Dead-zone compensation method for brushless motor phase-free current sampling

Abstract

The invention provides a dead-time compensation method for brushless motor phase-free current sampling, which comprises the following steps: performing sector division according to a real-time motor angle of a brushless motor to obtain a real-time SVPWM sector, and generating a three-phase PWM duty ratio signal corresponding to the real-time SVPWM sector; performing analog-digital sampling point setting and voltage sampling according to the real-time SVPWM sector and the three-phase PWM duty ratio signal to obtain a phase voltage and a three-phase bridge driving voltage; calculating the three-phase current polarity corresponding to the real-time SVPWM sector according to the phase voltage and the three-phase bridge driving voltage; and calculating a three-phase PWM compensation value according to preset dead zone time and the three-phase current polarity, performing compensation updating on the three-phase PWM duty ratio signal according to the three-phase PWM compensation value, and performing dead zone compensation on the brushless motor by using the compensated and updated three-phase PWM duty ratio signal.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a dead-zone compensation method for brushless motors without phase current sampling. Background Technology

[0002] In the field of high-performance control of brushless motors, space vector pulse width modulation (SVM) technology is widely used due to its high DC bus voltage utilization and excellent control performance. However, to prevent shoot-through short circuits of the upper and lower power transistors in the three-phase inverter bridge arm, a dead time must be inserted into the pulse width modulation drive signal. This causes a deviation between the actual output voltage and the ideal target voltage, resulting in distortion of the output current waveform, torque pulsation, and a decrease in system efficiency. This phenomenon is called the dead time effect. The dead time effect is particularly significant under low-speed, light-load, and low-current conditions, easily leading to distortion near the current zero-crossing point and even causing zero-current clamping, severely restricting the dynamic performance and static accuracy of motor control.

[0003] Currently, the industry commonly employs dead-zone compensation methods based on phase current sampling sensors, which determine the direction of voltage error and perform compensation by detecting the polarity of the phase current in real time. However, this type of method has significant limitations: First, high-precision current sensors increase system hardware costs and circuit complexity; second, under low-current conditions such as zero current crossing or low load, the signal-to-noise ratio of the current signal is low, easily leading to polarity misjudgment, which in turn causes incorrect compensation or even system oscillation. Furthermore, traditional methods are highly dependent on the accuracy and real-time performance of the current sampling circuit, making it difficult to maintain compensation accuracy over a wide speed range, and especially unable to meet the requirements of applications with strict dynamic response and torque stability requirements. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a dead-zone compensation method for brushless motors without phase current sampling. This method has the advantages of software-based current polarity determination and reduced phase current sampling, thus solving the problem of low compensation efficiency caused by current sensor accuracy limitations and polarity misjudgment in low signal-to-noise ratio environments in brushless motor dead-zone compensation.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: This invention provides a dead-zone compensation method for brushless motors without phase current sampling, comprising the following steps: The sectors are divided according to the real-time motor angle of the brushless motor to obtain the real-time SVPWM sector, and the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector is generated. Based on the preset dead time, the real-time SVPWM sector, and the three-phase PWM duty cycle signal, the analog-to-digital sampling points are set to obtain the sampling trigger point sequence; The voltages of the three-phase terminals and the three-phase bridge drive terminals of the brushless motor are sampled according to the sampling trigger point sequence to obtain the phase voltage and the three-phase bridge drive voltage. The three-phase current polarity corresponding to the real-time SVPWM sector is calculated based on the phase voltage and the three-phase bridge drive voltage. The three-phase PWM compensation value is calculated based on the dead time and the polarity of the three-phase current. The three-phase PWM duty cycle signal is then compensated and updated based on the three-phase PWM compensation value. Finally, the brushless motor is dead-time compensated using the compensated and updated three-phase PWM duty cycle signal.

[0006] According to a preferred embodiment of the present invention, the step of dividing the sector based on the real-time motor angle of the brushless motor to obtain the real-time SVPWM sector includes: The real-time motor angle of the brushless motor is standardized and overflow is corrected to obtain the standard motor angle. Determine whether the standard motor angle is within a preset boundary angle range; If so, the angular velocity of the brushless motor is obtained, the angle of the standard motor is compensated according to the angular velocity, and the SVPWM sector is mapped to the compensated standard motor angle to obtain the real-time SVPWM sector. If not, then SVPWM sector mapping is performed on the standard motor angle to obtain the real-time SVPWM sector.

[0007] According to another preferred embodiment of the present invention, the step of performing angle compensation on the standard motor angle based on the angular velocity includes: The angular velocity is subjected to Kalman filtering to obtain the filtered angular velocity; Obtain the total system delay and use the product of the total system delay and the filter angular velocity as the delay compensation angle; The standard motor angle is initially compensated based on the delay compensation angle, and it is determined whether the standard motor angle after initial compensation is at a boundary angle. If so, the preset boundary compensation angle is subtracted from the standard motor angle.

[0008] According to another preferred embodiment of the present invention, generating the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector includes: Angle mapping is performed on the real-time SVPWM sector to obtain the sector center angle, and voltage vector synthesis is performed based on the sector center angle to obtain the target voltage vector component; Obtain the PWM period corresponding to the real-time SVPWM sector, and calculate the basic vector action time of the target voltage vector component on the real-time SVPWM sector based on the PWM period; Obtain the duty cycle calculation formula corresponding to the real-time SVPWM sector, and calculate the duty cycle of the basic vector action time according to the duty cycle calculation formula and the PWM period to obtain the three-phase duty cycle reference value. The three-phase duty cycle reference value is subjected to saturation limiting and normalization operations to obtain a standard three-phase PWM duty cycle, and a three-phase PWM duty cycle signal is generated based on the standard three-phase PWM duty cycle.

[0009] According to another preferred embodiment of the present invention, the step of setting analog-to-digital sampling points based on a preset dead time, the real-time SVPWM sector, and the three-phase PWM duty cycle signal to obtain a sampling trigger point sequence includes: The freewheeling detection phase is retrieved based on the real-time SVPWM sector query. The dead time window is located for the freewheeling detection phase based on the preset dead time and the three-phase PWM duty cycle signal. Calculate the center point of the dead time window and use the center point of the window as the ADC sampling trigger point; The sampling sequence of the ADC sampling trigger point is set according to the PWM period to obtain the sampling trigger point sequence.

[0010] According to another preferred embodiment of the present invention, the step of locating the dead time window of the freewheeling detection phase based on a preset dead time duration and the three-phase PWM duty cycle signal to obtain the dead time window includes: Based on the freewheeling detection relative to the three-phase PWM duty cycle signal, the sampled phase PWM duty cycle signal is obtained; The rising edge time point and the falling edge time point are extracted from the sampled phase PWM duty cycle signal, respectively. The rising edge dead zone offset time point corresponding to the rising edge time point and the falling edge dead zone offset time point corresponding to the falling edge time point are calculated according to the preset dead zone duration. The rising edge dead zone window corresponding to the rising edge dead zone offset time point and the falling edge dead zone window corresponding to the falling edge dead zone offset time point are calculated based on the dead zone duration. The dead time window is obtained by periodically adjusting the dead time window on the rising edge and the dead time window on the falling edge.

[0011] According to another preferred embodiment of the present invention, the step of calculating the three-phase current polarity corresponding to the real-time SVPWM sector based on the phase voltage and the three-phase bridge drive voltage includes: The freewheeling detection phase is retrieved based on the real-time SVPWM sector, and the average value of the phase voltage is used as the target phase voltage. Determine whether the target phase voltage is greater than the three-phase bridge drive voltage; If so, then the current polarity of the freewheeling detection phase is negative. If not, then the current polarity of the freewheeling detection phase is positive. Based on the real-time SVPWM sector query, the corresponding current polarities other than the freewheeling detection phase are obtained, and the current polarities of all phases are aggregated into three-phase current polarities.

[0012] According to another preferred embodiment of the present invention, the step of calculating the three-phase PWM compensation value based on the dead time and the three-phase current polarity includes: The polarity of the three-phase current is mapped to a compensation direction to obtain a single-phase compensation direction group. Based on the dead time, the compensation value of each phase in the three-phase current polarity is calculated to obtain the three-phase basic compensation value group. The three-phase basic compensation value group is symbolically mapped according to the single-phase compensation direction group to obtain the three-phase mapped compensation value. The three-phase mapped compensation value is then subjected to range limiting and normalization to obtain the three-phase PWM compensation value.

[0013] According to another preferred embodiment of the present invention, the step of compensating and updating the three-phase PWM duty cycle signal based on the three-phase PWM compensation value includes: According to the phase type of the three-phase PWM duty cycle signals, the PWM duty cycle signals are selected one by one as the target phase duty cycle signals, and the compensation value corresponding to the target phase duty cycle signal in the three-phase PWM compensation values ​​is taken as the target phase compensation value. The target phase compensation value is superimposed with the target phase compensation duty cycle signal by superimposing the duty cycle based on the rising edge position and falling edge position of the target phase duty cycle signal to obtain the target phase compensation duty cycle signal. The target phase compensation duty cycle signal is subjected to amplitude limiting processing, and the target phase duty cycle signal in the three-phase PWM duty cycle signal is updated using the amplitude-limited target phase compensation duty cycle signal.

[0014] To achieve at least one of the above-mentioned objectives, the present invention further provides a dead-time compensation system for brushless motor phaseless current sampling, the system comprising an SVPWM modulation module, an AD sampling module, a current polarity detection module, and a dead-time compensation module, wherein: The SVPWM modulation module is used to divide the brushless motor into sectors based on the real-time motor angle to obtain real-time SVPWM sectors and generate the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector. The AD sampling module is used to set analog and digital sampling points according to the preset dead time, the real-time SVPWM sector and the three-phase PWM duty cycle signal, to obtain the sampling trigger point sequence, and to sample the voltage of the three-phase terminals and the three-phase bridge drive terminals of the brushless motor according to the sampling trigger point sequence, so as to obtain the phase voltage and the three-phase bridge drive voltage. The current polarity detection module is used to calculate the three-phase current polarity corresponding to the real-time SVPWM sector based on the phase voltage and the three-phase bridge drive voltage. The dead-zone compensation module is used to calculate the three-phase PWM compensation value based on the dead-zone duration and the three-phase current polarity, update the three-phase PWM duty cycle signal based on the three-phase PWM compensation value, and use the updated three-phase PWM duty cycle signal to perform dead-zone compensation on the brushless motor.

[0015] The present invention further provides a computer-readable storage medium storing a computer program, which is executed by a processor to implement the above-described dead-zone compensation method for sampling phaseless current in a brushless motor.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides a dead-zone compensation method and system for brushless motor phase current sampling, which has the following beneficial effects: This dead-zone compensation method for brushless motors without phase current sampling derives the effective voltage vector by using the sector center angle instead of the real-time motor angle. This significantly reduces the amount of trigonometric function calculations, decreases real-time control overhead, and improves the control response speed when the motor is running at high speed. By calculating the basic vector action time, the three-phase duty cycle is made mathematically rigorous and verifiable. Saturation limiting and normalization ensure that the duty cycle meets the value range requirements, avoiding voltage distortion caused by over-modulation or under-modulation. This allows the generated three-phase PWM duty cycle signal to accurately reflect the target voltage vector, ensuring the balance and continuity of the three-phase voltage output of the inverter, thereby improving the efficiency of dead-zone compensation for brushless motors.

[0017] This dead-zone compensation method for brushless motor phase-free current sampling determines the sampling trigger point sequence based on real-time SVPWM sector and three-phase PWM duty cycle signals, enabling precise positioning of the brushless motor's freewheeling region. By utilizing sector characteristics to determine the freewheeling detection phase, sampling always occurs in the phase where the current polarity is most easily identifiable. By extracting the rising and falling edges based on the PWM duty cycle and constructing a dead-zone window using a preset dead time, the sampling point falls within the stable range of intermittent MOS shutdown. By using the center point of the window as the ADC sampling trigger point, PWM switching spikes, reverse recovery noise, and bridge arm overlapping voltage interference can be effectively avoided. Consequently, reliable current polarity information can be obtained without a current sampling resistor, improving the accuracy and efficiency of current estimation.

[0018] This dead-zone compensation method for brushless motors without phase current sampling determines the current polarity of the freewheeling detection phase by comparing the target phase voltage with the three-phase bridge drive voltage. This enables sensorless current polarity detection, greatly simplifying hardware design and reducing system costs. By looking up tables, the current polarity of the other two phases is determined, reducing the steps of voltage measurement and polarity judgment. By combining the dead-zone duration with the real-time three-phase current polarity to calculate duty cycle compensation, phase voltage distortion caused by the dead zone can be specifically corrected. By calculating the basic duty cycle compensation amount based on the dead-zone duration and determining the compensation sign and lateral direction based on the current direction, the method can significantly reduce voltage deviation and polarity judgment errors caused by the dead zone without adding additional sensors, improving the low-speed and transient performance of the motor and enhancing the efficiency of dead-zone compensation. Attached Figure Description

[0019] Figure 1 The diagram shown is a flowchart of a dead zone compensation method for sampling phaseless current in a brushless motor according to the present invention.

[0020] Figure 2 This displays the SVPWM voltage vector diagram in the dead-zone compensation method for phaseless current sampling of a brushless motor according to the present invention.

[0021] Figure 3 The diagram shown is a three-phase PWM modulation waveform corresponding to sector I in the dead zone compensation method for phaseless current sampling of a brushless motor according to the present invention.

[0022] Figure 4 The diagram shown is a schematic of the ADC sampling trigger point in a dead-zone compensation method for phaseless current sampling of a brushless motor according to the present invention.

[0023] Figure 5 The diagram shown is a freewheeling phase voltage diagram in the positive current direction according to an embodiment of the present invention.

[0024] Figure 6 The diagram shown is a freewheeling phase voltage diagram in the negative current direction according to an embodiment of the present invention. Detailed Implementation

[0025] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious modifications will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0026] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0027] Example 1: Please combine Figure 1 This invention discloses a dead-zone compensation method for brushless motor phase-free current sampling, the method comprising the following steps: The sectors are divided according to the real-time motor angle of the brushless motor to obtain the real-time SVPWM sectors, and the three-phase PWM duty cycle signals corresponding to the real-time SVPWM sectors are generated.

[0028] The brushless motor is a DC motor without mechanical brushes and a commutator. It achieves high efficiency, long life, and low noise motor drive by using an electronic controller for commutation. The real-time motor angle refers to the real-time offset angle of the rotor relative to the stator of the brushless motor. The real-time motor angle can be obtained by a position sensor, such as a Hall sensor. When the brushless motor is working, it controls the direction of the current on the stator windings to generate magnetic forces in different directions. These magnetic forces act on the permanent magnets on the rotor, causing the rotor to deflect at an angle, thus generating the real-time motor angle.

[0029] Please combine Figure 2 This is the SVPWM voltage vector diagram, which is a voltage vector distribution diagram formed by the eight switching states of a three-phase inverter in the α-β coordinate plane. The SVPWM voltage vector diagram can be obtained by performing a Clarke transformation on the three-phase stationary coordinates of the three-phase inverter. The eight switching states refer to those shown in the diagram. , , , , , , , These 8 states, for example This refers to the voltage vector being The three-phase switch status is 100, where 1 indicates the switch is closed and 0 indicates the switch is open. Space Vector Pulse Width Modulation (SVPWM) is an advanced inverter modulation method that makes fuller use of the DC bus voltage than traditional sinusoidal pulse width modulation. The real-time SVPWM sector refers to the sector on the SVPWM voltage vector diagram corresponding to the real-time motor angle. The SVPWM voltage vector diagram consists of six 60-degree sectors, namely sectors I, II, III, IV, V, and VI in the figure. The three-phase PWM duty cycle signal is the duty cycle signal of the three-phase voltage generated by the three-phase bridge arm of the brushless motor through pulse width modulation (PWM), including the U-phase PWM duty cycle signal, the V-phase PWM duty cycle signal, and the W-phase PWM duty cycle signal. The duty cycle refers to the proportion of the high-level time to the total cycle time in one PWM cycle.

[0030] In this embodiment of the invention, the step of dividing the sector according to the real-time motor angle of the brushless motor to obtain the real-time SVPWM sector includes: The real-time motor angle of the brushless motor is standardized and overflow is corrected to obtain the standard motor angle. Determine whether the standard motor angle is within a preset boundary angle range; If so, the angular velocity of the brushless motor is obtained, the angle of the standard motor is compensated according to the angular velocity, and the SVPWM sector is mapped to the compensated standard motor angle to obtain the real-time SVPWM sector. If not, then SVPWM sector mapping is performed on the standard motor angle to obtain the real-time SVPWM sector.

[0031] The angle standardization refers to standardizing the unit of the real-time motor angle, for example, converting π to 180 degrees. The angle overflow correction refers to correcting the real-time motor angle when it exceeds the angle period range, so that the real-time motor angle is within the angle range of 0 to 360 degrees. For example, when the real-time motor angle is negative, add an integer multiple of 360 to the real-time motor angle until the sum of the angles is within the angle range. When the real-time motor angle exceeds 360, subtract an integer multiple of 360 from the real-time motor angle until the difference of the angles is within the angle range. The boundary angle interval is the angle interval corresponding to the boundary of each sector. For example, for the angle of each sector boundary, the angle range within 5 degrees before and after the angle is used as the boundary angle interval.

[0032] In detail, the angular velocity refers to the angular velocity of the brushless motor rotor. This angular velocity can be obtained by differential calculation of the real-time motor angle over a period of time. The angle compensation of the standard motor angle based on the angular velocity includes: performing Kalman filtering on the angular velocity to obtain a filtered angular velocity; obtaining the total system delay and using the product of the total system delay and the filtered angular velocity as the delay compensation angle; performing primary compensation on the standard motor angle based on the delay compensation angle, and determining whether the standard motor angle after primary compensation is at a boundary angle; if so, subtracting a preset boundary compensation angle from the standard motor angle. Here, primary compensation refers to adding the delay compensation angle to the standard motor angle; the boundary angle refers to the angle corresponding to the sector boundary, which is an integer multiple of 60 degrees; the boundary compensation angle can be 1 degree; and SVPWM sector mapping refers to mapping the standard motor angle to the SVPWM voltage vector diagram, and using the sector corresponding to the standard motor angle in the SVPWM voltage vector diagram as the real-time SVPWM sector.

[0033] By standardizing and correcting angle overflow, it can be ensured that the angle is always within the effective range, avoiding errors in sector numbering calculation. By compensating for the standard motor angle within the boundary angle range in combination with angular velocity, the real-time motor angle in the sensitive area at the sector boundary can be divided into more refined sectors, reducing sector misjudgment caused by delay and reducing pulse jumps during sector switching. This makes the subsequent three-phase PWM duty cycle signal smoother and more accurate, reducing the risk of voltage distortion in dead zone compensation and thus improving the accuracy of dead zone compensation.

[0034] Specifically, generating the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector includes: Angle mapping is performed on the real-time SVPWM sector to obtain the sector center angle, and voltage vector synthesis is performed based on the sector center angle to obtain the target voltage vector component; Obtain the PWM period corresponding to the real-time SVPWM sector, and calculate the basic vector action time of the target voltage vector component on the real-time SVPWM sector based on the PWM period; Obtain the duty cycle calculation formula corresponding to the real-time SVPWM sector, and calculate the duty cycle of the basic vector action time according to the duty cycle calculation formula and the PWM period to obtain the three-phase duty cycle reference value. The three-phase duty cycle reference value is subjected to saturation limiting and normalization operations to obtain a standard three-phase PWM duty cycle, and a three-phase PWM duty cycle signal is generated based on the standard three-phase PWM duty cycle.

[0035] The angle mapping refers to mapping the angle corresponding to the centerline of the real-time SVPWM sector. For example, the center angle of sector I is 30 degrees. The voltage vector synthesis refers to mapping out the two effective voltage vectors corresponding to the center angle of the sector, adjusting the voltage vectors in conjunction with the real-time motor angle to ensure smooth magnetic field rotation, and synthesizing the voltage vectors using a pre-set mapping table between voltage vectors and sector angles. By performing angle mapping instead of voltage vector synthesis based on the real-time motor angle, computational complexity can be reduced and motor control efficiency can be improved. The basic vector action time refers to the duration of action of each component of the target voltage vector in the real-time SVPWM sector for generating the target voltage, which can be calculated by consulting the SVPWM standard calculation formula.

[0036] In detail, the duty cycle calculation formula is the three-phase PWM waveform calculation formula corresponding to each sector in the SVPWM voltage vector diagram. It can be obtained by consulting the SVPWM standard calculation formula. The three-phase duty cycle reference value reflects the duration of the high level in the three-phase PWM signal, i.e., the proportion of the conduction time of the upper transistor in the three-phase bridge arm. The saturation limit refers to scaling the three-phase duty cycle reference value to the value range of the microcontroller's PWM register. The normalization refers to mapping the three-phase duty cycle reference value to the interval from 0 to 100% within the value range. Generating a three-phase PWM duty cycle signal based on the standard three-phase PWM duty cycle means accumulating the corresponding basic vector action time into the corresponding effective conduction time of each phase based on the standard three-phase PWM duty cycle and the three-phase switch state. Please refer to... Figure 3 This is a waveform diagram of the three-phase PWM modulation corresponding to sector I, which reflects the waveform of the three-phase PWM duty cycle signal when the real-time SVPWM sector is sector I. , These are two vectors in the target voltage vector component. , These are zero vectors used to fill the PWM cycle. In the diagram, PWM A, PWM B, and PWM C correspond to the U-phase PWM duty cycle signal, the V-phase PWM duty cycle signal, and the W-phase PWM duty cycle signal, respectively. , These are the basic vector action times. and Total duration of action, It is the zero vector , Total duration of action, It can be subtracted from the PWM period Calculated.

[0037] By using the sector center angle instead of the real-time motor angle for effective voltage vector derivation, the computational load of trigonometric functions can be significantly reduced, real-time control overhead can be decreased, and the control response speed of the motor during high-speed operation can be improved. By calculating the basic vector action time, the three-phase duty cycle is made mathematically rigorous and verifiable. Saturation limiting and normalization ensure that the duty cycle meets the value range requirements, avoiding voltage distortion caused by over-modulation or under-modulation. This allows the generated three-phase PWM duty cycle signal to accurately reflect the target voltage vector, ensuring the balance and continuity of the three-phase voltage output of the inverter, thereby improving the efficiency of dead-zone compensation of the brushless motor.

[0038] Based on the preset dead time, the real-time SVPWM sector, and the three-phase PWM duty cycle signal, the analog-to-digital sampling points are set to obtain the sampling trigger point sequence.

[0039] Specifically, the step of setting analog-to-digital sampling points based on the preset dead time, the real-time SVPWM sector, and the three-phase PWM duty cycle signal to obtain the sampling trigger point sequence includes: The freewheeling detection phase is retrieved based on the real-time SVPWM sector query. The dead time window is located for the freewheeling detection phase based on the preset dead time and the three-phase PWM duty cycle signal. Calculate the center point of the dead time window and use the center point of the window as the ADC sampling trigger point; The sampling sequence of the ADC sampling trigger point is set according to the PWM period to obtain the sampling trigger point sequence.

[0040] In the control process of the brushless motor, dead-time delay switching control of the metal-oxide-semiconductor field-effect transistors (MOS transistors) in the upper and lower bridges of the same phase will generate freewheeling current. The direction of the freewheeling current can reflect the polarity of the three-phase current. In the waveform diagram of the three-phase PWM duty cycle signal, by detecting the positive and negative changes of the current in each phase in each SVPWM sector, the phase in which the freewheeling current occurs can be obtained. By statistically analyzing the phases in the six SVPWM sectors in which the freewheeling current occurs, the following table 1 can be obtained. The freewheeling detection phase is obtained by querying the real-time SVPWM sector. For example, when the real-time SVPWM sector is sector I, the freewheeling detection phase is phase V.

[0041]

[0042] Table 1 The step of determining the dead-time window of the freewheeling detection phase based on the preset dead-time duration and the three-phase PWM duty cycle signal to obtain the dead-time window includes: Based on the freewheeling detection relative to the three-phase PWM duty cycle signal, the sampled phase PWM duty cycle signal is obtained; The rising edge time point and the falling edge time point are extracted from the sampled phase PWM duty cycle signal, respectively. The rising edge dead zone offset time point corresponding to the rising edge time point and the falling edge dead zone offset time point corresponding to the falling edge time point are calculated according to the preset dead zone duration. The rising edge dead zone window corresponding to the rising edge dead zone offset time point and the falling edge dead zone window corresponding to the falling edge dead zone offset time point are calculated based on the dead zone duration. The dead time window is obtained by periodically adjusting the dead time window on the rising edge and the dead time window on the falling edge.

[0043] The signal filtering refers to selecting the single-phase PWM duty cycle signal corresponding to the freewheeling detection phase in the three-phase PWM duty cycle signal as the sampling phase PWM duty cycle signal. The rising edge time point refers to the time point corresponding to the rising edge position of the signal in the sampling phase PWM duty cycle signal. The falling edge time point refers to the time point corresponding to the falling edge position of the signal in the sampling phase PWM duty cycle signal. The dead time refers to the preset dead time delay of the brushless motor. The rising edge dead time offset time point is the rising edge time point plus the dead time. The falling edge dead time offset time point is the falling edge time point plus the dead time. The rising edge dead time window is a window with the rising edge dead time offset time point as the starting point and the window length is the dead time. The falling edge dead time window is a window with the falling edge dead time offset time point as the starting point and the window length is the dead time. The period range correction refers to determining whether the rising edge dead time window and the falling edge dead time window are within the PWM period and filtering out the part that exceeds the range.

[0044] Specifically, the window center point refers to the midpoint of each window within the dead-time window; please refer to [reference needed]. Figure 4This is a schematic diagram of the ADC sampling trigger point. In the analog-to-digital converter (ADC), since the freewheeling detection phase is phase V, the sampling phase PWM duty cycle signal is the signal corresponding to PWM B. The steps of calculating the rising edge dead zone offset time point corresponding to the rising edge time point and the falling edge dead zone offset time point corresponding to the falling edge time point are omitted here. The rising edge dead zone window is the window corresponding to the first dead zone in the figure, and the falling edge dead zone window is the window corresponding to the second dead zone in the figure. ADC sampling trigger point 1 is the center point of the rising edge dead zone window and the center point of the falling edge dead zone window.

[0045] By jointly determining the sampling trigger point sequence based on real-time SVPWM sector and three-phase PWM duty cycle signals, the freewheeling region of the brushless motor can be accurately located. By utilizing sector characteristics to determine the freewheeling detection phase, sampling always occurs in the phase where the current polarity is most easily identified. By extracting the rising and falling edges based on the PWM duty cycle and constructing a dead-time window by combining it with a preset dead time, the sampling point can fall into the stable range of intermittent MOS shutdown. By using the center point of the window as the ADC sampling trigger point, PWM switching spikes, reverse recovery noise, and bridge arm overlapping voltage interference can be effectively avoided. Thus, reliable current polarity information can be obtained without a current sampling resistor, improving the accuracy and efficiency of current estimation.

[0046] Voltage samples are taken from the three-phase terminals and the three-phase bridge drive terminals of the brushless motor according to the sampling trigger point sequence to obtain the phase voltage and the three-phase bridge drive voltage.

[0047] Wherein, the three-phase terminals are the lead-out terminals of the three-phase windings of the brushless motor, and the three-phase bridge drive terminals are the output terminals of the three-phase bridge driver of the brushless motor. The step of sampling the voltages of the three-phase terminals and the three-phase bridge drive terminals of the brushless motor according to the sampling trigger point sequence to obtain the phase voltages and the three-phase bridge drive voltages refers to initializing the timer component according to the sampling trigger point sequence, triggering the sampling signal according to the timer component, and sampling the phase voltages corresponding to the freewheeling detection phases in the three-phase motor terminals and the voltages of the three-phase bridge driver through analog multi-channel scanning or synchronous sampling of the ADC.

[0048] The three-phase current polarity corresponding to the real-time SVPWM sector is calculated based on the phase voltage and the three-phase bridge drive voltage.

[0049] The three-phase current polarity refers to the current polarity of the U, V, and M phases. When the current flows out from the phase terminals of the brushless motor, it is a negative current polarity, and when the current flows in from the phase terminals of the brushless motor, it is a positive current polarity.

[0050] Specifically, the step of calculating the three-phase current polarity corresponding to the real-time SVPWM sector based on the phase voltage and the three-phase bridge drive voltage includes: The freewheeling detection phase is retrieved based on the real-time SVPWM sector, and the average value of the phase voltage is used as the target phase voltage. Determine whether the target phase voltage is greater than the three-phase bridge drive voltage; If so, then the current polarity of the freewheeling detection phase is negative. If not, then the current polarity of the freewheeling detection phase is positive. Based on the real-time SVPWM sector query, the corresponding current polarities other than the freewheeling detection phase are obtained, and the current polarities of all phases are aggregated into three-phase current polarities.

[0051] Since there are two dead zones in a single phase within a PWM cycle, there are two corresponding phase voltage values. By calculating the average value of the phase voltages, voltage noise can be smoothed and robustness improved. The step of querying the other two corresponding current polarities according to the real-time SVPWM sector means querying the corresponding current polarities other than the freewheeling detection phase from Table 1 according to the real-time SVPWM sector. For example, when the real-time SVPWM sector is sector I, the freewheeling detection phase is phase V, the current polarity corresponding to U is positive, and the current polarity corresponding to W is negative.

[0052] Please refer to Figure 5 , Figure 6 This is a schematic diagram of the freewheeling current phase voltage in one embodiment of the present invention. Figure 5 This is the freewheeling phase voltage diagram in the positive current direction. Figure 6 This is a freewheeling phase voltage diagram in the negative current direction. In the diagram, D1, D2, D3, D4, D5, and D6 correspond to the six MOSFETs of the three-phase switch. S1, S2, S3, S4, S5, and S6 are the MOSFET control signals of the brushless motor. D1 and D2 form the upper and lower bridge MOSFETs of phase U, D3 and D4 form the upper and lower bridge MOSFETs of phase V, and D5 and D6 form the upper and lower bridge MOSFETs of phase W. U_PHASE, V_PHASE, and W_PHASE are connected to the U, V, and W phases of the brushless motor, respectively. The arrows on the lines represent the current direction. Figure 5When the upper MOSFET corresponding to D1 is turned off, current cannot flow from the upper MOSFET of the S1 signal. Therefore, the current can only flow from GND through the body diode inside the MOSFET of the S4 signal to the MOSFET for freewheeling. Due to the characteristics of the diode, there will be a forward voltage drop when it is turned on. The forward voltage drop of the body diode will be different for different materials of MOSFETs. In this embodiment, the forward voltage is 0.7V. The drain of the MOSFET of the S4 signal is connected to GND, which is 0V. Since the body diode needs a voltage difference to turn on, the phase voltage of U_PHASE is -0.7V. Figure 6 When the lower MOSFET corresponding to D2 is turned off, current cannot flow into the lower MOSFET of the S4 signal. Therefore, the current can only flow into the MOSFET from U_PHASE through the body diode of the MOSFET of the S1 signal for freewheeling. Since the three-phase bridge drive voltage of the three-phase bridge drive power supply is VBAT, and the body diode needs a voltage difference to conduct, the phase voltage of U_PHASE is VBAT+0.7V.

[0053] By averaging the phase voltages, voltage noise can be smoothed and robustness improved. The polarity of the current in the freewheeling detection phase can be determined by comparing the target phase voltage with the three-phase bridge drive voltage, enabling sensorless current polarity detection, which greatly simplifies hardware design and reduces system cost. The current polarity of the other two phases can be determined by looking up a table, which reduces the steps of voltage measurement and polarity judgment, thereby improving the efficiency of dead-zone compensation for brushless motors.

[0054] The three-phase PWM compensation value is calculated based on the dead time and the polarity of the three-phase current. The three-phase PWM duty cycle signal is then compensated and updated based on the three-phase PWM compensation value. Finally, the brushless motor is dead-time compensated using the compensated and updated three-phase PWM duty cycle signal.

[0055] The three-phase PWM compensation value is a duty cycle calibration amount introduced for phases V, U, and W to correct voltage errors caused by dead time.

[0056] Specifically, the calculation of the three-phase PWM compensation value based on the dead time and the three-phase current polarity includes: The polarity of the three-phase current is mapped to a compensation direction to obtain a single-phase compensation direction group. Based on the dead time, the compensation value of each phase in the three-phase current polarity is calculated to obtain the three-phase basic compensation value group. The three-phase basic compensation value group is symbolically mapped according to the single-phase compensation direction group to obtain the three-phase mapped compensation value. The three-phase mapped compensation value is then subjected to range limiting and normalization to obtain the three-phase PWM compensation value.

[0057] The compensation direction mapping refers to mapping the phase corresponding to the positive current polarity in the three-phase current polarity to a positive compensation direction, and mapping the phase corresponding to the negative current polarity to a negative compensation direction. The compensation value calculation refers to using 1 / 2 of the dead time as the basic compensation value for each phase. The sign mapping refers to determining the sign of the corresponding three-phase basic compensation value based on the single-phase compensation direction. When the single-phase compensation direction is positive, the sign of the corresponding three-phase basic compensation value is positive, and when the single-phase compensation direction is negative, the sign of the corresponding three-phase basic compensation value is negative. The value range limiting and normalization processing restrict the three-phase mapped compensation value to the periodic value range of the three-phase PWM signal.

[0058] Specifically, the step of compensating and updating the three-phase PWM duty cycle signal based on the three-phase PWM compensation value includes: According to the phase type of the three-phase PWM duty cycle signals, the PWM duty cycle signals are selected one by one as the target phase duty cycle signals, and the compensation value corresponding to the target phase duty cycle signal in the three-phase PWM compensation values ​​is taken as the target phase compensation value. The target phase compensation value is superimposed with the target phase compensation duty cycle signal by superimposing the duty cycle based on the rising edge position and falling edge position of the target phase duty cycle signal to obtain the target phase compensation duty cycle signal. The target phase compensation duty cycle signal is subjected to amplitude limiting processing, and the target phase duty cycle signal in the three-phase PWM duty cycle signal is updated using the amplitude-limited target phase compensation duty cycle signal.

[0059] The duty cycle superposition refers to performing duty cycle compensation on the rising and falling edges of the target phase duty cycle signal. For example, when the target phase compensation value is positive, the duty cycle of the upper bridge arm of the three-phase bridge arm needs to be increased, and the signal length corresponding to the basic compensation value is increased on both sides of the target phase duty cycle signal. When the target phase compensation value is negative, the duty cycle of the lower bridge arm of the three-phase bridge arm needs to be decreased, and the signal length corresponding to the basic compensation value is decreased on both sides of the target phase duty cycle signal. The amplitude limiting process refers to setting upper and lower limits for the duty cycle of the signal to prevent the duty cycle from exceeding the limit value. The dead-zone compensation of the brushless motor using the compensated and updated three-phase PWM duty cycle signal refers to re-inputting the updated three-phase PWM duty cycle signal into the three-phase bridge drive hardware, generating the corresponding three-phase compensation voltage, and using the three-phase compensation voltage to compensate the brushless motor.

[0060] By combining the dead time with the real-time three-phase current polarity to calculate the duty cycle compensation, the phase voltage distortion caused by the dead time can be corrected in a targeted manner. By calculating the basic duty cycle compensation amount based on the dead time and determining the compensation sign and lateral direction according to the current direction, the voltage deviation and polarity determination error caused by the dead time can be significantly reduced without adding additional sensors, thereby improving the low-speed and transient performance of the motor and increasing the efficiency of dead time compensation.

[0061] Example 2: This invention discloses a dead-time compensation system for phase-free current sampling in a brushless motor. The system includes an SVPWM modulation module, an AD sampling module, a current polarity detection module, and a dead-time compensation module, wherein: The SVPWM modulation module is used to divide the brushless motor into sectors based on the real-time motor angle to obtain real-time SVPWM sectors and generate the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector. The AD sampling module is used to set analog and digital sampling points according to the preset dead time, the real-time SVPWM sector and the three-phase PWM duty cycle signal, to obtain the sampling trigger point sequence, and to sample the voltage of the three-phase terminals and the three-phase bridge drive terminals of the brushless motor according to the sampling trigger point sequence, so as to obtain the phase voltage and the three-phase bridge drive voltage. The current polarity detection module is used to calculate the three-phase current polarity corresponding to the real-time SVPWM sector based on the phase voltage and the three-phase bridge drive voltage. The dead-zone compensation module is used to calculate the three-phase PWM compensation value based on the dead-zone duration and the three-phase current polarity, update the three-phase PWM duty cycle signal based on the three-phase PWM compensation value, and use the updated three-phase PWM duty cycle signal to perform dead-zone compensation on the brushless motor.

[0062] The processes described above with reference to the flowcharts in the embodiments disclosed in this invention can be implemented as computer software programs. The embodiments disclosed in this invention include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication component, and / or installed from a removable medium. When the computer program is executed by a central processing unit (CPU), it performs the functions defined in the methods of this application. It should be noted that the computer-readable medium described above in this application can be a computer-readable signal medium or a computer-readable storage medium, or any combination of the two. The computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wire segments, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this application, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on a computer-readable medium may be transmitted using any suitable medium, including but not limited to: wireless segments, wire segments, optical fibers, RF, etc., or any suitable combination thereof.

[0063] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0064] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functions and structural principles of the present invention have been shown and explained in the embodiments. Without departing from the stated principles, the implementation of the present invention may have any variations or modifications.

Claims

1. A dead-zone compensation method for phase-free current sampling in a brushless motor, characterized in that, The method includes: The sectors are divided according to the real-time motor angle of the brushless motor to obtain the real-time SVPWM sector, and the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector is generated. Based on the preset dead time, the real-time SVPWM sector, and the three-phase PWM duty cycle signal, the analog-to-digital sampling points are set to obtain the sampling trigger point sequence; According to the sampling trigger point sequence, the voltage of the three-phase terminals and the three-phase bridge drive terminals of the brushless motor are sampled respectively to obtain the phase voltage and the three-phase bridge drive voltage. The three-phase current polarity corresponding to the real-time SVPWM sector is calculated based on the phase voltage and the three-phase bridge drive voltage. The three-phase PWM compensation value is calculated based on the dead time and the polarity of the three-phase current. The three-phase PWM duty cycle signal is then compensated and updated based on the three-phase PWM compensation value. Finally, the brushless motor is dead-time compensated using the compensated and updated three-phase PWM duty cycle signal.

2. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 1, characterized in that, The process of dividing sectors based on the real-time motor angle of the brushless motor to obtain real-time SVPWM sectors includes: The real-time motor angle of the brushless motor is standardized and overflow is corrected to obtain the standard motor angle. Determine whether the standard motor angle is within a preset boundary angle range; If so, the angular velocity of the brushless motor is obtained, the angle of the standard motor is compensated according to the angular velocity, and the SVPWM sector is mapped to the compensated standard motor angle to obtain the real-time SVPWM sector. If not, then SVPWM sector mapping is performed on the standard motor angle to obtain the real-time SVPWM sector.

3. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 2, characterized in that, The step of compensating the standard motor angle based on the angular velocity includes: The angular velocity is subjected to Kalman filtering to obtain the filtered angular velocity; Obtain the total system delay and use the product of the total system delay and the filter angular velocity as the delay compensation angle; The standard motor angle is initially compensated based on the delay compensation angle, and it is determined whether the standard motor angle after initial compensation is at a boundary angle. If so, the preset boundary compensation angle is subtracted from the standard motor angle.

4. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 1, characterized in that, The generation of the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector includes: Angle mapping is performed on the real-time SVPWM sector to obtain the sector center angle, and voltage vector synthesis is performed based on the sector center angle to obtain the target voltage vector component; Obtain the PWM period corresponding to the real-time SVPWM sector, and calculate the basic vector action time of the target voltage vector component on the real-time SVPWM sector based on the PWM period; Obtain the duty cycle calculation formula corresponding to the real-time SVPWM sector, and calculate the duty cycle of the basic vector action time according to the duty cycle calculation formula and the PWM period to obtain the three-phase duty cycle reference value. The three-phase duty cycle reference value is subjected to saturation limiting and normalization operations to obtain a standard three-phase PWM duty cycle, and a three-phase PWM duty cycle signal is generated based on the standard three-phase PWM duty cycle.

5. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 1, characterized in that, The step of setting analog-to-digital sampling points based on the preset dead time, the real-time SVPWM sector, and the three-phase PWM duty cycle signal to obtain a sampling trigger point sequence includes: The freewheeling detection phase is retrieved based on the real-time SVPWM sector query. The dead time window is located for the freewheeling detection phase based on the preset dead time and the three-phase PWM duty cycle signal. Calculate the center point of the dead time window and use the center point of the window as the ADC sampling trigger point; The sampling sequence of the ADC sampling trigger point is set according to the PWM period to obtain the sampling trigger point sequence.

6. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 5, characterized in that, The step of locating the dead time window of the freewheeling detection phase based on the preset dead time and the three-phase PWM duty cycle signal to obtain the dead time window includes: Based on the freewheeling detection relative to the three-phase PWM duty cycle signal, the sampled phase PWM duty cycle signal is obtained; The rising edge time point and the falling edge time point are extracted from the sampled phase PWM duty cycle signal, respectively. The rising edge dead zone offset time point corresponding to the rising edge time point and the falling edge dead zone offset time point corresponding to the falling edge time point are calculated according to the preset dead zone duration. The rising edge dead zone window corresponding to the rising edge dead zone offset time point and the falling edge dead zone window corresponding to the falling edge dead zone offset time point are calculated based on the dead zone duration. The dead time window is obtained by periodically adjusting the dead time window on the rising edge and the dead time window on the falling edge.

7. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 6, characterized in that, The step of calculating the three-phase current polarity corresponding to the real-time SVPWM sector based on the phase voltage and the three-phase bridge drive voltage includes: The freewheeling detection phase is retrieved based on the real-time SVPWM sector, and the average value of the phase voltage is used as the target phase voltage. Determine whether the target phase voltage is greater than the three-phase bridge drive voltage; If so, then the current polarity of the freewheeling detection phase is negative. If not, then the current polarity of the freewheeling detection phase is positive. Based on the real-time SVPWM sector query, the corresponding current polarities other than the freewheeling detection phase are obtained, and the current polarities of all phases are aggregated into three-phase current polarities.

8. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 1, characterized in that, The calculation of the three-phase PWM compensation value based on the dead time and the three-phase current polarity includes: The polarity of the three-phase current is mapped to a compensation direction to obtain a single-phase compensation direction group. Based on the dead time, the compensation value of each phase in the three-phase current polarity is calculated to obtain the three-phase basic compensation value group. The three-phase basic compensation value group is symbolically mapped according to the single-phase compensation direction group to obtain the three-phase mapped compensation value. The three-phase mapped compensation value is then subjected to range limiting and normalization to obtain the three-phase PWM compensation value.

9. The dead-zone compensation method for phase-free current sampling of a brushless motor according to claim 8, characterized in that, The step of compensating and updating the three-phase PWM duty cycle signal based on the three-phase PWM compensation value includes: According to the phase type of the three-phase PWM duty cycle signals, the PWM duty cycle signals are selected one by one as the target phase duty cycle signals, and the compensation value corresponding to the target phase duty cycle signal in the three-phase PWM compensation values ​​is taken as the target phase compensation value. The target phase compensation value is superimposed with the target phase compensation duty cycle signal by superimposing the duty cycle based on the rising edge position and falling edge position of the target phase duty cycle signal to obtain the target phase compensation duty cycle signal. The target phase compensation duty cycle signal is subjected to amplitude limiting processing, and the target phase duty cycle signal in the three-phase PWM duty cycle signal is updated using the amplitude-limited target phase compensation duty cycle signal.

10. A dead-zone compensation system for brushless motor phase-free current sampling, characterized in that, The system includes an SVPWM modulation module, an AD sampling module, a current polarity detection module, and a dead-time compensation module, wherein: The SVPWM modulation module is used to divide the brushless motor into sectors based on the real-time motor angle to obtain real-time SVPWM sectors and generate the three-phase PWM duty cycle signal corresponding to the real-time SVPWM sector. The AD sampling module is used to set analog and digital sampling points according to the preset dead time, the real-time SVPWM sector and the three-phase PWM duty cycle signal, to obtain the sampling trigger point sequence, and to sample the voltage of the three-phase terminals and the three-phase bridge drive terminals of the brushless motor according to the sampling trigger point sequence, so as to obtain the phase voltage and the three-phase bridge drive voltage. The current polarity detection module is used to calculate the three-phase current polarity corresponding to the real-time SVPWM sector based on the phase voltage and the three-phase bridge drive voltage. The dead-zone compensation module is used to calculate the three-phase PWM compensation value based on the dead-zone duration and the three-phase current polarity, update the three-phase PWM duty cycle signal based on the three-phase PWM compensation value, and use the updated three-phase PWM duty cycle signal to perform dead-zone compensation on the brushless motor.

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