SYSTEM AND METHOD FOR POSITION SENSING

• US 20130057263A1
• Filed: 08/30/2012
• Published: 03/07/2013
• Est. Priority Date: 09/02/2011
• Status: Active Grant

• Current Assignee: Massachusetts Development Finance Agency (STATE OF MASSACHUSETTS)
• Original Assignee: Persimmon Technologies Corporation (Sumitomo Heavy Industries Limited)
• Inventors: Hosek, Martin
• Granted Patent: US 9,222,804 B2
• Time in Patent Office: Days
• US Class Current: 324/207.18
• CPC Class Codes: G01D 5/2266 specially adapted circuits therefor

Abstract

A system for position sensing includes an incremental track including a plurality of sectors and a measurement subsystem. The measurement subsystem includes at least two differential read-heads each having at least one primary coil and at least two differential secondary coils, the at least two differential secondary coils of one of the at least two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track and the at least two differential secondary coils of the other of said two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track.

Claims

1. A system for position sensing comprising:

an incremental track including a plurality of sectors;

a measurement subsystem including;

at least two differential read-beads each having at least one primary coil and at least two differential secondary coils, the at least two differential secondary coils of one of the at least two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track and the at least two differential secondary coils of the other of said two differential read-heads configured to generate output signals having their amplitudes modulated by the sectors of the incremental track.

2. The system of claim 1 wherein the measurement subsystem further comprises a device configured to:

determine the amplitudes of each of output signals having their amplitudes modulated by the sectors of the incremental track,

determine substantially sinusoidal signals and substantially cosine signals with respect to a position of the sectors of the incremental track, and

determine the position of the track using the substantially sinusoidal signals and the substantially cosine signals.

3. The system of claim 1 in which the differential secondary coils of each of the two differential read heads are connected in reverse series.

4. The system of claim 2 in which the differential secondary coils of each of the two differential read heads are independently connected to the device.

5. The system of claim 2 in which the device is configured to determine the angular position of the track independent of the amplitudes of the output signals.

6. The system of claim 2 in which said differential read-heads are configured to determine the position irrespective of a change in a predetermined condition.

7. The system of claim 2 further comprising an absolute track having a pattern of non-uniform sections, the absolute track coupled to the incremental track, the plurality of sensors configured to determine the position by detecting transitions of the non-uniform sections.

8. The system of claim 1 further including a barrier between the incremental track and the measurement subsystem, the barrier configured to isolate said measurement subsystem from an external environment.

9. A system for position sensing comprising:

an incremental track including a plurality of sectors;

a measurement subsystem including

at least two differential read-heads each having at least one primary coil and at least two secondary coils, the at least two secondary coils of one of the at least two differential read-heads configured to generate output signals having substantially sinusoidal signed amplitudes based on a differential measurement between the secondary coils with respect to a position of the incremental track and the at least two secondary coils of the other of said two differential read-heads configured to generate output signals having substantially cosine signed amplitudes based on a differential measurement between the secondary coils with respect to the position of the track.

10. The system of claim 9 wherein the measurement subsystem further comprises a device configured to determine substantially sinusoidal signals and substantially cosine signals based on the output signals having substantially sinusoidal signed amplitudes and the output signals having substantially cosine signed amplitudes and configured to determine the position of the track using the substantially sinusoidal signals and the substantially cosine signals.

11. The system of claim 9 in which the secondary coils of each of the two differential read heads are connected in reverse series.

12. The system of claim 9 in which the secondary coils of each of the two differential read heads are independently connected to the device.

13. The system of claim 9 in which the device is configured to determine the angular position of the track independent of the amplitudes of the output signals having substantially sinusoidal signed amplitudes and the output signals having substantially cosine signed amplitudes.

14. The system of claim 9 in which said differential read-heads are configured to determine the position irrespective of a change in a predetermined condition.

15. The system of claim 9 further comprising an absolute track having a pattern of non-uniform sections, the absolute track coupled to the incremental track, the plurality of sensors configured to determine the position by detecting transitions of the non-uniform sections.

16. The system of claim 9 further including a barrier between the incremental track and the measurement subsystem, the barrier configured to isolate said measurement subsystem from an external environment.

17. A method for position sensing, the method comprising:

providing an incremental track including a plurality of sectors;

providing at least two differential read heads, each having at least one primary coil and at least two differential secondary coils;

generating output signals having their amplitudes modulated by the sectors of the incremental track by the at least two differential secondary coils of one of the at least two differential read heads; and

generating output signals having their amplitudes modulated by the sectors of the incremental track by the other of said two differential read heads.

18. The method of claim 17 further including the step of determining the amplitudes of each of the output signals having their amplitudes modulated by sectors of the incremental track, determining substantially sinusoidal signals and substantially cosine signals with respect to a position of the sectors of the incremental track, and determining the position of the track using the substantially sinusoidal signals and the substantially cosine signals.

19. The method of claim 17 further including connecting the differential secondary coils of each of the two differential read heads in reverse series.

20. The method of claim 17 further including the step of independently connecting each of the two differential read heads of the differential secondary coils of each of the two differential read heads to a device.