Control approaches for high-precision machine tools with air bearings

Numerous control strategies have been developed to compensate for the effects caused by friction in linear guideways of feed-drive systems. For ultraprecision machining applications, these offer a wide variety of powerful, nonlinear algorithms, but generally use rather complex computing algorithms, exhausting system resources. By the use of a special sophisticated aerostatic bearing technology, no friction and, therefore, no stick-slip exist within linear guideways. This entails a lack of damping in the feed direction, which is a considerable setback for the classic cascaded control concept usually implemented in commercially available servo systems. This paper presents an approach to obtain superior behavior of the controlled system by combining the cascaded concept with a control design in the state space. Both simulation and implementation results are presented, together with tuning methods and aspects.