Back electromotive force discharge method and system for direct-current brushless fan of breathing machine

Abstract

The invention discloses a back electromotive force discharge method and system for a direct-current brushless fan of a breathing machine. The method comprises the following steps: receiving a rotating speed adjusting instruction of the direct current brushless fan of the breathing machine, and calling a preset feedforward MAP to obtain an initial discharge duty ratio; according to the obtained initial discharge duty ratio, a discharge circuit is controlled to discharge, and whether rotating speed switching is completed or not is judged; if the judgment is completed, returning the discharge duty ratio to zero, and ending the control; and if the judgment is not completed, acquiring the voltage change rate of the direct current bus in real time by using a bus voltage change rate detection circuit, and dynamically adjusting the discharge duty ratio based on the voltage change rate until the rotation speed switching is completed. The direct-current brushless fan can solve the problems of serious heating, inaccurate discharge and the like of the bleeder resistor, and ensures that the direct-current brushless fan stably and reliably operates under different rotating speed working conditions on the basis of a simple circuit and low cost.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of back electromotive force bleeding of a fan, in particular to a back electromotive force bleeding method and circuit for a direct-current brushless fan of a breathing machine. BACKGROUND

[0002] In the technical field of medical devices, the application of a breathing machine is crucial, which can provide necessary breathing support for patients and save many lives. With the continuous progress of medical technology, the performance requirements of the breathing machine are also increasing, especially in terms of speed switching frequency, dynamic response and reliability. As a key component of the breathing machine, the performance of the direct-current brushless fan directly affects the overall performance of the breathing machine. Therefore, how to ensure the stable and reliable operation of the direct-current brushless fan under different speed conditions has become a research hotspot in this field.

[0003] In the breathing machine equipment, the direct-current brushless fan used needs to be frequently and quickly switched between different speed conditions. The most typical condition is to require the fan to rapidly rise from low speed to high speed in about 100 milliseconds, and rapidly drop from high speed to low speed in the same short time, with a switching frequency of up to 40 times per minute. In this severe deceleration process, the huge kinetic energy of the motor will be fed back to the DC bus through the freewheeling diode of the inverter bridge, causing the bus voltage to rise sharply. If the overshoot voltage exceeds the withstand voltage of the power device (such as MOSFET, IGBT), the device will be broken down, the system will fail, and it will pose a serious threat to medical safety. In response to the back electromotive force overshoot problem generated when the direct-current brushless fan decelerates, there are various solutions in the prior art. The most common and mature one is to use a bleeding circuit based on a fixed voltage threshold. When the bus voltage exceeds the preset voltage, the drive switch tube is turned on, and the bleeding resistor is connected to the circuit to consume excess energy and make the bus voltage fall. In addition, there is also a scheme using an energy storage module, which recovers the back electromotive force and releases it in the next cycle.

[0004] However, these existing technologies have obvious defects. In the condition of frequent speed reduction of the breathing machine, the bleeding circuit based on a fixed voltage threshold has a very short time for the voltage to rise above the bleeding threshold in the rapid speed reduction scenario, and the voltage spike is formed before the bleeding circuit is fully effective. In order to suppress the voltage spike, the bleeding threshold is set very low, which will lead to inaccurate bleeding of the bleeding circuit, premature and too frequent operation, and also cause the bleeding resistor to generate serious heat. The scheme using an energy storage module has the problems of complex circuit, high cost and short service life of energy storage devices under frequent charging and discharging. SUMMARY

[0005] In order to solve the problems of serious heating of the discharge resistor and inaccurate discharge, ensure the stable and reliable operation of the DC brushless fan under different rotating speed conditions, and on the basis of simple circuit and low cost, the application provides a back electromotive force discharge method and circuit for a DC brushless fan of a breathing machine.

[0006] In the first aspect, the application provides a back electromotive force discharge method for a DC brushless fan of a breathing machine, comprising: receiving a rotating speed adjustment instruction of the DC brushless fan of the breathing machine, and calling a preset feedforward MAP to obtain an initial discharge duty cycle; the preset feedforward MAP generation step comprises: setting the DC brushless fan to perform a rotating speed switching operation between a series of different initial rotating speeds and target rotating speeds; in each rotating speed switching operation, a different fixed discharge duty cycle is tested and the corresponding bus voltage peak value is recorded; for each pair of initial rotating speed and target rotating speed, the value that meets the bus voltage peak value limit and has the minimum discharge duty cycle is selected as the feedforward discharge control parameter under the corresponding working condition; and all input indexes and corresponding output parameters are stored as a feedforward MAP; According to the obtained initial discharge duty cycle, the discharge circuit is controlled to discharge, and it is judged whether the rotating speed switching is completed; if it is judged that the completion, the discharge duty cycle is returned to zero, and the control is ended; if it is judged that the completion is not completed, the bus voltage change rate detection circuit is used to collect the voltage change rate of the DC bus in real time, the discharge duty cycle is dynamically adjusted based on the voltage change rate, and the rotating speed switching is completed; the dynamic adjustment step comprises: when the voltage change rate is lower than a first preset threshold, the discharge duty cycle is increased; when the voltage change rate is higher than a second preset threshold, the discharge duty cycle is decreased; when the voltage change rate is between the first preset threshold and the second preset threshold, the current discharge duty cycle is kept; the discharge circuit and the bus voltage change rate detection circuit are both arranged in the breathing machine and connected with the DC brushless fan in the breathing machine.

[0007] By adopting the above scheme, after receiving the rotating speed adjustment instruction, the preset feedforward MAP is called to obtain the initial discharge duty cycle, the possible back electromotive force overshoot can be predicted in advance according to the known rotating speed switching law, the problems of serious heating of the discharge resistor and inaccurate discharge are solved; when the rotating speed switching is not completed, the bus voltage change rate detection circuit is controlled to collect the voltage change rate in real time and dynamically adjust the discharge duty cycle based on the voltage change rate, the discharge duty cycle can be accurately adjusted according to the bus voltage change during speed reduction, the back electromotive force overshoot is further inhibited, the problems of serious heating of the discharge resistor and inaccurate discharge are effectively solved, and the cost is reduced.

[0008] Preferably, the preset feedforward MAP generation step further comprises: During the process of setting up a DC brushless fan to perform speed switching operations between a series of initial speeds and target speeds, the speed change amplitude between each pair of initial speeds and target speeds in the series is calculated, and according to the preset speed change amplitude partitioning threshold, the speed change amplitude between each initial speed and target speed is divided into one of the amplitude intervals of low amplitude interval, medium amplitude interval and high amplitude interval. After performing the process of selecting the value that satisfies the peak bus voltage limit and has the smallest discharge duty cycle as the feedforward discharge control parameter for each pair of initial and target speeds under the corresponding operating conditions, for each pair of initial and target speeds belonging to different amplitude ranges, different multinomial fitting methods or pre-built neural network models with different structural parameters are used to obtain the optimal discharge duty cycle corresponding to different speed change amplitudes within the range; and the number of terms or the complexity of the model structure parameters of the multinomial fitting method gradually increases in the order of low amplitude range, medium amplitude range and high amplitude range, so as to obtain the feedforward discharge control parameters under different operating conditions.

[0009] By adopting the above scheme, the feedforward discharge control parameters under different operating conditions are obtained by partitioning the speed change amplitude and using different multinomial fitting methods or neural network models with different structural parameters. This can more accurately adapt to different speed switching conditions, improve the accuracy and pertinence of back EMF discharge control, and thus more effectively suppress back EMF overshoot.

[0010] Preferred options also include: If the determination is not completed, the voltage monitoring device installed in the ventilator is controlled to collect the voltage of the DC bus in real time; the method of dynamically adjusting the discharge duty cycle based on the voltage change rate is selected instead of the original method of dynamically adjusting the discharge duty cycle based on the voltage change rate; the dynamic coordinated adjustment step includes: When the voltage is greater than the preset overvoltage threshold, increase the discharge duty cycle; when the voltage is less than the preset over-discharge threshold, decrease the discharge duty cycle; when the voltage is between the preset overvoltage threshold and the preset over-discharge threshold, continue to judge; when the voltage change rate is lower than the first preset threshold, increase the discharge duty cycle; when the voltage change rate is higher than the second preset threshold, decrease the discharge duty cycle; when the voltage change rate is between the first preset threshold and the second preset threshold, maintain the current discharge duty cycle.

[0011] By adopting the above scheme and dynamically coordinating the voltage change rate and voltage-based discharge duty cycle, we can more accurately respond to changes in bus voltage, effectively suppress back EMF overshoot, avoid power device breakdown due to overvoltage, and ensure system reliability and medical safety.

[0012] Preferably, the dynamic coordinated adjustment step further includes: When the voltage is greater than the preset overvoltage threshold or less than the preset over-discharge threshold, the absolute value of the voltage error is calculated, and the current calculated voltage error is classified according to the preset voltage error absolute value classification standard. According to the classification level of the current voltage error absolute value, the first adjustment ratio coefficient is adaptively matched to increase the discharge duty cycle or the second adjustment ratio coefficient is matched to decrease the discharge duty cycle. The higher the voltage error absolute value level, the larger the first adjustment ratio coefficient and the second adjustment ratio coefficient are. When the voltage change rate is lower than the first preset threshold or higher than the second preset threshold, the absolute value of the voltage change rate error is calculated, and the current calculated voltage change rate error is classified according to the preset voltage change rate error absolute value classification standard. According to the classification level of the current voltage change rate error absolute value, the third adjustment ratio coefficient is adaptively matched to increase the discharge duty cycle or the fourth adjustment ratio coefficient is matched to decrease the discharge duty cycle. The higher the voltage error absolute value level, the larger the third and fourth adjustment ratio coefficients are.

[0013] By adopting the above scheme, the discharge duty cycle can be adjusted more precisely according to the absolute value of the error of voltage and voltage change rate, thereby enhancing the suppression effect on back EMF overshoot and improving the accuracy and reliability of discharge control.

[0014] Preferred options also include: Before the speed switching is completed, it is determined whether the speed switching is completed. If it is not completed, the cumulative number of times the discharge duty cycle is dynamically adjusted based on the voltage change rate is determined. Each time the cumulative number is updated, the threshold range of the cumulative number after the update is determined, and a correction gain that matches the threshold range of the cumulative number is matched. The larger the threshold range of the cumulative number is, the larger the value of the corresponding correction gain is. The adjusted discharge duty cycle is corrected by using the matched correction gain.

[0015] By adopting the above scheme, the discharge duty cycle is adjusted dynamically based on the voltage change rate during the speed switching process. The corresponding correction gain is then used to correct the discharge duty cycle, making the adjustment of the discharge duty cycle more precise, effectively suppressing back EMF overshoot, and ensuring stable system operation.

[0016] Preferred options also include: Upon receiving the speed adjustment command from the DC brushless fan of the ventilator, the system parses and obtains the global parameters of the cycle, including the total cycle duration, the phase percentage parameters including the inspiratory time, expiratory time and breath-holding time, and the speed amplitude parameters including the initial speed and the target speed. Acquire feature data for the current cycle, including: synchronizing the cycle with the start of the inhalation phase as the cycle start point, synchronously recording the peak inhalation speed, the trough inhalation speed of the current cycle, and the deceleration slope of the current cycle; cache features from the most recent few cycles to form a sliding window; The system predicts the speed switching for the next cycle and, based on the predicted speed switching, pre-calls a preset feedforward MAP to obtain the initial discharge duty cycle for the next cycle. It sets prediction logic adaptation rules for different operating conditions, including: a first prediction logic matching the first operating condition and a second prediction logic matching the second operating condition. The first operating condition is a stable operating condition, with no speed adjustment command in the next cycle. The first prediction logic includes: a data weighted fitting prediction logic adapted to the first operating condition, which calculates the predicted speed switching value for the next cycle based on the weighted calculation of data within a sliding window. The second operating condition is a dynamic adjustment operating condition, where a new target speed command is received in the next cycle. The second prediction logic includes: a linear transition cycle prediction logic adapted to the second operating condition, which calculates the predicted speed switching value for the transition cycle based on the latest cycle data within the sliding window and the target speed in the received new target speed command, and uses this as the predicted speed switching value for the next cycle. The predicted value of the next cycle speed switching is obtained by adapting the prediction logic to the actual working conditions, and the initial discharge duty cycle is obtained by calling the preset feedforward MAP diagram.

[0017] By adopting the above scheme, after receiving the speed adjustment command, the relevant parameters are parsed and obtained, the current cycle characteristic data is recorded synchronously and cached to form a sliding window, and the speed switching prediction logic is adapted according to different operating conditions to predict the next cycle. The feedforward MAP diagram is called in advance to obtain the initial discharge duty cycle, which can more accurately deal with the back EMF overshoot problem under different operating conditions.

[0018] Secondly, this application provides a back electromotive force discharge system for a DC brushless fan used in a ventilator, comprising: The feedforward control module is used to receive the speed adjustment command of the DC brushless fan of the ventilator and call the preset feedforward MAP to obtain the initial discharge duty cycle; The duty cycle adjustment module is used to control the discharge circuit to discharge according to the acquired initial discharge duty cycle and to determine whether the speed switching is complete. If the determination is complete, the discharge duty cycle is set to zero and the current control ends. If the determination is not complete, the bus voltage change rate detection circuit is used to collect the DC bus voltage change rate in real time and dynamically adjust the discharge duty cycle based on the voltage change rate until the speed switching is complete. The bus voltage change rate detection circuit includes: a voltage divider circuit, comprising a first resistor, a second resistor, and a first capacitor, for dividing the bus voltage; a voltage follower, with its input connected to the output of the voltage divider circuit, including a first operational amplifier for isolating the voltage divider circuit and the differentiating circuit; a differentiating circuit, with its input connected to the output of the voltage follower, including a differentiating resistor, a differentiating capacitor, and a second operational amplifier, for acquiring the bus voltage change rate after voltage division; and an adder circuit, with its input connected to the output of the differentiating circuit, including an adding resistor, a diode, and a third operational amplifier.

[0019] By adopting the above scheme, combined with feedforward control and bus voltage change rate feedback control, the discharge duty cycle can be predicted in advance and dynamically adjusted according to the speed switching conditions, effectively suppressing back EMF overshoot; by using the bus voltage change rate detection circuit for signal acquisition and processing, the discharge action can be precisely controlled, avoiding problems such as inaccurate, premature, and excessively frequent discharge actions, thus reducing circuit costs.

[0020] Preferably, the resistance ratio of the first resistor to the second resistor in the voltage divider circuit is configured to reduce the bus voltage according to a preset voltage division ratio.

[0021] By adopting the above scheme, the bus voltage is accurately reduced according to the preset voltage division ratio, so that the voltage signal processed by the subsequent circuit meets the requirements and ensures the stable operation of the back EMF discharge system.

[0022] Preferably, the differentiating circuit includes a correction capacitor connected in parallel with the differentiating resistor, and the capacitance ratio of the correction capacitor to the differentiating capacitor meets a preset frequency response requirement.

[0023] By adopting the above scheme, the frequency response of the differentiating circuit is optimized, making the detection of the bus voltage change rate more accurate, thereby adjusting the discharge duty cycle more precisely and effectively suppressing back EMF overshoot.

[0024] Preferably, the anode of the diode in the adder circuit is connected to the output terminal of the second operational amplifier, and the cathode is connected to the voltage clamping node.

[0025] By adopting the above scheme, voltage clamping protection is provided to prevent excessive voltage from damaging related devices such as MCUs and to ensure the stable operation of the system.

[0026] In summary, this application has the following beneficial effects: 1. A composite control method combining feedforward MAP prediction and bus voltage change rate feedback adjustment is adopted. The back EMF overshoot is predicted in advance by combining the known speed switching law, and the discharge duty cycle is adjusted according to the bus voltage change rate, which solves the problems of severe heating of the discharge resistor and inaccurate discharge. Only three operational amplifiers and external resistors and capacitors are used to realize the acquisition of bus voltage change rate signal, which reduces circuit cost. 2. During the feedforward MAP prediction process, the speed change amplitude is divided into intervals, and different complexity fitting methods or neural network models are used for different amplitude intervals to obtain the optimal discharge duty cycle. This can more accurately adapt to different operating conditions and improve the accuracy of feedforward discharge control parameters. For the adjustment of the bus voltage change rate, the error absolute value of the voltage and voltage change rate is calculated and graded to adjust the discharge duty cycle more accurately. In addition, the cumulative number of times the discharge duty cycle is adjusted is combined with the gain correction and the discharge duty cycle correction are matched according to the threshold range of the cumulative number of times, further improving the effect and stability of back EMF discharge control. 3. Parse the speed adjustment command to obtain key parameters, synchronously record the current cycle characteristic data and cache it to form a sliding window, adapt the prediction logic to predict the speed switching of the next cycle according to different operating conditions, and call the preset feedforward MAP diagram in advance to obtain the initial discharge duty cycle, so as to achieve more accurate pre-control of back EMF discharge, improve the suppression effect of back EMF overshoot and the dynamic response capability of the system. Attached Figure Description

[0027] Figure 1 A circuit diagram of the back electromotive force discharge circuit for a traditional DC brushless fan in a ventilator; Figure 2 This is a flowchart of the back electromotive force discharge method for the DC brushless fan of the ventilator described in a specific embodiment; Figure 3 This is a flowchart illustrating the process of setting the initial discharge duty cycle and dynamically adjusting the duty cycle in the back electromotive force discharge method of the DC brushless fan of the ventilator described in a specific embodiment. Figure 4 This is a schematic diagram of the back electromotive force discharge system of the DC brushless fan of the ventilator described in a specific embodiment; Figure 5 This is a circuit diagram of the bus voltage change rate detection circuit in the back electromotive force discharge system of the DC brushless fan of the ventilator described in a specific embodiment. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] To ensure stable and reliable operation of the DC brushless fan of the ventilator under different speed conditions, and considering the frequent switching between the two speeds of the ventilator, a new design is proposed based on the traditional discharge circuit with a fixed voltage threshold, such as... Figure 1 As shown, a composite control method combining feedforward MAP prediction and bus voltage change rate feedback adjustment is proposed. The initial discharge duty cycle is obtained through a preset feedforward MAP diagram, and the discharge duty cycle is dynamically adjusted according to the bus voltage change rate, achieving precise discharge of back EMF, reduced heating of the discharge resistor, and prevention of power device breakdown. Figure 2 As shown in the figure, the specific steps of a method for discharging the back electromotive force of a DC brushless fan for a ventilator disclosed in this application are as follows.

[0030] S1. Receive the speed adjustment command of the DC brushless fan of the ventilator, call the preset feedforward MAP diagram to obtain and set the initial discharge duty cycle.

[0031] Specifically, such asFigure 3 As shown, the device receives speed adjustment commands from the brushless DC fan of the ventilator. These commands include: global cycle parameters, phase percentage parameters, and speed amplitude parameters. For example, taking a cycle with 40 switching times per minute, rapidly increasing from a low speed to a high speed within 100 milliseconds, and then rapidly decreasing from a high speed to a low speed within the same short time, the global cycle parameters include a respiratory rate f (40 breaths / min), corresponding to a total respiratory cycle duration of 1.5 seconds. The phase percentage parameters include inspiratory time, expiratory time, and breath-holding time. The speed amplitude parameters include initial speed and target speed, which can be set for the inspiratory or exhalation phase, and a maintenance speed for the breath-holding phase.

[0032] Considering that in actual ventilator operation, the speed will rapidly decrease from high to low within 100 milliseconds, there will be back EMF overshoot during this drastic deceleration. To avoid back EMF overshoot, taking drastic deceleration as an example (the same applies to drastic acceleration), the optimal duty cycle of the bleed circuit is determined in advance through experimental calibration and a mapping table is constructed to achieve pre-matching of the duty cycle of the bleed circuit corresponding to the current speed adjustment command, so as to control the bleed circuit to bleed. Therefore, the initial bleed duty cycle is obtained by calling the preset feedforward MAP.

[0033] Specifically, the steps for generating the feedforward MAP diagram include: The DC brushless fan is configured to perform speed switching operations between a series of different initial speeds and target speeds. Taking deceleration as an example, during the operation, the change in speed amplitude leads to a change in the peak value of the back electromotive force, as shown in the formula: ;in, Let be the back electromotive force constant of the motor. This represents the magnitude of the speed change during the deceleration from the initial speed to the target speed. At that time, the excess power that needs to be released ;in, The rated voltage of the busbar For the motor winding resistance, This is the equivalent circuit for the discharge circuit; the discharge duty cycle is set according to the discharge power to achieve energy balance, i.e. ,in, The larger, The higher the value, the greater the required D value to ensure that excess energy is released quickly and does not cause overpressure.

[0034] During each speed switching operation, tests were conducted with different fixed discharge duty cycles, and the corresponding peak bus voltage was recorded. The fixed discharge duty cycle was manually set for testing (e.g., from 0.1 to 0.9 in 0.1 increments). Key indicators were recorded: the maximum overshoot value of the bus voltage (must be ≤ Udc + 1V, meeting ventilator requirements). Specifically, for each pair of initial and target speeds, the value that satisfies the peak bus voltage limit and has the smallest discharge duty cycle was selected as the feedforward discharge control parameter for the corresponding operating condition. For example: When = 300 rad / s, ( The test showed that when D=0.4, the maximum overshoot value of the bus voltage was 0.8V, which was the optimal value. Recorded: , D=0.4.

[0035] All input indices and their corresponding output parameters are stored as a feedforward MAP. Input indices include the initial speed and target speed, while corresponding output parameters include the peak back EMF and the optimal discharge duty cycle. The initial discharge duty cycle is set based on the currently acquired and set initial discharge duty cycle.

[0036] S2. Based on the obtained initial discharge duty cycle, control the discharge circuit to discharge, determine whether the speed switching is complete, and dynamically adjust the discharge duty cycle according to the determination result until the speed switching is complete.

[0037] Specifically, while the motor switches speeds according to the speed regulation command, the discharge circuit operates under control according to the initial discharge duty cycle. Throughout the speed switching process, it is necessary to check in a timely manner whether the speed switching is complete and to control the discharge circuit. A judgment is then set to determine whether the speed switching is complete. If the judgment is complete, the discharge duty cycle is reset to zero, ending the control of the discharge circuit for this period. If the judgment is incomplete, the voltage change rate of the DC bus is read. That is, when the judgment is incomplete, to continue to avoid back EMF overshoot during speed switching, the DC bus voltage change rate detection circuit is used to collect the DC bus voltage change rate in real time. Based on the voltage change rate, the discharge duty cycle is dynamically adjusted and updated to repeat the judgment and update process until the speed switching is complete. Both the discharge circuit and the bus voltage change rate detection circuit are located inside the ventilator and connected to the brushless DC fan inside the ventilator.

[0038] Specifically, the bus voltage change rate detection circuit can be implemented in various ways, such as using a differentiating circuit composed of operational amplifiers to acquire the voltage change rate. In this embodiment, the voltage change rate detection circuit includes a voltage divider circuit, a voltage follower, a differentiating circuit, and a signal conditioning circuit connected in sequence. Figure 3As shown, the dynamic adjustment steps include: increasing the discharge duty cycle when the voltage change rate is lower than a first preset threshold (threshold A); decreasing the discharge duty cycle when the voltage change rate is higher than a second preset threshold (threshold B); and maintaining the current discharge duty cycle when the voltage change rate is between the first and second preset thresholds (threshold A and threshold B). The first preset threshold is an under-discharge threshold, where the voltage is still switching rapidly and the back electromotive force is not fully discharged; the second preset threshold is an over-discharge threshold, where the voltage switching is too fast, resulting in excessive discharge and energy waste. Both the first and second preset thresholds are obtained through test experiments.

[0039] Using the above embodiments, the composite control method based on feedforward MAP prediction and bus voltage change rate feedback can predict possible back EMF overshoot in advance according to different speed switching conditions, and adjust the discharge duty cycle in real time, thereby accurately discharging back EMF, avoiding premature and excessive operation of the discharge circuit, reducing the heating of the discharge resistor, improving the reliability and stability of the system, and ensuring the medical safety of the ventilator equipment.

[0040] In a specific embodiment, by dividing the speed change amplitude into intervals and using different fitting methods or neural network models to obtain the optimal discharge duty cycle for different intervals, the method more accurately adapts to different speed switching conditions, further improving the accuracy of the feedforward MAP diagram and thus better suppressing back EMF overshoot. The method further includes: the preset feedforward MAP diagram generation step further includes: The process of setting up a DC brushless fan to perform deceleration operations between a series of initial speeds and target speeds. (Similarly for acceleration operation), calculate the speed change amplitude between each pair of initial speed and target speed in a series, and divide the speed change amplitude between each initial speed and target speed into one of the low amplitude interval, medium amplitude interval and high amplitude interval according to the preset speed change amplitude partitioning threshold.

[0041] Specifically, the preset speed variation zone thresholds can be obtained through theoretical calculations and experimental verification and correction. For example, the threshold for the low-amplitude range is the critical value for bus overshoot. The high-amplitude range threshold is the critical point at which the duty cycle begins to saturate. , This represents the minimum operating speed of the motor, with a mid-range value of [value missing]. For each Perform a duty cycle scan on values ​​(from 0 to maximum operating condition), record bus overshoot, and calculate D pair. sensitivity The partitioning point is taken at the inflection point of the S-curve, thereby verifying and correcting the preset threshold for the amplitude of rotational speed change partitioning.

[0042] After performing the process of selecting the value that satisfies the peak bus voltage limit and has the smallest discharge duty cycle as the feedforward discharge control parameter for each pair of initial speeds and target speeds under the corresponding operating conditions, for each pair of initial speeds and target speeds belonging to different amplitude ranges, the optimal discharge duty cycle corresponding to different speed change amplitudes within the range is obtained by using different polynomial fitting methods or pre-built neural network models with different structural parameters.

[0043] Among these methods, different multinomial fitting techniques were employed to obtain the optimal discharge duty cycle corresponding to different speed variation amplitudes within the interval. Specifically, this included: the low-amplitude interval compared to other amplitude intervals, Relatively closer D to The sensitivity is higher in this interval D and The relationship is approximately linear, and the least squares method can be used to fit D to the equation. The relationship between these factors allows us to obtain the untested values ​​within the tested speed change amplitude range. To obtain the corresponding optimal discharge ratio; compared to the low amplitude range, Far greater than The back electromotive force overshoot is significant, and D is related to... The relationship is non-linear, and a binomial approach is used to fit D and The relationship between these factors allows us to obtain the untested values ​​within the tested speed change amplitude range. To obtain the corresponding optimal discharge ratio, the high-amplitude range, compared to other amplitude ranges, Far greater than As D approaches saturation, the rate of change decreases; using a trinomial method, D is fitted to... The relationship between these factors allows us to obtain the untested values ​​within the tested speed change amplitude range. The optimal discharge ratio is obtained by using a multivariate fitting method with an increasing number of terms in the order of low amplitude range, medium amplitude range, and high amplitude range, thereby obtaining the feedforward discharge control parameters under different operating conditions.

[0044] Among these methods, deep learning is chosen to capture more complex nonlinear relationships. Pre-built neural network models with different structural parameters are used to obtain the optimal discharge duty cycle corresponding to different speed variation amplitudes within a given range. Specifically, the pre-built neural network model architecture includes an input layer, hidden layers, and an output layer. The input layer receives... , The output layer is the optimal D; multiple sets of data obtained through historical experiments. The optimal D-training is generated; and different neural network models with different structural parameters are used for different amplitude ranges. Considering that the nonlinear relationship is more complex as the amplitude range increases, the complexity of the model structural parameters (such as the number of hidden layers) gradually increases in the order of low amplitude range, medium amplitude range and high amplitude range, so as to obtain the feedforward discharge control parameters under different working conditions.

[0045] Correspondingly, the optimal discharge duty cycle corresponding to different speed change amplitudes within the interval can be obtained by comprehensively using different multinomial fitting methods or pre-constructed neural network models with different structural parameters. The optimal discharge duty cycles obtained by the two methods are then averaged or mutually verified to see if they are consistent or if the difference is greater than a preset difference, thereby obtaining a more accurate feedforward MAP diagram.

[0046] In addition to selecting the lowest possible discharge duty cycle, the method also considers limiting the temperature rise during the process of controlling the discharge circuit. Real-time temperature acquisition is performed using surface-mount temperature sensors installed on key components of the bleeder circuit to obtain the temperature of these components. The feedforward MAP generation step further includes: testing and recording the corresponding bus voltage peak value at different fixed bleeder duty cycles during each deceleration operation (the same applies to acceleration operations); the fixed bleeder duty cycle is manually set for testing (e.g., from 0.1 to 0.9 in 0.1 increments), and key indicators recorded include the temperature rise of key components in the bleeder circuit (MOSFET case temperature and resistance); for each pair of initial and target speeds, the bleeder duty cycle value that satisfies the bus voltage peak limit, the temperature rise limit of key components in the bleeder circuit, and minimizes the temperature rise of key components in the bleeder circuit is selected as the feedforward bleeder control parameter for the corresponding operating condition. Subsequently, the DC bus voltage change rate is acquired in real-time using a bus voltage change rate detection circuit. During the dynamic adjustment of the bleeder duty cycle based on the voltage change rate, the temperature rise limit of key components in the bleeder circuit must be met.

[0047] In a specific embodiment, by introducing voltage monitoring equipment and adopting a method of coordinating voltage change rate and voltage dynamic adjustment of the discharge duty cycle, the changes in bus voltage can be considered more comprehensively, further improving the accuracy and timeliness of discharge duty cycle adjustment and better suppressing back EMF overshoot. The method also includes: Considering that single rate of change feedback lacks a clear safety threshold, extreme operating conditions may lead to voltage overshoot due to misjudgment; therefore, a combined feedback mechanism is implemented: if the judgment is not completed, the voltage monitoring equipment installed on the wind turbine is controlled to collect the DC bus voltage in real time; a method based on voltage change rate and dynamic coordinated adjustment of the discharge duty cycle is selected instead of the original method based on the voltage change rate for dynamically adjusting the discharge duty cycle; the dynamic coordinated adjustment steps include: The system prioritizes feedback based on the bus voltage threshold. When the voltage exceeds the preset overvoltage threshold (e.g., 25.5V), the discharge duty cycle is increased (e.g., by 0.05) for emergency discharge to prioritize safety. When the voltage is below the preset over-discharge threshold (e.g., 23.5V), the discharge duty cycle is decreased (e.g., by 0.05) to stop excessive discharge. When the voltage is between the preset overvoltage threshold and the preset over-discharge threshold, feedback is provided on the voltage change rate. That is, the system continues to determine whether the voltage change rate is below the first preset threshold, increasing the discharge duty cycle; when the voltage change rate is above the second preset threshold, decreasing the discharge duty cycle; and when the voltage change rate is between the first and second preset thresholds, maintaining the current discharge duty cycle.

[0048] To further refine the adjustment of the discharge duty cycle and enhance the suppression effect on back EMF overshoot, the dynamic coordinated adjustment step further includes: calculating the absolute value of the voltage error when the voltage is greater than a preset overvoltage threshold or less than a preset over-discharge threshold. or The current calculated voltage error is classified according to a preset voltage error absolute value classification standard. The preset voltage error absolute value can be calibrated based on experimental statistics, such as low error level, medium error level, and high error level. Based on the classification of the current voltage error absolute value, an adaptive adjustment ratio coefficient is applied. To increase the discharge duty cycle (D=D+) Or match the second adjustment ratio coefficient To reduce the discharge duty cycle (D=D- The higher the absolute value of the voltage error, the larger the first and second adjustment ratios. For example, the first adjustment ratio for a low error level is 0.005-0.01, the first adjustment ratio for a medium error level is 0.01-0.03, and the first adjustment ratio for a high error level is 0.03-0.05.

[0049] Accordingly, the duty cycle is adjusted based on the difference between the voltage change rate and the set threshold to suppress voltage fluctuation trends; when the voltage change rate is lower than the first preset threshold or higher than the second preset threshold, the absolute value of the voltage change rate error is calculated. or The current calculated voltage change rate error is classified according to a preset voltage change rate error absolute value classification standard. The preset voltage change rate error absolute value can be calibrated based on experimental statistics, such as low error level, medium error level, and high error level. Based on the classification of the current voltage change rate error absolute value, a third adjustment ratio coefficient is adaptively matched. To increase the discharge duty cycle (D=D+) Or match the fourth adjustment ratio coefficient To reduce the discharge duty cycle (D=D- The higher the absolute value of the voltage error, the larger the third and fourth adjustment coefficients.

[0050] Furthermore, the dynamic adjustment process of the discharge duty cycle involves the number of feedback adjustments. The more cumulative adjustments, the more continuous or persistent the deviation, indicating a persistent mismatch in discharge and requiring stronger correction. Therefore, before the speed switching is completed, it is set to statistically determine whether the speed switching is complete. If it is not completed, the cumulative number of times the discharge duty cycle is dynamically adjusted based on the voltage change rate is determined. Each time the cumulative number is updated, the threshold range of the updated cumulative number is determined. For example, the threshold range of the cumulative number is set to 1-2, 3-5, and greater than 5 times. A correction gain is then matched to the corresponding cumulative number threshold range. Furthermore, the larger the cumulative count threshold range, the larger the corresponding correction gain value. For example, if the cumulative count threshold range is 1-2, the corresponding correction gain will be... The cumulative count threshold range is 3-5, corresponding to the appropriate correction gain. The cumulative count threshold range is greater than 6, corresponding to the appropriate correction gain. Finally, the adjusted discharge duty cycle is corrected using a matched correction gain, such as (D=D+). ) or (D=D- The above adjustment ratios can be combined and adjusted together to increase or decrease the discharge duty cycle.

[0051] In a specific embodiment, leveraging the strong periodicity of the ventilator's respiratory cycle (a fixed rhythm of inspiration-expiration-breath-hold) and the correlation between the rotational speed adjustment command (the command is directly bound to the cycle parameter), the method achieves cycle rotational speed prediction through steps such as current cycle analysis, baseline model establishment, dynamic correction extrapolation, and duty cycle preloading. This allows for the early invocation of the optimal discharge duty cycle, further improving the overshoot suppression response speed. The method also includes: Upon receiving the speed adjustment command from the DC brushless fan of the ventilator, the system parses and obtains the global parameters of the cycle, including the total cycle duration, the phase percentage parameters including the inspiratory time, expiratory time, and breath-holding time, and the speed amplitude parameters including the initial speed and the target speed, thus obtaining the speed adjustment command corresponding to the current cycle T1.

[0052] To acquire the characteristic data of the current cycle, taking the deceleration operation as an example, this includes: synchronizing the cycle with the start of the inhalation phase as the cycle starting point, and synchronously recording the peak inhalation speed, the trough inhalation speed, and the deceleration slope of the current cycle; for example, recorded as T1{ , , ...}; cache the features of the most recent few periods to form a sliding window; for example, for 2 periods, T0{ , , ...}、T1{ , , ...}

[0053] The system predicts the speed switching for the next cycle and, based on the predicted speed switching, pre-calls a preset feedforward MAP to obtain the initial discharge duty cycle for the next cycle. Specifically, the next cycle may not send a new adjustment command, maintaining the current cycle's stable operating condition; or the user may resend a new speed adjustment command in the next cycle, creating a new operating condition. Correspondingly, prediction logic adaptation rules are set for different operating conditions. These include: a first prediction logic matching the first operating condition and a second prediction logic matching the second operating condition. The first operating condition is a stable operating condition, with no speed adjustment command in the next cycle. The first prediction logic includes: a data-weighted fitting prediction logic adapted to the first operating condition, which calculates the predicted speed switching value for the next cycle based on weighted calculations of data within a sliding window. For example, based on window data, the peak speed of the next cycle (equivalent to the initial speed during deceleration operation) is: The next cycle's lowest rotational speed (equivalent to the target rotational speed during deceleration): The speed change range in the next cycle: The deceleration slope in the next cycle: .

[0054] The second operating condition is a dynamic adjustment condition, where a new target speed command is received in the next cycle. The second prediction logic includes: a linear transition cycle prediction logic adapted to the second operating condition, which calculates and obtains the speed switching prediction value for the next cycle based on the data of the latest cycle within the sliding window and the target speed in the received new target speed command. Specifically, to avoid a large difference between the received new target speed command and the target speed command in the previous cycle's speed adjustment command, leading to a sudden change in speed switching, a linear transition cycle is designed as the next cycle, and then the switching of the received new target speed command continues. The calculation process for the speed switching prediction value of the linear transition cycle is as follows: based on the window data, the peak speed of the next cycle (equivalent to the initial speed in the deceleration operation): The next cycle's lowest rotational speed (equivalent to the target rotational speed during deceleration): The speed change range in the next cycle: .

[0055] Finally, the predicted speed switching value for the next cycle is calculated based on the actual operating conditions and the prediction logic, and the initial discharge duty cycle is obtained by calling the preset feedforward MAP diagram. Furthermore, the prediction error is calculated immediately after the actual speed reduction of the next cycle ends, such as: , This corresponds to the actual reduction value in the next cycle. Greater than If the percentage is 3%, then the prediction coefficient for the next cycle will be adjusted. Increase the weight of recent data; otherwise, keep the weight unchanged.

[0056] Furthermore, considering the influence of temperature drift during discharge in the bleeder circuit, to avoid the impact of temperature drift on discharge, the method further includes: establishing mapping tables for temperature changes and parameter changes (e.g., equivalent resistance) in the bleeder circuit; in the feedforward MAP generation step, during each pair of speed switching processes tested experimentally, determining the impact of temperature changes on the bleeder circuit parameters based on the mapping tables. The numerical change of the temperature affects the acquisition of the optimal value of D. The experimental test data is analyzed to calculate the error value of the optimal D value within different preset temperature ranges. This error is used as the temperature drift compensation value for the optimal D value, thereby completing the compensation for the optimal D value and updating the feedforward MAP. Specifically, a surface-mount temperature sensor installed on a key component of the bleeder circuit is used to acquire real-time temperature data and obtain temperature change values.

[0057] like Figure 4 As shown in the figure, this application discloses a back electromotive force discharge system for a DC brushless fan used in a ventilator, specifically including: The feedforward control module 101 is used to receive the speed adjustment command of the DC brushless fan of the ventilator and call the preset feedforward MAP to obtain the initial discharge duty cycle. The duty cycle adjustment module 102 is used to control the discharge circuit to discharge according to the acquired initial discharge duty cycle, and to determine whether the speed switching is completed. If the determination is completed, the discharge duty cycle is set to zero and the current control ends. If the determination is not completed, the bus voltage change rate detection circuit is used to collect the DC bus voltage change rate in real time, and the discharge duty cycle is dynamically adjusted based on the voltage change rate until the speed switching is completed. Among them, such as Figure 5As shown, the bus voltage change rate detection circuit includes: a voltage divider circuit, comprising a first resistor, a second resistor, and a first capacitor, used to divide the bus voltage; that is, the bus voltage divider circuit composed of resistor R1, resistor R2, and capacitor C1 reduces the bus voltage to a voltage signal that can be processed by the MCU after subsequent circuit processing, and its input-output relationship is as follows; a voltage follower, including a first operational amplifier U1 used to isolate the voltage divider circuit and the differentiating circuit, and to solve the influence of the impedance of R3 and C2 on the voltage divider circuit at low frequencies, and its input terminal is connected to the output terminal of the voltage divider circuit; a differentiating circuit, comprising a differentiating resistor, a differentiating capacitor, and a second operational amplifier, used to acquire the bus voltage change rate after voltage division, and its input terminal is connected to the output terminal of the voltage follower, specifically including resistor R3, capacitor C2, capacitor C3, resistor R4, and operational amplifier U2, and its input-output relationship is as follows. The voltage follower includes a first operational amplifier U1 for isolating the voltage divider and differentiating circuits, addressing the impact of the impedance introduced by R3 and C2 on the voltage divider circuit at low frequencies, and its input is connected to the output of the voltage divider circuit. The differentiating circuit includes a differentiating resistor, a differentiating capacitor, and a second operational amplifier, used to acquire the rate of change of the bus voltage after voltage division. Its input is connected to the output of the voltage follower. Specifically, it includes resistor R3, capacitor C2, capacitor C3, resistor R4, and operational amplifier U2, with the following input-output relationship: The adder circuit includes an adding resistor, a diode, and a third operational amplifier, with its input connected to the output of the differentiating circuit. Since the negative voltage generated by the differentiating circuit is generally unmanageable by MCUs, a standard adder circuit consisting of resistors R5, R6, R7, and R8, diode D1, and operational amplifier U3 is added after the differentiating circuit. =1.65+ ; The signal will be directly connected to the MCU for acquisition. The voltage divider circuit's first and second resistors are configured to reduce the bus voltage by a preset voltage division ratio. The differentiating circuit includes a correction capacitor connected in parallel with the differentiating resistor; the capacitance ratio of the correction capacitor to the differentiating capacitor meets a preset frequency response requirement. In the adder circuit, the diode's anode is connected to the output of the third operational amplifier, and its cathode is connected to a voltage clamping node.

[0058] When a typical 24V DC brushless fan operates under the aforementioned ventilator conditions, the back electromotive force can boost the bus voltage by approximately 20V within 100ms as the fan speed decreases from high to low, surging about 40 times per minute, resulting in a fundamental frequency of 0.67Hz. Now, assume the resistance of R1 is 15KΩ. The resistance of R2 is 1K. That is, the partial pressure ratio is 1 / 16, and at the same time, it is desirable The maximum is 1V. Based on the above conditions, we can conclude... =(20 / 0.1) / 16=12.5V / s, from ; =-1V, therefore C2*R4=0.08. To make the differentiating circuit behave like a differentiator, the pole frequency must be... A fundamental frequency much higher than 0.67Hz, but not too high to avoid noise; here you can choose... For a frequency of 100Hz, R3*C2 = 0.00159. To simplify the design, R3*C2 is usually set to R4*C3. Based on experience, C2 = 220nF. From C2*R4 = 0.08, R3*C2 = 0.00159, and R3*C2 = R4*C3, we can calculate R3 = 7.23K. Take the standard value of 7.5K R4=363.6K Take the standard value 360K C3 = 4.42nF, take the standard value of 4.7nF. After passing through the subsequent standard adder circuit, the final expression formula of this circuit is: =1.65-0.08* When the bus voltage remains constant, =1.65-0.08* =1.65V; when the bus voltage rises at the maximum slope, that is, the bus voltage increases by 20V within 100ms, =1.65-0.08*12.5=0.65V; When the bus voltage drops, vo>1.65V. Diode D1 is used to protect the MCU and clamp vo to a maximum of about 3.3V.

[0059] In one specific embodiment, the system further includes: The duty cycle adjustment optimization module 103 is used to control the voltage monitoring device installed in the ventilator to collect the voltage of the DC bus in real time if the judgment is not completed; to select a method based on voltage change rate and voltage dynamic coordinated adjustment of the discharge duty cycle instead of the original method based on the voltage change rate; the dynamic coordinated adjustment steps include: when the voltage is greater than a preset overvoltage threshold, increasing the discharge duty cycle; when the voltage is less than a preset over-discharge threshold, decreasing the discharge duty cycle; when the voltage is between the preset overvoltage threshold and the preset over-discharge threshold, continuing to judge; when the voltage change rate is lower than a first preset threshold, increasing the discharge duty cycle; when the voltage change rate is higher than a second preset threshold, decreasing the discharge duty cycle; when the voltage change rate is between the first preset threshold and the second preset threshold, maintaining the current discharge duty cycle.

[0060] The duty cycle adjustment and optimization module 103 is also used to statistically determine whether the speed switching is completed before the speed switching is completed. If it is determined that the speed switching is not completed, the cumulative number of times the discharge duty cycle is dynamically adjusted based on the voltage change rate. Each time the cumulative number is updated, the threshold range of the cumulative number after the update is determined, and a correction gain that is compatible with the threshold range of the cumulative number is matched. The larger the threshold range of the cumulative number, the larger the value of the corresponding correction gain. The adjusted discharge duty cycle is corrected by using the matched correction gain.

[0061] In one specific embodiment, the system further includes: The feedforward control optimization module 104 is also used to, upon receiving a speed adjustment command from the ventilator's brushless DC fan, parse and obtain global parameters of the cycle including the total cycle duration, phase percentage parameters including inspiratory time, expiratory time, and breath-holding time, and speed amplitude parameters including initial speed and target speed; obtain feature data of the current cycle, including: cycle synchronization with the start of the inspiratory phase as the cycle start point, synchronously recording the peak inspiratory speed, the trough speed of the current cycle's expiration, and the current cycle's deceleration slope; cache the features of several recent cycles to form a sliding window; predict the speed switching of the next cycle, and pre-call a preset feedforward MAP map based on the predicted speed switching to obtain the initial discharge duty cycle of the next cycle; wherein, setting prediction logic adaptation rules under different operating conditions, including: the first prediction matching the first operating condition. The logic includes a second prediction logic that matches the second operating condition; the first operating condition is a stable operating condition, and there is no speed adjustment command in the next cycle; the first prediction logic includes: a data weighted fitting prediction logic adapted to the first operating condition, which calculates the speed switching prediction value for the next cycle based on the data weighted within the sliding window; the second operating condition is a dynamic adjustment operating condition, and a new target speed command is received in the next cycle; the second prediction logic includes: a linear transition cycle prediction logic adapted to the second operating condition, which calculates the speed switching prediction value for the transition cycle as the speed switching prediction value for the next cycle based on the data of the latest cycle within the sliding window and the target speed in the received new target speed command; the prediction logic is adapted to the actual operating condition to calculate the speed switching prediction value for the next cycle, and a preset feedforward MAP is called to obtain the initial discharge duty cycle.

[0062] This application also discloses a computer-readable storage medium.

[0063] Specifically, the computer-readable storage medium stores a computer program that can be loaded by a processor and executed, such as the back EMF discharge method of the DC brushless fan for the ventilator described above. The computer-readable storage medium includes, for example, various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0064] This application also discloses a computer device.

[0065] Specifically, the computer device includes a memory and a processor, and the memory stores a computer program that can be loaded by the processor and executed to perform the back electromotive force discharge method of the DC brushless fan for the ventilator described above.

[0066] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features.

Claims

1. A method for discharging the back electromotive force of a DC brushless fan in a ventilator, characterized in that, include: Receive the speed adjustment command of the DC brushless fan of the ventilator and call the preset feedforward MAP to obtain the initial discharge duty cycle; The preset feedforward MAP generation steps include: setting the brushless DC fan to perform speed switching operations between a series of different initial speeds and target speeds; in each speed switching operation, testing is performed with different fixed discharge duty cycles and the corresponding bus voltage peak values ​​are recorded; for each pair of initial speeds and target speeds, the value that satisfies the bus voltage peak limit and has the smallest discharge duty cycle is selected as the feedforward discharge control parameter under the corresponding operating condition; all input indices and corresponding output parameters are stored as a feedforward MAP. Based on the acquired initial discharge duty cycle, the discharge circuit is controlled to discharge, and it is determined whether the speed switching is complete. If the determination is complete, the discharge duty cycle is set to zero, and the current control ends. If the determination is incomplete, the DC bus voltage change rate detection circuit is used to collect the DC bus voltage change rate in real time, and the discharge duty cycle is dynamically adjusted based on the voltage change rate until the speed switching is complete. The dynamic adjustment steps include: increasing the discharge duty cycle when the voltage change rate is lower than a first preset threshold; decreasing the discharge duty cycle when the voltage change rate is higher than a second preset threshold; and maintaining the current discharge duty cycle when the voltage change rate is between the first and second preset thresholds. The discharge circuit and the bus voltage change rate detection circuit are both installed inside the ventilator and connected to the DC brushless fan inside the ventilator.

2. The method for discharging the back electromotive force of a brushless DC fan for a ventilator according to claim 1, characterized in that, The preset feedforward MAP generation step also includes: During the process of setting up a DC brushless fan to perform speed switching operations between a series of initial speeds and target speeds, the speed change amplitude between each pair of initial speeds and target speeds in the series is calculated, and according to the preset speed change amplitude partitioning threshold, the speed change amplitude between each initial speed and target speed is divided into one of the amplitude intervals of low amplitude interval, medium amplitude interval and high amplitude interval. After performing the process of selecting the value that satisfies the peak bus voltage limit and has the smallest discharge duty cycle as the feedforward discharge control parameter for each pair of initial and target speeds under the corresponding operating conditions, for each pair of initial and target speeds belonging to different amplitude ranges, different multinomial fitting methods or pre-built neural network models with different structural parameters are used to obtain the optimal discharge duty cycle corresponding to different speed change amplitudes within the range; and the number of terms or the complexity of the model structure parameters of the multinomial fitting method gradually increases in the order of low amplitude range, medium amplitude range and high amplitude range, so as to obtain the feedforward discharge control parameters under different operating conditions.

3. The method for discharging the back electromotive force of a brushless DC fan for a ventilator according to claim 1, characterized in that, Also includes: If the determination is not completed, the voltage monitoring device installed in the ventilator is controlled to collect the voltage of the DC bus in real time; the original method of dynamically adjusting the discharge duty cycle based on the voltage change rate is replaced by a method based on the voltage change rate and voltage dynamic coordinated adjustment. The dynamic collaborative adjustment steps include: When the voltage is greater than the preset overvoltage threshold, increase the discharge duty cycle; when the voltage is less than the preset over-discharge threshold, decrease the discharge duty cycle; when the voltage is between the preset overvoltage threshold and the preset over-discharge threshold, continue to judge; when the voltage change rate is lower than the first preset threshold, increase the discharge duty cycle; when the voltage change rate is higher than the second preset threshold, decrease the discharge duty cycle; when the voltage change rate is between the first preset threshold and the second preset threshold, maintain the current discharge duty cycle.

4. The method for discharging the back electromotive force of a brushless DC fan for a ventilator according to claim 3, characterized in that, The dynamic collaborative adjustment step also includes: When the voltage is greater than the preset overvoltage threshold or less than the preset over-discharge threshold, the absolute value of the voltage error is calculated, and the current calculated voltage error is classified according to the preset voltage error absolute value classification standard. According to the classification level of the current voltage error absolute value, the first adjustment ratio coefficient is adaptively matched to increase the discharge duty cycle or the second adjustment ratio coefficient is matched to decrease the discharge duty cycle. The higher the voltage error absolute value level, the larger the first adjustment ratio coefficient and the second adjustment ratio coefficient are. When the voltage change rate is lower than the first preset threshold or higher than the second preset threshold, the absolute value of the voltage change rate error is calculated, and the current calculated voltage change rate error is classified according to the preset voltage change rate error absolute value classification standard. According to the classification level of the current voltage change rate error absolute value, the third adjustment ratio coefficient is adaptively matched to increase the discharge duty cycle or the fourth adjustment ratio coefficient is matched to decrease the discharge duty cycle. The higher the voltage error absolute value level, the larger the third and fourth adjustment ratio coefficients are.

5. The method for discharging the back electromotive force of a brushless DC fan for a ventilator according to claim 3, characterized in that, Also includes: Before the speed switching is completed, it is determined whether the speed switching is completed. If it is not completed, the cumulative number of times the discharge duty cycle is dynamically adjusted based on the voltage change rate is determined. Each time the cumulative number is updated, the threshold range of the cumulative number after the update is determined, and a correction gain that matches the threshold range of the cumulative number is matched. The larger the threshold range of the cumulative number is, the larger the value of the corresponding correction gain is. The adjusted discharge duty cycle is corrected by using the matched correction gain.

6. The method for discharging the back electromotive force of a brushless DC fan for a ventilator according to claim 1, characterized in that... Also includes: Upon receiving the speed adjustment command from the DC brushless fan of the ventilator, the system parses and obtains the global parameters of the cycle, including the total cycle duration, the phase percentage parameters including the inspiratory time, expiratory time and breath-holding time, and the speed amplitude parameters including the initial speed and the target speed. Acquire feature data for the current cycle, including: synchronizing the cycle with the start of the inhalation phase as the cycle start point, synchronously recording the peak inhalation speed, the trough inhalation speed of the current cycle, and the deceleration slope of the current cycle; cache features from the most recent few cycles to form a sliding window; The system predicts the speed switching for the next cycle and, based on the predicted speed switching, pre-calls a preset feedforward MAP to obtain the initial discharge duty cycle for the next cycle. It sets prediction logic adaptation rules for different operating conditions, including: a first prediction logic matching the first operating condition and a second prediction logic matching the second operating condition. The first operating condition is a stable operating condition, with no speed adjustment command in the next cycle. The first prediction logic includes: a data weighted fitting prediction logic adapted to the first operating condition, which calculates the predicted speed switching value for the next cycle based on the weighted calculation of data within a sliding window. The second operating condition is a dynamic adjustment operating condition, where a new target speed command is received in the next cycle. The second prediction logic includes: a linear transition cycle prediction logic adapted to the second operating condition, which calculates the predicted speed switching value for the transition cycle based on the latest cycle data within the sliding window and the target speed in the received new target speed command, and uses this as the predicted speed switching value for the next cycle. The predicted value of the next cycle speed switching is obtained by adapting the prediction logic to the actual working conditions, and the initial discharge duty cycle is obtained by calling the preset feedforward MAP diagram.

7. A back electromotive force discharge system for a DC brushless fan used in a ventilator, characterized in that, include: The feedforward control module is used to receive the speed adjustment command of the DC brushless fan of the ventilator and call the preset feedforward MAP to obtain the initial discharge duty cycle; The duty cycle adjustment module is used to control the discharge circuit to discharge according to the acquired initial discharge duty cycle and to determine whether the speed switching is complete. If the determination is complete, the discharge duty cycle is set to zero and the current control ends. If the determination is not complete, the bus voltage change rate detection circuit is used to collect the DC bus voltage change rate in real time and dynamically adjust the discharge duty cycle based on the voltage change rate until the speed switching is complete. The bus voltage change rate detection circuit includes: a voltage divider circuit, comprising a first resistor, a second resistor, and a first capacitor, for dividing the bus voltage; a voltage follower, with its input connected to the output of the voltage divider circuit, including a first operational amplifier for isolating the voltage divider circuit and the differentiating circuit; a differentiating circuit, with its input connected to the output of the voltage follower, including a differentiating resistor, a differentiating capacitor, and a second operational amplifier, for acquiring the bus voltage change rate after voltage division; and an adder circuit, with its input connected to the output of the differentiating circuit, including an adding resistor, a diode, and a third operational amplifier.

8. The back electromotive force discharge system for a DC brushless fan for a ventilator according to claim 7, characterized in that, The resistance ratio of the first resistor to the second resistor in the voltage divider circuit is configured to reduce the bus voltage according to a preset voltage division ratio.

9. The back electromotive force discharge system for a brushless DC fan for a ventilator according to claim 7, characterized in that, The differentiating circuit includes a correction capacitor connected in parallel with the differentiating resistor, and the capacitance ratio of the correction capacitor to the differentiating capacitor meets a preset frequency response requirement.

10. The back electromotive force discharge system for a DC brushless fan for a ventilator according to claim 7, characterized in that, The diode in the adder circuit has its anode connected to the output of the third operational amplifier and its cathode connected to the voltage clamping node.

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