A comprehensive dynamic model of electric overhead cranes and the lifting operations

The design of electric cranes requires knowledge of not only the dynamic loads acting on the mechanisms and the structure, and the movement of the crane and payload during their various operations, but also the electromagnetic characteristics of the control system. This article puts forward a new comprehensive dynamic model for the whole system of electric cranes, which includes the mechanisms, the steel structure, the induction motors, and their drive systems. A general electric overhead travelling crane controlled by two types of control schemes (of changing the rotor resistance and the closed-loop rotor-flux-oriented vector control) during the operation of its lifting mechanism is studied. Hamilton's principle with a modified Lagrangian, and the theory of induction motors and drive systems are combined to build a dynamic model of electric cranes during lifting operations. This model aims at simulating the dynamic behaviour of the mechanical and structural systems for the transient and steady-state behaviour of the induction motors and their control during the operations of a real crane. It can be seen that the dynamic system of the whole crane is highly non-linear and non-stationary even for only the lifting operation.