Dynamic research of the shaft orbit of hydrostatic spindle under the sliding velocity

Based on the load increment method and the pressure perturbation method, the dynamic performance of liquid hydraulic spindle system was researched. Using the finite difference method, the nonlinear oil film force was calculated by solving the Reynolds equation of unsteady oil film pressure distribution which was included in the micro-scale velocity slip effect. Four dynamic stiffness and damping coefficients reflecting the dynamic characteristics of the oil film were calculated by using the load increment method and the pressure perturbation method, and were used to the analysis of hydraulic spindle system. The research results showed that: Velocity slip caused a certain impact on dynamics of hydraulic spindle stiffness and damping performance. The maximum decreasing ratios of dynamic stiffness coefficient K_xx, K_xy, K_yx and K_yy which were caused by velocity slip were 4.85%, 4.85%, 7.20%, 7.16% respectively. Velocity slip reduced the oil film damping coefficient C_yx, C_xy and C_yy, the change rule of damping coefficient C_xx by slippage effect was more complex. With the increasing eccentric quality of the rotor, running track of the spindle axis was in the expanding, and the stability of the system decreased continuously. The experiment of the measuring path of the shaft verified the correctness and validity of the orbit of shaft centre model.