Analysis Of Transmission Precision Of Reducing Mechanism For Actuator With Small Tooth Number Difference

Electromechanical actuator can control the motion of pitching,yawing and rolling as an essential actuator of control system in aerospace vehicle.Meanwhile,the transmission precision of reducing mechanism with small tooth number difference which acts on the electromechanical actuator can influence the flight path accuracy and dynamic qualities of aerospace vehicle directly.In recent years,with the development of China’s aviation industry,higher requirements have been put forward for the transmission quality of reducing mechanism used on electromechanical actuators.It has been urgent task to develop the high-precision and high-efficiency reducing mechanism and the industrial production to them.Therefore,it is necessary to study the transmission accuracy of reducing mechanism in both theory analysis and test research,and put forward the research method which can realize the reasonable distribution of the machining error of each component with a perfect transmission accuracy of the reducing mechanism in order to lower the production costs.The research work must be meaningful in theory guidance and valuable in engineering application to enhance the international competitiveness of China’s aviation industry.To figure out the issues of the transmission precision and control precision of electromechanical actuators in the flight control system,the present thesis has a comprehensive study for the planetary gear reducer with small tooth number difference.The prime contents and achievements are summarized as follows.(1)Based on the basic idea of the mass spring equivalent model and according to the basic structure and transmission principle of reducing mechanism for electromechanical actuator with small tooth number difference,the transmission error equivalent model of reducing mechanism with small tooth number is established considering the machining error,assembly error and minute displacement of each component.Furthermore,Combed with the specific movement state and geometric relationship of each component in reducing mechanism,the displacement produced by machining error,assembly error and minute displacement at the spring action line of each component are analyzed,which could lay a good foundation for deriving the dynamic transmission error equations in system.(2)The forces caused by the machining error,assembly error and micro-displacement of each part in the spring are analyzed.The principle of force judgment at the contact point between pin and pin hole is proposed,which can be used to calculate the number of force pin at the moment accurately.The equilibrium equation of force and moment is deduced,and the equation is written in matrix form.The calculation method of gear meshing stiffness,bearing stiffness and pin stiffness in transmission error model are discussed,and finally,the nonlinear differential equations are calculated by Newmark method.(3)According to the problem that how different error parameters influence the dynamic transmission accuracy of the reducing mechanism,the simulation is carried out used MATLAB.The main error factors that affect the transmission accuracy are found out.Meanwhile,the comprehensive influence of the machining accuracy grades of the components on the system transmission accuracy is studied.It is found that the cam eccentricity error of the eccentric input axis,the eccentric error of bearing hole and the eccentric error of the base circle of the planetary gear,the planetary gear shape error and base pitch error,the radius error and the eccentricity error of the pin and the pin hole all have great impacts on the system transmission error.For the comprehensive influence of different precision grade components on transmission error,the precision design principle of the reducer is put forward,which provides the basis for the design,production and assembling of the reducing mechanism with small tooth number difference.(4)The thesis carries out a study to the transmission accuracy of the reducing mechanism with small tooth number difference by means of the experimental method.The distribution of the dynamic transmission error and backlash of the reducer prototype at two different input speeds is revealed.The transmission error results of the test are analyzed using time domain spectrum method,and the main factors that affected the gearbox transmission accuracy are found out.The experimental findings validate the correctness of the analysis model and the calculation results.