Research On Vibration Isolation Of Main Reducer System Of Helicopter Using Magnetorheological Damper

Vibration has always been one of the most important challenges in the development of helicopter.Rotor is the most important vibration source of helicopter.As the essential transmission path of the rotor vibration load to the fuselage,the main reducer is usually connected to the fuselage by a set of vibration isolation devices to effectively isolate the rotor vibration load.In this paper,the basic technical problems of controlling vibration of the main reducer system was studied to achieve the principle of the fuselage vibration suppression,a semi-active vibration isolation platform of Stewart with magnetorheological damper was studied from the aspects of structural design,theoretical modeling and numerical simulation.Firstly,a three-dimensional model of MR damper for helicopter main reducer was established from the aspects of parameter estimation,structural design and magnetic circuit analysis respectively,the maximum damping output was 22956 N,the adaptive dynamic range was 11.4 times.Secondly,taking a helicopter as the object of vibration isolation design,a semi-active vibration isolation platform of Stewart with magnetorheological damper was proposed.It was based on cubic Stewart platform as the basic configuration,and a magnetorheological damper as the components of semi-active,in parallel with the elastic sleeve to achieve vibration isolation,and the overall structure of the platform and the leg structure and parameter calculation were carried out.The dynamic equations of the vibration isolation platform in workspace and joint space were established based on the Newton-Euler method.Comparing numerical and modeling simulation,it was shown that the analytical solution of the natural frequency of the platform was basically the same as the software solution,all six directions of excitation could respond in their own direction,which verified the accuracy of theoretical modeling.Finally,two kinds of semi-active control strategies were designed: On-off control and Fuzzy control based on equivalent skyhook damping,the dynamic simulation model of magnetorheological damper and platform were established respectively,and the characteristics of platform under fixed current and under semi-active control respectively were studied.The simulation showed that the platform could effectively suppress the vibration load of 23.9Hz which is the first order passing frequency of a helicopter rotor,and the vibration isolation efficiency was achieved 80% under equivalent sky-hook fuzzy control,and the platform could also restrain vibration in high frequency region.