Real-time Simulation Methods for Robots with a Flexible Arm Based on Computer Graphics Technology

A robot with a flexible arm that is controlled with a remotely operated water-pressure mechanism has been developed for dismantling objects that are heavily contaminated by radioactive materials during decommissioning of nuclear power plants. The objective of this research is to develop a process planning support system and method that can improve the accuracy of estimating the time required by the robot to complete its dismantling activity, support recovery from delays, and determine the feasibility of conducting a dismantling process in the reactor building. Since the flexible arm has a more complex mechanism and shapes those that of multi-axis robots, unique movable arm structures were modeled with a tool for three-dimensional (3D) computer graphics (CG) technology. The 3D CG model was used to make valid operation sequences for planning the motion of the robot. With the help of a prototype system, motion planning can perform to calculate the duration needed for the robot to complete its operation. The calculated duration is then used for updating the planned duration of a specific activity in a dismantling schedule. To plan the robot behaviors for complex dismantling processes, a simplified planning method with few virtual controllers based on a spline inverse kinematics (IK) with a non-uniform rational B-spline (NURBS) curve for an arm comprised of pistons and cylinders pressurized by water was studied. A prototype system for planning the behaviors of the robot was evaluated, and it was confirmed that the movement trajectory of the robot and the three-dimensional isometric display could be visualized using the mesh model generated from point-cloud data used to make the environment model of the robot. It was also confirmed that the operations involved in a specific activity of the robot could be completed within the duration determined in the simulation.