Radiometer absorption cavity temperature bistable control method based on adaptive Smith estimation

Abstract

The invention relates to the technical field of irradiance measurement, in particular to a radiometer absorption cavity temperature bistable control method based on self-adaptive Smith estimation, which combines feed-forward control, PI control and a self-adaptive Smith predictor. A self-adaptive Smith predictor is adopted to predict behaviors of a radiometer absorption cavity, electric heating output of the radiometer absorption cavity is completed through PI control, output of a temperature controller and the temperature of a controlled cavity are rapidly adjusted, the radiometer absorption cavity enters a steady state synchronously, and meanwhile the cavity temperature of the high-precision radiometer absorption cavity and stable electric heating output meeting the measurement precision requirement are obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of irradiance measurement, and particularly relates to a radiation meter absorption cavity temperature bistable control method based on adaptive Smith prediction. BACKGROUND

[0002] Long-term accurate monitoring of space solar total irradiance (TSI) provides scientific basis for climate change prediction, environmental protection policy making, and more accurate climate and weather prediction for China's military and civilian industrial production. The sun is the only external energy input source of the earth and the driving force for the formation, development and change of the ecological system, so the solar total irradiance is one of the key parameters of the earth's climate model. The solar radiation meter is the core measuring equipment of the solar radiation monitor, responsible for the TSI measurement and monitoring task. The radiation meter mainly consists of a radiation absorption cavity, a heat sink, an absorption cavity heating circuit, an absorption cavity temperature measurement circuit and other components. In the TSI measurement process, accurate measurement and control of the absorption cavity temperature is the key technology to achieve accurate TSI measurement.

[0003] The radiation meter absorption cavity temperature control model is a typical first-order delayed inertia model, so many methods in existing control technology can be used in the absorption cavity temperature control algorithm. In classical control theory, the cavity temperature control model can be quickly and accurately obtained by the flying curve method, and a good temperature control PID (proportional-integral-derivative control) algorithm can be obtained by the commonly used parameter tuning method in engineering practice. Affected by the pure delay link in the cavity temperature control transfer function, the traditional PID control usually needs 1-3 time constants to achieve the temperature control target and the temperature control controller output bistable. In modern control theory, the internal thermal state of the system can be described by state space, and the multi-input multi-output nonlinear time-varying system can be controlled. However, modern control theory is powerful, but the design and analysis process is complex, and in practical application, it may be limited by problems such as inaccurate mathematical model and difficult to express performance indicators in mathematical form. In the radiation meter measurement system, the measurement process is an electrical equivalent process, and the heat transfer process is affected by objective factors such as structure design and material selection, so it is difficult to obtain an accurate heat transfer model. Especially in the absorption cavity preparation process, the heat transfer link model is difficult to control and detect. Therefore, it is difficult to realize the synchronization of the radiation meter detector cavity temperature and the controller output into the steady state of the measurement target by using only the classical control theory and the modern control theory. SUMMARY

[0004] Therefore, the application aims to provide a radiometer absorption cavity temperature bistable control method based on adaptive Smith predictor, which predicts the output of PI controller with feedforward to realize the control of detector cavity temperature, so that the target cavity temperature and the output of the controller can be adjusted quickly and enter the steady state synchronously during the cavity temperature control process, and high-precision total solar irradiance measurement is realized.

[0005] To achieve the above-mentioned purpose, the technical scheme of the application is as follows: A radiometer absorption cavity temperature bistable control method based on adaptive Smith predictor, comprising: S1: open the shutter of the radiometer, and start the light measurement of the radiometer absorption cavity; adjust the motor heat power of the absorption cavity through feedforward control to stabilize the cavity temperature of the absorption cavity; after the cavity temperature is stabilized, close the shutter of the radiometer, and adjust the electric heating power of the absorption cavity through feedforward control to stabilize the cavity temperature of the absorption cavity; after the cavity temperature is stabilized, the measurement is completed; S2: use the PI controller to dynamically adjust the electric heating power of the absorption cavity in real time in combination with the set target cavity temperature of the absorption cavity to maintain the stability of the cavity temperature; S3: add a Smith predictor feedback loop to the original Smith predictor to obtain an adaptive Smith predictor; input the electric heating power of the PI controller output in step S2 into the adaptive Smith predictor to obtain the predicted cavity temperature of the absorption cavity; S4: integrate the predicted cavity temperature obtained in step S3 and the actual cavity temperature of the absorption cavity as the cavity temperature feedback of the closed-loop control loop of the PI controller, and adjust the electric heating power of the absorption cavity in real time by the PI controller to realize the consistency of the cavity temperature of the absorption cavity with the set cavity temperature.

[0006] Further, step S1 comprises: Set the electric heating power of the absorption cavity according to the historical light power measurement value; Light measurement stage: set the initial electric heating power of the absorption cavity as the difference between the calibration power and the light power obtained in the last light measurement when the shutter is opened; Calibration stage: set the initial electric heating power of the absorption cavity as the calibration power when the shutter is closed, and the calibration power is greater than the measured light power of the radiometer.

[0007] Further, in step S2, the parameters of the PI controller are set by using the Cohen-Coon method.

[0008] Further, in step S3, the feedback loop gain in the Smith predictor feedback loop is: ; Wherein, Ks represents feedback loop gain, Kp represents proportional coefficient in PI controller, Ki represents integral coefficient in PI controller, θ represents delay time of pure delay link in transfer function of absorption cavity cavity temperature, τ represents time constant, K represents gain of delay first-order inertia link transfer function in radiation meter absorption cavity model, represents difference between set cavity temperature and current cavity temperature.

[0009] Compared with the prior art, the application can achieve the following beneficial effects: In the radiation meter absorption cavity cavity temperature double-stable control method based on adaptive Smith prediction, the heating shock interference of the absorption cavity at the initial moment in the measurement stage and the calibration stage is suppressed by introducing a feedforward mechanism, the amplitude of the radiation meter absorption cavity cavity temperature instability is effectively reduced, the thermal shock to the heat sink is reduced, the possibility of designing a small volume and light quality heat sink is brought, and the device volume and structural complexity are effectively reduced. The adaptive Smith predictor is the core of the application, which makes the PI control ignore the pure delay link in the transfer function of the controlled object (the radiation meter absorption cavity cavity temperature). After entering the steady state, the controlled object is equivalent to the Smith prediction model, which is almost independent of the radiation meter absorption cavity model. This characteristic greatly improves the output stability of the controller output in the steady state of the temperature control process, and the output is no longer affected by the sampling system noise. The adaptive Smith prediction dynamically adjusts the input of the PI controller, improves the cavity temperature dynamic adjustment capability, reduces the parameter setting difficulty of the PI controller, improves the adaptability of the PI controller parameters, and through reasonable adaptation of the proportional coefficient and the integral coefficient, high-stable and high-precision cavity temperature control results can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0010] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The present application is not limited by the accompanying drawings. Fig. 1 The flowchart of the radiation meter absorption cavity cavity temperature double-stable control method based on adaptive Smith prediction according to the embodiment of the present application is shown. Fig. 2 The flowchart of the radiation meter absorption cavity cavity temperature double-stable control method based on adaptive Smith prediction according to the embodiment of the present application is shown. Fig. 3 The process diagram of the solar absolute radiation meter electrically replaced thermal equivalent measurement method according to the embodiment of the present application is shown. DETAILED DESCRIPTION

[0011] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application.

[0012] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0013] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited by "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0014] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0015] The present application will be described in detail below with reference to the drawings and embodiments.

[0016] As Figs. 1-3 shown, the radiation meter absorption cavity temperature bistable control method based on adaptive Smith prediction according to the embodiments of the present application comprises: S1: open the shutter of the radiation meter, the radiation meter absorption cavity starts to measure light, adjusts the heat power of the absorption cavity motor through feedforward control, so that the cavity temperature of the absorption cavity is stable; after the cavity temperature is stable, the shutter of the radiation meter is closed, the electric heating power of the absorption cavity is adjusted through feedforward control, so that the cavity temperature of the absorption cavity is stable; after the cavity temperature is stable, the measurement is completed.

[0017] The measurement process of the radiometer includes two measurement stages, i.e., a light measurement stage (measurement stage) with the shutter open and an electric heating calibration stage (calibration stage) with the shutter closed. Before the light measurement stage is started, the electric heating power Pe of the absorption cavity of the radiometer is configured as a stable heating power value, and the stable heating power value is greater than the measured light power of the radiometer, and the embodiment of the present application is 75 mW. However, after the superimposed light power, the temperature of the absorption cavity will be significantly away from the working point temperature, and the calibration stage has the same problem, therefore, the present application introduces a feedforward control to ensure the stability of the temperature of the absorption cavity, specifically, in some embodiments, step S1 includes: setting the electric heating power of the absorption cavity according to the historical light power measurement value; the light measurement stage: the initial electric heating power of the absorption cavity is set as the difference between the calibration power and the light power obtained in the last light measurement when the shutter is opened; the calibration stage: the initial electric heating power of the absorption cavity is set as the calibration power when the shutter is closed, and the calibration power is greater than the measured light power of the radiometer.

[0018] It can be understood that, in the embodiment of the present application, step S1 specifically includes: the light measurement stage: at the starting moment, the shutter is opened, the initial electric heating power Pe1 of the absorption cavity is set as the difference between the calibration power 75 mW and the light heating power obtained in the last light measurement, and the radiometer absorption cavity temperature is waited to be stable, at this time, the radiometer absorption cavity temperature is T1. In the present application, the feedforward control output value before the measurement stage is determined by the last light power measurement result, and therefore the absorption ratio of the radiometer absorption cavity to the light power is not considered here, and therefore the feedforward output value can be calculated more accurately by increasing the absorption ratio compensation and other variables.

[0019] the calibration stage: at the starting moment, the shutter is closed, the calibration power Pe2 is adjusted to 75 mW, and the radiometer absorption cavity temperature is waited to be stable, at this time, the radiometer absorption cavity temperature is T2.

[0020] Affected by the environmental temperature change of the absorption cavity of the radiometer, the difference between the light heating and the electric heating thermal characteristics, the light absorption rate and other factors, the absorption cavity temperatures T1 and T2 of different stages are usually not equal, at this time, the power measurement needs to be corrected through the responsivity parameter of the radiometer absorption cavity, the responsivity of the radiometer absorption cavity is represented by α, the unit is ℃ / mW, and then the measured light power measurement result Po is: Po=Pe2-Pe1-(T2-T1) / α.

[0021] S2: using a PI controller, combining the set target cavity temperature of the absorption cavity, and dynamically adjusting the output electric heating power of the absorption cavity in real time. In some embodiments, the incremental digital PI controller is obtained through the parameters such as transfer function gain, time constant, delay time, etc. by using the Cohen-Kuhn method, Fig. 2 wherein Gc (s) represents a transfer function of a PI controller, specifically, the PI controller G c (s) is combined with the set target cavity temperature X(s) of the absorption cavity to dynamically adjust the output electric heating power of the absorption cavity in real time, to keep the cavity temperature of the absorption cavity stable, and the dynamic adjustment time can be controlled within one time constant, and the PI controller can better resist external disturbance F(s).

[0022] In the embodiment of the present application, since the controlled object (cavity temperature of the radiometer absorption cavity) is constrained by a pure delay link of the transfer function, the control period of the PI controller must be strictly less than or equal to half of the delay time of the pure delay link, and the control method of the PI controller in the embodiment of the present application can be a traditional PI control method, a segmented PI control, a fuzzy PI control, and a neural network PI control. Specifically, in the segmented PI control, different parameters of the PI controller, including a proportional coefficient Kp and an integral coefficient Ki, or an additional output gain Kpe, are configured in different control stages through time segmentation or error segmentation. For example, for time segmentation, the proportional coefficient Kp is increased by 10% in the 0~τ / 2 time period, so as to quickly reduce the cavity temperature error; after τ / 2, the proportional coefficient Kp is restored to obtain a low-noise steady-state control effect; for error segmentation, when the error is greater than or equal to 0.1℃, the proportional coefficient Kp is increased by 10% to quickly reduce the cavity temperature error; when the error is less than 0.1℃, the proportional coefficient Kp is restored to obtain a steady-state control effect. The segmented PI control method can be integrated into an adaptive Smith predictor PI controller to improve the dynamic response performance at the shutter opening / closing time. On the basis of the segmented PI control, two or more membership functions are established according to the fuzzy control theory, different proportional coefficients Kp and integral coefficients Ki of the PI controller, or additional output gains Kpe are configured in different time periods / error periods, so as to realize fuzzy PI control. The fuzzy control can make the parameters linearly or piecewise linearly transition between different control stages through the membership function, and can integrate the membership intervals to integrate the time-segmented PI control and the error-segmented PI control, so as to obtain a better trade-off between real-time performance and control accuracy through flexible rules and parameter adjustment. The neural network PI control reconstructs the PI controller through a neuron structure, and dynamically optimizes the parameters of the PI controller, including the proportional coefficient Kp and the integral coefficient Ki, through neural network feedback iteration learning. The neural network learning algorithm can dynamically adjust the parameters of the PI controller in a timely manner by monitoring the cavity temperature, so as to obtain ideal real-time performance and control accuracy. Through controlling the learning rules, the parameters of the PI controller can be intelligently learned online. The neural network PI control method is quite different from the traditional PI controller in terms of theoretical basis, and cannot be integrated with the segmented PI control and the fuzzy PI control in terms of control theory, but can refer to the debugging experience of the two methods to set the parameter adjustment strategy required by the engineering.

[0023] S3: Add a Smith prediction feedback loop to the original Smith predictor to obtain an adaptive Smith predictor; input the output electric heating power obtained in step S2 into the Smith predictor to obtain the predicted output cavity temperature of the absorption cavity.

[0024] In some embodiments, the adaptive Mies predictor is as follows: Fig. 2 The dashed box in the figure represents the transfer function of the adaptive Smith predictor. An adaptive Smith predictor is obtained by adding a Smith predictor feedback loop to the traditional Smith predictor. This loop adjusts the Smith predictor input in real time, enabling rapid and accurate dynamic adjustment of the Smith predictor output to better reflect the cavity temperature output (G0(s)e). -τs The estimation is performed, where G0(s) is the first-order inertial transfer function of the delayed first-order inertial joint in the radiometer absorption cavity model, and τ represents the time constant of the first-order inertial transfer function G0(s). Specifically, Smith predicts the feedback loop, including the feedback loop gain; the feedback loop gain is: ; Where Ks represents the feedback loop gain, Kp represents the proportional coefficient in the PI controller, Ki represents the integral coefficient in the PI controller, θ represents the delay time of the pure delay element in the transfer function of the absorption cavity temperature, and K represents the gain of the first-order inertial transfer function G0(s). This indicates the difference between the set cavity temperature and the current cavity temperature.

[0025] S4: The predicted output cavity temperature obtained in step S3 is integrated with the actual output cavity temperature of the absorption cavity. Then, the PI controller is controlled to dynamically adjust the output electric heating power in real time based on the target cavity temperature and the integrated cavity temperature to ensure the stability of the cavity temperature of the absorption cavity. After the cavity temperature stabilizes, it is equivalent to the PI controller dynamically adjusting a delay-free inertial element, namely G0(s).

[0026] In embodiments of the present invention, such as Fig. 2 As shown, the predicted output cavity temperature is added to the actual output cavity temperature Y(s) of the absorption cavity and integrated. Then, the PI controller dynamically adjusts the output electric heating power in real time based on the target cavity temperature X(s) and the integrated cavity temperature to ensure the stability of the cavity temperature of the absorption cavity.

[0027] The radiometer absorption cavity temperature bistable control method based on adaptive Smith prediction provided by the application can realize consistent absorption cavity temperature, an error less than 0.05%, and a measurement result data repeatability of the absorption cavity temperature and the absorption cavity electric heating power less than 0.005%. In the light measurement stage and the electric calibration stage, the cavity temperature adjustment process and the dynamic adjustment process of the absorption cavity temperature and the absorption cavity electric heating power are basically consistent in time length, less than or equal to a time constant. However, the single PI controller without the Smith predictor cannot complete the dynamic adjustment process of the cavity temperature within a time constant. The method provided by the application is also applicable to a temperature control system with a known external disturbance and a transfer function with significant delay characteristics, that is, the method provided by the application can be applied to a temperature control scene described by a first-order delay inertia element, and the temperature control object with obvious delay.

[0028] It should be understood that the various forms of flow shown above can be reordered, added, or deleted steps. For example, the steps described in the present disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, which is not limited herein.

[0029] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for dual stable control of a radiometer absorption cavity temperature based on adaptive Smith predictor, characterized in that, Comprise: S1: open the shutter of the radiometer, the radiometer absorption cavity starts to measure light, adjust the motor heat power of the absorption cavity through feedforward control, so that the cavity temperature of the absorption cavity is stable; After the cavity temperature is stable, the shutter of the radiometer is closed, and the electric heating power of the absorption cavity is adjusted through feedforward control, so that the cavity temperature of the absorption cavity is stable; after the cavity temperature is stable, the measurement is finished once; S2: use PI controller to dynamically adjust the electric heating power of the absorption cavity in real time combined with the set target cavity temperature of the absorption cavity to maintain the stability of the cavity temperature; S3: add a Smith predictor feedback loop based on the original Smith predictor to obtain an adaptive Smith predictor; input the cavity electric heating power output by the PI controller in step S2 into the adaptive Smith predictor to obtain the predicted cavity temperature of the absorption cavity; S4: integrate the predicted cavity temperature obtained in step S3 and the actual cavity temperature of the absorption cavity as the cavity temperature feedback of the closed loop control loop of the PI controller, and adjust the electric heating power of the absorption cavity in real time by the PI controller to realize that the cavity temperature of the absorption cavity is consistent with the set cavity temperature.

2. The method of claim 1, wherein the method is a method of adaptive Smith predictor based radiometer absorption cavity temperature bistable control. Step S1 comprises: Set the electric heating power of the absorption cavity according to the historical light power measurement value; Light measurement stage: set the initial electric heating power of the absorption cavity as the difference between the calibration power and the light power obtained in the last light measurement while the shutter is opened; Calibration stage: set the initial electric heating power of the absorption cavity as the calibration power while the shutter is closed, and the calibration power is greater than the measured light power of the radiometer.

3. The method of claim 1, wherein the method is a method of adaptive Smith predictor based radiometer absorption cavity temperature bistable control. In step S2, the parameters of the PI controller are set by Cohen-Coon method.

4. The method of claim 1, wherein the method is a method of adaptive Smith predictor based radiometer absorption cavity temperature bistable control. The feedback loop gain in the Smith predictor feedback loop in step S3 is: ； where Ks represents a feedback loop gain, Kp represents a proportional coefficient in a PI controller, Ki represents an integral coefficient in the PI controller, θ represents a delay time of a pure delay link in a transfer function of the absorption cavity cavity temperature, τ represents a time constant, K represents a gain of a delay first-order inertia link transfer function in a model of the radiometer absorption cavity, represents a difference between the set cavity temperature and the current cavity temperature.

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