Zero-Power Magnetic Levitation Using Composite of Magnetostrictive/Piezoelectric Materials

We present a zero-power magnetic levitation technique using a composite of magnetostrictive and piezoelectric materials. The composite is bonded to iron yokes with an attached permanent magnet, by which the magnetic force exerted on movable yoke via air gap is controlled by the applied voltage on the piezoelectric material. The magnetic force control is based on the inverse magnetostrictive effect of the magnetostrictive material, i.e., the magnetization is varied with mechanical stress. The advantage of the composite is zero power consumption, because no current flows in static operation as a result of the capacitive property of the piezoelectric material. This feature will be useful in high-precision stage or conveyor systems using magnetic levitation where heat generation and power consumption should be avoided. The zero power characteristic of the composite is valid at any reference gap or load, whereas that of the conventional electromagnetic type is valid only at the equilibrium gap. We performed two levitation experiments: one using the composite to demonstrate the zero power advantage, and the other combining the composite to adjust the bias gap and electromagnet to stabilize the motion of the levitated yoke. The composite driven by a small dc-dc converter successfully varied the gap and maintained it constant with zero power consumption.