Design of a Magnetic Bearing

A popular approach to nano-positioning requirements in precision engineering in general and micro-lithography in particular is to subdivide the stage positioning architecture into a coarse positioning module with micrometer accuracy (Long Stroke), onto which a fine positioning module (Short Stroke) is cascaded. The latter is responsible for correcting the residual error of the coarse positioning module to the last nanometers. High accuracy positioning in 6 Degrees Of Freedom put severe constraints on the actuators and/or bearing systems. Actuators are used for generating a varying force being part of a control loop. Bearing systems should generate a force as constant as possible in the bearing direction, but the force perpendicular to that direction should be as low as possible. Actuators could serve as a bearing system, but on the one hand this would require the actuators to be large and thus heavy and on the other hand a substantial amount of heat is continuously dissipated in order to generate the static forces. Such heat generation does not contribute to the positioning performance of the actuators, but significantly affects the thermal stability of the application. The latter implication will be overcome if the bearing system is established by a system with permanent magnets

Design of a magnetic gravity compensation system

An extremely accurate positioning over relatively long ranges is accomplished by absorbing or suppressing vibrations. Highly accurate frames or stages should be supported against gravity. In addition, the external disturbance forces acting on these stages need to be cancelled in a feedback control loop. In this paper a new, low-cost, vacuum compatible gravity compensation system is presented, which eliminates vibrations and which is able to generate forces to counteract the disturbing ones as well

Novel types of the multi-degrees-of-freedom electromagnetic actuators

This paper presents an overview of the operating principles, electromagnetic analysis and design, shape configurations and system level performance of the novel types of the multi-degrees-of-freedom (mDOF) actuators for precision engineering applications developed during 2002-2005 at the EPE group of Eindhoven University of Technology, the Netherlands in closed co-operation with academic and industrial partner