| In order to attenuate or eliminate crane-load oscillations, the concept of a mechanical filter is introduced and studied. The words “mechanical filter” are used here to mean a device or a set of devices that will lead to suppression or elimination of undesired dynamics of a crane load. This concept is implemented on the basis of the premise that by actively and passively controlling the pivot point about which the load oscillations occur, one can effectively suppress crane-load oscillations. In a planar space and a three-dimensional space, the governing equations of the nonlinear systems without and with the mechanical filter are derived and presented. For the planar case, a filter with generalized geometry is also treated and analytical results obtained on the basis of a Lyapunov function are presented for this system. In the presence of weak harmonic disturbances, perturbation analysis is used to obtain an analytical approximation for the nonlinear response of the crane load. Analytical results obtained in the form of bifurcation diagrams are found to compare well with the corresponding numerical results. For large harmonic, large periodic, and large aperiodic excitations, numerical results are presented to obtain insights into the dynamics of the system with the mechanical filter. Comparisons between responses of systems without and with the filter are presented to demonstrate the potential of the mechanical filter for suppressing crane-load oscillations over a wide range of disturbance parameters. The studies conducted in this dissertation are indicative of the potential for wide applicability of mechanical filters to cranes on fixed and floating platforms. |
