Compensated integrated micro-machined yaw rate sensor with quadrature switching

• US 6,439,050 B1
• Filed: 03/10/2000
• Issued: 08/27/2002
• Est. Priority Date: 03/10/2000
• Status: Expired due to Fees

• Current Assignee: Melexis UK Limited
• Original Assignee: Melexis UK Limited
• Inventors: Musalem, Francois-Xavier, Betts, William R., Diels, Roger
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/522,667
• Time in Patent Office: 900 Days
• Field of Search: 73/17.7, 735/040.2, 735/040.3, 735/040.4, 735/041.2
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

An integrated circuit combines micro-machined elements, piezoelectric elements and signal processing components as part of a compensated oscillating gyroscopic sensor for angular motion detection. An oscillating mass is supported on a number of flexible beams micro-machined into an integrated circuit device, such as a silicon CMOS device. Several Piezo-electric elements, deposited on the beams, are provided to excite the mass and to measure the accelerations. Integrated in the device are electronic circuitry that initiates and maintains the oscillation and electronic circuitry that detects and measures the subsequent motion. Additional circuitry is also provided to eliminate the effects of quadrature oscillation and to determine the Coriolis acceleration and thus the magnitude of the external perturbing velocity.

Claims

1. A micro-machined gyro sensor capable of measuring an externally imposed velocity comprising:

a mass coupled to a rigid annular support by a first pair of opposing flexible members and a second pair of opposing flexible members, wherein the first pair of members define a first axis, and wherein the second pair of members define a second axis substantially orthogonal to the first axis;

a first pair of piezo electric driving elements deposited on the first pair of members;

a first piezo electric sensing element deposited on one of the first pair of members, wherein the first sensing element generates a first signal proportional to the oscillation of the mass along the first axis;

a second pair of piezo electric driving elements deposited on the second pair of members;

a second piezo electric sensing element deposited on one of the second pair of members, wherein the second sensing element generates a second signal proportional to the oscillation of the mass along the second axis;

a control circuit coupled to the first and second sensing elements and to the first pair of driving elements, wherein the control circuit generates a control signal which when applied to the first pair of driving elements causes the mass to oscillate along the first axis; and

a detection circuit coupled to the first and second sensing elements, wherein the detection circuit receives the first and second signals and generates an output signal proportional to the imposed velocity;

wherein the control circuit receives the first and second signals and generates a signal proportional to an undesired oscillation of the mass along the second axis so as to compensate for the undesired oscillation along the second axis when applied to the second pair of driving elements.

2. The gyro sensor of claim 1, wherein the detection circuit compares the phases of the first and second signals so as to determine the Coriolis acceleration caused by the imposed velocity.

3. The gyro sensor of claim 1, wherein the detection circuit is capable of determining the undesired oscillations of the mass along the second axis when no external velocity is imposed by comparing the phases of the first and second signals.

4. The gyro sensor of claim 3, wherein the detection circuit compensates for the undesired oscillations by subtracting out the undesired component from the output signal.

5. The gyro sensor of claim 1, wherein each of said piezo electric elements are deposited on the respective beams using silicon processing techniques.

6. The gyro sensor of claim 1, further comprising a third sensing element deposited on a second one of the first pair of members and a fourth sensing element deposited on a second one of the second pair of members, wherein the control circuit is coupled to the third and fourth sensing elements, and wherein the control circuit alters the control signal in response to signals received from the third and fourth sensing elements so as to maintain oscillation of the mass along the first axis at a desired amplitude and frequency.

7. The gyro sensor of claim 1, wherein the gyro sensor is micro-machined into a silicon substrate.

8. The gyro sensor of claim 1, wherein oscillation of the mass includes an oscillation component orthogonal to a plane defined by the first and second axes.

9. The gyro sensor of claim 1, wherein the mass oscillates orthogonal to a plane defined by the first and second axes.

10. A micro-machined gyro sensor capable of measuring an externally imposed velocity comprising:

a mass coupled to a rigid annular support by a first pair of opposing flexible members and a second pair of opposing flexible members, wherein the first pair of members define a first axis, and wherein the second pair of members define a second axis substantially orthogonal to the first axis;

first driving means coupled to the first pair of members for causing the mass to oscillate along the first axis;

second driving means coupled to the second pair of members for causing the mass to oscillate along the second axis;

detection means, coupled to the first pair of members and the second pair of the second pair of members, for detecting and comparing oscillations of the mass along the first axis and along the second axis so as to measure the Coriolis acceleration caused by the imposed velocity;

a first sensing means, deposited on one of the first pair of members, for generating a first signal proportional to the oscillation of the mass along the first axis;

a second sensing means, deposited on one of the second pair of members, for generating a second signal proportional to the oscillation of the mass along the second axis; and

a control means is coupled to the first and second sensing means and the first and second driving means and includes a means for comparing the first and second signals to determine an undesired oscillation of the mass along the second axis and for generating signals so as to compensate for the undesired oscillation when applied to the first and second driving means.

11. The gyro sensor of claim 10, wherein the detection means is capable of determining undesired oscillations of the mass along the second axis when no external velocity is imposed by comparing the phases of the first and second signals, and wherein the detection means compensates for the undesired oscillations by subtracting out the undesired component from the output signal.

12. The gyro sensor of claim 10, wherein each of the first and second driving means includes a pair of driving elements deposited on the respective pair of members.

13. The gyro sensor of claim 10, wherein the mass is able to oscillate orthogonal to a plane defined by the first and second axes.

14. A micro-machined gyro sensor capable of measuring an externally imposed velocity, comprising:

a mass coupled to a rigid annular support by a first pair of opposing flexible members and a second pair of opposing flexible members, wherein the first pair of members define a first axis, and wherein the second pair of members define a second axis substantially orthogonal to the first axis;

a first pair of piezo electric driving elements deposited on the first pair of members;

a first pair of piezo electric sensing elements deposited on the first pair of members, wherein the first pair of sensing elements generates first signals proportional to the oscillation of the mass along the first axis;

a second pair of piezo electric driving elements deposited on the second pair of members;

a second pair of piezo electric sensing elements deposited on the second pair of members, wherein the second pair of sensing elements generates second signals proportional to the oscillation of the mass along the second axis;

a control circuit coupled to at least one of each of the first and second pairs of sensing elements and to the first pair of driving elements, wherein the control circuit generates a control signal which when applied to the first pair of driving elements causes the mass to oscillate along the first axis; and

a detection circuit coupled to the first and second pairs of sensing elements, wherein the detection circuit receives the first and second signals and generates an output signal proportional to the imposed velocity;

wherein the control circuit receives the first and second signals and generates a signal proportional to an undesired oscillation of the mass along the second axis so as to compensate for the undesired oscillation along the second axis when applied to the second pair of driving elements.

15. A micro-machined gyro sensor capable of measuring an externally imposed velocity, comprising:

a mass coupled to a rigid annular support by a first pair of opposing flexible members and a second pair of opposing flexible members, wherein the first pair of members define a first axis, and wherein the second pair of members define a second axis substantially orthogonal to the first axis;

first driving means coupled to the first pair of members for causing the mass to oscillate along the first axis;

second driving means coupled to the second pair of members for causing the mass to oscillate along the second axis;

detection means, coupled to one of the first pair of members and the second pair of members, for detecting oscillations of the mass along the first axis and along the second axis so as to measure the Coriolis acceleration caused by the imposed velocity;

a first sensing means, deposited on one of the first pair of members, for generating a first signal proportional to the oscillation of the mass along the first axis;

a second sensing means, deposited on one of the second pair of members, for generating a second signal proportional to the oscillation of the mass along the second axis; and

a control means is coupled to the first and second sensing means and the first and second driving means and includes a means for comparing the first and second signals to determine an undesired oscillation of the mass along the second axis and for generating signals so as to compensate for the undesired oscillation when applied to the first and second driving means.