The container crane represents the link between the containership and the port. It dictates the general conditions for the efficiency of container handling from the ship to the land and vice versa. While containers are handled by the crane, load swing reduces the rate of container turnover. In order to reduce load swing control systems are employed. Closed-loop control systems contain devices to track the position of the load with respect to the trolley's position. Accurate tracking of the load's motion during operation requires additionally installed sensors. Alternatively, the principle of state estimation can be employed. The observation of the motion of the container is carried out by a system model in parallel to the real system, taking into account the available rope force sensor information. Both, nonlinear system model and nonlinear sensor model are taken into consideration. An unscented Kalman filter is designed to estimate the states of the motion of the load. The observer is validated at the container crane test stand in order to provide accurate states for load swing control. Results are presented and discussed.

Oscillation control of container handling is dominated by open-loop or closed-loop control of the crane trolley, which highly effects the crane operator's well-being. An alternative actuating approach is presented using the hoists of the crane system. Simulation and test stand results prove the effect of modal coupling control of container handling and its capability to assure improved work environment conditions for the operator of container cranes. MotivationThe container cranes in ports are exposed to disturbances i.e. load oscillations, trolley movement and wind. In order to increase the throughput one has to assure the load oscillations are avoided. The underactuated container crane does not account for direct load oscillation suppression. The present damping strategies only effect the in-plane load oscillations below the boom but not the out-of-plane nor rotational swing. An alternative approach uses the hoists of the crane for modal coupling for active damping of load swing. This contribution first investigates the modal coupling of the structural response of a container crane and the swinging load, represented by an elastic pendulum. The second part is devoted to the design of a load swing control comprising a 2:1 internal resonance and results are presented. Modal Coupling at Container CranesThe investigation of modal coupling at container cranes is based on a loaded (load swing, trolley, wind) finite element beam model of the crane:The structural displacements arise from the effected mode shapes y i , which are identified by mode decomposition. The jth mode shape y j (see Figure 1, solid crane structure) vertically displaces the container crane boom and thereby may lead to nonlinear coupling with the load oscillations (Figure 1, dashed crane and arrows). This idea originates from [1] and is valid for parametrically excited systems for which the internal resonance condition states:The 2:1 autoparametric resonance relates the vertical oscillation ω el to the load oscillation ω p by ω el = 2ω p . This phenomenon takes place for any possible load swing orientation. Figure 2 depicts the lowest container crane eigenfrequencies f i with respect to the trolley position p along the beam (measured from the landside of the crane). Some modes are effected by this position variation and similar effects are observed for the variance of the load mass m and the pendulum's modulus of elasticity E. The highlighted vertical displacement mode is coupled with the pendulum's load oscillation ω p by the resonance condition. The internal 2:1 resonance only occurs for a certain length L of the load displacement from the crane boom, which can be derived from (acceleration due to gravity g):The maximum length L max does not exceed 3m for any of the varied parameters (p, m, E). This value is small compared to actual hoisting distances of container cranes. Thus we conclude that there exists no structural risk from structure-load interaction from nonlinear coupling of structural displacements and load swing. Load Swing ControlNonl...

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Nearly every cargo that is transported by ship is boxed in standardized containers. The land to ship and ship to land handling of containers is performed by container cranes. These cranes dominate the throughput of the containers in ports. The operators need to be well-trained and skilled because of the requirements of the task to load or unload the ships. During container handling, the crane-load system can be compared to a pendulum of rope length L and deflection φ. It is referred to as an underactuated system. Whenever the fixed point of the pendulum is displaced, the load starts oscillating. In the nonlinear dynamics literature, one finds the field of resonant coupling to transfer energy from actuated controllable modes to underactuated uncontrollable modes. This work presents a novel normal form approach in order to identify the mode coupling. The proposed method decomposes a nonlinear control system into controllable and uncontrollable subsystem. Only the normal form terms in the controllable subsystem are utilized to design a general controller. Simulation results are given to highlight the load oscillation suppression.