Affordable digital fly-by-wire flight control systems for small commercial aircraft

Project members: M. Oosterom, R. Babuška, V. Verdult

Sponsored by: European Community GROWTH project ADFCS-II

The objective of this project is to apply the fly-by-wire (FBW) technology in flight control systems of a smaller category of aircraft (see Figure 9). In FBW digital flight control systems, there is no direct link between the control stick and pedals, which are operated by the pilot, and the control surfaces. All measured signals, including the pilot inputs, are processed by the flight control computer that computes the desired control surface deflections. This scheme enables the flight control engineer to alter the dynamic characteristics of the bare aircraft through an appropriate design of the flight control laws. Moreover, important safety features can be included in the control system, such as flight envelope protection. This increases the safety level compared to aircraft with mechanical control systems.

Figure 9: Galaxy business jet (left) and validation of the control system through pilot-in-the-loop simulations at the Research Flight Simulator of the NLR (right).

Our task in the project is to assess the benefits and to verify the validity of the soft-computing techniques in the FBW control system design and sensor management. These novel techniques are combined with standard, well-proven methods of the aircraft industry. The research topics are the design of gain-scheduled control laws, fault detection, isolation and reconfiguration, and an expert system monitoring of the overall operational status of both the pilot and the aircraft. For the FCL optimization and the fault detection and identification system, fuzzy logic approaches are adopted in order to extend linear design techniques to nonlinear systems. Moreover, a neuro-fuzzy virtual sensor is being developed in close cooperation with Alenia to replace hardware sensors. For the pilot-aircraft status monitor a fuzzy expert system will be developed that has the functionality of a warning and advisory/decision aiding system.