CN-121994350-A - Continuous laser power density distribution measurement system and method based on flat plate calorimetric

CN121994350ACN 121994350 ACN121994350 ACN 121994350ACN-121994350-A

Abstract

The invention provides a continuous laser power density distribution measurement system and method based on flat plate calorimetric, which are used for solving the technical problems that the training time is long and convergence is difficult due to the fact that the physical information neural network method possibly faces the conditions of frequency spectrum bias, unbalance and incompatibility among multiple loss functions, high calculation complexity of higher derivative and the like when solving three-dimensional field inversion. According to the continuous laser power density distribution measurement system based on flat plate calorimetric, a physical information neural network is introduced, a heat flow generation network and a heat conduction numerical calculation model which share weight parameters are arranged in each circulation unit, a numerical algorithm is utilized to integrate a heat conduction physical rule, inversion of heat flow density distribution is achieved, accuracy and stability of complex heat flow field reconstruction are remarkably improved, and the problem of three-dimensional heat flow field inversion when a flat plate calorimetric technology is applied to continuous laser power density distribution measurement is solved.

Inventors

FANG BOLANG
HAN FENG
WU JUNJIE
ZHANG YIFAN
WU HAOLONG
JIANG XIAOWEI
WANG JIANGUO
YANG PENGLING
WANG DAHUI

Assignees

西北核技术研究所

Dates

Publication Date: 20260508
Application Date: 20251231

Claims (10)

1. A continuous laser power density distribution measurement system based on flat plate calorimeter is characterized in that: The device comprises a flat temperature field measuring device, a heat flow inversion unit and a power density calculating module; the flat temperature field measuring device comprises a flat (1) and a thermal imager (8); The flat plate (1) is made of high-heat-conductivity high-temperature-resistant material, the front surface of the flat plate is plated with a coating for uniform absorption, the rear surface of the flat plate is plated with a high-emissivity coating, and the hemispherical emissivity of the high-emissivity coating is more than or equal to 0.95; the thermal imager (8) is positioned behind the flat plate (1) and is used for acquiring the temperature field distribution of the flat plate (1) through the rear surface of the flat plate (1) in real time to obtain a temperature field sequence; The heat flow inversion unit realizes inversion based on a physical information neural network, wherein the physical information neural network comprises a plurality of circulation units and a loss function, and each circulation unit comprises a heat flow generation network and a heat conduction numerical calculation model; the heat flow generating network adopts a deep neural network architecture, and the heat flow generating network of all circulating units shares weight parameters, wherein the input end of the heat flow generating network is used for receiving the space coordinates of a temperature field of a flat plate (1) and time steps at different moments and generating heat flow density distribution at corresponding moments according to the received space coordinates and the corresponding time steps; The heat conduction numerical calculation model is constructed based on a flat plate heat conduction partial differential equation, a first input end of the heat conduction numerical calculation model is connected with an output end of a heat flow generation network in a corresponding circulation unit, a second input end of the heat conduction numerical calculation model is used for receiving an initial temperature field or connecting an output end of the heat conduction numerical calculation model in a previous circulation unit, and a temperature field at the current moment is calculated according to heat flow density distribution at the corresponding moment and the initial temperature field or a temperature field at the previous moment; the loss function is used for calculating the difference between the temperature field sequences output by the thermal conduction numerical calculation models and the temperature field sequences measured by the thermal imager (8), optimizing the weight parameters of the heat flow generation network through a back propagation algorithm, and enabling the temperature field sequences output by the thermal conduction numerical calculation models to be gradually matched with the temperature field sequences measured by the thermal imager (8), so that the training of the heat flow generation network is completed; The input end of the power density calculation module is connected with the output end of each heat flow generation network and is used for calculating the power density distribution of the continuous laser to be measured according to the heat flow density distribution output by the heat flow generation network after training.
2. The slab calorimeter-based continuous laser power density distribution measurement system according to claim 1, wherein: the heat flow generation network adopts a fully-connected neural network or a convolutional neural network; The heat conduction numerical calculation model is constructed by adopting a finite difference or finite element method; the loss function takes the form of an L2 norm.
3. The flat plate calorimetric based continuous laser power density distribution measurement system according to claim 1 or 2, characterized in that: the flat temperature field measuring device further comprises a pressing frame (2), M first heat insulation cushion blocks (4), M second heat insulation cushion blocks (5), a supporting frame (6) and a light shield (7), wherein M is more than or equal to 2; the pressing frame (2) is of a frame structure, and one end face of the pressing frame is circumferentially connected with the outer edge of the front surface of the flat plate (1) through M first heat insulation cushion blocks (4); the support frame (6) comprises an annular frame (61) and a hollowed-out conical structure (62) with a large end connected to the rear end face of the annular frame (61), wherein the front end face of the annular frame (61) is circumferentially connected with the outer edge of the rear surface of the flat plate (1) through N second heat insulation cushion blocks (5); the light shield (7) is coaxially sleeved on the outer side of the hollow conical structure (62) and used for inhibiting stray light; the thermal imager (8) is connected to the small end of the hollow conical structure (62), and the optical axis of the thermal imager is perpendicular to the surface of the flat plate (1) and penetrates through the geometric center of the flat plate (1).
4.A continuous laser power density distribution measurement system based on flat plate calorimetric according to claim 3, characterized in that: the external structures of the pressing frame (2), the flat plate (1) and the annular frame (61) are square, and the side lengths of the pressing frame (2) and the annular frame (61) are larger than the side length of the flat plate (1); The M first heat insulation cushion blocks (4) are circumferentially arranged along the rear surface of the pressing frame (2), the M second heat insulation cushion blocks (5) are circumferentially arranged along the front surface of the annular frame (61), and the M second heat insulation cushion blocks are in one-to-one correspondence connection with the M first heat insulation cushion blocks (4); The inner side of one side surface of each of the M second heat insulation cushion blocks (5) connected with the corresponding first heat insulation cushion block (4) is provided with a notch, and a mounting groove is formed between the notch and the corresponding position of the corresponding first heat insulation cushion block (4); The flat plate (1) is arranged between the first heat insulation cushion block (4) and the second heat insulation cushion block (5) through a plurality of circumferential mounting grooves, and gaps are reserved between the flat plate (1) and the bottoms of the plurality of mounting grooves.
5. The slab calorimeter-based continuous laser power density distribution measurement system according to claim 4, wherein: the flat temperature field measuring device further comprises a plurality of first connecting screws (3) and a plurality of second connecting screws (9); One end of the first connecting screw (3) sequentially penetrates through the press frame (2), the corresponding first heat insulation cushion block (4) and the corresponding second heat insulation cushion block (5) and then is in threaded connection with the corresponding position of the annular frame (61); A circle of mounting rings are arranged at the small end of the hollow conical structure (62) inwards in the circumferential direction, the collecting end of the thermal imager (8) extends into the hollow conical structure (62) through the mounting rings, and one end of the second connecting screw (9) penetrates through the mounting rings and is in threaded connection with the main body of the thermal imager (8).
6. The slab calorimeter-based continuous laser power density distribution measurement system according to claim 5, wherein: the base material of the flat plate (1) is aluminum alloy, red copper or copper alloy; The high-emissivity coating is made of a super-black material; the first heat insulation cushion block (4) and the second heat insulation cushion block (5) are made of ceramic or composite heat insulation materials; The light shield (7) is an aluminum-based film material with the surface subjected to blackening treatment; The pressing frame (2) and the supporting frame (6) are made of aluminum alloy materials.
7. The flat plate calorimetric based continuous laser power density distribution measurement system according to claim 1 or 2, characterized in that: The flat temperature field measuring device further comprises a metal press frame, a supporting frame and a light shield; The supporting frame comprises an annular frame and a hollow conical structure with a large end connected to the rear end face of the annular frame; The metal pressing frame is used for fixing the flat plate (1) on the front end face of the annular frame; the light shield is coaxially sleeved on the outer side of the hollow conical structure and used for inhibiting stray light; The thermal imager is connected to the small end of the hollow conical structure, and the optical axis of the thermal imager is perpendicular to the surface of the flat plate and penetrates through the geometric center of the flat plate.
8. The slab calorimeter-based continuous laser power density distribution measurement system according to claim 7, wherein: the metal pressing frame is of a hollow structure, and cooling water is arranged in the metal pressing frame; Or an air cooling device is arranged outside the metal pressing frame.
9. The continuous laser power density distribution measuring method based on flat plate calorimetric is characterized by comprising the following steps of: Step1, constructing the continuous laser power density distribution measuring system based on flat plate calorimeter according to any one of claims 1-8; Step 2, making continuous laser to be detected enter from the front surface of the flat plate (1) normally, and acquiring the temperature field distribution of the flat plate (1) through a thermal imager (8) to obtain a temperature field sequence; Step 3, inverting the temperature field sequence of the flat plate (1); Respectively inputting the space coordinates of the temperature field of the flat plate (1) and the time at different moments into the heat flow generating networks of each circulation unit, and inputting an initial temperature field into the heat conduction numerical calculation model of the first circulation unit, wherein each heat flow generating network generates the heat flow density distribution at the corresponding moment according to the received space coordinates and the corresponding time steps, and each heat conduction numerical calculation model calculates the temperature field at the current moment according to the heat flow density distribution at the corresponding moment and the initial temperature field or the temperature field at the last moment; Generating gradient information by the loss function according to the difference between the temperature field sequence output by each thermal conductivity numerical calculation model and the temperature field sequence measured by the thermal imager (8), transmitting the generated gradient information to a heat flow generation network through a back propagation algorithm so as to update the weight parameters of the heat flow generation network until the temperature field sequence output by each thermal conductivity numerical calculation model is consistent with the temperature field sequence measured by the thermal imager (8), and completing the training of the heat flow generation network; And 4, calculating and obtaining the power density distribution of the continuous laser to be tested by the power density calculation module according to the heat flux density distribution output by the heat flux generation network after training and the absorptivity of the front surface of the flat plate (1).
10. The flat plate calorimetric-based continuous laser power density distribution measurement method according to claim 9, characterized in that: In the step 3, the temperature field sequence of the flat plate (1) measured by the thermal imager (8) is segmented and input into the heat flow generating network of each circulation unit section by section for training.

Description

Continuous laser power density distribution measurement system and method based on flat plate calorimetric Technical Field The invention relates to a continuous laser power density distribution measuring system and a method, in particular to a continuous laser power density distribution measuring system and a method based on flat plate calorimetric. Background The continuous laser power density distribution measurement has important academic significance and practical value in the fields of laser technology, industrial processing, communication, medical treatment and the like. The continuous laser power density distribution measurement refers to a measurement of the distribution state of power density over time and two-dimensional spatial variation over a given cross section in the propagation path of the beam. Through continuous laser power density distribution measurement, an optical theoretical model, diagnosis of optical system aberration, evaluation of beam quality of a laser system and the like can be verified, and meanwhile, high-resolution and high-precision measurement data are key inputs for finely researching interaction of laser and substances. The flat plate calorimetric technique is an important laser parameter measurement means. The technology is based on the laser thermal effect, and the metal flat plate is heated by laser and the temperature rise is measured to obtain the total energy or energy distribution of the laser, so that the technology has the advantages of simple device, high reliability, high spatial resolution, high measurement precision and the like. However, the conventional slab calorimetric technology is difficult to realize continuous laser power density two-dimensional spatial distribution measurement, and because of heat accumulation caused by continuous laser irradiation and heat conduction of a slab, a very complex coupling relation exists between a slab temperature field and laser spot distribution, so that accurate inversion of heat flow density distribution is difficult to realize based on the slab temperature field. At present, various means for realizing inversion of a thermal flow field through a temperature field exist in the industry, but difficulties exist in inversion of the thermal flow field in a flat plate calorimetric technology. For heat conduction problems, calculating the temperature from the heat flow is a positive problem, while calculating the heat flow from the temperature is a negative problem. The inverse problem solving has the pathogenicity, is easy to be interfered by noise, has high solving difficulty, and the inversion of the heat flow field in the flat plate calorimetric technique belongs to the inversion of a three-dimensional field (time and two-dimensional space), and has larger challenges. The existing heat flow field inversion method comprises a traditional optimization algorithm, a physical information neural network-based method and the like, wherein the traditional optimization algorithm, such as a Beck sequence function assignment method, a regularization method, an iterative regularization method, an optimization algorithm and the like, is limited to zero-dimensional to two-dimensional field inversion, and the physical information neural network-based method can realize three-dimensional field inversion, but can face the problems of frequency spectrum bias, unbalance and imbalance among multiple loss functions, high calculation complexity of higher derivative and the like when solving the three-dimensional field inversion, so that the training time is long and convergence is difficult. Disclosure of Invention The invention aims to solve the technical problems that the traditional optimization algorithm is limited to zero-dimensional to two-dimensional field inversion, and the physical information neural network-based method possibly faces the conditions of spectrum bias, unbalance and imbalance among multiple loss functions, high calculation complexity of higher derivative and the like when solving three-dimensional field inversion, so that the training time is long and convergence is difficult to realize, and provides a continuous laser power density distribution measurement system and a continuous laser power density distribution measurement method based on flat plate calorimetric. In order to achieve the above purpose, the technical scheme provided by the invention is as follows: the continuous laser power density distribution measurement system based on flat plate calorimetric is characterized by comprising a flat plate temperature field measurement device, a heat flow inversion unit and a power density calculation module; the flat temperature field measuring device comprises a flat plate and a thermal imager; The flat plate is made of high-heat-conductivity high-temperature-resistant material, the front surface of the flat plate is plated with a coating for uniform absorption, the rear surface of the flat plate is plated with a