US 7,022,975 B2Granted

Angular position sensor

AssigneeTRW LucasVarity Electric Steering Ltd.

InventorSteven John Horton

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Abstract

An angular position sensor (1) suitable for use in combination with the rotor of an electric motor comprising both absolute and incremental encoders (3) where a first signal of the absolute encoder produces a period corresponding to an electric revolution of the motor and less than a mechanical revolution of the rotor, a second output of the incremental encoder varies periodically over a complete revolution of the rotor, where the two signals provide sufficient information to determine the absolute mechanical position of the rotor. Typically, transitions in the first output signal combined with the state of the second output signal provide such information. Also, an angular position sensor (1) comprising an encoder mask (6) with at least one annular track (7) and at least two detectors arranged to detect the elements of the tracks, the detectors arranged such that area swept across each detector by a radius of the encoder mask is the same for each detector as the encoder mask (6) is rotated about a point at the centre of the annular track.

Claims39

Dependent claims

An angular position sensor suitable for use in combination with the rotor of an electrical motor comprising:

an absolute angular position encoder having a plurality of tracks of encoder elements and producing a first output signal having a period corresponding to an electrical revolution of said motor and less than a mechanical revolution of said rotor, said first output signal from said absolute position encoder changing state at a plurality of predetermined transition points within a period;
an incremental encoder having at least one track of encoder elements and producing a second output signal which varies periodically over a complete revolution of said rotor;
and
a common encoding mask including encoder tracks of each of said absolute and incremental encoders that comprise annular sets of tracks of encoding elements with which said absolute angular position encoder and said incremental encoder are constructed and arranged so that said first output signal from said absolute encoder and said second output signal from said incremental encoder provide sufficient information to produce a third output signal indicative of the absolute mechanical position of said rotor.

1 more element

Dependencies are inferred from the claim text.