Papers - Mashimo Tomoaki

Micro Linear Ultrasonic Motor With a Hall Sensor-Based Feedback Control System Reviewed

Shunsuke Izuhara, Tomoaki Mashimo

IEEE Access   12   131656 - 131663   2024

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2024.3454295

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Earthworm-Inspired Robot Design: Reducing the Number of Actuators Through Embedded Motor Between Segments Reviewed

William Leonard Liem, Ayato Kanada, Tomoaki Mashimo

IEEE Access   12   114636 - 114644   2024

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2024.3445330

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A Suspended Pollination Robot With a Flexible Multi-Degrees-of-Freedom Manipulator for Self-Pollinated Plants Reviewed

Naoya Masuda, Mohamed M. Khalil, Seitaro Toda, Kotaro Takayama, Ayato Kanada, Tomoaki Mashimo

IEEE Access   12   142449 - 142458   2024

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2024.3469784

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Fabrication and characterization of a submillimeter-scale ultrasonic motor Reviewed

Kohei Kikuchi, Mudassir Hussain, Tomoaki Mashimo

Sensors and Actuators A: Physical   360   114524 - 114524   2023.10

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sna.2023.114524

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Tilting ultrasonic motor using extension and shear vibration modes Reviewed

Shunsuke Izuhara, Tomoaki Mashimo

Sensors and Actuators A: Physical   357   114390 - 114390   2023.8

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sna.2023.114390

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Miniature camera module with a hollow linear ultrasonic motor-based focus feature Reviewed

Naoya Masuda, Shunsuke Izuhara, Tomoaki Mashimo

Sensors and Actuators A: Physical   354   114248 - 114248   2023.5

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sna.2023.114248

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A Closed-Loop Micro-Ultrasonic Motor Control System With Extremum Seeking Reviewed

Mohamed M. Khalil, Naoya Masuda, Kotaro Takayama, Tomoaki Mashimo

IEEE Access   11   22329 - 22341   2023.4

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2023.3252003

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A Palm-Sized Omnidirectional Mobile Robot Driven by 2-DOF Torus Wheels Reviewed

Yunosuke Sato, Ayato Kanada, Tomoaki Mashimo

IEEE Robotics and Automation Letters   8 ( 1 )   105 - 112   2023.1

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/lra.2022.3223296

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Caterpillar-Inspired Insect-Scale Climbing Robot Using Dry Adhesives Reviewed

Mohamed M. Khalil, Tomoaki Mashimo

IEEE Robotics and Automation Letters   7 ( 3 )   7628 - 7635   2022.7

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/lra.2022.3183897

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Performance improvement of micro-ultrasonic motors using the thickness shear mode piezoelectric elements Reviewed

Tomoaki Mashimo, Yoshinari Oba

Sensors and Actuators A: Physical   335   113347 - 113347   2022.3

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sna.2021.113347

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Design of a Micro Linear Ultrasonic Motor with a Preload Mechanism Reviewed

Shunsuke Izuhara, Tomoaki Mashimo

Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering   88 ( 1 )   51 - 56   2022.1

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We present a micro linear piezoelectric ultrasonic motor, which can be used for zooming and autofocusing features in camera modules inside cellphones and endoscopes, it consists of a cuboid stator with a hole and an elastic cylindrical slider. The motor design, in which the slider inserted into the stator hole expands outward, enables a hollow structure for an optimal preload for enhancing the motor thrust force, (n this study, we model the relationship between the dimensions and the preload to quantify the preload value and clarify the design methodology. The size of the prototype stator with piezoelectric elements measures 2,6 mm in height and width and 2.2 mm in depth (the length in slider travel direction). There is a hole of 1,7 mm in diameter at the stator center, and the slider inserted into the hole operates when voltages are applied to the piezoelectric elements. Applying an optimized preload, we evaluate the fundamental characteristics of the motor in experiments, A thrust force of approximately 40 mN and a resolution of about 1 μm were obtained, which may satisfy the specification of a certain type of camera modules.

DOI： 10.2493/JJSPE.88.51

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Lift Generation by a Miniature Piezoelectric Ultrasonic Motor-Driven Rotary-Wing for Pico Air Vehicles Reviewed

Eric TanKai Chiang, Takateru Urakubo, Tomoaki Mashimo

IEEE Access   10   13210 - 13218   2022

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2022.3146866

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Design and characterization of a thin linear ultrasonic motor for miniature focus systems Reviewed

Shunsuke Izuhara, Tomoaki Mashimo

Sensors and Actuators A: Physical   329   112797 - 112797   2021.10

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sna.2021.112797

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A Millimeter-Scale Rolling Microrobot Driven by a Micro-Geared Ultrasonic Motor Reviewed

Rudolf Yoga Hutama, Mohamed M. Khalil, Tomoaki Mashimo

IEEE Robotics and Automation Letters   6 ( 4 )   8158 - 8164   2021.10

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/lra.2021.3104227

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Comparison study of bending and three-wave vibration modes for micro ultrasonic motors Reviewed

Eric TanKai Chiang, Tomoaki Mashimo

Sensors and Actuators A: Physical   329   112801 - 112801   2021.10

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sna.2021.112801

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Switching Between Continuum and Discrete States in a Continuum Robot With Dislocatable Joints Reviewed

Ayato Kanada, Tomoaki Mashimo

IEEE Access   9   34859 - 34867   2021

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2021.3062284

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Characterization of bulk piezoelectric element-based ultrasonic motors Reviewed

Shunsuke Izuhara, Tomoaki Mashimo

ROBOMECH Journal   7 ( 1 )   2020.12

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

We propose miniature ultrasonic motors using stators made of a single bulk piezoelectric element. The bulk piezoelectric stator has the potential to increase output by reducing the dissipation that occurs in the adhesion layer between the PZTs and a metallic component in the stator. In this paper, we build two kinds of bulk piezoelectric stators: a cubic bulk stator with a side length of 4.2 mm and a hole of 3 mm in diameter, and a cylindrical bulk stator with an outer diameter of 4.2 mm and the same hole diameter. We evaluate their electrical and mechanical characteristics, such as impedance and vibration velocity. The experiments clarify the advantages of the bulk piezoelectric stators, such as low dissipation. The cubic bulk stator, which shows higher performance than the cylindrical one, is compared with a similar-shaped stator using a bronze cube and thin piezoelectric plates. The performance measures of the cubic bulk ultrasonic motor are optimized by the preload between the stator and rotor.

DOI： 10.1186/s40648-020-00179-w

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Other Link： https://link.springer.com/article/10.1186/s40648-020-00179-w/fulltext.html

CRACKS IN BRIDGE FLOOR DETECTED BY 2-DIMENSIONAL COMPLEX DISCRETE WAVELET PACKET TRANSFORM Reviewed

Zhong Zhang, Ohzora Hamata, Takuma Akiduki, Tomoaki Mashimo, Taiki Saito, Kazuhiro Hayashi

INTERNATIONAL JOURNAL OF INNOVATIVE COMPUTING INFORMATION AND CONTROL   16 ( 6 )   2007 - 2019   2020.12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ICIC INTERNATIONAL  

Bridge inspection is usually done visually on-site, and for this reason is problematic in places inaccessible to inspectors. In this paper we propose a solution through the analysis of features in captured images that suggest potential problems. We focus on the ability to detect cracks, and a complex-valued Haar wavelet is designed and applied to a 2D-CWPT, which is then combined with an anisotropic diffusion filter. A detection method for linear cracks is proposed through interpolation of the crack loss area and extraction processing according to the shape feature. The main results are: 1) we confirm that the complex-valued Haar wavelet is more effective for edge enhancement than the complex-valued Meyer wavelet; 2) quantitative evaluation of the proposed method for crack detection using the correct rate, sensitivity, specificity, precision rate, and F-value confirms the effectiveness of the method.

DOI： 10.24507/ijicic.16.06.2007

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Self-Sensing and Feedback Control for a Twin Coil Spring-Based Flexible Ultrasonic Motor Reviewed

Yunosuke Sato, Ayato Kanada, Tomoaki Mashimo

IEEE Robotics and Automation Letters   5 ( 4 )   5425 - 5431   2020.10

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/lra.2020.3008118

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Linear piezoelectric motor using a hollow rectangular stator Reviewed

Shunsuke Izuhara, Tomoaki Mashimo

Sensors and Actuators A: Physical   309   112002 - 112002   2020.7

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

We propose a linear piezoelectric motor using a hollow rectangular stator that can translate a load placed inside it by a direct-drive. This stator structure enables a quick response and high resolution by few components. These advantages are suited for controlling autofocus and zoom mechanisms in imaging devices. In this study, we verify the feasibility of the driving principle that uses two vibration modes in the bending and longitudinal direction of a hollow rectangular plate. We design a hollow linear piezoelectric motor by a finite element method analysis and evaluate the performance of the prototype motor by experiments. In the prototype motor, the stator measures 60 mm in height and width and 4.1 mm in thickness (the length in slider travel direction), and a slider with a side length of 42 mm is inserted into the stator. The performance parameters of the linear motion, such as thrust force and speed, are evaluated experimentally. By optimizing the preload between the stator and the slider, the motor thrust force has improved to over 0.5 N at 70 Vp-p, which is a practical force for moving a certain lens unit. (C) 2020 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sna.2020.112002

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Design and Experiments of Flexible Ultrasonic Motor Using a Coil Spring Slider Reviewed

Ayato Kanada, Tomoaki Mashimo

IEEE/ASME Transactions on Mechatronics   25 ( 1 )   468 - 476   2020.2

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/tmech.2019.2959614

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Efficient Energy Supply from Joint Torques near Singular Configurations for a Two-link Robot Arm with Joint Friction

Takateru Urakubo, Xianglong Wan, Tomoaki Mashimo

Proceedings of the 2020 IEEE/SICE International Symposium on System Integration, SII 2020   1193 - 1198   2020.1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Kinematic singularity of a robot arm can be dynamically advantageous in achieving tasks with the arm. In this paper, we examine dynamic features of singular configurations by theoretical analysis and numerical simulations, for a two-link robot arm that performs dynamic tasks such as lifting heavy objects and opening heavy doors. If no friction torque is applied to the joints, the mechanical energy necessary for the tasks can be generated from joint torques at a high rate near a singular configuration. Even when the joints suffer from viscous friction, the singular configuration has an advantage in supplying energy for a highly dynamic task whose duration is short. As the duration of task becomes longer, the arm configuration that can supply the energy at the highest rate becomes away from the singular configuration.

DOI： 10.1109/SII46433.2020.9026178

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High-Speed Visual Feedback Control of Miniature Rotating Mirror System Using a Micro Ultrasonic Motor Reviewed

Tomoaki Mashimo, Shunsuke Izuhara, Shiro Arai, Zhong Zhang, Hiromasa Oku

IEEE Access   8   38546 - 38553   2020

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2019.2957298

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Review: Recent Advances in Micromotors Reviewed

Tomoaki Mashimo, Shunsuke Izuhara

IEEE Access   8   213489 - 213501   2020

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers (IEEE)  

DOI： 10.1109/access.2020.3041457

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Research on surface defects detection of reflected curved surface based on convolutional neural networks Reviewed

Zhong Zhang, Borui Zhang, Takuma Akiduki, Tomoaki Mashimo, Tianbiao Yu

ICIC Express Letters, Part B: Applications   10 ( 7 )   627 - 634   2019.7

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Language：English   Publishing type：Research paper (scientific journal)  

© 2019, ICIC International. All rights reserved. Surface inspection relying on computer vision has been widely used in many fields. However, the existing computer vision-based industrial parts surface defect detection methods mostly adopt an image registration algorithm. This method is limited by environmental factors, and the image preprocessing process is complex. On the other hand, with the rapid development of deep learning, the appearance of Convolutional Neural Network (CNN) has led to the rapid development of computer vision research based on deep learning. CNNs have excellent performance for image processing and do not require a manual image extraction feature. In this study, the two type CNNs are trained through a large number of pictures, and then they are integrated to an ensemble CNN for the surface defect detection, and encouragement results are obtained.

DOI： 10.24507/icicelb.10.07.627

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A new risk estimation model of bayesian network for adapting to driving environment changing Reviewed

Zhong Zhang, Taira Furuichi, Takuma Ueda, Takuma Akiduki, Tomoaki Mashimo

ICIC Express Letters, Part B: Applications   10 ( 6 )   515 - 521   2019.6

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Language：English   Publishing type：Research paper (scientific journal)  

© 2019, ICIC International. All rights reserved. In recent years, research on automated driving of automobiles is being promoted, and accidents caused by human error by driving support systems are also expected to decrease. However, most of the accidents occur because the risk that the driver feels subjectively is too small. Therefore, to reduce the number of traffic accidents, it is necessary to raise danger perception while driving. There are two kinds of risk in the driving environment: the subjective risk felt by the driver and the objective risk existing in the driving environment. In this research, we construct a model to estimate each risk value by using two pieces of information: traffic environment information obtained from the front image of the vehicle and driving operation information of the driver. Furthermore, by combining them the risk of adapting to the driving environment is determined, and acts to raise drivers’ perception of danger.

DOI： 10.24507/icicelb.10.06.515

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Reachability Improvement of a Climbing Robot based on Large Deformations induced by Tri-Tube Soft Actuators Reviewed

A. Kanada, F. Giardina, T. Howison, T. Mashimo, F. Iida

Soft Robotics   6 ( 4 )   483 - 494   2019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Mary Ann Liebert Inc  

DOI： 10.1089/soro.2018.0115

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Other Link： https://www.liebertpub.com/doi/pdf/10.1089/soro.2018.0115

Mobile Continuum Robot with Unlimited Extensible Sections

Ayato Kanada, Tomoaki Mashimo

IEEE International Conference on Intelligent Robots and Systems   7117 - 7122   2018.12

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Typical continuum robots, such as pneumatic and tendon-driven robots, have a restricted section length and require a large external component for pulleys and a compressor, making them unsuitable for locomotion. This paper presents a new mobile continuum robot design with virtually unlimited extensible sections. A driving unit, which has a mechanism similar to the rack-and-pinion, consists of three DC motors with gears, each of which moves each flexible tube. The rotation of the motor translates the flexible tube, which has a helical groove on the surface that meshes with the gear. The long flexible tube provides a large traveling distance as long as it does not buckle. The elongation and bending motion of each section may be controlled during operation by varying the speed of each flexible tube. This design not only allows the expansion of the robot to otherwise unreachable work areas but also improves the locomotion velocity by generating a large traveling distance of the flexible tubes. The most important point in this paper is to use multiple driving units for locomotion. Since all the driving units can be mounted on the same tubes, by increasing the number of them, the robot can take various forms without expanding its diameter. A preliminary prototype was built, and its crawling locomotion performance was tested using two operating sequences. The results indicate that earthworm-like locomotion can be achieved with good performance by elongating the sections even when the ground is slippery. The proposed design can be easily be rebuilt by anyone with access to a basic 3D printer.

DOI： 10.1109/IROS.2018.8594340

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Dragging motion of a two-link mobile manipulator with large pull force through singular configuration: theoretical analysis and experimental verification Reviewed

Takateru Urakubo, Eri Kitagawa, Xianglong Wan, Tomoaki Mashimo

Advanced Robotics   32 ( 11 )   623 - 634   2018.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/01691864.2018.1476180

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Micro-Flat Ultrasonic Motor for a Miniature Direct-Drive Two-Link Reviewed

K. Miyoshi, T. Mashimo

Advanced Robotics   2018

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Language：English   Publishing type：Research paper (scientific journal)  

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Design and Evaluation of Micro Linear Ultrasonic Motor Reviewed

S. Iduhara, T. Mashimo

Sensors and Actuators A: Physical   278   60 - 66   2018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We propose a micro linear ultrasonic motor, which is one of the smallest linear actuators that can generate practical force. Such a small actuation mechanism can be used for a wide range of applications, such as auto-focus systems used in thinner cell phones and smaller endoscopes. In this paper, we design the micro linear ultrasonic motor and evaluate the performance of the prototype motor. The size of the prototype stator with piezoelectric elements measures 2.6 mm in height, 2.6 mm in width, and 2.2 mm in depth (the length in slider travel direction). There is a hole of 1.4 mm in diameter at the stator center, and the slider inserted into the hole moves back and forth when voltages are applied to the piezoelectric elements. By optimizing the preload between the stator and slider experimentally, the motor thrust force has been improved to over 10 mN, which is a practical force for moving small objects. Experiments clarify the output characteristics in response to the input voltages. Finally, a maximum thrust force of 20 mN has been obtained at applied voltages with an amplitude of 150 Vp-p. (C) 2018 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sna.2018.05.022

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Micro Geared Ultrasonic Motor Reviewed

T. Mashimo, T. Urakubo, Y. Shimizu

IEEE/ASME Transactions on Mechatronics   2018

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Scaling of piezoelectric ultrasonic motors at submillimeter range Reviewed

Tomoaki Mashimo

IEEE/ASME Transactions on Mechatronics   22 ( 3 )   1238 - 1246   2017.6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

The scaling of physical effects is of great interest not only to understand the behavior in microengineering but also to design next-generation micromachines. This study presents the scaling of piezoelectric ultrasonic motors using theoretical and experimental methodologies. The motor performance parameters, such as torque, angular velocity, and efficiency, are modeled to predict how they behave at millimeter to submillimeter scales. Two types of ultrasonic motors are examined as case studies: Typical traveling wave ultrasonic motors using a ring stator and micro ultrasonic motors using a cubic stator. Although the miniaturization of the ring stator is limited because of its complicity, the simple cubic stator design enables miniaturization even up to a side length of 0.5 mm, which is the smallest ultrasonic motor reported to date. Using several prototype micro ultrasonic motors, the scaling of the motor performance parameters predicted by the models are experimentally confirmed. It is shown that the ultrasonic motors are advantageous to other driving-principle-based motors at millimeter to submillimeter range.

DOI： 10.1109/TMECH.2017.2691805

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Miniature preload mechanisms for a micro ultrasonic motor Reviewed

Tomoaki Mashimo

SENSORS AND ACTUATORS A-PHYSICAL   257   106 - 112   2017.4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We propose the smallest preload generation mechanisms that provide force between the rotor and the one cubic millimeter stator in a micro ultrasonic motor. Miniaturizing the preload mechanism is key for implementation of a micro ultrasonic motor with the best performance into micro devices. In this paper, we evaluate two kinds of preloads that exert in the axial and radial directions: an axial preload mechanism and a radial preload mechanism. The experiments clarify how both preload mechanisms improve motor performance measures such as angular velocity, torque, and efficiency. The micro ultrasonic motors with both preload mechanisms generated torque over 10 plslin at the experimentally optimized preload of approximately 6 g. By designing the miniature preload mechanisms using a micro coil spring, the preload mechanisms are miniaturized with similar motor performance. At present, they represent the smallest and most powerful ultrasonic motors with preload mechanisms. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sna.2017.02.009

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Micro Ultrasonic Motor Using a Cube With a Side Length of 0.5 mm Reviewed

Tomoaki Mashimo

IEEE-ASME TRANSACTIONS ON MECHATRONICS   21 ( 2 )   1189 - 1192   2016.4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Actuator miniaturization to submillimeter scales encounters difficult fabrication and serious torque dissipation caused by adhesion forces. This study presents a design for micro ultrasonic motors that enables microfabrication and motor actuation. The stator prototype, which is the smallest ultrasonic motor reported to date, comprises a metallic cube with a side length of 0.5 mm and a through-hole of 0.33-mm diameter at its center, and two piezoelectric elements adhered to its sides. Under two different applied voltages, the stator generates a driving force and transfers it to the rotor inserted in the through-hole. Performance assessments show that this micromotor generates an average angular velocity of 123 rad/s and a peak torque of 0.2 mu N.m. This torque value exceeds that of the existing micromotors.

DOI： 10.1109/TMECH.2015.2511782

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Study of rotary-linear ultrasonic motor output shafts Reviewed

Ayato Kanada, Tomoaki Mashimo, Kazuhiko Terashima

International Journal of Automation Technology   10 ( 4 )   549 - 556   2016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press  

We propose output shafts with a preload generation mechanism to improve the output torque and thrust force of the rotary-linear ultrasonic motor. The stator is comprised of a single metallic cube with a throughhole, and the output shafts are inserted into the hole to generate motion in both its circumferential and axial directions arbitrarily. In this paper, two design concepts for optimizing the preload using the output shafts are examined. The first involves a cylinder shaft with micron-order accuracy diameter realization. The cylinder shaft makes contact with the entire inner surface of the stator and generates a preload between the stator and shaft. The second concept employs a spring shaft having a slightly larger diameter than the stator hole, which expands in the radial direction and generates the preload. Experiments show that these design concepts improve the output torque and thrust force.

DOI： 10.20965/ijat.2016.p0549

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Performance Evaluation of a Micro Ultrasonic Motor Using a One-Cubic-Millimeter Stator Reviewed

Tomoaki Mashimo

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL   62 ( 10 )   1819 - 1826   2015.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A piezoelectric ultrasonic motor has two significant advantages, high energy density and simple structure, and these advantages can help in the miniaturization of the motor. We build a prototype micro ultrasonic motor using a stator with a volume of approximately 1 cubic millimeter. To evaluate its representative performance values (torque, angular velocity, and energy efficiency), we built an experimental setup and operated the prototype motor by varying experimental conditions, such as the preload between the stator and rotor and the amplitude of voltages applied to motor. The performance values obtained at the millimeter to sub-millimeter scale are discussed analytically using the macro scale models of ultrasonic motors. Experimentally, the prototype motor has generated a torque of more than 10 mu Nm with a 1-cubic-millimeter stator. The motor described herein is now the smallest micro ultrasonic motor with a practical torque, although its efficiency is still low.

DOI： 10.1109/TUFFC.2014.006834

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Dynamic Analysis of an Ultrasonic Motor using Point Contact Model Reviewed

T. Mashimo, K. Terashima

Sensors and Actuators A: Physical   233   15 - 21   2015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We propose the dynamic modeling of a traveling wave ultrasonic motor using a point contact model between the stator and rotor. This model can simply and accurately estimate the transient response of the rotor motion. In this paper, we model the dynamic behavior of the motor torque and angular velocity based on the vibration amplitude of the elliptical motion generated in the ultrasonic motor. The use of a recent high-speed camera with a high-power lens (high-speed microscope) enables the observation of elliptical motion and the measurement of vibration amplitudes. We build a synchronous motor drive system including the high-speed microscope and verify the model experimentally. The proposed model has been in good agreement with the experimental results. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sna.2015.05.009

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特異姿勢付近における2リンクロボットアームの動力学的性質に関する考察 Reviewed

浦久保孝光, 万象隆, 真下智昭

システム制御情報学会論文誌   28 ( 9 )   377 - 383   2015

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE INSTITUTE OF SYSTEMS, CONTROL AND INFORMATION ENGINEERS (ISCIE)  

For a serial linkage mechanism, the kinematic relationship between the end effector and the joint angles is nonlinear. The kinematics highly affects the dynamics of the mechanism near singular configurations where the relationship is singular. In this paper, we examine dynamic characteristics of singular configurations for a two-link robot arm, and show that the singular configurations are advantageous in reducing the joint torques necessary to achieve the task of pulling a heavy object.

DOI： 10.5687/iscie.28.377

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Other Link： https://jlc.jst.go.jp/DN/JLC/20015547284?from=CiNii

Study on the Responsiveness of Ultrasonic Motors in Change of Elliptical Motion Reviewed

Takahito Yamashita, Tomoaki Mashimo, Kazuhiko Terashima

Journal of the Robotics Society of Japan   33 ( 9 )   696 - 703   2015

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Robotics Society of Japan  

DOI： 10.7210/jrsj.33.696

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Experimental Verification of Elliptical Motion Model in Travelling Wave Ultrasonic Motors Reviewed

T. Mashimo, K. Terashima

IEEE/ASME Transactions on Mechatronics   20 ( 6 )   2699 - 2707   2015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We propose a model of a traveling wave ultrasonic motor that includes the elliptical motion amplitudes of the stator and verify this model experimentally using a high-speed camera with a high-power lens (i.e., a high-speed microscope). This approach makes it easy to estimate the motor characteristics, such as the rotational speed and torque. In this paper, we build a mechanical model of the stator and rotor that incorporates the elliptical motion amplitudes. The elliptical motion of a few microns at ultrasonic frequencies is captured and measured by the high-speed microscope. When modeling parameters are determined from the observed vibration amplitudes, the model can predict the motor characteristics. We study how the observed elliptical motion is related to the motor output by varying the frequency of applied voltages, and verify the proposed model by comparison with the experimental results.

DOI： 10.1109/TMECH.2015.2392126

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Singularity-Based Four-Bar Linkage Mechanism for Impulsive Torque With High Energy Efficiency Reviewed

T. Mashimo, T. Urakubo, T. Kanade

ASME Journal of Mechanisms and Robotics   7 ( 3 )   2015

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We propose a mechanism that exploits the singular configuration in a closed-loop four-bar linkage that can produce a high impulsive torque (a high torque for a short period in time) at the start of motion and high angular velocity during the successive motion. Such characteristics make the mechanism suitable for executing with high energy efficiency a certain class of tasks, such as lifting heavy objects. In this paper, we define the singularity-based linkage mechanism (SLM), analyze its characteristics of torque generation and energy efficiency theoretically, and then confirm them experimentally by using an SLM prototype. The performance of the SLM is compared with that of a comparable size parallelogram mechanism (PM). It is shown that the energy efficiency of the SLM comes from the fact that it achieves the high acceleration of the output link in the neighborhood of the singular configuration by providing energy with low current and high voltage to the motor; whereas the typical PM requires high current to produce the comparable impulsive torque.

DOI： 10.1115/1.4028930

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Micro ultrasonic motor using a one cubic millimeter stator Reviewed

Tomoaki Mashimo

SENSORS AND ACTUATORS A-PHYSICAL   213   102 - 107   2014.7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Ultrasonic motors are expected to be used as micro-actuators, and the miniaturization of these devices is an interesting subject. We present a micro ultrasonic motor using a stator with a volume of approximately 1 mm(3), which is one of the smallest ultrasonic motors. The stator consists of a metallic cube with a through-hole and piezoelectric elements adhered to its sides; the simplicity of the stator allows it to be miniaturized without special machining processes. The vibration mode that the stator generates for rotation is three waves around the circumference of the hole. This vibration mode can generate certain vibration amplitudes and driving torques even when the stator is miniaturized. In this paper, we build a prototype micro ultrasonic motor and examine its basic characteristics, including impedances and vibration amplitudes. The basic motor performance, such as its torque and rotational speed, is demonstrated experimentally. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sna.2014.03.018

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Piezoelectric Rotational Mixer Based on a First Bending Vibration Mode Reviewed

Tomoaki Mashimo

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL   60 ( 10 )   2098 - 2104   2013.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We propose a miniature piezoelectric mixer that can rotate a liquid inside a hole of several millimeters diameter. The mixer has dimensions 14 x 14 x 10 mm with a through-hole (7 mm), and piezoelectric elements bonded to its four identical sides. When the first bending vibration mode of the mixer is excited by ac voltages, rotational flow of liquid is generated by the rotation of an acoustic field (acoustic streaming) in the through-hole. This technology is useful in automating mixing processes such as the mixing by hand of a few drops of blood in medical testing. In this paper, we verify the driving principle experimentally and examine the characteristics of a prototype mixer, including the induced flow velocity, under changes of the amplitude and frequency of the applied voltages. A plastic test tube, used to prevent contamination, is inserted to the through-hole, and the liquid inside the tube is mixed by rotation of the acoustic field.

DOI： 10.1109/TUFFC.2013.2800

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Spherical ultrasonic motor drive system for camera orientation in pipe inspection Reviewed

Masahiko Hoshina, Tomoaki Mashimo, Naoki Fukaya, Osamu Matsubara, Shigeki Toyama

ADVANCED ROBOTICS   27 ( 3 )   199 - 209   2013.2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We propose a camera actuating system using a spherical ultrasonic motor for inspection of the inside wall of a small pipe. The spherical ultrasonic motor has advantages that include three degrees of freedom, high responsiveness and high accuracy all within a compact body. We describe here the development of an outer rotor spherical ultrasonic motor (OR-SUSM) that enables a camera to rotate by more than 360 degrees along the side of the pipe. All components, including the OR-SUSM, the sensing system, and the electric circuits, are designed to be assembled in the pipe inspection device with outer diameter of 52mm. To control the system, the phase difference and frequency of the applied voltages are used. The rotational direction is determined by the phase difference and the angular velocity is controlled by the frequency. The completed system can be controlled to within 2 degrees in an experimental pipe inspection test.

DOI： 10.1080/01691864.2012.754077

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Vibration Analysis of Cubic Rotary-Linear Piezoelectric Actuator Reviewed

Tomoaki Mashimo, Shigeki Toyama

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL   58 ( 4 )   844 - 848   2011.4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Cubic design of a stator in a rotary-linear piezoelectric actuator is sophisticated and interesting, but the vibration theory of the cubic stator remains unclear when using the finite element method (FEM). In this paper, we analyze the vibration behavior of the cubic stator by applying the energy method, which distinguishes the component of mechanical energy. By changing the design of the stator (especially the length in the direction of the through-hole axis), we clarify how the vibration modes are in accordance at one equal frequency in cubic shape. The behavior of the vibration modes is discussed using conventional vibration theory of a beam and a plate.

DOI： 10.1109/TUFFC.2011.1877

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Rotary-Linear Piezoelectric Microactuator With a Cubic Stator of Side Length 3.5 mm Reviewed

Tomoaki Mashimo, Shigeki Toyama

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL   57 ( 8 )   1825 - 1830   2010.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We report a miniature rotary-linear piezoelectric actuator with a single cubic stator of side length 3.5 mm which can generate rotary motion around the center axis and linear motion in the axial direction. The stator is fabricated as a single metallic cube of side length 3.5 mm with a 2.5-mm-diameter through-hole and four piezoelectric elements bonded to the sides of the stator. The simplicity makes the actuator compact without any special manufacturing. In the design for miniaturization, the modal analysis using the finite element method indicates the natural frequency of the stator from the side length 14 mm to 3.5 mm. In the experiments, rotary motion of 24 rad/s and 2.5 mu Nm were obtained at a resonant frequency of 280 kHz, and linear motion of 80 mm/s and 2.6 mN was observed at 305 kHz by driving the system at an applied voltage of 42 V(rms).

DOI： 10.1109/TUFFC.2010.1621

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Development of spherical ultrasonic motor as a camera actuator for pipe inspection robot

Masahiko Hoshina, Tomoaki Mashimo, Shigeki Toyama

2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009   2379 - 2384   2009.12

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Language：English   Publishing type：Research paper (international conference proceedings)  

We present a pipe inspection robot using a newly developed spherical ultrasonic motor (SUSM) as a camera actuator. The novel SUSM has improved the range of movement compared to previous SUSMs, and the robot can point a camera in any direction. In this study, we determined a method for controlling the rotational direction and strategic control from the kinematics and characteristics of ultrasonic motors. The rotational directions were defined by the phase differences of the applied voltages, and the rotational speeds were changed with the frequencies. Additionally, we developed a very small position sensing system using rotary potentiometers. In the control experiment performed using the sensing system, the SUSM showed the returnability to the default position from several specified points, within an accuracy of 1°. © 2009 IEEE.

DOI： 10.1109/IROS.2009.5354315

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Design and Implementation of a Spherical Ultrasonic Motor Reviewed

T. Mashimo, S. Toyama, H. Ishida

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control   56 ( 11 )   2514 - 2521   2009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We present a mechanical design and implementation of spherical ultrasonic motor (SUSM) that is an actuator with multiple rotational degrees of freedom (multi-DOF). The motor is constructed of 3 annular stators and a spherical rotor and is much smaller and simpler than conventional multi-DOF mechanisms such as gimbals using servomotors. We designed a novel SUSM using experimental data from a single annular stator and a finite element method. The SUSM using a spherical rotor of diameter 20 mm without any reduction gear has demonstrated advantages of high responsiveness, good accuracy, and high torque at low speed. The dynamic implementation of SUSM was consistent with the driving model of SUSM based on a friction drive.

DOI： 10.1109/TUFFC.2009.1338

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単一ステータによる回転直動圧電アクチュエータの開発(第2報)−TRモータの特性− Reviewed

真下智昭, 遠山茂樹

精密工学会誌   2009

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Rotary-Linear Piezoelectric Actuator using a Single Stator Reviewed

T. Mashimo, S. Toyama

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control   2009

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Development of micro ultrasonic motor for surgery Reviewed

S. Toyama, T. Mashimo

Journal of Vibroengineering   11 ( 1 )   27 - 33   2009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOURNAL VIBROENGINEERING  

We present a micro ultrasonic motor having rotary and linear motions for endovascular diagnosis and surgery. The stator prototype is a cube of side 3.5mm, and the main body is fabricated as a single metallic cube with a through-hole at the center. Four piezoelectric elements are bonded to the sides of the stator. When AC voltage is applied to the piezoelectric elements, the circumference of the stator generates elliptical motions. We can obtain the Output from a shaft inserted through the hole. We developed the first prototype of the stator, and determined the rotary-linear motion.

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球面超音波モータを用いたMRI環境下手術支援マニピュレータの開発（第2報）−光ファイバを用いた姿勢センシングの開発− Reviewed

真下智昭, 粟賀宏介, 遠山茂樹

精密工学会誌   74 ( 4 )   400 - 404   2008

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

We present theoretical and experimental analyses of an optical attitude sensing system for an MRI-compatible surgical assist manipulator using a spherical ultrasonic motor. In the system, a laser light passes through an optical fiber to a flat mirror of a spherical rotor; the reflection from the mirror is caught by optical fibers. The observed light intensity is converted to attitude information by a neural network, and the rotation of the spherical rotor is detected. The system uses optical fibers and allows the spherical rotor to be miniaturized and inexpensive. In this report, we developed the optical attitude sensing system and tested the drive of spherical ultrasonic motor with the sensing system. As the result, the attitude sensing resolution was less than 0.5°. The sensing system has indicated the feasibility for the control of the manipulator.

DOI： 10.2493/jjspe.74.400

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超音波を用いた血栓吸引カテーテルの開発 Reviewed

高見沢悟, 真下智昭, 遠山茂樹

ライフサポート学会誌   18   74 - 74   2008

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Society of Life Support Engineering  

DOI： 10.5136/lifesupport.18.Supplement_74

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単一ステータによる回転直動圧電アクチュエータの開発(第1報)−駆動原理と有限要素法を用いたステータの設計− Reviewed

真下智昭, 遠山茂樹

精密工学会誌   2008

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球面超音波モータを用いたMRI環境下手術支援マニピュレータの開発（第1報）−MRI対応球面超音波モータの試作− Reviewed

真下智昭, 遠山茂樹, 石田寛

精密工学会誌   73 ( 2 )   275 - 280   2007

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

In this paper we report the development of a novel actuator for surgical assist manipulator to perform minimally invasive surgery with magnetic resonance imaging (MRI) guidance. The actuator, which is called the spherical ultrasonic motor (SUSM), is constructed of a spherical rotor and three ring-type stators, and has multi-degrees of freedom. In this study, the principle of the SUSM is described. A novel SUSM composed of non-magnetic materials has been constructed, the stator of which was designed using the finite element method. Evaluation of the driving characteristics revealed the SUSM to have good responsiveness and high positioning accuracy. In MRI environment, the noise effects of the SUSM on MRI images were examined. The results demonstrate the feasibility of the surgical assist manipulator using the SUSM.

DOI： 10.2493/jjspe.73.275

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