IVUS (Intravascular Ultrasound) is a useful medical device to observe the thrombus in blood vessels, and such a micro motor less than 1.0 mm in outer diameter is desired to apply IVUS in narrow brain vessels. In our previous works, ultrasonic motor consisting of a wire coil type stator, a waveguide, a cylindrical rotor, an ultrasonic vibrator has been developed. This motor is rather easy to miniaturize because of its simple structure. However, this motor behavior is unstable rotate. To improve these problems, a foil type stator has been applied in stead of a wire coiled stator. An ultrasonic motor with 0.05 mm thick foil type stator was manufactured and tested their performances. It was able to verify that this ultrasonic motor with a foil type stator has the right quality. So, simplified IVUS system using ultrasonic motor with a foil type stator was manufactured and tested their fundamental performances. In order to expand development of new application, ultrasonic motor with a shortened waveguide and ultrasonic motor integrated driving unit with a stator was developed

S. Toyama

T. Kaga

Y. Furukawa

English

Journal of Vibroengineering

 ? VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716 165 
933. Development of ultrasonic motor with a coil type 
stator and its application to vascular endoscope 
S. Toyama, T. Kaga, Y. Furukawa 
933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  
S. TOYAMA, T. KAGA, Y. FURUKAWA 
S. Toyama1, T. Kaga2, Y. Furukawa3 
1, 2Tokyo Noko University of Technology, Koganei, Tokyo, Japan 
3Polytechnic University, Tokyo, Japan 
E-mail: 1toyama@cc.tuat.ac.jp, 2t-kaga@cc.tuat.ac.jp, 3furukawa@uitec.ac.jp 
Phone: +81 423 88 7207; Fax: +81 423 88 7207 
(Received 30 November 2012; accepted 28 February 2013) 
Abstract. IVUS (Intravascular Ultrasound) is a useful medical device to observe the thrombus 
in blood vessels, and such a micro motor less than 1.0 mm in outer diameter is desired to apply 
IVUS in narrow brain vessels. In our previous works, ultrasonic motor consisting of a wire coil 
type stator, a waveguide, a cylindrical rotor, an ultrasonic vibrator has been developed. This 
motor is rather easy to miniaturize because of its simple structure. However, this motor behavior 
is unstable rotate. To improve these problems, a foil type stator has been applied in stead of a 
wire coiled stator. An ultrasonic motor with 0.05 mm thick foil type stator was manufactured 
and tested their performances. It was able to verify that this ultrasonic motor with a foil type 
stator has the right quality. So, simplified IVUS system using ultrasonic motor with a foil type 
stator was manufactured and tested their fundamental performances. In order to expand 
development of new application, ultrasonic motor with a shortened waveguide and ultrasonic 
motor integrated driving unit with a stator was developed. 
Keywords: micro motor, IVUS, ultrasonic motor. 
1. Introduction 
Micro ultrasonic motor that uses a coiled waveguide and its driving performance is reported. 
The invented ultrasonic motor [1] has a simple structure and is easy to be miniaturized compared 
to existing ones. This ultrasonic motor consists of vibrator, rotor and waveguide. In the 
waveguide, there are two parts of the arm and the coil. The arm is thin wire, and one end of arm 
is a shape of the helical coil. The arm plays the role to propagate the ultrasonic vibration. The 
coil plays the role of stator. The rotor is supported with coil. Because of this structure, this 
ultrasonic motor is no need for a spring for preloading and any piezo-electric element at driving 
point. Therefore it is more suitable for micro ultrasonic motor. So, for a practical use of this 
motor, we are trying to apply it to a catheter for medical treatment. For the first trial, we apply it 
to the catheter used for a blood vessel thrombus. This motor is installed at the top of catheter and 
gives turbulence to the flow for stirring the thrombus dissolution medicine, it is thought more 
effective for thrombus treatment. 
2. Driving principle and composition of motor 
Driving principle of the motor is described. A feature in driving principle of this motor is to 
propagate the ultrasonic wave to coiled Stator. Moreover, the composition of the motor that 
dimension is 0.8 mm in diameter and 4 mm in length is described. 
3. Driving principle 
Driving principles are shown in Fig. 1. The motor is consisted by a coiled (stator) with arm 
and a rotor and a vibrator. The one end of arm is connected to an ultrasonic vibrator and 
supplied with ultrasonic vibration, and the other end is kept free as shown in Fig. 1a. Applied 
ultrasonic vibration induce flexural wave in an arm, and it becomes a traveling wave, and 
propagates in arm. Then traveling wave propagates to a coil, coil’s surface performs elliptic 
933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  
S. TOYAMA, T. KAGA, Y. FURUKAWA 
166 ? VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716  
motion, and rotor performs rotational and transverse movement by frictional force which is 
generated by contacts between the rotor and the wave which propagates in coil as shown in 
Fig. 1b. At this time, frictional force works opposite direction of advance direction of traveling 
wave.  
In Fig. 1a and Fig. 1b, rotor is arranged inside of coil, but motor can drive when coil is 
arranged inside of pipe type rotor. 
 
Fig. 1. Driving principle 
4. Composition of motor 
Figure 2 shows the composition of motor. The Langevin type vibrator is used for the wave 
transducer. The one end of arm is fixed on the ????? stage set up under the vibrator, and 
pressed against the tip of vibrator. The flexural wave propagates in arm, and reaches to coil. The 
rotor which arranged outside is driven. To prevent the rotor from flying out from coil, a steel 
ball is bonded to the top of the coil. The dimension of the motor is 0.8 mm in diameter and 
4.0 mm in length. The photograph in the upper right of Figure 2 is a cross section view of the 
rotor and the coil which steel ball is not bonded. 
 
Fig. 2. Composition of motor 
933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  
S. TOYAMA, T. KAGA, Y. FURUKAWA 
 ? VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716 167 
5. Driving performance  
It reports about the rotational speed when the preload that gives rotor is changed. Moreover, 
the torque calculated from the rotational angular speed is reported. 
6. Change in rotational speed by preload 
Preload that gives rotor is greatly related to driving performance. This motor’s preload is 
decided by the outside diameter of coil and inside diameter of rotor. Therefore, the rotational 
speed measurement was done by using the coil that outside diameter is 544 μm and the rotor that 
inside diameter is shown in Table 1 and outside diameter is 0.8mm. The rotational speed was 
measured by the digital tachometer (SANWA Co. Ltd., SE-100). Figure 3 shows the 
measurement result. The line in the figure shows the outside diameter of the coil. The rotational 
speed was faster when preload is given, and tended to rise by high preload.  
Table 1. Inside diameter of rotor 
Rotor No. 1 2 3 4 5 
Inside diameter [μm] 530 532.5 535 540 546 
 
Fig. 3. Rotational speed measurement of rotor with various inside diameters 
7. Detailed measurement of rotational speed 
The rotational speed of the motor was measured more in detail to calculate driving 
performance. Measurement system is shown in Fig. 4. The measurement method is described. 
The laser of the laser displacement sensor is irradiated to the teeth of the gear that is installed to 
the rotor. When the motor rotates, the displacement data of teeth of the gear is collected by the 
oscilloscope. The rotational speed is calculated from the time taken between the teeth and teeth. 
The torque is calculated from rotational angular acceleration at the rise time of the rotation speed. 
The measurement result of the rotation speed and the torque is shown in Figure 5. The used rotor 
is No. 1 in Table 1. From the N-T curve in the figure, start torque was about 0.2 μN m. This 
torque value is very small, so it should be made the most suitable preload.  
8. Application to catheter medical treatment 
The application to the thrombus catheter treatment in the blood vessel is thought as a 
practical use idea of the motor. The thrombus in the blood vessel is treated by pouring the 
thrombus dissolution medicine from the catheter. The improvement of the therapeutic gain is 
expected by stirring the dissolution medicine by the motor. Figure 6 is the appearances of the 
examination for practical use. The catheter that attached the motor was inserted into the silicon 
tube of 3 mm in the diameter which the inside was filled with pseudo blood. As a result, the stir 
933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  
S. TOYAMA, T. KAGA, Y. FURUKAWA 
168 ? VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716  
action by motor drive was confirmed. It will be thought that the examination in an environment 
that is nearer the human body is necessary in the future. 
 
Fig. 4. Measurement system 
 
Fig. 5. Detailed measurement of rotational speed 
 
Fig. 6. Driving test in pseudo blood 
9. Conclusions 
Driving performance of the motor and the application to the catheter treatment were 
examined. The driving performance improvement of the motor and the practical use examination 
in an environment near the human body is needed in the future. 
References 
[1] Moriya T., Furukawa Y., Akano Y., Nakajima A. Experimental Study on a Miniature Ultrasonic 
Motor Using a Coiled Stator. IECEI Technical Report, No. US2005-29, July, 2005, (in Japanese). 


Development of ultrasonic motor with a coil type stator and its application to vascular endoscope

Toyama, S.

Kaga, T.

Furukawa, Y.

Journal of Mechatronics and Artificial Intelligence in Engineering

  VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716 165 933. Development of ultrasonic motor with a coil type stator and its application to vascular endoscope S. Toyama, T. Kaga, Y. Furukawa 933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  S. TOYAMA, T. KAGA, Y. FURUKAWA S. Toyama1, T. Kaga2, Y. Furukawa3 1, 2Tokyo Noko University of Technology, Koganei, Tokyo, Japan 3Polytechnic University, Tokyo, Japan E-mail: 1toyama@cc.tuat.ac.jp, 2t-kaga@cc.tuat.ac.jp, 3furukawa@uitec.ac.jp Phone: +81 423 88 7207; Fax: +81 423 88 7207 (Received 30 November 2012; accepted 28 February 2013) Abstract. IVUS (Intravascular Ultrasound) is a useful medical device to observe the thrombus in blood vessels, and such a micro motor less than 1.0 mm in outer diameter is desired to apply IVUS in narrow brain vessels. In our previous works, ultrasonic motor consisting of a wire coil type stator, a waveguide, a cylindrical rotor, an ultrasonic vibrator has been developed. This motor is rather easy to miniaturize because of its simple structure. However, this motor behavior is unstable rotate. To improve these problems, a foil type stator has been applied in stead of a wire coiled stator. An ultrasonic motor with 0.05 mm thick foil type stator was manufactured and tested their performances. It was able to verify that this ultrasonic motor with a foil type stator has the right quality. So, simplified IVUS system using ultrasonic motor with a foil type stator was manufactured and tested their fundamental performances. In order to expand development of new application, ultrasonic motor with a shortened waveguide and ultrasonic motor integrated driving unit with a stator was developed. Keywords: micro motor, IVUS, ultrasonic motor. 1. Introduction Micro ultrasonic motor that uses a coiled waveguide and its driving performance is reported. The invented ultrasonic motor [1] has a simple structure and is easy to be miniaturized compared to existing ones. This ultrasonic motor consists of vibrator, rotor and waveguide. In the waveguide, there are two parts of the arm and the coil. The arm is thin wire, and one end of arm is a shape of the helical coil. The arm plays the role to propagate the ultrasonic vibration. The coil plays the role of stator. The rotor is supported with coil. Because of this structure, this ultrasonic motor is no need for a spring for preloading and any piezo-electric element at driving point. Therefore it is more suitable for micro ultrasonic motor. So, for a practical use of this motor, we are trying to apply it to a catheter for medical treatment. For the first trial, we apply it to the catheter used for a blood vessel thrombus. This motor is installed at the top of catheter and gives turbulence to the flow for stirring the thrombus dissolution medicine, it is thought more effective for thrombus treatment. 2. Driving principle and composition of motor Driving principle of the motor is described. A feature in driving principle of this motor is to propagate the ultrasonic wave to coiled Stator. Moreover, the composition of the motor that dimension is 0.8 mm in diameter and 4 mm in length is described. 3. Driving principle Driving principles are shown in Fig. 1. The motor is consisted by a coiled (stator) with arm and a rotor and a vibrator. The one end of arm is connected to an ultrasonic vibrator and supplied with ultrasonic vibration, and the other end is kept free as shown in Fig. 1a. Applied ultrasonic vibration induce flexural wave in an arm, and it becomes a traveling wave, and propagates in arm. Then traveling wave propagates to a coil, coil’s surface performs elliptic 933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  S. TOYAMA, T. KAGA, Y. FURUKAWA 166  VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716  motion, and rotor performs rotational and transverse movement by frictional force which is generated by contacts between the rotor and the wave which propagates in coil as shown in Fig. 1b. At this time, frictional force works opposite direction of advance direction of traveling wave.  In Fig. 1a and Fig. 1b, rotor is arranged inside of coil, but motor can drive when coil is arranged inside of pipe type rotor.  Fig. 1. Driving principle 4. Composition of motor Figure 2 shows the composition of motor. The Langevin type vibrator is used for the wave transducer. The one end of arm is fixed on the  stage set up under the vibrator, and pressed against the tip of vibrator. The flexural wave propagates in arm, and reaches to coil. The rotor which arranged outside is driven. To prevent the rotor from flying out from coil, a steel ball is bonded to the top of the coil. The dimension of the motor is 0.8 mm in diameter and 4.0 mm in length. The photograph in the upper right of Figure 2 is a cross section view of the rotor and the coil which steel ball is not bonded.  Fig. 2. Composition of motor 933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  S. TOYAMA, T. KAGA, Y. FURUKAWA   VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716 167 5. Driving performance  It reports about the rotational speed when the preload that gives rotor is changed. Moreover, the torque calculated from the rotational angular speed is reported. 6. Change in rotational speed by preload Preload that gives rotor is greatly related to driving performance. This motor’s preload is decided by the outside diameter of coil and inside diameter of rotor. Therefore, the rotational speed measurement was done by using the coil that outside diameter is 544 μm and the rotor that inside diameter is shown in Table 1 and outside diameter is 0.8mm. The rotational speed was measured by the digital tachometer (SANWA Co. Ltd., SE-100). Figure 3 shows the measurement result. The line in the figure shows the outside diameter of the coil. The rotational speed was faster when preload is given, and tended to rise by high preload.  Table 1. Inside diameter of rotor Rotor No. 1 2 3 4 5 Inside diameter [μm] 530 532.5 535 540 546  Fig. 3. Rotational speed measurement of rotor with various inside diameters 7. Detailed measurement of rotational speed The rotational speed of the motor was measured more in detail to calculate driving performance. Measurement system is shown in Fig. 4. The measurement method is described. The laser of the laser displacement sensor is irradiated to the teeth of the gear that is installed to the rotor. When the motor rotates, the displacement data of teeth of the gear is collected by the oscilloscope. The rotational speed is calculated from the time taken between the teeth and teeth. The torque is calculated from rotational angular acceleration at the rise time of the rotation speed. The measurement result of the rotation speed and the torque is shown in Figure 5. The used rotor is No. 1 in Table 1. From the N-T curve in the figure, start torque was about 0.2 μN m. This torque value is very small, so it should be made the most suitable preload.  8. Application to catheter medical treatment The application to the thrombus catheter treatment in the blood vessel is thought as a practical use idea of the motor. The thrombus in the blood vessel is treated by pouring the thrombus dissolution medicine from the catheter. The improvement of the therapeutic gain is expected by stirring the dissolution medicine by the motor. Figure 6 is the appearances of the examination for practical use. The catheter that attached the motor was inserted into the silicon tube of 3 mm in the diameter which the inside was filled with pseudo blood. As a result, the stir 933. DEVELOPMENT OF ULTRASONIC MOTOR WITH A COIL TYPE STATOR AND ITS APPLICATION TO VASCULAR ENDOSCOPE.  S. TOYAMA, T. KAGA, Y. FURUKAWA 168  VIBROENGINEERING. JOURNAL OF VIBROENGINEERING. MARCH 2013. VOLUME 15, ISSUE 1. ISSN 1392-8716  action by motor drive was confirmed. It will be thought that the examination in an environment that is nearer the human body is necessary in the future.  Fig. 4. Measurement system  Fig. 5. Detailed measurement of rotational speed  Fig. 6. Driving test in pseudo blood 9. Conclusions Driving performance of the motor and the application to the catheter treatment were examined. The driving performance improvement of the motor and the practical use examination in an environment near the human body is needed in the future. References [1] Moriya T., Furukawa Y., Akano Y., Nakajima A. Experimental Study on a Miniature Ultrasonic Motor Using a Coiled Stator. IECEI Technical Report, No. US2005-29, July, 2005, (in Japanese). 

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Development of ultrasonic motor with a coil type stator and its application to vascular endoscope

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