Overview
Technologies and prototypes exist for either damage detection or vibration damping but which are not able to combine both tasks under the same system. In addition, very few systems can perform the work in real time during the service life of the protected structure, without having to resort to dynamically intruding instrumentation and sacrifices in the electrical power of the structure.
The majority of existing technologies rely on retrofits of the damage detection and vibration control systems, usually constrained by existing designs and are therefore not optimising the locations and performance of their corresponding instrumentation.
The technology of ADVICE will overcome the shortcomings of existing fragmented approaches and will supply combined damage detection and vibration damping, a self-powered, wireless data transmitting system optimised for the location and whose effect on the dynamics of the protected structure will be known and controlled.
Indeed, compared with completed and current European projects with similar objectives and addressing similar issues, the ADVICE project presented the following differences, listed by order of originality:
- it tackled the problem of power supply for the network of sensors;
- it incorporated vibration damping and damage detection at the same time, which is very beneficial from the point of view of probabilistic fracture analysis;
- the data collection was ensured through a reliable network which operates with minimum energy and RF pollution;
- ADVICE set the focus on the structural integrity of the actuators, sensors and interfaces;
- data was collected and analysed both locally and globally and the severity of damage was determined by a self-learning system.
The global objective of ADVICE was to design, model, develop and validate a smart wireless network of self-powered devices that can be used for the simultaneous damping of structural vibrations and detection of damage in airplane and helicopter structures.
ADVICE incorporated the following technical objectives:
- to use the vibrations of the structure as an energy source for the actuators, sensors and other electrical loads. This will induce significant space and weight savings compared with various existing smart systems;
- to manage the sensor data collection through a smart RF network;
- to address several monitoring strategies aiming at defining new condition-based maintenance programmes and inspection procedures;
- to investigate the robustness of the system thoroughly, including the structural integrity of the device itself and of the interface between the device and the support made of composite material;
- in terms of damage evolution, to couple both vibration damping and real-time monitoring towards a synergetic mechanism between delaying the occurrence of critical damage and accelerating its detection.
Among the ADVICE benefits, one can highlight:
- the definition of custom-tailored maintenance programmes;
- an increase in the lifetime of the parts and of the vehicle.
All these elements help to reduce the total ownership cost while being a major contribution to the aircraft safety and reliability.
The project was divided into four technical Work Packages (WP).
- WP1 was mainly concerned with specifications of the target applications, definition of the basic and performance requirements of the autonomous damage detection and vibration control system, and specification of the test applications for validation. It also included an exhaustive technological review and the evaluation of the economical impact of structural health monitoring on the total cost of ownership.
- WP2 gathered the tasks dedicated to the design of the vibration and damage control units (VDCus), of the smart RF network and of other hardware and software, including the central treatment station. WP2 was also concerned with the definition of measurement/structural health monitoring strategies.
- WP3 consisted of the development and manufacture of the system and led to recommendations for SYSTEM integration.
- WP4 was concerned with the integration, reliability and safety assessment, testing and validation of the system. The vibration damping and damage detection efficiencies of a set of VDCus on a simple structure were evaluated.
Among the technical innovations, the following advances can be highlighted: optimisation of semi-passive damping systems, on chip energy conversion and regulation from SOI technology, optimised network topology and management, ultra low energy components, simulation of the structural integrity of the system, etc.
Funding
Results
Most of the initial objectives of the project were achieved, although some difficulties were encountered and some changes in strategy or objectives were made during the project. A nine-month extension of the project was requested due to problems in the developments and testing of electronic boards as well as delays in the different testing phases due to compatibility issues during integration. Actions were taken on problems that were identified, but a few issues still remained at the time of the demonstration mostly in terms of robustness and communication errors between the gateway and the end-nodes.
The project led to interesting results in the characterisation of a direct coupling harvesting solution installed on a composite panel. An important amount of additional effort was put in the identification and the proper exploitation of vibration harvesting tests on the shaker. Damage detection algorithms such as neural networks were investigated throughout the project and led also to interesting outputs related to the parameters that can influence the healthy / damaged signal as well as the possible solutions and the requirements to be able to identify damage and eventually locate it. These elements show a high potential of damage detection through Lamb waves, but require further research work that can based on the outcome and conclusions of this project.
The major deliverables of the project are:
- a complete and operational autonomous damage detection and vibration control system with several VDC units, associated RF network, central station, data treatment software, management APIs, etc.
- optimised and validated components (semi-passive piezoelectric patch, semi-passive visco-elastic constrained layer, on-chip energy management module from SOI technology, Lamb Wave transmitters and receivers, RF transmission module, etc.)
- a review of the structural health monitoring strategies and their technical and economical impact
- a list of recommendations for the integration and use of VDC units.
Technical Implications
The ADVICE project was a multidisciplinary research project that aimed at the development of state-of-the-art technologies for structural health monitoring and vibration damping in aeronautical structures. Bringing together different research activities in one common project is expected to drive new synergies that can lead to new possibilities for aircraft design, maintenance and cabin environment concepts.