Ir I. L. van Eykeren
The research into this topic was initiated by the European FP7 project ADDSAFE: Advanced Fault Diagnosis for Sustainable Flight Guidance and Control. The ADDSAFE project aimed at overcoming the technological gap in aircraft Guidance, Navigation and Control (GNC) Fault Detection and Diagnosis (FDD). The state-of-practice of aircraft manufactures to provide FDD is to rely on hardware redundancy and coherency tests, completely in accordance with current aircraft certification processes and assuring the highest level of safety standards. However, these FDD solutions increase the aircraft weight and complexity and thus its manufacturing and maintenance costs. Moreover, its applicability is becoming increasingly problematic when used in conjunction with the many innovative solutions being developed by the aeronautical sector towards achieving the future sustainable (More Affordable, Safer, Cleaner and Quieter) aircraft.
This applicability gap has resulted in a de facto “fault diagnosis bottleneck”, a technological barrier constraining the full realization of the next generation of air transport due to the need to ensure the current highest levels of aircraft safety when implementing novel green and efficient technologies.
ADDSAFE addresses the fault detection and diagnosis challenges arising from this “fault diagnosis bottleneck”. The overall aim is to research and develop model-based FDD methods for aircraft flight control systems faults, predominantly sensor and actuator malfunctions. Highlighting the link between aircraft sustainability and FDD, it can be demonstrated for example that improving the fault diagnosis performance in flight control systems allows to optimize the aircraft structural design (resulting in weight saving), which in turn helps improve aircraft performance and to decrease its environmental footprint. The results will help achieve the European Vision 2020 challenges related to the “greening” of the aircraft, by supporting the application of already developed sustainable solutions, as well as to “safety”, by opening the door to develop new technologies to maintain the current highest aircraft safety levels regardless of the increase in air traffic. ADDSAFE will try to overcome the technological gap in aircraft G&C FDD by facing the following three challenges:
- Helping the scientific community to develop the best suited FDD methods capable of handling the real-world problems faced in the aircraft G&C diagnosis.
- Ensuring acceptance and widespread use of these advanced theoretical methods by the aircraft industry.
- Contribute towards reducing the aircraft development and maintenance costs by using model-based diagnostic systems in conjunction with reliable software verification & validation (V&V) tools.
The solution proposed in this research is a physical model-based approach to solving the FDD problems. The main idea is to use all available knowledge of the aircraft physical model to perform both the sensor and actuator FDD.
For the sensor FDD, the knowledge about the physical relations between the available measurements of the aircraft are exploited in addition the already available hardware redundancy. This approach has several advantages, as these relations are exactly known (reducing model inaccuracies) and the method becomes independent of actuator faults. Furthermore the effects of external disturbances such as atmospheric turbulences on the developed methods are investigated.
The actuator FDD is based on the knowledge available of the complete physical aircraft model. By estimating the control derivatives of the monitored control surfaces, and combining this information with available measurements detailed FDD can be obtained for the actuators of aircraft through an advanced decision logic.