Electromagnetic linear actuators with inductive position sensing

Magnetically driven linear micro-actuators with 1 mN output force and hundreds of microns of total travel have been realized using LIGA-like processing techniques. These devices are driven at resonance frequencies of around 350 Hz and exhibit quality factors of about 300 in air. Exploiting wire-wound electromagnets, 300 mu m resonant displacements have been demonstrated with drive signal currents of about 1 mA and power dissipation of less than 200 mu W. In addition, the self inductance of the coils in these actuators varies linearly with plunger displacement. The inductance changes of about 1 mu H mu m(-1) may be used for inductive position sensing and as a measure of output force.