Guaranteed Cost-Based Disturbance Observer and Controller Design for Path Tracking Control of a Powered Paraglider Under Unknown Rudder Trim and Wind Disturbances

This paper presents a guaranteed-cost disturbance observer and controller design to achieve accurate path tracking control for a powered paraglider (PPG) in the presence of unknown rudder trim and wind disturbances. The key contribution of this paper is a theoretical approach that ensures given flight control performance even in the presence of these unknown variables. Due to the complex and highly nonlinear nature of PPG dynamics, our approach utilizes a nonlinear control framework based on Takagi-Sugeno fuzzy models. Although this paper designs a nonlinear controller that compensates the rudder input not only with the trim but also with the wind estimated by the disturbance observer, it successfully derives guaranteed-cost design conditions that allow the separate design of the disturbance observer and the nonlinear controller within this framework. In addition, the influence of observer estimation errors on control performance degradation is discussed in terms of considering the upper bound of given control performance. The effectiveness of the proposed approach is demonstrated through extensive flight simulations using a high-precision PPG simulator, which accurately models the real-world flight dynamics of two rigid bodies with seven degrees of freedom. This validates the practical utility of the guaranteed-cost disturbance observer and controller design in maintaining control performance under unknown rudder trim and wind disturbances.