Multi-body Dynamics Modeling And Optimization Design Of Tilt-rotor Rotating Mechanism

With the development of the unmanned aerial vehicles in recent years,the unmanned aerial vehicle(UAV)with the capability of vertical landing has drawn more attention from the research institutions,business units and military units.The tilt-rotor UAV is one of the most important types in the unmanned aerial vehicle with this function and can achieve the recovery of dynamic in the process of landing and cruising through the rotating mechanism.The rotating mechanism,as the core of tiltrotor UAV,has a large capability to decide the steady of the modality's transfer and the safety in the flight.However some problems,such as the pitch angle increase,yaw to the left and roll to the left and height drop can be found in the transfer of the modality of tilt-rotor UAV in the early research and all of these have the relation with the movement of the rotating mechanism and the aerodynamics characteristics of tiltrotor.Due to the obvious campaign,the analysis of rigid body dynamic mechanism is not enough to give an explanation to these problems.Therefore in this dissertation,the object of study is changed to “Lingying I tilt-rotor UAV” designed by the independent research,and through the FEM simulative analysis of kinematics and dynamics to its rotated mechanism,optimized design method will be given.The main working and contribution will be shown in the following part:(1)The accomplishment of the configuration optimization design and the analysis of basic sports rules through the establishment of mult-body dynamic modeling and finite element modeling of the tilt mechanismIn order to establish an accurate model and know more about the working mechanism of the tilting,the tension,torque and resistance torque of the propeller and the multi rigid body mechanical model of the linkage need to be considered in the process.Based on Blade Element Theory,the dynamic model of the propeller in the process of tilting has been established in this dissertation which also includes the deduction of the model of the four-bar linkage mechanism and the motion model driving by the steering gear.Using the model with intergrated power,transmission and ouput,the previous physical parameter and Matlab numerical simulation method,the dissertation has analysed the motion law of the tilting mechanism and the change of internal force in its movement.Besed on the kinematic limitation of multiconnecting rods,the dimensional limitation of the steering's torque,the speed requirment of the rotor tilting,the dissertation has discuessed the design constriction of the mechanism of four-bar linkages and given an optimized design parameter to the four-bar linkage.(2)the kinematic analysis and optimized motion strategy of the tilting mechanism through the establishment of the analytical model of the tilting's finite element.The multi-body dynamic model can be used to describe the internal transport and kinematic features of transmission mechanism,but this explaination is a little simple and some condition,such as the constriction of joint-friction and the internal force condition of links can not be included.The method of limited analysis is comparatively easy to know the whole structure of linkages and the force and moment on the link-joint can be calculated directly.So in the first part,the establishment of finite element model of the tilting mechnism will be established and then the analysis of motion rules driving by the steering engine will also be finished.Due to the aerodynamic drag caused in the accelerate and decelerate process of rotors,the nonlinear accelerate and decelerate process should be reduced and the design of optimized motion process of steering engine will be provided.The theoretical analysis is combined with the finite element simulation,breaking the limitations of the single method,finding a research method for complex models.(3)the analysis of kinematic of the tilting mechanism through the simultion method of hydromechanicsThe rotor model based on Blade Element Theory can not give a detailed analysis about its motor process,and also solve some problems such as air friction in the tilting and the stressing change in the single period shown on the rotor disc.Then the finite element model of the tilting has been established based on the simultion method of hydromechanics.In this model,it designs the motion process of rotor disc,according to the additional motion rule of four-bar linkages mechanism and then give an explaination about the stressing change in different sites of rotor disc,the different speed in the tilting and the force and moment of force in its movement.Then it shows the mechanism of the pitch angle increase,roll to the left in the process of tilting.(4)the establishment of vertification platform on the ground of the tilting rotor to achieve the theoretical analysisThe design is based on the real using of the tilting mechanism of UAV with the torque sensor on the joints and measuring transducer of the revolving of the tilting and the measure of tilting angles.Through the analysis of real data and the simulation of the motion of the tilting meachnaism in the flying,the analysis of establishing the model and the analysis before the conclusion has been verified.It can been found the tilting rotor will be decline with the engagement of tilting and the decline of the speed of tilting,the tilting rotor will also be down.The consequence is proven to be well matched with the theory and the simulation analysis and the reliable of the research,which means an important meaning to solve the real problem.