Automatic temperature control system for in-vitro digestion simulation device of animal

Abstract

This invention discloses an automatic temperature control system for an animal in vitro digestion simulation device, belonging to the field of temperature control technology. The system includes: a temperature sensing module, a constant temperature medium circulation module, a temperature control module, a multi-channel PWM power drive module, and a human-machine interface module. This invention uses probe-type sensors inserted through sealed plugs into the middle of the digestive tract to directly contact the contents for temperature measurement. When environmental fluctuations occur, hot air or a water bath at a temperature lower than the target temperature is used to assist in stabilization. The system receives temperature signals from each channel and independently adjusts the energizing time ratio of each heating film through the multi-channel PWM power drive module to precisely control the heating power of each simulated digester. It also supports dynamic temperature curve programming and over-temperature protection. The human-machine interface is used for parameter setting and status display, achieving independent temperature control for multiple channels.

Description

Technical Field

[0001] This invention relates to the field of temperature control technology, and in particular to an automatic temperature control system for an animal in vitro digestion simulation device. Background Technology

[0002] In the field of experimental instruments for animal nutrition and feed science, existing temperature control schemes for animal in vitro digestion simulation devices mainly include constant-temperature air bath shakers, jacketed circulating water baths, and local heating with sensor feedback. However, existing technologies still face many technical challenges in practical applications. Current air bath schemes control the ambient air temperature rather than directly controlling the temperature of the digested contents. Because the enzymatic reactions within the digestion tube may involve endothermic or exothermic phenomena, a significant deviation exists between the actual temperature inside the digestion tube and the set temperature of the external air bath. Experimental data shows that when the air bath is set to 39℃, the measured temperature at the center of the digestion tube can fluctuate between 37.2℃ and 40.1℃, with a maximum temperature difference of 2.9℃, far exceeding the allowable fluctuation range (±0.5℃) for normal body temperature in monogastric animals, severely affecting the accuracy and reliability of experimental results. In a single parallel experiment, existing devices typically require the simultaneous placement of 6 to 12 simulated digestive tracts. Due to the uneven distribution of the air bath's circulating airflow, temperature differences between different digestive tract locations can reach 1.2°C to 1.8°C, resulting in poor reproducibility of parallel experiments. The published coefficient of variation for existing equipment is 1.5%, but this data is based on the air bath temperature rather than the actual temperature within the digestive tract, making it difficult to accurately reflect the uniformity of experimental conditions. Most existing technologies employ a single-temperature zone uniform control method, failing to achieve differentiated temperature settings between the stomach and intestine. Furthermore, monogastric animals (such as pigs and chickens) exhibit physiological temperature gradients between their stomach and intestines, and the optimal temperature varies between animals of different ages. Existing systems cannot meet the independent temperature control requirements of different digestive stages, limiting the adaptability of in vitro simulation devices to complex digestive processes. Existing air bath solutions achieve temperature rise by heating the entire reaction chamber space. The system has a large heat capacity and a long temperature response time, making it difficult to simulate the rapid dynamic changes in stomach temperature after eating (such as temperature fluctuations caused by the introduction of cold food). This makes it impossible to achieve rapid temperature regulation and dynamic temperature curve programming control, further limiting the ability of in vitro digestion simulation to reproduce the real physiological environment. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide an automatic temperature control system for an animal in vitro digestion simulation device. This system can measure the temperature by inserting probe-type sensors through a sealed plug into the middle of the digestive tube to directly contact the contents. When the environment fluctuates, it uses hot air or a water bath at a temperature lower than the target temperature to help stabilize the field. It receives temperature signals from each channel and independently adjusts the energizing time ratio of each heating film through a multi-channel PWM power drive module to precisely control the heating power of each simulated digester. It also supports dynamic temperature curve programming and over-temperature protection. A human-machine interface is used for parameter setting and status display to achieve independent temperature control of multiple channels.

[0004] This invention provides an automatic temperature control system for an animal in vitro digestion simulation device. The system includes: a temperature sensing module, a constant-temperature medium circulation module, a temperature control module, a multi-channel PWM power drive module, and a human-machine interface module. The temperature sensing module comprises multiple independently configured probe-type temperature sensors, each corresponding to a simulated digester, used to collect the temperature signal of the digested contents in real time and output a corresponding electrical signal. The constant-temperature medium circulation module is located within the digestion reaction chamber housing the simulated digester and is activated when the ambient temperature fluctuation exceeds a preset threshold to maintain a stable ambient temperature within the reaction chamber. The temperature control module receives real-time temperature signals of the digested contents from temperature sensors within each simulated digester, drives each heating membrane to independently adjust its heating power, and supports dynamic temperature curve programming and over-temperature safety protection. The multi-channel PWM power drive module independently adjusts the energizing time ratio of each flexible heating membrane based on the multi-channel pulse width modulation control signals output by the main controller, thereby independently controlling the heating output power of each simulated digester. The human-machine interface module allows operators to set the target temperature value, PID parameters, and dynamic temperature curve parameters for each simulated digester, and displays the measured temperature, operating status, and alarm information of each channel in real time.

[0005] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: Real-time temperature measurement is achieved by directly contacting the digested contents with a probe-type temperature sensor, combined with direct heating from a flexible heating film. Closed-loop PID regulation is implemented using the digested contents as the direct temperature control target, achieving a temperature control accuracy of ±0.2℃ and controlling the intra-batch coefficient of variation to within 1.0%. Simultaneously, multi-channel independent PID control, combined with a PWM power drive module, allows for independent and precise adjustment of the energizing time ratio of each heating film, ensuring that the temperature difference between parallel tubes does not exceed 0.25℃. The digestibility range is reduced from 2.1% in traditional schemes to 0.7%, improving the reproducibility of parallel experiments. Furthermore, the system integrates dynamic temperature curve programming and independent temperature control for different zones, supporting the simulation of differentiated temperature gradients between the stomach and intestine segments and the accurate reproduction of the dynamic temperature recovery process after feeding cold materials. Coupled with a dual safety interlock mechanism of over-temperature protection and sensor fault detection, the system comprehensively ensures operational safety, environmental adaptability, and operational flexibility under complex experimental conditions, effectively solving core technical challenges such as temperature control target deviation, inconsistent temperatures across multiple tubes, and insufficient dynamic simulation capabilities in existing air bath / water bath schemes. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of the structure of an automatic temperature control system for an animal in vitro digestion simulation device provided in an embodiment of this application. Detailed Implementation

[0007] like Figure 1 The diagram shown is a structural schematic of an automatic temperature control system for an animal in vitro digestion simulation device provided in this application embodiment. The automatic temperature control system for an animal in vitro digestion simulation device provided in this application embodiment includes: a temperature sensing module, a constant temperature medium circulation module, a temperature control module, a multi-channel PWM power drive module, and a human-machine interface module. The temperature sensing module includes multiple independently configured probe-type temperature sensors, each corresponding to a simulated digester, used to collect the temperature signal of the digested contents in real time and output the corresponding electrical signal; wherein, the sensor extends into the middle of the inner cavity of the simulated digester through the opening reserved in the sealing plug at the upper end of the simulated digester, and its probe is in direct contact with the digested contents inside the simulated digester. The constant temperature medium circulation module is located in the digestion reaction chamber that houses the simulated digester. It is used to start operation when the ambient temperature fluctuation exceeds a preset threshold in order to maintain the stability of the ambient temperature in the reaction chamber. It operates by circulating hot air or a jacketed circulating water bath, and its set temperature is 2-3°C lower than the target temperature of the simulated digester. The temperature control module is used to receive the temperature signal of the digested contents collected in real time by the temperature sensors in each simulated digester, drive each heating film to independently adjust the heating power, and support dynamic temperature curve programming execution and over-temperature safety protection. The multi-channel PWM power drive module is used to independently adjust the energizing time ratio of each flexible heating film according to the multi-channel pulse width modulation control signal output by the main controller, thereby independently controlling the heating output power of each analog digester. The human-machine interface module is used by operators to set the target temperature value, PID parameters and dynamic temperature curve parameters for each simulated digester, and to display the measured temperature, working status and alarm information of each channel in real time.

[0008] In this embodiment, the temperature sensing module is equipped with multiple independently configured probe-type temperature sensors, each uniquely corresponding to a simulated digester. Each probe-type temperature sensor extends into the inner cavity of the simulated digester through an opening pre-drilled in the sealing plug at the top of the corresponding simulated digester, allowing the sensor probe to directly contact the digested contents inside the simulated digester. This allows for direct acquisition of the actual temperature of the digested contents, and the collected temperature physical quantity is converted into a corresponding electrical signal for output. The constant temperature medium circulation module is located inside the digestion chamber containing all the simulated digesters. This module serves as an auxiliary temperature control component, activating only when the external ambient temperature fluctuates above a preset system threshold, thereby maintaining a relatively stable internal temperature within the digestion chamber. The constant temperature medium circulation module can operate in either a circulating hot air mode or a circulating water bath mode within the digestion tube jacket. The set temperature of the constant temperature medium circulation module is 2-3°C lower than the target temperature of the simulated digester, serving only as an environmental buffer and not directly undertaking the primary temperature control task for the digested contents. The temperature control module, as the system's control core, receives the electrical signals of the digested contents temperature collected in real-time from the probe-type temperature sensors inside each simulated digester. The system performs calculations based on preset target temperatures, outputs multiple control signals, and drives the flexible heating films of each simulated digester to achieve independent adjustment of heating power. The temperature control module also features dynamic temperature curve programming execution, automatically running temperature change programs according to user-preset time-temperature nodes. It integrates over-temperature safety protection logic for fault identification and safety protection. The multi-channel PWM power drive module is electrically connected to the temperature control module, receiving multiple pulse width modulation control signals from the temperature control module. Each drive channel corresponds to a flexible heating film, independently adjusting the energizing time ratio of the corresponding flexible heating film to achieve individual control of the heating output power of each simulated digester. The human-machine interface module is connected to the temperature control module, allowing operators to configure and input target temperature values, PID control parameters, and dynamic temperature curve parameters for each simulated digester. The human-machine interface module also displays real-time measured temperature values ​​and equipment operating status for each control channel. In case of over-temperature or sensor malfunctions, corresponding alarm information is displayed simultaneously, facilitating parameter setting, experimental process monitoring, and fault diagnosis.

[0009] Furthermore, the specific process of real-time acquisition of the temperature signal of the digested contents and outputting the corresponding electrical signal is as follows: The temperature sensing module includes multiple independently configured probe-type temperature sensors, each probe-type temperature sensor corresponding to a simulated digester. The probe portion of the probe-type temperature sensor extends into the inner cavity of the simulated digester through the mounting hole reserved in the upper sealing plug of the simulated digester. The end of the probe is submerged below the liquid surface of the digested contents and is placed in the geometric center region of the inner cavity of the simulated digester, so that the probe and the digested contents form direct contact thermal coupling. The temperature sensing element of the probe-type temperature sensor is in direct contact with the digested contents. The heat from the digested contents is transferred to the temperature sensing element through thermal conduction, causing the resistance value or digital value of the temperature sensing element to change accordingly with the temperature change of the digested contents.

[0010] The method of real-time acquisition of temperature signals of digested contents and outputting corresponding electrical signals also includes: The sensor is electrically connected to the signal conditioning circuit of the temperature control module via a three-wire or four-wire connection. The signal conditioning circuit provides a constant excitation current to the sensor and acquires the voltage signal across the sensor. The voltage signal is amplified by the differential amplifier circuit in the signal conditioning circuit and then filtered by the low-pass filter circuit to remove high-frequency noise, generating an analog voltage signal. The analog voltage signal is transmitted to the main controller of the temperature control module. The analog-to-digital converter built into the main controller converts the analog voltage signal into a corresponding digital temperature value to obtain the real-time measured temperature value of the digested contents. When the temperature sensor experiences a disconnection, short circuit, or exceeds its range, the signal conditioning circuit or the main controller generates a corresponding fault status signal. The fault status signal, along with the temperature signal, is transmitted to the main controller to trigger the heating cut-off protection of the corresponding channel.

[0011] In this embodiment, the specific process by which the temperature sensing module acquires and outputs the corresponding electrical signal of the digested contents in real time is as follows: The temperature sensing module is equipped with multiple independently configured probe-type temperature sensors, each corresponding to a simulated digester. The probe of the probe-type temperature sensor extends into the inner cavity of the simulated digester through the mounting hole reserved in the upper sealing plug. The tip of the probe is submerged below the liquid surface of the digested contents and is arranged in the geometric center area of ​​the inner cavity of the simulated digester, allowing the probe to form a direct contact thermal coupling relationship with the digested contents. The temperature sensing element inside the probe-type temperature sensor is in direct contact with the digested contents. The heat carried by the digested contents is transferred to the temperature sensing element by thermal conduction, causing the resistance value or digital value of the temperature sensing element to change accordingly with the temperature change of the digested contents. The probe-type temperature sensor uses a three-wire or four-wire wiring method to connect with the signal conditioning circuit inside the temperature control module. Electrically connected, the signal conditioning circuit outputs a constant excitation current to the probe-type temperature sensor and simultaneously acquires the voltage signal across the sensor. This voltage signal is amplified by the differential amplifier circuit of the signal conditioning circuit, then filtered by a low-pass filter circuit to remove high-frequency noise introduced by line coupling. After processing, an analog voltage signal is output, which is further sent to the main controller of the temperature control module. The analog-to-digital converter built into the main controller converts the received analog voltage signal into a corresponding digital temperature value, thereby obtaining the real-time measured temperature value of the digested contents. During temperature acquisition, if the temperature sensor experiences an abnormal condition such as a broken wire, short circuit, or measurement signal exceeding the range, the signal conditioning circuit or the main controller will generate a corresponding fault status signal. This fault status signal is sent to the main controller along with the temperature signal. Upon receiving the fault status signal, the main controller triggers the heating cut-off protection action of the corresponding channel to prevent abnormal heating from adversely affecting the experimental devices and samples.

[0012] Furthermore, the temperature control module includes a main controller and a signal conditioning circuit; The main controller uses an STM32 microcontroller or a programmable logic controller and has multiple independently operating PID operation units built in. The number of PID operation units matches the number of analog digesters, and each operation unit independently corresponds to one analog digester. The signal conditioning circuit is electrically connected to the temperature sensing module and is used to amplify and filter the electrical signal output by the temperature sensor, and transmit the processed signal to the main controller. The specific process for driving each heating film to independently adjust its heating power is as follows: The main controller has a built-in multi-channel independently operating proportional-integral-derivative (PI-DI) arithmetic unit that matches the number of analog digesters. Each PI-DI-DI arithmetic unit corresponds to an independent control channel. The main controller calls the preset target temperature value stored in the corresponding channel to calculate the temperature deviation value of the current control cycle. The temperature deviation value is the preset target temperature value minus the current temperature value. The main controller compares the temperature deviation value with a preset first deviation threshold and a preset second deviation threshold; wherein the first deviation threshold is 2℃ and the second deviation threshold is 0.5℃. When the temperature deviation value is greater than the first deviation threshold, it is determined that the measured temperature of the digested contents is far lower than the target temperature. The corresponding channel needs to perform full-power heating. The main controller sets the control output value of the channel to the upper limit of the control quantity, that is, outputs a pulse width modulation control parameter with a duty cycle of 100%, so that the heating film continues to heat at the rated power until the digested contents are rapidly heated to close to the target temperature.

[0013] The method of driving each heating film to independently adjust the heating power also includes: When the temperature deviation value is less than or equal to the first deviation threshold and greater than the second deviation threshold, the main controller calls the proportional-integral-derivative (PID) operation unit corresponding to the channel to perform incremental PID operation based on the temperature deviation value and generate the control output increment for the current control cycle. The incremental proportional-integral-derivative (PI-DI) operation takes the temperature deviation value of the current control cycle, the temperature deviation value of the previous control cycle, and the temperature deviation values ​​of the two previous control cycles as inputs. It then performs weighted calculations on these three deviation values ​​using proportional, integral, and derivative coefficients, respectively, to calculate the control output increment for the current control cycle. The main controller calculates the control output value for the current control cycle based on the sum of the control output value of the previous control cycle and the control output increment for the current control cycle. The main controller performs amplitude limiting processing on the control output value, confining it between the lower and upper limits of the control quantity. The control output value corresponds to the duty cycle parameter of the pulse width modulation (PWM) control signal. When the temperature deviation value is less than or equal to the second deviation threshold, the main controller sets the control output value of the channel to the lower limit of the control quantity, that is, outputs a pulse width modulation control parameter with a duty cycle of 0%, cuts off the power supply to the heating film of the channel, and stops heating to prevent overheating.

[0014] The main controller generates a pulse width modulation control signal with a corresponding duty cycle based on the control output value calculated by each channel. The frequency of the pulse width modulation control signal is a fixed value. The main controller outputs the pulse width modulation control signal of each channel to the pulse width modulation power drive module of the corresponding channel. According to the received pulse width modulation control signal, it controls the high-speed turn-on and turn-off of the power switching device in the power supply circuit of the heating film of the corresponding channel. The ratio of the turn-on time to the turn-off time of the power switching device is determined by the duty cycle of the pulse width modulation control signal, thereby adjusting the effective value of the effective power supply voltage and the heating power of the heating film. At the end of each control cycle, the main controller updates the stored historical deviation value, stores the temperature deviation value of the current control cycle as the temperature deviation value of the previous control cycle, stores the temperature deviation value of the previous control cycle as the temperature deviation value of the two previous control cycles, and stores the control output value of the current control cycle as the control output value of the previous control cycle, for use in the incremental proportional-integral-derivative operation of the next control cycle.

[0015] The main controller performs safety protection interlock judgment: when the measured temperature value detected by any of the temperature sensors exceeds the preset safety upper limit threshold of that channel, the main controller immediately cuts off the pulse width modulation output of all channels, causing all heating films to stop heating, and at the same time issues an audible and visual alarm signal and records the fault information through the human-machine interface; when the main controller detects that any of the temperature sensors has a broken wire, short circuit, or signal over-range fault, the main controller immediately cuts off the pulse width modulation output of the corresponding channel, and displays the fault channel number and fault type through the human-machine interface, while the remaining normal channels maintain independent temperature regulation operation.

[0016] In this embodiment, the temperature control module includes a main controller and a signal conditioning circuit. The main controller is an STM32 microcontroller or a programmable logic controller. The main controller is internally configured with multiple independently operating PID arithmetic units, the number of which matches the number of simulated digesters. Each PID arithmetic unit corresponds to one simulated digester. The signal conditioning circuit is electrically connected to the temperature sensing module, receiving the electrical signal output from the temperature sensing module and amplifying and filtering it before sending the processed signal to the main controller. The specific process for driving each heating film to independently adjust its heating power in this embodiment is as follows: The main controller is internally configured with multiple independently operating proportional-integral-derivative (PI-DI) arithmetic units corresponding one-to-one with the number of simulated digesters. Each PI-DI unit corresponds to an independent control channel. The main controller retrieves the pre-stored target temperature value for the corresponding channel and calculates the temperature deviation value for the current control cycle. This temperature deviation value is the preset target temperature value minus the current measured temperature value of the digested contents. The main controller compares the calculated temperature deviation value with a first deviation threshold preset to 2°C and a threshold preset to 0°C.A comparison is made using a second deviation threshold of 5℃. When the temperature deviation is greater than the first deviation threshold, it is determined that the measured temperature of the digested contents is far below the target temperature. The corresponding channel executes a full-power heating strategy, and the main controller sets the control output value of this channel to the upper limit of the control quantity, outputting pulse width modulation control parameters with a duty cycle of 100%, driving the heating film to continuously heat at rated power, causing the digested contents to rapidly heat up to near the target temperature. When the temperature deviation is less than or equal to the first deviation threshold and greater than the second deviation threshold, the main controller calls the proportional-integral-derivative (PI-DE) operation unit corresponding to this channel, performs incremental PI-DE operations based on the temperature deviation value, and outputs the current control cycle. The incremental control output increment is calculated using a proportional-integral-derivative (PI-DE) operation. This operation takes the temperature deviation values ​​of the current control cycle, the previous control cycle, and the two previous control cycles as inputs. The proportional, integral, and derivative coefficients are used to weight these three sets of deviation values ​​to obtain the control output increment for the current control cycle. The main controller then adds the control output value from the previous control cycle to the current control cycle's increment to calculate the control output value for the current control cycle. This control output value is then limited to a range between the lower and upper limits of the control quantity. This control output value represents the duty cycle of the pulse width modulation (PWM) control signal. The main controller sets the control output value of the channel to the lower limit of the control quantity when the temperature deviation is less than or equal to the second deviation threshold, outputs a pulse width modulation control parameter with a duty cycle of 0%, cuts off the power supply circuit of the heating film of that channel, and stops the heating operation to avoid temperature overshoot. Based on the control output values ​​obtained from each channel, the main controller generates a pulse width modulation control signal with a corresponding duty cycle and fixed frequency, and then sends each pulse width modulation control signal to the corresponding channel's pulse width modulation power drive module. The pulse width modulation power drive module controls the power switch inside the power supply circuit of the heating film of the corresponding channel based on the received pulse width modulation control signal. The high-speed on / off switching of the power switching devices is determined by the duty cycle of the pulse width modulation control signal, thereby changing the effective value of the supply voltage across the heating film and ultimately regulating the heating power of the heating film. After each control cycle, the main controller updates the historical deviation data stored internally, saving the temperature deviation value of the current control cycle as the temperature deviation value of the previous control cycle, and saving the temperature deviation value of the previous control cycle as the temperature deviation value of the two control cycles prior. Simultaneously, the control output value of the current control cycle is saved as the control output value of the previous control cycle, providing historical calculation data for the incremental proportional-integral-derivative (PI-DE) calculations in the next control cycle.

[0017] Furthermore, the specific process for independently adjusting the energizing time ratio of each flexible heating film is as follows: The input terminal of the multi-channel PWM power drive module is electrically connected to the multi-channel pulse width modulation signal output port of the main controller, and its output terminal is electrically connected to the power supply terminal of each of the flexible heating films. The multi-channel PWM power drive module includes multiple power drive sub-modules that match the number of independent control channels, and each power drive sub-module independently corresponds to a flexible heating film of an analog digester. Each of the power drive submodules includes a signal isolation circuit, a power switching device, and a freewheeling protection circuit. The signal isolation circuit uses an optocoupler, whose input terminal is electrically connected to the corresponding pulse width modulation signal output port of the main controller. It is used to receive the pulse width modulation control signal output by the main controller and transmit the pulse width modulation control signal from the control side to the control electrode of the power switching device after electrical isolation, thereby realizing electrical isolation between the control circuit and the power circuit. The power switching device uses a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor. Its control electrode is electrically connected to the output terminal of the signal isolation circuit, its first conducting terminal is electrically connected to the positive terminal of the power supply, its second conducting terminal is electrically connected to the first power supply terminal of the flexible heating film, and the second power supply terminal of the flexible heating film is electrically connected to the negative terminal of the power supply, forming a heating power supply circuit.

[0018] The method of independently adjusting the energizing time ratio of each flexible heating film also includes: The power switching device rapidly switches between its on and off states according to the level of the pulse width modulation control signal received by its control electrode: when the pulse width modulation control signal is high, the power switching device is turned on, the heating power supply circuit is closed, the power supply supplies power to the flexible heating film, and the flexible heating film heats up. When the pulse width modulation control signal is low, the power switch is turned off, the heating power supply circuit is disconnected, the power supply stops supplying power to the flexible heating film, and the flexible heating film stops heating. The freewheeling protection circuit uses a fast recovery diode, which is connected in reverse parallel across the two ends of the flexible heating film. Its anode is connected to the second conducting terminal of the power switching device, and its cathode is connected to the positive terminal of the power supply. It is used to provide a freewheeling discharge circuit for the reverse induced electromotive force generated by the inductive characteristics of the flexible heating film at the instant when the power switching device switches from conducting to turning off, absorbs reverse peak voltage, and protects the power switching device from overvoltage breakdown. The main controller converts the independently calculated control output values ​​of each channel into pulse width modulation control signals with corresponding duty cycles according to the control cycle. The duty cycle is defined as the ratio of the high-level duration of the pulse width modulation signal to the total pulse cycle time within a complete cycle. The main controller outputs the pulse width modulation control signals of each channel to the signal isolation circuit input terminal of the corresponding power drive submodule. After receiving the pulse width modulation control signal of the corresponding channel, the signal isolation circuit of each power drive submodule electrically isolates and converts the pulse width modulation control signal through an optocoupler to generate the drive voltage signal required to drive the power switching device, and transmits it to the control electrode of the power switching device.

[0019] The method of independently adjusting the energizing time ratio of each flexible heating film also includes: Based on the drive voltage signal received by the control electrode, high-speed on / off switching is performed within one pulse width modulation period according to the time ratio determined by the duty cycle, specifically: During the high-level duration of the pulse width modulation period, the driving voltage signal drives the power switching device to turn on, energizing and heating the flexible heating film during the high-level duration; during the remaining time from the end of the high-level duration of the pulse width modulation period to the end of the period, the driving voltage signal controls the power switching device to turn off, de-energizing and stopping the heating of the flexible heating film during the remaining time; the power switching device repeats the above-mentioned on / off switching action in each pulse width modulation period according to the frequency of the pulse width modulation signal; The effective on-time ratio of each flexible heating film on a continuous time scale is the duty cycle of its corresponding pulse width modulation control signal. The actual heating power of the flexible heating film is directly proportional to the duty cycle; wherein, the larger the duty cycle, the higher the on-time ratio of the flexible heating film and the greater the actual heating power; the smaller the duty cycle, the lower the on-time ratio of the flexible heating film and the smaller the actual heating power; when the duty cycle is 100%, the power switching device is continuously turned on throughout the entire control cycle, and the flexible heating film is continuously energized and heated at its rated power; when the duty cycle is 100%, the power switching device is continuously turned on throughout the entire control cycle, and the flexible heating film is continuously energized and heated at its rated power; when the duty cycle is 100%, the power switching device is continuously turned on throughout the entire control cycle, and the power switching device is continuously energized and heated at its rated power. When the duty cycle is 0%, the power switching device remains off throughout the entire control cycle, and the flexible heating film is completely de-energized and stops heating. Each of the power drive sub-modules independently executes the above-mentioned pulse width modulation signal driving and power switch switching process. The duty cycle of each channel is determined by the main controller based on the independent temperature deviation and proportional-integral-derivative calculation results of each channel, without affecting each other. This enables independent and precise adjustment of the energizing time ratio of the flexible heating film of each simulated digester, so that the heating output power of each simulated digester is adapted to the real-time temperature adjustment requirements of its respective digested contents. When the main controller outputs an over-temperature protection cut-off command, the power switching devices of all power drive sub-modules in the multi-channel PWM power drive module are simultaneously forced to turn off, cutting off the power supply path of all flexible heating films. When the main controller outputs a single-channel fault cutoff command, only the power switching devices of the power drive submodule corresponding to the faulty channel are forcibly turned off, while the power drive submodules of other non-faulty channels maintain normal operation.

[0020] In this embodiment, the input terminal of the multi-channel PWM power drive module is electrically connected to the multi-channel pulse width modulation signal output port of the main controller, and the output terminal of the multi-channel PWM power drive module is electrically connected to the power supply terminal of each flexible heating film. The multi-channel PWM power drive module internally contains multiple power drive sub-modules, the number of which matches the number of independent control channels. Each power drive sub-module uniquely corresponds to a flexible heating film configured in the analog digester. Each power drive sub-module integrates a signal isolation circuit, a power switching device, and a freewheeling protection circuit. The signal isolation circuit uses an optocoupler, and the input terminal of the optocoupler is electrically connected to the corresponding pulse width modulation signal output port of the main controller. The circuit is connected to receive pulse width modulation (PWM) control signals from the main controller and transmits these signals to the control electrode of the power switching device after achieving electrical isolation on the control side. This achieves electrical isolation between the control circuit and the power circuit. The power switching device is a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT). The control electrode of the power switching device is electrically connected to the output terminal of the signal isolation circuit. The first conducting terminal of the power switching device is connected to the positive terminal of the power supply, and the second conducting terminal is connected to the first power supply terminal of the flexible heating film. The second power supply terminal of the flexible heating film is connected to the negative terminal of the power supply, thus forming a complete heating power supply circuit. The power switching device is based on its... The high and low levels of the pulse width modulation (PWM) control signal received by the control electrode enable high-speed switching between the on and off states. When the PWM control signal is high, the power switch is on, the heating power supply circuit is closed, and the power supply supplies power to the flexible heating film, generating heat. When the PWM control signal is low, the power switch is off, the heating power supply circuit is open, the power supply stops supplying power to the flexible heating film, and the flexible heating film stops generating heat. The freewheeling protection circuit uses fast recovery diodes, which are connected in reverse parallel across the flexible heating film. The anode of the fast recovery diode is connected to the second on terminal of the power switch, and the cathode of the fast recovery diode is connected to the positive terminal of the power supply. When... At the instant the power switching device switches from the on state to the off state, the fast recovery diode provides a freewheeling discharge circuit for the reverse induced electromotive force generated by the flexible heating film due to its inductive characteristics, absorbs the reverse voltage spikes that appear on the line, and protects the power switching device from overvoltage breakdown damage. The main controller converts the control output values ​​obtained by the independent calculation of each channel into pulse width modulation control signals with corresponding duty cycles according to a predetermined control cycle. The duty cycle is defined as the ratio of the high level duration within a complete cycle of the pulse width modulation signal to the total pulse cycle time. The main controller outputs the pulse width modulation control signals generated by each channel to the signal isolation circuit input terminal of the corresponding power drive submodule.After receiving the pulse width modulation (PWM) control signal from its respective channel, the signal isolation circuit of each power drive submodule uses an optocoupler to achieve electrical isolation and level conversion, generating a drive voltage signal capable of driving the power switching device. This drive voltage signal is then sent to the control electrode of the power switching device. Based on the drive voltage signal received from the control electrode, the power switching device performs high-speed on / off switching according to a time ratio determined by the duty cycle within a single PWM period. Specifically, during the high-level duration of the PWM period, the drive voltage signal drives the power switching device to conduct, and the flexible heating film is energized during this high-level duration. During the remaining time period after the high level of the pulse width modulation (PWM) cycle ends and until the cycle concludes, the drive voltage signal controls the power switch to turn off. The flexible heating film is de-energized and stops heating during this remaining time. The power switch cyclically repeats this on / off switching action within each PWM cycle according to the frequency of the PWM signal. The effective on-time ratio of each flexible heating film in the continuous time dimension is equal to the duty cycle of the corresponding channel's PWM control signal. The actual heating power of the flexible heating film is directly proportional to the duty cycle; the larger the duty cycle, the higher the proportion of the flexible heating film's on-time, and the greater the actual heating power. The smaller the duty cycle, the lower the percentage of time the flexible heating film is energized, and the lower the actual heating power. When the duty cycle is 100%, the power switching device remains continuously on throughout the control cycle, and the flexible heating film is continuously energized and heated at its rated power. When the duty cycle is 0%, the power switching device remains continuously off throughout the control cycle, and the flexible heating film is completely de-energized and stops heating. Each power drive submodule independently executes the pulse width modulation signal reception, drive output, and power switch switching process. The duty cycle of each channel is calculated and determined by the main controller based on the independent temperature deviation of the corresponding channel and the proportional-integral-derivative calculation results. The channels do not interfere with each other. This allows for independent and precise adjustment of the energizing time ratio of the flexible heating film for each simulated digester, ensuring that the heating output power of each simulated digester can be adapted to the real-time temperature regulation requirements of its digested contents. When the main controller issues an over-temperature protection cutoff command, the power switching devices of all power drive submodules within the multi-channel PWM power drive module are simultaneously and forcibly shut down, cutting off the power supply path to all flexible heating films. When the main controller issues a single-channel fault cutoff command, only the power switching devices of the power drive submodule corresponding to the faulty channel are forcibly shut down, while the power drive submodules of the other non-faulty channels continue to operate normally.

[0021] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An automatic temperature control system for an animal in vitro digestion simulation device, characterized in that, include: Temperature sensing module, constant temperature medium circulation module, temperature control module, multi-channel PWM power drive module, and human-machine interface module; The temperature sensing module includes multiple independently configured probe-type temperature sensors, each corresponding to a simulated digester, used to collect the temperature signal of the digested contents in real time and output the corresponding electrical signal. The constant temperature medium circulation module is located in the digestion reaction chamber that houses the simulated digester. It is used to start operation when the ambient temperature fluctuation exceeds a preset threshold in order to maintain the stability of the ambient temperature in the reaction chamber. The temperature control module is used to receive the temperature signal of the digested contents collected in real time by the temperature sensors in each simulated digester, drive each heating film to independently adjust the heating power, and support dynamic temperature curve programming execution and over-temperature safety protection. The multi-channel PWM power drive module is used to independently adjust the energizing time ratio of each flexible heating film according to the multi-channel pulse width modulation control signal output by the main controller, thereby independently controlling the heating output power of each analog digester. The human-machine interface module is used by operators to set the target temperature value, PID parameters and dynamic temperature curve parameters for each simulated digester, and to display the measured temperature, working status and alarm information of each channel in real time.

2. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 1, characterized in that, The specific process for real-time acquisition of temperature signals from digested contents and outputting corresponding electrical signals is as follows: The temperature sensing module includes multiple independently configured probe-type temperature sensors, each probe-type temperature sensor corresponding to a simulated digester. The probe portion of the probe-type temperature sensor extends into the inner cavity of the simulated digester through the mounting hole reserved in the upper sealing plug of the simulated digester. The end of the probe is submerged below the liquid surface of the digested contents and is placed in the geometric center region of the inner cavity of the simulated digester, so that the probe and the digested contents form direct contact thermal coupling. The temperature sensing element of the probe-type temperature sensor is in direct contact with the digested contents. The heat from the digested contents is transferred to the temperature sensing element through thermal conduction, causing the resistance value or digital value of the temperature sensing element to change accordingly with the temperature change of the digested contents.

3. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 2, characterized in that, The method of real-time acquisition of temperature signals of digested contents and outputting corresponding electrical signals also includes: The sensor is electrically connected to the signal conditioning circuit of the temperature control module via a three-wire or four-wire connection. The signal conditioning circuit provides a constant excitation current to the sensor and acquires the voltage signal across the sensor. The voltage signal is amplified by the differential amplifier circuit in the signal conditioning circuit and then filtered by the low-pass filter circuit to remove high-frequency noise, generating an analog voltage signal. The analog voltage signal is transmitted to the main controller of the temperature control module. The analog-to-digital converter built into the main controller converts the analog voltage signal into a corresponding digital temperature value to obtain the real-time measured temperature value of the digested contents. When the temperature sensor experiences a disconnection, short circuit, or exceeds its range, the signal conditioning circuit or the main controller generates a corresponding fault status signal. The fault status signal, along with the temperature signal, is transmitted to the main controller to trigger the heating cut-off protection of the corresponding channel.

4. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 1, characterized in that, The temperature control module includes a main controller and a signal conditioning circuit. The main controller uses an STM32 microcontroller or a programmable logic controller and has multiple independently operating PID operation units built in. The number of PID operation units matches the number of analog digesters, and each operation unit independently corresponds to one analog digester. The signal conditioning circuit is electrically connected to the temperature sensing module and is used to amplify and filter the electrical signal output by the temperature sensor, and transmit the processed signal to the main controller. The specific process for driving each heating film to independently adjust its heating power is as follows: The main controller has a built-in multi-channel independently operating proportional-integral-derivative (PI-DI) arithmetic unit that matches the number of analog digesters. Each PI-DI-DI arithmetic unit corresponds to an independent control channel. The main controller calls the preset target temperature value stored in the corresponding channel to calculate the temperature deviation value of the current control cycle. The temperature deviation value is the preset target temperature value minus the current temperature value. The main controller compares the temperature deviation value with a preset first deviation threshold and a preset second deviation threshold; When the temperature deviation value is greater than the first deviation threshold, it is determined that the measured temperature of the digested contents is far lower than the target temperature. The corresponding channel needs to perform full-power heating. The main controller sets the control output value of the channel to the upper limit of the control quantity, that is, outputs a pulse width modulation control parameter with a duty cycle of 100%, so that the heating film continues to heat at the rated power until the digested contents are rapidly heated to close to the target temperature.

5. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 4, characterized in that, The method of driving each heating film to independently adjust the heating power also includes: When the temperature deviation value is less than or equal to the first deviation threshold and greater than the second deviation threshold, the main controller calls the proportional-integral-derivative (PID) operation unit corresponding to the channel to perform incremental PID operation based on the temperature deviation value and generate the control output increment for the current control cycle. The incremental proportional-integral-derivative (PI-DI) operation takes the temperature deviation value of the current control cycle, the temperature deviation value of the previous control cycle, and the temperature deviation values ​​of the two previous control cycles as inputs. It then performs weighted calculations on these three deviation values ​​using proportional, integral, and derivative coefficients, respectively, to calculate the control output increment for the current control cycle. The main controller calculates the control output value for the current control cycle based on the sum of the control output value of the previous control cycle and the control output increment for the current control cycle. The main controller performs amplitude limiting processing on the control output value, confining it between the lower and upper limits of the control quantity. The control output value corresponds to the duty cycle parameter of the pulse width modulation (PWM) control signal. When the temperature deviation value is less than or equal to the second deviation threshold, the main controller sets the control output value of the channel to the lower limit of the control quantity, that is, outputs a pulse width modulation control parameter with a duty cycle of 0%, cuts off the power supply to the heating film of the channel, and stops heating to prevent overheating.

6. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 5, characterized in that, The main controller generates a pulse width modulation control signal with a corresponding duty cycle based on the control output value calculated by each channel. The frequency of the pulse width modulation control signal is a fixed value. The main controller outputs the pulse width modulation control signal of each channel to the pulse width modulation power drive module of the corresponding channel. According to the received pulse width modulation control signal, it controls the high-speed turn-on and turn-off of the power switching device in the power supply circuit of the heating film of the corresponding channel. The ratio of the turn-on time to the turn-off time of the power switching device is determined by the duty cycle of the pulse width modulation control signal, thereby adjusting the effective value of the effective power supply voltage and the heating power of the heating film. At the end of each control cycle, the main controller updates the stored historical deviation value, stores the temperature deviation value of the current control cycle as the temperature deviation value of the previous control cycle, stores the temperature deviation value of the previous control cycle as the temperature deviation value of the two previous control cycles, and stores the control output value of the current control cycle as the control output value of the previous control cycle, for use in the incremental proportional-integral-derivative operation of the next control cycle.

7. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 6, characterized in that, The main controller performs safety protection interlock judgment: when the measured temperature value detected by any of the temperature sensors exceeds the preset safety upper limit threshold of that channel, the main controller immediately cuts off the pulse width modulation output of all channels, causing all heating films to stop heating, and at the same time issues an audible and visual alarm signal and records the fault information through the human-machine interface; when the main controller detects that any of the temperature sensors has a broken wire, short circuit, or signal over-range fault, the main controller immediately cuts off the pulse width modulation output of the corresponding channel, and displays the fault channel number and fault type through the human-machine interface, while the remaining normal channels maintain independent temperature regulation operation.

8. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 1, characterized in that, The specific process for independently adjusting the energizing time ratio of each flexible heating film is as follows: The input terminal of the multi-channel PWM power drive module is electrically connected to the multi-channel pulse width modulation signal output port of the main controller, and its output terminal is electrically connected to the power supply terminal of each of the flexible heating films. The multi-channel PWM power drive module includes multiple power drive sub-modules that match the number of independent control channels, and each power drive sub-module independently corresponds to a flexible heating film of an analog digester. Each of the power drive submodules includes a signal isolation circuit, a power switching device, and a freewheeling protection circuit. The signal isolation circuit uses an optocoupler, whose input terminal is electrically connected to the corresponding pulse width modulation signal output port of the main controller. It is used to receive the pulse width modulation control signal output by the main controller and transmit the pulse width modulation control signal from the control side to the control electrode of the power switching device after electrical isolation, thereby realizing electrical isolation between the control circuit and the power circuit. The power switching device uses a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor. Its control electrode is electrically connected to the output terminal of the signal isolation circuit, its first conducting terminal is electrically connected to the positive terminal of the power supply, its second conducting terminal is electrically connected to the first power supply terminal of the flexible heating film, and the second power supply terminal of the flexible heating film is electrically connected to the negative terminal of the power supply, forming a heating power supply circuit.

9. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 8, characterized in that, The method of independently adjusting the energizing time ratio of each flexible heating film also includes: The power switching device rapidly switches between its on and off states according to the level of the pulse width modulation control signal received by its control electrode: when the pulse width modulation control signal is high, the power switching device is turned on, the heating power supply circuit is closed, the power supply supplies power to the flexible heating film, and the flexible heating film heats up. When the pulse width modulation control signal is low, the power switch is turned off, the heating power supply circuit is disconnected, the power supply stops supplying power to the flexible heating film, and the flexible heating film stops heating. The freewheeling protection circuit uses a fast recovery diode, which is connected in reverse parallel across the two ends of the flexible heating film. Its anode is connected to the second conducting terminal of the power switching device, and its cathode is connected to the positive terminal of the power supply. It is used to provide a freewheeling discharge circuit for the reverse induced electromotive force generated by the inductive characteristics of the flexible heating film at the instant when the power switching device switches from conducting to turning off, absorbs reverse peak voltage, and protects the power switching device from overvoltage breakdown. The main controller converts the independently calculated control output values ​​of each channel into pulse width modulation control signals with corresponding duty cycles according to the control cycle. The duty cycle is defined as the ratio of the high-level duration of the pulse width modulation signal to the total pulse cycle time within a complete cycle. The main controller outputs the pulse width modulation control signals of each channel to the signal isolation circuit input terminal of the corresponding power drive submodule. After receiving the pulse width modulation control signal of the corresponding channel, the signal isolation circuit of each power drive submodule electrically isolates and converts the pulse width modulation control signal through an optocoupler to generate the drive voltage signal required to drive the power switching device, and transmits it to the control electrode of the power switching device.

10. The automatic temperature control system for an animal in vitro digestion simulation device as described in claim 9, characterized in that, The method of independently adjusting the energizing time ratio of each flexible heating film also includes: Based on the drive voltage signal received by the control electrode, high-speed on / off switching is performed within one pulse width modulation period according to the time ratio determined by the duty cycle, specifically: During the high-level duration of the pulse width modulation period, the driving voltage signal drives the power switching device to turn on, energizing and heating the flexible heating film during the high-level duration; during the remaining time from the end of the high-level duration of the pulse width modulation period to the end of the period, the driving voltage signal controls the power switching device to turn off, de-energizing and stopping the heating of the flexible heating film during the remaining time; the power switching device repeats the above-mentioned on / off switching action in each pulse width modulation period according to the frequency of the pulse width modulation signal; The effective energizing time ratio of each flexible heating film on a continuous time scale is the duty cycle of its corresponding pulse width modulation control signal, and the actual heating power of the flexible heating film is proportional to the duty cycle. When the main controller outputs an over-temperature protection cut-off command, the power switching devices of all power drive sub-modules in the multi-channel PWM power drive module are simultaneously forced to turn off, cutting off the power supply path of all flexible heating films. When the main controller outputs a single-channel fault cutoff command, only the power switching devices of the power drive submodule corresponding to the faulty channel are forcibly turned off, while the power drive submodules of other non-faulty channels maintain normal operation.

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