JP2000213666A - Hydraulic servo control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely control a control object even in case of partial abnormality of a multiple control system. SOLUTION: A control system is constituted of three systems, and deviation of an opening command and a detected value of an opening meter 20 are found by a subtracter 26. When this deviation is higher than a set value, a proportional gain 30 is selected, and when the deviation becomes lower than the set value, the proportional gain 30 and an integrating gain 32 are selected. Deviation is corrected with the selected gains as control gains, an opening signal in accordance with the corrected deviation is produced by a servo amplifier 42, this opening signal is supplied to three servo coils, and opening of a flow rate regulating valve 18 is regulated in accordance with an electric current flowing in each of the servo coils.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic servo control device, and more particularly to a hydraulic servo control device suitable for controlling an opening of a hydraulic servo valve in a thermal power plant.

[0002]

2. Description of the Related Art In a thermal power plant, a valve for adjusting a main steam amount and a valve for adjusting a fuel flow rate are used. For example, a main steam control valve for adjusting a main steam amount of a steam turbine in a steam plant, a fuel flow control valve for adjusting a fuel flow in a gas turbine-combined plant are used, and these valves include: In consideration of control responsiveness and accuracy, a hydraulic servo valve is usually employed.

[0003] A hydraulic servo valve includes a valve inserted into a fluid passage forming a passage for a fluid such as steam, a piston connected to the valve, and a cylinder accommodating the piston reciprocally. And a hydraulic actuator for supplying hydraulic pressure to the cylinder, and the hydraulic actuator is connected to the torque motor. The torque motor that adjusts the hydraulic pressure of the hydraulic actuator is provided with a servo coil that generates an electromagnetic force in response to the opening signal. This servo coil is usually composed of two or three in order to improve reliability, and a multi-coil hydraulic servo valve is configured by employing a plurality of coils. In a drive circuit for driving a torque motor, a deviation between an output signal of an opening meter for detecting an opening of a valve and an opening command is obtained, and the opening signal is obtained by multiplying the opening deviation by a control gain. A circuit configuration that generates and supplies a current according to the opening signal to the servo coil is employed. The control gain of the drive circuit used for the multi-coil type hydraulic servo valve is configured by using a proportional gain as an element because high responsiveness to the opening deviation is required.

Further, a coil spring is wound around a piston rod inserted into a cylinder of the multi-coil type hydraulic servo valve, and the elastic force of the coil spring always acts on the valve in a closing direction. ing. For this reason, when the power of the control system is cut off and the current is no longer supplied to the servo coil, the valve closes the fluid flow path by the elastic force of the coil spring, and shifts the entire system in a safe direction. . In this case, the offset is set as a null bias in the drive circuit in consideration of the elastic force of the coil spring that biases the valve in the valve closing direction when the power is cut off. Then, a configuration is employed in which the opening degree of the valve is controlled by adding an offset signal indicating the null bias to the opening degree signal, while maintaining the balance with the elastic force of the coil spring. That is, a transmission system for transmitting a signal obtained by correcting an opening deviation (control deviation) with a control gain to multiple coils is divided into a plurality of transmission systems, and an amplifier (servo amplifier) is provided for each transmission system. As a null bias considering the elastic force of the spring, a configuration is used in which the value obtained by dividing the elastic force of the coil spring when the power is cut off according to the number of coils is used, and this value is added to the input side of each amplifier as an offset signal. ing.

[0005]

In the prior art,
Since the system that connects the control gain element and each coil is simply composed of multiple transmission systems, when some of the coils are disconnected, the signal from the amplifier connected to the disconnected coil is supplied to the coils. This causes the offset of the entire control system to shift by the offset allocated to the failed system, resulting in a deviation in the valve opening, making it impossible to control the servo valve with high accuracy.

Further, in the drive circuit, only the system connecting the control gain element and each coil is configured as a multiplex system, but the other elements are formed as a single system. If a common element such as a coil breaks down, the servo valve cannot be controlled, and the reliability of the system may be impaired. In addition, since the drive circuit does not maintain the independence of each coil, it is not possible to maintain the common parts of each coil during operation even when performing maintenance, and a maintenance procedure considering the common parts of each coil is required And maintenance work is troublesome. Further, when the common portion of each coil is damaged due to a human error, the operation of the system is stopped even if the servo amplifier has a multiplex redundant configuration.

[0007] As a double servo amplifier, a two-stage amplifier is connected to two servo coils, and each amplifier is
If a configuration in which a resistor constituting the positive feedback circuit is connected is adopted, when one servo coil is disconnected, the gain of one amplifier is doubled to absorb an offset caused by the disconnection of one servo coil. be able to. However, even if this method is adopted, if some resistors or amplifiers fail, the entire system will stop.

It is an object of the present invention to provide a hydraulic servo control device and a hydraulic servo control system that can control a control target even when a part of the multiplex control system is abnormal.

[0009]

In order to achieve the above object, the present invention relates to a hydraulic servo valve for controlling a hydraulic servo valve for adjusting a flow rate of a fluid flowing through a fluid flow path in response to an electromagnetic force. A plurality of control systems for controlling the drive of the, each control system, a flow rate detection means for detecting a flow rate by adjusting the hydraulic servo valve, a command value for the hydraulic servo valve and a detection value of the flow rate detection means When the deviation between the two is out of the range of the set value, a single element gain is selected. When the deviation between the two is within the range of the set value, a gain including a plurality of elements is selected. Hydraulic servo control comprising: a control signal generating means for correcting a deviation between the two with a gain to generate a control signal; and an electromagnetic force generating means for applying an electromagnetic force according to the control signal to the hydraulic servo valve. It constitutes the device.

When the hydraulic servo control device is constructed, the control signal generating means has a function of selecting a proportional gain for a single element gain and selecting a proportional integral gain for a gain including a plurality of elements. Can be configured.

Further, the present invention is directed to a flow control valve for controlling a flow rate of a fluid flowing through a fluid flow passage with an opening in accordance with a hydraulic pressure, wherein the flow control valve is controlled by an electromagnetic force. A plurality of control systems connected via a hydraulic servo circuit driven by hydraulic pressure to control the driving of the hydraulic servo circuit, wherein each of the control systems detects an opening of the flow regulating valve. Means, a deviation calculating means for calculating a deviation between the opening command value and the detection value of the opening detecting means, and selecting a single element gain when the calculated value of the deviation calculating means exceeds a set value. When the calculated value of the deviation calculating means is equal to or less than the set value, a gain including a plurality of elements is selected, and the calculated value of the deviation calculating means is corrected by the selected gain. Signal and the deviation correction An opening signal generating means for amplifying a signal related to the calculated value corrected by the step to generate an opening signal, and a servo coil for applying an electromagnetic force according to the opening signal to the hydraulic servo circuit. The hydraulic servo control device is constituted as follows.

In the construction of the hydraulic servo control device, the deviation correcting means has a function of selecting a proportional gain as a single element gain and a function of selecting a proportional integral gain as a gain including a plurality of elements. can do.

Further, the present invention provides, as a system, any one of the hydraulic servo control devices described above, a flow control valve for adjusting the flow rate of the fluid flowing through the fluid flow passage with an opening according to the hydraulic pressure, and this flow control valve. This constitutes a hydraulic servo control system including a hydraulic servo circuit driven by hydraulic pressure according to electromagnetic force.

According to the above-described means, the command value (flow rate command value) for the hydraulic servo valve is compared with the actual detection value (opening or flow rate), and the deviation (control deviation) between the two is out of the range of the set value. If not, select a single element gain or proportional gain.If the deviation between them is within the set value range, select a gain including multiple elements or proportional integral gain. Since the control signal is generated by correcting the deviation and the electromagnetic force according to the generated control signal is applied to the hydraulic servo valve, the deviation of the flow rate is corrected even if some of the electromagnetic force generating means fails. can do.

Further, a deviation between the opening of the flow control valve and the opening command value is calculated, and when the calculated value exceeds a set value, a single element gain or a proportional gain is selected, and the calculated value is set to the set value. In the following cases, a gain including a plurality of elements or a proportional integral gain is selected, a deviation calculation value is corrected with each selected gain, and an opening signal based on the corrected calculation value is supplied to the servo coil. Therefore, even if an abnormality such as disconnection occurs in some of the servo coils, the deviation of the valve opening can be corrected.

Further, since the control systems for the electromagnetic force generating means or the servo coil are formed independently of each other, even if some of the control systems become abnormal due to a failure or the like,
The control target can be controlled with high accuracy, and maintenance and inspection can be performed for each control system, so that maintenance and inspection work can be easily performed. Further, even if a part of the control system becomes abnormal due to a human error, it is possible to prevent the entire system from stopping.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a system showing an embodiment of the present invention. In FIG. 1, a hydraulic servo control system is, for example, a system for controlling main steam or fuel flow rate in a thermal power plant.
It is configured to include drive circuits 10, 12, and 14, a hydraulic servo valve 16, and opening meters 20, 22, and 24. The flow rate control valve 18 of the hydraulic servo valve 16 is provided in a fluid flow path (not shown) for supplying main steam or fuel. The supply amount (flow rate) is controlled. The flow rate due to the adjustment of the hydraulic servo valve 16 or the opening degree of the flow rate adjusting valve 18 is detected by the opening degree meters 20, 22, 24, and the detection values of the respective opening degree meters 20 to 24 are input to the drive circuits 10, 12, 14 respectively. Have been. That is, the opening meters 20 to 24 are configured as flow rate detecting means or opening degree detecting means, respectively, and the opening meters 20 to 24 and the drive circuits 10 to 14 are configured as one element of a control system. In the present embodiment, only the configuration of a triple control system is shown as a plurality of control systems (multiplex control systems), but the same configuration can be applied to a quadruple system or more.
Further, since each of the drive circuits 10 to 14 has the same configuration, the following description will be made based on the configuration of the drive circuit 10.

The drive circuit 10 includes a subtractor 26, a deviation starter 28, a proportional gain 30,
It comprises an integral gain 32, a zero gain 34, a switch 36, an adder 38, an offset 40, and a servo amplifier 42. The subtracter 26 compares a command value for the hydraulic servo valve 16, specifically, a command value (valve opening command value) for the flow rate regulating valve 18, with a detection value obtained by measurement of the opening meter 20, and calculates a deviation between the two. This is configured as a deviation calculating means for calculating the control deviation, and the calculated value of the subtracter 26 is input to the deviation monitor 28, the proportional gain 30, and the integral gain 32. The deviation monitor 28 monitors the value calculated by the subtractor 26, and when the calculated value of the deviation is out of the range of the set value or when the calculated value of the deviation is larger than the set value, a signal for selecting the zero gain 34. Is output to the switch 36, and when the calculated value of the deviation is within the range of the set value or when the calculated value of the deviation is smaller than the set value, a signal for selecting the integral gain 32 is output to the switch 36. ing. The calculated value of the deviation is multiplied by the proportional gain 30 and input to the adder 38. The calculated value of the deviation is multiplied by the integral gain 32 and input to the switch 36. The switch 36 selects the zero gain 34 or the integral gain 32 in response to a signal from the deviation monitor 28, and outputs the selected signal to the adder 38. The adder 38 has an integral gain of 30.
Is added to the signal from the switch 36, and the added signal is output to the servo amplifier 40. That is, the deviation monitor 28, the proportional gain 30, the integral gain 32, the zero gain 34, the switch 36, and the adder 3
8, when the calculated value of the deviation is out of the range of the set value or when the calculated value of the deviation is larger than the set value, the proportional gain 30 is selected as a single element gain, and the calculated value of the deviation is When the value is within the range or when the calculated value of the deviation is smaller than the set value, a proportional integral gain (proportional gain 30 + integral gain 32) is selected as a gain including a plurality of elements, and the calculated value of the deviation is selected by each selected gain. It is configured as a deviation correction means for correcting.

An adder 38 is provided on the input side of the servo amplifier 42.
, And a signal related to the offset 40 are input. The signal relating to the offset 40 is set in correspondence with a value obtained by dividing the elastic force of the coil spring into three parts in consideration of the elastic force of the coil spring that applies the elastic force in the valve closing direction to the flow regulating valve 18. Then, the servo amplifier 42 outputs the signal related to the offset 40 and the adder 38.
The opening signal is supplied to a torque motor 44 shown in FIG. 2 by amplifying an opening signal as a control signal.

The torque motor 44 includes a U-shaped stator 4
6, 48, and a rotor 50, and stators 46, 48
Magnets having different magnetic poles are fixed to both ends of the. The rotor 50 has its center portion rotatably fixed by a shaft 52, and a pipe 54 crossing the rotor 52 is rotatably fixed to the shaft 52. On the outer peripheral side of the rotor 50, three servo coils 56, 58, and 60 are wound as a multi-coil, and each of the servo coils 56, 58, and 60 is provided with a drive circuit 10-1.
4 is connected to the servo amplifier. Each servo coil 5
When a current based on the opening signal flows through 6 to 60, magnetic poles corresponding to the polarity of the current are formed at both ends of the rotor 50, and the magnetic poles attract or repel the magnets of the stators 46 and 48, thereby causing the rotor to rotate. The pipe 50 and the pipe 54 rotate about the shaft 52. That is, the servo coil 5
Numerals 6, 58 and 60 are configured as electromagnetic force generating means, and the rotor 50 and the pipe 54 rotate around the shaft 52 by the electromagnetic force generated from the servo coils 56 to 60, that is, the magnetomotive force. I have.

The pipe 54 is provided as an element of the hydraulic servo valve 16 in the middle of a pipe 62 for supplying control oil, and a nozzle 64 is provided at one end of the pipe 54. The nozzle 64 is disposed at the control oil inlet 68 of the hydraulic actuator 66, and the control oil inlet 68
Are connected to both sides of a cylinder chamber 72 via a pipe 70. A movable portion 74 is inserted into the cylinder chamber 72 so as to be reciprocally movable. When the nozzle 64 rotates with the rotation of the pipe 54, the control oil supply path is switched, and the control oil supply path is switched. Movable part 7 according to the switching of
4 reciprocates in the cylinder chamber 72.
The cylinder chamber 72 is connected to the pipe 62 via a pipe 74 and to a hydraulic cylinder 76. The hydraulic cylinder 76 includes a hydraulic actuator 66 and a pipe 5
4. A hydraulic servo circuit is configured together with the pipes 62 and 74, and a cylinder chamber 78 of the hydraulic cylinder 76 is provided.
A piston 80 is reciprocally inserted therein. The piston rod 82 of the piston 80 is connected to the flow control valve 1
8 and connected to the opening meters 20, 22, 24. Further, a coil spring 84 is wound around the outer periphery of the piston rod 82. An elastic force in the direction indicated by the arrow is generated from the coil spring 84, and the elastic force acts on the flow control valve 18 in the valve closing direction. The opening meters 22 to 24 are configured using, for example, a differential transformer, and each of the opening meters 22 to 24 outputs an AC opening signal whose amplitude changes according to the movement of the piston rod 82. It has become.

Here, when an electromagnetic force in the direction indicated by the arrow is generated from the rotor 50 in accordance with the current of the opening signal supplied to the servo coils 56 to 60, the pipe 54 rotates in the direction indicated by the arrow, Control oil flows in the direction indicated by the arrow in 70 and the hydraulic cylinder 7
6 is supplied with hydraulic pressure, and the opening of the flow control valve 18 is adjusted with the movement of the piston 80.

Next, the operation of the system according to the present embodiment will be described with reference to FIG.

First, when an opening command value for the hydraulic servo valve 16 is input to the drive circuit 10, a deviation between the opening command value and a detection value of the opening meter 22 is calculated in a subtractor 26, and this calculation is performed. The value is compared with a set value in a deviation initiator 28. The range or the magnitude of the set value G is set to 1-2% of the deviation from the full stroke of the hydraulic servo valve 16 when one of the servo coils 56, 58, and 60 is disconnected. In consideration of the case where two of the three servo coils 56, 58 and 60 are disconnected, the magnitude of the set value G may be set to 2 to 3%.

When the calculated value of the control deviation is out of the range of the set value or larger than the set value G, the zero gain 34 is selected, and the adder 38 corrects the calculated value of the deviation only with the proportional gain 30. . Thereafter, when the calculated value relating to the control deviation falls within the set value range or becomes smaller than the set value G, the integral gain 32 is set by the switch 36, and the proportional gain 30 and the integral gain 32 are added by the adder 38. The calculated value of the deviation is corrected by the proportional integral gain. Then, an opening signal amplified by the servo amplifier 42 is generated after the calculated value of the control deviation is corrected by the proportional gain 30 and the proportional integral gain (proportional gain 30 + integral gain 32). When this opening signal is input to the servo coil 56, the hydraulic servo valve 16 exhibits a response characteristic indicated by a solid line. As a result, when the control deviation is large, a responsive control characteristic is indicated by the proportional gain 30. When the control deviation is within the range of the set value G, a characteristic in which the steady-state deviation is corrected by the proportional integral gain is indicated. The deviation can be corrected with high accuracy.

In the course of performing such control, for example, if one of the three servo coils 56 to 60 is disconnected at timing t1, part of the offset 40 may be lost. Causes a deviation once. However, since this deviation is within the range of the set value G, the control gain is a proportional integral gain, and the deviation of the valve opening is corrected with high accuracy by the function of the integral gain 32.
The valve opening can be maintained with high accuracy even when one servo coil is disconnected.

When only the proportional gain 30 is used as the control gain, as shown in FIG. 4, the followability to the step response shows a good result according to the follow characteristic of the hydraulic servo valve 16 itself. . However, as shown at timing t1, when some of the servo coils are disconnected,
The loss of a part of the offset makes it impossible to balance with the elastic force of the coil spring 84, so that the valve opening constantly has a deviation from the command value.

When only the proportional-integral gain is used as the control gain, as shown in FIG. 5, the characteristic of the step response has a delay element in the control system itself. The delay is further delayed by the superimposition of the delay of the control system from the target follow-up characteristic. However, when some of the servo coils are disconnected, as shown at timing t1, the deviation due to the partial loss of the offset is absorbed by the steady deviation correction function of the integral element gain, and as a result, the deviation of the valve opening is reduced. Will be corrected.

According to the present embodiment, since the control gain is switched in accordance with the magnitude of the control deviation, the responsiveness of the control can be enhanced, and the control gain can be opened even when a part of the servo coil is disconnected. The degree of deviation can be corrected, and the valve opening of the hydraulic servo valve 16 can be controlled with high accuracy. Furthermore, since the control systems are configured independently of each other, it is possible to prevent the entire system from stopping due to an abnormality in some of the control systems, and to perform maintenance and inspection for each control system, thereby improving reliability and This can contribute to improvement in maintainability.

[0030]

As described above, according to the present invention,
Since the control gain is switched in accordance with the magnitude of the control deviation, control responsiveness can be improved, and the control target can be controlled with high accuracy even when some control system is abnormal. . Further, since the control systems are configured independently of each other, it is possible to prevent the entire system from stopping due to an abnormality in some control systems,
Maintenance inspection can be performed for each control system, which can contribute to improvement in reliability and maintainability.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a system according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a hydraulic servo valve.

FIG. 3 is a step response characteristic diagram of the system according to the embodiment.

FIG. 4 is a step response characteristic diagram only when only a proportional gain is used.

FIG. 5 is a step response characteristic diagram when only a proportional-integral gain is used.

[Explanation of symbols]

 10, 12, 14 Drive circuit 16 Hydraulic servo valve 18 Flow rate regulating valve 20, 22, 24 Opening meter 26 Calculator 28 Deviation monitor 30 Proportional gain 32 Integral gain 34 Zero gain 36 Switch 38 Adder 40 Offset 42 Servo amplifier 44 Torque Motor 56, 58, 60 Servo coil 66 Hydraulic actuator 76 Hydraulic cylinder

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Ishida 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside the Omika Plant, Hitachi, Ltd. (72) Inventor Takashi Kamei 5-chome, Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd., Omika Plant (72) Inventor Teppei Nomura 5-2-1, Omika-cho, Hitachi City, Ibaraki Pref., Ltd., Hitachi, Ltd., Omika Plant F-term (reference) CC13 CD02 DD01 DD10 GG02 GG04 GG07 GG09 GG11 3H106 DA08 DA23 DA35 DC09 DC16 EE04 EE27 EE45 EE48 FA01 FA07 FB07 FB11 FB12 FB16 FB17 FB27 KK03 KK03 5H303 AA30 BB01 BB06 CC10 KK03 KK03 KK03 KK03 KK07

Claims (5)

[Claims] 1. A hydraulic servo valve for adjusting a flow rate of a fluid flowing through a fluid flow path in response to an electromagnetic force, wherein a plurality of control systems for controlling the driving of the hydraulic servo valve are provided. Compares a command value for the hydraulic servo valve with a value detected by the flow rate detecting means, and a deviation between the two values is out of a set value range. Sometimes, a single element gain is selected, and when the difference between the two is within the range of the set value, a gain including a plurality of elements is selected, and the control signal is generated by correcting the difference between the two with each selected gain. A hydraulic servo control device comprising: a control signal generating unit; and an electromagnetic force generating unit that applies an electromagnetic force according to the control signal to the hydraulic servo valve. 2. A hydraulic servo valve for adjusting a flow rate of a fluid flowing through a fluid flow path in response to an electromagnetic force, wherein a plurality of control systems for controlling the driving of the hydraulic servo valve are provided. Compares a command value for the hydraulic servo valve with a value detected by the flow rate detecting means, and a deviation between the two values is out of a set value range. Control signal generating means for selecting a proportional gain, selecting a proportional integral gain when the deviation between the two is within the set value range, correcting the deviation between the two with each selected gain, and generating a control signal, A hydraulic servo control device comprising: an electromagnetic force generating means for applying an electromagnetic force according to the control signal to the hydraulic servo valve. 3. A flow control valve for controlling a flow rate of a fluid flowing through a fluid flow path with an opening according to a hydraulic pressure as a control target, wherein the flow control valve is driven by a hydraulic pressure according to an electromagnetic force. A plurality of control systems connected via a hydraulic servo circuit to control the driving of the hydraulic servo circuit,
The control systems each include an opening detection unit that detects an opening of the flow control valve, a deviation calculation unit that calculates a deviation between an opening command value and a detection value of the opening detection unit, and a deviation calculation unit. When the calculated value exceeds a set value, a single element gain is selected. When the calculated value of the deviation calculating means is equal to or less than the set value, a gain including a plurality of elements is selected, and the deviation calculation is performed with each selected gain. Deviation correction means for correcting the calculated value of the means,
An opening signal generation unit that amplifies a signal related to the offset of the flow rate regulating valve and a signal related to the calculated value corrected by the deviation correction unit to generate an opening signal, and the electromagnetic force according to the opening signal is A hydraulic servo control device comprising a servo coil provided to a hydraulic servo circuit. 4. A flow control valve for controlling a flow rate of a fluid flowing through a fluid flow path with an opening according to a hydraulic pressure as a control target, wherein the flow control valve is driven by a hydraulic pressure corresponding to an electromagnetic force. A plurality of control systems connected via a hydraulic servo circuit to control the driving of the hydraulic servo circuit,
The control systems each include an opening detection unit that detects an opening of the flow control valve, a deviation calculation unit that calculates a deviation between an opening command value and a detection value of the opening detection unit, and a deviation calculation unit. When the calculated value exceeds the set value, the proportional gain is selected, and when the calculated value of the deviation calculating means is equal to or less than the set value, the proportional integral gain is selected, and the calculated value of the deviation calculating means is corrected by each selected gain. Deviation correction means, an opening signal generation means for generating an opening signal by amplifying a signal relating to the offset of the flow rate regulating valve and a signal relating to the calculated value corrected by the deviation correction means, and And a servo coil for applying the electromagnetic force to the hydraulic servo circuit. 5. A flow control valve for adjusting a flow rate of a fluid flowing through a fluid flow path with an opening according to a hydraulic pressure, a hydraulic servo circuit for driving the flow control valve with a hydraulic pressure according to an electromagnetic force, and a hydraulic servo circuit. A plurality of control systems for controlling the driving of the circuit, wherein each of the control systems is a degree detecting and opening means for detecting an opening of the flow regulating valve, an opening command value and a detection value of the opening detecting means. A deviation calculating means for calculating a deviation from the predetermined value, and selecting a proportional gain when a value calculated by the deviation calculating means exceeds a set value, and selecting a proportional integral gain when the calculated value of the deviation calculating means is equal to or less than the set value. A deviation correction means for correcting the value calculated by the deviation calculation means with each selected gain; and an opening degree signal by amplifying a signal relating to the offset of the flow rate regulating valve and a signal relating to the calculation value corrected by the deviation correction means. Generating the opening signal A hydraulic servo control system comprising: a generating unit; and a servo coil that applies an electromagnetic force according to the opening signal to the hydraulic servo circuit.