MODELLING, DESIGN AND FABRICATION OF ULTRASONIC LINEAR MOTOR

Abstract

This thesis is concerned with the relevant research in ultrasonic linear motors. An ultrasonic linear motor using single layer piezoelectric actuator is studied. In addition an ultrasonic linear motor using multilayer piezoelectric actuator is also studied. For the ultrasonic linear motor using single layer piezoelectric actuator, a theoretical model is established. Improving upon the simple beam model, it takes into account the influence of piezoelectric actuators on the resonant frequencies of vibrator. This model shows the relationship between the effectiveness or the excitation by electric sources and the position of the actuators. lt also shows the relationship between the generalised forces of vibration and the electric sources. Moreover, it shows the relationship between the elliptic locus and the phase difference of two electric sources. This model gives us a better theoretical basis for design. Based on this model, a design program is developed. For the ultrasonic linear motor using multilayer piezoelectric actuator, a theoretical model is also established. The model shows the relationship between the generalised forces of vibrations and the electric sources. It also shows the relationship between the elliptic locus and the electric sources. Thus this model gives a better theoretical basis for the design of ultrasonic linear motor using multilayer piezoelectric actuator. A frequency adjustment theory is proposed. This theory is very useful in design and fabrication to ensure the coincidence of two resonant frequencies. Based on the above theoretical study, prototypes are successfully designed and fabricated. A better understanding of the characteristics of ultrasonic linear motor is obtained by the experimental tests. Finally, finite element analyses are performed for the vibrator or two prototypes. The results obtained from simulation are very close to the measured results.