Aircraft Dynamic Model Aided Airborne Integrated Navigation System For Small-scaled Fixed-wing UAVs

Unmanned Aircraft Vehicles(UAVs)have drawn extensive attention in military and civilian fields due to its long endurance,low cost and zero damage of personnel.With the improvement of the diversification of flight tasks and the complexity of flight environment,accounting for the flight requirements of long endurance,high precision and high reliability,people have set higher standards for the performance of the UAVs' navigation system,and how to maintain the navigation precision when the satellite signal runs out is a hot issue.Based on the small-scaled fixed-wing UAV,the paper focuses on the research of the novel integrated navigation of the Aircraft Dynamic Model(ADM)aided Strap-down Inertial Navigation System(SINS),including the mechanism of the SINS/ADM,the calculation of the aerodynamic parameters of ADM and the improvement of the filter in SINS/ADM,aiming at increasing the accuracy and reliability of the airborne navigation system of UAV.The main contents of this paper are as follows:The mechanism of the SENS integrated with ADM is studied.The noulinear ADM of the fixed-wing UAV is established and the sources of error are analyzed.The construction of the linear error model of SINS and that of ADM,the integration mode and the choice of measurements are analyzed.Then the simulation research based on a small-scaled fixed-wing UAV is conducted to study the process of SINS/ADM under the condition of steady-state flight and maneuvering flight with complex route.The related research pointed out that the precision of ADM itself predominates in the SINS/ADM process,and the promotion of SINS precision promotes that of correction of ADM.Moreover,the maneuvering flight siruulation demonstrated that the maneuvering flight brings about error in ADM as well as SINS/ADM.The mechanism analysis provides theoretical basis for further SINS/ADM research.A complete set of aerodynamic parameters calculation scheme for small fixed wing UAV is studied and designed.First,based on the aerodynamics theory,or the "Semi-empirical Method",with the simplification of structural characteristics and flight conditions of the small fixed wing UAV,the aerodynamic derivatives of each force and moment are analyzed and calculated,and the initial aerodynamic derivatives can be obtained.Secondly,in order to further correct the initial error of the aerodynamic derivatives,an online identification scheme based on Extended Kalman Filter(EKF)is carried out.The airborme inertial navigation/satellite integrated navigation results are utilized,and the maneuvering flight is designed to improve the observability of the error of the aerodynamic derivative,thus achieving the estimation and correction of the initial value of the aerodynamic derivative.And a more accurate ADM is obtained,as well as the precision of SINS/ADM.Based on a small fixed wing UAV,the feasibility of the parameter calculation scheme for the estimation of the error of the aerodynamic derivatives in the longitudinal channel is verified with simulations.The filter in the SINS/ADM integration is studied.Considering the uncertainty of the system equation,the observation equation and the noise caused by the complex environment change during the actual flight,this paper studies and improves the filter structure and filtering algorithm in the SINS/ADM integrated navigation process with the Hco filtering thought.On the one hand,the Extended Hoa Filter(EHF)is used to replace the common EKF to complete the integrated navigation and improve the robustness of the whole system against kinds of uncertainty.On the other hand,on an account of the fast updating rate of ADM data in the actual flight,the direct filtering method based on Unscented Kalman Filter(UKF)is used to integrate the SINS and ADM to solve the various defects in the linear way.Furthermore,an Improved Square-Root Unscented Hoo Filter(ISRUHF)is proposed.The idea of square-root filtering is introducedand the robustness of the whole integrated navigation system is further improved by the novel calculation of the robust factor matrix ?.Flight tests based on the small-scaled fixed-wing UAV,Extra300,is studied.Firstly,with the standards of the relatively high precision airborne SINS/GPS integrated navigation results,the rationality of the aerodynamic derivatives calculated by the "Semi-empirical method" is verified by the separate calculation of ADM.Secondly,the aerodynamic derivative is identified and compensated via the real flight data,and the result is verified by the comparison with the ADM calculation results.Therefore,the aerodynamic derivative identification scheme proposed in this paper is proved to be feasible and the precision of the aerodynamic model has been greatly improved.After obtaining a high precision ADM,the SINS/ADM integrated navigation process is further verified,and the accuracy of the SINS/ADM integrated navigation can be accomplished in the actual flight conditions without the GNSS signal.In 3 minutes,the error of the horizontal position is about 40m,and that of the velocity is about 2m/s.At last,the advantage of ISRUHF in SINS/ADM integrated navigation is verified by the data of real flight.