Researcher List

Department of Electrical and Electronic Systems Engineering

Decomposition of persistent organic compounds in water using discharge on water

Argon discharge on water
Argon discharge on water

This research investigates the action of hydroxyl radicals for efficient water purification. Hydroxyl radicals generated by the discharge of electrical currents on water have a high oxidation potential but a short lifetime. To simulate the decomposition of persistent organic compounds, we explored the influence of supply gas and discharge power on acetic acid decomposition. Helium was found to be a more effective supply gas than argon for decomposing acetic acid, and the acid was decomposed more quickly as the discharge power was increased.

Purification of exhaust gas from diesel engines to achieve super-clean diesel engines

Exhaust-gas purification system
Exhaust-gas purification system

Extended image

Diesel engines are widely used and have recently attracted considerable attention owing to their relatively low CO2 emission levels. However, conservative exhaust gas purification techniques increase fuel consumption or running cost. Our aim is to develop a purification system with very low, or zero energy penalty. The main methods we explore are pollutant concentration and plasma decomposition, and the figure shows the system. Gas-phase pollutants are concentrated by temperature swing adsorption. The concentrated gas, processed using a plasma reactor, or not processed, is injected into the engine to improve the exhaust gas characteristics and lower fuel consumption.

Application of linear induction motor for maglev system

Maglev transportation system with LIM
Maglev transportation system with LIM

Extended image

Linear induction motors (LIMs) have several merits and thus have many potential applications. In our laboratory, we have focused on applying LIMs for maglev transportation systems. A typical maglev transportation system has independently controlled traction and levitation systems. We have proposed a novel maglev system using only single-sided LIMs (SLIMs) by eliminating the levitation magnets. The attractive and thrust forces of the SLIM are controlled simultaneously and independently. We have proposed the use of a power source with two different frequency components to control these forces, and verified the performance of the proposed system. Maglev systems are expected to help provide quick and efficient public transportation in the future.

Development of high-performance phase-lockedloop circuits in analog integrated circuits

Micrograph of analog IC
Micrograph of analog IC
PLL bread board model
PLL bread board model

In our high frequency circuit design laboratory, we study new architectures for analog integrated circuits, by designing and producing new electric PLL (phase-locked loop ) circuits and data converters.
Recently, long-term variations in device characteristics and reductions in noise immunity are becoming critical issues when designing VLSI circuits. To overcome these problems, we explore new circuit configuration architectures and develop new approaches for the analysis of analog integrated circuits, through the design of GHz-class PLL circuits and data recovery systems, using CAD tools provided by the VDEC (the VLSI design and education center). The following are just two of our many research subjects:

  • Analysis of interference noise in closed-loop circuits
  • Design of high-frequency data recovery systems

Intelligent Robot Design

Quadruped robot with torso structure
Quadruped robot with torso structure

One of the challenging issues in the robotics field is to have robots obtain adaptive and dynamic behavior at low energy and calculation costs. Based on the idea of "Morphological Computation" that seeks to integrate well-balanced designs of controllers and body structures, we focus on animal-like musculoskeletal designs and investigate the effects of different designs on performance and adaptability. We believe that applications of this intelligent design are similar to, but will outperform, conventional sensor-actuator systems that require high energy and calculation costs. Currently, we are investing a quadruped robot with an animal-like torso (pictured), and a sensor-less robot hand driven by pneumatic actuators (artificial muscles).

Research on animals' adaptive motor-functions and application to control systems for autonomous robots

Autonomous Robotics Lab : Research on animals' adaptive motor-functions and application to control systems for autonomous robots

Recent remarkable progress in robot technology has enabled us to build and use various types of mobile robots. Much research on autonomous robots deals with designing robots that will perform dangerous tasks in place of people, such as for rescue missions, planet exploration, and operations in a variety of hazardous environments. Such robots typically require high adaptability and mobility on rough terrain. Biological research during the last few years has made great contributions in clarifying the adaptation mechanisms of animal behavior, and this knowledge inspires us as robotics researchers. The following are two of the themes we are exploring in our laboratory. One is the dynamic analysis of human locomotion, to clarify the control architecture of dexterous behavior by human bodies. Another is to develop biologically-inspired control systems for locomotion robots that can be adapted to unknown environments based on the information processing of neuronal systems.

Road Traffic Control Based on Genetic Algorithm for Reducing Traffic Congestion

Results obtained by computer simulation
Results obtained by computer simulation

Extended image

We have proposed a road traffic control method for reducing traffic congestion, using a genetic algorithm. In the not-too-distant future, systems that control the routes of all vehicles within a certain area may be implemented. Such systems will have to optimize the routes of all vehicles, but the solution space for this kind of problem is enormous. Therefore, to enable obtaining solutions more rapidly, we have applied genetic algorithms that encode the route of all vehicles as fixed length chromosomes.

Flexible ZnO transparent transistor

Fig.1 ZnO-TFTs on a plastic substrate.
Fig.1 ZnO-TFTs on a plastic substrate.

Oxide semiconductors have attracted growing attention as one of the key materials for transparent and flexible electronic devices since they exhibit higher electron mobility than that of amorphous silicon currently used for LCDs. We fabricated high-performance ZnO-based thin-film transistors (TFTs) by pulsed laser deposition (PLD) on a plastic substrate. The PLD fabrication process enables us to obtain both a high transconductance of 7.2 mS/mm and high on/off current ratio of 2.8×106. The transistor operations were confirmed even under a bent condition (Fig. 1).

Development of an intense THz light source

Fig.2 Newly developed THz source outperforms the current THz sources using bulk substrates.
Fig.2 Newly developed THz source outperforms the current THz sources using bulk substrates.

Terahertz (THz) is an electromagnetic spectral region which is locates between "Radio waves" and "Lights". Recently, THz has attracted growing attention for various practical applications for the promotion of a safe and secure society. For this purpose, intense THz emitting devices compact are strongly in demand. We have succeeded in the development of an intense THz emitter using InAs thin films grown on a GaAs substrate. This enables us to develop low-cost and easy-to-use THz emitting devices compared to the currently popular photoconductive switches.