Analysis of derrikingand slewing of the tower crane with consideration to driving mechanisms characteristics

Abstract

The variational problem of the movement mode selection for the load outreach change mechanism during a steady-state tower crane slewing was formulated and solved in the paper, that ensures the minimization of the drive motor power. The variational problem is nonlinear, and so we used the modified PSO-Rot-Ring particle swarm met heuristic method for its solution. Low- and high-frequency oscillations of the outreach change mechanism elements during the start-up were detected in the optimization process. These oscillations are eliminated in the section of steady-state movement due to the selection of the motion boundary conditions.
 In order to increase the productivity during a tower crane exploitation the overlapping of the mechanisms operation is used. The article considers the overlapping of operations of the derriking and slewing mechanisms of the crane. To study the dynamic processes in the joint work of the derriking and slewing of the tower crane, a dynamic model was built. It takes into account the main movement of the derriking and slewing of the crane, as well as oscillation processes in the drive mechanisms and load oscillation on flexible suspension in two planes: in the plane of the derrikingand in the plane of slewing of the crane. The developed dynamic model takes into account the elastic-dissipative characteristics of the transfer mechanisms, as well as the dynamic mechanical characteristics of the drive motors, which describe the transient electromagnetic processes. On the basis of the developed dynamic model with the help of Lagrangeʼs equations six differential equations of the second order which describe a mechanical part of the mechanisms movement were found. In addition, the transient dynamic electromagnetic processes of each of the engines are described by four differential equations. As a result, a system of fourteen differential equations was obtained. It describes the common dynamics of the mechanical part of the crane mechanisms and electromagnetic processes in the electric engines of the derriking and slewing mechanisms. The obtained system of differential equations was solved by numerical methods with the help of developed computer program. For the actual construction of the tower crane in the overlapping work of the derriking and slewing mechanisms, kinematic, power, and energy characteristics were determined, which made it possible to estimate the actual loads in the elements of the construction and drive mechanisms. From the obtained results it was established that the elements of the construction and drive mechanisms are under significant dynamic and energy overloads.High-frequency oscillations of drive mechanisms at the beginning of the movement and low-frequency oscillations of elements of the construction and load were revealed. This significantly reduces the reliability of tower cranes, increases their energy losses, and affects the work of the crane operator and maintenance staff.