Contactless angular position sensor and method for sensing angular position of a rotatable shaft

A contactless angular position sensor comprising:

• a shaft rotatable through a first rotational angle;
• a gear train having an input connected for rotation responsive to rotation of the shaft and an output responsive to rotation of the input according to a rotational ratio therebetween;
• a single-turn annular magnet connected for rotation with one of the input and the output of said gear train for maximum rotation of 360 degrees associated with rotation of the shaft through said first rotational angle;
• a multi-turn annular magnet connected for rotation with the other of the input and the output of said gear train for multiple rotations degrees associated with said maximum rotation of the single-turn magnet;
• the magnets each having two poles spaced 180 degrees apart to establish to establish a periodic variation in magnetic field intensity as the magnets rotate;
• a pair of magnetic field sensors associated with each of the magnets, the magnetic field sensors being positioned to sense the periodic variation of the magnetic field as the magnets rotate and having output signals indicative of the magnetic fields sensed and phase-shifted 90 degrees from one another;
• and
• a signal processing block receiving said output signals and operative to compute the angular position of said magnets therefrom, and to provide a resultant signal indicative of the rotational angle of the shaft as a function of the rotational ratio of the gear train and the computed angular positions of the magnets.

A contactless angular position sensor comprising:

• a shaft rotatable through a fractional rotation of a turn;
• a first, step-up gear train having an input element connected for rotation with the shaft and an output element connected for rotation responsive to rotation of said input element according to a rotational ratio therebetween of greater than one and less than or equal to 360 divided by the angle associated with said fractional rotation;
• a first magnet connected for rotation with said output element for a maximum of one rotation associated with said fractional rotation of the shaft;
• a second, step-up gear train having an input connected for rotation with said first magnet and an output connected for rotation responsive to rotation of said input according to a step-up rotational ratio therebetween whereby said output rotates through multiple revolutions for a single revolution of the first magnet,
• a second magnet connected for rotation with the output of said second gear train;
• first and second stationary magnetic field sensors positioned to measure the magnetic flux of the first and second magnets, respectively, as they rotate, said first and second sensors having respective output signals indicative of the magnetic fields sensed;
• and
• a microprocessor-based circuit receiving said output signals and operative to compute the angular positions of the magnets therefrom and to provide a resultant signal indicative of the rotational angle of the shaft as a function of said rotational ratios and the computed angular positions of the magnets.

A contactless angular position sensor comprising:

• a shaft rotatable through multiple turns to a maximum rotational angle;
• a first, step-down gear train having a rotational input element connected for rotation with the shaft and a rotational output element operatively responsive to rotation of the input element according to a step-down rotational ratio therebetween;
• a first magnet connected for rotation with the output element of said gear train;
• a second, step-down gear train having an input connected for rotation with said first magnet and an output connected for rotation responsive to rotation of said input according to a step-down rotational ratio therebetween;
• a second magnet connected for rotation with the output of the second gear train;
• relationship with rotation of the shaft;
• the rotational ratios of the gear trains being further characterized as establishing a maximum of one rotation of the second magnet associated with the maximum rotational angle of the shaft;
• first and second stationary magnetic field sensors positioned for measuring the magnetic flux of the first and second magnets, respectively, as they rotate, said first and second sensors having respective output signals indicative of the magnetic fields sensed;
• and
• a microprocessor-based circuit receiving said output signals and operative to compute the angular positions of the magnets therefrom and to provide a resultant signal indicative of the rotational angle of the shaft as a function of the rotational ratios and the computed angles of the magnets.

A method for sensing angular position comprising the steps of:

• A) providing a shaft rotatable through a maximum rotational angle,
• B) dividing an approximate maximum rotational angle associated with said maximum rotational angle of the shaft into multiple segments of equal angular rotation less than 360 degrees;
• C) further providing a rotary signal generator having first and second rotating magnetic field elements responsive to rotation of the shaft and operative to provide a first periodic signal indicative of the angular position of the shaft through said approximate maximum angular rotation, and a second periodic signal indicative of the angular position of the shaft in each of said angular segments, respectively;
• D) determining in which one of said angular segments the shaft is in from said first signal, and the angular position of the shaft in said one determined angular segment from said second signal;
• and
• E) establishing a resultant signal indicative of the rotational angle of the shaft as a function of the ratio between said approximate maximum rotational angle and said one angular segment, and the angular positions of the shaft from said determining step.

A method for sensing angular position comprising the steps of:

• A) providing a shaft rotatable through a maximum rotational angle,
• B) dividing the maximum rotational angle of the shaft into multiple segments of equal angular rotation;
• B) further providing a first sinusoidal signal indicative of the angular position of the shaft through said maximum rotational angle, and a second sinusoidal signal indicative of the angular position of the shaft in each of said segments of angular rotation;
• C. determining in which one of said angular segments shaft is in from said first signal, and the angular position of the shaft in said one angular segment portion from said second signal;
• and
• D. establishing a resultant signal indicative of the rotational angle of the shaft as a function of the ratio of said maximum rotation and said one angular segment, and the angular position of the shaft from said determining step.