FORCE REBALANCE CONTROL SYSTEM AND METHOD USING AUTOMATIC GAIN CONTROL LOOP

• US 20090007662A1
• Filed: 01/31/2008
• Published: 01/08/2009
• Est. Priority Date: 07/06/2007
• Status: Active Grant

• Current Assignee: Konkuk University Industrial Cooperation Corp
• Original Assignee: Konkuk University Industrial Cooperation Corp
• Inventors: SUNG, Sang-Kyung, SUNG, Woon-Tahk
• Granted Patent: US 7,861,588 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces

Abstract

The present invention relates to a force rebalance control system and method using an automatic gain control loop, which are configured to perform the force rebalance feedback control of a vibratory gyroscope using the automatic gain control loop for controlling the velocity signal of a mass body. Accordingly, the present invention is advantageous in that a conventional digital circuit, which is complicated and sensitive to noise, can be implemented using a simple analog circuit, and the present invention can be extended and applied to general-purpose vibratory gyroscopes or various sensor fields, such as those of an inertial sensor, a pressure sensor, and a temperature sensor, as well as micro-gyroscopes.

Further, a force rebalance control system using an automatic gain control loop according to the present invention is applied to various sensors, thus improving performance, such as the dynamic range, bandwidth, and linearity of the sensors.

Claims

1. A force rebalance control system using an automatic gain control loop, comprising:

a gyroscope for detecting a displacement signal of a mass body corresponding to an input angular velocity, and adjusting a displacement of the mass body;

a charge amplifier for converting the displacement signal detected by the gyroscope into a voltage signal, and outputting the voltage signal;

a differentiator for outputting a velocity signal of the mass body on a basis of the displacement signal, output from the charge amplifier as the voltage signal;

a unity gain reference frequency output unit for outputting a sine wave signal having a phase, frequency, and unity gain identical to those of the velocity signal output from the differentiator;

a reference value input unit for generating a reference signal required to induce vibration of a sensing axis having uniform intensity regardless of the angular velocity applied to the gyroscope;

a controller for outputting a control signal, required for the gyroscope to vibrate with a predetermined amplitude, using the reference signal output from the reference value input unit; and

a multiplier for performing a multiplication operation on the sine wave signal, output from the unity gain reference frequency output unit, and the control signal, output from the controller, and applying a resulting voltage signal to the gyroscope.

2. The force rebalance control system according to claim 1, wherein the gyroscope comprises:

a sensing axis output unit for detecting the displacement signal of the mass body corresponding to the input angular velocity; and

a sensing axis driving unit for adjusting the displacement of the mass body.

3. The force rebalance control system according to claim 2, wherein the charge amplifier is connected to the sensing axis output unit and is configured to convert variation in an amount of charge corresponding to variation in capacitance between the mass body and an electrode of the sensing axis output unit into a voltage signal, and to output the voltage signal.

4. The force rebalance control system according to claim 2, wherein the voltage signal, output from the multiplier, is applied to the sensing axis driving unit.

5. The force rebalance control system according to claim 1, wherein the velocity signal, output from the unity gain reference frequency output unit, is fed back into the multiplier.

6. The force balance control system according to claim 1, wherein the unity gain reference frequency output unit comprises:

a gain unit for amplifying an input signal by a high gain factor;

a limiter for outputting a square wave signal having a same phase as the input signal; and

a band pass filter having a center frequency corresponding to a resonant frequency of the gyroscope.

7. The force balance control system according to claim 6, wherein the gain unit is implemented with an amplifier, which uses an Operational Amplifier (OP-Amp).

8. The force balance control system according to claim 6, wherein the limiter is implemented using a comparator that exploits an OP-Amp.

9. The force balance control system according to claim 1, further comprising:

a rectifier for half-wave rectifying the velocity signal output from the differentiator; and

a low pass filter for outputting a signal half-wave rectified by the rectifier as an envelope signal.

10. The force rebalance control system according to claim 9, wherein the velocity output from the low pass filter is fed back into the controller.

11. The force rebalance control system according to claim 10, wherein the controller outputs the control signal required for the gyroscope to vibrate with the predetermined amplitude using both the envelope signal output from the low pass filter and the reference signal output from the reference value input unit.

12. The force rebalance control system according to claim 9, wherein the velocity signal output from the differentiator is applied both to the unity gain reference frequency output unit and to the rectifier.

13. The force rebalance control system according to claim 9, wherein the controller adds a value, obtained by multiplying a proportional value by a difference value between the envelope signal, output from the low pass filter, and the reference signal, generated by the reference value input unit, to a value, obtained by integrating the difference value and multiplying an integral gain by a result of integration, and then outputs a resulting value.

14. The force rebalance control system according to claim 13, wherein the controller comprises:

an integral unit for performing an integration operation on the difference value between the envelope signal, output from the low pass filter, and the reference signal, generated by the reference value input unit;

a proportional gain unit for multiplying a gain value by the difference value; and

an integral gain unit for multiplying a gain value by the result of integration output from the integral unit.

15. A force rebalance control method using an automatic gain control loop, comprising:

a first step of detecting a fine displacement of a sensing axis provided in a gyroscope;

a second step of generating a velocity signal of a mass body on a basis of a displacement signal corresponding to the detected fine displacement;

a third step of generating a sine wave signal having a phase, frequency, and unity gain identical to those of the velocity signal, and a control signal required for the gyroscope to vibrate with a predetermined amplitude;

a fourth step of performing a multiplication operation on the sine wave signal and the control signal, thus generating an amplitude-modulated signal; and

a fifth step of applying the amplitude-modulated signal to the gyroscope so as to maintain the displacement of the mass body at a uniform value.

16. The force rebalance control method according to claim 15, wherein the first to fifth steps are repeated when an angular velocity is input to the gyroscope after the fifth step.

17. The force rebalance control method according to claim 15, further comprising the step of adjusting a resonant frequency to cause the sensing axis and a driving axis of the gyroscope to have a same resonant frequency when the sensing axis and the driving axis of the gyroscope do not have the same resonant frequency before the first step.

18. The force rebalance control method according to claim 15, wherein the velocity signal is a signal obtained by differentiating the displacement signal.

19. The force rebalance control method according to claim 15, wherein the third step of generating the control signal comprises:

a first sub-step of detecting a high frequency envelope signal from the velocity signal;

a second sub-step of generating a reference signal required to induce vibration of the sensing axis having uniform intensity regardless of the angular velocity applied to the gyroscope; and

a third sub-step of generating a control signal required for the gyroscope to vibrate with a predetermined amplitude using both the envelope signal, detected at the first sub-step, and the reference signal.

20. The force rebalance control method according to claim 19, wherein the third sub-step comprises:

an integral gain step of performing an integration operation on a difference value between the envelope signal and the reference signal, and multiplying a predetermined gain value by a result of integration; and

a proportional gain step of multiplying a predetermined gain value by the difference value between the envelope signal and the reference signal.