Electronics for Coriolis force and other sensors

• US 5,608,351 A
• Filed: 05/24/1995
• Issued: 03/04/1997
• Est. Priority Date: 03/28/1994
• Status: Expired due to Term

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Ward, Paul
• Primary Examiner(s): MOTTOLA, STEVEN J
• Application Number:
  US08/449,724
• Time in Patent Office: 650 Days
• Field of Search: 330/107, 330/109, 330/294, 330/302, 330/303, 330/306
• US Class Current: 330/107
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: H03F 1/083 in transistor amplifiers H03F1/10 - H03F1/22 take precedence

Abstract

Electronics for use in Coriolis and other sensors for reducing errors in the sensor output signal. An off-frequency drive scheme includes a frequency translation circuit in the excitation feedback loop of a sensor system to suppress components of the sensor drive signal at a predetermined frequency so that coupling of the drive signal to the sensor output signal can be readily removed by conventional filtering techniques. An amplifier circuit having a bandpass circuit in cascade with the forward loop gain is provided, with the bandpass circuit having a transfer function approximating one plus a bandpass characteristic, the passband of which corresponds to the information band. This arrangement increases the open-loop gain of the amplifier circuit around the information frequency without affecting the open-loop gain at DC and crossover so as to reduce phase and gain errors around the information frequency. A quadrature hulling system is provided for an in-plane micromechanical gyroscope. A signal having an in-phase component due to Coriolis induced out-of-plane motion and a quadrature component due to mechanical misalignments is mixed with a voltage in-phase with motor position. The mixer output is used to apply a DC potential to motor drive electrodes and is automatically adjusted by the integral compensator until the mixer output is zero, resulting in a nulled quadrature component.

Claims

1. An amplifier circuit comprising:

a bandpass circuit having an input and an output and a transfer function approximating one plus a bandpass characteristic, wherein said output of said bandpass circuit provides an output terminal of said amplifier circuit;

a first operational amplifier having an input coupled to an input terminal of said amplifier circuit and an output coupled to said input of said bandpass circuit; and

a global feedback network coupled around said first operational amplifier and said output terminal.

2. The amplifier circuit recited in claim 1 wherein the bandpass circuit comprises a second operational amplifier having a non-inverting input coupled to said output of said first operational amplifier, an output providing said output terminal of said amplifier circuit, and a local feedback network coupled between said output terminal and an inverting input of said second operational amplifier, said local feedback network providing said transfer function of said bandpass circuit.

3. The amplifier circuit recited in claim 2 wherein said local feedback network comprises a first resistor having a first terminal coupled to said output terminal and a second terminal coupled to said inverting input of said second operational amplifier, a capacitor coupled between said inverting input of said second operational amplifier and a first terminal of a second resistor, a second terminal of said second resistor being coupled to ground, and a capacitor coupled between said first terminal of said second resistor and said output terminal.

4. An amplifier circuit having a composite open-loop gain associated therewith, comprising:

a first operational amplifier;

a bandpass circuit having a resonance frequency and an open-loop gain associated therewith, said bandpass circuit disposed in cascade with said first operational amplifier and comprising two parallel signal paths, a first one of said signal paths having unity gain and dominating said open-loop gain of said bandpass circuit at frequency extremes so that said composite open-loop gain is governed by said first operational amplifier at said frequency extremes, and a second one of said signal paths having a frequency dependent gain dominating said open-loop gain of said bandpass circuit at said resonance frequency so that said composite open-loop gain is governed by said bandpass circuit at said resonance frequency; and

a global feedback network coupled around said first operational amplifier and said bandpass circuit.

5. The amplifier circuit recited in claim 4 wherein said bandpass circuit has an input and an output, said output providing an output terminal of said amplifier circuit, wherein said first operational amplifier has an inverting input coupled to an input terminal of said amplifier circuit through a feedforward impedance, a non-inverting input coupled to a reference potential, and an output coupled to said input of said bandpass circuit, and wherein said global feedback network is coupled between said inverting input of said first operational amplifier and said output terminal.

6. The amplifier circuit recited in claim 5 wherein the bandpass circuit comprises a second operational amplifier having a noninverting input coupled to said output of said first operational amplifier, an output providing said output terminal of said amplifier circuit, and a local feedback network coupled between said output terminal and an inverting input of said second operational amplifier.

7. The amplifier circuit recited in claim 6 wherein said local feedback network comprises a first resistor having a first terminal coupled to said output terminal and a second terminal coupled to said inverting input of said second operational amplifier, a capacitor coupled between said inverting input of said second operational amplifier and a first terminal of a second resistor, a second terminal of said second resistor being coupled to ground, and a capacitor coupled between said first terminal of said second resistor and said output terminal.