Abstract: Experiments have shown that a new controllable restrictor technology can significantly improve the stiffness and radial accuracy of hydrostatic spindles, but the transient process of the journal radial accuracy improvement is unrevealed. Since the existing theories can hardly explain the transient process of journal stabilization and radial error reduction, a novel numerical journal orbit model is developed on theories of journal inertial force, nonlinear oil film force, controllable restrictor principle, and restrictor parameters. By the new model, transient physical phenomenon during the journal stabilizing process can be numerically simulated and quantitively analyzed. The journals of controllable restrictor hydrostatic spindles and constant restrictor hydrostatic spindles are calculated, assuming they have the same hydrostatic journal bearing parameters and the same hydraulic system parameters. The results illustrate that controllable spindle could vastly reduce the orbit stabilizing time, the journal eccentricity, and the static radial error motion. Hence, the mechanism of the bearing oil film stiffness increment and radial accuracy improvement on the controllable restrictor hydrostatic spindles can be theoretically interpreted by the program.

Key words: controllable restrictor, hydrostatic journal bearing, journal orbit, nonlinear oil film force