Anti-Sway Control on a Harbor Crane System Using a Command Smoothing Iterative Method

Abstract

The requests for relatively large-sized mobile harbor cranes are increasing. Typically, harbor cranes are self-traveling but do not require any additional civil works to improve the bearing strength of foundation soil. This work describes a novel method able to reduce the sway of a suspended load during the slewing motion of a Harbor Crane. The proposed method is based on an iterative calculation of the sway angle, and the corresponding applied velocity profiles as input to the crane motors. The 'command smoothing' method is used to reduce the sway: additional damping is introduced into the system to control the sway. The multiple-input and multiple-output (MIMO) mechanical system is modeled by a set of non-linear differential equations in which the mathematical model is divided into two subsystems: the first for actuated outputs and the second for underactuated outputs. After defining the stability of the proposed solution and the kinematics of the hydraulic actuators on the boom, a detailed mathematical model is developed, taking into account the non-linear components of the forces, such as centrifugal and Coriolis forces, on the system. Simulation results show that the proposed anti-sway method can dampen the suspended load's oscillations during the harbor crane's slewing movement.