Dynamics Analysis of Electromechanical Actuator System Considering Multiple Frictional Nonlinearities

The electromechanical actuator system is the main executive mechanism of the aircraft control system and consists mainly of the electromechanical actuator (EMA) and the rudder. Due to the multiple frictional nonlinearities in the transmission mechanism of the EMA system, it is difficult to accurately predict the dynamic characteristics, thus making it important to establish a high-fidelity electromechanical coupling dynamic analysis model for precise prediction. In the present study, an electromechanical coupling dynamic modelling and analysis method considering multiple frictional nonlinearities is proposed for a typical ball-screw-type EMA system. A high-fidelity finite element method is used to obtain the friction backbone curve and a hysteretic model is established to describe the nonlinear behavior of friction. Based on the modular modelling strategy, an electromechanical coupling dynamics model of EMA system is established, with different friction parts considered. A numerical simulation is carried out to study the influence of the friction parts on the dynamic characteristics of the EMA system. It is found that the friction factor near the rudder has much less influence on the dynamic characteristics of the system than that far from the rudder. Within a certain range, the degree of friction nonlinearity has a positive influence on the dynamic stiffness of the EMA system. And, increasing the external excitation amplitude decreases the dynamic stiffness. However, when the friction is larger than a certain critical value, the resonance frequency of the rudder system falls suddenly, then increases gradually and finally remains the same.