Ultra-high temperature black body cavity radiation source self-adaptive closed-loop temperature control method and system

Abstract

The invention discloses an ultrahigh-temperature blackbody cavity radiation source self-adaptive closed-loop temperature control method and system, and belongs to the field of radiation temperature control, and the method comprises the following steps: S1, collecting a multi-source observation signal of a blackbody cavity in real time, carrying out the time domain alignment processing of the multi-source observation signal to eliminate the dynamic response lag, and carrying out the time domain alignment processing of the multi-source observation signal; performing frequency domain decomposition to separate out a high-frequency component for temperature tracking and a low-frequency component for emissivity identification; s2, constructing a state space observation model, and operating a nonlinear state estimation algorithm based on the state space observation model to update a temperature estimation value and an effective emissivity estimation value; and S3, performing compensation calculation on the target radiation exitance based on the effective emissivity identified in real time, generating a compensation temperature, generating a final heating power instruction, identifying a fault type according to a time-varying feature of an effective emissivity estimation value, and triggering a corresponding maintenance instruction, thereby improving the accuracy of adaptive precise temperature control of the ultra-high temperature black body cavity radiation source.

Description

Technical Field

[0001] This invention relates to the field of radiation temperature control technology, and in particular to an adaptive closed-loop temperature control method and system for an ultra-high temperature blackbody cavity radiation source. Background Technology

[0002] Blackbody radiation sources are indispensable standard metrological instruments in fields such as radiation thermometry, infrared remote sensing, spectral analysis, and the study of high-temperature material properties. As the core equipment for reproducing thermodynamic temperature values, the performance of a blackbody radiation source directly determines the accuracy and reliability of temperature value transmission. In high-end applications such as aerospace engine testing, nuclear reactor monitoring, advanced ceramic sintering processes, and solar simulator calibration, the temperature requirements for radiation sources are increasingly stringent, often needing to cover ultra-high temperature ranges of 2000℃ to 3000℃ or even higher.

[0003] In ultra-high temperature environments, graphite is the preferred material for manufacturing ultra-high temperature blackbody cavities due to its excellent high-temperature resistance, good machinability, and high emissivity. These blackbody sources are typically equipped with high-power DC or AC heating power supplies and require integrated complex water-cooling protection systems to maintain the integrity of the furnace structure. They also operate in a vacuum or high-purity inert gas atmosphere to prevent material oxidation. Current ultra-high temperature blackbody systems have the hardware architecture to generate temperatures exceeding 3000℃, and their temperature measurement methods have generally shifted from contact to non-contact, primarily relying on optical pyrometers, colorimetric pyrometers, or radiation thermometers to infer the temperature value by detecting the radiant brightness at the bottom of the cavity.

[0004] Existing ultra-high temperature blackbody control systems mostly employ classic linear control strategies or model control methods based on fixed parameters. During system startup, open-loop power input or simple closed-loop regulation is typically performed based on a preset temperature rise curve. In the steady-state holding phase, temperature is maintained by fixed PID parameters set by the operator's experience or by static feedforward compensation. Some advanced systems have introduced multi-sensor data fusion technology, attempting to combine voltage and current monitoring signals with optical temperature measurement signals to improve system robustness. Furthermore, to address the drastic temperature-resistivity changes in graphite materials, some solutions embed the material's resistance-temperature characteristic curve into the control model to achieve a certain degree of power pre-compensation.

[0005] For example, the blackbody furnace temperature control system disclosed in Chinese invention patent CN115729139A includes: an AD sampling module, an MCU core module, an RS232 communication module, an isolated RS485 communication module, a four-channel isolated analog output module, a three-channel isolated DO output terminal, and a power supply module; the AD sampling module, RS232 communication module, isolated RS485 communication module, four-channel isolated analog output module, three-channel isolated DO output terminal, and power supply module are respectively connected to the MCU core module.

[0006] For example, Chinese invention patent CN116880156A discloses a reheat steam temperature control method, system, and device based on a dual closed-loop control structure, which includes: obtaining the predicted value of the intermediate variable for the next moment using a fast-changing link nominal model, a slow-changing link nominal model, and an error compensator based on the current flue gas damper opening, the current reheat steam temperature prediction value, and the current reheat steam temperature measurement value; obtaining the intermediate variable target value using an integral-enhanced PID controller based on the error between the reheat steam temperature target value and the current reheat steam temperature measurement value; and obtaining the flue gas damper opening for the next moment using a predictive loop PID controller based on the intermediate variable target value and the next moment's intermediate variable prediction value.

[0007] The above-mentioned technology has at least the following technical problems:

[0008] In existing technologies, the effective emissivity of a blackbody cavity is assumed to be a fixed constant, neglecting the dynamic drift of emissivity caused by graphite sublimation, changes in surface micro-roughness, impurity adsorption, and slight geometric changes in thermal expansion under ultra-high temperature environments. This simplification of the model results in a systematic temperature measurement deviation of 3-5°C caused by an emissivity drift of only 0.1% under high-temperature conditions such as 3000°C. Moreover, this deviation accumulates non-linearly over operating time and is difficult to detect by conventional methods.

[0009] Furthermore, existing temperature control strategies primarily rely on temperature feedback deviations for adjustment. Their internal thermal models do not treat effective emissivity as a time-varying parameter, meaning changes in effective emissivity directly alter the system's radiative heat transfer coefficient. When cavity aging leads to a decrease in emissivity, the actual temperature should rise to maintain the same radiative exitance. However, traditional controllers, due to model mismatch, may incorrectly maintain heating power, resulting in a "false stability" phenomenon. This means that while the temperature sensor readings appear stable based on the incorrect emissivity, the actual output radiant energy deviates significantly from the target value, indicating poor accuracy in adaptive and precise temperature control of ultra-high temperature blackbody cavity radiation sources. Summary of the Invention

[0010] To address the technical problem of poor accuracy in adaptive and precise temperature control of ultra-high temperature blackbody cavity radiation sources in existing technologies, this invention provides an adaptive closed-loop temperature control method and system for ultra-high temperature blackbody cavity radiation sources. The technical solution is as follows:

[0011] On the one hand, an adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source is provided. This method includes: S1, real-time acquisition of multi-source observation signals from the blackbody cavity; time-domain alignment processing of the multi-source observation signals to eliminate dynamic response lag; and frequency-domain decomposition to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. The multi-source observation signals include at least two bands of radiance signals characterizing the thermal radiation state and heating power signals characterizing energy input; S2, establishment of a state vector containing the true thermodynamic temperature and time-varying effective emissivity; construction of a measurement equation describing the nonlinear relationship between radiance and the state vector; and a state equation describing the dynamic evolution of the blackbody cavity's thermal equilibrium, to construct a state-space observation model. A nonlinear state estimation algorithm is run based on the state-space observation model to update the temperature estimate and effective emissivity estimate; S3, compensation calculation of the target radiative exitance based on the real-time identified effective emissivity, generation of a compensation temperature, execution of graded safety control in conjunction with the material safety upper limit, generation of the final heating power command, identification of fault types based on the time-varying characteristics of the effective emissivity estimate, and triggering corresponding maintenance commands.

[0012] On the other hand, an adaptive closed-loop temperature control system for an ultra-high temperature blackbody cavity radiation source is provided. This system includes: a multi-source signal synchronous acquisition and preprocessing module, a real-time parameter inversion module, and a parameter calibration and anomaly diagnosis module. The multi-source signal synchronous acquisition and preprocessing module is used to acquire multi-source observation signals from the blackbody cavity in real time, perform time-domain alignment processing on the multi-source observation signals to eliminate dynamic response hysteresis, and perform frequency-domain decomposition to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. The multi-source observation signals include at least two bands of radiance signals characterizing the thermal radiation state and heating power signals characterizing energy input. The real-time parameter inversion module is used to establish a parameter calibration and anomaly diagnosis module. The state vectors of actual thermodynamic temperature and time-varying effective emissivity are used to construct measurement equations describing the nonlinear relationship between radiance and state vectors, as well as state equations describing the dynamic evolution of thermal equilibrium in a blackbody cavity. This forms a state-space observation model. Based on the state-space observation model, a nonlinear state estimation algorithm is run to update the temperature and effective emissivity estimates. The parameter calibration and anomaly diagnosis module is used to calculate the compensation for the target radiative exitance based on the real-time identified effective emissivity, generate a compensation temperature, perform graded safety control in conjunction with the material safety upper limit, generate the final heating power command, identify the fault type based on the time-varying characteristics of the effective emissivity estimate, and trigger the corresponding maintenance command.

[0013] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0014] 1. This invention provides an adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source. It achieves this by real-time acquisition of multi-source observation signals, time-domain alignment to eliminate dynamic response lag, and frequency-domain decomposition to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. Then, combined with a state-space observation model containing a state vector of the actual thermodynamic temperature and time-varying effective emissivity, a nonlinear state estimation algorithm is used to achieve accurate estimation of temperature and effective emissivity, providing a solid basis for precise temperature control and significantly improving the accuracy of temperature control. Furthermore, an adaptive compensation mechanism based on the real-time identified effective emissivity can adjust the target radiative exitance and temperature setpoint in a timely manner according to changes in actual operating conditions and environmental conditions, effectively adapting to complex and variable operating conditions in ultra-high temperature environments. Finally, a graded safety control strategy is adopted, combining the material safety upper limit to generate the final heating power command, strictly limiting the heating power at multiple levels to prevent overheating and other safety issues. Moreover, by monitoring the time-varying characteristics of the effective emissivity estimate, fault types are identified, timely maintenance commands are triggered, and potential faults are detected and addressed in advance, greatly reducing the risk of safety accidents caused by faults.

[0015] 2. This invention determines the pure time delay between the heating power signal and the temperature response signal based on the cross-correlation function. Compared with traditional estimation methods, it can more accurately quantify the time delay between signals. Combined with ring buffer storage technology to achieve time domain alignment, it not only ensures that the heating power signal and the radiance signals of each band are strictly synchronized on the time axis, but also avoids data distortion caused by time misalignment at the source. Finally, the preprocessed signal is decomposed in the frequency domain using a filtering decomposition algorithm, dividing the signal into high-frequency and low-frequency components. The high-frequency component is extracted from the dynamic change information of the ratio between the radiance signals of each band, which can provide the state observer with key data reflecting the instantaneous temperature fluctuations, helping it to quickly adjust the temperature estimate, greatly improving the real-time performance and dynamic response capability of the temperature estimate, and accurately capturing rapid temperature changes. The low-frequency component is extracted from the trend information of absolute radiance. When it is used to drive the state observer to slowly identify the drift of effective emissivity, since it does not contain high-frequency measurement noise, it effectively suppresses the interference of noise on the effective emissivity estimate, significantly improving the accuracy and stability of the estimate and reducing the estimation fluctuation.

[0016] 3. By identifying the effective emissivity of the blackbody cavity material surface in real time, the required compensation temperature is accurately calculated. Since the surface state of the material changes dynamically with various factors, the effective emissivity changes continuously, making traditional fixed emissivity control methods difficult to adapt. However, this invention can dynamically adjust the compensation temperature based on real-time data. Combined with a feedforward compensation control strategy, the heating power can be predicted and adjusted in advance without waiting for errors to occur before correction, thus significantly improving the accuracy of radiation control. This allows the radiation source to quickly and accurately reach the target radiation state. Finally, the preset safe upper limit of the blackbody cavity material is obtained, and the final control target is set to the smaller value between the compensation temperature and the safe upper limit. When there is a risk that the compensation temperature will exceed the safe upper limit, the control target temperature is forcibly limited to the safe upper limit, and an alarm is triggered, effectively ensuring the safety of the material and preventing damage. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a product structure diagram of the ultra-high temperature tubular cavity blackbody radiation source provided in the embodiments of this application;

[0019] Figure 2 A structural diagram of the temperature controller provided in an embodiment of this application;

[0020] Figure 3 A flowchart of an adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source provided in this application embodiment;

[0021] Figure 4 Emittance tracking and decoupling performance diagrams provided in embodiments of this application;

[0022] Figure 5 Anti-interference comparison diagram provided for embodiments of this application;

[0023] Figure 6 A flowchart for identifying fault types provided in embodiments of this application;

[0024] Figure 7 The lifetime prediction and aging fitting diagram provided for the embodiments of this application.

[0025] The annotations in the attached figures are explained as follows:

[0026] 1. Temperature controller; 2. Start switch; 3. Gas path switching switch; 4. Flow meter; 5. Radiation port; 6. Main power switch; 7. Automatic / Manual; 8. Programming; 9. Run / Pause. Detailed Implementation

[0027] Embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of the present disclosure are shown in the drawings, it should be understood that embodiments of the present disclosure may be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure.

[0028] It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure. In the description of the embodiments of this disclosure, the term "comprising" and similar terms should be understood as open-ended inclusion, i.e., "including but not limited to". The term "based on" should be understood as "at least partially based on". The term "one embodiment" or "this embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc., may refer to different or the same objects.

[0029] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0030] like Figure 1 The diagram shows the product structure of an ultra-high temperature tubular cavity blackbody radiation source. In this diagram, 1 is the temperature controller, 2 is the start switch, 3 is the gas path switching switch, 4 is the flow meter, 5 is the radiation aperture, and 6 is the main power switch. Figure 2The image shows a partial enlarged view of the temperature controller location. In this view, 7 is Automatic / Manual, 8 is Programming, and 9 is Run / Pause. The first key in the second row is the page feed key; press this key to select a new menu. Press the second key in the second row to select a new parameter in the menu. Press the third key in the second row to decrease the parameter value or change the parameter status. Press the fourth key in the second row to increase the parameter value or change the parameter status. Automatic / Manual switches between manual and automatic modes. Manual mode changes the output power, and the PID controller does not operate. Press the first and fourth keys in the second row to select the previous menu. Press the first and third keys in the second row to quickly select the next menu item. Press the second and fourth keys in the second row to select the next parameter item. Press the second and third keys in the second row to quickly select the next parameter item. Press the first and second keys in the second row to return to the main interface / alarm confirmation reset. Turn the main power switch clockwise. Press the power start button. The temperature controller will perform a self-test, and the cooling fan will start. Wait for the temperature controller to complete its self-test. Open the argon gas source valve. Adjust the pressure reducing valve to approximately 0.12 MPa. Turn the gas path switching switch clockwise to the argon bypass position. At this point, the argon flow rate is the same as the argon source flow rate, i.e., the high flow rate. Cover the radiation port for at least 10 seconds. Then maintain the high flow rate for 1 minute. Turn the gas path switching switch counterclockwise to the flow valve position and adjust the flow meter to 5L / Min. Open the water valve, check for leaks, and observe whether water is flowing from the drain outlet. Use the up and down buttons on the temperature controller to set the temperature value, then press the heating switch. You should hear the contactor engage and the transformer make a sound, indicating that the blackbody is heating up according to the power set by the PID parameters. Wait for the blackbody temperature to stabilize before proceeding with infrared calibration.

[0031] like Figure 3 The diagram shown is a flowchart of an adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source provided in this application embodiment. The method includes the following steps:

[0032] S1 acquires multi-source observation signals of the blackbody cavity in real time via a sensor at a frequency of 100Hz. The multi-source observation signals are time-domain aligned to eliminate dynamic response lag, and frequency-domain decomposed to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. The multi-source observation signals include at least two bands of radiance signals characterizing the thermal radiation state and heating power signals characterizing energy input. The radiance signals are output values ​​from photodetectors in two different bands. This solves the dynamic error caused by sensor response lag, improves the initial accuracy of state estimation, and initially separates temperature and emissivity at the physical signal level, thereby improving the accuracy of subsequent temperature control.

[0033] Furthermore, real-time acquisition of multi-source observation signals from the blackbody cavity, previously included:

[0034] Because ultra-high temperature blackbodies undergo thermal expansion and deformation during heating, the center of the radiation aperture can shift by micrometers or even millimeters relative to the fixedly mounted sensor. Furthermore, mechanical vibration or installation errors can also cause optical axis misalignment. If the optical axis deviates, the sensor will receive gray body radiation from the cavity walls or external stray light instead of blackbody radiation from the bottom of the cavity, leading to severe temperature measurement inaccuracies. Therefore, a pan-tilt unit is needed to dynamically compensate for thermal deformation and mechanical errors, achieving real-time automatic alignment of the optical axis with the center of the radiation aperture to ensure the sensor always collects the purest blackbody radiation signal.

[0035] The motorized pan-tilt unit performs a scanning motion, directly causing the optical temperature sensor mounted on it to change its spatial orientation. This ensures that the center of the sensor's field of view covers the potential offset area of ​​the radiation aperture. The scanning motion follows a pre-defined, small-angle two-dimensional scanning path, covering the possible offset area of ​​the radiation aperture. Using a modulated laser beam integrated into the sensor as an auxiliary beacon, and through a photoelectric detection unit associated with the laser beam's optical path, coupled with lock-in amplification detection technology, the maximum reflected light intensity is captured to automatically lock the center position of the radiation aperture. Specifically, during the scanning process, the modulated laser beam integrated within the sensor is synchronously emitted to the blackbody cavity radiation aperture region, and the laser beam's amplitude is modulated using a pre-defined modulation frequency. To distinguish the reflected light from the high-temperature background radiation, a photoelectric detection unit coaxially positioned with the laser beam path receives the reflected light signal. Since the blackbody cavity is in an ultra-high temperature state, there is a strong continuous spectrum thermal radiation background. Using lock-in amplification detection technology, only the signal component with the same frequency as the modulated laser is extracted, thereby filtering out background thermal radiation interference, improving the signal-to-noise ratio of the reflected signal, and recording the demodulated reflected light intensity value at different scanning angles in real time. A correspondence between the reflected light intensity and the scanning angle is established. When the detected reflected light intensity reaches its peak, the center position of the radiation aperture corresponding to the current posture is determined, the motorized pan-tilt unit stops performing the scanning action, and the current position of the motorized pan-tilt unit is locked, thus completing the automatic alignment of the radiation aperture center. Through this method, the traditional manual edge positioning method is automatically replaced, improving alignment accuracy and repeatability. Sub-millimeter-level automatic locking of the radiation aperture center is achieved, eliminating subjective errors of manual alignment and deviations caused by thermal deformation.

[0036] After completing automatic optical path locking, the lens self-diagnostic function is performed to determine whether there is contamination or obstruction in the optical window or lens. Under stable operating conditions, optical observation signals of each band are acquired, and the background noise level and standard optical transmittance baseline value of each detection band are recorded. If the signal attenuation of the current transmittance of any band or multiple bands relative to the optical transmittance baseline exceeds the preset signal attenuation threshold, it is determined that the optical path is abnormal. The high-precision multi-band mode is automatically disabled and switched to single-band temperature measurement mode, while a lens cleaning and maintenance command is output. Otherwise, the optical path is determined to be normal, the high-precision multi-band mode is maintained or enabled, and the optical path is updated in real time according to the currently detected multi-source observation signals. A transmittance baseline is used to compensate for long-term, slow changes. The optical transmittance baseline characterizes the transmission capability of the optical system under normal, clean conditions. The absolute value of the difference between the current optical observation signal in each band and the corresponding transmittance baseline is calculated to obtain the current transmittance attenuation. Optical path anomalies include, but are not limited to, lens dust accumulation, optical window contamination, or partial obstruction. The single-band temperature measurement mode uses a preset empirical emissivity or conservative estimate for temperature calculation. Although the accuracy is slightly reduced, it ensures the continuity of temperature monitoring and avoids data interruption. The high-precision multi-band mode relies on the accurate energy ratio of multiple bands to invert temperature and emissivity, which can produce significant errors when transmittance is uneven. By monitoring transmittance in real time and dynamically switching operating modes, the risk of multi-band algorithm divergence or outputting incorrect high-temperature commands due to lens contamination is avoided, ensuring adaptability of temperature control under different operating conditions.

[0037] Furthermore, due to the thermal inertia of the blackbody cavity heating process, there is a time lag between the heating power signal and the temperature response signal. If this lag is not compensated for, the input data time of the state observer will be inconsistent, thus affecting the accuracy of the joint estimation of temperature and effective emissivity. To eliminate this dynamic response lag, time-domain alignment processing is performed, specifically including:

[0038] The system acquires heating power signals and radiance signals from at least two bands in real time. Based on the cross-correlation function, it analyzes the correlation between the heating power signal and the temperature response signal, identifying the time shift corresponding to the peak value of the cross-correlation function—the pure time lag from power input to temperature response. After obtaining the pure time lag, a ring buffer storage technique is used to align the heating power signal and the radiance signals of each band on the time axis. Specifically, time compensation is applied to the heating power signal based on the pure time lag, aligning it with the radiance signal on the time axis. If the response of the heating power signal is faster than that of the radiance signal, the heating power signal is shifted backward. This process ensures the consistency of multi-source observation data input to the state observer at the same physical moment, thereby avoiding model error propagation due to time misalignment and improving the accuracy of subsequent state estimation.

[0039] After completing time-domain alignment, frequency-domain decomposition is performed to extract information on rapid temperature changes and slow drift of effective emissivity, specifically including:

[0040] A filtering decomposition algorithm is applied to the preprocessed radiance signal and heating power signal. The filtering decomposition algorithm can be a digital filter bank, wavelet decomposition algorithm, or other signal processing methods that can achieve frequency band separation. After filtering decomposition, the signal is divided into high-frequency components and low-frequency components.

[0041] The high-frequency component is extracted from the dynamic change information of the ratio between the radiance signals of each band. This information is used to drive the state observer to quickly track instantaneous temperature fluctuations, thereby improving the response capability to rapid temperature changes. Specifically, the ratio signal is obtained by performing ratio calculation on the radiance signals of each band. According to Wien's displacement law and Planck's formula, this ratio mainly depends on temperature and is not sensitive to changes in emissivity, because emissivity is usually assumed to be equal or have a consistent trend in adjacent bands. A high-pass filter or band-pass filter is applied to the ratio signal, for example, the cutoff frequency is set to 0.1Hz, and its high-frequency component is extracted.

[0042] The low-frequency component is extracted from the trend information of the absolute radiance changing over time. This drives the state observer to slowly identify the drift in effective emissivity, thereby suppressing the interference of high-frequency measurement noise on effective emissivity estimation in the frequency domain. Specifically, a single-band or multi-band absolute radiance signal is selected, representing the absolute value of radiance. This signal is affected by both temperature and effective emissivity. A low-pass filter is applied to the absolute radiance signal, and its low-frequency component is extracted. The cutoff frequency of the low-pass filter can be set to less than 0.001 Hz, corresponding to a time constant greater than 15 minutes. Changes in effective emissivity typically exhibit slow drift characteristics, with a frequency significantly lower than the transient frequency of temperature changes. By decoupling temperature dynamics from emissivity drift in the frequency domain, the interference of high-frequency measurement noise on the effective emissivity estimation results can be effectively suppressed, avoiding spurious oscillations or unreasonable jumps in emissivity estimation.

[0043] S2 establishes a state vector containing the true thermodynamic temperature and time-varying effective emissivity. It constructs measurement equations describing the nonlinear relationship between radiance and the state vector, as well as state equations describing the dynamic evolution of the blackbody cavity's thermal equilibrium, to build a state-space observation model. Based on this model, nonlinear state estimation algorithms, such as extended Kalman filtering, are run to estimate the current temperature and emissivity. The observed radiance signal is used, combined with energy balance relationships, to continuously refine the estimated values ​​of temperature and emissivity. The measurement equations describe the nonlinear relationship between radiance and the state vector. According to Planck's radiation law, there is a complex mathematical relationship between radiance, temperature, and emissivity; this equation helps link radiance with temperature and emissivity. The state equations, based on thermodynamic principles, describe the dynamic changes in the blackbody cavity's thermal equilibrium. This equation reflects the influence of factors such as input heating power, emissivity, radiation loss, and environmental heat loss on temperature. Temperature and emissivity are separated in real time without requiring offline calibration, completely resolving the inherent error in single-band temperature measurement when emissivity changes.

[0044] Furthermore, a nonlinear state estimation algorithm is run, specifically including:

[0045] A state vector is constructed, with the true temperature and effective emissivity of the blackbody cavity serving as both state variables. The true temperature is used as the first state variable, and the effective emissivity as the second state variable, together forming a two-dimensional state vector. This state vector characterizes the thermal state and radiation characteristics of the blackbody cavity at the current moment. By unifying temperature and effective emissivity into the state variables, coupled modeling and decoupled estimation of these two parameters can be achieved within a unified mathematical framework.

[0046] The current state is predicted to obtain the predicted temperature and effective emissivity. The state equation, i.e., the prediction model, is constructed as follows: Temperature prediction: The temperature value at the previous moment is added to a correction factor, which is equal to the control cycle duration multiplied by the net heating power and then divided by the set heat capacity value. The net heating power is equal to the input heating power minus the radiative heat dissipation power. The radiative heat dissipation power is calculated according to the Stefan-Boltzmann law, i.e., the Stefan constant, the radiant area, and the fourth power of the previous emissivity estimate and the previous temperature estimate. Emissivity prediction: The previous emissivity estimate is directly used as the predicted value at the current moment, and a small process noise term is superimposed to characterize the slow drift of emissivity over time. The process noise term is set by the pre-set personnel based on practical experience.

[0047] like Figure 4The emissivity tracking and decoupling performance graphs are shown. The horizontal axis represents time (0-200s), the left vertical axis represents temperature (2490-2510K), and the right vertical axis represents effective emissivity (0.85-1.00). A contamination fault, where the emissivity suddenly drops from 0.98 to 0.92, was simulated at t=100s. The results show that this application achieved emissivity reconvergence within 5 seconds, and the temperature reading remained stable throughout without spurious drops. In contrast, the traditional algorithm with a fixed emissivity assumption produced a temperature measurement bias of nearly 40K, demonstrating that the hierarchical update strategy can achieve decoupling between temperature and emissivity; that is, when emissivity changes abruptly, the temperature estimate does not drift, and the emissivity converges quickly.

[0048] Within each preset control cycle, such as a ten-millisecond control cycle, an extended Kalman filter algorithm is executed to predict and update the state vector. A measurement equation is constructed based on the spectral characteristics of the radiance signal in each band to obtain prior estimates of temperature independent of effective emissivity. According to Planck's blackbody radiation law, the measurement equation is a nonlinear function. The measured radiance value for any band is equal to the effective emissivity multiplied by the first radiation constant, then multiplied by the wavelength to the power of negative five, and finally compared with the result of a product of the second radiation constant and wavelength and temperature minus one, with the natural constant as the base and the exponent being the second radiation constant divided by the product of wavelength and temperature. Measurement noise is then added. The emissivity constant, the second emissivity constant, and the measurement noise are set by pre-set personnel based on practical experience. The prior estimate information for temperature that does not depend on changes in effective emissivity is obtained by calculating the ratio of the radiance of the first band to the radiance of the second band. This ratio depends only on temperature and is independent of the specific value of emissivity. In the filter update step, the Kalman gain is first calculated using the prior estimate information to correct the temperature component in the state vector. This step obtains the prior temperature estimate information that does not depend on changes in effective emissivity. Even if the emissivity drifts drastically, the temperature estimate will not be directly misled, thus achieving preliminary decoupling.

[0049] Constraints are constructed using the energy balance relationship between input power and absolute radiance to correct estimation biases in effective emissivity. Based on the principle of energy conservation, the relationship between heating input power, radiative loss, and non-radiative heat loss is used as a constraint equation and introduced into the filtering update process. This constraint couples the estimation of effective emissivity with the actual energy exchange process, thereby suppressing spurious emissivity fluctuations caused by observation noise. The constraint is that, in steady-state or quasi-steady-state conditions, the input power should approximately equal the sum of radiative heat dissipation power and non-radiative heat loss; that is, the input power is approximately equal to the electrothermal conversion efficiency multiplied by the Stefan constant and the radiative heat loss. The product of the radiation area, the current emissivity estimate, and the fourth power of the current temperature estimate, plus a non-radiative heat loss term (which can be identified from historical data and is usually a function of temperature), is used to correct the estimation bias of the effective emissivity. Specifically, the corrected temperature estimate from the previous step is substituted into the constraints to back-calculate the theoretically required emissivity value. The back-calculated theoretical emissivity is compared with the emissivity estimate in the current state vector to calculate the residual. This residual is used to drive the Kalman gain, specifically correcting the emissivity component in the state vector, effectively preventing emissivity estimation divergence caused by sensor drift or background interference.

[0050] like Figure 5 The anti-interference comparison chart shown has the horizontal axis representing time (0-100s) and the vertical axis representing temperature estimation error (-15K to +15K). Under Gaussian white noise with a standard deviation of 50K, the error fluctuation of the traditional single-band temperature measurement method is as high as ±10K. However, this application, by combining multi-band radiance signals and an extended Kalman filter algorithm, strictly limits the error to within ±0.8K, demonstrating the robustness of this application compared to traditional single-band temperature measurement under strong noise. The state is updated based on the measurement equations and constraints, outputting the optimal estimates of the true temperature and effective emissivity at the current moment. This involves combining the state equations and measurement equations into a final matrix form, which serves as the observation model. The extended Kalman filter algorithm is used to calculate the observation residuals, and the predicted state is corrected based on the Kalman gain. After the state update is completed, the optimal estimates of the true temperature and effective emissivity at the current moment are obtained. This achieves accurate estimation of the true temperature and effective emissivity of the ultra-high temperature blackbody cavity radiation source, improving the stability and accuracy of temperature control, reducing temperature fluctuations caused by emissivity variations and measurement errors, and providing a crucial basis for precise temperature control of the ultra-high temperature blackbody cavity radiation source.

[0051] S3 calculates the target radiative exitance based on real-time identified effective emissivity. It then calculates the compensation temperature based on the real-time emissivity to ensure the target radiative exitance is achieved. Combined with the material safety upper limit, it performs graded safety control, generates the final heating power command, identifies the fault type based on the time-varying characteristics of the effective emissivity estimate, and triggers the corresponding maintenance command. This command is sent to the heating control unit to ensure the accuracy of the heating power output, thereby achieving precise control of the blackbody cavity temperature. This approach largely solves the problem of insufficient actual radiant energy despite achievable temperature readings in traditional temperature control, improves the accuracy of radiative measurement of the radiation source output, and prevents accidents caused by excessive heating power and burnout of the blackbody cavity due to blindly pursuing the target radiative exitance.

[0052] Furthermore, based on the material safety upper limit, graded safety controls are implemented, specifically including:

[0053] The target radiative exitance is determined based on the set standard emissivity and the preset temperature set by the user according to actual requirements. The target radiative exitance is equal to the product of the Stefan-Boltzmann constant, the set standard emissivity, and the fourth power of the set temperature. The standard emissivity of the new cavity is typically 0.99. The target radiative exitance represents the radiation power per unit area that the user expects to obtain under ideal conditions. Clearly defining the target radiation energy that the blackbody cavity radiation source needs to achieve provides a benchmark for subsequent temperature control and compensation, ensuring that the radiation source can output radiation energy as expected.

[0054] The required compensation temperature is calculated by back-calculating the effective emissivity identified in real time. The compensation temperature is equal to the fourth root of the quotient obtained by dividing the target radiative exitance by the product of the Stefan-Boltzmann constant and the effective emissivity. Taking into account the changes in the actual emissivity of the material surface, the temperature is dynamically adjusted and compensated to make the radiation characteristics of the radiation source closer to the target state and improve the accuracy of radiation control.

[0055] A preset safe upper limit for the blackbody cavity material is obtained. This value is typically set as a safety margin below the material's melting point; for example, for graphite, it might be set to 3000K, while its melting point is approximately 3600K. The final control target is set as the minimum of the compensation temperature and the safe upper limit, and the heating power of the ultra-high temperature blackbody cavity radiation source is output in conjunction with feedforward compensation. By taking the minimum value as the final control target, the temperature of the blackbody cavity material is ensured not to exceed the safe upper limit, guaranteeing the material's safety and stability. Feedforward compensation control can adjust the heating power in advance, improving the system's response speed and control accuracy to temperature changes, enabling the radiation source to quickly and accurately reach the target radiation state.

[0056] Specifically: If the compensated temperature exceeds the upper limit of the safe temperature, the final control target temperature will be forcibly limited to the upper limit of the safe temperature, and an alarm will be triggered. The alarm indicates that the current radiant energy is lower than the target radiant output, informing the operator that due to material safety limitations, the system can no longer maintain the set radiant brightness and requires maintenance, such as replacing the cavity or recalibrating. In this case, the heating power will only be output with the upper limit of the safe temperature as the target to ensure that the equipment operates under maximum safety capacity and avoids burnout. Otherwise, the final control target temperature will be set to the compensated temperature, and the non-alarm state will be cleared or maintained. The heating power output of the ultra-high temperature blackbody cavity radiation source is as follows: the feedforward power is calculated. Using the real-time identified effective emissivity estimate and the final control target temperature, the theoretical radiative heat dissipation power required to maintain this state is accurately calculated based on the Stefan-Boltzmann law, and the non-radiative heat loss is superimposed to form the feedforward base value. Then, the feedback power is calculated. The deviation between the real-time temperature and the final control target temperature is collected, and a correction value is generated through a PID algorithm to eliminate model errors and external interference, ensuring accurate temperature tracking. Finally, the feedforward and feedback power are added together, and after limiting processing, the power is limited to between 0 and the maximum rated power, which is then converted into a control signal to drive a solid-state relay or a thyristor power regulator.

[0057] like Figure 6 The flowchart shown further illustrates the identification of fault types based on the time-varying characteristics of the effective emissivity estimate, specifically including:

[0058] When the change in effective emissivity exceeds a threshold within a preset time period, and the dispersion of radiance signals across different bands is greater than a dispersion threshold, an optical window occlusion or contamination fault is identified, marked as a Type I fault, and a cleaning and maintenance command is output. The change in effective emissivity is the difference between the effective emissivity at the current moment and the effective emissivity at the start of the time period. The dispersion of radiance signals across different bands is the standard deviation or coefficient of variation between the radiance signals of each band. Under ideal blackbody conditions, the radiance of each band should be highly consistent after emissivity correction. If there is local occlusion or window contamination, the transmittance changes in different bands will be inconsistent, leading to a significant increase in dispersion. By simultaneously monitoring and judging these two parameters, the fault condition of the optical window can be accurately identified. Outputting a cleaning and maintenance command can promptly remind operators to clean or treat the contamination of the optical window, restore its normal function, and ensure the accuracy of radiation measurements.

[0059] like Figure 7The lifespan prediction and aging fitting graph shown has the x-axis representing cumulative operating time (0-2000h) and the y-axis representing effective emissivity. The scatter plot represents simulated long-term aging monitoring data, and the solid line represents the fitting result based on the exponential model in this application. It can be seen that the fitting curve highly overlaps with the measured data, accurately predicting the moment when the emissivity drops to the safe threshold of 0.90, approximately 1850h, providing a reliable basis for preventative maintenance. Based on the time series of effective emissivity, a sliding window linear regression or differential filtering algorithm is used to calculate the real-time decay rate. ,Right now , Let t be the effective emissivity and t be time. When the real-time decay rate of the effective emissivity within a preset time period conforms to the preset material aging trend (i.e., the decay rate is stable and follows an exponential law, rather than a sudden change), it is determined to be an aging fault in the blackbody cavity material, marked as a second type of fault identification. The preset material aging trend is then updated based on the current decay trend, such as updating the aging coefficient. The preset material aging trend characterizes the exponential decay relationship of the effective emissivity of blackbody cavity materials, such as graphite and silicon carbide, with the cumulative high-temperature exposure time. ,in, This represents the effective emission rate at the current moment. Here, k represents the initial emissivity, t represents the aging coefficient, C represents the cumulative high-temperature time, and e represents the noise factor set by the operator. During long-term use, blackbody cavity materials age due to factors such as cumulative high-temperature exposure, leading to a gradual decrease in effective emissivity. By calculating the real-time decay rate and comparing it with the preset aging trend, it is possible to accurately determine whether the material has experienced aging failure. This provides a scientific basis for equipment maintenance and replacement, preventing production accidents caused by sudden material failure.

[0060] When the effective emissivity is less than the lower limit of the preset emissivity constraint range, such as 0.9, it is marked as a maintenance decision, and a maintenance instruction to replace the cavity is generated, so as to maintain the equipment in a timely manner and avoid problems such as increased measurement error caused by severe degradation of material properties.

[0061] If the first type of fault identification, the second type of fault identification, and maintenance decision mentioned above are not triggered, the system is determined to be in normal operation and the current operating state is maintained.

[0062] This application provides an adaptive closed-loop temperature control system for an ultra-high temperature blackbody cavity radiation source, comprising: a multi-source signal synchronous acquisition and preprocessing module, a real-time parameter inversion module, and a parameter calibration and anomaly diagnosis module.

[0063] The multi-source signal synchronous acquisition and preprocessing module is used to acquire multi-source observation signals from the blackbody cavity in real time. It performs time-domain alignment processing on the multi-source observation signals to eliminate dynamic response lag, and frequency-domain decomposition to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. The multi-source observation signals include at least two bands: radiance signals characterizing the thermal radiation state and heating power signals characterizing energy input. Synchronous acquisition of multi-source signals ensures data integrity and consistency, providing a foundation for accurate subsequent analysis of temperature state and effective emissivity. Time-domain alignment processing eliminates dynamic response lag, avoiding analysis errors caused by time differences and improving the accuracy of signal processing. Frequency-domain decomposition separates signal components for different purposes, facilitating specialized processing for temperature tracking and emissivity identification, thus improving processing efficiency and accuracy.

[0064] The real-time parameter inversion module is used to establish a state vector containing the true thermodynamic temperature and time-varying effective emissivity, construct measurement equations describing the nonlinear relationship between radiance and the state vector, and state equations describing the dynamic evolution of the thermal equilibrium of the blackbody cavity, in order to build a state-space observation model. Based on the state-space observation model, a nonlinear state estimation algorithm is run to update the temperature and effective emissivity estimates. By establishing the state vector, measurement equations, and state equations, a complete state-space observation model is constructed. The nonlinear state estimation algorithm can handle complex nonlinear relationships and accurately update the temperature and effective emissivity estimates based on real-time measurement data, providing key parameters for precise temperature control.

[0065] The parameter calibration and anomaly diagnosis module is used to compensate for the target radiative exitance based on the real-time identified effective emissivity, generate a compensated temperature, implement graded safety control in conjunction with the material safety upper limit, generate the final heating power command, identify the fault type based on the time-varying characteristics of the effective emissivity estimate, and trigger corresponding maintenance commands. Parameter calibration improves the accuracy of measurement results through compensation calculation, making the temperature setpoint more reasonable. Graded safety control flexibly adjusts the heating power according to the material safety upper limit, effectively ensuring the safety of the material and avoiding material damage due to overheating. Anomaly diagnosis can promptly detect system faults and guide operators to perform maintenance by triggering corresponding maintenance commands, reducing the impact of faults on system operation and improving the reliability and stability of the system.

[0066] Example 2: Based on Example 1, the nonlinear state estimation algorithm is run, and the following is also included:

[0067] A state vector is constructed, with the true thermodynamic temperature of the blackbody cavity as the first state variable and the effective emissivity as the second state variable, together forming the state vector. Estimating both temperature and emissivity within a single state vector allows for a comprehensive consideration of their mutual influence, resulting in a more complete and accurate description of the blackbody cavity's radiation characteristics and providing complete state information for subsequent filtering algorithms.

[0068] In the filter update phase, instead of the traditional single-step update, a hierarchical update strategy is adopted to execute the extended Kalman filter algorithm, separating high-frequency dynamics from low-frequency dynamics. The hierarchical update strategy includes:

[0069] During the high-frequency component update process, the radiance ratio is calculated in real time. Consistent with the aforementioned prior estimate of temperature independent of effective emissivity changes, this ratio is insensitive to emissivity changes and mainly reflects temperature information. The observation residual between the measured radiance ratio and the theoretical ratio predicted based on the current state is calculated. The estimated temperature state is updated based on the first correction coefficient to track instantaneous temperature fluctuations. That is, the first correction coefficient is introduced, which corresponds to the time constant of the temperature dynamic response, usually on the order of seconds or sub-seconds. The observation residual mentioned above is weighted using this coefficient and is specifically used to update the temperature estimate in the state vector. This process enables the filter to quickly track instantaneous temperature changes caused by power fluctuations or environmental disturbances with high bandwidth, without being disturbed by slow emissivity drift. It adjusts the temperature estimate in a timely manner, improves the tracking ability of instantaneous temperature changes, and makes the temperature estimate closer to the actual value.

[0070] During the low-frequency component update process, the observation residual between absolute radiance and the theoretical radiance predicted based on the aforementioned energy balance relationship is used. This residual primarily reflects the deviation caused by emissivity drift. The estimated effective emissivity is updated based on a second correction coefficient to identify the effective emissivity drift. This second correction coefficient corresponds to the time constant of the emissivity drift dynamic characteristics, typically on the order of minutes, hours, or even days, much larger than the temperature time constant. This coefficient is used to weight the aforementioned observation residual, specifically for updating the effective emissivity estimate in the state vector. By comparing absolute radiance and theoretical radiance, the emissivity drift can be accurately identified and corrected, ensuring the accuracy of the effective emissivity estimate.

[0071] During the filtering iteration process, the process noise covariance matrix is ​​dynamically adjusted based on the statistical characteristics of the observed residuals.

[0072] After the state update is completed and before the final estimate is output, a physical constraint-based projection correction step is performed to output the optimal estimate of the true temperature and the optimal estimate of the effective emissivity at the current moment. The input here is to obtain the temporary output value of the state observer, which includes the temporary temperature and the temporary effective emissivity.

[0073] The set values ​​of the first correction coefficient and the second correction coefficient correspond to the time constant difference between the temperature dynamic response and the emissivity drift dynamic characteristics, respectively, and are preset by the designated personnel.

[0074] Furthermore, the process noise covariance matrix is ​​dynamically adjusted based on the statistical characteristics of the observed residuals, specifically including:

[0075] Calculate the observation residual vector at the current moment. The observation residual vector is the difference between the measured value vector of the sensor at the current moment and the theoretical predicted value vector predicted by the state observer based on the state at the previous moment. Accurately obtaining the observation residual vector is the basis for subsequent analysis of model prediction error and adjustment process noise covariance matrix, and can reflect the difference between model prediction and actual observation.

[0076] A fixed-length sliding window is established, for example, containing the most recent 50 sampling points. The root mean square value of the observation residual vector within this window is calculated to obtain the sliding root mean square value, which reflects the overall energy level of the prediction error at the current moment and provides a quantitative indicator for judging the magnitude of the model prediction error.

[0077] The matrix adjustment index is obtained by comparing the moving root mean square value of the observed residual vector with the preset noise reference value. The matrix adjustment index is used to characterize the deviation of the model prediction error from the measurement noise level. Specifically, it is obtained by adding the base value and the dynamic adjustment term. The base value can be set to 1. The dynamic adjustment term is equal to the product of the sensitivity adjustment factor and the relative residual strength. The relative residual strength is calculated by dividing the absolute value of the moving root mean square value of the observed residual vector at the current moment by the preset noise reference value that represents the normal noise level of the sensor. The sensitivity adjustment factor and the preset noise reference value are set by the preset personnel.

[0078] The process noise covariance matrix is ​​updated in real time based on a matrix adjustment index. The index is multiplied by the covariance matrix. If the index is greater than a preset index (e.g., 1) set by a predefined operator, the covariance matrix value is increased to accelerate filter convergence; otherwise, it is decreased to suppress filter divergence. By dynamically adjusting the process noise covariance matrix, the filtering algorithm can better adapt to the actual changes in the system, improving convergence and stability, and ensuring the accuracy of state estimation.

[0079] Furthermore, a projection correction step based on physical constraints is performed, specifically including:

[0080] The temporary output values ​​of the state observer are obtained from the update step of the extended Kalman filter. These temporary output values ​​include temporary temperature and temporary effective emissivity, providing basic data for subsequent physical constraint corrections.

[0081] If the temporary temperature exceeds the preset temperature constraint range, such as 500K to 3200K, depending on the blackbody material limit, it will be forcibly constrained to the temperature constraint range; otherwise, the temporary temperature will not be corrected. This prevents non-physical high or low temperature estimations caused by abnormal sensor jumps, ensures that the temperature estimation value conforms to physical reality, and improves the reliability of the estimation results.

[0082] If the temporary effective emissivity exceeds the preset emissivity constraint range, it is forcibly constrained to the emissivity constraint range; otherwise, the temporary effective emissivity is not corrected. The lower limit of the emissivity constraint range is 0.9, and the upper limit is 0.999. This ensures that the emissivity estimation is always within the physically feasible range of the blackbody cavity, which is consistent with the actual emission characteristics of the blackbody cavity.

[0083] The change in temporary effective emissivity between the current time and the previous time is calculated. If the change in temporary effective emissivity between the current time and the previous time exceeds a preset change threshold, it is forcibly constrained to the change threshold to filter out emissivity estimation jitter caused by high-frequency interference. Otherwise, the temporary effective emissivity at the current time is retained as a candidate value for the effective emissivity at the current time. This prevents the effective emissivity from changing too much in a short period of time, ensuring the smoothness and stability of the emissivity estimation and making it more consistent with the actual situation.

[0084] The temperature and effective emissivity values, corrected for all the constraints mentioned above, are output as the optimal estimates of the true temperature and effective emissivity at the current moment, for subsequent control loop and state monitoring. The final state estimate output has higher reliability and accuracy, providing accurate state information for the adaptive closed-loop temperature control of the ultra-high temperature blackbody cavity radiation source.

[0085] Through the above description of the implementation methods, those skilled in the art can clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the above functions can be divided into different functional modules to complete all or part of the functions described above.

[0086] In the several embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of systems or units may be electrical, mechanical, or other forms.

[0087] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units, located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0088] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0089] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to the solution, or all or part of the technical solution, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0090] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source, characterized in that, Includes the following steps: S1, real-time acquisition of multi-source observation signals of the blackbody cavity, time-domain alignment processing of the multi-source observation signals to eliminate dynamic response lag, and frequency-domain decomposition to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. The multi-source observation signals include at least two bands of radiance signals characterizing the thermal radiation state and heating power signals characterizing energy input. S2. Establish a state vector containing the real thermodynamic temperature and time-varying effective emissivity, construct a measurement equation describing the nonlinear relationship between radiance and state vector, and a state equation describing the dynamic evolution of thermal equilibrium in the blackbody cavity, in order to construct a state space observation model. Run a nonlinear state estimation algorithm based on the state space observation model to update the temperature estimate and effective emissivity estimate. S3 calculates the target radiative exitance compensation based on the real-time identified effective emissivity, generates a compensation temperature, performs graded safety control in conjunction with the material safety upper limit, generates the final heating power command, identifies the fault type based on the time-varying characteristics of the effective emissivity estimate, and triggers the corresponding maintenance command.

2. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 1, characterized in that: The real-time acquisition of multi-source observation signals from the blackbody cavity previously included: The motorized pan-tilt unit is driven to perform scanning actions to adjust the sensor angle. The modulated laser beam integrated into the sensor is used as an auxiliary beacon. Through the photoelectric detection unit associated with the laser beam optical path and in conjunction with phase-locked amplification detection technology, background thermal radiation interference is filtered out, and the maximum value of reflected light intensity is captured to automatically lock the center position of the radiation aperture. Simultaneously, the lens performs self-diagnosis, analyzes the background noise level and optical transmittance baseline in real time, and if the signal attenuation of the current transmittance relative to the optical transmittance baseline exceeds the preset signal attenuation threshold, it is determined that the optical path is abnormal, the high-precision multi-band mode is automatically disabled and switched to single-band temperature measurement mode, and the lens cleaning and maintenance command is output at the same time. Otherwise, the optical path is determined to be normal, the high-precision multi-band mode is maintained or enabled, and the optical transmittance baseline is updated in real time according to the currently detected multi-source observation signals.

3. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 1, characterized in that: The time-domain alignment process specifically includes: The pure time lag between the heating power signal and the temperature response signal is determined based on the cross-correlation function. The heating power signal and the radiance signals of each band are aligned on the time axis using the ring buffer storage technology to ensure that the multi-source data input to the state observer belong to the same physical moment. The frequency domain decomposition specifically includes: The preprocessed signal is decomposed into high-frequency and low-frequency components using a filtering decomposition algorithm. The high-frequency component is extracted from the dynamic change information of the ratio between the radiance signals of each band, and is used to drive the state observer to quickly track the instantaneous fluctuations of temperature. The low-frequency component is extracted from the trend information of absolute radiance and is used to drive the state observer to slowly identify the drift of effective emissivity, thereby suppressing the interference of high-frequency measurement noise on the effective emissivity estimation in the frequency domain.

4. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 1, characterized in that: The nonlinear state estimation algorithm specifically includes: Construct a state vector, using the true temperature and effective emissivity of the blackbody cavity as the state variables of the state vector; Within each preset control cycle, the extended Kalman filter algorithm is executed to construct measurement equations using the spectral characteristics of the radiance signals of each band, so as to obtain prior estimation information on temperature that is independent of changes in effective emissivity. Constraints are constructed using the energy balance relationship between input power and absolute radiance to correct the estimation bias of effective emissivity; The state is updated based on the measurement equation and constraints, and the optimal estimates of the true temperature and effective emissivity at the current moment are output.

5. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 4, characterized in that: The nonlinear state estimation algorithm further includes: Construct a state vector, using the true temperature and effective emissivity of the blackbody cavity as the state variables of the state vector; The extended Kalman filter algorithm is executed using a hierarchical update strategy, which includes: During the high-frequency component update process, the estimated temperature state is updated based on the first correction coefficient using the observation residuals of the radiance ratio of each band to track instantaneous temperature fluctuations. During the low-frequency component update process, the estimated effective emissivity is updated based on the second correction coefficient using the observation residual between the absolute radiance and the theoretical radiance predicted based on the energy balance relationship, in order to identify the drift of the effective emissivity. During the filtering iteration process, the process noise covariance matrix is ​​dynamically adjusted based on the statistical characteristics of the observed residuals; After the state update is completed and before the final estimate is output, a projection correction step based on physical constraints is performed to output the optimal estimate of the true temperature and the optimal estimate of the effective emissivity at the current moment. The set values ​​of the first correction coefficient and the second correction coefficient correspond to the time constant difference between the temperature dynamic response and the emissivity drift dynamic characteristics, respectively.

6. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 5, characterized in that: The dynamic adjustment of the process noise covariance matrix based on the statistical characteristics of the observed residuals specifically includes: Calculate the observation residual vector at the current moment, where the observation residual vector is the difference between the measured value and the state observer's predicted value; Calculate the moving root mean square value of the observed residual vector; A matrix adjustment index is obtained based on the moving root mean square value of the observed residual vector and the preset noise benchmark value. The matrix adjustment index is used to characterize the degree of deviation of the model prediction error relative to the measurement noise level. The process noise covariance matrix is ​​updated in real time based on the matrix adjustment index. If the matrix adjustment index is greater than the preset matrix adjustment index, the value of the process noise covariance matrix is ​​increased to accelerate the filtering convergence; otherwise, the value of the process noise covariance matrix is ​​decreased to suppress the filtering divergence.

7. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 5, characterized in that: The step of performing projection correction based on physical constraints specifically includes: Acquire temporary output values ​​from the state observer, including temporary temperature and temporary effective emissivity; If the temporary temperature exceeds the preset temperature constraint range, it will be forcibly constrained to within the temperature constraint range. If the temporary effective emissivity exceeds the preset emissivity constraint range, it will be forcibly constrained to within the emissivity constraint range. Calculate the change in temporary effective emissivity between the current time and the previous time. If the change in temporary effective emissivity between the current time and the previous time exceeds a preset change threshold, then force the constraint to the change threshold. Otherwise, retain the temporary effective emissivity of the current time as a candidate value for the effective emissivity of the current time. The constrained temperature and effective emissivity are output as the final state estimate.

8. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 1, characterized in that: The safety upper limit of the bonding material is subject to graded safety control, specifically including: The target radiative exitance is determined based on the set standard emissivity and the set temperature. The required compensation temperature is calculated based on the real-time identified effective emissivity. Obtain the preset safe upper limit of the blackbody cavity material, set the final control target to the minimum value between the compensation temperature and the safe upper limit, and combine the feedforward compensation to output the heating power of the ultra-high temperature blackbody cavity radiation source. If the compensation temperature is greater than the upper limit of the safe temperature, the final control target temperature will be forcibly limited to the upper limit of the safe temperature, and an alarm state will be triggered. The alarm state is used to indicate that the current radiation energy is lower than the target radiation output. Otherwise, the final control target temperature will be set to the compensation temperature, and the non-alarm state will be cleared or maintained.

9. The adaptive closed-loop temperature control method for an ultra-high temperature blackbody cavity radiation source as described in claim 1, characterized in that: The method of identifying fault types based on the time-varying characteristics of the effective emissivity estimate specifically includes: When the change in effective emissivity exceeds the change threshold within a preset time period, and the dispersion between the radiance signals of each band is greater than the dispersion threshold, it is determined to be an optical window occlusion or contamination fault, marked as a first-class fault identification, and a cleaning and maintenance command is output. The real-time decay rate is calculated based on the time series of effective emissivity. When the real-time decay rate corresponding to the effective emissivity within a preset time period is found to conform to the preset material aging trend, it is determined to be a blackbody cavity material aging fault, marked as a second type of fault identification, and the preset material aging trend is updated based on the current downward trend. The preset material aging trend characterizes the exponential decay relationship of effective emissivity with the cumulative high temperature exposure time. When the effective emissivity is less than the lower limit of the preset emissivity constraint range, it is marked as a maintenance decision, and a maintenance instruction to replace the cavity is generated. If the first type of fault identification, the second type of fault identification, or maintenance decision mentioned above is not triggered, the system is determined to be in normal operation and the current operating state is maintained.

10. An adaptive closed-loop temperature control system for an ultra-high temperature blackbody cavity radiation source, characterized in that, include: Multi-source signal synchronous acquisition and preprocessing module, real-time parameter inversion module, and parameter calibration and anomaly diagnosis module; The multi-source signal synchronous acquisition and preprocessing module is used to acquire multi-source observation signals of the blackbody cavity in real time, perform time-domain alignment processing on the multi-source observation signals to eliminate dynamic response lag, and perform frequency-domain decomposition to separate high-frequency components for temperature tracking and low-frequency components for emissivity identification. The multi-source observation signals include at least two bands of radiance signals characterizing the thermal radiation state and heating power signals characterizing energy input. The real-time parameter inversion module is used to establish a state vector containing the real thermodynamic temperature and time-varying effective emissivity, construct a measurement equation describing the nonlinear relationship between radiance and the state vector, and a state equation describing the dynamic evolution of the thermal equilibrium of the blackbody cavity, so as to construct a state space observation model. Based on the state space observation model, a nonlinear state estimation algorithm is run to update the temperature estimate and the effective emissivity estimate. The parameter calibration and anomaly diagnosis module is used to calculate the compensation of the target radiative exitance based on the real-time identified effective emissivity, generate the compensation temperature, perform graded safety control in combination with the material safety upper limit, generate the final heating power command, identify the fault type based on the time-varying characteristics of the effective emissivity estimate, and trigger the corresponding maintenance command.

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