Dynamic Modeling of 5-DOF Aerostatic Bearing Rotor System with Adjustable Gas Film Gap

In the application of an aerostatic motorized spindle, given the different requirements for the optimal gas film thickness of gas bearing under various processing conditions, this paper puts forward the tapered aerostatic bearing as the radial support element of the spindle and realizes the adjustability of gas film gap in a particular range through the axial fine-tuning mechanism. A 5-DOF dynamic model of the bearing rotor system is established, and the transient Reynolds equation is solved using the finite difference method to obtain the pressure distribution characteristics of the gas film. Based on this, the spindle's translation and angular displacement responses are determined by solving the spindle's motion equation. The simulation results show that the tilting motion of the spindle significantly affects the pressure distribution of the gas film, and the nonlinear gas film force will lead to nonlinear severe vibration of the spindle. The study also reveals that reducing the gas film thickness under low-speed and heavy-load conditions effectively decreases the amplitude and offset of the spindle. However, increasing the gas film thickness enhances the system's speed and stability under high-speed and light-load conditions.