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Controlling the sway of the load of a tower crane increases
safety, simplifies its operation, and increases the speed of load
positioning, thereby saving time and money. The development of this
anti-sway controller consists of several parts: modelling the
dynamic crane behaviour, selection of an appropriate control
structure, tuning of the control parameters and validation based on
the developed crane model, implementation of the controller on a
crane, fine tuning and experimental validation of the
performance.
The development of a non-linear dynamic crane model was
completed in 2002. Based on that model, an appropriate control
structure was selected, tested and improved. The selected control
structure consists of two independent adaptive controllers (one for
the tower, and one for the trolley) consisting of model-based
feedforward and 2dof sway angle measurement feedback. The control
parameters are independent of the load, but vary with the length of
the cable. Due to the limited availability of a crane, only the
feedforward controller could be implemented successfully. The
feedforward controller is able to reduce the sway angle by a factor
of 3 or more, which is significant. The main advantages of this
feedforward controller is its simplicity and robustness, and the
fact it requires no sensors. Its main disadvantage is that it can
only avoid load sway induced by the motion of the crane, and cannot
react on disturbances, such as wind. This requires a feedback
controller that will be further developed and implemented in 2004.
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