Extended accuracy flexured plate dual capacitance accelerometer

• US 7,296,470 B2
• Filed: 04/14/2005
• Issued: 11/20/2007
• Est. Priority Date: 04/14/2005
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Campbell, Ray F., Wada, Joan D., Quan, Patricia S.
• Primary Examiner(s): Kwok; Helen
• Application Number:
  US10/907,751
• Publication Number:
  US 20070220974A1
• Time in Patent Office: 950 Days
• Field of Search: 735/140.1, 735/143.2, 735/140.2, 735/10, 735/141.5, 735/141.8, 701/3, 701/1, 361/280, 361/283.3, 318/649
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

A flexure plate accelerometer system includes a flexure plate and two fixed plates on either side of the flexure plate. The flexure plate generates a flexure plate signal as a function of reference signals received in the fixed plates. A precision transformer generates the reference signals from a precision sine wave generated by a symbol generator controlled by a microprocessor. The microprocessor controls the symbol generator and activates an analog-to-digital converter in response to a signal coincident with a positive and negative peak of the precision sine wave. The analog-to-digital converter generates a digital word from the flexure plate signal, which is processed further in the microprocessor.

Claims

1. An accelerometer system comprising:

a housing;

a flexure plate system enclosed within said housing and comprising a first fixed plate, a second fixed plate spaced apart from and in parallel relation to said first fixed plate, and a flexure plate disposed between and in substantially parallel relation to said first fixed plate and said second fixed plate, wherein all the flexure plate system is generated within said flexure plate, and wherein said first fixed plate and said second fixed plate receive reference signals;

said flexure plate is rigidly fixed to said housing along at least an edge and electrically isolated from said housing, said flexure plate and the first fixed plate defining a first distance and a first capacitor and said flexure plate and said second fixed plate defining a second distance and a second capacitor, wherein said first and second distances vary in response to acceleration forces acting upon said flexure plate;

a symbol generator generating a precision sine wave at a known phase angle; and

a precision transformer receiving said precision sine wave and generating said reference signals therefrom.

2. The system of claim 1 further comprising a precision clock driving said symbol generator.

3. The system of claim 1, wherein said reference signals comprise a first signal having a positive polarity received in said first fixed plate and a second signal having a negative polarity received in said second fixed plate, and wherein said flexure plate divides a voltage between said first fixed plate and said second fixed plate as a function of acceleration and generates therefrom a flexure plate voltage signal.

4. The system of claim 3 further comprising an A/D converter receiving said flexure plate voltage signal and converting said flexure plate voltage signal to a digital word signal.

5. The system of claim 4, further comprising a microprocessor comprising a conversion clock coincident with a positive and negative peak of said precision sine wave and generating a convert signal for controlling said A/D converter.

6. The system of claim 5, wherein said convert signal commands said A/D converter to convert a peak value of said flexure plate voltage signal.

7. The system of claim 5 further comprising an amplifier adjusting an amplitude of said flexure plate voltage signal.

8. The system of claim 6 further comprising a heated structure mounted on said housing, wherein said amplifier is mounted on said heated structure.

9. The system of claim 1 further comprising microprocessor adapted to receive a flexure plate voltage signal and rectify said flexure plate voltage signal as a function of a said precision sine wave thereby generating a rectified waveform.

10. The system of claim 9, wherein said microprocessor further generates n-pole filtering for reducing clock jitter and general noise.

11. The system of claim 9, wherein said microprocessor co-adds data to reduce noise.

18. The system of claim 1 further comprising a computer activating an object control device in response to a first digital word.

12. An accelerometer system comprising:

a housing;

a flexure plate system enclosed within said housing and comprising a first fixed plate, a second fixed plate spaced apart from and in parallel relation to said first fixed plate;

a first flexure plate accelerometer rigidly fixed to said housing and electrically isolated from said housing wherein all the flexure plate system is generated within said first flexure plate accelerometer;

an amplifier adjusting an amplitude of a flexure plate signal from said first flexure plate accelerometer;

an analog-to-digital converter converting said flexure plate signal to a first digital word;

a symbol generator generating a precision sine wave at a known phase angle;

a precision transformer receiving said precision sine wave and generating reference signals therefrom, whereby said flexure plate signal is generated from said first flexure plate accelerometer as a function of said reference signals; and

a microprocessor comprising logic for controlling said symbol generator, said microprocessor further comprising logic activating said analog-to-digital converter in response to a signal coincident with a positive and negative peak of said precision sine wave, said microprocessor further comprising logic digitally filtering and rectifying said digital word, said microprocessor linearizing and co-adding said digital word.

13. The system of claim 12, wherein digitally filtering further comprises n-pole filtering.

14. The system of claim 12 further comprising:

a second accelerometer and a third accelerometer, wherein said second and third accelerometers are arranged with said first flexure plate accelerometer to receive cross axis thrust data.

15. The system of claim 14 further comprising:

a data bus adapted to receive acceleration signals from said first, second and third accelerometers, said data bus further adapted to exchange information with a computer.

16. The system of claim 15, wherein said first accelerometer is coupled to a yaw torque motor, said second accelerometer is coupled to a pitch torque motor, and said third accelerometer is coupled to a roll torque motor.

17. The system of claim 15 further comprising a precision heating device coupled to said housing adapted to reduce temperature gradients in said first flexure plate accelerometer.

19. A method for operating an accelerometer system having a flexure plate system comprising a first fixed plate, a second fixed plate spaced apart from and in parallel relation to the first plate, and a flexure plate disposed between and in substantially parallel relation to the first fixed plate and the second fixed plate wherein said flexure plate is rigidly fixed to a housing and electrically isolated from said housing and wherein all the flexure plate system is generated within said flexure plate, comprising:

accelerating the flexure plate;

generating a precision sine wave at a known phase angle;

generating reference signals as a function of said precision sine wave;

generating a flexure plate waveform from the flexure plate as a function of said reference signals being received by at least one of the first fixed plate and the second fixed plate;

activating analog-to-digital conversion of a flexure plate waveform in response to a signal coincident with a positive and negative peak of said precision sine wave; and

converting said flexure plate waveform signal to a digital word.

20. The method of claim 19 further comprising generating said reference signals through transforming said precision sine wave in a transformer.

21. The method of claim 19 further comprising adjusting an amplitude of said flexure plate waveform.

22. The method of claim 19 further comprising linearizing said digital word.

23. The method of claim 19 further comprising digitally filtering said digital word to rectify said digital word.

24. The method of claim 23, wherein digitally filtering further comprises n-pole filtering.

25. The method of claim 23 further comprising a co-adding said digital word.