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A newly designed diagnostic robot, Mark II, basically consisting of three modules with a joint between modules has capabilities of straight and spiral movement along the outside of pipelines, and of freely passing over obstacles such as flanges, T-joints and other plant equipment by sensing and recognizing obstacles in from of it; and of controlling its attitude automatically. By calculating the position and orientation of the robot using a transformation matrix, a method of motion control in the passing of T-joints is shown. A method of compensating for the torque generated by gravitational forces is also applied for each module, independently, to keep the holding torque constant, which leads to less vibrations in movement and, hence, yields better diagnostic results. The Mark II equipped with diagnosis sensors can identify the location and depth of flaws on the surface by inspecting pipelines in the spiral-moving mode. The Mark II also has intelligent abilities, such as routing the most efficient path for inspection in plants, provided a plant map has been previously furnished.
HOSOKAI et al. (1987) studied this question.