A hydraulic transmission system of a pump-controlled asymmetric hydraulic cylinder

Abstract

The present invention relates to the field of hydraulic drive technology and discloses a pump-controlled asymmetric hydraulic cylinder control system. The pump-controlled asymmetric hydraulic cylinder control system includes a four-quadrant fixed-displacement pump and a four-quadrant variable displacement pump, each coaxially connected to a permanent magnet synchronous motor, an asymmetric oil cylinder, and a matching control system. The control system includes a PLC controller and a permanent magnet synchronous motor driver connected thereto. A position sensor and a load force sensor are connected to the input end of the PLC controller. The load force sensor is used to collect a load force signal on the asymmetric oil cylinder and upload it to the PLC controller. The load force sensor combines the input position command signal with the position feedback signal of the position sensor and the direction of the load force, and then determines the current operating mode. The PLC controller sends a command to a bidirectional DC converter based on the current operating mode, causing the bidirectional DC converter to switch between outputting electrical energy and recovering energy. The present invention generates back pressure at the outlet of the hydraulic cylinder by fine-tuning the displacement of the four-quadrant variable displacement pump, thereby increasing the stability of the system. The bidirectional DC converter converts the energy of the negative load into electrical energy storage, thereby achieving energy recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic transmission control, and in particular relates to a hydraulic transmission system of a pump-controlled asymmetric hydraulic cylinder. Background Art

[0002] As energy shortages and environmental pollution issues are gaining increasing attention across society, research on pump control systems has increased significantly in recent years. Currently, electro-hydraulic control systems are primarily categorized into valve-controlled systems and pump-controlled systems. Valve-controlled systems offer advantages such as rapid response and the ability to achieve high-precision control of position or pressure, but they also suffer from significant throttling losses and low energy efficiency. Pump-controlled systems, on the other hand, have the advantages of minimal energy loss and higher system efficiency due to the pump's direct drive of the load and the absence of throttling losses.

[0003] Regarding pump control system technologies, we discovered the following related patents. Patent application number CN2019112922915 discloses a dual-servo motor pump-controlled, independently driven asymmetric hydraulic cylinder control system. This system utilizes two servo motor + gear pump systems to supply oil to the two chambers of the asymmetric hydraulic cylinder. Independently controlling the speed of the two servo motors enables reciprocating motion of the hydraulic cylinder and high-precision position control of the asymmetric hydraulic cylinder. The invention patent with application number CN2019106155193 discloses an electro-hydraulic control system for a hydraulic bending machine with a closed pump-controlled asymmetric cylinder. During operation, the servo motor drives the bidirectional quantitative pump to directly drive the piston of the pressure cylinder, which has the characteristics of energy saving, high efficiency, high power-to-weight ratio, high integration, and low cost. The invention patent with application number CN201910646195.X discloses a low-energy and high-dynamic pump-valve combined position servo system. The two oil outlets of the bidirectional pump are respectively connected to the rod chamber and the rodless chamber of the asymmetric hydraulic cylinder. At the same time, the servo valve is connected in parallel with the two oil ports of the bidirectional pump. The coordinated control of the pump and valve ensures the energy utilization efficiency of the hydraulic system while taking into account the dynamic response of the system. The invention patent with application number CN201811209556.6 discloses a pump control system that uses three pumps to simultaneously drive an asymmetric cylinder. It has the characteristics of balanced flow between the two chambers of the asymmetric cylinder, low system power loss, and the ability to accurately control the dynamic and static positions. Compared with the valve control system, the pump control systems disclosed above have better solved the energy saving problem.

[0004] However, since there is no back pressure in the cylinder in the pump control system, unstable cylinder movement is likely to occur when driving a negative load; at the same time, the above pump control system does not solve the problem of energy recovery under negative load conditions. Summary of the Invention

[0005] In view of the problems of unstable operation and energy recovery under negative load conditions in the pump control system formed by the pump-controlled volumetric electro-hydraulic servo in the above background technology, the present invention adjusts the displacement of the pump to provide back pressure to the cylinder outlet, thereby solving the problem of instability under load change conditions; the energy of the negative load is recovered through a permanent magnet synchronous motor through a bidirectional DCDC converter, thereby achieving the purpose of energy saving. Based on the above design ideas, the present invention provides a pump-controlled asymmetric hydraulic cylinder control system.

[0006] In order to achieve the above-mentioned purpose, according to the guidance of the above-mentioned theoretical design, we propose the following creative transformation to the existing pump control system. Therefore, the technical solution adopted by the present invention is: a pump-controlled asymmetric hydraulic cylinder control system, including an asymmetric oil cylinder, the asymmetric oil cylinder includes three parts: a cylinder body, a piston and a piston rod, wherein the piston rod is fixed on the piston and a load weight block is fixedly connected to its end, wherein the piston is movably arranged in the cylinder body and the cylinder body is divided into a rod chamber and a rodless chamber, and two oil ports respectively connected to the rod chamber and the rodless chamber are provided on the cylinder body, and a four-element metering pump is connected to the oil port of the rodless chamber through the rodless chamber oil circuit and is connected to the oil tank, and the four-element metering pump is relied upon to provide oil pressure to the rodless chamber. In addition, the pump-controlled asymmetric hydraulic cylinder control system also includes a four-quadrant variable pump and a permanent magnet synchronous motor coaxially connected to the four-quadrant variable displacement pump, and a matching energy recovery control system. The four-quadrant variable pump is connected to the oil port of the rod chamber and the oil tank through the rod chamber oil circuit, and relies on the four-quadrant variable pump to provide oil pressure to the rod chamber, and by fine-tuning the displacement of the four-quadrant variable pump, the back pressure of the cylinder is increased to maintain the stability of the cylinder movement when driving a negative load. The control system includes a PLC controller and a permanent magnet synchronous motor driver connected to it. The permanent magnet synchronous motor is electrically connected to the energy storage battery through the permanent magnet synchronous motor driver and the bidirectional DC converter in turn, and the permanent magnet synchronous motor driver is used to enable the output of electrical energy or energy recovery between the permanent magnet synchronous motor and the energy storage battery.

[0007] As a further supplement to the above technical solution, it also includes a load force sensor connected to the input end of the PLC controller. The load force sensor is installed between the end of the asymmetric cylinder piston rod and the load weight block. It is used to collect the load force signal on the asymmetric cylinder and upload it to the PLC controller.

[0008] As a further supplement to the above technical solution, it also includes a position sensor connected to the input end of the PLC controller. The position sensor collects information on the movement of the weight block and uploads it to the PLC editing controller as a position feedback signal of the piston. Combined with the input position command signal and load force signal, it determines the movement direction and load force direction of the asymmetric cylinder, and then determines the current working mode. The PLC controller sends instructions to the bidirectional DC converter according to the current working mode to enable the bidirectional DC converter to output electrical energy or switch to energy recovery.

[0009] As a further supplement to the above technical solution, an angle sensor is installed on the four-quadrant variable pump corresponding to its swash plate. The signal output end of the angle sensor and the proportional control valve of the four-quadrant variable pump are respectively connected to the input end and output end of the PLC controller. The PLC controller is used to receive the swash plate inclination angle feedback signal collected by the angle sensor and combine it with the displacement command signal to control the displacement of the four-quadrant variable pump.

[0010] As a further supplement to the above technical solution, a first oil replenishing valve and a second oil replenishing valve are respectively connected between the rodless chamber oil circuit and the rod chamber oil circuit, and the two are connected to an oil replenishing pump and an oil tank through the oil replenishing oil circuit. The oil replenishing pump replenishes oil to the two chambers of the asymmetric cylinder through the oil replenishing pump motor through the first oil replenishing valve and the second oil replenishing valve to prevent the system from sucking air.

[0011] As a further supplement to the above technical solution, a first overflow valve and a second overflow valve are respectively connected to the two oil ports of the asymmetric cylinder, and both are connected to the oil tank through an oil circuit, and are used to limit the pressure in the two oil chambers to prevent the pressure from exceeding the set value during overload and serve as overflow protection.

[0012] As a further supplement to the above technical solution, a third overflow valve is connected to the oil outlet of the oil replenishment pump, which is connected to the oil tank through an oil circuit to ensure the outlet pressure of the oil replenishment pump and provide pressure for the proportional control valve of the four-quadrant variable pump.

[0013] Compared with the existing pump control system, the present invention has the following beneficial effects:

[0014] 1. The pump-controlled asymmetric hydraulic cylinder control system disclosed in the present invention includes an asymmetric hydraulic cylinder that drives a load, wherein the two oil chambers of the asymmetric hydraulic cylinder are respectively connected to a four-quadrant fixed-displacement pump and a four-quadrant variable pump, and the two pumps are coaxially connected to a permanent magnet synchronous motor. By fine-tuning the displacement of the four-quadrant variable, back pressure is generated at the hydraulic cylinder outlet, thereby increasing the stability of the system; 2. The present invention controls a bidirectional DC converter through a PLC controller to convert the energy of the negative load into electrical energy storage, thereby realizing energy recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the hydraulic transmission system of the pump-controlled asymmetric hydraulic cylinder disclosed in the present invention;

[0016] Figure 2 Schematic diagram for simulation experiment using the principle of hydraulic transmission system of pump-controlled asymmetric hydraulic cylinder;

[0017] Figure 3 This is a control flow chart of an embodiment of the present invention;

[0018] Figure 4 Based on Figure 2 Simulation results of simulation principle Figure 1 ;

[0019] Figure 5 Based on Figure 2 Simulation results of simulation principle Figure 2 .

[0020] In the figure: control system 1, permanent magnet synchronous motor 2, four-quadrant variable displacement pump 3, asymmetric oil cylinder 4, four-quadrant variable displacement pump 5, load weight block 6, position sensor 7, oil supply pump motor 8, oil supply pump 9, angle sensor 10, first oil supply valve 11, second oil supply valve 12, first relief valve 13, second relief valve 14, third relief valve 15, oil tank 16,

[0021] The energy recovery control system includes a PLC editing controller 1.1, a permanent magnet synchronous motor driver 1.2, a permanent magnet synchronous motor driver 1.2, a bidirectional DC converter 1.3, and an energy storage battery 1.4. DETAILED DESCRIPTION

[0022] In order to further illustrate the technical solution of the present invention, the present invention is further described below through examples.

[0023] See Figure 1A pump-controlled asymmetric hydraulic cylinder control system includes a four-quadrant fixed-flow pump 3 and a four-quadrant variable pump 5 coaxially connected to a permanent magnet synchronous motor 2, an asymmetric oil cylinder 4 and a matching control system 1, wherein the asymmetric oil cylinder 4 includes three parts: a cylinder body, a piston and a piston rod, wherein the piston rod is fixed on the piston and a load weight block 6 is fixedly connected to the end thereof, wherein the piston is movably arranged in the cylinder body and the cylinder body is divided into a rod chamber and a rodless chamber, and two oil ports are provided on the cylinder body that are respectively connected to the rod chamber and the rodless chamber, and the two oil ports are respectively connected through the rod chamber oil circuit and the rodless chamber oil circuit. The oil circuit connects the four-quadrant variable pump 5, the four-quadrant metering pump 3 and the oil tank 16, and relies on the four-quadrant metering pump 3 and the four-quadrant variable pump 5 to provide oil pressure to the rodless chamber and the rod chamber, so as to maintain the stability of the cylinder movement when driving a negative load. The first oil replenishment valve 11 and the second oil replenishment valve 12 are respectively connected between the rodless chamber oil circuit and the rod chamber oil circuit. The two are connected to the oil replenishment pump 9 through the oil replenishment oil circuit and are connected to the oil tank 16. The oil replenishment pump 9 replenishes oil to the two chambers of the asymmetric cylinder through the oil replenishment pump motor 8 through the first oil replenishment valve 11 and the second oil replenishment valve 12 to prevent the system from sucking air. The control system 1 includes a PLC controller 1.1 and a permanent magnet synchronous motor driver 1.2 connected thereto. The position sensor 7 and the load force sensor 17 are connected to the input end of the PLC controller 1.1. The load force sensor 17 is installed between the end of the piston rod of the asymmetric oil cylinder 4 and the load weight block 6. The load force sensor 17 is used to collect the load force signal of the asymmetric oil cylinder 4 and upload it to the PLC controller 1.1. The position sensor 7 collects the information of the movement of the weight block 6 and uploads it to the PLC controller 1.1 as the position feedback signal of the piston. The position sensor 7 combines the input position command signal and the load force signal to determine the movement direction and load force direction of the asymmetric oil cylinder 4, and then The PLC controller 1.1 determines the current operating mode and sends instructions to the bidirectional DC converter 1.3 based on the current operating mode, causing the bidirectional DC converter 1.3 to switch between power output and energy recovery. An angle sensor 10 is mounted on the four-quadrant variable displacement pump 5, corresponding to its swash plate. The signal output terminal of the angle sensor 10 and the proportional control valve of the four-quadrant variable displacement pump 5 are connected to the input and output terminals of the PLC controller 1.1, respectively. The PLC controller 1.1 is configured to receive the swash plate angle feedback signal acquired by the angle sensor 10 and, based on the movement direction of the asymmetric cylinder 4, send a displacement command signal to the proportional control valve to control the displacement of the four-quadrant variable displacement pump 3. The permanent magnet synchronous motor 2 is electrically connected to the energy storage battery 1.4 via the permanent magnet synchronous motor driver 1.2 and the bidirectional DC converter 1.3. The permanent magnet synchronous motor driver 1.2 enables power output or energy recovery between the permanent magnet synchronous motor 2 and the energy storage battery 1.4.

[0024] Furthermore, a first overflow valve 13 and a second overflow valve 14 are respectively connected to the two oil ports of the asymmetric oil cylinder 4, and both are connected to the oil tank 16 through an oil circuit, and are used to limit the pressure in the two oil chambers to prevent the pressure from exceeding the set value during overload and play an overflow protection role.

[0025] Furthermore, a third relief valve 15 is connected to the oil outlet of the oil charge pump 9 and is connected to the oil tank 16 via an oil circuit to ensure the set outlet pressure of the oil charge pump.

[0026] In the above embodiment, the PLC controller 1.1 controls the speed of the permanent magnet synchronous motor 2 via the permanent magnet synchronous motor driver 1.2. The PLC controller 1.1 detects the difference between the position command signal and the position feedback signal, adjusting the speed of the permanent magnet synchronous motor 2 in real time so that the cylinder position follows the command position signal. Based on the current operating conditions, the PLC controller 1.1 sends a displacement command signal to the proportional control valve to control the displacement of the four-quadrant proportional pump 3 and simultaneously adjusts the output voltage of the bidirectional DC converter 1.3. The permanent magnet synchronous motor 2 is coaxially connected to the four-quadrant proportional pump 3 and the four-quadrant variable displacement pump 5. Ignoring factors such as leakage and pressure fluctuations, the motor speed is proportional to the pump output flow rate, and the pump output flow rate is proportional to the cylinder movement speed. The four-quadrant variable displacement pump 5 is a publicly available technology. Specifically, reference is made to the variable displacement piston pump disclosed in Utility Model Patent No. CN 206144728 U, which discloses a common variable displacement pump.

[0027] The following is combined with Figure 3 Analyze the working process of the asymmetric cylinder under positive load and negative load conditions.

[0028] 1. Positive load condition

[0029] When the load weight block 6 needs to be driven to rise, assuming that the permanent magnet synchronous motor 2 drives the four-quadrant metering pump 3 and the four-quadrant variable pump 5 to rotate forward, the high-pressure oil at the outlet of the four-quadrant metering pump 3 pushes the piston rod of the asymmetric oil cylinder 4 to rise, and at the same time, the oil in the rod chamber of the asymmetric oil cylinder 4 flows into the four-quadrant variable pump 5. At this time, the PLC controller 1.1 controls the proportional control valve to make the displacement of the four-quadrant variable pump 5 Less than , pressure will be generated in the rod chamber of the cylinder, that is, the cylinder generates back pressure.

[0030] When the load weight block 6 needs to be driven to descend, the permanent magnet synchronous motor 2 drives the four-quadrant metered pump 3 and the four-quadrant variable pump 5 to reverse, and the high-pressure oil at the outlet of the four-quadrant variable pump 5 pushes the piston rod of the asymmetric oil cylinder 4 down, and at the same time, the oil in the rodless cavity of the asymmetric oil cylinder 4 flows into the four-quadrant metered pump 3. At this time, the PLC controller 1.1 controls the proportional control valve to make the displacement of the four-quadrant variable pump 5 Greater than , then pressure will be generated in the rodless chamber of the cylinder, that is, the cylinder will generate back pressure;

[0031] 2. Negative load conditions

[0032] When the load force on the asymmetric oil cylinder 4 is upward and the asymmetric oil cylinder 4 moves upward, the load force on the asymmetric oil cylinder 4 is in the same direction as the movement of the oil cylinder, which is a negative load condition. At this time, the PLC controller 1.1 controls the displacement of the four-quadrant variable pump 5 through the proportional control valve. Less than , pressure will be generated in the rodless cavity of the asymmetric cylinder 4, that is, the asymmetric cylinder 4 generates back pressure; under this working condition, the four-quadrant variable pump 5 works in motor mode, and the oil outlet of the asymmetric cylinder 4 will drive the four-quadrant variable pump 5 to rotate, thereby driving the permanent magnet synchronous motor 2 to rotate. At this time, the permanent magnet synchronous motor 2 works in generator mode. At this time, the PLC controller 1.1 controls the permanent magnet synchronous motor driver 1.2 so that the electric energy generated by the permanent magnet synchronous motor 2 is transmitted from the bidirectional DC converter 1.3 to the energy storage battery 1.4, thereby converting the energy of the negative load into electric energy and storing it in 1.2, completing energy recovery.

[0033] When the load force on the asymmetric oil cylinder 4 is downward and the asymmetric oil cylinder 4 moves downward, the load force on the asymmetric oil cylinder 4 is in the same direction as the movement of the asymmetric oil cylinder 4. This is a negative load condition. At this time, the PLC controller 1.1 controls the proportional control valve to make the displacement of the four-quadrant variable pump 5 Greater than , pressure will be generated in the rod cavity of the asymmetric cylinder 4, that is, the asymmetric cylinder 4 generates back pressure; under this working condition, the four-quadrant variable displacement pump 3 operates in motor mode, and the oil outlet of the asymmetric cylinder 4 will drive the four-quadrant variable displacement pump 5 to rotate, thereby driving the permanent magnet synchronous motor 2 to rotate. At this time, the permanent magnet synchronous motor 2 operates in generator mode. At this time, the PLC controller 1.1 enables the electric energy generated by the permanent magnet synchronous motor 2 to be transmitted to the energy storage battery 1.4 by the bidirectional DC converter 1.3. Therefore, the energy of the negative load is converted into electric energy and stored in the energy storage battery 1.4, completing energy recovery.

[0034] When the cylinder extends, the pressure in the rod cavity The speed of the piston rod of the asymmetric oil cylinder (4) The relationship is: ,in is the effective working area of ​​the rod chamber piston, is the rated displacement of the four-quadrant variable displacement pump, is the variable coefficient of the four-quadrant variable pump, is the rotation speed, is the leakage coefficient of the four-quadrant variable pump, is the elastic modulus of the oil, It is the closed volume, including the volume of the rod chamber of the cylinder and the volume of the outlet pipe of the rod chamber. The constants introduced to solve the differential equation can be determined by boundary conditions. When the cylinder extends, decreasing the variable coefficient increases the cylinder back pressure. This demonstrates that fine-tuning the variable pump displacement increases motion stability.

[0035] From the above analysis, we can see that no matter whether the cylinder is extending or retracting, and no matter whether the load is positive or negative, there is back pressure on the cylinder, so the cylinder operation is relatively stable; when driving a negative load, the system can convert the energy of the load into electrical energy and store it to achieve energy recovery.

[0036] Simulation simulates its working principle:

[0037] Simulation experiment: see Figures 2 to 5 , the electric pump is rigidly connected to the fixed displacement pump and the variable displacement pump through the connector. The displacement of the variable displacement pump is the product of its maximum displacement and the variable coefficient k ( ). The fixed pump and the variable pump are connected to the two oil ports of the oil cylinder respectively. The load force acts on the piston rod. The load force is a step load force, which jumps from 0 to the set value at the 3rd second. When k=0.5, the displacement of the variable pump is equal to ( 、 is the effective area of ​​the rodless cavity and the rod cavity of the cylinder, is the displacement of the fixed pump), when k=0.4, the displacement of the variable pump is slightly smaller than ,The simulation compares the system operation when k is equal to 0.5 and 0.4 respectively.

[0038] Other parameters during simulation are set as follows:

[0039] Motor speed: 1500rpm; fixed displacement pump: 10mL; variable displacement pump maximum displacement: 10mL; cylinder piston diameter: 63mm; cylinder piston rod diameter: 44.55mm; cylinder effective area ratio: 2:1; mass block mass: 80t; load force: 20kN; oil supply pressure: 5bar.

[0040] Simulation results:

[0041] When the variable pump coefficient k = 0.5, which is a situation currently disclosed in the patent, when the load force changes rapidly in the third second, the cylinder speed will fluctuate violently, and the speed will stabilize after 6 seconds;

[0042] When the variable pump coefficient k = 0.4, which is one of the conditions described in the patent, when the load force changes rapidly in the third second, the cylinder speed stabilizes after 3 seconds. This is because the back pressure generated by the cylinder after the variable pump displacement changes helps stabilize the cylinder.

[0043] The above simulations are sufficient to prove that, compared with the existing pump control system, the embodiment of the present invention adjusts the pump displacement to provide back pressure to the cylinder outlet, making the movement smoother, thereby solving the problem of unstable movement under load changing conditions.

[0044] The above shows and describes the main features and advantages of the present invention. It is obvious to those skilled in the art that the specific implementation of the present invention is not limited to the details of the above exemplary embodiments. Moreover, without departing from the spirit or essential characteristics of the present invention, the creative ideas and design concepts of the present invention can be implemented in other specific forms, which should be equivalent to the scope of protection disclosed in the technical solution of the present invention. Therefore, from all perspectives, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0045] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A pump-controlled asymmetric hydraulic cylinder control system, comprising an asymmetric oil cylinder (4), the asymmetric oil cylinder (4) comprising a cylinder body, a piston and a piston rod, wherein the piston rod is fixed on the piston and a load weight block (6) is fixedly connected to the end thereof, wherein the piston is movably arranged in the cylinder body and divides the cylinder body into a rod chamber and a rodless chamber, and two oil ports are provided on the cylinder body that are respectively connected to the rod chamber and the rodless chamber, the oil port located in the rodless chamber is connected to a four-element metering pump (3) through a rodless chamber oil circuit and is connected to an oil tank (16), and the four-element metering pump (3) is used to provide oil pressure to the rodless chamber, characterized in that: The invention also includes a four-quadrant variable displacement pump (5) and a permanent magnet synchronous motor (2) coaxially connected to the four-quadrant variable displacement pump (3), and a matching control system (1). The four-quadrant variable displacement pump (5) is connected to the oil port of the rod cavity and the oil tank (16) through the rod cavity oil circuit, and relies on the four-quadrant variable displacement pump (5) to provide oil pressure to the rod cavity. By fine-tuning the displacement of the four-quadrant variable displacement pump (5), the back pressure of the asymmetric oil cylinder (4) is increased, thereby maintaining the stability of the oil cylinder movement when driving a negative load. The control system (1) includes a PLC controller (1.1), a PLC controller (1.1) and a control system (1) connected to the PLC controller (1.1). ) connected to the permanent magnet synchronous motor driver (1.2), the load force sensor (17) connected to the input end of the PLC controller (1.1), and the position sensor (7) connected to the input end of the PLC controller (1.1), the permanent magnet synchronous motor (2) is electrically connected to the energy storage battery (1.4) through the permanent magnet synchronous motor driver (1.2), the bidirectional DC converter (1.3), and the permanent magnet synchronous motor (2) and the energy storage battery (1.4) are output or energy is recovered through the permanent magnet synchronous motor driver (1.2). The load force sensor (17) is installed Between the end of the piston rod of the asymmetric oil cylinder (4) and the load weight block (6), it is used to collect the load force signal on the asymmetric oil cylinder (4) and upload it to the PLC controller (1.1). The position sensor (7) collects the information of the movement of the weight block (6) and uploads it as the position feedback signal of the piston to the PLC controller (1.1). The position command signal and the load force signal are combined to determine the movement direction and load force direction of the asymmetric oil cylinder (4), and then determine the current working mode. The PLC controller (1.1) sends an instruction to the bidirectional DC converter (1.3) according to the current working mode. A bidirectional DC converter (1.3) switches between outputting electric energy and recovering energy. An angle sensor (10) is installed on the four-quadrant variable pump (5) corresponding to its swash plate. The signal output end of the angle sensor (10) and the proportional control valve of the four-quadrant variable pump (5) are respectively connected to the input end and the output end of the PLC controller (1.1). The PLC controller (1.1) is used to receive the swash plate inclination angle feedback signal collected by the angle sensor (10) and send a displacement command signal to the proportional control valve in combination with the movement direction of the asymmetric oil cylinder (4) to control the displacement of the four-quadrant variable pump (5).

2. A pump-controlled asymmetric hydraulic cylinder control system according to claim 1, characterized in that: A first oil replenishing valve (11) and a second oil replenishing valve (12) are respectively connected between the rodless chamber oil circuit and the rod chamber oil circuit, and the two are connected to an oil replenishing pump (9) and an oil tank (16) through the oil replenishing oil circuit. The oil replenishing pump (9) replenishes oil to the two chambers of the asymmetric cylinder through the oil replenishing pump motor (8) through the first oil replenishing valve (11) and the second oil replenishing valve (12), respectively, to prevent the system from cavitation.

3. A pump-controlled asymmetric hydraulic cylinder control system according to claim 2, characterized in that: A first overflow valve (13) and a second overflow valve (14) are connected to the two oil ports of the asymmetric oil cylinder (4), respectively. The two overflow valves are connected to the oil tank (16) via an oil circuit and are used to limit the pressure in the two oil chambers to prevent the pressure from exceeding a set value when overloaded, thereby providing overflow protection.

4. The pump-controlled asymmetric hydraulic cylinder control system according to claim 3, characterized in that: A third overflow valve (15) is connected to the oil outlet of the oil replenishment pump (9), which is connected to the oil tank (16) through an oil circuit, and is used to ensure the set oil replenishment pump outlet pressure and the pressure provided by the proportional control valve of the four-quadrant variable pump.

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