Absolute electromagnetic position encoder

Patent metadata

Field	Value
Publication number	US-9835473-B2
Application number	US-201615087679-A
Country	US
Kind code	B2
Filing date	Mar 31, 2016
Priority date	Mar 15, 2016
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

An absolute electromagnetic position encoder comprises a readhead and an absolute scale. The readhead comprises field generation and detection configuration and a readhead processor. The absolute scale comprises an active periodic signal pattern, an active absolute signal pattern, and timing and activation circuitry connected to the active signal pattern. During an energy transfer cycle, the timing and activation circuitry is configured to receive and store energy from the readhead. During a first signal generating cycle, the timing and activation circuitry is configured to drive the periodic spatially modulated signal generating element in order to generate first cycle spatially periodic signals in the first cycle field detector. During a second signal generating cycle, the timing and activation circuitry is configured to drive the first spatially modulated signal generating element in order to provide at least one corresponding second cycle signal in the readhead. The readhead processor is configured to determine an absolute position of the readhead relative to the absolute scale based on at least the second cycle signal and the first cycle spatially periodic signals.

First claim

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An absolute electromagnetic position encoder, comprising:
a readhead, comprising:
a field generation and detection configuration; and
a readhead processor connected to the field generation and detection configuration, and configured to operate the field generation and detection configuration as a field generator to provide an energy transfer cycle, and to operate the field generation and detection configuration as a first cycle field detector to provide a first signal generating cycle and to operate the field generation and detection configuration as a second cycle field detector to provide a second signal generating cycle; and

an absolute scale extending along a measuring axis of the position encoder, the readhead being movable relative to the absolute scale along the measuring axis, the absolute scale comprising:
an active periodic signal pattern comprising a periodic spatially modulated signal generating element that extends along the measuring axis and has a first wavelength and is configured to generate a corresponding periodic spatially modulated field that couples to the readhead to generate spatially periodic signals in the first cycle field detector as a function of readhead position relative to the absolute scale along the measuring axis; and
an active absolute signal pattern comprising at least a first spatially modulated signal generating element configured to generate a corresponding spatially modulated field that couples to the readhead to provide at least one corresponding signal in the second cycle field detector that exhibits a unique relationship with the spatially periodic signals for each unique readhead position relative to the absolute scale within a first absolute range that exceeds the first wavelength of the periodic spatially modulated signal generating element, wherein:
the absolute scale further comprises timing and activation circuitry connected to the active absolute signal pattern and the active periodic signal pattern;
the absolute electromagnetic position encoder comprises an energy transfer cycle configuration that is used to provide an energy transfer cycle wherein, during the energy transfer cycle, the readhead processor is configured to energize a winding of the field generation and detection configuration to operate as a field generator and generate an energy transfer cycle field, and at least one of the signal generating elements of the absolute scale couples to the energy transfer cycle field and provides energy to the timing and activation circuitry, and the timing and activation circuitry is configured to receive and store energy during the energy transfer cycle;
the absolute electromagnetic position encoder comprises a first signal cycle configuration that is used to provide a first signal generating cycle wherein, during the first signal generating cycle, the timing and activation circuitry is configured to drive the periodic spatially modulated signal generating element to generate a corresponding periodic spatially modulated first cycle field, and the first cycle field detector couples to the periodic spatially modulated first cycle field to generate first cycle spatially periodic signals in the first cycle field detector;
the absolute electromagnetic position encoder comprises a second signal cycle configuration that is used to provide a second signal generating cycle wherein, during the second signal generating cycle, the timing and activation circuitry is configured to drive the first spatially modulated signal generating element to generate a corresponding spatially modulated second cycle field, and the second cycle field detector couples to the spatially modulated second cycle field and provides a corresponding second cycle input to the readhead processor, and during the second signal generating cycle the readhead processor is configured to receive the second cycle input and provide at least one corresponding second cycle signal in the readhead that exhibits a unique relationship with the first cycle spatially periodic signals and is indicative of a unique position within the first absolute range; and
the readhead processor is further configured to determine an absolute position of the readhead relative to the absolute scale based on at least the second cycle signal and the first cycle spatially periodic signals.

2. The absolute electromagnetic position encoder of claim 1 , wherein:
the readhead processor is configured to operate the field generation and detection configuration as a third cycle field detector to provide a third signal generating cycle;
the active absolute signal pattern comprises a second spatially modulated signal generating element configured to generate a corresponding spatially modulated field that couples to the readhead to provide at least one corresponding signal in the third cycle field detector that exhibits a unique relationship with the spatially periodic signals for each unique readhead position relative to the absolute scale within a first absolute range that exceeds the first wavelength of the periodic spatially modulated signal generating element; and
the absolute electromagnetic position encoder comprises a third signal cycle configuration that is used to provide the third signal generating cycle wherein, during the third signal generating cycle, the timing and activation circuitry is configured to drive the second spatially modulated signal generating element to generate a corresponding spatially modulated third cycle field, and the third cycle field detector couples to the spatially modulated third cycle field and provides a corresponding third cycle input to the readhead processor, and during the third signal generating cycle the readhead processor is configured to receive the third cycle input and provide at least one corresponding third cycle signal in the readhead that exhibits a unique relationship with the first cycle spatially periodic signals and is indicative of a unique position within the first absolute range; and
the readhead processor is further configured to determine an absolute position of the readhead relative to the absolute scale based on at least the second cycle signal, the third cycle signal and the first cycle spatially periodic signals.

3. The absolute electromagnetic position encoder of claim 2 , wherein:
the readhead processor is configured to determine a value A for the second cycle signal and a value B for the third cycle signal; and
the readhead processor is configured to determine a processed signal (A−B)/(A+B) which is indicative of a unique position in the first absolute range.

4. The absolute electromagnetic position encoder of claim 2 , wherein the second cycle field detector and the third cycle field detector are provided by the same element of the field generation and detection configuration.

5. The absolute electromagnetic position encoder of claim 2 , wherein:
generating the second cycle periodic signal is initiated after generating the first cycle periodic signals; and
generating the third cycle periodic signal is initiated after generating the first cycle periodic signals.

6. The absolute electromagnetic position encoder of claim 2 , wherein the first spatially modulated signal generating element and the second spatially modulated signal generating element have substantially the same shape, but the shape of one is flipped relative to the other about the measuring axis and an axis perpendicular to the measuring axis.

7. The absolute electromagnetic position encoder of claim 1 , wherein generating the second cycle periodic signal is initiated after generating the first cycle periodic signals.

8. The absolute elec

Assignees

• Mitutoyo Corp

Inventors

• Nahum Michael

Classifications

• G01D5/2006 Primary

  by influencing the self-induction of one or more coils (G01D5/22 takes precedence) · CPC title

• G01D5/2451

  Incremental encoders (G01D5/2454 takes precedence) · CPC title

• G01D5/2086 Primary

  by movement of two or more coils with respect to two or more other coils · CPC title