CN113357181A

CN113357181A - Fault self-switching redundancy control device for electric air door of fan

Info

Publication number: CN113357181A
Application number: CN202110502389.XA
Authority: CN
Inventors: 成涛; 顾蓉; 蒋宝林
Original assignee: Shanghai Meishan Iron and Steel Co Ltd
Current assignee: Shanghai Meishan Iron and Steel Co Ltd
Priority date: 2021-05-08
Filing date: 2021-05-08
Publication date: 2021-09-07
Anticipated expiration: 2041-05-08
Also published as: CN113357181B

Abstract

The invention relates to a fault self-switching redundancy control device for an electric air release door of a fan, which comprises a power switch, a DCS control system, a power self-switching control loop, an intermediate relay control loop, a feedback signal isolator, a command signal isolator, an actual valve position signal isolator, an input and output terminal of an actuating mechanism, the actuating mechanism, a valve rod, a valve plate and a pneumatic valve driving and feedback device, wherein the power switch is connected with the DCS control system; the valve plate is arranged in the pipeline, the actuating mechanism is connected with the valve plate through the valve rod, the input and output terminals of the actuating mechanism receive a driving power supply from the power switch, and the power supply automatic switching control loop is arranged between the input and output terminals of the actuating mechanism and the control loop of the power switch; the scheme realizes automatic backup redundancy control of the valve after the fault of the actuating mechanism, and further ensures the stability of equipment and production.

Description

Fault self-switching redundancy control device for electric air door of fan

Technical Field

The invention relates to a control device, in particular to a fault self-switching redundancy control device for an electric air door of a fan, and belongs to the technical field of blast furnace blower control.

Background

At present, the existing domestic large blast furnace blast units are all provided with an electric air discharging valve of an air outlet pipeline, after the unit is started, the working condition needs air discharging operation before the blast furnace is formally supplied with air, or when the blast furnace is emergently stopped, the electric air discharging valve needs to be opened to perform air discharging operation, release air pressure and volume and match the production needs of the blast furnace. The electric air release door of the blast furnace blower unit of the thermal power plant of the plum steel company is in the operation process and often occurs after the formal air supply of the unit, and the electric air release door directly causes the valve to be uncontrolled due to the air release operation before, the field vibration influences the failure that the electronic components of the internal control circuit board of the electric air release door execution mechanism are damaged by the earthquake, the air release is automatically opened, the air supply pressure of the unit is greatly reduced and fluctuated, and the air supply safety is seriously influenced. In view of the situation that the valve is easily out of control in the severe operating environment of the conventional electric actuating mechanism, the invention of a self-locking position-keeping and backup redundancy control method aiming at the valve position drift caused by the failure of the electric air release door actuating mechanism is very necessary for fully ensuring the safety and stability of blast furnace air supply.

Disclosure of Invention

The invention provides a fault self-switching redundancy control device for an electric air release door of a fan, aiming at the problems in the prior art, the technical scheme triggers a main control loop of an actuating mechanism to cut off a power supply and maintain the position by comparing a control instruction with a valve feedback current signal, so that the working condition deterioration caused by the out-of-control valve is prevented; meanwhile, a pneumatic valve driving and feedback device is designed, automatic backup redundant control of the valve after the fault of the actuating mechanism is realized, and the stability of equipment and production is further ensured.

In order to achieve the purpose, the technical scheme of the invention is that the fan electric air release door fault automatic switching redundancy control device comprises a power switch, a DCS control system, a power automatic switching control loop, an intermediate relay control loop, a feedback signal isolator, a command signal isolator, an actual valve position signal isolator, an execution mechanism input and output terminal, an execution mechanism, a valve rod, a valve plate and a pneumatic valve driving and feedback device; the valve plate is installed inside a pipeline, the execution mechanism is connected with the valve plate through a valve rod, the input and output terminal of the execution mechanism receives a driving power supply from a power switch, a power supply automatic switching control loop is arranged between the input and output terminal of the execution mechanism and a control loop of the power switch, the DCS control system sends a valve instruction signal to enter the input and output terminal of the execution mechanism through an instruction signal isolator, the feedback signal of the execution mechanism enters the DCS control system through a feedback signal isolator to be subjected to closed-loop control, the DCS control system judges that the execution mechanism breaks down and then sends a control instruction to an intermediate relay control loop, the intermediate relay control loop directly controls the power supply automatic switching control loop to realize the power supply cutting and position keeping function of the execution mechanism, and the pneumatic valve is driven and fed back by a feedback device to drive the valve to act and realize real-time feedback signal conversion. Once the valve driving execution mechanism drifts because of the valve position of trouble, this scheme can realize cutting off actuating mechanism drive power, and driving motor loses the power supply in the twinkling of an eye, guarantees that the valve is protected the position, stops at the valve position before the trouble. Meanwhile, the backup redundancy control device is started, so that the continuous normal control of the electric air release door is realized, and the stable operation of a control system and a unit is fully ensured.

The pneumatic valve driving and feedback device comprises a cylinder, a reaction gas circuit amplifier, a positive gas circuit amplifier, a valve positioner, a gas source electromagnetic valve, a driving gear, a driving toothed bar, a primary coil, a feedback rod, a secondary coil, a limit stop, a pushing piston and a limit stop, wherein the pushing piston is additionally arranged on one side of the inside of the cylinder and is fixedly connected with the driving toothed bar, and the limit stop are additionally arranged on the strokes of two ends of the pushing piston; drive rack bar extends to drive gear department, drive rack bar and drive gear fixed coordination installation, realize the linkage of rack bar and gear, wherein drive gear fixed mounting is on the valve rod, the gear action drives the valve rod action and then drives the valve plate action, the inside opposite side feedback device who contains of cylinder is provided with the feedback pole, feedback pole and promotion piston fixed connection, the piston motion is followed to the feedback pole, the cylinder inner wall installs primary coil additional, secondary coil parcel feedback pole, realize that feedback pole displacement conversion current signal sends to the DCS system.

As an improvement of the present invention, the pneumatic valve driving and feedback device includes two functions: the backup redundancy driving and feedback device starts to work when the DCS detects that the actuating mechanism breaks down and cuts off a main control power supply, the DCS sends a control instruction to the valve positioner and directly controls the valve rod to move through the pneumatic device, meanwhile, the feedback device further converts the control signal into a feedback current signal through the magnetic field change of the primary coil and the secondary coil, which induces the movement of the feedback rod, and sends the feedback current signal to the DCS control system for closed-loop control by utilizing the principle of a built-in differential transformer, so that the backup redundancy control after the actuating mechanism breaks down is realized, and the stable operation of the unit and the control system is ensured.

As an improvement of the invention, the control method comprises the following steps: after judging the fault automatic switching and position-keeping of the executing mechanism, the DCS control system sends a control instruction to the air source electromagnetic valve and simultaneously sends a control instruction to the valve positioner, the size of an air source output by the valve positioner is controlled through the change of an instruction signal, the air source is further amplified by the air path amplifier and enters the air cylinder, the piston is controlled to operate, the valve rod is further pushed to move, and the opening and closing actions of the valve are controlled; when the valve needs to be opened, the DCS control instruction is increased, the output air source of the port A of the valve positioner is increased, the air source enters the upper part of a piston of the cylinder after passing through the positive action air path amplifier, the air is exhausted from the exhaust port of the reverse action air path amplifier below the piston, the piston is pushed to move under the pressure of the air source, and the driving rack bar linkage valve rod valve is driven to move towards the opening direction; when the valve needs to be closed, a DCS control instruction is reduced, an air source output by a port B of the valve positioner is increased, the air source enters the lower part of a piston of the air cylinder after passing through the reverse action air path amplifier, and the upper part of the piston exhausts through an exhaust port of the positive action air path amplifier to push the piston to move under the pressure of the air source and drive the driving rack bar linkage valve rod valve to move towards the closing direction.

As an improvement of the invention, when the electric actuating mechanism has malfunction, the DCS control command is unchanged, the valve is in malfunction, the DCS compares two groups of signals in real time by acquiring a valve position feedback signal and a command signal, once the command signal is unchanged, the DCS does not output, the variation of the valve position feedback signal exceeds 2 percent of the command signal, the DCS control system considers that the actuating mechanism has malfunction and immediately sends a command to control the action of an intermediate relay, a power supply of the actuating mechanism is directly cut off through an intermediate relay contact, the actuating mechanism loses a power source, the valve position stays at the valve position before the malfunction, the function of power failure and position protection is realized, and the working condition is prevented from deteriorating; after the DCS control system judges that the executing mechanism has a fault and is automatically switched off and kept, the DCS control system sends a control command to the air source electromagnetic valve and simultaneously sends a control command to the valve positioner, the size of an air source output by the valve positioner is controlled through the change of a command signal, the air source is further amplified by the air path amplifier and enters the air cylinder, the piston is controlled to operate, the valve rod is further pushed to move, and the opening and closing actions of the valve are controlled.

Compared with the prior art, the invention has the advantages that 1) the technical scheme designs an electric actuator fault detection and automatic switching-off and position-keeping control loop, the DCS control system judges and outputs to control the intermediate relay loop to switch off the actuator driving power supply, the valve position is guaranteed to stay at the position before the fault, the further deterioration of the working condition is avoided, and the smooth production is guaranteed; 2) the technology designs an automatic switching backup redundant valve control device, ensures that the valve after the main control loop is in fault is continuously controllable, and realizes stable production; 3) the technical scheme designs a multifunctional pneumatic valve driving and feedback device, which can drive the valve to act and feed back signal conversion in real time; 4) the scheme realizes the purpose of driving the valve rod to act by pushing and controlling the cylinder piston through the valve positioner, and simultaneously realizes the closed-loop accurate control of the redundant valve by utilizing the function of converting the displacement of the primary coil and the secondary coil induction feedback rod contained in the differential transformer, thereby further ensuring the stable production.

Drawings

FIG. 1 is a field layout diagram of a fault auto-switch position-keeping redundancy control device of an electric ventilation door;

FIG. 2 is a schematic view of a fail-safe control loop of the electric air release door actuator;

FIG. 3 is a DCS (distributed control system) layered control principle block diagram of the fault automatic switching of the electric ventilation door.

In the figure: 1. power switch, 2, DCS control system, 3, power supply auto-switch control loop, 4, intermediate relay control loop, 5, feedback signal isolator, 6, instruction signal isolator, 7, actual valve position signal isolator, 8, actuating mechanism input and output terminal, 9, actuating mechanism, 10, valve rod, 11, driving gear, 12, driving gear rod, 13, cylinder, 14, primary coil, 15, reaction gas circuit amplifier, 16, positive gas circuit amplifier, 17, valve positioner, 18, gas source solenoid valve, 19, feedback rod, 20, secondary coil, 21, limit stop, 22, pushing piston, 23, limit stop, 24, valve plate.

The specific implementation mode is as follows:

for the purpose of enhancing an understanding of the present invention, the present embodiment will be described in detail below with reference to the accompanying drawings.

Example 1: referring to fig. 1-3, the fan electric air release door fault self-switching redundancy control device comprises a power switch 1, a DCS control system 2, a power self-switching control loop 3, an intermediate relay control loop 4, a feedback signal isolator 5, a command signal isolator 6, an actual valve position signal isolator 7, an actuating mechanism input and output terminal 8, an actuating mechanism 9, a valve rod 10, a valve plate 24 and a pneumatic valve driving and feedback device; the valve plate 24 is arranged in the pipeline, the actuating mechanism 9 is connected with the valve plate 24 through the valve rod 10, the input and output terminal 8 of the actuating mechanism receives the driving power supply from the power switch 1, the power supply automatic switching control loop 3 is arranged between the input and output terminal 8 of the actuating mechanism and the control loop of the power switch 1, the DCS control system 2 sends out a valve command signal to enter the input and output terminal 8 of the actuating mechanism through the command signal isolator 6, an actuating mechanism feedback signal enters the DCS control system 2 through the feedback signal isolator 5 to carry out closed-loop control, the DCS control system 2 sends a control instruction to the intermediate relay control loop 4 after judging that the actuating mechanism has a fault, the intermediate relay control loop 4 directly controls the power supply automatic switching control loop 3 to realize the power supply cutting and position protecting function of the actuating mechanism, and the pneumatic valve driving and feedback device drives the valve to act and carries out real-time feedback signal conversion. Once the valve driving execution mechanism drifts because of the valve position of trouble, this scheme can realize cutting off actuating mechanism drive power, and driving motor loses the power supply in the twinkling of an eye, guarantees that the valve is protected the position, stops at the valve position before the trouble. Meanwhile, the backup redundancy control device is started, so that the continuous normal control of the electric air release door is realized, and the stable operation of a control system and a unit is fully ensured. The pneumatic valve driving and feedback device comprises a cylinder 13, a reaction gas circuit amplifier 15, a positive gas circuit amplifier 16, a valve positioner 17, a gas source electromagnetic valve 18, a driving gear 11, a driving toothed bar 12, a primary coil 14, a feedback bar 19, a secondary coil 20, a limit stop 21, a pushing piston 22 and a limit stop 23, wherein the pushing piston 22 is additionally arranged on one side of the inside of the cylinder 13 and is fixedly connected with the driving toothed bar 12, and the limit stop 21 and the limit stop 23 are additionally arranged on the strokes of the two ends of the pushing piston 22; drive rack bar 12 extends to install 11 departments of drive gear, drive

rack bar

12 and 11 fixed coordination installations of drive gear, realize the linkage of rack bar and gear, wherein drive gear 11 fixed mounting is on valve rod 10, the gear action drives the valve rod action and then drives the valve plate action, the inside opposite side feedback device who contains of cylinder 13 is provided with feedback rod 19, feedback rod 19 with promote piston 22 fixed connection, the piston motion is followed to the feedback rod, cylinder inner wall installs primary 14 additional, secondary coil 20 parcel feedback rod 19, realize that feedback rod displacement conversion current signal sends to the DCS system. The pneumatic valve driving and feedback device comprises two functions: the backup redundancy driving and feedback device starts to work when the DCS detects that the actuating mechanism breaks down and cuts off a main control power supply, the DCS sends a control instruction to the valve positioner and directly controls the valve rod to move through the pneumatic device, meanwhile, the feedback device further converts the control signal into a feedback current signal through the magnetic field change of the primary coil and the secondary coil, which induces the movement of the feedback rod, and sends the feedback current signal to the DCS control system for closed-loop control by utilizing the principle of a built-in differential transformer, so that the backup redundancy control after the actuating mechanism breaks down is realized, and the stable operation of the unit and the control system is ensured. According to the scheme, the pneumatic valve driving and feedback device is used as a backup redundancy control device after the executing mechanism fails, and when the DCS judges that the executing mechanism fails and the driving power supply is cut off, the main control loop loses effect. The DCS control system immediately controls the gas source electromagnetic valve to be electrified, and the working gas source enters the pneumatic valve driving device to work. The DCS control system can send command signals to the valve positioner, the valve positioner receives control current given by the DCS, air source pressure is amplified by the air path amplifier and enters the action surface of the piston of the air cylinder, and the air source pressure acts on the piston to directly control the driving gear rod to drive the valve rod and the valve to act. The action of the backup redundant pneumatic valve driving device after the electric actuating mechanism fails is realized, and meanwhile, a feedback mechanism contained in the pneumatic valve driving and feedback device converts the action stroke of a feedback rod into an actual valve position feedback current signal and transmits the actual valve position feedback current signal to a DCS (distributed control system) for closed-loop control by utilizing the principle of a differential transformer through the electromagnetic excitation action of a primary coil and a secondary coil. The technical problem solved by the scheme is that when the electric actuating mechanism has malfunction, the DCS control instruction is unchanged, the valve is in malfunction, the DCS compares two groups of signals in real time by acquiring a valve position feedback signal and a command signal, theoretically, the DCS outputs a command current signal which is consistent with the valve position feedback current signal, once the command signal is unchanged, the DCS does not output, the variation of the valve position feedback signal exceeds 2 percent of the command signal, the DCS control system considers that the actuating mechanism has malfunction and immediately sends a command to control the action of the intermediate relay, the power supply of the actuating mechanism is directly cut off through the intermediate relay contact, the actuating mechanism loses a power source, the valve position stops at the valve position before the fault, the function of power failure and position protection is realized, the working condition deterioration is prevented, an intermediate relay control power supply loop is designed, and the 24V intermediate relay normally closed contact is utilized to control whether the actuating mechanism drive power supply loop is conducted or not.

Example 2: referring to fig. 1-3, a method for controlling the fault self-switching redundancy of the electric air release door of the fan comprises the following steps: after judging that the executing mechanism has a fault and is automatically switched off and kept, the DCS control system 2 sends a control instruction to the air source electromagnetic valve 18 and simultaneously sends a control instruction to the valve positioner 17, the size of an air source output by the valve positioner is controlled through the change of an instruction signal, the air source is further amplified by the air path amplifier and enters the air cylinder, the piston is controlled to operate, the valve rod is further pushed to move, and the valve is controlled to open and close;

when the valve needs to be opened, the DCS control instruction is increased, the output air source of the port A of the valve positioner is increased, the air source enters the upper part of a piston of the cylinder after passing through the positive action air path amplifier, the air is exhausted from the exhaust port of the reverse action air path amplifier below the piston, the piston is pushed to move under the pressure of the air source, and the driving rack bar linkage valve rod valve is driven to move towards the opening direction; when the valve needs to be closed, a DCS control instruction is reduced, an air source output by a port B of the valve positioner is increased, the air source enters the lower part of a piston of the air cylinder after passing through the reverse action air path amplifier, and the upper part of the piston exhausts through an exhaust port of the positive action air path amplifier to push the piston to move under the pressure of the air source and drive the driving rack bar linkage valve rod valve to move towards the closing direction. When the DCS control system drives the pneumatic device to perform opening and closing actions on the valve, one end of the pushing piston is connected with the feedback rod, the primary coil and the secondary coil are wrapped and installed around the feedback rod, and the coils can convert the displacement of the feedback rod into current signals through magnetic induction in real time through the principle of the differential pressure transformer and send the current signals to the DCS control system for accurate closed-loop control. FIG. 2 is a fault self-switching and position-keeping control loop of an electric air release door actuating mechanism; DCS compares two sets of signals in real time through collecting valve position feedback signal and instruction signal, instruction signal is unchangeable, valve position feedback signal's variation exceeds 2% of instruction signal, DCS control system considers actuating mechanism trouble, DCS sends instruction control intermediate relay KA coil immediately and gets electric action, intermediate relay KA normally closed contact becomes normally open, because intermediate relay KA normally closed contact control actuating mechanism drive power supply circuit switches on, intermediate relay KA contact becomes normally open by the normally closed, directly cut off actuating mechanism power control return circuit, actuating mechanism loses power, the valve keeps the normal position.

FIG. 3 is a DCS (distributed control System) layered control principle diagram of the fault automatic switching of the electric air release door; under normal working conditions, the DCS control system sends a control instruction to the actuating mechanism to drive the valve to act, and a valve feedback signal is sent to the DCS to perform closed-loop control or display. When the DCS control system judges that the actuating mechanism has a fault, the DCS immediately sends an instruction to control the intermediate relay KA coil to be electrified, the intermediate relay KA contact is normally closed and normally opened, the power supply control loop of the actuating mechanism is directly cut off, the actuating mechanism loses power, and the valve is kept in the original position. Meanwhile, the DCS sends an instruction to control the solenoid valve of the air source to be electrified, and the air source enters the valve positioner of the pneumatic valve driving and feedback device to work. The DCS sends a control instruction to the valve positioner, the valve action is controlled directly through the pneumatic valve driving device, meanwhile, the feedback device utilizes the principle of a built-in differential transformer, the magnetic field change of the motion of a primary coil and a secondary coil is fed back through induction of a primary coil and a secondary coil, the magnetic field change is further converted into an actual valve position feedback signal and is sent to the DCS control system for closed loop control, backup redundancy control after the fault of an actuating mechanism is realized, the stable operation of a unit and the control system is ensured, when the fault occurs in the electric actuating mechanism, the DCS control instruction is unchanged, the valve is mistakenly moved, the DCS compares two groups of signals in real time by collecting the valve position feedback signal and the instruction signal, once the instruction signal is unchanged, the DCS does not output, the variable quantity of the valve position feedback signal exceeds 2 percent of the instruction signal, the DCS control system considers that the actuating mechanism is in fault and immediately sends an instruction to control the action of an intermediate relay, the power supply of the actuating mechanism is directly cut off through the intermediate relay contact, the actuating mechanism loses a power source, and the valve position stays at the valve position before the fault, so that the function of power-off and position-keeping is realized, and the working condition is prevented from deteriorating; after the DCS control system judges that the executing mechanism has a fault and is automatically switched off and kept, the DCS control system sends a control command to the air source electromagnetic valve and simultaneously sends a control command to the valve positioner, the size of an air source output by the valve positioner is controlled through the change of a command signal, the air source is further amplified by the air path amplifier and enters the air cylinder, the piston is controlled to operate, the valve rod is further pushed to move, and the opening and closing actions of the valve are controlled. When the DCS control system drives the pneumatic device to perform opening and closing actions on the valve, one end of the pushing piston is connected with the feedback rod, the primary coil and the secondary coil are wrapped and installed around the feedback rod, and the coils can convert the displacement of the feedback rod into current signals through magnetic induction in real time through the principle of the differential pressure transformer and send the current signals to the DCS control system for accurate closed-loop control. To sum up, this patent technology has designed an electric actuator fault detection and autogenous cutting and has kept a control loop, judges relay circuit through DCS control system and cuts off actuating mechanism drive power supply in the middle of the output control, guarantees that the valve position stops in the position before the trouble, stops the operating mode and further worsens, guarantees that the production is in the same direction as usual. This patent technique has still designed a multi-functional pneumatic valve drive and feedback device, not only can drive the valve action, through can real-time feedback signal conversion. This patent technique further through the redundant valve control device of backup of automatic switch-over, ensures that the valve after the master control return circuit trouble continues controllable, realizes that production is stable.

It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and all equivalent modifications and substitutions based on the above-mentioned technical solutions are within the scope of the present invention as defined in the claims.

Claims

1. The fault self-switching redundancy control device for the electric air release door of the fan is characterized by comprising a power switch, a DCS (distributed control system), a power self-switching control loop, an intermediate relay control loop, a feedback signal isolator, a command signal isolator, an actual valve position signal isolator, an execution mechanism input and output terminal, an execution mechanism, a valve rod, a valve plate and a pneumatic valve driving and feedback device, wherein the power switch is connected with the DCS control system; the valve plate is installed inside a pipeline, the execution mechanism is connected with the valve plate through a valve rod, the input and output terminal of the execution mechanism receives a driving power supply from a power switch, a power supply automatic switching control loop is arranged between the input and output terminal of the execution mechanism and a control loop of the power switch, the DCS control system sends a valve instruction signal to enter the input and output terminal of the execution mechanism through an instruction signal isolator, the feedback signal of the execution mechanism enters the DCS control system through a feedback signal isolator to be subjected to closed-loop control, the DCS control system judges that the execution mechanism breaks down and then sends a control instruction to an intermediate relay control loop, the intermediate relay control loop directly controls the power supply automatic switching control loop to realize the power supply cutting and position keeping function of the execution mechanism, and the pneumatic valve is driven and fed back by a feedback device to drive the.

2. The fan electric air release door fault self-cutting redundancy control device as claimed in claim 1, wherein the pneumatic valve driving and feedback device comprises a cylinder, a reaction air path amplifier, a positive air path amplifier, a valve positioner, an air source solenoid valve, a driving gear, a driving rack bar, a primary coil, a feedback rod, a secondary coil, a limit stop, a pushing piston and a limit stop, wherein the cylinder internally comprises a pushing piston additionally arranged on one side, the pushing piston is fixedly connected with the driving rack bar, and the limit stop are additionally arranged on strokes of two ends of the pushing piston; drive rack bar extends to drive gear department, drive rack bar and drive gear fixed coordination installation, realize the linkage of rack bar and gear, wherein drive gear fixed mounting is on the valve rod, the gear action drives the valve rod action and then drives the valve plate action, the inside opposite side feedback device who contains of cylinder is provided with the feedback pole, the feedback pole is with promoting the activity fixed connection, the piston motion is followed to the feedback pole, the cylinder inner wall installs primary coil additional, secondary coil parcel feedback pole, realize that feedback pole displacement conversion current signal sends to the DCS system.

3. The fan electric vent failure self-switching redundancy control device according to claim 2, wherein the pneumatic valve driving and feedback device comprises two functions: the backup redundancy driving and feedback device starts to work when the DCS detects that the actuating mechanism breaks down and cuts off a main control power supply, the DCS sends a control instruction to the valve positioner and directly controls the valve rod to move through the pneumatic device, meanwhile, the feedback device further converts the control signal into a feedback current signal through the magnetic field change of the primary coil and the secondary coil, which induces the movement of the feedback rod, and sends the feedback current signal to the DCS control system for closed-loop control by utilizing the principle of a built-in differential transformer, so that the backup redundancy control after the actuating mechanism breaks down is realized, and the stable operation of the unit and the control system is ensured.

4. The fan electric ventilation door fault self-switching redundancy control device according to claim 3, characterized in that the control method is as follows: after judging the fault automatic switching and position-keeping of the executing mechanism, the DCS control system sends a control instruction to the air source electromagnetic valve and simultaneously sends a control instruction to the valve positioner, the size of an air source output by the valve positioner is controlled through the change of an instruction signal, the air source is further amplified by the air path amplifier and enters the air cylinder, the piston is controlled to operate, the valve rod is further pushed to move, and the opening and closing actions of the valve are controlled;

when the valve needs to be opened, the DCS control instruction is increased, the output air source of the port A of the valve positioner is increased, the air source enters the upper part of a piston of the cylinder after passing through the positive action air path amplifier, the air is exhausted from the exhaust port of the reverse action air path amplifier below the piston, the piston is pushed to move under the pressure of the air source, and the driving rack bar linkage valve rod valve is driven to move towards the opening direction;

when the valve needs to be closed, a DCS control instruction is reduced, an air source output by a port B of the valve positioner is increased, the air source enters the lower part of a piston of the air cylinder after passing through the reverse action air path amplifier, and the upper part of the piston exhausts through an exhaust port of the positive action air path amplifier to push the piston to move under the pressure of the air source and drive the driving rack bar linkage valve rod valve to move towards the closing direction.

5. The fan electric air release door fault self-switching redundancy control device according to claim 4, characterized in that when an electric actuator has a malfunction, the DCS control command is unchanged, the valve itself is mistakenly operated, the DCS compares two sets of signals in real time by collecting a valve position feedback signal and a command signal, once the command signal is unchanged, the DCS does not output, the variation of the valve position feedback signal exceeds 2% of the command signal, the DCS control system considers that the actuator has a malfunction, immediately sends a command to control the action of the intermediate relay, the power supply of the actuator is directly cut off through the intermediate relay contact, the actuator loses a power source, the valve position stays at the valve position before the malfunction, the function of power failure and maintenance is realized, and the working condition is prevented from deteriorating; after the DCS control system judges that the executing mechanism has a fault and is automatically switched off and kept, the DCS control system sends a control command to the air source electromagnetic valve and simultaneously sends a control command to the valve positioner, the size of an air source output by the valve positioner is controlled through the change of a command signal, the air source is further amplified by the air path amplifier and enters the air cylinder, the piston is controlled to operate, the valve rod is further pushed to move, and the opening and closing actions of the valve are controlled.