Electromechanical modelling of overhead cranes

A non-linear electromechanical model describing the dynamical behaviour of overhead cranes is presented. The model takes into consideration the non-linear dependence of the load sway on transients of driving motors during voltage disturbances and start-ups. This is extremely useful in practice since load sway control schemes normally utilize input voltages as control variables. The mechanical subsystem within the model is that of the load sway and has the swing angles and their derivatives as state variables. Each of the two driving motors, namely, the girder motor and the trolley motor, is represented by the classical fifth-order model of induction machines where electrical transients as well as mechanical transients are considered. The model is linearized using Taylor series expansion around a normal operating point. A numerical example is presented to illustrate the usefulness of the results.