Digital hydraulic cylinder system and its dual closed loop control method

Abstract

The application provides a digital hydraulic cylinder system and a double closed loop control method thereof. The double closed loop control method of the digital hydraulic cylinder system comprises the following steps: setting a preset displacement value of a piston rod of a hydraulic cylinder, driving a valve core of a pilot valve to move by using a driving device, moving the valve core of the pilot valve from an initial position to a first position, generating a hydraulic pressure difference in a main valve, driving a valve core of the main valve to move, moving the valve core of the pilot valve from the first position to the initial position by a mechanical feedback device, and driving the piston rod of the hydraulic cylinder to move by the valve core of the main valve. The actual displacement value of the piston rod of the hydraulic cylinder is detected by using a detection element, and the actual displacement value and the preset displacement value are compared. The double closed loop control method of the digital hydraulic cylinder system has the advantage of high control precision.

Description

Technical Field

[0001] This invention relates to the field of hydraulic cylinder control technology, specifically to a digital hydraulic cylinder system and its dual closed-loop control method. Background Technology

[0002] A digital hydraulic cylinder mainly consists of a motor, a digital hydraulic valve, and a hydraulic cylinder. The digital hydraulic valve comprises a main valve and a pilot valve, with the pilot valve controlling the proportional regulation and directional switching of the main valve. In related technologies, the position feedback of hydraulic valves primarily relies on sensors to detect the valve core position, followed by electro-hydraulic feedback to energize a proportional electromagnet. This electro-hydraulic feedback method typically has a certain signal delay, which reduces the control accuracy of the hydraulic valve. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of the present invention propose a dual closed-loop control method for a digital hydraulic cylinder system, which has the advantage of high control accuracy.

[0005] The embodiments of the present invention propose a digital hydraulic cylinder system, which has high linearity of the main valve core and high control precision of the hydraulic cylinder.

[0006] The dual closed-loop control method for a digital hydraulic cylinder system according to an embodiment of the present invention includes the following steps:

[0007] S1. Set the preset displacement value for the piston rod movement of the hydraulic cylinder;

[0008] S2. The pilot valve core is driven to move by the driving device. The pilot valve core moves from the initial position to the first position, causing a hydraulic differential in the main valve, thereby driving the main valve core to move. The main valve core drives the pilot valve core to move from the first position toward the initial position through a mechanical feedback device, and the main valve core drives the piston rod of the hydraulic cylinder to move.

[0009] S3. Use a detection device to detect the actual displacement value of the piston rod of the hydraulic cylinder, and determine the magnitude of the actual displacement value compared with the preset displacement value.

[0010] If the actual displacement value is less than the preset displacement value, the drive device is controlled to continue driving the valve core of the pilot valve to move.

[0011] If the actual displacement value is equal to the preset displacement value, the driving device is controlled to stop driving the valve core of the pilot valve.

[0012] The dual closed-loop control method of the digital hydraulic cylinder system in this invention can utilize the combination of mechanical feedback device and detection device with drive device to form dual closed-loop control of mechanical signal and electrical signal, so that the response signal is timely and the pilot valve core and main valve core are more stable.

[0013] Therefore, the dual closed-loop control method of the digital hydraulic cylinder system in this embodiment of the invention has the advantage of high control accuracy.

[0014] In some embodiments, the mechanical feedback device can convert the displacement of the valve core of the main valve along a first direction into the displacement of the valve core of the pilot valve along a second direction, wherein the first direction is opposite to the second direction.

[0015] In some embodiments, in S2, a motor drives the valve core of the pilot valve to move, and the main valve drives the piston rod of the hydraulic cylinder to move, wherein the number of rotations of the output shaft of the motor corresponds to the displacement of the piston rod of the hydraulic cylinder. In some embodiments, in S3, a displacement sensor detects the actual displacement value of the piston rod of the hydraulic cylinder.

[0016] The digital hydraulic cylinder system of this invention includes a pilot valve, a main valve, and a hydraulic cylinder. The valve chamber of the pilot valve is connected to the valve chamber of the main valve, and the pilot valve is used to drive the valve core of the main valve to move. The main valve is connected to the hydraulic cylinder, and the movement of the valve core of the main valve can drive the piston rod of the hydraulic cylinder to move.

[0017] It also includes a mechanical feedback device, a drive device, and a detection element. The drive device includes a control element and a drive element. The drive element includes an output section, which is connected to the valve core of the pilot valve and is used to drive the valve core of the pilot valve to move.

[0018] The mechanical feedback device connects the valve core of the pilot valve and the valve core of the main valve. The mechanical feedback device is used to convert the displacement of the valve core of the main valve along a first direction into the displacement of the valve core of the pilot valve along a second direction, wherein the first direction is opposite to the second direction.

[0019] The detection element is connected to the control element and is used to detect the displacement of the piston rod of the hydraulic cylinder. The control element includes a controller, which is used to receive and process the displacement of the piston rod of the hydraulic cylinder detected by the detection element, so as to control the start or stop of the drive element.

[0020] In some embodiments, a coupling is further included, the first end of which is connected to the output section, and the second end of which is connected to the first end of the valve core of the pilot valve via a spline pair.

[0021] In some embodiments, the mechanical feedback device includes a first connector and a second connector. The first connector includes a first connecting portion and a first mating portion, and the second connector includes a second connecting portion and a second mating portion. The first connecting portion is connected to the valve core of the main valve, and the second connecting portion is connected to the valve core of the pilot valve. The first mating portion is connected to the second mating portion, so that the movement of the valve core of the main valve drives the rotation of the first mating portion and the second mating portion, thereby driving the movement of the valve core of the pilot valve.

[0022] The second end of the valve core of the pilot valve is connected to the second connecting part by a thread, and the valve core of the main valve is connected to the first connecting part by a ball screw pair.

[0023] In some embodiments, both the first mating part and the second mating part are sprockets, and the first mating part and the second mating part are connected by a chain.

[0024] In some embodiments, both the first mating part and the second mating part are gears, and the first mating part and the second mating part mesh with each other.

[0025] In some embodiments, the detection element is a displacement sensor. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the dual closed-loop control method of the digital hydraulic cylinder system according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of a digital hydraulic cylinder system according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of a digital hydraulic cylinder system according to an embodiment of the present invention.

[0029] Figure label:

[0030] Pilot valve 1; First valve chamber 11; First low-pressure chamber 111; First chamber 112; First high-pressure chamber 113; Second chamber 114; Second low-pressure chamber 115;

[0031] Pilot valve core 2; First protrusion 21; Second protrusion 22; Third protrusion 23;

[0032] Main valve 3; second valve chamber 31; third chamber 311; third low-pressure chamber 312; second high-pressure chamber 313; fourth low-pressure chamber 314; fourth chamber 315; high-pressure oil port 316; low-pressure oil port 317; first inlet / outlet oil port 318; second inlet / outlet oil port 319;

[0033] Main valve core 4; fourth protrusion 41; fifth protrusion 42; sixth protrusion 43; seventh protrusion 44;

[0034] Hydraulic cylinder 5; piston rod 51;

[0035] Mechanical feedback device 6; first connector 61; first connecting part 611; first mating part 612; second connector 62; second connecting part 621; second mating part 622;

[0036] Drive unit 7; drive component 71; output unit 711;

[0037] Coupling 8;

[0038] Item 9 was inspected. Detailed Implementation

[0039] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0040] The dual closed-loop control method of the digital hydraulic cylinder system according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0041] like Figure 1 As shown, the dual closed-loop control method of the digital hydraulic cylinder 5 system according to an embodiment of the present invention includes the following steps:

[0042] S1. Set the preset displacement value for the piston rod 51 of the hydraulic cylinder 5.

[0043] S2. The pilot valve core 2 is driven to move by the drive device 7. The pilot valve core 2 moves from the initial position to the first position, which generates a hydraulic differential in the main valve 3, thereby driving the main valve core 4 to move. The main valve core 4 drives the pilot valve core 2 to move from the first position to the initial position through the mechanical feedback device 6, and the main valve core 4 drives the piston rod 51 of the hydraulic cylinder 5 to move.

[0044] In other words, the mechanical feedback device 6 can ensure the timely reset of the pilot valve 1 valve core, and the mechanical feedback can effectively control the displacement of the valve core, further improving the movement accuracy of the valve core.

[0045] Understandably, taking the example of the pilot valve 1 spool being movable in the left-right direction, the pilot valve 1 spool can move from left to right or from right to left. If left-to-right is defined as positive, then right-to-left is negative. That is, when a positive value is input to the drive device 7, the pilot valve spool 2 moves from left to right; conversely, when a negative value is input to the drive device 7, the pilot valve spool 2 moves from right to left.

[0046] S3. Use the detection component 9 to detect the actual displacement value of the piston rod 51 of the hydraulic cylinder 5, and determine the size of the actual displacement value and the preset displacement value. If the actual displacement value is less than the preset displacement value, control the drive device 7 to continue driving the pilot valve core 2 to move. If the actual displacement value is equal to the preset displacement value, control the drive device 7 to stop driving the pilot valve core 2.

[0047] It is understandable that during the movement of the pilot valve core 2, the detection element 9 performs real-time detection. That is, when the actual displacement value detected by the detection element 9 is less than the preset displacement value, the drive device 7 continues to drive the pilot valve core 2 to move until the actual displacement value equals the preset position value, at which point the drive device 7 stops driving the pilot valve core 2 to move.

[0048] In addition, the drive device 7 also includes a controller, which is used to set a preset position value and compare it to obtain a signal for controlling the drive device 7 to start or stop. The controller is connected to the detection element 9, thereby receiving the actual displacement value detected by the detection element 9 and comparing it with the preset displacement value, thereby controlling the drive device 7 to start or stop.

[0049] In other words, the dual closed-loop control method of the digital hydraulic cylinder 5 system in this embodiment of the invention can utilize the combination of mechanical feedback device 6 and detection element 9 with drive device 7 to form dual closed-loop control of mechanical and electrical signals, making the response signal timely, which is beneficial to the recovery of pilot valve 1 valve core, and also makes pilot valve 1 valve core and main valve 3 valve core more stable, thus making the control accuracy of hydraulic cylinder 5 higher.

[0050] Therefore, the dual closed-loop control method of the digital hydraulic cylinder 5 system in this embodiment of the invention has the advantage of high control accuracy.

[0051] In some embodiments, the mechanical feedback device 6 can convert the displacement of the main valve core 4 along a first direction into the displacement of the pilot valve core 2 along a second direction, the first direction being opposite to the second direction.

[0052] Understandably, for example, when the pilot valve core 2 moves from left to right, it creates a hydraulic differential in the main valve 3, causing the main valve core 4 to move from left to right. The right end of the main valve core 4 can be connected to the mechanical feedback structure via a ball screw pair, so that the mechanical feedback structure converts the movement of the main valve core 3 into rotation. The mechanical feedback structure is also threadedly connected to the pilot valve core 2, so that the mechanical feedback structure converts the rotation into the movement of the pilot valve core 1. At this time, the pilot valve core 2 moves from right to left.

[0053] It should be noted that the drive device 7 includes a drive component 71, which includes an output part 711. The drive component 71 can be a motor, and the output part 711 is the output shaft of the motor. The output part 711 and the pilot valve core 2 can be connected through a communicating vessel. That is, one end of the coupling 8 is connected to the output part 711, and the other end of the coupling 8 is connected to the pilot valve core 2 through a spline pair to avoid interference between the pilot valve core 1 and the coupling 8 when it rotates.

[0054] In some embodiments, in S2, the pilot valve core 2 is moved by a motor, and the piston rod 51 of the hydraulic cylinder 5 is moved by the main valve 3, wherein the number of rotations of the output shaft of the motor corresponds to the displacement of the piston rod 51 of the hydraulic cylinder 5.

[0055] It is understandable that one end of the pilot valve core 2 can be connected to the output shaft of the motor through the coupling 8, and the other end of the pilot valve core 2 is threadedly connected to the mechanical feedback device 6. One end of the pilot valve core 2 is connected to the coupling 8 through a spline pair so that the pilot valve core 2 can move along its axial direction.

[0056] It should be noted that the number of rotations of the motor's output shaft corresponds to the displacement of the piston rod 51 of the hydraulic cylinder 5. That is, the displacement of the piston rod 51 of the hydraulic cylinder 5 is constant for each rotation of the motor's output shaft. Therefore, the actual displacement value is detected by the detection element 9, and the controller calculates and compares the actual displacement value with the preset displacement value. After obtaining the difference, the difference is converted into the number of rotations of the motor's output shaft to drive the motor to rotate, thereby making the piston rod 51 of the hydraulic cylinder 5 more accurate.

[0057] In some embodiments, in S3, a displacement sensor is used to detect the actual displacement value of the piston rod 51 of the hydraulic cylinder 5. It is understood that the displacement sensor can be a linear displacement sensor, or other sensors with displacement detection functions, such as a rope displacement sensor.

[0058] The digital hydraulic cylinder 5 system of an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0059] like Figure 2 and Figure 3 As shown, the digital hydraulic cylinder 5 system of this embodiment includes a pilot valve 1, a main valve 3 and a hydraulic cylinder 5. The valve chamber of the pilot valve 1 is connected to the valve chamber of the main valve 3, and the pilot valve 1 is used to drive the main valve core 4 to move. The main valve 3 is connected to the hydraulic cylinder 5, and the movement of the main valve core 4 can drive the piston rod 51 of the hydraulic cylinder 5 to move.

[0060] Specifically, such as Figure 2As shown, the pilot valve 1 has a first valve chamber 11 extending in the left-right direction. The first valve chamber 11 includes a first low-pressure chamber 111, a first chamber 112, a first high-pressure chamber 113, a second chamber 114, and a second low-pressure chamber 115 arranged sequentially in the left-right direction. The pilot valve core 2 includes a first protrusion 21, a second protrusion 22, and a third protrusion 23 arranged axially at intervals along the pilot valve core 2. When the pilot valve core 2 is in the initial position, the first protrusion 21 blocks the first low-pressure chamber 111 and the first chamber 112, the second protrusion 22 blocks the first chamber 112 from the first high-pressure chamber 113 and the second chamber 114 from the first high-pressure chamber 113, and the third protrusion 23 blocks the second chamber 114 from the second low-pressure chamber 115.

[0061] The main valve 3 has a second valve chamber 31 extending in a left-right direction. The second valve chamber 31 includes a third chamber 311, a third low-pressure chamber 312, a second high-pressure chamber 313, a fourth low-pressure chamber 314, and a fourth chamber 315 arranged sequentially in the left-right direction. The main valve core 4 includes a fourth protrusion 41, a fifth protrusion 42, a sixth protrusion 43, and a seventh protrusion 44 spaced apart along the axial direction of the main valve core 4. When the main valve core 4 is in its initial position, the fourth protrusion 41 blocks the third chamber 311 and the third low-pressure chamber 312; the fifth protrusion 42 blocks the third low-pressure chamber 312 and the second high-pressure chamber 313; the sixth protrusion 43 blocks the second high-pressure chamber 313 and the fourth low-pressure chamber 314; and the seventh protrusion 44 blocks the fourth low-pressure chamber 314 and the fourth chamber 315. The third chamber 311 communicates with the first chamber 112, and the fourth chamber 315 communicates with the second chamber 114.

[0062] In addition, the main valve 3 also includes a high-pressure port 316, a low-pressure port 317, a first inlet / outlet port 318, and a second inlet / outlet port 319. The first low-pressure chamber 111, the second low-pressure chamber 115, the third low-pressure chamber 312, and the fourth low-pressure chamber 314 are all connected to the low-pressure port 317, so that low-pressure liquid can flow into the first low-pressure chamber 111, the second low-pressure chamber 115, the third low-pressure chamber 312, and the fourth low-pressure chamber 314 respectively through the low-pressure port 317. The first high-pressure chamber 113 and the second high-pressure chamber 313 are both connected to the high-pressure port 316, so that high-pressure liquid can flow into the first high-pressure chamber 113 and the second high-pressure chamber 313 respectively through the high-pressure port 316. The first inlet / outlet port 318 and the second inlet / outlet port 319 are connected to the hydraulic cylinder 5, so that when liquids of different pressures flow out of the first inlet / outlet port 318 and the second inlet / outlet port 319, the piston rod 51 of the hydraulic cylinder 5 is driven to move in the left-right direction.

[0063] It should be noted that the pressure of high-pressure liquid is greater than 16 MPa, and the pressure of low-pressure liquid is less than 8 MPa.

[0064] It is understandable that, such as Figure 3As shown, when the pilot valve core 2 moves from left to right, the first chamber 112 connects to the first high-pressure chamber 113, and the second chamber 114 connects to the second low-pressure chamber 115. The high-pressure liquid in the first high-pressure chamber 113 flows into the third chamber 311 through the first chamber 112, and the low-pressure liquid in the second low-pressure chamber 115 flows into the fourth chamber 315 through the second chamber 114. Due to the different liquid pressures and the fact that the hydraulic pressure acting on the fourth protrusion 41 is greater than the pressure acting on the seventh protrusion 44, the main valve core 4 moves from left to right. The third low-pressure chamber 312 connects to the first inlet / outlet port 318, and the second high-pressure chamber 313 connects to the second inlet / outlet port 319. The low-pressure liquid in the third low-pressure chamber 312 can be discharged through the first inlet / outlet port 318, and the high-pressure liquid in the second high-pressure chamber 313 can be discharged through the second inlet / outlet port 319, thereby causing the piston rod 51 of the hydraulic cylinder 5 to move from right to left.

[0065] The digital hydraulic cylinder 5 system of this embodiment of the invention also includes a mechanical feedback device 6, a drive device 7, and a detection element 9. The drive device 7 includes a control element and a drive element 71. The drive element 71 includes an output part 711, which is connected to the pilot valve core 2 and is used to drive the pilot valve core 2 to move. The mechanical feedback device 6 is connected to the pilot valve core 2 and the main valve core 4. The mechanical feedback device 6 is used to convert the displacement of the main valve core 4 along the first direction into the displacement of the pilot valve core 2 along the second direction, wherein the first direction is opposite to the second direction.

[0066] Specifically, such as Figure 2 As shown, the mechanical feedback device 6 includes a first connecting member 61 and a second connecting member 62. The first connecting member 61 includes a first connecting part 611 and a first mating part 612. The second connecting member 62 includes a second connecting part 621 and a second mating part 622. The first connecting part 611 is connected to the main valve core 4, the second connecting part 621 is connected to the pilot valve core 2, and the first mating part 612 is connected to the second mating part 622. The movement of the main valve core 4 causes the first mating part 612 and the second mating part 622 to rotate, thereby causing the pilot valve core 2 to move. The second end of the pilot valve core 2 (i.e., the right end of the pilot valve 1 core) is connected to the second connecting part 621 by a thread. The main valve core 4 (i.e., the right end of the main valve 3 core) is connected to the first connecting part 611 by a ball screw pair.

[0067] Of course, the main valve core 4 and the first connecting part 611 can also be connected by a non-self-locking thread structure, or other mechanisms that can convert the movement of the main valve core 4 into the rotation of the second connecting part 621.

[0068] Optionally, both the first mating part 612 and the second mating part 622 are sprockets, and the first mating part 612 and the second mating part 622 are connected by a chain. It should be noted that the specifications of the sprockets need to be configured according to the feed amount of the pilot valve core 2 and the main valve core 4. That is to say, after the movement of the main valve core 3 is converted into the rotation of the first mating part 612 and the second mating part 622, and then the rotation is converted into the movement of the pilot valve core 1, it is necessary to ensure that the displacement of the pilot valve core 1 is equal to the displacement of the main valve core 3.

[0069] Similarly, optionally, the first mating part 612 and the second mating part 622 are both gears, and the first mating part 612 and the second mating part 622 mesh with each other.

[0070] like Figure 2 As shown, the detection element 9 is connected to the control element (not shown) and is used to detect the displacement of the piston rod 51 of the hydraulic cylinder 5. The control element includes a controller, which is used to receive and process the displacement of the piston rod 51 of the hydraulic cylinder 5 detected by the detection element 9, so as to control the start or stop of the drive element 71.

[0071] Optionally, the detection element 9 is a displacement sensor. Of course, the displacement sensor can be a linear displacement sensor, or other sensors with displacement detection functions, such as a rope linear displacement sensor, etc.

[0072] In some embodiments, the digital hydraulic cylinder 5 system of the present invention further includes a coupling 8, the first end of which is connected to the output part 711, and the second end of which is connected to the first end of the pilot valve core 2 via a spline pair.

[0073] Specifically, such as Figure 2 As shown, the drive device 7 includes a drive component 71, which includes an output part 711. The drive component 71 can be a motor, and the output part 711 is the output shaft of the motor. The output part 711 can be connected to the left end of the pilot valve core 2 through a communicating vessel. That is, the left end of the coupling 8 is connected to the output part 711, and the right end of the coupling 8 is connected to the left end of the pilot valve core 2 through a spline pair to avoid interference between the pilot valve core 1 and the coupling 8 when it rotates.

[0074] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0075] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0076] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0077] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0078] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A dual closed-loop control method for a digital hydraulic cylinder system, characterized in that, Includes the following steps: S1. Set the preset displacement value for the piston rod movement of the hydraulic cylinder; S2. The pilot valve core is driven to move by a drive device. The pilot valve core moves from the initial position to the first position, causing a hydraulic differential in the main valve, thereby driving the main valve core to move. The main valve core drives the pilot valve core to move from the first position toward the initial position through a mechanical feedback device. The main valve has an oil outlet, which is connected to the hydraulic cylinder. The movement of the main valve core causes the liquid in the main valve to flow into the hydraulic cylinder through the oil outlet, thereby driving the piston rod of the hydraulic cylinder to move. S3. Use a detection device to detect the actual displacement value of the piston rod of the hydraulic cylinder, and determine the magnitude of the actual displacement value compared with the preset displacement value. If the actual displacement value is less than the preset displacement value, the drive device is controlled to continue driving the valve core of the pilot valve to move. If the actual displacement value is equal to the preset displacement value, the driving device is controlled to stop driving the valve core of the pilot valve.

2. The dual closed-loop control method for a digital hydraulic cylinder system according to claim 1, characterized in that, The mechanical feedback device can convert the displacement of the valve core of the main valve along a first direction into the displacement of the valve core of the pilot valve along a second direction, wherein the first direction is opposite to the second direction.

3. The dual closed-loop control method for a digital hydraulic cylinder system according to claim 1, characterized in that, In S2, the valve core of the pilot valve is moved by a motor, and the piston rod of the hydraulic cylinder is moved by the main valve. The number of rotations of the output shaft of the motor corresponds to the displacement of the piston rod of the hydraulic cylinder.

4. The dual closed-loop control method for a digital hydraulic cylinder system according to claim 1, characterized in that, In S3, a displacement sensor is used to detect the actual displacement value of the piston rod of the hydraulic cylinder.

5. A digital hydraulic cylinder system, characterized in that, It includes a pilot valve, a main valve, and a hydraulic cylinder. The valve chamber of the pilot valve is connected to the valve chamber of the main valve, and the pilot valve is used to drive the valve core of the main valve to move. The main valve is connected to the hydraulic cylinder, and the movement of the valve core of the main valve can drive the piston rod of the hydraulic cylinder to move. It also includes a mechanical feedback device, a drive device, and a detection element. The drive device includes a control element and a drive element. The drive element includes an output section, which is connected to the valve core of the pilot valve and is used to drive the valve core of the pilot valve to move. The mechanical feedback device connects the valve core of the pilot valve and the valve core of the main valve. The mechanical feedback device is used to convert the displacement of the valve core of the main valve along a first direction into the displacement of the valve core of the pilot valve along a second direction, wherein the first direction is opposite to the second direction. The detection element is connected to the control element and is used to detect the displacement of the piston rod of the hydraulic cylinder. The control element includes a controller, which is used to receive and process the displacement of the piston rod of the hydraulic cylinder detected by the detection element, so as to control the start or stop of the drive element.

6. The digital hydraulic cylinder system according to claim 5, characterized in that, It also includes a coupling, the first end of which is connected to the output section, and the second end of which is connected to the first end of the valve core of the pilot valve via a spline pair.

7. The digital hydraulic cylinder system according to claim 6, characterized in that, The mechanical feedback device includes a first connector and a second connector. The first connector includes a first connecting portion and a first mating portion. The second connector includes a second connecting portion and a second mating portion. The first connecting portion is connected to the valve core of the main valve, and the second connecting portion is connected to the valve core of the pilot valve. The first mating portion is connected to the second mating portion, so that the movement of the valve core of the main valve drives the rotation of the first mating portion and the second mating portion, thereby driving the movement of the valve core of the pilot valve. The second end of the valve core of the pilot valve is connected to the second connecting part by a thread, and the valve core of the main valve is connected to the first connecting part by a ball screw pair.

8. The digital hydraulic cylinder system according to claim 7, characterized in that, Both the first mating part and the second mating part are sprockets, and the first mating part and the second mating part are connected by a chain.

9. The digital hydraulic cylinder system according to claim 7, characterized in that, Both the first mating part and the second mating part are gears, and the first mating part and the second mating part mesh with each other.

10. The digital hydraulic cylinder system according to claim 5, characterized in that, The detection device is a displacement sensor.

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