A working machine, a control system for a working machine, and a method for controlling a working machine.

Abstract

To easily control hydraulic cylinders. [Solution] The work machine comprises a vehicle body, a work implement attached to the vehicle body, a hydraulic cylinder for operating the work implement, and a controller for controlling the hydraulic cylinder. The controller outputs a cylinder speed v, which is the control output for operating the hydraulic cylinder, from a linear transfer function that represents the relationship between a control input based on a target value for the operation of the hydraulic cylinder and the control output for operating the hydraulic cylinder. The controller feeds back the cylinder speed v to generate a virtual control input u' based on the target value r for the operation of the hydraulic cylinder and the cylinder speed v, and inputs the virtual control input u' to the linear transfer function.

Description

Technical Field

[0001] The present disclosure relates to a working machine, a control system of the working machine, and a control method of the working machine.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2018-159210 (Patent Document 1) discloses an excavator including a controller that controls the displacement of a boom control valve, and the controller feedback-controls the displacement of the boom control valve based on an estimated flow rate of hydraulic oil passing through the boom control valve and an estimated flow rate of hydraulic oil flowing into a boom cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a working machine including a hydraulic cylinder that operates a working device, due to the characteristics of the hydraulic circuit through which the hydraulic oil supplied to the hydraulic cylinder flows, the transfer function representing the relationship between the target value of the operation of the hydraulic cylinder and the control output for operating the hydraulic cylinder becomes non-linear, so the control becomes complicated.

[0005] In the present disclosure, a technique for easily controlling a hydraulic cylinder is proposed.

Means for Solving the Problems

[0006] A working machine relating to a certain aspect of this disclosure comprises a vehicle body, a working machine attached to the vehicle body, a hydraulic cylinder for operating the working machine, and a controller for controlling the hydraulic cylinder. The controller outputs a control output for operating the hydraulic cylinder from a linear transfer function that represents the relationship between a control input based on a target value of the hydraulic cylinder's operation and a control output for operating the hydraulic cylinder. The controller feeds back the control output to generate a virtual control input based on the target value of the hydraulic cylinder's operation and the control output, and inputs the virtual control input to the linear transfer function.

[0007] A control method for a work machine according to a certain aspect of the present disclosure is a control method for controlling a hydraulic cylinder that operates a work machine mounted on the body of the work machine, and comprises the following steps: The first step is to obtain a linearized linear transfer function by applying a linearization function to a nonlinear transfer function that represents the relationship between a control output that operates the hydraulic cylinder and a control input based on a target value of the hydraulic cylinder's operation. The second step is to output a control output that operates the hydraulic cylinder from the obtained linear transfer function. The third step is to feed back the control output to generate a virtual control input based on the target value of the hydraulic cylinder's operation and the control output. The fourth step is to input the virtual control input to the linear transfer function.

[0008] A control system for a work machine according to one aspect of the present disclosure comprises a vehicle body, a work machine attached to the vehicle body, a hydraulic cylinder for operating the work machine, a controller for controlling the hydraulic cylinder, and an information processing device for processing information based on the operating characteristics of the hydraulic cylinder. The information processing device includes a memory and a processor. The memory stores a nonlinear transfer function that represents the relationship between a control input based on a target value for the operation of the hydraulic cylinder and a control output for operating the hydraulic cylinder. The processor applies a linearization function to the transfer function to generate a linearized linear transfer function. The controller obtains the linear transfer function generated by the information processing device, outputs a control output for operating the hydraulic cylinder from the linear transfer function, feeds back the control output to generate a virtual control input based on the target value for the operation of the hydraulic cylinder and the control output, and inputs the virtual control input to the linear transfer function. [Effects of the Invention]

[0009] According to this disclosure, hydraulic cylinders can be easily controlled. [Brief explanation of the drawing]

[0010] [Figure 1] This is an external view of a hydraulic excavator. [Figure 2] This is a diagram showing the configuration of a hydraulic circuit. [Figure 3] This is a schematic diagram showing the configuration of the playback circuit. [Figure 4] This is a schematic diagram showing the configuration of a swashplate-controlled pump. [Figure 5] This is a block diagram of the hydraulic system, including the regeneration circuit and swashplate-controlled pump. [Figure 6] This diagram shows the input / output characteristics of the hydraulic system. [Figure 7] This is a block diagram of an information processing device. [Figure 8] This is a block diagram showing the process for generating a linear transfer function. [Figure 9] This figure shows an example of a linearized function. [Figure 10] This figure shows an example of a linear transfer function. [Figure 11] This is a block diagram illustrating a control method applied to the hydraulic system specific to industrial machinery. [Figure 12] This is a block diagram illustrating the design process of a feedback controller. [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> In this embodiment, a hydraulic excavator 100 will be used as an example of a work machine. Figure 1 is an external view of a hydraulic excavator 100 as an example of a work machine.

[0013] As shown in Figure 1, the hydraulic excavator 100 has a main body 1 and a hydraulically operated work implement 2. The main body 1 has a slewing body 3 and a traveling body 5. The traveling body 5 has a pair of tracks 5Cr and a traveling motor 5M. The traveling motor 5M is provided as the drive source for the traveling body 5. The traveling motor 5M is a hydraulic motor that is operated by hydraulic pressure.

[0014] When the hydraulic excavator 100 is in operation, the vehicle 5, more specifically the track 5Cr, is in contact with the ground. The vehicle 5 is able to move on the ground by the rotation of the track 5Cr.

[0015] The rotating body 3 is positioned on and supported by the traveling body 5. The rotating body 3 is movable relative to the traveling body 5. The rotating body 3 is mounted on the traveling body 5 so as to be able to rotate relative to the traveling body 5 about the pivot axis RX. The rotating body 3 is attached to the traveling body 5 via a rotating circle section, and the rotating body 3 is able to rotate relative to the traveling body 5.

[0016] The slewing body 3 has a cab 4. The crew (operator) of the hydraulic excavator 100 sits in this cab 4 and operates the hydraulic excavator 100. The cab 4 is provided with a driver's seat 4S in which the operator sits. From inside the cab 4, the operator can operate the work implement 2, operate the slewing body 3 relative to the vehicle 5, and operate the hydraulic excavator 100 by the vehicle 5. In this disclosure, the hydraulic excavator 100 is operated from inside the cab 4, but it may also be remotely operated wirelessly from a location away from the hydraulic excavator 100.

[0017] In this embodiment, the positional relationships of each part of the slewing body 3 of the hydraulic excavator 100 will be described with reference to an operator seated in the driver's seat 4S inside the cab 4. The front-rear direction refers to the front-rear direction of the operator seated in the driver's seat 4S. The direction directly facing the operator seated in the driver's seat 4S is the front direction, and the direction behind the operator seated in the driver's seat 4S is the rear direction. The left-right direction refers to the left-right direction of the operator seated in the driver's seat 4S. The right and left sides are the right and left directions, respectively, when the operator seated in the driver's seat 4S is facing directly forward. The up-down direction refers to the up-down direction of the operator seated in the driver's seat 4S. The lower side is towards the operator's feet, and the upper side is towards their head.

[0018] In the forward and backward directions, the side from which the work implement 2 protrudes from the rotating body 3 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.

[0019] The slewing body 3 has an engine room 9 in which the engine is housed, and a counterweight located at the rear of the slewing body 3. The engine room 9 houses the engine that generates the driving force, a hydraulic pump that receives the driving force generated by the engine and supplies hydraulic fluid to the hydraulic actuator, and the like.

[0020] The work machine 2 is mounted on and supported by the slewing body 3. The work machine 2 has a boom 6, an arm 7, and a bucket 8. The boom 6 is rotatably connected to the slewing body 3. The arm 7 is rotatably connected to the boom 6. The bucket 8 is rotatably connected to the arm 7. The bucket 8 is located at the tip of the work machine 2. The tip of the bucket 8 is referred to as the cutting edge 8a. The bottom surface 8b is part of the outer surface of the bucket 8. The bottom surface 8b is formed as a flat surface.

[0021] The base end of the boom 6 is connected to the slewing body 3 via a boom foot pin 13. The boom 6 is rotatable relative to the slewing body 3 around the boom foot pin 13. The base end of the arm 7 is connected to the tip of the boom 6 via an arm connecting pin 14. The arm 7 is rotatable relative to the boom 6 around the arm connecting pin 14. The bucket 8 is connected to the tip of the arm 7 via a bucket connecting pin 15. The bucket 8 is rotatable relative to the arm 7 around the bucket connecting pin 15. The boom foot pin 13, arm connecting pin 14, and bucket connecting pin 15 extend approximately in the left-right direction.

[0022] The boom cylinder 10 drives the boom 6. The arm cylinder 11 drives the arm 7. The bucket cylinder 12 drives the bucket 8. Each of the boom cylinder 10, arm cylinder 11, and bucket cylinder 12 is a hydraulic cylinder driven by hydraulic fluid. The boom cylinder 10, arm cylinder 11, and bucket cylinder 12 constitute the work equipment actuator that operates the work equipment 2.

[0023] <Hydraulic circuit 30> Figure 2 shows the configuration of the hydraulic circuit 30, which is the drive circuit for the hydraulic cylinder. Figure 2 shows an example of the hydraulic circuit 30 through which the hydraulic fluid supplied to the boom cylinder 10 flows. The hydraulic circuit 30 mainly consists of a hydraulic fluid tank 32, a hydraulic pump 34, and a main valve 35.

[0024] The boom cylinder 10 includes a piston 10P, a rod 10R, a head-side oil chamber 10H, and a bottom-side oil chamber 10B. The hollow space inside the boom cylinder 10 is partitioned by the piston 10P. The head-side oil chamber 10H is the oil chamber on the cylinder head side relative to the piston 10P. The bottom-side oil chamber 10B is the oil chamber on the cylinder bottom side relative to the piston 10P. As hydraulic fluid is supplied to and discharged from the head-side oil chamber 10H and the bottom-side oil chamber 10B, the piston 10P moves axially (left-right direction in Figure 2), and the rod 10R also moves together with the piston 10P.

[0025] The hydraulic fluid tank 32 stores hydraulic fluid. The hydraulic pump 34, when driven, draws hydraulic fluid from the hydraulic fluid tank 32. The output shaft of an engine (not shown) is mechanically connected to the input shaft of the hydraulic pump 34, and the driving force of the engine is transmitted to the hydraulic pump 34 to drive the hydraulic pump 34. The power source that transmits the driving force to the hydraulic pump 34 may be an electric motor.

[0026] The hydraulic fluid discharged from the hydraulic pump 34 is supplied to the main valve 35 through the supply oil passage 41. By being driven, the hydraulic pump 34 supplies hydraulic fluid to the boom cylinder 10 through the main valve 35. The main valve 35 is located in the oil passage between the hydraulic pump 34 and the boom cylinder 10. The main valve 35 supplies and discharges the hydraulic fluid pumped from the hydraulic fluid tank 32 by the hydraulic pump 34 to the bottom oil chamber 10B of the boom cylinder 10 through the bottom oil passage 43, and to the head oil chamber 10H of the boom cylinder 10 through the head oil passage 44. The hydraulic fluid discharged from the boom cylinder 10 is returned to the hydraulic fluid tank 32 via the main valve 35 and the return oil passage 42.

[0027] The main valve 35 is a spool-type valve having a rod-shaped spool 360, and the direction of hydraulic fluid flow can be switched by moving the spool 360. The main valve 35 controls the supply and discharge of hydraulic fluid to the head-side oil chamber 10H and the bottom-side oil chamber 10B of the boom cylinder 10 by driving the spool 360. The main valve 35 has a pilot-driven spool 360 that moves when pilot oil is supplied to a pair of pressure-receiving chambers. The spool 360 of the main valve 35 may also be solenoid-driven. As the spool 360 of the main valve 35 moves, the flow rate of hydraulic fluid supplied to the boom cylinder 10 changes, and the extension and retraction speed of the boom cylinder 10 (the speed at which the piston 10P moves in the axial direction of the boom cylinder 10; hereinafter simply referred to as cylinder speed) increases or decreases.

[0028] The operating lever 61 is located inside the cab 4, for example, to the side of the driver's seat 4S. The operator seated in the driver's seat 4S manually operates the operating lever 61 to operate the boom 6. The operating lever 61 incorporates an operating amount detection sensor, such as a potentiometer. The operating amount of the operating lever 61 is detected by the operating amount detection sensor. The operating amount detection sensor outputs a detection signal indicating the operating amount of the operating lever 61 to the controller 50. The controller 50 may be, for example, a computer, server, or mobile terminal, and may also be a CPU (Central Processing Unit).

[0029] The controller 50 controls the spool 360 of the main valve 35 based on a detection signal indicating the amount of operation of the operating lever 61, obtained from the operation amount detection sensor. The electromagnetic proportional control valve 38 is located in the pilot oil path. The controller 50 outputs a command current to the electromagnetic proportional control valve 38 based on the amount of operation of the operating lever 61. The controller 50 controls the pressure of the pilot oil supplied to the main valve 35 by controlling the opening degree of the electromagnetic proportional control valve 38. As pilot oil with a predetermined pressure is supplied to each pressure-receiving chamber of the main valve 35, the position of the spool of the main valve 35 changes. This adjusts the amount of hydraulic fluid supplied to the boom cylinder 10, thereby controlling the boom cylinder 10.

[0030] If one end of the spool 360 is connected to a spring, and a force proportional to the input voltage u based on the amount of operation of the operating lever 61 is applied from the other end of the spool 360, then the equation of motion for the spool 360 is expressed by the following equation (1).

[0031]

number

[0032] In equation (1), x s This is the displacement of the spool 360, D s The damping coefficient of the spool 360 is k s The spring constant, m s The mass of the spool is 360, K s x is the proportionality constant, and u is the input voltage based on the amount of manipulation of the operating lever 61. The first and second terms on the left side of equation (1) cancel each other out in the steady state, so if the amount of manipulation of the operating lever 61 is kept constant, the position of the spool 360 is fixed at a constant level. The displacement x of the spool 360 is determined by the input voltage u based on the lever input. s It changes.

[0033] As the spool 360 of the main valve 35 moves, the flow rate of the hydraulic fluid changes. The orifice flow passing through the main valve 35 and the compression of the hydraulic fluid result in the differential equations shown in equations (2) and (3).

[0034] [Number]

[0035] [Number]

[0036] In equations (2) and (3), p + [[ID=2l]]is the pressure of the hydraulic oil in the bottom-side oil chamber 10B (bottom pressure), K(p) is the bulk modulus of elasticity, A + is the cross-sectional area of the bottom-side oil chamber 10B, y p is the position of the piston 10P, L is the length of the boom cylinder 10, c is the flow gain, P p is the pressure of the hydraulic oil discharged from the hydraulic pump 34 (pump pressure), x s is the displacement of the spool 360, p - is the pressure of the hydraulic oil in the head-side oil chamber 10H (head pressure), A - is the cross-sectional area of the head-side oil chamber 10H, P T is the pressure of the hydraulic oil in the hydraulic oil tank 32.

[0037] Due to the compression of the hydraulic oil, the pressures on both sides of the piston 10P (bottom pressure and head pressure) change, and the piston 10P moves due to the pressure difference between the two sides of the piston 10P. The velocity of the piston 10P is determined by the equation of motion of the piston 10P expressed by equation (4).

[0038] [Number]

[0039] In equation (4), M p is the mass of the piston 10P, y p is the position of the piston 10P, D p is the damping coefficient of the piston 10P, A + is the cross-sectional area of the bottom-side oil chamber 10B, p [[ID=GO]] + is the bottom pressure, A - is the cross-sectional area of the head-side oil chamber 10H, p- This is the head pressure.

[0040] <Hydraulic equipment specific to industrial machinery> In industrial machinery, the hydraulic system mechanism is complex in order to improve the performance of the hydraulic system or to increase the discharge pressure of the hydraulic pump 34 when excessive force is applied to the piston 10P. The hydraulic equipment that affects the actual behavior of the industrial machinery includes hydraulic equipment with nonlinear characteristics, such as the regeneration circuit of the hydraulic cylinder and the swashplate-controlled pump.

[0041] Figure 3 is a schematic diagram showing the configuration of the regeneration circuit. The main valve 35 has a hollow cylindrical sleeve 350. The sleeve 350 has a plurality of ports that connect the outer and inner surfaces of the sleeve 350. These plurality of ports include a supply port 351, a return port 352, a bottom-side port 353, a head-side port 354, a first regeneration port 355, and a second regeneration port 356.

[0042] The supply oil passage 41, through which the hydraulic fluid discharged from the hydraulic pump 34 flows, is connected to the supply port 351. The return oil passage 42, through which the hydraulic fluid returning to the hydraulic fluid tank 32 flows, is connected to the return port 352. In Figure 3, arrow F3 indicates the flow of hydraulic fluid discharged from the hydraulic pump 34 and flowing through the supply oil passage 41 toward the main valve 35, and arrow F2 indicates the flow of hydraulic fluid flowing through the return oil passage 42 toward the hydraulic fluid tank 32.

[0043] The bottom-side oil passage 43, which supplies and discharges hydraulic fluid to the bottom-side oil chamber 10B, is in communication with the bottom-side port 353. The head-side oil passage 44, which supplies and discharges hydraulic fluid to the head-side oil chamber 10H, is in communication with the head-side port 354. The regeneration circuit 370 connects the first regeneration port 355 and the second regeneration port 356.

[0044] The spool 360 is housed in the sleeve 350 and moves relative to the sleeve 350. The outer circumferential surface of the spool 360 has a plurality of recesses formed therein, where a portion of the outer circumferential surface is recessed. The plurality of recesses include a supply recess 361, a return recess 362, and a regeneration recess 363.

[0045] When the spool 360 is positioned relative to the sleeve 350 as shown in Figure 3, the supply recess 361 connects the supply port 351 and the bottom port 353. The hydraulic fluid discharged from the hydraulic pump 34 and reaching the main valve 35 through the supply oil passage 41 flows through the supply port 351, the supply recess 361, and the bottom port 353 in order to the bottom oil passage 43 and is supplied to the bottom oil chamber 10B. The arrow F4 shown in Figure 3 indicates the flow of hydraulic fluid from the main valve 35 towards the bottom oil chamber 10B, flowing through the bottom oil passage 43 and into the bottom oil chamber 10B.

[0046] The return recess 362 connects the head-side port 354 and the return port 352. The hydraulic fluid that flows out of the head-side oil chamber 10H of the boom cylinder 10, passes through the head-side oil passage 44 and reaches the main valve 35, then flows through the head-side port 354, the return recess 362, and the return port 352 in sequence, into the return oil passage 42, and returns to the hydraulic fluid tank 32. The arrow F1 shown in Figure 3 indicates the flow of hydraulic fluid that flows out of the head-side oil chamber 10H of the boom cylinder 10 and through the head-side oil passage 44 toward the main valve 35.

[0047] The regeneration recess 363 connects the head-side port 354 and the first regeneration port 355. A portion of the hydraulic fluid that flows out of the head-side oil chamber 10H of the boom cylinder 10 and reaches the main valve 35 through the head-side oil passage 44 flows to the regeneration circuit 370 via the head-side port 354, the regeneration recess 363, and the first regeneration port 355 in that order. The arrow FR shown in Figure 3 indicates the flow of hydraulic fluid through the regeneration circuit 370 from the first regeneration port 355 to the second regeneration port 356.

[0048] Assume that an external force, indicated by arrow AR in Figure 3, is applied to the rod 10R of the boom cylinder 10, moving the rod 10R out of the cylinder. At this time, the head-side oil chamber 10H of the boom cylinder 10 becomes high pressure, the bottom-side oil chamber 10B becomes low pressure, and the hydraulic fluid in the high-pressure head-side oil chamber 10H flows out of the head-side oil chamber 10H and flows to the main valve 35. Spool displacement x s This changes the flow rate of hydraulic fluid returning to the hydraulic fluid tank 32. Spool displacement x s When the amount exceeds a certain level, some of the hydraulic fluid is regenerated. Some of the hydraulic fluid flows from the head-side oil passage 44 through the regeneration recess 363 to the regeneration circuit 370, then sequentially through the second regeneration port 356, the supply recess 361, and the bottom-side port 353 to the bottom-side oil passage 43, and into the bottom-side oil chamber 10B.

[0049] The flow rate of the hydraulic fluid to be regenerated is expressed by the following equation (5).

[0050]

number

[0051] In equation (5), q s c is the regeneration flow rate, c is the flow coefficient, x s x is the spool displacement. sd The spool displacement at which regeneration begins is p + is bottom pressure, p - This is the head pressure.

[0052] However, if the spool displacement is smaller than the spool displacement that initiates regeneration, it means that the regeneration valve is closed, and the regeneration flow rate becomes 0, as shown by equation (6).

[0053]

number

[0054] Because the main valve 35 has a regeneration circuit 370, a portion of the hydraulic fluid that has flowed out from the high-pressure head-side oil chamber 10H is regenerated and flows into the low-pressure bottom-side oil chamber 10B. Due to this characteristic, the flow rate of hydraulic fluid flowing into the bottom-side oil chamber 10B increases, thus improving the cylinder speed. A nonlinearity occurs because the flow rate of hydraulic fluid that the hydraulic pump 34 tries to flow does not match the flow rate of hydraulic fluid actually supplied to the boom cylinder 10. When the hydraulic circuit 30 includes the regeneration circuit 370, the spool displacement x s The spool displacement x at which regeneration begins sd Since the flow rate of the hydraulic fluid changes depending on whether it exceeds a certain threshold, this point becomes a dead zone, resulting in nonlinearity.

[0055] Figure 4 is a schematic diagram showing the configuration of a swashplate-controlled pump. The hydraulic pump 34 is a swashplate-controlled pump. The swashplate-controlled pump is a mechanism that determines the pump pressure according to the bottom pressure of the boom cylinder 10. When a large external force is applied to the rod 10R of the boom cylinder 10, the pump pressure also increases in proportion to that external force, thus having the characteristic of being able to handle high loads.

[0056] The swashplate-controlled pump comprises a swashplate 440, an outer casing 442 housing the swashplate 440, and a pair of cylinder pumps 445 and 446. The rods of the cylinder pumps 445 and 446 are connected to the swashplate 440. The pump's performance changes as the angle of the swashplate 440 changes. Specifically, the flow rate of hydraulic fluid discharged by the cylinder pumps 445 and 446 changes during one rotation of the outer casing 442.

[0057] The swash plate control cylinder 450 includes a piston 451, a rod 452, and a return spring 453. The rod 452 is connected to the swash plate 440. As the piston 451 moves within the swash plate control cylinder 450, the rod 452 moves together with the piston 451, causing the angle of the swash plate 440 to change.

[0058] The piston 451 divides the internal space of the swash plate control cylinder 450 into a first oil chamber 454 and a second oil chamber 455. Part of the rod 452 is located in the first oil chamber 454. The return spring 453 is located in the second oil chamber 455. The first oil chamber 454 is in communication with the bottom oil chamber 10B of the boom cylinder 10. The pressure of the hydraulic fluid in the first oil chamber 454 becomes the bottom pressure of the boom cylinder 10. The second oil chamber 455 is in communication with the supply oil passage 41. The pressure of the hydraulic fluid in the second oil chamber 455 becomes the pump pressure.

[0059] When a large load is applied to the rod 10R of the boom cylinder 10 and the bottom pressure rises, the pressure in the first oil chamber 454 of the swash plate control cylinder 450 increases, causing the piston 451 to move toward the second oil chamber 455. The position of the piston 451 is determined by the balance between the pressure in the first oil chamber 454 and the biasing force of the return spring 453. The rod 452 moves together with the piston 451 in a direction that draws it into the swash plate control cylinder 450. As the rod 452 moves, the swash plate 440 moves. In Figure 4, the swash plate 440 moves so as to rotate counterclockwise. The inclination of the outer shell 442 of the swash plate 440 with respect to the axial direction of rotation becomes smaller.

[0060] As the swash plate 440 moves, the distance the pistons of the cylinder pumps 445 and 446 move increases. As a result, the flow rate of hydraulic fluid discharged from the hydraulic pump 34 increases during one rotation of the outer shell 442, and therefore the pump pressure also increases.

[0061] The equation of motion for the piston 451 of the swashplate control cylinder 450 is given by equation (7) below.

[0062]

number

[0063] In equation (7), m po The mass of the piston 451 of the swash plate control cylinder 450, x po This is the position of piston 451, D po The viscosity coefficient of the hydraulic fluid is k.po The spring constant of the return spring 453 is p p is pump pressure, A p The cross-sectional area of ​​the first oil chamber 454 is p + The bottom pressure of the boom cylinder 10, A + is the cross-sectional area of ​​the second oil chamber 455. The equation of motion for the piston 451 shows that the position of the piston 451 is determined by the mass of the piston 451, the viscosity of the hydraulic fluid, and the return spring 453.

[0064] The angle of the swash plate 440 is expressed by the following equation (8), with the counterclockwise direction in Figure 4 being positive.

[0065]

number

[0066] In equation (8), α is the angle of the swash plate 440, l p The length of the slanted plate is 440, l' p The horizontal length of the slanted plate 440, x po This is the position of piston 451. Equation (8) shows that the angle of the swash plate 440 changes depending on the position of piston 451.

[0067] The flow rate of the hydraulic fluid discharged from the pump is expressed by the following equation (9).

[0068]

number

[0069] In equation (9), q p is the pump volumetric flow rate, r is the turning radius, A po ω is the cross-sectional area of ​​the pump cylinder, ω is the angular velocity of the pump rotation, and α is the angle of the swash plate 440. Since the cylinder pumps 445 and 446 move a distance equal to the tangent of the angle of the swash plate 440 multiplied by the rotation radius of the cylinder pumps 445 and 446, the flow rate pushed out per second by the cylinder pumps is expressed by equation (9).

[0070] The formula for determining the pump pressure is expressed by the following formula (10).

[0071]

number

[0072] In equation (10), p p is the pump pressure, K(p p ) is the bulk modulus of the hydraulic fluid, V po q is the volume of the fluid that becomes the pump pressure. p q is the pump volumetric flow rate, q + is the head flow rate. Equation (10) is an equation in which the pressure is determined by the compression of the hydraulic fluid, q p q is the flow rate from the pump. + Since q is the flow rate into the cylinder, p -q + V represents the flow rate of the hydraulic fluid that is generating the pump pressure. po The pump pressure is determined by how much the hydraulic fluid is compressed compared to the original pressure.

[0073] If the hydraulic circuit 30 includes a swashplate-controlled pump, the inverse sine function in equation (8) and the tangent function in equation (9) are nonlinear, thus resulting in nonlinearity.

[0074] Figure 5 is a block diagram of the hydraulic system including the regeneration circuit 370 and the swash plate control pump. The spool system controls the displacement x of the spool in relation to the input voltage u based on the amount of operation of the operating lever 61. s The output is the spool displacement x. s bottom pressure p + and head pressure p - Obtain the regeneration flow rate q s The output is determined by the spool displacement x. s , pressure on both sides of the piston (bottom pressure p + and head pressure p - ), regeneration flow rate q s , and pump pressure p p Obtain the flow rate q entering both sides of the cylinder. +, q ー Outputs.

[0075] The pressure determination system determines the flow rate q entering both sides of the cylinder. + , q ー And, pump pressure p p Obtain the pressure p on both sides of the piston. + , p - It outputs the head flow rate q. The swashplate-controlled pump outputs the head flow rate q. + and bottom pressure p + Obtain the pump pressure p p It outputs the following: The piston-cylinder system is the pressure p on both sides of the piston. + , p - Obtain the cylinder speed v (y shown in equation (4)) p It outputs the same as the time derivative of .

[0076] Figure 6 shows the input-output characteristics of the hydraulic system. In the graph shown in Figure 6, the horizontal axis represents the magnitude of the input, specifically the input voltage u based on the amount of manipulation of the operating lever 61, and the vertical axis represents the steady-state value of the output, the cylinder speed v. The diagram shown in Figure 6 is not linear, indicating that the input-output characteristics of the hydraulic system are nonlinear. Since the theoretical equations (equations (5) to (10)) for the regeneration circuit 370 and the swashplate control pump are nonlinear, the mathematical model of the hydraulic system is also nonlinear.

[0077] The input used as the horizontal axis in the graph of Figure 6 is not limited to the input voltage u. The input may be the amount of operation of the operating lever 61 itself. The input may be an input command to the spool of the main valve 35. The input command may be a pilot pressure that fluctuates due to the operation of the operating lever 61, or a voltage when the spool moves in proportion to the applied voltage. The input may also be the displacement of the spool due to the operation of the operating lever 61. The output used as the vertical axis in the graph of Figure 6 is not limited to the cylinder speed v. The output may be the position of the piston.

[0078] <Generation of linear transfer functions> When feeding back cylinder velocity v, the transfer function of the hydraulic system becomes nonlinear due to the characteristics of the hydraulic equipment in the work machine, requiring complex nonlinear control. To use the common two-degree-of-freedom feedback control system, the transfer function must be linear. The following describes methods for treating the mathematical model of a nonlinear system as linear.

[0079] Figure 7 is a block diagram of the information processing device 150. The information processing device 150 processes information based on the operating characteristics of the boom cylinder 10 that operates the work implement 2 attached to the body (main unit 1) of the work machine. The information processing device 150 may be a personal computer or a portable information terminal such as a tablet computer. The information processing device 150 includes a memory 160, a processor 170, and an output device 180.

[0080] Memory 160 includes non-volatile memory such as ROM (Read Only Memory). Memory 160 may also include volatile memory such as RAM (Random Access Memory). Memory 160 stores the transfer function 161. The transfer function 161 represents the relationship between a control input based on a target value for the operation of the boom cylinder 10 and a control output that operates the boom cylinder 10. An example of a target value for the operation of the boom cylinder 10 is the input voltage u. An example of a control output is the cylinder speed v. The transfer function 161 is represented by the diagram shown in Figure 6. The transfer function 161 is nonlinear.

[0081] The processor 170 is, for example, a CPU. The processor 170 reads the nonlinear transfer function 161 from memory 160. The processor 170 applies a linearization function to the nonlinear transfer function 161 to generate a linearized transfer function. Figure 8 is a block diagram showing the process of generating a linear transfer function. The processor 170 generates a linearized transfer function by multiplying the nonlinear transfer function 161 by the linearization function.

[0082] Figure 9 shows an example of a linearized function. In the graph shown in Figure 9, the horizontal axis represents the steady-state value of the cylinder velocity v, and the vertical axis represents the input voltage u. The linearized function shown in Figure 9 is generated based on the inverse mapping of the nonlinear transfer function shown in Figure 6. More specifically, the linearized function is the transfer function shown in Figure 6 with the vertical and horizontal axes swapped.

[0083] Figure 10 shows an example of a linear transfer function. By multiplying the nonlinear transfer function shown in Figure 6 by its inverse mapping, which is a linearization function, the apparent input-output characteristics of the controlled system, where the input is voltage u' and the output is cylinder velocity v, become quite close to linear. By introducing the linearization function, which is the inverse mapping of the transfer function, before the nonlinear transfer function, it becomes possible to define a linearized linear transfer function.

[0084] The output device 180 outputs a linearized linear transfer function. The linear transfer function output from the output device 180 can then be used to control the boom cylinder 10.

[0085] The information processing device 150 may be mounted on the hydraulic excavator 100. The controller 50 that controls the spool of the main valve 35, as shown in Figure 2, may have the function of the information processing device 150. A computer separate from the controller 50 may also be mounted on the hydraulic excavator 100 as the information processing device 150.

[0086] Alternatively, the information processing device 150 does not have to be mounted on the hydraulic excavator 100. The information processing device 150 may be located outside the hydraulic excavator 100. The information processing device 150 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 hydraulic excavator 100 and the information processing device 150 located outside the hydraulic excavator 100 may constitute the control system of the hydraulic excavator 100.

[0087] <Two-degree-of-freedom control using linear transfer functions> To improve control performance relative to the target value response, a two-degree-of-freedom control system that combines feedforward control and feedback control is effective. Feedback control suppresses the effects of disturbances, reduces the impact of characteristic variations and modeling errors in the controlled system, and stabilizes unstable systems. Feedforward control allows for the determination of the input relative to the target value. In this control system, the current control output, cylinder velocity v, is fed back, enabling improvements in responsiveness and steady-state characteristics.

[0088] Figure 11 is a block diagram showing the configuration of a control system applied to a hydraulic system specific to a work machine. The controller 50 (Figure 2) calculates the command value, cylinder speed v, from the target value r of cylinder speed according to the control system shown in the block diagram of Figure 11. Since the hydraulic circuit of the work machine includes hydraulic equipment with nonlinear characteristics, a linear transfer function shown in Figure 10 is used to apply a two-degree-of-freedom control system. Because the input-output characteristics of the apparent controlled object, with the input (virtual control input) being voltage u' and the output being cylinder speed v, are linear, it becomes possible to control it using the control method of a two-degree-of-freedom control system. This simplifies the control process.

[0089] The controller 50 outputs a cylinder speed v, which is a control output for operating the boom cylinder 10, from a linear transfer function. The filter shown in Figure 11 is provided to specify the characteristic response of the output cylinder speed v and is designed to prevent the input from becoming excessive.

[0090] This section describes the design of a feedback controller. A feedback controller needs to be an integral controller to eliminate steady-state errors for step-like target values ​​and disturbances. Therefore, an integrator is attached to the transfer function P(s) of the hydraulic system. e (s) is considered a virtual control target, P e (s) Stabilizing feedback controller H e Design (s).

[0091] Figure 12 shows controller H applied to a virtual controlled object. eThis is a block diagram showing the design process of (s). K shown in Figure 12 is the feedback gain, which is determined by the optimal regulator so that J in equation (11) below is minimized.

[0092]

number

[0093] In equation (11), Q is a positive definite symmetric matrix and R is a constant; these are coefficients that determine the weights. From K thus obtained, the regulator poles, which are eigenvalues ​​of A-BK, are found, where A, B, and C shown in Figure 12 are P e This is the equation of state for (s).

[0094] It is known that the observer electrode should be slightly larger than the regulator electrode, so a regulator electrode 1.1 times larger is used. The observer system is represented by the following equations (12)(13), where L is the observer gain.

[0095]

number

[0096]

number

[0097] By performing a Laplace transform on equations (12) and (13) and eliminating the input, we get controller H e (s) is expressed by the following equation (14).

[0098]

number

[0099] Controller H designed in this way eBy dividing (s) by s, an integral-type feedback controller H(s) to be applied to the actual controlled object can be designed. As shown in Figure 11, in the feedback controller, the feedback value of the input voltage is calculated from the difference between the target value r of the cylinder speed via the filter and the command value, which is the cylinder speed v.

[0100] In the feedforward controller shown in Figure 11, the feedforward value of the input voltage is calculated from the target value r of the cylinder speed. The feedforward controller can be represented by the transfer function F(s) / P(s), which uses the transfer function P(s) of the hydraulic system and the target characteristic F(s) of the filter. The controller 50 performs feedforward control of the boom cylinder 10 based on the target value r.

[0101] The controller 50 generates a virtual control input u' by adding the output of the feedforward controller when a target value r is given to the feedforward controller and the output of the feedback controller when the cylinder speed v is fed back. The virtual control input u' is generated based on the target value r, which is the target value for the operation of the boom cylinder 10, and also based on the cylinder speed v, which is the control output. The controller 50 obtains the linear transfer function generated by the information processing device 150, inputs the virtual control input u' to the obtained linear transfer function, and outputs the cylinder speed v, which is the control output for operating the boom cylinder 10, from the linear transfer function.

[0102] <Mechanism of Action and Effects> The characteristic configuration and effects of this embodiment are summarized below.

[0103] As shown in Figure 7, the information processing device 150, which processes information based on the operating characteristics of the boom cylinder 10 that operates the work implement 2 attached to the body of the work machine, comprises a memory 160 and a processor 170. The memory 160 stores the transfer function 161. As shown in Figure 6, the transfer function 161 represents the relationship between the control input, which is based on the target value of the boom cylinder 10's operation, and the control output that operates the boom cylinder 10. The transfer function 161 is nonlinear. As shown in Figures 8 to 10, the processor 170 applies a linearization function to the transfer function 161 to generate a linearized linear transfer function.

[0104] The hydraulic circuit 30 through which the hydraulic fluid supplied to the boom cylinder 10 flows includes hydraulic equipment with nonlinear characteristics, such as a swashplate control pump and a regeneration circuit 370. Therefore, the input-output characteristics of the hydraulic system shown in Figure 6 are nonlinear. By applying a linearization function to the nonlinear transfer function 161 to generate a linearized transfer function, it becomes possible to control the boom cylinder 10 using a linear transfer function. Since the apparent input-output characteristics of the controlled object, with the input (virtual control input) being voltage u' and the output being cylinder speed v, are linear, it becomes possible to control it using a control method for a two-degree-of-freedom control system. This allows for easy control of the boom cylinder 10.

[0105] As shown in Figures 6 and 9, the linearization function may be generated based on the inverse mapping of the transfer function 161. By applying the linearization function shown in Figure 9, which is obtained by swapping the vertical and horizontal axes of the transfer function 161 shown in Figure 6, to the transfer function 161, a linearized linear transfer function can be reliably generated.

[0106] As shown in Figures 1 and 2, the work machine comprises a vehicle body, a work implement 2 attached to the vehicle body, a hydraulic cylinder that operates the work implement 2, and a controller 50 that controls the hydraulic cylinder. As shown in Figure 11, the controller 50 obtains a linear transfer function by applying a linearization function to a nonlinear transfer function that represents the relationship between a control input based on a target value for the operation of the hydraulic cylinder and the control output that operates the hydraulic cylinder, which is generated by the information processing device 150. From the obtained linear transfer function, the controller 50 outputs the cylinder speed v, which is the control output that operates the hydraulic cylinder. The controller 50 feeds back the cylinder speed v to generate a virtual control input u' based on the target value r for the operation of the hydraulic cylinder and the cylinder speed v, and inputs the virtual control input u' to the linear transfer function.

[0107] By using a linear transfer function, which is a linearized version of a nonlinear transfer function, for feedback control, hydraulic cylinders can be controlled with simple control without the need for complex nonlinear control.

[0108] As shown in Figure 11, the controller 50 may feedforward control the hydraulic cylinder based on the target value r of the hydraulic cylinder's operation. By using a linear transfer function, it becomes possible to apply a two-degree-of-freedom control system that combines feedforward control and feedback control, thereby simplifying the control.

[0109] Although the control of the boom cylinder 10 has been described in the embodiments, the ideas of this disclosure may also be applied to the control of other hydraulic cylinders, specifically the arm cylinder 11 or the bucket cylinder 12.

[0110] In the hydraulic excavator 100 of this embodiment, the hydraulic circuit 30 includes both a swash plate control pump and a regeneration circuit 370. The hydraulic circuit 30 may include only one of the swash plate control pump and the regeneration circuit 370. Alternatively, the hydraulic circuit 30 may not include the swash plate control pump and the regeneration circuit 370, but may include other types of hydraulic equipment with nonlinear characteristics, such as a relief valve.

[0111] 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 not only to the hydraulic excavator 100 but also to other types of work machines such as wheel loaders.

[0112] 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 to be included. [Explanation of Symbols]

[0113] 1 Main body, 2 Work implement, 3 Slewing body, 4 Cab, 5 Traveling body, 6 Boom, 7 Arm, 8 Bucket, 10 Boom cylinder, 10B Bottom side oil chamber, 10H Head side oil chamber, 10P,451 Piston, 10R,452 Rod, 11 Arm cylinder, 12 Bucket cylinder, 30 Hydraulic circuit, 32 Hydraulic oil tank, 34 Hydraulic pump, 35 Main valve, 38 Electromagnetic proportional control valve, 41 Supply oil passage, 42 Return oil passage, 43 Bottom side oil passage, 44 Head side oil passage, 50 Controller, 61 Operating lever, 100 Hydraulic excavator, 150 Information processing device, 160 Memory, 161 Transfer function, 170 Processor, 180 Output device, 350 Sleeve, 351 Supply port, 352 Return port, 353 Bottom side port, 354 Head-side port, 355 First regeneration port, 356 Second regeneration port, 360 Spool, 361 Supply recess, 362 Return recess, 365 Regeneration recess, 370 Regeneration circuit, 440 Swash plate, 442 Outer shell, 445, 446 Cylinder pump, 450 Swash plate control cylinder, 453 Return spring, 454 First oil chamber, 455 Second oil chamber.

Claims

1. The car body and, The work equipment attached to the vehicle body, A hydraulic cylinder for operating the aforementioned work machine, The system includes a controller for controlling the hydraulic cylinder, The controller outputs a control output for operating the hydraulic cylinder from a linear transfer function that represents the relationship between a control input based on a target value for the operation of the hydraulic cylinder and a control output for operating the hydraulic cylinder, feeds back the control output to generate a virtual control input based on the target value for the operation of the hydraulic cylinder and the control output, and inputs the virtual control input to the linear transfer function, in a work machine.

2. The working machine according to claim 1, wherein the linear transfer function is a function generated by applying a linearization function to a nonlinear transfer function that represents the relationship between the control input, which is based on a target value for the operation of the hydraulic cylinder, and the control output that operates the hydraulic cylinder.

3. The work machine according to claim 2, wherein the linearization function is generated based on the inverse mapping of the transfer function.

4. The hydraulic circuit further comprises a hydraulic circuit through which the hydraulic fluid supplied to the hydraulic cylinder flows. The working machine according to claim 1, wherein the hydraulic circuit includes hydraulic equipment having nonlinear characteristics.

5. The work machine according to claim 4, wherein the hydraulic equipment includes at least one of a swash plate control pump and a regeneration circuit for the hydraulic cylinder.

6. The work machine according to claim 1, wherein the controller feedforward controls the hydraulic cylinder based on the target value.

7. The car body and, The work equipment attached to the vehicle body, A hydraulic cylinder for operating the aforementioned work machine, A controller for controlling the hydraulic cylinder, The system includes an information processing device that processes information based on the operating characteristics of the hydraulic cylinder, The aforementioned information processing device is A memory that stores a nonlinear transfer function representing the relationship between a control input based on a target value for the operation of the hydraulic cylinder and the control output that operates the hydraulic cylinder, A processor that applies a linearization function to the transfer function to generate a linearized linear transfer function, The controller acquires the linear transfer function generated by the information processing device, outputs a control output from the linear transfer function to operate the hydraulic cylinder, feeds back the control output to generate a virtual control input based on the target value of the hydraulic cylinder's operation and the control output, and inputs the virtual control input to the linear transfer function. Control system for industrial machinery.

8. The control system according to claim 7, wherein the linearization function is generated based on the inverse mapping of the transfer function.

9. A control method for controlling a hydraulic cylinder that operates a work implement attached to the body of a work machine, Applying a linearization function to a nonlinear transfer function that represents the relationship between a control input based on a target value for the operation of the hydraulic cylinder and the control output that operates the hydraulic cylinder, a linearized linear transfer function is obtained. The linear transfer function outputs a control output for operating the hydraulic cylinder, The control output is fed back to generate a virtual control input based on the target value of the hydraulic cylinder's operation and the control output, A method for controlling a work machine, comprising inputting the virtual control input to the linear transfer function.

10. The control method according to claim 9, wherein the linearization function is generated based on the inverse mapping of the transfer function.

11. The control method according to claim 9, further comprising feedforward control of the hydraulic cylinder based on the target value.

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