Mathematical Model for the Kinematics of a Continuous Ship Unloader

摘要

Unlike traditional portal cranes, a Continuous Ship Unloader (CSU) is not hampered by an intermittent offloading mechanism. The digging foot, consisting of an endless chain with offloading buckets, allows reaching very high capacities when unloading large Panamax vessels carrying iron ore or coal. However, severe problems were reported with the hydraulic control system of the CSU during service. Measurements of cylinder displacements and hydraulic pressures revealed that the digging foot fails to follow the imposed positions. A profound kinematic analysis, presented in this paper, sheds a brighter light on the evolution of the chain length during the transition from idle state to bypass. The aberrations in the calculated chain sag can explain why some imposed positions cannot be obtained by the hydraulic control system.