Trajectory Tracking For Boom Cranes Using A Flatness Based Approach

In order to handle the increasing amount and variety of cargo which has to be transshipped in harbors more and more handling equipment such as the LIEBHERR harbor mobile crane (LHM) are used. With this kind of crane, the payload is suspended on a rope, which results in strong load oscillations. Because of safety and performance reasons this load sway should be rejected during and especially at the end of each transfer process. In order to reduce this load sway, it is state of the art to use linear control strategies. It is shown, that in the considered case the dynamics of the boom motion is characterized by some dominant nonlinear effects. Using linear controllers could cause high trajectory tracking errors and insufficient damping of load sway. To overcome these problems, a model based nonlinear control approach is presented. It based on a simplified nonlinear model. This simplified system representation is differentially flat. Because of that, the presented control strategy is based on the state-linearizing method. Additionally it is shown, that the zero dynamics of the not simplified nonlinear control loop guarantees a sufficient damping property. Measurement results are presented to validate the good performance of the nonlinear trajectory tracking controller