An active air bearing: a controlled-type bearing with ultra-precision, infinite static stiffness, high damping capability and new functions

The aim of the authors' work was to develop a linear table and a rotary bearing of controlled type with the following features: (i) ultra-precision, (ii) infinite static stiffness, (iii) high vibration damping capability and (iv) new functions such as table or axis positioning and dynamic stiffness control. Such features were first realized with a thrust-type active air bearing, which comprises an objective mass, a static air bearing mechanism, a non-contact sensor, a piezoelectric actuator and a controller. Secondly, a linear motion table of 1 m working length was introduced. Motion accuracies of the table with respect to solid references are less than 0.1 mu m and 0.1 arcsec. Finally, a journal bearing capable of controlling the radial motion of its axis was developed. The radial motion error at 1000 rpm is less than 25 nm.