Direct Drive and Vibration Analysis of Ultrasonic Motor for Robot Hand

与电磁电机相比，超声电机具有结构简单、无线圈、响应速度快、低速转矩大等优点。因此，USM的这些优点对于机器人操作臂的小型化和轻量化是非常有希望的。本研究提出一种以单相电源驱动圆柱形超声马达的技术。从理论和实验两个方面对振动状态进行了研究。从实验和讨论中总结出以下结论：(1)所提出的电极布置使圆柱形USM可以由单相电源驱动。内部和外部电极的巧妙安排产生的延伸振动不仅包括驻波，也包括行波。(2)单相驱动下超声电机的外延振动由驻波和行波组成，在圆周上有两个波长。振动面由驻波和行波组合而成。(3)在波的两个波峰处与定子接触的转子由于两种波的共同作用而旋转。这种运动机制可以用扰动使退化模式分离来解释。(4)气缸内外电极产生的方位角滞后为π/4，相位滞后为π/8的两种振动模式叠加在一起，可以一致地解释单相驱动下USM的振动。(5)单相驱动的转矩特性与常规驱动的转矩特性相似。单相驱动的可能性有望在不久的将来使采用USM的机器人操作臂小型化和轻量化。

Ultrasonic motors (USMs) have many excellent features compared to the electric-magnetic motors, such as simple structure without coils, a quick response, and high torque at low speed, etc. These advantages of USM are, therefore, very hopeful for robot manipulators to be downsized and light weighted.This research proposes a technique for a cylinder-shaped ultrasonic motor (USM) to be driven by a single-phase electric source. The state of vibration was examined from both the theoretical and the experimental aspects. The following conclusions are summarized from the experiments and the discussions.(1)The proposed arrangement of the electrodes enables the cylinder-shaped USM to be driven by a single-phase electric power source. An ingenious arrangement of the inside and outside electrodes produces the extensional vibration that includes not only the standing wave but also the traveling wave.(2)The extensional vibration of the USM under single-phase drive is composed of the standing and the traveling waves, that have two wavelengths on the circumference. Vibrating surface consists in the combination of standing wave and traveling wave.(3)The rotor in contact with the stator at two crests of the wave rotates resulting from the cooperation of both wave types. This moving mechanism can be explained by the separation of the degeneration mode by a perturbation.(4)The vibration of the USM under single-phase drive can be explained consistently by superimposing two vibration modes with azimuthal lag of π/4 and with the phase lag of π/8,which are produced by the electrodes on both inner and outer sides of the cylinder.(5)The torque characteristic by single-phase drive is similar to one by the conventional driving method.The possibility of single-phase drive would promise the robot manipulators that employ the USM to be downsized and light weighted in near future.