CN113970940B - Method for controlling internal temperature field of material - Google Patents

Method for controlling internal temperature field of material Download PDF

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CN113970940B
CN113970940B CN202111220688.0A CN202111220688A CN113970940B CN 113970940 B CN113970940 B CN 113970940B CN 202111220688 A CN202111220688 A CN 202111220688A CN 113970940 B CN113970940 B CN 113970940B
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heat
temperature field
power
beams
field
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CN113970940A (en
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李迎光
刘舒霆
刘强强
郝小忠
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05DSYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00Control of temperature
    • G05D23/19Control of temperature characterised by the use of electric means
    • G05D23/20Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B1/00Details of electric heating devices
    • H05B1/02Automatic switching arrangements specially adapted to apparatus ; Control of heating devices

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
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Abstract

A method for controlling the internal temp field of material features that multiple heat beams are generated in the material by inputting energy, the heat-map calculation is performed on the target temp field, and the powers of the heat beams are regulated and controlled according to the calculation result, so they are alternatively combined and overlapped in the material to form the target temp field. The method for controlling the internal temperature field of the material can realize high-resolution accurate control of the distribution of the internal temperature field of the material.

Description

Method for controlling internal temperature field of material
Technical Field
The invention relates to a method for controlling a temperature field in a material, in particular to a method for controlling a temperature field by a plurality of heat beams, and specifically relates to a method for controlling a temperature field in a material.
Background
Controlling the heat distribution within the material to form a target temperature field has long been a goal sought in the art, with significant application requirements in the areas of thermal coded communication, thermal therapy, thermally driven deformation, thermal reactors, thermal imaging, zoned thermal management, and the like. On one hand, the existing heat control methods are difficult to avoid introducing a large number of heating elements, pipelines or cables into materials, for example, in patent US20150336295a1, an electric heating wire and a flow channel are introduced into a mold material to form a plurality of independent temperature control areas, in patent CN105474382A, a plurality of array pixel resistance heaters are introduced into a substrate, in patent CN210111003U, a power-partitioned heating film structure is disclosed, the interior of the power-partitioned heating film structure is formed by arranging heating wires in a snake shape, and in patent CN112047297A, a large number of cables and elements are introduced into materials, so that the existing heat control methods are not favorable for material performance, and are difficult to be applied to the fields of airplane deicing, heat drive deformation and the like which have requirements on light weight and high strength of the materials. On the other hand, when the existing method requires n × n thermal pixel units, n × n independent temperature control channels are usually required, which makes the temperature control complex and makes it difficult to achieve precise thermal control with high resolution in a small number of control channels.
Disclosure of Invention
The invention aims to provide a novel method for controlling the internal temperature field of a material, aiming at the problems that the existing heat control method is difficult to avoid introducing a large number of heating elements into the material and realize high-resolution precise control. Inputting energy to form a plurality of heat beams in the material, carrying out thermal patterning calculation on the target temperature field, and regulating and controlling the power of each heat beam according to the calculation result, so that the heat beams are mutually staggered, combined and superposed in the material to form the target temperature field. The method firstly proposes that the tomography principle is utilized to the field of thermal control, any heating element or cable is not required to be introduced into the material, more densely distributed thermal pixel units can be realized under the same quantity of control channels, and high-resolution accurate thermal control in a three-dimensional space is realized.
The technical scheme of the invention is as follows:
a method for controlling the internal temperature field of a material is characterized in that energy is input to form a plurality of heat beams in the material, and the power of each heat beam is calculated and regulated according to a target temperature field, so that the heat beams are mutually staggered, combined and superposed in the material to form the target temperature field. And aiming at the target temperature field, calculating power values required by all the heat beams according to a thermal patterning calculation method, regulating and controlling the power of all the beams according to the calculation result, so that all the beam-shaped heat sources are mutually staggered in the material and combined and superposed according to the calculation result to form the target temperature field consisting of dense hot spots. The use of external energy to create an interdigitated beam heat source within the material eliminates the need to introduce any heating elements, piping, and cables into the material, and provides a higher thermal control resolution than conventional methods for the same number of control units.
The input energy source can be an external heat source distributed at the edge of the material, enters the material through heat conduction, and forms a heat beam after being conducted along a special heat conduction structure; other forms of energy are also possible, such as electrical energy, electromagnetic energy, optical energy, chemical energy, etc., and in a special loss structure, such as an anisotropic conductive material, energy is concentrated in a certain direction and lost to form a heat beam.
The heat beams are distributed in at least 2 directions in a two-dimensional plane, intersection points exist between any two heat beams in different directions, the number of the heat beams in the same direction is not less than 2, more than 1 layer of the two-dimensional plane can be distributed in parallel in the thickness direction of the material to form a three-dimensional temperature field, the number of the heat beams in each direction is preferably 18-32, and the number of the heat beams in each direction is preferably 32-400 in consideration of the correlation relationship of the increase of the number of the heat beams to the increase of the control precision of the temperature field, specific parameter selection is selected according to the control precision of the target temperature field.
The thermal patterning calculation method comprises the steps of firstly calculating a power distribution diagram under a target temperature field through a thermodynamic law, carrying out projection calculation on the power distribution diagram through Radon transformation to obtain a projection value, carrying out Fourier transformation on the projection value to convert the projection value into a frequency domain, carrying out filtering processing through a filter, carrying out Fourier inverse transformation on filtered data to return to a time domain, carrying out inverse thermal diffusion optimization on the filtered projection value, and finally outputting the optimal power value of each heat beam.
The regulation and control method comprises the steps of firstly, taking the power of each heat beam obtained through calculation as an initial value, collecting real-time temperature field data through temperature sensing or thermal imaging equipment in the temperature field control process, and regulating the power value of each heat beam obtained through calculation in real time through the collected temperature field data.
The specific heat conducting structure may be a thermally anisotropic structure, and the specific loss structure may be an electrically, magnetically, electromagnetically anisotropic structure or a non-homogeneous structure, such as a carbon fiber composite laminate having significant thermal and electromagnetic anisotropy.
The inverse thermal diffusion calculation method comprises the steps of firstly, carrying out Lato inverse transformation on a filtered power projection value to obtain a reconstructed power field, using the reconstructed power field as a heating source to calculate in an analytic or numerical three-dimensional heat transfer model to obtain a diffused temperature field, comparing the diffused temperature field with a target temperature field to obtain a temperature difference, converting the temperature difference into a power value to correct the original power field and obtain a new power field, then carrying out projection and filtering operation on the power field again to obtain a new power projection value, and finishing iterative optimization to output the latest power projection value when the temperature difference obtained by comparison meets an optimization target.
The correction process can be carried out in a temperature image domain or a power projection domain, when the correction process is carried out in the power projection domain, the temperature difference is converted into the power difference, the power difference is subjected to projection and filtering operation to obtain a projection value of the power difference, the original filtered power projection value is corrected according to the projection value of the power difference to directly obtain a new power projection value, and when the temperature difference obtained by comparison meets an optimization target, iterative optimization is ended to output the latest power projection value.
The invention has the following effective effects:
the obvious advantages of the invention for controlling the internal temperature field of the material are as follows: the use of external energy to create an interdigitated beam heat source within the material eliminates the need to introduce any heating elements, piping, and cables into the material, and provides a higher thermal control resolution than conventional methods for the same number of control units.
The method for controlling the internal temperature field of the material, named as Computed Thermal Patterning (CTP), adopts the tomography principle to the Thermal control field for the first time, and does not need to introduce any heating element or cable into the material. However, the conventional tomography principle based on light beams or rays only considers the problem of attenuation of the light beams in the propagation direction (patent CN108604047A), but the beam-shaped heat source also has a transverse thermal diffusion effect. The method is mainly characterized in that a plurality of heat beams are formed in the material by inputting energy, a target temperature field is subjected to heat pattern calculation, and the power of each heat beam is regulated and controlled according to the calculation result, so that the heat beams are mutually staggered, combined and superposed in the material to form the target temperature field. According to the invention, hot spots formed by staggered beam-shaped heat sources are used as heat pixel points, more densely distributed heat pixels can be realized under the same quantity of control channels, and high-resolution accurate heat control in a three-dimensional space is realized.
Drawings
FIG. 1 is a schematic diagram of the basic principle of the present invention for controlling the internal temperature field of a material.
Fig. 2 is a flow chart of a thermal patterning computation method.
Detailed description of the preferred embodiments
The invention is further elucidated with reference to the drawings and examples. It should be noted that the following examples are only intended to illustrate certain specific embodiments of the present invention, and are not intended to limit the scope of the present invention. In addition, after the present invention is disclosed, any modifications and changes of the principle of controlling the temperature field inside the material based on the present invention will be apparent to those skilled in the art, and they are within the scope of the present invention as defined in the appended claims.
As shown in fig. 1-2.
This example is a target temperature field in a two-dimensional "CTP" letter combination pattern formed by a computational thermal patterning method in an electrically anisotropic carbon fiber composite material, as shown in fig. 1. The control process of the thermal pattern is monitored by matching with a thermal infrared imager. The material realizes independent control of 576 bundle-shaped heat sources in 18 directions, 10 degrees of adjacent interval in each direction and 32 bundles in each direction in a self-resistance heating control mode, and each heat beam is heated under given calculation power and is crossed and superposed to form a required target temperature field. The size of each layer of carbon fiber epoxy material is 340mm multiplied by 290mm multiplied by 0.1mm, 32 thin copper sheets with the interval of 2mm and the width of 7mm are arranged on one side of the narrow edge of the carbon fiber epoxy material and used as negative electrode access points, long strip-shaped thin copper sheets with the same width as the material are arranged on the other side of the narrow edge of the carbon fiber epoxy material and used as positive electrode access points, and each heating strip bundle is connected into a control circuit with independent adjustable voltage through copper electrodes on the two sides. The calculated power is the power of each heat beam obtained by carrying out heat pattern calculation on the CTP pattern by a heat pattern calculation program, and the power is converted and burnt into a microprocessor, and then the voltage between electrodes at two sides of each heat source is adjusted to realize control. The specific steps of this example are as follows (see fig. 2):
step 1: calculating power: a 'CTP' gray image is manufactured in a computer to serve as a target of temperature field control, a power distribution diagram under a 'CTP' letter target temperature field is calculated through a thermodynamic law, the power distribution diagram is subjected to projection calculation through Radon transformation to obtain a projection value, the projection value is subjected to Fourier transformation and is converted into a frequency domain, then filtering processing is carried out through a filter, and then Fourier inverse transformation is carried out on the filtered data to return to a time domain, so that an initial power projection value is obtained. And then carrying out inverse thermal diffusion optimization on the power projection value, firstly carrying out Lato inverse transformation on the filtered power projection value to obtain a reconstructed power field, taking the reconstructed power field as a heating source, calculating in an analytic or numerical three-dimensional heat transfer model to obtain a diffused temperature field, comparing the diffused temperature field with a target temperature field of a 'CTP' letter to obtain a temperature difference, converting the temperature difference into a power value to correct the original power field and obtain a new power field, then carrying out projection and filtering operation on the power field again to obtain a new power projection value, carrying out 10 times of iterative comparison to obtain a temperature difference which accords with an optimization target, and finishing iterative optimization to output a new power projection value after 10 times of iteration. From this image, the heating power for each beam in the case of 32 × 18 heat beams is calculated in a program of the computational thermal patterning method. The adopted heating material is a unidirectional carbon fiber epoxy resin-based material, and the control voltage required by each bundle is calculated according to the resistance characteristic of the unidirectional carbon fiber epoxy resin-based material.
Step 2: preparing materials: taking out the carbon fiber epoxy prepreg, cutting 18 pieces of prepreg sheets with the size of 290mm multiplied by 340mm, and cutting 18 pieces of glass fiber prepreg sheets with proper size according to the size of the carbon fiber, wherein the two layers of carbon fiber prepreg and the copper sheets at two sides of the carbon fiber prepreg are required to be overlapped at an included angle of 10 degrees between the central lines and then cannot be in direct contact. And cutting auxiliary materials such as demolding cloth, an isolation film, an air-permeable felt, a vacuum bag and the like according to the size of the prepreg. Cutting the comb-shaped copper sheets according to the distance of 2mm and the width of 7mm, and cutting the strip-shaped copper sheets according to the size of the narrow edge of the carbon fiber.
And step 3: material laying: a piece of glass fiber prepreg is taken and placed on an operation table, the center of the carbon fiber prepreg is taken and placed on the glass fiber prepreg, then copper sheets and strip-shaped copper sheets are respectively placed on two sides of the prepreg at equal intervals, the copper sheets are overlapped with the prepreg for 15mm and fixed, the copper sheets are not convenient to be connected with a power supply in a follow-up process, and the copper sheets are welded with leads in advance and led out. And taking a glass fiber prepreg, taking the previous layer of glass fiber as a reference, anticlockwise rotating the previous layer of glass fiber in the direction of 10 degrees, placing the glass fiber prepreg at the upper side of the previous layer of glass fiber, compacting and extruding bubbles by using a press roller tool, and repeating the subsequent steps until 18 layers of carbon fiber materials are completely laid.
And 4, step 4: curing the composite material: taking out the flat metal mold, cleaning the surface with alcohol, sticking demolding cloth, laying the prepreg on the mold, laying demolding cloth, isolating film and air felt in sequence, installing temperature thermocouple and vacuum base, and packaging with vacuum bag. The material is placed in an oven, and PID control solidification is carried out according to a standard process curve. After completion, the carbon fiber composite material is demolded and removed, and the lead is cleaned.
And 5: connecting the materials with a power supply: connecting the lead wires on the copper sheet to a controller with 576 independent voltage adjustments, connecting each heat beam correspondingly to the output end of the controller, inputting the calculated voltage control signal into the microprocessor program control, and connecting the controller with a power supply with the maximum current of 400A and the maximum voltage of 10V.
Step 6: heating and infrared imaging: and erecting an infrared thermal imager above the carbon fiber material, wherein the imaging range of the infrared thermal imager comprises all the materials, correcting the thermal imager, turning on a power supply after the correction, and observing a required target temperature field and a formed thermal pattern in the thermal imager, wherein the similarity between the CTP thermal pattern and a target temperature graph can reach more than 60 percent, and the contrast between a heating area and a non-heating area can reach more than 30 percent. Other calculated voltage control signals are input according to the adjustable pattern reconstruction quality of the thermal imager, and can be converted between different thermal patterns.
The above examples reconstructed a "CTP" thermal pattern on the carbon fiber composite by computational patterning, and a clear desired target temperature field distribution was observed by thermal infrared imager.
The present invention is not concerned with parts which are the same as or can be implemented using prior art techniques.

Claims (5)

1. A method for controlling the internal temperature field of a material is characterized in that energy is input to form a plurality of heat beams in the material, and the power of each heat beam is calculated and regulated according to a target temperature field, so that the heat beams are mutually staggered, combined and superposed in the material to form the target temperature field; the method for calculating the power of each heat beam comprises the steps of firstly converting a target temperature field into a target power field according to a thermodynamic law, and secondly performing radon transform projection operation on the target power field to obtain power projection values of the heat beams in all directions.
2. The method of claim 1, wherein the source of the input energy is a material from which external heat is conducted into the special heat conducting structure, or electrical energy, electromagnetic energy, or chemical energy is lost in the special heat dissipating structure to generate heat.
3. The method according to claim 1, wherein the plurality of heat beams are distributed in not less than 2 directions in a two-dimensional plane, an intersection point exists between any two heat beams in different directions, the number of the heat beams in the same direction is not less than 2, more than 1 layer of two-dimensional plane is distributed in parallel in the thickness direction of the material to form a three-dimensional temperature field, and specific parameter selection is selected according to target temperature field control accuracy.
4. The method according to claim 1, wherein the controlling method comprises firstly using the power of each heat beam obtained by calculation as an initial value, collecting real-time temperature field data by a temperature sensing or thermal imaging device during the temperature field control, and adjusting the power of each heat beam obtained by calculation in real time by using the collected temperature field data.
5. The method of claim 2, wherein the specific heat conducting structure is a thermally anisotropic structure and the specific loss structure is an electrically, magnetically, electromagnetically anisotropic structure or a non-homogeneous structure.
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