Research On Critical Technology Of Nuclear Plant Inspection And Emergence Robot

Nuclear power as the only new clean energy, which can replace fossil fuels on a large scale and be able to achieve industrial application, has received the widespread attention and use of multiple countries around the world. In spite of the high safety and reliability of nuclear power plant, nuclear accident has happened many times in the past few decades which had caused human to suffer quite heavy losses. With the rapid development of nuclear industry, the nuclear plant inspection and emergency robot as an alternative to workers in nuclear irradiation environment has very important social meaning and value. In this thesis, the main line focused on the needs of the practical problems in applications of the nuclear plant inspection and emergency treatment. This thesis studys and analyzes the related researchs of the nuclear plant inspection and emergency robot, including indoor localization, steady climb stairs method and redundancy resolution of dual mobile manipulator when cooperating with each other.Firstly, according to the characteristics of inspection and the particularity of the emergency processing tasks in nuclear plant, a nuclear plant inspection and emergency robot system was designed and developed, including the mobile robot platform, small mechanical arm with four DOF, many kinds of end effectors and teleoperation control box, etc. With small volume and light weight of the robot, it could be able to enter into narrow area. The bus and multi-level electronic control system architecture and the three-tier architecture including communication transmission, control level and device level, could reduce the mutual influence between different levels and improve the reliability of the system. In addition, due to impact on the nuclear radiation environment, nuclear protection such as mechanical block, hardware redundancy and system error correction was designed, which effectively extended the robot’s working hours in the radiation environment.For the indoor localization in the nuclear plant of the robot, a positioning error checking method in nuclear environment with higher efficiency and lower energy consumption was provided based on the dynamic distribution of robot in SE(2) space. After getting the robot dead reckoning dynamic distribution, random interference noise forced on the robot was described through many qualitative experiments. Then, dead reckoning error correction was made by discrete Kalman filter, and then error compensation was given after re-checking by the dynamic distribution, which minimized indoor localization error of the robot. Based on this method, in order to increase the effectiveness of the robot motion in SE(2), control mechanism of robot in SE(2) space was proposed, including selection of criteria thresholds, efficiency and security mechanism and local path optimization mechanisms.For the stair-climb demands during the inspection and emergency tasks in the nuclear plant, ability of the robot climbing stairs was analysed, and plane stability was proposed to define the climb feasibility under random drift when climbing. To identify the climbing sequence status in different processes during climbings, characteristic parameter from the feedback current series of wheel-motors and the flipper-motor was defined and extracted, and prediction of the climbing sequence status was made by using SVM multi-classification, then the result of prediction was checked. According to the change rate of the centroid in climbing process, vertical stability was proposed, and then multi-mode switching control method was provided to make the robot climb stably, cinluding fuzzy control and asynchronous open loop control.For the actual needs of dual robot collaboration, motion analysis of multi redundancy of dual mobile manipulator system is proposed. Regarding the multiple redundant manipulator and the mobile robot platform as a whole to control improved the coordination capacity of the entire robot system. Based on the kinematics combined with mobile platform and manipulator kinematics, the speed kinematic model of mobile manipulator system was deducted. Then a comprehensive analysis of dual end constraints of mobile manipulator system was conducted, and according to the different categories of dual end constraints, different redundancy resolution methods was proposed to solve the redundancy problem. Especially when dual mobile manipulator system co-transfer a sample, the pair of end effectors was within fixed constraints and conflict between the pair always happened due to the motion error. Passive joints were selected to match the motion of initiave joints in order to avoid end conflict.Finally, this thesis gives a conclusion of all the research works and suggests the research task in future.