Research On The Key Technologies Of Ground Taxing And Vibration Control For UAV

With the widespread use of UAVs(unmanned aerial vehicle)in military and civilian fields,the operation characteristics of UAVs and the shock absorption of landing gear are required to be more rigorous than ever before.The structural components are required to not only have high strength but also have a good dynamic quality,so that the airborne equipment can withstand less noise interference from the harsh dynamic environment(shock and vibration),and its stability and working life can be ensured.When the UAV is taxing for take-off and landing process,its improper operation may cause an accident of UAV sideslip or tumbling.Thus,in terms of improving safety and mobility,studying the steering characteristics and correction control is of great engineering significance.Based on the objectives and requirements of the project,the buffer mechanism design of UAV landing gear,the analysis of ground steering characteristics and correction control,the optimization of the vibration isolation system and the investigation of the wing vibration control are studied in this thesis.The main contents are as follows:To fulfill the requirements of lightweight and structural simplification for UAV,the cushioning mechanism for an articulated landing gear,and the leaf spring attached with a mechanism of hinge slider for a main landing gear are designed:based on the dynamic analysis of UAV ground movement,the behavior and scheme of cushioning mechanism are discussed;by taking the requirements of each condition as constraint,the size of cushioning mechanism and the spring stiffness are optimized;according to the buffer theory,the stiffness range of main landing gear is calculated,and the design scheme for laminating the composite material of leaf spring is proposed;with the method of rigid-flexible coupling,the dynamic strength of leaf spring and key metal components are analyzed.The results show that there is a good correspondence between the experimental and theoretical values,and the error is less than 12%.The desired absorption of power is also satisfied.The aircraft overload and buffer stroke meet the requirements,and the structure achieves the expected strength and stiffness as well.For the safety of take-off and landing of UAV,the handle steering characteristics and the correction controlling of UAV taxing are studied:based on the nonlinear mathematical model of UAV taxing,the inertial parameters and state of wheel are obtained;the deviation performance is analyzed,and the extreme control angle corresponding to different taxing speeds are calculated;through the linearization method of perturbation,the transfer function is deduced and the deviation control law is designed;the method is verified through field taxing test,the results show that the UAV runs stably and can maintain its trajectory at the runway center effectively.Additionally,it has a good inhibition under the crosswind disturbance of less than 4.6m/s.To improve the anti-jamming ability of the airborne camera to random vibration,the dynamic modeling and optimization for ground vibration isolation system are investigated:the dynamic modeling of vibration isolation system is established,and the influence of ground random excitation on the airborne camera is analyzed by using the white nose filter to simulate the road roughness;to minimize the RMS(root mean square)values of camera acceleration and angle displacement,the parameters of vibration isolation system are optimized.The results indicate that the RMS acceleration has been decreased from 0.63 m/s~2 to 0.25 m/s~2(namely reduced by60.3%)and the RMS angle displacement has been decreased from 405’’to 147’’(namely reduced by 63.7%).To prevent the fatigue or resonance damage of the wing structure,bi-stablenonlinear energy sink is adopted to control the vibration:the dimensional model of the system is established;through the multi-scale method and complex variable analysis method,the response regimes at different types of excitation are studied;then the threshold of each response regime is calculated by asymptotic method,and the design criterion and the corresponding configuration of the absorber are proposed.The results show that this absorber has the advantages of high bandwidth,high efficiency and light weight.Additionally,due to the bi-stable property of the attachment of a negative stiffness mechanism,this absorber can efficiently improve the robustness of different types of energy excitation.