Dynamic analysis of the joint movement of derricking mechanism and lifting mechanism of a load during a steady-state turn of a jib crane

Increasing the productivity of jib cranes is an urgent problem of improving their operation. Combining the work of separate mechanisms is one of the ways to increase the productivity of jib cranes. The aim of the study is to build a mathematical model and conduct a dynamic analysis of the crane jib system with simultaneous operation of the derricking mechanism and lifting mechanism of the load during a steady-state crane rotation. Methods for constructing discrete dynamic models of a jib crane by using Lagrange equations of the second kind, numerical methods for solving the obtained differential equations, which are presented in the form of a computer program at a steady-state crane rotation, and methods for dynamic analysis of crane mechanisms are used in the conducted research. The task of researching the dynamics of the simultaneous movement of the mechanisms for turning the boom, extending its section and lifting the load during a steady-state crane turn is solved in the presented work. The method of dynamic analysis was developed to study dynamic processes in the hydro-mechanical system of a jib crane during the simultaneous operation of crane mechanisms. The crane boom system is represented by a dynamic model with six degrees of freedom, which takes into account the main movement of the mechanisms and the oscillations of the links and the load on a flexible suspension. The kinematic, dynamic, and energy characteristics of individual links of the crane jib system with simultaneous operation of several mechanisms are determined on the basis of the constructed mathematical model. The high-frequency oscillations of the drive links of the load lifting mechanism and the low-frequency oscillations of the load on a flexible suspension are investigated. It was found that high-frequency vibrations of the links damped within the start-up process, while low-frequency vibrations of the load practically did not damp and continued throughout the entire movement cycle. Drive modes that ensure smooth movement of the actuators, which leads to reduced loads and increased reliability of the crane are recommended to minimise oscillatory processes of simultaneous movement of the jib system mechanisms.