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Anti-sway controller

It is no secret that all crane movements produced with an attached and suspended load generate vibration. That is why an operator must regularly adjust their actions with due consideration of the generated swaying effect. An experienced and careful operator can relatively quickly reduce the load swaying through adequate countermeasures. And in case the operator has no significant experience or became less attentive due to over-fatigue, even the easiest operations can result in a significant waste of time and produce collision and accident risks.

Different sway prevention systems such as CeSAR free the operator from the need to control load sways and allows them to concentrate on the actual crane steering process, load elevation, its transportation, positioning and descent to the required point.

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Application scope

Sway prevention systems are intended for reducing the load swaying effect caused by acceleration of mechanisms during crane operation. Amortization is achieved by direct influence on the acceleration and braking processes. The sway prevention systems can be used inside the control systems for new cranes, and also as a component of already existing control systems. Sway reduction allows diminishing the collision and accidents and to quickly and precisely place various loads. Such systems can be implemented either for manual crane operations (when cranes are controlled by an operator) and for automated crane systems. CeSAR sway prevention system allows diminishing vibration simultaneously during bridge or trolley movements and crane turns. CeSAR does not require any mechanic damping (amortization) elements.

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There are two basic types of electronic sway prevention systems: the feed-forward systems that incorporate a camera and a reflector (baffler), and provide exact real-time information on load sways, and also the systems based on the mathematical model describing load vibrations during crane movements, i.e. the load deflection angle in any surface is calculated on the basis of various laws of physics and mathematics.

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In the feed-forward systems the incorporated high-resolution camera is used to measure deflections of hooks or other means of load gripping from their normal axis. To make it possible, it is necessary to install a special reflector on the load gripping mechanism. In its simplest configuration, the reflector represents a square-shaped surface with two white squares placed inside of it chequerwise. Such reflectors are called “passive”. In cases they are influenced by excess lighting or shading affecting the accuracy of measurements, it is recommended to use active reflectors equipped with a LED-matrix and a heating assembly to melt snow if used in open spaces. The best option for the “camera-reflector” systems is to implement infrared reflectors equipped with special infrared filters. The precision of vibration detection equals to 5 mm in case the distance between the camera and reflector is 10 m, the distance measurement precision between the camera and reflector is 1%. Such systems can as well eliminate load swaying in case of a strong side wind.

The “blind” sway prevention systems (CeSAR blind) were developed for cranes used in secluded spaces and not subject to outside influences (for example, winds).

Irrespective of the actual sway prevention system installed, their use allows decreasing operation times, increasing the load positioning accuracy, and cutting down operator fatigability and accident risks.

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