Measurement system design for sway motion based on image sensor

Speedy operation efficiency is constantly required of the container crane operators who work for cargo handling in the port. They are experts in suppressing the sway motion which is generated in the process of the handling. This undesirable motion may deteriorate the operation efficiency due to strained nerves of the operator. Therefore, an anti-sway controller has been required on practical job-site. To accomplish an adequate anti-sway control, sensors are also required to be able to measure the position of a crane spreader moving on. In this paper, we propose a position measurement system with an image sensor. The image sensor detects two devised landmarks attached to the upside surface of a spreader to measure the displacement and height to one. The image processing technique used for the sensor is a kind of robust template matching method, named vector code correlation (VCC), devised to consider the conditions of real environments. We employ the simple mechanism, so that the system can be easily applicable to existing container cranes. The details and performance of the measurement system are introduced together with the experimental results performed with the pilot system. We will also show that the system has the sufficient efficiency and accuracy for the use on practical job-site.