Research On Key Technologies Of Flight Control Algorithm Of A Ducted Fan Coaxial Rotor UAV

The rotor unmanned aerial vehicle(UAV)has great potential in the fields of intelligent military,agricultural mechanization,environmental monitoring,geological exploration and logistics.Compared with the fixed wing UAV,rotor UAV has vertical-takeoff and landing capabilities.This makes it an attractive choice when compared to fixed-wing aircrafts that need significant space for takeoff and nonzero forward speed to maintain flight.In this subset of rotor aerial vehicles,the ducted fan coaxial rotor configuration has numerous advantages compared with other rotor UAVs: compact structure,less noise,power train efficiency,stronger security and so on.Therefore,it is very urgent and necessary to carry out the research on the modeling of the ducted fan coaxial rotor UAV,the design of the flight control system and the control algorithm.Due to the unique aerodynamic characteristics of the ducted fan coaxial rotor UAV,the modeling and control method design are faced with many challenges.Special attention is given to the issue of robustness to plant uncertainties,nonlinear interconnections and disturbances.The main contents of the paper include the following aspects:(1)This part first introduces the ducted fan coaxial rotor UAV overallconfiguration and design parameters.Based on the related literatures at homeand abroad,the modularization method is adopted to systematical model theducted fan coaxial rotor UAV.Combined with the slipstream theory,bladetheory and momentum theory,the dynamic characteristics of the UAV isanalyzed.The relationship between the control surface deflection angle andcontrol moments is analyzed by the panel method.The nonlinear dynamicequations and kinematic equations of the aircraft are obtained by using therelated knowledge of the rigid body dynamics.Finally,the equations aresimplified by using the small perturbation linear method near the workingpoint to obtain the linear model of the aircraft.In order to improve the digitalsimulation accuracy,and ensure the rudder loop bandwidth to meet thebandwidth of the flight control system,it is necessary to perform sinusoidalsweep experiment on the real digital servo.Next,we use Matlab to processthe data to obtain the identification model.Since there are some unknowaerodynamic parameters in the mathematical model of the ducted fan,the liftand torque experiments are carried out to build the relationship between thelift and speed,and the relevant parameters of the model are identified,whichimproves the accuracy of digital 、simulation.(2)The model of the ducted fan coaxial rotor UAV has strong nonlinearitiesand uncertainties,meanwhile,it is easily affected by external interference.Asfor the robust control problem,this paper proposes a state back controller,which can meet the interference suppression indicator constraints and placethe closed-loop poles in the desired area at the same time.The controller canmake the UAV closed-loop system stable and satisfy some certain dynamicperformance indexes.By giving the form of a new linear matrix inequality,the controller gain can be obtained.Finally,the numerical simulationexperiments show that the closed-loop system with some uncertainties andinterferences can still guarantee the robust stability and the dynamicperformance at the same time.(3)When the ducted fan coaxial rotor UAV working in the complexenvironment,the sensors might fail in a limited frequency domain.It isnecessary to design a controller which can detect the fault and make the UAVsystem stable at the same time.This paper presents the control architecturecomposed of an observer and a controller,which can achieve the faultdetection objectives and control objectives.In addition,the GKYP lemma isintroduced to deal with the finite-frequency sensor fault detection problem.Through introducing a new form change-of-variables,the observer-basedcontroller design conditions converted into LMI-based optimization problem.The simulation results have illustrated the proposed control design canguarantee the H￥ performance to disturbance,H-performance whichmeasured the fault sensitivity and stability of the closed-loop system.(4)Special attention is given to the issue of robustness to plant uncertainties,nonlinear interconnections and disturbances.By combining the H￥ theorywith the dynamic observer(DO),we propose an H￥ dynamic observercontroller for the DCRUAV.The stability and robustness conditions for theexistence of the H￥DO-based controller is given in terms of a newformulation of linear matrix inequality(LMI).By using the obtainedcontroller guarantees that the transfer function from the disturbance to thecontrolled output satisfies a prescribed H￥ norm level.The whole designprocedure and parameterization of the H￥ DO-based controller isconducted within the paper.Finally,simulation results are carried out todemonstrate the efficiency and good performance of the proposed controldesign.(5)Semi physical simulation experiment is designed to prove the flightcontrol algorithm correct and effective.The semi-physical simulation resultsare in good agreement with the numerical simulation,which providestheoretical support for the estimation algorithm applied to practicalengineering.