A large forging manipulator hydraulic system and a control method thereof

Abstract

The present application relates to the technical field of forging equipment power system, and particularly discloses a large-scale hydraulic system of a forging manipulator and a control method thereof, which comprises a multi-stage power unit, at least one execution unit and a control unit; the power unit is used for providing at least two different levels of pressure oil sources; the execution unit comprises a hydraulic cylinder, the hydraulic cylinder has a first working chamber and a second working chamber for driving a load and a third compensation chamber and a fourth compensation chamber for pressure compensation; the two working chambers are connected with corresponding closed pump control circuits, and the two compensation chambers are connected with the multi-stage power unit; the control unit is signal-connected with the multi-stage power unit and each execution unit, and is used for controlling the multi-stage power unit to switch the matched pressure oil source to the third compensation chamber and / or the fourth compensation chamber according to the working condition type. The present application has good buffering characteristics, significantly reduces the installed power and heat generation, and improves the response speed, control accuracy, operation reliability and overall energy efficiency of the system.

Description

Technical Field

[0001] This invention relates to the field of power system technology for forging equipment, and in particular to a hydraulic system and control method for a large forging manipulator. Background Technology

[0002] Large forging manipulators are key equipment in heavy forging production lines, primarily used for clamping, flipping, moving, positioning, and adjusting the posture of high-temperature, heavy-weight forgings during the forging process. As the size and weight of forgings continue to increase, manipulators must frequently perform multi-degree-of-freedom movements such as forward and backward offset, lifting, and tilting, and withstand long-term heavy inertia loads and strong impacts from forging hammers or presses. Therefore, their execution system not only needs high output capacity and control precision, but also excellent impact resistance, operational stability, and reliability.

[0003] Currently, large forging manipulators mainly adopt the following two types of drive and control schemes:

[0004] The first type is a valve-controlled hydraulic system powered by a centralized power source, which controls the motion of each actuator through throttling. For example, patent document CN207178335U discloses a device for synchronizing the movement of a motor and cylinder in a hydraulic system of a forging manipulator. This type of system has a mature structure and simple control, but it suffers from significant throttling losses under heavy load conditions, resulting in low system efficiency, high installed power, and severe heat generation. In addition, under strong impact loads, the system is prone to pressure fluctuations, which exacerbates the fatigue of hydraulic components and affects the reliability of long-term operation.

[0005] The second category is a drive system that combines a motor-screw and a hydraulic system. For example, patent document CN120133428A discloses an electro-hydraulic integrated drive system and control method for a large forging manipulator. This solution improves positioning accuracy, but when subjected to periodic impacts and large inertia loads, the mechanical transmission chain has high rigidity and limited impact resistance. The impact load can easily act directly on the transmission components, causing jamming or damage, making it difficult to adapt to complex working conditions of heavy loads and strong impacts.

[0006] In summary, existing technologies are insufficient to effectively meet the operational requirements of large forging manipulators under heavy load, high inertia, and strong impact conditions while ensuring high control precision. There is an urgent need for a new hydraulic system and control method that can balance precision, energy efficiency, and reliability. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a hydraulic system and control method for a large forging manipulator. By adopting a collaborative architecture that combines a working chamber with a closed-loop pump control circuit for precise drive and a compensation chamber with a multi-stage pressure accumulator for load compensation and energy management, high-precision drive and strong impact resistance are achieved, while significantly improving system energy efficiency and reducing installed power.

[0008] As a first aspect of the present invention, the present invention provides a hydraulic system for a large forging manipulator, comprising: a multi-stage power unit for providing at least two different levels of pressure oil sources; at least one actuator unit, the actuator unit including a hydraulic cylinder and a corresponding closed-loop pump control circuit; the hydraulic cylinder including a first working chamber and a second working chamber for driving a load, and a third compensation chamber and a fourth compensation chamber for pressure compensation; the first working chamber and the second working chamber are connected to the corresponding closed-loop pump control circuit, and the third compensation chamber and the fourth compensation chamber are connected to the multi-stage power unit; a control unit, signal-connected to the multi-stage power unit and each of the actuator units, for identifying the working condition type of the hydraulic cylinder according to sensor signals, and controlling the multi-stage power unit to switch the matching pressure oil source to the third compensation chamber and / or the fourth compensation chamber.

[0009] Optionally, the execution unit includes at least one of a forward offset unit, a rear offset unit, a lifting unit, and a tilting unit; the forward offset unit includes a first forward offset cylinder, a second forward offset cylinder, and a first closed-loop pump control circuit; the rear offset unit includes a first rear offset cylinder, a second rear offset cylinder, and a second closed-loop pump control circuit; the lifting unit includes a first lifting cylinder, a second lifting cylinder, and a third closed-loop pump control circuit; and the tilting unit includes a tilting cylinder and a fourth closed-loop pump control circuit.

[0010] Optionally, the first rear offset cylinder, the second rear offset cylinder, the first lifting cylinder, and the second lifting cylinder are three-chamber structures, including a first working chamber, a second working chamber, and a third compensation chamber. The effective area of ​​the third compensation chamber is calculated and determined according to the load to be compensated.

[0011] Optionally, the multi-stage power unit includes a high-voltage accumulator, a medium-voltage accumulator, a low-voltage accumulator, a control valve group, an oil tank, and a replenishment circuit; the high-voltage accumulator, the medium-voltage accumulator, the low-voltage accumulator, and the oil tank are optionally connected to the third compensation chamber and the fourth compensation chamber of each of the execution units through the control valve group.

[0012] Optionally, the control valve assembly is an integrated hydraulic valve block, which integrates a pilot-operated proportional directional valve, a check valve, a safety valve, and a pressure sensor.

[0013] Optionally, the closed-loop pump control circuit is composed of a bidirectional servo motor driving a bidirectional variable hydraulic pump motor, forming a closed-loop volumetric speed regulation circuit.

[0014] Optionally, the control unit is used to identify the working condition type of the hydraulic cylinder as one of resistance extension, resistance retraction, overshoot extension, and overshoot retraction, and to control the switching of the pressure oil source according to the identified working condition type and load force.

[0015] As a second aspect of the present invention, the present invention provides a control method for a hydraulic system of a large forging manipulator, based on the hydraulic system of the large forging manipulator described in the first aspect above, the method comprising the following steps:

[0016] S1: Identify the current operating condition of the hydraulic cylinder based on sensor signals;

[0017] S2: Based on the working condition type and load size, control the third and fourth compensation chambers of the current hydraulic cylinder to connect with the matching pressure source in the multi-stage power unit to achieve pressure matching;

[0018] S3: Control the output flow rate through the corresponding closed-loop pump control circuit to drive the first and second working chambers of the current hydraulic cylinder to move.

[0019] Optionally, the control method of the hydraulic system of the large forging manipulator of the present invention further includes step S4: under overload conditions, the high-pressure oil discharged from the hydraulic cylinder is driven by the closed pump control circuit to drive the hydraulic pump motor, which in turn drives the motor to generate electricity, converting kinetic energy and potential energy into electrical energy for recovery; at the same time, through the connection between the compensation chamber and the accumulator, another part of the energy is stored in the accumulator in the form of hydraulic energy.

[0020] Optionally, in step S4, the recovered electrical energy is used to feed back to the power grid or stored in a supercapacitor bank, and the stored hydraulic and electrical energy is used to drive the system under subsequent impedance conditions.

[0021] Compared with existing technologies, this invention has good buffering characteristics, significantly reduces installed power and heat generation, and improves the system's response speed, control accuracy, operational reliability and overall energy efficiency. It is suitable for heavy-load, high-inertia and high-impact working conditions of forging manipulators. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the hydraulic system of the large forging manipulator provided in Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the hydraulic system of the large forging manipulator provided in Embodiment 2 of the present invention;

[0025] Figure 3 A flowchart of the control method for the hydraulic system of a large forging manipulator provided by the present invention;

[0026] Reference numerals: 1. Multi-stage power unit; 2. Front offset unit; 3. Rear offset unit; 4. Lifting unit; 5. Tilting unit; 6. Control unit; 7. High-voltage accumulator; 8. Medium-voltage accumulator; 9. Low-voltage accumulator; 10. Control valve group; 11. Oil tank; 12. Oil replenishment circuit; 13. First front offset cylinder; 14. Second front offset cylinder; 15. First closed-loop pump control circuit; 16. First rear offset cylinder; 17. Second rear offset cylinder; 18. Second closed-loop pump control circuit; 19. First lifting cylinder; 20. Second lifting cylinder; 21. Third closed-loop pump control circuit; 22. Tilting cylinder; 23. Fourth closed-loop pump control circuit. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] Reference Figure 1 As shown, Embodiment 1 of the present invention provides a hydraulic system for a large forging manipulator, including a multi-stage power unit 1, a front offset unit 2, a rear offset unit 3, a lifting unit 4, a tilting unit 5, and a control unit 6. The control unit 6 is communicatively connected to the multi-stage power unit 1, the front offset unit 2, the rear offset unit 3, the lifting unit 4, and the tilting unit 5, respectively, and is used to execute control logic based on sensor signals. Simultaneously, the front offset unit 2, the rear offset unit 3, the lifting unit 4, and the tilting unit 5 are all connected to the multi-stage power unit 1 via hydraulic pipelines to obtain different levels of pressure oil sources.

[0031] The multi-stage power unit 1 includes a high-pressure accumulator 7, a medium-pressure accumulator 8, a low-pressure accumulator 9, a control valve assembly 10, an oil tank 11, and a replenishment circuit 12. The control valve assembly 10 is an integrated hydraulic valve block that integrates multiple pilot-operated proportional directional valves, check valves, safety valves, and pressure sensors. The high-pressure accumulator 7, medium-pressure accumulator 8, low-pressure accumulator 9, and oil tank 11 are all connected to their respective interfaces in the control valve assembly 10 via independent pipelines. The replenishment circuit 12 is also connected to the control valve assembly 10 and includes a low-power fixed-displacement pump, a filter, and a cooler. It replenishes the system with clean hydraulic oil and maintains the pressure of the high-pressure accumulator 7, medium-pressure accumulator 8, and low-pressure accumulator 9, as well as the temperature and oil level in the oil tank 11. Through precise switching of the control valve assembly 10, this unit can provide high, medium, and low pressure oil to each actuator and dynamically match the pressure according to load requirements.

[0032] The forward offset unit 2 includes a first forward offset cylinder 13, a second forward offset cylinder 14, and a first closed-loop pump control circuit 15. The first and second forward offset cylinders 13 and 14 are identical double-acting hydraulic cylinders. Their cylinder bodies are fixed to the manning machine frame via hinged supports, while their piston rods are connected to the front of the manning machine's clamps. Each forward offset cylinder has four oil chambers: a first working chamber, a second working chamber, a third compensation chamber, and a fourth compensation chamber. The first and second working chambers are connected to the two main oil ports of the first closed-loop pump control circuit 15 via oil pipes. The first closed-loop pump control circuit 15 consists of a bidirectional servo motor driving a bidirectional variable hydraulic pump motor, forming a closed-loop volumetric speed control circuit for active, smooth, and unthrottling-free flow and direction control of the working chambers of the forward offset cylinders. The third and fourth compensation chambers are connected to the control valve group 10 in the multi-stage power unit 1 via two additional sets of oil pipes.

[0033] In one specific embodiment, the rear offset unit 3, lifting unit 4, and tilting unit 5 are structurally similar to the front offset unit 2. The rear offset unit 3 includes a first rear offset cylinder 16, a second rear offset cylinder 17, and a second closed-loop pump control circuit 18. The piston rods of the first and second rear offset cylinders 16 and 17 are connected to the rear of the manipulator clamp. Their first and second working chambers are connected to the second closed-loop pump control circuit 18, and their third and fourth compensation chambers are connected to the control valve group 10. The lifting unit 4 includes a first lifting cylinder 19, a second lifting cylinder 20, and a third closed-loop pump control circuit 21, used to drive the vertical lifting motion of the entire manipulator. The tilting unit 5 includes one or a group of tilting cylinders 22 and a fourth closed-loop pump control circuit 23, used to achieve the pitching and tilting motion of the clamp. The first and second working chambers of all hydraulic cylinders are driven by their corresponding closed-loop pump control circuits to achieve precise position and speed control; while the third and fourth compensation chambers of all hydraulic cylinders are connected to the high-pressure accumulator 7, medium-pressure accumulator 8, low-pressure accumulator 9 or oil tank 11 in the multi-stage power unit 1 through the control valve group 10.

[0034] Building upon the aforementioned embodiments, the coordinated operation of the first closed-loop pump control circuit 15, the second closed-loop pump control circuit 18, the third closed-loop pump control circuit 21, and the fourth closed-loop pump control circuit 23 with the high-pressure accumulator 7, the medium-pressure accumulator 8, the low-pressure accumulator 9, and the oil tank 11 is the core of this system's high precision and high energy efficiency. Based on the real-time feedback signals from the displacement and pressure sensors installed on the hydraulic cylinder, the control unit 6 first determines the current operating condition of the hydraulic cylinder, specifically categorized into four types: impedance extension, impedance retraction, overshoot extension, and overshoot retraction. Then, based on the operating condition and the calculated load force, the control unit 6 sends a command to the control valve assembly 10 to switch the hydraulic cylinder's compensation chamber to the most suitable pressure source. For example, under heavy-load lifting conditions, the control valve assembly 10 connects the third compensation chamber of the lifting cylinder to the high-pressure accumulator 7 and the fourth compensation chamber to the oil tank 11. At this time, the pressure energy stored in the high-voltage accumulator 7 can be directly used to balance most of the self-weight and inertial load of the working device, while the third closed pump control circuit 21 only needs to provide the small power required to overcome friction and make dynamic fine adjustments, thereby greatly reducing the load and installed power requirements of the drive system and improving the response speed.

[0035] Example 2

[0036] Reference Figure 2 As shown, Embodiment 2 of the present invention provides another hydraulic system for a large forging manipulator, which demonstrates the flexibility of system configuration based on Embodiment 1.

[0037] In this embodiment, the multi-stage power unit 1 can be flexibly configured according to the specific load characteristics and cost control requirements of different forging manipulators. For example, for models with relatively concentrated load ranges and clear impact energy recovery requirements, only one high-voltage accumulator 7 and one low-voltage accumulator 9 can be configured, and effective load compensation and energy management can still be achieved through optimization of the control strategy.

[0038] Meanwhile, to adapt to different spatial layouts and mechanical performance requirements, the structure of the hydraulic cylinders can also be customized. For example, the first rear offset cylinder 16 and the second rear offset cylinder 17 can be designed as a three-chamber structure containing only a first working chamber, a second working chamber, and a third compensation chamber. The first lifting cylinder 19 and the second lifting cylinder 20 can also adopt a three-chamber structure. The effective area of ​​the third compensation chamber is precisely calculated based on the self-weight load to be compensated. This structure simplifies cylinder design and manufacturing while reducing the complexity of sealing. The control method of the closed-loop pump control circuit can also be selected according to system performance requirements and cost. It can be motor variable speed control, hydraulic pump motor variable displacement control, or a more refined combined control of motor variable speed and hydraulic pump motor variable displacement. For example, each closed-loop pump control circuit in Embodiment 2 can adopt a combined control method of motor variable speed and hydraulic pump motor variable displacement to achieve a wider speed range and higher power density.

[0039] It should be understood that, in practical applications, the system of the present invention has good modularity. For the modification of existing forging manipulators, or the implementation of partial functions of new manipulators, only one or several units of the system of the present invention can be selectively applied. For example, only the lifting unit 4 can be replaced with the closed-loop pump control and accumulator compensation system of the present invention to focus on solving the problems of high energy consumption and impact during the lifting process, while the front offset unit 2 and the rear offset unit 3 retain their original valve control systems.

[0040] Example 3

[0041] Reference Figure 3 As shown, Embodiment 3 of the present invention also provides a control method for a hydraulic system of a large forging manipulator. This method is based on the hydraulic system of the large forging manipulator described in Embodiment 1 or Embodiment 2 above, and includes the following steps:

[0042] S1: Based on the working status of the forging manipulator, identify the current cylinder's working condition type, including resistance extension, resistance retraction, overshoot extension, and overshoot retraction;

[0043] S2: Depending on the working condition and load size, the third and fourth compensation chambers of the control cylinder are connected to the high-pressure accumulator 7, the medium-pressure accumulator 8, the low-pressure accumulator 9 or the oil tank 11 to achieve pressure matching.

[0044] S3: The output flow is controlled by a closed-loop pump control circuit to drive the movement of the first and second working chambers of the cylinder, thereby achieving precise position and speed control of the working device;

[0045] S4: Under overload conditions, kinetic and potential energy are converted into electrical energy to feed back to the grid or stored in the supercapacitor bank through a closed pump control circuit. At the same time, kinetic and potential energy are converted into hydraulic energy for storage through an accumulator. Under impedance conditions, the stored electrical and hydraulic energy is used for driving.

[0046] In one specific embodiment, the accumulator output pressure is preferentially used to compensate for the load and recover energy, so that the closed-loop pump control circuit is in a low-load regulation state.

[0047] In one specific embodiment, the method is run in the control unit 6 through program logic, and its control flow mainly includes the following steps:

[0048] First, the control unit 6 continuously collects signals from the displacement and pressure sensors on each hydraulic cylinder. The direction of piston rod movement is determined based on the rate of change of the displacement signal, and the direction and magnitude of the load force are calculated based on the pressure difference between the two working chambers. By comparing the direction of movement with the direction of the load force, the specific operating condition of the current cylinder can be accurately identified: when the direction of the load force is opposite to the direction of movement, it is an "impedance" condition; when the direction of the load force is the same as the direction of movement, it is an "overtaking" condition. Therefore, the operating conditions can be further subdivided into "impedance extension," "impedance retraction," "overtaking extension," and "overtaking retraction."

[0049] Next, the control unit 6 outputs a control signal to the control valve assembly 10 based on the identified operating condition type and the quantified load force, dynamically switching the pressure sources connected to the third and fourth compensation chambers of the corresponding hydraulic cylinder to achieve optimal pressure matching. The core idea of ​​this step is to prioritize the use of the accumulator's pressure to compensate for constant or large-proportion loads, ensuring that the actively driven closed-loop pump control circuit is always in an ideal state of "low-load regulation." For example, in the "overshoot retraction" condition, the control valve assembly 10 connects the compensation chamber of the lifting cylinder to the intermediate-pressure accumulator 8 and the oil tank 11, so that most of the released potential and kinetic energy is converted into hydraulic energy and stored in the intermediate-pressure accumulator 8.

[0050] Then, based on the target position and speed, as well as the real-time feedback from the displacement sensor, the control unit 6 precisely adjusts the flow rate into or out of the first and second working chambers of the hydraulic cylinder by controlling the speed and direction of the servo motors in each closed-loop pump control circuit. Since the compensation chamber already bears most of the load, the closed-loop pump control circuit only needs to handle dynamic position following and speed fine-tuning, thus achieving extremely high-precision motion control with minimal system heat generation.

[0051] Finally, the system achieves efficient energy recovery under "overshoot" conditions. On one hand, through a closed-loop pump control circuit, the high-pressure oil discharged from the hydraulic cylinder's working chamber drives the hydraulic pump motor, which in turn reverses to generate electricity, converting kinetic and potential energy into electrical energy. This electrical energy can be directly fed back to the grid or stored in the system's supercapacitor bank. On the other hand, through the connection between the compensation chamber and the accumulator, another portion of energy is stored as hydraulic energy in an accumulator at a corresponding pressure. Under subsequent "impedance" conditions, this stored electrical and hydraulic energy can be preferentially utilized to drive the system, thus forming a highly efficient energy closed loop. This significantly reduces the peak power demand of the external grid and the total energy consumption, improving the overall energy efficiency of the system.

[0052] When the system is subjected to impact loads, on the one hand, the accumulator actively absorbs and buffers the impact energy; on the other hand, the overflow valve in the closed pump control circuit passively protects the system safety by overflowing and releasing the load.

[0053] Based on the above three embodiments, the present invention discloses at least the following beneficial effects:

[0054] This invention compensates for the self-weight of the working device and overcomes inertial loads by pressure matching between the compensation chamber and the multi-stage pressure accumulator. This significantly reduces the load on the actively driven closed-loop pump control circuit and reduces interference from external loads on system control, thereby effectively improving the system's control accuracy and response speed. The pre-pressure effect of the accumulator further shortens the pressure build-up time during startup, enabling the system to enter the working state more quickly.

[0055] Regarding system reliability and shock resistance, this invention employs a closed-loop pump-controlled circuit to achieve compliant hydraulic transmission, replacing the rigid lead screw drive and fundamentally eliminating the risk of jamming due to impact deformation. Simultaneously, the multi-stage pressure accumulator effectively mitigates impact energy and distributes the load, significantly reducing the working stress of hydraulic components under long-term heavy loads and strong impact conditions, thus lowering the risk of fatigue damage. Furthermore, by eliminating vulnerable components such as proportional throttle valves, the overall reliability of the system is further improved.

[0056] In terms of energy efficiency and cost control, the active drive adopts a closed-loop pump control method, avoiding the significant throttling losses in traditional valve-controlled systems and significantly reducing system heat generation. The closed-loop pump control loop works in conjunction with the accumulator to effectively recover and utilize kinetic and potential energy, further improving the system's energy utilization efficiency. Simultaneously, since the accumulator bears most of the load, the active drive closed-loop pump control loop does not need to match peak loads, only undertaking dynamic adjustment tasks. This not only effectively reduces the system's operating load and installed power requirements but also significantly reduces initial investment and operating costs.

[0057] This invention features a compact structure and high adaptability, making it particularly suitable for heavy-load, high-inertia, and high-impact operating conditions of forging manipulators. The system allows for flexible configuration of the accumulator's pressure rating, volume, and number based on the load characteristics of different forging manipulators, achieving personalized optimization. Furthermore, this technical solution offers high flexibility, allowing for the selective application of one or more units of the system to existing or new forging manipulators according to actual needs, demonstrating promising prospects for widespread application.

[0058] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, 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, and therefore should not be construed as a limitation of this invention.

[0059] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A hydraulic system for a large forging manipulator, characterized in that, include: A multi-stage power unit (1) is used to provide at least two different levels of pressure oil sources; The execution unit includes a front offset unit (2), a rear offset unit (3), a lifting unit (4), and a tilting unit (5); each execution unit includes a hydraulic cylinder and a corresponding closed pump control circuit, which is composed of a bidirectional servo motor driving a bidirectional variable hydraulic pump motor to form a closed volumetric speed regulation circuit. The front offset unit (2) includes a first front offset cylinder (13), a second front offset cylinder (14), and a first closed-loop pump control circuit (15); the rear offset unit (3) includes a first rear offset cylinder (16), a second rear offset cylinder (17), and a second closed-loop pump control circuit (18); the lifting unit (4) includes a first lifting cylinder (19), a second lifting cylinder (20), and a third closed-loop pump control circuit (21); the tilting unit (5) includes a tilting cylinder (22) and a fourth closed-loop pump control circuit (23). The first front offset cylinder (13), the second front offset cylinder (14), and the tilting cylinder (22) are four-chamber structures, including a first working chamber, a second working chamber, a third compensation chamber, and a fourth compensation chamber. The first rear offset cylinder (16), the second rear offset cylinder (17), the first lifting cylinder (19), and the second lifting cylinder (20) are three-chamber structures, including a first working chamber, a second working chamber, and a third compensation chamber. The first working chamber and the second working chamber are connected to the corresponding closed-loop pump control circuit. The third compensation chamber and the fourth compensation chamber are connected to the multi-stage power unit (1). The effective area of ​​the third compensation chamber and the fourth compensation chamber is calculated and determined according to the load to be compensated. The multi-stage power unit (1) includes a high-voltage accumulator (7), a medium-voltage accumulator (8), a low-voltage accumulator (9), a control valve group (10), an oil tank (11), and a replenishment circuit (12); the high-voltage accumulator (7), the medium-voltage accumulator (8), the low-voltage accumulator (9), and the oil tank (11) are selectively connected to the third compensation chamber and the fourth compensation chamber of each of the execution units through the control valve group (10); The control valve group (10) is an integrated hydraulic valve block, which integrates a pilot-operated proportional directional valve, a check valve, a safety valve and a pressure sensor. The control unit (6) is connected to the multi-stage power unit (1) and each of the execution units, collects the displacement and pressure signals of each hydraulic cylinder, determines the movement direction of the hydraulic cylinder according to the rate of change of the displacement signal, and calculates the direction and magnitude of the load force according to the pressure difference between the first working chamber and the second working chamber. By comparing the movement direction with the load force direction, the working condition type of the hydraulic cylinder is identified as one of impedance extension, impedance retraction, overshoot extension and overshoot retraction. The control unit (6) is also used to output control signals to the control valve group (10) according to the identified working condition type and the quantified load force magnitude, and control the multi-stage power unit (1) to switch the matched pressure oil source to the third compensation chamber and / or the fourth compensation chamber.

2. A control method for the hydraulic system of a large forging manipulator as described in claim 1, characterized in that, Includes the following steps: S1: Identify the current operating condition of the hydraulic cylinder based on sensor signals; S2: Based on the working condition type and load size, control the third and fourth compensation chambers of the current hydraulic cylinder to connect with the pressure source matched in the multi-stage power unit (1) to achieve pressure matching; S3: Control the output flow rate through the corresponding closed-loop pump control circuit to drive the first and second working chambers of the current hydraulic cylinder to move.

3. The control method for the hydraulic system of a large forging manipulator according to claim 2, characterized in that, It also includes step S4: Under overload conditions, the high-pressure oil discharged from the hydraulic cylinder is driven by the closed-loop pump control circuit to drive the hydraulic pump motor, which in turn drives the motor to generate electricity, converting kinetic and potential energy into electrical energy for recovery; at the same time, through the connection between the compensation chamber and the accumulator, another part of the energy is stored in the accumulator in the form of hydraulic energy.

4. The control method for the hydraulic system of a large forging manipulator according to claim 3, characterized in that, In step S4, the recovered electrical energy is used to feed back to the power grid or stored in a supercapacitor bank, and the stored hydraulic and electrical energy is used to drive the system under subsequent impedance conditions.

5. The control method for the hydraulic system of a large forging manipulator according to any one of claims 2 to 4, characterized in that, When the hydraulic system is subjected to an impact load, the accumulator connected to the compensation chamber actively absorbs and buffers the impact energy, and the relief valve in the closed pump control circuit protects the hydraulic system by overflowing and relieving the load.

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