Automatic current control of magnet cranes for steel plate yard automation

This paper presents an automatic current-control method for magnet cranes f or thick steel plate yard automation. In moving the steel plates from stack to stack or from stack to shipping truck, it is difficult to lift the corr ect number of steel plates because the dimensions of the stacked steel plat es are in general different, and their other parameters are not completely known and may even vary in a nonlinear fashion. In this paper, recursive fo rm flux equations are first derived for the thick steel plates, and a curre nt equation is then determined for the magnet coil. Based on these equation s, an adaptive current predictor is developed to exert the right amount of current on the magnet, so as to lift the correct number of steel plates. Wh en the initial trial with this current fails, a current tuning method is in troduced to adjust the current and lift the correct number of plates. The d eveloped magnet current controller has been successfully tested on data obt ained from the storage yard at the Pohang Iron & Steel Co. (POSCO). (C) 199 8 Published by Elsevier Science Lid. All rights reserved.