Published papers

本研究では，繊維強化ゴムチューブの内圧制御に電界共役流体を用いた新たな人工筋アクチュエータを提案した．本流体のポンピングには数100 μmオーダーの微小電極対のみ必要であるため，直径3 mmのマイクロ人工筋アクチュエータを実現した．また，これを2つ並列に配置し片端を弾性ヒンジで連結することによって，マイクロアームを実現した．

ミミズは収縮する体節が直列につながった構造であり，各体節は従走筋と環状筋の働きによって軸方向へ収縮し，径方向には膨張する．本研究では，繊維強化チューブの内圧を電界共役流体に発生するジェット流を用いて変化させ，上記ミミズの体節のような変形を実現する液圧駆動セルを提案し，これを直列に配置したぜん動駆動型マイクロマシンを実現した．

先端が閉じ，断面に120度ごとの扇形チャンバを有するチューブにおいて，各チャンバの内圧を変化させるとチューブ先端に多自由度運動を生成できる．本研究では，電界共役流体に発生するジェット流によってこの内圧を制御した．特に，提案した構造では各チャンバ間においてジェット発生用電極対を介して電界共役流体を移動できるため，タンクとアクチュエータ部を共用化でき，またチャンバ間の差圧を利用できる．実験によってフィンガ先端の多自由度駆動を確認するとともに，先端部での発生力を明らかにした．

Electro-conjugate fluid (ECF) is a kind of functional fluid, which produces jet flow (ECF jet) when subjected to high DC voltage. It is ascertained that a strong ECF jet is generated under nonuniform electric field, for example, around a pair of a needle-electrode and a ring-electrode (a needle-ring electrode pair). This study proposes and develops a novel micro finger with two-DOF motion using ECF jet. First, we propose a concept of novel micro finger driven by ECF jet (ECF micro finger). The ECF micro finger consists of a finger tube with three chambers along its axis and an ECF jet generator with three needle-electrodes and a plate-electrode with three holes. When the ECF jet generated at the ECF jet generator is applied to the chambers of the finger tube, the pressurized chambers expand and the other chambers shrink resulting in the finger tube bending. Next, a large model of the proposed ECF micro finger, with finger tube diameter of 4.5 mm, is fabricated in order to confirm our concept. Finally, we investigate the static characteristics of the large model by experiments. (C) 2006 Elsevier B.V. All rights reserved.

This paper presents a new type of micromotor using electro-conjugate fluid (ECF). An electro-conjugate fluid is a kind of dielectric fluid, which works as a smart fluid. The fluid generates a powerful jet flow, which we call an ECF jet, when subjected to high DC voltage with highly non-uniform electric field, which means, it works as a fluid power source for mechanical components without bulky pumps. We introduce this attractive smart fluid to micromotors in this paper. Inside the motor is filled with the electro-conjugate fluid and a rotor has electrode pairs on the surface. By applying high DC voltage to the electrode pairs, the rotor rotates due to the ECF jet. In this paper, we design several types of electrode pairs and examine each influence on motor performances.

In the present paper, a newly developed ultrasonic brake is proposed. The ultrasonic brake can solve problems of conventional passive elements, such as time delay, instability, and large size, by using unique characteristics of ultrasonic motor, as fast response, silent motion, and non-magnetic feature. It can also be designed to be smaller than conventional elements due to its simple structure. The brake locks or releases the rotor by use of ultrasonic levitation phenomenon. First, we have designed the structure of the ultrasonic brake using an equation of ultrasonic levitation phenomenon, results from structural analysis and finite element (FE) analysis of piezoelectric material of the vibrator. Then we have manufactured the ultrasonic brake and have conducted a driving experiment. Finally, we have demonstrated that the maximum levitation force is around 40 N and the friction torque of the ultrasonic brake is up to 0.38 Nm. Moreover, we have confirmed that both response time and torque/inertia ratio of the ultrasonic brake are much more superior to the conventional ones.

多自由度超音波モータの多くは，複数の固有振動モードの固有振動数を縮退させ，これらの組み合わせによって回転子の多自由度運動を実現していた．この場合，振動設計が複雑となるため，実用上問題が多かった．本研究では，複数の振動子をマトリクス状に配置し，固有振動数が異なる複数の固有振動モードを選択的に組み合わせることによって振動子マトリクス上に置かれた移動子に多自由度運動を生成する新たな多自由度超音波モータを開発した．

As a man-machine interaction increases its importance in the robotic and mechatronic fields, a soft robot, which is inspired from natural systems, becomes one of the most important research trends. There are several research topics related to soft robots such as soft structures or artificial skins, compliance control, soft actuators or artificial muscles, and so on. For the natural muscle potentially has great flexibility, the authors believe that the artificial muscle actuator must be a promising technology for soft robots. Hence in this study, we develop a new type of micro artificial muscle cell, which is an element of an integrated artificial muscle, using electro-conjugate fluid (ECF) and measure its driving performances. In addition, position control characteristics are also clarified by experiments. Experimental results show the micro artificial muscle cell using electro-conjugate fluid has a quite good control performance. (c) 2006 Elsevier B.V. All rights reserved.

直流高電圧の印加によって活発なジェット流を発生する電界共役流体を用いると，単純構造で小型軽量なマイクロモータを比較的容易に構成できる．本研究では，上記マイクロモータの出力パワーの向上を目指して，ジェット発生のための電極形状を改良した．すなわち，従来の棒状電極対に代わって三角形電極を直列に配置し，より不均一な電界の形成および電極密度の向上を試みた．この結果，従来モータに比べて出力パワー密度が約3倍に向上した．

電界共役流体は直流高電圧の印加によって活発なジェット流を発生する機能性流体である．本研究では，断面に中心角120度の扇形チャンバ3つを有する直径4 mmのマイクロフィンガを試作し，各チャンバの内圧を上記ジェット流を用いて制御することによって先端に多自由度運動を実現するマイクロフィンガを開発した．特に，各チャンバ間の配管にバッファを設けることによって電界共役流体に発生するジェット圧力を効率的にフィンガの変形へと変換できることを明らかにした．

In attempt to improve haptic interaction and manipulation technique in surface computers, we propose an interactive haptic feedback display that utilizes 'direct touch' on a surface computer without using a mediation device. The proposed haptic display lets users interact with the virtual objects inside a pressure-sensitive screen directly using a virtual finger as if the user's finger can penetrate through the screen surface and sink in to the digital world inside the screen, as well as receive haptic feedback direct to their fingers from the display. Using the proposed display, users were able to perceive touch sensation with haptic feedback when they come in contact with virtual object surfaces and discriminate different stiffness using vibratory and pseudo-haptic feedback respectively. This innovation creates a new breakthrough in virtual interaction with more accessible and realistic haptic interaction approach for surface computing. © 2012 Springer-Verlag.

An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow (ECF jet) when subjected to high DC voltage. It is known that a strong ECF jet is generated under nonuniform electric field, for example, the field with a pair of needle and ring electrodes. We developed in our previous study a novel five-fingered flexible robot hand using the ECF. In this study, in order to improve the ECF hand we pay our attention to the flexion of palm because human often grasp an object with the flexion of palm. First, we propose a concept of five fingered robot hand which has balloon actuators driven by the ECF jet to produce the flexion of palm. The actuator is mainly composed of silicone rubber membrane and a rubber base with a slit, so that when the actuator is pressurized, the slit is opened, resulting in making the palm of the robot hand actuate. Finally we conduct grasping experiments based on Cutkosky's taxonomy of human grasping, and demonstrate the robot hand can grasp some objects with various shapes without any complex controller. The height, the width and the mass of the robot hand are approximately 70 mm, 40 mm and 40 g, respectively. (C) 2011 Elsevier B.V. All rights reserved.

An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a powerful flow when subjected to high DC voltage. It is known that a strong ECF flow is generated under non-uniform electric field, for example, the field with a pair of needle and ring electrodes. The ECF flow could be used as a micro fluid pressure source (an ECF pump) for actuators including an artificial muscle and a flexible finger etc. However, previous studies on ECF soft actuators only focused on confirmation of the driving principle. This means, an improvement of performance of ECF pumps and a control scheme for ECF soft actuators have yet to be studied in detail. Hence, this study improves the performance of the ECF pump, and proposes a novel control system for an ECF flexible finger. The ECF pump developed in this study generates maximum pressure of 92.6 kPa and maximum flow rate of 103.0 ml/min with 200.3 mm 3. The flexible finger (φ5 mm x 30 mm), driven by the ECF pump, bends 150 deg with a rise time of 1000 ms. In addition, we construct a master-slave system using the ECF flexible finger and confirm its performance. © 2011 IEEE.

An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow (ECF jet) when subjected to high DC voltage. It is known that a strong ECF jet is generated under nonuniform electric field, for example, the field with a pair of needle and ring electrodes. We developed in our previous study a novel five-fingered flexible robot hand using the ECF. In this study, in order to improve the ECF hand we pay our attention to the flexion of palm because human hand can grasp an object with the flexion of palm. First, we propose a concept of five fingered robot hand which has balloon actuators driven by ECF jet to produce the flexion of palm. The actuator is mainly composed of silicone rubber membrane and a rubber base with a slit, so that when the actuator is pressurized the slit is opened, resulting in making the palm of the robot hand actuate. When the actuator is pressurized with 20 kPa the rubber slit is opened with approximately 60 deg. Finally we investigate the characteristics of the actuator and introduce it into the ECF robot hand. © 2011 IEEE.