  Reluctance actuators are preferred for high-precision applications. Due to
resistive losses in the coils, the accuracy of this type of actuator will
reduce in quasi-static operation mode within a vacuum environment. By using
soft permanent magnets whose magnetization states are in-situ tuned, no
constant power is needed to create a force and thereby the resistive losses
will reduce. In this paper, a new tuning method is investigated in order to
reduce the resistive losses. By using a history-dependent and non-linear
hysteresis model, a more efficient tuning algorithm is designed. Besides this,
the position accuracy and control simplicity of a variable reluctance tunable
magnet actuator are improved by linearizing the non-linear force-flux
relationship. This is achieved by using bias fluxes generated by hard permanent
magnets.
