Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Construction or agricultural-type vehicle
Reexamination Certificate
2000-10-27
2001-11-13
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Construction or agricultural-type vehicle
C037S414000, C172S002000
Reexamination Certificate
active
06317669
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to an automatically operated shovel, and especially to an automatically operated shovel improved in digging performance.
b) Description of the Related Art
Power shovels are known as a representative example of construction machinery for many years. In recent years, power shovels are designed to perform work by an automated operation when the work consists of repetitions of a series of simple work ranging from digging to hauling or dumping. To permit an automatic operation of a power shovel, however, there are a variety of problems which must be solved.
For example, an object under digging may be soft like soil, may comprise soft portions and hard portions mixed together like soil and rocks, or may comprise only hard portions like rocks cut off from a working face. To assure an efficient, stable operation of an automatically operated shovel under control irrespective of the conditions of the object under digging, certain measures are required.
To meet such requirements, a method is proposed in JP 7-259117 A. This method features generation of control command values in an automatic digging apparatus on the basis of values preset depending on various soil conditions, respectively. These various soil conditions correspond to objects under digging in the present invention. Described more specifically, this apparatus is provided with hydraulic cylinders for operating a boom, an arm and a bucket, respectively, and also with a lookup table having, for example, control characteristics such that the boom is not raised within a range where the pressure of a cylinder for the arm is low but a command value for a boom-raising speed is changed proportionally depending on the condition of soil when the pressure exceeds a predetermined value. It is disclosed that based on a detected arm pressure, a command value is outputted for the control of the boom cylinder in accordance with the corresponding control characteristics set in the lookup table. In this prior art, the lookup table has to be set by making reference to soil conditions from time to time or has to be set separately in a different manner.
The method of the above-described conventional art, therefore, requires advance setting of soil conditions. It is hence necessary to furnish information on the soil conditions by a certain method. For example, with respect to soil and rocks cut out from a working front at a quarry, it is necessary to determine by a suitable method whether the soil and rocks contain more soil or more rocks. No problem arises for this determination in the case of a digging apparatus which is attended by an operator and automatically performs only digging. In the case of a fully operatorless digging apparatus, a system is additionally required to determine conditions of soil, resulting in a more complex and costly digging apparatus. Even if such a system is employed, it is still difficult to determine the kind of an object under digging on a real-time basis when the object under digging is not homogeneous at all like stone-mixed soil.
SUMMARY OF THE INVENTION
With the above-described various problems in view, the present invention has as an object the provision of an automatically operated shovel which can perform optimal servo control at a series of working positions and can effectively perform stable digging irrespective of the kind of an object under digging.
In one aspect of the present invention, there is thus provided an automatically operated shovel having a shovel and an automatic operation controller arranged on the shovel to store by a teaching operation plural working positions of the shovel, which comprises at least a digging position, and also to cause by a reproduction operation the shovel to repeatedly perform a series of reproduction operations on the basis of the stored plural working positions, wherein:
the automatic operation controller is provided with servo control means for outputting, as a servo control quantity, a sum of a compliance control quantity and a pressure control quantity, said compliance control quantity having been obtained by multiplying with a stiffness gain a difference between a target position of each operational element of the shovel, said target position comprising angle information indicative of an operational target of the operational element, and a current position of the operational element, said current position comprising current angle information on the operational element, and the pressure control quantity having been obtained by multiplying with a pressure gain a difference between a target pressure, which serves as a target when the operational element of the shovel is in contact with an object under digging, and a current pressure of the operational element; and the stiffness gain and the pressure gain are settable at varied values depending on the working positions. As the stiffness gain and pressure gain of each operational element of the shovel, that is, the main body of the automatically operated shovel are settable at varied values depending on the working positions, it is possible to perform optimal servo control in the series of reproducing operations by setting optimal stiffness gain and pressure gain for each working position.
As servo control of a boom at the digging position, pressure control may be performed by setting a stiffness gain for the boom at 0 or substantially 0 and a pressure gain for the boom at a first predetermined value before the bucket comes into contact with the object under digging, and compliance control and pressure control may be performed by setting the stiffness gain for the boom at a predetermined value and the pressure gain for the boom at a second predetermined value after the bucket has come into contact with the object under digging. According to this preferred embodiment, the object under digging can be smoothly and automatically dug irrespective of the conditions of the object. Further, the shovel is not jacked up during the digging so that an operatorless, continuous, automatic operation is feasible without positional deviation. Moreover, the digging can be performed with jack-up free, maximum digging force, thereby assuring good operation efficiency. Even if the object under digging varies in height, the digging can be continued following such height variations. If digging loads are low, the bucket can be operated drawing a locus as intended. Even if there is an obstacle on the course of the digging, the bucket can continue the digging by automatically circumventing the obstacle. It is therefore possible to perform the digging work without paying attention to the conditions of the object under digging.
In another preferred embodiment, the predetermined value set as the stiffness gain for the boom after the bucket has come into contact with the object under digging may be set at a value smaller than a value of the stiffness gain set for the boom at a working position other than the digging position. According to this preferred embodiment, the object under digging can be smoothly and automatically dug irrespective of the conditions of the object. Further, the shovel is not jacked up during the digging so that an operatorless, continuous, automatic operation is feasible without positional deviation. Moreover, the digging can be performed with jack-up free, maximum digging force, thereby assuring good operation efficiency. Even if the object under digging varies in height, the digging can be continued following such height variations. If digging loads are low, the bucket can be operated drawing a locus as intended. Even if there is an obstacle on the course of the digging, the bucket can continue the digging by automatically circumventing the obstacle. It is therefore possible to perform the digging work without paying attention to the conditions of the object under digging.
As servo control of aboomat the digging position, pressure control may be performed by setting a stiffness gain for the boom at 0 or substantially 0 and a pressure gain for th
Ishibashi Hideto
Kurenuma Tooru
Nagano Yoshiyuki
Hitachi Construction Machinery Co. Ltd.
Nguyen Tan
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