Electrical series connection drive for several hybrid-transducer ultrasonic motors

It is difficult to manufacture motors that combine superior characteristics and optimum driving conditions with a high mechanical Q value in torsional and longitudinal oscillation systems composed of hybrid-transducer ultrasonic motors. In a system that uses several motors at once, the drive and control systems become complicated, thereby creating problems. In this paper, the authors show that several motors may be treated as one vibration system by connecting the electrical terminals of each vibration system in series, even when the vibration system has differing mechanical impedances, and conversion coefficients for current-vibration velocity such as the torque factor and the force factor. The authors then show that a driving system for several motors using this method can be accomplished simply. In experiments using Langevin torsional transducers, the vibration velocity of two vibration systems with differing resonant frequencies and free motional admittance reaches a maximum at the same driving frequency in electrical series connections, and confirm that phase synchronization is complete. Furthermore, the authors confirm experimentally the effectiveness of series connections with respect to two applications of a velocity synchronization drive in which the torque accumulation combines several motors with hollow structures along the drive axis, and the rotational velocities of several independent motors match.