Digital Filter Based Motion Command Preconditioning of Time Varying Suspended Loads in Boom Cranes for Sway Suppression

Abstract

Due to the presence of suspended loads, transient and residual sway is present when a motion command is applied to a crane. Various methods for sway suppression have been proposed, based either on closed loop control or command preconditioning procedures. Among command preconditioning methods, conventional FIR filters, when properly designed, have been shown to present in general extremely robust behavior, combined with the introduction of the minimum possible delay. Thus, these filters are proposed for preconditioning the motion commands of boom cranes, the dynamic response of which is strongly non-linear and time varying, characterized by large variations of the sway natural frequencies. Signal processing techniques are exploited for the analysis of the dynamic response of the crane system, and the results of this analysis are applied for the design of the preconditioning procedures. Two alternative methodologies are presented, aiming at sway suppression of the system, and the minimum possible motion duration. It is shown that the use of filtered inputs effectively suppresses payload sway during and after the mechanism motion, while the smooth nature of the resulting response leads to significant decrease in the stress levels induced on the motors and the structure of the crane.

Keywords

Boom-crane non-linear dynamics time-varying system sway suppression digital filtering

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