Multi-scale induced current absolute position transducer

Abstract

An inductive absolute position transducer system, usable in high accuracy applications such as linear encoders, has two members movable relative to each other and includes three inductive position transducers. Each inductive position transducer includes at least one transmitter winding for generating a magnetic field and two or more receiver windings for receiving the magnetic field. Each inductive position transducer also includes a plurality of flux modulators which modulate the magnetic field generated by the transmitter winding. Each receiver winding has a plurality of symmetric loops arranged along a measurement axis. The receiver windings of two of the inductive position transducers define two wavelengths that are similar to each other, but not equal. Thus, a phase relationship between the inductive position transducers has a wavelength much longer than the wavelength of either of the two inductive position transducers. An electronic circuit coupled to the inductive position transducers determines the absolute position between the two members. In an alternative embodiment, the inductive absolute position transducer includes only one inductive position transducer, having a fine wavelength. The inductive absolute position transducer includes one or more inductive transducers with a relatively coarse wavelength. An electronic circuit coupled to the inductive position transducers determines the absolute position between the two members, first identifying a coarse absolute position measurement along the measuring axis using the relatively coarse wavelength transducer, and refining this position measurement using information from the inductive position transducer having a fine wavelength.