Research On ADRC Flight Control Technology Of Quad Tilt Rotor UAV

Tilt rotor UAVs have the advantages of both helicopters and fixed-wing aircraft.They have the characteristics of helicopter with vertical take-off and landing,hovering performance,and fixed-wing aircraft with long range and high cruising speed.Therefore,tilt rotor UAVs have broad prospects for military and civilian use.As a new type of aircraft,tilt rotor UAV has many difficulties in designing technology and needs to be broken.Tilt rotor UAV is a multi-input / multi-output,time varying,nonlinear strong coupling system,especially in the transition process.It has the characteristics of poor stability,susceptibility to external disturbances and redundant control.In order to make the tilt rotor UAV have better safety in the transition mode,the control system must have good decoupling and anti-interference ability.In this paper,the Active Disturbance Rejection Control(ADRC)is used to design and research control technology for a small electric quad tilt rotor UAV.Nonlinear flight dynamics model is the basis for the research on the stability characteristics,control strategy,tilt path and flight control technology of quad tilt rotor UAV.Based on the idea of component modeling,this paper establishes a full nonlinear flight dynamics model of a quad tilt rotor UAV,and conducts a detailed mathematical analysis of trimming.Aiming at the problems of the aerodynamic interference of the quad tilt rotor UAV’s rotor and wing,and the traditional trimming methods relying on the selection of initial values,slow convergence speed,and low convergence accuracy,this paper builds an Hybrid optimization trimming algorithm.Use CFD to calculate the aerodynamic interference forces and moments of components in each state,and compensate them to the flight dynamics model to realize the compensation calculation of aerodynamic interference;Utilizing the characteristics of the IA algorithm’s low dependence on the initial value and the fast convergence speed of the LM algorithm,a fast convergence trimming calculation that does not depend on the initial value is realized.The hybrid optimization trimming algorithm was used to analyze the trimming characteristics of the quad tilt rotor UAV in detail,and then the trimming state was linearized,and the stability characteristics in the transition mode were calculated and analyzed.The calculation results show the complicated coupling characteristics of the quad tilt rotor UAV in the transition mode.The quad tilt rotor UAV flight control system needs to implement both helicopter and fixed-wing control functions.It is operated in helicopter mode during hovering and fixed-wing mode during cruise.Mode transition to fixed-wing mode,there is a problem of manipulation redundancy.Aiming at the problem of manipulation redundancy in transition mode,this paper designs a manipulation allocation strategy,uses ACO optimization algorithm to analyze the tilting path,and optimizes the optimal tilting path in the transition corridor.The effectiveness of the maneuvering strategy and tilting path optimization strategy is verified by simulation calculation analysis.In order to overcome the problems of tilt rotor UAV being sensitive to external disturbances and strong manipulation coupling in the state of tilt transition,ADRC is independent of the model,and the internal and external disturbances of the model can be observed and compensated through the extended state observer to achieve decoupling control of quad tilt rotor UAV.In this paper,the flight control law of a quad tilt rotor UAV based on ADRC is designed.The principle of ADRC and the influence of various parameters on the controller performance are analyzed in detail.A combination of RBF neural network and SMC control optimization algorithm.In the ESO,the total disturbance is estimated and compensated through the RBF neural network.The SMC is introduced in the NLSEF to accelerate the response time of the system.The tilt rotor UAV is simulated and verified.The research results show that the optimized ADRC control algorithm has better robustness.There are many parameters to be tuned in ADRC.In the past,parameter tuning has mostly depended on experience,and parameter tuning is difficult.In this paper,the parameter tuning method of ADRC is optimized,and the parameter tuning method based on frequency domain is used to reduce the parameters of ADRC to be tuned to three.A new neural network optimization algorithm based on particle swarm bacterial foraging strategy is proposed.The neural network is used to realize the self-tuning of ADRC parameters.Aiming at the problem that neural networks are easily trapped in local optimal values,this paper proposes to use the bacterial foraging algorithm to optimize the learning algorithm of the neural network,and to use the particle swarm optimization algorithm to avoid the problem of weak bacteria information interaction in the bacterial foraging algorithm.By introducing the overshoot and rise time of the input signal and output signal into the fitness function,the overshoot of the system output is reduced and the response time of the system is accelerated.Using the optimization algorithm proposed in this paper,the parameter tuning of the ADRC controller is realized,and the effectiveness and correctness of the parameter tuning method are verified from Nyquist,time domain and Monte Carlo experiments,respectively.The research results show that the ADRC controller with self-tuning by the optimization algorithm has better time and frequency domain characteristics,and the system is more robust.In order to more intuitively and dynamically display the state of the quad tilt rotor UAV during transitional flight,a 3D quad tilt rotor UAV model based on Flight Gear is developed in this paper.Based on the quad tilt rotor manipulation strategy,tilting strategy,and flight control law source code writing and compilation,a 3D real-world simulation model was established,which verified the validity of the firmware source code and the manipulation strategy,tilting strategy,and control algorithm.In order to further verify the validity of the research done in this paper,this paper builds a principle prototype and flight test prototype flight control system based on the Pix Hawk flight control system,and conducts a test flight test on an electric quad tilt rotor UAV.Through the analysis of flight test data,the correctness and effectiveness of the flight dynamics model,tilt transition control strategy,tilt path optimization strategy,flight control algorithm,and firmware source code of the quad tilt rotor UAV are fully verified.