Six degree-of-freedom micro-machined multi-sensor

• US 6,848,304 B2
• Filed: 06/17/2003
• Issued: 02/01/2005
• Est. Priority Date: 04/28/2003
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Geen, John A.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/463,653
• Publication Number:
  US 20040211258A1
• Time in Patent Office: 595 Days
• Field of Search: 735/040.4, 735/041.2, 735/041.4, 735/041.6, 735/10
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass

Abstract

A six degree-of-freedom micro-machined multi-sensor that provides 3-axes of acceleration sensing, and 3-axes of angular rate sensing, in a single multi-sensor device. The six degree-of-freedom multi-sensor device includes a first multi-sensor substructure providing 2-axes of acceleration sensing and 1-axis of angular rate sensing, and a second multi-sensor substructure providing a third axis of acceleration sensing, and second and third axes of angular rate sensing. The first and second multi-sensor substructures are implemented on respective substrates within the six degree-of-freedom multi-sensor device.

Claims

1. A six degree-of-freedom multi-sensor, comprising:

a first substrate;

a second substrate;

a first multi-sensor substructure fabricated on the first substrate, the first multi-sensor substructure operative to provide a first plurality of sense signals indicative of acceleration sensing relative to mutually orthogonal first and second axes in the plane of the first substrate, and indicative of angular rate sensing relative to a third axis perpendicular to the first and second axes; and

a second multi-sensor substructure fabricated on the second substrate, the second multi-sensor substructure operative to provide a second plurality of sense signals indicative of angular rate sensing relative to mutually orthogonal fourth and fifth axes in the plane of the second substrate, and indicative of acceleration sensing relative to a sixth axis perpendicular to the fourth and fifth axes,

wherein the first multi-sensor substructure includes

a substantially planar accelerometer frame;

a first proof mass coupled to the frame;

a second proof mass coupled to the frame;

a first pair of diametrically opposed acceleration sense electrode structures coupled to the frame and disposed along the first axis; and

a second pair of diametrically opposed acceleration sense electrode structures coupled to the frame and disposed along the second axis,

wherein the first and second proof masses are configured to vibrate in antiphase along a vibration axis, the vibration axis being in a plane defined by the first and second axes, and

wherein each acceleration sense electrode structure is configured to produce a respective one of the first plurality of sense signals, each sense signal being electrically independent of the remaining sense signals.

2. The six degree-of-freedom multi-sensor of claim 1 further including a signal processing unit configured to extract information pertaining to acceleration sensing along the first and second axes, and to extract information pertaining to angular rate sensing relative to the third axis.

3. The six degree-of-freedom multi-sensor of claim 1 further including a resilient member resiliently coupling the first proof mass and the second proof mass.

4. The six degree-of-freedom multi-sensor of claim 1 further including a first amplifier configured to receive a differential sense signal from one of the first pair of acceleration sense electrode structures, and to produce a first sense signal, and a second amplifier configured to receive a differential sense signal from the other of the first pair of acceleration sense electrode structures, and to produce a second sense signal.

5. The six degree-of-freedom multi-sensor of claim 4 further including a third amplifier configured to receive the first and second sense signals, and to produce a third sense signal comprising the sum of the first and second sense signals, the third sense signal being indicative of acceleration sensing along the first axis.

6. The six degree-of-freedom multi-sensor of claim 1 further including a first amplifier configured to receive a differential sense signal from one of the second pair of acceleration sense electrode structures, and to produce a first sense signal, and a second amplifier configured to receive a differential sense signal from the other of the second pair of acceleration sense electrode structures, and to produce a second sense signal.

7. The six degree-of-freedom multi-sensor of claim 6 further including a third amplifier configured to receive the first and second sense signals, and to produce a third sense signal comprising the sum of the first and second sense signals, the third sense signal being indicative of acceleration sensing along the second axis.

8. The six degree-of-freedom multi-sensor of claim 1 further including a first amplifier configured to receive a differential sense signal from one of the first pair of acceleration sense electrode structures, and to produce a first sense signal, a second amplifier configured to receive a differential sense signal from the other of the first pair of acceleration sense electrode structures, and to produce a second sense signal, a third amplifier configured to receive a differential sense signal from one of the second pair of acceleration sense electrode structures, and to produce a third sense signal, and a fourth amplifier configured to receive a differential sense signal from the other of the second pair of acceleration sense electrode structures, and to produce a fourth sense signal.

9. The six degree-of-freedom multi-sensor of claim 8 further including a fifth amplifier configured to receive the first and second sense signals, and to produce a fifth sense signal comprising the difference of the first and second sense signals, and a sixth amplifier configured to receive the third and fourth sense signals, and to produce a sixth sense signal comprising the difference of the third and fourth sense signals.

10. The six degree-of-freedom multi-sensor of claim 9 further including a seventh amplifier configured to receive the fifth and sixth sense signals, and to produce a seventh sense signal comprising the sum of the fifth and sixth sense signals, the seventh sense signal being indicative of angular rate sensing relative to the third axis.

11. The six degree-of-freedom multi-sensor of claim 10 further including a velocity sense electrode structure configured to produce a velocity sense signal, the velocity sense signal being in phase with a vibration velocity of the first and second proof masses and asynchronous with a linear acceleration of the first and second proof masses.

12. The six degree-of-freedom multi-sensor of claim 11 further including a phase demodulator configured to receive the seventh sense signal and the velocity sense signal, and to produce an eighth sense signal indicative of angular rate sensing relative to the third axis.

13. The six degree-of-freedom multi-sensor of claim 1 wherein the first and second substrates are combined to form a single substrate.

14. A six degree-of-freedom multi-sensor, comprising:

a first substrate,

a second substrate;

a first multi-sensor substructure fabricated on the first substrate, the first multi-sensor substructure operative to provide a first plurality of sense signals indicative of acceleration sensing relative to mutually orthogonal first and second axes in the plane of the first substrate, and indicative of angular rate sensing relative to a third axis perpendicular to the first and second axes; and

a second multi-sensor substructure fabricated on the second substrate, the second multi-sensor substructure operative to provide a second plurality of sense signals indicative of angular rate sensing relative to mutually orthogonal fourth and fifth axes in the plane of the second substrate, and indicative of acceleration sensing relative to a sixth axis perpendicular to the fourth and fifth axes,

wherein the second multi-sensor substructure includes

at least one first mass coupled to and suspended over the second substrate, the first mass having associated longitudinal and lateral axes, and an associated rotation axis perpendicular to the longitudinal and lateral axes;

at least one second mass coupled to and suspended over the second substrate, the second mass having associated longitudinal and lateral axes, and an associated rotation axis perpendicular to the longitudinal and lateral axes, the second mass being adjacent to the first mass,

at least one drive structure operatively coupled to the first and second masses, the drive structure being configured to vibrate the first and second masses in antiphase about the respective rotation axes;

first and second pairs of diametrically opposed acceleration sensing structures operatively coupled to the first mass, the first and second acceleration sensing structure pairs being disposed along the longitudinal and lateral axes, respectively, of the first mass; and

third and fourth pairs of diametrically opposed acceleration sensing structures operatively coupled to the second mass, the third and fourth acceleration sensing structure pairs being disposed along the longitudinal and lateral axes, respectively, of the second mass,

wherein the respective longitudinal axes are parallel to the fourth axis, and the respective lateral axes are parallel to the fifth axis, and

wherein each acceleration sensing structure is configured to produce a respective sense signal, the respective sense signals being indicative of angular rate sensing relative to the fourth and fifth axes, and being further indicative of acceleration sensing relative to the sixth axis.

15. The six degree-of-freedom multi-sensor of claim 14 wherein each of the respective sense signals produced by the first and third pairs of acceleration sensing structures includes a linear component relative to the sixth axis and a rotational component relative to the fourth axis, and wherein each of the respective sense signals produced by the second and fourth pairs of acceleration sensing structures includes a linear component relative to the sixth axis and a rotational component relative to the fifth axis.

16. The six degree-of-freedom multi-sensor of claim 15 further including a signal processing unit configured to combine the respective linear sense signal components produced by the first, second, third, and fourth pairs of acceleration sensing structures to produce an output signal including information pertaining to acceleration sensing relative to the sixth axis.

17. The six degree-of-freedom multi-sensor of claim 15 further including a signal processing unit configured to combine the respective rotational sense signal components produced by the first and third pairs of acceleration sensing structures to produce an output signal including information pertaining to angular rate sensing relative to the fourth axis.

18. The six degree-of-freedom multi-sensor of claim 15 further including a signal processing unit configured to combine the respective rotational sense signal components produced by the second and fourth pairs of acceleration sensing structures to produce an output signal including information pertaining to angular rate sensing relative to the fifth axis.

19. The six degree-of-freedom multi-sensor of claim 14 further including a resilient member coupling the first mass and the second mass, the resilient member being configured to allow the antiphase vibrational movement, and to resist in phase vibrational movement, of the respective masses.

20. The six degree-of-freedom multi-sensor of claim 14 further including a first amplifier configured to receive a pair of first sense signals from the first pair of acceleration sensing structures, and a third amplifier configured to receive a pair of third sense signals from the third pair of acceleration sensing structures, the first and third amplifiers being further configured to produce first and third output signals comprising the difference of the pair of first sense signals, and the difference of the pair of third sense signals, respectively, the first and third output signals being indicative of angular rate sensing relative to the fourth axis.

21. The six degree-of-freedom multi-sensor of claim 14 further including a second amplifier configured to receive a pair of second sense signals from the second pair of acceleration sensing structures, and a fourth amplifier configured to receive a pair of fourth sense signals from the fourth pair of acceleration sensing structures, the second and fourth amplifiers being further configured to produce second and fourth output signals comprising the difference of the pair of second sense signals, and the difference of the pair of fourth sense signals, respectively, the second and fourth output signals being indicative of angular rate sensing relative to the fifth axis.

22. The six degree-of-freedom multi-sensor of claim 14 further including a first amplifier configured to receive a pair of first sense signals from the first pair of acceleration sensing structures, a second amplifier configured to receive a pair of second sense signals from the second pair of acceleration sensing structures, a third amplifier configured to receive a pair of third sense signals from the third pair of acceleration sensing structures, and a fourth amplifier configured to receive a pair of fourth sense signals from the fourth pair of acceleration sensing structures, the first, second, third, and fourth amplifiers being further configured to produce first, second, third, and fourth output signals comprising the sum of the pair of first sense signals, the sum of the pair of second sense signals, the sum of the pair of third sense signals, and the sum of the pair of fourth sense signals, respectively, the first, second, third, and fourth output signals being indicative of acceleration sensing relative to the sixth axis.

23. The six degree-of-freedom multi-sensor of claim 14 including two first masses and two second masses suspended over the substrate, the four masses being arranged so that each mass is adjacent to two other masses, and wherein the drive structure is configured to vibrate the four masses in antiphase about the respective rotation axes so that each mass moves in an equal and opposite manner relative to an adjacent mass.

24. A method of operating a six degree-of-freedom multi-sensor, comprising the steps of:

providing a first plurality of sense signals by a first multi-sensor substructure, the first plurality of sense signals being indicative of acceleration sensing relative to mutually orthogonal first and second axes in the plane of a first substrate, and indicative of angular rate sensing relative to a third axis perpendicular to the first and second axes, the first multi-sensor substructure being implemented on the first substrate;

providing a second plurality of sense signals by a second multi-sensor substructure, the second plurality of sense signals being indicative of angular rate sensing relative to mutually orthogonal fourth and fifth axes in the plane of a second substrate, and indicative of acceleration sensing relative to a sixth axis perpendicular to the fourth and fifth axes, the second multi-sensor substructure being implemented on the second substrate;

vibrating in antiphase a first proof mass and a second proof mass along a vibration axis by a drive electrode structure, the first proof mass being coupled to an accelerometer frame, and the second proof mass being coupled to the accelerometer frame;

producing respective first accelerometer sense signals by a first pair of diametrically opposed acceleration sense electrode structures coupled to the frame and disposed along the first axis; and

producing respective second accelerometer sense signals by a second pair of diametrically opposed acceleration sense electrode structures coupled to the frame and disposed along the second axis, the first and second proof masses, the drive electrode structure, and the first and second pairs of acceleration sense electrode structures being included in the first multi-sensor substructure,

wherein each sense signal produced in the first and second producing steps is electrically independent of the remaining sense signals.

25. The method of claim 24 further including the steps of extracting information pertaining to acceleration sensing along the first and second axes and extracting information pertaining to angular rate sensing relative to the third axis by a signal processing unit.

26. A method of operating a six degree-of-freedom multi-sensor, comprising the steps of:

providing a first plurality of sense signals by a first multi-sensor substructure, the first plurality of sense signals being indicative of acceleration sensing relative to mutually orthogonal first and second axes in the plane of a first substrate, and indicative of angular rate sensing relative to a third axis perpendicular to the first and second axes, the first multi-sensor substructure being implemented on the first substrate;

providing a second plurality of sense signals by a second multi-sensor substructure, the second plurality of sense signals being indicative of angular rate sensing relative to mutually orthogonal fourth and fifth axes in the plane of a second substrate, and indicative of acceleration sensing relative to a sixth axis perpendicular to the fourth and fifth axes, the second multi-sensor substructure being implemented on the second substrate;

vibrating in antiphase at least one first mass and at least one second mass about respective rotation axes by a drive structure, the first and second masses being adjacent to each other and being coupled to and suspended over the second substrate, each mass having associated longitudinal and lateral axes perpendicular to the respective rotation axis, the respective longitudinal axes being parallel to the fourth axis, and the respective lateral axes being parallel to the fifth axis;

producing respective sense signals by first and second pairs of diametrically opposed acceleration sensing structures operatively coupled to the first mass, the first and second acceleration sensing structure pairs being disposed along the longitudinal and lateral axes, respectively, of the first mass; and

producing respective sense signals by third and fourth pairs of diametrically opposed acceleration sensing structures operatively coupled to the second mass, the third and fourth acceleration sensing structure pairs being disposed along the longitudinal and lateral axes, respectively, of the second mass, the first and second masses, the drive structure, and the first, second, third, and fourth acceleration sensing structure pairs being included in the second multi-sensor substructure,

wherein the respective sense signals produced in the first and second producing steps are indicative of angular rate sensing relative to the fourth and fifth axes, and further indicative of acceleration sensing relative to the sixth axis.

27. The method of claim 26 further including the step of combining respective linear sense signal components produced by the first, second, third, and fourth pairs of acceleration sensing structures to produce an output signal including information pertaining to acceleration sensing relative to the sixth axis by a signal processing unit.

28. The method of claim 26 further including the step of combining respective rotational sense signal components produced by the first and third pairs of acceleration sensing structures to produce an output signal including information pertaining to angular rate sensing relative to the fourth axis by a signal processing unit.

29. The method of claim 26 further including the step of combining the respective rotational sense signal components produced by the second and fourth pairs of acceleration sensing structures to produce an output signal including information pertaining to angular rate sensing relative to the fifth axis by a signal processing unit.