Final Report Summary - FLITE-WISE (FLite Instrumentation TEst WIreless SEnsor)
The Flite-Wise project consortium was coordinated by CSEM – Centre Suisse d’Électronique et de Microtechnique, a Swiss R&D centre dedicated to the transfer of cutting-edge micro/nano/bio and communications technologies into industrial products. The energy harvesting is developed by Imperial College London, the UK’s premier science and technology university. The system is industrialised by SERMA INGENIERIE, a French aeronautic equipment manufacturer.
The project was under the supervision of its topic manager Airbus Operations GmbH from Germany.
The Flite-Wise project developed an autonomous wireless sensor node platform for continuous acoustic or pressure measurements on aircraft frames. The project addresses two use cases. The first one, aka the “propeller use case”, concerns pressure measurements on rotating frames (propeller blades) using nodes powered by an energy harvester with multiple sensors.
The second use case, aka the “patch use case”, defines acoustic pressure measurements along the aircraft skin using an ultra-thin, battery powered and wirelessly rechargeable sensor node.
The result is an integrated autonomous wireless system from existing, already proofed hardware and software combined with innovative concepts in the domains of robust and high performance networking, energy harvesting, sensor interfaces and data acquisition
The developed platform advances the state of the art in a number of aspects:
• energy harvesting and electronics capable of withstanding high accelerations and low temperatures;
• resilience to interferences and jamming;
• highly efficient and robust communication with ultra-low energy requirements;
• highly compact and slim design with fully wireless operations including charging;
• accurate synchronisation in WSN for the time-stamping of sensor data.
The evaluation done for both use cases demonstrated the good global performance of both sensor nodes. In particular, the nodes support 50 KHz sensor acquisition rate, logging in high-capacity SD card and deferred transmission at 40 KSamples/s. The power consumption of the devices in inactive state is as low as 27 µA. The total power consumption (active and inactive states) is compatible with the power supply capacity in both use cases. The network synchronisation accuracy is better than 40 µs. The patch use case batteries work at temperatures below -20°C and can be recharged by inductive coupling in about five hours.
Current flight test systems are wired and their installation is costly and cumbersome. The Flite-Wise project delivers a major contribution towards new wireless sensors with energy efficiency which allows them to be powered by batteries and energy harvesters. The wireless recharging feature helps reducing the thickness of the patch sensor by avoiding the need for connectors. Large on-board data storage allows high sensor sampling rates with deferred data transmission. The overall benefits of such sensors are reduced installation and maintenance costs.
From a short-term viewpoint, the Flite-Wise project allowed the consortium members to perform significant progress in their respective areas of expertise: ultra-low power communications and synchronisation (CSEM), energy harvesting and power regulation (Imperial College London) as well as electronics and industrialisation (Serma Ingénierie). The project partners wish to continue their collaboration and will keep in touch to monitor project opportunities.
Project Context and Objectives:
2.1 Project global objectives
The Flite-Wise project develops an autonomous wireless sensor node platform for continuous acoustic or pressure measurements on aircraft frames. This platform shall operate airborne on rotating blades in the long-term, thanks to the use of an embedded energy harvesting device. The same wireless technology shall also be used for connecting rechargeable battery-operated sensors located on the aircraft outer skin.
The technical strategy is to build an integrated autonomous wireless system from existing, already proofed hardware and software, and combine it with innovative concepts in the domains of robust and high performance networking, energy harvesting, sensor interfaces and data management, in order to provide a system specifically tailored to meet the objectives of the project. This strategy allows for saving costs and for benefiting from the past experience in designing and developing a wireless sensor network that is dedicated to aeronautics applications. This guarantees that a number of the aeronautics requirements are more easily met by the proposed system.
The resulting platform advances the state of the art in a number of aspects:
• energy harvesting and electronics capable of withstanding high accelerations and low temperatures;
• resilience to interferences and jamming;
• highly efficient and robust communication with ultra-low energy requirements;
• highly compact and slim design with fully wireless operations including charging;
• accurate synchronisation in WSN for the time-stamping of sensor data.
The project addresses two use cases.
2.1.1 Propeller use case
This use case involves acoustic pressure measurements along the blades of a turboprop engine propeller. The propeller is part of a new engine design based on an open contra-rotating rotor (Figure 1).
The measurements shall be correlated with acoustic measurements made on the ground along the take-off and landing paths of the test aircraft. Therefore, airborne and ground measurements have to share a common time for their correlation to be possible.
On a blade, up to 8 sensors can be distributed within the propeller length and wired to a Sensor Node (SN) integrated to the base of the blade. The sensor node is energy-autonomous and wireless. Sensor measurements are radio transmitted to a Wireless Data Concentrator (WDC) installed within the radio range of the engine.
The sensor node shall be autonomous, thus it shall be powered by an energy harvester located nearby.
Figure 1: open rotor engine with wireless autonomous sensor installation on the propeller
2.1.2 Patch use case
The second use case, aka the “patch use case” involves continuous acoustic pressure measurements taken on the outside of the aircraft fuselage. The measurements are to be taken by a single wireless sensor stuck against the aircraft skin. For obvious reasons, the sensor and accompanying electronics must be as thin and as aerodynamic as possible. It shall take the form of a circular patch applied to the fuselage. Low vibrations at the envisaged location, a maximal thickness of 4 mm and the fact that a micro wind turbine would disturb the air flow being measured imply that the only solution is to use batteries to power the sensor node. They shall be recharged wirelessly by inductive coupling while the test aircraft is not in use. This method has the advantage of avoiding a potentially large connector that would also make the sealing of the patch more difficult.
Figure 2 shows an example of patch sensor applied to an airframe.
Figure 2: example of patch sensor
2.2 Consortium
The consortium is made of three highly qualified complementary entities. The members are CSEM Centre Suisse d'Électronique et de Microtechnique (CH), Imperial College London (GB) and Serma Ingénierie (FR). CSEM brings its expertise in WSN and ultra-low power electronics. SERMA, an experienced actor in the aeronautics technology, brings expertise in the aeronautics environment and constraints, as well as production and test facilities. Imperial College London, one of the world leading laboratories, provides the scavenging and energy management expertise.
2.3 Project structure
2.3.1 Roles of the project partners
The project is coordinated by CSEM. The building blocks are under the responsibility of Imperial College (power supply) and CSEM (electronics, wireless communications, embedded software). Serma Ingénierie is responsible for the system integration, the industrialisation and the tests.
Airbus if the topic manager. Although not a consortium member, Airbus proposed the project topic, and also advises and reviews the project.
Figure 3: the roles of the project partners
2.3.2 Work packages
The Pert diagram in Figure 4 describes the project decomposition in work packages.
Figure 4: work packages decomposition
The contents of the different work packages are:
• WP1 – System architecture: analyse the requirements, derive assumptions, identify and select the system components.
• WP2 – Wireless Communications Systems: develop the wireless communication protocol derived from the existing protocol delivered by the StrainWISE project. Design and implement the data acquisition algorithm and study potential data compression techniques. Design and implement the synchronisation feature. Study jamming awareness and detection.
• WP3 – Electronics: design and realise the electronic boards of the rotating frame (propeller) and non-rotating frame (aircraft skin) sensor nodes.
• WP4 – Power supply: develop an energy harvester for the rotating frame sensor node. Propose a wireless-chargeable battery power supply for the non-rotating frame use case.
• WP5 – Packaging and integration: study and design the housing and fixing of the two sensor node types.
• WP6 – Evaluation: define and execute the tests that are necessary for the delivery of functional prototypes to the topic manager.
Project Results:
Please refer to the attached report.
Potential Impact:
The present section discusses the project impact with respect to what was expected when writing the proposal. Then a summary of the dissemination activities follows. Finally, the section concludes with the presentation of the current and future exploitation plan.
4.1 Impact
The first project outcome is a laboratory demonstrator of the rotating use case sensor node. The mock-up gives a good idea of the size and performance the chosen architecture can achieve. The experience gathered during the project will be extremely valuable to the development of a fully integrated system once the information on the engine and the form factor requirements become available.
The second outcome is a fully integrated wireless sensor node dedicated to acoustic measurements along the fuselage of an aircraft. The device is a circular flexible patch designed to be applied to the aircraft skin. It accommodates one acoustic sensor, communication capability and mass storage. It is powered by ultra-thin batteries which can be wirelessly recharged by inductive coupling. An attempt was made to coat the sensor node to protect it from the harsh environmental conditions. The specific gel application and de-moulding was difficult and did not convince. Alternative solutions such as epoxy can be tried in the future. The prototype will be tested on the ground by Airbus Flight Test department.
Current flight monitoring systems are wired and their installation is costly and cumbersome. They also involve high maintenance costs and they add a significant weight burden. The results of the Flite-Wise project consist a milestone step towards wireless monitoring, in demonstrating highly efficient sensor nodes that can operate within strict energy budgets. In particular, the combination of a low power protocol with energy aware duty cycling of operation with wirelessly recharging flat batteries has permitted integration of a complete system in a very flat package, which opens up new possibilities in system integration shapes and locations of installations. It also demonstrates that cable – free, energy autonomous propeller sensor systems are possible by harvesting the significant relative rotation motion that is internally available. Furthermore, large on-board data storage allows high sensor sampling rates with deferred data transmission. The overall benefits of such sensors are reduced installation and maintenance costs.
Finally, the study on jamming awareness for wireless sensor networks in the aeronautics will be used by the topic manager to support its internal developments in the cabin connectivity area.
From a short-term viewpoint, the Flite-Wise project allowed the consortium members to perform significant progress in their respective areas of expertise: ultra-low power communications and synchronisation (CSEM), energy harvesting and power regulation (Imperial College London) as well as electronics and industrialisation (Serma Ingénierie). The project partners wish to continue their collaboration and will keep in touch to monitor project opportunities.
4.2 Dissemination
Though not formally described in the description of work, the project conducted various dissemination activities. They are listed and classified below according to their nature.
4.2.1 Scientific papers
The following scientific paper has emerged from the FliteWISE project:
T. T. Toh, S. W. Wright, M. E. Kiziroglou, P. D. Mitcheson and E. M. Yeatman, Inductive Energy Harvesting for Rotating Sensor Platforms, Nov. 18–21, PowerMEMS, Hyogo, Japan, 2014.
This paper was presented as a poster in the PowerMEMS 2014 conference and has been published in the IOP Journal of Physics: Conference Series, 557 (2014) 012034
Two more scientific papers, one on the development and performance of the patch sensor node and one on the presentation of the full inductive energy harvesting power supply are expected to be prepared in 2015.
Moreover, an article describing the overall results of the previous project “StrainWISE” was submitted by the consortium to the AIAA Journal, a high impact periodic published by the American Institute of Aeronautics and Astronautics.
4.2.2 Within the topic manager Airbus
The topic managers were issued from Airbus departments “Materials & Processes, NDT and Mechanical Testing” and Cabin Design Office Connectivity. Also the project was closely followed by the Flight Test Instrumentation department in Toulouse who will evaluate the patch sensor node prototype on the ground.
The project was widely disseminated within Airbus. The project deliverables have been made available on a dedicated section of Airbus internal portal “iShare”.
In addition, specialists from other Airbus departments attended several project meetings remotely. Their interests ranged from analytical structural health monitoring to landing gear.
A joint brainstorming meeting was held between CSEM and Airbus Group Innovations in Munich.
4.2.3 To the general public
The previous project StrainWISE received the “Mechatronics Award 2013” in September of the same year at the European Mechatronics Meeting in Toulouse .
This award had an important impact on the consortium visibility and gave an opportunity to advertise the Flite-Wise project during the award ceremony.
Also, the consortium published a joint press release to inform the specialised and general media. The press release was taken over by the specialised press in Europe and the USA:
• http://www.lembarque.com/initie-par-airbus-le-projet-strainwise-sur-les-capteurs-sans-fil-communicants-a-ete-recompense_001216
• http://www.microwave-eetimes.com/en/strainwise-project-yields-autonomous-communicating-sensor-networks-for-aeronautics.html?cmp_id=7&news_id=222904447
• http://www.energie-und-technik.de/smart-energy/artikel/104007/
4.3 Exploitation
The content of this section is confidential.
There are several on-going and future plans for the exploitation of the Flite-Wise results. They are presented below in chronological order.
4.3.1 Patch sensor node prototype delivered to Airbus flight test
The prototype will be evaluated on the ground by Airbus. The consortium will provide limited post-project support.
4.3.2 Industrial partner Serma
Serma Ingénierie is the industrial partner of Flite-Wise. As such its plans for the exploitation of the project results are:
• Demonstrate to our main customers Airbus Helicopters and Airbus Toulouse, that SERMA and its partners have acquired sufficient maturity to be able to propose industrial sensors, within wireless networks and low consumption.
• Furthermore, the Flite-Wise development shows the capabilities to our team to manage, industrialise and test efficiently this kind of problem.
• The promising result of this study, allow a good positioning of our consortium for as example on Future Helicopter, a new research program for Airbus Helicopters (former Eurocopter).
Then at medium-term, SERMA intends to provide several type (temperature, strain gauge, pressure, acceleration, etc.) industrial autonomous sensors, allowing easily installation without bundle.
With this experience, we more easily find supplementary budgets, to pursue this research axis.
4.3.3 Imperial College London
Imperial has gained significant know-how from the FliteWISE project. In particular, it has developed a novel inductive energy harvesting method for rotating structures and a battery guarding system for wireless power transfer based power supplies in wireless sensor nodes. This know how is exploited in on-going energy harvesting related research and development activities at Imperial.
The joint development of two new self-powered wireless sensor node solutions by the FliteWISE partners has advanced the collective scientific and technical know - how of the consortium. In addition, the communication and collaboration level among partners has matured, with significant gains in trust, coordination on the interfacing of systems and cooperative problem solving. These benefits are being exploited in further joint scientific activities, including joint participation in Horizon 2020 proposals, conferences and journal publications.
4.3.4 CSEM
Partner CSEM will benefit from the results of FliteWISE through the application of its increased know-how and experience in the fields of low-power Wireless Sensor Networks (WSN), power management and sensor electronics. Low power WSN technology is needed to realize dependable, autonomous solutions for monitoring and surveillance capable of operation over extended periods and wide geographic areas. In accordance with CSEMs mission to bridge the gap between research and Industry, the technology developed in StrainWISE and Flite-Wise is already being transferred into industrial developments in collaboration with the Swiss aeronautics industry and the Swiss Federal Government innovation support commission (KTI/CTI). The results of StrainWISE and FliteWISE have also been used in a currently running project for ESA in which a MAC protocol was proposed for UWB system using IEEE 802.15.4a physical layer for intra-satellite communications and wireless connections of ground test sensors.
Technically, CSEM has added a new platform to its WSN solutions toolbox thanks to the FilteWISE project. This new platform complements the existing Wisenet system which is based on the ultra-low power random access MAC WiseMAC as the TDMA nature of the new platform will allow CSEM to work where deterministic systems are mandatory. Potential applications for this technology extend beyond the domains of aeronautics to, for example, safety, health, automotive and transport applications.
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