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
Hand-Eye Coordination of a Robot for the Automatic Inspection of Steam-Generator Tubes in Nuclear Power Plants
The inspection of steam-generator tubes in nuclear power plants needs to collect test signals in a highly radiated region that is not accessible by humans. In general, a robot equipped with a camera and a test probe is used to handle such a dangerous environment. The robot moves the probe to right below a tube to be inspected and then the probe is inserted into the tube. The inspection signals are acquired while the probe is pulling back. Currently, an operator in a control room controls all the process remotely. To make a fully automatic inspection system, first of all, a control mechanism is needed to position the probe to the proper location. This is so called a hand-eye coordination problem. In this paper, a hand-eye coordination method for a robot has been presented. The proposed method consists of the two consecutive control modes: rough positioning and fine-tuning. The rough positioning controller tries to position its probe near a target place using kinematics information and the known environments, and then the fine-tuning controller tries to adjust the probe to the target using the image acquired by the camera attached to the robot. The usefulness of the proposed method has been tested and verified through experiments.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.