Longitudinal stability augmentation using a fuzzy logic based PID controller

We develop a PID based fuzzy logic pitch attitude hold system for a typical fighter jet under a variety of performance conditions that include approach, subsonic cruise and supersonic cruise. In this approach, the gains found in a classic PID controller are replaced with fuzzy systems, still contributing the overall effects of a proportional, integral, and derivative controller. The response is compared to conventional PID control. In addition, the design is tested for an F-4 in the approach condition, then with a 50% reduction in both longitudinal stability and pitch damping, and finally subsonic and supersonic cruise conditions. The different cases allow analysis of the off-design performance characteristics, or fault-tolerant capabilities, for the fuzzy logic and proportional gain controllers. Results show that for all flight conditions, the fuzzy PID controller was able to perform comparably to the conventional controller, while exhibiting faster rise times.