The maintenance procedure is accomplished by usingthe robot to manipulate existing tools. The tools presently usedare a high pressure spray washer, a sandblast nozzle, and a paintnozzle. The motion that the robot needs to perform for the individualtools is quite similar. For sandblasting and spray washing thepath speed and distance from the surface are not critical, butfor painting they are. Painting is the critical operation defining theneeded precision of the arm movement.
Specific tolerances aregiven for the different paint layers from primer to top coat.
These are controlled by nozzle to surface distance, nozzle speedacross surface, and air pressure for spraying. The first twoconditions are controlled by the programming and the third isdetermined by an air pressure regulator set for the given paint,adjustable at the truck. From the truck the air line is run downthe boom of the crane along with the needed paint line. The coating thickness and appearance are used tomeasure the quality of steel bridge painting. These parameters were found to have a strong influenceon the coating thickness and the appearance.