Capacitively coupled position encoder

• US 7,123,027 B2
• Filed: 06/22/2005
• Issued: 10/17/2006
• Est. Priority Date: 06/23/2004
• Status: Expired due to Fees

• Current Assignee: Fe Technical Services, Inc.
• Original Assignee: Fe Technical Services, Inc.
• Inventors: Tola, Jeffry, Brown, Kenneth A.
• Primary Examiner(s): Nguyen, Vincent Q.
• Assistant Examiner(s): NGUYEN, HOAI AN D
• Application Number:
  US11/158,778
• Publication Number:
  US 20060071672A1
• Time in Patent Office: 482 Days
• Field of Search: 324/662, 324/661, 324/660, 324/658, 324/686, 324/690, 33/1.PT, 33/1.N, 337/06, 337/07, 337/08, 340/870.37, 714/724, 341/11, 341/15
• US Class Current: 324/662
• CPC Class Codes: G01D 5/2415 adapted for encoders
• CPC Class Codes: G01D 5/2497 Absolute encoders G01D5/2454 takes precedence
• CPC Class Codes: H03M 1/26 with weighted coding, i.e. the weight given to a digit depends on the position of the digit within the block or code word, e.g. there is a given radix and the weights are powers of this radix

Abstract

One embodiment of the present invention includes a sensor with a face having several tracks spaced apart from one another. One of these tracks has a first electrode and a second electrode separated by an electrically nonconductive gap. Also included is a detection device extending across the tracks to receive signals by capacitive coupling. Sensor circuitry electrically coupled to the tracks and the detection device is structured to generate a first number of bits from a sequential signal pattern applied to the tracks in accordance with an established sequence. The circuitry is also structured to generate a second number of bits as a function of a first signal and a second signal. The first bits and second bits represent a position of the detection device along the tracks with the first bits being more numerically significant than the second bits.

Claims

1. Apparatus, comprising:

a first sensor member defining a number of tracks spaced apart from one another, the tracks each including a plurality of capacitive electrode segments, the segments being spaced apart from one another by a corresponding electrically nonconductive gap;

a second sensor member including a capacitive electrode, the electrode being spaced apart from the tracks and spanning across the tracks to correspondingly overlap one or more of the segments of each of the tracks; and

circuitry including an electrical signal source, logic, and a detection circuit, the source generating a signal pattern over a sequence of time periods, the signal pattern providing a changing voltage to each one of the segments of a respective one of the tracks during a respective one of the time periods, the detection circuit being electrically coupled to the electrode, the electrode being capacitively coupled to the one or more electrode segments of each of the tracks to detect a sequence of emitted signals corresponding to the signal pattern, the logic being responsive to the source and the detection circuit to determine information corresponding to position of the electrode relative to the tracks.

2. The apparatus of claim 1, wherein the circuitry is at least partially provided as a microprocessor and the logic is at least partially provided as programming instructions executable by the microprocessor.

3. The apparatus of claim 1, wherein at least a portion of the logic is of a hardwired discrete form and at least a portion of the circuitry is provided by dedicated circuit components.

4. The apparatus of claim 1, wherein the second member and the first member are coupled together by a rotational coupling structured to move at least one of the first member and the second member relative to another of the first member and the second member, the first member includes an electrically nonconductive substrate carrying each of the tracks, and the tracks each follow a generally circular path.

5. The apparatus of claim 4, wherein the segments for each respective one of the tracks are comprised of a first subset and a second subset, the segments of the first subset being coupled to a first electrical node and the segments of the second subset being coupled to a second electrical node, the first node is electrically connected to an inverting output of the source, the second node is electrically connected to a noninverting output of the source, and the segments of the first subset alternate with the segments of the second subset.

6. The apparatus of claim 4, wherein the tracks each have a different length and each correspond to a different one of a number of radii, the radii each extending from a common reference point and each having a different length.

7. The apparatus of claim 1, wherein the segments are comprised of metallization formed on a substrate, the segments of one of the tracks each have a length at least twice as long as each of the segments of another of the tracks, and quantity of the segments for each of the tracks is different.

8. The apparatus of claim 7, wherein the tracks each have a length that is approximately equal from one to another.

9. The apparatus of claim 1, wherein at least one of the second member and the first member is structured to move to change the position of the electrode relative to the tracks, the circuitry includes means for sequentially providing a first voltage waveform at a first time to a first one of the segments of a designated one of the tracks and a second voltage waveform at a second time to a second one of the segments of the designated one of the tracks, and the circuitry includes means for determining a first number of bits from the sequence of emitted signals and a second number of bits from detected signals generated in response to the providing means, the first bits being more significant than the second bits.

10. Apparatus, comprising:

A sensing device including a face defining a plurality of tracks electrically isolated from one another, a first one of the tracks including a first set of electrodes each spaced apart from another by a corresponding one of a first set of electrically nonconductive gaps and a second one of the tracks including a second set of electrodes each spaced apart from another by a corresponding one of a second set of electrically nonconductive gaps, the first set of electrodes including a first subset of the electrodes electrically coupled to a first electrical node and a second subset of the electrodes electrically coupled to a second electrical node, and the electrodes of the first subset and the electrodes of the second subset alternating with one another along the first one of tracks;

electrical signal circuitry including a noninverting output coupled to the first node and an inverting output coupled to the second node; and

an electrode device positioned opposite the face to capacitively couple to one or more of the electrodes of the first set and one or more of the electrodes of the second set, the electrode device being operable to provide signals corresponding to position of the electrode device relative to the tracks.

11. The apparatus of claim 10, wherein the first set of electrodes each has a greater length than each of the second set of electrodes and the first set of electrodes number fewer than the second set of electrodes.

12. The apparatus of claim 11, wherein each one of the first set of electrodes overlap at least two electrodes in the second set of electrodes and at least one of the gaps in the second set of gaps, and each one of the second set of electrodes overlap two electrodes in the first set of electrodes and a corresponding one of the gaps in the first set of gaps.

13. The apparatus of claim 10, wherein a third one of the tracks includes a third set of electrodes spaced apart from one another by a corresponding one of a third set of electrically nonconductive gaps, a fourth one of the tracks includes a fourth set of electrodes spaced apart from one another by a corresponding one of a fourth set of electrically nonconductive gaps, the first set of electrodes numbers more than the second set of electrodes, the second set of electrodes numbers more than the third set of electrodes, the third set of electrodes numbers more than the fourth set of electrodes, the fourth set of electrodes each extend along the fourth one of the tracks a greater distance than each of the third set of electrodes extends along the third one of the tracks, the third set of electrodes each extend along the third one of the tracks a greater distance than each of the second set of electrodes extends along the second one of the tracks, and the second set of electrodes each extend along the second one of the tracks a greater distance than each of first set of electrodes extends along the first one of the tracks.

14. The apparatus of claim 13, wherein track segmentation corresponds to a gray code pattern to encode the position of the detecting device relative to the tracks.

15. The apparatus of claim 10, wherein the tracks each have a different length and are concentric relative to one another.

16. The apparatus of claim 10, wherein the electrode device includes a generally continuous electrode spanning across the tracks and being structured to detect through capacitive coupling an emitted signal pattern corresponding to signals provided by the electric signal circuitry to the tracks, the emitted signal pattern being representative of the position of the detecting device relative to the tracks.

17. The apparatus of claim 10, wherein:

the second set of the electrodes includes a first electrode subset and a second electrode subset with members that alternate from one to another, the second set having a quantity of electrodes greater than the first set;

the signal circuitry includes means for simultaneously applying a first voltage waveform to each of the electrodes in the first subset and a second voltage waveform to each of the electrodes in the second subset, the second voltage waveform being approximately an inverted form of the first voltage waveform;

the signal circuitry includes means for sequentially providing a first changing voltage to a member of the first electrode set at a first time and a second changing voltage to the second electrode set at a second time after the first time; and

further comprising means for determining a coarse position based on a signal pattern provided with the electrode device in response to said simultaneously applying means and means for refining the coarse position based on another signal pattern provided with the electrode device in response to said sequentially providing means.