A new robot system for auto-inspection of intersected welds of pipes used in nuclear power stations

A self-designed new robot system to be employed in the weld inspection of nuclear pipes is introduced in this paper. This robot system can effectively serve as a substitute for a worker who would otherwise be exposed to a hazardous environment. The robot system includes a half clamp as a mounting unit and a half base as circumferential rotation joint. This system can be mounted on a branch pipe at any position. Its arm is designed with six joints for controlling the position and orientation of the ultrasonic probe (USP), which serves as an end-effector. All of these seven joints, which yield seven degrees of freedom (DOF), are driven by stepper motors. The communication between the Industrial Personal Computer (IPC) and Micro Chip Unit (MCU) is based on RS-485, which allows the robot system to be operated and monitored away from a radiative environment and can therefore limit radiation exposure for the operator. Taking the application at different working sites in nuclear power stations into consideration, the design of the system is based on a modular structure, and the substitution of the clamp and base, as well as the adjustment of the size of the arm links are taken into account. Finally, a test unit for the designed robot system is set up, and experiments show that this system could meet the requirements of a real nuclear power station environment.