Inductive position sensor with common mode corrective winding and simplified signal conditioning

• US 20060233123A1
• Filed: 04/06/2006
• Published: 10/19/2006
• Est. Priority Date: 04/07/2005
• Status: Active Grant

• Current Assignee: KSR IP Holdings, LLC
• Original Assignee: KSR International Company
• Inventors: Lee, Joong K.
• Granted Patent: US 7,221,154 B2
• Time in Patent Office: Days
• US Class Current: 370/295
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence

Abstract

An inductive position sensor for rotary motion includes a transmitter coil and a receiver coil, the receiver coil generating a receiver signal when the transmitter coil is excited by an alternating current source. A moveable coupler element modifies the inductive coupling between the transmitter coil and the receiver coil so that the receiver signal is sensitive to the coupler element position. The ratio between the receiver signal and the reference signal is sensitive to the coupler element position, but substantially insensitive to common mode factors. The angular or positional range of the position sensor can be increased using a plurality of receiver coils.

Claims

1. An apparatus for providing an output signal correlated with a part position for a moveable part, the part position having a positional range, the positional range being divisible into segments, the apparatus comprising:

a transmitter coil, the transmitter coil generating electromagnetic radiation when excited by an exciter signal;

a plurality of receiver coils located proximate to the transmitter coil, each receiver coil generating a receiver signal when the transmitter coil is excited due to inductive coupling between the transmitter coil and the receiver coils;

a coupler element, having a coupler element position correlated with the part position, the inductive coupling between the transmitter coil and each receiver coil being sensitive to the coupler element position;

a reference coil, providing a reference signal substantially independent of the part position;

a signal conditioner receiving the receiver signals and the reference signal, and providing an output signal correlated with the position of the moveable part,

the output signal being derived from a selected receiver signal, the selected receiver signal being selected according to the segment of the positional range,

the signal conditioner including an analog divider, the selected receiver signal being divided by the reference signal in the analog divider so as to eliminate common mode noise effects from the output signal.

2. The apparatus of claim 1, wherein the output signal is derived from a first receiver signal over a first segment of the positional range, and from a second receiver signal over a second segment of the positional range.

3. The apparatus of claim 1, wherein the selected receiver signal is selected from a set of non-inverted receiver signals and inverted receiver signals.

4. The apparatus of claim 1, wherein the output signal has a substantially linear dependence on part position over the positional range,

the output voltage being adjusted by an adjustment value according to the segment of the positional range.

5. The apparatus of claim 1, wherein the signal conditioner includes a logic unit comprising a digital electronic circuit, segment information being stored in the logic unit.

6. The apparatus of claim 5, wherein the output voltage is adjusted by an adjustment voltage, the adjustment voltage being generated by a digital-to-analog converter according to the segment information stored in the logic unit.

7. The apparatus of claim 5, wherein the signal conditioner further includes a selector, the selector selecting a receiver signal according to the segment information stored in the logic unit.

8. The apparatus of claim 5, wherein segment information is determined from a comparison of receiver signals.

9. The apparatus of claim 5, wherein calibration data is storable in the logic unit,

the calibration data being used to modify the output signal to a desired form.

10. The apparatus of claim 9, wherein the signal conditioner further includes a calibration digital-to-analog converter, receiving calibration data stored in the logic unit and generating a voltage adjustment applied to the output voltage.

11. The apparatus of claim 1, wherein the plurality of receiver coils are substantially coplanar.

12. The apparatus of claim 11, wherein the plurality of receiver coils and the reference coil are formed on a single circuit board.

13. The apparatus of claim 1, wherein the single circuit board further supports an analog ASIC, the analog ASIC including the analog divider and phase sensitive rectifiers for each receiver signal and the reference signal.

14. The apparatus of claim 1, wherein the part position is an angular position, the coupler element rotating about a coupler axis.

15. The apparatus of claim 1, wherein the positional range is a rotation of theta degrees, the output signal having a sawtooth dependence on rotation angle with a period of theta degrees.

16. The apparatus of claim 15, wherein theta is 360.

17. The apparatus of claim 14, wherein the part position is a position of a pedal, movement of the pedal being mechanically coupled to the angular position of the coupler element.

18. The apparatus of claim 17, wherein the output signal is a speed control for an engine.

24. The apparatus of claim 1, wherein the signal conditioner includes a logic unit that keeps track of segment information using a memory stack,

selection of the receiver signal depending on the segment information.

19. An apparatus for providing an output signal correlated with a part position for a moveable part, the part position having a positional range, the apparatus comprising:

a transmitter coil, the transmitter coil generating electromagnetic radiation when excited by an exciter signal;

a first receiver coil providing a first receiver signal;

a second receiver coil producing a second receiver signal;

a coupler element, having a coupler element position correlated with the part position, the an inductive coupling between the transmitter coil and each receiver coil being sensitive to the coupler element position; and

a reference coil, providing a reference signal substantially independent of the coupler element position; and

a signal conditioner, receiving the first and second receiver signals and providing an output signal correlated with the position of the moveable part,

the output signal being derived from the first receiver signal over a first segment of the positional range, and from the second receiver signal over a second segment of the positional range.

20. The apparatus of claim 19, wherein the first receiver signal has a substantially linear dependence on part position over the first segment,

the second receiver signal having a substantially linear dependence on part position over the second segment.

21. The apparatus of claim 19, wherein the first and second receiver coils are configured so that the first and second receiver signals are approximately 90 degrees out of phase.

22. The apparatus of claim 19, wherein the output signal is derived from the first receiver signal over a first segment of the positional range, from the second receiver signal over a second segment of the positional range, from an inverted first receiver signal over a third segment of the positional range, and from an inverted second receiver signal over a fourth segment of the positional range.

23. The apparatus of claim 19, wherein the first and second receiver coils, the reference coil, and the signal conditioner are formed on a single printed circuit board.

25. A method of determining the position of a moveable part, the method comprising:

exciting a transmitter coil;

obtaining a plurality of receiver signals from a plurality of receiver coils;

selecting a chosen receiver signal according to the approximate position of the moveable part;

obtaining a reference signal substantially independent of the position of the moveable part, the reference signal and the chosen receiver signal being subject to common noise factors;

dividing the selected receiver signal by the reference signal in an analog divider circuit to provide a ratiometric signal so as to eliminate the common noise factors; and

determining the position of the moveable part using the ratiometric signal.

26. The method of claim 25, selecting a receiver signal according to the approximate position of the moveable part comprises selecting a receiver signal from which an output signal having a substantially linear dependence on position can be determined,

the approximate position being part of a positional range of the moveable part.