The efficiency of oscillatory direct drives significantly suffers from the repeated acceleration and deceleration of the mover mass. These phases with low speed but high force requirements are inefficient and thus degrade the overall performance of the oscillatory system. The kinetic energy of the reciprocating mass can be compensated for with elements featuring a force characteristic inverse to the moved masses acceleration force. The obvious solution, a mechanical spring, is adversely affected by constructional limitations, space requirement, fatigue and life time issues that limit their application. This is especially important in combination with magnetic bearings or bearing-less drives. This paper evaluates the properties and feasibility of repulsive magnetic springs as an alternative to mechanical springs. With the focus on a minimum additional space requirement and a simple application a bearing-less oscillatory linear motor is equipped with magnetic springs realized with repellent permanent magnets. Repulsive magnetic springs are simple in realization, but their force density is moderate and their axial working range is limited. Thus it is most important to make best use of their force capability and limit their parasitic destabilizing effects. For the proposed setup this is analyzed in detail. Finally the progressive force characteristics is seen as beneficial for a robust stroke control under disturbance influences.

linear oscillatory systems， magnetic springs， linear bearing-less drives， repulsive magnetic springs