US 5,886,519 A · 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.

Claims21

Dependent claims

An inductive absolute position transducer, comprising:

a scale member;
a read head member, the read head member and the scale member movable relative to each other along a measurement axis;
a plurality of inductive position transducers, each inductive position transducer comprising:
a winding portion formed on a first one of the scale member and the read head member, the winding portion including at least one transmitter winding and at least one receiver winding, one of each at least one transmitter winding and each at least one receiver winding having at least one segment formed in a continuous periodic pattern of winding loops of alternating polarity to form a continuous spatially modulated inductive coupling between the at least one receiver winding and the at least one transmitter winding over at least a length of each segment, and
a scale portion formed on a second one of the scale member and the read head member, the scale portion including at least one flux modulator distributed on the scale member along the measurement axis and further modulating the continuous spatially modulated inductive coupling between the at least one receiver winding and the at least one transmitter winding based on a relative position between the read head member and the scale member,
wherein the continuous periodic pattern of winding loops of each inductive position transducer has a wavelength which is different than a wavelength of the continuous periodic pattern of winding loops of the other inductive position transducers;
and
a signal generating and processing circuit electrically connected to the winding portions of each of the plurality of inductive position transducers.

5 more elements

A method for determining an absolute position of a first member relative to a second member, comprising:

taking a first fine wavelength incremental position measurement between the first and second members;
taking a second fine wavelength incremental position measurement between the first and second members;
determining an absolute coarse position measurement between the first and second members from the first and second fine wavelength incremental position measurements;
taking a third fine wavelength incremental position measurement between the first and second members;
determining an incremental medium position measurement between the first and second members from the third fine wavelength incremental position measurement and one of the first and second fine wavelength incremental position measurements;
determining an incremental fine position measurement from one of the first, second and third fine wavelength incremental position measurements;
and
determining an absolute fine position measurement between the first and second members from the absolute coarse position measurement, the incremental medium position measurement and the incremental fine position measurement.

5 more elements

Dependencies are inferred from the claim text.

Multi-scale induced current absolute position transducer

Life of this patent

Multi-scale induced current absolute position transducer

Life of this patent

Abstract

Claims21