Study of the dynamics of the movement mechanism of an overhead crane as a complex electromechanical system

Abstract

The article studies the dynamics of the crane movement mechanism to take measures for their reliable operation and reduce the wear of movement mechanisms. For this, the following assumptions are accepted: transverse motion is not considered, the dynamics of engines and electric drive is not considered; the crane is presented in the form of a seven–mass system, the load suspension is adopted as rigid.

It has been established that account of flexibility of the rope, with which the load is suspended, does not significantly affect (no more than 10%) the values of the largest dynamic loads in elastic connections; therefore, when determining the loads in the elastic connections of the movement mechanisms, it is possible to use a system with an elastic mechanism and a rigid suspension of the load. The processes in the movement mechanisms of load-lifting cranes are considered, using the calculated seven-mass dynamic scheme of structures. During the mechanism operation the oscillations occur in its metal structures and transmission shafts, in addition, the load sways (which, together with a rope of length L_s, forms a pendulum with a moving suspension point).

The graphs show the forces in the longitudinal, transverse beams of the crane and the linear speeds of wheels, with an external force applied to each wheel of 21700 N. All three types of oscillations have different frequencies, which allows them to be considered on simpler two-mass models. But when using synchronous rotation systems (SRS) on the movement mechanism, which are often prone to oscillations, the proposed model is better suited, because it takes into account the interaction of the SRS and the mechanism at different vibration frequencies. With these loads, the mismatch of the path of the sides Dx_c does not exceed 0,025 m, the relative swing of the load x_l is not more than 0,25 m.

The article found that according to the seven-mass model, when a driving force is applied, mechanical oscillations arise in which three frequencies of interaction are observed. For the crane designs discussed in the article, these frequencies are 0,2, 0,95 and 6,4 Hz; to study a more complete picture of the processes, it is necessary to consider the transverse displacement of the crane and the dynamics of electric drive movement.

The parameters of the calculated scheme for output data of the bridge are determined. Based on obtained results the calculated scheme of crane movement mechanism was constructed. The system is converted into a three-axle, the first of which is the rotor of engine, the second - the first gear together with the coupling, and the third - the axle with two gears.