JPH02232430A - Controller for depth of excavation of hydraulic shovel - Google Patents

Abstract

PURPOSE:To improve the accuracy of excavation by controlling a hydraulic shovel so that the depth of excavation by a working machine is brought to one set by a setting means on the basis of each angle of rotation detected by the detecting means of each arm section in response to the operation of one control lever. CONSTITUTION:A control lever 11 for a boom 2 and a control lever 14 for a boom 1 and the like are installed to a working machine 1 while a controller 20 with a computer CPU 22 for control and a console panel 30 are mounted. Each rotational-angle detector 7, 8, 9 of the boom 1, the arm 2 and a bucket 3 is input to the CPU 22 while the relationship of the angles of each arm section of the working machine 1 is stored previously in the CPU 22 in response to the aimed depth of excavation. When the levers are operated, a device is controlled so as to be brought to depth set while using the angles of other arm sections as desired values in response to the angle of the specified arm section by the CPU 22 as the future position of the arm section is predicted in response to the response delay of each section and the device is controlled. Accordingly, the accuracy of control can be improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an excavation depth control device for a hydraulic excavator that can freely control the posture of a working machine consisting of a boom, an arm, a baguette, etc. This invention relates to an excavation depth control device for a hydraulic excavator in which the movement trajectory of the tip of a working implement follows a predetermined set depth path by operating at least one operating lever without requiring any operation. [Prior Art 1] As is well known, some hydraulic excavators are equipped with a working machine consisting of a boom, an arm, and a packet that rotate in the vertical direction. In this type of hydraulic lift bell, each arm such as the boom and arm is operated by a manual operation lever, but each arm is connected by a joint and rotates. For example, manipulating the tip of a packet to follow a predetermined trajectory is an extremely difficult task. Various automatic control methods have been proposed to make this difficult task easier. For example, in method A of controlling the excavation depth of an excavator, the difference between the depth of the cutting edge of the working machine and the depth setting value is determined, and the boom cylinder is adjusted according to that value so that the value becomes zero. A method to control this has been proposed. In addition, Japanese Patent Publication No. 58-17939 r Work tool trajectory control device for hydraulic excavators, etc. and Japanese Patent Publication No. 6234888 1'
In method 1 for controlling the trajectory of an arm-type working machine, when operating the other working arm of an arm-type working machine configured with a plurality of arms, a control is calculated and set from the detected angle of each working arm.
One working arm is controlled to operate at an angular velocity according to a signal obtained by adding a position correction signal corresponding to the difference between the eye rubbing position and the actual position to the 31 speed signal. In addition, special public service 1986-3
In the control device j of the 8495F power excavator,
A method has been proposed in which only the quick melon component is controlled so that M = M i. In addition, in the planar excavation and shaping control device 1 of the Japanese Patent Application Laid-Open No. 61-270421F hydraulic excavator, an open loop method is proposed in which the boom cylinder speed is calculated according to the arm lever, and the oil flow rate of the hydraulic circuit according to the speed is calculated. We are proposing a method to control this by giving . [Problem to be Solved by the Invention 1] However, in the method j for controlling the excavation depth in the Japanese Patent Publication Showa 5g-361.35rl bending machine, the arm working machine moves by operating the arm lever, and the angle at which the arm moves is measured. Since a command is issued to the boom based on the calculation, there is a large response delay of the boom and poor accuracy.In addition, the error in the depth of the cutting edge is directly used as a flow rate command to the boom cylinder drive hydraulic circuit, but the difference between the boom cylinder displacement and the depth of the cutting edge is Since the ratio changes by [1] more than the arm angle and boom rotation angle, the control gain for correcting the error must be set to a low value that will not become unstable in any case, so accuracy cannot be improved. It is not possible to excavate well. Special fH1 Showa 5 8-1 7 9 3 9 'Hydraulic system: l
Hell” J (1) Work tool trajectory control device 1 and special public Sho 6
1-34888r In method 1 for controlling the trajectory of an arm-type work implement, a position correction signal is added to a speed signal obtained by differential calculation from an angle signal to obtain a speed change command value, so that accurate speed can be achieved. It is not possible to obtain a command signal, and it is difficult to excavate a trajectory other than horizontal. Furthermore, since the control device A of the JP-A-62-38495 r bower shovel and the surface excavation/shaping control device 1 of the JP-A-61-270421 r Hydraulic Shobel are speed command or open loop systems, the load pressure is not controlled in the hydraulic circuit. The flow characteristics may fluctuate due to fluctuations in
If an error occurs in the depth direction due to a disturbance such as a change in oil temperature or a change in engine speed, there is no function to correct the positional deviation, and the error occurs because the control is performed to excavate in parallel. The problem is that it is easy to drill and the accuracy of excavation is poor. Therefore, the object of the present invention is to solve the above-mentioned problems and provide an excavation depth control device for a hydraulic excavator with good controllability. Means for Solving the Problem] The present invention provides a hydraulic excavator equipped with a working machine comprising at least a plurality of arms each driven by an actuator and respective joints connecting the arms. detection means for detecting the rotation angle of each arm;
A working lever for controlling and driving at least one arm of the plurality of arms in accordance with the amount of operation thereof, a means for detecting the operating angle of the operating lever, and a means for setting a desired excavation depth. The excavation depth of the working machine is determined based on each rotation angle detected by the excavation depth setting means and the detection means corresponding to the operation of the at least one operating lever and detecting the rotation angle of each of the arms. In the second and third aspects of the present invention, the rotation angle of the arm manually operated by the operating lever is provided. In accordance with the fourth invention, a leap number generator is provided in order to calculate the rotation angle of the arm controlled by the automatic IIJ which is necessary to excavate to the desired set excavation depth. Control is performed so that the calculated rotation angle of the arm matches the detected rotation angle of the arm to be controlled, and in the fifth invention, the future position of the arm is predicted and controlled. In addition, in the sixth and seventh aspects of the invention, other automatic controls are provided for excavating to a desired set excavation depth in accordance with a rotation angle at a predicted future position of the arm manually operated by the operating lever. It is characterized by being equipped with a leap number generator for calculating the rotation angle of the controlled arm,
The eighth aspect of the invention is characterized in that control is performed so that the detected rotation angle of the arm to be controlled matches the predicted rotation angle of the arm that has been calculated. [Function] According to the present invention, the relationship between the angles of each arm of the working machine of the hydraulic excavator is determined in advance in accordance with the target excavation depth, and the relationship between the angles of each arm of the working machine of the hydraulic excavator is determined in advance in accordance with the target excavation depth, and Therefore, control is performed using the angle of the other arm as a target value.
The amount of calculations in the MI controller is reduced, which reduces the calculation cycle time of the MI control device.Also, since the future positions of the arms are predicted and controlled, the time constant for prediction can be adjusted to the response delay time of each arm. By making adjustments accordingly, the target angle predicted in response to the response delay of each part can be used as the command value, improving control accuracy regarding the operating trajectory of the tip of the work equipment.
In addition, since the relational expressions for each part are calculated in advance and stored in the memory circuit and recalled when necessary, the calculation cycle time of the control device can be shortened, resulting in further improvements in accuracy. You can get the desired effect. Embodiments] Hereinafter, embodiments of the excavation depth control device for a hydraulic excavator according to the present invention will be described in detail with reference to the drawings. Figures 1 and 2 show a configuration diagram of an embodiment of a hydraulic excavator according to the present invention and a coordinate system necessary for calculation of the work equipment system, and Figure 3 shows a diagram of an embodiment of a hydraulic excavator according to the present invention. An example of the system configuration of the excavation depth control device is shown in FIG. 4, and FIG. A block diagram is shown, and Fig. 5 shows an example of the characteristics of the above-mentioned working machine system. Figure 1 shows the side view of a hydraulic excavator, and Figure 2 shows a simplified representation of the construction of the working machine as a right-angled r7iJR system. As shown in the figure, a general hydraulic excavator has a boom 1 that rotates vertically relative to the vehicle body 10.
The working machine is equipped with a tR structure consisting of three rotating arms, arm 2 and packet 3. The boom 1 has a length of Ta 1 and is centered on the O point with respect to the vehicle body.
It is mounted so as to be rotatable at an angle α from the vertical axis in the right-angled seat support system, and the rotation angle can be detected by a rotation angle detector 7, such as a potentiometer, attached to the O point. The arm 2 has a length of '2' and is rotatably mounted to the boom 1 at a rotation angle β by a hydraulic cylinder 5 about a point B.
The rotation angle detector 8PA attached to the point can detect the rotation angle using a potentiometer. The bucket 3 has a length 93 up to the cutting edge point D at its tip, and is rotatably attached to the arm 2 at a rotation angle γ about the point C by a hydraulic cylinder 6.
The rotation angle can be detected by a rotation angle detector 9 attached to a point, such as a potentiometer. A straight line connecting the point B of the rotation center of the arm 2 and the point D of the cutting edge of the bagevut rotates at a rotation angle β0 with respect to the boom due to the combined movement of the rotation angle β of the arm and the rotation angle γ of the packet, The distance between and the above point D is [,2. Therefore, in FIG. 2, the angle between the line segment DB and the line segment CB, that is, the difference between the rotation angle β0 and the rotation angle β is shown as Δβ. Next, FIG. 3 shows an embodiment of a system for controlling the excavation depth of a hydraulic excavator according to the present invention. In the figure, numerals 1 to 9 indicate the working machines described above in Figs. arm 2 by controlling the flow of oil in the connected hydraulic circuit.
The rotation of is being manipulated. Reference numeral 12 denotes a detector for the operating angle of the operating lever, such as a potentiometer. Reference numeral 14 denotes a control lever for rotating the boom 1, and is a manual control valve 1.
5. The rotation of the boom 1 is controlled by controlling the oil flow in the hydraulic circuit connected to the hydraulic cylinder 4. Reference numeral 30 denotes an operation panel that includes a depth setting device 31 and an automatic/manual switching mode switch 32. 20 is III
The control device includes an input interface 21, a control computer 22 with a storage function, and a control signal output driver 23. The control signal from the control device 20 controls the manual automatic switching valve 16 and the i611-operated electromagnetic ratio @ control valve 17 of the hydraulic cylinder 4 of the boom 1.
In addition, each rotation angle detector 7 of the boom, arm, and baguette,
8 and 9 are input to the control computer 22 via the input interface 21. Next, the operation of this system will be explained using diagrams. Once the working conditions are determined, a predetermined working depth is set using the depth setter 31 according to the working specifications. A signal indicating the set depth is input to the control computer 22 via the input interface 21. Automatic manual switching mode switch 3
When the automatic mode is set by the operation 2, the automatic control operation of the control computer 22 is started via the input interface 2l in the same way as the depth setting device 31, and the signal from the control computer 22 is transmitted by the driver 23. The output is amplified, the manual automatic switching valve 16 is switched to automatic, the electromagnetic proportional control valve 17 is put into operation, and the manually operated valve l5 is switched to automatic mode.
Make it inoperable. When the operator operates the manual operating lever 11 of the arm, the operating angle ψ of the manual operating lever is converted by the input interface 21 into a signal suitable for the operation of the control computer 22 and is input. The operating angle of the operating lever and the current rotation angle β of the arm output from the rotation angle detector 8 are converted into signals suitable for the operation of the control computer 22 by the input interface 21 and input to the control computer 22. Then, from the angle signal, the rotation angular velocity of the arm and the target rotation angle are calculated using the calculation function of the control computer 22, which is designed and stored in advance according to the function of the drive system determined from the design conditions of the hydraulic excavator. The angle of rotation of the arm is calculated and predicted after a predetermined period of time corresponding to the operating performance of the work equipment, and the rotation angle is inputted in advance by the depth setting device 31 in accordance with the predicted value. In order to excavate according to the trajectory based on the set excavation depth, the drive command value for other arms to be automatically controlled, such as the boom, is retrieved from the memory stored in advance in the storage device, and the rotation angle detector 7 The input interface 21 converts the signal into a signal suitable for the operation of the control computer 22, compares it with the input current rotation angle α of the boom, and uses a hydraulic cylinder to rotate the boom so as to eliminate the deviation. Create a command signal to shift the oil amount to 4 by $1 f31. The command signal is the driver 2
After amplifying the output to an appropriate level by 3, the electromagnetic proportional control valve 17
The hydraulic cylinder 4 is automatically operated by controlling the amount of oil in the hydraulic circuit to automatically rotate the boom l at a predetermined speed and a predetermined rotation angle. Next, in the explanation given in -F, the control function described as the function of the I1 computer will be explained using the block diagram in FIG. 4 and the characteristic diagram in FIG. 5. In this explanation, for convenience of explanation, the circuit is explained as a hardware circuit. Therefore, for computer processing, you only need to create a program according to the contents based on this explanation. 41 is a lever for operating the bucket and notebook;
'# = Manual. The hydraulic cylinder 5 for driving the baguette is operated by operating the hydraulic control valve 42, and the rotation angle γ of the packet is detected by the angle detector 9 attached to the rotation shaft of the packet. The rotation angle γ of the packet detected by the angle detector 9 is determined by the arm/cutting edge total length calculation circuit 43 from the arm length recorded in advance 2 and the bucket cutting edge length 93. The length I-2 from the center to the cutting edge is calculated, and the arm offset angle calculation circuit 44 calculates the packet rotation angle γ, the calculated L2, the pre-recorded arm length 2, and the bucket cutting edge length. From No. 3, calculate the arm offset 1 angle Δβ,
An adder circuit 46 calculates the angle between the line segment connecting the rotation center of the boom and the arm to the cutting edge, ie, the arm cutting edge angle βO, from the measured value β from the arm rotation angle detector 8 and the calculated arm offset angle Δβ. ．． The packet rotation angle detector 9 described above is not necessarily required, and it is also possible to calculate L2 and Δβ using a control function such as holding the packet at a fixed position. The operating lever 11 of the arm 2 operates the hydraulic valve 13 to operate the arm driving hydraulic cylinder 5, and the rotation angle β of the arm is detected by the angle detector 8 mounted on the rotation axis of the arm. ．． Also, the operating angle of the arm operating lever is φ
is detected by the angle detector 12, and the estimated speed of the arm cylinder ◇ is calculated by the calculation formula created and recorded based on the mechanical conditions including the hydraulic circuit designed in advance corresponding to the operating angle of the operating lever. circuit 4
Calculate the calculation in step 7. Estimated speed of arm cylinder O
A is input to the arm link correction circuit 48, and the arm link correction circuit 48 calculates the estimated arm rotational angular velocity 6 using an arithmetic expression determined from the design conditions of the side of the arm machine created in advance. The arm estimated rotational angular velocity i is input to the arm angle prediction calculation circuit 49 together with the arm cutting edge angle β0 described above, and is determined in advance.
The predicted value β of the arm cutting edge angle after a certain period of time recorded in
Output r. This predicted value βr of the arm cutting edge angle is inputted to the function generator 51 together with the output I of the excavation depth setter 31 and the above-mentioned L2, and the function generator 51 generates the boom rotation angle according to calculation conditions created in advance based on the mechanical conditions. The target value αr is calculated and output. The boom rotation angle target value αr is subtracted from the output α of the boom rotation angle detector 7 by a subtraction circuit 52 to output a boom rotation angle m difference Δα. The boom rotation angular deviation Δα is input to the proportional gain multiplication circuit 53 to output the boom rotation angular velocity command value a, and the boom rotation angular velocity command value h is further converted to the boom cylinder speed command value vB by the boom link correction circuit 54 for control. It is input to the boom control valve 17 via the amplifier circuit 55 to drive the boom driving hydraulic cylinder 4 to rotate the boom. Next, according to the locus system shown in Figure 2 mentioned above, the fourth
The calculation formulas performed in each calculation circuit are explained using diagrams. The main results of the calculation are shown in No. 5113. In the arm/cutting edge total length calculation circuit 43, the arm/cutting edge total length calculation formula: L2-(Jll22+J)32-2]2. Ct3 c
o s 7 ) 1/! (1) The arm offset angle calculation circuit 44 uses the arm offset angle calculation formula: △β-sun-1 (.03 sin7/I-2)
-(2> or more is a constant value if the packet rotation angle γ is constant, that is, if the packet is fixed.

The calculation formula in the function generator 51 is Lo 1 (.0 12 +
L22 +2.01 L2 cosβr )V2-
(3) 11r: π, z'''2-3 1 n (H/
LO)cos((J)t2+Lo2-L22
)/2. QL Lo )・・・・・・ (4) Using the above equations (3) and (4.), the predicted value β of the arm cutting edge angle is
The boom rotation angle target value αr for r can be found. This is the excavation depth H and arm packet cutting edge length r
, 2, or a table of the boom rotation angle α relative to βr may be set in advance in the storage device using [1 and I, 2 as parameters. In the arm cylinder estimated speed calculation circuit 47, the arm cylinder estimated speed calculation formula: ◇82 ft (φ) Medium... (5
) This is determined by the characteristics of the manually operated valve in the arm, resulting in the characteristics shown in Figure 5a. In the arm link correction circuit 48, the arm link correction formula: ;t=oAX7z (β)...
...(6) f2 (β) is determined by arm link horizontal formation and becomes a function as shown in Figure 5b. In addition times &846, addition formula: β0 = β + Δβ ・・・・
(7) The arm rotation angle prediction calculation circuit 49 uses the arm rotation angle prediction formula B: βr=β0+ΔT7 (
8) Here, ΔT is a predicted time constant determined by the horizontal construction of the hydraulic excavator and other conditions. This βr is input to the function generator to output the boom rotation angle target value αr. The boom angle deviation is determined by a subtraction circuit 52 between αr and α. Subtraction formula: Δα=αr−α ・・・・・・(9
>>In the proportional gain multiplication circuit 53, the proportional gain multiplication formula: a-KΔα...(1
0) Here K is the proportional gain. In the boom link correction circuit 53, the boom link correction formula: VB=a/f3 (a') -=-<
11>Here /3 (α) is determined by the link configuration of the boom and becomes a function as shown in Figure 5C. In the two series of explanations, it was explained that the depth was set using a depth setting device, but if a computer with a memory function is used as the Le 1 #4 device, it is possible to simply set the depth according to the work specifications. It is possible to set an excavation trajectory with a complex shape that is a continuation of the depth rather than just a constant value, and it is also possible to set a drilling trajectory with a complex shape that is a continuation of the depth.Also, it is possible to set a drilling trajectory with a complex shape that is a continuation of the depth. To make it possible to create a signal for automatically controlling the current rotation angle of each arm of a working machine to a position matching a desired set depth or trajectory along an optimal route by setting conditions in advance even when is also possible. It is also possible to set not only the position of the cutting edge of the packet, which is a working machine, but also the direction of the cutting edge to suit the working conditions. In addition, in the above explanation, it was explained that the operation command value of the arm to be automatically operated is obtained from the pre-recorded memory contents from the information from the manual arm of the work equipment and the operation command, but the memory contents As explained above, it is possible to record the calculation formula in a table with pre-calculated values, and to control by predicting the position after a certain period of time. However, depending on the conditions of the work equipment, may simply perform control based only on current information. Also, although the boom was controlled by operating the arm lever, the arm may also be controlled by operating the boom lever. Furthermore, the arms that make up the work machine are a boom and an arm, and although the work machine has been described as a packet, even if the work machine has a more complicated structure, the calculation formula will only become more complicated, and the same idea as above will apply. It is possible to implement this through development. [Effects of the Invention] As explained above, according to the present invention, the relationship between the angles of the respective arms of the working equipment of the hydraulic excavator is determined in advance in accordance with the target excavation depth, and Since control is performed using the angle of the pond's arm as a target value in response to the angle of the two arms, the number of calculation operators during control is reduced, reducing the calculation cycle time of the control device. Since the future position of each arm is predicted and controlled, by adjusting the prediction time constant according to the response delay time of each arm, the predicted target angle can be adjusted according to the response delay of each part. Since it can be used as a command value, the control accuracy regarding the operation trajectory of the tip of the work equipment has been improved. In addition, since the relational expressions for each part are calculated in advance and stored in the memory circuit and recalled when necessary, the calculation cycle time of the control device can be shortened, making it possible to further improve accuracy. You can get excellent results.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a hydraulic cicobel according to an embodiment of the present invention. The second Eji is a coordinate diagram necessary for calculation of the working machine system of the hydraulic excavator of the embodiment shown in FIG. FIG. 3 is a system tM diagram of a hydraulic excavator according to an embodiment of the present invention. FIG. 4 is a block diagram of a control circuit of a hydraulic excavator according to an embodiment of the present invention. FIG. 5 is a characteristic diagram of a working machine system of a hydraulic excavator according to an embodiment of the present invention. 1...Boom 2...Arm 3...Packet 4, 5, 6, 45...Hydraulic cylinder 7, 8, 9, l2...Angle detector IO...Hydraulic excavator 11.14, 41...Operation levers l3, l5, 42...Manual operation valve 16...Switching valve 17...Solenoid proportional ffil1 control valve 20...Control device 43, 48,...Input interface... - Computer - Driver - Operation panel - Depth setting device - Switches 44, 47, 49 - Arithmetic circuit - Addition circuit 54 - Correction circuit - Function generator...・Subtraction circuit...Multiplication circuit...Amplification circuit tail Qll

Claims (1)

[Scope of Claims] 1. In a hydraulic excavator equipped with a working machine comprising at least a plurality of arms each driven by an actuator and respective joints connecting the arms, rotation of each arm a detection means for detecting each angle; a control lever for controlling and driving at least one of the plurality of arms in accordance with the amount of operation thereof; and a means for detecting the operation angle of the control lever; and an excavation depth setting means for setting an excavation depth, corresponding to the operation of the at least one operating lever, and corresponding to each rotation angle detected by the detection means for respectively detecting the rotation angle of each arm. 1. An excavation depth control device for a hydraulic excavator, comprising an arithmetic control function for controlling the excavation depth by the working machine to the depth set by the excavation depth setting means based on the excavation depth setting means. 2. The arithmetic control function calculates other automatically controlled rotation angles of the arm necessary for excavating to the desired set excavation depth in response to the rotation angle of the arm manually operated by the operating lever. 2. The excavation depth control device for a hydraulic excavator according to claim 1, further comprising a function generator for calculating the excavation depth. 3. The function generator stores a value of a rotation angle of another automatically controlled arm for excavating to a desired set excavation depth corresponding to a rotation angle of the arm manually operated by the operating lever. Claim 2 characterized in that it is recorded in advance in the device.
An excavation depth control device for a hydraulic excavator as described in . 4. In a hydraulic excavator equipped with a working machine comprising at least a plurality of arms each driven by an actuator and respective joints connecting the arms, a detection means for detecting the rotation angle of each arm; , an operating lever for controlling and driving at least one arm of the plurality of arms in accordance with the amount of operation thereof, a means for detecting an operating angle of the operating lever, and a means for setting a desired excavation depth. excavation depth setting means; and another automatically controlled arm so that the excavation depth of the work implement is set by the excavation depth setting means in response to the operation of the at least one operating lever. It is equipped with a calculation function that calculates the rotation angle of each arm, and uses a detection means that detects the calculated value by the calculation function necessary to excavate to the desired set excavation depth and the rotation angle of each controlled arm. An excavation depth control device for a hydraulic excavator, characterized in that control is performed so that detected rotation angles match each other. 5. In a hydraulic excavator equipped with a working machine comprising at least a plurality of arms each driven by an actuator and respective joints connecting the arms, a detection means for detecting the rotation angle of each arm; , an operating lever for controlling and driving at least one arm of the plurality of arms in accordance with the amount of operation thereof, a means for detecting an operating angle of the operating lever, and a means for setting a desired excavation depth. and calculating and estimating the rotational angular velocity of the arm operated by the operating lever from the operating angle of the operating lever according to the operation of the at least one operating lever, and calculating the rotational angular velocity of the arm operated by the operating lever after a certain time. The rotation angle is calculated and predicted, and the target angle of the other controlled arm is calculated in accordance with the rotation angle, and each rotation angle is detected by the detection means that detects the rotation angle of each arm. An excavation depth control device for a hydraulic excavator, characterized in that the excavation depth control device for a hydraulic excavator is equipped with an arithmetic control function for controlling the excavation depth by the work machine to the depth set by the excavation depth setting means based on . 6. The arithmetic control function is configured to control another automatically controlled arm that excavates to a desired set excavation depth in accordance with the rotation angle predicted after a certain period of time of the arm manually operated by the operating lever. 5. The excavation depth control device for a hydraulic excavator according to claim 4, further comprising a function generator for calculating a target rotation angle. 7. The function generator is configured to provide another automatically controlled arm that excavates to a desired set working depth in accordance with a rotation angle predicted after a certain period of time of the arm manually operated by the operating lever. 6. The excavation depth control device for a hydraulic excavator according to claim 5, wherein the value of the target rotation angle is recorded in the storage device. 8. In a hydraulic excavator equipped with a working machine comprising a plurality of arms each driven by an actuator and respective joints connecting the arms, a detection means for detecting the rotation angle of each arm; An operating lever for controlling and driving at least one of the plurality of arms in accordance with the amount of operation thereof, means for detecting an operating angle of the operating lever, and excavation for setting a desired excavation depth. and a depth setting means, and according to the operation of the at least one operating lever, calculate and estimate the rotational angular velocity of the arm operated by the operating lever from the operating angle of the operating lever, and calculate the rotational angle of the arm after a certain period of time. Equipped with a calculation function that performs calculation prediction and calculates the target rotation angle of other controlled arm parts corresponding to the rotation angle, and the calculation function necessary for excavating to the desired set excavation depth. Excavation depth of a hydraulic excavator, characterized in that control is performed so that each rotation angle detected by a detection means for detecting the rotation angle of each arm to be controlled coincides with a predicted value calculated by a function. control device.