| Aiming at the problem that a small high-speed UAV has strong maneuverability and poor stability,which leads to insufficient safety in high-speed section,this paper establishes the longitudinal control strategy of angular rate damping inner loop in low-speed section and angular rate instruction inner loop in high-speed section,and designs the transition mode to realize the switch of control law,completes the longitudinal control in the whole process of takeoff,cruise,acceleration and high-speed flight.The problem that UAV is sensitive to longitudinal centroid offset when UAV is flying in high speed is solved.Firstly,the UAV is modeled by rigid body motion model and aerodynamic data interpolation,and the CMEX model library is imported into MATLAB for trimming linearization.By analyzing the characteristics of the model,the characteristics of the small UAV,such as wide flight envelope,strong maneuverability and poor stability,are obtained.Then,the longitudinal control law is designed for the low speed section of 120 m/s and the high speed section of 200 m/s.Because of the static stability in the longitudinal direction,the conventional angular rate damping inner loop control is adopted,and the robustness of the control law is verified by the simulation of parameter uncertainties.The angular rate inner loop is proposed as the longitudinal control law in high speed flight.By comparing with the damped inner loop in time domain,frequency domain and robustness,it is concluded that the instruction inner loop is more suitable.Finally,the transition between low speed and high speed of UAV is designed.The transition process is realized in flight mode from two aspects of selection of handover airspeed and switching of control law.After completing the longitudinal control design of the whole flight process,a complete mission route is designed,and the whole process simulation of various interference cases is carried out,which proves that the longitudinal control law designed has sufficient security. |
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