Sung-Uk Lee

Analysis and Optimal Design of a New 6 DOF Parallel Type Haptic Device

This paper proposes a new haptic device by using a parallel mechanism and a gimbal mechanism. This device has three legs actuated by 2-DOF gimbal mechanisms, which makes the device simple and light by fixing all the actuators to the base. The reference axis of the gimbal mechanism is rotated about the z axis with 45 degrees, which distributes the end-effector load to each actuator uniformly. Three extra sensors are placed at passive joints to obtain a unique solution for the forward kinematics problem. The proposed haptic device is developed for an operator to use it on a desktop in due consideration of the size of an average Korean person. The proposed haptic device has a small workspace for an operator to use it on a desktop and it has more sensitivity than a serial type haptic device. Therefore, the motors of the proposed haptic device are fixed at the base plate so that the proposed haptic device has a better dynamic bandwidth due to a low moving inertia. With this conceptual design, optimization of the design parameters is carried out by using a genetic algorithm. The objective function is defined by the minimum of the global design indices, the global force/moment isotropy index, the global force/moment payload index, and the workspace. Each global index is calculated by a SVD (singular value decomposition) of the force and moment parts of the jacobian matrix. Division of the jacobian matrix assures a consistency of the units in the matrix. Due to the nonlinearity of this objective function, genetic algorithms are adopted for a global optimization

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.

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.

Development of a Robotic System for Searching Human Victims in Disasters

This paper introduces a mobile robotic system being developed for urban search and rescue. In order to search human victims in narrow spaces, we developed two types of serially linked mobile robots, named KAEROT-Centipede and KAEROT-SnakeTV1, that can climb over large vertical steps or travel inside narrow vertical pipes. To send such mobile robots to the disaster areas coping with large obstacles, we also developed a assistant mobile robot, named KAEROT-QuadTrack, that has 4 articulated track modules. This paper describes the mechanical structure and control architecture of the serially linked mobile robots and the supporting configuration for torque reduction of the assistant mobile robot during spinning motion that usually requires large driving torque. The experimental results show that such robotic systems have good mobility over the various terrains in disaster areas.

Development of a Tele-operated Underwater Robotic System for maintaining a light-water type power reactor

The safety and reliability of nuclear power plants is very important. An inspection and maintenance of nuclear power plants should be achieved simultaneously. However, the limitation of a radiation exposure makes it difficult to work in nuclear power plants. Therefore, a tele-operated robotic system is very useful for inspecting and maintaining the components of nuclear power plants because it reduces the level of a radiation exposure to the human operators and it improves the reliability of an operation. A tele-operated underwater robotic system is needed for detecting and removing a loose part in a nuclear reactor vessel. A loose part, which can come 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. In this paper, an underwater robotic system is developed for inspecting the bottom of a nuclear reactor vessel and a reactor coolant system and also for removing some particles in them. In order to evaluate the performance of the developed underwater robotic system, an experiment was performed in a small swimming tank. In the experiments, the developed robotic system could inspect the state of the tank and remove some particles successfully

Design of a heavy-duty manipulator for dismantling of a nuclear power plant

Some of the nuclear power plants in Korea have reached their end of life-cycle, and the importance of developing dismantling techniques has been emphasized. We designed a manipulator for decommissioning a reactor pressure vessel. We analyzed the work environment for disassembly and the workspace of the manipulator, and verified the validity of kinematic variables through a kinematic simulation. We verified through a dynamics simulation that each joint of the designed manipulator can be operated within the maximally allowed torque despite a load of 250 kg. Finally, we verified through the stress analysis that the manipulator is designed to secure at least two times higher safety factor.

Camera calibration and measurement using circular grooves inside pipes

A tele-operated robot should be used to maintain and inspect nuclear power plants to reduce the radiation exposure to the human operators. During an overhaul of the nuclear power plants in Korea, a ROV (remotely operated vehicle) may enter a cold-leg connected to the reactor to examine the state of the thermal sleeves and their positions in the safety injection nozzle. To measure the positions of the thermal sleeves or scratches from the video images captured during the examination, the camera parameters should be identified. However, the focal length of camera could be varied to a close up of the target and the aspect ratio and the center of the image could also be varied with video recording or digitizing devices. So, it is desired to calibrate the intrinsic parameters of the camera and digitizing device with the video images captured during the examination. In the video image of the safety injection nozzle, two or more circular grooves around the nozzle are shown as ellipse contours. In this paper, we propose a camera calibration method using a single image containing two circular grooves of the cylindrical nozzle whose radius and distance are known

A study on the climbing strategy over vertical steps for the QuadTrack-III

This paper introduces a mobile robot named QuadTrack-III developed for urban search and rescue. This robot has four modular tracks which can be driven and lifted independently. Thus the configuration of the robot can be varied for adapting to uneven terrain. Each modular track consists of two sprockets with an attachment chain and two BLDC motors are embedded in the track module. It also includes BLDC motor drivers for each joint. Because the modular track mechanism embodies all of the things required for driving, the weight of the main body is smaller than the tracks. From this feature, the mass center of the robot can be lowered and the distribution of reaction forces can be varied. This paper describes the mechanical structure, the control architecture and a climbing strategy over vertical step for the QuadTrack-III. It also shows some experimental results of the vertical step climbing strategy.

QuadTrack-II:A Remotely Operated Mobile Robot with Four Articulated Tracks

This paper introduces a remotely operated robotic system being developed for urban search and rescue. QuadTrack-II 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. It has some observation module for gathering information of disaster areas. Inside main body frame, it can carry a small serial multi-linked mobile robot to collapsed areas to find human victims under the rubbles. This paper describes the structures of the robot and some advantages of mobile robotic system with articulated modular tracks and shows some experimental result for various environments.