Research On Anti-disturbance Attitude And Altitude Tracking Control Method Of Unmanned Helicopters

Unmanned helicopters can complete operations such as hovering,vertical take-off and landing,side-flight,and inverted flight.They can flexibly enter and exit in harsh environments and are widely used in civil,military,and commercial fields.The unmanned helicopter is a typical multi-input multi-output,strong coupling,under-driven,and non-linear system,and due to the complex aerodynamic properties generated by thrust,there exist large parameter and model uncertainties.In addition,the system is susceptible to external disturbances during the actual flight.Therefore,it is extremely challenging and exploratory to study high-performance flight control methods.In this dissertation,the anti-disturbance attitude and altitude tracking control algorithms of unmanned helicopters are studied,and the following control schemes are designed.On the one hand,due to the influence of periodically harmonic disturbances,composite controllers combining the harmonic disturbance observer technology and the backstepping control technology are designed.Firstly,some harmonic disturbance observers are designed to accurately estimate the helicopter’s disturbances in different channels,and the Routh-Hurwitz theorem is used to prove that the disturbance estimation error systems have exponential convergences.Secondly,based on the disturbance estimates and the backstepping control method,composite backstepping tracking controllers are designed.The Lyapunov stability theorem is used to strictly prove the asymptotic stability of the closed-loop control system.The efficiency of the proposed controllers are verified by MATLAB numerical simulations.Compared with feedback controllers based on the backstepping method and the integral technology,the closed-loop helicopter system under the proposed composite controllers has a stronger anti-disturbance performance and a better robustness.On the other hand,feedforward feedback composite controllers that integrate the nonlinear disturbance observer technology and the dynamic surface control technology are designed.The dynamic surface control technology effectively solves the complex calculation problems caused by frequent derivatives of the virtual controllers in the backstepping method.Nonlinear disturbance observers accurately estimate many types of disturbances,including ramp,parabolic,high-order disturbances,etc.The asymptotic stability of disturbance observation error systems is strictly proved.The Lyapunov stability theorem is used to prove the uniform ultimate boundedness of the closed-loop system.In the numerical simulation,the influence of the parameter perturbation during the actual flight of the helicopter is considered.As a comparison,simulation results also show control effects of the baseline dynamic surface feedback controllers without disturbance compensations.Simulation results show that the closed-loop helicopter system under the composite dynamic surface controllers still maintains good tracking performances even in the presence of parameter uncertainties and external disturbances,and its dynamic and steady-state performances are better than the system controlled by baseline dynamic surface feedback controllers.