Microelectromechanical gyroscope with inversion of actuation forces, and method for actuating a microelectromechanical gyroscope

• US 8,714,012 B2
• Filed: 02/15/2011
• Issued: 05/06/2014
• Est. Priority Date: 02/16/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Caminada, Carlo, Prandi, Luciano, Rizzo Piazza Roncoroni, Alessandra Maria
• Primary Examiner(s): MacChiarolo, Peter
• Assistant Examiner(s): Shah, Samir M
• Application Number:
  US13/027,892
• Publication Number:
  US 20110197675A1
• Time in Patent Office: 1,176 Days
• Field of Search: 735/041.2, 735/041.8, 735/033, 735/040.2, 735/143.2
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5762 the sensing mass being connected to a driving mass, e.g. driving frames

Abstract

A microelectromechanical gyroscope includes a body and a driving mass, which is movable with respect to the body according to a driving axis and is capacitively coupled to the body. The gyroscope moreover includes a driving device, which forms a microelectromechanical control loop with the body and the driving mass and is configured for supplying to the driving mass driving signals having a common-mode component and respective differential components so as to maintaining the driving mass in oscillation according to the driving axis. The driving device is provided with an actuation stage configured for inverting in a controlled way the sign of the differential components of the driving signals.

Claims

1. A microelectromechanical gyroscope comprising:

a body;

a driving mass configured to move with respect to the body with a first degree of freedom according to a driving axis;

a capacitive coupling that couples the driving mass to the body; and

a driving device configured to form a microelectromechanical control loop with the body and the driving mass and configured to provide the driving mass with driving signals having a common-mode component and respective differential components so as to maintain the driving mass in oscillation according to the driving axis with a driving frequency, the driving device including an actuation stage configured to selectively invert a sign of the differential components of the driving signals.

2. The gyroscope according to claim 1, comprising:

a sensing mass mechanically coupled to the driving mass so as to be drawn in motion according to the driving axis and movable with respect to the driving mass with a second degree of freedom according to a sensing axis, in response to rotations of the body;

a read generator configured to provide the sensing mass with a square-wave read signal; and

a read device configured to provide output signals indicative of a position of the sensing mass in response to the read signal;

wherein the actuation stage is configured to invert the sign of the differential components of the driving signals in concurrence with first edges of the read signal.

3. The gyroscope according to claim 2, wherein the actuation stage is configured to invert the sign of the differential components of the driving signals with an advance with respect to second edges of the read signal, consecutive to the first edges.

4. The gyroscope according to claim 3, wherein the advance is programmable.

5. The gyroscope according to claim 2, wherein the actuation stage comprises:

an amplifier having a first amplifier output and a second amplifier output; and

a switching module having a first input and a second input, coupled respectively to the first amplifier output and the second amplifier output, and a first switching output and a second switching output coupled to the driving mass through respective driving terminals and the capacitive coupling, wherein the switching module is configured, in a first operating configuration, to couple the first input to the first switching output and couple the second input to the second switching output and, in a second operating configuration, to couple the first input to the second switching output and couple the second input to the first switching output.

6. The gyroscope according to claim 5, comprising a timing generator configured to control the read generator and the read device through a set of timing signals and switch the switching module between the first operating configuration and the second operating configuration through a further timing signal.

7. The gyroscope according to claim 6, wherein the timing generator is configured to switch the switching module from the first operating configuration to the second operating configuration in concurrence with the first edges of the read signal.

8. The gyroscope according to claim 6, wherein the actuation stage is configured to invert the sign of the differential components of the driving signals with an advance with respect to second edges of the read signal, consecutive to the first edges, and the timing generator is configured to switch the switching module from the second operating configuration to the first operating configuration with the advance with respect to the second edges of the read signal.

9. The gyroscope according to claim 5, wherein the amplifier is a variable-gain amplifier.

10. The gyroscope according to claim 1, wherein the driving device comprises a detection interface capacitively coupled to the driving mass and configured to provide feedback signals indicative of a position of the driving mass with respect to the driving axis.

11. The gyroscope according to claim 10, wherein the actuation stage is coupled to the detection interface and is configured to generate the driving signals based on the feedback signals.

12. The gyroscope of claim 1 wherein the driving device is configured to detect feedback signals from the driving mass and generate the driving signals based on the feedback signals.

13. A system comprising:

a control unit; and

a microelectromechanical gyroscope coupled to the control unit, the gyroscope including;

a substrate;

a driving mass configured to receive driving signals, to output feedback signals, and to move with respect to the substrate with a first degree of freedom along a driving axis;

a driving device configured to generate the driving signals based on the feedback signals, the driving signals having a common-mode component and differential components that maintain the driving mass in oscillation according to the driving axis with a driving frequency, the driving device including;

an actuation stage configured to selectively invert a sign of the differential components of the driving signals.

14. The system according to claim 13, wherein the gyroscope includes:

a sensing mass mechanically coupled to the driving mass so as to be drawn in motion according to the driving axis and movable with respect to the driving mass with a second degree of freedom along a sensing axis, in response to rotations of the substrate;

a read generator configured to provide the sensing mass with a square-wave read signal; and

a read device configured to provide output signals indicative of a position of the sensing mass in response to the read signal;

wherein the actuation stage is configured to invert the sign of the differential components of the driving signals in concurrence with first edges of the read signal.

15. The system according to claim 13, wherein the actuation stage comprises:

an amplifier having a first amplifier output and a second amplifier output; and

a switching module having a first input and a second input, coupled respectively to the first amplifier output and second amplifier output, and a first switching output and a second switching output coupled to the driving mass through respective driving terminals, the switching module being configured, in a first operating configuration, to couple the first input to the first switching output and couple the second input to the second switching output and, in a second operating configuration, to couple the first input to the second switching output and couple the second input to the first switching output.

16. The system according to claim 15, wherein the gyroscope includes:

a sensing mass mechanically coupled to the driving mass so as to be drawn in motion along the driving axis and movable with respect to the driving mass with a second degree of freedom according to a sensing axis, in response to rotations of the substrate;

a read generator configured to provide the sensing mass with a square-wave read signal;

a read device configured to provide output signals indicative of a position of the sensing mass in response to the read signal, wherein the actuation stage is configured to invert the sign of the differential components of the driving signals in concurrence with first edges of the read signal; and

a timing generator configured to control the read generator and the read device through a set of timing signals and switch the switching module between the first operating configuration and the second operating configuration through a further timing signal.

17. The system according to claim 16, wherein the timing generator is configured to switch the switching module from the first operating configuration to the second operating configuration in concurrence with the first edges of the read signal.

18. The system according to claim 16, wherein the actuation stage is configured to invert the sign of the differential components of the driving signals with an advance with respect to second edges of the read signal, consecutive to the first edges, and the timing generator is configured to switch the switching module from the second operating configuration to the first operating configuration with the advance with respect to the second edges of the read signal.

19. A method, comprising:

actuating a microelectromechanical gyroscope that includes a substrate, a driving mass configured to move with respect to the substrate with a first degree of freedom according to a driving axis, and a driving device configured to form a microelectromechanical control loop with the substrate and the driving mass, the actuating including;

maintaining the driving mass in oscillation according to the driving axis with a driving frequency by providing the driving mass with the driving signals from the driving device, the driving signals having a common-mode component and respective differential components; and

selectively inverting the sign of the differential components of the driving signals with an actuation stage in the driving device.

20. The method according to claim 19, further comprising:

generating square-wave read signal in a read generator;

providing a sensing mass with the square-wave read signal, the sensing mass being mechanically coupled to the driving mass so as to be drawn in motion according to the driving axis and movable with respect to the driving mass with a second degree of freedom according to a sensing axis, in response to rotations of the substrate; and

detecting a position of the sensing mass in response to the read signal;

wherein selectively inverting the sign of the differential components of the driving signals includes inverting the sign of the differential components of the driving signals in concurrence with first edges of the read signal.

21. The method according to claim 19, wherein selectively inverting the sign of the differential components of the driving signals comprises inverting the sign of the differential components of the driving signals with an advance with respect to second edges of the read signal, consecutive to the first edges.

22. The method of claim 19 wherein maintaining the driving mass in oscillation includes:

detecting feedback signals from the driving mass; and

generating the driving signals in the driving device based on the feedback signals.