Blade control device, working machine and blade control method

When a blade load is reduced from a value greater than or equal to a first set load value to a value less than the first set load value, a blade control device is configured to set a virtual designed surface to be closer to a blade than a designed surface is, and is configured to allow the blade to pivot above the virtual designed surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2012-236465 filed on Oct. 26, 2012. This application is a U.S. National stage application of International Application No. PCT/JP2012/080015 filed on Nov. 20, 2012.

FIELD OF THE INVENTION

The present invention relates to a blade control device for controlling the height of a blade, a working machine and a blade control method.

BACKGROUND INFORMATION

Working machines have been widely used so far, which are equipped with a blade as a work implement in use for digging and leveling the ground, transporting earth and sand, and so forth. Further, a method has been proposed for automatically regulating the height of the blade in such a working machine so that a blade load acting on the blade can fall in a target range (see Japan Laid-open Patent Application Publication No. JP-A-H07-54374).

SUMMARY

However, according to the method described in Japan Laid-open Patent Application Publication No. JP-A-H07-54374, the blade is elevated in conjunction with the fact that the blade load becomes greater than the upper limit of the target range, and subsequently, is configured to be lowered in conjunction with the fact that the blade load becomes less than the lower limit of the target range. Therefore, the method described in Japan Laid-open Patent Application Publication No. JP-A-H07-54374 has a drawback that continuous undulations are inevitably formed on a digging surface.

The present invention has been produced in view of the aforementioned situation, and is intended to provide a blade control device, a working machine and a blade control method, whereby undulation of a digging surface can be inhibited.

A blade control device according to a first aspect is used for controlling an up-and-down position of a blade as a work implement to be pivotally attached to a vehicle body. The blade control device includes a blade load obtaining part, a blade controlling part, a distance obtaining part and a virtual designed surface setting part. The blade load obtaining part is configured to obtain a blade load acting on the blade. The blade controlling part is configured to: lower the blade when the blade load is less than a first set load value; and elevate the blade when the blade load is greater than a second set load value, and is configured to allow the blade to pivot above a designed surface as a three-dimensional designed landform indicating a target shape of a digging object. The distance obtaining part is configured to obtain a distance between the designed surface and the blade. The virtual designed surface setting part is configured to set a virtual designed surface to be arranged in parallel to the designed surface and be closer to the blade than the designed surface is to the blade based on a reference distance to be obtained by the distance obtaining part at the time the blade load is reduced from a value greater than or equal to the first set load value to a value less than the first set load value. The blade controlling part is configured to allow the blade to pivot above the virtual designed surface even though the blade load is less than the first set load value if the virtual designed surface had been set by the virtual designed surface setting part.

According to the blade control device of the first aspect, the blade is controlled so as not to be closer to the designed surface than the virtual designed surface is, even when the blade load became less than the first set load value after blade elevation executed in accordance with the fact that the blade load had become greater than the second set load value during execution of a digging work. The blade can be thereby inhibited from being greatly lowered. Accordingly, continuous undulations can be inhibited from being formed on the digging surface.

A blade control device according to a second aspect relates to the blade control device according to the first aspect, and wherein the virtual designed surface setting part is configured to set the virtual designed surface so that a distance between the virtual designed surface and the designed surface is equal to the reference distance.

A blade control device according to a third aspect relates to the blade control device according to the first aspect, and wherein the virtual designed surface setting part is configured to set the virtual designed surface so that a distance between the virtual designed surface and the designed surface can be less than the reference distance.

According to the blade control device of the third aspect, a required dozing amount can be reliably obtained, while a large undulation can be prevented from being formed on the digging surface.

A blade control device according to a fourth aspect relates to the blade control device according to the third aspect, and wherein the virtual designed surface setting part is configured to set the virtual designed surface in a position farther away from the designed surface than a previously set virtual designed surface is.

According to the blade control device of the fourth aspect, even when the virtual designed surface is set so that the distance between the virtual designed surface and the designed surface can be less than the reference distance, an updated virtual designed surface can be inhibited from being set to be below the previous virtual designed surface. Therefore, an undulation can be further inhibited from being formed on the digging surface.

A working machine according to a fifth aspect includes: a vehicle body; a blade as a work implement to be pivotally attached to the vehicle body; and the blade control device according to the first aspect.

A blade control method according to a sixth aspect is used for controlling an up-and-down position of a work implement to be pivotally attached to a vehicle body. The blade control method includes the steps of: setting a virtual designed surface to be arranged in parallel to a designed surface as a three-dimensional designed landform indicating a target shape of a digging object and be closer to the blade than the designed surface is to the blade based on a reference distance between the designed surface and the blade at the time a blade load acting on the blade is reduced from a value greater than or equal to a first set load value to a value less than the first set load value; and allowing the blade to pivot above the virtual designed surface.

A blade control method according to a seventh aspect is used for controlling an up-and-down position of a blade as a work implement that is used for digging and pivotally attached to a vehicle body of a working machine. The blade control method includes the steps of obtaining a blade load acting on the blade in the digging; and lowering the blade when the blade load is less than a first set load value and elevating the blade when the blade load becomes greater than a second set load value, while allowing the blade to pivot only above a designed surface as a three-dimensional designed landform indicating a target shape of a digging object. The step of lowering the blade includes: setting a virtual designed surface to be above the designed surface; and allowing the blade to pivot above the virtual designed surface.

According to the present invention, it is possible to provide a blade control device whereby undulation of a digging surface can be inhibited, a working machine and a blade control method.

DESCRIPTION OF EMBODIMENTS

A bulldozer will be hereinafter explained as an example of “working machine” with reference to the drawings. In the following explanation, “up”, “down”, “front”, “rear”, “left” and “right” are terms defined with reference to an operator seated on an operator seat.

Overall Structure of Bulldozer100

FIG. 1is a side view of an entire structure of a bulldozer100.

The bulldozer100includes a vehicle body10, a driving unit20, a lift frame30, a blade40, a lift cylinder50, an angle cylinder60, a tilt cylinder70, a GPS receiver80, an IMU (Inertial Measurement Unit)90and a pair of sprockets95. Further, the bulldozer100is embedded with a blade control device200(seeFIG. 3). A structure and an action of the blade control device200will be described below.

The vehicle body10includes a cab11and an engine compartment12. The operator seat and a variety of operating devices (which are not illustrated in the figures) are installed inside the cab11. The engine compartment12is disposed forwards of the cab11.

The driving unit20is formed by a pair of crawler belts (only the left side crawler belt is illustrated inFIG. 1). The driving unit20is attached to the lower part of the vehicle body10. The pair of crawler belts is configured to be circulated in conjunction with driving of the pair of sprockets95, and this enables the bulldozer100to travel.

The lift frame30is disposed inwards of the driving unit20in the vehicle width direction (i.e., the right-and-left direction). The lift frame30is attached to the vehicle body10while being pivotable up and down about an axis X arranged in parallel to the vehicle width direction. The lift frame30supports the blade40through a ball-and-socket joint31, a pitching support link32and a bracing strut33.

The blade40is disposed forwards of the vehicle body10. The blade40includes: a universal coupling41coupled to the ball-and-socket joint31; and a pitching coupling42coupled to the pitching support link32. The blade40is configured to be moved up and down in conjunction with up-and-down pivot of the lift frame30. The blade40has a cutting edge40P formed on the bottom end thereof. The cutting edge40P is shoved into the ground in a leveling work or a digging work.

The lift cylinder50is coupled to the vehicle body10and the lift frame30. In conjunction with extension and contraction of the lift cylinder50, the lift frame30is configured to pivot up and down about the axis X.

Now,FIG. 2is a schematic diagram representing a structure of the bulldozer100. InFIG. 2, the original position of the lift frame30is depicted with a dashed two-dotted line. When the lift frame30is positioned in the original position, the cutting edge40P of the blade40is configured to make contact with the ground. As illustrated inFIG. 2, the bulldozer100includes a lift cylinder sensor50S. The lift cylinder sensor50S is formed by: a rotatable roller for detecting the position of a rod; and a magnetic sensor for returning the rod to its original position. The lift cylinder sensor50S is configured to detect the stroke length of the lift cylinder50(hereinafter referred to as “a lift cylinder length L”). As described below, a blade controller210(seeFIG. 3) is configured to calculate a lift angle θ of the blade40based on the lift cylinder length L. The lift angle θ corresponds to a lowered angle of the blade40from the original position, i.e., the depth of the cutting edge40P shoved into the ground. The bulldozer100is configured to execute a digging work, when being forwardly moved while the blade40is lowered from its original position.

The angle cylinder60is coupled to the lift frame30and the blade40. In conjunction with extension or contraction of the angle cylinder60, the blade40is configured to pivot about an axis Y passing through the rotary center of the universal coupling41and that of the pitching coupling42.

The tilt cylinder70is coupled to the bracing strut33of the lift frame30and the right upper end of the blade40. In conjunction with extension or contraction of the tilt cylinder70, the blade40is configured to pivot about an axis Z connecting the ball-and-socket joint31and the bottom end of the pitching support link32.

The GPS receiver80is disposed on the cab11. The GPS receiver80is an antenna for GPS (Global Positioning System). The GPS receiver80is configured to receive a set of GPS data indicating the position thereof.

The IMU90is an inertial measurement unit configured to obtain a set of vehicle body slant angle data indicating front, rear, right and left slant angles of the vehicle body with respect to the horizontal direction. The IMU90is configured to transmit the set of vehicle body slant angle data to the blade controller210.

The pair of sprockets95is configured to be driven by an engine (not illustrated in the figures) accommodated in the engine compartment12. The driving unit20is configured to be driven in conjunction with driving of the pair of sprockets95.

Structure of Blade Control Device200

FIG. 3is a configuration block diagram of the blade control device200according to an exemplary embodiment.

The blade control device200includes the blade controller210and a designed surface data storage220. Further, as represented inFIG. 3, the bulldozer100includes a proportional control valve230, a hydraulic pump240and a hydraulic sensor250in addition to the aforementioned components, i.e., the lift cylinder50, the lift cylinder sensor50S, the GPS receiver80and the IMU90.

The blade controller210is configured to obtain the lift cylinder length L from the lift cylinder sensor50S. The blade controller210is configured to obtain the set of GPS data from the GPS receiver80. The blade controller210is configured to obtain the set of vehicle body slant angle data from the MU90. The blade controller210is configured to obtain, from the hydraulic sensor250, a set of pressure data of the operating oil to be supplied to the pair of sprockets95from the hydraulic pump240. The blade controller210is configured to output a control signal (electric current) to the proportional control valve230based on the sets of data. Accordingly, the blade controller210is configured to automatically regulate the height of the blade40so that the load acting on the blade40(hereinafter referred to as “blade load”) can fall in a target range. Functions of the blade controller210will be described below.

The designed surface data storage220has preliminarily stored a set of designed surface data indicating a position and a shape of a three-dimensional designed landform (hereinafter referred to as “a designed surface ASTD”) that indicates a target shape of a digging object within a work area.

The proportional control valve230is disposed between the lift cylinder50and the hydraulic pump240. The opening degree of the proportional control valve230is configured to be controlled by means of electric current as a control signal from the blade controller210.

The hydraulic pump240is configured to be operated in conjunction with the engine and is configured to supply the operating oil for driving the pair of sprockets95. The hydraulic pump240is configured to supply the operating oil to the lift cylinder50via the proportional control valve230.

The hydraulic sensor250is configured to detect the pressure of the operating oil to be supplied to the pair of sprockets95from the hydraulic pump240. The pressure to be detected by the hydraulic sensor250corresponds to the traction force of the driving unit20. Therefore, the blade load can be comprehended based on the pressure to be detected.

Functions of Blade Controller210

FIG. 4is a functional block diagram of the blade controller210.FIGS. 5 to 7are schematic diagrams for explaining conditions of a digging work by the bulldozer100. InFIGS. 5 to 7, the conditions of a digging work by the bulldozer100are sequentially aligned in a time-series manner.

As represented inFIG. 4, the blade controller210includes a blade load obtaining part211, a blade load determining part212, a blade coordinate obtaining part213, a distance obtaining part214, a virtual designed surface setting part215, a blade controlling part216and a storage part217.

The blade load obtaining part211is configured to obtain, from the hydraulic sensor250, the set of pressure data of the operating oil to be supplied to the pair of sprockets95. The blade load obtaining part211is configured to obtain the blade load acting on the blade40based on the set of pressure data.

The blade load determining part212is configured to determine whether or not the blade load obtained by the blade load obtaining part211falls within a predetermined range. Specifically, the blade load determining part212is configured to determine whether or not the blade load is less than a first set load value FLOW. Further, the blade load determining part212is configured to determine whether or not the blade load is greater than a second set load value FHIGHthat is greater than the first set load value FLOW. The blade load determining part212is configured to inform the virtual designed surface setting part215and the blade controlling part216of the determination result. It should be noted that the first set load value FLOWcan be set as a value less than a target load F0(e.g., roughly 0.4 to 0.8 times as much as the weight of the bulldozer100) by the amount of a predetermined load α. The second set load value FHIGHcan be set as a value greater than the target load F0by the amount of the predetermined load α.

The blade coordinate obtaining part213is configured to obtain the lift cylinder length L, the set of GPS data and the set of vehicle body slant angle data. The blade coordinate obtaining part213is configured to compute a global coordinate of the GPS receiver80based on the set of GPS data. The blade coordinate obtaining part213is configured to calculate the lift angle θ (seeFIG. 2) based on the lift cylinder length L. The blade coordinate obtaining part213is configured to compute a local coordinate of the blade40(specifically, the blade cutting edge40P) with respect to the GPS receiver80based on the lift angle θ and a set of vehicle body size data. The blade coordinate obtaining part213is configured to compute a global coordinate of the blade40based on the global coordinate of the GPS receiver80, the local coordinate of the blade40and the set of vehicle body slant angle data.

The distance obtaining part214is configured to obtain the global coordinate of the blade40and the set of designed surface data. The distance obtaining part214is configured to compute a distance between the designed surface ASTDand the blade40(hereinafter referred to as “a reference distance DSTD”) based on the global coordinate of the blade40and the set of designed surface data. In the present exemplary embodiment, the distance obtaining part214is configured to compute, as the reference distance DSTD, a distance from the designed surface ASTDto the cutting edge40P in a direction perpendicular to the designed surface ASTD(hereinafter referred to “a perpendicular direction”).

The virtual designed surface setting part215is configured to obtain the determination result of the blade load determining part212. The virtual designed surface setting part215is configured to recognize that the blade load has been reduced from a value greater than or equal to the first set load value FLOWto a value less than the first set load value FLOWbased on the determination result of the blade load determining part212. In response to this, the virtual designed surface setting part215is configured to obtain, from the distance obtaining part214, the reference distance DSTDwhere the blade load has been reduced to the value less than the first set load value FLOW.

Further, based on the reference distance DSTD, the virtual designed surface setting part215is configured to set a virtual designed surface ATEMPto be closer to the blade40than the designed surface ASTDis. The virtual designed surface setting part215is configured to set the virtual designed surface ATEMPto be in parallel to the designed surface ASTD.

The virtual designed surface setting part215may set the virtual designed surface ATEMPso that the distance between the virtual designed surface ATEMPand the designed surface ASTDcan be equal to the reference distance DSTD, or alternatively, may set the virtual designed surface ATEMPso that the distance between the virtual designed surface ATEMPand the designed surface ASTDcan be less than the reference distance DSTD. In other words, the virtual designed surface setting part215may set the virtual designed surface ATEMPto pass through the cutting edge40P of the blade40, or alternatively, may set the virtual designed surface ATEMPto be closer to the designed surface ASTDthan the blade40is.

In the present exemplary embodiment, the virtual designed surface setting part215is configured to set the virtual designed surface ATEMPto be in a position closer to the designed surface ASTDfrom the blade40by a correction interval ΔD (e.g., roughly several cm). In other words, a virtual distance DTEMPbetween the virtual designed surface ATEMPand the designed surface ASTDcan be calculated by the following formula (1).
DTEMP=DSTD−ΔD(1)

Further, when the blade load is once increased to a value greater than or equal to the first set load value FLOWand is then reduced again to a value less than the first set load value FLOW, the virtual designed surface setting part215is configured to reset (i.e., update) the virtual designed surface ATEMPbased on the reference distance DSTDto be obtained anew. At this time, the virtual designed surface setting part215is configured to set the virtual designed surface ATEMPto be in a position farther away from the designed surface ASTDthan the previous position is. Therefore, the virtual designed surface ATEMPis gradually separated away from the designed surface ASTDevery time update is executed.

The blade controlling part216is configured to obtain the determination result of the blade load determining part212. Based on the determination result of the blade load determining part212, the blade controlling part216is configured to lower the blade40when the blade load is less than the first set load value FLOWand is configured to elevate the blade40when the blade load is greater than the second set load value FHIGH. The blade40can be lowered and elevated in conjunction with a control signal to be outputted to the proportional control valve230from the blade controlling part216. The blade controlling part216may be configured to regulate the lowering speed and the elevating speed of the blade40independently from each other.

The blade controlling part216is configured to control the blade40not to downwardly go beyond the designed surface ASTD. Specifically, the blade controlling part216is configured to obtain the reference distance DSTDfrom the distance obtaining part214and is configured to output a control signal (electric current) to the proportional control valve230in order to prevent the reference distance DSTDfrom being less than 0.

Further, when the virtual designed surface ATEMPhas been set by the virtual designed surface setting part215even though the blade load is less than a predetermined range, the blade controlling part216is configured to control the height of the blade40in order to prevent the blade40from getting closer to the designed surface ASTDthan the virtual designed surface ATEMPis. In other words, even though the blade load is insufficient, the blade controlling part216is configured to control the blade40not to downwardly go beyond the virtual designed surface ATEMP.

Now, with reference to the drawings, explanation will be made for an exemplary relation between a blade load transition and setting of the virtual designed surface ATEMP.FIG. 8is a chart representing a blade load transition in a digging work. InFIG. 8, the horizontal axis represents time, while the vertical axis represents the magnitude of the blade load. Further, inFIG. 8, clock times T1to T3correspond to the respective timings inFIGS. 5 to 7.

As represented inFIG. 8, the blade load is gradually increased from the start of a digging work and becomes greater than the second set load value FHIGHat the clock time T1. The blade controlling part216elevates the blade40due to the blade load that is greater than the second set load value FHIGH.

Thereafter, the blade load is gradually reduced and becomes less than the first set load value FLOWat the clock time T2. At this time, the virtual designed surface setting part215recognizes that the blade load has been reduced from a value greater than or equal to the first set load value FLOWto a value less than the first set load value FLOW, and sets a virtual designed surface ATEMP1in a position away from the designed surface ASTDat a virtual distance DTEMP1(reference distance DSTD1−correction interval ΔD) (seeFIG. 6).

Due to the blade load that is less the first set load value FLOW, the blade controlling part216thereafter controls the blade40not to downwardly go beyond the virtual designed surface ATEMP1, although lowering the blade40as much as possible. Accordingly, the blade load is gradually increased and becomes greater than the second set load value FHIGH. In response, the blade controlling part216elevates the blade40again.

Thereafter, the blade load is gradually reduced and becomes less than the first set load value FLOWat the clock time T3. At this time, the virtual designed surface setting part215recognizes that the blade load has been reduced from a value greater than or equal to the first set load value FLOWto a value less than the first set load value FLOW, and sets a virtual designed surface ATEMP2in a position away from the designed surface ASTDby a virtual distance DTEMP2(reference distance DSTD2−correction interval ΔD) (seeFIG. 7).

Thereafter, the virtual designed surface setting part215and the blade controlling part216repeats the aforementioned steps, but discards a set of data regarding the previous virtual designed surface ATEMPin response to backward travelling of the bulldozer100by an operator. Further, the virtual designed surface setting part215may configured to finish updating the virtual designed surface ATEMPwhen the virtual designed surface ATEMPis matched with a ground surface GRD.

The storage part217stores the first set load value FLOWand the second set load value FHIGHthat are used by the blade load determining part212and the blade controlling part216. The second set load value FHIGHis greater than the first set load value FLOW. Pieces of information stored in the storage part217may be rewritable by an operator through an input device260.

Action of Blade Control Device200

FIG. 9is a flowchart for explaining an action of the blade control device200.

It should be noted that the following action is actuated when an operator selects a control mode for actuating the following action.

In Step S1, the blade controller210determines whether or not the operator has moved the bulldozer100rearwards. When the operator has moved the bulldozer100rearwards, the processing is finished. When the operator has not moved the bulldozer100rearwards, the processing proceeds to Step S2.

In Step S2, the blade controller210computes the global coordinate of the blade40.

In Step S3, the blade controller210determines whether or not the height coordinate of the blade40is greater than or equal to either the designed surface ASTDor the virtual designed surface ATEMP. When the height coordinate of the blade40is not greater than or equal to either the designed surface ASTDor the virtual designed surface ATEMP, the blade controller210elevates the blade40in Step S4. When the height coordinate of the blade40is greater than or equal to either the designed surface ASTDor the virtual designed surface ATEMP, the processing proceeds to Step S10.

In Step S10, the blade controller210obtains the blade load acting on the blade40.

In Step S20, the blade controller210determines whether or not the blade load obtained this time is less than or equal to the second set load value FHIGH. When the blade load obtained this time is not less than or equal to the second set load value FHIGH, the blade controller210elevates the blade40in Step S30. When the blade load obtained this time is less than or equal to the second set load value FHIGH, the processing proceeds to Step S40.

In Step S40, the blade controller210determines whether or not the blade load obtained this time is less than the first set load value FLOW. When the blade load is greater than or equal to the first set load value FLOW, the processing returns to Step S1. When the blade load is less than the first set load value FLOW, the processing proceeds to Step S50.

In Step S50, the blade controller210determines whether or not the blade load previously obtained was greater than or equal to the first set load value FLOW. When the blade load was not greater than or equal to the first set load value FLOW, the blade controller210lowers the blade40in Step S60. When the blade load was greater than or equal to the first set load value FLOW, the processing proceeds to Step S80. Through the aforementioned processing from Step S10to Step S60, the load of the blade40during execution of a work is controlled to fall within an appropriate range.

In Step S80, the blade controller210computes the reference distance DSTDbetween the designed surface ASTDand the blade40.

In Step S90, the blade controller210determines whether or not the present reference distance DSTDis greater than the previous reference distance DSTD. When the present reference distance DSTDis greater than the previous reference distance DSTD, the processing proceeds to Step S100. When the present reference distance DSTDis not greater than the previous reference distance DSTD, the processing proceeds to Step S1.

In Step S100, the blade controller210sets the virtual designed surface ATEMPto be closer to the blade40than the designed surface ASTDis. Specifically, the blade controller210sets the virtual designed surface ATEMPin a position higher than the designed surface ASTDby the virtual distance DTEMP(reference distance DSTD−correction interval ΔD). Then, the processing returns to Step S1.

Actions and Effects

(1) When the blade load is reduced from a value greater than or equal to the first set load value FLOWto a value less than the first set load value FLOW, the blade control device200is configured to set the virtual designed surface ATEMPto be closer to the blade40than the designed surface ASTDis, and is configured to allow the blade40to only pivot above the virtual designed surface ATEMP.

Therefore, even when the blade load became less than the first set load value FLOWafter blade elevation executed in accordance with the fact that the blade load had become greater than the second set load value FHIGHduring a digging work, the blade40is controlled so as not to get closer to the designed surface ASTDthan the virtual designed surface ATEMPis. The blade40can be thereby inhibited from being greatly lowered. Accordingly, continuous undulations can be inhibited from being formed on the digging surface.

(2) The blade control device200is configured to set the virtual designed surface ATEMPso that the distance between the virtual designed surface ATEMPand the designed surface ASTDcan be less than the reference distance DSTDbetween the blade40and the designed surface ASTD.

Therefore, a required dozing amount can be reliably obtained while a large undulation can be prevented from being formed on the digging surface.

(3) The blade control device200is configured to set a new virtual designed surface ATEMPin a position farther away from the designed surface ASTDthan the previously set virtual designed surface ATEMPis.

Therefore, even when the virtual designed surface ATEMPis set so that the distance between the virtual designed surface ATEMPand the designed surface ASTDcan be less than the reference distance DSTD, the updated virtual designed surface ATEMPcan be inhibited from being set to be below the previous virtual designed surface ATEMP. Accordingly, an undulation can be further inhibited from being formed on the digging surface.

Other Exemplary Embodiments

An exemplary embodiment of the present invention has been explained above. However, the present invention is not limited to the aforementioned exemplary embodiment, and a variety of changes can be herein made without departing from the scope of the present invention.

(A) In the aforementioned exemplary embodiment, the virtual designed surface ATEMPis configured to be set so that the distance between the virtual designed surface ATEMPand the designed surface ASTDcan be less than the reference distance DSTDbetween the blade40and the designed surface ASTD. However, the present invention is not limited to this. The virtual designed surface ATEMPmay be set so that the distance between the virtual designed surface ATEMPand the designed surface ASTDcan be equal to the reference distance DSTDbetween the blade40and the designed surface ASTD.

(B) In the aforementioned exemplary embodiment, the blade controller210is configured to compute the distance from the designed surface ASTDto the cutting edge40P in the perpendicular direction. However, the present invention is not limited to this. The blade controller210may be configured to compute a distance in a direction intersecting with the perpendicular direction. Further or alternatively, the blade controller210may be configured to compute a distance from the designed surface ASTDto a portion of the blade40other than the cutting edge40P.

(C) The aforementioned exemplary embodiment has been explained by exemplifying the bulldozer as a working machine. However, the present invention is not limited to this. For example, a motor grader or the like can be exemplified as a working machine.

According to the illustrated embodiments, it is possible to provide a blade control device whereby undulation of a digging surface can be inhibited, a working machine and a blade control method. Therefore, the blade control device according to the illustrated embodiments is useful for the field of working machines.