A prototype of a specialized robotic system for repairing hydraulic turbine blades

This article presents an ongoing R&D project aiming at designing and constructing a specialized welding robotic system for repairing hydraulic turbine blades eroded by cavitation pitting, reducing human risks and increasing the efficiency of the process. The robotic system has a spherical topology with 5 degrees of freedom, electric stepper motors and a 2.5m-diameter workspace. The system has an embedded measurement system with a vision sensor built to produce range images by scanning laser beams on the blade surface. The range images are used to construct 3-D models of the blade surface and locate the damaged spots to be recorded into the robot controller in 3-D coordinates, enabling the robot to repair the flaws automatically by welding in layers. The robot controller and measurement system are built in an FPGA based reconfigurable system. The welding process is the GMAW with a tubular metal cored electrode with a pulsed GMA welding machine.