Analysis on parametric vibration of hydraulic opposing cylinders controlled by a servo valve considering pressure pulsation

During the working process of the system of hydraulic opposing cylinders controlled by a servo valve, the fluid equivalent stiffness changes dynamically due to the pressure pulsation of the pump source. Therefore, the transmission system has obvious nonlinear effects, and its dynamic performance is difficult to improve further. Thus, a nonlinear dynamic model of the system of hydraulic opposing cylinders controlled by a servo valve was established. By using the multiscale method, the steady-state approximate solutions of the primary resonance and the combination resonance of the system were derived to reveal their characteristic laws. The results showed that the dominant frequency of the system's primary resonance is the frequency of the external excitation source, and the dominant frequency of the system's combination resonance is the sum of the natural frequency of each order and the fluctuation frequency of the fluid equivalent stiffness. The amplitude of the combination resonance was smaller than that of the primary resonance. The maximum error between the theoretical natural frequency and the experimental modal frequency was 3.77%, which verified the correctness of the system's nonlinear dynamic model. The research can provide a theoretical reference for the dynamics optimization design of the hydraulic transmission system.