Multifunctional electro-hydraulic flow control valve and flow control method

Abstract

A multifunctional electro-hydraulic flow control valve and a flow control method. The control valve comprises a main valve, a proportional pilot valve, a flow sensor, a multifunctional valve controller, a control cavity pressure sensor, an oil inlet pressure sensor, an oil outlet pressure sensor, a temperature sensor and a cloud storage. The invention has the characteristics that a flow of the main valve is continuously controlled without being influenced by load change without installing a pressure compensator in the system, and meanwhile, the valve has the function of a flow sensor, has low pressure loss and wide flow control range, and realizes integration of flow detection and control; and information such as flow, power and efficiency of each part in a hydraulic system is monitored in real time based on a multifunctional controller, key operation state monitoring, service life prediction and fault positioning of the control valve are achieved.

Claims

1. A multifunctional electro-hydraulic flow control valve, comprising a main valve (2) and a proportional pilot valve (12), wherein a flow sensor, a multifunctional valve controller (21), a control cavity pressure sensor (17), an oil inlet pressure sensor (18), an oil outlet pressure sensor (19), a temperature sensor (20), and a cloud storage (30) are additionally provided; the main valve (2) comprises a main valve core (1), a main valve spring (3), a main valve oil inlet cavity V.sub.A, a main valve oil outlet cavity V.sub.B, and a main valve control cavity V.sub.C, a main valve oil inlet A is in communication with a feedback groove M through an internal flow channel of the main valve core (1), the feedback groove M is in communication with the main valve control cavity V.sub.C through a throttling edge on a valve sleeve, the main valve control cavity V.sub.C is in communication with a flow sensor oil inlet B, a flow sensor oil outlet C is in communication with a pilot valve oil inlet H, and a pilot valve oil outlet F is in communication with a main valve oil outlet D; the control cavity pressure sensor (17) is in communication with the main valve control cavity V.sub.C; the oil inlet pressure sensor (18) is in communication with the main valve oil inlet A; the oil outlet pressure sensor (19) is in communication with the main valve oil outlet D; and the temperature sensor (20) is in communication with the main valve oil outlet D; the proportional pilot valve (12) comprises a pilot valve core (11), a pilot valve spring (10), a pilot valve electromagnet (13), a proportional amplifier (14), a flow controller (15), and a displacement sensor (16), an output end of the proportional amplifier (14) is connected to the pilot valve electromagnet (13), the flow controller (15) receives a flow setting signal q.sub.s and a flow feedback signal q.sub.f, an output end of the flow controller (15) is connected to an input end of the proportional amplifier (14), the displacement sensor (16) detects displacement of the pilot valve core (11), and outputs a pilot valve core displacement signal y to a feedback end of the proportional amplifier (14); the multifunctional valve controller (21) comprises a signal processing module (22), a calculation module (23), an integration module (24), a data storage module (25), a control module (26), a display module (27), a fault prediction module (28), and a communication interaction module (29); the signal processing module (22) comprises a digital filter and a normalization processor, wherein the pilot valve core displacement signal y, a control cavity pressure signal p.sub.C, an oil inlet pressure signal p.sub.A, an oil outlet pressure signal p.sub.B, a flow sensor signal q.sub.p, and a temperature sensor signal T are connected to the digital filter of the signal processing module, an output signal of the digital filter is connected to the normalization processor, an output signal of the normalization processor is connected to an output end of the signal processing module, the output end of the signal processing module is connected to the calculation module (23) and an input end of the data storage module (25); an output end of the calculation module (23) is connected to an input end of the integration module (24) and the input end of the data storage module (25); the calculation module (23) inputs the calculated flow feedback signal q.sub.f to a feedback end of the flow controller (15); an output end of the integration module (24) is connected to the input end of the data storage module (25), the data storage module (25) is connected to an input end of the control module (26), an input end of the display module (27), an input end of the fault prediction module (28) and an input end of the communication interaction module (29) through a bidirectional data bus; and an output end of the communication interaction module (29) is connected to the cloud storage (30); the control module (26) calculates the flow setting signal q.sub.s and inputs the flow setting signal q.sub.s to an input end of the flow controller (15); and the control module (26) calculates a flow sensor compensation signal u.sub.z and inputs the signal to an electro-mechanical converter of the flow sensor; the flow sensor is connected between the main valve control cavity V.sub.C and the pilot valve oil inlet H, the main valve control cavity V.sub.C is in communication with the pilot valve oil inlet H, the pilot valve oil outlet F is in communication with the flow sensor oil inlet B, and the flow sensor oil outlet C is in communication with the main valve oil outlet D; the calculation module (23) calculates following parameters according to a calculation formula (1), a calculation formula (2), a calculation formula (3), a calculation formula (4), a calculation formula (5) and a calculation formula (6):
main valve flow q=(g(x)+1).Math.q.sub.b(1)
pressure difference between an inlet and an outlet of the main valve?p=P.sub.A?P.sub.B(2)
main valve input power P.sub.1=P.sub.A.Math.q(3)
main valve output power P.sub.2=P.sub.B.Math.q(4)
main valve throttling loss power P.sub.3=?p.Math.q(5)
flow feedback signal q.sub.f=k.Math.q.sub.b(6); the integration module performs integral calculation to obtain following parameters according to a formula (7), a calculation formula (8), a calculation formula (9) and a calculation formula (10):
main valve input energy E.sub.1=?.sub.0.sup.1P.sub.1dt(7)
main valve output energy E.sub.2=?.sub.0.sup.1P.sub.2dt(8)
main valve throttling loss energy E.sub.3=?.sub.0.sup.1P.sub.3dt(9)
main valve efficiency?=E.sub.2/E.sub.1(10); in the formulae, g(x) refers to flow amplification coefficient, qb refers to flow sensor signal, pA refers to oil inlet pressure signal, pB refers to oil outlet pressure signal, and k refers to flow feedback gain; the fault prediction module (28) performs active operation and maintenance and fault early warning on an integrated unit according to the stored main valve input power P.sub.1, the main valve input energy E1, the oil inlet pressure signal p.sub.A and the oil outlet pressure signal p.sub.B; once the accumulated energy reaches a fault alarm threshold g.sub.y, the system actively performs detection and maintenance, completes identification work from fault characteristics to fault causes, accurately gives fault location and analyzes fault diagnosis results, and is capable of predicting a service life of the valve, diagnosis and prediction results are transmitted to the data storage module, and the display module (27) displays information stored in the data storage module (25) in real time.

2. The multifunctional electro-hydraulic flow control valve according to claim 1, wherein the flow sensor comprises: a flow sensor valve core (5), a flow sensor spring (6), a hydraulic resistor (7), an electro-mechanical converter (8) and a second displacement sensor (9), the flow sensor oil outlet C is in communication with a flow sensor spring cavity Vy through the hydraulic resistor (7), the flow sensor valve core (5), the flow sensor spring (6), the electro-mechanical converter (8) and the second displacement sensor (9) are coaxially connected, an output force of the electro-mechanical converter (8) acts on an end surface of the flow sensor valve core, and the flow sensor oil outlet C is in communication with the pilot valve oil inlet H.

3. The multifunctional electro-hydraulic flow control valve according to claim 1, wherein the flow sensor comprises: a spool valve sleeve (31), a spool valve core (32), a second hydraulic resistor (33), a third displacement sensor (34), a left end surface spring (35), a right end surface spring (36) and a second electro-mechanical converter (37), the spool valve core (32), the third displacement sensor (34), the left surface face spring (35), the right end surface spring (36) and the second electro-mechanical converter (37) are coaxially connected, an output force of the second electro-mechanical converter acts on a right end surface of the valve core, the flow sensor oil outlet C is in communication with a right end containing cavity V.sub.F of the flow sensor through the second hydraulic resistor (33), a left end containing cavity V.sub.E of the flow sensor is in communication with the flow sensor oil inlet B, and the control module (26) calculates the flow sensor compensation signal u.sub.z and inputs the signal to the second electro-mechanical converter (37).

4. The multifunctional electro-hydraulic flow control valve according to claim 1, wherein the communication interaction module (29) is an Ethernet, an industrial Internet, or a Bluetooth, and transmits data stored in the data storage module (25) to the cloud storage (30), and receives data information stored in the cloud storage.

5. A flow control method using the multifunctional electro-hydraulic flow control valve according to claim 1, comprising the following steps of: step 1: receiving, by the calculation module (23), the pilot valve core displacement signal y, the control cavity pressure signal p.sub.C, the oil inlet pressure signal p.sub.A, the oil outlet pressure signal p.sub.B, the flow sensor signal q.sub.p and the temperature sensor signal T output by the sensor; and inputting the main valve flow q, the flow feedback signal q.sub.f, the pressure difference between the inlet and the outlet of the main valve ?p, the main valve input power P.sub.1, the main valve output power P.sub.2 and the main valve throttling loss power P.sub.3 which are calculated by using the received data to the integration module (24); step 2: receiving, by the integration module (24), the output data of the calculation module (23), and performing integral calculation to obtain the main valve input energy E.sub.1, the main valve output energy E.sub.2, the main valve throttling loss energy E.sub.3 and the main valve efficiency ?; and inputting the data of the calculation module and the integration module together to the data storage module (25); step 3: receiving, by the flow controller (15), the flow setting signal q.sub.s output by the control module (26) and the flow feedback signal q.sub.f calculated by the calculation module (23) in step 1, and calculating, by the flow controller, an output control signal and controlling the pilot valve electromagnet (13) through an amplifier; and meanwhile, receiving, by the electric-mechanical converter (8), the flow sensor compensation signal u.sub.z output by the control module (26); and step 4: displaying, by the display module (27), information stored in the data storage module (25) in real time through a program; performing, by the fault prediction module (28), active operation and maintenance and fault early warning on the integrated unit according to the stored main valve signal, and once the accumulated energy reaches the fault alarm threshold g.sub.y, actively performing, by the system, detection and maintenance, completing the identification work from fault characteristics to fault causes, accurately giving fault location and analyzing fault diagnosis results, and predicting the service life of the valve at the same time; and transmitting, by the communication interaction module (29) being an Ethernet, an industrial Internet, or a Bluetooth, the data stored in the data storage module (25) to the cloud storage (30), and receiving data information stored in the cloud storage.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a multifunctional electro-hydraulic flow control valve in the first embodiment of the present invention; and

(2) FIG. 2 is a schematic diagram of a multifunctional electro-hydraulic flow control valve in the second embodiment of the present invention.

(3) Wherein: 1main valve core, 2main valve, 3main valve spring, 4flow sensor, 5flow sensor valve core, 6flow sensor spring, 7hydraulic resistor, 8electro-mechanical converter, 9second displacement sensor, 10pilot valve spring, 11pilot valve core, 12proportional pilot valve, 13pilot valve electromagnet, 14proportional amplifier, 15flow controller, 16displacement sensor, 17control cavity pressure sensor, 18oil inlet pressure sensor, 19oil outlet pressure sensor, 20temperature sensor, 21multifunctional valve controller, 22signal processing module, 23calculation module, 24integration module, 25data storage module, 26control module, 27display module, 28fault prediction module, 29communication interaction module, 30cloud storage, 31spool valve sleeve, 32spool valve core, 33second hydraulic resistor, 34third displacement sensor, 35left end surface spring, 36right end surface spring, and 37second electro-mechanical converter.

(4) V.sub.Amain valve oil inlet cavity, V.sub.Bmain valve oil outlet cavity, V.sub.Cmain valve control cavity, V.sub.Zflow sensor oil inlet cavity, V.sub.Yflow sensor spring cavity, Amain valve oil inlet, Bflow sensor oil inlet, Cflow sensor oil outlet, Dmain valve oil outlet, Hpilot valve oil inlet, Fpilot valve oil outlet, Mfeedback groove, Nvalve core left end surface, Rvalve core right end surface, Uspool valve core left end surface, Wspool valve core right end surface, V.sub.Eflow sensor left end cavity, and V.sub.Fflow sensor right end cavity.

(5) p.sub.Aoil inlet pressure signal, P.sub.Boil outlet pressure signal, p.sub.Ccontrol cavity pressure signal, q.sub.bflow sensor signal, Ttemperature sensor signal, q.sub.sflow setting signal, q.sub.fflow feedback signal, ypilot valve core displacement signal, g(x)flow amplification factor, qmain valve flow, ?ppressure difference between inlet and outlet of main valve, P.sub.1main valve input power, P.sub.2main valve output power, P.sub.3main valve throttling loss power, E.sub.1main valve input energy, E.sub.2main valve output energy, E.sub.3main valve throttling loss energy, ?main valve efficiency, g.sub.yfault alarm threshold, kflow feedback gain, and u.sub.zflow sensor compensation signal.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(6) The principle and structure of the present invention will be further explained in detail with reference to the drawings and embodiments, so that those of ordinary skills in the art can understand and implement the present invention after reading the specific embodiments. The embodiments are detailed description of the present invention, and do not impose any restrictions on the present invention.

First Embodiment

(7) As shown in FIG. 1, a multifunctional electro-hydraulic flow control valve comprises a main valve 2 and a proportional pilot valve 12; further, a flow sensor 4, a multifunctional valve controller 21, a control cavity pressure sensor 17, an oil inlet pressure sensor 18, an oil outlet pressure sensor 19, and a temperature sensor 20 are additionally provided.

(8) A main valve oil inlet A is in communication with a feedback groove M through an internal flow channel of the main valve core 1, the feedback groove M is in communication with the main valve control cavity V.sub.C through a throttling edge on a valve sleeve, the main valve control cavity V.sub.C is in communication with a flow sensor oil inlet B, a flow sensor oil outlet C is in communication with a pilot valve oil inlet H, and a pilot valve oil outlet F is in communication with a main valve oil outlet D.

(9) The feedback groove M in the main valve core 1 and an internal flow channel of the valve core are in communication with the main valve control cavity V.sub.C and the main valve oil inlet A, which is the basis for realizing a flow-displacement feedback function. When the proportional pilot valve 12 is closed, a fluid flows into the main valve control cavity V.sub.C through the feedback groove M due to a pre-opening amount of the feedback groove M. In this case, an inlet pressure and a control cavity pressure are almost completely equal, and the main valve core remains closed under the effect of an area difference. When the proportional pilot valve 12 is opened, the feedback groove M in the main valve core and a pilot valve opening form an A-type hydraulic half-bridge, and a fluid at the main valve oil inlet flows out through the feedback groove M and the proportional pilot valve, so that the pressure in the control cavity is less than the inlet pressure of the main valve. When the pressure in the control cavity is less than a certain value, the main valve core will be opened, and a flow area of the feedback groove M will also be increased after the main valve core 1 is opened, until pressures at upper and lower ends of the valve core are equal and the valve core is balanced.

(10) The flow sensor 4 is of a plug-in type and comprises: a flow sensor valve core 5, a flow sensor spring 6, a hydraulic resistor 7, an electro-mechanical converter 8 and a second displacement sensor 9. The flow sensor oil inlet B is in communication with the flow sensor oil inlet cavity V.sub.Z, the flow sensor valve core 5, the flow sensor spring 6, the electro-mechanical convert 8 and the second displacement sensor 9 are coaxially connected, an output force of the electro-mechanical converter 8 acts on an end surface of the flow sensor valve core, and the flow sensor oil outlet C is in communication with the pilot valve oil inlet H. An input end of the electro-mechanical converter 8 is connected with a control module. The control module 26 calculates the flow sensor compensation signal u.sub.z and inputs the signal to the second electro-mechanical converter 8.

(11) The flow sensor 4 is installed between the main valve control cavity V.sub.C and the proportional pilot valve oil inlet H, and the flow sensor oil outlet C is in communication with the flow sensor spring cavity V.sub.Y through the hydraulic resistor 7. The pressure of the flow sensor oil inlet B acts on a valve core left end surface N of the flow sensor valve core 5, and the flow through the flow sensor is proportional to a valve opening pressure difference, so that the flow sensor valve core is opened by the hydraulic pressure, and a hydraulic pressure, a hydraulic force and a spring force on the flow sensor valve core are balanced. Because the flow sensor signal q.sub.b has a linear relationship with displacement of the flow sensor valve core 5, the displacement of the flow sensor valve core 5 is measured by the second displacement sensor 9, so that the flow sensor signal q can be obtained.

(12) The accuracy of the flow sensor may be affected by oil temperature change and hydrodynamic force. A temperature of the oil in the flow valve is measured by the temperature sensor 20, and the control module 26 feeds back the compensation signal u.sub.z to the electro-mechanical converter 8 to compensate the nonlinear relationship between the flow rate and the displacement z of the flow sensor valve core 5, thus reducing the influence of the temperature and the hydrodynamic force on the flow measured.

(13) The control cavity pressure sensor 17 is in communication with the main valve control cavity V.sub.C to output a control cavity pressure signal P.sub.C; the oil inlet pressure sensor 18 is in communication with the main valve oil inlet A to output an oil inlet pressure signal p.sub.A; the oil outlet pressure sensor 19 is in communication with the main valve oil outlet D to output an oil outlet pressure signal p.sub.B; and the temperature sensor 20 is in communication with the main valve oil outlet D to output a temperature sensor signal T.

(14) An output end of the proportional amplifier 14 is connected to the pilot valve electromagnet 13, the flow controller 15 receives a flow setting signal q.sub.s and a flow feedback signal q.sub.f, and an output end of the flow controller 15 is connected to an input end of the proportional amplifier 14. The pilot valve electromagnet 13 receives a signal from the proportional amplifier 14, and an output force thereof and a spring force of a pilot valve spring 10 jointly control displacement of a pilot valve core 11. The displacement sensor 16 detects displacement of the pilot valve core 11, and outputs a pilot valve core displacement signal y to a feedback end of the proportional amplifier 14.

(15) The multifunctional valve controller 21 comprises a signal processing module 22, a calculation module 23, an integration module 24, a data storage module 25, a control module 26, a display module 27, a fault prediction module 28, and a communication interaction module 29.

(16) The data storage module 25 is connected to the control module 26, the display module 27, the fault prediction module 28 and the communication interaction module 29 through a bidirectional data bus.

(17) The signal processing module 22 receives the pilot valve core displacement signal y, a control cavity pressure signal p.sub.C, an oil inlet pressure signal p.sub.A, an oil outlet pressure signal p.sub.B, a flow sensor signal q.sub.p, and a temperature sensor signal 7. After the signal processing module filters and normalizes the above signals, the signals are input to the calculation module 23 and an input end of the data storage module 25 through an output end of the signal processing module.

(18) The control module 26 calculates the flow setting signal q.sub.s, and the flow setting signal q.sub.s is connected to an input end of the flow controller 15. All the data in the data storage module 25 are analyzed, compared, judged and associated, and knowledge is continuously accumulated. According to the changes of load pressure and oil temperature, a multi-control mode switching strategy based on working condition identification may be designed to realize displacement closed-loop control and flow closed-loop control mode to adapt to the changes of external environment. In addition, PID control, fuzzy control, neural network, deep learning and other algorithms are used to realize functions of parallel regulation, state monitoring, self-learning and self-adaptation of electro-hydraulic proportional flow direction continuous control valve.

(19) The calculation module 23 calculates following parameters according to a calculation formula (1), a calculation formula (2), a calculation formula (3), a calculation formula (4), a calculation formula (5) and a calculation formula (6):
main valve flow q=(g(x)+1).Math.q.sub.b(1)
pressure difference between an inlet and an outlet of the main valve?p=P.sub.A?P.sub.B(2)
main valve input power P.sub.1=P.sub.A.Math.q(3)
main valve output power P.sub.2=P.sub.B.Math.q(4)
main valve throttling loss power P.sub.3=?p.Math.q(5)
flow feedback signal q.sub.f=k.Math.q.sub.b(6).

(20) The calculation module 23 inputs the main valve flow q, the flow feedback signal q.sub.f, the pressure difference ?p between an inlet and an outlet of the main valve, the main valve input power P.sub.1, the main valve output power P.sub.2 and the main valve throttling loss power P.sub.3 calculated to an input end of the integration module 24 and the data storage module 25. The calculation module 23 inputs the calculated flow feedback signal q.sub.f to a feedback end of the flow controller 15.

(21) The integration module performs integral calculation to obtain following parameters according to a formula (7), a calculation formula (8), a calculation formula (9) and a calculation formula (10):
main valve input energy E.sub.1=?.sub.0.sup.1P.sub.1dt(7)
main valve output energy E.sub.2=?.sub.0.sup.1P.sub.2dt(8)
main valve throttling loss energy E.sub.3=?.sub.0.sup.1P.sub.3dt(9)
main valve efficiency

(22) $\begin{array}{cc}?=\frac{E_2}{E_1}.& \left(10\right)\end{array}$

(23) The main valve input energy E.sub.1, the main valve output energy E.sub.2, the main valve throttling loss energy E.sub.3 and the main valve efficiency ? calculated by the integration module 24 are input to the data storage module 25.

(24) The display module 27 displays information stored in the data storage module 25 in real time through a program, comprising a dynamic signal curve for displaying state parameters such as the flow sensor signal q.sub.b, the oil inlet pressure signal p.sub.A, the oil outlet pressure signal P.sub.B, the pilot valve core displacement signal y, the temperature sensor signal 7, the main valve flow q, the main valve input power P.sub.1, the main valve output power P.sub.2, the main valve throttling loss power P.sub.3, the main valve input energy E.sub.1, the main valve output energy E.sub.2, the main valve throttling loss energy E.sub.3 and the main valve efficiency n in real time.

(25) The fault prediction module 28 performs active operation and maintenance and fault early warning on the integrated unit according to the stored signals such as the main valve input power P.sub.1, the main valve input energy E.sub.1, the oil inlet pressure signal p.sub.A, the oil outlet pressure signal p.sub.B and the like, and once the accumulated energy reaches the fault alarm threshold g.sub.y, the system may actively perform detection and maintenance, complete the identification work from fault characteristics to fault causes by using expert knowledge and expert database, accurately give fault location and analyze fault diagnosis results, and predict the service life of the valve at the same time.

(26) The communication interaction module 29 is an Ethernet, an industrial Internet, or a Bluetooth, and transmits the data stored in the data storage module 25 to a cloud storage 30, and receives data information stored in the cloud storage.

(27) A flow control method using a multifunctional electro-hydraulic flow control valve comprises the following steps of: step 1: receiving, by a calculation module 23, a pilot valve core displacement signal y, a control cavity pressure signal p.sub.C, an oil inlet pressure signal p.sub.A, an oil outlet pressure signal p.sub.B, a flow sensor signal q.sub.p and a temperature sensor signal T output by a sensor; and inputting a main valve flow q, a flow feedback signal q.sub.f, a pressure difference between an inlet and an outlet of the main valve ?p, a main valve input power P.sub.1, a main valve output power P.sub.2 and the main valve throttling loss power P.sub.3 which are calculated by using the received data to an integration module 24; step 2: receiving, by the integration module 24, the output data of the calculation module 23, and performing integral calculation to obtain a main valve input energy E.sub.1, a main valve output energy E.sub.2, a main valve throttling loss energy E.sub.3 and a main valve efficiency ? and inputting the data of the calculation module and the integration module together to a data storage module 25; step 3: receiving, by a flow controller 15, a flow setting signal q.sub.s output by a control module 26 and the flow feedback signal q.sub.f calculated by the calculation module 23 in step 1, and calculating, by the flow controller, an output control signal and controlling a pilot valve electromagnet 13 through an amplifier; and meanwhile, receiving, by an electric-mechanical converter 8, a flow sensor compensation signal u.sub.z output by the control module 26; and step 4: displaying, by a display module 27, information stored in the data storage module 25 in real time through a program; performing, by a fault prediction module 28, active operation and maintenance and fault early warning on the integrated unit according to the stored main valve signal, and once the accumulated energy reaches a fault alarm threshold g.sub.y, actively performing, a system, detection and maintenance, completing the identification work from fault characteristics to fault causes by using expert knowledge and expert database, accurately giving fault location and analyzing fault diagnosis results, and predicting a service life of the valve at the same time; and transmitting, by a communication interaction module 29 being an Ethernet, an industrial Internet, or a Bluetooth, the data stored in the data storage module 25 to a cloud storage 30, and receiving data information stored in the cloud storage.

Second Embodiment

(28) The second embodiment of the multifunctional electro-hydraulic flow control valve of the present invention is the same as the first embodiment in structure and function, but the difference is that the structure of the flow sensor 4 is changed.

(29) As shown in FIG. 2, the specific implementation is to use a spool valve flow sensor, which comprises a spool valve sleeve 31, a spool valve core 32, a second hydraulic resistor 33, a third displacement sensor 34, a left end surface spring 35, a right end surface spring 36, and a second electro-mechanical converter 37. The spool valve core 32, the third displacement sensor 34, the left end surface spring 35, the right end surface spring 36 and the second electro-mechanical converter 37 are coaxially connected. An output force of the second electro-mechanical converter 37 acts on a right end surface W of the spool valve core, the flow sensor oil outlet C is in communication with a right end containing cavity V.sub.F of the flow sensor through the second hydraulic resistor 33, and a left end containing cavity V.sub.E of the flow sensor is in communication with the flow sensor oil inlet B. The control module 26 calculates the flow sensor compensation signal u.sub.z and inputs the signal to the second electro-mechanical converter 37.

(30) In the above embodiment, the spool valve flow sensor is installed between the main valve control cavity V.sub.C and the pilot valve oil inlet H. The electro-mechanical converter 8, the left end surface spring 35 and the right end surface spring 36 are coaxially arranged with the spool valve core 32, the flow sensor oil inlet B is in communication with the left end containing cavity V.sub.C of the flow sensor, and the flow sensor oil outlet C is in communication with the right end containing cavity V.sub.F of the flow sensor through the second hydraulic resistor 33. The flow through the flow sensor is proportional to a valve opening pressure difference, so that the flow sensor valve core is opened by the hydraulic pressure, and a hydraulic pressure, a hydraulic force and a spring force on the flow sensor valve core are balanced. Because the flow sensor signal g.sub.b has a linear relationship with displacement of the spool valve core 32, the displacement of the flow sensor valve core is measured by the third displacement sensor 34, so that the flow sensor signal g can be obtained.