System and method for sensor replication for ensemble averaging in micro-electromechanical systems (MEMS)

• US 20060082463A1
• Filed: 10/20/2004
• Published: 04/20/2006
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Pozidis, Charalampos, Sharma, Arun, Eleftheriou, Evangelos S., Lantz, Mark A., Sri-Jayantha, Sri M., Dang, Hien
• Granted Patent: US 7,426,416 B2
• Time in Patent Office: Days
• US Class Current: 340/635
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown
• CPC Class Codes: G01K 2215/00 Details concerning sensor power supply

Abstract

A MEMs-based system (and method), includes a sensor array including at least two sensors providing a basis for ensemble averaging.

Claims

1. A MEMs-based system, comprising:

a sensor array including at least two sensors providing a basis for ensemble averaging.

2. The system of claim 1, wherein said at least two sensors comprise at least two replicated sensors.

3. The system of claim 1, further comprising:

an optimal ratio combiner that extends the ensemble averaging when the sensor array includes non-uniform noise statistics.

4. The system of claim 1, further comprising:

a system controller for controlling a power of the sensor array such that the power is selectively adjusted depending upon a desired precision.

5. The system of claim 4, wherein the system controller controls said power by limiting a number of sensors activated for servo control.

6. The system of claim 1, further comprising:

means for detecting a sensor failure and for providing a redundancy against failure.

7. The system of claim 1, wherein at least one sensor of said at least two sensors is segmentable to selectively adjust a signal-to-noise ratio in relation to a desired range and complexity.

8. The system of claim 1, further comprising:

an alarm unit that notifies a user of a failure of a predetermined number of said at least two sensors.

9. The system of claim 8, further comprising:

a low-pass filter coupled to receive an output of said ensemble averaging; and

a servo loop coupled to said low-pass filter, such that when said user is notified about a last remaining functioning sensor by said alarm unit, the servo loop allows for data backup with an increased level of filtering by said low-pass filter.

10. The system of claim 1, wherein said at least two sensors operate based on a transduction process comprising any of a pressure, temperature, and acceleration.

11. The system of claim 1, wherein said ensemble averaging is performed with servo control.

12. The system of claim 1, wherein said ensemble averaging is performed devoid of servo control.

13. The system of claim 1, wherein said at least two sensors are substantially identical.

14. The system of claim 13, further comprising:

a summer that sums outputs of the substantially identical sensors; and

a gain amplifier that applies a uniform weighting factor to one of an output of the summer and the outputs of the substantially identical sensors.

15. The system of claim 1, further comprising:

a low-pass filter that receives an output of the amplifier;

a sampler that samples the output of the low pass filter; and

a second low pass filter that receives the output of the sampler.

16. The system of claim 1, wherein the ensemble averaging comprises a weighted ensemble averaging such that the output of each of said at least two sensors is weighted according to its signal-to-noise ratio (SNR).

17. The system of claim 1, wherein said ensemble averaging comprises a uniformly-weighted ensemble averaging such that equal weight is given to all outputs of said at least two sensors.

18. The system of claim 16, further comprising:

a gain unit that adjusts an output of a sensor of said at least two sensors depending upon a behavior of said sensor.

19. The system of claim 1, further comprising:

a gain unit that, depending upon a behavior of said at least two sensors, adjusts any of the outputs of said at least two sensors by using different gains depending upon a performance and a noise level of said any of said at least two sensors.

20. The system of claim 1, further comprising:

an optimal ratio combiner that combines the sensor outputs; and

a calibrator that calibrates said sensors to determine a required correction gain for each sensor prior to computation of the ensemble average.

21. The system of claim 1, further comprising:

a system controller that selectively controls an activation and deactivation of a sensor of said at least two sensors.

22. The system of claim 21, wherein the system controller controls said at least two sensors to select a best sensor or a best group of sensors for a predetermined operation, and powers-down remaining sensors that are not needed for the predetermined operation.

23. The system of claim 22, further comprising:

a filtering and ensemble averaging module, wherein information regarding the sensors selected by said system controller, is concurrently transmitted from said system controller to the filtering and ensemble averaging module to account for a change in number of sensors.

24. The system of claim 22, wherein in a case of inadvertent failure of an activated sensor, said system controller activates a second sensor which is powered-down.

25. The system of claim 22, wherein first and second sensors of said at least two sensors are located at two extreme positions of said MEMs device, and provide rotation information of a component of said MEMs device.

26. The system of claim 25, further comprising:

first and second low pass filters for receiving outputs from the first and second sensors, said first and second lowpass filters providing an input to a summer,

said summer receiving a gain signal having been applied to sensor outputs other than those from the first and second sensors and an ensemble averaged linear position signal,

wherein the output of summer is combined with a signal representing a rotation of an edge of said component of said MEMs device, said component comprising a movable platform.

27. The system of claim 22, wherein same sensors of said at least two sensors contributing to the ensemble averaging also contribute to rotation measurement of a component of said MEMs device.

28. The system of claim 1, wherein a sensor of said at least two sensors includes multiple sub-sensing elements with an overlapping region.

29. The system of claim 1, wherein said at least two sensors comprise a segmented and replicated sensor array.

30. The system of claim 1, wherein the ensemble averaging reduces noise across an entire bandwidth of said at least two sensors.

31. The system of claim 1, further comprising:

a system controller controlling said at least two sensors; and

an alarm unit that notifies any of said system controller and a user that a predetermined number of sensors of said at least two sensors have failed, and initiates a backup of data collected by said at least two sensors.

32. A method of reducing noise in a MEMs-based system, comprising:

providing a sensor array including at least two sensors; and

ensemble averaging outputs of said sensor array.

33. The method of claim 32, wherein said at least two sensors are replicated to measure a same position variable, and

wherein said ensemble averaging reduces an effective sensor noise to (σ

/N^0.5), where N is a number of sensors of said at least two sensors.

34. The method of claim 32, further comprising:

sensing a motion of an object using a common feature of said object, said ensemble average providing a mean position of the common feature with rotation of the common feature.

35. The method of claim 32, further comprising:

sensing a motion of an object using a common feature of said object, said ensemble average providing a mean position of the common feature without any rotation of the common feature.

36. The method of claim 32, further comprising:

taking a difference between output of sensors positioned at extreme locations, thereby to extract a rotation measurement.

37. The method of claim 32, further comprising:

selectively powering-up a number of sensors for the ensemble averaging.

38. The method of claim 32, further comprising:

modifying one of a servo loop and a filtering characteristic to recover a user data in a lower performance mode.

39. The method of claim 32, further comprising:

segmenting a sensor range of said sensor array into a plurality of segments; and

engaging multiple sensors progressively covering each segment to produce a single continuous output with predetermined noise properties.

40. A signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method of reducing noise in a MEMs-based system, comprising:

providing a sensor array including at least two sensors; and

ensemble averaging outputs of said sensor array.

41. A system for reducing noise in a MEMs-based system, comprising:

a sensor array including at least two sensors; and

means for ensemble averaging outputs of said sensor array.