| Electro-hydraulic servo system combines both electric and hydraulic expertise, which has many advantages, its application has been widely used in military industry and civil industry. But electro hydraulic servo system is a typical complex automatic control system processing mechatronics and hydraulics integration, which has strong nonlinear, the system in the process of using often appears complex vibration phenomenon, resulting in the system can not work properly. In view of the vibration problem of electro-hydraulic servo system, the researchers mainly studied based on linear vibration theory in the early stage, but many of these vibrations are caused by nonlinear factors, therefore some vibration phenomenon can not give a reasonable explanation. In order to further explore the cause of the system vibration and suppress adverse effects, improve the performance of the system, it is necessary to analyze the nonlinear factors of the system, and to reveal its influence on the motion of the system.In this paper, the state space model of electro-hydraulic servo system is established by considering the port flow characteristic of electro-hydraulic servo valve, nonlinear hydraulic elastic force and nonlinear friction. Then, the nonlinear dynamic equation and the vibration model of the hydraulic cylinder are established, and the stability analysis and frequency response analysis are carried out. In nonlinear vibration theory and nonlinear dynamics theory as the instruction, using nonlinear dynamics research methods(bifurcation diagram, time history, power spectrum diagram, phase track diagram, poincare diagram), we focus the law of the vibration of hydraulic cylinder in the nonlinear hydraulic elastic force and the nonlinear friction independently influence as well as the coupling influence, and through experiments verify the validity of the theoretical analysis. This provide a theoretical reference for research and suppression of the vibration of electro-hydraulic servo system. |
