Abstract
To simplify the design process and improve the motor performance, a rotary ultrasonic motor with rotationally symmetrical structure has been designed, fabricated, and characterized. The stator consists of four connected sandwich-type transducers and eight driving feet. The rotor, a disk, and a disk-shaft are pressed on the two sides of the stator by a nut–spring system. To drive the rotor, two orthogonal longitudinal vibration modes of the stator should be excited. The operating principle of the rotary motor was analyzed by a mathematical model. By using finite element analysis, the feasibility of the operating principle was validated, and the optimal structure dimensions of stator were determined in order to improve the driving teeth motion. The overall dimensions of the prototype stator are 30 mm (width) × 30 mm (width) × 50 mm (length). Driven by alternating current signals with the driving frequency of 50.93 kHz and voltage 300 VP-P, the motor gave a maximal no-load speed of 157.9 r/min and a maximal output torque of 11.76 mN m.
Highlights
Ultrasonic motors (USMs) can be an attractive alternative to electromagnetic motors for their advantages, such as high torque at low speed, light weight, simple structure, large holding force without power supply, and no electromagnetic field induction.[1,2,3] Piezoelectric ceramic is the common material which is used as drive elements.[4]
The well-known SHINSEI USR series is a typical example of bonded-type traveling wave USM, with the merits of simple structure and low cost in manufacture.[5]
According to equation (7), a conclusion can be drawn that the vibration amplitude of point PA in x-direction should increase with the decrease in length of connecting beam (LB) and the increase in Ht
Summary
Ultrasonic motors (USMs) can be an attractive alternative to electromagnetic motors for their advantages, such as high torque at low speed, light weight, simple structure, large holding force without power supply, and no electromagnetic field induction.[1,2,3] Piezoelectric ceramic is the common material which is used as drive elements.[4]. The longitudinal vibrations of transducers A and C can be excited, and the deformation of the stator is shown in Figure 3(a) as mode A. The longitudinal vibrations of the transducers B and D are excited by the sinusoidal voltage VB (VB = Vsin(vt + p/2)), and the deformation of the stator is shown in Figure 3(b) as mode B. According to equation (7), a conclusion can be drawn that the vibration amplitude of point PA in x-direction should increase with the decrease in LB and the increase in Ht. A finite element model was initially used to confirm theoretical operation principle and find the proper driving frequencies of the orthogonal longitudinal vibration modes. To obtain larger vibration amplitude of the teeth, the tooth height (Ht) was changed during the simulation process, while the beam length (L) was fixed as 40 mm. Because C is fixed as 10 mm, the optimized width of the motor is 30 mm
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