Gi-Hun Yang

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.

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.

A safe joint with a joint torque sensor

In this study, a safe joint with a joint torque sensor is presented. The safe joint, named “Spring-Clutch”, is a simple passive mechanism that consists of a spring, a cam, and a joint torque sensor. When the torque applied is less than a pre-set threshold, the Spring-Clutch acts as a rigid joint between the input and output. However, if the applied torque exceeds the threshold, the Spring-Clutch is released and acts as a revolute joint, which results in reduction of the collision force to prevent damage of human and robot. After the applied torque is removed, the Spring-Clutch is immediately re-engaged. In addition, a compact joint torque sensor is installed in the Spring-Clutch to measure the torque at the joint. This paper describes the design principles and performance evaluation of Spring-Clutch, and discusses practical applications to a joint mechanism for safe manipulator.

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.

Online retargeting for multi-lateral teleoperation

Retargeting is a kind of mapping function between input of the master device and output of the slave robot. If the slave robot should conduct a teleoperation task like tele-surgery, operation in the space, operation in a dangerous place, the point of the end-effector becomes very important. In this paper, we have developed a retargeting system for teleoperation task, using data glove and vision sensor, and magnetic sensor. The system can sense motion and position of human wrist, hand motion including the fingers. With this system, the user can manipulate teleoperated robotic arm and robotic hand without any difficulties. The proposed system can provide intuitive and precise teleoperation mode. Also, hand gesture-based control mode was investigated using data glove.

Development of vibrotactile cradle for smart cell-phone providing spatial and directional cues

In this paper, we applied famous sensory illusions to generate spatial and directional vibrotactile cues using a vibrotactile cradle for the smart cell-phone. A grooved and slim design is applied to the contact side of the cradle for comfortable gripping, and the contact part consists of twelve vibrotactile areas which can operate independently. To maintain isolation among vibrotactile actuators, the surface of the cover is specially designed to absorb propagating vibration over the surface. The cradles backside consists of twelve linear resonant actuators, a soft covering intersections and supporting area for actuators. For an evaluation of the developed device, two experiments were conducted to test whether directional information and spatial information according to visual data can be successfully displayed by the developed device. As a result, spatial and directional information is useful for displaying intuitive information for smart cell-phone application with the cradle.

Study on measure to shorten work time, through the haptic device in teleoperation system

When controlling the slave device through the teleoperation, the haptic device is often used as the master device. Recently, the image information through the camera and the virtual guide are used for the stability of the teleoperation. In this study, it is assumed that the freedom constraint of the master device will shorten the work time of the teleoperation work and increase the accuracy of the teleoperation work. Experiments were carried out through three kinds of freedom constraint cases and the position data of the master and slave devices were analyzed. Experimental results show that it reduces the working time and increase accuracy for teleoperation work using the freedom constraint of the master device.

Singularity avoidance in teleoperation system through force feedback of master device

The singularity problem, which makes the robot arm in poor kinematic condition, is one of the problems to be considered in teleoperation system. Because the master device is controlled on the remote side, the user has to operate the master device depending on the camera screen that attached to the end-effector of the slave robot or fixed to the specific spot to monitor the working environment. It is difficult to understand the condition of slave robot perfectly because the user controls the slave robot by only depending on the limited view of a camera screen. Although the slave robot approaches to the poor kinematic condition such as singularity position, the operator can proceed without recognizing the situation that is far from the operators intention. In this paper, singularity avoidance of slave robot in teleoperation system is introduced. The system provides helpful information to the operator to feel the singularity information of slave robot that can prevent cases where the results are different from the users intention in teleoperation system.

A novel wireless vibrotactile display device for representing 3DOF force feedback in teleoperation

A vibrotactile display is one of possible methods to supersede force-feedback in teleoperation task. It can apply to an existing teleoperation system such as a master interface which is based on a vision sensor to provide reliable contact force. A novel wireless vibrotactile display device which can perform independently and can be used by constituting a vibrotactile array has been developed in this paper. In addition, it is applied to an existing retargeting system which can sense the position of the human wrist and the hand motions including the fingers using the CyberGlove and a magnetic sensor to implement a bi-lateral teleoperation system. Therefore, a new modified force-feedback method using vibrotactile display in telemanipulation is suggested in this research. With this system, an operator can manipulate a teleoperated robotic arm and a robotic hand without any difficulties, and it also can prevent an object or a slave robot from being damaged. Experimental results show distinguishability of vibrational cueing patterns and the improvement of the performance in telemanipulation.

A novel master interface using vibrotactile display for Bi-lateral teleoperation

Tactile display is one of possible method to replace force-feedback in teleoperation task. It enables size of the master device compact, cost-effective, since there is no need to integrate electrical motor, which has relatively large size, inside the master device. On the other hand, retargeting is a kind of mapping function between input of the master device and output of the slave robot. If the slave robot should conduct a teleoperation task like tele-surgery, operation in the space, operation in a dangerous place, the point of the end-effector becomes very important. In this paper, we have developed a novel retargeting system for teleoperation task, using data glove and vision sensor, magnetic sensor, and vibrotactile display. The system can sense motion and position of human wrist, hand motion including the fingers and it can provide a vibrotactile feedback instead of force-feedback. With this system, the user can manipulate teleoperated robotic arm and robotic hand without any difficulties. The proposed system can provide intuitive and precise teleoperation mode.