Eddy current heating device and heating method for thermoluminescence element

Abstract

The invention relates to an eddy current heating device for a thermoluminescence element and a heating method. The device comprises a heating disc, a copper coil assembly, a supporting frame, a temperature measuring sensor assembly and a control circuit, the heating disc is in a disc shape, and the copper coil assembly is composed of four multi-layer closely-wound fan-shaped copper coils which are arranged in four quadrant areas of the heating disc respectively; the temperature measuring sensor assembly is provided with four temperature sensors which are embedded into the bottom of the heating disc through heat-conducting glue and connected with the control circuit. The control circuit adopts a PID (Proportion Integration Differentiation) algorithm to independently adjust the current of each sector according to feedback signals of each temperature sensor, realizes rapid temperature rise and accurate temperature control through frequency adjustment and power compensation, and has an over-temperature protection function. According to the device, the temperature of the heating disc can be raised to 300 DEG C within 3 seconds, and the temperature deviation is controlled within + / -0.5 DEG C. Compared with traditional resistance heating, the device has the advantages of being fast in temperature rise, low in energy consumption, high in temperature uniformity, convenient to maintain and the like, and meets the high-precision temperature control requirement of thermoluminescence measuring and reading equipment.

Description

Technical Field

[0001] This invention relates to the field of thermoluminescence measurement and heating technology, and in particular to an eddy current heating device and heating method for thermoluminescence elements. Background Technology

[0002] Thermoluminescence dating technology is widely used in radiation dose monitoring, archaeological dating, and materials testing. Its core element is the controlled heating of a thermoluminescent element, causing it to release a radiation dose-related signal according to a preset heating curve. Existing thermoluminescence readers mostly use stainless steel or nickel-chromium alloy sheets as heating elements, converting electrical energy into heat energy through resistance heating. However, this method has several drawbacks: First, the small surface area and low resistance of the resistance element necessitate a large resistor in series in the circuit to limit the current, resulting in significant energy loss due to the additional resistance, thus limiting heating efficiency and the rate of temperature rise, affecting measurement efficiency. Second, temperature detection often uses spot-welded thermocouple sensors, whose weld points are fragile and prone to detachment when replacing heating plates of different models, leading to heating plate failure and increased maintenance costs. Third, due to insufficient uniformity of the resistance element material, resistivity differences in different areas cause uneven heating, making it difficult to control the surface temperature difference of the heating plate within ±0.5℃, thus affecting the accuracy and repeatability of the thermoluminescence curve.

[0003] In view of the above problems, this invention is proposed. Summary of the Invention

[0004] This invention discloses an eddy current heating device and heating method for thermoluminescent elements, aiming to solve the technical problems existing in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, an eddy current heating device for a thermoluminescent element is provided, comprising a heating plate, a copper coil assembly, a support frame, a temperature sensor assembly, and a control circuit. The heating plate is disc-shaped, the copper coil assembly is disposed on one side surface of the heating plate, the support frame is disposed on the other side of the heating plate, the temperature sensor assembly is disposed at the bottom center of the heating plate, and the control circuit is disposed outside the heating plate and is connected to the copper coil assembly and the temperature sensor assembly, respectively. The copper coil assembly includes four sector-shaped copper coils, which are respectively set in the four quadrants of the heating plate. All four sector-shaped copper coils adopt a multi-layer dense winding structure and are closely arranged along the arc path of the sector. The temperature sensor assembly has four temperature sensors, which are respectively arranged in the center area of ​​the four sector-shaped copper coils. The four temperature sensors are embedded in the bottom of the heating plate with thermally conductive adhesive and are in close contact with the heating plate. The control circuit adjusts the current of the four sector-shaped copper coils according to the temperature feedback signals of the four temperature sensors.

[0006] As a preferred technical solution, a thermally conductive silicone grease layer or a graphene thermally conductive sheet is provided between the heating plate and the copper coil assembly.

[0007] As a preferred technical solution, the thickness of the thermally conductive silicone grease layer or graphene thermally conductive sheet is 0.5 mm.

[0008] As a preferred technical solution, the number of turns in each of the four sector-shaped copper coils is 15-20, and the input current intensity is 5-10A.

[0009] As a preferred technical solution, all four temperature sensors employ miniature K-type thermocouples.

[0010] According to another aspect of the present invention, a heating method for the above-described eddy current heating device is also provided, comprising the following steps: After the power is turned on, the target temperature is set through the control interface, and the copper coil assembly is driven to work through the control circuit. The temperature sensor assembly collects temperature data from each area of ​​the heating plate in real time and sends the temperature signal to the control circuit. The control circuit dynamically adjusts the AC current of the corresponding sector-shaped copper coil based on the temperature data of each area.

[0011] As a preferred technical solution, the control circuit dynamically adjusts the AC current of the corresponding sector-shaped copper coils. The control circuit is equipped with a PID controller, which regulates the temperature by calculating the output temperature using a PID algorithm and comparing the output temperature with the average temperature. When the output temperature is higher than the average temperature, the power in the corresponding area is reduced by the PID controller; conversely, the power in the corresponding area is increased by the PID controller.

[0012] As a preferred technical solution, the PID algorithm calculation includes: Let the four sector-shaped copper coil regions be i=1,2,3,4, Ti(t) be the real-time temperature of region i measured by the thermocouple, and Tset be the target set temperature value; Each of the four sector-shaped copper coil regions is equipped with a PID controller. The continuous-time domain output of the PID controller is: in, , K p , K i , K d Let be the PID gain for region i; Control output u i (t) is mapped to the current parameters of the copper coil, and the power is changed by adjusting the PWM duty cycle: in K D Sat(·) is the duty cycle gain, and Sat(·) is the saturation function. ; The control circuit is equipped with a frequency adjustment module, which helps optimize the heating rate. in, f base Based on the base frequency, K f For frequency-adjustable gain; To ensure temperature uniformity across the four sector-shaped copper coil regions, the average temperature is calculated: The regional temperature deviation is: The revised compensation item is as follows: in K c To coordinate and control gain; The final controlled output temperature (plus supplement) is: .

[0013] As a preferred technical solution, the control circuit dynamically adjusts the AC current of the corresponding sector copper coils, and when the temperature data of each area deviates from the target set value, the control circuit performs power compensation.

[0014] As a preferred technical solution, the control circuit is also equipped with an over-temperature protection module, which automatically cuts off or reduces the output power when the temperature data of each area exceeds the preset threshold.

[0015] The technical solution adopted in this invention can achieve at least one of the following beneficial effects: 1. This invention utilizes eddy currents to directly act on the bottom of the heating plate, achieving efficient energy transfer and significantly improving the heating rate. Compared to traditional resistance heating, the heating plate can reach 300°C within 3 seconds, effectively avoiding signal distortion caused by heating lag, thus ensuring the accuracy and stability of the measurement.

[0016] 2. This invention sets up sector-shaped copper coils in each of the four quadrants of the heating plate, and uses four embedded temperature sensors for independent temperature monitoring. Through a control circuit and PID algorithm, the current in each sector is dynamically adjusted to achieve zoned temperature control and real-time compensation. This solution can control the temperature difference in the central area of ​​the heating plate within ±0.5℃, significantly improving temperature uniformity, avoiding localized overheating or excessive temperature differences, and ensuring the repeatability and consistency of the thermoluminescent element during the heating process.

[0017] 3. This invention adopts a modular structural design, with a thermally conductive silicone grease layer or graphene thermally conductive sheet placed between the heating plate and the copper coil assembly to ensure good thermal conductivity. Simultaneously, the heating plate is installed using screws, eliminating the need to disassemble the sensor or damage the thermally conductive layer during replacement. Compared to traditional resistance heating methods that use thermocouples for spot welding, which are difficult to install and remove and prone to damage, this invention significantly reduces maintenance complexity and repair costs, extends the lifespan of the device, and improves its reliability during long-term operation.

[0018] 4. This invention introduces a PID control and frequency adjustment module into the control circuit, which can dynamically adjust the current and frequency based on real-time temperature feedback and automatically compensate for power deviations when the temperature deviates from the set value. Simultaneously, an over-temperature protection module is included, which automatically reduces or cuts off power when the temperature exceeds a threshold to prevent overheating damage. This solution not only improves temperature control accuracy and system safety but also achieves an energy conversion efficiency of over 85%, saving approximately 30-40% energy compared to traditional resistance heating methods, thus realizing highly efficient and energy-saving operation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the structure of an eddy current heating device for thermoluminescent elements according to the present invention; Figure 2 This is a schematic diagram of the heating plate and support frame of an eddy current heating device for thermoluminescent elements according to the present invention; Figure 3 This is a schematic flowchart of a heating method for an eddy current heating device for thermoluminescent elements according to the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Heating plate; 2. Copper coil assembly; 21. First copper coil; 22. Second copper coil; 23. Third copper coil; 24. Fourth copper coil; 3. Support frame; 4. Temperature sensor assembly; 41. First temperature sensor; 42. Second temperature sensor; 43. Third temperature sensor; 44. Fourth temperature sensor; 5. Support spring; 6. Control circuit; 61. High-frequency inverter; 62. PID controller; 63. Frequency adjustment module; 64. Over-temperature protection module. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0023] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0024] To address the problems existing in the prior art, embodiments of the present invention provide an eddy current heating device for thermoluminescent elements, such as... Figure 1 As shown, the device includes a heating plate 1, a copper coil assembly 2, a support frame 3, and a temperature sensor assembly 4. The heating plate 1 has an overall disc-shaped structure and is used to support the thermoluminescent element to be heated. The copper coil assembly 2 is disposed on one side surface of the heating plate 1 and is used to generate an alternating magnetic field under the action of an AC power supply, thereby forming an eddy current heating effect in the heating plate 1. The support frame 3 is disposed on the other side of the heating plate 1, that is, below the heating plate 1, and is used to provide stable support for the heating plate 1 and the copper coil assembly 2. The temperature sensor assembly 4 is disposed below the center of the heating plate 1, in the bottom area, and is used to detect the temperature status of the heating plate 1 in real time.

[0025] like Figure 1As shown, the copper coil assembly 2 consists of four independent sector-shaped copper coils, corresponding to the four quadrant regions of the heating plate 1 (first copper coil 21, second copper coil 22, third copper coil 23, and fourth copper coil 24). Preferably, each sector-shaped copper coil adopts a multi-layer dense winding structure, arranged closely along the arc path of the sector region. The aforementioned sector-shaped copper coils are wound on the support frame 3, which is made of high-temperature resistant insulating ceramic material. This support frame not only provides stable support for the four coils but also maintains good insulation and heat insulation performance in high-temperature environments, thereby avoiding electrical interference and heat conduction problems caused by high-frequency current. Furthermore, the copper coil assembly 2 is arranged on the surface of the heating plate 1. When an external power source supplies high-frequency alternating current with a frequency of 20-50kHz to the copper coil assembly 2, the copper coil assembly 2 generates an alternating magnetic field inside the heating plate 1, forming an eddy current field in the metal material of the heating plate 1. By adjusting the number of turns of a single sector-shaped coil and the input current intensity, the intensity and distribution characteristics of the eddy current field can be effectively controlled. Preferably, the number of turns in a single sector coil is 15-20, and the input current intensity is 5-10A. Since the eddy current density gradually decreases from the edge of the heating plate 1 to the center, the four sector copper coils (first copper coil 21, second copper coil 22, third copper coil 23 and fourth copper coil 24) working together can form a uniform temperature distribution inside the heating plate 1, avoiding local overheating or excessive temperature difference.

[0026] The first copper coil 21, the second copper coil 22, the third copper coil 23, and the fourth copper coil 24 independently heat their respective areas and cooperate with the temperature sensor assembly 4. For example... Figure 1As shown, the temperature sensor assembly 4 is located in the bottom area of ​​the heating plate 1, and is used for real-time monitoring and feedback control of each fan-shaped heating area (first copper coil 21, second copper coil 22, third copper coil 23, and fourth copper coil 24). The temperature sensor assembly 4 includes four independent temperature sensors, namely the first temperature sensor 41, the second temperature sensor 42, the third temperature sensor 43, and the fourth temperature sensor 44, which are correspondingly arranged in the central areas of the first copper coil 21, the second copper coil 22, the third copper coil 23, and the fourth copper coil 24. Preferably, the first temperature sensor 41, the second temperature sensor 42, the third temperature sensor 43, and the fourth temperature sensor 44 are all miniature K-type thermocouples, which are small in size, have a fast response speed, and can work stably in a high-frequency electromagnetic environment. Each thermocouple is embedded in the bottom of the heating plate 1 with thermally conductive adhesive, and is in close contact with the heating plate 1, thereby ensuring the real-time performance and accuracy of temperature acquisition. In terms of control, the embodiments of the present invention also include a control circuit 6 (not shown in the figure), which is disposed outside the heating plate 1 and the copper coil assembly 2, and is connected to the copper coil assembly 2 and the temperature sensor assembly 4 (i.e., the first copper coil 21, the second copper coil 22, the third copper coil 23 and the fourth copper coil 24) respectively. The temperature signals of the first temperature sensor 41, the second temperature sensor 42, the third temperature sensor 43 and the fourth temperature sensor 44 are input to the external control circuit 6. The control circuit integrates a Hall sensor to monitor the magnetic field strength generated by the copper coil assembly 2, and adjusts the coil current of the copper coil assembly 2 in combination with the temperature feedback signal. The control algorithm preferably adopts the proportional-integral-derivative (PID) algorithm.

[0027] Heating plate 1 is made of magnetically conductive stainless steel, such as 430 stainless steel. This type of material has good magnetic permeability, which enhances the eddy current effect under the action of a high-frequency alternating magnetic field, thereby significantly improving heating efficiency. At the same time, stainless steel possesses excellent mechanical strength and high-temperature resistance, enabling long-term stable operation. Figure 1As shown, the bottom of the heating plate 1 is machined into a planar structure to maximize the contact area of ​​the magnetic lines of force, allowing the alternating magnetic field generated by the copper coil assembly 2 to penetrate the heating plate more fully, thereby forming a uniformly distributed eddy current field inside the heating plate. This structural design not only improves the energy utilization rate of the eddy currents but also effectively ensures the uniformity of the overall temperature distribution of the heating plate. Preferably, a 0.5 mm thick thermally conductive silicone grease layer is provided between the heating plate 1 and the copper coil assembly 2, or alternatively, a graphene thermal conductive sheet is used. The above-mentioned thermally conductive medium has good thermal conductivity and flexible fit, which can form a tight thermal coupling path between the heating plate 1 and the copper coil assembly 2, thereby reducing the interface thermal resistance and ensuring that the heat generated by eddy current heating can be efficiently conducted to the surface of the heating plate 1. In addition, the heating plate 1 adopts a detachable structural design, which facilitates replacement and maintenance during experiments or use. Through cooperation with the support frame 3 and the temperature sensor assembly 4, the heating plate 1 can achieve efficient heating while maintaining a stable and uniform operating temperature under the closed-loop regulation of the control system, thereby ensuring the precise and controllable heating process of the thermoluminescent element.

[0028] Through the above structural design, by setting a copper coil assembly 2 consisting of four independent fan-shaped closely wound coils on the surface of the heating plate 1, and using a support frame 3 made of high-temperature resistant insulating ceramic material, zoned eddy current heating and stable insulation support are achieved. The heating plate 1 is preferably made of magnetically conductive stainless steel (such as 430 stainless steel), and the bottom is processed into a planar structure to enhance the eddy current effect. A 0.5 mm thick thermally conductive silicone grease layer or graphene thermally conductive sheet is introduced between it and the copper coil assembly 2 to reduce the interface thermal resistance and achieve efficient thermal coupling. The temperature sensor assembly 4 adopts an embedded miniature K-type thermocouple, which forms a temperature-magnetic field dual closed-loop feedback with the Hall sensor. Combined with the PID algorithm, the coil current, frequency and duty cycle are dynamically adjusted, thereby ensuring a temperature control accuracy of ±0.5℃ while having an over-temperature protection function. In this embodiment of the invention, after a 20–50 kHz high-frequency alternating current is passed through the copper coil, a uniform eddy current field is formed in the heating plate. Through zoned temperature control and coordinated compensation, the overall heating is uniform, the response is fast, and the energy efficiency is high. This overcomes the defects of uneven heating, low energy efficiency and insufficient temperature control accuracy in the prior art, and has significant innovation and practical value.

[0029] In some preferred embodiments, such as Figure 2 As shown, both the heating plate 1 (gray) and the support frame 3 (purple) have symmetrical fixing ears on both sides, each with through holes for screw fixing. That is, the heating plate 1 and the support frame 3 are connected by screws. When replacing, simply loosen the screws to remove the heating plate, avoiding mechanical stress on the heat-conducting layer and the sensor.

[0030] In some preferred embodiments, such as Figure 1As shown, a support spring 5 is provided in the center of the heating plate 1 to ensure that the heating plate 1 and the copper coil assembly 2 maintain a fixed distance.

[0031] This invention also provides a heating method for the above-mentioned eddy current heating device, such as... Figure 3 As shown, it includes the following steps: S1: Target temperature setting and activation; After the eddy current heating device is powered on, the user sets the target temperature (e.g., 300℃) through the control interface. An external control circuit 6 (not shown in the figure) is installed. After receiving the setting command, the control circuit starts the high-frequency inverter 61 (not shown in the figure) to drive the copper coil assembly 2. A high-frequency alternating current of 20–50 kHz is passed through the copper coil assembly 2, which generates an alternating magnetic field in the heating plate 1 and excites the eddy current effect, causing the heating plate 1 to rapidly heat up to the target set value within 3 to 5 seconds. S2: Real-time temperature measurement and zone feedback; The temperature sensor assembly 4 collects temperature data from each area of ​​the heating plate 1 in real time. Preferably, the temperature sensor assembly 4 includes four miniature K-type thermocouples, namely a first temperature sensor 41, a second temperature sensor 42, a third temperature sensor 43, and a fourth temperature sensor 44, which are embedded in the bottom center of the heating plate 1 in the corresponding areas of the first copper coil 21, the second copper coil 22, the third copper coil 23, and the fourth copper coil 24, forming four independent temperature monitoring channels. The temperature signals from each thermocouple are sent to the control circuit 6 as real-time feedback data for zoned control. S3: Zone power adjustment; Four sector-shaped copper coils (21, 22, 23, 24) correspond to four heating zones. Control circuit 6 dynamically adjusts the AC current of the corresponding coil based on the temperature signal of each zone, achieving precise temperature control within each zone. The preferred control strategy employs a PID algorithm. Let the regions of the four sector copper coils be i=1,2,3,4, Ti(t) be the real-time temperature of region i measured by the thermocouple, and Tset be the target set temperature value; Each region is equipped with an independent PID controller 62 (not shown in the figure), whose continuous time domain output is: in, , K p , K i , K d Let be the PID gain for region i; Control output u i (t) is mapped to coil current parameters, and the power is changed by adjusting the PWM duty cycle: in K D Sat(·) is the duty cycle gain, and Sat(·) is the saturation function. ; The heating rate is further optimized using a frequency adjustment module 63 (not shown in the figure): in, f base Based on the base frequency, K f For frequency-adjustable gain; To ensure consistent temperatures across the four zones, the average temperature is calculated: The regional temperature deviation is: The revised compensation item is as follows: in K c To coordinate and control gain; The final controlled output temperature (plus supplement) is: Determine if the final output temperature is higher than the average temperature: When T i > T avg If the temperature is above average, the power in that area will be reduced by the PID controller 62; conversely, the power in that area will be increased by the PID controller 62.

[0032] S4: Automatic compensation and safety protection; When the detected temperature deviates from the set value, the control circuit 6 system automatically performs power compensation to ensure that the center temperature deviation of the heating plate 1 is less than ±0.5℃. At the same time, the control circuit 6 is equipped with an over-temperature protection module 64 (not shown in the figure), which automatically cuts off or reduces the output power when the temperature exceeds the preset threshold to avoid damage to the device and failure of the thermoluminescent element; S5: Heating plate replacement; When heating plate 1 needs to be replaced, the user only needs to loosen the fixing screws, remove the old plate, clean off any residual heat-conducting material, install the new plate, and retighten the screws to ensure stable contact between heating plate 1 and copper coil assembly 2. Since the temperature sensor assembly 4 is fixed to the support frame 3 and the bottom of heating plate 1, it can continue to be used without recalibration, ensuring ease of maintenance.

[0033] By setting a target temperature, providing zoned temperature measurement feedback, implementing independent PID control, and automatically compensating for temperature changes, the heating method provided in this embodiment of the invention can raise the heating plate 1 to the target temperature in a short time and maintain uniform temperature distribution and high control accuracy throughout the heating process. It also features over-temperature protection and easy replacement, significantly improving the reliability and practicality of the device.

[0034] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. An eddy current heating device for thermoluminescent elements, characterized in that, The device includes a heating plate, a copper coil assembly, a support frame, a temperature sensor assembly, and a control circuit. The heating plate is disc-shaped. The copper coil assembly is disposed on one side of the heating plate, the support frame is disposed on the other side of the heating plate, the temperature sensor assembly is disposed at the bottom center of the heating plate, and the control circuit is disposed outside the heating plate and is connected to the copper coil assembly and the temperature sensor assembly, respectively. The copper coil assembly includes four sector-shaped copper coils, which are respectively arranged in the four quadrants of the heating plate. The four sector-shaped copper coils all adopt a multi-layer dense winding structure and are closely arranged along the arc path of the sector. The temperature sensor assembly has four temperature sensors, which are respectively arranged in the central area of ​​the four fan-shaped copper coils. The four temperature sensors are embedded in the bottom of the heating plate with thermally conductive adhesive and are in close contact with the heating plate. The control circuit adjusts the current of the four fan-shaped copper coils according to the temperature feedback signals of the four temperature sensors.

2. The eddy current heating device according to claim 1, characterized in that, A thermally conductive silicone grease layer or a graphene thermally conductive sheet is provided between the heating plate and the copper coil assembly.

3. The eddy current heating device according to claim 2, characterized in that, The thickness of the thermally conductive silicone grease layer or graphene thermally conductive sheet is 0.5 mm.

4. The eddy current heating device according to claim 1, characterized in that, The four sector-shaped copper coils each have 15-20 turns in their windings, and the input current intensity is 5-10A.

5. The eddy current heating device according to claim 1, characterized in that, All four temperature sensors are miniature K-type thermocouples.

6. A heating method for the eddy current heating device as described in any one of claims 1 to 5, characterized in that, Includes the following steps: After the power is turned on, the target temperature is set through the control interface, and the copper coil assembly is driven to work through the control circuit. The temperature sensor assembly collects temperature data from each area of ​​the heating plate in real time and sends the temperature signal to the control circuit. The control circuit dynamically adjusts the magnitude of the AC current corresponding to the sector-shaped copper coil based on the temperature data of each region.

7. The heating method according to claim 6, characterized in that, The control circuit dynamically adjusts the magnitude of the AC current corresponding to each of the sector-shaped copper coils. The control circuit includes a PID controller for temperature regulation, which involves calculating the output temperature using a PID algorithm and comparing the output temperature with the average temperature. When the output temperature is greater than the average temperature, the power of the corresponding area is reduced by the PID controller; conversely, the power of the corresponding area is increased by the PID controller.

8. The heating method according to claim 7, characterized in that, The PID algorithm calculation includes: Let the four sector-shaped copper coil regions be i = 1, 2, 3, 4, Ti(t) be the real-time temperature of region i measured by the thermocouple, and Tset be the target set temperature value; The four sector-shaped copper coil regions are each equipped with a PID controller, and the continuous time domain output of the PID controller is: Among them, e i (t)=T set -T i (t), K p K i K d Let be the PID gain for region i; Control output u i (t) is mapped to the current parameters of the copper coil, and the power is changed by adjusting the PWM duty cycle: D i (t)=sat(K D u i (t)) Where K D Sat(·) is the duty cycle gain, and Sat(·) is the saturation function. The control circuit is equipped with a frequency adjustment module, which helps to optimize the heating rate. f i (t)=f base +K f |e i (t)| Among them, f base Based on the base frequency, K f For frequency-adjustable gain; To ensure temperature coordination in the four sector-shaped copper coil regions, the average temperature is calculated as follows: The regional temperature deviation is: ΔT i (t)=T i (t)-T avg (t) The revised compensation item is as follows: δ ui (t)=K c ·ΔT i (t) Where K c To coordinate and control gain; The final controlled output temperature (plus supplement) is:

9. The heating method according to claim 7, characterized in that, After the control circuit dynamically adjusts the magnitude of the AC current corresponding to the sector-shaped copper coil, when the temperature data of each region deviates from the target set value, the control circuit performs power compensation.

10. The heating method according to claim 6, characterized in that, The control circuit is also equipped with an over-temperature protection module, which automatically cuts off or reduces the output power when the temperature data of each area exceeds a preset threshold.

Images