Nuclear power plant pneumatic valve limit switch status monitoring and automatic calibration device

Abstract

This disclosure pertains to the field of nuclear power technology, specifically relating to a device for monitoring and automatically correcting the status of limit switches on pneumatic valves in nuclear power plants. The device can collect the output voltage of the limit switches in real time to monitor their status and display it visually, facilitating maintenance personnel to obtain the limit status in real time. By setting logic to determine the status of the pneumatic valve, if a double limit switch situation exists, maintenance personnel can input a correction command through a human-machine interface. The controller then drives a robotic arm to automatically adjust the relative position of the limit switches to avoid the double limit switch situation. This is of great significance for the correct output signal and feedback control of the limit switches, as well as for maintenance convenience.

Description

Technical Field

[0001] This disclosure belongs to the field of nuclear power technology, specifically relating to a device for monitoring and automatically correcting the status of pneumatic valve limit switches in nuclear power plants. Background Technology

[0002] The primary function of limit switches on pneumatic valves in nuclear power plants is to automatically output signals and provide feedback control when the pneumatic valve opens or closes to a designated position. However, some valves in nuclear sampling systems have short strokes. When the valve's intake action reaches the closed limit trigger, the valve stem, acting as a stop block, triggers the closed limit cam before disengaging from the open limit cam, resulting in a double-limit state. The reverse action has the same effect, leading to serious operational problems, potentially causing downstream logic block malfunctions, equipment misoperations, and alarms that cannot be cleared quickly, affecting operators' ability to assess valve status. Furthermore, these short-stroke valves require limited installation space, hindering on-site maintenance, and manual adjustment of the limit switches makes it difficult to control the installation position and trigger margin. Therefore, there is an urgent need for technologies or methods to monitor and avoid double-limit states by automatically correcting the limit switch position. Summary of the Invention

[0003] To overcome the problems existing in related technologies, a device for monitoring and automatically correcting the status of pneumatic valve limit switches in nuclear power plants is provided. The device includes: a controller, a human-machine interface, and a robotic arm.

[0004] The controller is used to monitor the voltage of the upper limit switch and the lower limit switch in real time, and determine the status of the limit switches based on the relationship between the voltage status of the upper limit switch and the lower limit switch set in the human-machine interface and the preset high voltage dead zone and low voltage dead zone, and display the determination result on the human-machine interface.

[0005] The controller is also used to control the robotic arm to adjust the upper limit switch according to the settings of the human-machine interface when the limit switch is in the double limit state, so that the limit switch returns to the normal state.

[0006] In one possible implementation, the controller performs limit switch status monitoring using the following steps:

[0007] Step 11: The controller collects the voltage of the upper limit switch and the lower limit switch in real time and updates it in real time on the human-machine interface;

[0008] Step 12: When the controller detects that the upper limit switch is in the high voltage dead zone and the lower limit switch is in the low voltage dead zone, it indicates on the HMI that the limit switches are in the lower limit state, thus disabling the button options; when the controller detects that the upper limit switch is in the low voltage dead zone and the lower limit switch is in the high voltage dead zone, it indicates on the HMI that the limit switches are in the upper limit state, thus disabling the button options; when the controller detects that both the upper and lower limit switches are in the low voltage dead zone, it triggers the dual limit state and enters automatic calibration.

[0009] In one possible implementation, the controller performs automatic correction using the following steps:

[0010] Step 21: After receiving the instruction to start adjustment, the controller begins automatic correction, controlling the servo motor of the robotic arm to output a preset angle displacement each time, moving the upper limit switch upward.

[0011] Step 22: During the calibration process, if the controller detects that the upper limit switch is in the high-pressure dead zone and the lower limit switch is in the low-pressure dead zone, and the pneumatic valve limit switch is in the lower limit state, then the calibration work will stop and all control buttons will be disabled.

[0012] Step 23: If the controller receives a stop adjustment command during the calibration process, it will stop the calibration work, activate the start adjustment button, and disable the stop adjustment button.

[0013] In one possible implementation, the low-voltage dead zone is 0–16V and the high-voltage dead zone is 28–48V.

[0014] In one possible implementation, the controller performs a reset upon receiving a reset command, and then enters an initialization state to continue working.

[0015] In one possible implementation, the device further includes two indicator lights connected to the controller, one indicator light indicating the state of the upper limit switch and the other indicator light indicating the state of the lower limit switch.

[0016] In one possible implementation, the robotic arm includes a servo housing, an end cap, a gripping mechanism, a lead screw, a chassis mechanism, a slider, and a guide rail;

[0017] The servo housing is equipped with a DS digital servo connected to a lead screw. The output rotational torque is converted into linear motion of the slider through the lead screw transmission. The end cover, lead screw, and guide rail together constitute the lead screw mechanism.

[0018] The clamping mechanism is used to clamp and fix the limit switch during the calibration process; a chassis mechanism is added to the end of the guide rail.

[0019] In one possible implementation, the chassis mechanism is made of an elastic material, which can distribute the load evenly when bearing a load and has an anti-tipping function to ensure the stability of the device during the calibration process.

[0020] The beneficial effects of this disclosure are as follows: The device disclosed herein can collect the output voltage of the limit switch in real time to monitor the status of the limit switch and display it visually, which is convenient for maintenance personnel to obtain the limit status in real time; by setting logic to determine the status of the pneumatic valve, if there is a double limit situation, the maintenance personnel can input a correction command through the human-machine interface, and the controller drives the robotic arm to automatically adjust the relative position of the limit switch to avoid the double limit situation. This is of great significance for the correct output signal and feedback control of the limit switch and the convenience of maintenance. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a controller shown in an embodiment of this disclosure.

[0022] Figure 2 This is a schematic diagram illustrating a limit switch status monitoring process according to an embodiment of this disclosure.

[0023] Figure 3 This is a schematic diagram of an automatic correction process shown in an embodiment of this disclosure.

[0024] Figure 4 This is a schematic diagram of a robotic arm shown in an embodiment of this disclosure. Detailed Implementation

[0025] The present disclosure will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Unless otherwise defined, the technical and scientific terms used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains; the terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure; the term "comprising" and any variations thereof in this disclosure are intended to cover non-exclusive inclusion. Clearly, the embodiments described in this disclosure are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0027] In this disclosure, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] Figure 1 This is a schematic diagram of a nuclear power plant pneumatic valve limit switch status monitoring and automatic correction device according to an embodiment of this disclosure, as shown below. Figure 1As shown, the device includes: a controller 1, a human-machine interface 2, and a robotic arm 3.

[0029] The controller 1 includes: a display screen 11 (which can be a TFTLCD screen), a power interface 12 (which can be a 3.3V power interface), a chip 13, an STLINK interface 14, buttons 15, indicator lights 16, a USB interface 17, and a GPIO interface 18.

[0030] Chip 13 can be, for example, an STM32F103RCT6, powered by a 3.3V external power supply connected to power interface 12. The voltage rating of chip 13 should not exceed 3.3V. When the externally input electrical signal is acquired at 48VDC via an ADC (Analog-to-Digital Converter), it is connected to a step-down module (e.g., LM2596) and outputs a 3.3V voltage via a DC-DC chopper, thus ensuring that chip 13 accurately acquires the voltage signal. The upper limit switch (e.g., SM3) in the pneumatic valve body BC box is connected to an ADC, and the lower limit switch (e.g., SM5) is connected to an ADC to collect the line voltages of the upper and lower limit switches in real time. However, since there is a response dead zone at the voltage range boundary, and the pneumatic valve body is related to the on / off response of the solenoid valve signal, the trigger voltage of the upper limit switch is set to be consistent with the start voltage of the solenoid valve, and the trigger voltage of the lower limit switch is set to be consistent with the response voltage of the solenoid valve. For example, the start voltage of the upper limit switch of the pneumatic valve 4REN194VL can be set to 23.9V and the release voltage to 12.2V. The parameters are for reference. The low-pressure dead zone is calculated and set to 0-16V and the high-pressure dead zone is set to 28-48V based on a large amount of solenoid valve test data.

[0031] A 16-bit counter is used to output a high-precision PWM waveform based on the processing result of chip 13. The duty cycle is set to control the servo motor action and output the expected rotational angular displacement. Two GPIO interfaces 18 are used to drive the indicator lights 16, which display the status of the upper and lower limit switches respectively. Three GPIO interfaces 18 are used as input channels for buttons 15, which are used to input start calibration, stop calibration, and microcontroller reset commands (RESET). The STLINK is connected to the PC and STLINK interface 14 respectively, which allows the controller 1 to be debugged and downloaded through the PC. The STLINK can power the controller 1, but the voltage of the display screen 11 is insufficient due to its high power consumption. Therefore, a USB cable is also needed to connect to the USB interface 17 to achieve dual power supply.

[0032] The human-machine interface 2 can, for example, use a 2.8-inch, 320*240 resolution TFT LCD module, directly powered by a microcontroller, with a 16-bit 8080 parallel port interface, enabling parallel communication with the microcontroller and featuring built-in capacitive touch functionality. The display screen 11 shows the status of SM3 and SM5, as well as whether the dual limit switches are triggered, through continuous signal acquisition, data reading and writing, and screen refresh for real-time visualization. Since displaying Chinese characters requires installing and retrieving fonts, English is used to simplify operation. The screen displays "SM3: ON / OFF" on the first line, "SM5: ON / OFF" on the second line, and "Dual LimitSwitch: Triggered / NonTriggered" on the third line. At the bottom of the screen, "Start Adjusting" and "Stop Adjusting" are provided for button input selection.

[0033] After the device is wired, the controller's control logic includes limit switch status monitoring and automatic correction. For example... Figure 2 As shown, the controller uses the following steps to monitor the status of the limit switches.

[0034] Step 11: The controller collects the voltage of the upper limit switch and the lower limit switch in real time and updates it in real time on the human-machine interface;

[0035] Step 12: When the controller detects that the upper limit switch is in the high voltage dead zone and the lower limit switch is in the low voltage dead zone, it instructs the limit switch to be in the lower limit state, thus disabling the button options; when the controller detects that the upper limit switch is in the low voltage dead zone and the lower limit switch is in the high voltage dead zone, it instructs the limit switch to be in the upper limit state, thus disabling the button options; when the controller detects that both the upper and lower limit switches are in the low voltage dead zone, it triggers the dual limit state and enters automatic calibration.

[0036] In this disclosure, the controller determines the low-voltage dead zone (0-16V) and high-voltage dead zone (28-48V) based on historical solenoid valve test data. A duty cycle is set in the PWM waveform to precisely control the servo motor output angular displacement for calibration. Two LEDs display the real-time status of the upper and lower limit switches for easy observation by maintenance personnel. Three buttons allow maintenance personnel to control the device as needed. A 2.8-inch TFT LCD serves as the human-machine interface, displaying the limit switch status and dual-limit triggering status, allowing maintenance personnel to input commands to control the device's operation—a true human-machine interaction. The robotic arm uses a lead screw mechanism, converting torque input from the servo motor into linear motion. After stably clamping the limit switches, the calibration displacement of the limit switches can be precisely controlled. The elastic chassis has an anti-tipping function to ensure the stability of the device during calibration.

[0037] For example, after the controller is connected to the step-down module, it collects the output voltage of the limit switch in real time through the ADC, analyzes the status of the pneumatic valve limit switch, and updates it in real time on the human-machine interface. The low voltage dead zone indicates that the circuit is open, and the high voltage dead zone indicates that the circuit is open. When the controller detects that the upper limit switch is in the high-pressure dead zone and the lower limit switch is in the low-pressure dead zone, it instructs the pneumatic valve limit switch to be in the lower limit state. The display shows: SM3:OFF (upper limit switch open), SM5:ON (lower limit switch closed), Dual Limit Switch:NonTriggered (limit switch not triggered), and the button options are disabled. When the controller detects that the upper limit switch is in the low-pressure dead zone and the lower limit switch is in the high-pressure dead zone, it instructs the pneumatic valve limit switch to be in the upper limit state. The display shows: SM3:ON (upper limit switch closed), SM5:OFF (lower limit switch open), Dual Limit Switch:NonTriggered (limit switch not triggered), and the button options are disabled. When the controller detects that both the upper and lower limit switches are in the low-pressure dead zone, it instructs the upper limit switch to be triggered and the lower limit switch to be triggered, i.e., triggering the dual limit state. The display shows: SM3:ON (upper limit switch closed), SM5:ON (lower limit switch closed), Dual Limit Switch:NonTriggered (limit switch not triggered), and the button options are disabled. LimitSwitch:Triggered (Limit switch triggered), enters automatic calibration.

[0038] like Figure 3 As shown, the controller performs automatic calibration using the following steps.

[0039] Step 21: After receiving the start adjustment command, for example, when the user triggers the Start Adjusting button, the controller starts automatic correction and controls the servo motor of the robotic arm to output a preset angle (e.g., 15°) displacement each time, moving the upper limit switch upward.

[0040] Step 22: During the calibration process, if the controller detects that the upper limit switch is in the high-pressure dead zone and the lower limit switch is in the low-pressure dead zone, and the pneumatic valve limit switch is in the lower limit state, then the calibration work will stop and all control buttons will become ineffective.

[0041] Step 23: During the calibration process, if the controller receives a stop adjustment command (e.g., the user triggers the Stop Adjusting button), the calibration work is stopped, the start adjustment button is activated, and the stop adjustment button is disabled. During the controller's operation, if it receives a reset command (e.g., the user triggers the RESET button), the controller resets and enters the initialization state to continue operation.

[0042] like Figure 4As shown, the robotic arm 3, acting as the actuator, includes a servo housing 31, an end cap 32, a clamping mechanism 33, a lead screw 34, a chassis mechanism 35, a slider 36, and a guide rail 37. A DS3218 digital servo is installed in the servo housing 31 and connected to the lead screw 34. The output rotational torque is transmitted through the lead screw 34 and converted into linear motion of the slider 36. The end cap 32, lead screw 34, and guide rail 37 together constitute the lead screw mechanism. The clamping mechanism 33 is used to clamp and fix the limit switch during the calibration process. Four chassis mechanisms 35 are added to the end of the guide rail 37. The chassis mechanisms 35 are made of elastic material, which can evenly distribute the load when bearing a load and has an anti-tipping function to ensure the stability of the device during the calibration process.

[0043] In related technologies, there is currently no technology or method for automatically correcting the position of limit switches to monitor limit switch status and avoid double limit switches. The nuclear power plant pneumatic valve limit switch status monitoring and automatic correction device provided in this disclosure uses an ADC to collect the limit switch output voltage in real time after the controller is connected to a step-down module. Considering the dead zone effect at the voltage range boundary, the low-voltage dead zone is determined to be 0-16V and the high-voltage dead zone to be 28-48V based on a large amount of solenoid valve test data. The duty cycle is set in the PWM waveform to precisely control the servo motor output angular displacement to achieve correction. Two indicator lights 16 display the status of the upper and lower limit switches in real time, facilitating observation by maintenance personnel. Three buttons allow maintenance personnel to control the device as needed. A 2.8-inch TFTLCD serves as the human-machine interface, displaying the limit switch status and double limit triggering status, allowing maintenance personnel to input commands to control the device's operating status, representing true human-machine interaction. The robotic arm uses a lead screw mechanism, which converts torque input from a servo motor into linear motion. After the limit switch is stably clamped, the correction displacement of the limit switch can be precisely controlled. The elastic chassis has an anti-tipping function to ensure the stability of the device during the correction process.

[0044] In addition, the device of this invention occupies little horizontal space, making it more suitable for use in narrow areas where maintenance personnel cannot easily carry out their work. It also provides convenience for maintenance personnel to calibrate limit switches. This invention is highly safe, easy to operate, and easy to maintain.

[0045] In one application example, the operation of the device disclosed herein is as follows.

[0046] The maintenance personnel install the device next to the pneumatic valve to be calibrated, clamp the upper limit switch using the clamping mechanism, and after confirming the device is stable, connect the voltage acquisition line to the SM3 and SM5 terminals of the BC box of the pneumatic valve body, and connect the servo control line to the digital servo. The maintenance personnel control the opening and closing of the pneumatic valve from the IA workstation on the first floor. During this process, the device can automatically and in real-time determine the limit status of SM3 and SM5, which can be observed by the maintenance personnel through the HMI 2 and 16 LEDs. If both limits are triggered, a calibration command must be manually input via buttons, and the device will begin automatic calibration until it returns to normal or the calibration is manually stopped. This human-machine interface provides a safer, more stable, and reliable experience. After calibration, disconnect the cables, release the limit switches, and retrieve the device.

[0047] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A device for monitoring and automatically correcting the status of limit switches of pneumatic valves in nuclear power plants, characterized in that, The device includes: a controller, a human-machine interface, and a robotic arm; The controller is used to monitor the voltage of the upper limit switch and the lower limit switch in real time, and determine the status of the limit switches based on the relationship between the voltage status of the upper limit switch and the lower limit switch set in the human-machine interface and the preset high voltage dead zone and low voltage dead zone, and display the determination result on the human-machine interface. The controller is also used to control the robotic arm to adjust the upper and lower limit switches according to the settings of the human-machine interface when the limit switches are in the double limit state, so that the limit switches return to the normal state. The controller uses the following steps to monitor the status of the limit switches: Step 11: The controller collects the voltage of the upper limit switch and the lower limit switch in real time and updates it in real time on the human-machine interface; Step 12: When the controller detects that the upper limit switch is in the high voltage dead zone and the lower limit switch is in the low voltage dead zone, it indicates on the HMI that the limit switches are in the lower limit state, thus disabling the button options; when the controller detects that the upper limit switch is in the low voltage dead zone and the lower limit switch is in the high voltage dead zone, it indicates on the HMI that the limit switches are in the upper limit state, thus disabling the button options; when the controller detects that both the upper and lower limit switches are in the low voltage dead zone, it triggers the dual limit state and enters automatic calibration. The controller performs automatic calibration using the following steps: Step 21: After receiving the instruction to start adjustment, the controller begins automatic correction, controlling the servo motor of the robotic arm to output a preset angle displacement each time, moving the upper limit switch upward. Step 22: During the calibration process, if the controller detects that the upper limit switch is in the high-pressure dead zone and the lower limit switch is in the low-pressure dead zone, and the pneumatic valve limit switch is in the lower limit state, then the calibration work will stop and all control buttons will be disabled. Step 23: If the controller receives a stop adjustment command during the calibration process, it will stop the calibration work, activate the start adjustment button, and disable the stop adjustment button.

2. The apparatus according to claim 1, characterized in that, The low-voltage dead zone is 0~16V, and the high-voltage dead zone is 28~48V.

3. The apparatus according to claim 1, characterized in that, When the controller receives a reset command, it performs a reset and then enters the initialization state to continue working.

4. The apparatus according to claim 1, characterized in that, The device also includes two indicator lights connected to the controller, one of which indicates the state of the upper limit switch and the other of which indicates the state of the lower limit switch.

5. The apparatus according to claim 1, characterized in that, The robotic arm includes a servo gear box, end cap, gripping mechanism, lead screw, chassis mechanism, slider, and guide rail; The servo housing is equipped with a DS digital servo connected to a lead screw. The output rotational torque is converted into linear motion of the slider through the lead screw transmission. The end cover, lead screw, and guide rail together constitute the lead screw mechanism. The clamping mechanism is used to clamp and fix the limit switch during the calibration process; a chassis mechanism is added to the end of the guide rail.

6. The apparatus according to claim 5, characterized in that, The chassis mechanism is made of elastic material, which can evenly distribute the load when bearing a load, and has an anti-tipping function to ensure the stability of the device during the calibration process.

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