Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Construction or agricultural-type vehicle
Reexamination Certificate
1999-02-19
2001-08-14
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Construction or agricultural-type vehicle
C037S234000, C172S006000, C340S686100
Reexamination Certificate
active
06275757
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an area limiting excavation control system which can perform excavation while limiting an area where a front device is movable, and which is installed in a construction machine having a multi-articulated front device, and particularly, in a hydraulic excavator having a front device comprised of front members such as an arm, a boom and a bucket.
BACKGROUND ART
In a hydraulic excavator, front members such as a boom are operated by an operator manipulating respective manual control levers. However, because the front members are coupled to each other through articulations for relative rotation, it is very difficult to carry out excavation work within a predetermined area by operating the front members. In view of the above, area limiting excavation control systems are proposed in JP, A, 8-333768, WO 95/30059 and WO 95/33100, aiming to facilitate such excavation work.
The area limiting excavation control system for a construction machine disclosed in JP, A, 8-333768 comprises a multi-articulated front device made up of a plurality of front members being rotatable in a vertical direction, a plurality of hydraulic actuators for driving the plurality of front members, a plurality of operating means for instructing operation of the plurality of front members, and a plurality of hydraulic control valves driven upon manipulation of the plurality of operating means and controlling respective flow rates of a hydraulic fluid supplied to the plurality of hydraulic actuators, wherein the control system further comprises area setting means for setting an area where the front device is movable; first detecting means for detecting status variables relating to the position and posture of the front device; first calculating means for calculating the position and posture of the front device based on signals from the first detecting means; second calculating means for calculating the speed of the front device which depends on driving of at least a first particular actuator associated with a first particular front member among the plurality of hydraulic actuators; third calculating means for receiving values calculated by the first and second calculating means and calculating, based on the received values, a limit value of the speed of the front device which depends on driving of at least a second particular actuator associated with a second particular front member among the plurality of hydraulic actuators so that when the front device is inside the set area near the boundary thereof, the moving speed of the front device in the direction toward the boundary of the set area is restricted; and signal modifying means for modifying an operation signal from the operating means associated with the second particular actuator so that the speed of the front device which depends on driving of the second particular actuator will not exceed the limit value. When the front device is inside the set area near the boundary thereof, the third calculating means calculates a limit value of the speed of the front device which depends on driving of the second particular actuator associated with the second particular front member, and the signal modifying means modifies an operation signal from the operating means associated with the second particular actuator so that the speed of the front device which depends on driving of the second particular actuator will not exceed the limit value. Therefore, direction change control is carried out in such a manner as to slow down motion of the front device in the direction toward the boundary of the set area, enabling the front device to be moved along the boundary of the set area. It is hence possible to smoothly and efficiently perform excavation with the boundary of the set area set as a target excavation plane, while a bucket is kept from moving out beyond the boundary of the set area, i.e., the set depth of excavation.
According to the area limiting excavation control system disclosed in WO 95/30059, an area where a front device is movable is set beforehand. A control unit calculates the position and posture of the front device based on signals from angle sensors, and also calculates a target speed vector of the front device based on signals from control lever units. When the front device is inside the set area not near the boundary thereof, the target speed vector is maintained as it is. When the front device is inside the set area near the boundary thereof, the target speed vector is modified to reduce a vector component in the direction toward the boundary of the set area. Hydraulic control valves are then operated so that the modified target speed vector is obtained. As a result, excavation in a limited area can efficiently and smoothly performed.
According to the area limiting excavation control
1
system disclosed in WO 95/33100, in consideration of the fact that the metering characteristic of a hydraulic control valve I(flow control valve) changes depending on the load of a front device in the control system disclosed in WO 95/30059, the function relationship used in a target pilot pressure calculating portion is modified in accordance with change in load of the metering characteristic of the flow control valve, and a target pilot pressure is calculated using the modified function relationship. Highly accurate control can be thus achieved regardless of load change so that a tip of the front device moves as per the target speed vector.
DISCLOSURE OF THE INVENTION
When carrying out excavation work, generally, hardness of the ground to be excavated is not uniform in the whole area to be excavated. The ground often includes an area where hardness is partly increased. There is, for example, such a ground condition that the nature of a part of the ground is harder than the other part, or that stones, concrete, scrap wood, etc. are locally piled in the ground. If the prior art proposed in the above-cited JP, A, 8-333768 is applied to excavation work under such a ground condition, the front device fails to move at the speed of the front device that is calculated by the second calculating means, and the direction change control is no longer performed in an appropriate manner.
Supposing, for example, the case that in a condition By where the front device is extended forwardly of the body of a construction machine, i.e., in a condition where a boom as one component of the front members is moved in the lowering direction and an arm is operated in the rising (dumping) direction with respect to the boom, the arm is moved in the crowding direction to perform excavation work under the area limiting excavation control. In such a case, when a bucket reaches a hard ground portion, the load of an arm driving actuator is increased, whereupon a hydraulic fluid becomes harder to flow into the arm driving actuator. Therefore, the arm performs the crowding operation at a lower speed than commanded. As a result, the speed of the front device calculated by the second calculating means is higher than the actual speed of the front device, and the limit value is calculated based on the relatively higher speed to perform control for moving the boom in the rising direction. Hence, the boom is positioned too high relative to the arm crowding operation, and the locus, along which a bucket tip moves until reaching the boundary of the set area, tends to depart away from the boundary in the rising direction.
For that reason, in the above application example, the bucket cannot sufficiently excavate the hard ground portion and the hard ground portion therefore remains only partly excavated, and an unexpected projection is left on the excavation plane. This has raised the problem that additional work must be performed several times to complete the excavation to the boundary of the set area, and a working time required for forming the target excavation plane is increased to such an extent as to delay the scheduled term of work.
Also, with the prior art proposed in WO 95/30059, when a bucket reaches a hard ground portion under a similar ground condition, a tip
Fujishima Kazuo
Haga Masakazu
Watanabe Hiroshi
Cuchlinski Jr. William A.
Hitachi Construction Machinery Co. Ltd.
Mattingly, Stanger & Malur
Pipala Edward
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