Design of two-wheeled ultrasonic wheel is proposed for 
applications in micro-stepping displacement devices. The ultrasonic 
wheel includes a beam and two displacement members which are 
respectively pivoted on the beam. Two displacement members are 
not rotatable. In addition, each displacement member includes a 
wheel sheet and a piezoelectricity element embedded on its surface. 
When the piezoelectricity element generates and transmits power to 
the wheel sheet, the wheel induces vibration and deformation. 
Therefore, due to the wheel sheets and the touched ground 
involving their relative motion, the displacement device can move 
and orient its motion direction in a micro manner. The two-wheeled 
ultrasonic wheel driven by two piezoelectric elements is direct 
movement, no rotor requirement. In this research, a 3-D mechanical 
element with an extra electrical degree of freedom is employed to 
simulate the dynamic vibration modes of the linear piezoelectric, 
mechanical and piezoelectric-mechanic behaviours of the two
wheeled ultrasonic wheel.