Research On Ducted Fan Unmanned Vehicle Modeling And Control Strategies

Ducted fan UAV (unmanned aerial vehicle) is a special unmanned aircraft,whose power comes from the thrust or lift device composed of the fan beingplaced inside the ring duct. Compared with ordinary fixed-wing and rotary-wingUAV, it has the following advantages: more compact construction, loweraerodynamic noise, better security, and greater thrust than the isolated fan in thesame power and diameter. Therefore, it has wider application prospect. Sinceducted fan UAV unique aerodynamic shape, its modeling and control designmethods are faced with many challenges. This ducted fan UAV dynamicsmodeling is complex, and the model has serious uncertainty. On the other hand,the vehicle body can be interfered easily by external environment. This paperconsiders the following problems.First, this paper introduces ducted fan UAV overall configuration and designparameters. Combined with flow theory, blade theory and momentum theory, theducted fan’s dynamic characteristics is analyzed. Using the panel method analysesthe relationship between the control surface deflection angle and pressuredistribution. Then rigid-body dynamical model is derived with the knowledge ofrigid-body dynamics. This can also give vehicle’s nonlinear dynamic equation andkinematics equation. Finally, the above equations can be simplified by smallperturbations linearization method, and thus the linearized aircraft model can begiven.Second, the model of ducted fan UAV has serious uncertainty and its loadlikely changes. Meanwhile the vehicle body can be interfered easily by crosswind.To solve the problems above, the state feedback controller and output feedbackcontroller are designed. These controllers can help the flight control system meetthe interference suppression indicator constraints, and make the closed-loop polesbe configured into the designated area. The existense conditions of thesecontrollers is given in the form of linear matrix inequalities. The stability analysisand proof are given. The results of numerical simulations show that, this controlmethod has good robust stability to crosswind interference and load change, andsatisfactory dynamic performance. Third, for the complex work environment, the ducted fan UAV actuators andsensors might fail possibly. This paper designs-D stabilization robust fault-tolerant controller, which can ensure the closed-loop poles be configured into thedesignated area, and the flight control system meet the interference suppress ionindicator constraints, in the actuator or sensor failure (only part of work). Theexistense conditions of this controller are given in the form of linear matrixinequalities. The results of numerical simulations show that, this control methodcan still meet the performance requirements, in the actuator or sensor failure dueto the change of vehicle work environment.Finally, an adaptive sliding mode control theory is used to control formultiple-input and multiple-output nonlinear system. Considering the couplingbetween the axes, using sliding mode control can give system strong robustnessand anti-interference ability to uncertainties. Using adaptive control can identifysystem parameters online, and adjust controller parameters in real time. Therebyit can eliminate the affect from the parameter uncertainty. Using the integral termof the tracking error in switching function design can avoid obtaining all-orderderivatives terms of tracking signal. And it can eliminate the steady-state error ofthe system. Selecting rationally reaching law of the switch function can inhibiteffectively the chattering of the system. The results of numerical simulations showthat, this method has good inhibition to the nonlinear uncertainties of ducted fanUAV system. The trajectory control law is designed for the ducted fan UAV. Therobustness of control system is tested in example path with the crosswind.