To suppress the low-frequency vibrations of large space structures, the possibility of using a proof-mass-based actuator is discussed. In order to avoid instabilities caused by the effect of the actuator's own natural frequency on the low-frequency components of the structural vibration, it is proposed that the only control force be the electromagnetic force generated by the actuator and that there be no mechanical spring between the moving and the fixed parts of the actuator. In this configuration, it is easy for the moving mass of the actuator to exceed the stroke limit, so the actuator must be controlled to avoid these limits. Using the proposed actuator, three kinds of intelligent control methods are considered in order to achieve reliable control of the low-frequency vibrations : fuzzy control, dithered fuzzy control, and rule-based crisp control. Simulation and experimental results show the effectiveness of the proposed control algorithms.