Method for improving the performance of micromachined devices

• US 6,636,819 B1
• Filed: 10/05/2000
• Issued: 10/21/2003
• Est. Priority Date: 10/05/1999
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: McLaughlin, James Michael, Sprague, Randy, Abbott, Eric
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): Tsai, Carol S. W.
• Application Number:
  US09/680,375
• Time in Patent Office: 1,111 Days
• Field of Search: 702/72, 702/74, 702/75, 702/92-95, 702/106, 702/107, 702/115, 702/116, 702/124, 702/126, 702/182, 702/183, 702/141, 702/189, 702/194, 702/136, 702/99, 702/FOR-103, 702/FOR.107, 702/FOR-134, 702/FOR.142, 702/FOR-150, 702/FOR-156, 702/FOR-170, 735/040.2, 735/040.3, 735/040.4, 735/041.2, 735/041--50, 735/10, 735/143.6, 735/143.7, 375/327, 375/322
• US Class Current: 702/96
• 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: G01P 15/097 by vibratory elements

Abstract

A method for improving the performance of a micromachined device, preferably an angular rate microsensor, is provided. The method includes collecting data on rate bias over a selected operating phase demodulation angles for at least one tine of a microsensor and determining optimum settings for phase demodulation angles at which the rate bias hysteresis over temperature is at a minimum by applying dynamic programming.

Claims

1. A method for improving performance of a micromachined device having at least one sensing element, said sensing element having a rate bias used for determining a rate bias hysteresis over temperature, said method comprising:

determining at least two phase demodulation angles (φ

₁,φ

₂) at which said rate bias hysteresis is at a minimum according to the following steps

(i) collecting data on rate bias over a selected operating temperature range at selected phase demodulation angles for said at least one sensing element; and

(ii) selecting said at least two phase demodulation angles by applying a dynamic programming optimization method to the data collected in step (i).

2. The method of claim 1, wherein said dynamic programming optimization method comprises:

(i) assigning to each node of a dynamic programming grid said at least two phase demodulation angles φ

₁,φ

₂;

(ii) assigning to each level of said dynamic programming grid a discrete temperature T, at which φ

₁, and φ

₂ are measured;

(iii) assigning a cost penalty of occupying each node, said cost penalty being a function of said rate bias hysteresis over temperature.

3. The method of claim 2, wherein said cost penalty is determined according to the following formula:

4. The method of claim 3, further comprising a restriction on said cost penalty, wherein the difference between φ

₁ and φ

₂ remains constant.

5. A method of optimizing a cost function over an initially chosen temperature range by determining optimum phase settings, said method comprising:

(i) choosing a pair of phase demodulation angles, φ

₁ and φ

₂, at the highest temperature;

(ii) evaluating said cost function for said pair of phase demodulation angles;

(iii) determining a lowest-cost path by recording the minimum cumulative cost incurred in moving backward from the highest temperature to the next highest temperature until the lowest temperature is reached;

(iv) recording phase demodulation angles, φ

₁ and φ

₂, that lie on said lowest-cost path, at each temperature.