Gyroscope noise reduction and drift compensation

• US 5,795,988 A
• Filed: 07/01/1996
• Issued: 08/18/1998
• Est. Priority Date: 07/01/1996
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Geoca, Eric, Lo, Pei-hwa, Halatyn, Peter, Archibald, James B.
• Primary Examiner(s): Oda, Christine K.
• Application Number:
  US08/674,389
• Time in Patent Office: 778 Days
• Field of Search: 73/504.02, 73/503.3, 73/504.04, 73/504.12, 73/1.77, 73/1.78, 73/1.76, 364/454, 74/5.6 D
• US Class Current: 73/1.77
• CPC Class Codes: F41G 5/16 gyroscopically influenced
• CPC Class Codes: G01C 19/42 for indicating rate of turn; for integrating rate of turn
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A low-cost gyroscope can provide an output approaching the accuracy of more precise instruments by processing the gyroscope output signal. First, a calibration algorithm develops a set of coefficients to predict drift. Second, an adaptive operational algorithm updates the coefficients during periods of inactivity and filters out high and low frequency noise components. An accurate, low-cost, rugged aiming device for a weapon can be realized with a simple, relatively-inexpensive gyroscope by utilizing the foregoing algorithms.

Claims

1. A system for processing the output of an angular rate sensor, comprising:

means for reducing noise in the sensor output; and

compensation means for compensating for drift, the compensation means comprising

means for initially adjusting the sensor output for a pre-determined rate of drift; and

means for subsequently computing a new rate of drift when the angular rate is less than a pre-defined threshold and adjusting the sensor output in response to the new rate of drift.

2. A system as set forth in claim 1, further including calibrating means for deriving the pre-determined rate of drift.

3. A system as set forth in claim 2, where the calibrating means includes curve-fitting means for determining the pre-determined rate of drift through a least-squares curve-fit method.

4. A system for processing the output of an angular rate sensor, comprising:

(a) means for calibrating the sensor output, the means for calibrating including

an analog-to-digital converter for converting the sensor output to a digital signal;

averaging means for averaging the digital signal;

an integrator for integrating the averaged signal; and

curve-fitting means, responsive to the integrated signal, for determining an initial set of coefficients of drift through a least-squares curve-fit method; and

(b) means for determining the angular movement of the sensor, the means for determining the angular movement including

an analog-to-digital converter for converting the sensor output to a digital signal;

averaging means for averaging the digital signal;

calculation means for calculating drift based on the initial set of coefficients of drift;

means for subtracting the calculated drift from the averaged signal;

an integrator for integrating the averaged signal less the calculated drift to provide a system output;

computation means, responsive to the system output, for computing a new set of coefficients when the angular rate is less than a pre-defined threshold; and

means for adjusting the system output in response to the new set of coefficients.

5. A system for accurately determining the position of a device rotatable about an axis, comprising:

(a) an angular rate sensor, the sensor having an output;

(b) means for mounting the sensor to the device and orienting the sensor to sense rotation of the device; and

(c) means for processing the sensor output, comprising;

means for reducing noise in the sensor output; and

compensation means comprising

means for initially adjusting the sensor output for a pre-determined rate of drift; and

means for subsequently computing a new rate of drift when the angular rate is less than a pre-defined threshold and adjusting the sensor output in response to the new rate of drift.

6. A system as set forth in claim 5, further including calibrating means for deriving the pre-determined rate of drift.

7. A system as set forth in claim 6, where the calibrating means includes curve-fitting means for determining the pre-determined rate of drift through a least-squares curve-fit method.

8. A system for accurately determining the azimuth of a rotatable weapon, comprising:

(a) an angular rate sensor, the sensor having an output;

(b) means for mounting the sensor to the weapon and orienting the sensor to sense rotation of the weapon; and

(c) means for processing the sensor output, comprising;

i) means for calibrating the sensor output, the means for calibrating including

an analog-to-digital converter for converting the sensor output to a digital signal;

averaging means for averaging the digital signal;

an integrator for integrating the averaged signal; and

curve-fitting means, responsive to the integrated signal, for determining an initial set of coefficients of drift through a least-squares curve-fit method; and

ii) means for determining the angular movement of the sensor, the means for determining the angular movement including

an analog-to-digital converter for converting the sensor output to a digital signal;

averaging means for averaging the digital signal;

calculation means for calculating drift based on the initial set of coefficients of drift;

means for subtracting the calculated drift from the averaged signal;

an integrator for integrating the averaged signal less the calculated drift to provide a system output;

computation means, responsive to the system output, for computing a new set of coefficients when the angular rate is less than a pre-defined threshold; and

means for adjusting the system output in response to the new set of coefficients.

9. A method of processing the output of an angular rate sensor, comprising the steps of:

reducing noise in the sensor output; and

compensating for drift, the step of compensating comprising the steps of

initially adjusting the sensor output for a pre-determined rate of drift; and

subsequently computing a new rate of drift when the angular rate is less than a pre-defined threshold and adjusting the sensor output in response to the new rate of drift.

10. A method as set forth in claim 9, further including the step of deriving the pre-determined rate of drift.

11. A method as set forth in claim 10, where the step of deriving includes the step of determining the pre-determined rate of drift through a least-squares curve-fit method.