Patent Application
20070283759
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:
The monitoring system 14 generally includes a calibrated micro-electro-mechanical structures (MEMS) matrix 16 in communication with a controller 18. The MEMS 16 are preferably MEMS elements 20 of various sizes which create a continuum of vibration stress-resistant elements. It should be understood that elements of various widths, lengths, and depths will resist various levels of vibration stress. That is, each MEMS element 20 will resist failure until a predetermined vibration stress is experienced. The predetermined vibration stress is determined in a controlled environment. It should be understood that the number and configuration of the MEMS elements 20 will provide a desired fidelity. It should also be understood that although elements are disclosed in the illustrated embodiment, other shapes will likewise be usable with the present invention. The elements will flex in response to flexing of the printed circuit board or other surface 12 due to mechanical vibration. The total accumulated flexure will initiate cracking and failure of the elements in order of the least-vibration-stress resistant elements to the more-vibration stress-resistant element. The controller 18 monitors the continuity of the MEMS matrix 16 to determine which elements of the MEMS matrix 16 have failed such that the total amount of accumulated printed circuit board 12 flexure is accurately determined. The MEMS matrix 16 preferably includes a multitude of MEMS elements of various sizes to provide an accurate probabilistic estimate. The vibration-fatigue life based on the life-environment actually experienced by the particular printed circuit board (or other surface) 12 is thereby determined. It should be understood that the thermal-fatigue life based on the life-environment actually experienced by the particular printed circuit board (or other surface) 12 may also be determined by the monitoring system 14 utilizing MEMS elements which respond to thermal gradients and thermal fatigue cycles.
One monitoring system 14A includes a MEMS matrix 16A having a multitude of MEMS elements 20 mounted in a cantilever arrangement to a support 22 mounted to the printed circuit board 12. The MEMS elements 20 in the MEMS matrix 16A are arranged generally normal to the vibrations to be experienced by the printed circuit board 12 and include a range of sizes such that each of the MEMS elements 20 will progressively fail as the printed circuit board 12 experiences progressively increasing mechanical vibration. That is, each of the MEMS elements 20 in the MEMS matrix 16A will fail in order from the least-vibration-stress resistant MEMS element 20a to the most-vibration stress-resistant MEMS element 20n (
Each of the MEMS elements 20 in the MEMS matrix 16A includes a detection element 24 to provide communication of MEMS elements 20 failure to the controller 18 (only one shown in
Preferably, the MEMS matrix 16 is mounted within a casing 25 (
Referring to
Referring to
A rod 38 is attached between each of the MEMS elements 20 and the flexible membrane 12F through the opening 34. It should be understood that the term “rod” as utilized herein may include any attachment between the printed circuit board 12F and each MEMS element 20 intermediate the first support 30 and the second support 32. The rod 38 transfers the mechanical vibration of the surface on which the MEMS sensor is mounted through the flexible membrane 12F to the MEMS elements 20 such that failure thereof is determined as described above. Direct contact of the rod to the surface to be monitored is also possible. As each MEMS element 20 is calibrated through experimental testing to a particular vibration stress level, sequential failure of the MEMS elements 20 within the MEMS matrix 16c provide an accurate measure of the vibration-fatigue life experienced by the flexible printed circuit board 12F based on the life-environment actually experienced.
Referring to
It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.
It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit from the instant invention.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.
The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
