MehrotraPrince
FULL MEMBER
- Joined
- Jan 13, 2011
- Messages
- 211
- Reaction score
- 0
- Country
- Location
Importance of Fiber Optic based technology for UAV Structural Health Monitoring
Research Work by: IAI (Israel), School of Electrical Engineering, Tel-Aviv University, ADE & NAL (India).
Program Implementation: Nishant UAV (India) and other UAV's of Israel.
The increasing value of modern Unmanned Aerial Vehicles (UAVs), together with their high usage, demand constant monitoring of their structural airworthiness over their life span. Safety and economic implications of maintaining aging UAV fleets subject to fatigue, corrosion, wear and material degradation are a prime concern of both the operator and the UAV manufacturer due to their logistics implications.
For manned air vehicles, structural design criteria such as 'Safe-Life' and more recently, 'Damage-Tolerance' have been developed over the years to cover safe usage under a variety of missions, taking into account the associated environmental conditions.
At present, most commercial aircraft airworthiness capability is maintained by performing inspections at scheduled intervals. The time interval between such inspections is based on the worst-case scenario, derived by a damage tolerance statistical evaluation. An alternative approach, based on the 'Safe-Life' design criteria requires the operator to replace structural components at their design service life. This commonly used approach, being statistical in nature, may lead to costlier maintenance as 'healthy' components are being replaced for no real reason.
The increasing use of advanced composite materials for UAV structural components requires special attention. Extensive use of bonded, integral structural concepts for main components, including the wing and fuselage, imposes a great challenge since conventional periodic inspection methods of such critical structural components are hindered by limited accessibility and require highly trained. i.e., costly technicians. Special care should also be given to inspection methodologies since UAVs are often operated at remote sites where technical resources are limited.
The recently introduced Structural Health Monitoring (SHM) concept is aimed towards real-time structural assessment of the individual air vehicle, alerting for maintenance action only upon need. Airworthiness deterioration may now be monitored in real time, reducing maintenance costs by increasing and even eliminating, the present scheduled maintenance intervals.
One of the ways of implementing an online SHM system is by using fiber optic sensing technology. This technology enables the incorporation of a fiber optic nervous network into the composite structure that senses, measures and communicates various environmental and structural parameters to an off- or on-board processing brain. Optical fibers are extremely well suited for strain (static and dynamic, up to ultra-sonic) and temperature sensing. Due to their small diameters they can be easily attached to metallic surfaces or embedded within composite materials. They are flexible, quite tolerant to environmental conditions and insensitive to electromagnetic disturbances. The key to an effective SHM system for aircraft structures is not only the appropriate sensor selection and measurement but also the processing of the sensor data to deduce information in terms of operating loads and/or structural damage, if any. SHM enables the structural health of aeronautical structures to be monitored online, such that health can be assessed continuously and even remotely, and corrective action, if needed for the flight, can be taken. This also enables aircrafts to be flown without unnecessarily grounding them. This is of immense strategic importance from considerations of readiness of the fleet and safety.
Research Work by: IAI (Israel), School of Electrical Engineering, Tel-Aviv University, ADE & NAL (India).
Program Implementation: Nishant UAV (India) and other UAV's of Israel.
The increasing value of modern Unmanned Aerial Vehicles (UAVs), together with their high usage, demand constant monitoring of their structural airworthiness over their life span. Safety and economic implications of maintaining aging UAV fleets subject to fatigue, corrosion, wear and material degradation are a prime concern of both the operator and the UAV manufacturer due to their logistics implications.
For manned air vehicles, structural design criteria such as 'Safe-Life' and more recently, 'Damage-Tolerance' have been developed over the years to cover safe usage under a variety of missions, taking into account the associated environmental conditions.
At present, most commercial aircraft airworthiness capability is maintained by performing inspections at scheduled intervals. The time interval between such inspections is based on the worst-case scenario, derived by a damage tolerance statistical evaluation. An alternative approach, based on the 'Safe-Life' design criteria requires the operator to replace structural components at their design service life. This commonly used approach, being statistical in nature, may lead to costlier maintenance as 'healthy' components are being replaced for no real reason.
The increasing use of advanced composite materials for UAV structural components requires special attention. Extensive use of bonded, integral structural concepts for main components, including the wing and fuselage, imposes a great challenge since conventional periodic inspection methods of such critical structural components are hindered by limited accessibility and require highly trained. i.e., costly technicians. Special care should also be given to inspection methodologies since UAVs are often operated at remote sites where technical resources are limited.
The recently introduced Structural Health Monitoring (SHM) concept is aimed towards real-time structural assessment of the individual air vehicle, alerting for maintenance action only upon need. Airworthiness deterioration may now be monitored in real time, reducing maintenance costs by increasing and even eliminating, the present scheduled maintenance intervals.
One of the ways of implementing an online SHM system is by using fiber optic sensing technology. This technology enables the incorporation of a fiber optic nervous network into the composite structure that senses, measures and communicates various environmental and structural parameters to an off- or on-board processing brain. Optical fibers are extremely well suited for strain (static and dynamic, up to ultra-sonic) and temperature sensing. Due to their small diameters they can be easily attached to metallic surfaces or embedded within composite materials. They are flexible, quite tolerant to environmental conditions and insensitive to electromagnetic disturbances. The key to an effective SHM system for aircraft structures is not only the appropriate sensor selection and measurement but also the processing of the sensor data to deduce information in terms of operating loads and/or structural damage, if any. SHM enables the structural health of aeronautical structures to be monitored online, such that health can be assessed continuously and even remotely, and corrective action, if needed for the flight, can be taken. This also enables aircrafts to be flown without unnecessarily grounding them. This is of immense strategic importance from considerations of readiness of the fleet and safety.
