A fuzzy control approach

Pilot heuristics of flying an aircraft are implemented in the design of a fuzzy logic controller (FLC). The FLC design exists of longitudinal and lateral outer loop tracking controllers combined with classical inner loop attitude controllers. The first step includes tuning the inner loop controllers using classical control techniques. Next, the FLCs outer loop controllers are initialized as linear, MIMO controllers in which the rules are derived from control strategies based on the experience of pilots. The final step includes fine-tuning of the FLCs by modifying the rules based on an initial evaluation of time responses with respect to the specifications. Additional rules for low airspeed and engine failure are included as well, which show that gain scheduling and exception handling can be incorporated in a straightforward way. Following this three-step procedure, a compromise is found in which performance and robustness properties are met at the cost of a slightly too high vertical and lateral acceleration. The obtained FLC is of low order, deterministic and transparent.