Faculty Profiles - Mashimo Tomoaki

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

Review: Recent Advances in Micromotors Reviewed

Tomoaki Mashimo, Shunsuke Izuhara

IEEE Access 8 213489 - 213501 2020

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

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

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

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

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

Mobile Continuum Robot with Unlimited Extensible Sections

Ayato Kanada, Tomoaki Mashimo

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

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

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

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

K. Miyoshi, T. Mashimo

Advanced Robotics 2018

Design and Evaluation of Micro Linear Ultrasonic Motor Reviewed

S. Iduhara, T. Mashimo

Sensors and Actuators A: Physical 278 60 - 66 2018

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

Micro Geared Ultrasonic Motor Reviewed

T. Mashimo, T. Urakubo, Y. Shimizu

IEEE/ASME Transactions on Mechatronics 2018

Scaling of piezoelectric ultrasonic motors at submillimeter range Reviewed

Tomoaki Mashimo

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

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

Miniature preload mechanisms for a micro ultrasonic motor Reviewed

Tomoaki Mashimo

SENSORS AND ACTUATORS A-PHYSICAL 257 106 - 112 2017.4

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

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

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

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

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

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

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

Dynamic Analysis of an Ultrasonic Motor using Point Contact Model Reviewed

T. Mashimo, K. Terashima

Sensors and Actuators A: Physical 233 15 - 21 2015

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

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

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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