Electronics for Coriolis force and other sensors
First Claim
1. A Coriolis force sensor system comprising:
- an input transducer receiving a drive voltage signal and converting said drive voltage signal into a force signal having a nonlinear relationship with respect to said drive voltage signal;
a sensor responsive to said force signal from said input transducer and Coriolis forces induced by an inertial input for providing an inertial sense signal having a predetermined frequency and an amplitude related to said inertial input and a force sense signal having said predetermined frequency and an amplitude related to said force signal;
an output transducer for converting said force sense signal into a feedback voltage signal; and
a frequency translation circuit, disposed in a feedback relationship between said output transducer and said input transducer, for suppressing a component of said feedback voltage signal at said predetermined frequency to provide said drive voltage signal.
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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 nulling 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.
75 Citations
22 Claims
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1. A Coriolis force sensor system comprising:
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an input transducer receiving a drive voltage signal and converting said drive voltage signal into a force signal having a nonlinear relationship with respect to said drive voltage signal; a sensor responsive to said force signal from said input transducer and Coriolis forces induced by an inertial input for providing an inertial sense signal having a predetermined frequency and an amplitude related to said inertial input and a force sense signal having said predetermined frequency and an amplitude related to said force signal; an output transducer for converting said force sense signal into a feedback voltage signal; and a frequency translation circuit, disposed in a feedback relationship between said output transducer and said input transducer, for suppressing a component of said feedback voltage signal at said predetermined frequency to provide said drive voltage signal. - View Dependent Claims (2, 3, 4, 5)
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6. A Coriolis force sensor comprising:
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a proof mass adapted for being vibrated in a plane at a predetermined frequency, said proof mass being responsive to an inertial input for deflecting about an output axis orthogonal to said plane; a sense electrode for sensing said deflection of said proof mass about said output axis to generate a sensor output signal; and a composite amplifier circuit for converting said sensor output signal into a voltage signal, said amplifier circuit comprising; (a) a bandpass circuit having an input and an output and a transfer function comprising a bandpass characteristic, wherein said output of said bandpass circuit provides an output terminal of said composite amplifier circuit at which said voltage signal is provided; (b) a first operational amplifier having an inverting input coupled to an input terminal of said composite amplifier circuit though a feedforward impedance, a non-inverting input coupled to a reference potential, and an output coupled to said input of said bandpass circuit; and (c) a global feedback network coupled between said inverting input of said first operational amplifier and said output terminal. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A tuning fork gyroscope comprising:
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a pair of proof masses adapted for being vibrated in a plane at a predetermined frequency, said proof masses being responsive to an input rotational rate about an input axis coincident with said plane for deflecting about an output axis orthogonal to said plane; a pair of drive electrodes, each one in electrostatic communication with a corresponding one of said pair of proof masses, said drive electrodes receiving an excitation signal having an amplitude and a frequency associated therewith and converting said excitation signal into a force signal for vibrating said pair of proof masses in said plane; a first sense electrode for sensing said vibration of said proof masses in said plane; an excitation feedback circuit coupled to said first sense electrode and said drive electrode for controlling said amplitude and said frequency of said excitation signal; a second sense electrode for sensing said deflection of said proof masses about said output axis to generate a sensor output signal; and processing electronics for processing said sensor output signal to provide a signal indicative of said input rotational rate, said processing electronics comprising; (a) a composite amplifier circuit for converting said sensor output signal into a voltage signal, said amplifier circuit comprising; (i) a bandpass circuit having an input and an output and a transfer function comprising a bandpass characteristic, wherein said output of said bandpass circuit provides an output terminal of said composite amplifier circuit at which said voltage signal is provided; (ii) a first operational amplifier having an inverting input coupled to an input terminal of said composite amplifier circuit though a feedforward impedance, a non-inverting input coupled to a reference potential, and an output coupled to said input of said bandpass circuit; and (iii) a global feedback network coupled between said inverting input of said first operational amplifier and said output terminal; and (b) a demodulator, receiving said amplified voltage signal and a reference signal having a frequency corresponding to said predetermined frequency, for demodulating said voltage signal to provide a signal indicative of said input rotational rate.
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13. A micromechanical, in-plane gyroscope having automatic quadrature nulling, said gyroscope comprising:
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a substrate; two opposing end stator combs disposed on said substrate, said end stator combs having a first stator comb and a second stator comb; a center stator comb disposed on said substrate between said end stator combs; two proof masses suspended above and parallel to said substrate, each of said proof masses disposed between said center stator comb and a respective one of said end stator combs; a plurality of electrodes, each of said electrodes disposed on said substrate between a respective proof mass and said substrate; means for receiving and applying a first motor drive signal to said center stator comb and for producing an in-plane signal indicative of in-plane motion; means for receiving and applying a second motor drive signal to respective ones of said end stator combs; means for receiving and applying an electrode signal to respective ones of said plurality of electrodes; an out-of-plane charge amplifier circuit responsive to an out-of-plane signal induced by out-of-plane movement of said proof masses, said out-of-plane charge amplifier circuit providing an out-of-plane charge amplifier output; an in-plane charge amplifier circuit responsive to said means for producing said in-plane signal, said in-plane charge amplifier providing an in-plane charge amplifier output; excitation feedback means for receiving said in-plane charge amplifier output and for providing an AC input to said means for receiving and applying said second motor drive signal; an in-plane gain stage for amplifying said in-plane charge amplifier output and for producing an amplified in-plane output; an out-of-plane gain stage for amplifying said out-of-plane charge amplifier output and for producing an amplified out-of-plane output; first mixer means for mixing said amplified out-of-plane output with said amplified in-plane output and for providing a first mixer output; integrator means responsive to said first mixer output and providing a DC input to said means for receiving and applying said second motor drive signal; means for receiving and phase shifting said amplified in-plane output to provide a shifted in-plane output; and second mixer means for mixing said amplified out-of-plane output with said shifted in-plane output to provide a gyroscope output indicative of a rate input. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification