# Research Developments of Aerostatic Thrust Bearings: A Review
## 4 Advances in Dynamic Performance  
### Parametric Research and Optimization  
The dynamic performance of aerostatic bearings is related to bearing types, restrictor types, and corresponding operating conditions. A lot of research has been conducted by scholars on the dynamic performance of bearings. [PERSON] studied the dynamic performance of a compensated flat pad aerostatic bearing, as shown in Figure 11[39]. When the thickness of the gas film gap was relatively large (greater than 20 \(\upmu\)m), negative damping was observed. There was no negative stiffness with the variation of gap height. At low perturbation frequencies, the stiffness coefficient maintained a low constant value. The damping coefficient decreased at a larger gap height. At high perturbation frequencies, the stiffness coefficient increased with higher gap height. The damping coefficient gradually approached zero. Other detailed research contents are listed in Table 2. From the presented literature, research on the dynamic performance of ATBs is still focused on the dynamic stiffness damping coefficient and stability analysis. Stability analysis mainly includes dynamic response analysis, vibration signal analysis, air hammer phenomena, and so on. With the development of computer technology, the numerical simulation methods and experiment methods of ATBs have become more abundant. At present, more attention is placed on the annular restrictor type and orifice restrictor type. Research on the porous restrictor type and other types is relatively less. Figure 10: The pressure-equalizing groove. (**a**) front view, (**b**) section view. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Year** & **Focus** & **Evaluation** & **Methodology** & **Bearing Type** & **Restrictor** & **Major Conclusions** \\
**Author** & **Parameters** & **Index** & **Methodology** & **Type** & **Type** & Theoretically and experimentally \\ \hline
2001 & The annular & & & & & & \\  & groove supply & Dynamic stiffness & Experiments and & Circular & Porous & & \\ [PERSON] [71] & and the hole & and damping & numerical model & aerostatic thrust & restrictor & characteristics of \\  & supply & & & & & bearing with different \\  & & & & & & air supply methods \\ \hline
2002 & Initial film & & Experiments and & & & & The vibrations are \\ [PERSON] [72] & thickness, bearing & Dynamic & modified the & & & & \\  & width, X-shaped & response & & & & \\  & groove width & & (RNM) & & & \\ \hline
2002 & & & & & & \\ [PERSON] [33] & Supply pressure & Stability, & Experiments and & Aerostatic & & & \\  & straightness error & CFD simulation & & & & \\  & & & & & & \\ \hline
2009 & / & Motion error & Experiments and & & & & \\ [PERSON] [73] & & & & & & \\ \hline
2009 & & & & & & \\ [PERSON] [38] & External Load, air & & & & & \\ [PERSON] [38] & Pressure & Linear stiffness & Experimental & Aerostatic table & & \\  & & & & & & \\ \hline
2011 & & & & & & \\ [PERSON] [8] & Gas fluctuation & Vibration signals & Experiments and & & & \\  & & & & & \\ \hline
2012 & Air film & & & & & \\ [PERSON] [74] & thickness, & Time response & & & & \\ \end{tabular}
\end{table} 
Table 2: Dynamic performance of ATBs. Figure 11: The effects of gap height and perturbation frequency on the dynamic performance of the compensated flat pad aerostatic bearing: (**a**) dynamic stiffness, (**b**) damping coefficients [39].