Characteristics of a V-type ultrasonic rotary motor Seong-Su Jeong a , Tae-Gone Park a, * , Myong-Ho Kim b , Tae-Kwon Song b a Department of Electrical Engineering, Changwon National University, 9 Sarim-dong, Changwon 641-773, Republic of Korea b School of Nano and Advanced Materials Engineering, Changwon National University, Changwon 641-773, Republic of Korea article info Article history: Received 26 June 2010 Received in revised form 28 January 2011 Accepted 7 March 2011 Available online 13 April 2011 Keywords: V-type ultrasonic motor USM Piezo motor Piezo actuator FEM abstract In this study, a novel structured V-type ultrasonic rotary motor has been proposed to enable use in small precision machines. A thin metal plate was used as a V-shaped vibrator and four ceramic plates were attached on the upper and bottom sides of the metal plate. By applying two electric fields having a 90  phase difference on the ceramics, rotational displacement occurs at the contact point. A finite element analysis was used to simulate the motional pattern dependent on the angle between the legs of the stator. The motor was fabricated on the basis of the results of the FEM analysis. The rotor and stator were connected to a push-pull gauge and the pre-load between them was controlled with this gauge. Char- acteristics of the motor such as pre-load, speed, torque, and temperature were measured by using a driver and measurement equipment. The difference of resonance frequency of each model was lower than 5[Hz] and driving frequencies were applied equally to each model. As a result, when the angle of the leg decreased, torque increased. On the contrary, when the angle increased, speed increased. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Demand for small size ultrasonic motors is currently increasing in various fields such as medical treatment and robotics. The minimum size of an electromagnetic motor is generally constrained to about 1 cm. In order to enhance the torque and reduce the speed of the motor, a gearbox must be used [1e6]. However, this signifi- cantly reduces the efficiency of the motor. Since electromagnetic motors are limited in terms of possible miniaturization, ultrasonic motors can be an alternative for applications involved restricted space. Furthermore, ultrasonic motors produce no electromagnetic interference [7e10]. Ultrasonic motors offer outstanding response speed, accuracy, and high efficiency. However, they are expensive and have a complex structure. The V-type ultrasonic rotary motor proposed in this paper can be applied to small precision instruments and it also has a simple structure and is economical [11,12]. It is possible to fabricate a V-type ultrasonic rotary motor by using a simple punching technique [1,9].A finite element analysis (ATILA 5.2.4) was used to simulate the motional pattern of the stator. Displace- ment characteristics relative to changes of the frequency, imped- ance, and angle of legs were analyzed through a FEM analysis, and then optimal model was determined and fabricated. Characteristics of speed and torque according to changes of pre-load, voltage, and frequency were measured by using the fabricated ultrasonic motor. 2. V-type ultrasonic rotary motor Fig. 1 shows the structure of the stator of the V-type ultrasonic motor and the motional pattern depending on the applied voltage at the contact tip. The stator is configured such that four ceramics polarized in each direction are attached to the upper and bottom areas of the elastic body; the polarization directions and applied voltages are represented in Fig. 1 . When two harmonic voltages having a 90  phase difference were applied to the ceramics, symmetric and anti-symmetric displacements were generated at the tip, resulting in elliptical motion. The rotation direction of the rotor is determined through the motion of the contact tip. Inverse motion can be realized by applying inverse phase of the applied voltage to the stator. Fig. 1 shows the motion of the contact tip. The horizontal direction of the motion is defined as y axis and the vertical direction of y axis is defined as x axis. Table 1 shows the stator composed of the ceramics and elastic body. The thickness of elastic body is 0.1[mm] and the length of the body is 15[mm]. The length, width and thickness of the ceramics are 11[mm], 2[mm] and 0.2[mm], respectively. The material and size of stator are defined to generate maximum vibration mode of longitudinal direction [13]. The ceramics used here is NEPC-6 of TOKIN Ltd., the elastic body is brass. Each physical property of the material is shown as in Table 2. 3. FEM simulations A finite element analysis (ATILA 5.2.4) was used to simulate the motional pattern and stress of the contact tip of the stator. Brass is * Corresponding author. Tel.: þ82 55 213 3631; fax: þ82 55 263 9956. E-mail address: tgpark@changwon.ac.kr (T.-G. Park). Contents lists available at ScienceDirect Current Applied Physics journal homepage: www.elsevier.com/locate/cap 1567-1739/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2011.03.013 Current Applied Physics 11 (2011) S364eS367