Research On High Reliability Nonlinear Adaptive Fault Tolerant Flight Control

Tranditional flight control law is designed by pretty known and accuracy flight dynamics model.When the aircraft suddently encounts control surface deadlock asymmetrically in limited position or even one side of wing damage severely,not only the flight dynamic equations will change in a short time,but longitudinal and lateral motion will be coupled severally in low lateral maneuverability of one side,so the tranditional flight control law could not fix out this problem.In order to achieve high reliability passive fault tolerant control(HRPFTC)for the problem above with no active diagnose,hardware/software redundancy flight control system,under which each axe has equivalently only one control surface(control allocation unavailable),the dissertation researches the sideslip flight robust model reference adaptive attitude control(MRAC)and the neural network based robust adaptive nonlinear model-inversion(MI)attitude control for stablilizing flight attitude angles quickly and passively after the deadlock or damage.Further,the established enroute flight guidance laws and inergrated adaptive guidance & control(IAG&C)achieve flight in-route in performace recovering.The effectiveness and practicability(E&P)of all these algorithms for HRPFTC are vertified in simulation/flight test.The main work and achievements are as below.1.For the problem of one-side aileron deadlock in limited position or even one side of wing damage severely,the cascaded sideslip flight(CSF)MRAC is proposed which utilizes PI control of sideslip angle,general output feedback based reference model configuration method,lateral/directional adaptive attitude control,to achieve the fast stabilization by giving sideslip angle,and the bounded stability of attitude errors respectively under the parameter uncertainty,external disturbance(ED),unmodelled dynamics(UD)in transfer functions of relative degrees n~?=1 and n~??2. Further,in order to improve filght performance,the e-?-modification hybrid adaptive law is proposed to shrink ultimate lateral/directional attitude error boundary in traditional e-modification adaptive law by the proposed method of choosing adaptive gains..2.For the problem of uncontrolled attitude due to deadlock above,especially large nonlinear model errors after one side of wing damage severely,the single hidden layer neural network(SHL NN)based robust adaptive nonlinear MI attitude control(RANMIC)in three-axis is established under bounded stability proof in ED.Then,the design of PD gains for transient index is also established.Further,In order to adapt unmodelled actuator dynamics(UAD),the pseudo control law extended by dynamic nonlinear damping singal is synthesized.Finally,for solving system stability degradation coused by static and dynamic actuator saturation,the reference model and pseudo control limited signal based SHL NN adaptive nonlinear MI flight control algorithem is then proposed.The algorithms above together achieve not only fast & passive stability and transient performance recovering(FS&PC)adaptively,but also separation from uncontrollable state due to control supersaturation.3.For the problem of enroute flight in low capability after deadlock or damage above,the linear acceleration commands based flight guidance law and SHL NN based robust adaptive model-inversion guidance(AMIG)law are established which being connected to control algorithem conveniently.The former proposes to ultilizes altitude error and side distance to route to calculate linear acceleration for attitude commands.It gives waypoint guidance resolution when lacking moility.The latter combines linear acceleration equation,adaptive MI algorithem,pseudo control limited signal and reference model.It not only realizes inputing waypoint's position as its guidance commands to create flight trajectory through reference model for enroute flight,but also could adaptive modify trajectory commands when lacking moility.Further,three sorts of passive fault tolerant IAG&C systems are constrcted for waypoint flight before and after deadlock / wing damage.4.In the application of left aileron up-deadlock in limited position,the e-?-modification robust adaptive law based CSFMRAC is simulated under attitude disturbance and unmodeled aileron / rudder dynamics.The robustness and capable of thrinking ultimate error boundary are verified.Then,the three IAG&C systems are simulated in the situation above.The E&P of the algorithm systems of HRPFTC capability are vertified after the analysis and summarization of performace,pros and cons.5.For the problem of dramatic changes in flight dynamics after one side of wing damage severely,the new features in the characteristics of geometry,mass,aerodynamics after the damage are analyzed and the changing trend of them is also discussed.After deriving the nonlinear motion equations of wing-damaged aircraft,the multidimensional Newton iteration method in global convergence for solving trim points is proposed.On the basis above,the changes of eigenvalues and flight motion modes,stability & handling performance in different damage degrees of one side of wing are researched.The changing rules of them are then revealed,which provide relevant knowledge of high reliability damage tolerant control.6.In the application of left wing's 40% area moment loss suddenly in flight,the SHL NN based RANMIC under ED and UAD is simulated to verify its capability of FS&PC.Then,the three IAG&C systems are tested in simulation under ED,limited static control authority,UAD together in the scenario of enroute flight before and after wing damage above.After the analysis,the E&P of high reliability passive damage-tolerant control capability for fast stabilization and continuing enroute flight of subnormal aircraft.Finally,The first modified IG&C system is verified in flight test for enroute flight,hold altitude & direction(HA&D)of undamaged aircraft,and for fast stabilization,HA&D,tracking waypoints,flight in-route of aircraft in one side of wing's 40% area moment loss suddenly.