N101-095 TITLE: Distributed Sensor Network for Structural Health Monitoring of Ships

TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles, Materials/Processes

OBJECTIVE: To develop a distributed network of sensors for load monitoring of ship structures. The target attributes of the system are outlined below, but in general the system should be reliable and durable in a sea environment, capable of monitoring a minimum span of 400 ft, the sensors should have a small footprint so as to be cost effective and non-intrusive, with good dynamic range and sensitive, reconfigurable, adaptive and scalable up to 500 sensors, with good frequency response. Other attributes include EMI resistance and have minimal wiring and maintenance requirements (no batteries, no switches).

DESCRIPTION: A highly reliable, non-intrusive system for monitoring loads in Naval structures (ships and submarines) as well as next generation weapon systems is critically needed. Strain monitoring is a proven method for assessing the performance of a structure and for determining the remaining fatigue life left on the structure. However, present strain monitoring systems suffer from various limitations. The sensors need two or four wire leads to pick up the signal, the sensors and wire leads have to be heavily shielded to minimize EMI, each sensor needs a pre-amplifier and signal conditioner nearby, and two more wire leads are required for each amplifier as well as powering. These limitations make current technologies intrusive, cumbersome, heavy, susceptible to EMI, overly complicated and with many failure points. New and promising technologies are being sought that might address these issues. Techniques that use fiber optic sensors or wireless MEMS sensor nodes are two examples that could offer the opportunity to overcome all these limitations. Overall objectives for this program are simplicity, reliability, scalability and affordability.

PHASE I: During the phase I the contractor will demonstrate the ability to monitor strains in a loaded aluminum or steel panel by using the advanced distributed sensor concept. The system will have a minimum of 50 sensors and monitor a large aluminum or steel cantilever with a proof mass producing a 10 Hz resonance. The software development component for the Phase I will be limited to data acquisition and display of the strain data in a pictorial manner. Some of the target system parameters are: system reliability (this includes the sensor, the signal and the attachment method = 10 years in a sea environment); small footprint size (= 1 cm2), weight (= 1 gram), and cost (cents); large dynamic range (=� 5,000 microstrain); with good sensitive (1 microstrain or better); good frequency response (up top a 200 Hz); large range (around 400 feet); minimum maintenance requirements (no batteries, no switches).

PHASE II: During the Phase II the contractor will develop all the necessary components for a standalone unit capable of monitoring 500 sensors for loads monitoring. The system will be dynamically reconfigurable, adaptive, have a small foot print and be capable of self diagnosing. By dynamically reconfigurable it is meant that the system should be able to reconfigure itself so as to monitor a fraction of the 500 sensors with higher fidelity when appropriate. By adaptive it is meant that as the region of interest shifts from one location to another, the system should be capable of quickly adapting to that new circumstance. By stand alone it is meant that the system will collect, analyze, compress and store the entire strain state and strain history of the ship hull for a specified period of time. By self diagnosing it is meant that the system can identify those sensors that are providing faulty information so that they can be removed. One of the main components of this effort during the Phase II will be software development. The software should be able to adjust the sampling rates in response to the structural behavior, compress or reduce the massive amounts of data to a meaningful set of parameters, be able to reconstruct the strain history from that set, store and display the data.

PHASE III: A strain monitoring system of this nature could be installed in many DoD platforms (including destroyers, cruiser, amphibious ships, submarines, fighter, patrol and transport aircraft) which have key structural components (such as pressurized bulkheads, rudders, propellers, superstructures and wing attachment point) that require strain or loads monitoring. Significant cost savings could be achieved by the installation of such a system and therefore, performing maintenance at longer time intervals or only when the system indicates that it is required. The contractor, in collaboration with the Navy monitoring team, will seek a potential military application and/or demonstration during Phase III.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial shipping industry would benefit significantly from a system of this nature as well. The same problems that we experience in our Naval platforms (ships, subs and aircraft) are experienced by equivalent commercial platforms. For example, wide spread area fatigue damage has been determined to be a major source of problem for commercial aviation.

REFERENCES:
1. G. Wang, K. Pran, G. Sagvolden, G. B. Havsgard, A. E. Jensen, G. A. Johnson and S. T. Vohra, "Ship hull structure monitoring using fiber optic sensors", Smart. Mater. Struct, 10:472-478 (2001).

2. L. W. Salvino, and T. F. Brady, "Hull structure monitoring for high-speed naval ships", Structural Health Monitoring 2007: Quantification Validation, and Implementation, Vols. 1 and 2, FK Chang, Ed. (DEStech, Lancaster PA, 2007), pp. 1465-1472.

3. P. E. Hess, III, "Structural health monitoring for high-speed naval ships", Structural Health Monitoring 2007: Quantification Validation, and Implementation, Vols. 1 and 2, FK Chang, Ed. (DEStech, Lancaster PA, 2007), pp. 3-15.

4. American Bureau of Shipping (ABS). Guide for hull condition monitoring systems, # 73, ABS: Houston, TX, 2003.

KEYWORDS: Strain Monitoring, Load Monitoring, Condition based maintenance (CBM), Structural Health Monitoring (SHM), MEMS, Optical Fibers, Bragg Gratings, Wireless

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between November 12 and December 9, 2009, you may talk directly with the Topic Authors to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting December 10, 2009, when DoD begins accepting proposals for this solicitation.

However, proposers may still submit written questions about solicitation topics through the DoD's SBIR/STTR Interactive Topic Information System (SITIS), in which the questioner and respondent remain anonymous and all questions and answers are posted electronically for general viewing until the solicitation closes. All proposers are advised to monitor SITIS (10.1 Q&A) during the solicitation period for questions and answers, and other significant information, relevant to the SBIR 10.1 topic under which they are proposing.

If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (866) 724-7457 or email weblink.