An Automatic Analog Instrument Reading System Using Computer Vision and Inspection Robot

Abstract

Since the manual inspection of analog instruments is inefficient, many computer vision-based automatic reading systems have been proposed recently. However, most of them use fixed cameras that are costly due to a large number of used cameras. Although some other systems adopting the pan–tilt–zoom camera and the movable inspection robot can avoid using many cameras, they have to overcome high computational cost in aligning the camera to the tested instrument. Meanwhile, most existing systems are instrument type-dependent and, hence, cannot handle multiple types of instruments simultaneously. In this article, first, based on an inspection robot, an automatic reading system equipped with a pan–tilt–zoom camera is designed for different types of round-shape analog instruments. Then, a fast camera alignment algorithm based on visual servo is proposed, in which YOLOv3 is applied and improved to locate the instrument and guide the camera to iteratively align with the instrument. Finally, a monocular-vision pointer reconstruction algorithm is proposed to accurately read the instrument. Experimental results demonstrated that our proposed system is fast and reliable in the camera-alignment process and is effective in reading different types of analog instruments during the robot-based inspection.