A multiphysics coupled model for active aerostatic thrust bearings

Aerostatic thrust bearings are used in linear guideways as an alternative to contact bearings. The absence of friction in the motion makes aerostatic guideways most suitable for high precision and high speed machines. The low stiffness and damping of the aerostatic support limits their application to machining processes. Active compensation, applied to the bearing films, is proposed as a solution to overcome this limitation and achieve further performance improvements in terms of stiffness and damping, adding positioning capabilities. Active compensation based on gap shape control offers the most promising results, but the need of a flexible bearing surface increases the complexity of the design. This paper aims to show the need of a multiphysics model that considers the coupling between the structural, fluid dynamics and piezoelectric fields present in the active bearings. A finite element model of the fluid dynamics behavior in the air gap based on Reynolds equation is presented, and a coupling strategy to the structural problem is proposed. Simulation results show the validity of the modeling strategy and the relevance of the influence of structural flexibility of the bearing surfaces on the final performance.