DYNAMICS OF SPREADER MOTION IN A GANTRY CRANE

This paper illustrates the steps necessary to model the dynamics of a model rubber-tyred gantry (RTG) crane as used in container-handling op erations. Various modelling criteria are discussed with the emphasis p laced on the importance of non-linear coupling between the chosen syst em coordinates. The machine is treated as three rigid bodies, these be ing the gantry itself, the trolley (which is constrained to lateral mo tion across the top beam) and the spreader. Tyre deformations and stru ctural deflections are not considered in this work. The paper culminat es in three non-linear ordinary differential equations, which are then solved numerically for a variety of different cases. An important fea ture of this work is that the dynamic simulations include complicated gantry motions, not currently designed for, such as combined translati ons and simultaneous rotations. Such motions are more commonly encount ered in mobile robots. However, RTG design needs to move in this gener al direction in the future if significant and potential performance ga ins are actually to be realized in practise. The paper concludes with suggestions for implementation of the dynamic model within a fuzzy log ic control system.