The Determine Of Loss Of Control And Envelope Protection For Supper-maneuverable Fighters

In order to obtain and maintain the advantages of close combat, a new generation fighter requiresupper-maneuverablity. But in the supper-maneuvering flight, how to avoid access to the loss ofcontrol and ensure flight safety, while develope the full performance of the aircraft, complete combatmissions, is a new task and challenges. This paper focuses on super-maneuvering flight motion,determine of loss of control and envelope protection for supper-maneuverable fighters.First of all, given a6-DOF flight motion mathematical model, analyze the expression ofaerodynamic coefficients, establish the actuator model, set up the engine and thrust vector model offighter, characteristics of open-loop dynamic and channels coupling were analysis.Then, controller was designed for super-maneuverable fighter with parameter uncertainties andexternal disturbance. Dynamic inverse method was used to design flight control law, for systemswith uncertain parameters and external disturbance exist, the sliding mode disturbance observer weredesigned to approximate it, the dynamic inverse combined with the sliding mode disturbanceobserver, flight control law for super-maneuverable fighter were designed based on sliding modedisturbance observer and prove the stability of the closed-loop system. Simulation results show theeffectiveness in propose method.Following, studied the determination method of state boundary of critical loss of control forfighter during super-maneuverable flight motion. The load factor boundary is determined based onthe limits of the fighter’s structural strength and physiological capacity of pilot. Attainableequilibrium set method is applied to calculate the safe boundary for the bank angle rate about thevelocity vector at high angle of attack.Finally, super-maneuverable fighter flight envelope protection in case of a problem. A newflight envelope protection method called avoid obstacle envelope protection is proposed. Accordingto the current state and control input, from the avoid obstacle envelope protection method, safetrajectory of limit variable can be obtained. The load factor and bank angle rate exceeds a safeboundary for the case of Herbst maneuver, envelope protection was carried out. Simulation resultsshow that this method can effectively achieve the envelope protection of the load factor and bankangle rate about the velocity vector while being able to give full play to the aircraft’smaneuverability.