Gra MEMS accelerometer

Abstract

An accelerometer that lies generally in a plane, for detecting acceleration along an input axis. There is a substrate, a generally planar Servo Member (SM) flexibly coupled to the substrate such that it is capable of oscillatory motion about a servo axis that lies in the plane, a generally planar Torque Summing Member (TSM) coplanar with and flexibly coupled to the SM such that the TSM is capable of rotary motion relative to the SM about an output axis that is in the plane and orthogonal to the servo axis, wherein the TSM is mass-imbalanced relative to the output axis, and a generally planar rotor coplanar with and flexibly coupled to the TSM such that it is capable of rotary oscillatory motion relative to the TSM about a rotor axis that is orthogonal to the plane of the members. There are drives for oscillating the rotor about the rotor axis and for oscillating the SM about the servo axis. Output sensors detect oscillation of the rotor about the rotor axis and of the SM about the servo axis. Output sensors detect rotation of the TSM about the output axis.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims priority of provisional application Ser. No. 60 / 702,422 filed on Jul. 26, 2005, the disclosure of which is incorporated herein by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH[0002]This invention was made with government support under contract number HQ0006-05-C-2718 issued by the MDA. The government has certain rights in this invention.FIELD OF THE INVENTION[0003]This invention relates to accelerometer designs.BACKGROUND OF THE INVENTION[0004]Closed loop MEMS pendulous accelerometers typically use torque rebalance with a voltage-controlled capacitive actuator to hold the pendulum at null. Assuming the actuator is stable, the voltage applied is proportional to acceleration. The accelerometers are calibrated to obtain the scale factor (acceleration to voltage proportionality). In this implementation, the torque applied is not measured directly. The accuracy and stability will be dependent on the accuracy...

AI Technical Summary

Benefits of technology

"This patent describes a new design for an accelerometer called a Gyro Rebalanced Accelerometer (GRA). The GRA is a MEMS-based device that can detect acceleration along a specific axis. It consists of a rotor, a servo member, and a torque summing member, which all move in a plane. The rotor and servo member are flexibly coupled to a substrate, while the torque summing member is flexibly coupled to the rotor and servo member. The rotor and servo member can move about a servo axis, while the torque summing member can rotate about an output axis. The GRA can detect acceleration by measuring the movement of the rotor and servo member. The design of the GRA allows for open-loop operation and is optimized for MEMS fabrication processes. The patent also describes the components of the GRA and how they function."

Problems solved by technology

The accuracy and stability will be dependent on the accuracy and stability of the applied voltage and the actuator functionality, thereby limiting scale factor accuracy if only the voltage is measured.

Under acceleration, the unbalanced mass generates a torque that tends to rotate the gimbal about the OA.

Images