U.S. patent application number 17/271109 was filed with the patent office on 2021-08-19 for blade control device for work machine.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.). The applicant listed for this patent is KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.), KOBELCO CONSTRUCTION MACHINERY CO., LTD.. Invention is credited to Yusuke KAMIMURA, Satoshi MAEKAWA, Daisuke NODA, Naoki SUGANO, Shohei UEMURA.
Application Number | 20210254313 17/271109 |
Document ID | / |
Family ID | 1000005610975 |
Filed Date | 2021-08-19 |
United States Patent
Application |
20210254313 |
Kind Code |
A1 |
UEMURA; Shohei ; et
al. |
August 19, 2021 |
BLADE CONTROL DEVICE FOR WORK MACHINE
Abstract
In a blade control device, in a case where an update condition
set in advance is satisfied, a virtual design surface setting part
sets a virtual design surface, using a blade position when the
update condition is satisfied as a reference, at an angle
equivalent to a vehicle body angle, and a blade operation control
part restricts raising and lowering operation of a blade such that
the blade conducts the raising and lowering operation above the
virtual design surface.
Inventors: |
UEMURA; Shohei; (Kobe-shi,
JP) ; SUGANO; Naoki; (Kobe-shi, JP) ; MAEKAWA;
Satoshi; (Kobe-shi, JP) ; NODA; Daisuke;
(Hiroshima, JP) ; KAMIMURA; Yusuke; (Hiroshima,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA KOBE SEIKO SHO (Kobe Steel, Ltd.)
KOBELCO CONSTRUCTION MACHINERY CO., LTD. |
Kobe-shi
Hiroshima-shi |
|
JP
JP |
|
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO SHO
(Kobe Steel, Ltd.)
Kobe-shi
JP
KOBELCO CONSTRUCTION MACHINERY CO., LTD.
Hiroshima-shi
JP
|
Family ID: |
1000005610975 |
Appl. No.: |
17/271109 |
Filed: |
August 7, 2019 |
PCT Filed: |
August 7, 2019 |
PCT NO: |
PCT/JP2019/031271 |
371 Date: |
February 24, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/262 20130101;
E02F 3/964 20130101; E02F 3/844 20130101 |
International
Class: |
E02F 9/26 20060101
E02F009/26; E02F 3/84 20060101 E02F003/84 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2018 |
JP |
2018-162284 |
Claims
1. A blade control device which is provided in a work machine
including a machine body having a travelling device and a vehicle
body supported by the travelling device and a blade attached to the
machine body so as to be raised and lowered and which controls
raising and lowering operation of the blade, the blade control
device comprising: a target design surface setting part which sets
a target design surface that specifies a target shape of an object
to be dug by the blade; a position information acquiring part which
acquires position information related to the work machine; a blade
position calculating part which calculates a blade position as a
position of the blade on the basis of the position information
acquired by the position information acquiring part; a virtual
design surface setting part which sets a virtual design surface
above the target design surface; and a blade operation control part
which controls the raising and lowering operation of the blade,
wherein in a case where an update condition set in advance is
satisfied, the virtual design surface setting part sets the virtual
design surface, using the blade position when the update condition
is satisfied as a reference, at an angle equivalent to a vehicle
body angle as an angle of inclination of the vehicle body with
respect to a horizontal surface, the angle of inclination being
obtained on the basis of the position information, and the blade
operation control part restricts the raising and lowering operation
of the blade such that the blade conducts the raising and lowering
operation above the virtual design surface.
2. The blade control device according to claim 1, further
comprising an estimated position calculating part which calculates
an estimated position of a part of a present surface which is the
ground as the object to be dug, the part being associated with at
least one of the blade and the travelling device, on the basis of
the position information acquired by the position information
acquiring part, wherein the update condition includes a condition
that the estimated position is below the virtual design
surface.
3. The blade control device according to claim 1, wherein the
update condition includes a condition corresponding to non-setting
of the virtual design surface.
4. The blade control device according to claim 1, further
comprising: a blade load acquiring part which acquires a blade load
as a load applied to the blade; and a storage part which stores a
load threshold value as a threshold value of the blade load,
wherein the update condition includes a condition that the blade
load changes from a value equal to or greater than the load
threshold value to a value smaller than the load threshold
value.
5. The blade control device according to claim 1, further
comprising a vehicle body average angle calculating part which
calculates an average value of vehicle body angles acquired by the
position information acquiring part, wherein the virtual design
surface setting part uses the average value of the vehicle body
angles as the vehicle body angle to be a reference for setting the
virtual design surface.
Description
TECHNICAL FIELD
[0001] The present invention relates to a blade control device
provided in a work machine including a blade.
BACKGROUND ART
[0002] Conventionally, a work machine including a blade for use in
digging of the ground, land grading, transport of sediments, and
the like has been used widely. Although there is proposed a method
of automatically controlling raising and lowering operation of a
blade such that a blade load applied to the blade becomes
substantially constant in such a work machine, the method has a
problem of waviness of an execution surface generated due to
raising and lowering operation of a blade.
[0003] Patent Literature 1 discloses a blade control device
intended to suppress waviness of an execution surface. In the blade
control device of Patent Literature 1, while restricting
fluctuation of a blade to above a virtual design surface set in
parallel to a design surface and closer to the blade than to the
design surface, a blade operation control part lowers the blade in
a case where a blade load is smaller than a first set load value,
and raises the blade in a case where the blade load is greater than
a second set load value which is greater than the first set load
value. A virtual design surface setting part resets the virtual
design surface parallel to the design surface when the blade load
is lowered from a value equal to or greater than the first set load
value to a value smaller than the first set load value. In the
blade control device of Patent Literature 1, the virtual design
surface setting part also sets a virtual design surface at a
position more away from the design surface than a virtual design
surface set last time. In other words, a virtual design surface
will be upwardly moved more away from the design surface every time
the virtual design surface is updated.
[0004] However, since in such a blade control device recited in
Patent Literature 1 as described above, in a case, for example,
where a present surface (the ground) has an up-grade or a
down-grade with respect to a horizontal design surface and a work
machine conducts digging work while ascending a slope along the
present surface or descending the slope along the present surface,
a blade load is greatly affected by a gradient of the present
surface, raising and lowering operation of the blade is increased,
so that an effect of suppressing waviness of an execution surface
cannot be always considered sufficient.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: JP 5285805 B
SUMMARY OF INVENTION
[0006] An object of the present invention is to provide a blade
control device which is provided in a work machine including a
blade and controls raising and lowering operation of the blade, the
blade control device being capable of effectively suppressing
waviness of an execution surface.
[0007] A blade control device of the present invention is a device
which is provided in a work machine including a machine body having
a travelling device and a vehicle body supported by the travelling
device and a blade attached to the machine body so as to be raised
and lowered and which controls raising and lowering operation of
the blade. The blade control device includes a target design
surface setting part which sets a target design surface that
specifies a target shape of an object to be dug by the blade; a
position information acquiring part which acquires position
information related to the work machine; a blade position
calculating part which calculates a blade position as a position of
the blade on the basis of the position information acquired by the
position information acquiring part; a virtual design surface
setting part which sets a virtual design surface above the target
design surface; and a blade operation control part which controls
the raising and lowering operation of the blade. In a case where an
update condition set in advance is satisfied, the virtual design
surface setting part sets the virtual design surface, using the
blade position when the update condition is satisfied as a
reference, at an angle equivalent to a vehicle body angle as an
angle of inclination of the vehicle body with respect to a
horizontal surface, the angle of inclination being obtained on the
basis of the position information. The blade operation control part
restricts the raising and lowering operation of the blade such that
the blade conducts the raising and lowering operation above the
virtual design surface.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a side view showing a hydraulic excavator as an
example of a work machine in which a blade control device according
to an embodiment of the present invention is provided.
[0009] FIG. 2 is a block diagram showing a main function of the
blade control device according to the embodiment.
[0010] FIG. 3 is a flowchart showing one example of control
operation to be executed by a controller included in the blade
control device.
[0011] FIG. 4 is a flowchart showing one example of control
operation to be executed by a blade operation control part out of
the control operation to be executed by the controller.
[0012] FIG. 5 is a flowchart showing one example of control
operation to be executed by a virtual design surface setting part
out of the control operation to be executed by the controller.
[0013] FIG. 6 is a schematic side view for explaining an estimated
position in the blade control device.
[0014] FIG. 7 is a schematic side view for explaining setting of a
virtual design surface in the blade control device.
[0015] FIG. 8 is a flowchart showing one example of control
operation to be executed by a blade control restricting part out of
the control operation to be executed by the controller.
[0016] FIG. 9 is a schematic side view showing one example of a
design surface, a present surface, a virtual design surface, and an
execution surface when the work machine provided with the blade
control device conducts digging work while ascending a slope along
the present surface.
[0017] FIG. 10 is a schematic side view showing one example of a
design surface, a present surface, a virtual design surface, and an
execution surface when the work machine provided with the blade
control device conducts the digging work while descending a slope
along the present surface.
[0018] FIG. 11 is a schematic side view showing one example of a
design surface, a present surface, a virtual design surface, and an
execution surface when the work machine provided with the blade
control device conducts the digging work while ascending and
descending a slope along the present surface.
[0019] FIG. 12 is a block diagram showing a main function of a
blade control device according to a modification example of the
embodiment.
[0020] FIG. 13 is a flowchart showing one example of control
operation to be executed by a controller included in the blade
control device according to the modification example.
[0021] FIG. 14 is a schematic side view showing one example of a
design surface, a present surface, a virtual design surface, and an
execution surface when a work machine provided with the blade
control device according to the modification example conducts
digging work while ascending and descending a slope along a present
surface.
[0022] FIG. 15 is a schematic side view showing one example of a
design surface, a present surface, a virtual design surface, and an
execution surface when a work machine provided with a blade control
device according to a reference example conducts digging work while
ascending a slope along a present surface.
[0023] FIG. 16 is a schematic side view showing one example of a
design surface, a present surface, a virtual design surface, and an
execution surface when the work machine provided with the blade
control device according to the reference example conducts the
digging work while descending a slope along the present
surface.
DESCRIPTION OF EMBODIMENTS
[0024] A preferred embodiment of the present invention will be
described with reference to the drawings.
Overall Structure of Work Machine
[0025] FIG. 1 is a side view showing a hydraulic excavator 1 as an
example of a work machine in which a blade control device according
to an embodiment of the present invention is provided. The
hydraulic excavator 1 includes a travelling device 2 (lower
travelling body) capable of travelling on the ground G, a vehicle
body 3 (upper slewing body) mounted on the travelling device 2, a
work device mounted on the vehicle body 3, and a blade 4 mounted on
the travelling device 2 or the vehicle body 3. The travelling
device 2 and the vehicle body 3 constitute a machine body of the
work machine. The vehicle body 3 has a slewing frame, an engine, a
driver's room, and the like.
[0026] The work device mounted on the vehicle body 3 includes a
boom 5, an arm 6, and a bucket 7. The boom 5 has a base end portion
supported at a front end of the slewing frame so as to go up and
down, i.e., to be turnable around a horizontal axis, and a distal
end portion on the opposite side. The arm 6 has a base end portion
attached to the distal end portion of the boom 5 so as to be
turnable around the horizontal axis, and a distal end portion on
the opposite side. The bucket 7 is turnably attached to the distal
end portion of the arm 6.
[0027] The hydraulic excavator 1 has a boom cylinder, an arm
cylinder, and a bucket cylinder provided for the boom 5, the arm 6,
and the bucket 7, respectively. The boom cylinder is interposed
between the vehicle body 3 and the boom 5 and extends and contracts
so as to cause the boom 5 to conduct up-down operation. The arm
cylinder is interposed between the boom 5 and the arm 6 and extends
and contracts so as to cause the awl 6 to conduct turning
operation. The bucket cylinder is interposed between the arm 6 and
the bucket 7 and extends and contracts so as to cause the bucket 7
to conduct turning operation.
[0028] The blade 4 mounted on the travelling device 2 or the
vehicle body 3 is provided for conducting digging of the ground,
land grading, transport of sediments, and the like. Specifically,
the blade 4 is supported by a lift frame 4a, and the lift frame 4a
is supported to be turnable around a horizontal axis 4b with
respect to the travelling device 2. Accordingly, the blade 4 can be
displaced in an up-down direction with respect to the travelling
device 2.
[0029] The hydraulic excavator 1 has a lift cylinder 8 provided for
the blade 4. The lift cylinder 8 has a head chamber 8h and a rod
chamber 8r (see FIG. 1), and extends to thereby cause the blade 4
to move in a down direction when a hydraulic oil is supplied to the
head chamber 8h, as well as discharging the hydraulic oil in the
rod chamber 8r, and also contracts to thereby cause the blade 4 to
move in an up direction when the hydraulic oil is supplied to the
rod chamber 8r, as well as discharging the hydraulic oil in the
head chamber 8h.
[0030] The hydraulic excavator 1 has a hydraulic circuit not shown.
The hydraulic circuit includes the boom cylinder, the arm cylinder,
the bucket cylinder, and the lift cylinder 8. The hydraulic circuit
further includes a hydraulic pump 9 (see FIG. 1), a lift cylinder
control proportional valve 41 (see FIG. 2), and a lift cylinder
flow rate control valve not shown.
Blade Control Device
[0031] FIG. 2 is a block diagram showing a main function of a blade
control device 100. The blade control device 100 is provided for
controlling raising and lowering operation of the blade 4. The
blade control device 100 includes a controller 10 (mechatronic
controller), a position information acquiring part, a blade load
acquiring part 34, an automatic control switch 35, and a travelling
lever 36 for manipulating the travelling device 2. The controller
10, which is configured with, for example, a microcomputer,
controls operation of each element included in the hydraulic
circuit.
[0032] The position information acquiring part is configured to
acquire position info,. nation about the hydraulic excavator 1.
Specifically, in the present embodiment, the position information
acquiring part includes a vehicle body position acquiring part 31,
a vehicle body angle acquiring part 32, and a blade angle acquiring
part 33. The vehicle body position acquiring part 31 is configured
to acquire a vehicle body position as a position of the machine
body. The vehicle body position acquiring part 31 is configured
with, for example, a receiver, such as a GNSS receiver (GNSS
sensor), capable of receiving satellite data (positioning signal)
from a satellite measurement system, such as GNSS (Global
Navigation Satellite System), and receives GNSS data indicative of
a vehicle body position as a position of the vehicle body 3 in a
global coordinate system. The global coordinate system is a
three-dimensional coordinate system using an origin point defined
on the earth as a reference, which is a coordinate system
indicating an absolute position defined by the satellite
measurement system.
[0033] The vehicle body angle acquiring part 32 is configured to
acquire a vehicle body angle as an angle of the vehicle body 3. The
vehicle body angle acquiring part 32 is configured with, for
example, a vehicle body angle sensor which detects an angle of the
vehicle body 3 in a global coordinate system. Specifically, the
vehicle body angle sensor may be configured with, for example, one
or a plurality of receivers provided in the machine body and
capable of receiving satellite data (positioning signal) from a
satellite measurement system. The vehicle body angle is an angle of
inclination of the vehicle body with respect to a horizontal
surface.
[0034] The blade angle acquiring part 33 is configured to acquire
an angle of the blade 4. The blade angle acquiring part 33 is
configured with, for example, a blade angle sensor which detects
the angle of the blade 4 in a global coordinate system.
Specifically, the blade angle sensor may be configured with, for
example, one or a plurality of receivers provided in the machine
body and capable of receiving satellite data (positioning signal)
from a satellite measurement system.
[0035] A local coordinate system may be used in place of the global
coordinate system. Both the global coordinate system and the local
coordinate system may be used together. Examples of the local
coordinate system include a three-dimensional coordinate system
using the vehicle body position as a reference and a
three-dimensional coordinate system using a specific position at a
work site as a reference. In the above case, the vehicle body angle
sensor may be configured with, for example, an inertia measurement
device, or may be configured with, for example, the inertia
measurement device and the receiver capable of receiving the
satellite data. The inertia measurement device may be configured to
be capable of, for example, measuring an acceleration and an
angular velocity of the vehicle body 3, and detecting an
inclination (e.g., a pitch indicative of rotation with respect to
an X-axis, a yaw indicative of rotation with respect to a Y-axis,
and a roll indicative of rotation with respect to a Z-axis) of the
vehicle body 3 on the basis of a measurement result. The blade
angle sensor may be configured with, for example, a stroke sensor
which detects a cylinder stroke of the blade cylinder 8, or may be
configured with the stroke sensor and the receiver capable of
receiving the satellite data.
[0036] Although, in the present embodiment, the vehicle body
position acquiring part 31 and the vehicle body angle acquiring
part 32 are attached to an upper portion of the vehicle body 3 and
the blade angle acquiring part 33 is attached to an upper portion
of the blade 4 as shown in FIG. 1, the attachment positions are not
limited to the specific example shown in FIG. 1. Detection signals
as electrical signals generated by these acquiring parts 31, 32,
and 33 are input to the controller 10.
[0037] In the present embodiment, the blade load acquiring part 34
is configured to acquire a blade load as a load applied on the
blade 4 during digging work. The blade load corresponds to, for
example, a pump pressure of the hydraulic pump 9 which drives the
blade 4. Accordingly, the blade load acquiring part 34 is capable
of detecting the blade load by detecting the pump pressure. In the
present embodiment, the blade load acquiring part 34 includes a
head pressure sensor 34H which detects a head pressure P1 as a
pressure of a hydraulic oil in the head chamber 8h of the lift
cylinder 8, and a rod pressure sensor 34R which detects a rod
pressure P2 as a pressure of a hydraulic oil in the rod chamber 8r
of the lift cylinder 8. The sensors 34H and 34R respectively
convert their detected physical quantities into detection signals
as electrical signals corresponding to the physical quantities and
input the detection signals to the controller 10.
[0038] The automatic control switch 35 is arranged in the driver's
room and is electrically connected to the controller 10. Upon
receiving manipulation for switching a control mode of the
controller 10 from a manual manipulation mode to an automatic
control mode, the automatic control switch 35 inputs a mode command
signal related to the manipulation to the controller 10. The
controller 10 switches setting of the control mode from the manual
manipulation mode to the automatic control mode by the mode command
signal input from the automatic control switch 35.
[0039] In the automatic control mode, the controller 10 is
configured to automatically control operation of the lift cylinder
8 such that an execution surface to be executed by the blade 4
approaches a target design surface set in advance. When a command
value (command current) to the lift cylinder control proportional
valve 41 for controlling operation of the lift cylinder 8 is output
from the controller 10, a secondary pressure of the proportional
valve 41 changes according to the command value and opening of the
lift cylinder flow rate control valve changes according to the
secondary pressure. As a result, a supply flow and a supply
direction of a hydraulic oil to be supplied from the hydraulic pump
9 to the lift cylinder 8 via the lift cylinder flow rate control
valve change to control an operation speed and a driving direction
of the lift cylinder 8. On the other hand, in the manual
manipulation mode, when a worker manipulates the travelling lever
36, a manipulation signal of the manipulation is input to the
controller 10, and the command value to the lift cylinder control
proportional valve 41 or a command value to the lift cylinder flow
rate control valve is output from the controller 10 according an
amount of manipulation of a manipulation lever not shown for
manipulating raising and lowering of the blade 4.
[0040] The controller 10 has a target design surface setting part
11, a blade position calculating part 12, a storage part 13, a
virtual design surface setting part 14, a blade operation control
part 15, a load threshold value setting part 16, a blade control
restricting part 20, and an estimated position calculating part 22
as a function for executing the automatic control.
[0041] The target design surface setting part 11 sets a target
design surface SD (see FIG. 7) which specifies a target shape of an
object to be dug by the blade 4. The target design surface setting
part 11 may store a design surface input by a target design surface
input part provided in the driver's room and set the design surface
as a target design surface. The target design surface setting part
11 may also store data of a design surface acquired via various
kinds of storage media, a communication network, or the like and
set the design surface as a target design surface. The target
design surface setting part 11 inputs the set target design surface
to the virtual design surface setting part 14. The target design
surface SD is a surface which specifies a three-dimensional design
topography as a target shape of the ground which is an object to be
dug. The target design surface SD may be specified by external data
such as BIM, CIM (Building/Construction Information Modeling,
Management), etc., or may be set using a position of the work
machine as a reference.
[0042] The blade position calculating part 12 calculates a blade
position as a position of the blade 4 in the global coordinate
system on the basis of the position information acquired by the
position information acquiring part. In the present embodiment, the
blade position calculating part 12 calculates the blade position on
the basis of the vehicle body position acquired by the vehicle body
position acquiring part 31, the vehicle body angle acquired by the
vehicle body angle acquiring part 32, and the angle of the blade 4
acquired by the blade angle acquiring part 33. In other words, the
blade position is calculated from a sum of a vector from a
reference point to the vehicle body position and a vector from the
vehicle body position to the blade position. Although in the
present embodiment, a blade position is thus calculated from a
relative angle between the vehicle body angle and the angle of the
blade 4 in the global coordinate system, a blade position
calculation method is not limited thereto. The blade position may
be calculated on the basis of, for example, a length of the lift
cylinder 8, or may be calculated on the basis of GNSS data received
by a GNSS receiver (GNSS sensor) attached to the blade 4.
[0043] Although in the present embodiment, the blade position is
set at a blade edge position (a position of a lower edge of a
distal end of the blade 4) as the distal end of the blade 4, the
blade position may be set at other part of the blade 4.
[0044] The storage part 13 stores a first load threshold value f1
as a load threshold value which is a threshold value of the blade
load f. In the present embodiment, the storage part 13 further
stores a second load threshold value f2 which is a threshold value
of the blade load f. The first load threshold value f1 and the
second load threshold value f2 will be described later.
[0045] Additionally, the storage part 13 stores an update condition
set in advance. The update condition is used as a reference for
determining whether or not the virtual design surface setting part
14 should update a virtual design surface to be described later.
The update condition includes one or a plurality of conditions. The
update condition will be detailed later.
[0046] In a case where the update condition is satisfied, the
virtual design surface setting part 14 sets a virtual design
surface to be above the target design surface using the blade
position when the update condition is satisfied as a reference, the
virtual design surface being parallel to the vehicle body angle
acquired by the vehicle body angle acquiring part 32. The virtual
design surface setting part 14 sets a virtual design surface on the
basis of a blade position calculated by the blade position
calculating part 12, the first load threshold value f1 set by the
load threshold value setting part 16, the blade load f acquired by
the blade load acquiring part 34, a vehicle body position acquired
by a GNSS receiver (the vehicle body position acquiring part 31), a
vehicle body angle acquired by a vehicle body angle sensor (the
vehicle body angle acquiring part 32), and a target design surface
set by the target design surface setting part 11. A specific
setting method will be described later.
[0047] The load threshold value setting part 16 sets a load
threshold value for use in calculation in the virtual design
surface setting part 14 and the blade operation control part 15. In
the present embodiment, the load threshold value setting part 16
sets the above-described first load threshold value f1 and second
load threshold value f2. The second load threshold value f2 is set
to be a value greater than the first load threshold value f1. The
first load threshold value f1 is set to be a value corresponding to
a proper blade load f with which the hydraulic excavator 1 can
stably travel. The second load threshold value f2 is a value set to
realize stable and efficient digging operation. Because of being a
value set for preventing occurrence of such a situation that the
blade load f becomes excessively large to cause a stuck state, the
second load threshold value f2 is preferably set to be a value
smaller than a blade load with which such a situation occurs. In
other words, even when the blade load f reaches the second load
threshold value f2, the second load threshold value f2 is
preferably set to be a value with which the work machine can
travel. These load threshold values f1 and f2 may be manually input
to the controller 10 by a worker before the digging work or
appropriately calculated by the controller 10 and stored during the
digging work.
[0048] The blade operation control part 15 calculates and outputs a
command value to the lift cylinder control proportional valve 41
for controlling operation of the lift cylinder 8. The blade
operation control part 15 calculates a temporary command current to
be output to the lift cylinder control proportional valve 41 on the
basis of an automatic control switch manipulation signal of the
automatic control switch 35, a travelling lever manipulation signal
of the travelling lever 36, the blade load f acquired by the blade
load acquiring part 34, and the first load threshold value f1 and
the second load threshold value f2 set by the load threshold value
setting part 16. A specific calculation method will be described
later.
[0049] The blade control restricting part 20 calculates a command
current to be output to the lift cylinder control proportional
valve 41 on the basis of a virtual design surface calculated by the
virtual design surface setting part 14 and the temporary command
current calculated by the blade operation control part 15. A
specific calculation method will be described later.
[0050] The estimated position calculating part 22 calculates an
estimated position of a present surface configuring a part of
conditions included in the update condition. Specifically, the
estimated position calculating part 22 calculates an estimated
position of a part of the present surface which is the ground as
the object to be dug, the part being associated with at least one
of the blade 4 and the travelling device 2, on the basis of the
position information acquired by the position information acquiring
part. A specific calculation method will be described later.
[0051] Next, description will he made of control operation
conducted by the controller 10 for the driving of the blade 4 in
the automatic control mode with reference to the flowchart of FIG.
3.
[0052] The controller 10 acquires an automatic control switch
manipulation signal related to the automatic control switch 35 and
a travelling lever manipulation signal related to the travelling
lever 36 (Step S1).
[0053] Next, the controller 10 determines whether a condition is
satisfied or not, the condition being that the automatic control
switch manipulation signal indicates that the automatic control
switch 35 is in an ON state and the travelling lever manipulation
signal indicates that the travelling lever 36 has been manipulated
(Step S2). In a case where the condition is not satisfied (NO in
Step S2), the controller 10 resets a virtual design surface and
finishes the processing.
[0054] In a case where the condition is satisfied (YES in Step S2),
the load threshold value setting part 16 sets the first load
threshold value f1 and the second load threshold value f2 (Step
S3).
[0055] Next, the blade load acquiring part 34 acquires a blade load
f applied to the blade 4 (Step S4).
[0056] Next, the blade operation control part 15 calculates the
temporary command current (Step S5). FIG. 4 is a diagram showing a
flow for calculation of the temporary command current by the blade
operation control part 15 of the controller 10. As shown in FIG. 4,
the blade operation control part 15 determines whether a condition
that the blade load f acquired by the blade load acquiring part 34
is equal to or greater than the second load threshold value f2 is
satisfied or not (Step S101). In a case where the condition is
satisfied (YES in Step S101), the blade operation control part 15
outputs a temporary command current corresponding to "lift-up" and
finishes the processing. The temporary command current is input to
the blade control restricting part 20. "Lift-up" corresponds to
operation of raising the blade 4.
[0057] In a case where the condition of Step S101 is not satisfied
(NO in Step S101), the blade operation control part 15 determines
whether a condition is satisfied or not, the condition being that
the blade load f is equal to or greater than the first load
threshold value f1 (Step S102). In a case where the condition of
Step S102 is satisfied (YES in Step S102), the blade operation
control part 15 outputs a temporary command current corresponding
to "lift-fixed" and finishes the processing. The temporary command
current is input to the blade control restricting part 20. "Lift
fixed" corresponds to refraining from conducting the raising and
lowering operation of the blade 4.
[0058] In a case where the condition of Step S102 is not satisfied
(NO in Step S102), the blade operation control part 15 outputs a
temporary command current corresponding to "lift-down" and finishes
the processing. The temporary command current is input to the blade
control restricting part 20. "Lift-down" corresponds to operation
for lowering the blade 4.
[0059] The flow shown in FIG. 4 represents processing intended to
maintain a blade load f during the digging work within a range
between the first load threshold value f1 and the second load
threshold value f2. In the flow, when the blade load f is equal to
or greater than the second load threshold value f2, a load
exceeding a digging capacity of the blade 4 is considered to be
applied to the blade 4, and "lift-up" operation is conducted for
lessening the blade load f. When the blade load f is smaller than
the first load threshold value f1, a load applied to the blade 4 is
considered excessively small for the digging capacity, so that
"lift-down" operation is conducted for increasing a digging amount.
Otherwise, processing of fixing a position of the, blade 4, i.e.,
processing of refraining from conducting the raising and lowering
operation of the blade 4 is conducted.
[0060] Next, in Step S6 shown in FIG. 3, the controller 10
determines whether a condition that the temporary command current
output by the blade operation control part 15 corresponds to
"lift-up" is satisfied or not (Step S6). In a case where the
condition is satisfied (YES in Step S6), the blade control
restricting part 20 conducts processing of Step S11. In a case
where the condition is not satisfied (NO in Step S6), a series of
processing of subsequent Steps S7 to S11 is conducted.
[0061] The vehicle body position acquiring part 31 acquires the
vehicle body position, the vehicle body angle acquiring part 32
acquires the vehicle body angle, and the blade angle acquiring part
33 acquires the angle of the blade 4 (Step S7). The blade position
calculating part 12 calculates the blade position on the basis of
the vehicle body position, the vehicle body angle, and the angle of
the blade 4 (Step S8).
[0062] Next, the virtual design surface setting part 14 sets a
virtual design surface (Step S9). FIG. 5 is a diagram showing a
flow for setting a virtual design surface by the virtual design
surface setting part 14 of the controller 10. First, the virtual
design surface setting part 14 determines whether a condition
corresponding to non-setting of a virtual design surface is
satisfied or not (Step S201). In the specific example shown in FIG.
5, the virtual design surface setting part 14 determines in Step
S201 whether the Step S201 is the first time in the automatic
control or not. In a case where the Step S201 is the first time in
the automatic control, inevitably, a virtual design surface is not
set, so that the determination whether the step is the first time
in the automatic control or not can be determination whether a
condition corresponding to non-setting of a virtual design surface
is satisfied or not. The determination whether the condition
corresponding to non-setting of a virtual design surface is
satisfied or not may be also made on the basis of, for example, a
flag (setting flag) indicative of setting or non-setting of a
virtual setting surface.
[0063] In a case of determining that the Step is the first time in
the automatic control (YES in Step S201), the virtual design
surface setting part 14 newly sets a virtual design surface and
finishes the processing. In a case of determining that the Step is
not the first time in the automatic control (NO in Step S201), the
virtual design surface setting part 14 determines whether a
condition is satisfied or not, the condition being that a blade
load f acquired last time by the blade load acquiring part 34 is
equal to or greater than the first load threshold value f1 and a
blade load f acquired this time by the blade load acquiring part 34
is smaller than the first load threshold value f1 (Step S202). In a
case where the condition in question is satisfied (YES in Step
S202), the virtual design surface setting part 14 newly sets a
virtual design surface (update the virtual design surface) and
finishes the processing.
[0064] In a case where the condition of Step S202 is not satisfied
(NO in Step S202), determination is made whether a condition that
the estimated position is below the virtual design surface is
satisfied or not (Step S203). In a case of determining that the
condition of Step 5203 is satisfied (YES in Step S203), the virtual
design surface setting part 14 newly sets a virtual design surface
(update the virtual design surface) and finishes the processing. In
a case where the condition of Step S203 is not satisfied (NO in
Step S203), the virtual design surface setting part 14 refrains
from updating the virtual design surface and finishes the
processing.
[0065] The flow shown in FIG. 5 represents processing intended to
appropriately set a virtual design surface SV. In the flow,
processing of newly setting the virtual design surface SV
(processing of updating the virtual design surface SV) is conducted
in a case where at least one of the conditions is satisfied, the
conditions including the condition that "the step is the first time
in the automatic control" (Step S201), the condition that "a blade
load f acquired last time is equal to or greater than the first
load threshold value f1 and a blade load f acquired this time is
smaller than the first load threshold value f1" (Step S202), and
the condition that "the estimated position is below the currently
set virtual design surface SV" (Step S203). Execution of the
processing in question causes the virtual design surface SV to be
set at an appropriate time to realize stable digging work with high
work execution efficiency.
[0066] FIG. 6 is a schematic side view for explaining the estimated
position. An estimated position PB shown in FIG. 6 is calculated by
the estimated position calculating part 22. Because of being
arranged in a lower portion of the work machine, the blade 4 and
the travelling device 2 are positioned at a height close to a
height position of a present surface SP. Accordingly, at least one
of the blade 4 and the travelling device 2 can be an index for
determining a positional relationship between the virtual design
surface SV and the present surface SP. The estimated position PB
calculated by the estimated position calculating part 22 is
obtained by calculating and estimating a part of the present
surface SP, the part being associated with at least one of the
blade 4 and the travelling device 2, by the estimated position
calculating part 22 on the basis of the position information.
Accordingly, when the condition that the estimated position PB is
below the virtual design surface SV is satisfied, a possibility
that the blade 4 enters a state of floating above the present
surface SP will be increased. Since when the update condition
including this condition is satisfied, the virtual design surface
SV is updated to have an angle parallel to the vehicle body angle
with the blade position as a reference, the state where the blade 4
floats above the present surface SP is eliminated.
[0067] In the present embodiment, the estimated position PB is an
intersection point between a line (line on the present surface SP
in FIG. 6) parallel to a lower portion of the travelling device 2
in the work machine and a line L passing the blade position and
extending perpendicularly from the virtual design surface SV as
shown in FIG. 6. Since the estimated position PB is an estimated
height position of the present surface SP at the blade position,
the estimated position can be a point of intersection, for example,
at which the line parallel to the lower portion of the travelling
device 2 in the work machine and the blade 4 intersect with each
other.
[0068] FIG. 7 is a schematic side view for explaining a method of
setting the virtual design surface SV in the blade control device
100. In the present embodiment, in a case where the update
condition is satisfied, the virtual design surface setting part 14
calculates a reference position, on a straight line passing the
blade position and perpendicular to the target design surface SD,
below the blade position by a reference distance 6 set in advance,
and sets, as the virtual design surface SV, a plane passing the
reference position and parallel to the vehicle body angle as shown
in FIG. 7.
[0069] Next, the blade control restricting part 20 calculates a
command current in Step S10 shown in FIG. 3. FIG. 8 is a diagram
showing a flow for calculating the command current by the blade
control restricting part 20 of the controller 10. As shown in FIG.
8, the blade control restricting part 20 determines whether a
condition is satisfied or not, the condition being that a blade
position calculated by the blade position calculating part 12 is
below the virtual design surface SV (Step S301). In a case where
the condition in question is satisfied (YES in Step S301), the
blade control restricting part 20 sets the command current to
correspond to "lift-up" and finishes the processing . "Lift-up"
corresponds to operation of raising the blade 4. On the other hand,
in a case where the condition is not satisfied (NO in Step S301),
the blade control restricting part 20 sets the command current to
be the same as the temporary command current input from the blade
operation control part 15 and finishes the processing.
[0070] The flow shown in FIG. 8 is processing intended to maintain
the blade position above the virtual design surface SV. For
example, even when a calculation result obtained by the blade
operation control part 15 corresponds to "lift-down" or
"lift-fixed" (i.e., even when the blade load f is small for the
digging capacity of the blade 4), in a case where the blade control
restricting part 20 determines that the blade position is below the
virtual design surface SV, processing is conducted for overwriting
the command current with "lift-up" such that the blade position
does not fall below the virtual design surface SV. This prevents
generation of waviness on an execution surface SC.
[0071] In Step S11 shown in FIG. 3, the blade control restricting
part 20 outputs the command current to the lift cylinder control
proportional valve 41. Specifically, in a case where a condition
that the temporary command current output by the blade operation
control part 15 corresponds to "lift-up" is satisfied (YES in Step
S6), the blade control restricting part 20 outputs the same command
current as the temporary command current to the proportional valve
41. Additionally, in a case of NO in the Step S6, the blade control
restricting part 20 outputs a command current calculated in Step
S10 to the proportional valve 41. When the processing of Step S11
is finished, the controller 10 again conducts the processing of
Step S1.
[0072] In the following, advantages of the blade control device 100
according to the above-described present embodiment will be
specifically described in comparison with a blade control device
according to a reference example.
[0073] FIG. 15 is a schematic side view showing one example of a
design surface SD (target design surface), present surfaces SP1 and
SP2, virtual design surfaces SV11, SV12, SV13, and SV21, and
execution surfaces SC1 and SC2 when a work machine provided with
the blade control device according to the reference example
conducts digging work while ascending a slope along the present
surfaces SP1 and SP2.
[0074] In the reference example shown in FIG. 15, since the virtual
design surface SV11 is parallel to the design surface SD, a
distance between the present surface SP1 and the virtual design
surface SV11 is increased toward an upper part of the upward slope.
Accordingly, as shown in the upper view of FIG. 15, as the work
machine ascends the slope along the present surface SP1 while
digging the present surface SP1, a blade load will be remarkably
increased. Then, when the blade load becomes greater than a
predetermined second threshold value, the blade operation control
part raises a blade 104, so that the blade load will he gradually
decreased. When the blade load becomes smaller than a predetermined
first threshold value (a value smaller than the second threshold
value), the virtual design surface setting part updates the virtual
design surface SV11 to the virtual design surface SV12. The updated
virtual design surface SV12 is set to be parallel to the horizontal
design surface SD and is set to be above the virtual design surface
SV11 set last time. While first digging work is thus conducted in
which the work machine ascends the slope along the present surface
SP1 to dig the whole of the present surface SP1, the plurality of
horizontal virtual design surfaces SV11, SV12, and SV13 is set in a
stepped manner as shown in the upper view of FIG. 15, and the
execution surface SC1 executed by the first digging work is also
formed to be stepped. Thus formed stepped first execution surface
SC1 will make the present surface SP2 as an object to be dug in
second digging work to be conducted next (see a lower view of FIG.
15). Accordingly, as shown in the lower view of FIG. 15, when the
work machine ascends the slope along the present surface SP2 while
digging the present surface SP2 in the second digging work, the
vehicle body of the work machine greatly fluctuates in its pitch
direction. This will be a cause of reduction in controllability of
controlling a posture of the work machine and ride comfort of a
worker.
[0075] FIG. 16 is a schematic side view showing one example of a
design surface SD, a present surface SP, a virtual design surface
SV11, and an execution surface SC when the work machine provided
with the blade control device according to the reference example
conducts the digging work while descending a slope along the
present surface SP. The virtual design surface SV21 in the lower
view of FIG. 15 is a virtual design surface set for the second
digging work and is a virtual design surface parallel to the target
design surface SD.
[0076] In the reference example shown in FIG. 16, since the virtual
design surface SV11 is parallel to the design surface SD, a
distance between the present surface SP and the virtual design
surface SV11 is decreased toward a lower part of the downward
slope. Accordingly, as shown in an upper view of FIG. 16, when the
work machine descends the slope along the present surface SP while
digging the present surface SP, there is inevitably generated a
region where the horizontal virtual design surface SV11 goes above
the present surface SP. In such a region where the horizontal
virtual design surface SV11 goes above the present surface SP, the
blade 104 restricted to fluctuate above the virtual design surface
SV11 will inevitably float above the present surface SP, which
prevents digging of the present surface SP as shown in a middle
view of FIG. 16 and a lower view of FIG. 16. Besides, since a
virtual design surface to be updated when a blade load becomes
smaller than the first threshold value is set further above the
virtual design surface SV11 of the last time, the blade 104 will
float further above the present surface SP. This will be a cause of
reduction in work execution efficiency.
[0077] On the other hand, since in the blade control device 100
according to the present embodiment, the virtual design surface SV
set by the virtual design surface setting part 14 is not parallel
to the target design surface SD but parallel to the vehicle body
angle, waviness of the execution surface SC can be suppressed and
controllability of a posture of the work machine, ride comfort of a
worker, and work execution efficiency during the digging work can
be also suppressed. Specifics are as follows.
[0078] FIG. 9 is a schematic side view showing one example of a
design surface SD (target design surface), a present surface SP, a
virtual design surface SV, and an execution surface SC when the
work machine provided with the blade control device 100 according
to the present embodiment conducts the digging work while ascending
a slope along the present surface SP, and FIG. 10 is a schematic
side view showing one example in which the work machine conducts
the digging work while descending a slope along the present surface
SP. FIG. 11 is a schematic side view showing one example in which
the work machine conducts the digging work while ascending and
descending a slope along a present surface SP.
[0079] As shown in FIG. 9, since in the present embodiment, the
virtual design surface SV is set in parallel to the vehicle body
angle of the work machine ascending the slope along the present
surface SP of the up-grade, the virtual design surface SV will not
be set in a stepped manner as in the reference example shown in the
upper view of FIG. 15, resulting in suppressing also the execution
surface SC from being formed in a stepped manner. This suppresses
fluctuation of the vehicle body in a pitch direction at the time of
again digging the execution surface SC, thereby obtaining an effect
of eliminating deterioration in controllability of a posture of the
work machine and deterioration in ride comfort of a worker.
[0080] Additionally, setting the virtual design surface SV to be
parallel to the vehicle body angle of the work machine descending
the slope along the present surface SP of the down-grade as shown
in FIG. 10 enables resetting of the virtual design surface SV (the
virtual design surface SV of the down-grade) parallel to the
vehicle body angle of the work machine having a posture along the
present surface SP of the down-grade. This enables, even if the
virtual design surface SV enters a state of being above the present
surface SP, elimination of the state to thereby suppress reduction
in work execution efficiency.
[0081] Further, the blade control device 100 according to the
present embodiment is effective also in a case where the present
surface has a relatively large uneven spot as shown in FIG. 11. In
the present embodiment, the virtual design surface SV can have
various angles according the vehicle body angle. As shown in FIG.
11, this suppresses a plurality of virtual design surfaces SV1,
SV2, SV3, and SV4 from being formed in a horizontal stepped manner
as in the reference example, the virtual design surfaces being set
during the first digging work in which the work machine ascends the
slope along the present surface SP to dig the whole of the present
surface. In other words, since each of the plurality of virtual
design surfaces SV1, SV2, SV3, and SV4 formed in the first digging
work is set in parallel to the vehicle body angle of the work
machine having a posture along the present surface SP of the
up-grade, the plurality of virtual design surfaces SV is liable to
follow the up-grade of the present surface SP. This suppresses
stepped formation of the execution surface SC which is to be formed
in the first digging work by the blade 4 having raising and
lowering operation restricted on the basis of the virtual design
surfaces SV1, SV2, SV3, and SV4, so that the execution surface SC
is liable to be less uneven as compared with the reference example.
Accordingly, when in the second digging work in which the execution
surface SC of the first digging work is used as a present surface,
the work machine ascends the slope along the present surface while
digging the present surface, fluctuation of the vehicle body of the
work machine in its pitch direction can be suppressed. This
suppresses deterioration in controllability of controlling a
posture of the work machine and deterioration in ride comfort of a
worker. Additionally, waviness of such an execution surface dug by
the blade 4 as described above will be suppressed, the blade having
raising and lowering operation restricted on the basis of the
virtual design surfaces SV1, SV2, SV3, and SV4.
Modification Example
[0082] FIG. 12 is a block diagram showing a main function of a
blade control device 100 according to a modification example of the
present embodiment. FIG. 13 is a flowchart showing one example of
control operation to be executed by a controller 10 included in the
blade control device 100 according to the modification example.
FIG. 14 is a schematic side view showing one example of a design
surface SD, a present surface SP, a virtual design surface SV, and
an execution surface SC when a work machine provided with the blade
control device 100 according to the modification example conducts
digging work while ascending and descending a slope along the
present surface SP.
[0083] The blade control device 100 according to the modification
example shown in FIG. 12 is different from the blade control device
100 shown in FIG. 2 in that the controller 10 further includes a
vehicle body average angle calculating part 21, and has the
remaining configuration being the same as that of the blade control
device 100 shown in FIG. 2. Additionally, the flowchart shown in
FIG. 13 is different from the flowchart shown in FIG. 3 in that
between the processing of Step S8 and the processing of Step S9,
processing of Step S12 is added, and includes the remaining
processing being the same as that of the flowchart shown in FIG.
3.
[0084] The vehicle body average angle calculating part 21
calculates an average value of vehicle body angles acquired by the
position information acquiring part. In the modification example,
the virtual design surface setting part 14 is configured to use the
average value of the vehicle body angles as the vehicle body angle
to be a reference for setting the virtual design surface SV.
[0085] Since in this modification example, even in a case where the
present surface SP as an object to be dug has a relatively large
uneven spot, the virtual design surfaces SV1, SV2, SV3, and SV4 are
set to be parallel to an average value of the vehicle body angles
as shown in FIG. 14, update time of the virtual design surfaces
SV2, SV3, and SV4 is less liable to depend on a local uneven spot
and the like. This enables reduction in an amount of change in
angles of the virtual design surfaces SV2, SV3, and SV4 at the time
of update to thereby enable more stable digging work.
[0086] Although it is possible to adopt, as the average value of
the vehicle body angles, for example, a moving average value of a
plurality of vehicle body angles acquired by the vehicle body angle
acquiring part 32 between time when the virtual design surface SV
is updated and time before the update time by a predetermined time
period, an average value calculation method is not limited to the
above-described method.
[0087] In this modification example, in a case where the update
condition is satisfied, the virtual design surface setting part 14
calculates a reference position, on a straight line passing the
blade position and perpendicular to the target design surface SD,
below the blade position by a reference distance S set in advance,
and sets, as the virtual design surface SV, a plane passing the
reference position and parallel to the average value of the vehicle
body angles. In other words, in this modification example, a plane
parallel to the average value of the vehicle body angles in
continuous time is set as a virtual design surface, and this
arrangement allows the virtual design surface SV to follow an
average angle of the vehicle body, i.e., follow an average gradient
of the present surface even in a case where the present surface has
an uneven spot. This enables reduction in an amount of change in an
angle of the virtual design surface at the time of update to
thereby enable more stable digging work.
[0088] As a specific example, since in the modification example
shown in FIG. 14, the virtual design surface SV is set to be
parallel to the average value of the vehicle body angles in
continuous time, an amount of change in an angle of the virtual
design surface at the time of update can be reduced, resulting in
having an effect of eliminating deterioration of work execution
efficiency and an effect of enabling more stable digging as
compared with the embodiment shown in FIG. 11.
[0089] The present invention is not limited to the above-described
embodiments. The present invention may include the following modes,
for example.
[0090] A work machine to which the blade control device according
to the present invention is applied is not limited to a hydraulic
excavator. The present invention is widely applicable to other work
machine provided with a blade, such as a wheel loader, a bulldozer,
and the like.
[0091] As described in the foregoing, there is provided a blade
control device capable of effectively suppressing waviness of an
execution surface.
[0092] The blade control device is a device which is provided in a
work machine including a machine body having a travelling device
and a vehicle body supported by the travelling device and a blade
attached to the machine body so as to be raised and lowered and
which controls raising and lowering operation of the blade. The
blade control device includes a target design surface setting part
which sets a target design surface that specifies a target shape of
an object to be dug by the blade; a position information acquiring
part which acquires position information related to the work
machine; a blade position calculating part which calculates a blade
position as a position of the blade on the basis of the position
information acquired by the position information acquiring part; a
virtual design surface setting part which sets a virtual design
surface above the target design surface; and a blade operation
control part which controls the raising and lowering operation of
the blade. In a case where an update condition set in advance is
satisfied, the virtual design surface setting part sets the virtual
design surface, using the blade position when the update condition
is satisfied as a reference, at an angle equivalent to a vehicle
body angle as an angle of inclination of the vehicle body with
respect to a horizontal surface, the angle of inclination being
obtained on the basis of the position information. The blade
operation control part restricts the raising and lowering operation
of the blade such that the blade conducts the raising and lowering
operation above the virtual design surface.
[0093] In the blade control device, the virtual design surface is
set not to be parallel to the target design surface but to be
parallel to the vehicle body angle. Accordingly, in a case, for
example, where a present surface (the ground) has an up-grade or a
down-grade with respect to a horizontal target design surface and a
work machine conducts digging work while ascending a slope along
the present surface or descending the slope along the present
surface, the virtual design surface is liable to follow the
up-grade or the down-grade. This suppresses fluctuation of a
distance between the present surface and the virtual design
surface, thereby suppressing fluctuation of a blade load as well.
When fluctuation of a blade load is suppressed, the raising and
lowering operation of the blade will be suppressed, so that
waviness of an execution surface will be suppressed.
[0094] Preferably, the blade control device further includes an
estimated position calculating part which calculates an estimated
position of a part of a present surface which is the ground as the
object to be dug, the part being associated with at least one of
the blade and the travelling device, on the basis of the position
information acquired by the position information acquiring part, in
which the update condition includes a condition that the estimated
position is below the virtual design surface.
[0095] In a case where a present surface (the ground) as an object
to be dug has a relatively large uneven spot, a vehicle body angle
of the work machine relatively greatly fluctuates, and a virtual
design surface set in parallel to the vehicle body angle is liable
to be set in a relatively large angle range. In such a case, there
occurs a case where during the digging work, the virtual design
surface may be temporarily positioned above a part, of the present
surface, corresponding to the blade, or a part, of the present
surface, corresponding to the travelling device. As a result, the
blade restricted to be above the virtual design surface enters a
state of floating above the present surface. When such a state
continues long, efficiency of the digging work is deteriorated.
Here, because of being arranged in a lower portion of the work
machine, the blade and the travelling device are positioned at a
height close to a height position of a present surface.
Accordingly, at least one of the blade and the travelling device
can be an index for determining a positional relationship between
the virtual design surface and the present surface. In the present
mode, the estimated position calculated by the estimated position
calculating part is obtained by calculating and estimating a part
of the present surface, the part being associated with at least one
of the blade and the travelling device, by the estimated position
calculating part on the basis of the position information.
Accordingly, when the condition that the estimated position is
below the virtual design surface is satisfied, a possibility that
the blade enters a state of floating above the present surface will
be increased. Since in the present mode, when the update condition
including this condition is satisfied, the virtual design surface
is updated to have an angle parallel to the vehicle body angle with
the blade position as a reference, the state where the blade floats
above the present surface is eliminated.
[0096] In the blade control device, the update condition preferably
includes a condition corresponding to non-setting of the virtual
design surface. In a case, for example, where at the start of
automatic control of the blade, a virtual design surface is not
set, when the update condition including the condition in question
is satisfied, a virtual design surface parallel to a vehicle body
angle is set. This enables digging work to have high work execution
efficiency from an initial stage of the automatic control of the
blade.
[0097] Preferably, the blade control device further includes a
blade load acquiring part which acquires a blade load as a load
applied to the blade; and a storage part which stores a load
threshold value as a threshold value of the blade load, in which
the update condition includes a condition that the blade load
changes from a value equal to or greater than the load threshold
value to a value smaller than the load threshold value.
[0098] Time when the blade load changes from a value equal to or
greater than the load threshold value to a value smaller than the
load threshold value, in many cases, corresponds to time when
operation of reducing a load applied to the blade is conducted.
Such a state of a reduced blade load is a more desirable state as
compared with a state of an increased blade load in view of
stability of the digging work. Accordingly, stability of the
digging work is improved by setting, when the update condition
including the condition in question is satisfied, a virtual design
surface, and conducting the digging work in which the raising and
lowering operation of the blade is restricted on the basis of the
virtual design surface.
[0099] The blade control device is preferably configured to further
include a vehicle body average angle calculating part which
calculates an average value of vehicle body angles acquired by the
position information acquiring part, in which the virtual design
surface setting part uses the average value of the vehicle body
angles as the vehicle body angle to be a reference for setting the
virtual design surface. Since in this mode, even in a case where a
present surface as an object to be dug has a relatively large
uneven spot, a virtual design surface is set to be parallel to the
average value of the vehicle body angles, update time of the
virtual design surface is less liable to depend on a local uneven
spot and the like. This enables reduction in an amount of change in
an angle of the virtual design surface at the time of update to
thereby enable more stable digging work.
* * * * *