Mushtyn D. Optimization of movement modes of mechanisms of luffing and slewing of the tower crane

A set of mathematical models of motion of mechanisms of luffing and slewing of the crane has been developed: one of mechanisms in the steady mode and another starts, at simultaneous start of both mechanisms. The obtained mathematical models are represented by systems of nonlinear differential equations. The analysis of the modes of simultaneous movement of mechanisms showed that the drives of mechanisms during transient modes of movement are overloaded by torque and power (up to 55,4% for the slewing mechanism and up to 44,7% for the luffing mechanism). The steady value of power of the mechanism the crane slewing is proportional to the distance from the trolley to the axis of tower rotation. It was found that the maximum value of the total power of both mechanisms at different initial positions of the trolley on the boom is approximately the same. In addition, the occurrence of pendulum oscillations of the load and their dissipation, which are connected with the effect of centrifugal force, Coriolis force and damping features of the drives, have been studied. The structural-functional scheme of the system of optimal control of the mechanisms of trolley movement and crane slewing is developed. It allows to realize obtained in the work optimal laws of mechanisms motion. They eliminate pendulum oscillations of the load on the flexible suspension. In order to develop a control system that implements the optimal laws, recommendations have been given regarding the selection of microcontroller, flexible suspension length sensor, load weight sensor, boom trolley position and boom angular position sensors, and frequency inverter. In addition, recommendations for selection a data transfer protocol between the devices of the control system have been given. The calculation of the cost-effectiveness of exploitation the system of optimal control of the movement of the trolley, which was based on increasing the capacity of the crane by reducing the load cycle movement, showed that the annual savings for Liebherr 140 hc tower crane is 10035 UAH. Other positive effects from the application of the optimal control system include: increase of energy efficiency of electric drives of mechanisms, increase of durability of elements of mechanisms and decrease of complications of work of the crane operator.