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Driving characteristics of an ultrasonic rotary motor consisting of four line contact type stators
Available online at www.sciencedirect.com
CERAMICS INTERNATIONAL
Ceramics International 41 (2015) S618–S624 www.elsevier.com/locate/ceramint
Driving characteristics of an ultrasonic rotary motor consisting of four line contact type stators Seong-Kyu Cheona, Seong-Su Jeonga, Yong-Woo Haa, Byung-Ha Leea, Jong-Kyu Parkb, Tae-Gone Parka,n a Department of Electrical Engineering, Changwon National University, Gyeongnam 641-773, Republic of Korea Department of Mechanical Engineering, Changwon National University, Gyeongnam 641-773, Republic of Korea
b
Received 26 October 2014; accepted 4 March 2015 Available online 9 April 2015
Abstract A new type of ultrasonic rotary motor that can replace existing ultrasonic motors for driving camera zoom lenses was proposed and investigated experimentally. The proposed motor composed of four roof-shaped stators. On the upper surfaces of each roof-shaped stator, two rectangular ceramics were attached. When two AC voltages with a 901 phase difference were applied to the ceramics, elliptical displacements occurred at the tip line of the actuator. By combining these elliptical displacements of the four stators, rotational motion of the stator could be achieved. If a circular disk rotor was positioned on the stator, vibrations of the stator were transferred through the four contact lines between the stator and the rotor. Preload of the motor could be controlled by the jointing bolt, which went through the center of the disk rotor and the ball bearings. The finite element analysis (FEA) simulation program ANSYS was used to analyze the elliptical displacement characteristics in relation to changes in the size of the elastic body, piezoelectric ceramics, friction tips, frequency, and applied voltages. A prototype motor was fabricated, and its driving characteristics such as impedances, vibration amplitudes, rotational speed, and torque were measured. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Keywords: Ultrasonic rotary motor; Piezoelectric motor; Piezoelectric actuator; Piezoelectric application; ATILA
1. Introduction An ultrasonic motor is a type of electric motor that is powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider, depending on the operation scheme (rotation or linear translation) [1,2]. Ultrasonic motors differ from piezoelectric actuators in several ways, although both typically use some form of piezoelectric material: generally lead zirconate titanate and occasionally lithium niobate or other single-crystal materials [3]. Ultrasonic motors offer excellent performance and many useful features including a high torque at low speed, a large power output per unit weight, the possibility of precise positioning, a simple structure, compactness, n
Corresponding author. Tel.: þ82 55 213 3631; fax: þ 82 55 263 9956. E-mail address: [email protected] (T.-G. Park).
http://dx.doi.org/10.1016/j.ceramint.2015.03.218 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
and the absence of electromagnetic interferences. Ultrasonic motors can be applied in precision industries, for example, circular type ultrasonic motors for digital cameras and small ultrasonic motors for cell phones. The ultrasonic rotary motor with line contact has been extensively studied. In contrast, ultrasonic motors with a simple structure and principle have not been sufficiently explored [4,5]. In this paper, a driving ultrasonic motor that uses four line contacts is proposed, and its output characteristics were simulated using the ATILA FEM (finite element method) program. The proposed motor consists of four lambda-shaped stators and eight rectangular plate ceramics. Most importantly, it can be fabricated as a small and simple structure. The proposed ultrasonic motor was designed to match the fundamental size of a compact camera lens. Therefore, the stator and the piezoelectric ceramic thickness were set to 0.5 mm and the overall size had a diameter of 40 mm
S.-K. Cheon et al. / Ceramics International 41 (2015) S618–S624
and a height of 15 mm. A prototype motor was fabricated for testing its driving characteristics, and the output characteristics were analyzed in relation to the preload.
2. Structure and principle of the proposed motor Fig. 1 shows the structure of a four line-contact-shaped ultrasonic motor. The stator consists of elastic bodies and piezoelectric ceramics attached to its surface. Stainless steel SUS304 and piezoelectric ceramics Pb(Zr,Ti)O3 (PZT, Piezo system Ltd.) were
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used for fabricating the stator. The four elastic bodies of the ring stator were identical in size and were bilaterally symmetrical. If the rotor surface was placed on the stator, the rotor and stator would be in contact through four contact lines at each four tops of the stators. The parameters of the stator used for the designed motor are presented in table in Fig. 1. And also Fig. 1 shows the polarization directions of the piezoelectric ceramics at the stator. As shown, the piezoelectric ceramics were bonded at both sides of the elastic bodies, such that the polarization directions of the piezoelectric ceramics were in opposite directions. The hollow arrow and the filled arrow were applied to each other with a voltage with 901 phase difference [6–8]. Application of voltages of resonance frequencies in this way produces combined longitudinal and bending waves, which generates elliptical motions of the contact tip [9]. These elliptical displacements of the four contact lines rotate the rotor by using friction forces. Fig. 2 shows the principle of the elliptical motion at one of the four lines. In one cycle of applied voltages (t0–t3), one elliptical motion is completed at the line and the same elliptical motion is simultaneously generated at the four lines, which rotates the rotor. 3. FEA simulations and results Fig. 1 shows before the analysis, the thickness of the elastic body was set to 0.5 T to endure sufficient preload. When thickness of the elastic body and the ceramic through previous
Fig. 1. Structure of lambda-type ultrasonic motor.
Fig. 2. Principle of the elliptical motion.
Fig. 4. Displacement characteristics at the resonance frequency above 150 kHz.
Fig. 3. Impedance curve of models (SUS304, Brass).
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Fig. 5. The displacement characteristics depending on the material and the tip (901). (a) No tip stator (SUS304), (b) Tip stator (SUS), (c) No tip stator (Brass) and (d) Tip stator (Brass).
study was similar, the larger elliptical displacement characteristics were confirmed by Cheon et al. [10]. Therefore, the thickness of the ceramic was set to 0.5 T. In this paper, the stators are named by the size of the parameters. For example, if the length, thickness, and width of the elastic body are 21, 0.5, and 12 mm, and the length and thickness of the ceramic are 5 and 0.5 mm, respectively, the stator is named EL20ET0.5EW5CL12CT0.5. Fig. 3 shows the impedance characteristics obtained by the FEA. Resonance and anti-resonance frequencies could be determined from this curve. A model was selected based on these results. The selected model was analyzed by changing the angle of the elastic body depending on whether there was a tip. Stator driving was performed at frequencies below 150 kHz, because there was a tip distortion phenomenon at higher frequencies. It was assumed that this phenomenon was caused by the interference between the vibrations, which generated irregular vibration at the tip at the high-frequency band [11]. Fig. 4 shows the displacement characteristics and their form generated at a resonance frequency above 150 kHz. Stator tip displacement can be confirmed as shown in Fig. 4. This does not mention it because of the severe abrasion phenomenon and decline of the output characteristics. A finite element analysis (FEA) was conducted using these conditions. The analysis used stator EL21ET0.5EW5CL12CT0.5 with
SUS304 or brass at angles of 601, 901, and 1201. The elastic body materials were SUS304 and brass, and the legs of the stator were fixed to the floor. However, one of the most important factors was whether there was a tip. The tip thickness was the same as that of the elastic body, and its length was limited to 2 mm. Piezoelectric ceramics of the PZT hard series were used. By default, the FEA simulation used a 901 angle between the legs of the stator. Fig. 6 shows the elliptical displacement characteristics at each resonance frequency of the selected model (EL21ET0.5EW5CL12CT0.5 SUS304 901). Fig. 5 shows the displacement characteristics of the model without a tip. It can be seen that the rotation axis of the displacement varies according to the frequency, and this confirms the area of the elliptical displacement. These results affect the speed and torque of the motor when driving it. Fig. 5(b) shows the elliptical displacement depending on the stator tip. Similarly, the distortion of the tip at the resonance mode above 150 kHz can be confirmed. The displacement with a tip is larger than without a tip [12]. Fig. 5(c) and (d) shows the displacement when using brass, similar to Fig. 5(a) and (b). Again, the displacement with a tip is larger than without a tip. Analysis was performed by changing the angle of the stator legs in the same way. Fig. 6 shows the analysis results of changing the angle of the legs to 601. Again, the displacement of the stator with a tip is larger than without a tip. The shape does not change
S.-K. Cheon et al. / Ceramics International 41 (2015) S618–S624
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Fig. 6. The displacement characteristics depending on the material and the tip (601). (a) No tip stator (SUS), (b) Tip stator (SUS304), (c) No tip stator (Brass) and (d) Tip stator (Brass).
Fig. 7. The displacement characteristics depending on the material and the tip (1201). (a) No tip stator (SUS), (b) Tip stator (SUS304), (c) No tip stator (Brass) and (d) Tip stator (Brass).
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Fig. 8. The stator and rotor of fabricated motor.
Fig. 9. The driving device of ultrasonic motor.
significantly with the angle, but the size of the entire displacement is rather small. This can be predicted that the combination of vibration is unstable than 901. Fig. 7 shows the analysis results of changing the angle of the legs to 1201. Again, the displacement of the stator with a tip is larger than without a tip. When at 601, the displacement can be confirmed by the formation around the X axis. And at 1201 it can be confirmed around the Y axis. But at 901 various displacements depending on the resonance frequency can be seen. So, the stator at 901 was fabricated.
4. Fabrication, experiment and results The stable and large elliptical displacement of the FEA simulations was confirmed and fabricated. Fig. 8 shows the stator and rotor of the ultrasonic motor. The size of the stator and the piezoelectric ceramic was the same as that used in the FEA. The speed and the torque of the ultrasonic motor were measured by driving the device with an applied voltage and frequency (Fig. 9). A framework was designed to minimize unnecessary vibration of the motor. The length and thickness of the elastic body were 21 and 0.5 mm, respectively. The size of the rectangular
Fig. 10. Impedance curve of a 901 angle (upper SUS304, lower Brass).
ceramics attached to the surface of the elastic body was 12 mm 5 mm. The piezoelectric ceramics were attached using glue (353ND, Epotech). The rotor was placed on top of the stator and they were combined inside a case. Sine and cosine wave voltages, which have a 901 phase difference, were generated by a function generator and they were amplified by a power amplifier that was applied to the motor. The rotational speed and torque of the motor were measured using a non-contact speed gauge and a torque
S.-K. Cheon et al. / Ceramics International 41 (2015) S618–S624
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Fig. 11. The speed and torque depending on the resonance frequency.
Speed Torque
250
60
Speed (rpm)
45 150 30
Torque (gfcm)
200
100 15 50 5
10
15
20
25
30
35
Voltage (V) Fig. 12. The speed and torque depending on the applied voltage.
gauge, respectively. Fig. 10 shows the impedance curve of EL21ET0.5EW5CL12CT0.5 with SUS304 and brass at 901 obtained using an impedance analyzer. The corresponding speed and the torque graphs are shown in Figs. 11 and 12. The speed and torque characteristics were confirmed by experiments. It can be confirmed that the output characteristics with brass are much better than with SUS304 (Figs. 11 and 12), and are related to Young's modulus. SUS304 has high Young's modulus of about 200 GPa, but brass has a low value of 90 GPa [13]. Under the same input conditions, increasing the degree of the elastic body is because different, but the SUS304 is because good wear resistance and heat resistance, the application may be advantageous. 5. Conclusion An ultrasonic motor was designed by combining four roofshaped stators. The output characteristics were simulated using the ATILA FEA program. A prototype was fabricated in agreement with the vibration shaped and displacement size of each model. The results confirmed that the output characteristics of brass were much better than those of SUS304 and were related to Young's modulus. Also, the maximum speed and torque were obtained at the resonance frequency. The motor measured depending on the changed resonance frequency and applied voltage. The maximum speed 246 [rpm]
and torque 63 [gfcm] were obtained when the frequency was 97.675 [kHz]. To strengthen the friction surface of a process such as anodizing processing in order to reduce the wear between the elastic bodies, it will be helpful in improving the output characteristics. Conflict of interest We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted. Acknowledgments Following are results of a study on the “Leaders In-dustryuniversity Cooperation” Project, supported by the Ministry of Education (MOE). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MEST) (No. 2011-0030058). This work was supported by the Technological Innovation R&D Program (S2195708) funded by the Small and Medium Business Administration (SMBA, Korea). References [1] T. Sashida, T. Kenjo, An Introduction to Ultrasonic Motors, Oxford Clarendon Press, 1993, p. 17–23. [2] T. Sashida, T. Kenjo, An Introduction to Ultrasonic Motors, Oxford University Press, New York, 1994, p. 84–100. [3] S. Ueha, Y. Tomikawa, M. Kurosawa, N. Nakamura, Ultrasonic Motors Theory and Applications, Oxford, 1993, pp. 4–7. [4] H.W. Kim, D. Shuxiang, L. Pitak, K. Uchino, T.G. Park, Novel method for driving the ultrasonic motor, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49 (2002) 1356–1361. [5] K. Uchino, FEM and Micromechatronics with ATILA Software, Florida CRC press, 2008, p. 245–270. [6] H.H. Chong, T.G. Park, M.H. Kim, A study on driving characteristics of the cross type ultrasonic rotary motor, J. Electroceram. 17 (2006) 561–564. [7] T.G. Park, S.S. Jeong, H.H. Chong, K. Uchino, Design of thin cross type ultrasonic motor, J. Electroceram. 24 (2009) 288–293. [8] S.S. Jeong, H.H. Chong, M.H. Park, T.G. Park, M.H. Kim, Driving characteristics of the thin-type ultrasonic motor using microcontroller, Ferroelectrics 409 (1) (2010) 152–160.
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[9] T.G. Park, H.H. Chong, S.S. Jeong, K. Uchino, Motional characteristics of thin piezoelectric rotary motor using cross shaped stator, J. Electroceram. 23 (2008) 317–321. [10] S.K. Cheon, S.S. Jeong, N.L. Kim, Y.W. Ha, M.H. Kim, T.G. Park, Design and fabrication of a hollow tray shaped ultrasonic motor, J. Electroceram. 33 (2014) 42–46. [11] S.S. Jeong, T.G. Park, T.K. Song, Characteristics of a V-type ultrasonic rotary motor, Curr. Appl. Phys. 11 (2011) S364–S367.
[12] T.G. Park, B.J. Kim, M.H. Kim, K. Uchino, Characteristics of the first longitudinal fourth bending mode linear ultrasonic motors, Jpn. J. Appl. Phys. 41 (2002) 7139–7143. [13] J.W. Kim, C.H. Park, J.H. Lim, S.S. Jeong, J.K. Park, T.G. Park, Driving characteristics of octagon type ultrasonic motor, J. Cent. South Univ. 20 (2013) 71–75.
CERAMICS INTERNATIONAL
Ceramics International 41 (2015) S618–S624 www.elsevier.com/locate/ceramint
Driving characteristics of an ultrasonic rotary motor consisting of four line contact type stators Seong-Kyu Cheona, Seong-Su Jeonga, Yong-Woo Haa, Byung-Ha Leea, Jong-Kyu Parkb, Tae-Gone Parka,n a Department of Electrical Engineering, Changwon National University, Gyeongnam 641-773, Republic of Korea Department of Mechanical Engineering, Changwon National University, Gyeongnam 641-773, Republic of Korea
b
Received 26 October 2014; accepted 4 March 2015 Available online 9 April 2015
Abstract A new type of ultrasonic rotary motor that can replace existing ultrasonic motors for driving camera zoom lenses was proposed and investigated experimentally. The proposed motor composed of four roof-shaped stators. On the upper surfaces of each roof-shaped stator, two rectangular ceramics were attached. When two AC voltages with a 901 phase difference were applied to the ceramics, elliptical displacements occurred at the tip line of the actuator. By combining these elliptical displacements of the four stators, rotational motion of the stator could be achieved. If a circular disk rotor was positioned on the stator, vibrations of the stator were transferred through the four contact lines between the stator and the rotor. Preload of the motor could be controlled by the jointing bolt, which went through the center of the disk rotor and the ball bearings. The finite element analysis (FEA) simulation program ANSYS was used to analyze the elliptical displacement characteristics in relation to changes in the size of the elastic body, piezoelectric ceramics, friction tips, frequency, and applied voltages. A prototype motor was fabricated, and its driving characteristics such as impedances, vibration amplitudes, rotational speed, and torque were measured. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Keywords: Ultrasonic rotary motor; Piezoelectric motor; Piezoelectric actuator; Piezoelectric application; ATILA
1. Introduction An ultrasonic motor is a type of electric motor that is powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider, depending on the operation scheme (rotation or linear translation) [1,2]. Ultrasonic motors differ from piezoelectric actuators in several ways, although both typically use some form of piezoelectric material: generally lead zirconate titanate and occasionally lithium niobate or other single-crystal materials [3]. Ultrasonic motors offer excellent performance and many useful features including a high torque at low speed, a large power output per unit weight, the possibility of precise positioning, a simple structure, compactness, n
Corresponding author. Tel.: þ82 55 213 3631; fax: þ 82 55 263 9956. E-mail address: [email protected] (T.-G. Park).
http://dx.doi.org/10.1016/j.ceramint.2015.03.218 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
and the absence of electromagnetic interferences. Ultrasonic motors can be applied in precision industries, for example, circular type ultrasonic motors for digital cameras and small ultrasonic motors for cell phones. The ultrasonic rotary motor with line contact has been extensively studied. In contrast, ultrasonic motors with a simple structure and principle have not been sufficiently explored [4,5]. In this paper, a driving ultrasonic motor that uses four line contacts is proposed, and its output characteristics were simulated using the ATILA FEM (finite element method) program. The proposed motor consists of four lambda-shaped stators and eight rectangular plate ceramics. Most importantly, it can be fabricated as a small and simple structure. The proposed ultrasonic motor was designed to match the fundamental size of a compact camera lens. Therefore, the stator and the piezoelectric ceramic thickness were set to 0.5 mm and the overall size had a diameter of 40 mm
S.-K. Cheon et al. / Ceramics International 41 (2015) S618–S624
and a height of 15 mm. A prototype motor was fabricated for testing its driving characteristics, and the output characteristics were analyzed in relation to the preload.
2. Structure and principle of the proposed motor Fig. 1 shows the structure of a four line-contact-shaped ultrasonic motor. The stator consists of elastic bodies and piezoelectric ceramics attached to its surface. Stainless steel SUS304 and piezoelectric ceramics Pb(Zr,Ti)O3 (PZT, Piezo system Ltd.) were
S619
used for fabricating the stator. The four elastic bodies of the ring stator were identical in size and were bilaterally symmetrical. If the rotor surface was placed on the stator, the rotor and stator would be in contact through four contact lines at each four tops of the stators. The parameters of the stator used for the designed motor are presented in table in Fig. 1. And also Fig. 1 shows the polarization directions of the piezoelectric ceramics at the stator. As shown, the piezoelectric ceramics were bonded at both sides of the elastic bodies, such that the polarization directions of the piezoelectric ceramics were in opposite directions. The hollow arrow and the filled arrow were applied to each other with a voltage with 901 phase difference [6–8]. Application of voltages of resonance frequencies in this way produces combined longitudinal and bending waves, which generates elliptical motions of the contact tip [9]. These elliptical displacements of the four contact lines rotate the rotor by using friction forces. Fig. 2 shows the principle of the elliptical motion at one of the four lines. In one cycle of applied voltages (t0–t3), one elliptical motion is completed at the line and the same elliptical motion is simultaneously generated at the four lines, which rotates the rotor. 3. FEA simulations and results Fig. 1 shows before the analysis, the thickness of the elastic body was set to 0.5 T to endure sufficient preload. When thickness of the elastic body and the ceramic through previous
Fig. 1. Structure of lambda-type ultrasonic motor.
Fig. 2. Principle of the elliptical motion.
Fig. 4. Displacement characteristics at the resonance frequency above 150 kHz.
Fig. 3. Impedance curve of models (SUS304, Brass).
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Fig. 5. The displacement characteristics depending on the material and the tip (901). (a) No tip stator (SUS304), (b) Tip stator (SUS), (c) No tip stator (Brass) and (d) Tip stator (Brass).
study was similar, the larger elliptical displacement characteristics were confirmed by Cheon et al. [10]. Therefore, the thickness of the ceramic was set to 0.5 T. In this paper, the stators are named by the size of the parameters. For example, if the length, thickness, and width of the elastic body are 21, 0.5, and 12 mm, and the length and thickness of the ceramic are 5 and 0.5 mm, respectively, the stator is named EL20ET0.5EW5CL12CT0.5. Fig. 3 shows the impedance characteristics obtained by the FEA. Resonance and anti-resonance frequencies could be determined from this curve. A model was selected based on these results. The selected model was analyzed by changing the angle of the elastic body depending on whether there was a tip. Stator driving was performed at frequencies below 150 kHz, because there was a tip distortion phenomenon at higher frequencies. It was assumed that this phenomenon was caused by the interference between the vibrations, which generated irregular vibration at the tip at the high-frequency band [11]. Fig. 4 shows the displacement characteristics and their form generated at a resonance frequency above 150 kHz. Stator tip displacement can be confirmed as shown in Fig. 4. This does not mention it because of the severe abrasion phenomenon and decline of the output characteristics. A finite element analysis (FEA) was conducted using these conditions. The analysis used stator EL21ET0.5EW5CL12CT0.5 with
SUS304 or brass at angles of 601, 901, and 1201. The elastic body materials were SUS304 and brass, and the legs of the stator were fixed to the floor. However, one of the most important factors was whether there was a tip. The tip thickness was the same as that of the elastic body, and its length was limited to 2 mm. Piezoelectric ceramics of the PZT hard series were used. By default, the FEA simulation used a 901 angle between the legs of the stator. Fig. 6 shows the elliptical displacement characteristics at each resonance frequency of the selected model (EL21ET0.5EW5CL12CT0.5 SUS304 901). Fig. 5 shows the displacement characteristics of the model without a tip. It can be seen that the rotation axis of the displacement varies according to the frequency, and this confirms the area of the elliptical displacement. These results affect the speed and torque of the motor when driving it. Fig. 5(b) shows the elliptical displacement depending on the stator tip. Similarly, the distortion of the tip at the resonance mode above 150 kHz can be confirmed. The displacement with a tip is larger than without a tip [12]. Fig. 5(c) and (d) shows the displacement when using brass, similar to Fig. 5(a) and (b). Again, the displacement with a tip is larger than without a tip. Analysis was performed by changing the angle of the stator legs in the same way. Fig. 6 shows the analysis results of changing the angle of the legs to 601. Again, the displacement of the stator with a tip is larger than without a tip. The shape does not change
S.-K. Cheon et al. / Ceramics International 41 (2015) S618–S624
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Fig. 6. The displacement characteristics depending on the material and the tip (601). (a) No tip stator (SUS), (b) Tip stator (SUS304), (c) No tip stator (Brass) and (d) Tip stator (Brass).
Fig. 7. The displacement characteristics depending on the material and the tip (1201). (a) No tip stator (SUS), (b) Tip stator (SUS304), (c) No tip stator (Brass) and (d) Tip stator (Brass).
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Fig. 8. The stator and rotor of fabricated motor.
Fig. 9. The driving device of ultrasonic motor.
significantly with the angle, but the size of the entire displacement is rather small. This can be predicted that the combination of vibration is unstable than 901. Fig. 7 shows the analysis results of changing the angle of the legs to 1201. Again, the displacement of the stator with a tip is larger than without a tip. When at 601, the displacement can be confirmed by the formation around the X axis. And at 1201 it can be confirmed around the Y axis. But at 901 various displacements depending on the resonance frequency can be seen. So, the stator at 901 was fabricated.
4. Fabrication, experiment and results The stable and large elliptical displacement of the FEA simulations was confirmed and fabricated. Fig. 8 shows the stator and rotor of the ultrasonic motor. The size of the stator and the piezoelectric ceramic was the same as that used in the FEA. The speed and the torque of the ultrasonic motor were measured by driving the device with an applied voltage and frequency (Fig. 9). A framework was designed to minimize unnecessary vibration of the motor. The length and thickness of the elastic body were 21 and 0.5 mm, respectively. The size of the rectangular
Fig. 10. Impedance curve of a 901 angle (upper SUS304, lower Brass).
ceramics attached to the surface of the elastic body was 12 mm 5 mm. The piezoelectric ceramics were attached using glue (353ND, Epotech). The rotor was placed on top of the stator and they were combined inside a case. Sine and cosine wave voltages, which have a 901 phase difference, were generated by a function generator and they were amplified by a power amplifier that was applied to the motor. The rotational speed and torque of the motor were measured using a non-contact speed gauge and a torque
S.-K. Cheon et al. / Ceramics International 41 (2015) S618–S624
S623
Fig. 11. The speed and torque depending on the resonance frequency.
Speed Torque
250
60
Speed (rpm)
45 150 30
Torque (gfcm)
200
100 15 50 5
10
15
20
25
30
35
Voltage (V) Fig. 12. The speed and torque depending on the applied voltage.
gauge, respectively. Fig. 10 shows the impedance curve of EL21ET0.5EW5CL12CT0.5 with SUS304 and brass at 901 obtained using an impedance analyzer. The corresponding speed and the torque graphs are shown in Figs. 11 and 12. The speed and torque characteristics were confirmed by experiments. It can be confirmed that the output characteristics with brass are much better than with SUS304 (Figs. 11 and 12), and are related to Young's modulus. SUS304 has high Young's modulus of about 200 GPa, but brass has a low value of 90 GPa [13]. Under the same input conditions, increasing the degree of the elastic body is because different, but the SUS304 is because good wear resistance and heat resistance, the application may be advantageous. 5. Conclusion An ultrasonic motor was designed by combining four roofshaped stators. The output characteristics were simulated using the ATILA FEA program. A prototype was fabricated in agreement with the vibration shaped and displacement size of each model. The results confirmed that the output characteristics of brass were much better than those of SUS304 and were related to Young's modulus. Also, the maximum speed and torque were obtained at the resonance frequency. The motor measured depending on the changed resonance frequency and applied voltage. The maximum speed 246 [rpm]
and torque 63 [gfcm] were obtained when the frequency was 97.675 [kHz]. To strengthen the friction surface of a process such as anodizing processing in order to reduce the wear between the elastic bodies, it will be helpful in improving the output characteristics. Conflict of interest We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted. Acknowledgments Following are results of a study on the “Leaders In-dustryuniversity Cooperation” Project, supported by the Ministry of Education (MOE). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MEST) (No. 2011-0030058). This work was supported by the Technological Innovation R&D Program (S2195708) funded by the Small and Medium Business Administration (SMBA, Korea). References [1] T. Sashida, T. Kenjo, An Introduction to Ultrasonic Motors, Oxford Clarendon Press, 1993, p. 17–23. [2] T. Sashida, T. Kenjo, An Introduction to Ultrasonic Motors, Oxford University Press, New York, 1994, p. 84–100. [3] S. Ueha, Y. Tomikawa, M. Kurosawa, N. Nakamura, Ultrasonic Motors Theory and Applications, Oxford, 1993, pp. 4–7. [4] H.W. Kim, D. Shuxiang, L. Pitak, K. Uchino, T.G. Park, Novel method for driving the ultrasonic motor, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49 (2002) 1356–1361. [5] K. Uchino, FEM and Micromechatronics with ATILA Software, Florida CRC press, 2008, p. 245–270. [6] H.H. Chong, T.G. Park, M.H. Kim, A study on driving characteristics of the cross type ultrasonic rotary motor, J. Electroceram. 17 (2006) 561–564. [7] T.G. Park, S.S. Jeong, H.H. Chong, K. Uchino, Design of thin cross type ultrasonic motor, J. Electroceram. 24 (2009) 288–293. [8] S.S. Jeong, H.H. Chong, M.H. Park, T.G. Park, M.H. Kim, Driving characteristics of the thin-type ultrasonic motor using microcontroller, Ferroelectrics 409 (1) (2010) 152–160.
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[9] T.G. Park, H.H. Chong, S.S. Jeong, K. Uchino, Motional characteristics of thin piezoelectric rotary motor using cross shaped stator, J. Electroceram. 23 (2008) 317–321. [10] S.K. Cheon, S.S. Jeong, N.L. Kim, Y.W. Ha, M.H. Kim, T.G. Park, Design and fabrication of a hollow tray shaped ultrasonic motor, J. Electroceram. 33 (2014) 42–46. [11] S.S. Jeong, T.G. Park, T.K. Song, Characteristics of a V-type ultrasonic rotary motor, Curr. Appl. Phys. 11 (2011) S364–S367.
[12] T.G. Park, B.J. Kim, M.H. Kim, K. Uchino, Characteristics of the first longitudinal fourth bending mode linear ultrasonic motors, Jpn. J. Appl. Phys. 41 (2002) 7139–7143. [13] J.W. Kim, C.H. Park, J.H. Lim, S.S. Jeong, J.K. Park, T.G. Park, Driving characteristics of octagon type ultrasonic motor, J. Cent. South Univ. 20 (2013) 71–75.