Electricity: motive power systems – Positional servo systems – Vehicular guidance systems with single axis control
Patent
1996-02-23
1998-09-01
Ip, Paul
Electricity: motive power systems
Positional servo systems
Vehicular guidance systems with single axis control
3185681, 180167, 180169, 901 1, 364443, 36442401, G05D 100, G05D 102, G05D 103
Patent
active
058015060
DESCRIPTION:
BRIEF SUMMARY
This application is a national stage application, according to Chapter II of the Patent Cooperation Treaty. This application claims the priority date of Jul. 22, 1993, Swedish Patent No. 9302475-0.
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a method and a device for controlling AGV according to the preamble of the enclosed claims 1 and 5 respectively.
There is a widespread demand for rationalization of e.g. cargo handling during trans-shipment from one means of transport to another. This applies to unloading and loading of ships, railway cars, lorrys, containers, aircraft etc. To this end, experiments have been made using Automatically Guided Vehicles, or AGV, which, so far, has demanded an adversely high precision in positioning of the mobile work area, onto which cargo is to be loaded or from which it is to be unloaded.
Generally, this is a problem comprising a number of as such known "spaces" with unknown relative positions, which has meant an obstacle when trying to automate activities to be performed within and between these spaces.
From e.g. WO 90/11561 it is previously known to use AGV for automatic loading and unloading of cargo-carrying vehicles, which are parked at a loading platform or other fixed loading space substantially level with the mobile loading space of the vehicle. As is evident from the known solution, it is necessary that the vehicle has been connected to the loading platform with a relatively high precision. This is because the known loading platform is quipped with photo detectors which sense that reflectors on the load-carrying vehicle are located at a fixed longitudinal as well as angular position relative to the loading platform. The system indicates that the mobile loading area is in a predetermined position relative to the fixed loading area, in which case a "ready" signal is transmitted to the AGV for unloading of the mobile load area. Not until the AGV has passed to the mobile load area, will the navigation, including the position determination of the AGV, be achieved by means of a plurality of reference devices inside the loading area.
The known system has, for it's function, to consider the mobile work area or space as a part of the stationary work area or space, i.e. the mobile space must have an orientation which is fixed relative to the stationary space so that the mobile space forms a part of the stationary space.
The known system described above will certainly tolerate some smaller deviations from an ideal position, but in practice demands that the mobile space is positioned with a high accuracy. A change in the position of the mobile space during on-going loading and unloading may bring about that said space will fall outside of the system tolerances. These disadvantages thus entail time needs for position adaptation and/or costs for special adaptation equipment.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and a device, by which the above drawbacks are eliminated, so that considerably larger positional and angular deviations between different work areas or spaces for AGV are tolerated, whereby the needs for special devices in order to allow automatic loading and unloading are eliminated.
Said object is achieved by a method and a device according to the present invention, the characteristics of which will be apparent from the enclosed patent claims 1 and 2 respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be further described by way of an embodiment example and with reference to the enclosed drawings, in which:
FIG. 1 depicts a schematical view of a cargo transshipment terminal at which the method and device according to the invention is utilized, and
FIG. 2 depicts, in an enlarged view, an AGV unit and a load-carrying unit during on-going loading or unloading.
DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE
The example shown in FIG. 1 is a cargo trans-shipment terminal which in the known way comprises a warehouse 1 for loading in or out of general cargo a
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Apogeum AB
Ip Paul
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