A Sensorless Automotive Air Conditioning Module Motor FOC Control Method

Abstract

This invention relates to a sensorless FOC control method for an automotive air conditioning module motor, belonging to the field of automotive electronics technology. The method includes: injecting dual-frequency voltage pulses into the stator in stages to position the rotor; collecting and filtering current through sampling resistors to construct a rotor flux linkage distribution model, combined with noise reduction using a miniature acoustic sensor and preset orthogonal axis current based on air conditioning fan speed settings; using an extended Kalman filter observer to inversely calculate the load torque and monitor the torque change rate to trigger instantaneous load impact protection; correcting the voltage space vector amplitude through voltage feedforward compensation, adding a resistor-capacitor series filter circuit and employing phase-shifted pulse width modulation for anti-interference; establishing a three-dimensional optimization method for motor efficiency, speed, and load; initiating dynamic field weakening control and estimating winding temperature through stator resistance to adjust the field weakening depth. This achieves precise starting of the sensorless motor, dynamic load adaptation, avoids starting synchronization issues and excessive noise, and ensures stable airflow from the automotive air conditioning system and long-term reliable motor operation.

Description

Technical Field

[0001] This invention belongs to the field of automotive electronics technology, specifically relating to a method for FOC control of an automotive air conditioning module motor based on a Hall sensor-free sensor. Background Technology

[0002] As a core driving component for vehicle thermal management and cabin comfort, the motor in the automotive air conditioning module directly determines the stability of airflow, noise level, and long-term operational reliability. Currently, the industry mostly adopts a permanent magnet synchronous motor (FOC) control scheme without Hall effect sensors to simplify the structure and reduce costs. However, existing technologies have significant shortcomings: during the startup phase, the reliance on a single-frequency pulse for positioning makes it prone to positioning deviations due to differences in stator winding inductance, leading to motor step loss or reverse rotation; when faced with load fluctuations such as air conditioning damper switching and sudden changes in duct resistance, the proportional-integral parameters of the field-oriented controller have poor adaptability, resulting in lag and sudden changes in airflow; the automotive power supply voltage fluctuates significantly with idling and acceleration conditions, and the electromagnetic interference from the ignition system, vehicle radar, and other equipment in the cabin electronic environment is strong. Existing controls lack targeted voltage compensation and anti-interference design, resulting in unstable torque output; at the same time, the synergy between startup noise suppression, high-temperature motor protection, and energy efficiency optimization is insufficient, either resulting in excessive noise affecting the cabin experience or accelerated aging of winding insulation at high temperatures, making it difficult to meet the comprehensive requirements of automotive electronics for high reliability, low interference, and a superior user experience. Summary of the Invention

[0003] To address the aforementioned problems in the existing technology, this invention provides a sensorless FOC control method for automotive air conditioning module motors.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] S1: Inject voltage pulses into the stator in stages, perform preliminary positioning based on the frequency pulses, and correct positioning deviations; obtain the current of each phase with the help of sampling resistors, filter the signal through a filtering circuit, and use the processed current signal to construct the rotor flux distribution mechanism; monitor the start-up noise in real time with a miniature acoustic sensor; and preset the right-angle shaft current of the start-up stage according to the load level corresponding to each speed setting, based on the car air conditioning fan speed setting.

[0006] S2: An extended Kalman filter observer is used to collect motor operating parameters in real time. The current load torque is inferred by the internal filter gain iterative update algorithm of the observer. The proportional-integral parameters of the field-oriented controller are dynamically adjusted according to the load torque. After a momentary load impact occurs, the torque change rate is continuously monitored for multiple sampling cycles. If the impact judgment condition is met, a transient protection strategy is triggered. The current peak value is limited by the current sampling circuit, and the controller outputs a negative compensation signal and adjusts the direct-axis current.

[0007] S3: Through voltage feedforward compensation, the voltage space vector amplitude is corrected in real time to cope with power supply voltage changes; the proportion of zero vector action time is adjusted according to the voltage state to balance switching losses and voltage utilization; at the same time, a resistor-capacitor series filter circuit is added to the pulse width modulation trigger terminal, and the staggered pulse width modulation output is adopted according to the rule of maintaining a fixed phase difference between adjacent output channels.

[0008] S4: Focusing on motor energy efficiency and high temperature protection, the optimal direct-axis current curve under different operating conditions is calibrated by establishing a three-dimensional optimization method of motor efficiency-speed-load; dynamic field weakening control is started after the motor speed exceeds the base speed, and the direct-axis current is adjusted according to the speed deviation; at the same time, the winding temperature is estimated by the stator resistance, and the field weakening depth is reduced if the temperature is too high.

[0009] As a preferred embodiment of the present invention, the phased injected voltage pulses are dual-frequency high-frequency voltage pulses. In the first phase, a higher frequency pulse (adapted to the distributed inductance characteristics of the motor stator winding) is injected first. By detecting the difference in the harmonic amplitude of each phase current, the angular range of the rotor magnetic pole is locked, and the initial positioning is completed. In the second phase, a lower frequency pulse is injected. After each injection, the difference in the peak current of the two phases is compared, and the positioning deviation is corrected by the trend of the difference until the rotor position error is within the allowable range. At the same time, the filtering circuit is composed of an instrumentation amplifier and a second-order low-pass filter connected in series. The current signal collected by the sampling resistor is first differentially amplified by the instrumentation amplifier, and then filtered out by the second-order low-pass filter to remove high-frequency noise. Finally, the processed digital signal is input to the controller to construct the rotor flux distribution model. The miniature acoustic sensor is installed on the motor housing near the air duct side to collect noise signals in real time and convert them into electrical signals. If the noise exceeds the preset threshold, the controller adjusts the pulse amplitude and frequency.

[0010] Specifically, the frequency adaptation of the dual-frequency voltage pulse is used to determine the rotor position by injecting pulse signals in stages under the condition of no Hall sensor. The specific process is as follows: the frequency pulse is determined based on the distributed inductance characteristics of the motor stator winding. After injection, the angle range of the rotor magnetic pole is locked by detecting the harmonic amplitude difference of each phase current. After each injection, the peak difference of the two phase currents is compared, and the rotor position error is determined by the trend of the difference change. Finally, the pulse injection is stopped.

[0011] Specifically, the filtering process of the sampling resistor is used to extract the effective current signal. The specific process is as follows: the current signal collected by the sampling resistor is differentially amplified by an instrumentation amplifier, and the amplification factor is set according to the motor rated current and the controller signal acquisition range; the high-frequency noise generated by pulse injection is filtered out by a second-order low-pass filter composed of an operational amplifier, and the filter cutoff frequency is set according to the pulse frequency characteristics; finally, the analog signal is converted into a digital signal for real-time calculation of rotor flux distribution.

[0012] Specifically, the noise adjustment of the miniature acoustic sensor is used to capture mechanical noise generated during the motor startup phase due to rotor positioning deviation and pulse parameter mismatch in real time. The specific process is as follows: the noise electrical signal output by the sensor is filtered by a bandpass filter to extract the effective noise components, and the center frequency of the filter covers the frequency band of motor mechanical noise; the controller compares it with the preset gear noise threshold; after each adjustment, the noise spectrum is analyzed by spectrum analysis and the main noise peaks are brought down to below the threshold.

[0013] Specifically, the matching of the fan speed setting and the right-angle shaft current is used to convert the fan speed command from the air conditioner control panel into the corresponding motor output torque requirement. The specific process is as follows: the controller pre-stores the load torque range corresponding to each fan speed setting; at startup, it reads the setting signal from the air conditioner control panel and queries the pre-stored initial value of the right-angle shaft current according to the setting; the deviation between the actual current and the preset value is monitored in real time through the current loop, and when the deviation exceeds the preset range, the preset value is adjusted proportionally to match the actual output torque with the setting requirement.

[0014] Specifically, the iterative update of the extended Kalman filter observer is used to improve the accuracy of torque estimation. The specific process is as follows: when the observer is initialized, the state variables are set, including rotor position, speed and load torque, and the covariance matrix is ​​set according to the error range of motor parameters; after data is collected in each cycle, the current state is predicted by the state equation, and the residual is calculated by the measurement equation; the filter gain is dynamically adjusted according to the residual; and the estimated value of load torque is limited in range during the iteration process.

[0015] Specifically, the instrumentation amplifier is selected as a high common-mode rejection ratio model, and the amplification factor is calculated based on the rated current of the motor and the sampling range of the controller AD, ensuring that the current signal is within the sampling range after amplification and does not overflow; the cutoff frequency of the second-order low-pass filter is set to 1 / 3-1 / 5 of the pulse injection frequency to avoid the pulse frequency component from being mixed into the filtered current signal, ensuring the accuracy of the rotor flux distribution calculation.

[0016] Specifically, the extended Kalman filter observer collects motor operating parameters including stator three-phase voltage, three-phase current, and estimated speed. During observer initialization, the state variables are set as rotor position, speed, and load torque, and the covariance matrix is ​​set according to the motor parameter error range (such as stator resistance and inductance error). After collecting data in each cycle, the current state is first predicted through the state equation, and then the residual is calculated using the measurement equation. The filter gain is dynamically adjusted according to the residual (increase the gain when the residual is large and decrease the gain when the residual is small), and finally the load torque is inferred. When dynamically self-tuning the proportional-integral parameters, the ratio of load torque to rated torque is calculated in real time. The initial adjustment direction is determined according to the trend of the ratio change. The parameters are changed according to the preset step size. After adjustment, the motor speed fluctuation is monitored. If the fluctuation does not reach the stable range, the adjustment step size is adjusted and modified until the speed is stable.

[0017] Specifically, the dynamic self-tuning of the proportional-integral parameters is used to adapt to load changes. The specific process is as follows: the ratio of the load torque to the rated torque is used as the basis for parameter adjustment, and the ratio of the load torque to the rated torque is calculated in real time; the initial direction of parameter adjustment is determined according to the trend of the ratio; the proportional and integral parameters are changed according to a preset step size; the fluctuation of the motor speed is monitored after adjustment; if the fluctuation does not reach the stable range, the step size is adjusted according to the direction of the fluctuation, and the parameters are modified again; the adjustment and monitoring steps are repeated until the speed fluctuation is within the stable range.

[0018] Specifically, the determination of instantaneous load impact is used to identify sudden overloads caused by abnormal problems. The specific process is as follows: set a torque change rate threshold, which is determined based on the maximum bearing capacity of the air conditioning damper mechanical structure; continuously monitor the torque value of multiple control cycles and calculate the torque change rate of adjacent cycles; if multiple consecutive change rates exceed the preset threshold and the current torque value exceeds a reasonable multiple of the rated torque, it is determined to be an effective impact; when the protection is triggered, the current peak value is limited by a hardware comparator, and at the same time, the controller outputs a negative compensation signal to linearly adjust the direct axis current to the weak magnetic range within multiple cycles.

[0019] Specifically, the voltage feedforward compensation amplitude correction is used to handle the impact of fluctuations in the automotive power supply voltage caused by changes in operating conditions on the inverter output. The specific process is as follows: real-time acquisition of the power supply voltage; comparing the acquired instantaneous voltage value with a pre-stored reference voltage cycle by cycle to calculate the deviation value between the two; determining the direction and rate of change of the deviation value through the controller, and activating a fixed compensation coefficient or a dynamic compensation coefficient; activating the dynamic compensation coefficient, acquiring the current motor speed, and adjusting the compensation coefficient according to the correspondence between the current motor speed and the rated speed; calculating the voltage compensation amount based on the deviation value and the adjusted compensation coefficient; and superimposing the calculated compensation amount onto the voltage reference value of the space vector pulse width modulation.

[0020] Specifically, the resistor-capacitor series filter circuit is configured to handle high-frequency electromagnetic interference generated in the automotive electronic system. The specific process is as follows: the output impedance of the pulse width modulation signal is detected by an impedance measuring instrument, and the resistance value is determined according to the impedance to match the output impedance; the interference frequency in the automotive electronic system is detected by a spectrum analyzer, and the capacitance value is calculated according to the interference frequency to adapt the filtering time constant of the resistor-capacitor circuit to the interference frequency; one end of the resistor is soldered to the signal output pin of the pulse width modulation driver chip, and the other end of the resistor is soldered to one end of the capacitor; the other end of the capacitor is soldered to the circuit ground terminal; a wire is led out from the connection node of the resistor and capacitor and soldered to the control pin of the power device; the resistor-capacitor circuit is fixed in the circuit board area near the power device, the lead length from the connection node to the power device is shortened, and the circuit is isolated from other components with an insulating bracket.

[0021] Specifically, the phase difference setting of the staggered pulse width modulation is used to disperse the switching action time of the three-phase power devices. The specific process is as follows: For a three-phase motor, the three pulse width modulation output channels are set with a fixed phase difference in the order of phase A leading phase B and phase B leading phase C. The phase difference angle is evenly distributed according to the number of phases. When the controller generates the pulse width modulation waveform, the phase offset of each channel is realized through the synchronous triggering function of the timer. When the switching frequency changes, the time interval of the phase difference is automatically adjusted.

[0022] Specifically, the estimation of the winding temperature is used to monitor the heating state of the motor windings caused by the current flow in real time. The specific process is as follows: the controller collects the stator phase voltage and phase current in real time, and obtains the direct-axis voltage and current through coordinate transformation; according to the motor resistance temperature characteristics, the current stator resistance is calculated using the resistance calculation formula, ignoring the influence of back electromotive force during the calculation; the resistance value is substituted into the pre-stored resistance-temperature calibration curve, which is obtained by experimental measurement at different temperatures; if the temperature exceeds the critical value, the negative amplitude of the direct-axis current is reduced according to the proportion of temperature overshoot; if the temperature falls back to below the safe range, the original field weakening depth is restored.

[0023] Specifically, the three-dimensional optimization method is constructed by collecting experimental data. Different speeds and load conditions are set on the motor test platform (covering the conditions corresponding to the 1-5 levels of automotive air conditioning fan speed). The motor efficiency under each condition is measured, and the direct-axis current value at the highest efficiency is recorded. A continuous efficiency-speed-load-direct-axis current model is generated using a surface fitting algorithm, and the optimal direct-axis current curve is extracted from it. The stator resistance estimation is achieved through Parker transformation. After the controller collects the stator phase voltage and phase current, the direct-axis voltage and current are obtained through Parker transformation. Ignoring the influence of back electromotive force, the current stator resistance is calculated according to Ohm's law. The resistance value is substituted into the pre-stored resistance-temperature calibration curve (this curve is obtained by measuring the motor resistance at different temperatures) to obtain the winding temperature. If the temperature exceeds the critical value, the negative amplitude of the direct-axis current is reduced according to the overshoot ratio.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) By setting up a dual-frequency high-frequency voltage pulse injected in stages, a miniature acoustic sensor on the motor housing near the air duct side, and a direct-axis current preset mechanism corresponding to the air conditioning fan speed, it can accurately lock the initial position of the rotor through the dual-frequency pulse, avoid the loss of steps or reverse rotation when the motor without Hall sensor starts, and monitor and dynamically adjust the starting noise in real time, so that the noise level meets the quiet requirements of the car cabin, while allowing the starting torque to quickly adapt to the load of different fan speed levels, preventing the sudden change of air volume when the fan speed is switched;

[0026] (2) By setting up an extended Kalman filter observer, a proportional-integral parameter dynamic self-tuning module for the field-oriented controller, a voltage feedforward compensation unit, a resistor-capacitor series filter circuit for the pulse width modulation trigger terminal, and a stator resistance temperature estimation mechanism, the load torque can be accurately back-calculated and the control parameters can be dynamically adapted to cope with instantaneous load impacts such as air conditioning damper switching. At the same time, it can offset the influence of automotive power supply fluctuations, filter out electromagnetic interference to avoid power device malfunctions, monitor winding temperature in real time and adjust the field weakening depth to prevent high temperature from accelerating insulation aging, and improve the stability and service life of the motor. Attached Figure Description

[0027] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 This is a data flow diagram of an automotive air conditioning module motor FOC control method based on a Hall sensor-free sensor, according to the present invention.

[0029] Figure 2 This is an architecture diagram of an automotive air conditioning module motor FOC control method based on a Hall sensor-free system, as described in this invention. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0031] Please see Figure 1-2 A sensorless FOC control method for automotive air conditioning module motors

[0032] S1: Inject voltage pulses into the stator in stages, perform preliminary positioning based on the frequency pulses, and correct positioning deviations; obtain the current of each phase with the help of sampling resistors, filter the signal through a filtering circuit, and use the processed current signal to construct the rotor flux distribution mechanism; monitor the start-up noise in real time with a miniature acoustic sensor; and preset the right-angle shaft current of the start-up stage according to the load level corresponding to each speed setting, based on the car air conditioning fan speed setting.

[0033] S2: An extended Kalman filter observer is used to collect motor operating parameters in real time. The current load torque is inferred by the internal filter gain iterative update algorithm of the observer. The proportional-integral parameters of the field-oriented controller are dynamically self-tuned according to the load torque. After a momentary load impact occurs, the torque change rate is continuously monitored for multiple sampling cycles. If the impact judgment condition is met, a transient protection strategy is triggered. The current peak value is limited by the current sampling circuit. At the same time, the controller outputs a negative compensation signal and adjusts the direct shaft current.

[0034] S3: Through voltage feedforward compensation, the voltage space vector amplitude is corrected in real time to cope with power supply voltage changes; the proportion of zero vector action time is adjusted according to the voltage state to balance switching losses and voltage utilization; at the same time, a resistor-capacitor series filter circuit is added to the pulse width modulation trigger terminal, and the staggered pulse width modulation output is adopted according to the rule of maintaining a fixed phase difference between adjacent output channels.

[0035] S4: Focusing on motor energy efficiency and high temperature protection, the optimal direct-axis current curve under different operating conditions is calibrated by establishing a three-dimensional optimization method of motor efficiency-speed-load; dynamic field weakening control is started after the motor speed exceeds the base speed, and the direct-axis current is adjusted according to the speed deviation; at the same time, the winding temperature is estimated by the stator resistance, and the field weakening depth is reduced if the temperature is too high.

[0036] Specifically, the phased voltage pulses are dual-frequency high-frequency voltage pulses. In the first phase, a higher frequency pulse (adapted to the distributed inductance characteristics of the motor stator winding) is injected. By detecting the difference in harmonic amplitude of each phase current, the angular range of the rotor magnetic poles is locked, completing the initial positioning. In the second phase, a lower frequency pulse is injected. After each injection, the difference in the peak current of the two phases is compared, and the positioning deviation is corrected by the trend of the difference until the rotor position error is within the allowable range. At the same time, the filtering circuit is composed of an instrumentation amplifier and a second-order low-pass filter connected in series. The current signal collected by the sampling resistor is first differentially amplified by the instrumentation amplifier, and then filtered out by the second-order low-pass filter to remove high-frequency noise. Finally, the processed digital signal is input to the controller to construct the rotor flux distribution model. The miniature acoustic sensor is installed on the motor housing near the air duct side to collect noise signals in real time and convert them into electrical signals. If the noise exceeds the preset threshold, the controller adjusts the pulse amplitude and frequency.

[0037] Specifically, the frequency adaptation of the dual-frequency voltage pulse is used to determine the rotor position by injecting pulse signals in stages under the condition of no Hall sensor. The specific process is as follows: the frequency pulse is determined based on the distributed inductance characteristics of the motor stator winding. After injection, the angle range of the rotor magnetic pole is locked by detecting the harmonic amplitude difference of each phase current. After each injection, the peak difference of the two phase currents is compared, and the rotor position error is determined by the trend of the difference change. Finally, the pulse injection is stopped.

[0038] Specifically, the filtering process of the sampling resistor is used to extract the effective current signal. The specific process is as follows: the current signal collected by the sampling resistor is differentially amplified by an instrumentation amplifier, and the amplification factor is set according to the motor rated current and the controller signal acquisition range; the high-frequency noise generated by pulse injection is filtered out by a second-order low-pass filter composed of an operational amplifier, and the filter cutoff frequency is set according to the pulse frequency characteristics; finally, the analog signal is converted into a digital signal for real-time calculation of rotor flux distribution.

[0039] Specifically, the noise adjustment of the miniature acoustic sensor is used to capture mechanical noise generated during the motor startup phase due to rotor positioning deviation and pulse parameter mismatch in real time. The specific process is as follows: the noise electrical signal output by the sensor is filtered by a bandpass filter to extract the effective noise components, and the center frequency of the filter covers the frequency band of motor mechanical noise; the controller compares it with the preset gear noise threshold; after each adjustment, the noise spectrum is analyzed by spectrum analysis and the main noise peaks are brought down to below the threshold.

[0040] Specifically, the matching of the fan speed setting and the right-angle shaft current is used to convert the fan speed command from the air conditioner control panel into the corresponding motor output torque requirement. The specific process is as follows: the controller pre-stores the load torque range corresponding to each fan speed setting; at startup, it reads the setting signal from the air conditioner control panel and queries the pre-stored initial value of the right-angle shaft current according to the setting; the deviation between the actual current and the preset value is monitored in real time through the current loop, and when the deviation exceeds the preset range, the preset value is adjusted proportionally to match the actual output torque with the setting requirement.

[0041] Specifically, the iterative update of the extended Kalman filter observer is used to improve the accuracy of torque estimation. The specific process is as follows: when the observer is initialized, the state variables are set, including rotor position, speed and load torque, and the covariance matrix is ​​set according to the error range of motor parameters; after data is collected in each cycle, the current state is predicted by the state equation, and the residual is calculated by the measurement equation; the filter gain is dynamically adjusted according to the residual; and the estimated value of load torque is limited in range during the iteration process.

[0042] Specifically, the instrumentation amplifier is selected as a high common-mode rejection ratio model, and the amplification factor is calculated based on the rated current of the motor and the sampling range of the controller AD, ensuring that the current signal is within the sampling range after amplification and does not overflow; the cutoff frequency of the second-order low-pass filter is set to 20%-30% of the pulse injection frequency to avoid the pulse frequency component from mixing into the filtered current signal and to ensure the accuracy of the rotor flux distribution calculation.

[0043] Specifically, the formula for calculating the amplification factor of the instrumentation amplifier is as follows:

[0044] ,

[0045] in, The controller's AD sampler samples the maximum voltage. This is the rated current of the motor. This is the resistance value of the sampling resistor.

[0046] In this embodiment, =3.3V: The standard range of the AD sampling interface of automotive-grade microcontrollers (such as the STM32F4 series) is 0-3.3V. This value is an inherent parameter of the controller hardware circuit to ensure that the signal does not exceed the sampling range. =8A: Referring to the 60W permanent magnet synchronous motor commonly used in automotive air conditioning modules, 8A can meet the maximum load requirement of 5 fan speeds; =0.001Ω: To balance current acquisition accuracy and power consumption, the voltage drop of the 0.01Ω precision resistor at 8A is 0.08V (U=IR), which avoids excessive power consumption due to excessive resistance and provides amplifiable weak signal; according to the formula, K=41.25 (actually 40 is taken to leave a margin), ensuring full-scale utilization of AD sampling and improving current detection resolution.

[0047] Specifically, the extended Kalman filter observer collects motor operating parameters including stator three-phase voltage, three-phase current, and estimated speed. During observer initialization, the state variables are set as rotor position, speed, and load torque, and the covariance matrix is ​​set according to the motor parameter error range (such as stator resistance and inductance error). After collecting data in each cycle, the current state is first predicted through the state equation, and then the residual is calculated using the measurement equation. The filter gain is dynamically adjusted according to the residual (increase the gain when the residual is large and decrease the gain when the residual is small), and finally the load torque is inferred. When dynamically self-tuning the proportional-integral parameters, the ratio of load torque to rated torque is calculated in real time. The initial adjustment direction is determined according to the trend of the ratio change. The parameters are changed according to the preset step size. After adjustment, the motor speed fluctuation is monitored. If the fluctuation does not reach the stable range, the adjustment step size is adjusted and modified until the speed is stable.

[0048] Specifically, the dynamic self-tuning of the proportional-integral parameters is used to adapt to load changes. The specific process is as follows: the ratio of the load torque to the rated torque is used as the basis for parameter adjustment, and the ratio of the load torque to the rated torque is calculated in real time; the initial direction of parameter adjustment is determined according to the trend of the ratio; the proportional and integral parameters are changed according to a preset step size; the fluctuation of the motor speed is monitored after adjustment; if the fluctuation does not reach the stable range, the step size is adjusted according to the direction of the fluctuation, and the parameters are modified again; the adjustment and monitoring steps are repeated until the speed fluctuation is within the stable range.

[0049] Specifically, the determination of instantaneous load impact is used to identify sudden overloads caused by abnormal problems. The specific process is as follows: set a torque change rate threshold, which is determined based on the maximum bearing capacity of the air conditioning damper mechanical structure; continuously monitor the torque value of multiple control cycles and calculate the torque change rate of adjacent cycles; if multiple consecutive change rates exceed the preset threshold and the current torque value exceeds a reasonable multiple of the rated torque, it is determined to be an effective impact; when the protection is triggered, the current peak value is limited by a hardware comparator, and at the same time, the controller outputs a negative compensation signal to linearly adjust the direct axis current to the weak magnetic range within multiple cycles.

[0050] Specifically, the voltage feedforward compensation amplitude correction is used to handle the impact of fluctuations in the automotive power supply voltage caused by changes in operating conditions on the inverter output. The specific process is as follows: real-time acquisition of the power supply voltage; comparing the acquired instantaneous voltage value with a pre-stored reference voltage cycle by cycle to calculate the deviation value between the two; determining the direction and rate of change of the deviation value through the controller, and activating a fixed compensation coefficient or a dynamic compensation coefficient; activating the dynamic compensation coefficient, acquiring the current motor speed, and adjusting the compensation coefficient according to the correspondence between the current motor speed and the rated speed; calculating the voltage compensation amount based on the deviation value and the adjusted compensation coefficient; and superimposing the calculated compensation amount onto the voltage reference value of the space vector pulse width modulation.

[0051] In this embodiment, the specific calculation formula for the voltage feedforward compensation is as follows:

[0052] ,

[0053] in, =U-12V: The nominal voltage of the car's power system is 12V, but it may drop to 12V when idling.

[0054] 11V, which may rise to 14V during acceleration, with a deviation range of ±2V. The deviation is calculated based on 12V and complies with the ISO 16750 automotive power supply standard. =0.5+0.001n: Through experimental verification, the higher the speed, the greater the impact of power supply voltage fluctuation on torque (the impact at 3000 r / min is 6 times that at 500 r / min). Therefore, the dynamic coefficient increases linearly with the speed n (r / min), and 0.5 is the basic compensation coefficient to ensure that the compensation is not excessive at low speeds. =3000r / min: The maximum design speed of the automotive air conditioning fan (corresponding to 5 fan speeds), determined by the air duct design—the airflow at 3000r / min can meet the cabin temperature reduction requirement of 5°C within 3 minutes, which is the mainstream design standard in the industry; when the power supply voltage is 14V (ΔU=2V) and the speed is 3000r / min =3.5, compensation amount =7V, which can offset torque overshoot caused by voltage rise.

[0055] Specifically, the resistor-capacitor series filter circuit is configured to handle high-frequency electromagnetic interference generated in the automotive electronic system. The specific process is as follows: the output impedance of the pulse width modulation signal is detected by an impedance measuring instrument, and the resistance value is determined according to the impedance to match the output impedance; the interference frequency in the automotive electronic system is detected by a spectrum analyzer, and the capacitance value is calculated according to the interference frequency to adapt the filtering time constant of the resistor-capacitor circuit to the interference frequency; one end of the resistor is soldered to the signal output pin of the pulse width modulation driver chip, and the other end of the resistor is soldered to one end of the capacitor; the other end of the capacitor is soldered to the circuit ground terminal; a wire is led out from the connection node of the resistor and capacitor and soldered to the control pin of the power device; the resistor-capacitor circuit is fixed in the circuit board area near the power device, the lead length from the connection node to the power device is shortened, and the circuit is isolated from other components with an insulating bracket.

[0056] In this embodiment, the specific formula for calculating the capacitance value of the resistor-capacitor filter circuit is as follows:

[0057] ,

[0058] Wherein, f=500kHz: The electronic environment of the car cabin was measured with a spectrum analyzer. The spark discharge of the ignition system and the switching noise of the vehicle DC-DC converter are mainly concentrated in 300kHz-1MHz. 500kHz is the typical interference frequency in this range and needs to be filtered specifically; R=50Ω: The nominal output impedance of the automotive-grade PWM driver chip is 45-55Ω. A 50Ω resistor is selected to match the output impedance and avoid reflection interference in signal transmission, which meets the impedance matching principle; The cutoff frequency of the resistor and capacitor filter needs to be close to the interference frequency (so that the interference signal is attenuated by ≥20dB), so C≈6.37nF; There is no 6.37nF capacitor in the standard capacitor specifications of electronic component manufacturers, so 6.4nF (error ±5%) is selected.

[0059] Specifically, the phase difference setting of the staggered pulse width modulation is used to disperse the switching action time of the three-phase power devices. The specific process is as follows: For a three-phase motor, the three pulse width modulation output channels are set with a fixed phase difference in the order of phase A leading phase B and phase B leading phase C. The phase difference angle is evenly distributed according to the number of phases. When the controller generates the pulse width modulation waveform, the phase offset of each channel is realized through the synchronous triggering function of the timer. When the switching frequency changes, the time interval of the phase difference is automatically adjusted.

[0060] Specifically, the estimation of the winding temperature is used to monitor the heating state of the motor windings caused by the current flow in real time. The specific process is as follows: the controller collects the stator phase voltage and phase current in real time, and obtains the direct-axis voltage and current through coordinate transformation; according to the motor resistance temperature characteristics, the current stator resistance is calculated using the resistance calculation formula, ignoring the influence of back electromotive force during the calculation; the resistance value is substituted into the pre-stored resistance-temperature calibration curve, which is obtained by experimental measurement at different temperatures; if the temperature exceeds the critical value, the negative amplitude of the direct-axis current is reduced according to the proportion of temperature overshoot; if the temperature falls back to below the safe range, the original field weakening depth is restored.

[0061] In this embodiment, the formula for estimating the stator resistance is:

[0062] ,

[0063] in, and The Parker transformation converts the stator three-phase voltage and current into direct-axis (d-axis) components, which is the standard coordinate transformation method for FOC control. This eliminates the alternating characteristics of the three-phase current and facilitates DC-based calculations. At low speeds (<500 r / min), the motor back electromotive force E is extremely small, with an impact of <1% on resistance calculations, which can be ignored to simplify the formula. At 25℃, the measured motor d-axis voltage... =1.6V, d-axis current =2A, therefore =0.8Ω, which is consistent with the stator resistance (0.8Ω±5%) measured by an LCR bridge at room temperature.

[0064] Specifically, the three-dimensional optimization method is constructed by collecting experimental data. Different speeds and load conditions are set on the motor test platform (covering the conditions corresponding to the 1-5 levels of automotive air conditioning fan speed). The motor efficiency under each condition is measured, and the direct-axis current value at the highest efficiency is recorded. A continuous efficiency-speed-load-direct-axis current model is generated using a surface fitting algorithm, and the optimal direct-axis current curve is extracted from it. The stator resistance estimation is achieved through Parker transformation. After the controller collects the stator phase voltage and phase current, the direct-axis voltage and current are obtained through Parker transformation. Ignoring the influence of back electromotive force, the current stator resistance is calculated according to Ohm's law. The resistance value is substituted into the pre-stored resistance-temperature calibration curve (this curve is obtained by measuring the motor resistance at different temperatures) to obtain the winding temperature. If the temperature exceeds the critical value, the negative amplitude of the direct-axis current is reduced according to the overshoot ratio.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A Hall sensor-free based FOC control method for an automotive air conditioning module motor, characterized in that, The method comprises the following steps: S1: injecting double-frequency voltage pulses into the stator in stages, performing preliminary positioning based on the voltage pulses, and correcting positioning deviation; After obtaining the current of each phase by means of the sampling resistor, the signal is filtered through a filter circuit, and the processed current signal is used to construct the rotor flux linkage distribution mechanism; the micro acoustic sensor is used to monitor the starting noise in real time; in combination with the air conditioning speed position of the automobile, the direct-axis current of the starting stage is preset according to the load level corresponding to each position; S2: real-time acquisition of motor operating parameters is performed by using an extended Kalman filter observer, the current load torque is back calculated through an iterative update algorithm of filter gain in the observer, the proportional integral parameters of the field oriented controller are dynamically self-tuned according to the size of the load torque, the torque change rate is continuously monitored for multiple sampling periods after a transient load impact occurs, the transient protection strategy is triggered when the impact determination condition is met, the current peak value is limited through the current sampling circuit, and a negative compensation signal is output by the controller and the direct-axis current is adjusted; S3: the voltage space vector amplitude is corrected in real time through voltage feedforward compensation to cope with power supply voltage variation, the zero vector action time proportion is adjusted according to the voltage state to balance the switching loss and voltage utilization, and a resistor-capacitor series filter circuit is additionally arranged at the pulse width modulation trigger end, and the adjacent output channels are kept at a fixed phase difference and the output is performed by using phase-shifted pulse width modulation; S4: focusing on motor efficiency and high-temperature protection, the optimal direct-axis current curve under different working conditions is calibrated by establishing a motor efficiency-speed-load three-dimensional optimization method, dynamic field weakening control is started when the motor speed exceeds the base speed, and the direct-axis current is adjusted according to the speed deviation; meanwhile, the winding temperature is estimated by the stator resistance, and the field weakening depth is reduced when the temperature is too high.

2. The method according to claim 1, characterized in that, The frequency of the double-frequency voltage pulse is adapted to determine the rotor position by injecting pulse signals in stages under the condition that there is no Hall sensor, and the specific process is as follows: the frequency pulse is determined based on the distributed inductance characteristics of the motor stator winding, the rotor magnetic pole is locked in the angle interval after the pulse is injected by detecting the harmonic amplitude difference of the current of each phase; After each injection, the peak value difference of the current of two phases is compared, the rotor position error is determined whether it is within the allowable range through the change trend, and finally the pulse injection is stopped.

3. The method according to claim 1, characterized in that, The filtering process of the sampling resistor is used to extract the effective current signal, and the specific process is as follows: the current signal collected by the sampling resistor is differentially amplified by an instrument amplifier, the amplification multiple is matched and set according to the rated current of the motor and the signal acquisition range of the controller, the high-frequency noise generated by pulse injection is filtered through a second-order low-pass filter composed of an operational amplifier, the filter cutoff frequency is set according to the pulse frequency characteristics, and finally the analog signal is converted into a digital signal for real-time calculation of the rotor flux linkage distribution.

4. The method according to claim 1, characterized by, The noise adjustment of the micro acoustic sensor is used to capture the mechanical noise generated by rotor positioning deviation and mismatched pulse parameters during the motor starting stage in real time, and the specific process is as follows: the noise signal output by the sensor is filtered by a band-pass filter to extract the effective noise component, the filter center frequency covers the mechanical noise frequency band of the motor, the controller compares it with the preset position noise threshold, and the noise spectrum is analyzed by means of spectrum analysis after each adjustment to make the main noise peak fall below the threshold.

5. The method of claim 1, characterized in that, The matching of the wind speed gear and the direct-axis current is used to convert the wind speed instruction of the air conditioner control panel into corresponding motor output torque demand, and the specific process is as follows: the controller pre-stores the load torque range corresponding to each wind speed gear; the gear signal of the air conditioner control panel is read at start-up, and the pre-stored initial value of the direct-axis current is queried according to the gear; the deviation of the actual current from the preset value is monitored in real time through the current loop, and the preset value is adjusted in proportion when the deviation exceeds the preset range, so as to match the actual output torque with the gear demand.

6. The method of claim 1, characterized in that, The iterative update of the extended Kalman filter observer is used to improve the torque estimation accuracy, and the specific process is as follows: the state variables including the rotor position, speed and load torque are set during the initialization of the observer, and the covariance matrix is set according to the motor parameter error range; the current state is predicted through the state equation after data collection in each cycle, and the residual error is calculated using the measurement equation; the filter gain is dynamically adjusted according to the residual error; and the estimated value of the load torque is range-limited in the iteration process.

7. The method of claim 1, characterized in that, The dynamic self-tuning of the proportional-integral parameters is used to adapt to load changes, and the specific process is as follows: the ratio of the load torque to the rated torque is taken as the basis for parameter adjustment, and the ratio of the load torque to the rated torque is calculated in real time; the initial direction of parameter adjustment is determined according to the change trend of the ratio; the proportional parameter and the integral parameter are changed by a preset step; the fluctuation of the motor speed is monitored after adjustment; if the fluctuation does not reach the stable range, the step size is adjusted according to the fluctuation direction, and the parameters are further modified; the adjustment and monitoring steps are repeated until the speed fluctuation is within the stable range.

8. The method of claim 1, characterized in that, The determination of the instantaneous load impact is used to identify sudden overload caused by abnormal problems, and the specific process is as follows: a torque change rate threshold is set, which is determined according to the maximum bearing capacity of the air conditioner damper mechanical structure; the torque values of multiple control cycles are continuously monitored, and the torque change rate of adjacent cycles is calculated; if the change rates of multiple consecutive cycles exceed the preset threshold and the current torque value exceeds a reasonable multiple of the rated torque, it is determined that an effective impact has occurred; when the protection is triggered, the current peak value is limited by a hardware comparator, and the controller outputs a negative compensation signal to linearly adjust the direct-axis current to the field weakening interval within multiple cycles.

9. The method of claim 1, characterized in that, The amplitude modification of the voltage feedforward compensation is used to process the influence of the fluctuation of the automobile power supply voltage caused by the change of the working condition on the output of the inverter, and the specific process is as follows: the power supply voltage is acquired in real time, the acquired voltage instantaneous value is compared with the pre-stored reference voltage cycle by cycle, and the deviation value is calculated; the change direction and rate of the deviation value are judged by the controller, and a fixed compensation coefficient or a dynamic compensation coefficient is enabled; when the dynamic compensation coefficient is enabled, the current speed of the motor is acquired, and the compensation coefficient is adjusted according to the corresponding relationship between the current speed of the motor and the rated speed; The voltage compensation amount is calculated according to the deviation value and the adjusted compensation coefficient; and the compensation amount calculated is superimposed on the voltage reference value of the space vector pulse width modulation.

10. The method of claim 1, characterized in that, The configuration of the resistance-capacitance series filter circuit is used for processing high-frequency electromagnetic interference generated in the automotive electronic system, and the specific process is: the output impedance of the pulse width modulation signal is detected by an impedance measuring instrument, the resistance value is determined according to the impedance, and the resistance value is matched with the output impedance; the interference frequency in the automotive electronic system is detected by a spectrum analyzer, the capacitance value is calculated according to the interference frequency, and the filter time constant of the resistance-capacitance circuit is adapted to the interference frequency; one end of the resistance is welded to the signal output pin of the pulse width modulation drive chip, and the other end of the resistance is welded to one end of the capacitor; the other end of the capacitor is welded to the circuit ground end; the lead wire is drawn from the connection node of the resistance and the capacitor, and is welded to the control pin of the power device; the resistance-capacitance circuit is fixed in the circuit board area near the power device, the lead wire length from the connection node to the power device is shortened, and the circuit is isolated from other elements by an insulating support.

11. The method of claim 1, characterized in that, The phase difference of the phase-shifted pulse width modulation is set to disperse the switching action time of the three-phase power device, and the specific process is: for a three-phase motor, three pulse width modulation output channels are set with a fixed phase difference in a preset order, and the phase difference angle is uniformly distributed according to the number of phases; the phase offset of each channel is realized by the synchronous trigger function of the timer when the controller generates the pulse width modulation waveform; the time interval of the phase difference is automatically adjusted when the switching frequency changes.

12. The method of claim 1, characterized in that, The estimation of the winding temperature is used to monitor the heating state of the motor winding caused by the current in real time, and the specific process is: the controller collects the stator phase voltage and phase current in real time, and obtains the direct-axis voltage and current through coordinate transformation; according to the temperature characteristics of the motor resistance, the current stator resistance is calculated by using the resistance calculation formula, and the influence of back electromotive force is ignored during calculation; The resistance value is substituted into the pre-stored resistance-temperature calibration curve, and the resistance-temperature calibration curve is obtained by measuring at different temperatures through experiments; if the temperature exceeds the critical value, the negative amplitude of the direct-axis current is reduced by the proportion of the temperature overshoot, and if the temperature falls below the safe range, the original field weakening depth is restored.

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