Fuzzy Controller Design and Stability Analysis for an Aircraft Model

Fuzzy control systems are generally considered applicable to processes that are mathematically ill-understood and where human experience is available for control rule synthesis. An equally important characteristic of fuzzy control is the ability to encompass qualitative and highly nonlinear control objectives. This ability makes fuzzy control applicable to processses for which the control objective cannot be adequately expressed in a form amenable to standard control synthesis methods. We describe a fuzzy roll controller design for Rockwell International´s Advanced Technology Wing (ATW) aircraft model. The controller modulates six control surface on the ATW to achieve the desired roll rate while maintaining wing loads within safe bounds. The use of fuzzy control rules enabled highly flexible control behavior that operated the system close to the constraint limits, thereby achieving excellent roll performance. We also present a method of stability analysis for fuzzy control systems based on partitioning the state space and applying a Lyapunov stability criterion to the individual partitions. A subset of the control rules is analyzed using this method and shown to provide asymptotically stable control.