Suppression of Crane-Load Oscillations Using Shape-Controlled Mechanical Filters

Abstract

In the present study, control of ship board crane-load oscillations using a shape-controlled mechanical filter is investigated. The pivot point about which the load oscillations occur is constrained to follow an actively controlled surface, which is referred to as the mechanical filter. Planar load oscillations in the presence of ship roll motions are considered, and a nonlinear system with nonautonomous terms is used to describe the motions. For the case without shape control, it is shown that with only state feedback applied to the pivot point, it is not possible to stabilize the equilibrium position (i.e., absence of load oscillations and pivot motions). In the presence of shape control, it is shown that it is possible to have an equilibrium position even in the presence of persistent disturbances. A Lyapunov function-based analysis conducted to gain insight into the system dynamics is also presented. Through numerical simulations, it is verified that the equilibrium position is stable over a range of excitation frequencies. Efforts undertaken to examine the system dynamics in the presence of both state feedback applied to the pivot and shape control are also discussed.