Sensors based on the anisotropic magnetoresistance effect are used in a growing number of automotive, consumer and industrial applications. The deciding factors for their use are their mechanical robustness due to the non-contact measurement principle, their large insensitivity to mechanical adjustment tolerances, their very large operating temperature range and a very high measurement accuracy that can be achieved at relatively low costs. In addition, they provide several features concerning the ability of error recognition and localization. In this paper, an AMR sensor is presented, which measures rotational angles with high precision and double redundancy, i.e. even if one sensor bridge breaks down, still an angular error can be calculated from the remaining sensor signals. Angular encoders based on the anisotropic magnetoresistance effect are often used to measure rotations with high accuracy. Using three instead of two Wheatstone bridges results in an improved performance with respect to the angular error. In addition, it provides double redundancy, i.e. a first error can be handled, a second error will be recognized. Equipped with an integrated planar coil, the sensor is further able to detect a full 360 period. Besides an improved error performance, three instead of two bridges provide signal redundancy on one chip. Using the half bridge signals for angle calculations even provides double redundancy: a first error can be detected and corrected and the occurrence of a second error can be detected. The correlation between the bridge amplitudes is used to identify malfunctioning bridge branches. As the main reported failures in automotive electronic systems contribute from faulty cables and connections, this redundancy covers the most probable failure.
Novel redundant magnetoresistive angle sensors
2006
4 Seiten, 2 Bilder, 5 Quellen
Aufsatz (Konferenz)
Englisch
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