Honeywell International Inc.

John Reinke

Daniel Endean

Grant Lodden

The disclosure describes techniques to damp the proof mass motion of an accelerometer while achieving an underdamped resonator. In an example of an in-plane micro-electromechanical systems (MEMS) VBA, the proof mass may contain one or more damping combs that include one or more banks of rotor comb fingers attached to the proof mass. The rotor comb fingers may be interdigitated with stator comb fingers that are attached to fixed geometry. These damping comb fingers may provide air damping for the proof mass when the MEMS die is placed into a package containing a pressure above a vacuum. The geometry of the damping combs with a reduced air gap and large overlap area between the rotor comb fingers and stator comb fingers. The geometry of resonator of the VBA of this disclosure may be configured to avoid air damping.

Vibrating beam accelerometer with pressure damping

An example system comprising: a microelectromechanical system (MEMS) vibrating beam accelerometer (VBA) comprising: a proof mass; and a first resonator mechanically coupled to the proof mass; a first electrode configured to apply a force to the proof mass.

MEMS vibrating beam accelerometer with built-in test actuators

The disclosure describes techniques to adjust the geometry of a pendulous proof mass VBA to operate with sufficient signal-to-noise performance while avoiding nonlinear mechanical coupling at specified frequencies. The techniques of this disclosure include adding anchor support flexures to a resonator connection structure, adjusting shape, thickness, and the material of VBA components and of the VBA support structure to both control the frequency of any mechanical resonant modes and to adjust the mechanical mode frequencies away from desired operating frequencies and, in some examples, away from harmonics of desired operating frequencies.

Vibrating beam accelerometer with additional support flexures to avoid nonlinear mechanical coupling

This disclosure describes techniques of configuring capacitive comb fingers of an accelerometer resonator into discreet electrodes with drive electrodes and at least two sense electrodes. The routing of electrical signals is configured to produce parasitic feedthrough capacitances that are approximately equal. The sense electrodes may be placed on opposite sides of the moving resonator beams such that the changes in capacitance with respect to displacement (e.g. dC/dx) are approximately equal in magnitude and opposite in sign. The arrangement may result in sense currents that are also opposite in sign and result in feedthrough currents of the same sign. The sense outputs from the resonators may be connected to a differential amplifier, such that the difference in output currents may mitigate the effect of the feedthrough currents and cancel parasitic feedthrough capacitance. Parasitic feedthrough capacitance may cause increased accelerometer noise and reduced bias stability.

Resonator electrode configuration to avoid capacitive feedthrough for vibrating beam accelerometers

Systems and methods for suppressing bias in a non-degenerate vibratory structure are provided. In certain embodiments, a vibratory structure includes a first proof mass; a second proof mass, wherein the first proof mass and the second proof mass are driven into motion along a first axis, wherein the first proof mass and the second proof mass move in anti-phase along a second axis, wherein the motion of the first proof mass and the second proof mass along the second axis is such that the centers of mass of the first proof mass and the second proof mass move collinearly along a same axis.

Systems and methods for bias suppression in a non-degenerate MEMS sensor

This disclosure is related to devices, systems, and techniques for determining an acceleration of a vibrating beam accelerometer (VBA). For example, a system includes processing circuitry configured to receive, from a first resonator, one or more electrical signals indicative of a frequency of a first mechanical beam and a frequency of a second mechanical beam, determine, based on the one or more electrical signals, the frequency of the first mechanical beam and the frequency of the second mechanical beam, and calculate, based on the frequency of the first mechanical beam and the frequency of the second mechanical beam, an acceleration of a proof mass assembly.

Resonator including one or more mechanical beams with added mass

A vibrating beam accelerometer (VBA) with an in-plane translational proof mass that may include at least two or more resonators and be built with planar geometry, discrete lever arms, four-fold symmetry and a single primary mechanical anchor between the support base and the VBA. In some examples, the VBA of this disclosure may be built according to a micro-electromechanical systems (MEMS) fabrication process. Use of a single primary mechanical anchor may minimize bias errors that can be caused by external mechanical forces applied to the circuit board, package, and/or substrate that contains the accelerometer mechanism.

In-plane translational vibrating beam accelerometer with mechanical isolation and 4-fold symmetry

A vibrating beam accelerometer (VBA) with an in-plane pendulous proof mass, which may include one or more resonators, planar geometry, a single primary mechanical anchor between the support base and the VBA, a resonator connector structure connecting the resonators to the single primary anchor and a hinge flexure mechanically connecting the proof mass to the single primary anchor. The techniques of this disclosure specify how the resonators can be solidly attached to the single anchor without compromising performance caused by forces applied on or by the support base. The geometry of the VBA may prevent bias errors that may otherwise result from a force applied to the support base that reaches the mechanism of the VBA. An example of force applied to the support base, may include the thermal expansion mismatch between the material of the support base and the material of the VBA.

Mechanically-isolated in-plane pendulous vibrating beam accelerometer

Systems and methods for noise and drift calibration using dithered calibration, a system comprising a processing unit; and two or more dithered calibrated sensors that provide directional measurements to the processing unit, wherein a dithered calibrated sensor in the dithered calibrated sensors has an input axis that rotates about an axis such that bias error can be removed by the processing unit; wherein the dithered calibrated sensor provides a zero-bias measurement along a first axis and a low-noise measurement along a second axis, the second axis being orthogonal to the first axis; wherein the dithered calibrated sensors are arranged such that the dithered calibrated sensor provide low-noise and zero-bias measurements along the measured axes; and wherein the processing unit executes an algorithm to combine measurements that are along the same axis to produce a measurement for each measured axis that has both low-noise and zero-bias.

Systems and methods for noise and drift calibration using dithered calibration

A method for fabricating a thermally isolated microelectromechanical system (MEMS) structure is provided. The method includes processing a first wafer of a first material with a glass wafer to form a composite substrate including at least one sacrificial structure of the first material and glass; forming a MEMS device in a second material; forming at least one temperature sensing element on at least one of: the composite substrate; and the MEMS device; and etching away the at least one sacrificial structure of the first material in the composite substrate to form at least one thermally isolating glass flexure. The MEMS device is thermally isolated on a thermal isolation stage by the at least one thermally isolating glass flexure. The at least one temperature sensing element in on a respective at least one of: the thermal isolation stage; and the MEMS device.

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Plymouth, MN, United States of America

John Reinke