A linear heat detector sensing element testing device

Abstract

This invention discloses a testing device for sensitive components of a linear temperature-sensitive fire detector, belonging to the field of fire detector testing technology. It includes a housing, a heating system, a temperature control system, and a heat dissipation system. The heating system employs a surface-mount heat conduction heating cavity and a matching heating device. The temperature control system is based on a PLC industrial control integrated computer. This invention designs standardized testing methods for both constant-temperature and differential-temperature alarm-type sensitive components. During the heating process, online thermal characteristic identification and predictive temperature control algorithms achieve precise regulation of the temperature rise rate. During the constant-temperature process, a Smith predictor combined with an adaptive PI algorithm achieves stable temperature control. Multiple safety protection functions are also included. This invention solves the problems of low temperature control accuracy, non-standardized testing procedures, inability to realistically simulate the temperature rise process, low testing efficiency, and potential safety hazards in existing testing methods. The testing process closely matches the actual working environment of the component, and the results meet standard testing requirements.

Description

Technical Field

[0001] This invention relates to the field of fire detector sensitive component testing technology, specifically a testing device for sensitive components of a linear heat-sensing fire detector. Background Technology

[0002] Linear heat-sensing fire detectors, as temperature measurement devices for fire-prone areas, are widely used in power, petrochemical, steel, subway, and integrated utility tunnel applications. The sensing element is the core component of the fire detector, converting characteristic physical quantities of fire combustion (such as temperature) into electrical signals. To ensure long-term operational reliability, the installed sensing elements need to be periodically inspected to verify their thermal accuracy and the effectiveness of their alarm functions.

[0003] Currently, on-site testing of installed sensitive components often employs simple methods such as boiling in water, burning, or heating with a hot air gun. These methods lack precise temperature control of the heating device, failing to accurately simulate the actual temperature rise process of the sensitive component's environment. This results in deviations between the test temperature and the product's design alarm parameters, making it difficult to accurately verify the design precision and creating safety hazards for the fire detection system.

[0004] To address the aforementioned problems, some dedicated testing devices have been proposed in the prior art. For example, Chinese patent document CN113963504A discloses a portable linear heat-sensitive fire detector testing device. This device includes a housing, and internal AC power module, temperature control module, and heater module. The heater module consists of a heating plate and a heat transfer plate, with the sensitive component to be tested and the temperature sensor contacts fixed to the surface of the heat transfer plate by a fixing clip. The temperature sensor is connected to a controller, which adjusts the operation of the heating plate by controlling a heating switch based on the set value displayed on the temperature input screen, thereby achieving heating and heat preservation. This device has a small housing size, making it easy to carry, and its heater module can heat and preserve temperatures between 0℃ and 120℃, used for some performance tests.

[0005] However, this existing technical solution still has significant shortcomings: First, its measurement temperature range is narrow, making it difficult to cover more stringent environments or higher standard testing conditions. Second, the device lacks clear design and requirements for the accuracy of test chamber temperature error control, constant temperature fluctuation accuracy, temperature resolution accuracy, and heating rate control accuracy. Furthermore, the device is deficient in safety features, lacking overload protection and maximum temperature protection, posing certain safety hazards. In addition, the device lacks rapid cooling capabilities, requiring a considerable time for natural cooling after each test, hindering rapid and continuous multiple tests and reducing testing efficiency. Due to its limitations in control accuracy, safety features, and testing efficiency, the test results of this device cannot fully meet the requirements.

[0006] Therefore, there is an urgent need for a new type of linear heat-sensing fire detector sensitive component testing solution that offers more precise temperature control, complete safety functions, higher testing efficiency, and can fully meet national standard testing requirements. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a testing device for the sensitive components of a linear heat-sensing fire detector, which aims to solve the problems in the background technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a test device for sensitive components of a linear heat-sensitive fire detector, comprising: a housing, a heating system, a temperature control system, and a heat dissipation system; The heating system includes a heating chamber and a heating device disposed inside the chamber. The heating chamber forms a test area for placing the sensitive component to be tested. The heating device is connected to the heating chamber and is used to provide a heat source for the heating chamber. The temperature control system includes a PLC industrial control all-in-one computer, a temperature acquisition probe, and a heating control circuit. The temperature acquisition probe is installed in the heating cavity, and the PLC industrial control all-in-one computer and the heating control circuit are installed in the cavity inside the box. The PLC industrial control all-in-one computer is signal-connected to the temperature acquisition probe and electrically connected to the heating device through the heating control circuit to control the heating process according to the set program. The heat dissipation system includes an air inlet and a heat dissipation outlet disposed on the housing, and a heat dissipation fan disposed in the cavity. The heat dissipation fan is used to introduce external cooling air through the air inlet, and after forcibly cooling the heating cavity and the components in the cavity, it is discharged from the heat dissipation outlet.

[0009] Furthermore, the heating cavity is a heat conduction heating cavity that is applied to the surface and is made of heat-resistant silicone rubber or aluminum alloy.

[0010] Furthermore, the heating device is composed of heat-resistant silicone rubber or heat-resistant ceramic with an embedded resistance wire; the heating control circuit includes a solid-state relay electrically connected to the resistance wire.

[0011] Furthermore, it also includes a freely openable and closable heat-insulating cover plate, which is installed on the box body by a hinge and covers the heating cavity, and is made of heat-resistant foamed silicone rubber.

[0012] Furthermore, the front of the housing is provided with a panel made of aluminum alloy, which also serves as the cover of the chamber. The display screen of the PLC industrial control all-in-one machine is embedded and fixed on the panel.

[0013] Furthermore, the control program of the PLC industrial control integrated machine includes a constant temperature control mode and a differential temperature control mode.

[0014] Furthermore, the PLC industrial control all-in-one machine has a built-in high-speed pulse output port, which is electrically connected to the control input terminal of the solid-state relay in the heating control circuit. The PLC industrial control all-in-one machine outputs a pulse width modulation (PWM) signal through the high-speed pulse output port. The duty cycle of the PWM signal is generated by the PLC industrial control all-in-one machine. The PWM signal is used to control the ratio of the on and off time of the solid-state relay within a unit cycle, thereby linearly adjusting the average input power of the heating resistance wire in the heating device.

[0015] Furthermore, the PLC industrial control integrated computer executes corresponding test methods based on the type of the sensitive component under test. The sensitive components under test include constant temperature alarm type and differential temperature alarm type. The test methods include: If the sensitive component under test is a constant temperature alarm type, select the constant temperature control mode to perform the test, including: A1. Obtain the rated operating temperature and rated response time of the sensitive components; A2. Obtain the current heating chamber temperature. If the heating chamber temperature is greater than 25℃, proceed directly to A3. If the heating chamber temperature is less than 25℃, heat the heating chamber to 25℃ at a heating rate of 5℃ / min before proceeding to A3. A3. Set the first target operating temperature and the first target heating rate, put the sensitive component to be tested into the heating chamber, and control the heating chamber to heat up at the first target heating rate. A4. When the sensitive component under test issues an alarm signal, record the actual operating temperature of the heating chamber at this time; A5. Remove the sensitive component under test from the heating chamber and cool the heating chamber to the ambient temperature through the heat dissipation system. At the same time, the sensitive component under test is simultaneously cooled to the ambient temperature. Set the second target operating temperature and the second target heating rate, and control the heating chamber to start heating to the second target operating temperature and keep it constant. A6. After cooling, put the sensitive component under test back into the constant temperature heating chamber and start the timer simultaneously. When the sensitive component under test issues an alarm signal, record the measured response time at this time. A7. When the measured operating temperature meets the preset operating temperature qualification range and the measured response time is ≤ the rated response time, the sensitive component is judged to be of qualified quality. If the sensitive component under test is a differential temperature alarm type, select the differential temperature control mode to perform the test, including: B1. Obtain the upper limit values ​​of the rated operating temperature rise rate and rated response time of sensitive components; B2. Obtain the current heating chamber temperature. When the heating chamber temperature is greater than 25℃, proceed directly to B3. When the heating chamber temperature is less than 25℃, heat the heating chamber to 25℃ at a heating rate of 5℃ / min before proceeding to B3. B3. Set the third target operating temperature and the third target heating rate, place the sensitive component to be tested into the heating chamber, control the heating chamber to heat up at a uniform rate according to the set third target heating rate and start the timing synchronously. B4. When a sensitive component issues an alarm signal, record the measured response time at that moment; B5. When the measured response time is less than or equal to the upper limit of the rated response time, the sensitive component is deemed to be of acceptable quality.

[0016] Furthermore, the PLC industrial control all-in-one computer also includes: During the A3 and A5 heating processes in constant temperature control mode, and during the B3 heating process in differential temperature control mode, the PLC industrial control all-in-one computer executes a predictive temperature control algorithm, including: C1. Record the pure time delay of the system from the start of heating to the detection of temperature change. With a fixed sampling period, collect the current heating chamber temperature and ambient temperature in real time, and obtain the actual temperature rise per second within a specified time after heating starts. At the same time, calculate the target temperature rise per second based on the set target heating rate. C2. In each sampling period, a recursive least squares method with a forgetting factor is used to identify the real-time thermal characteristic parameters of the system online based on the thermal balance mathematical model of the thermal system: First, a thermal balance physical model of the heating system is established, which covers four core thermal characteristic parameters: the total equivalent heat capacity of the heating cavity and the sensitive component under test, the pure time delay of the heating system, the effective heating power of the heating device, and the equivalent heat dissipation coefficient; then, the thermal balance physical model is converted into a discrete-time linear regression equation, which includes three coefficients to be identified, the duty cycle of the PWM signal, the ambient temperature, and the identification residual. The recursive least squares method with a variable forgetting factor is adopted to update the values ​​of the three coefficients to be identified in each sampling period, and simultaneously calculate the total equivalent heat capacity, equivalent heat dissipation coefficient, and pure lag time in the current sampling period based on the coefficients. C3. Compare the target temperature rise per second with the actual temperature rise per second: If the difference between the target temperature rise per second and the actual temperature rise per second is within a preset range, then the predicted temperature of the heating chamber is calculated. If the predicted temperature of the heating chamber is greater than or equal to the target temperature of the current test stage, then the heating device will be controlled to stop heating. If the predicted temperature of the heating chamber is less than the target temperature of the current test stage, calculate the continuous heating time required to reach the target temperature without changing the rate of temperature rise. If the difference between the target temperature rise per second and the actual temperature rise per second exceeds the preset range, the duty cycle of the PWM signal output to the heating control circuit is adjusted according to the magnitude of the difference, and the corresponding theoretical temperature rise rate is obtained after adjustment. Based on the adjusted theoretical temperature rise rate, the predicted temperature of the heating chamber is recalculated; If the predicted temperature of the heating chamber is greater than or equal to the target temperature of the current test stage, then the heating device will be controlled to stop heating. If the predicted temperature of the heating chamber is less than the target temperature of the current test stage, then calculate the continuous heating time required to reach the target temperature of the current test stage under the condition of changing the temperature rise rate. When the predicted temperature of the heating chamber is within a preset range similar to the target temperature of the current test stage, and the current heating chamber temperature is less than the target temperature of the current test stage, a low duty cycle PWM signal with a duty cycle not exceeding the first preset ratio is output for temperature fine-tuning. C4. Using temperature data from multiple consecutive sampling periods, calculate the current actual smooth temperature rise rate; calculate the deviation between the target temperature rise per second and the actual smooth temperature rise rate; based on the thermal characteristic parameters identified in real time by C2, adaptively tune the PI controller parameters; according to the tuned PI controller parameters, calculate the adjustment amount of the PWM signal duty cycle; add this adjustment amount to the PWM signal duty cycle level value output by C3 to obtain the final PWM signal duty cycle; C5. Based on the pure time delay of the heating system in C2, an adaptive prediction time domain is set; combined with the measured temperature, the actual smooth temperature rise rate, the prediction time domain length, the real-time equivalent heat dissipation coefficient, the total equivalent heat capacity, and the difference between the current measured temperature and the ambient temperature, the prediction temperature with heat dissipation loss correction is calculated. Execute feedforward overshoot suppression logic: When the predicted temperature with heat dissipation loss correction does not meet the first preset condition, enter the deceleration phase and limit the upper limit of the duty cycle of the PWM signal to the steady-state maintenance value. This steady-state maintenance value is calculated and determined based on the real-time equivalent heat dissipation coefficient, the difference between the target temperature and the ambient temperature in the current test phase, and the rated power of the heating device; when the predicted temperature with heat dissipation loss correction does not meet the second preset condition, control the heating device to stop heating; when the predicted temperature with heat dissipation loss correction does not meet the third preset condition, calculate the heating time required to reach the target temperature in the current test phase based on the thermal balance model.

[0017] Furthermore, during the A5 constant temperature maintenance process in constant temperature control mode, the PLC industrial control integrated computer executes a constant temperature control algorithm, including: D1. If the measured temperature of the heating chamber is greater than the target temperature, then control the heating device to stop heating. If the measured temperature of the heating chamber equals the target temperature, then a low duty cycle PWM signal with a preset duration and a duty cycle not exceeding the second preset ratio is output for temperature compensation. If the measured temperature of the heating chamber is less than the target temperature, the temperature state at the previous moment is determined: if the measured temperature at the previous moment is equal to the target temperature, the output time of the PWM signal used for temperature compensation is extended; if the measured temperature at the previous moment is greater than the target temperature, a medium duty cycle PWM signal with a preset duration and a duty cycle not exceeding the third preset ratio is output for temperature compensation. D2. Based on thermal characteristic parameters, construct a Smith predictor to calculate the hysteresis-free predicted temperature of the heating chamber; calculate the prediction deviation used for closed-loop control based on the difference between the constant temperature target temperature and the hysteresis-free predicted temperature. D3. Based on the thermal characteristic parameters, tune the PI controller parameters for the isothermal scenario; calculate the duty cycle output of the PI controller based on the deviation between the tuned PI controller parameters for the isothermal scenario and the prediction used for closed-loop control; add the steady-state holding value, the duty cycle output of the PI controller, and the duty cycle of the PWM signal output in D1 to obtain the final PWM signal duty cycle for isothermal control.

[0018] Compared with existing technologies, the present invention has the following advantages: (1) This invention constructs a standardized, full-process sensitive component testing system. For the sensitive components of two types of linear heat-sensing fire detectors, namely fixed-temperature alarm type and differential-temperature alarm type, special test methods are designed respectively. Through the standardized closed-loop process of temperature preprocessing, action temperature verification, cooling reset, response time verification, and qualification judgment, the core performance parameters such as rated action temperature, response time, and differential-temperature action characteristics of sensitive components are standardized and tested. This solves the problems of inconsistent operation, single test dimension, and insufficient reliability of existing testing methods. The test process and judgment criteria are fully in line with the standard requirements of linear heat-sensing fire detectors and the actual working scenarios on site, which greatly improves the authority and consistency of test results.

[0019] (2) This invention designs a temperature control algorithm that integrates online thermal characteristic identification and feedforward prediction for the heating stage of the entire test process. By using the recursive least squares method with a variable forgetting factor, the core thermal characteristic parameters such as the total equivalent heat capacity, pure lag time, and equivalent heat dissipation coefficient of the system are identified in real time in each sampling period. Combined with adaptive PI parameter tuning, predicted temperature calculation with heat dissipation loss correction, and graded overshoot suppression logic, the influence of pure lag of the thermal system, sampling noise, and environmental heat dissipation disturbance on the heating process is effectively eliminated. The linear high-precision control of the heating rate is achieved, which completely simulates the real temperature rise process when a fire occurs. At the same time, the temperature overshoot problem in the heating stage is completely avoided, ensuring a high degree of matching between the test temperature and the product design alarm parameters, and greatly improving the accuracy of the action temperature and differential temperature characteristic test.

[0020] (3) For the constant temperature holding stage of constant temperature test, the present invention designs a constant temperature control algorithm with Smith predictor and adaptive PI. By eliminating the adverse effects of pure time delay of thermal system on closed-loop control through Smith predictor, and combined with temperature deviation grade compensation and real-time correction logic for environmental disturbance, high-precision stable control of constant temperature target temperature is achieved, effectively suppressing temperature fluctuation in constant temperature stage, providing a stable reference temperature environment for response time test, solving the problem of large response time test error caused by insufficient constant temperature accuracy of existing device, and further improving the accuracy of test results.

[0021] (4) This invention comprehensively improves the detection efficiency and safety of the device through the synergistic optimization of structure and function: the heat-resistant silicone rubber / aluminum alloy adhesive heat conduction heating cavity is used, and the heat-resistant foamed silicone rubber insulation cover plate is used to ensure the uniformity of heat conduction and ensure that the sensitive parts under test are heated in a consistent manner; a forced air cooling heat dissipation system is set up to realize the rapid cooling of the heating cavity and the parts under test after the test, and supports multiple tests in a continuous manner, which solves the problems of long natural cooling waiting time and low detection efficiency of existing devices; at the same time, it integrates multiple safety protection functions such as overload, over-temperature, and probe fault verification, and can quickly cut off the heating circuit under abnormal conditions, eliminating safety hazards in the test process and improving the long-term operational reliability and on-site environmental adaptability of the device. Attached Figure Description

[0022] Figure 1 This is an overall structural diagram of the experimental device of the present invention.

[0023] Figure 2 This is a side view of the test apparatus of the present invention.

[0024] In the diagram, 1. Insulation cover; 2. Heating chamber; 3. Heat dissipation air vent; 4. Panel; 5. PLC industrial control all-in-one machine; 6. Chamber; 7. Heating device; 8. Box body; 9. Heat dissipation fan; 10. Air inlet; 11. Power interface. Detailed Implementation

[0025] like Figure 1 As shown, the present invention provides a technical solution: a test device for sensitive components of a linear heat-sensitive fire detector, comprising: a housing 8, a heating system, a temperature control system, and a heat dissipation system; The heating system includes a heating chamber 2 and a heating device 7 disposed inside the housing 8. The heating chamber 2 forms a test area for placing the sensitive component to be tested, and the heating device 7 is connected to the heating chamber 2 to provide a heat source for it. The temperature control system includes a PLC industrial control computer 5, a temperature acquisition probe, and a heating control circuit. The temperature acquisition probe is installed in the heating cavity 2. The PLC industrial control computer 5 and the heating control circuit are installed in the chamber 6 inside the housing 8. The PLC industrial control computer 5 is signal-connected to the temperature acquisition probe and electrically connected to the heating device 7 through the heating control circuit to control the heating process according to the set program. The heat dissipation system includes an air inlet 10 and a heat dissipation air outlet 3 disposed on the housing 8, and a heat dissipation fan 9 disposed in the chamber 6. The heat dissipation fan 9 is used to introduce external cooling air through the air inlet 10, and after forcibly cooling the heating chamber 2 and the components in the chamber 6, it is discharged from the heat dissipation air outlet 3.

[0026] The heating chamber 2 is a heat conduction heating chamber that is applied to the surface and is made of heat-resistant silicone rubber or aluminum alloy.

[0027] The heating device 7 is composed of heat-resistant silicone rubber or heat-resistant ceramic with an embedded resistance wire; the heating control circuit includes a solid-state relay electrically connected to the resistance wire.

[0028] It also includes a freely openable and closable heat-insulating cover 1, which is installed on the box body 8 by a hinge and covers the heating chamber 2. It is made of heat-resistant foamed silicone rubber.

[0029] The front of the housing 8 is provided with a panel 4, which is made of aluminum alloy and also serves as the cover of the chamber 6. The display screen of the PLC industrial control all-in-one machine 5 is embedded and fixed on the panel 4.

[0030] The control program of the PLC industrial control all-in-one machine 5 includes a constant temperature control mode and a differential temperature control mode, and provides a corresponding operation interface through its touch screen.

[0031] The chamber 6 is also equipped with a 24-volt power supply for powering the temperature control system and a transmitter for processing temperature probe signals.

[0032] The housing 8 is made of aluminum alloy and has a 220V power interface 11 on its side for connecting to a power supply. The PLC industrial control computer 5 has a built-in high-speed pulse output port, which is electrically connected to the control input terminal of the solid-state relay in the heating control circuit. The PLC industrial control computer 5 outputs a pulse width modulation (PWM) signal through the high-speed pulse output port. The PWM signal is a 24V DC pulse signal adapted to the control requirements of the solid-state relay, and its duty cycle is determined by the test method control logic and prediction logic built into the PLC industrial control computer 5. The temperature control algorithm and constant temperature control algorithm are generated in real time, with a duty cycle adjustment range covering 0%~100%, supporting both preset level adjustment and continuous fine-tuning modes. The PWM signal is used to control the on and off time ratio of the solid-state relay within a unit cycle, thereby linearly adjusting the average input power of the heating resistance wire in the heating device 7, realizing closed-loop control of the heating rate, real-time temperature and constant temperature accuracy of the heating chamber 2. When the PLC industrial control all-in-one computer 5 triggers overload protection or over-temperature protection, it immediately outputs a PWM signal with a duty cycle of 0% to forcibly cut off the power supply circuit of the heating device 7.

[0033] The sensitive components of fire detectors include fixed-temperature alarm type and differential-temperature alarm type; the fixed-temperature alarm type will trigger an alarm when the preset temperature threshold is reached; the differential-temperature alarm type will trigger an alarm when the preset heating rate threshold is reached.

[0034] The PLC industrial control integrated computer executes the corresponding test method based on the type of the sensitive component under test. The sensitive components under test include constant temperature alarm type and differential temperature alarm type. The specific test method is as follows: If the sensitive component under test is a constant temperature alarm type, select the constant temperature control mode to perform the test, and follow the steps below: A1. Obtain the rated operating temperature of sensitive components Rated response time ; A2. Obtain the current heating chamber temperature (through a temperature sensor installed inside the heating chamber). When the heating chamber temperature is greater than 25°C, proceed directly to A3. When the heating chamber temperature is less than 25°C, heat the heating chamber to 25°C at a heating rate of 5°C / min before proceeding to A3. A3. Set the first target motion temperature. , Set the first target heating rate , ℃ / min, place the 1m long sensitive component to be tested into the heating chamber, and control the heating chamber to heat up at the first target heating rate; A4. When the sensitive component under test issues an alarm signal, record the measured operating temperature of the heating chamber at that moment. ; A5. Remove the sensitive component under test from the heating chamber, and cool the heating chamber to ambient temperature using the heat dissipation system, while simultaneously cooling the sensitive component under test to ambient temperature; set the second target operating temperature. , Set a second target heating rate , ℃ / min, control the heating chamber to start heating up to the second target operating temperature. And remain constant; A6. Place the cooled sensitive component back into the constant-temperature heating chamber and start the timer simultaneously. When the sensitive component emits an alarm signal, record the measured response time. ; A7. When the measured operating temperature meets the preset operating temperature acceptable range ( And the actual response time ≤ Rated response time At that time, the sensitive components are deemed to be of acceptable quality.

[0035] If the sensitive component under test is a differential temperature alarm type, select the differential temperature control mode to perform the test, and follow the steps below: B1. Obtain the rated operating temperature rise rate of sensitive components. Maximum rated response time ; B2. Obtain the current heating chamber temperature. When the heating chamber temperature is greater than 25℃, proceed directly to B3. When the heating chamber temperature is less than 25℃, heat the heating chamber to 25℃ at a heating rate of 5℃ / min before proceeding to B3. B3. Set the third target's action temperature. , ℃, set the third target heating rate , Place the 1m long sensitive component to be tested into the heating chamber, control the heating chamber to heat up at a uniform rate according to the set third target heating rate and start the timing simultaneously; B4. When the sensitive component issues an alarm signal, record the measured response time at that moment. ; B5. When the measured response time ≤ Maximum value of rated response time At that time, the sensitive components are deemed to be of acceptable quality.

[0036] In the PLC industrial control integrated computer, during the A3 and A5 heating processes in the constant temperature control mode and the B3 heating process in the differential temperature control mode, a predictive temperature control algorithm is executed. The specific steps are as follows: C1. Record the system's pure time delay from the start of heating to the detection of a temperature change, with a fixed sampling period. Real-time acquisition of current heating chamber temperature Ambient temperature , This indicates the current sampling period number and retrieves the actual temperature rise per second within 5 seconds after heating starts. Simultaneously, the target temperature rise per second is calculated based on the set target heating rate. .

[0037] C2. In each sampling period, a recursive least squares method with a forgetting factor is used to identify the real-time thermal characteristic parameters of the system online based on the thermal balance mathematical model of the thermal system, providing physical model support for predictive control: First, a thermal equilibrium physical model of the heating system is established. This model encompasses four core thermal characteristic parameters: the total equivalent heat capacity of the heating cavity and the sensitive component under test, the pure time delay of the heating system, the effective heating power of the heating device, and the equivalent heat dissipation coefficient. These parameters can be expressed as follows: ; In the formula, This represents the total equivalent heat capacity of the heating cavity and the sensitive component under test; Indicates the pure time delay of the heating system; Indicates the effective heating power of the heating device, which meets the requirements. ,in Indicates the rated power of the heating device; express The duty cycle of the PWM signal output at any given time; Indicates the equivalent heat dissipation coefficient; Represents the differential symbol; Indicates time; Then, this thermal equilibrium physical model is based on a fixed sampling period. The equation is converted to a discrete-time linear regression equation, which includes three coefficients to be identified, the duty cycle of the PWM signal corresponding to the lag step, the ambient temperature, and the identification residual, and can be expressed as: ; In the formula, Indicates the first The measured temperature of the heating cavity during each sampling period; Indicates the first The measured temperature of the heating cavity during each sampling period; , , This represents three coefficients to be identified; Indicates the first During each sampling period, the number of discrete lag steps corresponding to the pure lag time of the heating system satisfies the following condition: , where is a positive integer; Indicates the first The duty cycle of the PWM signal output to the heating control circuit during each sampling period; Indicates the first The pure time delay of the heating system during each sampling period; Indicates the first The identification residual at each sampling period; Using a variable forgetting factor Recursive least squares method (forgetting factor) The value range is 0.90~0.98, which can be adaptively adjusted within this range or manually preset according to the thermal inertia of the sensitive component under test and the degree of environmental disturbance at the test site. The values ​​of the three identification coefficients are updated in each sampling period, and the total equivalent heat capacity, equivalent heat dissipation coefficient, and pure lag time under the current sampling period are calculated simultaneously based on the coefficients, which can be expressed as: ; In the formula, Indicates the first The total equivalent heat capacity of the heating cavity and the sensitive component under test in each sampling period; Indicates the rated power of the heating device; Indicates a fixed sampling period; Indicates the first The identification residual for each sampling period; by An alternative inverse formula for the equivalent heat dissipation coefficient can be derived: ; Pure time delay The recognition range is limited to between 1 second and 10 seconds, and the recognition is based on the minimum value of the residual identified within 10 consecutive sampling periods.

[0038] C3. Compare the target's temperature rise per second. Compared to the actual temperature rise per second : If the target temperature rises per second Compared to the actual temperature rise per second If the difference is within a preset range, then the predicted temperature of the heating chamber is calculated. ; If the predicted temperature of the heating chamber ≥Target temperature in the current testing phase If so, the heating device will stop heating; If the predicted temperature of the heating chamber Target temperature during the current testing phase Then calculate the required heating time to reach the target temperature without changing the heating rate. The timing of stopping the heating should be controlled according to this time to achieve a smooth temperature rise (due to the thermal inertia of the heating process: the actual temperature rise will be delayed due to heat capacity and heat dissipation. If heating is continued without prediction, "overshoot and overheating" is very likely to occur). If the target temperature rises per second Compared to the actual temperature rise per second If the difference exceeds the preset range of ±0.01℃ / s, the duty cycle of the PWM signal output to the heating control circuit (the PWM signal is output by the PLC industrial control unit) is adjusted according to the magnitude of the difference. There are 6 duty cycle levels: 0%, 20%, 40%, 60%, 80%, and 100%. After adjustment, the corresponding theoretical temperature rise rate is obtained. ; Based on the adjusted theoretical temperature rise rate, the predicted temperature of the heating chamber is recalculated. ; If the predicted temperature of the heating chamber ≥Target temperature in the current testing phase If so, the heating device will stop heating; If the predicted temperature of the heating chamber Target temperature during the current testing phase Then, calculate the target temperature for the current experimental stage under the condition of changing the temperature rise rate. Required heating time ; When the predicted temperature of the heating chamber Compared with the target temperature in the current test phase It is within a preset similar range, and the current heating chamber temperature is... Target temperature during the current testing phase At that time, a low duty cycle PWM signal with a duty cycle not exceeding a first preset ratio (10%) is output for temperature fine-tuning. The output duration of this PWM signal is based on... Calculation, where This represents the current temperature rise rate.

[0039] C4. To eliminate noise interference from single-cycle sampling, temperature data from three consecutive sampling cycles are used to calculate the current actual smooth temperature rise rate, which can be expressed as: ; In the formula, Indicates the first The actual smooth temperature rise rate under each sampling period; Calculate the deviation between the target temperature rise per second and the actual smooth temperature rise rate. Based on the thermal characteristic parameters obtained in real time by C2, the parameters of the PI controller are adaptively tuned, which can be expressed as: ; In the formula, This represents the proportional gain of the PI controller; This represents the integral coefficient of the PI controller; Based on the PI controller parameters after tuning, the adjustment amount of the PWM signal duty cycle is calculated. This adjustment amount is then added to the base gear adjustment result (the PWM signal duty cycle gear value output by C3) to obtain the final PWM signal duty cycle. The final output PWM signal duty cycle is limited to the range of 0% to 100%, which can be expressed as: ; ; In the formula, Indicates the first The adjustment amount of the PWM signal duty cycle in each sampling period; Indicates the first The duty cycle of the final output PWM signal under each sampling period; This indicates the result of the basic gear adjustment; This represents the amplitude limiting function.

[0040] C5, Pure time delay of heating system based on C2 Set an adaptive prediction time domain, with a prediction time domain length equal to the pure time lag plus 5 seconds, expressed as: Combining the measured temperature, actual smooth temperature rise rate, prediction time domain length, real-time equivalent heat dissipation coefficient, total equivalent heat capacity, and the difference between the current measured temperature and the ambient temperature, the predicted temperature with heat dissipation loss correction is calculated and expressed as: ; In the formula, Indicates the first Predicted temperature after considering heat loss correction under each sampling period; Execute feedforward overshoot suppression logic: when During the deceleration phase, the upper limit of the duty cycle of the PWM signal is limited to the steady-state maintenance value. This steady-state maintenance value is calculated and determined based on the real-time equivalent heat dissipation coefficient, the difference between the target temperature and the ambient temperature during the current test phase, and the rated power of the heating device, and is expressed as: ;when When the heating device stops heating, the control device stops heating; when At that time, the target temperature for the current experimental stage is calculated based on the thermal balance model. The required precise heating time is calculated by comprehensively considering the heating power corresponding to the current duty cycle, heat loss, total equivalent heat capacity, and the target temperature at the current experimental stage. The difference between the predicted and actual temperatures can be calculated as follows: ; In the formula, Indicates the first Under each sampling period, the target temperature for the current experimental stage is achieved. The required precise heating time; After the heating process is completed, the final converged thermal characteristic parameters, total equivalent heat capacity, equivalent heat dissipation coefficient, and steady-state maintenance value will be solidified and stored for subsequent isothermal control processes.

[0041] In the constant temperature control mode (A5), the PLC industrial control all-in-one computer executes the constant temperature control algorithm. The specific steps are as follows: D1. If the actual measured temperature of the heating chamber > Target temperature at constant temperature If so, the heating device will stop heating; If the actual measured temperature of the heating chamber = Target temperature at constant temperature Then, a low duty cycle PWM signal with a preset duration and a duty cycle not exceeding the second preset ratio is output for temperature compensation (short-duty-cycle low duty cycle PWM signal). If the actual measured temperature of the heating chamber <Target temperature at constant temperature Then determine the temperature state at the previous moment: if the measured temperature at the previous moment... = Target temperature at constant temperature If the measured temperature at the previous moment is [not specified], then the output time of the PWM signal currently used for temperature compensation will be extended; if the measured temperature at the previous moment [is not specified], then [the output time will be extended]. > Target temperature at constant temperature Then, a medium duty cycle PWM signal with a preset duration and a duty cycle not exceeding the third preset ratio is output for temperature compensation (a short-duration medium duty cycle PWM signal).

[0042] D2. Based on the thermal characteristic parameters of the solidification storage during the heating process, a Smith predictor is constructed to calculate the hysteresis-free predicted temperature of the heating chamber. The calculation of the hysteresis-free predicted temperature, taking into account the current measured temperature, the hysteresis response prediction based on the pure hysteresis characteristics of the system, and the ideal response prediction without hysteresis characteristics, can be expressed as: ; In the formula, Indicates the first Hysteresis-free predicted temperature of the heating chamber under each sampling period; Indicates the first Estimated hysteresis response value over one sampling period; Indicates the first Hysteresis-free response estimate over one sampling period; Both the hysteresis response estimate and the hysteresis-free response estimate are calculated based on thermal characteristic parameters, historical and current PWM signal duty cycles, and real-time ambient temperature. Lagged response estimate It can be represented as: ; In the formula, Indicates the first Estimated hysteresis response value over one sampling period; Indicates the first PWM signal duty cycle under each sampling period; No-hysteresis response estimate It can be represented as: ; In the formula, Indicates the first Hysteresis-free response estimate over one sampling period; The prediction deviation used for closed-loop control is calculated based on the difference between the target temperature and the hysteresis-free predicted temperature, and is expressed as: .

[0043] D3. Based on the thermal characteristic parameters of solidification storage during the heating process, adjust the PI controller parameters for constant temperature scenarios; Based on the deviation between the PI controller parameters tuned for the isothermal scenario and the predicted values ​​used in closed-loop control, the duty cycle output of the PI controller is calculated. The steady-state hold value, the duty cycle output of the PI controller, and the duty cycle of the PWM signal output from D1 are then superimposed to obtain the final PWM signal duty cycle for isothermal control. This final PWM signal duty cycle is limited to the range of 0% to 30% to avoid temperature overshoot caused by high-power heating during the isothermal phase. This can be expressed as: ; ; In the formula, Indicates the first The duty cycle output of the PI controller adjusted in each sampling period; Indicates the first The duty cycle of the final PWM signal for constant temperature control under each sampling period.

[0044] D4. Perform deviation grading compensation and disturbance correction: When the measured temperature of the heating cavity is higher than the target temperature, immediately control the heating device to stop heating, and simultaneously clear the integral term of the PI controller used in the constant temperature scenario to avoid integral saturation; when the difference between the measured temperature of the heating cavity and the target temperature is within the preset range, execute the Smith prediction of D2 to D3 combined with the closed-loop control of the adaptive PI to maintain the constant temperature accuracy; when the measured temperature of the heating cavity is lower than the target temperature, trigger the fast temperature compensation logic, output the PWM signal for temperature compensation within the limited duty cycle range, and quickly pull the heating cavity temperature back to the target temperature range; every 10 sampling cycles, update the steady-state maintenance value according to the change of the current ambient temperature, and correct the heat dissipation characteristic disturbance caused by the change of ambient temperature.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A testing device for the sensitive component of a linear heat-sensing fire detector, characterized in that, include: Cabinet, heating system, temperature control system, and heat dissipation system; The heating system includes a heating chamber and a heating device disposed inside the chamber. The heating chamber forms a test area for placing the sensitive component to be tested. The heating device is connected to the heating chamber and is used to provide a heat source for the heating chamber. The temperature control system includes a PLC industrial control all-in-one computer, a temperature acquisition probe, and a heating control circuit. The temperature acquisition probe is installed in the heating cavity, and the PLC industrial control all-in-one computer and the heating control circuit are installed in the cavity inside the box. The PLC industrial control all-in-one computer is signal-connected to the temperature acquisition probe and electrically connected to the heating device through the heating control circuit to control the heating process according to the set program. The heat dissipation system includes an air inlet and a heat dissipation outlet disposed on the housing, and a heat dissipation fan disposed in the cavity. The heat dissipation fan is used to introduce external cooling air through the air inlet, and after forcibly cooling the heating cavity and the components in the cavity, it is discharged from the heat dissipation outlet.

2. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 1, characterized in that: The heating chamber is a heat conduction heating chamber that is applied to the surface and is made of heat-resistant silicone rubber or aluminum alloy.

3. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 2, characterized in that: The heating device is composed of heat-resistant silicone rubber or heat-resistant ceramic with an embedded resistance wire; the heating control circuit includes a solid-state relay electrically connected to the resistance wire.

4. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 3, characterized in that: It also includes a freely openable and closable heat-insulating cover plate, which is installed on the box body by a hinge and covers the heating cavity. The heat-insulating cover plate is made of heat-resistant foamed silicone rubber.

5. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 4, characterized in that: The front of the enclosure is provided with a panel made of aluminum alloy, which also serves as the cover of the chamber. The display screen of the PLC industrial control all-in-one machine is embedded and fixed on the panel.

6. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 5, characterized in that: The control program of the PLC industrial control all-in-one computer includes a constant temperature control mode and a differential temperature control mode.

7. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 6, characterized in that: The PLC industrial control all-in-one machine has a built-in high-speed pulse output port, which is electrically connected to the control input terminal of the solid-state relay in the heating control circuit. The PLC industrial control all-in-one machine outputs a pulse width modulation (PWM) signal through the high-speed pulse output port. The duty cycle of the PWM signal is generated by the PLC industrial control all-in-one machine. The PWM signal is used to control the ratio of the on and off time of the solid-state relay within a unit cycle, thereby linearly adjusting the average input power of the heating resistance wire in the heating device.

8. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 7, characterized in that: The PLC industrial control integrated computer executes corresponding test methods based on the type of sensitive component under test. The sensitive components under test include constant temperature alarm type and differential temperature alarm type. The test methods include: If the sensitive component under test is a constant temperature alarm type, select the constant temperature control mode to perform the test, including: A1. Obtain the rated operating temperature and rated response time of the sensitive components; A2. Obtain the current heating chamber temperature. If the heating chamber temperature is greater than 25℃, proceed directly to A3. If the heating chamber temperature is less than 25℃, heat the heating chamber to 25℃ at a heating rate of 5℃ / min before proceeding to A3. A3. Set the first target operating temperature and the first target heating rate, put the sensitive component to be tested into the heating chamber, and control the heating chamber to heat up at the first target heating rate. A4. When the sensitive component under test issues an alarm signal, record the actual operating temperature of the heating chamber at this time; A5. Remove the sensitive component under test from the heating chamber and cool the heating chamber to the ambient temperature through the heat dissipation system. At the same time, the sensitive component under test is simultaneously cooled to the ambient temperature. Set the second target operating temperature and the second target heating rate, and control the heating chamber to start heating to the second target operating temperature and keep it constant. A6. After cooling, put the sensitive component under test back into the constant temperature heating chamber and start the timer simultaneously. When the sensitive component under test issues an alarm signal, record the measured response time at this time. A7. When the measured operating temperature meets the preset operating temperature acceptable range and the measured response time is ≤ the rated response time, the sensitive component is judged to be of acceptable quality. If the sensitive component under test is a differential temperature alarm type, select the differential temperature control mode to perform the test, including: B1. Obtain the upper limit values ​​of the rated operating temperature rise rate and rated response time of sensitive components; B2. Obtain the current heating chamber temperature. When the heating chamber temperature is greater than 25℃, proceed directly to B3. When the heating chamber temperature is less than 25℃, heat the heating chamber to 25℃ at a heating rate of 5℃ / min before proceeding to B3. B3. Set the third target operating temperature and the third target heating rate, place the sensitive component to be tested into the heating chamber, control the heating chamber to heat up at a uniform rate according to the set third target heating rate and start the timing synchronously. B4. When a sensitive component issues an alarm signal, record the measured response time at that moment; B5. When the measured response time is less than or equal to the upper limit of the rated response time, the sensitive component is deemed to be of acceptable quality.

9. The testing device for the sensitive component of a linear heat-sensing fire detector according to claim 8, characterized in that: The PLC industrial control all-in-one computer also includes: During the A3 and A5 heating processes in constant temperature control mode, and during the B3 heating process in differential temperature control mode, the PLC industrial control all-in-one computer executes a predictive temperature control algorithm, including: C1. Record the pure time delay of the system from the start of heating to the detection of temperature change. With a fixed sampling period, collect the current heating chamber temperature and ambient temperature in real time, and obtain the actual temperature rise per second within a specified time after heating starts. At the same time, calculate the target temperature rise per second based on the set target heating rate. C2. In each sampling period, a recursive least squares method with a forgetting factor is used to identify the real-time thermal characteristic parameters of the system online based on the thermal balance mathematical model of the thermal system: First, a thermal balance physical model of the heating system is established, which covers four core thermal characteristic parameters: the total equivalent heat capacity of the heating cavity and the sensitive component under test, the pure time delay of the heating system, the effective heating power of the heating device, and the equivalent heat dissipation coefficient; then, the thermal balance physical model is converted into a discrete-time linear regression equation, which includes three coefficients to be identified, the duty cycle of the PWM signal, the ambient temperature, and the identification residual. The recursive least squares method with a variable forgetting factor is adopted to update the values ​​of the three coefficients to be identified in each sampling period, and simultaneously calculate the total equivalent heat capacity, equivalent heat dissipation coefficient, and pure lag time in the current sampling period based on the coefficients. C3. Compare the target temperature rise per second with the actual temperature rise per second: If the difference between the target temperature rise per second and the actual temperature rise per second is within a preset range, then the predicted temperature of the heating chamber is calculated. If the predicted temperature of the heating chamber is greater than or equal to the target temperature of the current test stage, then the heating device will be controlled to stop heating. If the predicted temperature of the heating chamber is less than the target temperature of the current test stage, calculate the continuous heating time required to reach the target temperature without changing the rate of temperature rise. If the difference between the target temperature rise per second and the actual temperature rise per second exceeds the preset range, the duty cycle of the PWM signal output to the heating control circuit is adjusted according to the magnitude of the difference, and the corresponding theoretical temperature rise rate is obtained after adjustment. Based on the adjusted theoretical temperature rise rate, the predicted temperature of the heating chamber is recalculated; If the predicted temperature of the heating chamber is greater than or equal to the target temperature of the current test stage, then the heating device will be controlled to stop heating. If the predicted temperature of the heating chamber is less than the target temperature of the current test stage, then calculate the continuous heating time required to reach the target temperature of the current test stage under the condition of changing the temperature rise rate. When the predicted temperature of the heating chamber is within a preset range similar to the target temperature of the current test stage, and the current heating chamber temperature is less than the target temperature of the current test stage, a low duty cycle PWM signal with a duty cycle not exceeding the first preset ratio is output for temperature fine-tuning. C4. Using temperature data from multiple consecutive sampling periods, calculate the current actual smooth temperature rise rate; calculate the deviation between the target temperature rise per second and the actual smooth temperature rise rate; based on the thermal characteristic parameters identified in real time by C2, adaptively tune the PI controller parameters; according to the tuned PI controller parameters, calculate the adjustment amount of the PWM signal duty cycle; add this adjustment amount to the PWM signal duty cycle level value output by C3 to obtain the final PWM signal duty cycle; C5. Based on the pure time delay of the heating system in C2, an adaptive prediction time domain is set; combined with the measured temperature, the actual smooth temperature rise rate, the prediction time domain length, the real-time equivalent heat dissipation coefficient, the total equivalent heat capacity, and the difference between the current measured temperature and the ambient temperature, the prediction temperature with heat dissipation loss correction is calculated. Execute feedforward overshoot suppression logic: When the predicted temperature with heat dissipation loss correction does not meet the first preset condition, enter the deceleration phase and limit the upper limit of the duty cycle of the PWM signal to the steady-state maintenance value. This steady-state maintenance value is calculated and determined based on the real-time equivalent heat dissipation coefficient, the difference between the target temperature and the ambient temperature in the current test phase, and the rated power of the heating device; when the predicted temperature with heat dissipation loss correction does not meet the second preset condition, control the heating device to stop heating; when the predicted temperature with heat dissipation loss correction does not meet the third preset condition, calculate the heating time required to reach the target temperature in the current test phase based on the thermal balance model.

10. A test device for the sensitive component of a linear heat-sensing fire detector according to claim 9, characterized in that: During the constant temperature maintenance process (A5) in constant temperature control mode, the PLC industrial control all-in-one computer executes the constant temperature control algorithm, including: D1. If the measured temperature of the heating chamber is greater than the target temperature, then control the heating device to stop heating. If the measured temperature of the heating chamber equals the target temperature, then a low duty cycle PWM signal with a preset duration and a duty cycle not exceeding the second preset ratio is output for temperature compensation. If the measured temperature of the heating chamber is less than the target temperature, the temperature state at the previous moment is determined: if the measured temperature at the previous moment is equal to the target temperature, the output time of the PWM signal used for temperature compensation is extended; if the measured temperature at the previous moment is greater than the target temperature, a medium duty cycle PWM signal with a preset duration and a duty cycle not exceeding the third preset ratio is output for temperature compensation. D2. Based on thermal characteristic parameters, construct a Smith predictor to calculate the hysteresis-free predicted temperature of the heating chamber; calculate the prediction deviation used for closed-loop control based on the difference between the constant temperature target temperature and the hysteresis-free predicted temperature. D3. Based on the thermal characteristic parameters, tune the PI controller parameters for the isothermal scenario; calculate the duty cycle output of the PI controller based on the deviation between the tuned PI controller parameters for the isothermal scenario and the prediction used for closed-loop control; add the steady-state holding value, the duty cycle output of the PI controller, and the duty cycle of the PWM signal output in D1 to obtain the final PWM signal duty cycle for isothermal control.

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