Triaxial angular rate and acceleration sensor

• US 20030005767A1
• Filed: 08/29/2002
• Published: 01/09/2003
• Est. Priority Date: 02/08/1991
• Status: Active Grant

• Current Assignee: Rand H. Hulsing II
• Original Assignee: Rand H. Hulsing II
• Inventors: Hulsing, Rand H. II
• Granted Patent: US 6,843,126 B2
• Time in Patent Office: Days
• US Class Current: 73/514.02
• CPC Class Codes: F02G 1/044 having at least two working members, e.g. pistons, delivering power output
• CPC Class Codes: F02G 1/0445 Engine plants with combined cycles, e.g. Vuilleumier
• CPC Class Codes: F16L 37/24 in which the connection is made by inserting one member axially into the other and rotating it to a limited extent, e.g. with bayonet action
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

A triaxial sensor substrate is adapted for use in measuring the acceleration and angular rate of a moving body along three orthogonal axes. The triaxial sensor substrate includes three individual sensors that are arranged in the plane of the substrate at an angle of 120 degrees with respect to one another. Each sensor is formed from two accelerometers having their sensing axes canted at an angle with respect to the plane of the substrate and further being directed in opposite directions. The rate sensing axes thus lie along three orthogonal axes.

In order to reduce or eliminate angular acceleration sensitivity, a two substrate configuration may be used. Each substrate includes three accelerometers that are arranged in the plane of the substrate at an angle of 120 degrees with respect to one another. The sensing axes of the accelerometers of the first substrate are canted at an angle with respect to the plane of the first substrate toward the central portion thereof so that they lie along three skewed axes. Similarly, the sensing axes of the accelerometers of the second substrate are canted at an angle with respect to the plane of the second substrate away from the central portion thereof so that they lie along same three but oppositely directed axes. The sensing axes of the first and second substrates are aligned to prevent angular acceleration sensitivity.

Claims

1. A generally planar substrate adapted for use in a triaxial angular rate and acceleration sensor comprising:

a first set of coplanar accelerometers formed in said substrate, each of said first set of accelerometers having a sensing axis canted at an angle with respect to the plane of said substrate, said first set of accelerometers being arranged in the plane of said substrate to place said sensing axes of said first set of accelerometers skewed to one another;

a second set of coplanar accelerometers formed in said substrate, each of said second set of accelerometers having a sensing axis canted at an angle with respect to the plane of said substrate, said second set of accelerometers being arranged in the plane of said substrate to place said sensing axes of said second set of accelerometers skewed to one another, each of said second set of accelerometers being paired with a corresponding accelerometer of said first set of accelerometers, corresponding accelerometer pairs having sensing axes that are parallel or anti-parallel;

connecting means formed in said substrate for connecting said first and second sets of accelerometers to one another to allow a pair of said accelerometers of said first and second sets of accelerometers to dither at the same frequency.

2. A generally planar substrate as claimed in claim 1 wherein said connecting means comprises:

linking means respectively associated with each corresponding accelerometer pair for connecting each accelerometer of said corresponding accelerometer pair together so that a dither motion on one accelerometer of said corresponding accelerometer pair creates an opposite dither motion on the other accelerometer of said corresponding accelerometer pair;

a central hub;

a radial hub member respectively associated with each of said corresponding accelerometer pairs, each of said radial hub members connecting the respective linking means to said central hub.

3. A generally planar substrate as claimed in claim 1 wherein said connecting means comprises:

a main frame;

a hub having a plurality of arms, each arm of said plurality of arms being associated with a respective corresponding accelerometer pair;

a plurality of spokes connecting said hub to said main frame, said spokes providing means for connecting said first and second set of accelerometers to said main frame;

linking means respectively connected to each arm of said hub for connecting each accelerometer of said corresponding accelerometer pair together so that a dither notion on one accelerometer of said corresponding accelerometer pair creates an opposite dither motion on the other accelerometer of said corresponding accelerometer pair.

4. A generally planar substrate as claimed in claim 1 wherein said connecting means comprises:

a hub in the form of an equilateral triangle, each side of said triangle being attached to a corresponding accelerometer pair by a plurality of parallel flexures, said hub having an arm extending from each side of said equilateral triangle; and

linking means respectively connected to each arm of said hub for connecting each accelerometer of said corresponding accelerometer pair together so that a dither motion on one accelerometer of said corresponding accelerometer pair creates an opposite dither motion on the other accelerometer of said corresponding accelerometer pair.

5. A structure adapted for use in a triaxial angular rate and acceleration sensor comprising:

a first set of coplanar accelerometers formed in a first generally planar substrate, each of said first set of accelerometers having a sensing axis canted at an angle with respect to the plane of said first substrates said first set of accelerometers being arranged in the plane of said first substrate to place said sensing axes of said first set of accelerometers skewed to one another;

a second set of coplanar accelerometers formed in a second generally planar substrate, each of said second set of accelerometers having a sensing axis canted at an angle with respect to the plane of said second substrate, said second set of accelerometers being arranged in the plane of said second substrate to place said sensing axes of said second set of accelerometers skewed to one another, each of said second set of accelerometers being paired with a corresponding accelerometer of said first set of accelerometers, corresponding accelerometer pairs having sensing axes that are parallel or anti-parallel;

connecting means for connecting said first and second sets of accelerometers to one another to allow said accelerometers of said first and second sets of accelerometers to dither at the same frequency.

6. A structure as claimed in claim 5 wherein the sensing axes of said corresponding pairs of accelerometers are co-axially aligned.

7. A structure as claimed in claim 5 wherein said connecting means comprises:

a first hub formed in said first substrate;

linking means formed in said first substrate for linking said first hub to a respective accelerometer of said first set of accelerometers so that dither motion of said first hub in a first direction produces a dither motion of the respective accelerometer in a second direction generally opposite said first direction;

a second hub formed in said second substrate and connected in fixed alignment with said first hub;

radial hub members formed in said second substrate, each radial hub member associated with a respective accelerometer of said accelerometers pairs, each of said radial hub members connecting the respective accelerometer to said hub.

8. A structure as claimed in claim 7 wherein each of said radial hub members comprises:

a rigid portion; and

a back-to-back, S-bending flexure unit connecting said rigid portion to said second hub.

9. A structure as claimed in claim 5 wherein said connecting means comprises:

a first hub formed in said first substrate;

a first main frame formed in said first substrate and interconnecting said first set of accelerometers in fixed alignment with one another;

a first plurality of flexures formed in said first substrate and connecting said first hub to said first main frame;

a second hub formed in said second substrate and connected in fixed alignment with said first hub;

a second main frame formed in said second substrate and interconnecting said second set of accelerometers in fixed alignment with one another;

a second plurality of flexures formed in said first substrate and connecting said first hub to said first main frame; and

means for linking said first main frame to said second main frame to allow said first and second main frames to dither at the same frequency.

10. A structure as claimed in claim 9 wherein said means for linking said first main frame to said second main frame further provides means for translating dither motion of one of said main frames of said first and second main frames in a first direction to a dither motion of the other of said main frames in a second direction opposite said first direction.

11. An accelerometer comprising:

a sensor frame formed in a substrate;

a proof mass having a pendulum formed in said substrate and a mass plate connected to said pendulum, said mass plate having a density different from said pendulum; and

means for elastically connecting said proof mass to said sensor frame.

12. An accelerometer as claimed in claim 11 wherein said substrate is silicon and said mass plate is formed from a material selected from the group consisting of tungsten and invar.

13. An accelerometer as claimed in claim 11 wherein said substrate is quartz and said mass plate is formed from a material selected from the group consisting of elgiloy, berillium copper, and havar.

16. A sensor structure as claimed in claim 15 wherein the sensing axes of said corresponding pairs of accelerometers are aligned.

17. A sensor structure as claimed in claim 15 wherein said first sensor stack comprises:

a hub portion;

a main frame portion;

a plurality of flexures connecting said hub portion to said main frame portion to allow said main frame portion to dither with respect to said hub portion.

18. A sensor structure as claimed in claim 17 wherein said second sensor stack comprises:

a further hub portion connected in fixed alignment with said hub portion of said first sensor stack;

a further main frame portion;

a further plurality of flexures connecting said further hub portion to said further main frame portion to allow said further main frame portion to dither with respect to said further hub portion.

19. A sensor structure as claimed in claim 18 wherein said means for linking comprises a stack link interconnecting said first and second sensor stacks.

20. A sensor structure as claimed in claim 19 wherein said stack link provides means for translating dither motion imposed on said main frame portion of said first sensor stack in a first direction into a dither motion on said main frame portion of said second sensor stack in a second direction opposite said first direction.

21. A sensor structure as claimed in claim 20 wherein said stack link comprises:

a first stepped member;

a second stepped member directed opposite said first stepped member;

a back to back, S-bending flexure unit connecting said first and second stepped members;

first means for connecting said first stepped member to said main frame portion of said first sensor stack;

second means for connecting said second stepped member to said further main frame portion of said second sensor stack;

third means for connecting said first and second stepped members to said further hub portion.

22. A sensor structure as claimed in claim 15 wherein said first sensor stack further comprises:

a mass plate disposed over a first surface of said first substrate;

a first damping plate disposed over a second surface of said first substrate, said second surface being opposite and generally parallel to said first surface;

a second damping plate disposed over said mass plate.

23. A sensor structure as claimed in claim 15 wherein said second sensor stack further comprises:

a mass plate disposed over a first surface of said second substrate;

a first damping plate disposed over a second surface of said second substrate, said second surface being generally parallel to said first surface;

a second damping plate disposed over said mass plate.

25. A sensor structure as claimed in claim 24 wherein said linking means comprises a linking member formed from a third planar substrate and disposed in a third plane that is generally parallel to said first and second planes, said third plane lying between said first and second planes.

14. A method for altering response characteristics of an accelerometer wherein said accelerometer includes a sensor frame formed in a substrate, a pendulum formed in said substrate, and an elastic suspension connecting said pendulum to said sensor frame, said method comprising the step of disposing a material over said pendulum, said material having a density that differs from the density of said substrate.

15. A sensor structure adapted for use in a triaxial angular rate and acceleration sensor comprising:

a first sensor stack including a first generally planar substrate, said first substrate having a first set of coplanar accelerometers formed therein, each accelerometer of said first set of accelerometers having a sensing axis canted at an angle with respect to the plane of said first substrate, said first set of accelerometers being arranged in the plane of said first substrate to place said sensing axes of said first set of accelerometers skewed to one another;

a second sensor stack including a second generally planar substrate, said second substrate including a second set of coplanar accelerometers formed therein, each of said second set of accelerometers having a sensing axis canted at an angle with respect to the plane of said second substrate, said second set of accelerometers being arranged in the plane of said second substrate to place said sensing axes of said second set of accelerometers skewed to one another, each of said second set of accelerometers being paired with a corresponding accelerometer of said first set of accelerometers, corresponding accelerometer pairs having sensing axes that are parallel or anti-parallel;

means for linking said first and second stacks so that said first and second sets of accelerometers dither at the same frequency.

24. A sensor structure comprising:

a first accelerometer formed in a first planar substrate and disposed in a first plane, said first accelerometer having a sensing axis;

a second accelerometer formed in a second planar substrate and disposed in a second plane that is generally parallel to said first plane, said second accelerometer having a sensing axis that is aligned with and anti-parallel or parallel with said sensing axis of said first accelerometer;

means for linking said first and second accelerometers so that movement of said first accelerometer in said first plane causes a corresponding movement of said second accelerometer in said second plane.