Ground strength estimation system and ground strength estimation method

Abstract

This system provides the ability to estimate the strength of the ground from information acquired when operating construction machinery. [Solution] The ground strength estimation system comprises a work machine having an attachment at its tip, an actuator that drives the attachment, a sensor that detects information about the actuator, and a controller. The controller estimates the ground strength using the change in information about the actuator when the attachment receives a reaction force from the ground.

Description

Technical Field

[0001] The present disclosure relates to a ground strength estimation system and a ground strength estimation method.

Background Art

[0002] In Japanese Unexamined Patent Application Publication No. 2020 - 2531 (Patent Document 1), the target ground is pressed by an attachment, and based on the magnitude of the hydraulic pressure of the boom cylinder when pressed, the distance between the axial direction of the boom cylinder and the rotation center of the rear end of the boom, and the distance between the action line of the pressing load on the target ground by the attachment and the rotation center of the rear end of the boom, the pressing load on the target ground by the attachment is calculated, and the strength of the target ground is estimated using the calculated pressing load.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The introduction of work machines having ICT (Information and Communication Technology) functions is progressing. The information that can be obtained when operating the work machine is increasing. It is expected that this information can be utilized to improve the productivity of the work machine.

[0005] In the present disclosure, a system and a method for estimating the strength of the ground from the information obtained when operating a work machine are proposed.

Means for Solving the Problems

[0006] A ground strength estimation system according to a certain aspect of this disclosure comprises a work machine having an attachment at its tip, an actuator for driving the attachment, a sensor for detecting information about the actuator, and a controller. The controller estimates the ground strength using changes in information about the actuator when the attachment receives a reaction force from the ground.

[0007] A ground strength estimation system according to a certain aspect of this disclosure comprises a work machine having a bucket at its tip that is rotatable around a pivot axis, an actuator for driving the bucket, a sensor for detecting information about the actuator, and a controller. The bucket has teeth at its tip and a front lip that supports the teeth. The controller estimates the ground strength using information about the actuator when the bucket receives a reaction force from the ground in a posture where the angle at which a reference line connecting the pivot axis of the bucket and the tip of the front lip is inclined with respect to the ground is plus or minus 5° or less.

[0008] A ground strength estimation method according to a certain aspect of this disclosure comprises the following steps: The first step is to detect information about an actuator that drives an attachment at the tip of a work machine. The second step is to estimate the ground strength using the change in information about the actuator when the attachment receives a reaction force from the ground. [Effects of the Invention]

[0009] According to this disclosure, a system and method can be realized that can estimate the strength of the ground from information acquired when operating a work machine. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view illustrating the configuration of the work machine. [Figure 2] This is an enlarged side cross-sectional view of the bucket. [Figure 3] This is a block diagram illustrating the schematic configuration of a work machine system. [Figure 4] This diagram shows the functional blocks within the main controller. [Figure 5] This is a flowchart showing the process for estimating the strength of the ground. [Figure 6] This is a side view of the work machine when it is in its initial position. [Figure 7] This diagram shows the temporal changes in the boom lowering command. [Figure 8] This is a side view of a work machine with the bucket in contact with the ground. [Figure 9] This is a schematic diagram showing the configuration of a bucket cylinder. [Figure 10] This figure shows the change in head pressure of the bucket cylinder when the bucket comes into contact with hard ground. [Figure 11] This figure shows the change in head pressure of the bucket cylinder when the bucket comes into contact with soft ground. [Figure 12] This figure shows an example of the relationship between the rise gradient of the head pressure of a bucket cylinder and the ground strength. [Figure 13] This flowchart shows another example of a process for estimating ground strength. [Figure 14] This figure shows the change in the velocity of the bucket cylinder when the bucket makes contact with the ground. [Figure 15] This figure shows an example of the relationship between the peak velocity of a bucket cylinder and ground strength. [Modes for carrying out the invention]

[0011] The embodiments will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated. In the drawings, some configurations may be omitted or simplified for the sake of explanation. It is also intended from the outset that any configuration may be extracted from the embodiments and combined in any way.

[0012] <Configuration of the working machine> FIG. 1 is a side view schematically showing the configuration of a hydraulic excavator 100 as an example of a working machine according to the present disclosure. As shown in FIG. 1, the hydraulic excavator 100 of the present embodiment mainly includes a traveling body 1, a revolving body 2, and a working device 3. The traveling body 1 and the revolving body 2 constitute the vehicle body of the hydraulic excavator 100.

[0013] The traveling body 1 has a pair of left and right crawler devices 1a. Each of the pair of left and right crawler devices 1a has a traveling motor 1b and a crawler. The traveling motor 1b is provided as a driving source of the traveling body 1. The traveling motor 1b is a hydraulic motor driven by hydraulic pressure. When the traveling motor 1b rotationally drives the pair of left and right crawlers, the hydraulic excavator 100 travels on its own.

[0014] The revolving body 2 is disposed on the traveling body 1 and supported by the traveling body 1. The revolving body 2 mainly includes a cab 2a, a driver's seat 2b, an engine room 2c, a counterweight 2d, and a slewing motor 2e. The cab 2a is disposed, for example, on the front left side (front side of the vehicle) of the revolving body 2. Inside the cab 2a, a driver's seat 2b for an operator to sit on is disposed.

[0015] Each of the engine room 2c and the counterweight 2d is disposed on the rear side (rear side of the vehicle) of the revolving body 2 with respect to the cab 2a. The engine room 2c houses an engine unit (engine, exhaust treatment structure, etc.). The upper part of the engine room 2c is covered by an engine hood. The counterweight 2d is disposed behind the engine room 2c.

[0016] In this embodiment, the positional relationships of each part of the slewing body 2 of the hydraulic excavator 100 will be described with reference to an operator seated in the driver's seat 2b within the cab 2a. The front-rear direction refers to the front-rear direction of the operator seated in the driver's seat 2b. The direction directly facing the operator seated in the driver's seat 2b is the front direction, and the direction behind the operator seated in the driver's seat 2b is the rear direction. The left-right direction refers to the left-right direction of the operator seated in the driver's seat 2b. The right and left sides are the right and left directions, respectively, when the operator seated in the driver's seat 2b is facing directly forward. The up-down direction refers to the up-down direction of the operator seated in the driver's seat 2b. The lower side is towards the operator's feet, and the upper side is towards their head.

[0017] In the forward and backward directions, the side from which the work implement 3 protrudes from the rotating body 2 is the forward direction, and the opposite direction is the backward direction. Looking in the forward direction, the right and left sides are the right and left directions, respectively. In the up and down directions, the side with the ground is the down side, and the side with the sky is the up side.

[0018] The slewing body 2 is mounted on the traveling body 1 via a slewing circle section. The slewing circle section has a roughly annular shape and has internal teeth for slewing on its inner circumference. A pinion that meshes with these internal teeth is mounted on the slewing motor 2e. By transmitting driving force from the slewing motor 2e and rotating the slewing circle section, the slewing body 2 is made capable of relative rotation to the traveling body 1. The slewing motor 2e is a hydraulic motor driven by hydraulics. The slewing motor 2e may also be an electric motor.

[0019] The work implement 3 is pivotally supported on the front side of the slewing body 2, for example, on the right side of the driver's cab 2a. The work implement 3 has a boom 3a, an arm 3b, and a bucket 3c. The base end (one end) of the boom 3a is rotatably connected to the slewing body 2 by a boom bottom pin 5a. The base end (one end) of the arm 3b is rotatably connected to the tip (other end) of the boom 3a by a boom top pin 5b. The bucket 3c (one end) is rotatably connected to the tip (other end) of the arm 3b by an arm top pin 5c.

[0020] The bucket 3c is positioned at the tip of the work implement 3. The bucket 3c is an example of an attachment that can be mounted on the tip of the work implement 3. The tip of the bucket 3c is referred to as the cutting edge. The bottom surface 3cb is part of the outer surface of the bucket 3c. The bottom surface 3cb is formed as a flat surface.

[0021] The boom bottom pin 5a is supported by the body of the hydraulic excavator 100. The boom bottom pin 5a is supported by a pair of longitudinal plates (not shown) on the frame of the slewing body 2. The boom top pin 5b is attached to the tip of the boom 3a. The arm top pin 5c is attached to the tip of the arm 3b. The boom bottom pin 5a, boom top pin 5b, and arm top pin 5c all extend in the left-right direction. The boom bottom pin 5a is also called the boom foot pin.

[0022] The boom 3a can rotate vertically relative to the slewing body 2 around the boom bottom pin 5a, driven by the boom cylinder (boom hydraulic cylinder) 4a. The arm 3b can rotate vertically relative to the boom 3a around the boom top pin 5b, driven by the arm cylinder (arm hydraulic cylinder) 4b. The bucket (attachment) 3c can rotate vertically relative to the arm 3b around the arm top pin 5c, driven by the bucket cylinder (attachment hydraulic cylinder) 4c. In this way, the work machine 3 is drivable.

[0023] The work machine 3 has a bucket link 3d. The bucket link 3d has a first link member 3da and a second link member 3db. The tip of the first link member 3da and the tip of the second link member 3db are connected to each other so as to be rotatable relative to each other via a bucket cylinder top pin 3dc. The bucket cylinder top pin 3dc is connected to the tip of the bucket cylinder 4c. Therefore, the first link member 3da and the second link member 3db are pin-connected to the bucket cylinder 4c.

[0024] The base end of the first link member 3da is rotatably connected to the arm 3b by the first link pin 3dd. The base end of the second link member 3db is rotatably connected to the bracket at the base of the bucket 3c by the second link pin 3de.

[0025] A pressure sensor 6a is attached to the head side of the boom cylinder 4a. The pressure sensor 6a can detect the pressure of the hydraulic fluid (head pressure) in the cylinder head side oil chamber 40A of the boom cylinder 4a. A pressure sensor 6b is attached to the bottom side of the boom cylinder 4a. The pressure sensor 6b can detect the pressure of the hydraulic fluid (bottom pressure) in the cylinder bottom side oil chamber 40B of the boom cylinder 4a. The pressure sensors 6a and 6b output hydraulic fluid pressure information, consisting of the head pressure and bottom pressure, to the main controller 50 described later.

[0026] A pressure sensor 6c is mounted on the head side of the arm cylinder 4b. The pressure sensor 6c can detect the pressure of the hydraulic fluid in the cylinder head side oil chamber of the arm cylinder 4b (head pressure). A pressure sensor 6d is mounted on the bottom side of the arm cylinder 4b. The pressure sensor 6d can detect the pressure of the hydraulic fluid in the cylinder bottom side oil chamber of the arm cylinder 4b (bottom pressure). Pressure sensors 6c and 6d output hydraulic fluid pressure information, consisting of the head pressure and bottom pressure, to the main controller 50 described later.

[0027] A pressure sensor 6e is mounted on the head side of the bucket cylinder 4c. The pressure sensor 6e can detect the pressure of the hydraulic fluid in the cylinder head side oil chamber of the bucket cylinder 4c (head pressure). A pressure sensor 6f is mounted on the bottom side of the bucket cylinder 4c. The pressure sensor 6f can detect the pressure of the hydraulic fluid in the cylinder bottom side oil chamber of the bucket cylinder 4c (bottom pressure). Pressure sensors 6e and 6f output hydraulic fluid pressure information, consisting of the head pressure and bottom pressure, to the main controller 50 described later.

[0028] The boom 3a, arm 3b, and bucket 3c are equipped with position sensors to obtain information on their respective positions and orientations. The position sensors output boom information, arm information, and attachment information, which are used to obtain the positions of the boom 3a, arm 3b, and bucket 3c, to the main controller 50, which will be described later.

[0029] A stroke sensor 7a is attached to the boom cylinder 4a as a position sensor. The stroke sensor 7a detects the displacement of the cylinder rod 4ab relative to the cylinder 4aa in the boom cylinder 4a as boom information. A stroke sensor 7b is attached to the arm cylinder 4b as a position sensor. The stroke sensor 7b detects the displacement of the cylinder rod in the arm cylinder 4b as arm information. A stroke sensor 7c is attached to the bucket cylinder 4c as a position sensor. The stroke sensor 7c detects the displacement of the cylinder rod in the bucket cylinder 4c as attachment information.

[0030] The position sensor may also be an angle sensor. An angle sensor 9a is mounted around the boom bottom pin 5a. An angle sensor 9b is mounted around the boom top pin 5b. An angle sensor 9c is mounted around the arm top pin 5c. The angle sensors 9a, 9b, and 9c may be potentiometers or rotary encoders. The angle sensors 9a, 9b, and 9c output rotation angle information (boom information, arm information, and attachment information) of the boom 3a, etc. to the main controller 50 described later.

[0031] As shown in Figure 1, in a side view, the boom angle θb is defined as the angle between the straight line L1 (shown as a dashed line in Figure 1) passing through the boom bottom pin 5a and the boom top pin 5b, and the straight line Lv (shown as a dashed line in Figure 1) extending in the vertical direction. The boom angle θb is usually acute. The boom angle θb represents the angle of the boom 3a relative to the slewing body 2. The boom angle θb can be calculated from the detection result of the stroke sensor 7a, or from the measurement value of the angle sensor 9a.

[0032] In a side view, the angle between the straight line L1 passing through the boom bottom pin 5a and the boom top pin 5b and the straight line L2 (shown as a dashed line in Figure 1) passing through the boom top pin 5b and the arm top pin 5c is defined as the arm angle θa. The arm angle θa represents the angle of arm 3b relative to boom 3a in the region where arm 3b rotates in a side view. The arm angle θa can be calculated from the detection result of the stroke sensor 7b, or from the measurement value of the angle sensor 9b.

[0033] In a side view, the angle between the straight line L2 passing through the boom top pin 5b and the arm top pin 5c and the straight line L3 (shown as a dashed line in Figure 1) passing through the arm top pin 5c and the cutting edge of the bucket 3c is defined as the bucket angle θk. The bucket angle θk represents the angle of the bucket 3c relative to the arm 3b in the region where the bucket 3c rotates in a side view. The bucket angle θk can be calculated from the detection result of the stroke sensor 7c, or from the measurement value of the angle sensor 9c.

[0034] The position sensor may be an IMU (Inertial Measurement Unit). IMUs 8a, 8b, 8c, and 8d are attached to the slewing body 2, boom 3a, arm 3b, and first link member 3da, respectively. IMU 8a measures the acceleration of the slewing body 2 in the longitudinal, lateral, and vertical directions, and the angular velocity of the slewing body 2 around the longitudinal, lateral, and vertical directions. IMUs 8b, 8c, and 8d each measure the acceleration of the boom 3a, arm 3b, and first link member 3da in the longitudinal, lateral, and vertical directions, and the angular velocity of the boom 3a, arm 3b, and first link member 3da around the longitudinal, lateral, and vertical directions.

[0035] Based on the difference between the acceleration measured by IMU 8a attached to the slewing body 2 and the acceleration measured by IMU 8b attached to the boom 3a, the acceleration of the extension and retraction of the boom cylinder 4a (the change in the extension and retraction speed of the boom cylinder 4a) can be obtained. The boom angle θb, arm angle θa, and bucket angle θk may be calculated from the detection results of IMU 8b, 8c, and 8d, respectively.

[0036] As position sensors, we have listed stroke sensors for each hydraulic cylinder, angle sensors for each link such as boom 3a, and an IMU, but the position sensor may also be a six-axis accelerometer. The position sensor may also be a combination of some of the above sensors. In addition to the above sensors, the position sensor may also be a combination of GNSS (Global Navigation Satellite System).

[0037] Figure 2 is an enlarged side cross-sectional view of bucket 3c. A hollow space is formed inside bucket 3c. Bucket 3c is open in one direction. Bucket 3c has a bottom plate facing the opening (opening 3ch). The bottom plate is made of plate material. The bottom plate has an inner surface facing the space inside bucket 3c and an outer surface opposite to the inner surface. The planar bottom surface 3cb, also shown in Figure 1, constitutes part of the outer surface of the bottom plate of bucket 3c. The outer surface of the bottom plate constitutes part of the outer surface of bucket 3c. The bottom plate has a flat portion that makes up the bottom surface 3cb and a curved portion 3cd with a curved shape. The flat portion and the curved portion 3cd of the bottom plate are smoothly connected.

[0038] The bucket 3c has a pair of side plates 3ce. The side plates 3ce are made of sheet material. The pair of side plates 3ce are provided on both sides of the bottom plate, facing each other. The pair of side plates 3ce extend parallel to each other.

[0039] The bucket 3c has a front lip 3ca. The front lip 3ca is connected to the end of the bottom plate. The front lip 3ca is provided along the opening 3ch. The front lip 3ca is made of a plate material having a certain thickness. The front lip 3ca has a greater thickness than the bottom plate. The plate-shaped front lip 3ca extends in the direction in which the bottom surface 3cb of the bucket 3c extends. The bottom surface 3cb of the bucket 3c is connected to the front lip 3ca, and the curved portion 3cd is further away from the front lip 3ca than the bottom surface 3cb. A tooth 3ck is connected to the front lip 3ca via a tooth adapter 3cj. The tip of the tooth 3ck becomes the cutting edge of the bucket 3c.

[0040] A hollow space for loading excavated material such as soil is formed inside the bucket 3c, in a location enclosed by a pair of side plates 3ce, a bottom plate, and a front lip 3ca. The side plates 3ce have opening edges 3cf that form the edge of the opening 3ch of the bucket 3c. The opening edges 3cf are a portion of the edge of the side plates 3ce that is not connected to the bottom plate. The bucket 3c has a rear edge 3cg. The opening 3ch of the bucket 3c is defined by the tip 3ci of the front lip 3ca, the opening edges 3cf of the pair of side plates 3ce, and the rear edge 3cg of the bucket 3c.

[0041] The bucket 3c has a bracket 3cm. The bracket 3cm is a component for connecting the bucket 3c to the arm 3b. The bracket 3cm is positioned outside the space formed inside the bucket 3c for loading the excavated material. An opening 3ch of the bucket 3c is formed between the front lip 3ca and the bracket 3cm. The bracket 3cm has multiple plates 3cn. The plates 3cn protrude from the outer surface of the bottom plate of the bucket 3c. The multiple plates 3cn are spaced apart from each other.

[0042] Bracket 3cm has holes 3cp and 3cq formed therein. Holes 3cp and 3cq are formed to penetrate plate 3cn in the thickness direction. Hole 3cp has its center on the axis of central axis 3cr. Central axis 3cr is the pivot axis of bucket 3c. The pivot axis of bucket 3c corresponds to the central axis 3cr of hole 3cp that penetrates bracket 3cm. Hole 3cp has a circular opening centered on central axis 3cr. An arm top pin 5c (Figure 1) is inserted into hole 3cp, and bucket 3c is connected to arm 3b so as to be rotatable around central axis 3cr. As shown in Figure 2, a reference straight line 3ct is defined passing through central axis 3cr and the tip 3ci of front lip 3ca.

[0043] Hole 3cq has its center on the axis of the central axis 3cs. The central axis 3cs extends parallel to the central axis 3cr. Hole 3cq has a circular opening centered on the central axis 3cs. The second link pin 3de (Figure 1) is inserted into hole 3cq, and the second link member 3db (Figure 1) is connected to the bracket 3cm.

[0044] The curved portion 3cd of the bottom plate of bucket 3c has a deepest point 3cc. The deepest point 3cc is the part of the bottom plate of bucket 3c that is furthest from the reference line 3ct. The deepest point 3cc is the part of bucket 3c that has the greatest depth. The length from the reference line 3ct to the bottom plate of bucket 3c in the direction perpendicular to the reference line 3ct is greatest at the deepest point 3cc.

[0045] <Outline configuration of the work machine system> Next, the schematic configuration of the work machine system will be explained using Figure 3. Figure 3 is a block diagram showing the schematic configuration of the work machine system shown in Figure 1.

[0046] As shown in Figure 3, the system in this embodiment includes a hydraulic excavator 100 as an example of a work machine shown in Figure 1, and a main controller 50 shown in Figure 3.

[0047] Engine 31 is, for example, a diesel engine. The output shaft of engine 31 is connected to a hydraulic pump 34. Engine 31 generates the driving force to rotate the hydraulic pump 34. Governor 32 adjusts the amount of fuel injected by the fuel injector in engine 31.

[0048] The engine controller 41 adjusts the rotational speed of the engine 31 by outputting a command value for the fuel injection amount based on the commanded rotational speed of the engine 31 to the governor 32, thereby controlling the amount of fuel injected by the fuel injector. A rotation sensor 33 is provided on the output shaft of the engine 31. The rotation sensor 33 detects the rotational speed of the engine 31. The rotation sensor 33 outputs the detected rotational speed of the engine 31 to the engine controller 41.

[0049] The hydraulic pump 34 is driven by the rotational force transmitted from the engine 31 and discharges pressurized oil to generate hydraulic pressure to drive the hydraulic actuator. The hydraulic actuator includes hydraulic cylinders, namely boom cylinder 4a, arm cylinder 4b, and bucket cylinder 4c, as shown in Figure 1, and hydraulic motors, namely travel motor 1b and slewing motor 2e, as also shown in Figure 1. The hydraulic actuator is connected to the hydraulic pump 34 via an operating valve 35.

[0050] The hydraulic pump 34 is a variable displacement hydraulic pump that has, for example, a swash plate, and changes the discharge volume by changing the tilt angle of the swash plate. A swash plate drive unit 39 is connected to the hydraulic pump 34. The swash plate drive unit 39 changes the tilt angle of the swash plate of the hydraulic pump 34. A pressure sensor 36 detects the pressure of the oil discharged from the hydraulic pump 34. The pressure sensor 36 outputs the hydraulic pressure detection result to the pump controller 42. A portion of the oil discharged from the hydraulic pump 34 is supplied to the operating valve 35 as hydraulic fluid. A portion of the oil discharged from the hydraulic pump 34 is reduced to a constant pressure by a self-pressure reducing valve 37 and used as pilot oil.

[0051] The control valve 35 is a spool-type valve that switches the direction of hydraulic fluid flow by moving, for example, a rod-shaped spool. The amount of hydraulic fluid supplied to the hydraulic actuator is adjusted by the axial movement of the spool. The control valve 35 is equipped with a stroke sensor 35a that detects the distance the spool moves (spool stroke). By controlling the supply and discharge of hydraulic fluid to the hydraulic actuator, the operation of the work machine 3, the rotation of the slewing body 2, and the travel operation of the traveling body 1 are controlled.

[0052] In this example, the oil supplied to the hydraulic actuator to operate it is referred to as the hydraulic fluid. The oil supplied to the control valve 35 to operate its spool is referred to as the pilot oil. The pressure of the pilot oil is referred to as the pilot hydraulic pressure.

[0053] The hydraulic pump 34 may supply both hydraulic fluid and pilot oil as described above. The hydraulic pump 34 may also have a separate hydraulic pump for supplying hydraulic fluid (main hydraulic pump) and a hydraulic pump for supplying pilot oil (pilot hydraulic pump).

[0054] An EPC (electromagnetic proportional control) valve 38 is provided in the pilot oil path. The EPC valve 38 outputs pilot hydraulic pressure to the control valve 35 according to the command current from the main controller 50. The control valve 35 controls the hydraulic actuator according to the pilot hydraulic pressure.

[0055] The engine controller 41 and the pump controller 42 are mounted on the hydraulic excavator 100. The engine controller 41 and the pump controller 42 are electrically connected and can send and receive information from each other. The engine controller 41 and the pump controller 42 are also electrically connected to the main controller 50.

[0056] The main controller 50 is a controller that controls the entire hydraulic excavator 100 and consists of a CPU (Central Processing Unit), non-volatile memory, timers, etc. The main controller 50 controls the engine controller 41 and the pump controller 42.

[0057] The main controller 50 may be mounted on the hydraulic excavator 100. The main controller 50 may be installed outside the hydraulic excavator 100. The main controller 50 may be located at the work site of the hydraulic excavator 100, or it may be located in a remote location away from the work site of the hydraulic excavator 100. The main controller 50 may be, for example, a computer, server, or mobile terminal.

[0058] The control device 25 is located inside the operator's cab 2a (Figure 1). The control device 25 is operated by an operator. The control device 25 receives operator commands to drive the work implement 3. The control device 25 also receives operator commands to rotate the slewing body 2. The control device 25 is, for example, an electric control device and has an operating lever 25a and an operating amount sensor 25b.

[0059] The operating lever 25a is operated by an operator. The operating amount sensor 25b detects the operator's operation of the operating lever 25a. The operating amount sensor 25b is, for example, a potentiometer or a Hall element. The operating amount sensor 25b outputs the detection result of the operation of the operating lever 25a to the main controller 50. Based on the operation command from the operating device 25, the main controller 50 controls the EPC valve 38 to drive the hydraulic actuator.

[0060] The operating device 25 is not limited to an electric type, but may also be a pilot hydraulic type operating device. If the operating device 25 is a pilot hydraulic type, the operation of the operating lever 25a is detected, for example, by a pressure sensor that detects the pressure of the pilot oil.

[0061] The main controller 50 also receives detection signals from stroke sensors 7a-7c, IMUs 8a-8d, angle sensors 9a-9c, and pressure sensors 6a-6f. The main controller 50 may be electrically connected to each sensor by wire, or it may be capable of wireless communication.

[0062] The main controller 50 estimates the strength of the ground, such as the ground where the hydraulic excavator 100 is working, or the ground in the direction of travel of the hydraulic excavator 100, as will be described in detail later. The main controller 50 outputs the estimated ground strength to the output unit 60. The output unit 60 may be hardware such as a monitor or printer. The output unit 60 may be mounted on the hydraulic excavator 100. The output unit 60 may be an external controller located outside the hydraulic excavator 100. The external controller may be a computer, server, or mobile terminal. The external controller may be a computer that constitutes the construction management system.

[0063] <Functional blocks within the main controller 50> Next, the functional blocks within the main controller 50 will be explained using Figure 4. Figure 4 is a diagram showing the functional blocks within the main controller 50 as shown in Figure 3.

[0064] The work equipment control unit 51 controls the work equipment 3. A command current is output from the work equipment control unit 51 to the EPC valve 38. In accordance with this command current, the EPC valve 38 outputs pilot hydraulic pressure to the operating valve 35. In accordance with this pilot hydraulic pressure, the operating valve 35 supplies a predetermined amount of hydraulic fluid to the boom cylinder 4a, the arm cylinder 4b, and the bucket cylinder 4c, respectively. When the boom cylinder 4a extends and retracts, the boom 3a moves up and down. When the arm cylinder 4b extends and retracts, the arm 3b moves in the digging direction (towards the slewing body 2) and the dumping direction (away from the slewing body 2). When the bucket cylinder 4c extends and retracts, the bucket 3c moves in the digging direction (the cutting edge moves towards the arm 3b) and the dumping direction (the cutting edge moves away from the arm 3b).

[0065] The spool of the operating valve 35 is not limited to a system that operates by pilot hydraulic pressure, but may also be solenoid-driven. The work implement control unit 51 may control the work implement 3 by outputting a control signal to the solenoid-driven spool and controlling the position of the spool.

[0066] The detection result of the pressure sensor 6e is input to the main controller 50. The information about the bucket cylinder 4c input to the main controller 50 includes the hydraulic fluid pressure information detected by the pressure sensor 6e. The cylinder pressure acquisition unit 53 acquires the head pressure of the bucket cylinder 4c based on the input hydraulic fluid pressure information.

[0067] The detection result of the stroke sensor 7c is input to the main controller 50. The information about the bucket cylinder 4c input to the main controller 50 includes attachment information detected by the stroke sensor 7c. The cylinder stroke acquisition unit 54 acquires the relative position of the cylinder rod with respect to the cylinder in the bucket cylinder 4c based on the input attachment information.

[0068] Timer 58 measures time. Memory unit 59 is a non-volatile memory and is provided as an area for storing necessary data. Memory unit 59 stores control programs for controlling various operations of the hydraulic excavator 100, and various data necessary for executing those control programs. Memory unit 59 also temporarily stores working data generated in conjunction with the operation of the hydraulic excavator 100. The main controller 50 executes various processes for controlling the operation of the hydraulic excavator 100 by executing the control programs stored in memory unit 59.

[0069] The calculation unit 55 determines the change in the head pressure of the bucket cylinder 4c over time, for example, based on the head pressure of the bucket cylinder 4c acquired by the cylinder pressure acquisition unit 53 and the time measured by the timer 58. The calculation unit 55 calculates the increase in head pressure per unit time from the start of the increase in head pressure until the head pressure reaches its first maximum value when the head pressure of the bucket cylinder 4c is rising. This increase in head pressure per unit time will be referred to below as the rise gradient of the head pressure.

[0070] The calculation unit 55 determines the moving speed of the cylinder rod of the bucket cylinder 4c based, for example, the relative position of the cylinder rod with respect to the cylinder in the bucket cylinder 4c acquired by the cylinder stroke acquisition unit 54 and the timing measured by the timer 58. The calculation unit 55 can determine the moving speed of the cylinder rod by differentiating the time-series position of the cylinder rod with respect to time. Furthermore, the calculation unit 55 calculates the maximum value of the moving speed of the cylinder rod of the bucket cylinder 4c. This maximum value of speed will be referred to below as the peak value of the speed of the bucket cylinder 4c.

[0071] The ground strength estimation unit 57 estimates the ground strength using the rise gradient of the head pressure or the peak value of the velocity calculated by the calculation unit 55. The storage unit 59 stores a data table in which the rise gradient of the head pressure changes depending on the ground strength. The ground strength estimation unit 57 can estimate the ground strength by applying the calculated rise gradient of the head pressure to the data table. The storage unit 59 also stores a data table in which the peak value of the velocity changes depending on the ground strength. The ground strength estimation unit 57 can estimate the ground strength by applying the calculated peak value of the velocity to the data table.

[0072] <Flowchart for Estimating Ground Strength> Figure 5 is a flowchart showing the process for estimating the strength of ground 200. The details of the process for estimating the strength of ground 200 will be explained below, referring to Figure 5 and subsequent figures as appropriate.

[0073] In step S1, the work machine 3 is set to its initial position. Figure 6 is a side view of the work machine 3 when it is in its initial position. The initial position is the position of the work machine 3 when the process of estimating the strength of the ground 200 using the hydraulic excavator 100 is started. When the work machine 3 is in its initial position, the bucket 3c is located away from the ground 200. The bucket 3c is above the ground 200 in the vertical direction by a predetermined height H shown in Figure 6.

[0074] The initial position of the work implement 3 is stored in the memory unit 59. The boom angle θb, arm angle θa, and bucket angle θk when the work implement 3 is in its initial position are stored in the memory unit 59. The lengths of the boom cylinder 4a, arm cylinder 4b, and bucket cylinder 4c when the work implement 3 is in its initial position are stored in the memory unit 59. The work implement control unit 51 outputs a command current to the EPC valve 38, causing the boom cylinder 4a, arm cylinder 4b, and bucket cylinder 4c to extend and retract as appropriate, thereby returning the work implement 3 to its initial position.

[0075] In step S2, the boom 3a is lowered. The work machine control unit 51 outputs a command current to the EPC valve 38, which retracts the boom cylinder 4a, causing the boom 3a to lower and the bucket 3c to approach the ground 200. At this time, the cylinder lengths of the arm cylinder 4b and the bucket cylinder 4c are maintained. During the boom lowering, the relative position of the arm 3b with respect to the boom 3a remains unchanged, and the relative position of the bucket 3c with respect to the arm 3b remains unchanged. While the boom 3a is lowered and the bucket 3c is brought closer to the ground 200, the relative position between the bucket 3c and the boom 3a is maintained.

[0076] The work equipment control unit 51 brings the bucket 3c closer to the ground 200 by executing predetermined movements of the boom 3a. Figure 7 shows the temporal change of the boom lowering command. The horizontal axis of Figure 7 shows the passage of time, and the vertical axis, "boom lowering lever opening," indicates the operation of the operating lever 25a when the operator operates the operating device 25 to lower the boom 3a. The lever opening when the operating lever 25a is in the neutral position is defined as 0%. The lever opening when the tilt of the operating lever 25a is at its maximum is defined as 100%. The lever opening is detected by the operating amount sensor 25b and input to the main controller 50. The main controller 50 (work equipment control unit 51) outputs a command current according to the lever opening to the EPC valve 38 to control the lowering operation of the boom 3a.

[0077] In the boom lowering command shown in Figure 7, when the operation to lower the boom 3a in step S2 begins, the boom opening increases linearly from 0% over time to 100% at time T1. From time T1 to time T2, the boom opening is maintained at 100%. At time T2, the boom opening rapidly decreases from 100% to 0%, and the lowering operation of the boom 3a stops. The work machine control unit 51 lowers the boom 3a according to the predetermined boom lowering command shown in Figure 7. As the boom 3a is lowered, the bucket 3c approaches the ground 200. The distance from the ground 200 to the bucket 3c decreases from the height H shown in Figure 6 and approaches zero.

[0078] It should be noted that the boom lowering command shown in Figure 7 is a control signal output from the main controller 50 (work equipment control unit 51) to the EPC valve 38, and may not necessarily correspond to the actual speed of the boom 3a.

[0079] In step S3, the bucket 3c makes contact with the ground 200. Figure 8 is a side view of the work machine in the position where the bucket 3c makes contact with the ground 200. The curved portion 3cd of the bucket 3c, typically the deepest portion 3cc, makes contact with the ground 200. The bucket 3c makes contact with the ground 200 in a position where the reference line 3ct, which connects the central axis 3cr shown in Figure 2 and the tip 3ci of the front lip 3ca, is parallel to the ground 200. When the bucket 3c makes contact with the ground 200, the bottom surface 3cb of the bucket 3c is away from the ground 200. When the bucket 3c makes contact with the ground 200, the curved portion 3cd of the bucket 3c is in contact with the ground 200. When the bucket 3c makes contact with the ground 200, the arm 3b takes a position where the line L2 passing through the boom top pin 5b and the arm top pin 5c is perpendicular to the ground 200.

[0080] The orientation of the bucket 3c when it contacts the ground 200 includes an orientation in which the reference line 3ct is strictly parallel to the ground 200, and an orientation in which the angle of inclination of the reference line 3ct with respect to the ground 200 is sufficiently small. For example, an orientation of the bucket 3c in which the angle of inclination of the reference line 3ct with respect to the ground 200 is plus or minus 5° or less may be included in the orientation in which the reference line 3ct is parallel to the ground 200. After pretreatment in which the bottom surface 3cb of the bucket 3c is pressed against the ground 200 to flatten the ground 200, the bucket 3c may be brought into contact with the ground 200 from a predetermined height in a predetermined orientation. This pretreatment is particularly effective when the ground 200 has fine irregularities.

[0081] In step S4, the main controller 50 acquires information about the bucket cylinder 4c. In this example, the main controller 50 acquires the head pressure of the bucket cylinder 4c.

[0082] Figure 9 is a schematic diagram showing the configuration of a bucket cylinder 4c. The bucket cylinder 4c has a piston 4cp, a rod 4cr, a head-side oil chamber 4ch, and a bottom-side oil chamber 4cb. The hollow space inside the bucket cylinder 4c is partitioned by the piston 4cp. The head-side oil chamber 4ch is the oil chamber on the cylinder head side relative to the piston 4cp. The bottom-side oil chamber 4cb is the oil chamber on the cylinder bottom side relative to the piston 4cp. As hydraulic fluid is supplied to and discharged from the head-side oil chamber 4ch and the bottom-side oil chamber 4cb, the piston 4cp moves axially (up and down in Figure 9), and the rod 4cr also moves together with the piston 4cp.

[0083] When the deepest part 3cc of the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200, a force acts on the bucket 3c from the ground 200 in a direction that rotates the bucket 3c in the excavation direction around the arm top pin 5c. As a result, an external force is applied to the rod 4cr of the bucket cylinder 4c in a direction that moves the rod 4cr, indicated by the white arrow in Figure 9, out of the cylinder. At this time, the pressure of the hydraulic fluid in the head-side oil chamber 4ch of the bucket cylinder 4c increases, and the pressure of the hydraulic fluid in the bottom-side oil chamber 4cb decreases.

[0084] The pressure sensor 6e detects an increase in the head pressure of the bucket cylinder 4c. The cylinder pressure acquisition unit 53 of the main controller 50 acquires the detected head pressure of the bucket cylinder 4c from the pressure sensor 6e.

[0085] In step S5, the main controller 50 generates a time-dependent change in the head pressure of the bucket cylinder 4c. The calculation unit 55 obtains the time at which the detection result of the head pressure of the bucket cylinder 4c was obtained from the timer 58. The calculation unit 55 determines the time-dependent change in the head pressure of the bucket cylinder 4c by plotting the head pressure of the bucket cylinder 4c obtained by the cylinder pressure acquisition unit 53 with the time at which the head pressure was acquired.

[0086] Figure 10 shows the change in head pressure of the bucket cylinder 4c when the bucket 3c is in contact with hard ground 200. Figure 11 shows the change in head pressure of the bucket cylinder 4c when the bucket 3c is in contact with soft ground 200. In the graphs shown in Figures 10 and 11, the horizontal axis represents time, and the vertical axis represents the head pressure of the bucket cylinder 4c. Figures 10 and 11 show the change in head pressure of the bucket cylinder 4c over time when the bucket 3c is in contact with the ground 200 at time 0.

[0087] In step S6, the main controller 50 calculates the rise gradient of the head pressure of the bucket cylinder 4c. As shown in Figure 10, when the bucket 3c contacts hard ground 200, the head pressure of the bucket cylinder 4c rises steeply, and at time Tpk1, the head pressure of the bucket cylinder 4c reaches its first maximum value Pk1. As shown in Figure 11, when the bucket 3c contacts soft ground 200, the head pressure of the bucket cylinder 4c rises gradually, and at time Tpk2, which is later than time Tpk1, the head pressure of the bucket cylinder 4c reaches its first maximum value Pk2.

[0088] From the moment bucket 3c makes contact with the ground 200 and the head pressure of bucket cylinder 4c begins to rise, the head pressure of bucket cylinder 4c continues to increase macroscopically until it reaches its first maximum value. The rate of increase in head pressure per unit time during this increase, i.e., the rise gradient of the head pressure, is relatively large when bucket 3c is in contact with hard ground 200 and relatively small when bucket 3c is in contact with soft ground 200.

[0089] The information about the bucket cylinder 4c acquired by the main controller 50 includes the pressure of the hydraulic fluid inside the bucket cylinder 4c. The information about the bucket cylinder 4c acquired by the main controller 50 also includes the rise gradient of the head pressure in the bucket cylinder 4c.

[0090] The ground strength estimation unit 57 of the main controller 50 estimates the strength of the ground 200 using the change in head pressure of the bucket cylinder 4c when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200. The ground strength estimation unit 57 estimates the strength of the ground 200 using the increase per unit time of the pressure of the hydraulic fluid in the bucket cylinder 4c, which rises when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200.

[0091] Figure 12 shows an example of the relationship between the rise gradient of the head pressure of the bucket cylinder 4c and the ground strength. The horizontal axis of Figure 12 represents the ground strength, specifically the simplified N-value, and the vertical axis represents the rise gradient of the head pressure of the bucket cylinder 4c. The simplified N-value is a value used as an indicator of the hardness of soil-based materials and is measured using a known simplified N-value meter. Figure 12 shows a semi-logarithmic graph with the horizontal axis being logarithmic. The circles shown in Figure 12 are plots of the relationship between the rise gradient of the head pressure and the ground strength, which were determined experimentally in advance. A dashed line in Figure 12 approximates each plot. The data table shown in Figure 12, in which the rise gradient of the head pressure changes depending on the strength of the ground 200, is stored in the storage unit 59.

[0092] As shown in Figures 10-12, the harder the ground 200 (the greater the strength of the ground 200), the greater the rise gradient of the head pressure of the bucket cylinder 4c. In step S7, the ground strength estimation unit 57 of the main controller 50 reads the data table shown in Figure 12 from the storage unit 59. In step S8, the ground strength estimation unit 57 applies the rise gradient of the head pressure of the bucket cylinder 4c calculated in step S6 to the data table shown in Figure 12. As a result, in step S9, the main controller 50 can estimate the strength of the ground 200.

[0093] When the bucket 3c comes into contact with the ground 200, causing the cylinder stroke of the bucket cylinder 4c to extend by Δx, the change in head pressure ΔP of the bucket cylinder 4c is expressed by the following equation (1).

[0094]

number

[0095] In equation (1), P is the head pressure of the bucket cylinder 4c, K is a constant representing the bulk modulus of the hydraulic fluid and the bucket cylinder 4c, Vcyl is the amount of oil in the bucket cylinder 4c, and A is the cross-sectional area of ​​the bucket cylinder 4c. The first factor (K) on the right side of equation (1) is a constant that includes the compression characteristics of the hydraulic fluid and the characteristics of the bucket cylinder 4c. The second factor (A × Δx / Vcyl) on the right side of equation (1) indicates how much the hydraulic fluid is compressed as the cylinder stroke of the bucket cylinder 4c extends by Δx, and how much the volume of the bucket cylinder 4c changes.

[0096] Dividing both sides of equation (1) by Δt yields equation (2).

[0097]

number

[0098] The first factor (KA / Vcyl) on the right-hand side of equation (2) is a constant. When the limit of Δt in the denominator of equation (2) is taken to zero, we obtain the following equation (3).

[0099]

number

[0100] The left side of equation (3) represents the rate of pressure change within the bucket cylinder 4c and indicates the rise in head pressure within the bucket cylinder 4c. The second factor (dx / dt) on the right side of equation (3) represents the rate at which the bucket cylinder 4c is compressed.

[0101] Equation (3) shows that the rise in head pressure within the bucket cylinder 4c depends on the rate at which the bucket cylinder 4c is compressed. Equation (3) shows that the way the head pressure within the bucket cylinder 4c rises changes as the compression rate of the bucket cylinder 4c changes due to the difference in hardness of the ground 200.

[0102] Therefore, the strength of the ground 200 can also be estimated using the velocity of the bucket cylinder 4c when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200. Figure 13 is a flowchart showing another example of the process flow for estimating the strength of the ground. The processes of steps S1 to S3 shown in Figure 13 are the same as the processes described with reference to Figure 5.

[0103] In step S14 shown in Figure 13, the main controller 50 acquires information about the bucket cylinder 4c. In the example shown in Figure 13, the main controller 50 acquires the velocity of the bucket cylinder 4c. When the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200, an external force, indicated by the white arrow in Figure 9, is applied to the rod 4cr of the bucket cylinder 4c, causing the piston 4cp and rod 4cr to move together. The moving speed of the piston 4cp and rod 4cr at this time is the velocity of the bucket cylinder 4c.

[0104] The stroke sensor 7c detects the relative position of the rod 4cr with respect to the cylinder in the bucket cylinder 4c. The cylinder stroke acquisition unit 54 of the main controller 50 acquires the detection result of the relative position of the rod 4cr from the stroke sensor 7c.

[0105] The calculation unit 55 obtains the time at which the relative position of rod 4cr was acquired from the timer 58. The calculation unit 55 calculates the velocity of the bucket cylinder 4c by differentiating the time-series position of rod 4cr acquired by the cylinder stroke acquisition unit 54 with respect to time.

[0106] In step S15, the main controller 50 generates a time-dependent change in the speed of the bucket cylinder 4c. The calculation unit 55 plots the speed of the bucket cylinder 4c calculated in step S14 with the time at which the relative position of the rod 4cr was obtained to determine the time-dependent change in the speed of the bucket cylinder 4c.

[0107] Figure 14 shows the change in velocity of the bucket cylinder 4c when the bucket 3c contacts the ground 200. In the graph shown in Figure 14, the horizontal axis represents time, and the vertical axis represents the velocity of the bucket cylinder 4c. Figure 13 shows the change in velocity of the bucket cylinder 4c over time when the bucket 3c contacts the ground 200 at time 0.

[0108] In step S16, the main controller 50 calculates the peak velocity Vpk of the bucket cylinder 4c. When the bucket 3c contacts the ground 200, the rod 4cr moves, and the velocity of the bucket cylinder 4c increases. The velocity of the bucket cylinder 4c reaches a maximum value Pk3. The velocity of the bucket cylinder 4c at the time of the maximum value Pk3 is the peak velocity value Vpk. The peak velocity value Vpk of the bucket cylinder 4c is relatively large when the bucket 3c contacts hard ground 200, and relatively small when the bucket 3c contacts soft ground 200.

[0109] The information about the bucket cylinder 4c acquired by the main controller 50 includes the speed of the bucket cylinder 4c. The information about the bucket cylinder 4c acquired by the main controller 50 includes the peak value Vpk of the speed of the bucket cylinder 4c.

[0110] Figure 15 shows an example of the correspondence between the peak velocity of the bucket cylinder 4c and the ground strength. The horizontal axis of Figure 15 represents the ground strength, specifically the simplified N value, and the vertical axis represents the peak velocity of the bucket cylinder 4c. Figure 15 shows a semi-logarithmic graph with the horizontal axis being logarithmic. The circles shown in Figure 15 plot the correspondence between the peak velocity Vpk of the bucket cylinder 4c and the ground strength, which were determined experimentally in advance. A dashed line approximates each plot. The data table shown in Figure 15, in which the peak velocity Vpk of the bucket cylinder 4c changes depending on the ground strength 200, is stored in the storage unit 59.

[0111] As shown in Figure 15, the harder the ground 200 (the greater the strength of the ground 200), the larger the peak value of the bucket cylinder 4c's velocity. In step S17, the ground strength estimation unit 57 of the main controller 50 reads the data table shown in Figure 15 from the storage unit 59. In step S18, the ground strength estimation unit 57 applies the peak value Vpk of the bucket cylinder 4c's velocity calculated in step S16 to the data table shown in Figure 15.

[0112] As a result, in step S19, the ground strength estimation unit 57 of the main controller 50 estimates the strength of the ground 200 using the change in velocity of the bucket cylinder 4c when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200. The ground strength estimation unit 57 can estimate the strength of the ground 200 using the peak value Vpk of the velocity of the bucket cylinder 4c, which rises when the bucket 3c contacts the ground 200.

[0113] <Mechanism of Action and Effects> The characteristic configuration and effects of this embodiment are summarized below.

[0114] As shown in Figures 1 and 3, the work machine 3 has a bucket 3c at its tip. The bucket cylinder 4c drives the bucket 3c. The pressure sensor 6e and stroke sensor 7c acquire information about the bucket cylinder 4c. As shown in Figures 12 and 15, the ground strength estimation unit 57 of the main controller 50 may estimate the strength of the ground 200 using the change in information about the bucket cylinder 4c when the bucket 3c receives a reaction force from the ground 200.

[0115] A sensor attached to the hydraulic excavator 100 acquires information about the bucket cylinder 4c. When the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200, the information about the bucket cylinder 4c changes, and the ground strength estimation unit 57 uses this change in information to estimate the strength of the ground 200. It should be noted that the change in information about the bucket cylinder 4c refers to a macroscopic change, not a microscopic change in the value when the information about the bucket cylinder 4c is approximately constant.

[0116] By effectively utilizing the information acquired when operating the numerous hydraulic excavators 100 present at the work site, the strength of the ground 200 can be easily estimated. This eliminates the need for dedicated measuring instruments to measure the strength of the ground 200, reducing the time and cost required to confirm the strength of the ground 200. The number of measurement points for the strength of the ground 200 at the work site can be easily increased, and the increased measurement density allows for a more accurate understanding of the ground 200's strength, improving construction accuracy. The hydraulic excavator 100 itself can recognize whether the ground 200 at the work site has sufficient strength for it to operate or travel on. This technology is also useful for the hydraulic excavator 100 to determine whether it is safe to enter the work site when operating automatically or autonomously.

[0117] As shown in Figures 10-12, the information regarding the bucket cylinder 4c may also be the pressure of the hydraulic fluid inside the bucket cylinder 4c. The ground strength estimation unit 57 may estimate the strength of the ground 200 using the increase per unit time of the hydraulic fluid pressure inside the bucket cylinder 4c, which rises when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200. The head pressure of the bucket cylinder 4c can be obtained with the pressure sensor 6e, and the strength of the ground 200 can be easily estimated using the rise gradient of the head pressure when the bucket 3c contacts the ground 200.

[0118] As shown in Figures 13-15, the information regarding the bucket cylinder 4c may be the velocity of the bucket cylinder 4c. The ground strength estimation unit 57 may estimate the strength of the ground 200 using the peak velocity Vpk of the bucket cylinder 4c when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200. The stroke sensor 7c can acquire the displacement of the piston 4cp and rod 4cr of the bucket cylinder 4c, and the strength of the ground 200 can be easily estimated using the peak velocity Vpk of the bucket cylinder 4c when the bucket 3c contacts the ground 200.

[0119] As shown in Figure 8, the bucket 3c may contact the ground 200 in a position where the angle at which the reference line 3ct, which connects the central axis 3cr (the pivot axis of the bucket 3c) and the tip 3ci of the front lip 3ca, is inclined with respect to the ground 200 is ±5° or less. When the bucket 3c contacts the ground 200 in a position where the reference line 3ct is parallel to the ground 200 and receives a reaction force from the ground 200, an external force acts on the bucket cylinder 4c, as shown in Figure 9. The head pressure of the bucket cylinder 4c changes, and the velocity of the bucket cylinder 4c also changes.

[0120] The ground strength estimation unit 57 can easily estimate the strength of the ground 200 using information acquired when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200. This makes it possible to estimate the strength of the ground 200 using the hydraulic excavator 100 without damaging the ground 200. Compared to the case where the bottom surface 3cb contacts the ground 200, the area in contact between the outer surface of the bucket 3c and the ground 200 is reduced, and the external force acting on the bucket cylinder 4c can be increased, making it easier to detect information about the bucket cylinder 4c.

[0121] As shown in Figure 8, when the bucket 3c contacts the ground 200 and receives a reaction force from the ground 200, the bottom surface 3cb of the bucket 3c is away from the ground 200, and the curved portion 3cd of the bucket 3c may be in contact with the ground. This makes it possible to reliably apply an external force to the bucket cylinder 4c by bringing the bucket 3c into contact with the ground 200 in a position where the reference straight line 3ct is parallel to the ground 200. When the bucket 3c contacts the ground 200, the cutting edge of the bucket 3c is reliably in a position away from the ground 200, so the strength of the ground 200 can be estimated without damaging the ground 200.

[0122] As shown in Figures 6 and 8, the bucket 3c may approach the ground 200 from a position away from it and make contact with it. By performing an action similar to the compaction operation when compacting the ground 200, and using the information acquired at that time, the strength of the ground 200 can be easily estimated. By performing an action similar to the measurement of the strength of the ground 200 by impact tests such as a small-scale FWD (Falling Weight Deflectometer) test, and using the information acquired at that time, the strength of the ground 200 can be easily estimated.

[0123] As shown in Figure 7, the work machine control unit 51 of the main controller 50 may bring the bucket 3c closer to the ground 200 by executing a predetermined movement of the boom 3a. By bringing the bucket 3c into contact with the ground 200 with a certain movement and using the information acquired at that time, variations due to operator operation can be reduced, and the strength of the ground 200 can be estimated with greater accuracy.

[0124] As shown in Figures 6 and 8, the work machine control unit 51 of the main controller 50 may maintain the relative position between the bucket 3c and the boom 3a while the bucket 3c is approaching the ground 200. By bringing the bucket 3c into contact with the ground 200 in a constant work machine posture and using the information acquired at that time, variations due to operator operation can be reduced, and the strength of the ground 200 can be estimated with greater accuracy.

[0125] <Other> The sensor that detects information about the bucket cylinder 4c that drives the bucket 3c at the tip of the work machine 3 may be a sensor that is equipped on the hydraulic excavator 100 at the time of shipment. The sensor may also be a sensor that is retrofitted to the hydraulic excavator 100 after shipment.

[0126] Information regarding the bucket cylinder 4c is not limited to information detected when the operator manually operates the hydraulic excavator 100. Information regarding the bucket cylinder 4c may also be detected when the hydraulic excavator 100 is operated under automatic control. The hydraulic excavator 100 may be equipped with a ground strength estimation mode, and when the operator selects the ground strength estimation mode, the hydraulic excavator 100 may be operated automatically to estimate the strength of the ground 200.

[0127] Information regarding the bucket cylinder 4c is not limited to information detected in real time. Information regarding the bucket cylinder 4c may be extracted from operational data from past operations of the work machine and used to estimate the strength of the ground 200.

[0128] The ground strength estimation unit 57 is not limited to estimating the strength of the ground 200 by reading a data table stored in the storage unit 59. The data table representing the correspondence between attachment information and the strength of the ground 200 may be stored in an external storage device rather than in the storage unit 59 inside the main controller 50.

[0129] The ground strength estimation unit 57 may have a ground strength estimation model that has been trained by machine learning. The trained ground strength estimation model may be generated by a training process using training data. The training data may be data in which the strength of the ground 200 measured by a measuring device such as a simple N-value meter is labeled with information about the actuator when the attachment at the tip of the work machine 3 is in contact with the ground 200. The trained ground strength estimation model may have undergone a training process using the training dataset so that when information about the actuator is input, it outputs the strength of the ground 200 from that information.

[0130] As described above, the main controller 50 may be mounted on the hydraulic excavator 100 or installed outside the hydraulic excavator 100. Therefore, the estimation of the ground strength 200 may be performed inside the hydraulic excavator 100 or on a server, tablet computer, or the like outside the hydraulic excavator 100.

[0131] In the embodiments, a hydraulic excavator 100 was described as an example of a work machine, but the concept of this disclosure may be applied to other types of work machines. The work machine is not limited to a tracked vehicle 1 having a tracked vehicle 1a, but may also have a wheeled vehicle. Furthermore, the work machine may be remotely operated and controllable via wireless communication.

[0132] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0133] 1 Traveling body, 2 Slewing body, 3 Working equipment, 3a Boom, 3b Arm, 3c Bucket, 3ca Front lip, 3cb Bottom surface, 3cc Deepest part, 3cd Curved part, 3ce Side plate, 3cf Opening edge, 3cg Rear edge, 3ch Opening, 3ci Tip, 3cj Tooth adapter, 3ck Tooth, 3cm Bracket, 3cn Plate, 3cp,3cq Hole, 3cr,3cs Central axis, 3ct Reference line, 4a Boom cylinder, 4b Arm cylinder, 4c Bucket cylinder, 4cb Bottom side oil chamber, 4ch Head side oil chamber, 4cp Piston, 4cr Rod, 6a,6b,6c,6d,6e,6f Pressure sensor, 7a,7b,7c Stroke sensor, 25 Operating device, 25a Operating lever, 25b Operating amount sensor, 38 EPC valve, 50 Main controller, 51 work machine control unit, 53 cylinder pressure acquisition unit, 54 cylinder stroke acquisition unit, 55 calculation unit, 57 ground strength estimation unit, 58 timer, 59 memory unit, 100 hydraulic excavator, 200 ground.

Claims

1. A work machine having an attachment at the tip, An actuator for driving the aforementioned attachment, A sensor that detects information related to the actuator, A ground strength estimation system comprising: a controller that estimates the strength of the ground using the change in the information when the attachment receives a reaction force from the ground.

2. The actuator is a hydraulic cylinder, The ground strength estimation system according to claim 1, wherein the information is the pressure of the hydraulic fluid in the hydraulic cylinder.

3. The ground strength estimation system according to claim 2, wherein the controller estimates the strength of the ground using the increase per unit time of the pressure that rises when the attachment receives a reaction force from the ground.

4. The ground strength estimation system according to claim 1, wherein the aforementioned information is the speed of the actuator.

5. The ground strength estimation system according to claim 4, wherein the controller estimates the strength of the ground using the peak value of the velocity when the attachment receives a reaction force from the ground.

6. The ground strength estimation system according to claim 1, wherein the controller estimates the strength of the ground by using the change in information when the attachment is brought closer to the ground from a position away from the ground and the attachment comes into contact with the ground.

7. The aforementioned work machine has a boom that supports the attachment, The ground strength estimation system according to claim 6, wherein the controller brings the attachment closer to the ground by performing a predetermined operation of the boom.

8. The controller maintains the relative position between the attachment and the boom while the attachment is brought closer to the ground. The ground strength estimation system according to claim 7.

9. A work machine having a bucket at its tip that is rotatable around a pivot axis, the bucket having a tooth at its tip and a front lip that supports the tooth, An actuator for driving the bucket, A sensor that detects information related to the actuator, A ground strength estimation system comprising: a controller that estimates the strength of the ground using information obtained when the bucket receives a reaction force from the ground in a posture in which the angle at which a reference line connecting the pivot axis of the bucket and the tip of the front lip is inclined with respect to the ground is plus or minus 5° or less.

10. The bucket has a flat bottom surface and a curved portion, the curved portion being further away from the front lip than the bottom surface. The ground strength estimation system according to claim 9, wherein when the bucket receives a reaction force from the ground, the bottom surface is separated from the ground and the curved portion is in contact with the ground.

11. The ground strength estimation system according to claim 9, wherein the controller estimates the strength of the ground by using the information obtained when the bucket approaches the ground from a position away from the ground and the bucket comes into contact with the ground.

12. The aforementioned work machine has a boom that supports the bucket, The ground strength estimation system according to claim 11, wherein the controller brings the bucket closer to the ground by performing a predetermined operation of the boom.

13. The controller maintains the relative position between the bucket and the boom while the bucket is being brought closer to the ground. The ground strength estimation system according to claim 12.

14. To detect information about the actuator that drives the attachment at the tip of the work machine, A method for estimating ground strength, comprising: estimating the strength of the ground using the change in the information when the attachment receives a reaction force from the ground.

15. The actuator is a hydraulic cylinder, The ground strength estimation method according to claim 14, wherein the detection includes detecting the pressure of the hydraulic fluid in the hydraulic cylinder.

16. The method for estimating ground strength according to claim 15, wherein the estimation includes estimating the strength of the ground using the increase per unit time of the pressure that rises when the attachment receives a reaction force from the ground.

17. The ground strength estimation method according to claim 14, wherein the detection includes detecting the speed of the actuator.

18. The ground strength estimation method according to claim 17, wherein the estimation includes estimating the strength of the ground using the peak value of the velocity when the attachment receives a reaction force from the ground.

19. The attachment is a bucket that can rotate around a pivot axis, and the bucket has teeth at its tip and a front lip that supports the teeth. The method for estimating ground strength according to claim 14, wherein the estimation includes estimating the strength of the ground using the change in information when the bucket receives a reaction force from the ground in a posture in which the reference line connecting the pivot axis of the bucket and the tip of the front lip is inclined with respect to the ground at an angle of plus or minus 5° or less.

20. The ground strength estimation method according to claim 14, wherein the estimation includes estimating the strength of the ground using the change in information when the attachment is brought closer to the ground from a position away from the ground and the attachment comes into contact with the ground.

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