Design Of A Small Unmanned Folding Coaxial Rotor Helicopter Platform

Coaxial twin-rotor unmanned helicopter as one type of aircrafts has wide application prospects due to its compact structure,large payload and high hovering efficiency.However,it is restricted by its research difficulties and there are not enough mature products in china.The two-layer rotors in a traditional coaxial helicopter are generally driven by gears and internal and external axles,which restricts the development of coaxial helicopter miniaturization and lightweight.In this study,we proposed and set up a new folding unmanned helicopter with an electric small coaxial double-rotor.This unmanned helicopter can be equipped with functional loads to meet military operational needs.According to the requirements and flight environment of the small unmanned helicopter,we first determined that its upper and lower part were composed of rotor and operating mechanisms,and control and bearing systems,respectively.On these bases,a transmission mode derived by motor and a large angle rotation of the paddle was proposed.The folding scheme of the blade is free to sag,and the main technical parameters of the drone were designed and explained.Then,the prototype of the design was shown.The design and analyses of the rotor system were based on the overall design scheme.The single-layer rotor and the coaxial double-rotor inflow model were applied to analyze the aerodynamic interference between the upper and lower rotors.The rotor system load can be obtained through integration.Subsequently the structural design of the rotor system and the finite element simulation analysis was conducted.Besides,we also simulated the aerodynamic calculation based on CFD.The relationship among the geometrical angle,the rotational speed and the tension was discussed.In additions,we analyzed the flight principle,mechanism kinematics and the design of the operating mechanism which was based on the flight principle.A carbon plate design associating with the steering gear layout was introduced.To satisfy the relatively wide range of total distance,a control system was used in this study.The output of data was obtained by a transformation from the steering mechanism to an equivalent mechanism,calculating the degree of freedoms,modular kinematics positive and negative solutions,and the usage of MATLAB.As for the flight control hardware and software designs,they were mainly selected by existing configurations and six modules,respectively.Finally,the UAV was debugged and tested to achieve the expected function.we proposed a preliminary design scheme of electric coaxial twin-rotor folding unmanned helicopter was proposed.According to the requirements and flight environment,the overall layout design,technical parameters,theoretical modeling,simulation calculation,machine debugging and so on were carried out.Besides,a new folding unmanned helicopter was set up.Some achievements have been achieved,but there is still much work to be done in flight control and experiment.