Purpose <p>Electromechanical Actuator (EMA) is regarded as a core component in high-precision control systems such as aerospace applications. Its inherent nonlinearities, including clearance and friction, have been shown to significantly degrade control accuracy and system reliability. In this study, the influence mechanisms of gear pair clearance, shifting fork and screw clearance, and friction on the complex dynamic behavior of the EMA are systematically investigated.</p> Methods <p>A combined approach of theoretical calculation and numerical simulation was adopted in this study. The 3D physical model of the EMA system was first established. The rotational speeds of each gear in the two-stage reducer and the theoretical gear backlash derived from the end-face tooth profile method were calculated, and compared with simulation results to validate the model accuracy. Excellent agreement was observed, with the maximum error kept below 5%. A collision contact force model was then constructed based on Hertz contact theory and the Coulomb friction model. Dynamic analyses were carried out using multibody dynamics simulation software. A single-variable control method was employed to investigate the system response under different nonlinear factors.</p> Results <p>The effects of different nonlinear factors on the system dynamic performance are significantly different. When more pronounced nonlinearities are present in the EMA system, the peak contact force is markedly increased. Meanwhile, a greater time delay is observed in the rudder shaft’s output response, and the response accuracy is reduced.</p> Conclusion <p>The modular simulation method adopted in this study is shown to effectively isolate and analyze the effects of multiple nonlinear factors on the dynamic performance of EMA. A feasible analytical framework is thus provided for performance prediction and design of electromechanical actuation systems under coupled nonlinearities.</p>