Extended-range linear magnetostrictive motor with double-sided three-phase stators

The authors have developed a novel extended-range linear magnetostrictive motor using the peristaltic motion of a laminated Terfenol-D (Tb/sub 0.3/Dy/sub 0.7/Fe/sub 2/) element. This element migrates in the opposite direction of the traveling magnetic field generated by prevailing three-phase armature commutation. The actuator mechanical design is in an open structure in order to allow easy assembly and access to internal actuator components. Eight sets of Belleville washers guarantee uniform squeeze preload in spite of wear, thermal expansion, or motion of the moving element. We incorporated a laminated Terfenol-D slab in this actuator to reduce the eddy current, leading to high-frequency high-speed operation. We have also designed and constructed the power electronics and control units for the magnetostrictive actuator's open-loop and closed-loop operations. With a series-resonant capacitor, we were able to achieve a near-unity power factor and decrease the reactive power requirement by a factor of 20. The magnetostrictive motor has demonstrated 12-mm/s speed at excitation frequency of 1600 Hz, and shown 140-N load capacity. The effective travel range of the present motor is 25 mm, and can be extended further. This linear magnetostrictive motor shows great potential in high-force precision positioning applications such as automotive actuators, robotics, and flight control surface actuators.