Sensor and method for sensing linear acceleration and angular velocity

• US 7,950,281 B2
• Filed: 02/28/2007
• Issued: 05/31/2011
• Est. Priority Date: 02/28/2007
• Status: Expired due to Fees

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Hammerschmidt, Dirk
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US11/680,275
• Publication Number:
  US 20080202237A1
• Time in Patent Office: 1,553 Days
• Field of Search: 735/040.4, 735/041.2, 735/041.6
• 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 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A sensor has a suspended mechanical resonator being responsive to one of a linear acceleration and an angular velocity of the sensor such that a first area and a second area are subjected to opposite elongation movements and responsive to the other such that the first area and the second area are subjected to a common elongation movement, a first mechanical-electrical interface interacting with the first area, a second mechanical-electrical interface interacting with the second area, a common mode signal generator coupled to the mechanical-electrical interfaces with a common mode signal output, a differential mode signal generator coupled to the mechanical-electrical interfaces with a differential mode signal output, a first processing circuit coupled to the differential mode output, with an output for a first processed signal, and a second processing circuit coupled to the common mode output with an output for a second processed signal.

Claims

1. A sensor comprising:

a suspended mechanical resonator comprising a first oscillating plate and a second oscillating plate which are suspended via spring beams and interconnected by a connecting beam being collinear to the spring beams on a common axis such that the suspended mechanical resonator extends, in an equilibrium state, in a resonator plane and is configured to oscillate in an intermediate mode, a first detection mode and a second detection mode;

an exciter with an exciter mechanical-electrical interface configured to excite the intermediate mode, wherein the suspended mechanical resonator is designed such that, in the intermediate mode, the first and second plate perform opposite rotating in-plane oscillation movements within the resonator plane, wherein the suspended mechanical resonator is further adapted such that a linear acceleration of the sensor along a first direction perpendicular to the resonator plane, with the suspended mechanical resonator having the intermediate mode excited, results in the suspended mechanical resonator exhibiting the first detection mode in which lateral portions of the first and second oscillating plates, being laterally displaced from the common axis, are bent in an oscillating manner synchronously upwards and downwards relative to the resonator plane, and an angular velocity of the sensor in a second direction parallel to the resonator plane, with the suspended mechanical resonator having the intermediate mode excited, results in the suspended mechanical resonator exhibiting the second detection mode in which the lateral portions of the first and second oscillating plates are subject to counter-oscillating movements upwards and downwards relative to the resonator plane;

a first detection electrode arranged offset to the resonator plane, facing a first one of the lateral portions of the first and second oscillating plates and comprising a terminal, at which a first signal indicative of the displacement of the first lateral portion from the resonator plane is provided;

a second detection electrode arranged offset to the resonator plane, facing a second one of the lateral portion of the first and second oscillating plates and comprising a terminal, at which a second signal indicative of the displacement of the second lateral portion from the resonator plane is provided;

a common mode signal generator coupled to the first detection electrode and the second detection electrode, the common mode signal generator comprising a common mode signal output configured to provide a common mode signal based upon the first and the second signals;

a differential mode signal generator coupled to the first detection electrode and the second detection electrode the differential mode signal generator comprising a differential mode signal output configured to provide a differential mode signal based upon the first and the second signals;

a first processing circuit coupled to the differential mode output, with an output for a first processed signal based upon the differential mode signal, indicative of the angular velocity of the sensor; and

a second processing circuit coupled to the common mode output with an output for a second processed signal based upon the common mode signal, indicative of the linear acceleration of the sensor.

2. The sensor according to claim 1, further comprising a first analog/digital converter coupled in between the terminal of the first mechanical-electrical interface, the terminal of the second mechanical-electrical interface and the common mode signal generator and the differential mode signal generator, such that the common mode signal generator and the differential mode signal generator are configured to digitally process the first and second signals.

3. The sensor according to claim 1, wherein the exciter mechanical-electrical interface is configured to influence a first excitation area and a second excitation area of the suspended mechanical resonator.

4. The sensor according to claim 1, further comprising a differential mode feedback controller coupled to a differential mode feedback signal output with an output for a differential feedback signal, a common mode feedback controller coupled to the common mode signal output with an output for a common mode feedback signal and a signal generator coupled to the common mode feedback controller and the differential mode feedback controller with an output for a first feedback signal and an output for a second feedback signal, wherein the first and the second feedback signals are based on the common mode feedback signal and the differential mode feedback signal, and wherein the output for the first feedback signal is coupled to the first detection electrode and the output for the second feedback signal is coupled to the second detection electrode such that the counter-oscillating movement and the movement in the oscillating manner of the first and second lateral portions are compensable.

5. The sensor according to claim 4, further comprising a multiplexer configured to provide the first signal and the second signal to the common mode signal generator and the differential mode signal generator without influence by the first feedback signal and the second feedback signal.

6. The sensor according to claim 4, wherein the sensor further comprises an analog/digital converter coupled in between the terminals of the first and the second detection electrodes and the differential mode feedback controller and the common mode feedback controller, and wherein the differential mode feedback controller and the common mode feedback controller are configured to perform digital signal processing.

7. The sensor according to claim 1, wherein the suspended mechanical resonator is a MEMS mechanical resonator.

8. The sensor according to claim 1, wherein the exciter is configured to excite the suspended mechanical resonator in a closed feedback loop.

9. The sensor according to claim 8, wherein the exciter comprises an analog/digital converter and a digital/analog converter such that the closed feedback loop is based on a digital signal processing.

10. The sensor according to claim 1, wherein the connecting beam interconnecting the first oscillating plate and the second oscillating plate is an asymmetric beam, and the exciter mechanical-electrical interface comprises first and second excitation electrodes facing a first excitation area of the first oscillating plate and a second excitation area of the second oscillating plate, respectively, and the exciter is configured to excite the intermediate mode indirectly by causing alternating electrostatic attraction between the first excitation area and first excitation electrode in the direction perpendicular to the resonator plane and between the second excitation area and second excitation electrode in the direction perpendicular to the resonator plane.

11. The sensor according to claim 1, wherein a resonance frequency of the first detection mode is different from a resonance frequency of the second detection mode.

12. The sensor according to claim 1, wherein the connecting beam interconnecting the first oscillating plate and the second oscillating plate is an asymmetric beam, and the suspended mechanical resonator is configured to oscillate in an excitation mode, the intermediate mode, the first detection mode and the second detection mode, wherein the exciter is configured to indirectly excite the intermediate mode by exciting the excitation mode of the suspended mechanical resonator at a frequency approximately matching a resonance frequency of the intermediate mode and being different from a resonance frequency of the excitation mode such that an excitation energy provided by the exciter is distributed, by the asymmetric beam, in the intermediate mode more than in the excitation mode.

13. The sensor according to claim 1, wherein the suspended mechanical resonator is further adapted such that, in the first detection mode, the lateral portions of the first and second oscillating plates are bent in the oscillating manner synchronously upwards and downwards relative to the resonator plane at a resonance frequency substantially determined by a stiffness of the first and second oscillating plates, and that in the second detection mode, the lateral portions of the first and second oscillating plates are subjected to counter-oscillating movements upwards and downwards relative to the resonator plane at a resonance frequency determined by a stiffness of a suspension of the first and second oscillating plates and being lower than a resonance frequency of the first detection mode.

14. A method for sensing a linear acceleration and an angular velocity using a suspended mechanical resonator comprising a first oscillating plate and a second oscillating plate which are suspended via spring beams and interconnected by a connecting beam being collinear to the spring beams on a common axis such that the suspended mechanical resonator extends, in an equilibrium state, in a resonator plane and is configured to oscillate in an intermediate mode, a first detection mode and a second detection mode, comprising:

exciting the intermediate mode such that, in the intermediate mode, the first and second plate perform opposite rotating in-plane oscillation movements within the resonator plane, and such that a linear acceleration of the sensor along a first direction perpendicular to the resonator plane, with the suspended mechanical resonator having the intermediate mode excited, results in the suspended mechanical resonator exhibiting the first detection mode in which lateral portions of the first and second oscillating plates, being laterally displaced from the common axis, are bent in an oscillating manner synchronously upwards and downwards relative to the resonator plane, and an angular velocity of the sensor in a second direction parallel to the resonator plane, with the suspended mechanical resonator having the intermediate mode excited, results in the suspended mechanical resonator exhibiting the second detection mode in which the lateral portions of the first and second oscillating plates are subject to counter-oscillating movements upwards and downwards relative to the resonator plane;

detecting a displacement of a first one of the lateral portions of the suspended mechanical resonator from the resonator plane;

detecting a displacement of a second one of the lateral portions of the suspended mechanical resonator from the resonator plane;

generating a common mode signal based upon the displacement of the first lateral portion and the displacement of the second lateral portion;

generating a differential mode signal based upon the displacement of the first lateral portion and the displacement of the second lateral portion;

processing the differential mode signal to a first processed signal indicative of the angular velocity of a sensor; and

processing the common mode signal to a second processed signal indicative of the linear acceleration of the sensor.

15. The method of claim 14, wherein the suspended mechanical resonator is further adapted such that, in the first detection mode, the lateral portions of the first and second oscillating plates are bent in the oscillating manner synchronously upwards and downwards relative to the resonator plane at a resonance frequency substantially determined by a stiffness of the first and second oscillating plates, and that in the second detection mode, the lateral portions of the first and second oscillating plates are subjected to counter-oscillating movements upwards and downwards relative to the resonator plane at a resonance frequency determined by a stiffness of a suspension of the first and second oscillating plates and being lower than a resonance frequency of the first detection mode.

16. The method of claim 14, wherein the connecting beam interconnecting the first oscillating plate and the second oscillating plate is an asymmetric beam, and the excitation is performed via first and second excitation electrodes facing a first excitation area of the first oscillating plate and a second excitation area of the second oscillating plate, respectively, by exciting the intermediate mode indirectly by causing alternating electrostatic attraction between the first excitation area and first excitation electrode in the direction perpendicular to the resonator plane and between the second excitation area and second excitation electrode in the direction perpendicular to the resonator plane.

17. Computer executable instructions stored on a computer readable medium with a computer program product comprising code, said code, when running on a computer, performing a method for sensing a linear acceleration and an angular velocity using a suspended mechanical resonator comprising a first oscillating plate and a second oscillating plate which are suspended via spring beams and interconnected by a connecting. beam being collinear to the spring beams on a common axis such that the suspended mechanical resonator extends, in an equilibrium state, in a resonator plane and is configured to oscillate in an intermediate mode, a first detection mode and a second detection mode, comprising:

exciting the intermediate mode such that, in the intermediate mode, the first and second plate perform opposite rotating in-plane oscillation movements within the resonator plane, and such that a linear acceleration of the sensor along a first direction perpendicular to the resonator plane, with the suspended mechanical resonator having the intermediate mode excited, results in the suspended mechanical resonator exhibiting the first detection mode in which lateral portions of the first and second oscillating plates, being laterally displaced from the common axis, are bent in an oscillating manner synchronously upwards and downwards relative to the resonator plane, and an angular velocity of the sensor in a second direction parallel to the resonator plane, with the suspended mechanical resonator having the intermediate mode excited, results in the suspended mechanical resonator exhibiting the second detection mode in which the lateral portions of the first and second oscillating plates are subject to counter-oscillating movements upwards and downwards relative to the resonator plane;

causing a first detection electrode to detect a displacement of a first one of lateral portions of a suspended mechanical resonator from a resonator plane;

causing a second detection electrode to detect a displacement of a second one of lateral portions of the suspended mechanical resonator from the resonator plane;

generating a common mode signal based upon the displacement of the first lateral portion and the displacement of the second lateral portion;

generating a differential mode signal based upon the displacement of the first lateral portion and the displacement of the second lateral portion;

processing the differential mode signal to a first processed signal indicative of the angular velocity of a sensor; and

processing the common mode signal to a second processed signal indicative of the linear acceleration of the sensor.

18. The computer-readable medium of claim 17, wherein the suspended mechanical resonator is further adapted such that, in the first detection mode, the lateral portions of the first and second oscillating plates are bent in the oscillating manner synchronously upwards and downwards relative to the resonator plane at a resonance frequency substantially determined by a stiffness of the first and second oscillating plates, and that in the second detection mode, the lateral portions of the first and second oscillating plates are subjected to counter-oscillating movements upwards and downwards relative to the resonator plane at a resonance frequency determined by a stiffness of a suspension of the first and second oscillating plates and being lower than a resonance frequency of the first detection mode.

19. The computer-readable medium of claim 17, wherein the connecting beam interconnecting the first oscillating plate and the second oscillating plate is an asymmetric beam, and the excitation is performed via first and second excitation electrodes facing a first excitation area of the first oscillating plate and a second excitation area of the second oscillating plate, respectively, by exciting the intermediate mode indirectly by causing alternating electrostatic attraction between the first excitation area and first excitation electrode in the direction perpendicular to the resonator plane and between the second excitation area and second excitation electrode in the direction perpendicular to the resonator plane.