RealSysId: A software tool for real-time aircraft model structure selection and parameter estimation

This work presents a new computational tool developed for online selection, identification and validation of the aerodynamic model structure of a fixed-wing aircraft. This tool, named RealSysId, brings the possibility to choose and compute, during real-time of the experimental test flight, the most relevant aerodynamic stability and control derivatives, also giving visual and analytical indications about the quality of the excitation maneuver. The selection of the coefficients is performed through a graphical interface prior to the execution of the maneuver. During the execution, the identification is done using a time-based technique known as Recursive Orthogonal Least Squares method, requiring negligible computational effort. In a third step, the validation occurs using a separate maneuver, where the computed aerodynamic global coefficients are compared with the prediction interval of the recent identified model. The usage of the interval of prediction defined on a certain level of confidence, instead the predicted model, offers a realistic assessment of the computed model. The entire process comprised by the functionalities of the RealSysId tool, which gives immediate result, improves significantly the decision making and updating of the flight test maneuvers, increasing the efficiency of the flight test campaign. The benefits and applicability of this tool, including the possibility to identify variations in the aerodynamic coefficients caused by configuration changes, are demonstrated with two real flight test cases.