In the hydropower industry, in situ maintenance work of turbine runners to address issues such as cavitation damage and cracking is mainly performed manually. Alternatively, the entire turbine requires disassembly and is repaired off site at greater cost. This paper presents the development and fundamentals of robotic technology designed to perform work in situ on hydroelectric equipment. A second paper surveys field implementations carried out with the technology over the past 15 years. A new portable manipulator was designed with unique track-based kinematics well suited to accessing turbine blades in a confined space. The robot is driven by position-controlled stepper motors but relies on a hybrid force/position controller to perform processes in contact with the work piece, such as grinding. A major obstacle for robotic repair is excessive programming time. As most work is done on curved surfaces, the robot relies on a model of curvilinear space for trajectory generation. The robot is coupled to an accurate measurement system to scan surface topography in three dimensions. It has been equipped to perform several processes, such as welding and grinding, to facilitate the manufacture and maintenance of hydropower equipment. Despite the robot's inaccuracy and flexibility, surface profiles may be reconstructed with great accuracy through the use of a controlled metal removal rate strategy that relies on an innovative dynamic model of the grinding process. C

Field repair work on large hydropower equipment is rarely automated due to the high complexity of the task. Generally, the work is done manually or the equipment is dismantled and repaired off site at greatly added cost and time. This paper surveys work carried out with the SCOMPI robot in the field on large hydropower equipment. SCOMPI is a small, portable, multiprocess, track-based robot. This paper is the continuation of another paper in which the fundamentals of the robot technology are described in greater detail. Over the past 15 years, SCOMPIs have been extensively employed for a variety of field applications on equipment such as turbines, head gates, spillway gates, and penstocks. Initially designed to repair cavitation damage to turbines, the robots are now applied to reinforce turbines or to improve their performance in terms of efficiency. More recently, they have been used for the refurbishment of gates and for the construction of penstocks. C 2011 Wiley Periodicals, Inc.

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This paper presents an innovative technique to repair head gate and spillway gate wheel tracks at a fraction of the cost and time usually required, without compromising quality. A small portable robot is used to rectify the wheel track to within very tight tolerances. This is accomplished by coupling the small and flexible robot to an accurate measurement system to scan the wheel track surface topography. Robotic grinding is then performed, using a controlled metal removal rate strategy to iterate toward the desired target profile. If required, a stainless steel plate can be welded over the existing track with an innovative method involving post-heat treatment and hammer peening. This particular welding procedure was developed due to the high carbon content of the steel of the existing track. The technique was successfully tested on a few occasions on gates owned by Rio Tinto Alcan and Hydro Quebec.

Synopsis:A new approach to optimising production process procedures is applied to the multipass welding of a butt joint with a single V groove, for a range of thicknesses. The process used is CO, gas shielded automatic welding with a 1.6 mm diameter cored wire. The chosen optimisation criterion is the minimum of a performance index based on the weld penetration and section.