Closed-loop control method and system for internal gas pressure of neutron tubes

Abstract

This invention belongs to the field of vacuum electronic device control technology, specifically relating to a closed-loop control method and system for the internal gas pressure of a neutron tube. The method includes the following steps: S1, constructing a multi-dimensional parameter synchronous acquisition and preprocessing link, establishing a high-frequency synchronous acquisition mechanism, and acquiring the real-time operating status parameters of the neutron tube system, including ion source current, anode high voltage, and tube temperature; S2, performing soft measurement of the actual gas pressure based on the Penning discharge equation, constructing a decoupled observer based on the real-time operating status parameters, eliminating the interference of anode high voltage fluctuations and tube temperature changes on the ion source current, and calculating the actual observed gas pressure value inside the neutron tube. This invention achieves rapid gas pressure response with no overshoot throughout, significantly reducing the risk of neutron tube high-voltage breakdown and ensuring consistent control across the entire temperature range.

Description

Technical Field

[0001] This invention belongs to the field of vacuum electronic device control technology, specifically relating to a closed-loop control method and system for the internal gas pressure of a neutron tube. Background Technology

[0002] In a neutron tube, a suitable and stable internal gas pressure is crucial for ensuring stable neutron production and preventing high-pressure breakdown. Gas pressure regulation is typically achieved by controlling the heating current of the hydrogen storage device: during heating, the hydrogen storage material releases gas, increasing the pressure; during cooling, the material adsorbs gas, decreasing the pressure.

[0003] However, existing technologies face two major challenges in controlling neutron tube pressure. First, the lack of direct measurement methods leads to inaccurate readings. Since a vacuum gauge cannot be installed inside the sealed neutron tube, current technologies typically use ion source current as a simple indicator of pressure. However, the ion source current is not only affected by pressure but also strongly influenced by anode voltage fluctuations and magnetic field temperature drift. For example, if the anode high voltage fluctuates, the controller may misinterpret this as a pressure change and incorrectly adjust the hydrogen storage tank, causing system oscillations.

[0004] Secondly, there is a significant thermal inertia hysteresis, leading to instability. From the change in heating current to the heating filament temperature rise, and then to the gas release and diffusion to the ion source, the hydrogen storage device experiences a pure hysteresis of seconds and a thermal inertia of tens of seconds. Traditional PID controllers only adjust when errors are detected, often resulting in over-adjustment and significant gas pressure overshoot, which can easily trigger high-voltage insulation breakdown accidents. Therefore, a control method that can accurately decouple the gas pressure signal and overcome thermal inertia is urgently needed. Summary of the Invention

[0005] This invention provides a closed-loop control method and system for the internal gas pressure of a neutron tube, in order to solve the technical problems in the prior art where the gas pressure of a neutron tube is inaccurately measured and unstable, which easily leads to high-voltage insulation breakdown.

[0006] In a first aspect, the present invention provides a closed-loop control method for the internal gas pressure of a neutron tube, comprising the following steps:

[0007] S1. Construct a multi-dimensional parameter synchronous acquisition and preprocessing link, establish a high-frequency synchronous acquisition mechanism, and obtain the real-time operating status parameters of the neutron tube system, including ion source current, anode high voltage and tube temperature.

[0008] S2, based on the Penning discharge equation, performs real gas pressure soft measurement, constructs a decoupled observer based on real-time operating status parameters, removes the interference of anode high pressure fluctuation and tube temperature change on ion source current, and calculates the real gas pressure observation value inside the neutron tube.

[0009] S3 executes feedforward predictive control based on the thermodynamic inverse model. Based on the deviation between the actual gas pressure observation value and the target gas pressure and the rate of change of gas pressure, the total thermal power demand of the hydrogen storage tank is calculated in reverse using the inverse dynamic model to compensate for the thermal inertia lag of the hydrogen storage tank.

[0010] S4 calculates and outputs the heating control current, converts the total heat power demand into the corresponding heating current command, and applies a non-negative limit to the heating current command to drive the hydrogen storage tank to regulate the internal gas pressure.

[0011] Furthermore, the actual observed pressure inside the neutron tube is calculated, satisfying the following expression:

[0012]

[0013] in, For the first Real-time air pressure readings at any given moment; The ion source current after power frequency notch filtering; High voltage at the anode; This is a temperature correction factor; This is the sensitivity normalization coefficient; A very small constant to prevent division by zero errors.

[0014] Furthermore, temperature correction factor Satisfy the following expression:

[0015]

[0016] in, For the first The temperature of the neutron tube at any given time; For calibration reference temperature; is the magnetocaloric attenuation coefficient, used to characterize the change in ionization efficiency caused by the weakening of the magnetic field of the ion source at high temperatures.

[0017] Furthermore, the total thermal power requirement of the hydrogen storage tank is calculated using the inverse dynamics model, satisfying the following expression:

[0018]

[0019] in, For the first Total heat power demand at any given time; This is the proportional driving coefficient; This represents the current air pressure error. The differential damping coefficient; This refers to the rate of change of air pressure. To maintain power for heat dissipation.

[0020] Furthermore, the heat loss sustaining power is achieved by... The pressure is obtained by multiplying the real-time observed value of the gas pressure at any given moment by the preset comprehensive heat dissipation coefficient; the comprehensive heat dissipation coefficient is used to characterize the proportion of energy injected to maintain the temperature of the hydrogen storage filament at the current gas pressure.

[0021] Furthermore, the heating control current is calculated and output, specifically including:

[0022] The calculated total heat power demand is subject to a non-negative constraint. If the total heat power demand is less than zero, it is set to zero; if it is greater than or equal to zero, it is kept as is.

[0023] Divide the total thermal power demand after non-negative constraints by the hot resistance of the hydrogen storage filament to obtain the power-resistance ratio.

[0024] The final output heating current control command is obtained by taking the square root of the power-resistance ratio.

[0025] Furthermore, in S1, the lower-level FPGA of the Aohua IPS ground system synchronously collects the ion source current, anode high voltage, and tube temperature at a frequency of 100Hz.

[0026] Furthermore, the ion source current needs to be processed by a 50Hz power frequency notch filter after acquisition to filter out power grid frequency interference.

[0027] Furthermore, the anode high voltage ranges from 2kV to 4kV.

[0028] Secondly, the present invention provides a closed-loop control system for the internal gas pressure of a neutron tube, including a memory and a processor. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the above-mentioned closed-loop control method for the internal gas pressure of a neutron tube is implemented.

[0029] The beneficial effects are as follows: This invention proposes a composite control architecture of multi-parameter decoupled soft measurement + thermodynamic inverse model feedforward. First, by constructing a decoupled observer, the influence of high-pressure fluctuations and temperature on ion flow is eliminated, solving the problem of inaccurate gas pressure measurement inside the sealed neutron tube and preventing erroneous adjustments caused by voltage fluctuations. Second, by utilizing the thermodynamic inverse model of the hydrogen storage device, the required heating power is calculated backward based on the target gas pressure change rate, realizing early braking and overpressure drive, effectively overcoming the large hysteresis thermal inertia of the hydrogen storage device, achieving rapid gas pressure response with no overshoot throughout the process, significantly reducing the risk of neutron tube high-pressure breakdown, and ensuring consistent control across the entire temperature range. Attached Figure Description

[0030] Figure 1 This is a flowchart of the present invention.

[0031] Figure 2This is a comparison diagram of the pressure step response and thermal inertia suppression effect in this invention.

[0032] Figure 3 This is a graph showing the heating current control based on the inverse dynamics model in this invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] An embodiment of the closed-loop control method for internal gas pressure in a neutron tube provided by this invention:

[0035] like Figure 1 As shown, the closed-loop control method for the internal gas pressure of a neutron tube includes the following steps:

[0036] S1. Construct a multi-dimensional parameter synchronous acquisition and preprocessing link, establish a high-frequency synchronous acquisition mechanism, and obtain the real-time operating status parameters of the neutron tube system, including ion source current, anode high voltage and tube temperature.

[0037] Specifically, the stable operation of a neutron tube depends on precise sensing of its internal state. However, since sensors cannot be directly implanted, it must rely on externally measurable electrical and environmental parameters. Therefore, this embodiment establishes a high-frequency synchronous acquisition mechanism, using the lower-level FPGA of the Aohua IPS ground system to synchronously acquire the following signals at a frequency of 100Hz:

[0038] Ion source current This is the discharge current flowing through the anode of the ion source, which is the most important signal reflecting changes in internal gas pressure. Since there may be high-frequency noise during the discharge process, this signal needs to be processed by a 50Hz power frequency notch filter after acquisition to filter out power grid frequency interference.

[0039] Anode high pressure The pulsed high voltage applied to the ion source, typically ranging from 2kV to 4kV, directly affects the ionization efficiency of the gas and is therefore a necessary decoupling parameter.

[0040] Tube body temperature The ambient temperature of the neutron tube casing affects the thermal motion speed of the gas and the magnetic field strength of the magnet inside the ion source, which in turn affects the discharge current.

[0041] By establishing a high-frequency synchronous acquisition and preprocessing link, key parameters reflecting the operating status of the neutron tube can be obtained in real time and accurately, providing a reliable data foundation for subsequent real gas pressure decoupling calculations.

[0042] S2, based on the Penning discharge equation, performs real gas pressure soft measurement. A decoupled observer is constructed based on real-time operating status parameters to eliminate the interference of anode high pressure fluctuations and tube temperature changes on the ion source current, and calculates the real gas pressure observation value inside the neutron tube.

[0043] Specifically, in order to obtain accurate air pressure observations It must be from the ion source current High voltage stripped from the anode and tube temperature Interference. Based on Townsend discharge theory and Penning source characteristics in gas discharge physics, ion flow With air pressure Approximately The relationship is such that this step performs an inverse transformation to construct a decoupled observer.

[0044] The calculation of actual air pressure observations satisfies the following expression:

[0045]

[0046] in, Indicates the first The actual air pressure observation value at any given time is the net air pressure after removing disturbances, and it serves as the feedback quantity for closed-loop control. This is the measured ion source current; This is the anode high voltage, which is used to eliminate false pressure fluctuations caused by high voltage power supply ripple. It is a very small constant, such as 1V, used to prevent division by zero errors when the instrument has not ignited or when the high voltage drops to 0 instantaneously; The sensitivity normalization coefficient is determined by the factory calibration and maps the current value to the pressure value.

[0047] Temperature correction factor in the formula Defined as:

[0048]

[0049] in, This represents the currently measured tube temperature. To calibrate the reference temperature, such as 25℃; This is the magnetocaloric attenuation coefficient; its physical significance lies in the fact that high temperatures weaken the magnetic field of the ion source magnet, thereby reducing the electron cyclotron radius and ionization efficiency, leading to a decrease in current at the same gas pressure. To obtain the true gas pressure, this coefficient needs to be multiplied for gain compensation. This coefficient is obtained by fitting the ion current changes at the same gas pressure under different temperatures through a temperature chamber experiment.

[0050] The calculation example is as follows:

[0051] Let the sensitivity normalization coefficient be set V / A·Pa, minimum constant V, magnetothermal attenuation coefficient / ℃, Calibration reference temperature ℃;

[0052] The currently collected data is: ion source current. A, Anode high pressure V, tube temperature ℃;

[0053] First, calculate the temperature correction factor. :

[0054] ;

[0055] Then calculate the actual air pressure observation value. :

[0056] .

[0057] Through the above decoupled observation formula, regardless of the fluctuation of high pressure or the change of temperature, the controller can accurately assess the actual density of deuterium and tritium molecules inside the tube, effectively eliminating false pressure interference and providing accurate feedback for closed-loop control.

[0058] S3 executes feedforward predictive control based on the thermodynamic inverse model. Based on the deviation between the actual gas pressure observation value and the target gas pressure and the rate of change of gas pressure, the total thermal power demand of the hydrogen storage tank is calculated in reverse using the inverse dynamic model to compensate for the thermal inertia lag of the hydrogen storage tank.

[0059] Specifically, the hydrogen storage device is a typical first-order thermal inertial element. In order to eliminate hysteresis, this step adopts the inverse dynamics approach, which decomposes the complex control law into two sub-steps: power demand calculation and current command conversion.

[0060] First, calculate the total heat power requirement. :

[0061]

[0062] in, This is due to air pressure error; It is the proportional drive coefficient with dimensions [W / Pa], which provides positive heating power when the gas pressure is low; The differential damping coefficient is... This constitutes the differential damping term. When the air pressure rises rapidly, this term becomes negative, forcibly deducting the heating power. This is the core of preventing overshoot. To maintain power for heat dissipation.

[0063] Among them, heat loss maintenance power The estimate is:

[0064]

[0065] The overall heat dissipation coefficient, in its physical sense, means that even if the gas pressure reaches the target, in order to maintain the temperature of the hydrogen storage filament, energy equal to the heat dissipation power must be continuously injected.

[0066] Example calculation based on the following parameters:

[0067] Set target air pressure Pa, current air pressure Pa (rising), air pressure error Pa, rate of change of air pressure Pa / s (rapid rate of increase);

[0068] Setting coefficients: W / Pa, W·s / Pa, W / Pa;

[0069] First, calculate the heat loss sustaining power: Then calculate the total heat power requirement: .

[0070] As can be seen, although the air pressure has not yet reached the target value, i.e., the error... However, due to the rapid ascent, the differential damping term deducted 5W of power, which served as an early brake to prevent the air pressure from overshooting.

[0071] By introducing inverse mode control based on the thermal balance equation, the controller has the ability to predict. Before the gas pressure approaches the set value, the control power will decrease in advance according to the rate of change of gas pressure, which perfectly offsets the thermal inertia of the hydrogen storage tank and achieves a fast response without overshoot.

[0072] S4 calculates and outputs the heating control current, converts the total heat power demand into the corresponding heating current command, and applies a non-negative limit to the heating current command to drive the hydrogen storage tank to regulate the internal gas pressure.

[0073] Specifically, since the calculated total heat power demand may be negative, for example, when a rapid pressure reduction is required, the differential term is very large, and physically, negative power cannot be injected, i.e., active cooling is not possible. Therefore, a non-negative power limit needs to be imposed on the power, and Joule's law needs to be applied. Convert power into current.

[0074] Heating control current The calculation satisfies the following logic:

[0075]

[0076] in, The hot resistance of the hydrogen storage filament is a function. The negative power is forcibly set to 0, that is, the current is cut off, and natural cooling is relied upon.

[0077] Continuing with the example data from S3: Calculated total heat power demand W; Assuming the thermal resistance of the hydrogen storage filament. Then the heating control current is:

[0078]

[0079] If calculated -5W, for example, when there is a severe pressure overshoot. When the current output is 0A, the system will stop heating and wait for natural cooling.

[0080] Figure 2 The paper presents a comparison between the pressure step response and the thermal inertia suppression effect after applying this method. It can be seen that there is a large overshoot and oscillation after the pressure reaches the set value; the pressure decelerates smoothly and converges monotonically when it approaches the target value, with no overshoot throughout the process.

[0081] Figure 3 The heating current control curve is shown. During the start-up phase, the current is output at full amplitude. When the air pressure is close to the target value but has not yet reached it, the current curve shows a significant trough, such as dropping to or even below the steady-state value, which is to counteract thermal inertia. Subsequently, the current rises and stabilizes at the thermal equilibrium maintenance baseline.

[0082] This nonlinear control law based on power balance is more in line with the physical nature of Joule heating than linear PID, and can achieve predictive control effect of current dropping before air pressure arrives, ensuring the safety and stability of air pressure control.

[0083] An embodiment of the closed-loop control system for the internal gas pressure of a neutron tube provided by the present invention:

[0084] The closed-loop control system for the internal gas pressure of a neutron tube includes a processor and a memory. The memory stores computer program instructions, which, when executed by the processor, implement the aforementioned closed-loop control method for the internal gas pressure of a neutron tube.

[0085] The closed-loop control system for the internal gas pressure of the neutron tube also includes other components well known to those skilled in the art, such as communication interfaces, the setup and functions of which are known in the art and will not be described in detail here.

[0086] In this invention, the aforementioned memory can be any tangible medium containing or storing a program that can be used or combined with an instruction execution system, apparatus, or device. For example, a computer-readable storage medium can be any suitable magnetic or magneto-optical storage medium, such as Resistive Random Access Memory (RRAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Enhanced Dynamic Random Access Memory (EDRAM), High-Bandwidth Memory (HBM), Hybrid Memory Cube (HMC), etc., or any other medium that can be used to store desired information and can be accessed by an application, module, or both. Any such computer storage medium can be part of a device or accessible to or connected to a device. Any application or module described in this invention can be implemented using computer-readable / executable instructions stored or otherwise maintained by such a computer-readable medium.

[0087] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A closed loop control method for the internal gas pressure of a neutron tube, characterized in that, Includes the following steps: S1. Construct a multi-dimensional parameter synchronous acquisition and preprocessing link, establish a high-frequency synchronous acquisition mechanism, and obtain the real-time operating status parameters of the neutron tube system, including ion source current, anode high voltage and tube temperature. S2, based on the Penning discharge equation, performs real gas pressure soft measurement. A decoupled observer is constructed based on real-time operating parameters to isolate the interference of anode high-pressure fluctuations and tube temperature changes on the ion source current. The actual gas pressure observation value inside the neutron tube is then calculated, satisfying the following: For the first Real-time air pressure readings at any given moment; The ion source current after power frequency notch filtering; High voltage at the anode; This is a temperature correction factor; This is the sensitivity normalization coefficient; A very small constant to prevent division by zero errors; Temperature correction factor satisfy: For the first The temperature of the neutron tube at any given time; For calibrating the reference temperature; is the magnetocaloric attenuation coefficient, used to characterize the change in ionization efficiency caused by the weakening of the magnetic field of the ion source at high temperatures; S3 executes feedforward predictive control based on an inverse dynamics model. Based on the deviation between the actual observed gas pressure and the target gas pressure, as well as the rate of change of gas pressure, the total thermal power demand of the hydrogen storage tank is calculated using the inverse dynamics model to compensate for the thermal inertia lag of the hydrogen storage tank. The total thermal power demand satisfies: For the first Total heat power demand at any given time; This is the proportional driving coefficient; This represents the current air pressure error. The differential damping coefficient; This refers to the rate of change of air pressure. To maintain power for heat dissipation; The heat loss sustaining power is achieved by... The pressure is obtained by multiplying the real-time observed value of the gas pressure at any given moment by the preset comprehensive heat dissipation coefficient; the comprehensive heat dissipation coefficient is used to characterize the proportion of energy injected to maintain the temperature of the hydrogen storage filament at the current gas pressure. S4 calculates and outputs the heating control current, converts the total heat power demand into the corresponding heating current command, and applies a non-negative limit to the heating current command to drive the hydrogen storage tank to regulate the internal gas pressure.

2. The closed-loop control method for internal gas pressure of a neutron tube according to claim 1, characterized in that, Calculate and output the heating control current, specifically including: The calculated total heat power demand is subject to a non-negative constraint. If the total heat power demand is less than zero, it is set to zero; if it is greater than or equal to zero, it is kept as the original value. Divide the total thermal power demand after non-negative constraints by the hot resistance of the hydrogen storage filament to obtain the power-resistance ratio. The final output heating current control command is obtained by taking the square root of the power-resistance ratio.

3. The closed-loop control method for internal gas pressure of a neutron tube according to claim 1, characterized in that, In S1, the lower-level FPGA of the Aohua IPS ground system synchronously collects the ion source current, anode high voltage, and tube temperature at a frequency of 100Hz.

4. The closed-loop control method for internal gas pressure of a neutron tube according to claim 3, characterized in that, After acquisition, the ion source current needs to be processed by a 50Hz power frequency notch filter to filter out power grid frequency interference.

5. The closed-loop control method for internal gas pressure of a neutron tube according to claim 1, characterized in that, The anode high voltage ranges from 2kV to 4kV.

6. A closed-loop control system for the internal gas pressure of a neutron tube, characterized in that, It includes a memory and a processor, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the closed-loop control method for the internal gas pressure of a neutron tube as described in any one of claims 1-5 is implemented.

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