Research On Dynamics Modeling And Longitudinal Control Of Rotated Wing Aircraft During Transition Stage

The rotated wing aircraft,as a new structure of aircraft,is an improved version of the traditional tilt-rotor aircraft.The wings of rotated wing aircraft can be divided into two parts:fixed-wing and rotated wing,in which rotated wing and rotor wing are fixed connection and tilting synchronously.In this way,the lift loss caused by the downward wash of the rotor impinging on the fixed wing in the stage of vertical take-off and landing can be overcome,then the upper limit of aircraft take-off weight can be increased and the maximum range can also enhanced.The rotated wing aircraft has three flight modes that can be converted to each other.:helicopter mode for vertical take-off and landing in the take-off and landing phase,fixed-wing mode for high-speed cruise in long-distance flight and transition mode for switching between helicopter and fixed wing mode.Rotated wing aircraft has the dual characteristics of helicopter and fixed wing aircraft and three flight modes.So there is an extremely complex flight system behind the powerful flight performance,in which the worst safety and reliability and the most difficult to control is the transition mode.The rotation of rotor and tilting wing will bring a series of aerodynamic interference,time-varying,strong coupling and other problems when rotated wing aircraft is flying in transition stage,which will make the longitudinal control of aircraft become particularly difficult.So the realization of the safe and stable control in transition has a significant promoting effect in the research of rotated wing aircraft.In this paper,the dynamic characteristics and longitudinal control problems of rotated wing aircraft which is in the stage of transition mode are studied as follows:First of all,in order to analyze the dynamic characteristics of rotated wing aircraft we need to build an aerodynamic model of the aircraft.For the reason of simplifying the model problem,the main aerodynamic components of rotated wing aircraft were modeled by using the split method,and then the nonlinear dynamics and kinematics equations were established.Based on some assumptions,the rotated wing aircraft model is simplified as a longitudinal nonlinear simulation model,and then to study longitudinal control on these basics.Secondly,it is necessary to balance the nonlinear simulation model of rotated wing aircraft and design the conversion channel.The nonlinear model was linearized to analyze the longitudinal stability of flight in transition stage and the analysis resultsshow that the rotated wing aircraft could maintain stability in this stage at a constant altitude.Then the pole assignment method is used to design the longitudinal control system of rotated wing aircraft.According to simulation to verify the control effect,and the effect is well,which can meet the requirements of the constant flight and pitch stability of the transition section.Finally,it is necessary to add the nonlinear model control of the rotated wing aircraft in transition mode,and PID control is used to study the nonlinear model.The simulation results show that the control of each flight parameter can meet the requirements of constant altitude flight and pitch balance.In this paper,the control system of the rotated wing aircraft to maintain a fixed altitude flight and pitch stability in the transition mode is designed,which lays a foundation for the control system design of the rotated wing aircraft in full mode.