Automatic control liquid storage tank and control method

Abstract

The invention provides an automatic control liquid storage tank and a control method. The automatic control liquid storage tank comprises a liquid storage tank; the liquid storage tank is provided with a pressure relief pipeline and a pressurization pipeline; the pressurizing pipeline can be manually opened and closed and automatically opened and closed; the pressure relief pipeline can be manually opened and closed and automatically opened and closed. The method comprises the following steps: S1, initializing a system and judging whether initialization is successful; if the result is yes, executing the step S3; if not, executing the step S2; s2, notifying an operator to manually control a solenoid valve to adjust the pressure through an interface interaction device, and ending; s3, collecting a real-time pressure value P by automatically controlling a measurement and control system of the liquid storage tank, and setting a pressure limit; and S4, according to the real-time pressure value P and the pressure limit, the pressure value of the liquid storage tank is adjusted by automatically controlling a pressure loosening device of the liquid storage tank. According to the liquid nitrogen storage tank provided by the invention, an automatic pressurization and decompression control system can be realized, the test quality and stability are improved, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to explosion-proof pressure relief technology, and in particular, relates to an automatic control liquid storage tank and a control method. Background Art

[0002] With the rapid development of the global aerospace satellite industry, the number of satellites shipped worldwide has increased year by year. Excellent satellite manufacturers are eager to realize mass production of satellites, which has put forward higher requirements for automation in all stages of satellite manufacturing.

[0003] Thermal testing of spacecraft is used to verify the correctness of the spacecraft thermal design, assess the adaptability of the thermal design to the flight thermal environment, and verify the working status of the spacecraft instruments and equipment and the matching between the subsystems. Spacecraft thermal testing can test the performance of each subsystem of the spacecraft and the instruments and equipment in various working modes on orbit, and is an effective and necessary means to improve the reliability of spacecraft. In other words, thermal testing is an important part of the satellite manufacturing process. It has other functions such as obtaining the temperature distribution data of the satellite and verifying the rationality and effectiveness of the satellite thermal control design.

[0004] The liquid nitrogen storage tank used in satellite thermal tests is a key device for vacuum tests. During the experiment, the precise control of liquid nitrogen has an important impact on the experimental results. The main function of the liquid nitrogen storage tank is to store liquid nitrogen. During the test, the liquid nitrogen is sent to the vacuum container through the liquid nitrogen pipeline to reduce the background temperature of the container heat sink to below 100K required by the test standard. Therefore, whether the liquid nitrogen tank can provide a stable liquid nitrogen flow is crucial to the test results.

[0005] At present, the pressure of traditional liquid nitrogen storage tanks is adjusted and balanced by manually controlling the boost stop valve and the pressure relief stop valve. Specifically, the test personnel observe the pressure data of the pressure gauge, manually control the opening and closing degree of the boost valve to control the amount of liquid nitrogen flowing into the vaporizer, and control the opening and closing degree of the vent valve to release the pressure, and then reach the pre-specified target pressure value of the liquid storage tank. However, it was found in previous test processes that this scheme is easily affected by human factors. Different test personnel need different times to stabilize the liquid storage tank within the target pressure value range, and even the liquid storage tank pressure overshoot and underpressure phenomenon may occur, thus affecting the test results. Frequent manual adjustment of the liquid storage tank pressure during the test increases the loss of liquid nitrogen and increases the test cost.

[0006] In other words, the traditional control method of liquid nitrogen storage tanks mainly adopts manual adjustment, which is cumbersome to operate and has low control accuracy. During the satellite thermal test phase, the existing liquid nitrogen storage tanks have problems such as low automation of pressurization and pressure relief, untimely pressurization, and labor-intensive manual pressurization, which affects the quality of the test process and the overall benefits of the enterprise. The need to automate the pressurization and pressure relief of existing liquid nitrogen storage tanks is imminent. Summary of the invention

[0007] In view of the defects in the prior art, an object of the present invention is to provide an automatic control liquid storage tank and a control method.

[0008] An automatic control liquid storage tank provided according to the present invention comprises: a liquid storage tank;

[0009] The liquid storage tank is provided with a pressure relief pipeline and a pressure boost pipeline;

[0010] The boost pipeline can be opened and closed manually or automatically; the pressure relief pipeline can be opened and closed manually or automatically.

[0011] Preferably, the boost pipeline comprises: a manually controlled boost on-off pipeline and an automatic boost on-off pipeline; the manually controlled boost on-off pipeline is connected to the liquid storage tank, and a manual stop valve is provided along the liquid outlet direction; the automatic boost on-off pipeline is connected to the liquid storage tank, and a manual stop valve and a solenoid valve A1 are provided in sequence along the liquid outlet direction;

[0012] Preferably, the pressure relief pipeline includes: a manually controlled pressure relief on-off pipeline and an automatic pressure relief on-off pipeline; the manually controlled pressure relief on-off pipeline is connected to the liquid storage tank, and a manual stop valve is arranged along the liquid outlet direction; the automatic pressure relief on-off pipeline is connected to the liquid storage tank, and a manual stop valve and a solenoid valve A2 are arranged in sequence along the liquid outlet direction.

[0013] Preferably, it also includes: a pressure measuring pipeline; the pressure measuring pipeline is arranged on the liquid storage tank; the pressure measuring pipeline is installed with a pressure sensor for collecting the pressure value of the liquid storage tank.

[0014] Preferably, it also includes: a measurement and control system and a pressure transmitter;

[0015] The measurement and control system is connected to the pressure transmitter; the pressure transmitter is connected to the solenoid valve A1 and the solenoid valve A2;

[0016] The measurement and control system comprises: a CRIO-9066 controller;

[0017] The pressure transmitter includes: a 3501 type pressure transmitter.

[0018] Preferably, it also includes: an interface interaction device; the interface interaction device is connected to the measurement and control system and is used to feed back the pressure condition of the liquid storage tank.

[0019] According to the present invention, a method for automatically controlling the pressure of a liquid nitrogen storage tank is provided, which is used for the automatic control liquid storage tank, and comprises:

[0020] Step S1: Initialize the system and determine whether the initialization is successful; if the result is yes, execute step S3; if the result is no, execute step S2;

[0021] Step S2: Notify the operator to manually control the solenoid valve to adjust the pressure through the interface interaction device, and then end;

[0022] Step S3: Collect the real-time pressure value P and set the pressure limit by automatically controlling the measurement and control system of the liquid storage tank;

[0023] Step S4: According to the real-time pressure value P and the pressure limit, the pressure value of the liquid storage tank is adjusted by automatically controlling the pressure regulator of the liquid storage tank.

[0024] Preferably, in step S3, the pressure limits are set by an operator, including: a boost lower limit P1, a boost upper limit P2, a pressure relief lower limit P3, and a pressure relief upper limit P4;

[0025] In step S4: the pressure of the liquid storage tank is adjusted by a PID increment algorithm; the mathematical expression of the PID increment algorithm is:

[0026]

[0027] Among them, u(k) is the output of the k-th controller; e(k) is the input error of the k-th controller, that is, the difference between the set value and the actual value; Kp, Ki, Kd are the control parameters of the three links of proportional coefficient, integration and differentiation respectively; T is the control period; e(i) is the cumulative sum of the errors up to the k-1th time.

[0028] Preferably, in the step S4, when the real-time pressure value P is less than the boost lower limit P1, the solenoid valve A1 is opened;

[0029] When the real-time pressure value P is greater than or equal to the boost lower limit P1 and less than or equal to the boost upper limit P2, the solenoid valve A1 remains closed;

[0030] If the real-time pressure value P is greater than the boost upper limit P2, the solenoid valve A1 is closed;

[0031] If the real-time pressure value P is less than the pressure relief lower limit P3, the solenoid valve A2 is closed;

[0032] When the real-time pressure value P is greater than or equal to the pressure relief lower limit P3 and less than or equal to the pressure relief upper limit P4, the solenoid valve A2 remains closed;

[0033] When the real-time pressure value P is greater than the pressure relief upper limit P4, the solenoid valve A2 opens.

[0034] Preferably, in step S4, the solenoid valve is adjusted so that a manual control mode and an automatic control mode can be selected through an interface interaction device.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The liquid nitrogen storage tank provided by the present invention stabilizes the pressure of the storage tank through pipeline transformation and measurement and control system, improves the test quality and stability, improves production efficiency, and saves labor.

[0037] 2. The present invention sets the range of boost and relief pressure values, and after calculation and judgment by the controller, controls the on and off of the solenoid valves of the boost and relief pipelines, thereby achieving automatic pressure regulation and stabilization of the liquid storage tank pressure during the test process.

[0038] 3. The automatic pressure control method of the liquid nitrogen storage tank provided by the present invention realizes the precise control of the pressure of the liquid storage tank, thereby improving the experimental efficiency and control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0040] Figure 1 A schematic diagram of a pipeline provided by the present invention;

[0041] Figure 2 A hardware schematic diagram of the liquid storage tank pressure automatic control system provided by the present invention;

[0042] Figure 3 A schematic diagram of the control flow provided by the present invention;

[0043] Figure 4 A human-machine interface block diagram provided by the present invention;

[0044] Figure 5 A comparison chart of the voltage stabilization fluctuation provided by the present invention; the red line indicates automatic; the blue line indicates manual;

[0045] Figure 6 This is a schematic diagram of the comparison of liquid nitrogen usage provided by the present invention, where the red line represents automatic and the blue line represents manual. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0047] Embodiment 1 An automatic control liquid storage tank provided according to the present invention comprises: a liquid storage tank;

[0048] The liquid storage tank is provided with a pressure relief pipeline and a pressure boosting pipeline; and is also provided with a pressure measuring pipeline.

[0049] The pressure measuring pipeline is arranged on the liquid storage tank; the pressure measuring pipeline is installed with a pressure sensor for collecting the pressure value of the liquid storage tank.

[0050] The boost pipeline can be opened and closed manually or automatically; the pressure relief pipeline can be opened and closed manually or automatically.

[0051] The boost pipeline includes: a manually controlled boost on-off pipeline and an automatic boost on-off pipeline; the manually controlled boost on-off pipeline is connected to the liquid storage tank, and a manual stop valve is arranged along the liquid discharge direction; the automatic boost on-off pipeline is connected to the liquid storage tank, and a manual stop valve and a solenoid valve A1 are arranged in sequence along the liquid discharge direction; the pressure relief pipeline includes: a manually controlled pressure relief on-off pipeline and a pressure relief automatic on-off pipeline; the manually controlled pressure relief on-off pipeline is connected to the liquid storage tank, and a manual stop valve is arranged along the liquid discharge direction; the automatic pressure relief on-off pipeline is connected to the liquid storage tank, and a manual stop valve and a solenoid valve A2 are arranged in sequence along the liquid discharge direction.

[0052] The automatic control liquid storage tank also includes: a measurement and control system and a pressure transmitter;

[0053] The measurement and control system is connected to the pressure transmitter; the pressure transmitter is connected to the solenoid valve A1 and the solenoid valve A2;

[0054] The measurement and control system comprises: a CRIO-9066 controller;

[0055] The pressure transmitter includes: a 3501 type pressure transmitter.

[0056] Preferably, it also includes: an interface interaction device; the interface interaction device is connected to the measurement and control system and is used to feed back the pressure condition of the liquid storage tank.

[0057] According to the present invention, a method for automatically controlling the pressure of a liquid nitrogen storage tank is provided, which is used for the automatic control liquid storage tank, and comprises:

[0058] Step S1: Initialize the system and determine whether the initialization is successful; if the result is yes, execute step S3; if the result is no, execute step S2;

[0059] Step S2: Notify the operator to manually control the solenoid valve to adjust the pressure through the interface interaction device, and then end;

[0060] Step S3: Collect the real-time pressure value P and set the pressure limit by automatically controlling the measurement and control system of the liquid storage tank;

[0061] Step S4: According to the real-time pressure value P and the pressure limit, the pressure value of the liquid storage tank is adjusted by automatically controlling the pressure regulator of the liquid storage tank.

[0062] Embodiment 2 A method for automatically controlling the pressure of a liquid nitrogen storage tank according to the present invention comprises:

[0063] Step 1: Modify the original liquid nitrogen storage tank booster pipeline and pressure relief pipeline;

[0064] Step 2: Install the pressure automatic control hardware system;

[0065] Step 3: Install the automatic control software system;

[0066] Step 4: Run the software through the pressure automatic control system host computer.

[0067] Specifically, in step 1:

[0068] Step 1.1: Lead out a pressure measuring pipe under the liquid storage tank and install a digital pressure sensor to control the control system to collect the pressure value of the liquid storage tank in real time.

[0069] Step 1.2: Reconstruct the boost and pressure relief pipelines by connecting an automatic control disconnection pipeline in parallel to the original manually controlled disconnection pipeline, that is, connect a boost automatic disconnection pipeline in parallel to the manually controlled boost disconnection pipeline; connect a pressure relief automatic disconnection pipeline in parallel to the manually controlled pressure relief disconnection pipeline; the boost and pressure relief automatic disconnection pipelines are respectively equipped with solenoid valve A1 and solenoid valve A2, and a manual stop valve is installed in front of each solenoid valve for protection and control; in other words, the manual stop valve and the solenoid valve A2 are installed in sequence on the pressure relief automatic disconnection pipeline along the liquid outlet direction; the manual stop valve and the solenoid valve A1 are installed in sequence on the boost automatic disconnection pipeline along the liquid outlet direction.

[0070] In step 2:

[0071] The pressure automatic control hardware system includes: a pressure transmitter, a controller, and an actuator solenoid valve;

[0072] The controller, i.e. the measurement and control system, is CRIO-9066 produced by National Instruments, Inc. of the United States.

[0073] The pressure transmitter is Rosemount's 3501 pressure transmitter.

[0074] The actuator solenoid valves, namely the solenoid valve A1 and the solenoid valve A2, are specifically low-temperature solenoid valves with a model number of DJ061F-25P from Xiaoli Machinery.

[0075] Liquid storage tank pressure automatic control hardware system, such as Figure 2 As shown;

[0076] The measurement and control system is connected to the pressure transmitter of the liquid nitrogen storage tank, and the measurement and control system is connected to the actuator solenoid valve of the pipeline of the liquid nitrogen storage tank, so as to detect and adjust the pressure control condition of the liquid nitrogen storage tank;

[0077] Specifically, the measurement and control system is connected to a host computer, and feeds back the working conditions to the operator through a human-machine interface provided by the host computer.

[0078] In step 3:

[0079] Step 3.1: The target pressure value of the liquid storage tank implements the on-off strategy of the two solenoid valves. The controller collects the pressure value P of the liquid storage tank in real time. After the hot test starts, the test personnel preset the lower limit of the liquid storage tank pressure increase P1, the upper limit of the pressure increase P2, the lower limit of the pressure relief P3, and the upper limit of the pressure relief P4.

[0080] Step 3.2: The solenoid valve automatic control strategy is divided into six states:

[0081] 1. When the real-time pressure P value collected by the controller is less than or equal to the lower limit of the boost pressure target of the liquid storage tank, that is, the boost lower limit P1, the pressure of the liquid storage tank is too low and needs to be pressurized. The automatic boost solenoid valve, that is, the solenoid valve A1, opens and the liquid storage tank starts to be pressurized;

[0082] 2. When the collected real-time pressure value P is between the preset boost pressure values ​​P1 and P2 of the liquid storage tank, and the current boost pressure of the liquid storage tank is within the target requirement range, the automatic boost solenoid valve, i.e., solenoid valve A1, is closed, and the liquid storage tank pressure maintains the current pressure value.

[0083] 3. When the collected real-time pressure value P is greater than the target upper limit of the boosting of the liquid storage tank, that is, the boosting upper limit P2, the pressure of the liquid storage tank reaches the preset upper limit and the boosting stops, and the automatic boosting solenoid valve, that is, the solenoid valve A1, is closed;

[0084] 4. When the collected real-time pressure value P is less than the pressure relief lower limit P3, the automatic pressure relief solenoid valve, that is, the solenoid valve A2, is closed, and the liquid storage tank stops releasing pressure;

[0085] 5. When the collected real-time pressure value P is between the preset pressure relief pressure values ​​P3 and P4 of the liquid storage tank, that is, between the lower pressure relief limit P3 and the upper pressure relief limit P4, the current pressure relief pressure of the liquid storage tank is within the target requirement range, the automatic pressure relief solenoid valve is closed, and the pressure relief pressure of the liquid storage tank maintains the current pressure value;

[0086] 6. When the collected real-time pressure value P is greater than the target upper limit of the pressure relief of the liquid storage tank, the pressure relief upper limit P4, the pressure relief pressure of the liquid storage tank reaches the preset pressure relief upper limit, the automatic pressure relief solenoid valve, that is, the solenoid valve A2 opens, and the liquid storage tank starts to relieve pressure.

[0087] Step 3.3: The controller performs calculations through the control strategy designed by the system, and controls the on and off of the boost and pressure relief solenoid valves according to the results of the system calculations to perform the boost and pressure relief actions.

[0088] In step 4:

[0089] Step 4.1: Select Labview development software. The software of the liquid storage tank pressure automatic control system consists of user login module, automatic control module, manual control module, monitoring module, data recording module, etc.

[0090] Step 4.2: Run the software. After the test personnel power on the hardware equipment, open the host computer software and log in. When the host computer software enters the running state, the monitoring module is also started at the same time to monitor the system status in real time, including the on-off status of the two solenoid valves and all pressure and liquid level signals. By inputting the preset set pressure range, the controller adjusts the on-off of the solenoid valve according to the program to achieve the regulation and control of the pressure of the liquid storage tank. The data recording module records the pressure and liquid level of the liquid storage tank once a minute and stores them in real time in the formulated document.

[0091] The automatic control method of the liquid nitrogen storage tank provided by the present invention adopts the PID control method, which automatically adjusts the valve switch by real-time monitoring of the pressure, liquid level, and flow sensor signals to achieve precise control of the liquid nitrogen flow in the system. Figure 2 shown.

[0092] Specifically, the system hardware involved in this solution includes: liquid nitrogen storage tank, liquid level sensor, flow sensor, valve, PID controller, and human-machine interface;

[0093] The liquid level sensor is used to monitor the amount of liquid nitrogen stored in the liquid nitrogen storage tank in real time;

[0094] The pressure sensor is used to monitor the pressure in the system pipeline and tank in real time and input the signal into the PID controller.

[0095] The PID controller automatically adjusts the valve switch according to the error between the set value and the actual value to achieve accurate control of the liquid nitrogen flow in the system.

[0096] The human-machine interface is used to display the real-time liquid level of the liquid nitrogen storage tank, the pressure and flow value in the pipeline, the set value, the control parameters, etc., which is convenient for users to operate and monitor.

[0097] Specifically, the liquid storage tank pressure automatic control system consists of a liquid nitrogen pipeline system and a measurement and control system;

[0098] Among them, the liquid nitrogen pipeline system is divided into a liquid nitrogen gasification boosting pipeline and a liquid storage tank pressure relief pipeline. The liquid nitrogen gasification boosting pipeline and the liquid storage tank pressure relief pipeline are modified in the same way, and an automatic control disconnecting pipeline is connected in parallel next to the original manual control disconnecting pipeline; the boosting and pressure relief automatic disconnecting pipelines are respectively equipped with solenoid valves A1 and solenoid valves A2, and a manual stop valve is installed in the front section of the solenoid valve for protection and control. A pressure measuring pipeline is led out from under the liquid nitrogen storage tank, and a digital pressure sensor is installed so that the control system can collect the pressure value of the liquid storage tank in real time. The schematic diagram of the pipeline of the automatic control system of the liquid storage tank pressure is as follows: Figure 1 shown.

[0099] This solution uses PID control algorithm to realize automatic control of vacuum tank. The mathematical expression of PID control algorithm is:

[0100] U(t)=Kp×e(t)+Ki×∫e(t)dt+Kd×de(t)÷dt

[0101] Among them, U(t) is the controller output; Kp, Ki, Kd are the proportional coefficient, integral coefficient, and differential coefficient respectively; e(t) is the controller input error; ∫e(t)dt is the error integral; de(t) / dt is the error differential.

[0102] However, due to the fact that the traditional PID control algorithm may cause sudden changes in the output of the control actuator for engineering control, especially for control of pressure, temperature, liquid level, etc., causing vibration or even collapse of the entire system, this solution adopts an improved incremental PID control algorithm that is more suitable for industrial control.

[0103] Incremental PID control algorithm, mathematical expression is:

[0104]

[0105] Among them, u(k) is the output of the kth controller; e(k) is the input error of the kth controller, that is, the difference between the set value and the actual value; Kp, Ki, and Kd are the control parameters of the three links of proportional coefficient, integral, and differential, respectively; T is the control period; e(i) represents the cumulative sum of the errors up to the k-1th time, which is used to calculate the integral term; e(k)-e(k-1) is used to calculate the differential term.

[0106] The advantages of the incremental PID algorithm are that it has a small amount of calculation, is suitable for fast-response systems, and is easy to implement computer control. However, it also has disadvantages, such as the difficulty in adjusting parameters and the high accuracy requirements of the system model.

[0107] In practical applications, the three parameters Kp, Ki, and Kd need to be adjusted according to the specific system characteristics and control objectives. Usually, the best parameter settings are obtained through experiments and debugging.

[0108] According to the experimental requirements, the parameters of the PID control algorithm are optimized to achieve precise control of the vacuum tank.

[0109] Specifically, in the fourth embodiment, the measurement and control system software can design the on-off strategy of the two solenoid valves according to the target pressure value of the liquid storage tank. In the pipeline of the automatic control system for the pressure of the liquid storage tank is the measurement and control system, that is, the solenoid valve automatically controlled by the controller.

[0110] Among them, A1 is a boost solenoid valve, and A2 is a pressure relief solenoid valve. The controller collects the pressure value P of the liquid storage tank in real time. After the hot test begins, the tester presets the lower limit of boost pressure P1, the upper limit of boost pressure P2, the lower limit of pressure relief P3, and the upper limit of pressure relief P4 for the liquid storage tank. The controller calculates through the control strategy designed by the system, and controls the on and off of the boost and pressure relief solenoid valves according to the results of the system calculation to perform boost and pressure relief actions, so that the liquid storage tank reaches and stabilizes within the target pressure range.

[0111] The solenoid valve control strategy functions are shown in Table 1.

[0112]

[0113] Table 1 Solenoid valve control strategy function table

[0114] As shown in Table 1, the solenoid valve automatic control strategy is divided into six states:

[0115] 1. When the real-time pressure P value collected by the controller is less than the target lower limit of the boost pressure of the liquid storage tank, that is, the boost lower limit P1, the pressure of the liquid storage tank is too low and needs to be pressurized. The automatic boost solenoid valve, that is, the solenoid valve A1, opens and the liquid storage tank starts to be pressurized;

[0116] 2. When the collected real-time pressure value P is between the preset boost pressure values ​​P1 and P2 of the liquid storage tank, the current boost pressure of the liquid storage tank is within the target requirement range, the automatic boost solenoid valve is closed, and the liquid storage tank pressure maintains the current pressure value.

[0117] 3. When the collected real-time pressure value P is greater than the target upper limit P2 of the liquid storage tank pressure increase, the liquid storage tank pressure reaches the preset upper limit and the pressure increase stops, and the automatic pressure increase solenoid valve A1 is closed;

[0118] 4. When the collected real-time pressure value P is less than the pressure relief lower limit P3, the automatic pressure relief solenoid valve A2 is closed and the liquid storage tank stops releasing pressure;

[0119] 5. When the collected real-time pressure value P is between the preset pressure relief pressure values ​​P3 and P4 of the liquid storage tank, the current pressure relief pressure of the liquid storage tank is within the target requirement range, the automatic pressure relief solenoid valve is closed, and the pressure relief pressure of the liquid storage tank maintains the current pressure value;

[0120] 6. When the collected real-time pressure value P is greater than the target upper limit P4 of the liquid storage tank pressure relief, the liquid storage tank pressure relief reaches the preset upper limit, the automatic pressure relief solenoid valve A1 opens, and the liquid storage tank begins to relieve pressure. The software of the liquid storage tank automatic pressure boosting control system is developed using the LabVIEW computer language developed by National Instruments Corporation of the United States.

[0121] The automatic control system for the liquid storage tank pressure is divided into manual and automatic control; in the automatic control system process, the controller reads the preset pressure values ​​P1, P2, P3, and P4 input by the host computer software, and collects the real-time pressure P of the liquid storage tank. The controller will perform calculations and logical judgments according to the control strategy in Table 1, and control the on and off of the boost and relief solenoid valves according to the corresponding judgment results. The program control logic of the control system software, such as Figure 3 shown.

[0122] The manual control module can directly click or close the solenoid valve A1 or solenoid valve A2, and directly send an on-off signal to the solenoid valve without the controller logic calculation to adjust the pressure of the liquid storage tank. The manual control and automatic control in the program complement each other in the actual test process, and the appropriate control module can be selected according to different test conditions or on-site equipment status.

[0123] Labview is a graphical editing language G for writing programs, and the generated programs are in the form of block diagrams. Like C and C# languages, Labview is also a general programming system with a huge database that can complete any programming task. The software of the automatic control system of the liquid storage tank pressure consists of a user login module, an automatic control module, a manual control module, a monitoring module, a data recording module, etc. Figure 4 shown.

[0124] After the test personnel power on the hardware equipment, they open the host computer software and log in. When the host computer software enters the running state, the monitoring module is also started at the same time to monitor the system status in real time, including the on-off status of the two solenoid valves and all pressure and liquid level signals. By inputting the predetermined set pressure range, the controller adjusts the on-off of the solenoid valve according to the program to achieve the regulation and control of the pressure of the liquid storage tank. The data recording module records the pressure and liquid level of the liquid storage tank once a minute and stores them in real time in the formulated document.

[0125] The hardware of the automatic pressurization measurement and control system for liquid storage tanks is based on the CRIO-9066 controller of National Instruments. The CRIO series controller is developed by National Instruments for the small automation business market. It is equipped with an Intel Atoms quad-core processor and provides NI-DAQmx support for SD card slots for data, monitoring and control. The controller includes Labview FPGA module support, and the use of a unified development platform helps improve system performance, simplify system design, and enable developers to develop systems more quickly. In addition, it also has an SDCH slot and various connection ports, including: an RJ-45 Gigabit Ethernet, a USB host, a USB device, and an RS-232 serial port. It can provide a variety of protocols for communication with the host computer, which can meet the control requirements of the automatic pressurization measurement and control system for liquid nitrogen tanks.

[0126] The pressure transmitter is Rosemount's 3501 pressure transmitter, which can measure and transmit various pressure parameters and is widely used in various industries such as energy, chemical, food, and aerospace. Its working principle is to use a sensor made of a special silicon microelastic material. When the measured pressure acts on the sensor, the sensor will produce a smile deformation and convert the pressure into an electrical signal. After circuit processing and amplification, the signal is output as a standard voltage or current signal to achieve pressure measurement and control. The measurement accuracy of the 3501 pressure transmitter reaches 0.05%, the range ratio is 100:1, and the maximum working pressure is 17.3MPa. It has stable and reliable performance and can meet the requirements of liquid tank pressure measurement. The actuator solenoid valve selects the low-temperature solenoid valve of Xiaoli Machinery Model DJ061F-25P, whose minimum operating temperature can reach -196℃. It has the characteristics of long working life, simple internal structure, few faults, and easy maintenance. It is suitable for controlling the on and off of liquid nitrogen pipelines. The hardware design of the automatic control system of liquid tank pressure is as follows Figure 2 shown.

[0127] According to this embodiment, the control system uses the CRIO-9066 controller and Labview programming software of National Instruments Co., Ltd. of the United States to design the liquid storage tank control system, which can collect and display the pressure of the liquid storage tank in real time. The upper computer pre-sets the pressure value range of the boost and pressure relief, and after the controller calculates and judges, the electromagnetic valve of the boost and pressure relief pipeline is controlled to be on and off, thereby realizing the automatic pressure regulation and stabilization of the pressure of the liquid storage tank during the test process.

[0128] The results of twenty actual thermal tests of BZ1200 vacuum equipment show that after the automatic voltage stabilization system is used, the heat sink temperature fluctuation decreases by an average of 53%. Figure 5 As shown, the amount of liquid nitrogen used was reduced by 15.1%. The comparison of liquid nitrogen usage is shown in the figure below. Figure 6As shown in the figure, the on-duty personnel changed from irregularly operating the manual stop valve to regularly inspecting the liquid storage tank pressure, which greatly reduced the workload. The automatic control system of the liquid nitrogen storage tank pressure operated stably and reliably during the test process. The control of pressure and heat sink temperature during the test met the requirements of relevant test standards. Compared with manual control, it reduced the temperature fluctuation of the heat sink, saved the use of liquid nitrogen, improved the work efficiency of the test personnel, and improved the safety of operation.

[0129] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0130] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0131] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. An automatic control liquid storage tank, characterized in that: include: Liquid storage tank; the liquid storage tank is provided with a pressure relief pipeline and a pressure boost pipeline; The boost pipeline can be opened and closed manually or automatically; the pressure relief pipeline can be opened and closed manually or automatically.

2. The automatic control liquid storage tank according to claim 1, characterized in that: The boost pipeline includes: a manually controlled boost on-off pipeline and an automatic boost on-off pipeline; the manually controlled boost on-off pipeline is connected to the liquid storage tank, and a manual stop valve is arranged along the liquid outlet direction; the automatic boost on-off pipeline is connected to the liquid storage tank, and a manual stop valve and a solenoid valve A1 are arranged in sequence along the liquid outlet direction.

3. The automatic control liquid storage tank according to claim 2, characterized in that: The pressure relief pipeline includes: a manually controlled pressure relief on-off pipeline and an automatic pressure relief on-off pipeline; the manually controlled pressure relief on-off pipeline is connected to the liquid storage tank, and a manual stop valve is arranged along the liquid outlet direction; the automatic pressure relief on-off pipeline is connected to the liquid storage tank, and a manual stop valve and a solenoid valve A2 are arranged in sequence along the liquid outlet direction.

4. The automatic control liquid storage tank according to claim 1, characterized in that: Also includes: A pressure measuring pipeline; the pressure measuring pipeline is arranged on the liquid storage tank; the pressure measuring pipeline is installed with a pressure sensor for collecting the pressure value of the liquid storage tank.

5. The automatic control liquid storage tank according to claim 3, characterized in that: Also includes: Measurement and control system, pressure transmitter; The measurement and control system is connected to the pressure transmitter; The pressure transmitter is connected to the solenoid valve A1 and the solenoid valve A2; The measurement and control system comprises: a CRIO-9066 controller; The pressure transmitter includes: a 3501 type pressure transmitter.

6. The automatic control liquid storage tank according to claim 5, characterized in that: Also includes: Interface interaction equipment; The interface interaction device is connected to the measurement and control system and is used to feed back the pressure condition of the liquid storage tank.

7. A method for automatically controlling the pressure of a liquid nitrogen storage tank, used for the automatic control liquid storage tank according to any one of claims 1 to 6, characterized in that: include: Step S1: Initialize the system and determine whether the initialization is successful; If the answer is yes, execute step S3; If the answer is no, then execute step S2; Step S2: Notify the operator to manually control the solenoid valve to adjust the pressure through the interface interaction device, and then end; Step S3: Collect the real-time pressure value P and set the pressure limit by automatically controlling the measurement and control system of the liquid storage tank; Step S4: According to the real-time pressure value P and the pressure limit, the pressure value of the liquid storage tank is adjusted by automatically controlling the pressure regulator of the liquid storage tank.

8. The method for automatic pressure control of a liquid nitrogen storage tank according to claim 7, characterized in that: In the step S3, the pressure limits are set by the operator, including: a boost lower limit P1, a boost upper limit P2, a pressure relief lower limit P3, and a pressure relief upper limit P4; In step S4: the pressure of the liquid storage tank is adjusted by a PID increment algorithm; the mathematical expression of the PID increment algorithm is: Among them, u(k) is the output of the k-th controller; e(k) is the input error of the k-th controller, that is, the difference between the set value and the actual value; Kp, Ki, Kd are the control parameters of the three links of proportional coefficient, integration and differentiation respectively; T is the control period; e(i) is the cumulative sum of the errors up to the k-1th time.

9. The method for automatic pressure control of a liquid nitrogen storage tank according to claim 8, characterized in that: In the step S4, when the real-time pressure value P is less than the boost lower limit P1, the solenoid valve A1 is opened; When the real-time pressure value P is greater than or equal to the boost lower limit P1 and less than or equal to the boost upper limit P2, the solenoid valve A1 remains closed; If the real-time pressure value P is greater than the boost upper limit P2, the solenoid valve A1 is closed; If the real-time pressure value P is less than the pressure relief lower limit P3, the solenoid valve A2 is closed; When the real-time pressure value P is greater than or equal to the pressure relief lower limit P3 and less than or equal to the pressure relief upper limit P4, the solenoid valve A2 remains closed; When the real-time pressure value P is greater than the pressure relief upper limit P4, the solenoid valve A2 opens.

10. The method for automatic pressure control of a liquid nitrogen storage tank according to claim 9, characterized in that: In the step S4, the solenoid valve is adjusted, and a manual control mode and an automatic control mode can be selected through an interface interaction device.

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