Validation of a novel underwater wireless strain monitoring system for a smart composite propeller under static and fatigue loading
Topic(s) : Multifunctional and smart composites
Co-authors :
Aldyandra Hami SENO (UNITED KINGDOM), Swaroop Narayanan NAIR (UNITED KINGDOM), Sofia SAMPETHAI (UNITED KINGDOM), Stuart LEWIS (UNITED KINGDOM), Dimitrios FAKIS , Akram ZITOUN , Nithin Amirth JAYASREE , Mihalis KAZILAS (UNITED KINGDOM)Abstract :
The Copropel project is a Horizon EU/Innovate UK funded project that aims to develop novel marine propellers using composite materials instead of the common metal construction. The application of composite materials significantly reduces the weight of the propeller and allows the hydroelastic tailoring of its stiffness to increase fuel efficiency, as well as reduce underwater radiated noise. The application of composite materials also produces a non-monolithic construction that provides additional benefits in terms of embedding sensors to support Structural Health Monitoring (SHM) of the propeller which is a vital component for the operation of a ship.
Embedding sensors within the structure provides protection from the marine environment whilst also avoiding the hydrodynamic performance reduction of surface mounted sensors. However, significant challenges remain for the development a sensor system, mainly related to transmitting data from the sensor on the rotating underwater propeller to the data acquisition system inside the ship hull. Common wireless data transmission methods using electromagnetic far field radiation are heavily attenuated underwater and may be severely disrupted by the mix of media around the propeller (water, air bubbles, mud/particulates). Additionally, the frequency bandwidths available for transmission are highly limited by the space available to place the antenna.
Thus, in this study the development of a novel sensor system that uses the near field radiation in the form of inductive coupling is presented, aiming for more reliable data transmission underwater. Since the distance between the propeller and the shaft/hull is relatively close and does not change, the range constraints of inductive coupling are not an issue. Additionally, inductive coupling is much less constrained by the size of the transmitting/receiving loop making it more adaptable to various shaft configurations. Transmission tests are conducted in multiple mediums (air, fresh- and sea water) with simulated conditions (namely air bubbles and particulates/mud) to demonstrate the consistency of signal transmission.
Since the system will be used for SHM purposes, the sensing element chosen is a strain gauge which will allow the monitoring of loads experienced by the propeller. To convert the strain measurements to a transmissible signal and to also allow multiplexing of signals from multiple sensors, a Frequency Modulation (FM) approach is employed using an embedded microcontroller to provide a programmable frequency range for each sensor. To validate this modulation approach, static (tensile) and dynamic (fatigue) tests are conducted on coupon laminate specimens to benchmark the measurements of the wireless strain gauge system to a normal strain gauge setup.
The results of the tests conducted will provide validation to integrate the system into the propeller demonstrator which will be tested during sea trials at the end of the project.
Embedding sensors within the structure provides protection from the marine environment whilst also avoiding the hydrodynamic performance reduction of surface mounted sensors. However, significant challenges remain for the development a sensor system, mainly related to transmitting data from the sensor on the rotating underwater propeller to the data acquisition system inside the ship hull. Common wireless data transmission methods using electromagnetic far field radiation are heavily attenuated underwater and may be severely disrupted by the mix of media around the propeller (water, air bubbles, mud/particulates). Additionally, the frequency bandwidths available for transmission are highly limited by the space available to place the antenna.
Thus, in this study the development of a novel sensor system that uses the near field radiation in the form of inductive coupling is presented, aiming for more reliable data transmission underwater. Since the distance between the propeller and the shaft/hull is relatively close and does not change, the range constraints of inductive coupling are not an issue. Additionally, inductive coupling is much less constrained by the size of the transmitting/receiving loop making it more adaptable to various shaft configurations. Transmission tests are conducted in multiple mediums (air, fresh- and sea water) with simulated conditions (namely air bubbles and particulates/mud) to demonstrate the consistency of signal transmission.
Since the system will be used for SHM purposes, the sensing element chosen is a strain gauge which will allow the monitoring of loads experienced by the propeller. To convert the strain measurements to a transmissible signal and to also allow multiplexing of signals from multiple sensors, a Frequency Modulation (FM) approach is employed using an embedded microcontroller to provide a programmable frequency range for each sensor. To validate this modulation approach, static (tensile) and dynamic (fatigue) tests are conducted on coupon laminate specimens to benchmark the measurements of the wireless strain gauge system to a normal strain gauge setup.
The results of the tests conducted will provide validation to integrate the system into the propeller demonstrator which will be tested during sea trials at the end of the project.