Apparatus and method for low power position sensing systems

• US 6,469,499 B2
• Filed: 02/06/2001
• Issued: 10/22/2002
• Est. Priority Date: 02/06/2001
• Status: Expired due to Fees

• Current Assignee: Strattec Power Access LLC (Strattec Security Corporation)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Delaporte, Dany Paul
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): KINDER, DARRELL D
• Application Number:
  US09/777,327
• Publication Number:
  US 20020105319A1
• Time in Patent Office: 623 Days
• Field of Search: 324/207.13, 324/207.25, 49/28, 340/672
• US Class Current: 324/207.13
• CPC Class Codes: G01D 5/24476 Signal processing G01D5/2448 - G01D5/24495 take precedence
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01P 3/4815 using a pulse wire sensor, e.g. Wiegand wire

Abstract

A very low power quadrature position sensing system that includes a first sensor, which defines a starting point of a first channel. First sensor is coupled to a first square wave generator. A second sensor, in quadrature with first sensor, defining a starting point of a second channel, with second sensor coupled to a second square wave generator. The system further includes a moving member having a magnetized surface with a magnetic distribution disposed on the magnetized surface. The magnetized surface is sensed by the first sensor, and the second sensor during movement by the moving member, the first sensor generates a high signal forming a rising edge of a square wave generated by the first square wave generator and the first sensor generates a low signal forming a falling edge of a square wave generated by the first square wave generator, and during movement of the moving member, the second sensor generates a high signal forming a rising edge of a square wave generated by the second square wave generator and the second sensor generates a low signal forming a falling edge of the square wave generated by the second square wave generator. A method for very low power quadrature position sensing includes the determination of a first set of sensed signals using a first sensor and the determination of a second set of sensed signals using a second sensor. The method includes the derivation of a first sequence of square waves from the first set of sensed signals. The method further includes the derivation of a second sequence of square waves from the second set of sensed signals that are in quadrature with the first sequence of square waves. The method also includes the generation of a redundancy sequence signal using a redundancy circuit that comprises a switch.

Claims

1. A position sensing system, comprising:

a first sensor defining a starting point of a first channel with said first sensor coupled to a first square wave generator;

a second sensor, in quadrature with said first sensor, defining a starting point of a second channel with said second sensor coupled to a second square wave generator; and

a movable member having a magnetized surface having a magnetic distribution disposed on said magnetized surface for being sensed by said first sensor and said second sensor, said first sensor generates a high signal forming a rising edge of a square wave signal generated by said first square wave generator, and said first sensor generates a low signal forming a falling edge of said square wave signal generated by said first square wave generator during said movement of said movable member, said second sensor generates a high signal forming a rising edge of a square wave generated by said second square wave generator and said second sensor generates a low signal forming a falling edge of a square wave generated by said second square wave generator.

2. The position sensing system as in claim 1, further comprising:

a first signal transform circuitry having,

a first end coupled to said first sensor; and

a second end coupled to a first input of a first latch means.

3. The position sensing system as in claim 2, further comprising:

a second signal transform circuitry having,

a first end coupled to said second sensor; and

a second end coupled to a first input of a second latch means.

4. The position sensing system as in claim 3, wherein said first and said second signal transform circuitry include CMOS gates designed to be in the off non-active state until said first sensor and said second sensor generate voltage pulses.

5. The position sensing system as in claim 4, wherein said movable member is a shaft of an electric motor coupled to a liftgate of a vehicle, said electric motor providing an urging force for manipulating a position of said liftgate.

6. The position sensing system as in claim 2, wherein said first signal transform circuitry comprises a first NAND gate having an input and an output having said input coupled to said first sensor and said output coupled to said first input of said first latch means;

a second NAND gate having an input end and an output end, said NAND gate input end is coupled to said first sensor; and

a third NAND gate having an input end, and an output end, said third NAND gate output end is coupled to a second input end of said first latch means, said second NAND gate and said third NAND gate being connected in series having said output of said second NAND gate coupled to said input end of said third NAND gate, thereby said high signal being disposed to pass therethrough.

7. The position sensing system as in claim 2, further comprising:

a redundancy circuit coupled to said second sensor, said redundancy circuit including, a switch having an input end and an output end, said switch being switchably triggered by a signal derived from said second sensor acting upon said input end of said switch; and

an output of said redundancy circuit dependent upon a set of conditions at said input end of said switch with said output of said redundancy circuit being coupled to said output end of said switch.

8. The position sensing system as in claim 7, wherein said switch comprises a transistor.

9. The position sensing system as in claim 1, further comprising:

a controller coupled to said first square wave generator, said second square wave generator, and a redundancy circuit for controlling said position sensing system including counting a number of square waves generated by said first square wave generator, and counting a number of square waves generated by said second square wave generator.

10. The position sensing system as in claim 2, wherein, said first latch means comprises a set-reset latch.

11. The position sensing system as in claim 3, wherein, said second latch means comprises a set-reset latch.

12. The position sensing system as in claim 2, wherein, said first sensor is a zero power sensor capable of generating a voltage pulse as said magnetized surface moves with respect to said first sensor.

13. The position sensing system as in claim 2, wherein,said second sensor is a zero power sensor capable of generating a voltage pulse as said magnetized surface moves with respect to said second sensor.

14. The position sensing system as in claim 1, wherein said first sensor and said first square wave generator exhibit a total quiescent operation current of less than one milliampere.

15. The position sensing system as in claim 1, wherein said quiescent operation current is less than ten microamperes.

16. The position sensing system as in claim 1, wherein said second sensor and said second square wave generator exhibit a total quiescent operation current of less than one milliampere.

17. A position sensing system for a vehicle, comprising:

a first sensor defining a starting point of a first channel with said first sensor coupled to a first square wave generator;

a second sensor, in quadrature with said first sensor, defining a starting point of a second channel with said second sensor coupled to a second square wave generator; and

a moving member having a magnetized surface having a magnetic distribution disposed on said magnetized surface for being sensed by said first sensor, and said second sensor, said moving member being configured, dimensioned and positioned to move within a range defined by a first position and a second position, said first position corresponding to an open position of a vehicle door and said second position corresponding to a closed position of said vehicle door, and said moving member moves within said range as said vehicle door moves from said first position to said second position or moves from said second position to said first position, said first sensor generates a high signal forming a rising edge of a square wave signal generated by said first square wave generator and said first sensor generates a low signal forming a falling edge of said square wave signal generated by said first square wave generator, and during said movement by said moving member, said second sensor generates a high signal forming a rising edge of a square wave generated by said second square wave generator and said second sensor generates a low signal forming a falling edge of a square wave generated by said second square wave generator.

18. A position sensing system as in claim 17, wherein said vehicle door is a sliding door of a van.

19. The position sensing system as in claim 17, wherein said moving member is a shaft of an electric motor, said electric motor being configured and positioned to provide an urging force to said vehicle door.

20. The position sensing system as in claim 17, wherein said moving member is a hinge pin of said vehicle door.

21. The position sensing system as in claim 17, wherein the location of said first and second sensors in relation to the moving member at a starting position is n*(one period of the magnetic field)+¼

period of the magnetic field of said moving member, where n is the number of magnetic pole pairs.

22. A method for position sensing comprising:

generating a first set and a second set of output signals using a first and sensor and a second sensor, said first set and said second set of output signals generating a pulse waveform;

inputting said first set and said second set of output signals into a square wave generator;

deriving a first sequence of square waves from said first set of sensed signals; and

deriving a second sequence of square waves from said second set of sensed signals that are in quadrature with said first sequence of square waves; and

generating a redundancy sequence signal using a redundancy circuit comprising a switch.