Nonlinear dynamic model identification of airplanes including inertial parameters and force-torque relations based on real flight data

The primary scope of the paper lies on the identification of an aircraft´s nonlinear dynamic model together with the inertial parameters (center of mass and inertia matrix). It is assumed that the aircraft has no inbuilt navigational system, nor any sensors mounted on its control surfaces. The flight of the airplane is influenced by the control column and pedals manipulated by the pilot whose positions can only be observed visually. For the time of data logging, an external sensory system (GPS, IMU) and a camera system were deployed on the airplane supporting the collection of flight data for state estimation and model identification. An earlier paper discussed the computation of the actuator signals and the state estimation. The present paper concentrates on the identification of the unknown COG and inertia matrix together with the force-torque model if the sensory information is available in a frame parallel with the geometrically chosen frame of the airplane. The force-torque model is based on the dynamical equations of rigid body with additional weighted nonlinear terms for 3D forces and torques. Dominating nonlinear functions are selected by physical considerations and their parameters are determined using SVD technique. From the inertial parameters only the mass is known. Wind effects are taken into consideration. Inertial parameters are computed by constrained global search based on an appropriately chosen objective function. The results are presented for a sailplane using real flight data.