Drive power minimization of outreach change mechanism of tower crane during steady-state slewing mode

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. We used a dynamic model of the outreach change mechanism for research work, which presented the mechanical system with three degrees of freedom. The formulated variational problem is nonlinear, and so we used the modified PSO-Rot-Ring particle swarm metaheuristic method for its solution. The analytical solution of another variational problem for the same model of the crane mechanism and an optimization criterion close in physical content was used as the solution initial approximation of the nonlinear variational problem to save calculated resources. The starting mode of the mechanism drive for the load outreach change was determined during the solution of the nonlinear variational problem, which ensures the root-mean-square value minimization of the drive motor power. Low- and high-frequency oscillations of the outreach change mechanism elements during the start-up were detected in the optimization process. The first oscillations are caused by the load rocking on the flexible suspension during the start-up, and the second – by the nature of the change in the driving moment and drive power. These oscillations are eliminated in the section of steady-state movement due to the selection of the motion boundary conditions, which are taken into account in the solution process of the variational problem.