Design Of Variable Speed Semi Differential Control Mechanism For Small Coaxial Unmanned Helicopter

In recent years,coaxial unmanned helicopter has mainly developed to two extremes,one is miniaturization for reconnaissance and patrol,and the other is heavy-duty for transportation.However,due to its certain research difficulty,domestic products are not mature.The main reason lies in the complex control system of coaxial unmanned helicopter and its body weight.This paper provides a variable speed semi differential control mechanism for miniaturized coaxial helicopter.The mechanism has the advantages of simple structure,small weight and outstanding control stability.Innovatively change the lift caused by the semi differential heading control from the total distance compensation to the change of rotor speed,so as to save the weight of steering gear and mechanism required for the total distance control of upper and lower rotors;The mechanism also reduces the required power of the coaxial unmanned helicopter during cruise flight and improves the flight time of the unmanned helicopter.After obtaining the mechanism prototype,build the unmanned helicopter platform,conduct flight test and verify the mechanism.Firstly,according to the design requirements of small coaxial unmanned helicopter,the control scheme of semi differential variable speed of single automatic tilter controlled by double steering gear placed at 90 ° is determined by comparing the common control modes of four existing coaxial unmanned aerial vehicles.The structure of the rotor system is designed and analyzed,and the aerodynamic simulation of the double rotor is carried out based on CFD.The relationship between blade pitch angle,rotor speed and rotor tension is discussed;The form of the control mechanism is selected,and its working principle and mechanism kinematics are analyzed,so that it can carry out a wide range of periodic variable distance motion,carry out the forward and inverse kinematics solutions,and use matlab programming for output.Analyze the strength of key components and calculate the hinge torque.The trim calculation of variable speed helicopter is carried out,and the algorithm that can be used to calculate the rotor speed and required power of variable speed helicopter under different forward flight speeds is obtained.The unmanned helicopter platform is built for debugging and flight test,and the rotor speed and required power are measured,which achieves the expected power saving effect of the mechanism.In this paper,the overall scheme selection,detailed component design,theoretical modeling analysis,simulation analysis,flight platform test flight and so on are carried out,but there is still a lot of work in the follow-up flight test and aircraft control.