Aerostatic thrust bearings active compensation: Critical review

•Using aerostatic thrust bearings: pros, cons applications.•Methods to enhance aerostatic thrust bearing performance: passive and active compensation.•Active compensation state of the art and categorization.•Examples of active compensation systems.

Aero-static thrust bearings are widely used in high precision conventional applications, e.g., in machine tools, measuring instruments, precise positioning systems, manufacturing and medical equipment. Their appeal is due to the absence of contact between moving and stationary parts, which ensures their low friction, limited heat generation and long life. Moreover, the use of air bearings usually does not contribute to the environmental contamination.However, aerostatic thrust bearings have usually lower stiffness and load capacity than rolling or oil bearings. For this reason, active and passive compensation are currently used to enhance these properties, thus extending the bearing's operating range. Recently, active compensation methods have become more popular thanks to improvements in mechatronics technology, and because they can provide the very high accuracy required by current high precision applications. This paper reviews the state of the art of the active compensation method and provides general classification criteria, outlining dissimilarities and the pros and cons of the available solutions.The paper concludes with several considerations and comments regarding the main performance features of each solution.