Payload sway suppression in rotary cranes by digital filtering of the commanded inputs

Abstract

A method is proposed for the suppression of the sway of rotary crane payloads. In contrast to closed-loop control methods which encounter significant practical application problems, the proposed method is based simply on the preprocessing of all the commanded crane inputs by a properly designed finite impulse response (FIR) filter. A four-degrees-of-freedom (4DOF) model for the rotary crane system is considered, incorporating both the hoisting and the slewing motions and thus able to handle cases where hoisting can be simultaneously applied to the rotary motion. Although the resulting dynamic system is strongly non-linear and time varying, the method is shown effectively to suppress, in a quite robust, time and energy efficient way, both the transient as well as the residual sway of the payload. Moreover, additional advantages of the proposed method are that no dynamic modelling of the crane is required, and that the applicability of the method is quite easy and general, without the need for any additional instrumentation and control equipment.