Micro Piezoelectric Ultrasonic Motor Optimization

T. J. Plummer

Mentors: K. Uchino and S. Cagatay

 

            In understanding the gearless design of piezoelectric actuators, the uses of piezoelectric materials applied in ultrasonic micro-motors are investigated.  The converse piezoelectric effect, in which an applied electric field on a piezoelectric component causes a mechanical strain, gives the general means of operation for the motor.  With this strain of a piezoelectric plate bonded on an elastic cylinder shaft  (stator), at a given resonance frequency of the applied AC current matched to that of the stator, a vibrating effect is produced.  With idealized geometry of the stator an elliptical wobble motion can be achieved.   With a center axle rod or a rotor inside the cylindrical stator, by means of contact friction we have a spinning effect.  That is the basic idea of how an ultrasonic micro-motor operates. 

            The main objective is to find the benefits of a squared off tube stator design over the conventional circular tube in terms of a simpler manufacturing process, leading to cost reduction.   Further we will adopt the usage of the max center displacement of the square tube from that of the circular tube’s max head and tail displacement with optimum use in ultrasonic micro-motors.  Experimental values of efficiency, max power, and max torque will aid in the comparison. The output specifications should range as follows: (1) size= 1-10 mm, (2) speed= 100-1000 rpm, (3) torque= 1-100 mNm, which is 10-100 times higher than the electromagnetic micro motors, silicon MEMS or the previously reported micro ultrasonic motors.  The plan is to achieve a smaller sized, more efficient and cheaper ultrasonic micro-motor by simplifying its structure and fabrication along with reducing the number of components.