XTreme Motion

Involved People
Nilles VrijsenPhD student
Prof. dr. E.A. Lomonova, M.Sc.First promotor

The force density and accuracy of short-stroke actuators in high-precision applications, e.g. semiconductor lithography systems, increase rapidly. The demands on the force density of actuation systems are rising to improve the throughput and hence the profit per computer chip. Simultaneously the accuracy of the actuators should increase to keep track with Moore’s law, which predicts that the number of transistors on integrated circuits doubles every two years.

The force density and accuracy of high-precision actuation systems should increase, to improve the throughput and to obtain a precision in the nanometer range, respectively. The force density of the moving mass over a short-stroke (millimeter range), is increased by the use of reluctance actuators, which are able to achieve a more than 10 times higher force density than frequently applied voice-coil actuators. One of the major challenges of reluctance actuators is the predictability of the force, which is directly related to the final accuracy of the actuation system. The force of a reluctance actuator has a nonlinear relationship with respect to the current and position. Furthermore, magnetic hysteresis effects occur in the soft-magnetic material. For the nonlinear current-force and position-force a nonlinear actuator model can be applied. However, magnetic hysteresis is nonlinear, rate-dependent and history dependent.