Published papers

An electro-conjugate fluid (ECF) is a kind of low conductivity dielectric fluid, which produces a strong flow when subjected to high DC voltage. ECFs are potentially useful in a variety of applications, including microactuators, microgyroscopes, and CPU liquid cooling systems. However, the biggest hindrance to the commercial development of applications involving ECFs is the lack of theoretical understanding of the fluid flow mechanisms associated with ECFs. This study presents a numerical simulation based on a physical model for the flow of ECFs that arises due to the generation of electric (Maxwell) stress gradients. Validation of the results from the numerical simulation against experimental data obtained using particle image velocimetry (PIV) provides confidence that the model is capable of quantitatively reproducing the flow of these ECFs. (C) 2010 Elsevier B.V. All rights reserved.

チップ上での化学分析や医療診断を目指したμTAS（Micro Total Analysis System）の研究において，流体の駆動や撹拌に必要なマイクロポンプやマイクロミキサの小型化が急がれている．このため，流路の一部を振動子とし，適切な固有振動を励振することによってポンプ／ミキサの機能を選択的実現する微小流体デバイスを提案，開発した．また，実験によって提案手法の有効性を明らかにした．

An electro-conjugate fluid (ECF) is a kind of dielectric fluid which produces a strong jet flow (ECF jet) when subjected to high DC voltage. Namely, a pair of electrodes generates nonuniform electric field, which induces the ECF jet. It is known that some kinds of ECF may possibly produce an impingement jet which occurs between electrodes. This study proposes an impingement type micro fluidic device whose power source is integrated by using the ECF. We developed a prototype and confirmed our concept.

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. 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, 200.3 mm(3), generates maximum pressure of 92.6 kPa and maximum flow rate of 103.0 ml/min. The flexible finger (empty set 5 mm x 30 mm), driven by the ECF pump, bends 150 degrees with a rise time of 1 s. In addition, we construct a master-slave system using the ECF flexible finger and confirm its performance. (C) 2012 Elsevier By. All rights reserved.

This paper presents a novel ungrounded force feedback device which is capable of making the user confuse as if a pulling force is displayed by utilizing non-linear characteristics of human perception. The force feedback device is mainly composed of a spring-mass system and a voice coil motor. By hitting a weight against a wall periodically, the device generates a vibration impact to the user. The device is 140 x 41.5 x 41.5 mm3 with total mass of 230 g. A sensitivity of the pulling force perception are evaluated and presented in this paper. © 2012 Springer-Verlag.

An ultrasonic motor is generally composed of a vibrator and a rotor, and is driven by the frictional force between the vibrator/rotor. Since the contact points on the vibrator draw elliptic trajectory, relative speed of the point against the rotor varies even when the rotor rotates with a constant speed. This may cause abrasion between the vibrator/rotor and decrease in driving efficiency. This research proposes a novel method to reduce the relative speed to improve the driving efficiency of ultrasonic motors by superimposing harmonic vibrations with driving vibration. Results of numerical calculation show that driving efficiency may be improved by 27% by the proposed method.

When developing a multi-fingered robot hand driven by ultrasonic motors (USM), complicated wiring may become one of the essential problems. This study introduces a novel driving method for multiple USMs using superimposed signal input to overcome this problem. First, we designed a robot finger driven by built-in USMs. The robot finger has four joints with three-degree-of-freedom, i.e., DIP joint is dependent to PIP joint. Second, we developed USMs which are suitable for the robot finger actuation. Finally, we developed and characterized the robot finger with the superimposed signal input.

Introducing tactile sensation to robotic system is one of the biggest challenges for robotic researchers. Since several sensations such as audio, visual, force and kinetic sensation have already been installed in robotic systems, tactile sensation may bring a next breakthrough for intelligent systems. Hence, this study proposes a new idea of tactile sensor for robotic systems using a cosmetic powder brush. That is, the brush is used in our system as a tracing element against an object. The vibration during the brush traces an object is measured using a piezoelectric vibration sensor which is attached to the base of brush's bristles. Tracing experiments are conducted with 9 samples of underclothes' fabrics and a paper. Vibration data obtained shows distinct differences between the samples. This may suggest that the cosmetic powder brush could be used as a tracing element of tactile sensor because it can distinguishes a slight difference of texture of objects.

An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a flow (ECF flow) when high DC voltage is subjected. Since it only requires a tiny electrode pair in micrometer-scale size in order to generate ECF flow, ECF is a promising micro fluid pressure source. Hence, by using ECF as the power source, we realize a micro inchworm robot. In this study, first, we have proposed the concept of a novel micro inchworm robot driven by the ECF. Second, we have designed, fabricated and characterized each component of the micro robot. Third, we have developed the micro inchworm robot by using each component. The length, width and mass of the micro robot are approximately 23 mm, 8.5 mm and 1.9 g, respectively. Finally, we observed the characteristics of micro robot with conducting an experiment. Experimental results proved that the micro robot could move on a horizontal acrylic surface with maximum speed of 5.2 mm/s. The micro robot has superior ability in migration speed, compared with previously developed micro inchworm robots. (C) 2014 Elsevier BM. All rights reserved.