A comparison of control strategies for feed-drive systems of ultraprecision machine tools-effects of frictionless 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 sophisticated aerostatic bearing technology (FVM-air bearings) no friction and therefore no stick-slip exists 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 a superior behaviour of the controlled system by combining the cascaded concept with a control design in the state space