CN215719882U

CN215719882U - Multi-mode control system suitable for EHA

Info

Publication number: CN215719882U
Application number: CN202122230381.0U
Authority: CN
Inventors: 谭洁; 李江水; 何克前; 郑威尔
Original assignee: Sichuan Kouke Intelligent Equipment Co ltd
Current assignee: Sichuan Kouke Intelligent Equipment Co ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2022-02-01
Anticipated expiration: 2031-09-15

Abstract

The utility model discloses a multi-mode control system suitable for EHA, which comprises a pump control unit, an action execution unit, a proportional valve branch circuit used for providing a valve control function for the system, a flow balance switching branch circuit used for balancing volume flow difference in the action execution unit, a first pressure sensor used for detecting hydraulic pressure on the branch circuit and sending an instruction to the proportional valve branch circuit, and a second pressure sensor used for detecting hydraulic pressure on the branch circuit and sending an instruction to the proportional valve branch circuit. The utility model has the beneficial effects that: the flow-rate balance switching branch circuit is used for timely balancing the volume flow rate difference of the two working cavities on the action execution unit under the condition that the two working cavities on the action execution unit are asymmetric, and three control modes of pump control, valve control and pump valve joint control can be automatically switched through software according to actual conditions through the matching of the proportional valve branch circuit and the pump control unit.

Description

Multi-mode control system suitable for EHA

Technical Field

The utility model relates to a hydraulic transmission system, in particular to a multi-mode control system suitable for an EHA.

Background

The airplane is controlled by a control surface when flying, and the airplane control surface is controlled by an actuator. The actuator is a key part for implementing active vibration control on the airplane, mainly plays a role in applying control force to the airplane according to a determined control rule, and is an important link of an active control system.

Conventional on-board actuation systems transmit Power from a Power source to the rams By means of Hydraulic transmission, so-called Power-By-Hydraulic (PBH). The power liquid transmission system has the advantages of quick response, high power and excellent self-lubricating property, but the aircraft performance is greatly influenced because the hydraulic oil is inflammable and explosive under high temperature and high pressure and has high quality.

The advent of new materials and new technologies in the late 70 s has prompted the development of Power-By-Wire (PBW) actuation systems. The electric power transmission refers to the transmission of power from the second energy source system of the airplane to each actuating mechanism of the actuating system through an electric lead. The power fly-by-wire type actuation system has the advantages of improving the maintainability of the airplane, having great flexibility of system layout, reducing the possibility of burning hydraulic oil, improving the survivability of the damaged airplane and the like.

Currently, Power By Wire (PBW) actuators are evolving towards electro-hydrostatic actuators (EHAs) and electro-mechanical actuators (EMA), and the present invention relates to electro-hydrostatic actuators (EHAs).

However, in the existing EHA control system, when the oil cylinder is not symmetrical, the volume flow difference at two sides of the oil cylinder is balanced in time, and in the existing EHA control system, the control mode is single and fixed, and the appropriate control mode cannot be flexibly switched according to the actual situation.

Therefore, it is necessary to provide a multi-mode control system suitable for EHA, which not only can balance the volume flow difference in the motion execution unit in time under the condition that two working chambers of the motion execution unit are asymmetric, but also can automatically switch three control modes of pump control, valve control and pump valve joint control through software according to the actual situation.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome the defects of the prior art and provides a multi-mode control system suitable for EHA, which not only can balance the volume flow difference in an action execution unit in time under the condition that two working chambers of the action execution unit are asymmetrical, but also can automatically switch three control modes of pump control, valve control and pump valve joint control through software according to actual conditions.

The purpose of the utility model is realized by the following technical scheme: including pump control unit, action execution unit, pump control unit is provided with first working port and second working port, action execution unit is provided with two working chambers, and every working chamber all is provided with the hydraulic fluid port, divide into A mouth and B mouth, its characterized in that, an EHA pump control system for still include: the proportional valve branch is used for providing a valve control function for a system, the proportional valve branch is provided with four ports, namely a, B, c and d, the port c is communicated with the port A of the action execution unit, the port d is communicated with the port B of the action execution unit, and the proportional valve branch comprises a first proportional valve for controlling the flow of liquid oil flowing into the port A of the action execution unit, a third proportional valve for controlling the flow of liquid oil flowing into the port B of the action execution unit and a third proportional valve for providing an additional unloading function; the first branch is used for driving a certain working cavity in the action execution unit, and two ends of the first branch are respectively communicated with a first working port of the pump control unit and an a port on the branch of the proportional valve; the second branch is used for driving the other working cavity in the action execution unit, and two ends of the second branch are respectively communicated with a second working port of the pump control unit and a port b on the branch of the proportional valve; the flow balance switching branch is used for balancing the volume flow difference in the action execution unit, the flow balance switching branch is provided with two inlets and an outlet, the two inlets are respectively communicated with the port a and the port b on the proportional valve branch, and the outlet is communicated with the pump control unit; the first pressure sensor is used for detecting the hydraulic pressure on the branch and sending an indication to the proportional valve branch, and the first pressure sensor is arranged on the first branch; and the second pressure sensor is used for detecting the hydraulic pressure on the branch and sending an indication to the proportional valve branch, and the second pressure sensor is arranged on the second branch.

The first proportional valve is a first two-position two-way electromagnetic proportional valve, the second proportional valve is a three-position four-way electromagnetic proportional valve, the third proportional valve is a second two-position two-way electromagnetic proportional valve, the first two-position two-way electromagnetic proportional valve is provided with two working ports, one of the working ports is communicated with a port of a proportional valve branch, the other working port is communicated with a port c of the proportional valve branch, the three-position four-way electromagnetic proportional valve is provided with 4 working ports which are respectively communicated with a port, b port, c port and d port on the proportional valve branch, the second two-position two-way electromagnetic proportional valve is provided with two working ports, one of the working ports is communicated with a port b of the proportional valve branch, and the other working port is communicated with a port d of the proportional valve branch.

The flow balance switching branch is provided with a flow balance switching valve, the flow balance switching valve is a three-position three-way electromagnetic valve electromagnetic switching valve, the three-position three-way electromagnetic switching valve is provided with two inlets and an outlet, the two inlets are respectively communicated with the ports a and b of the proportional valve branch, and the outlet is communicated with the flow balance switching branch.

The pump control unit comprises a bidirectional pump and a servo motor for driving the bidirectional pump to rotate.

And the switching branch is provided with a pressure oil tank for providing certain oil supply pressure.

And a filtering branch is arranged on the switching branch. The filtering branch consists of a filter, a one-way pump and a motor for driving the one-way pump to operate. The inlet of the one-way pump is communicated with the flow balance switching branch, the outlet of the one-way pump is communicated with the inlet of the filter, and the outlet of the filter is communicated with the switching branch.

The first communication branch is provided with a first two-position two-way electromagnetic valve, the first two-position two-way electromagnetic valve is provided with an inlet and an outlet, the inlet is communicated with the first working port of the pump control unit, and the outlet is communicated with the flow balance switching branch; the second branch is provided with a second communication branch which is used for enabling a second working opening of the pump control unit to be communicated with the switching branch, so that the working cavity communicated with the second branch is quickly closed, the second communication branch is provided with a second two-position two-way electromagnetic valve, the second two-position two-way electromagnetic valve is provided with an inlet and an outlet, the inlet is communicated with the second working opening of the pump control unit, and the outlet is communicated with the flow balance switching branch.

The first branch is provided with a first one-way valve for limiting the suction pressure of the pump control unit, the inlet of the first one-way valve is communicated with the flow balance switching branch, and the outlet of the first one-way valve is communicated with a first working port of the pump control unit; and a second check valve for limiting the suction pressure of the pump control unit is arranged on the second branch, the inlet of the second check valve is communicated with the flow balance switching branch, and the outlet of the second check valve is communicated with a second working port of the pump control unit.

The flow balance switching branch is provided with a cooler for cooling liquid flow, an inlet of the cooler is communicated with the flow balance switching branch, and an outlet of the cooler is communicated with the pump control unit.

The multi-mode control system suitable for the EHA is provided with a one-way valve for preventing oil leakage and oil drainage of the system.

The utility model has the beneficial effects that:

1) through the flow balance switching branch, the volume flow difference of the two working cavities on the action execution unit is balanced in time under the condition that the two working cavities on the action execution unit are asymmetric.

2) Through the matching of the proportional valve branch and the pump control unit, three control modes of pump control, valve control and pump valve joint control can be automatically switched through software according to actual conditions.

Drawings

FIG. 1 is a schematic connection diagram of the present invention;

in the figure, 1-servo motor, 2-two-way pump, 3-pressure sensor, 4-three-position three-way electromagnetic switching valve, 5-proportional valve branch, 6-oil cylinder, 7-two-position two-way electromagnetic valve, 8-overflow valve, 9-one-way valve, 10-filtering branch, 11-oil pressing tank, 301-first pressure sensor, 302 second pressure sensor, 501-first two-position two-way electromagnetic proportional valve, 502-three-position four-way electromagnetic proportional valve, 503-second two-position two-way electromagnetic proportional valve, 701-first two-position two-way electromagnetic valve, 702-second two-way electromagnetic valve, 801-first overflow valve, 802-second overflow valve, 901-first one-way valve, 902-second one-way valve, 1001-motor, 1002-one-way pump, 1003-filter.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

In the following description, the directional concepts of "left", "right", "up" and "down" are relative directions, and are not listed here.

Referring to fig. 1, the multi-mode control system suitable for EHA includes a pump control unit and an action execution unit, the pump control unit includes a bidirectional pump 2 and a servo motor driving the bidirectional pump 2 to rotate, the action execution unit is an oil cylinder 6, and oil ports a and B provided on two working chambers are respectively an oil port on a rod chamber and an oil port on a rodless chamber. The bidirectional pump 2 is provided with 3 ports, two of which are working ports X1 and X2, and the other port is a return port X3. The port X1 of the bidirectional pump is communicated with the rod cavity of the oil cylinder 6, the communicating branch is a first branch, the port X2 of the bidirectional pump is communicated with the rodless cavity of the oil cylinder 6, and the communicating branch is a second branch. The first branch and the second branch are respectively provided with a first pressure sensor 301 and a second pressure sensor 302 which can detect the hydraulic pressure of the branch and send feedback signals. When the servo motor 1 drives the bidirectional pump 2 to rotate in the forward direction, the port 2X1 of the bidirectional pump outputs liquid oil to the rod cavity of the oil cylinder 6, the piston in the oil cylinder 6 is extruded to realize the descending of the piston, and the liquid oil in the rodless cavity is extruded and discharged by the piston and is sucked by the port 2X2 of the bidirectional pump; when the servo motor 1 drives the bidirectional pump 2 to rotate reversely, the port 2X2 of the bidirectional pump outputs liquid oil to the rodless cavity of the oil cylinder 6, the piston in the oil cylinder 6 is extruded to rise, and the liquid oil in the rod cavity is extruded by the piston and discharged to be sucked by the port 2X1 of the bidirectional pump. The ports of the two-way pump 2X1 and the X2 are connected with an oil inlet of a three-position three-way electromagnetic switching valve 4, the three-position three-way electromagnetic switching valve 4 is connected with an oil cylinder 6 in parallel and is arranged on the right side of the two-way pump 2, and an oil outlet of the three-position three-way electromagnetic switching valve 4 is communicated with a return port X3 of the two-way pump 2 to form a flow balance switching branch. Two oil inlets of the three-position three-way electromagnetic switching valve 4 are connected with X1 and X2 ports of the two-way pump 2. When the electromagnetic valve at the lower end of the three-position three-way electromagnetic switching valve 4 is electrified, the oil inlet working position of the three-position three-way electromagnetic switching valve 4 connected with the port of the two-way pump 2X1 is in a disconnection state, the oil inlet working position connected with the port of the two-way pump 2X2 and the oil outlet working position of the return port X3 of the two-way pump 2 are in a connection state; when the three-position three-way electromagnetic switching valve 4 is powered off; the working positions of the three-position three-way electromagnetic switching valve 4, the X1, the X2 and the X3 of the two-way pump 2 are all in a disconnected state; when the electromagnetic valve at the upper end of the three-position three-way electromagnetic switching valve 4 is electrified; the oil inlet working position of the three-position three-way electromagnetic switching valve 4 connected with the port of the two-way pump 2X2 is in a disconnection state, the oil inlet working position connected with the port of the two-way pump 2X1 and the oil outlet working position connected with the return port X3 of the two-way pump 2 are in a connection state. When the bidirectional pump 2 rotates in the forward direction, the oil cylinder 6 sucks liquid oil in a rod cavity and outputs the liquid oil in a rodless cavity, when the volume of the sucked liquid oil in the rod cavity is larger than that of the output liquid oil in the rodless cavity, the upper end of the three-position three-way electromagnetic switching valve 4 is electrified electromagnetically, a two-way pump 2X1 port and a return port X3 form a loop, and the excessive part of the sucked liquid oil in the oil cylinder 6 returns to the bidirectional pump 2 through the three-position three-way electromagnetic switching valve 4; when the bidirectional pump 2 runs reversely, the rodless cavity of the oil cylinder 6 sucks in liquid oil, the rod cavity outputs the liquid oil, and when the volume of the liquid oil sucked by the rodless cavity is larger than that output by the rod cavity, the lower end of the three-position three-way electromagnetic switching valve 4 is electromagnetically electrified; the three-position three-way electromagnetic switching valve 4 is positioned at the upper position, a two-way pump 2X2 port and a return port X3 form a loop, and the part of the oil cylinder 6 which sucks more liquid oil passes through; the three-position three-way electromagnetic switching valve 4 returns to the two-way pump 2; when there is no flow difference between the suction volume and the output volume of the oil cylinder 6; the two ends of the three-position three-way electromagnetic switching valve 4 are not electrified and are positioned at the middle position, and no action is performed; the different switching of the three-position three-way electromagnetic switching valve 4 realizes that the volume flow difference at two sides of the oil cylinder is balanced in time under the condition that the oil cylinder 6 is asymmetric. And a proportional valve branch 5 is arranged on a pipeline from the bidirectional pump 2 to the oil cylinder 9. And the proportional valve branch 5 is positioned between the three-position three-way electromagnetic switching valve 4 and the oil cylinder. The proportional valve branch 5 is provided with four ports, namely a, b, c and d, the port a is connected with a port 2X1 of the bidirectional pump, the port b is connected with a port 2X2 of the bidirectional pump, the port c is connected with an oil port on a rod cavity of the oil cylinder 7, and the port d is connected with an oil port on a rodless cavity. The proportional valve branch 5 comprises a first two-position two-way electromagnetic proportional valve 501 connected with the first branch in series, a second two-position two-way electromagnetic proportional valve 503 connected with the second branch in series, and a three-position four-way electromagnetic proportional valve 502 connected with the first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 in parallel at the same time. The first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 are normally connected, and are disconnected when being electrified. The three-position four-way electromagnetic proportional valve 502 is normally disconnected with four ports, when the lower end electromagnetic valve is electrified, two connecting points which are connected with the first two-position two-way electromagnetic proportional valve 501 in parallel are oil inlets, two connecting points which are connected with the second two-position two-way electromagnetic proportional valve 503 in parallel are oil outlets, when the upper end electromagnetic valve is electrified, an oil inlet is connected with a rodless cavity of the oil cylinder 6 and a port X1 of the two-way pump, and an oil outlet is connected with a rod cavity of the oil cylinder 6 and a port X2 of the two-way pump. When the first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 are powered off, the liquid oil does not pass through the three-position four-way electromagnetic proportional valve 502, and a certain range of electric signals can be provided for the electromagnetic coils of the first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503, so that proportional valve port opening degrees can be obtained. The first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 can receive feedback signals of the pressure sensor 3 on the pipeline where the valves are located, make corresponding proportional valve port opening degrees, control the target to run at constant pressure, and have faster valve control response than pump control, so that high dynamic performance is obtained; when the bidirectional pump rotates in a fixed rotating direction and a fixed rotating speed, the system is consistent with a common hydraulic system. When the first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 are powered on, the first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 are in an off state, and the first two-position two-way electromagnetic proportional valve 501 and the second two-position two-way electromagnetic proportional valve 503 do not participate in work. When the bidirectional pump discharges the liquid oil from the port X1 and the piston in the oil cylinder 6 needs to move up and down in a reciprocating manner, the rotation direction of the bidirectional pump 2 does not need to be adjusted all the time, and the rotation direction of the bidirectional pump can be unchanged and the piston can rise and fall only by electrifying the three-position four-way electromagnetic proportional valve 503 and changing the flow direction of the liquid oil. When the unloading operation needs to be carried out on the loop in emergency, the proportional solenoid valve can be electrified in a unidirectional way according to the rotation direction of the bidirectional pump 2, so that the additional unloading function in emergency is realized. And three control modes of dynamic switching pump control, valve control and pump valve joint control in the loop are realized through the proportional valve branch 5. A first two-position two-way electromagnetic valve 701, a first overflow valve 801 and a first one-way valve 901 are arranged on a closed loop formed by the first branch and the switching branch from left to right and are connected with the bidirectional pump 2 in parallel; a second two-position two-way electromagnetic valve 702, a second overflow valve 802 and a second one-way valve 902 are arranged on a closed loop formed by the second branch and the switching branch from left to right and are connected with the bidirectional pump 2 in parallel, and the two loops form a symmetrical relation. The first two-position two-way solenoid valve 701 and the second two-position two-way solenoid valve 702 are normally disconnected and are connected in an electrified state. When the bidirectional pump 2 works, the pressure in the pipeline exceeds a safety set value, the safety valve on the overflow valve 8 of the pipeline is opened, and a part of liquid flow is discharged, so that the pressure of the system does not exceed an allowable value, and the system is ensured not to have an accident due to overhigh pressure. The check valve 9 limits the suction pressure of the bidirectional pump 2. And in an emergency state, the two ends of the suction and output of the pump and the two sides of the oil cylinder need to be communicated and quickly closed, the first two-position two-way electromagnetic valve 701 and the second two-position two-way electromagnetic valve 702 are electrified, so that the X1 and the X2 of the two-way pump 2 are directly communicated with the return port X3, and liquid oil does not pass through the oil cylinder, so that the two ends of the suction and output of the pump and the two sides of the oil cylinder need to be communicated and quickly closed in the emergency state. The switching branch is sequentially provided with a cooler, a filtering branch 10 and an oil pressing tank 11 from left to right. The inlet of the cooler is communicated with the switching branch, and the outlet of the cooler is communicated with the bidirectional pump 2; the oil tank 11 provides a certain oil supply pressure to enable the liquid oil to flow back to the return port X3; the filter branch 10 is used for filtering the liquid oil returned to the return port X3 to return to the bidirectional pump 2, and the filter branch 10 is composed of a motor 1001, a unidirectional pump 1002, and a filter 1003. The whole loop system is provided with a one-way valve, so that oil leakage and oil leakage in the whole loop system are prevented.

Claims

1. The utility model provides a multi-mode control system suitable for EHA, includes pump control unit, action execution unit, the pump control unit is provided with first working port and second working port, action execution unit is provided with two working chambers, and every working chamber all is provided with the hydraulic fluid port, divide into A mouth and B mouth, a characterized in that, an EHA still include with pump control system:

the proportional valve branch circuit (5) is used for providing a valve control function for a system, the proportional valve branch circuit (5) is provided with four ports, namely a, B, c and d, the port c is communicated with the port A of the action execution unit, the port d is communicated with the port B of the action execution unit, and the proportional valve branch circuit (5) comprises a first proportional valve used for controlling the flow of liquid oil flowing into the port A of the action execution unit, a third proportional valve used for controlling the flow of liquid oil flowing into the port B of the action execution unit and a second proportional valve providing an additional unloading function;

the first branch is used for driving a certain working cavity in the action execution unit, and two ends of the first branch are respectively communicated with a first working port of the pump control unit and an a port on the branch of the proportional valve;

the second branch is used for driving the other working cavity in the action execution unit, and two ends of the second branch are respectively communicated with a second working port of the pump control unit and a port b on the branch of the proportional valve;

the flow balance switching branch is used for balancing the volume flow difference in the action execution unit, the flow balance switching branch is provided with two inlets and an outlet, the two inlets are respectively communicated with the port a and the port b on the proportional valve branch, and the outlet is communicated with the pump control unit;

the first pressure sensor (301) is used for detecting the hydraulic pressure on the branch and sending an indication to the proportional valve branch (5), and the first pressure sensor (301) is arranged on the first branch;

and the second pressure sensor (302) is used for detecting the hydraulic pressure on the branch and sending an indication to the proportional valve branch (5), and the second pressure sensor (302) is arranged on the second branch.

2. The multi-mode control system for an EHA of claim 1, wherein: the first proportional valve is a first two-position two-way electromagnetic proportional valve (501), the second proportional valve is a three-position four-way electromagnetic proportional valve (502), the third proportional valve is a second two-position two-way electromagnetic proportional valve (503), the first two-position two-way electromagnetic proportional valve (501) is provided with two working ports, one of the working ports is communicated with a port a of the proportional valve branch (5), the other working port is communicated with a port c of the proportional valve branch (5), the three-position four-way electromagnetic proportional valve (502) is provided with 4 working ports which are respectively communicated with a, b, c and d on the proportional valve branch (5), the second two-position two-way electromagnetic proportional valve (503) is provided with two working ports, one of the working ports is communicated with a port b of the proportional valve branch (5), and the other working port is communicated with a port d of the proportional valve branch (5).

3. The multi-mode control system for an EHA of claim 1, wherein: the flow balance switching branch is provided with a flow balance switching valve, the flow balance switching valve is a three-position three-way electromagnetic switching valve (4), the three-position three-way electromagnetic switching valve is provided with two inlets and an outlet, the two inlets are respectively communicated with the ports a and b of the proportional valve branch, and the outlet is communicated with the flow balance switching branch.

4. The multi-mode control system for an EHA of claim 1, wherein: the pump control unit comprises a bidirectional pump (2) and a servo motor (1) for driving the bidirectional pump to rotate.

5. The multi-mode control system for an EHA of claim 1, wherein: and a pressure oil tank (9) for providing a certain oil supply pressure is arranged on the flow balance switching branch.

6. The multi-mode control system for an EHA of claim 1, wherein: the flow balance switching branch is provided with a filtering branch (10), the filtering branch is composed of a filter (1003), a one-way pump (1002) and a motor (1001) for driving the one-way pump to operate, an inlet of the one-way pump (1002) is communicated with the flow balance switching branch, an outlet of the one-way pump is communicated with an inlet of the filter (1003), and an outlet of the filter (1003) is communicated with the switching branch.

7. The multi-mode control system for an EHA of claim 1, wherein: the first communication branch is used for enabling a first working port of the pump control unit to be communicated with the flow balance switching branch so as to enable a working cavity communicated with the first branch to be quickly closed, a first two-position two-way electromagnetic valve (701) is arranged on the first communication branch, the first two-position two-way electromagnetic valve (701) is provided with an inlet and an outlet, the inlet is communicated with the first working port of the pump control unit, and the outlet is communicated with the flow balance switching branch; the second branch is provided with a second communication branch used for enabling the second working port of the pump control unit to be communicated with the switching branch, so that the working chamber communicated with the second branch is quickly closed, the second communication branch is provided with a second two-position two-way electromagnetic valve (702), the second two-position two-way electromagnetic valve (702) is provided with an inlet and an outlet, the inlet is communicated with the second working port of the pump control unit, and the outlet is communicated with the flow balance switching branch.

8. The multi-mode control system for an EHA of claim 1, wherein: a first overflow valve (801) ensuring the pressure of the first branch is arranged on the first branch, the inlet of the first overflow valve (801) is communicated with a first working port of the pump control unit, and the outlet of the first overflow valve is communicated with the flow balance switching branch; and a second overflow valve (802) capable of ensuring the pressure of the second branch is arranged on the second branch, the inlet of the second overflow valve (802) is communicated with a second working port of the pump control unit, and the outlet of the second overflow valve is communicated with the flow balance switching branch.

9. The multi-mode control system for an EHA of claim 1, wherein: a first check valve (901) for limiting the suction pressure of the pump control unit is arranged on the first branch, the inlet of the first check valve (901) is communicated with the flow balance switching branch, and the outlet of the first check valve (901) is communicated with a first working port of the pump control unit; and a second check valve (902) for limiting the suction pressure of the pump control unit is arranged on the second branch, the inlet of the second check valve (902) is communicated with the flow balance switching branch, and the outlet of the second check valve is communicated with a second working port of the pump control unit.

10. The multi-mode control system for an EHA of claim 1, wherein: the flow balance switching branch is provided with a cooler for cooling liquid flow, an inlet of the cooler is communicated with the flow balance switching branch, and an outlet of the cooler is communicated with the pump control unit.