Community Research and Development Information Service - CORDIS


TSA Report Summary

Project ID: 323494
Funded under: FP7-JTI
Country: Portugal

Final Report Summary - TSA (Telemharsh - Telemetric System Acquisition in harsh Environment)

Executive Summary:
Periodic preventive maintenance activities associated with aircraft subsystems is a significant part of the high costs associated with through life aircraft operations. Also, the understandably conservative approach to risk management, leads to premature component retirement, which is both highly inefficient and leading to a considerable carbon footprint. Minimizing maintenance costs and carbon footprint are both major concerns within the whole aerospace industry.

If key critical components, such as turbine engines, own the ability to robustly, autonomously and continuously evaluate their structural health, and anticipate potential failures, maintenance costs will drastically decrease without compromising aircraft safety and reliability. This new maintenance paradigm of real-time in-situ health monitoring, would eliminate the need for the usual periodic preventive actions, allowing maintenance activities to evolve into a reactive paradigm, with extremely high savings as a result.

Long term Active Space Technologies' developments aim at providing such capability for real-time continuous in-situ monitoring of critical parameters for evaluating the health of critical components, such as turbine shafts, gear teeth, and bearings. Although the current low TRL TSA activity was focused in lab applications, where monitoring physical parameters directly in rotating elements, and in harsh environments, were not possible with current available technology.

In the scope of TSA activity, Active Space Technologies developed a new telemetric concept, embracing several technical challenges requested by the Topic Manager, such as:
- Modularity: capability to adapt to different arrangements of strain and temperature channels;
- Reduced dimensions: allowing for integration inside the turboshaft engine;
- High speed measurement: acquire multiple strain gages with bandwidth in the order of 25 kHz;
- Resist to harsh environment:
> Rotating speed (up to 45,000 rpm);
> High temperature (up to 150 ºC);
> Oil mist.

The developed TSA concept is split in a highly innovative low power wireless slip ring and a miniaturized signal processing and conditioning unit, capable of multiplexing several simultaneous input channels, both systems fully developed in the scope of TSA. The designed wireless slip ring is composed by an inductive energy transfer link, capable of transmitting up to 10 W continuously and stable, avoiding the need for larger energy storage capacitors at the harsh environment, as well as transmitting low data rate communications for configuration and unit control; a complete high speed RF coupler (up to 10 Mbps) was designed to transmit the acquired sensory data from the rotating module, to the static gateway. The requested modularity was achieved by splitting the electronics design into three small boards: power conditioning; data acquisition, processing and communications; sensors signal conditioning. This approach allows a good modularity, because as long as the power and processing capacity is not exceeded, only the signal conditioning board needs to be redesigned for different applications.

The high accelerations imposed by the rotation of the shaft, which will be experienced by the rotating electronics, shown to be a major issue for the electronic components packages, which are not prepared to such high forces, induced by the acceleration. The solution adopted to overcome this problem was the reduction of the components mass, which drove the development to the use of bare die components, and wire bonding directly to the PCBs, a manufacturing technique known as chip-on-board.

The very final testing of TSA performance is still to be performed, but the test campaign carried out so far, has demonstrated the full potential of both wireless slip ring, and the complete control and acquisition loop of the TSA system. Further testing and performance analysis is to be performed in the near future, using the high speed test rig designed and manufactured by Active Space Technologies. This test rig is capable to spin up to 50,000 rpm, and has the possibility include a thermal chamber to heat up the testing unit, up to 200ºC.

Project Context and Objectives:
Acquiring signals from a broad range of sensor types in lab environment is a common need among most technological companies, and many manufacturers provide top quality equipment that can do the job very efficiently. The problem comes up when the need does not fit inside the major manufacturers mass market range, or the environment is not suitable for these equipment, such as limited volume for installation, high temperature, high acceleration, or the specific situation of TSA, which intends to measure physical parameters directly in the rotating shaft of turboshaft engines.

A preliminary technological market research was initially performed during the preparation of the proposal, and it was noticed that no solutions in the market were even close to the need of the Topic Manager. A more detailed research of the SOTA was carried out, at the beginning of the project, to evaluate the status of the technology to meet the most critical requirements of the TSA project, namely high g acceleration (40,000 g) and continuous high temperature of operation (150 ºC).

From the SOTA study, it was clear that ordinary electronic components cannot withstand the high accelerations required for TSA, because the packages are not designed for that purpose. Even the high reliability military and space graded components are usually limited to a few thousands of g. Therefore the technology that most likely suits the acceleration needs is the so called Hybrid-Multi-Chip module, which can use bare die chips, instead of the packaged ones. Both the literature research and queries to suppliers of components in die form, confirm that this technology have been successfully tested at accelerations above 100,000 g.

A formal specifications document was elaborated, taking into consideration the CfP, further clarifications with the Topic Leader, and outcomes of the SOTA study. The identified verification methods revealed the need for a dedicated test rig to validate the developments. Thus, it was developed a complete test bench to carry on all the preliminary verifications required along the project developments, either components or subsystems at high acceleration and high temperature, as well as the final testing of the complete TSA system.

After the initial specification and technological research study, the acquired knowledge of the technical challenges and available potential choices, the physical architecture of the TSA telemetric system was laid out. This system is composed by subsystems internal and external to the turboshaft engine.

Externally, a Command and Logging System (CLS) that is implemented in an personal computer, and a Static Interface Unit (SIU) which performs as a data communication gateway between the CLS and the internal subsystem, as well as power conditioner and transmitter to the internal subsystem. The SIU was designed to use COTS components and development kits, because it is to be installed outside of the engine (exception for the communications RF coupler and the induction power transmission coil).

Internally, a Rotating Sensing Unit (RSU) will be attached to the rotating part to be monitored, and comprises the functions of analogue signal conditioning and acquisition, and data communication, powered up by the energy transferred inductively by the SIU.

The proposed architecture was sound, because it was supported by the previous studies and simulations, even though the need to develop several sub modules from scratch raised additional uncertainties for the development. The expected major difficulties were the permanent high temperature, high forces from the centripetal accelerations due to high rotating speed, and the wireless transmitting technologies fully surrounded by heavy duty steel structures. To mitigate these risks/uncertainties, the project was conducted in two phases, a first preliminary design and respective verification, followed by the detailed design activities.

>> Preliminary Design
At the preliminary design phase, the major risks previously identified were addressed either by designing strategies or prototyping and testing of technical concepts, depending on the most effective solution found to mitigate each risk.

The high temperature issue had to be tackled by the selection of qualified components for high temperatures as well as suitable materials and assembly/manufacture methods, because there was no room for cooling down the temperature inside the available volume.

The second major issue pertains to the survivability and good operation of the system on its ability to support sustained centripetal acceleration from the shaft rotating at very high speeds. Assuming the applied accelerations are mostly constant, the only way to tackle this issue is to use bare die components, because as it was noticed in the SOTA, the electronic packages are not prepared for those high loads.

Finally, due to the metal surroundings and available space/mechanical constraints, the wireless power and data transmission needed to be designed for the specific purpose of TSA, and prototyped in the scope of preliminary design phase, to give confidence on the adopted technologies. The results of the tested wireless communication and power transmission concepts demonstrated their capacity to perform as needed by TSA.

>> Detailed Design, manufacturing and testing
Starting from the system architecture defined and validated in the preliminary design phase, all the electronic and mechanical components were re-evaluated according to the specific requirements of TSA final prototype, such as dimensions, mass, availability/lead time, performance, bare die format, footprint, among many other details that are very relevant, whenever so much constrained by all the TSA specific requirements. This was a long iterative task, starting by the selection of the best technical solution, followed by the supplier identification and inquiry, and ending up choosing the component that best satisfies the trade off between performance, price and availability.

Having all the electronic circuits and mechanical design stable, reviewed and approved, the PCBs layouts were designed in Altium Designer, considering the usage of a hydrocarbon ceramic laminate for the TSA PCBs. The manufacturing of the PCBs was sub-contracted, but all the assembly was performed in-house, namely die and wire bonding. This was a process with several unexpected problems, having had a large impact in the project schedule. However, the final the results were very good, and the wire pull tests results showed that the process is beyond usual parameters defined in military standards.

The assembly process was performed in parallel with the unit testing activities, in order to ensure a stable progress in the first prototype. Instead of assembling everything at once, which would increase the likelihood of ruining the very expensive prototype. This approach showed to be a good strategy for the sake of progressing steadily, but had a large impact in the project schedule.

Only after having the TSA prototype completely assembled and unit tested, it was possible to proceed to the functional testing of the unit, and integration of the software application. During this stage, several software problems were detected and successfully corrected. The prototype is currently almost ready to move to the final testing phase, which is the rotating tests, in the high speed test rig.

The installation of the TSA prototype in the high speed test rig was performed simultaneously with the unit and functional testing, but the final stage of the testing campaign, which is the performance testing at high rotating speed and hot environment was not performed in the framework of TSA, due to time limitations. These tests are planned to be carried on the next weeks, and the results will be shared with CSJU and the Topic Manager.

Project Results:
The most relevant S&T outcomes of the TSA activity are:
1. Innovative small dimension wireless slip ring concept for low power (up to 10 W) and high speed data transmission (up to 10 Mbps), ready to operate at harsh environments characterized by high temperature (up to 150 ºC) and high acceleration (up to 40,000 g);

2. Development of electronic devices for high temperature, using high quality bare die components, supporting up to 200 ºC;

3. Optimized mechanical design to allow for in-situ monitoring of high speed rotating shafts (up to 50,000 rpm);

4. Closed loop control of inductive wireless power transmission, for improved efficiency and power quality in the receiver side;

5. High efficiency design of the inductive coupler, reaching efficiencies above 80%.

Potential Impact:
>> Potential Impact
The results of the project advance the development and understanding of wireless power and wireless signal transmission for the rotorcraft industry, in particular for systems with high rotating speeds. The benefits for helicopter noise reduction, reduced fuel burn and reduced associated environmental footprint are indirectly attained by measuring parameters on the main shaft thus enabling its optimization.

In fact, the goals of the Clean Sky JTI, as set by ACARE - Advisory Council for Aeronautics Research in Europe, are to demonstrate and to validate "the technology breakthroughs that are necessary to make major steps towards the environmental goals sets the European Technology Platform for Aeronautics & Air Transport and to be reached in 2020":
- 50% reduction of CO2 emissions through drastic reduction of fuel consumption;
- 80% reduction of NOx (nitrogen oxide) emissions;
- 50% reduction of external noise;
- A green product life cycle: design, manufacturing, maintenance and disposal / recycling.
Within the framework of Clean Sky, the results of the project have the potential to indirectly support the above mentioned objectives since it allows studying and understanding turbine shaft behaviour. This knowledge will enable optimization of helicopters turbines by measuring parameters in a range of different regimes such as lower rotation whilst preserving current flight performance capabilities.

>> Dissemination Activities
The dissemination activities of the project included presentation of the results in fairs (namely Le Bourget), press releases which resulted in several online and paper newspaper articles.

The Telemharsh (TSA) project was published on the FP7 catalogue of projects coordinated by Portuguese entities, prepared by the Portuguese Gabinete de Promoção do Programa-Quadro de I&DT (GPPQ).

Active Space Technologies exhibited the running Cleansky projects at the Le Bourget 2015 air show, where the objectives of the Telemharsh project were presented to potential customers, and relevant industrial players.

>> Exploitation of Results
The TSA project, which was included in Clean Sky's SAGE has a clear bridge to the programs Engine ITD and Fast Rotorcraft IADP in the framework of Clean Sky 2. Actually, Active Space Technologies is currently implementing i-Bearing (FRC) and i-Gear (FRC) within Clean Sky 2 contracts.

The long term goals of the above mentioned projects, among others, are to provide a strong contribution to the definition and development of a future end-to-end maintenance operation concept, to the condition monitoring business model, and to real-time operational analysis. Ultimately, the next generation fast rotorcraft is designed for 20-25 people or 2,500 kg payload, with a recurring cost below 1.5 times a conventional helicopter. These projects, leveraging on the TSA technologies, will enhance condition monitoring capabilities and directly contribute to reducing recurrent cost, namely maximizing the periods between maintenance and overhauls. Hence, enhancing condition based maintenance strategies.

From a technical point of view, the project is expected to contribute to the development of knowledge in the design and manufacturing of sensing, data acquisition, and wireless power transmission which are required by the European aeronautical industry to improve its competitiveness regarding sensing, deeper understanding and measurement of engines, gearboxes, and propellers behaviour. As a consequence, an optimization of engine and gearbox components and of propellers can be expected.

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Reported by

Active Space Technologies, Actividades Aeroespaciais S.A.
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