Damping of oscillations of load lifted by handling equipment

Abstract

This work is aimed at improving the performance of various handling equipment by optimizing the transportation cycle, e.g., decreasing the time of acceleration and deceleration by damping load oscillations, increasing the steady-state motion speed, and decreasing the time of pauses. The object of modeling is an overhead crane with a capacity of 15 ton, a stroke of 15 m, and three degrees of freedom. A Lagrange equation of the first kind as a non-linear heterogeneous system was used. A mathematical analysis of the damping process was carried out by energy balance modeling. As a result, the optimal amplitude and frequency of damping impulses required to change the suspension length within 5% were obtained. These impulses have a maximum frequency of three oscillations per second and are supplied in a reversed phase to load oscillations. According to calculations, energy costs for damping load oscillations are below 3–4% of the lifting motor power. It is shown how damping is implemented in manual control, and coefficients are calculated to define the amplitude of changes in the load and arm suspension length. The ranges of changes in these coefficients comprise 0.85–0.9 and 1.1–1.15 for setting the amplitude and frequency of damping impulses when using an automatic system. On this basis, a load oscillation damping system for a moving overhead crane is developed. Options are proposed for the damping system: by an operator or an automatic control system. The mathematical model of a crane is suitable for studying various types of equipment. Due its high efficiency and relatively low cost, the proposed method of damping is recommended when designing new equipment or improving the existing equipment.