Kyungmin Jeong

Development of a snake robot moving in a small diameter pipe

This paper presents a snake robot moving in a small diameter pipe. A snake robot is a multi-linked modular robot. The snake robot, KAEROT-snake IV consists of 11 2-DOF actuator modules, a head, and a tail module. Each of the 2-DOF actuator modules has two small DC motors and worm gear boxes to increase the torque output and an embedded motor controller. The snake robot can move in a small diameter pipe with a sequence of holding motion as well as with a sinusoidal motion. Some modules holds the robot itself by pressing outward to induce friction while the other modules move forward/backward and hold the robot at a more front/rear position. A sequence of holding moves the robot forward/backward in a small diameter pipe.

Water and Ground-Running Robotic Platform by Repeated Motion of Six Spherical Footpads

Bioinspired robotic platforms are based on knowledge from nature. Most robots focus on a single type of locomotion, such as walking or flying. However, multilocomotive robots have recently attracted considerable attention from researchers. In this study, an amphibious robotic platform was developed for operating on water and ground surfaces with a single design. The robot uses spherical footpads to remain on the water surface based on buoyancy and drag forces. Ground walking is also achieved by repeated tripod motion of the spherical footpads. Klann mechanism was adopted and optimized to achieve the footpad motion for stable locomotion on both surfaces. The velocity and pitching angle were analyzed by simulation and experiments at various operating frequencies to validate the performance of the platform. This robot could be applied in nuclear power plant accidents after hydrodynamic-force-based steering by the tail is achieved.

Empirical Study on Shapes of the Foot Pad and Walking Gaits for Water-Running Robots

Recently, various kinds of biomimetic robots have been studied. Among these biomimetic robots, water-running robots that mimic the characteristics of basilisk lizards have received much attention. However, studies on the performance with respect to different geometric parameters and gaits have been lacking. To run on the surface of water, a water-running robot needs sufficient force with high stability to stay above the water. We experimentally measured the performance of the foot pads with different geometric parameters and with various gaits. We measured and analyzed the forces in the vertical direction and rolling angles of five different foot pad shapes: a circular shape, square shape, half-spherical shape, open half-cylinder shape, and closed half-cylinder shape. Additionally, the rolling stabilities of three kinds of gaits: biped, trotting, and tripod, were also empirically analyzed. The results of this research can be used as a guideline to design a stable water-running robot.

VISUAL MEASUREMENT METHOD USING A CIRCULAR GROOVE IMAGE FOR MEASURING INTERNAL DEFECTS OF PIPES IN NUCLEAR POWER PLANT

During the overhaul period of nuclear power plants in Korea, an ROV(Remotely Operated Vehicle) enters the cold-leg pipes connected with the reactor to examine the state of the thermal sleeves and their positions in the safety injection nozzles. To measure the positions of the thermal sleeves or scratches with video images recorded during the examination, time- varying camera parameters should be known, such as the focal length and principal points used for the capturing each video image. In this paper, we propose a camera calibration and measurement scheme by using a single image containing two circular grooves of a cylindrical nozzle whose radius and distance are known.

Development of an underwater manipulator for maintaining nuclear power reactor

The safety and reliability of nuclear power plants has become more important recently. Inspection and maintenance of nuclear power plants should be continuously implemented. However, the limitation of a radiation exposure makes it difficult to work in nuclear power plants. So a robot is very useful to inspect and maintain the components of nuclear power plants because of reducing radiation exposure to human operators and improving reliability of the operation. Particularly, a nuclear reactor vessel is a restricted area because it has a high radiation level under water during an overhaul. An underwater manipulator is needed for detecting and removing a loose part in a nuclear reactor vessel. The loose part, that comes from any failed component or an item left during a construction, refueling or maintenance like metallic parts, bolts, nuts and washers, affects the safety of a nuclear power plant. An underwater manipulator is developed in this study for removing some particles at the bottom of a nuclear reactor vessel and a reactor coolant system. We developed a 5-DOF underwater manipulator. The developed underwater manipulator could work at 30 m under water with the radiation exposure.

Hexapedal Robotic Platform for Amphibious Locomotion on Ground and Water Surface

Bio-inspiration is a starting point from which to design engineering products by learning the secrets of living creatures. We present the design, analysis, and experimental results of a robotic platform inspired by the basilisk lizard, which is well known for its ability to run on water surface. The goal is to develop a robotic platform for amphibious locomotion on ground and water using a single configuration. A tripod gait is achieved with a hexapedal configuration and four-bar-based repeated motion of the legs. The hexapedal configuration is empirically proven to have an advantage in terms of rolling stability on water. On ground, the tripod gait can satisfy the requirements of static stability to make the center of gravity and center of pressure occur at the same position. The footpad design was determined based on an empirical study of the rolling stability and lifting force. The theoretical background and experimental results are presented to validate the ability of the proposed design to run on water and on the ground.

Control of undirected four-agent formations in 3-dimensional space

We investigate a four-agent tetrahedral formation consisting of mobile autonomous agents in 3-dimensional space. The formation shape is required to be maintained only by the given inter-agent distance constraints. We use the gradient control to maneuver the agents to achieve the desired inter-agent distances. We provide analysis on the global behavior of the agents to explain whether or not the agents converge to the desired equilibrium set. Numerical simulation results are also included.

DEVELOPMENT OF A STEAM GENERATOR TUBE INSPECTION ROBOT WITH A SUPPORTING LEG

This paper presents details on a tube inspection robotic system and a positioning method of the robot for a steam generator (SG) in nuclear power plants (NPPs). The robotic system is separated into three parts for easy handling, which reduces the radiation exposure during installation. The system has a supporting leg to increase the rigidity of the robot base. Since there are several thousands of tubes to be inspected inside a SG, it is very important to position the tool of the robot at the right tubes even if the robot base is positioned inaccurately during the installation. In order to obtain absolute accuracy of a position, the robot kinematics was mathematically modeled with the modified DH(Denavit-Hartenberg) model and calibrated on site using tube holes as calibration points. To tune the PID gains of a commercial motor driver systematically, the time delay control (TDC) based gain tuning method was adopted. To verify the performance of the robotic system, experiments on a Framatome 51B Model type SG mockup were undertaken.

A remotely operated mobile robot with modular track mechanisms

This paper introduces a remotely operated robotic system being developed for urban search and rescue. The developed QuadTrack-I has four modular track arms which can be driven independently to get a traction force. The modular track arms can also be rotated with respect to their arm axes to lift the body or step over larger obstacles. The QuadTrack-I can carry a small articulated robot to collapsed areas where victims could be under rubble. QuadTrack-II is also under development to increase the traction power and mobility of QuadTrack-I. This paper describes the structures of the robots and shows some experimental results.

Hexapedal robot for amphibious locomotion on ground and water

Many bio-inspired robots have been developed. Generally, these robots can drive in one environment. It is hard to drive in multiple environments. Therefore, in this study, we developed a robotic platform that can drive in two environments: on the water and the ground. We made a hexapedal robotic platform and analyzed its locomotion when the robot drove on the water and the ground. This analysis considered running speed and pitch motion when the robot drove in the two environments. In addition, we performed an experiment to compare the analyzed results. As a result, this research can be an example to help develop robotic platform amphibious locomotion.