Research On Key Technology And Prototype Development Of Steam Generator Overhaul Robot

Nuclear power is an important part of human's applied energy, and nuclear power generation accounts for 17% of the world electricity generation. With the implementation of "China's Mid Long Term Development Plan of Nuclear Power", China's nuclear power industry will maintain a sustained and rapid development in the next 20 years, and the demand of nuclear power plant in-service overhaul will increase dramatically. Steam generator (SG) is a key equipment of the nuclear power devices, which connects the primary loop and secondary loop, and it is also one of the equipments which are usually in fault. SG overhaul robot is a key technology among in-service inspection and maintenance of nuclear power station. The research work is from the project of "Development of manipulator arm for In-service overhaul of steam generator primary side" which is supported by the project of "the government financial for high-tech projects". The paper reviews the present situation of SG overhaul robot, further studies system scheme, configuration, kinematics modeling, collision detecting, high-performance joints and so on key techniques of the SG overhaul robot, and develops engineering prototype.In order to meet the needs of different SG and various inspections and maintenance scheduling, a universal SG overhaul robot scheme based on virtual master is proposed. The modular structure of the robot is designed, and different sizes of linkages and foot module can assemble to suitable robot for special SG. The workstation+CAN bus+mutil-DSP based open architecture control system is built. For the virtual master manipulator, the modular virtual master scheme is putted forward.The paper researches the configuration of the SG overhaul robot. According to topological classification based on D-H link parameters,32 categories 3-DOF regional structure are concluded, and the relationship between the regional Jacobian and configuration singularities, as well as configuration load capacity are studied. The paper distinguishes 12 categories of structural singular configurations and 20 categories of non-structural singular configurations, and identifies 10 categories of non-structural singular configurations which have better configuration load capacity. The results of configuration classification are listed in a form that can be used to guide the design work of robot configuration. Combined with the application requirements of SG overhaul, a quasi 7-DOF configuration with the feature of "exchange hand and foot" is designed. To prove the feasibility of the robot installing, the paper puts forward the expression of constrained workspace, solves the constrained workspace by Monte Carlo method, and then obtains the feasible setting area of the robot.For the inverse kinematics problem of redundant robot, a novel inverse solution method of "pseudo-fixed joints" is proposed, and its application conditions are presented accordingly. Combined with the movement characteristics of the robot, the closed-form inverse kinematics equations are established by using the "pseudo-fixed joints" method. Under the operation mode of virtual master-slave, the inverse solutions of collision avoidance are obtained by modifying the angle value of fixed joint timely. Based on geometry modeling method, collision detection between the robot and SG is researched. The geometry model of robot and SG chamber is built, the distance algorithm of geometry model is deduced, and the problem of robot's collision detection is solved by calculating the minimum distance between geometry models.The high-performance robot joint that is suitable for working in the SG water chamber is researched. The robot's accuracy is designed based on error probability model, and the servo precision of the robotic joints is figured out. Aiming at the problem that single resolver is lack of measurement accuracy, a special detection strategy that uses signal combination of dual resolver and high precision harmonic reducer is proposed, and high precision position feedback is achieved. Qualified joint that meets the special requirement of SG overhaul is designed.The experimental platform including SG overhaul robot is put up. Joint module, foot module, and the whole prototype are studied experimentally to verify the correctness of theory analysis and overall scheme. The robot prototype has completed the task of automatic "mechanical plugging" in the simulated field successfully.