Method of correcting the gain of a capacitive member, and a device for implementing the method

• US 9,000,779 B2
• Filed: 12/19/2008
• Issued: 04/07/2015
• Est. Priority Date: 12/19/2007
• Status: Active Grant

• Current Assignee: Safran Electronics & Defense
• Original Assignee: Sagem Defense Securite SA (Safran SA)
• Inventors: Caron, Jean-Michel, Ragot, Vincent
• Primary Examiner(s): Koval, Melissa
• Assistant Examiner(s): HOQUE, FARHANA AKHTER
• Application Number:
  US12/745,065
• Publication Number:
  US 20100326166A1
• Time in Patent Office: 2,300 Days
• Field of Search: 324/637, 324658-690, 7351418-517, 737/24, 73/13.7, 73/17.7, 735/041.2, 735/041.4
• US Class Current: 324/658
• CPC Class Codes: G01C 19/5691 of essentially three-dimensional vibrators, e.g. wine glass-type vibrators
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

A method of correcting the gain of a capacitive member having electrodes that are movable relative to each other including the steps of successively applying to one of the electrodes, reduced bias voltages having opposite signs and a common value below a threshold for which a remanent field generated by said reduced bias voltages can be measured, making corresponding measurements of the output signals from the capacitive member; taking an average, and correcting the gain of the capacitive member as a function of the measured output signal.

Claims

1. A method of correcting the gain of a capacitive member comprising electrodes that are movable relative to each other, with a remanent field established between the electrodes, for detecting and controlling deformation of a mechanical resonator in a vibrating gyro, wherein the method comprises the steps of:

applying a reduced DC bias voltage to one of the electrodes, the voltage having a value below a threshold for which a remanent field generated by said reduced bias voltage can'"'"'t be measured;

measuring an output signal from the capacitive member; and

calculating a correction for the gain of the capacitive member as a function of the measured output signal, thereby detecting the deformation of the mechanical resonator.

2. The method according to claim 1, wherein the reduced bias voltage is greater than an estimated bias voltage (VE) equivalent to the remanent field.

3. The method according to claim 2, wherein the calculation of the gain correction comprises a step of determining the direction of the remanent field from a measurement of the output signal from the capacitive member while a reduced bias voltage is being applied, and a step of determining the value of the remanent field from a measurement of the output signal from the capacitive member while no reduced bias voltage is being applied.

4. The method according to claim 2, wherein the calculation of the gain correction includes the step of subtracting a component that results directly from the reduced bias voltage from the output signal.

5. The method according to claim 1, including steps of performing two successive measurements of the output signal for reduced bias voltages having the same values but opposite signs, and taking the average of the resulting output signals.

6. The method according to claim 1, including a prior step) of applying a nominal bias voltage.

7. The method according to claim 1, including an initialization and gain correction storage stage, followed by a stage of applying the correction.

8. The method according to claim 7, used with a capacitive member incorporated in an axisymmetric vibrating gyro generating vibration that can be moved into various positions, wherein the gain corrections are performed at a plurality of vibration positions.

9. A control method for a sensor having a capacitive member comprising electrodes that are movable relative to each other, the method comprising:

a measuring stage during which a nominal bias voltage is applied to the electrodes;

an initialization stage during which the method of correcting the gain of claim 1 is implemented, the value of the reduced DC bias voltage being below a value of the nominal bias voltage and the gain correction calculated with said method being used during the measuring stage.

10. A method according to claim 9, wherein the initialization stage is implemented periodically, where the period is a function of a length of time the remanent field is retained after interrupting the nominal bias voltage.

11. A device for correcting the gain of a capacitive member comprising electrodes that are movable relative to each other, for detecting and controlling deformation of a mechanical resonator in a vibrating gyro;

and means for applying a bias signal to one of the electrodes, wherein the device includes means for applying a reduced DC bias voltage to one of the electrodes at a value that is below a threshold for which a remanent field generated by said reduced bias voltage can be measured, means for measuring an output signal from the capacitive member, and means for correcting the gain of the capacitive member as a function of the measured output signal, thereby detecting the deformation of the mechanical resonator.

12. The device according to claim 11, that is incorporated in an axisymmetric vibrating gyro that generates vibration that can be taken to various positions, the device including means for storing gain corrections for a plurality of vibration positions.