Alliedsignal Inc.

Honeywell International Inc.

Michael J Robinson

James R Woodruff

Eric Charles Abbott

Donny F Rojo

Eric C Abbott

Systems and methods for minimizing vibration rectification error (VRE) for a closed-loop accelerometer. In one embodiment, the method includes applying a known vibration signal to the closed-loop accelerometer along a first axis and adjusting a feedback gain setting until VRE is below a first threshold value. After the feedback gain setting has been adjusted, applying a random vibration signal to the closed-loop accelerometer along the first axis and adjusting a servo system proportional gain value until VRE is below a second threshold value.

Methods and apparatus for reducing vibration rectification errors in closed-loop accelerometers

An electromagnetically-excited silicon micromachined vibrating beam accelerometer includes a proof mass or pendulum attached to an outer casing by way of a pair of flexures defining a hinge axis HA. A double-ended tuning fork (DETF) is connected between the proof mass and the casing along an axis generally perpendicular to the hinge axis (HA) defining a sensitive axis SA such that forces applied along the hinge axis HA will cause the DETF to go into either compression or tension. Electromagnetic excitation causes the vibrating beams to vibrate at a resonant frequency when the proof mass is at rest. In response to a force along the sensitive axis SA, the vibrating beams go into either tension or compression resulting in a change in the resonant frequency which, in turn, is used as a measure of the force. The excitation includes a magnetic field B, applied in a direction generally perpendicular to the plane of the DETF and perpendicular to the sensitive axis SA. In order to eliminate the effects of variations in the resistance path of the vibrating beams due to either manufacturing tolerances and temperature, the DETF in accordance with the present invention is formed as a dual-port device with separate conducting paths for the drive circuit and the pick-off circuit. By providing separate conducting paths, the effects of changes in the resistance path of the drive circuit have little effect on the overall performance of the oscillator. Since the beams are separated, the DETFs are configured to provide sufficient mechanical coupling of the beams forming the DETF.

Two-port electromagnetic drive for a double-ended tuning fork

A vibrating beam force transducer is comprised of an oscillating sensing element having a frequency output indicative of the force applied to the sensing element. The sensing element has a variable electrical resistance which can vary in accordance with temperature fluctuations over the operating range of the transducer. A drive circuit is electrically coupled to the sensing element for causing the sensing element to oscillate at a resonant frequency that is a function of the force applied to the sensing element. The drive circuit includes a source of DC voltage, which is utilized for altering the electrical characteristics of the drive circuit in response to variations in the electrical resistance of the sensing element.

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Mukilteo, WA, United States of America

Michael J Robinson