Work machine

Abstract

A control device of this work machine is configured to calculate a control target value for controlling a control valve on the basis of the operation amount of an operation device and control the control valve. The control device calculates a flow rate supplied to a hydraulic actuator on the basis of a posture detected by a posture detector, estimates fluid force acting on the control valve on the basis of a differential pressure across the control valve obtained on the basis of a detection value of the posture detector and the calculated flow rate of the hydraulic actuator, calculates a correction value on the basis of the estimated fluid force, corrects the control target value by using the calculated correction value, and outputs the corrected control target value to the control valve as a control command.

Description

Working machinery

[0001] The present invention relates to a work machine, and more particularly to a work machine in which a driven object, such as a work device, is driven by a hydraulic actuator.

[0002] Construction machinery such as hydraulic excavators perform excavation and transportation tasks using working devices and slewing bodies as driven units driven by hydraulic actuators. In the field of construction machinery, the introduction of information-based construction, which aims to streamline construction work by applying information and communication technology to construction processes, has been progressing in recent years. Construction machinery that supports information-based construction requires precise control of the movement of the working devices and slewing bodies using detection information from sensors that detect the posture and position of the working devices and slewing bodies. In order to accurately control the movement of the working devices and slewing bodies, it is necessary to control the drive of the hydraulic actuators that operate the working devices and slewing bodies with high precision. In the hydraulic system of construction machinery, the drive of the hydraulic actuators is controlled by controlling the flow of pressurized oil to the hydraulic actuators using control valves. In order to control the drive of hydraulic actuators with high precision, it is necessary to improve the control precision of the control valves.

[0003] As an example of a method for improving the control accuracy of a control valve, the technology described in Patent Document 1 is known. The control device for hydraulic equipment described in Patent Document 1 controls the position of the operating valve by using the position (stroke amount) of the operating valve detected by a sensor circuit (stroke sensor) as a feedback amount. Furthermore, the control device incorporates a disturbance observer that estimates the state variables of the controlled object when a disturbance is applied to the controlled object. The disturbance observer of the control device estimates the disturbance applied to the actual controlled object (operating valve) based on the control model of the actual controlled object, using information on the input (position control signal) and output (position as detected data from the stroke sensor) to the actual controlled object, and feeds back the estimated disturbance to the control input side to cancel it out. The disturbance here is a fluid force called flow force that acts on the operating valve when fluid (pressurized oil) flows through the operating valve of the actual controlled object. Since this fluid force also changes when the flow rate passing through the operating valve changes, the position of the operating valve changes in accordance with the change in flow rate even if the same control signal is input to the operating valve. The technology described in Patent Document 1 aims to improve the responsiveness of the operating valve by accurately estimating the fluid force, which is a disturbance applied to the operating valve, by accurately identifying the control parameters of the control model of the actual controlled object (operating valve).

[0004] Furthermore, as another example of a measure to improve the control accuracy of a control valve, the technology described in Patent Document 2 is known. The technology described in Patent Document 2 aims to improve the accuracy of control regarding the movement of the valve body without using a sensor (stroke sensor) that detects the position of the valve device. Specifically, in this technology, the stroke command, which is the amount of stroke the valve body of the valve device should move, is calculated taking into account the flow force, which is the fluid force acting on the valve body. The flow force is estimated based on a value (estimated stroke amount) that is deviated from the stroke command by the amount of dynamic deviation included in the state variables of the valve body estimated by the observer. This dynamic deviation is the amount of stroke of the spool that fluctuates due to the dynamic load, which is the load (e.g., inertial force, viscous friction, and Coulomb friction) generated by the movement of the valve body when the valve body is moved in response to the stroke command. The observer estimates the dynamic load and estimates the state variables of the valve body, including the dynamic deviation, from the dynamic load estimated based on a predetermined linear state equation (control model of the valve device). Patent Document 2 states that when a stroke command is calculated using static equilibrium conditions, the stroke command is calculated based on a flow force that is not referenced, thus enabling the calculation of a highly accurate stroke command.

[0005] Japanese Patent Publication No. 2003-167604 Japanese Patent Publication No. 2021-148160

[0006] In the technology described in Patent Document 1, the operating valve is controlled using the detection value of a sensor (stroke sensor) that detects the position of the operating valve. However, some work machines compatible with information-based construction do not have such a sensor, and the technology described in Patent Document 1 cannot be applied to such work machines.

[0007] In the technology described in Patent Document 2, the stroke command to the valve device is calculated taking flow force into consideration. The flow force is estimated from the state variables (dynamic deviations) of the valve body, which are calculated by an observer using a control model (linear state equation) of the valve device. In order to estimate the flow force with high accuracy, it is necessary to appropriately identify the control parameters of the control model. However, when applying the technology described in Patent Document 2 to working machines with different conditions such as attachments, the above-mentioned control parameters must be identified according to the individual conditions of the working machine, which requires a great deal of effort. Therefore, there is a need for a method that can easily estimate the fluid force (flow force) acting on the valve device even for working machines with different conditions.

[0008] The present invention was made to solve the above-mentioned problems, and its objective is to provide a work machine that can easily apply highly accurate control of a control valve, taking into account the fluid force acting on the control valve, to work machines under various conditions, without using a sensor to detect the position of the control valve.

[0009] The present invention includes multiple means for solving the above problems. One example is a work machine comprising a hydraulic pump, a hydraulic actuator that drives a driven body by the discharge pressure of the hydraulic pump, a control valve provided between the hydraulic pump and the hydraulic actuator and controlling the flow of pressurized oil supplied to the hydraulic actuator, an operating device for operating the hydraulic actuator, a posture detector for detecting the posture of the driven body, and a control device that calculates a control target value for controlling the control valve based on the amount of operation of the operating device and controls the control valve, wherein the control device is configured to calculate the flow rate supplied to the hydraulic actuator based on the posture detected by the posture detector, estimate the fluid force acting on the control valve based on the differential pressure across the control valve obtained from the detected value of the posture detector and the calculated flow rate supplied to the hydraulic actuator, calculate a correction value to correct the control target value based on the estimated fluid force, correct the control target value with the calculated correction value and output it to the control valve as a control command value.

[0010] According to one example of the solution of this invention, the fluid force (flow force) acting on the control valve is estimated based on the flow rate of the hydraulic actuator (i.e., the flow rate passing through the control valve and supplied to the hydraulic actuator) calculated based on the detected value of an attitude sensor commonly installed in work machines compatible with information-based construction, and the differential pressure across the control valve obtained from the detected value of the attitude sensor. Therefore, the fluid force can be estimated with high accuracy without using a control model for the control valve. Accordingly, high-precision control of the control valve, taking into account the fluid force acting on the control valve, can be easily applied to work machines under various conditions without using a sensor to detect the position of the control valve. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

[0011] Figure 1 is an external view showing a hydraulic excavator as a work machine according to the first embodiment of the present invention. Figure 1 is a hydraulic circuit diagram showing the schematic configuration of the hydraulic system provided in the work machine according to the first embodiment shown. Figure 2 is a block diagram showing the control logic of the control device for the hydraulic system (directional control valve) of the work machine according to the first embodiment shown. Figure 2 is a time chart showing an example of the time change of the control pressure for the directional control valve as a control result of the control device in the work machine according to the first embodiment. Figure 3 is a time chart showing an example of the time change of the control target value of the control device and the flow rate of the directional control valve (hydraulic actuator) as a control result in the work machine according to the first embodiment. Figure 4 is a block diagram showing the control logic of the control device for the hydraulic system (directional control valve) of the work machine according to the second embodiment of the present invention.

[0012] Hereinafter, embodiments of the work machine of the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator will be used as an example of a work machine. [First Embodiment] First, the schematic configuration of the hydraulic excavator as a work machine according to the first embodiment will be described with reference to Figure 1. Figure 1 is an external view showing the hydraulic excavator as a work machine according to the first embodiment. Here, the description will be based on the view from the operator seated in the driver's seat.

[0013] In Figure 1, the hydraulic excavator as a work machine comprises a self-propelled vehicle 1, a slewing body 2 mounted on the vehicle 1 so as to be rotatable, and a work device 3 provided on the front of the slewing body 2 so as to be rotatable in the vertical direction. The slewing body 2 is configured to rotate relative to the vehicle 1 by a slewing device 4 including a slewing hydraulic motor 4a (see Figure 2 below), which is a hydraulic actuator, and is the driven body of the slewing hydraulic motor 4a.

[0014] The vehicle 1 has, for example, crawler-type travel devices 11 on both the left and right sides (only the left side is shown in Figure 1). The travel devices 11 are configured to move using a travel hydraulic motor 12, which is a hydraulic actuator.

[0015] The slewing body 2 consists of a slewing frame 14 as a support structure rotatably mounted on the traveling body 1, a cab 15 installed on the left front side of the slewing frame 14, a counterweight 16 provided at the rear end of the slewing frame 14, and a machine room 17 provided between the cab 15 and the counterweight 16. Inside the cab 15 are an operator's seat (not shown) where the operator sits and operating devices 55 (see Figure 2 below) operated by the operator. The counterweight 16 is for balancing the weight with the work device 3. The machine room 17 houses various equipment such as a hydraulic pump 31 and directional control valves 33 and 34 (both see Figure 2 below).

[0016] The work device 3 is a device for performing various tasks such as excavation work, and is a multi-jointed work device composed of multiple driven bodies connected in a way that allows them to rotate vertically. The multiple driven bodies consist of, for example, a boom 19, an arm 20, and a bucket 21 as a work tool. The base end of the boom 19 is supported on the front of the slewing frame 14 of the slewing body 2 so as to be able to rotate vertically. The base end of the arm 20 is supported on the tip of the boom 19 so as to be able to rotate in the front-rear direction. The base end of the bucket 21 is supported on the tip of the arm 20 so as to be able to rotate vertically. The boom 19, arm 20, and bucket 21 are operated by hydraulic actuators, namely a boom cylinder 22, an arm cylinder 23, and a bucket cylinder 24, respectively.

[0017] The rotating body 2, which acts as the driven body, is equipped with a first attitude detector 27 that detects attitude information, which is a physical quantity related to the attitude of the rotating body 2 (such as the rotation angle), and motion information, which is a physical quantity related to the operating state (such as the rotation speed and rotation acceleration). The first attitude detector 27 is composed of, for example, an inertial measurement unit (IMU). The first attitude detector 27 outputs a detection signal corresponding to the detected value to the control device 60 (see Figure 2 below), which will be described later. The first attitude detector 27 only needs to be capable of detecting the attitude information and motion information of the rotating body 2, and can also be composed of an angle sensor or the like.

[0018] The boom 19, arm 20, and bucket 21 of the working device 3, which is the driven body, are each equipped with second attitude detectors 28a, 28b, and 28c, respectively, which detect attitude information, which is a physical quantity relating to the posture of the boom 19, arm 20, and bucket 21, and motion information, which is a physical quantity relating to the operating state. Each of the second attitude detectors 28a, 28b, and 28c outputs a detection signal corresponding to the detected value to the control device 60 (see Figure 2 below), which will be described later. Each attitude detector 28a, 28b, and 28c is composed of, for example, an inertial measuring unit (IMU). The multiple second attitude detectors 28a, 28b, and 28c constitute a second attitude detection device 28 that detects the attitude information and motion information of the working device 3. Furthermore, the second attitude detectors 28a, 28b, and 28c, which constitute the second attitude detection device 28, only need to be capable of detecting attitude information and operation information of the work device 3. They can also be composed of tilt sensors that detect the angle of inclination of the driven body (boom 19, arm 20, bucket 21) relative to a reference, angle sensors that detect the relative angle of the driven body (boom 19, arm 20, bucket 21), and stroke sensors that detect the stroke of the hydraulic cylinders (boom cylinder 22, arm cylinder 23, bucket cylinder 24) that drive the driven body (boom 19, arm 20, bucket 21).

[0019] Next, the configuration of the hydraulic system provided in the work machine according to the first embodiment will be described with reference to Figure 2. Figure 2 is a hydraulic circuit diagram showing the schematic configuration of the hydraulic system provided in the work machine according to the first embodiment shown in Figure 1.

[0020] In FIG. 2, the hydraulic excavator includes a hydraulic system 30 that operates a traveling body 1, a revolving body 2, and a working device 3 (both shown in FIG. 1) hydraulically. In FIG. 2, a hydraulic circuit related to a swing hydraulic motor 4a that swings the revolving body 2 and an arm cylinder 23 that operates an arm 20 of the working device 3 is shown. Hydraulic circuits related to a travel hydraulic motor 12 that operates a traveling device 11 other than the swing hydraulic motor 4a and an arm cylinder 23, a boom cylinder 22 that operates a boom 19 of the working device 3, and a bucket cylinder 24 are omitted. Also, various hydraulic devices not related to the present invention are omitted.

[0021] The hydraulic system 30 shown in FIG. 2 includes a plurality of hydraulic pumps 31 that discharge pressure oil, a hydraulic oil tank 32 that stores hydraulic oil sucked by the hydraulic pumps 31, a swing hydraulic motor 4a and an arm cylinder 23 as hydraulic actuators that drive driven bodies (revolving body 2 and arm 20) by the discharge pressure from the hydraulic pumps 31, a swing direction control valve 33 that controls the flow of pressure oil supplied from the hydraulic pumps 31 to the swing hydraulic motor 4a and the flow of return oil discharged from the swing hydraulic motor 4a to the hydraulic oil tank 32, and an arm direction control valve 34 that controls the flow of pressure oil supplied from the hydraulic pumps 31 to the arm cylinder 23 and the flow of return oil discharged from the arm cylinder 23 to the hydraulic oil tank 32. The hydraulic pump 31 is, for example, a variable displacement pump.

[0022] A discharge line 36 of the hydraulic pump 31 is connected to the hydraulic oil tank 32 via a center bypass line 37. On the center bypass line 37, a swing direction control valve 33 and an arm direction control valve 34 are arranged in order from the upstream side. The swing direction control valve 33 is connected to the swing hydraulic motor 4a via a pair of first actuator lines 38, 38. The arm direction control valve 34 is connected to the arm cylinder 23 via a pair of second actuator lines 39, 39. That is, the swing direction control valve 33 and the arm direction control valve 34 are provided between the swing hydraulic motor 4a and the arm cylinder 23 (corresponding hydraulic actuators) and the hydraulic pump 31, respectively.

[0023] The swing direction control valve 33 and the arm direction control valve 34 are each composed of a spool valve. The swing direction control valve 33 and the arm direction control valve 34 are, for example, hydraulic pilot type, and the control pressure generated in a pilot hydraulic circuit 40 described later is applied to the pressure receiving portion of the spool, so that their driving (switching direction and stroke amount) is configured to be controlled. The swing direction control valve 33 and the arm direction control valve 34 each have springs 33a and 34a at both end portions of the spool, and are configured to be located at the neutral position at normal times by the action of the springs 33a and 34a.

[0024] A first pressure sensor 51 for detecting the discharge pressure of the hydraulic pump 31 is provided on the discharge line 36. The first pressure sensor 51 outputs a pressure detection signal Pp corresponding to the detected discharge pressure of the hydraulic pump 31 to the control device 60. Second pressure sensors 52 and 53 for detecting the pressure of the arm cylinder 23 are provided on the pair of second actuator lines 39 and 39, respectively. The second pressure sensors 52 and 53 output pressure detection signals Ps1 and Ps2 corresponding to the detected pressure of the arm cylinder 23 to the control device 60. In FIG. 2, the configuration of the pressure sensor for detecting the pressure of the swing hydraulic motor 4a is omitted.

[0025] The hydraulic system 30 further includes a pilot hydraulic circuit 40 for controlling the driving of the hydraulic pilot type direction control valves 33 and 34. The pilot hydraulic circuit 40 includes a pilot pump 41 which is a pilot hydraulic source, and pilot solenoid valves 42 and 43 for generating a control pressure applied to the arm direction control valve 34. The pilot pump 41 is connected to the pilot solenoid valves 42 and 43 via a pilot line 45. The pilot line 45 is connected to the hydraulic oil tank 32 via a pilot relief valve 46. The pilot solenoid valves 42 and 43 are provided on the pilot line 45 between the pilot pump 41 and the pressure receiving portion of the arm direction control valve 34 (spool valve). In FIG. 2, the pilot solenoid valve for generating the control pressure applied to the swing direction control valve 33 is omitted.

[0026] The pilot pump 41 generates the pilot primary pressure, which is the source pressure for the control pressure applied to each directional control valve 33, 34, and is, for example, a fixed-displacement type pump. The pilot relief valve 46 is configured to open when the discharge pressure (pilot primary pressure) of the pilot pump 41 exceeds a set pressure, and is for maintaining the pilot primary pressure at the set pressure.

[0027] The pilot solenoid valves 42 and 43 reduce the discharge pressure (primary pilot pressure) of the pilot pump 41 in accordance with control commands Cv1 and Cv2 from the control device 60 to generate a secondary pilot pressure as a control pressure. The solenoid sections 42a and 43a of the pilot solenoid valves 42 and 43 are electrically connected to the control device 60, and the control commands Cv1 and Cv2 from the control device 60 are input to the solenoid sections 42a and 43a.

[0028] The control device 60 is electrically connected to an operating device 55 that instructs the operation of the traveling body 1, the slewing body 2, and the working device 3 (boom 19, arm 20, bucket 21). In other words, the operating device 55 operates the hydraulic actuators 4a, 12, 22, 23, and 24 that operate the traveling body 1, the slewing body 2, and the working device 3 (boom 19, arm 20, bucket 21). The operating device 55 is, for example, electrically operated and outputs an operation signal as an electrical signal to the control device 60 according to the input (operated) amount and direction of operation. The operating device 55 has, for example, an operating lever 55a that is grasped and operated by an operator, and an electrical signal generation unit 55b that detects the direction and amount of operation of the operating lever 55a and generates an operation signal as an electrical signal according to the detected value.

[0029] The control device 60 receives an operation signal from the operating device 55, a detection signal from the second attitude detection device 28 (second attitude detectors 28a, 28b, 28c), a pressure detection signal Pp from the first pressure sensor 51, and pressure detection signals Ps1, Ps2 from the second pressure sensors 52, 53, respectively. The control device 60 according to this embodiment controls the drive of the arm directional control valve 34 by directly controlling the opening degree of the pilot solenoid valves 42, 43 of the pilot hydraulic circuit 40 based on the operation signal (operation amount and operation direction) from the operating device 55 and the detection signal (attitude information and operation information) from the second attitude detection device 28 (second attitude detectors 28a, 28b, 28c), and ultimately controls the drive of the arm cylinder 23. The control device 60 controls the control pressure generated by the pilot solenoid valves 42, 43 by controlling the opening degree of the pilot solenoid valves 42, 43 with excitation currents as control commands Cv1, Cv2 output to the pilot solenoid valves 42, 43. Details of the control by the control device 60 will be described later.

[0030] The control device 60 is configured as a microcomputer comprising, for example, a storage device 61 consisting of RAM or ROM, and a processing device 62 consisting of a CPU or MPU. The storage device 61 has programs and various information necessary for controlling the directional control valves 33 and 34 pre-stored in it. The processing device 62 reads programs and various information from the storage device 61 as appropriate and executes processing according to the programs to realize various functions for controlling the directional control valves 33 and 34.

[0031] Next, the drive control of the control device for the hydraulic actuator in the work machine according to the first embodiment will be explained using Figure 3. Figure 3 is a block diagram showing the control logic of the control device for the hydraulic system (directional control valve) of the work machine according to the first embodiment shown in Figure 2.

[0032] In general terms, the control device 60 according to this embodiment controls the drive of the hydraulic actuators 4a, 22, 23, and 24 that operate the slewing body 2 and the work device 3, by taking into consideration the fluid force (flow force) acting on the valve bodies (spools) of the directional control valves 33 and 34 for the hydraulic actuators 4a, 22, 23, and 24. This fluid force is generated when an imbalance occurs in the pressure acting on the wall surface of the valve body (spool) when fluid (hydraulic oil) flows in and out of the valve chamber of the directional control valves 33 and 34, and is one of the factors that cause deterioration in the control accuracy of the directional control valves 33 and 34. Here, only the drive control of the arm cylinder 23 will be described, but the same method can be applied to the drive control of the boom cylinder 22, bucket cylinder 24, and slewing hydraulic motor 4a, so their explanation will be omitted.

[0033] The control device 60 (processing device 62 shown in Figure 2) executes the control logic shown in Figure 3 in response to, for example, the operation signal L from the operating device 55 and the detection signal Si from the second attitude detection device 28, and outputs the calculated control commands Cv1 and Cv2 to the pilot solenoid valves 42 and 43. As a result, the pilot solenoid valves 42 and 43 generate a control pressure in accordance with the control commands Cv1 and Cv2 from the control device 60 and apply it to the directional control valve 34, thereby controlling the drive of the directional control valve 34.

[0034] Specifically, in Figure 3, the control device 60 has a control target calculation processing unit that calculates a control target value for controlling the control valve based on the operation signal L (operation amount and operation direction) of the operating device 55, and includes a target flow rate calculation unit 71, a target opening calculation unit 72, and a target command pressure calculation unit 73. Furthermore, it has a correction calculation processing unit that calculates a correction value to correct the control target value based on the detection signal Si (attitude information and operation information of the work device 3) of the second attitude detection device 28, and includes an actuator flow rate calculation unit 74, an actuator pressure estimation unit 75, a valve opening estimation unit 76, a valve stroke estimation unit 77, a fluid force estimation unit 78, and a correction pressure calculation unit 79. In addition, it has an adder 80 as a control command calculation processing unit that calculates a control command value by correcting the control target value with the correction value and outputs a control command according to the calculation result.

[0035] The target flow rate calculation unit 71 receives the operation signal L (operation amount and operation direction) from the operating device 55 and calculates the target flow rate Qt, which is the target value of the inflow or outflow flow rate of pressurized oil to the arm cylinder 23 (hydraulic actuator), based on the operation signal L. The target flow rate calculation unit 71 calculates the target flow rate Qt by, for example, using a characteristic table that pre-defines the correspondence between the operation amount of the operating device 55 and the flow rate of the arm cylinder 23 (hydraulic actuator). The calculated target flow rate Qt is output to the target opening calculation unit 72.

[0036] The target opening calculation unit 72 calculates the target opening At, which is the target value of the opening (opening degree or opening area) of the arm directional control valve 34, based on the target flow rate Qt calculated by the target flow rate calculation unit 71. The target opening calculation unit 72 calculates the target opening At by, for example, using a characteristic table that pre-defines the correspondence between the flow rate of the arm cylinder 23 (hydraulic actuator) and the opening amount of the directional control valve 34. The calculated target opening At is output to the target command pressure calculation unit 73.

[0037] The target command pressure calculation unit 73 calculates the target command pressure Pt, which is the target value of the control pressure to be applied to the directional control valve 34, based on the target opening At, which is the calculation result of the target opening calculation unit 72. The target command pressure calculation unit 73 calculates the target command pressure Pt by, for example, using a characteristic table that pre-defines the correspondence between the opening amount of the directional control valve 34 and the control pressure of the directional control valve 34. Alternatively, the target command pressure Pt can also be calculated using the spring characteristics of the spring 34a of the directional control valve 34. These spring characteristics are, for example, stored in advance in the storage device 61. The calculated target command pressure Pt is output to the adder 80.

[0038] The actuator flow rate calculation unit 74 takes in the detected value Si (position information and operation information of the work device 3) from the second posture detection device 28 and calculates the actuator flow rate Q, which is the actual flow rate of pressurized oil at the time of calculation for the arm cylinder 23, based on the detected value Si from the second posture detection device 28. ＥIt is to estimate. The second posture detectors 28a, 28b, 28c that constitute the second posture detection device 28 detect the actual posture state and operation state of the driven bodies 19, 20, 21 of the working device 3. Therefore, based on the geometric relationship between each driven body 19, 20, 21 and each hydraulic actuator (boom cylinder 22, arm cylinder 23, bucket cylinder 24), the actuator flow rate calculation unit 74 can accurately estimate the flow rate of the pressure oil that actually flows into or out of each hydraulic actuator directly based on the actual posture state and operation state of the driven bodies 19, 20, 21. The calculated actuator flow rate Q Ｅ is output to the valve opening estimation unit 76 and the fluid force estimation unit 78.

[0039] The actuator pressure estimation unit 75 takes in the detection value Si (posture information and operation information of the working device 3) of the second posture detection device 28, and based on the detection value Si of the second posture detection device 28, estimates the actuator pressure P which is the actual load pressure during the operation of the arm cylinder 23. Ｅ It is to estimate. For example, the actuator pressure estimation unit 75 estimates the force generated in the arm cylinder 23 (hydraulic cylinder) by gravity when the working device 3 takes a certain posture from an equation of balance of gravity or the like, and divides the estimated force by the cross-sectional area of the arm cylinder 23 (hydraulic cylinder) to calculate the actuator pressure P Ｅ The specifications such as the equation of balance and the cross-sectional area of the arm cylinder 23 (hydraulic cylinder) are stored in the storage device 61 in advance. The calculated actuator pressure P Ｅ is output to the valve opening estimation unit 76 and the fluid force estimation unit 78.

[0040] The valve opening estimation unit 76 estimates the valve opening A which is the actual opening during the operation of the direction control valve 34 based on the actuator flow rate Q Ｅ [[ID=十六]]calculated by the actuator flow rate calculation unit 74 and the actuator pressure P Ｅ estimated by the actuator pressure estimation unit 75. Ｅ The calculated valve opening A Ｅ is output to the valve stroke estimation unit 77. The valve opening estimation unit 76 estimates the valve opening A based on, for example, the relational expression (1) of fluid mechanics used in an orifice or the like.Ｅ Perform the calculation.

[0041]

[0042] Here, C represents a coefficient and ρ represents the density of the hydraulic fluid. These values ​​of C and ρ are pre-stored in the memory device 61. ΔP is the differential pressure across the directional control valve 34, and is the actuator pressure P, which is the estimated result of the actuator pressure estimation unit 75. Ｅ It is obtained from.

[0043] The valve stroke estimation unit 77 determines the valve opening A estimated by the valve opening estimation unit 76. Ｅ Based on this, the valve stroke S is the actual stroke amount of the directional control valve 34 during calculation. Ｅ The valve stroke estimation unit 77 estimates the valve stroke S by using, for example, a valve opening characteristic in which the correspondence between the opening and stroke amount of the directional control valve 34 is predetermined. Ｅ The valve opening characteristics are calculated based on the specifications of the directional control valve 34 and are stored in the storage device 61 beforehand. Ｅ This is output to the fluid force estimation unit 78.

[0044] The fluid force estimation unit 78 calculates the valve stroke S estimated by the valve stroke estimation unit 77. Ｅ and the actuator flow rate Q calculated by the actuator flow rate calculation unit 74 Ｅ and the actuator pressure P estimated by the actuator pressure estimation unit 75 Ｅ Based on this, the fluid force Ff (flow force) acting on the valve body (spool) of the directional control valve 34 is estimated. The calculated fluid force Ff is output to the corrected pressure calculation unit 79.

[0045] The fluid force estimation unit 78 calculates the fluid force Ff from the stroke amount of the directional control valve 34, the flow rate of the arm cylinder 23, and the pressure of the arm cylinder 23, for example, by using a fluid force characteristic set in advance for the directional control valve 34. This fluid force characteristic is stored in the storage device 61 in advance. As the fluid force characteristic, for example, a characteristic is used in which the fluid force acting on the opening of the directional control valve 34 is predetermined from the stroke amount of the directional control valve 34, the flow rate of the hydraulic actuator (arm cylinder 23) (an item corresponding to the flow rate passing through the directional control valve 34), and the pressure of the hydraulic actuator (arm cylinder 23) (an item related to the differential pressure across the directional control valve 34). In addition to the above-mentioned fluid force acting on the opening of the directional control valve 34, it is also possible to consider the fluid force generated by the collision of fluid (pressurized oil) with the spool wall surface of the directional control valve 34 as part of the fluid force characteristic. In this case, the fluid force F due to the fluid collision with the spool wall surface is ｆｊ This can be calculated based on the following relation (2) concerning the momentum of the jet.

[0046]

[0047] Here, Q represents the flow rate of the fluid (pressurized oil) flowing through the opening of the directional control valve 34, and A represents the area of ​​the opening of the directional control valve 34. θ is the angle of the jet relative to the spool wall of the directional control valve 34, and is estimated from the stroke amount of the directional control valve 34 using a preset table. ρ represents the density of the hydraulic fluid.

[0048] Furthermore, as a fluid dynamics characteristic, experimental values ​​obtained by varying the flow rate, pressure, and stroke amount of the directional control valve 34, as well as the results of fluid simulations, can be used. Alternatively, the opening of the directional control valve 34 can be used instead of the flow rate.

[0049] The corrected pressure calculation unit 79 calculates a corrected pressure Pi that cancels out the effect of the fluid force Ff estimated by the fluid force estimation unit 78. The calculated corrected pressure Pi is output to the adder 80. For example, the corrected pressure calculation unit 79 calculates the corrected pressure Pi by dividing the fluid force Ff estimated by the fluid force estimation unit 78 by the pressure receiving area Sp of the pressure receiving part of the directional control valve 34 (spool valve). That is, the corrected pressure Pi is calculated using the following equation (3). The pressure receiving area Sp is based on the design specifications of the directional control valve 34 and is stored in the memory device 61 in advance.

[0050]

[0051] The adder 80 calculates the control pressure to be applied to the directional control valve 34 as a control command value by adding the correction pressure Pi calculated by the correction pressure calculation unit 79 to the target command pressure Pt calculated by the target command pressure calculation unit 73. The adder 80 outputs excitation currents to generate the calculated control pressure as control commands Cv1 and Cv2 to the pilot solenoid valves 42 and 43. The pilot solenoid valves 42 and 43 receive the excitation currents as control commands Cv1 and Cv2 and generate a control pressure corresponding to the calculation result of the adder 80. The control pressure generated by the pilot solenoid valves 42 and 43 is applied to the valve body (spool) of the directional control valve 34, thereby driving the directional control valve 34.

[0052] Next, the operation and effects of the work machine according to the first embodiment will be described. Here, for the sake of simplicity, the case of operating the arm independently will be described using Figures 2 to 5. Figure 4 is a time chart showing an example of the time change of the control pressure on the directional control valve as a control result of the control device in the work machine according to the first embodiment. Figure 5 is a time chart showing an example of the time change of the control target value of the control device and the flow rate of the directional control valve (arm cylinder) as a control result in the work machine according to the first embodiment. In Figures 4 and 5, the horizontal axis T represents time. In Figure 4, the vertical axis Pc represents the control pressure on the directional control valve 34. In Figure 5, the vertical axis Q represents the flow rate of the arm cylinder (flow rate passing through the directional control valve 34), and the vertical axis Ff represents the fluid force acting on the directional control valve 34 (spool).

[0053] At time t0 shown in Figures 4 and 5, an operation input to the operating device 55 shown in Figure 2 is initiated, and thereafter, the amount of operation of the operating device 55 gradually increases and is held at a constant value. As a result, the control device 60 shown in Figure 3 calculates the target flow rate Qt (solid line in Figure 5) of the arm cylinder 23 according to the amount of operation L from the operating device 55, and finally calculates the target command pressure Pt based on the calculated target flow rate Qt (executes processing units 71 to 73 shown in Figure 3). In other words, the target command pressure Pt calculated by the control device 60 is a value corresponding to the operation of the operating device 55. Furthermore, the control device 60 calculates the actuator flow rate Q, which is the flow rate of pressurized oil to the arm cylinder 23, based on the detected value Si of the second attitude detection device 28 (second attitude detectors 28a, 28b, 28c). Ｅ The actuator pressure P, which is the pressure of the arm cylinder 23, is calculated and calculated. Ｅ The actuator flow rate Q is estimated and calculated. Ｅ and actuator pressure P ＥBased on this, the fluid force Ff acting on the directional control valve 34 is estimated, and a correction pressure Pi that cancels out the effect of the estimated fluid force Ff is calculated (processing units 74 to 79 are executed). Furthermore, the control device 60 calculates the control pressure to be applied to the directional control valve 34 by adding the correction pressure Pi calculated by processing units 74 to 79 to the target command pressure Pt, which is the calculation result of processing units 71 to 73, and outputs control commands Cv1 and Cv2 corresponding to the calculated control pressure to the pilot solenoid valves 42 and 43.

[0054] The pilot solenoid valves 42 and 43 generate a control pressure in which a correction pressure Pi is added to the target command pressure Pt, according to the control commands Cv1 and Cv2 from the control device 60. The control pressure generated by the pilot solenoid valves 42 and 43 is applied to the directional control valve 34, which drives the directional control valve 34. This controls the flow rate of pressurized oil supplied from the hydraulic pump 31 to the arm cylinder 23, thereby controlling the drive of the arm cylinder 23.

[0055] The control pressure applied to the directional control valve 34 by the control device 60 changes as shown by the solid line (line indicated as corrected) in Figure 4. This control is performed based on a control command value (control pressure) obtained by adding a correction pressure Pi that cancels out the effect of the estimated fluid force Ff to the target command pressure Pt corresponding to the operation of the operating device 55. That is, the control pressure applied to the directional control valve 34 by the control device 60 (solid line in Figure 4) is the control pressure of the dashed line (line indicated as uncorrected) in Figure 4, which corresponds to the target command pressure Pt, plus the control pressure of the dashed line (line indicated as correction amount) in Figure 4, which corresponds to the correction pressure Pi. In other words, the directional control valve 34 is controlled to have a higher control pressure applied by the amount of the correction pressure Pi that cancels out the effect of the estimated fluid force Ff, compared to when the drive of the directional control valve 34 is controlled according to the operation of the operating device 55. For this reason, the directional control valve 34 is controlled with high precision, taking fluid force into consideration.

[0056] The control device 60's high-precision control of the directional control valve 34 enables high-precision drive control (flow rate control) of the arm cylinder 23. The target flow rate Qt calculated by the control device 60 changes according to the amount of operation L from the operating device 55, as shown by the solid line in Figure 5. In contrast, when a control pressure (dashed line in Figure 4) similar to the target command pressure Pt corresponding to the operation of the operating device 55 is applied to the directional control valve 34, the flow rate of the arm cylinder 23 changes as shown by the dashed line (uncorrected flow rate) in Figure 5. The uncorrected flow rate shown by the dashed line in Figure 5 deviates significantly from the target flow rate Qt because the fluid force acting on the directional control valve 34 is not taken into account. On the other hand, when the control device 60 applies a control pressure (solid line in Figure 4) obtained by adding a correction pressure Pi to the target command pressure Pt to the directional control valve 34, the flow rate of the arm cylinder 23 changes as shown by the dashed line (corrected flow rate) in Figure 5. The corrected flow rate, shown by the dashed line in Figure 5, takes into account the fluid force acting on the directional control valve 34, so it changes with relatively small error relative to the target flow rate Qt. The fluid force acting on the directional control valve 34 changes as shown by the closely spaced dotted line in Figure 5.

[0057] In this embodiment, the control device 60 controls the directional control valve 34 based on a control command value (control pressure) obtained by adding a correction pressure Pi that cancels out the effect of the estimated fluid force Ff to the target command pressure Pt calculated in response to the operation of the operating device 55. As a result, the directional control valve 34 is driven by a control pressure that is higher by the amount of the correction pressure that cancels out the effect of the fluid force, and is controlled to a stroke amount (position) that realizes an opening that is closer to the target opening At of the directional control valve 34 in response to the operation of the operating device 55. Therefore, the flow rate of pressurized oil supplied to the arm cylinder 23 via the directional control valve 34 can be brought closer to the target flow rate Qt of the hydraulic actuator in response to the operation of the operating device 55. In other words, the control device 60 can perform highly accurate drive control of the arm cylinder 23.

[0058] Furthermore, in this embodiment, the flow rate Q of the hydraulic actuator is calculated based on the detection values ​​of the second posture detection device 28 (second posture detectors 28a, 28b, 28c) which is commonly installed in work machines compatible with information-based construction. Ｅ (That is, the flow rate passing through the directional control valve 34 and the flow rate supplied to the hydraulic actuator) and the differential pressure across the directional control valve 34 are used to estimate the fluid force (flow force) acting on the directional control valve 34. Therefore, the fluid force can be estimated with high accuracy without using a control model for the directional control valve 34. Consequently, high-precision control of the directional control valve 34, taking into account the fluid force acting on the directional control valve 34, can be easily applied to work machines under various conditions without using a sensor to detect the position of the directional control valve 34. [Second Embodiment] Next, a work machine according to the second embodiment of the present invention will be described with reference to Figure 6. Figure 6 is a block diagram showing the control logic of the control device for the hydraulic system (directional control valve) of the work machine according to the second embodiment. In Figure 6, parts with the same reference numerals as those shown in Figures 1 to 5 are similar parts, so a detailed explanation will be omitted. Here, only the drive control of the arm cylinder 23 will be described, but the same can be applied to the drive control of the boom cylinder 22, bucket cylinder 24, and slewing hydraulic motor 4a.

[0059] The differences between the work machine according to the second embodiment and the first embodiment are that the valve opening estimation unit 76A and the fluid force estimation unit 78A in the control device 60A shown in Figure 6 use the detected values ​​Pp, Ps1, and Ps2 of the pressure sensors 50, 51, and 52 for calculations instead of the pressure value estimated from the detected value Si of the second attitude detection device 28 (second attitude detectors 28a, 28b, and 28c), and the processing unit of the actuator pressure estimation unit 75 (see Figure 3) of the control device 60 according to the first embodiment has been removed. The other processing units in the control device 60A according to the second embodiment shown in Figure 6 are the same as the processing units 71 to 74, 77, 79, and 80 of the control device 60 according to the first embodiment, and their description is omitted. In this embodiment, the first pressure sensor 51 and the second pressure sensors 52 and 53 shown in Figure 2 constitute a front-to-rear differential pressure detector 50 that detects the front-to-rear differential pressure of the directional control valve 34. Furthermore, since the posture of the arm 20 (driven body) can be estimated based on the pressure of the arm cylinder 23 (hydraulic actuator) detected by the second pressure sensors 52 and 53, the second pressure sensors 52 and 53 can be considered to have the function of posture detectors for detecting the posture of the driven body.

[0060] Specifically, the valve opening estimation unit 76A of the control device 60A estimates the actuator pressure P estimated by the actuator pressure estimation unit 75 of the control device 60 according to the first embodiment. Ｅ Instead, the valve opening A is obtained using the front-to-back differential pressure ΔP of the directional control valve 34, which is directly obtained from the detected values ​​Pp, Ps1, and Ps2 of the front-to-back differential pressure detector 50 (first pressure sensor 51 and second pressure sensors 52, 53). Ｅ The valve opening estimation unit 76A estimates the actuator flow rate Q calculated by the actuator flow rate calculation unit 74. Ｅ And based on the detected values ​​Pp, Ps1, and Ps2 of the front-rear differential pressure detector 50, the valve opening A of the directional control valve 34 is adjusted. Ｅ The valve opening estimation unit 76A estimates the valve opening A using the above formula (1), similar to the first embodiment. Ｅ The following calculations are possible.

[0061] The fluid force estimation unit 78A of the control device 60A calculates the actuator pressure P estimated by the actuator pressure estimation unit 75 of the control device 60 according to the first embodiment. Ｅ Instead, the fluid force Ff acting on the directional control valve 34 is estimated using the differential pressure across the directional control valve 34, which is directly obtained from the detected values ​​Pp, Ps1, and Ps2 of the differential pressure detector 50. That is, the valve opening estimation unit 76A estimates the valve stroke S estimated by the valve stroke estimation unit 77. Ｅ and the actuator flow rate Q calculated by the actuator flow rate calculation unit 74 Ｅ Based on the detected values ​​Pp, Ps1, and Ps2 of the front-to-back differential pressure detector 50, the fluid force Ff is estimated. The fluid force estimation unit 78A calculates the fluid force Ff by using a fluid force characteristic set in advance for the directional control valve 34, for example, in the same manner as in the first embodiment. As the fluid force characteristic, for example, a characteristic is used in which the fluid force acting on the opening of the directional control valve 34 is predetermined from the stroke amount of the directional control valve 34, the flow rate of the arm cylinder 23 (an item corresponding to the flow rate passing through the directional control valve 34), and the front-to-back differential pressure of the directional control valve 34.

[0062] In this embodiment as well, the control device 60A controls the directional control valve 34 based on a control command value (control pressure) obtained by adding a correction pressure Pi that cancels out the effect of the estimated fluid force Ff to the target command pressure Pt calculated by the control device 55 in response to the operation of the operating device 55. As a result, the directional control valve 34 is driven by a control pressure that is higher by the amount of the correction pressure that cancels out the effect of the fluid force, and is controlled to a stroke amount (position) that realizes an opening closer to the target opening At of the directional control valve 34 in response to the operation of the operating device 55. Therefore, the flow rate of pressurized oil supplied to the arm cylinder 23 via the directional control valve 34 can be brought closer to the target flow rate Qt of the hydraulic actuator in response to the operation of the operating device 55. In other words, the control device 60A can perform highly accurate drive control of the arm cylinder 23.

[0063] Furthermore, in this embodiment, the flow rate Q of the hydraulic actuator is calculated based on the detection values ​​of the second posture detection device 28 (second posture detectors 28a, 28b, 28c) which is commonly installed in work machines compatible with information-based construction.Ｅ The fluid force (flow force) acting on the directional control valve 34 is estimated based on the differential pressure across the directional control valve 34, which is obtained from the flow rate passing through the directional control valve 34 and the detected values ​​Pp, Ps1, and Ps2 of the differential pressure detector 50 (first pressure sensor 51 and second pressure sensors 52, 53). Therefore, the fluid force can be estimated with high accuracy without using a control model for the directional control valve 34. Consequently, high-precision control of the directional control valve 34, taking into account the fluid force acting on the directional control valve 34, can be easily applied to working machines under various conditions without using a sensor to detect the position of the directional control valve 34.

[0064] [Other Embodiments] In the first and second embodiments described above, examples of applying the present invention to a hydraulic excavator were shown. However, the present invention can be broadly applied to various types of work machines equipped with work devices driven by hydraulic actuators.

[0065] Furthermore, the present invention is not limited to the embodiments described above, and includes various modifications. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0066] For example, in the embodiment described above, an example was shown in which the target flow rate calculation unit 71 calculates the target flow rate Qt of the hydraulic actuator (arm cylinder 23) based on the operation signal L from the operating device 55. It is also possible for the target flow rate calculation unit 71 to calculate the target flow rate Qt of the hydraulic actuator (arm cylinder 23) using, in addition to the operation signal L from the operating device 55, the detected value Si (attitude information and operation information) from the second attitude detection device 28 as an auxiliary value. Furthermore, if the operation signal L from the operating device 55 is a remote control signal from a remote control device for remotely operating the hydraulic excavator, it is also possible to configure the system to calculate the target flow rate Qt of the hydraulic actuator (arm cylinder 23) based on that remote control signal. [Summary] In summary, the hydraulic excavator (working machine) according to the above embodiment comprises a hydraulic pump 31, a boom cylinder 22, arm cylinder 23, bucket cylinder 24, or slewing hydraulic motor 4a as hydraulic actuators that drive the working device 3 (boom 19, arm 20, bucket 21) or slewing body 2 as driven bodies by the discharge pressure of the hydraulic pump 31, and a boom cylinder 22, arm cylinder 23, bucket cylinder 24, or slewing hydraulic motor 4a (hydraulic actuator) provided between the hydraulic pump 31 and the boom cylinder 22, arm cylinder 23, bucket cylinder 24, or slewing hydraulic motor 4a (hydraulic actuator). The system includes directional control valves 33, 34 (control valves) that control the flow of pressurized oil supplied to the Eta, an operating device 55 that operates the boom cylinder 22, arm cylinder 23, bucket cylinder 24 or slewing hydraulic motor 4a (hydraulic actuator), attitude detectors (first attitude detector 27 and second attitude detection device 28, second pressure sensors 52, 53) that detect the attitude of the work device 3 (boom 19, arm 20, bucket 21), and control devices 60, 60A that calculate a target command pressure Pt as a control target value for controlling the directional control valves 33, 34 (control valves) based on the amount of operation of the operating device 55 and control the directional control valves 33, 34 (control valves). The control devices 60, 60A control the flow rate (actuator flow rate Q) supplied to the hydraulic actuators 22, 23, 24, 4a based on the attitude detected by the attitude detectors (first attitude detector 27 and second attitude detection device 28). ＥThe differential pressure across the directional control valves 33 and 34 (control valves) obtained based on the detected values ​​of the attitude detectors (first attitude detector 27 and second attitude detection device 28, second pressure sensors 52 and 53) and the calculated flow rate (actuator flow rate Q) supplied to the hydraulic actuators 22, 23, 24, and 4a are calculated, and the differential pressure across the directional control valves 33 and 34 (control valves) is calculated. Ｅ Based on this, the system estimates the fluid force Ff acting on the directional control valves 33 and 34 (control valves), calculates a correction pressure Pi as a correction value to correct the control target value based on the estimated fluid force Ff, corrects the target pressure Pt as the control target value using the calculated correction pressure Pi, and outputs the control commands Cv1 and Cv2 to the directional control valves 33 and 34 (control valves).

[0067] According to this configuration, the flow rate Q supplied to the hydraulic actuator is calculated based on the detected values ​​of the attitude detectors (first attitude detector 27 and second attitude detection device 28) that are commonly installed in work machines compatible with information-based construction. Ｅ Since the fluid force (flow force) acting on the directional control valves 33 and 34 (control valves) is estimated based on the differential pressure across the directional control valves 33 and 34 (control valves) obtained from the flow rate passing through the directional control valves 33 and 34 (control valves) and the detected values ​​of the attitude detectors (first attitude detector 27 and second attitude detection device 28 or second pressure sensors 52 and 53), the fluid force can be estimated with high accuracy without using a control model for the directional control valves 33 and 34 (control valves). Therefore, high-precision control of the directional control valves 33 and 34 (control valves) that takes into account the fluid force acting on them can be easily applied to working machines under various conditions without using sensors to detect the position of the directional control valves 33 and 34 (control valves).

[0068] Furthermore, in the first embodiment described above, the attitude detectors 28a, 28b, and 28c consist of one of the following: an inertial measuring device installed on the driven body (boom 19, arm 20, bucket 21), an angle sensor for detecting the angle of the driven body (boom 19, arm 20, bucket 21), an inclination sensor for detecting the tilt of the driven body (boom 19, arm 20, bucket 21), and a stroke sensor for detecting the stroke of the hydraulic cylinders (boom cylinder 22, arm cylinder 23, bucket cylinder 24). In addition, the control devices 60 and 60A control the pressure P of the hydraulic actuators 22, 23, and 24 based on the detected values ​​of the attitude detectors 28a, 28b, and 28c. Ｅ It is configured to estimate the pressure P of the hydraulic actuators 22, 23, 24, and 4a. The differential pressure across the directional control valves 33 and 34 (control valves) is the pressure P of the hydraulic actuators 22, 23, 24, and 4a that has been estimated. Ｅ This is obtained based on [the following].

[0069] With this configuration, the fluid force acting on the directional control valves 33 and 34 (control valves) can be estimated using only one of the inertial measuring devices, angle sensors, tilt sensors, and stroke sensors 28a, 28b, and 28c that are commonly installed in work machines compatible with information-based construction. As a result, highly accurate control of the directional control valves 33 and 34 (control valves) can be achieved with a simple configuration.

[0070] Furthermore, in the hydraulic excavator (working machine) according to the second embodiment described above, the attitude detector includes sensors 28a, 28b, and 28c which are any of the following: an inertial measuring device installed on the driven body (boom 19, arm 20, bucket 21), an angle sensor for detecting the angle of the driven body (boom 19, arm 20, bucket 21), an inclination sensor for detecting the tilt of the driven body (boom 19, arm 20, bucket 21), and a stroke sensor for detecting the stroke of the hydraulic cylinder (boom cylinder 22, arm cylinder 23, bucket cylinder 24); and second pressure sensors 52 and 53 which are pressure sensors for detecting the pressure of the hydraulic actuator (boom cylinder 22, arm cylinder 23, bucket cylinder 24). The flow rate supplied to the hydraulic actuators (boom cylinder 22, arm cylinder 23, bucket cylinder 24) is obtained based on the detection values ​​of one of the above-mentioned inertial measuring devices, angle sensors, tilt sensors, and stroke sensors, while the differential pressure across the directional control valves 33 and 34 (control valves) is obtained based on the detection values ​​of the second pressure sensors 52 and 53 (pressure sensors).

[0071] With this configuration, the differential pressure across the directional control valves 33 and 34 (control valves), used to estimate the fluid force acting on the directional control valves 33 and 34 (control valves), can be directly obtained from the detected values ​​of the second pressure sensors 52 and 53 (pressure sensors), rather than from the pressure estimates of the hydraulic actuators 22, 23, 24, and 4a as in the first embodiment. Therefore, the fluid force can be estimated with high accuracy. Consequently, the control accuracy for the directional control valves 33 and 34 (control valves) can be improved.

[0072] Furthermore, in the first and second embodiments described above, the control devices 60 and 60A further control the differential pressure across the directional control valves 33 and 34 (control valves) and the flow rate Q supplied to the hydraulic actuators 22, 23, 24, and 4a. Ｅ Based on this, the opening A of the directional control valves 33 and 34 (control valves) Ｅ The opening A of the estimated directional control valves 33 and 34 (control valves) is estimated. Ｅ Based on this, the stroke amount (valve stroke S) of the directional control valves 33 and 34 (control valves) ＥThe control devices 60 and 60A are configured to estimate the fluid force Ff, which is determined by the differential pressure across the directional control valves 33 and 34 (control valves) and the flow rate Q supplied to the hydraulic actuator. Ｅ In addition, the estimated stroke amount (valve stroke S) of the directional control valves 33 and 34 (control valves) Ｅ It is carried out based on the following.

[0073] According to this configuration, the stroke amount S of the directional control valves 33 and 34 (control valves) Ｅ By estimating the fluid force while considering the position, the accuracy of the fluid force estimation is improved, thereby improving the control accuracy for the directional control valves 33 and 34 (control valves).

[0074] Furthermore, in the first and second embodiments described above, the control devices 60 and 60A estimate a portion of the fluid force acting on the directional control valves 33 and 34 (control valves) based on a relational expression relating to the momentum of the jet generated by the directional control valves 33 and 34 (control valves).

[0075] With this configuration, by estimating the fluid force considering the jet generated in the directional control valves 33 and 34 (control valves), the accuracy of the fluid force estimation is improved, and thus the control accuracy for the directional control valves 33 and 34 (control valves) can be improved.

[0076] 2...Slewing body (driven body), 4a...Slewing hydraulic motor (hydraulic actuator), 19...Boom (driven body), 20...Arm (driven body), 21...Bucket (driven body), 22...Boom cylinder (hydraulic actuator), 23...Arm cylinder (hydraulic actuator), 24...Bucket cylinder (hydraulic actuator), 31...Hydraulic pump, 33...Slewing direction control valve (control valve), 34...Arm direction control valve (control valve), 27...First attitude detector, 28a, 28b, 28c...Second attitude detector, 52, 53...Second pressure sensor (pressure sensor), 55...Operating device, 60, 60A...Control device, Pt...Target command pressure (control target value), Q Ｅ ...Actuator flow rate (calculated hydraulic actuator flow rate), P Ｅ ...Actuator pressure (estimated hydraulic actuator pressure), A Ｅ...Valve opening (estimated opening of the directional control valve), S Ｅ ...Valve stroke (estimated stroke amount of the directional control valve), Ff...Hydraulic force (estimated result), Pi...Corrected pressure (corrected value), Cv1, Cv2...Control command

Claims

1. A work machine comprising: a hydraulic pump; a hydraulic actuator that drives a driven body by the discharge pressure of the hydraulic pump; a control valve provided between the hydraulic pump and the hydraulic actuator and controlling the flow of pressurized oil supplied to the hydraulic actuator; an operating device for operating the hydraulic actuator; a posture detector for detecting the posture of the driven body; and a control device that calculates a control target value for controlling the control valve based on the amount of operation of the operating device and controls the control valve, wherein the control device calculates the flow rate supplied to the hydraulic actuator based on the posture detected by the posture detector; estimates the fluid force acting on the control valve based on the differential pressure across the control valve obtained from the detected value of the posture detector and the calculated flow rate supplied to the hydraulic actuator; calculates a correction value to correct the control target value based on the estimated fluid force; and corrects the control target value with the calculated correction value and outputs it to the control valve as a control command value.

2. The work machine according to claim 1, wherein the attitude detector comprises one of the following: an inertial measuring device installed on the driven body, an angle sensor for detecting the angle of the driven body, an inclination sensor for detecting the inclination angle of the driven body, and a stroke sensor for detecting the stroke of the hydraulic actuator; the control device is configured to estimate the pressure of the hydraulic actuator based on the value detected by the attitude detector; and the differential pressure across the control valve is obtained based on the estimated pressure of the hydraulic actuator.

3. The working machine according to claim 1, wherein the attitude detector includes an inertial measuring device installed on the driven body, an angle sensor for detecting the angle of the driven body, an inclination sensor for detecting the inclination angle of the driven body, and a stroke sensor for detecting the stroke of the hydraulic actuator, and a pressure sensor for detecting the pressure of the hydraulic actuator, wherein the flow rate supplied to the hydraulic actuator is obtained based on the detected value of any of the inertial measuring device, the angle sensor, the inclination sensor, and the stroke sensor, and the differential pressure across the control valve is obtained based on the detected value of the pressure sensor.

4. The work machine according to claim 1, wherein the control device is further configured to estimate the opening of the control valve based on the differential pressure across the control valve and the flow rate supplied to the hydraulic actuator, and to estimate the stroke amount of the control valve based on the estimated opening of the control valve, and the estimation of the fluid force by the control device is performed based on the differential pressure across the control valve and the flow rate supplied to the hydraulic actuator, in addition to the estimated stroke amount of the control valve.

5. The work machine according to claim 4, wherein the control device estimates a portion of the fluid force based on a relational expression relating to the momentum of the jet generated by the control valve.

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