A hydraulic actuator based on a servomotor plunger pump

Abstract

The application relates to a hydraulic actuator based on a servo motor plunger pump and belongs to the technical field of servo mechanisms; the hydraulic actuator comprises a servo motor pump, a first oil supplement check valve, a second oil supplement check valve, a first safety valve, a second safety valve, a manual bypass valve, an electromagnetic bypass valve, damping, a balance valve, a filter, a pressurized oil tank and a hydraulic cylinder; the integrated servo motor plunger pump is coaxial with the servo motor and is connected with the plunger pump in a shell, without a shaft coupling. The plunger pump has small leakage, high efficiency and realizes high-precision speed control of the actuator; the integrated design solves the problems of miniaturization and reliability; an integrated driving control module is adopted, and driving modules, control modules and power modules are integrated; bidirectional active control of the actuator is realized, and the actuator can be driven to retract or extend under any working condition through the servo motor pump. While the control precision of the actuator is improved, the deficiency of one-way controllable output of the existing actuator is solved.

Description

Technical Field

[0001] This invention belongs to the field of servo mechanism technology and relates to a hydraulic actuator based on a servo motor plunger pump. Background Technology

[0002] The hydraulic actuator is the driving device for the deformation of the active reflector surface of the FAST telescope and is an important component of the FAST telescope. Existing technical solutions mainly use a stepper motor or servo motor paired with a bidirectional gear pump as the power source; the motor and pump are connected by a separate coupling; separate driver and controller modules are used, connected by an external cable. When the motor-pump rotates forward, the actuator retracts actively; when the motor-pump rotates in reverse, it opens the hydraulically controlled check valve or balance valve, and the actuator passively extends under external tensile load; when the motor-pump rotates forward, the actuator extends through differential operation under the action of a solenoid valve.

[0003] 1) Tianjin Yourenas Hydraulic Machinery Co., Ltd.'s patent "CN103629171 B" discloses a hydraulic actuator with a speed control device. This actuator uses a stepper motor paired with a bidirectional gear pump as its power source. The actuator has a hydraulically controlled check valve installed in the rod chamber oil circuit, and a flow control valve is installed before the solenoid valve. The actuator has active retraction, passive extension, and differential extension functions, and the differential extension speed can be controlled by the flow valve.

[0004] 2) Patent CN107489665A from the National Astronomical Observatories of the Chinese Academy of Sciences discloses a direct-drive volumetric control electro-hydraulic servo single-acting hydraulic actuator. This hydraulic actuator uses a stepper motor paired with a bidirectional gear pump as a power source. The actuator has a hydraulically controlled check valve installed in the rod chamber oil circuit. When the motor pump rotates forward, the output pressure oil can directly drive the piston rod to retract actively; when the motor pump rotates in reverse, the output pressure oil opens the hydraulically controlled check valve, and the piston rod can be passively extended under the action of an external tensile load. The extension speed of the piston rod is controlled by controlling the speed of the motor pump; when there is no external tensile load, the motor pump rotates forward and outputs pressure oil, and the differential extension of the piston rod is completed by controlling the switch of the solenoid valve.

[0005] 3) Jiangsu Hengli Hydraulic Technology Co., Ltd. and the National Astronomical Observatories of the Chinese Academy of Sciences disclosed a pump-controlled double-acting hydraulic actuator in patent "CN112901572A". The actuator uses a servo motor and a gear pump as the power source. The actuator has a rod chamber with a balance valve. When the motor pump rotates forward, it can drive the actuator to retract actively. When the motor pump rotates in reverse, it outputs pressure oil to open the balance valve. Under the action of external tensile load, the piston rod can be passively extended. The extension speed of the piston rod is controlled by controlling the speed of the motor pump. When there is no external tensile load, the motor pump rotates forward and outputs pressure oil. The differential extension of the piston rod is completed by controlling the switch of the solenoid valve.

[0006] 4) In his master's thesis "Research on Hydraulic Actuator of Active Reflector of FAST Project", Wang Tiantian of Yanshan University proposed a new scheme of direct-drive volume control hydraulic actuator. The scheme uses AC asynchronous motor frequency conversion speed regulation to drive bidirectional gear pump to realize bidirectional speed change of actuator. The frequency conversion motor pump works in forward and reverse directions to drive actuator to retract or extend.

[0007] 5) In his master’s thesis “Research and Performance Analysis of New Hydraulic Actuator for FAST”, Wang Liugen of Yanshan University proposed a new electro-hydraulic actuator for the FAST active reflector adjustment system. The scheme adopts a servo motor + bidirectional plunger pump controlled asymmetric cylinder scheme. The servo motor pump drives the actuator to retract or extend by working in both forward and reverse directions.

[0008] Problems exist:

[0009] 1) In the existing technology, the hydraulic pump and the motor are connected by an independent coupling, which is prone to wear, has poor reliability, and low transmission efficiency;

[0010] 2) In the existing technology, the driver module and the controller module are separate and independent structures. The two modules are connected by an external cable, which is complicated and has poor reliability.

[0011] 3) In existing patented technologies, the actuator can only passively extend under the action of external tensile load. When there is no external tensile load, the actuator can only achieve differential extension by switching the oil circuit through the hydraulic valve. The control accuracy and controllability of the actuator extension process are poor, and the complexity of the hydraulic system is increased. Summary of the Invention

[0012] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a hydraulic actuator based on a servo motor plunger pump, which solves the problems of wear of the servo motor pump coupling, low integration of the drive control module, and inability of the actuator to extend actively in the prior art.

[0013] The solution of the present invention is:

[0014] A hydraulic actuator based on a servo motor piston pump includes a servo motor pump, a first replenishing check valve, a second replenishing check valve, a first safety valve, a second safety valve, a manual bypass valve, a solenoid bypass valve, a damper, a balance valve, a filter, a booster tank, and a hydraulic cylinder.

[0015] Among them, the oil port A of the servo motor plunger pump is connected to the oil inlet of the balance valve; the oil outlet of the balance valve is connected to the rod chamber A of the hydraulic cylinder; the control oil port of the balance valve is connected to the oil port B of the motor pump; and the oil ports at both ends of the filter are connected to the rodless chamber B of the hydraulic cylinder and the oil port B of the servo motor plunger pump, respectively.

[0016] The outlet of the first replenishing check valve is connected to the motor pump oil port A; the inlet of the first replenishing check valve is connected to the booster oil tank; the control port of the first replenishing check valve is connected to the motor pump oil port B; the outlet of the second replenishing check valve is connected to the motor pump oil port B; the inlet of the second replenishing check valve is connected to the booster oil tank; the control port of the second replenishing check valve is connected to the motor pump oil port A.

[0017] The inlet of the first safety valve is connected to port A of the rod chamber of the hydraulic cylinder; the outlet of the first safety valve is connected to the booster oil tank; the inlet of the second safety valve is connected to port B of the rodless chamber of the hydraulic cylinder; the outlet of the second safety valve is connected to the booster oil tank.

[0018] The three ports of the manual bypass valve are connected to port A of the rod-side chamber, port B of the rodless chamber, and the booster oil tank of the hydraulic cylinder, respectively.

[0019] The inlet of the electromagnetic bypass valve is connected to port A of the rod chamber of the hydraulic cylinder; the outlet of the electromagnetic bypass valve is connected to port B of the rodless chamber of the hydraulic cylinder via damping.

[0020] In the aforementioned hydraulic actuator based on a servo motor piston pump, the operating states of the hydraulic actuator include active retraction state, active extension state, position holding state, electrically controlled follow-up extension state, and manually followed-up extension state.

[0021] In the aforementioned hydraulic actuator based on a servo motor plunger pump, the working process of the active retraction state is as follows:

[0022] The servo motor pump receives a command from the host computer to rotate in the forward direction; the pressure oil output from port A of the servo motor pump enters the rod chamber of the hydraulic cylinder through the balance valve; at this time, the replenishing check valve is closed, and the replenishing check valve opens in the reverse direction under the action of the control oil pressure; port B of the servo motor pump is connected to the booster oil tank; the oil in the rodless chamber of the hydraulic cylinder flows out through the filter; a portion of the oil enters port B of the servo motor pump; the remaining oil flows back to the booster oil tank through the replenishing check valve; the hydraulic cylinder actively retracts, and the actuator forms a retraction action circulation oil circuit.

[0023] In the aforementioned hydraulic actuator based on a servo motor piston pump, in the active retraction state, the safety valve, manual bypass valve, and solenoid bypass valve are all in the closed state.

[0024] In the aforementioned hydraulic actuator based on a servo motor plunger pump, the working process of the active extension state is as follows:

[0025] The servo motor pump receives a command from the host computer to rotate in the reverse direction; the pressure oil output from port B of the servo motor pump enters the rodless chamber of the hydraulic cylinder through the filter; at this time, the replenishing check valve is closed; the replenishing check valve opens in the reverse direction under the action of control oil pressure; the motor pump port A and the booster oil tank are connected; the balance valve opens in the reverse direction to a certain degree under the action of control oil pressure, and the oil in the rod chamber of the hydraulic cylinder flows back to the motor pump port A through the balance valve; at the same time, a part of the oil in the booster oil tank enters the motor pump port A through the replenishing check valve to complete the replenishment, the hydraulic cylinder actively extends, and the actuator forms an extension action circulation oil circuit.

[0026] In the aforementioned hydraulic actuator based on a servo motor plunger pump, in the active extension state, the safety valve, manual bypass valve, and electromagnetic bypass valve are all in the closed state.

[0027] In the aforementioned hydraulic actuator based on a servo motor piston pump, in the position holding state, the servo motor pump stops working; both the manual bypass valve and the solenoid bypass valve are closed; the balance valve is in the reverse closed state; the oil circuit of the rod chamber of the hydraulic cylinder and the oil port A of the motor pump are disconnected; the oil in the rod chamber of the hydraulic cylinder cannot flow, and the hydraulic cylinder remains in the current position.

[0028] In the aforementioned hydraulic actuator based on a servo motor plunger pump, the working process in the electrically controlled follow-up extension state is as follows:

[0029] The servo motor pump stops working; the manual bypass valve is closed; the balance valve is closed in the reverse direction; the oil circuit of the rod chamber of the hydraulic cylinder and the oil port A of the motor pump are disconnected; the host computer sends a follow-up command, the electromagnetic bypass valve is energized and opened, and the oil circuit of the rod chamber and the rodless chamber of the hydraulic cylinder is connected through the electromagnetic bypass valve and the damper; the hydraulic cylinder extends under the action of external tensile load.

[0030] In the aforementioned hydraulic actuator based on a servo motor plunger pump, the working process in the manual follow-up extension state is as follows:

[0031] The servo motor pump stops working; the electromagnetic bypass valve is closed; the balance valve is closed in the reverse direction; the oil circuit of the rod chamber of the hydraulic cylinder and the oil port A of the motor pump are disconnected; the manual bypass valve is opened; the rod chamber and rodless chamber of the hydraulic cylinder are connected to the booster tank through the manual bypass valve; the hydraulic cylinder extends under the action of external tensile load.

[0032] In the aforementioned hydraulic actuator based on a servo motor plunger pump, the servo motor pump adopts a coaxial and shared-shell connection between the servo motor and the plunger pump, without a coupling.

[0033] The beneficial effects of this invention compared to the prior art are:

[0034] (1) The present invention adopts an integrated servo motor pump module, in which the servo motor and the plunger pump are connected coaxially and in the same housing, without a separate coupling; compared with the existing solution, there is no coupling wear problem, and the reliability is higher; the plunger pump has high volumetric efficiency and the speed control accuracy of the actuator is higher;

[0035] (2) The present invention adopts an integrated drive control module, which integrates the drive module, control module, power module and other components; there are no external cables between the modules, resulting in high reliability, compact structure and convenient use and maintenance;

[0036] (3) This invention uses a servo motor plunger pump to achieve bidirectional active control of the actuator. The actuator can be directly driven to retract or extend under any operating condition by the servo motor pump, thus improving controllability. Based on solving the extension control accuracy problem, the retraction control accuracy is improved. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the hydraulic actuator system of the present invention;

[0038] Figure 2 This is a schematic diagram of the hydraulic actuator structure of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the embodiments.

[0040] This invention provides a hydraulic actuator based on a servo motor plunger pump, which solves the problems of wear of the servo motor pump coupling, low integration of the drive control module, and inability of the actuator to extend actively in the prior art.

[0041] Hydraulic actuators based on servo motor piston pumps, such as Figure 1 As shown, the system specifically includes a servo motor pump 1, a first replenishing check valve 21, a second replenishing check valve 22, a first safety valve 31, a second safety valve 32, a manual bypass valve 4, a solenoid bypass valve 5, a damper 6, a balance valve 7, a filter 8, a booster tank 9, and a hydraulic cylinder 10. Specifically, port A of the servo motor plunger pump 1 is connected to the inlet of the balance valve 7; the outlet of the balance valve 7 is connected to port A of the rod chamber of the hydraulic cylinder 10; the control port of the balance valve 7 is connected to port B of the motor pump 1; and the two ports of the filter 8 are connected to port B of the rodless chamber of the hydraulic cylinder 10 and port B of the servo motor plunger pump 1, respectively.

[0042] The outlet of the first replenishing check valve 21 is connected to port A of the motor pump 1; the inlet of the first replenishing check valve 21 is connected to the booster tank 9; the control port of the first replenishing check valve 21 is connected to port B of the motor pump 1; the outlet of the second replenishing check valve 22 is connected to port B of the motor pump 1; the inlet of the second replenishing check valve 22 is connected to the booster tank 9; the control port of the second replenishing check valve 22 is connected to port A of the motor pump 1. The inlet of the first safety valve 31 is connected to port A of the rod chamber of the hydraulic cylinder 10; the outlet of the first safety valve 31 is connected to the booster tank 9; the inlet of the second safety valve 32 is connected to port B of the rodless chamber of the hydraulic cylinder 10; the outlet of the second safety valve 32 is connected to the booster tank 9. The three ports of the manual bypass valve 4 are respectively connected to port A of the rod chamber, port B of the rodless chamber, and the booster tank 9 of the hydraulic cylinder 10. The oil inlet of the electromagnetic bypass valve 5 is connected to port A of the rod chamber of the hydraulic cylinder 10; the oil outlet of the electromagnetic bypass valve 5 is connected to port B of the rodless chamber of the hydraulic cylinder 10 via the damper 6.

[0043] The working states of the hydraulic actuator include active retraction, active extension, position holding, electrically controlled follow-up extension, and manually followed-up extension.

[0044] The servo motor pump 1 adopts a coaxial and common housing connection between the servo motor and the plunger pump, without a coupling.

[0045] The process of actively retracting the state is as follows:

[0046] Servo motor pump 1 receives a command from the host computer to rotate in the forward direction; the pressure oil output from port A of servo motor pump 1 enters the rod chamber of hydraulic cylinder 10 through balance valve 7; at this time, replenishment check valve 21 is closed, and replenishment check valve 22 opens in the reverse direction under the action of control oil pressure; port B of servo motor pump 1 is connected to the booster oil tank 9; the oil in the rodless chamber of hydraulic cylinder 10 flows out through filter 8; a portion of the oil enters port B of servo motor pump 1; the remaining oil flows back to booster oil tank 9 through replenishment check valve 22; hydraulic cylinder 10 actively retracts, and the actuator forms a retraction action circulation oil circuit. In the active retraction state, safety valve 31, safety valve 32, manual bypass valve 4, and solenoid bypass valve 5 are all in the closed state.

[0047] The active extension process is as follows:

[0048] Servo motor pump 1 receives a command from the host computer to rotate in the reverse direction; the pressure oil output from port B of servo motor pump 1 enters the rodless chamber of hydraulic cylinder 10 through filter 8; at this time, the replenishing check valve 22 is closed; the replenishing check valve 21 opens in the reverse direction under the action of control oil pressure; port A of motor pump 1 is connected to the booster oil tank 9; the balance valve 7 opens in the reverse direction to a certain degree under the action of control oil pressure, and the oil in the rod chamber of hydraulic cylinder 10 flows back to port A of motor pump 1 through the balance valve 7; at the same time, a part of the oil in the booster oil tank 9 enters port A of motor pump 1 through the replenishing check valve 21 to complete the replenishment, and hydraulic cylinder 10 actively extends, and the actuator forms an extension action circulation oil circuit. In the active extension state, safety valve 31, safety valve 32, manual bypass valve 4, and solenoid bypass valve 5 are all in the closed state.

[0049] In the position holding state, the servo motor pump 1 stops working; the manual bypass valve 4 and the solenoid bypass valve 5 are both closed; the balance valve 7 is in the reverse closed state; the oil circuit of the rod chamber of the hydraulic cylinder 10 is disconnected from the oil port A of the motor pump 1; the oil in the rod chamber of the hydraulic cylinder 10 cannot flow, and the hydraulic cylinder remains in the current position.

[0050] The working process in the electrically controlled follow-up extension state is as follows:

[0051] Servo motor pump 1 stops working; manual bypass valve 4 is in the closed state; balance valve 7 is in the reverse closed state; the oil circuit of the rod chamber of hydraulic cylinder 10 is disconnected from the oil port A of motor pump 1; the host computer sends a follow-up command, the electromagnetic bypass valve 5 is energized and opened, and the oil circuit of the rod chamber and rodless chamber of hydraulic cylinder 10 is connected through the electromagnetic bypass valve 5 and damping 6; hydraulic cylinder 10 extends under the action of external tensile load.

[0052] The working process in the manual follow-up extension state is as follows:

[0053] Servo motor pump 1 stops working; electromagnetic bypass valve 5 is closed; balance valve 7 is closed in the reverse direction; the oil circuit of the rod chamber of hydraulic cylinder 10 is disconnected from the oil port A of motor pump 1; manual bypass valve 4 is opened; the rod chamber and rodless chamber of hydraulic cylinder 10 are connected to the booster oil tank 9 through manual bypass valve 4; hydraulic cylinder 10 extends under the action of external tensile load.

[0054] like Figure 2As shown, the hydraulic cylinder has a single-rod asymmetric structure and integrates a magnetostrictive displacement sensor. A servo motor is paired with an axial piston pump as its power source. One-way valves are installed at the outlets of the motor and pump to replenish oil for the servo motor pump and to drain excess oil from the rodless chamber back to the oil tank when the asymmetric hydraulic cylinder retracts. A balance valve is installed in the rod chamber oil circuit of the hydraulic cylinder to maintain its position. High and low pressure safety valves are installed in the oil circuits of both chambers of the hydraulic cylinder to protect the actuator and facilitate adjustment. A filter is installed in the rodless chamber oil circuit of the hydraulic cylinder to maintain the cleanliness of the medium and ensure long-term operation of the device. Solenoid valves and damping orifices are installed in both chambers of the hydraulic cylinder to enable the electric control follow-up function of the actuator and to limit the follow-up speed through dampers. A manual bypass valve is installed between the two chambers of the hydraulic cylinder to enable the manual follow-up function of the actuator.

[0055] This invention employs an integrated servo motor pump module, with the servo motor and plunger pump connected coaxially and sharing a common housing, eliminating the need for a separate coupling. Compared to existing solutions, this eliminates coupling wear issues, resulting in higher reliability; the plunger pump boasts high volumetric efficiency, and the actuator achieves higher speed control precision.

[0056] This invention employs an integrated drive and control module, combining the drive module, control module, and power supply module into a single design. There are no external cables connecting the modules, resulting in high reliability, a compact structure, and convenient use and maintenance.

[0057] This invention employs a servo motor plunger pump to achieve bidirectional active control of the actuator. The actuator can be directly driven to retract or extend under any operating condition via the servo motor pump, improving controllability. While addressing the extension control accuracy issue, the retraction control accuracy is also improved.

[0058] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A hydraulic actuator based on a servo motor plunger pump, characterized in that: Includes a servo motor pump (1), a first replenishing check valve (21), a second replenishing check valve (22), a first safety valve (31), a second safety valve (32), a manual bypass valve (4), a solenoid bypass valve (5), a damper (6), a balance valve (7), a filter (8), a booster tank (9), and a hydraulic cylinder (10); Among them, the oil port A of the servo motor plunger pump (1) is connected to the oil inlet of the balance valve (7); the oil outlet of the balance valve (7) is connected to the rod chamber A of the hydraulic cylinder (10); the control oil port of the balance valve (7) is connected to the oil port B of the motor pump (1); the oil ports at both ends of the filter (8) are connected to the rodless chamber B of the hydraulic cylinder (10) and the oil port B of the servo motor plunger pump (1) respectively. The outlet of the first replenishing check valve (21) is connected to the oil port A of the motor pump (1); the inlet of the first replenishing check valve (21) is connected to the booster oil tank (9); the control oil port of the first replenishing check valve (21) is connected to the oil port B of the motor pump (1); the outlet of the second replenishing check valve (22) is connected to the oil port B of the motor pump (1). The inlet of the second replenishing check valve (22) is connected to the booster oil tank (9); the control port of the second replenishing check valve (22) is connected to the oil port A of the motor pump (1); The inlet of the first safety valve (31) is connected to port A of the rod chamber of the hydraulic cylinder (10); the outlet of the first safety valve (31) is connected to the booster oil tank (9); the inlet of the second safety valve (32) is connected to port B of the rodless chamber of the hydraulic cylinder (10); the outlet of the second safety valve (32) is connected to the booster oil tank (9); The three ports of the manual bypass valve (4) are connected to the rod chamber A port, the rodless chamber B port, and the booster oil tank (9) of the hydraulic cylinder (10), respectively. The inlet of the electromagnetic bypass valve (5) is connected to the rod chamber A port of the hydraulic cylinder (10); the outlet of the electromagnetic bypass valve (5) is connected to the rodless chamber B port of the hydraulic cylinder (10) via the damper (6).

2. The hydraulic actuator based on a servo motor plunger pump according to claim 1, characterized in that: The working states of the hydraulic actuator include active retraction, active extension, position holding, electrically controlled follow-up extension, and manually followed-up extension.

3. A hydraulic actuator based on a servo motor plunger pump according to claim 2, characterized in that: The working process of the active retraction state is as follows: The servo motor pump (1) receives the instruction from the host computer to rotate in the forward direction; the pressure oil output from port A of the servo motor pump (1) enters the rod chamber of the hydraulic cylinder (10) through the balance valve (7); at this time, the replenishing check valve (21) is closed, and the replenishing check valve (22) is opened in the reverse direction under the action of the control oil pressure; port B of the servo motor pump (1) is connected to the booster oil tank (9); the oil in the rodless chamber of the hydraulic cylinder (10) flows out through the filter (8); a part of the oil enters port B of the servo motor pump (1); the remaining oil flows back to the booster oil tank (9) through the replenishing check valve (22); the hydraulic cylinder (10) actively retracts, and the actuator forms a retraction action circulation oil circuit.

4. A hydraulic actuator based on a servo motor plunger pump according to claim 3, characterized in that: In the active retraction state, safety valve (31), safety valve (32), manual bypass valve (4), and electromagnetic bypass valve (5) are all in the closed state.

5. A hydraulic actuator based on a servo motor plunger pump according to claim 2, characterized in that: The working process of the active extension state is as follows: The servo motor pump (1) receives the instruction from the host computer to rotate in the reverse direction; the pressure oil output from port B of the servo motor pump (1) enters the rodless chamber of the hydraulic cylinder (10) through the filter (8); at this time, the oil replenishment check valve (22) is closed; the oil replenishment check valve (21) is opened in the reverse direction under the action of the control oil pressure; the oil port A of the motor pump (1) and the booster oil tank (9) are connected; the balance valve (7) is opened in the reverse direction to a certain degree under the action of the control oil pressure, and the oil in the rod chamber of the hydraulic cylinder (10) flows back to port A of the motor pump (1) through the balance valve (7); at the same time, a part of the oil in the booster oil tank (9) enters port A of the motor pump (1) through the oil replenishment check valve (21) to complete the oil replenishment, and the hydraulic cylinder (10) actively extends, and the actuator forms an extension action circulation oil circuit.

6. A hydraulic actuator based on a servo motor plunger pump according to claim 5, characterized in that: In the active extension state, safety valve (31), safety valve (32), manual bypass valve (4), and electromagnetic bypass valve (5) are all in the closed state.

7. A hydraulic actuator based on a servo motor plunger pump according to claim 2, characterized in that: In the position holding state, the servo motor pump (1) stops working; the manual bypass valve (4) and the electromagnetic bypass valve (5) are both closed; the balance valve (7) is in the reverse closed state; the oil circuit of the rod chamber of the hydraulic cylinder (10) and the oil port A of the motor pump (1) are disconnected; the oil in the rod chamber of the hydraulic cylinder (10) cannot flow, and the hydraulic cylinder remains in the current position.

8. A hydraulic actuator based on a servo motor plunger pump according to claim 2, characterized in that: The working process in the electrically controlled follow-up extension state is as follows: The servo motor pump (1) stops working; the manual bypass valve (4) is closed; the balance valve (7) is closed in the reverse direction; the oil circuit of the rod chamber of the hydraulic cylinder (10) and the oil port A of the motor pump (1) are disconnected; the host computer sends a follow-up command, the electromagnetic bypass valve (5) is energized and opened, and the oil circuit of the rod chamber and the rodless chamber of the hydraulic cylinder (10) is connected through the electromagnetic bypass valve (5) and the damper (6); the hydraulic cylinder (10) extends under the action of external tensile load.

9. A hydraulic actuator based on a servo motor plunger pump according to claim 2, characterized in that: The working process in the manual follow-up extension state is as follows: Servo motor pump (1) stops working; electromagnetic bypass valve (5) is closed; balance valve (7) is closed in reverse; the oil circuit of the rod chamber of hydraulic cylinder (10) and oil port A of motor pump (1) are disconnected; manual bypass valve (4) is opened; the rod chamber and rodless chamber of hydraulic cylinder (10) are connected to booster oil tank (9) through manual bypass valve (4); hydraulic cylinder (10) extends under the action of external tensile load.

10. A hydraulic actuator based on a servo motor plunger pump according to claim 1, characterized in that: The servo motor pump (1) adopts a coaxial and common shell connection between the servo motor and the plunger pump, without a coupling.

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