Young-Sun Ryuh

A school of robotic fish for mariculture monitoring in the sea coast

This paper presents a multi-agent robotic fish system used for mariculture monitoring. Autonomous robotic fish is designed to swim underwater to collect marine information such as water temperature and pollution level. Each robotic fish has 5 degrees of freedom for controlling its depth and speed by mimicking a sea carp. Its bionic body design enables it to have high swimming efficiency and less disturbance to the surrounding sea lives. Several onboard sensors are equipped for autonomous 3D navigation tasks such as path planning, obstacle avoidance and depth maintenance. A robotic buoy floating on the water surface is deployed as a control hub to communicate with individual robots, which in turn form a multi-agent system to monitor and cover a large scale sea coast cooperatively. Both laboratory experiments and field testing have been conducted to verify the feasibility and performance of the proposed multi-agent system.

Robust mobile robot localization with combined Kalman filter-perturbation estimator

In this paper, a robust localization method for mobile robot based on the combination of Kalman filter and perturbation estimator is presented. It remarkably enhances the robustness of localization performance, specifically when large odometric errors are occurred. The perturbation estimator in the combined Kalman filter (CKF) is to estimate systematic errors which perturbs the behavior of nominal state transition equation. Intrinsically, it has the property of integrating the innovation, i.e., the difference between measurement and predicted measurement and thus gives a chance of more reducing the gap between real states and their estimates. After formulation of the CKF recursion, we show how the design parameters can be determined and how much beneficial it is through simulation and experiment for a two-wheeled mobile robot under indoor GPS.

Design and implementation of user-friendly remote controllers for rescue robots used at fire sites

Many robotic applications have been developed for rescue operations during disasters; these applications involve the use of different types of robots such as fire-fighting robots, rescue robots, and surveillance robots. In this paper, we propose two novel wireless remote controllers that not only offer a user-friendly operating interface but also enable easy control of a robot. The handheld controller can be easily carried by fire-fighters and the joystick-based controller allows more accurate and rapid control for specific tasks in emergency situations. Both controllers are designed to gather situational information such as video feed and temperature and gas concentration data. We analyze the efficiency of the two controllers by carrying out a performance evaluation. To determine the usefulness of these controllers to firefighters, a questionnaire survey was conducted. Based on the opinions of firefighters, we suggest scenarios in which both controllers may be applicable at expected fire sites.

Optimization of Input Parameters by Using DOE for Dynamic Analysis of Bio-inspired Robotic Fish `Ichthus`

Recently, there is a rising interest on studying bio-inspired robotic fish because of real fish’s great maneuverability and high energy efficiency. However, the researches about the robotic fish have not been done so much and there are still lots of problems to use them in the real environment such as in the river. This paper describes a bio-inspired robotic fish ‘Ichthus’ which is developed in KITECH and has 3 DOF propulsive mechanism. We develop the dynamic motion equation of ‘Ichthus’ in the underwater environment and analyze response characteristics of ‘Ichthus’ according to the input parameters of tail fin’s amplitude and oscillation frequency. Then we propose control parameters at the various velocities. These parameters are useful to increase energy efficiency and it can be used when the fish robot moves in the real environment, for example, we can propose proper amplitude and oscillation frequency when the fish robot passes through the narrow space between obstacles.

A Focus on Practical Assessment of MAC Protocols for Underwater Acoustic Communication with Regard to Network Architecture

Abstract Underwater acoustic communication is a rapidly growing research area nowadays and many related studies have already been conducted in recent decades. Underwater acoustic communication can be easily applied to many fields, such as oceanic data collection, undersea exploration, disaster prevention, underwater environmental monitoring, and tactical surveillance. However, there are many challenges associated with underwater communication, including bandwidth limitations, multi-path propagation, padding, long end-to-end propagation delay, high bit error, temporary loss of connectivity, and limited battery power. To overcome these problems, existing implementable MAC protocols need to be classified in terms of network topology. To improve network mobility, two kinds of network topologies, which include cluster-head-based and ad-hoc-based MAC protocols, are considered. In this paper, we summarize some selected MAC protocols and analyze their performance by comparing a number of factors. We obtain experimental results by developing and simulating the existing numerical models of each protocol practically using simulation tools.

Control and design of a 3 DOF fish robot ‘ICHTUS’

Recently, there is a rising interest on studying fish-like underwater robots because of real fishs great maneuverability and high energy efficiency. However, the researches about the fish-like underwater robots have not been done so much and there are still diverse problems in respect of using of the fish robot in the real environment such as in the river. For example, the fish robot has a short operating time and cannot move narrow passage such as swimming between aquatic plants. Therefore, this paper mainly describes a control method according to propulsion algorithm for improving energy efficiency and obstacle avoidance. The fish robot ‘Ichthus’ has a 3-DOF serial link-mechanism and is developed in KITECH. Also, we propose a dynamic equation of the fish robot to use the underwater environment. In the control portion, response characteristics of the fish robot were analyzed according to the input parameters of tail fins amplitude and oscillation frequency. In consequence of this result, Control parameters of robot fish were found. These parameters are useful to increase energy efficiency and it can be used when the fish robot moves in the real environment.

Implementation and navigation of a 3-DOF fish robot ‘Ichthus V5.5’

In recent years, there is a rising interest on studying biomimetic fish-like underwater robots because of advantages from mimicking real fishs great maneuverability and high energy efficiency. However, researches about these kinds of underwater robots have not been investigated so much and there are still diverse problems in respect of using of the robotic fish in the real environment such as in the river for monitoring water pollution. Therefore, this study mainly describes development of a robotic fish which can be used for water quality monitoring system. The robotic fish ‘Ichthus V5.5’ has a 3-DOF serial link-mechanism for its propulsion, which is developed in KITECH. Furthermore, we propose a dynamic equation of the fish robot to use the underwater environment. We added several sensors to navigate autonomously in the real environment like river. Also, we installed two kinds of sensor to detect temperature, electric conductivity, pH (hydrogen ion concentration) of water. Therefore, the developed robotic system can be applied to environmental monitoring system for detect pollution or quality of river.

Angle measurements for mobile robots with filtering of short-term noise in MEMS gyroscopes

This paper presents a simple, yet very effective filtering method to suppress short-term broadband noise in micro-electro-mechanical system (MEMS) gyros for yaw angle measurement with minimized drift. This method is suitable for autonomous indoor mobile robots that use two low-cost sensors: an inertial one, which uses a gyroscope, and an odometric one, which uses encoders mounted on the vehicle’s wheels. The main idea of the proposed approach is consists of two phases: (1) a threshold filter for translational motions, and (2) a moving average filter for rotational motions to reject the broadband noise component that affects short-term performance. Experimental results with the proposed phased method applied to an Epson XV3500 MEMS gyro demonstrate that it effectively suppresses short-term broadband noise and yields accurate yaw angle with minimized drift.

Design and Implementation of a Micro-Modem for Underwater Acoustic Communications

As the interest in ocean environment monitoring and ocean development has been increased, the need for researches on underwater wireless sensor network (UWSN) and low power consuming acoustic modem for UWSN has been arisen. In this paper, we design and implement a micro-modem equipped with a tiny and omnidirectional transducer for underwater acoustic communications. In addition, we make experiments in a water tank and a pond in order to verify the performance of the developed modem in terms of supply voltage and communication distance, and analyze the results. According to the outdoor experiments, the modem can send data wirelessly in underwater at a distance of 40 meter with a data rate of 200 bps and a bit error rate of when the supply voltage is 12 V. Due to its small size, low power consumption and omnidirectional property, it is expected that the modem which is implemented in this paper could be utilized for various applications based on UWSN.

Research and development of an acoustic modem for underwater bio-mimetic fish robots

Acoustic communication is one of the essential technologies for many promising underwater systems. In this paper, we focus on the research and development of an acoustic modem for a real-time water quality monitoring system using bio-mimetic fish robots. Challengeable issues from the viewpoint of acoustic communication for the application are first classified and then the detailed study is conducted to meet each design criterion. Also, the implemented modem hardware is verified in terms of functionality and performance through experiments in a lake and a river.