US 4,782,700 A · Frame assembly and dither drive for a coriolis rate sensor

Abstract

An apparatus for producing signals indicative of both a Coriolis rate and an acceleration along a preferred axis while decoupling extraneous vibration and motion that would introduce errors into the signals, and a driving mechanism for vibrating the apparatus at a dither frequency. The apparatus includes a parallelogram frame (50) including two accelerometer support surfaces (24, 26) on which are mounted two accelerometers (20 and 22) having their sensitive axes in parallel alignment. The accelerometer support surfaces are connected to opposite ends of a flex member (52), which includes six flexures (32, 34, 36, 38, 40, 42) having parallel bending axes. Two of the flexures (34, 38) are disposed at opposite ends of one side of each flexure member, and have a "long" axis that is substantially parallel to the sensitive axes of the accelerometers and aligned with a line connecting their centers of percussion. The centers of mass of the accelerometers and their associated supporting surfaces are coincident with the centers of percussion, and are rigidly connected by the two flexures and by one side (30) of each flex member. This solid metal path between the centers of percussion minimizes common mode errors. A driving mechanism (64) is connected to the parallelogram frame and is opertive to drive the accelerometers at a desired frequency, causing them to vibrate back and forth in a direction substantially transverse to their sensitive axes. The driving mechanism includes a mounting plate (72) and a coil frame (66) on which are mounted two electromagnetic coils (70) having a "C" shaped core (80). The driving mechanism is mounted so that the core faces a pole piece (84) attached to the parallelogram frame and its moment of inertia is trimmed to equal that of the parallelogram frame. It is connected to the parallelogram by a link (88) and provides a reactionless driving force.

Claims14

Dependent claims

A frame for use in a Coriolis rate sensor including two accelerometers each having a preferred axis, comprising:

two accelerometer carriers disposed on opposite sides of the frame and adapted for mounting the two accelerometers with their preferred axes in alignment;
two substantially parallel flex members, each extending between the two accelerometer carriers at opposite sides thereof, the flex members each including a cross brace disposed at their center, adapted for attaching the frame to a supporting structure, and further including a plurality of flexures having parallel bending axes, the flexures being disposed at the corners of a parallelogram, with one of the flexures connecting two sides of the parallelogram at each corner and one of the flexures disposed at each end of the cross brace and connecting the centers of two sides of the parallelogram, the flexures at each end of one of said two sides of each flex member being oriented to provide maximum stiffness on a line between the two carriers and disposed so that when the two accelerometers are mounted on the carriers, the centers of mass of each carrier and the accelerometer mounted thereon are aligned with the flexures at each end of said one side.

A frame for use in a Coriolis rate sensor having two accelerometers mounted with their preferred axes in alignment, comprising:

(a) two accelerometer mounting pads disposed on opposite sides of the frame, each being adapted to mount one of the accelerometers so that their preferred axes are aligned;
(b) parallelogram means for linking the accelerometer mounting pads in parallel alignment and including a plurality of flexures enabling the accelerometer mounting pads and accelerometers mounted thereon to vibrate back and forth in a direction transverse to their preferred axes;
(c) attachment means for attaching a central portion of the frame to a supporting structure, the attachment means being pivotably connected to the parallelogram means by the plurality of flexures;
and
(d) common mode connection means for rigidly connecting the two accelerometer mounting pads along a path that is aligned with a line extending through a center of percussion associated with each accelerometer, the common mode connection means comprising a portion of the parallelogram means and including a plurality of flexures oriented in alignment with said path and differently than other of the flexures of the parallelogram means, the orientation insuring that both accelerometers are subjected to the same motion directed along their preferred axes.

2 more elements

Dependencies are inferred from the claim text.

Frame assembly and dither drive for a coriolis rate sensor

Life of this patent

Frame assembly and dither drive for a coriolis rate sensor

Life of this patent

Abstract

Claims14