetic field to detect variations therebetween, said monitoring means combining said output signals to convert said approximate angular position into a compensated absolute angular position reading.