In a wide-area working site such as quarries and mines, in order to avoid accidents of workers due to fatigue caused by performing the carrying task of earth and sand, to achieve manpower saving and to improve productivity by elongating working hours, unmanned vehicular driving systems for putting unmanned dump trucks in operation in place of manned vehicles such as manned off-road dump trucks have been introduced.
Referring to FIG. 7, in a working site where unmanned dump trucks drive, there are areas called a loading site 1 and an earth unloading site 301. These areas are connected by a well-maintained conveying road called a haul road 302, by a side track called an access road 303 leading from the haul road 302 to each area or by a crossing.
The loading site 1, which is one of the areas, is a place where a loading operation of loading earth and sand onto dump trucks (called “vehicle” in the present invention) is performed, and an excavation operation by working vehicles (called “loader” in the present invention) such as wheel loaders (front-end loaders), backhoes and shovels (for example, hydraulic shovels) and a loading operation of loading earth and sand onto dump trucks are performed.
FIG. 1A illustrates a loading site 1.
Referring to FIG. 1A, a driving path 10 is created along which a vehicle 20 is to drive from an entry point 11 of the loading site 1 to a loading point 12 where a loader 30 exists, and the vehicle 20 is controlled to drive along the created driving path 10.
In this case, the vehicle 20 drives from the entry point 11 to arrive at the loading point 12 by way of a switch-back point 13 located near the loading point 12. In this regard, however, depending on loading patterns, the switch-backing is not always necessary. For example, there is a case in which the vehicle 20 drives from the entry point 11 toward the loader 30 while describing an arc and goes out the loading site 1.
Referring now to FIG. 1B, as the loader 30 such as a wheel loader conducts a movement or the like to a new excavation site, the loading point 12 changes its position accordingly. Incidentally, the reason why the above phrase, “a movement or the like” is used is that there is an occasion in which the loading point 12 changes as the working machine (bucket) swivels while the loader 30 itself is unmoved. For example, there is an occasion in which the loading point 12 moves by changing an approach angle relative to the loader 30 by swiveling the working machine or the like action while the loader 30 is unmoved. That is to say, the loading point 12 will change in the following three actions.
1) movement+swivel
2) movement only
3) swivel only
There is often a case where a loading point 12 changes while the vehicle 20 is driving toward the loading point 12. When the loading point 12 changes, it is necessary to guide the vehicle 20 to a new loading point 12′ by making the vehicle 20 drive along a corresponding new driving path 10′ (shown in dashed line in FIG. 1B).
It is, however, difficult to make the vehicle 20 drive along the new driving path 10′ while the vehicle 20 is driving along the driving path 10 after having passed through the entry point 11. This is because when the vehicle 20 has come sufficiently close to the entry point 11, time required for a computer to perform operations, etc. cannot be secured, which makes it difficult to change the driving paths in a short time. For the same reason, there may be a case where it is difficult to perform an abrupt change control in the driving path even though the vehicle 20 has not passed the entry point 11 yet.
Conventionally, to cope with the positional change in the loading point 12, the vehicle 20 is made stopped before the entry point 11 of the loading site 1 until a movement or the like of the loader 30 is completed so that a new loading point 12′ is established and a new drive path 10′ is created, and after the new drive path 10′ is created, the vehicle 20 is allowed to enter the loading site 1 and drive along the new drive path 10′.
Incidentally, the following patent document 1 discloses that when loading point changes its position, a branching point is established on the drive path in accordance with the change of the position, and a branching path leading to the position changed loading point is created.
Patent document 1: Official gazette of Japanese patent no. 2920017