Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
1999-04-23
2001-06-26
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
active
06250156
ABSTRACT:
BACKGROUND
The present invention relates generally to micro-fabricated sensors, and more particularly to microfabricated gyroscopic sensors.
Multi-axis sensors are highly desirable for inertial sensing of motion in three dimensions. Previously, such sensors were constructed of relatively large and expensive electromagnetic devices. More recently, micromechanical sensors have been fabricated using semiconductor processing techniques. Specifically, micromechanical accelerometers and gyroscopes have been formed from silicon wafers by using photolithographic techniques. Such microfabricated sensors hold the promise of large scale production and therefore low cost.
One objective in the construction of microfabricated sensors is to increase the sensitivity and improve the signal to noise ratio of the device. Another objective is to simplify the fabrication steps so as to reduce the cost and complexity and to increase the yield in the manufacturing process.
The integration of three gyroscopic sensors to measure the rotation rates about the three separate axes coupled with three accelerometric sensors to measure the acceleration along the three axes on a single chip would provide a monolithic, six degree-of-freedom inertial measurement system capable of measuring all possible translations and orientations of the chip. There has been some difficulty in constructing a vibratory rate gyroscope to measure the rotation about the axis normal to the plane of the silicon chip, i.e., the Z-axis.
SUMMARY
In one aspect, the invention is directed to a microfabricated gyroscopic sensor to measure rotation about an input axis. The sensor includes a substrate, a first mass, a second mass, a coupling system connecting the first mass and the second mass, a suspension system connecting the first mass and the second mass to the substrate, a drive system to cause the first mass and the second mass to vibrate in an antiphase mode along a drive axis, and a position sensor to measure a displacement of the first mass and the second mass along a sense axis perpendicular to the drive axis and generally parallel to the surface of the substrate. Rotation of the first mass and the second mass about the input perpendicular to the surface of the substrate and vibration of the first mass and the second mass along the drive axis generates a Coriolis force to vibrate the first mass and the second mass along the sense axis in antiphase to each other.
Implementations of the invention may include the following features. The position sensor may uses a difference in deflection of the first mass and the second mass along the sense axis to measure the Coriolis force. A signal processor may be coupled to an output of the position sensor to generate a signal varying with the rate of rotation of the first mass and the second mass about the input axis. The first mass and the second mass may have substantially the same mass. The coupling system may include a first coupling spring and a second coupling spring. Each coupling spring may have a first linear portion coupled to the first mass, a second linear portion coupled to the second mass, and a coupling beam extending outward perpendicularly from the first and second linear portions. The first and second linear portions may be substantially linearly aligned and parallel to the drive axis and may have substantially the same length. The suspension system may include a plurality of hairpin suspension elements. Each hairpin suspension element may have a first connecting portion joined to the substrate, a second connecting portion joined to the first mass or the second mass, and a suspension beam which extends outward perpendicularly from the first connecting portion and the second connecting portion. The first and second connecting portions may be linearly aligned and may have substantially the same length.
The drive system may includes a first drive electrode connected to the substrate, a second drive electrode connected to the substrate and positioned substantially in parallel to the first drive electrode, a first voltage source coupled to the first drive electrode and the second drive electrode to apply an alternating voltage to the first drive electrode and the second drive electrode, and a second voltage source coupled to the first mass and the second mass to apply a DC voltage to the first mass and the second mass. The first and second masses may vibrate in opposing directions in response to alternating voltages being applied to the first and second drive electrode. A first plurality of drive fingers may project along the drive axis from the first drive electrode, and a second plurality of drive fingers may project along the drive axis toward the first drive electrode from the first mass. The second plurality of drive fingers may be interdigitated with the first plurality of drive fingers. A third plurality of drive fingers may project along the drive axis from the second drive electrode, and a fourth plurality of drive fingers may project along the drive axis toward the second drive electrode from the second mass. The fourth plurality of drive fingers may be interdigitated with the third plurality of drive fingers. A first feedback electrode may connected to the substrate and having a first plurality of feedback fingers projecting along the drive axis toward the first mass, and a second plurality of feedback fingers may project along the drive axis toward the first feedback electrode from the first mass, the second plurality of feedback fingers being interdigitated with the first plurality of feedback fingers. A second feedback electrode may be connected to the substrate and have a third plurality of feedback fingers projecting along the drive axis toward the second mass, and a fourth plurality of feedback fingers may project along the drive axis toward the second feedback electrode from the second mass, the fourth plurality of feedback fingers being interdigitated with the third plurality of feedback fingers.
In another aspect, the invention is directed to a microfabricated gyroscopic sensor to measure rotation about an input axis. The sensor has a substrate, a first mass connected to the substrate by a suspension system, a second mass connected to the substrate by the suspension system, a drive system to apply an oscillatory force to the first mass and the second mass along a drive axis to cause the first mass and the second mass to vibrate in an antiparallel mode, and a position sensor to measure a deflection of the first mass and the second mass along a sense axis perpendicular to the drive axis and generally parallel to the surface of the substrate. Rotation of the first mass and the second mass about the input axis perpendicular to the surface of the substrate and vibration of the first mass and the second mass along the drive axis generates a Coriolis force to vibrate the first mass and the second mass along the sense axis in antiphase to each other.
Implementations of the invention may include the following. A coupling system may connect the first mass and the second mass.
In another aspect, the invention is directed to a method of sensing rotation with a microfabricated gyroscopic sensor. In the method, a microfabricated first mass connected to a substrate vibrates along a drive axis, a microfabricated second mass connected to the substrate and to the first mass vibrates along the drive axis, and a first mass and the second mass are rotated about an input axis. Rotation of the first mass and the second mass about the input axis and vibration of the first mass and the second mass along the drive axis generates a Coriolis force to vibrate the first mass and the second mass along a sense axis perpendicular to the drive axis. A displacement of the first mass and the second mass along the sense axis is measured.
Implementations of the invention may include the following. The first mass and the second mass may vibrate in antiphase along the drive axis. The input axis may be perpendicular to the drive axis and the sense axis. A difference in displacements of the first and s
Howe Roger T.
Seshia Ashwin A.
Fish & Richardson P.C.
Moller Richard A.
The Regents of the University of California
LandOfFree
Dual-mass micromachined vibratory rate gyroscope does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dual-mass micromachined vibratory rate gyroscope, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dual-mass micromachined vibratory rate gyroscope will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2519555