Position Measurement of a Crane Spreader using an Image Sensor for Efficient Container Handling

An image sensor that can accurately measure the position and height of a crane spreader has been proposed for suppressing the sway motion generated in the process of manually operating a crane. The image sensor consists of a pair of landmarks attached to the upper surface of the spreader, a CCD camera installed in the trolley on the top of the crane, and a PC, and has the following several advantages. (1) The image sensor is safe for the operators handling cranes due to the passive measurement method. (2) It employs a specific landmark. (3) It uses a robust template matching method “Vector Code Correlation method”, which is suitable for the landmark detection under outdoor light conditions. We verified these features through the fundamental experiments such as the position change of a crane spreader using a moving stage and the illumination condition change. As in the results, we estimated that the absolute error of the image sensor is within 3.3mm in sway motion and within 0.5% while moving from 5m to 20m in height. In addition, we also confirmed the usefulness of the image sensor by applying the measured data to an anti-sway controller on a model crane.