Design and relay-based control of a novel linear magnetostrictive motor

Design and relay-based control of a novel linear magnetostrictive motor is presented in this paper. The magnetostrictive material used here is Terfenol-D, an alloy of the formula Tb_0.3Dy_0.7Fe_1.9. In response to a traveling magnetic field inside the Terfenol-D element, it moves in the opposite direction with a peristaltic motion. The proposed design offers the flexibility to operate the motor in various configurations including local and conventional three-phase excitation. In this paper, we demonstrate that the power consumption can be reduced significantly by the local-excitation approach. A new force transmission assembly incorporates spring washers to avoid the wear due to its sudden collision with the Terfenol-D element. The closed-loop control system was implemented using relay control which resulted in an optimal closed-loop performance. The magnetostrictive motor has demonstrated 410-N load capacity with a travel range of 45 mm, and the speed is around 9 mm/min currently. The low speed is due to the local three-phase operation mode, and it could be increased to 60 mm/min by using the conventional three-phase operation. The maximum power consumption by the motor is 95 W.