A machine vision system for enhancing the teleoperation of an industrial robot

This paper describes a real-time vision system that enhances the teleoperation of a servicing tool used in the heat exchangers of nuclear power plants. The vision system is used to track the position of the tool as it moves over a sheet of tube ends. A map-based strategy is adopted for the estimation of the position. The system incorporates a novel method for a foreshortening correction that is applied prior to map referencing. A hypothesize and verify scheme locates two image features that correspond to two map features. An efficient scheme for extracting image features is developed to locate these two features (tube-end centers) in the image. Two different types of heat-exchanger tube sheets are accounted for. They are those with tube ends placed in a square grid and those with tube ends placed in a triangular grid. The map-based strategy minimizes the cumulative errors in the estimate of the tool head position. The resulting low-cost system has been tested on synthetic and real data. Performance results are given.