Patent Application
20220178106
The present disclosure relates to a work machine, a system, and a method of controlling a work machine.
A load within a bucket is important for knowing a workload of a work machine. For example, Japanese Patent Laying-Open No. 2010-89633 (PTL 1) and WO2018/087834 (PTL 2) each disclose a technique for calculating a payload value of a load within a bucket.
In PTL 1, a current payload value of a load is obtained by calculation, based on a posture of a work machine and a pressure applied to a boom cylinder. By integrating the current payload value, an integrated payload value is calculated. When the integrated payload value attains to a target payload value, an operator is notified of that state.
In PTL 2, a payload value of a load within a bucket is corrected based on an acceleration in extension and contraction of a boom cylinder. An error caused by inertia of a work implement based on an operation of a boom, an arm, a bucket, and the like can thus be eliminated from the payload value and measurement accuracy in measurement of a load can be improved.
In works for excavating soil with a work machine such as a hydraulic excavator and loading soil onto a dump truck, a carrying capacity should be equal to or lower than a maximum carrying capacity of the dump truck. As a plurality of times of excavation and a plurality of times of loading onto the dump truck are performed, an operator is notified of a carrying capacity calculated by measuring an amount of soil loaded each time and summing the amounts. In order to measure an amount of soil each time, an angle of the boom, the arm, and the bucket of the work implement and a hydraulic pressure of the boom cylinder are required. Therefore, a sensor is attached to measure an amount of soil in the bucket during a boom raising operation after soil is excavated and loaded in the bucket.
A boom cylinder pressure during the raising operation varies (pulsates) as the boom is operated. Therefore, it is difficult to accurately measure a load.
An object of the present disclosure is to provide a work machine, a system, and a method of controlling a work machine that allow improvement in accuracy in measurement of a load.
A work machine in the present disclosure includes a boom, an arm, a bucket, a boom cylinder, and a controller. The arm is attached to a tip end of the boom. The bucket is attached to a tip end of the arm. The boom cylinder drives the boom. The controller calculates a payload calculation value of a load within the bucket based on load of the boom cylinder, detects an amount of change per unit time in information on at least one of an operation command value for operating the boom cylinder and a speed of extension and contraction of the boom cylinder, and determines a payload value by correcting based on the amount of change per unit time, the payload calculation value obtained by calculation.
According to the present disclosure, a work machine, a system, and a method of controlling a work machine that allow improvement in accuracy in measurement of a load can be achieved.
An embodiment of the present disclosure will be described below with reference to the drawings.
The same or corresponding components in the specification and the drawings have the same reference characters allotted and redundant description will not be repeated. In the drawings, a feature may not be shown or simplified for the sake of convenience of illustration.
The present disclosure is applicable to a work machine other than a hydraulic excavator so long as the work machine includes a boom, an arm, and a bucket. In the description below, “up”, “down”, “front”, “rear”, “left”, and “right” refer to directions with an operator seated in an operator's seat 2b within an operator's cab 2a being defined as the reference.
<Construction of Work Machine>
Travel unit 1 includes a pair of left and right crawler belt apparatuses 1a. Each of the pair of left and right crawler belt apparatuses 1a includes a crawler belt. As a pair of left and right crawler belts is rotationally driven, hydraulic excavator 100 travels.
Revolving unit 2 is provided as being revolvable with respect to travel unit 1. Revolving unit 2 mainly includes operator's cab (cab) 2a, operator's seat 2b, an engine compartment 2c, and a counterweight 2d. Operator's cab 2a is arranged, for example, on the forward left (on a front side of a vehicle) of revolving unit 2. Operator's seat 2b where the operator takes a seat is arranged in an internal space in operator's cab 2a.
Each of engine compartment 2c and counterweight 2d is arranged in a rear portion (on a rear side of the vehicle) of revolving unit 2 with respect to operator's cab 2a. An engine unit (an engine and an exhaust treatment structure) is accommodated in engine compartment 2c. An engine hood covers the top of engine compartment 2c. Counterweight 2d is arranged in the rear of engine compartment 2c.
Work implement 3 is pivotably supported on the front side of revolving unit 2, and for example, on the right of operator's seat 2a. Work implement 3 includes, for example, a boom 3a, an arm 3b, a bucket 3c, a boom cylinder 4a, an arm cylinder 4b, and a bucket cylinder 4c. Boom 3a has a base end pivotably coupled to revolving unit 2 with a boom foot pin 5a being interposed. Arm 3b has a base end pivotably coupled to a tip end of boom 3a with a boom tip end pin 5b being interposed. Bucket 3c is pivotably coupled to a tip end of arm 3b with a pin 5c being interposed.
Boom 3a can be driven by boom cylinder 4a. As a result of this drive, boom 3a can pivot around boom foot pin 5a in an upward/downward direction with respect to revolving unit 2. Arm 3b can be driven by arm cylinder 4b. As a result of this drive, arm 3b can pivot around boom tip end pin 5b in the upward/downward direction with respect to boom 3a. Bucket 3c can be driven by bucket cylinder 4c. As a result of this drive, bucket 3c can pivot around pin 5c in the upward/downward direction with respect to arm 3b. Work implement 3 can thus be driven.
Work implement 3 includes a bucket link 3d. Bucket link 3d includes a first link member 3da and a second link member 3db. A tip end of first link member 3da and a tip end of second link member 3db are coupled to each other as being pivotable relative to each other with a bucket cylinder top pin 3dc being interposed. Bucket cylinder top pin 3dc is coupled to the tip end of bucket cylinder 4c. Therefore, first link member 3da and second link member 3db are coupled to bucket cylinder 4c with the pin being interposed.
First link member 3da has a base end pivotably coupled to arm 3b with a first link pin 3dd being interposed. Second link member 3db has a base end pivotably coupled to a bracket at a root of bucket 3c with a second link pin 3de being interposed.
A pressure sensor 6a is attached to a head side of boom cylinder 4a. Pressure sensor 6a can detect a pressure (a head pressure) of hydraulic oil within a cylinder-head-side oil chamber 40A of boom cylinder 4a. A pressure sensor 6b is attached to a bottom side of boom cylinder 4a. Pressure sensor 6b can detect a pressure (a bottom pressure) of hydraulic oil within a cylinder-bottom-side oil chamber 40B of boom cylinder 4a.
Stroke sensors (sensing units) 7a, 7b, and 7c are attached to boom cylinder 4a, arm cylinder 4b, and bucket cylinder 4c, respectively.
A boom angle θb can be calculated from an amount of displacement of a cylinder rod 4ab with respect to a cylinder 4aa in boom cylinder 4a. An arm angle θa can be calculated from an amount of displacement of a cylinder rod in arm cylinder 4b.
A bucket angle θk can be calculated from an amount of displacement of a cylinder rod in bucket cylinder 4c.
Potentiometers 9a, 9b, and 9c may be attached around boom foot pin 5a, boom tip end pin 5b, and pin 5c, respectively. Boom angle θb can be calculated from a measurement value from potentiometer 9a. Arm angle θa can be calculated from a measurement value from potentiometer 9b. Bucket angle θk can be calculated from a measurement value from potentiometer 9c.
Inertial measurement units (IMUS) 8a, 8b, 8c, and 8d are attached to revolving unit 2, boom 3a, arm 3b, and first link member 3da, respectively. IMU 8a measures an acceleration of revolving unit 2 in a fore/aft direction, a lateral direction, and the upward/downward direction and an angular acceleration of revolving unit 2 around the fore/aft direction, the lateral direction, and the upward/downward direction. IMUS 8b, 8c, and 8d measure accelerations of boom 3a, arm 3b, and bucket 3c in the fore/aft direction, the lateral direction, and the upward/downward direction and angular accelerations of boom 3a, arm 3b, and bucket 3c around the fore/aft direction, the lateral direction, and the upward/downward direction, respectively.
Based on a difference between the acceleration measured by IMU 8a attached to revolving unit 2 and the acceleration measured by IMU 8b attached to boom 3a, an acceleration in extension and contraction of boom cylinder 4a (an amount of change in speed of extension and contraction of boom cylinder 4a) can be obtained.
Though boom angle θb, arm angle θa, and bucket angle θk are measured by the potentiometers in the present embodiment, they may be measured by the IMUS.
<Schematic Configuration of System of Work Machine>
A schematic configuration of a system of the work machine will now be described with reference to
An operation apparatus 25 is arranged in operator's cab 2a. Operation apparatus 25 is operated by an operator. Operation apparatus 25 accepts an operation by the operator for driving work implement 3. Operation apparatus 25 accepts an operation by the operator for revolving revolving unit 2. Operation apparatus 25 provides an operation signal in response to an operation by the operator. Though operation apparatus 25 is, for example, a pilot hydraulic operation apparatus in the present example, it may be an electrical operation apparatus.
A hydraulic pump 33 is driven by drive force from an engine 31. Hydraulic oil delivered from hydraulic pump 33 is supplied to operation apparatus 25. Hydraulic oil supplied to operation apparatus 25 is supplied to various hydraulic actuators 40 through a direction control valve 34 in correspondence with an operation onto operation apparatus 25 by the operator.
As supply and release of a hydraulic pressure to hydraulic actuator 40 is controlled, an operation of work implement 3, revolution of revolving unit 2, and a traveling operation of travel unit 1 are controlled. Hydraulic actuator 40 includes boom cylinder 4a, arm cylinder 4b, and bucket cylinder 4c shown in
Engine 31 is, for example, a diesel engine. Output from engine 31 is controlled by control of an amount of injection of fuel into engine 31 by controller 10.
Hydraulic pump 33 is coupled to engine 31. As rotational drive force from engine 31 is transmitted to hydraulic pump 33, hydraulic pump 33 is driven.
Hydraulic pump 33 is a variable displacement hydraulic pump that includes, for example, a swash plate and varies a delivery capacity as an angle of tilt of the swash plate is varied. Hydraulic oil delivered from hydraulic pump 33 is supplied to direction control valve 34 as being reduced in pressure to a certain pressure by a pressure reduction valve.
Direction control valve 34 is a spool type valve that switches a direction of flow of hydraulic oil, for example, by moving a rod-shaped spool. As the spool moves in an axial direction, an amount of supply of hydraulic oil to hydraulic actuator 40 is regulated. Direction control valve 34 is provided with a spool stroke sensor that detects a distance of movement of the spool (spool stroke).
In the present example, oil supplied to hydraulic actuator 40 for activating hydraulic actuator 40 is referred to as hydraulic oil. Oil supplied to direction control valve 34 for activating direction control valve 34 is referred to as pilot oil. A pressure of pilot oil is referred to as a PPC pressure (pilot hydraulic pressure).
Hydraulic pump 33 may deliver both of hydraulic oil and pilot oil. For example, some of hydraulic oil delivered from hydraulic pump 33 may be reduced in pressure by the pressure reduction valve and hydraulic oil reduced in pressure may be used as pilot oil. Hydraulic pump 33 may separately include a hydraulic pump (a main hydraulic pump) that delivers hydraulic oil and a hydraulic pump (pilot hydraulic pump) that delivers pilot oil.
Operation apparatus 25 includes a first control lever 25R and a second control lever 25L. First control lever 25R is arranged, for example, on the right of operator's seat 2b. Second control lever 25L is arranged, for example, on the left of operator's seat 2b. Operations in front, rear, left, and right directions onto first control lever 25R and second control lever 25L correspond to biaxial operations.
For example, boom 3a and bucket 3c are operated by operating first control lever 25R. An operation onto first control lever 25R in the fore/aft direction corresponds, for example, to an operation of boom 3a, and an operation to raise boom 3a and an operation to lower boom 3a are performed in accordance with the operation in the fore/aft direction. An operation onto first control lever 25R in the lateral direction corresponds, for example, to an operation of bucket 3c, and an operation in the upward/downward direction of bucket 3c is performed in accordance with the operation in the lateral direction.
For example, arm 3b and revolving unit 2 are operated by operating second control lever 25L. An operation in the fore/aft direction onto second control lever 25L corresponds, for example, to an operation of arm 3b, and the operation of arm 3b in the upward/downward direction is performed in accordance with the operation in the fore/aft direction. An operation onto second control lever 25L in the lateral direction corresponds, for example, revolution of revolving unit 2, and a right revolution operation and a left revolution operation of revolving unit 2 are performed in accordance with an operation in the lateral direction.
In the present example, an operation to raise boom 3a is also referred to as a raising operation and an operation to lower boom 3a is also referred to as a lowering operation. Operations of arm 3b in the upward/downward direction are also referred to as a dumping operation and an excavation operation, respectively. Operations of bucket 3c in the upward/downward direction are also referred to as a dumping operation and an excavation operation, respectively.
The operations in the lateral direction onto first control lever 25R may correspond to the operation of boom 3a and the operation in the fore/aft direction may correspond to the operation of bucket 3c. The fore/aft direction of second control lever 25L may correspond to the operation of revolving unit 2 and the operation in the lateral direction may correspond to the operation of arm 3b.
Pilot oil delivered from hydraulic pump 33 and reduced in pressure by the pressure reduction valve is supplied to operation apparatus 25.
Operation apparatus 25 and direction control valve 34 are connected to each other through a pilot oil channel 450. A PPC pressure is regulated based on contents of an operation onto operation apparatus 25. As operation apparatus 25 is operated, a PPC pressure corresponding to the contents of operation onto operation apparatus 25 is supplied to direction control valve 34 through pilot oil channel 450. Direction control valve 34 is thus regulated to regulate a direction of flow and a flow rate of hydraulic oil supplied to boom cylinder 4a, arm cylinder 4b, and bucket cylinder 4c, so that operations in the upward/downward direction of boom 3a, arm 3b, and bucket 3c are performed.
A pressure sensor 36 is arranged in pilot oil channel 450. Pressure sensor 36 detects a PPC pressure. A result of detection by pressure sensor 36 is provided to controller 10. The PPC pressure regulated by an operation onto operation apparatus 25 and detected by pressure sensor 36 corresponds to an operation command value in the present embodiment.
Though shown in a simplified manner in
For example, when boom 3a is operated, pressure sensor 36 that detects increase in PPC pressure in the operation to raise boom 3a is different from pressure sensor 36 that detects increase in PPC pressure in the operation to lower boom 3a. For example, pressure sensor 36 that detects increase in PPC pressure in the dumping operation by arm 3b is different from pressure sensor 36 that detects increase in PPC pressure in the excavation operation by arm 3b. For example, when bucket 3c is operated, pressure sensor 36 that detects increase in PPC pressure in the dumping operation by bucket 3c is different from pressure sensor 36 that detects increase in PPC pressure in the excavation operation by bucket 3c.
An amount of increase in PPC pressure is different depending on an angle of tilt of each of control levers 25L and 25R from a neutral position. Thus, contents of the operation onto operation apparatus 25 can be determined based on a result of detection of the PPC pressure by each pressure sensor 36.
Detection signals from stroke sensors 7a to 7c, IMUs 8a to 8d, potentiometers 9a to 9c, and pressure sensors 6a and 6b are also provided to controller 10.
Controller 10 may electrically be connected to each of stroke sensors 7a to 7c, IMUs 8a to 8d, potentiometers 9a to 9c, and pressure sensors 6a, 6b, and 36 through wires, or may wirelessly communicate therewith. Controller 10 may be implemented, for example, by a computer, a server, or a portable terminal, or by a central processing unit (CPU).
<Functional Block in Controller 10>
A functional block in controller 10 will now be described with reference to
Operation command value obtaining unit 11 receives input of a signal indicating a PPC pressure detected by pressure sensor 36. Operation command value obtaining unit 11 detects, for example, an operation command value for operating boom cylinder 4a from the signal indicating the PPC pressure detected by pressure sensor 36. The operation command value obtained by operation command value obtaining unit 11 is provided to storage 14 and stored therein.
Boom cylinder extension and contraction speed obtaining unit 12 receives input of a signal indicating an acceleration or the like detected by each of IMUs 8a to 8d. Boom cylinder extension and contraction speed obtaining unit 12 detects an acceleration in extension and contraction of boom cylinder 4a (an amount of change in speed of extension and contraction of boom cylinder 4a), for example, based on a difference between the acceleration detected by IMU 8a attached to revolving unit 2 and the acceleration detected by IMU 8b attached to boom 3a.
Boom cylinder extension and contraction speed obtaining unit 12 receives input of signals indicating amounts of displacement of the cylinder rods or angles of the work implement (boom angle θb, arm angle θa, and bucket angle θk) detected by stroke sensors 7a to 7c. Boom cylinder extension and contraction speed obtaining unit 12 detects a speed of extension and contraction of boom cylinder 4a, for example, based on an amount of displacement of the cylinder rod or an angle of the work implement (boom angle θb) detected by stroke sensor 7a.
Boom cylinder extension and contraction speed obtaining unit 12 receives input of signals indicating angles of the work implement (boom angle θb, arm angle θa, and bucket angle θk) detected by potentiometers 9a to 9c. Boom cylinder extension and contraction speed obtaining unit 12 detects a speed of extension and contraction of boom cylinder 4a, for example, based on an angle of the work implement (boom angle θb) detected by potentiometer 9a.
The speed of extension and contraction (or the amount of change in speed of extension and contraction) of boom cylinder 4a detected by boom cylinder extension and contraction speed obtaining unit 12 is provided to storage 14 and stored therein.
Payload calculation value arithmetic unit 13 receives input of signals indicating a head pressure and a bottom pressure of boom cylinder 4a detected by pressure sensors 6a and 6b. Payload calculation value arithmetic unit 13 receives input of signals indicating amounts of displacement of the cylinder rods or angles of the work implement (boom angle θb, arm angle θa, and bucket angle θk) detected by stroke sensors 7a to 7c. Payload calculation value arithmetic unit 13 receives input of signals indicating angles of the work implement (boom angle θb, arm angle θa, and bucket angle θk) detected by potentiometers 9a to 9c.
Payload calculation value arithmetic unit 13 calculates a payload calculation value from the provided signal. The payload calculation value calculated by payload calculation value arithmetic unit 13 is transmitted to storage 14 and stored therein.
Change amount obtaining unit 15 obtains an amount of change per unit time in information on at least one of the operation command value for operating boom cylinder 4a and the speed of extension and contraction of boom cylinder 4a, from information stored in storage 14.
Change amount obtaining unit 15 obtains the amount of change per unit time in operation command value for operating boom cylinder 4a, for example, from the signal indicating the PPC pressure obtained by operation command value obtaining unit 11 and stored in storage 14.
Change amount obtaining unit 15 obtains the amount of change per unit time in speed of extension and contraction of boom cylinder 4a, for example, from the amount of change in speed of extension and contraction of boom cylinder 4a obtained by operation command value obtaining unit 11 and stored in storage 14.
Change amount obtaining unit 15 obtains the amount of change per unit time in speed of extension and contraction of boom cylinder 4a, for example, from the speed of extension and contraction of boom cylinder 4a obtained by operation command value obtaining unit 11 and stored in storage 14.
The amount of change obtained by change amount obtaining unit 15 is provided to weight calculator 16. Weight calculator 16 calculates a weight (a weighted value) to be used for weighted average based on the amount of change provided from change amount obtaining unit 15. The weight calculated by weight calculator 16 is provided to storage 14 and stored therein.
Weight ranking unit 17 ranks a plurality of weights stored in storage 14 based on magnitude of the weights.
Payload value determination unit 18 determines a payload value by weighted average, based on the payload calculation values and the weights stored in storage 14. When a calculation section is long (for example, not shorter than three seconds), payload value determination unit 18 may determine the payload value by weighted average using only data large in weight among the weights ranked by weight ranking unit 17 (that is, rather than data small in weight). In the present embodiment, the payload value may be determined by weighted average using only N pieces of data large in weight ranked by weight ranking unit 17.
<Method of Controlling Work Machine>
A method of controlling the work machine in the present embodiment will now be described with reference to
Initially, moment MXwe caused by self-weight of work implement 3 is calculated in accordance with an expression (1) below.
In the expression (1), Mboom represents a weight of boom 3a. MboomC represents a weight of a cylinder portion of boom cylinder 4a. MboomCR represents a weight of a cylinder rod portion of boom cylinder 4a. Marm represents a weight of arm 3b. MarmC represents a weight of a cylinder portion of arm cylinder 4b. MarmCR represents a weight of a cylinder rod portion of arm cylinder 4b. Mbucket represents a weight of bucket 3c.
Each of weights Mboom, MboomC, MboomCR, Marm, MarmC, MarmCR, and Mbucket is stored in storage 14, for example, by an operation for input to storage 14 onto input operation portion 21 as shown in
In the expression (1), Xboom_c represents a distance from boom foot pin 5a to the center of gravity of boom 3a. XboomC_c represents a distance from boom foot pin 5a to the center of gravity of the cylinder portion of boom cylinder 4a. XboomCR_c represents a distance from boom foot pin 5a to the cylinder rod portion of boom cylinder 4a. Xarm_c represents a distance from boom foot pin 5a to the center of gravity of arm 3b. Xarmc_c represents a distance from boom foot pin 5a to the center of gravity of the cylinder portion of arm cylinder 4b. XarmCR_c represents a distance from boom foot pin 5a to the center of gravity of the cylinder rod portion of arm cylinder 4b. Xbucket_c represents a distance from boom foot pin 5a to the center of gravity of bucket 3c.
Each of these distances Xboom_c, XboomC_c, XboomCR_c, Xarm_c, XarmC_c, XarmCR_c, and Xbucket can be calculated from results of detection by stroke sensors 7a to 7c and potentiometers 9a to 9c.
Moment MXwe is calculated by payload calculation value arithmetic unit 13 shown in
Balance of moments around boom foot pin 5a is expressed in an expression (2) below.
[Expression 2]
F×h=CalcuPayload×Xpayload_c+MXwe (2)
In the expression (2), F represents load (pressing force) of boom cylinder 4a and it is obtained from a head pressure and a bottom pressure of boom cylinder 4a. Therefore, F is obtained from a pressure (head pressure) detected by pressure sensor 6a and a pressure (bottom pressure) detected by pressure sensor 6b.
In the expression (2), h represents a shortest distance between boom foot pin 5a and boom cylinder 4a (a distance in a direction orthogonal to a direction of extension of boom cylinder 4a). h can be calculated from detection values from stroke sensor 7a and potentiometer 9a.
In the expression (2), Xpayload_c represents a distance between boom foot pin 5a and the center of gravity of a load within bucket 3c. Xpayload_c can be calculated from detection values from stroke sensors 7a to 7c and potentiometers 9a to 9c.
Based on the expression (2), a payload calculation value (CalcuPayload) is expressed in an expression (3) below.
As shown in the expression (3), the payload calculation value (CalcuPayload) of a load within bucket 3c is calculated based on load F of boom cylinder 4a. The payload calculation value is constantly calculated.
Then, whether or not an operation to raise boom 3a is being performed is determined (step S2:
When it is determined that the operation to raise boom 3a is not being performed, calculation of the payload calculation value (CalcuPayload) is continued. When it is determined that the operation to raise boom 3a is being performed, the amount of change in boom raising PPC pressure per unit time is calculated (step S3:
In calculating the amount of change, an amount of change X in boom raising PPC pressure per unit time is calculated based on the boom raising PPC pressure at a first time point before the moment of calculation of the payload calculation value and the boom raising PPC pressure at a second time point before the first time point.
As set forth above, amount of change X per unit time in operation command value (boom raising PPC pressure) for operating boom cylinder 4a is detected. Detection by calculation of amount of change X is done by change amount obtaining unit 15 shown in
The payload calculation value (CalcuPayload) obtained in calculation above is corrected based on thus detected amount of change X per unit time, to thereby determine a payload value Wpayload (step S4:
Weight W is calculated, for example, from a reciprocal of amount of change X. Thus, weight W at the time when amount of change X per unit time is large is small, whereas weight W at the time when amount of change X per unit time is small is large. Weight W is calculated by weight calculator 16 shown in
Amount of change X per unit time and weight W are constantly calculated, and weight W calculated at each moment is stored in storage 14 shown in
Then, weights W stored in storage 14 are ranked (step S4b). Weights W are ranked in the order of magnitude of weight W. Weights W are ranked by weight ranking unit 17 shown in
Then, payload value Wpayload is determined by weighted average of the payload calculation values (CalcuPayload) using weight W obtained above (step S4c:
In the expression (4), CalcuPayload1, CalcuPayload2, CalcuPayload3, and CalcuPayloadt represent payload calculation values obtained as above at respective time points 1, 2, 3, and t. W1, W2, W3, and Wt represent weights obtained as above at respective time points 1, 2, 3, and t.
As shown in the expression (4), the weighted average of the payload calculation values is calculated, with the weight at the time when the amount of change per unit time is large being made smaller and with the weight at the time when the amount of change per unit time is small being made larger. Payload value Wpayload is determined by payload value determination unit 18 shown in
In the present embodiment, the payload value may be determined by the weighted average shown in the expression (4), using only data of top thirty weights larger in weight (the weight and the payload calculation value corresponding to the weight), rather than data of a plurality of weights smaller in weight (the weight and the payload calculation value corresponding to the weight) among the plurality of weights ranked by weight ranking unit 17.
As the payload calculation value (CalcuPayload) is corrected based on amount of change X per unit time as set forth above, payload value Wpayload is determined.
Determined payload value Wpayload is corrected for eliminating an error that the individual work machine has (step S5:
Thereafter, whether or not the load has been removed from bucket 3c is determined (step S6:
When it is determined that the load has not been removed from bucket 3c, the payload calculation value is calculated again (step S1:
The corrected payload value and the carrying capacity of the dump truck are shown, for example, on a display within operator's cab 2a. An operator in operator's cab 2a can thus perform excavation and loading works while the operator checks the corrected payload value of the load within bucket 3c and the carrying capacity of the dump truck.
As set forth above, the payload value of the load within bucket 3c is determined and added to the carrying capacity of the dump truck.
Though the case of pilot hydraulic operation apparatus 25 is described above, electrical operation apparatus 25 may be applicable. When electrical operation apparatus 25 is provided, an amount of operation onto each of first control lever 25R and second control lever 25L is detected, for example, by a potentiometer. The potentiometer refers to a displacement sensor that obtains an electrical (voltage) output in proportion to a mechanical position. Therefore, an amount of change per unit time in electrical (voltage) output obtained from the potentiometer as the amount of change per unit time in operation command value may be used for calculating weight W for weighted average.
Though an example of weighted average by calculating a weight based on amount of change X per unit time in operation command value is described above, weighted average may be calculated by calculating a weight based on the amount of change per unit time in speed of extension and contraction of the boom cylinder. Alternatively, weighted average may be calculated by calculating a weight based on both of amount of change X per unit time in operation command value and the amount of change per unit time in speed of extension and contraction of the boom cylinder.
Functions and effects of the present embodiment will now be described together with findings made by the present inventors as shown in
The present inventors have also found that accuracy of the payload calculation value (CalcuPayload) is poorer when the speed of raising boom 3a is high. Therefore, the operation to raise boom 3a should carefully be performed. When the operation to raise boom 3a is carefully performed, however, productivity becomes poor.
Then, in the present embodiment, payload value Wpayload is determined by correcting the payload calculation value (CalcuPayload) based on the amount of change per unit time in information on at least one of the operation command value for operating boom cylinder 4a and the speed of extension and contraction of boom cylinder 4a. Thus, payload value Wpayload less in pulsation in the payload calculation value (CalcuPayload) in the operation of boom 3a can be obtained. Therefore, the load within bucket 3c can accurately be measured in the operation of boom 3a. Therefore, the operator can accurately measure the load within bucket 3c simply by performing operations as usual, and high productivity can also be maintained.
According to the present embodiment, payload value Wpayload is determined by weighted average of the payload calculation values (CalcuPayload), with weight W at the time when amount of change X per unit time is large being made smaller and with weight W at the time when amount of change X per unit time is small being made larger. By thus increasing weight W at the time when amount of change X is small, a result of calculation can be stabilized.
Payload value Wpayload is determined by calculating an average rather than by using an instantaneous measurement value. Therefore, even when the head pressure and the bottom pressure of boom cylinder 4a are disturbed like noise due to a sudden operation, such disturbance does not greatly affect a measurement result.
According to the present embodiment, a plurality of weights are calculated, and payload value Wpayload is determined by calculating weighted average using payload calculation values large in weight among the plurality of weights, rather than payload calculation values small in weight among the plurality of weights. Thus, even when a calculation section is, for example, as short as three seconds, stable payload value Wpayload can be calculated.
According to the present embodiment, the operation command value and the speed of extension and contraction of boom cylinder 4a are the operation command value and the speed of extension and contraction of boom cylinder 4a at the time when the operation to raise boom 3a is performed. Thus, payload value Wpayload less in pulsation in the payload calculation value (CalcuPayload) at the time when the operation to raise boom 3a is performed can be obtained.
It should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims rather than the description above and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-056145 | Mar 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/010746 | 3/12/2020 | WO | 00 |
