Constant-temperature air bath box based on mean value coordination controller and top cover refrigeration

Abstract

The invention discloses a constant-temperature air bath box based on a mean value coordination controller and top cover refrigeration. The constant-temperature air bath box comprises a ceramic heating sheet module, a circulating water refrigerating unit, a temperature acquisition device and a top cover semiconductor refrigerator TEC auxiliary cooling system. The temperature control system adopts proportion-integration-differentiation (PID) control based on mean value coordination, and comprises a controller for controlling the mean value tracking set value of each path of temperature measurement value and a controller for eliminating the deviation between each path of temperature measurement value and the mean value. When the TEC refrigeration sheet and the cooling fan on the top cover of the constant temperature box work, heat of upper-layer air in the constant temperature box is dissipated to the outside, the situation that the upper portion is hot and the lower portion is cold due to natural convection of air in the box is reduced, and the uniformity and the stability of the temperature are improved. According to the temperature control system, the temperature coupling effect between the heating pieces is fully considered, and the accuracy and uniformity of temperature control are improved; and meanwhile, each hot module and each cold module have certain symmetry, so that the setting difficulty of control parameters is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of constant temperature control, in particular to a constant temperature air bath box based on a mean value coordination controller and top cover refrigeration. Background Art

[0002] With the rapid development of precision machining processes such as semiconductor manufacturing, photolithography, and atomic layer deposition (ALD), the demand for temperature control accuracy is increasing. In particular, in a constant-temperature gas bath environment, temperature uniformity and stability directly impact process quality and product performance. For example, in the semiconductor ALD process, the reactant gases must be evenly distributed within a constant temperature environment to ensure uniform and consistent thin film deposition. In photolithography, the coating and development processes of the photoresist require extremely precise control of the gas bath temperature; any slight temperature fluctuation can lead to pattern distortion or reduced resolution.

[0003] However, existing gas bath thermostats still have significant deficiencies in temperature control. First, the heating efficiency is low, making it difficult to quickly reach the target temperature and maintain stability; second, the temperature uniformity of the gas bath is poor, especially under large volume or complex flow field conditions. The unevenness of gas flow can easily lead to local temperature deviations, thereby affecting the process effect. In addition, traditional thermostats usually rely on refrigerators for temperature regulation, which not only increases additional equipment costs and energy consumption, but also violates the current policy orientation of energy conservation and emission reduction. Therefore, existing gas bath thermostats have obvious limitations in temperature uniformity, stability and energy efficiency, and are difficult to meet the needs of high-precision processes. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a constant temperature gas bath box based on a mean coordinated controller and top cover refrigeration, which can achieve uniform gas bath temperature distribution in the gas environment inside the constant temperature box and achieve stable temperature control on this basis.

[0005] To solve the above technical problems, the present invention provides a constant temperature air bath based on a mean value coordination controller and top cover cooling, comprising a heating drive module, a temperature acquisition module, and a circulating water refrigeration unit; the temperature acquisition module is composed of four thermocouple temperature sensors, a temperature transmitter, and a single-board computer; a plurality of temperature sensors are provided for detecting the temperature inside the constant temperature chamber and transmitting the temperature signal to the single-board computer; the heating drive module comprises a first heating plate module, a second heating plate module, a third heating plate module, and a fourth heating plate module, the first heating plate module and the second heating plate module being symmetrically arranged on the side walls of the constant temperature chamber, and the third heating plate module and the fourth heating plate module being arranged on the bottom of the constant temperature chamber; automatic control of the constant temperature chamber is achieved by the single-board computer, which is embedded with a mean value coordination controller and drives the heating plates to operate so that the four groups of heating plates can effectively reach the predetermined value; circulating water is passed through the interlayers between the four side walls of the chamber to provide a stable constant temperature environment, and the circulating water is supplied by the circulating water refrigeration unit.

[0006] Furthermore, the mean coordination controller is a multi-input multi-output PID controller, which is composed of K a Controller, G a Controller and G c The controller consists of three parts, the K a The controller is a 4×4 order constant conversion matrix that averages the four signals, G a The controller is a controller that controls the average value to track the set value, G c The controller is a controller that the actual value tracks the average value. Finally, G a Controller and G c The outputs of the controllers are added together as the overall control signal.

[0007] Furthermore, K a The controller is a 4×4 constant matrix used to calculate the average value of the four inputs and output them; the G a The controller is a fourth-order diagonal matrix, the K a The output of the controller is G a The input of the controller is used to control the average value of the four temperature signals to track the set value; the G a The diagonal elements of the controller matrix are proportional-integral controllers with different parameters, and the rest of the elements are zero.

[0008] Furthermore, the G c The controller is a fourth-order square matrix, the K a The difference between the controller and the actual temperature measurement is G c The input of the controller is used to eliminate the deviation between the temperature measurement value of each channel and the average value; the G cThe diagonal elements of the controller matrix are proportional-integral controllers with different parameters.

[0009] Furthermore, when the second heating plate module is working, the measuring point of the first temperature sensor is affected, G c The (2, 1) element in the matrix of the controller is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (1, 1) position; when the first group of heating plate modules is working, the second temperature sensor measuring point is affected, G c The (1, 2) element in the controller matrix is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (2, 2) position; the third heating plate module affects the fourth temperature measurement point, G c The (3, 4)th element in the matrix of the controller is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (3, 3) position; the fourth heating plate module affects the third temperature sensor measuring point, the (4, 3)th element in the matrix of the Gc controller is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (4, 4) position, the G c The remaining elements of the controller are all zero.

[0010] Furthermore, the top cover of the box is configured to be hollow and adopts circulating water cooling to improve the heat exchange of the upper layer inside the constant temperature box and improve the uniformity and stability of the internal temperature.

[0011] Furthermore, a glass window is reserved on the top cover for observing the real-time situation inside the constant temperature box; a copper sheet is also arranged around the glass window, which conducts heat from the upper area inside the constant temperature box to the outside of the constant temperature box and dissipates it using the TEC refrigeration sheet, thereby improving the uniformity of the temperature field inside the box.

[0012] Beneficial effects of the present invention:

[0013] The present invention innovatively proposes a design scheme and control principle for a precision constant temperature air bath chamber without ventilation and internal gas agitation. In particular, the present invention avoids the "hot on top and cold on the bottom" phenomenon of conventional constant temperature air bath environments by adding an independent circulating water cooling system and TEC auxiliary refrigeration system to the top cover of the constant temperature chamber. The present invention is a multi-input and multi-output mean coordinated controller for the constant temperature chamber device, which fully considers the coupling relationship between multi-channel temperature sensors and multi-channel heating actuators, thereby achieving highly uniform local air bath temperature environment control. In addition, the constant temperature air bath system is simple and easy to maintain, has a compact geometric size, and can be used in conjunction with various common testing environments, providing a high-quality, low-destructive constant temperature environment for related scientific research and inspection and testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the thermostat of the present invention;

[0015] Figure 2 It is an external view and a central cross-sectional view of the thermostat of the present invention;

[0016] Figure 3 It is a schematic structural diagram of the semiconductor refrigerator (TEC) auxiliary cooling system of the present invention;

[0017] Figure 4 It is a structural block diagram of the thermostat and its peripheral system of the present invention;

[0018] Figure 5 It is a block diagram of the controller system structure of the present invention;

[0019] Figure 6 It is a graph showing the experimental effect in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0021] Figure 2 This figure shows the exterior structure of a thermostatic air bath chamber based on mean-coordinated proportional-integral-derivative (PID) control, along with central cross-sectional views AA and BB of the chamber, according to one embodiment of the present invention. The chamber comprises four components: a top cover system 10, a thermostatic chamber peripheral system 20, a temperature acquisition module 30, and a heating element 40 for the heating drive module. As shown in the figure, the constant temperature box body also includes: a first heating plate module 41, marked as U1, a second heating plate module 42, marked as U2, a third heating plate module 43, marked as U3, a fourth heating plate module 44, marked as U4, a first temperature measuring point 31, marked as T1, a second temperature measuring point 32, marked as T2, a third temperature measuring point 33, marked as T3, a fourth temperature measuring point 34, marked as T4, a semiconductor cooler TEC external power cord 11, a cooling fan 12, a TEC temperature measuring point 13, a TEC cooling plate 14, a cooling fin 16, a top cover circulating water inlet 21, a top cover circulating water outlet 22, a box body circulating water inlet 23 and a box body circulating water outlet 24.

[0022] Figure 2The cross-section diagrams AA and BB of the thermostat box are shown, and the cross-section position is the center cross-section of the thermostat box, as shown in the figure. The positions of the four groups of heating plates and the four temperature measuring points refer to Figures AA and BB. The heating plates are grouped in twos, U1 and U2 are located on the front wall and the rear wall of the thermostat respectively, and the heating plates that make up U1 and U2 are symmetrically arranged and arranged at the same height. U3 and U4 are located at the bottom of the thermostat, and the two heating plates of U3 are located directly below U1 and U2 respectively, and the two heating plates of U4 are distributed on both sides of the other end of the bottom of the box. Among them, U1, U2, U3, and U4 are connected in parallel to ensure that the heating plates are subjected to the same control voltage and evenly distribute the current to achieve uniform heating of the heating area. U4 is used to achieve different heating requirements or control the heating intensity of a specific area. With the center of the chamber as the origin, the first and second temperature measurement points, T1 and T2, are symmetrically located on the right side of the diagram, with the sensors positioned near the top cover. The third and fourth temperature measurement points, T3 and T4, are symmetrically located on the left side of the diagram, with the sensors positioned close to the bottom. This layout ensures that the temperature sensors can measure temperature changes throughout the entire constant temperature chamber as closely as possible.

[0023] Specifically, the structure of the thermostat is described in detail herein. The thermostat includes a heating drive module, a temperature acquisition module, a top cover semiconductor cooler (TEC) auxiliary cooling system, and a circulating water refrigeration unit.

[0024] The heating drive module is mainly realized by four sets of ceramic heating plates and pulse width modulation (PWM) amplifier circuit;

[0025] The first heating plate module is attached to the same side of the inner wall of the constant temperature box;

[0026] The second heating plate module is symmetrical to the first heating plate module and is arranged on the other side of the inner wall of the constant temperature box;

[0027] A third heating plate module is provided at the bottom of the constant temperature box, with two heating plates directly below the first and second heating plate modules respectively;

[0028] The fourth heating plate module is arranged on both sides of the bottom of the constant temperature box and is placed vertically with the third heating plate module;

[0029] The pulse width modulation (PWM) amplifier circuit is used to precisely control the heating process of the heater by adjusting the emitted heating signal.

[0030] The temperature acquisition module is realized by four thermocouple temperature sensors, a temperature transmitter and a single-chip microcomputer;

[0031] Four thermocouples are fixed to the top cover of the constant temperature chamber in an armored manner, symmetrically distributed with the center of the top cover as the symmetric point, and are located directly above the third heating plate module. The ends of the thermocouple measuring points extend into the hollow space inside the chamber. Specifically, with the center of the chamber as the origin, the left side of the origin in the structure diagram is numbered as the third and fourth temperature sensor measuring points, both of which are at the same height; the right side is numbered as the first and second temperature sensor measuring points, which are at the same height and are located closer to the top cover than the third and fourth temperature measuring points.

[0032] A temperature transmitter is used to receive the temperature signal from the thermocouple temperature sensor and convert it into a current signal to achieve integration with the control system;

[0033] Serial line communication converter, used to convert serial port signals into a format that can be received by other devices. This purpose is achieved by using the converter to connect the main control chip single board computer and the temperature sensor;

[0034] The single-board computer includes the main control chip and is used to achieve detailed adjustment of the heating power of the heating plate.

[0035] Combining the aforementioned heating drive module and temperature acquisition module, the acquisition process begins with real-time monitoring of the controlled object's temperature via thermocouples. This signal is then sent to a temperature transmitter, where it is processed and converted into a signal format acceptable to the single-board computer. Finally, the heating control signal output by the main control unit is processed by the PWM signal amplification circuit and the mean-coordinated PID controller to generate a PWM signal, achieving dynamic power output for the heater module.

[0036] Figure 3 The structure diagram of the semiconductor cooler (TEC) auxiliary cooling system is shown. Figure 1 The TEC auxiliary cooling system shown is located on the upper side of the box lid, mounted at both ends of the top center window. The system consists of a fan 12, a TEC external power cord 11, two TEC temperature measuring points 13, a TEC cooling plate 14, a copper plate 15, and fins 16. The copper plate is in direct contact with the internal gas at the upper end of the constant temperature box body, and the TEC temperature measuring points are fixed at both ends above the copper plate. In operation, heat from the upper part of the constant temperature box is transferred to the copper plate by convection. When the temperature at the TEC temperature measuring point reaches the set value, the TEC cooling plate and the cooling fan start simultaneously. The heat conducted by the upper air inside the constant temperature box through the copper plate is absorbed by the TEC cooling plate and dissipated to the outside through the cooling fan, achieving the effect of auxiliary temperature control inside the constant temperature box. It is worth mentioning that the temperature control of the TEC cooling plate is not included in the overall controller, but is independently powered by the TEC external power cord. This reduces the parameters of the controller and reduces the complexity of the controller.

[0037] Figure 4The block diagram of the thermostat and its peripheral system structure implemented in the present invention is shown, which includes: a temperature acquisition module 30, a temperature transmitter 26, an amplifier 27, and a single-board computer 28. In this embodiment, the temperature collector uses a high-precision K-type thermocouple, the temperature transmitter has a serial communication function of the Modbus protocol, and the single-board computer uses a Raspberry Pi 4b;

[0038] The control process is as follows: the temperature inside the box is monitored in real time through thermocouples distributed at the four temperature measuring points of the constant temperature box. These temperature data are transmitted to the Raspberry Pi through the temperature transmitter using the Modbus protocol. On the Raspberry Pi, a Python program is written to generate a 0-3.3V PWM voltage signal through the GPIO pin based on the collected temperature data. This signal is amplified to 0-24V by the amplifier and drives the U1 to U4 heating plates to achieve continuously adjustable electric heating power, thereby adjusting the temperature inside the constant temperature box. The Python program implements a mean coordinated controller to control the heating plate to achieve constant temperature;

[0039] Furthermore, the external circulating water system 20 delivers circulating water with a ±1°C temperature fluctuation to the circulating water inlets of the thermostat body and top cover via the cooling water unit 25. This heat-exchanged circulating water is then further delivered to the cooling water unit through the water outlets of the thermostat body and top cover, forming a continuous cycle to stabilize the thermostat's internal temperature. Furthermore, the use of a semiconductor condenser (TEC) in the top cover as an auxiliary cooling system ensures a more uniform air temperature within the thermostat, preventing a "hot top, cold bottom" situation.

[0040] Figure 5 The block diagram of the thermostat controller system used in the embodiment of the present invention is shown. It is a temperature uniformity controller based on a distributed heat source. It controls the operation of the heating plate according to the difference between the detected signal and its average value. It mainly relies on the average output and the deviation from the set value to adjust the controller. The block diagram consists of four modules: K a Controller, G a Controller, G c Controller and the resulting control object H;

[0041] K a The controller is constructed as a 4×4 constant matrix in the present invention, which is responsible for averaging the four input signals and outputting the average value of the four signals;

[0042] G a The controller is constructed as a fourth-order diagonal matrix, which is mainly used to process the gap between the average signal and the set value, in order to make the average value track the set value;

[0043] G cThe controller is constructed as a fourth-order matrix, which is responsible for processing the gap between the measured value and the average value, so that the measured value of each channel can track the average value. c The controller is designed to a Based on the controller adjustment, reduce the unevenness of temperature distribution;

[0044] Specifically, the G a With G c The controller is characterized in that G a , G c They are all 4×4 matrices composed of proportional-integral (PI) control. Figure 5 Medium G a , G c As shown in the detailed structure diagram, G a Since the average value signals of the input controllers are equal, the diagonal elements are set as controllers with the same form and parameters in this embodiment, which are all K paj +K iaj* (1 / s), where j takes values of 1, 2, 3, and 4. In this embodiment, the diagonal elements of the Gc controller are not equal to each other, resulting in different function forms and involving multiple different parameters. Specifically, since T1 is significantly affected when U2 is working, G c The element (2, 1) in the controller matrix is in the form of K ic1* (1 / s); When U1 is working, T2 will also be significantly affected, so G c The element (1, 2) in the controller matrix is in the form of K ic2* (1 / s). U3 affects T4, and U4 also affects T3, resulting in G c The elements (3, 4) and (4, 3) in the controller matrix are K ic4* (1 / s) and K ic3* (1 / s). This improvement makes the controller more suitable for models with non-completely symmetrical distributed heat sources, thus having a wider range of practical applications.

[0045] In this embodiment, the parameters of the mean value coordination controller are set as follows: K pa1 =0.095,K ia1 =0.014,K pa2 =0.095,K ia2 =0.014,K pa3 =0.095,K ia3 =0.014,K pa4 =0.095,K ia4 =0.014,K pc1 =0.072,K ic1 =0.012,Kpc2 =0.031,K ic2 =0.018,K pc3 =0.068,K ic3 =0.021,K pc4 =0.087,K ic4 =0.011.

[0046] The position of each parameter in the controller matrix is as follows:

[0047]

[0048] Control object H, a comprehensive control signal is output to the controlled object, describing the relationship between the input control voltage u(s) of the heater and the output of the four temperature sensors T(s);

[0049] Figure 5 The system structure diagram works as follows: Input the set value to assign K a Controller, K a The output value of the controller acts directly on G a Controller, G a The module is mainly used to process the difference between the average signal and the set value, in order to make the average value track the set value. a The difference between the controller and the actual temperature measurement acts on G c The controller input, G c The module processes the difference between the measured value and the average value, so that the measured value of each channel can track the average value. c The controller is designed to a Based on the controller adjustment, the unevenness of temperature distribution is reduced. a , G c The output signals of the controllers are combined to form a comprehensive control signal output, forming the controlled object H. At the same time, H will also react to adjust other controllers to form a closed-loop control system;

[0050] Figure 6 This graph shows the temperature control results of the thermostat under the aforementioned settings. Without ventilation or internal airflow, this embodiment achieved temperature control uniformity <±0.75°C, temperature stability <±0.1°C, and average accuracy <±0.05°C, reaching leading levels in the field.

[0051] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A constant temperature air bath based on a mean value coordination controller and top cover refrigeration, characterized in that: It includes a heating drive module, a temperature acquisition module and a circulating water refrigeration unit; the temperature acquisition module is composed of four thermocouple temperature sensors, a temperature transmitter and a single-board computer; there are several temperature sensors for detecting the temperature inside the constant temperature box and transmitting the temperature signal to the single-board computer; the heating drive module includes a first heating plate module, a second heating plate module, a third heating plate module and a fourth heating plate module, the first heating plate module and the second heating plate module are arranged on the side wall of the constant temperature box and are symmetrical, and the third heating plate module and the fourth heating plate module are arranged at the bottom of the constant temperature box; the automatic control of the constant temperature box is realized by the single-board computer, and the single-board computer is embedded with a mean coordination controller to drive the heating plates to work so that the four groups of heating plates can effectively reach the predetermined value; circulating water is introduced into the interlayers between the four side walls of the box to provide a stable constant temperature environment, and the circulating water is supplied by the circulating water refrigeration unit.

2. The constant temperature air bath based on mean value coordination controller and top cover refrigeration according to claim 1, characterized in that: The mean value coordination controller is a multi-input and multi-output PID controller. a Controller, G a Controller and G c The controller consists of three parts, the K a The controller is a 4×4 order constant conversion matrix that averages the four signals, G a The controller is a controller that controls the average value to track the set value, G c The controller is a controller that the actual value tracks the average value. Finally, G a Controller and G c The outputs of the controllers are added together as the overall control signal.

3. The constant temperature air bath based on mean value coordination controller and top cover refrigeration according to claim 2, characterized in that: K a The controller is a 4×4 constant matrix used to calculate the average value of the four inputs and output them; the G a The controller is a fourth-order diagonal matrix, the K a The output of the controller is G a The input of the controller is used to control the average value of the four temperature signals to track the set value; the G a The diagonal elements of the controller matrix are proportional-integral controllers with different parameters, and the rest of the elements are zero.

4. The constant temperature air bath based on mean value coordination controller and top cover refrigeration according to claim 2, characterized in that: The G c The controller is a fourth-order square matrix, the K a The difference between the controller and the actual temperature measurement is G c The input of the controller is used to eliminate the deviation between the temperature measurement value of each channel and the average value; the G c The diagonal elements of the controller matrix are proportional-integral controllers with different parameters.

5. The constant temperature air bath based on mean value coordination controller and top cover refrigeration according to claim 4, characterized in that: When the second heating plate module is working, the measuring point of the first temperature sensor is affected, G c The (2, 1) element in the matrix of the controller is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (1, 1) position; when the first group of heating plate modules is working, the second temperature sensor measuring point is affected, G c The (1, 2) element in the controller matrix is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (2, 2) position; the third heating plate module affects the fourth temperature measurement point, G c The (3, 4)th element in the matrix of the controller is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (3, 3) position; the fourth heating plate module affects the third temperature sensor measuring point, the (4, 3)th element in the matrix of the Gc controller is in the form of an integral controller and has the same coefficient as the integral controller in the proportional-integral controller at the (4, 4) position, the G c The remaining elements of the controller are all zero.

6. The constant temperature air bath based on mean value coordination controller and top cover refrigeration according to claim 1, characterized in that: The top cover of the box is set as a hollow structure and adopts circulating water cooling to improve the heat exchange of the upper layer inside the constant temperature box and improve the uniformity and stability of the internal temperature; a semiconductor refrigerator is set on the top cover surface corresponding to the hollow structure.

7. The constant temperature air bath based on mean value coordination controller and top cover refrigeration according to claim 6, characterized in that: A glass window is reserved on the top cover for observing the real-time situation inside the constant temperature box; a copper sheet is also arranged around the glass window, which conducts heat from the upper area inside the constant temperature box to the outside of the constant temperature box and dissipates it using the TEC refrigeration sheet, thereby improving the uniformity of the temperature field inside the box.

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