P3M-1 Effect of Enhancing Amplitude in a Tip of Fine Outstanding Leg on a Vibrator and its Application to a Very Thin Linear Ultrasonic Motor

The transverse dimension of linear ultrasonic motor is usually too large for many usages. Thus, a thin ultrasonic motor similar to hydraulic cylinders is needed to be developed. However, the suitable vibration modes for the thin motor are difficult to be obtained by the current method of linear ultrasonic motor design, and exciting enough elliptic motion in a small sized transverse configuration is a challenge. The authors have discovered what a tip of fine outstanding leg on a vibrator can possess extraordinary effect to amplify its deformation amplitude in the former researches. By using this effect, the method of ultrasonic motor design can be changed. That means what the effect is very useful to design very thin linear ultrasonic motors. This paper describes the primary theoretical analysis and some explanations about the effect. Based on the effect, a new kind of very thin linear ultrasonic motor is presented. A long and narrow metal plate is used as the elastic base of the motor´s vibrator. Two second bending vibration modes with the different phase of 90 degrees are exited by six piezoelectric ceramics which are adhered to both side of the plate to form a quasi-traveling wave propagating in the plate. In the both end of the plate, there are four outstanding pins. Thus, the vibratory amplitudes are enlarged on the tip of the pins dramatically and a valid driving operation can act upon the stator. We designed the configuration of the motor and fabricated its prototype. The dimensions of movable vibrator are 40 mm length, 5 mm width and 4 mm thickness. Eight outstanding pins, 3 mm long and 0.7 mm in diameter, are put in both end of vibrator plate respectively. When driving electrical signal is turn on the motor with a appropriate frequency, it can move in high speed along a tube guide which internal size is 10mm and a flat glass surface. Results from testing the motor demonstrate that the design concept mentioned in this paper is a feasible scheme