Traversing hoists – Methods
Patent
1996-02-13
1999-03-09
Brahan, Thomas J.
Traversing hoists
Methods
212275, B66C 1306
Patent
active
058788964
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for controlling the swinging of a hanging load.
It also relates to a device for the implementation of this method.
In the field of the handling and lifting of loads, especially for moving containers using cranes or container gantries, it is very important to move the loads accurately from one point to another, and more particularly to obtain no swinging of the load at the end of its path.
A load, such as a container, suspended using cables from a mobile support consisting, for example, of a motorized trolley designed to move horizontally along the rails of a gantry, forms a pendulum which is generally subjected to a great amount of swinging owing to the high operating speeds which may reach 3 meters per second, and the great length of the lifting cables, lying between 10 and 40 meters.
In reality, there is some damping brought about by the friction of the cables on the pulleys, the elastic deformation of the cables, friction from the surrounding air, etc.
However, this is not sufficient to completely damp out the oscillatory motion of the load and obtain no swinging of the latter at the end of its trajectory.
Patent FR 90-09145 discloses a method for controlling the movement of a hanging load, in which method the actual position of the hanging load is slaved to a theoretical position, the latter satisfying a theoretical law which gives no swinging of the load at the end of its journey.
This method consequently implies that the movement of the mobile support also has to follow a theoretical law deduced from the theoretical movement of the load and the theoretical swinging thereof.
The movement datum for the mobile support is therefore imposed and the slaving method cannot therefore be used for manual operation and arbitrary movement of the mobile support.
Furthermore, the theoretical law governing the movement of the load has to comply with conditions of continuity and of differentiability which, being associated with the conditions at the extremities of the trajectory, restrict the options for choosing this law (the initial position of the trajectory being from the position which the load is moved and the end of the trajectory being the position to which the load is moved). The known slaving method is therefore not applicable to arbitrary movement laws for the load and for the mobile support.
Finally, the condition under which the sway of the load is null is only required at the end of the trajectory and is not a priority provided for while the load is being moved.
The swing of the load may therefore remain very great as it is being moved.
The object of the present invention is to overcome the aforementioned drawbacks and provide numerous advantages in the field of the movement of suspended loads, particularly using dockside lifting gear.
In particular, it makes it possible to move a hanging load, whilst limiting as far as possible the swinging of this load and also eliminating all restrictions in the movement of the mobile support.
The subject of the invention is a method for controlling the swinging of a hanging load suspended from a mobile support, wherein the movement of the mobile support is driven by any speed datum for said support.
According to the invention, this method is one which comprises a step of slaving the actual value of the sway of the hanging load to a zero sway datum and a step of adjusting the speed datum for the support as a function of a correction value determined during the sway slaving step.
Thus, by virtue of the method of the invention, the speed of the mobile support is continually adjusted to constantly maintain a small amount of swinging of the hanging load.
Slaving the sway makes it possible, when moving this load, to take into account all the effects of damping or deflections which may move this load away from its vertical position.
In addition, the movement of this hanging system does not require a reference model. Only the datum regarding the sway of the load is zero, that is to say that the pendulum formed by the load suspended
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patent: 5550733 (1996-08-01), Yun et al.
E. Ohnishi et al., "Automatic Control of an Overhead Crane", Control Science and Technology for the Progress of Society, Aug. 1981, vol. 4, pp. 1885-1890.
DeMoustier Vincent
Eudier Jean-Yves
Brahan Thomas J.
Caillard
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