Sensorless single-phase brushless direct current motor driving method and motor controller

Abstract

The invention discloses a sensorless single-phase brushless direct current motor driving method and a motor controller. The driving method comprises the following steps: obtaining a first back electromotive force value according to all current values and voltage reference values in a preset sampling moment; obtaining a rotor position angle and a rotor speed at the current sampling moment according to the first back electromotive force value; and generating a control signal according to the preset voltage duty ratio and the rotor position angle, and sending the control signal to a motor driver to realize driving control of the single-phase motor. According to the invention, firstly, the counter electromotive force value of the motor is estimated through the voltage reference value and the motor phase current, the current rotor position is determined, finally, the control signal is generated and the motor is driven by combining the preset voltage duty ratio and the rotor position, and a solution of the position-sensorless single-phase motor driving system based on the estimator is provided.

Description

Technical Field

[0001] The invention relates to the technical field of single-phase brushless DC motors, and in particular to a position sensorless single-phase brushless DC motor driving method and a motor controller. Background Art

[0002] Single-phase brushless DC motors are widely used in low-power fans, water pumps and other application scenarios due to their low cost. Single-phase motors usually require Hall sensors to sense the rotor position information of the motor, and the controller outputs the appropriate phase voltage based on the rotor position information to achieve efficient motor control.

[0003] In the prior art, the position sensorless driving method of a single-phase motor generally suspends the phase winding when the motor is in continuous flow during operation, determines the zero-crossing point of the back electromotive force by comparing the magnitudes of the two back electromotive forces on the inverter, and then identifies the rotor position. However, this method relies on the voltage change of the suspended phase, and the generation of the suspended phase requires rapid current continuous flow; therefore, it is difficult to apply to control areas with high duty cycles. Summary of the invention

[0004] The main purpose of the present invention is to provide a position sensorless single-phase brushless DC motor driving method and a motor controller based on an estimator, aiming to solve the problem of position sensorless single-phase motor driving under high duty cycle.

[0005] To achieve the above object, the present invention provides a method for driving a position sensorless single-phase brushless DC motor, the method comprising: Receiving a current value obtained by sampling a motor phase current, receiving a voltage reference value at a previous sampling moment, and obtaining a first back electromotive force value according to all current values ​​within a preset sampling moment and the voltage reference value; Obtaining the rotor position angle and rotor speed at the current sampling moment according to the first back electromotive force value; According to the preset voltage duty cycle and the rotor position angle, a voltage reference value and a control signal at the current sampling moment are generated, and the control signal is sent to the motor driver to realize the drive control of the single-phase motor.

[0006] Optionally, obtaining the first back electromotive force value according to all current values ​​within a preset sampling moment and the voltage reference value includes: Inputting all current values ​​within a preset sampling time and the voltage reference value into a preset back electromotive force estimation formula; The first back electromotive force value is calculated using the preset back electromotive force estimation formula.

[0007] Optionally, the preset back electromotive force estimation formula is:

[0008] Where, e(t) is the first back electromotive force value at time t, is the estimation window corresponding to the preset sampling time, α is the preset parameter, i(t) is the current value at time t, and u(t) is the voltage reference value at time t.

[0009] Optionally, obtaining the rotor position angle and the rotor speed at the current sampling moment according to the first back electromotive force value includes: Performing low-pass filtering on the first back electromotive force value to obtain a second back electromotive force value, and performing full-pass filtering on the second back electromotive force value to obtain a third back electromotive force value; The second back electromotive force value and the third back electromotive force value are input into a phase-locked loop module to obtain a rotor position angle and a rotor speed.

[0010] Optionally, the low-pass filtering of the first back electromotive force value to obtain the second back electromotive force value, and the full-pass filtering of the second back electromotive force value to obtain the third back electromotive force value, further includes: Get the rotor speed at the last sampling moment; The cutoff frequency of the low-pass filter and the center frequency of the all-pass filter are determined according to the rotor speed at the last sampling moment.

[0011] Optionally, generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle includes: Determine the voltage sector of the motor at the current moment according to the rotor position angle, the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle; The voltage reference value and control signal at the current moment are generated according to the preset voltage duty cycle, the voltage sector of the motor at the current moment, and the voltage sector of the motor at the previous moment.

[0012] Optionally, the position sensorless single-phase brushless DC motor driving method further includes: The preset first switching angle, the second switching angle, the preset third switching angle and the preset fourth switching angle are determined according to the preset first freewheeling angle and the preset first commutation angle.

[0013] Optionally, generating a voltage reference value and a control signal at a current moment according to a preset voltage duty cycle, a voltage sector of the motor at a current moment, and a voltage sector of the motor at a previous moment includes: If the voltage sector of the motor at the current moment is the same as the voltage sector of the motor at the previous moment, a voltage reference value and a control signal at the current moment are generated according to the voltage sector of the motor at the current moment and a preset voltage duty cycle; If the voltage sector of the motor at the current moment is different from the voltage sector of the motor at the previous moment, the voltage reference value and control signal at the current moment are generated according to the voltage sector of the motor at the current moment, the voltage sector of the motor at the previous moment, the preset voltage duty cycle, the rotor position angle at the previous moment and the rotor position angle at the current moment.

[0014] Optionally, generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle includes: generating a sinusoidal voltage duty cycle according to the rotor position angle and a preset voltage duty cycle; A control signal and a voltage reference value are generated according to the duty cycle of the sinusoidal voltage.

[0015] The present invention also proposes a motor controller, which is connected to a motor driver. The motor controller includes: a memory, a processor, and a motor driver program stored in the memory and executable on the processor. The motor driver program is configured to implement the steps of the position sensorless single-phase brushless DC motor driving method.

[0016] The present invention discloses a method for driving a single-phase brushless DC motor without position sensor and a motor controller, wherein the method for driving a single-phase brushless DC motor without position sensor comprises: receiving a current value obtained by sampling a motor phase current, receiving a voltage reference value at a previous sampling moment, and obtaining a first back electromotive force value according to all current values ​​within a preset sampling moment and the voltage reference value; obtaining a rotor position angle and a rotor speed at the current sampling moment according to the first back electromotive force value; generating a voltage reference value and a control signal at the current sampling moment according to a preset voltage duty cycle and the rotor position angle, and sending the control signal to a motor driver to realize the drive control of a single-phase motor. The present invention first obtains the back electromotive force value through all voltage reference values ​​within a preset sampling moment and the collected motor phase current, obtains two orthogonal sinusoidal signals through low-pass filtering and full-pass filtering of the back electromotive force value, and then inputs the back electromotive force value into a phase-locked loop module to obtain the rotor position at the current moment, and finally generates a control signal in combination with a preset voltage duty cycle to realize the drive control of the motor, thereby avoiding the motor phase being suspended, and solving the problem of driving a single-phase motor without position sensor under a high duty cycle. In addition, the sensorless single-phase brushless DC motor driving method proposed in the present invention can realize sensorless control of full voltage duty cycle. A strong robust back-electromotive force observer is established, which has low sensitivity to motor inductance and does not require permanent magnet flux parameters. Through the all-pass filter, a real-time signal with a 90° delay in the back-electromotive force signal is obtained. Compared with the recording array method, the dynamic response is high, which enhances the rapidity of the drive system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of the steps of an embodiment of a method for driving a position sensorless single-phase brushless DC motor according to the present invention; Figure 2 A schematic diagram of the steps of another embodiment of the method for driving a position sensorless single-phase brushless DC motor according to the present invention; Figure 3 It is a first control block diagram of a motor control system according to an embodiment of a method for driving a position sensorless single-phase brushless DC motor of the present invention; Figure 4 The waveform diagram of the inverter first phase voltage, the inverter second phase voltage and the rotor position angle in one electrical cycle of the position sensorless single-phase brushless DC motor driving method of the present invention; Figure 5 A schematic diagram of steps of another embodiment of a method for driving a position sensorless single-phase brushless DC motor according to the present invention; Figure 6 A second control block diagram of a motor control system according to an embodiment of a method for driving a position sensorless single-phase brushless DC motor of the present invention; Figure 7 This is a first principle diagram of a phase-locked loop according to an embodiment of a method for driving a position sensorless single-phase brushless DC motor according to the present invention.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] Single-phase brushless DC motors are widely used in low-power fans, water pumps and other application scenarios due to their low cost. Single-phase motors usually require Hall sensors to sense the rotor position information of the motor, and the controller outputs the appropriate phase voltage based on the rotor position information to achieve efficient motor control.

[0025] The present invention provides a method for driving a position sensorless single-phase brushless DC motor, aiming to solve the problem of driving a position sensorless single-phase motor under a high duty cycle.

[0026] The method for driving a position sensorless single-phase brushless DC motor comprises: Step S10, receiving the current value obtained by sampling the motor phase current, receiving the voltage reference value at the last sampling moment, and obtaining the first back electromotive force value according to all the current values ​​within the preset sampling moment and the voltage reference value; Step S20, obtaining the rotor position angle and rotor speed at the current sampling moment according to the first back electromotive force value; Step S30: Generate a voltage reference value and a control signal at the current sampling moment according to a preset voltage duty cycle and the rotor position angle, and send the control signal to the motor driver to realize drive control of the single-phase motor.

[0027] It should be noted that back electromotive force (BEMF) refers to the voltage induced in the stator winding due to the rotation of the rotor during the operation of the motor. Specifically, back electromotive force is the voltage signal generated by the motor stator cutting the rotor magnetic field during the operation of the motor. By estimating the back electromotive force, the actual position and speed of the rotor can be calculated, thereby achieving precise control of the motor.

[0028] For a brushless DC motor, the voltage equation can be expressed as: , Among them, u is the phase voltage, R is the resistance of the motor winding, i is the phase current, e is the back electromotive force, and L is the motor inductance.

[0029] It should be noted that the present invention implements the sampling of phase current through a current sampling module. Therefore, the current value obtained by sampling the motor phase current at the current sampling moment can be obtained through the current sampling module. It is easy to understand that the position sensorless single-phase brushless DC motor driving method of the present invention is applied to the motor controller, the phase current of the motor is an analog quantity, and the interval time between two adjacent sampling moments is affected by the operating frequency of the analog-to-digital converter in the motor controller or the current sampling module. Specifically, the operating frequency of the processor in the analog-to-digital converter affects the interval time. Considering that the level of the processor's operating frequency is generally greater than the kHz level, that is, the time interval is less than 1ms.

[0030] The running state of the motor changes dynamically. The back electromotive force is the voltage generated by the motor when it rotates, which is closely related to the speed and rotor position of the motor. Unlike multi-phase motors, single-phase motors have only one back electromotive force signal. Therefore, how to generate stable angle and speed signals through a back electromotive force signal becomes a difficult problem that needs to be solved. It should be noted that in the control method without position sensor, the voltage reference value at the last sampling moment can simplify the control algorithm, reduce the dependence on real-time calculation, and reduce the calculation burden. In addition, during the motor control process, the current and voltage signals may be affected by noise. Using the voltage reference value at the last sampling moment helps to obtain more stable results. In addition, the phase current value at the current sampling moment is the result of the phase voltage action of the previous cycle. Therefore, it is reasonable to use the voltage reference value at the last sampling moment. It should be noted that the preset sampling moment can be the current sampling moment, and the last sampling moment is specifically the last sampling moment of the preset sampling moment.

[0031] The step of obtaining a first back electromotive force value according to all current values ​​within a preset sampling time and the voltage reference value comprises: Inputting all current values ​​within a preset sampling time and the voltage reference value into a preset back electromotive force estimation formula; The first back electromotive force value is calculated using the preset back electromotive force estimation formula.

[0032] The preset back electromotive force estimation formula is:

[0033] Where, e(t) is the first back electromotive force value at time t, is the estimation window corresponding to the preset sampling time, =nT, usually the value of n can be selected from 3 to 50, T is the interval between adjacent sampling moments. α is the preset parameter, i(t) is the current value at time t, and u(t) is the voltage reference value at time t. and In <0, yes , .

[0034] It should be noted that the preset sampling moment is the first n sampling moments including the current sampling moment, and the value of n can usually be selected as 3~50. α is a coefficient that makes u(t) and di(t) / dt in the same order of magnitude, which is determined by the designer. The above formula is a calculation formula for the continuous domain. The present invention does not give a specific calculation formula in the digital system. In practical applications, a variety of numerical methods can be used for discretization and solved according to the current value and voltage reference value within the preset sampling moment. There is no restriction here. It is worth noting that the current value and voltage reference value at a single moment may be affected by instantaneous fluctuations. The above calculation formula uses the result of integrating multiple current values ​​and voltage reference values. Therefore, it can greatly reduce the influence of white noise in the signal on the estimation result, and improve the estimation accuracy and anti-interference ability.

[0035] It should be noted that the voltage drop on the resistor is small when the motor is running, and the current is generally in phase with the back electromotive force, so the influence of the voltage drop on the resistor is ignored in the above calculation. In practical applications, if the designer wants to add the voltage drop on the resistor to the calculation, just replace u(t) in the formula with u(t)-Ri(t).

[0036] After obtaining the first back electromotive force value, the rotor position angle and the rotor speed at the current sampling moment are obtained according to the first back electromotive force value.

[0037] Back EMF is closely related to the speed and position of the rotor. In the sensorless control method, back EMF is used as important information to infer the rotor position. Based on the known first back EMF value, the controller processes the first back EMF value and extracts two stable orthogonal sinusoidal signals. These processed signals can more accurately reflect the current rotor position and rotor speed.

[0038] The obtaining of the rotor position angle and the rotor speed at the current sampling moment according to the first back electromotive force value includes: Step S210, low-pass filtering the first back electromotive force value to obtain a second back electromotive force value, and full-pass filtering the second back electromotive force value to obtain a third back electromotive force value; Step S220: input the second back electromotive force value and the third back electromotive force value into a phase-locked loop module to obtain a rotor position angle and a rotor speed.

[0039] It should be noted that in motor control, the back electromotive force signal may contain high-frequency noise (such as electrical interference, switching noise, etc.), which will have a negative impact on the subsequent control algorithm. In order to improve the signal based on a more real and stable signal, the first back electromotive force value is first low-pass filtered to filter out the high-frequency component to obtain the second back electromotive force. Since the phase-locked loop that tracks one sine wave signal is not as effective as the phase-locked loop that tracks two orthogonal sine signals, the present invention performs full-pass filtering on the second back electromotive force, and uses the characteristic of changing the phase of the signal without changing its amplitude to adjust the phase of the second back electromotive force signal to obtain a real-time signal that delays the second back electromotive force by 90°, thereby improving the control accuracy, and compared with the recording array method, the dynamic response is high, which enhances the rapidity of the drive system.

[0040] Figure 7 A schematic diagram of a phase-locked loop module is provided. represents the second back EMF, represents the third back EMF, θ r is the rotor angle reference value, is the estimated value of the rotor angle, K p is the proportional operation coefficient, K i is the integral operation coefficient. It is easy to get that ω r ψ f [cos( θ r )sin( )-sin( θ r )cos( )]=ω r ψ f sin( - θ r ), when sin( - θ r ) is a smaller number, sin( - θ r )= - θr =Δ θ r Therefore, the input signal of this module contains the rotor position difference information. Designers can adjust K p With K i The response speed of the phase-locked loop can be adjusted. As a common means of tracking phase in control systems, there is a lot of information on the control framework, design process and parameter selection of the phase-locked loop, which will not be described in detail here.

[0041] It should be noted that the speed of the motor may change during operation, which will affect the back electromotive force signal characteristics of the motor. In order to ensure that high-frequency noise can be effectively suppressed at different speeds while retaining useful signal components. The method of obtaining the rotor position angle at the current sampling moment according to the first back electromotive force value also includes: Get the rotor speed at the last sampling moment; The cutoff frequency of the low-pass filter and the center frequency of the all-pass filter are determined according to the rotor speed at the last sampling moment.

[0042] It is easy to understand that changes in rotor speed will cause changes in the frequency components of the back EMF signal. If the filter cutoff frequency is fixed, it may cause important signals to be filtered out or noise to be effectively suppressed. By dynamically adjusting the cutoff frequency, the accuracy of signal processing can be improved to ensure that the state information of the motor can be accurately extracted under different operating conditions. By adjusting the filter cutoff frequency according to the rotor speed, it can be ensured that high-frequency noise can be effectively suppressed at different speeds while retaining useful signal components. The signal delay phase of the all-pass filter is closely related to the center frequency, so the generation of a third back EMF signal that delays the second back EMF signal by 90° can only be guaranteed when the rotor speed is accurate.

[0043] Step S30: Generate a voltage reference value and a control signal at the current sampling moment according to a preset voltage duty cycle and the rotor position angle, and send the control signal to the motor driver to realize drive control of the single-phase motor.

[0044] It should be noted that the preset voltage duty cycle refers to a parameter that characterizes the length of time that the voltage signal is at a high level within an electrical cycle. The preset voltage duty cycle is used to control the output power and speed of the motor, and is usually set by the system designer based on the characteristics of the motor and application requirements. In actual applications, the preset voltage duty cycle is directly obtained from the external command duty cycle, or is generated by the external command speed through a speed loop. The rotor position angle represents the angular position of the motor rotor at the current moment.

[0045] It is worth noting that the present invention provides two PWM drive modes, the first of which is a square wave mode, in which the inverter applies a voltage corresponding to a preset voltage duty cycle to the first phase or the second phase in different sectors, respectively, and during the sector switching cycle, the voltage duty cycle corresponding to the preset voltage duty cycle and the rotor position angle is calculated and applied, thereby realizing a single-phase brushless DC motor drive with a fixed frequency square wave control. The second is a sine wave mode, in which the controller calculates a real-time sinusoidal voltage duty cycle according to the rotor position angle and the preset voltage duty cycle, and applies a corresponding voltage to the first phase or the second phase of the inverter according to the sinusoidal voltage duty cycle.

[0046] The present invention discloses a method for driving a single-phase brushless DC motor without a position sensor and a motor controller, wherein the method for driving a single-phase brushless DC motor without a position sensor comprises: receiving a current value obtained by sampling a motor phase current, receiving a voltage reference value at a previous sampling moment, and obtaining a first back electromotive force value according to all current values ​​within a preset sampling moment and the voltage reference value; obtaining a rotor position angle and a rotor speed at a current sampling moment according to the first back electromotive force value; generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle, and sending the control signal to a motor driver to realize drive control of the single-phase motor. The present invention first obtains the back electromotive force value by presetting all the voltage reference values ​​and the collected motor phase current within the sampling time, obtains two orthogonal sinusoidal signals through low-pass filtering and full-pass filtering of the back electromotive force value, and then inputs the back electromotive force value into the phase-locked loop module to obtain the rotor position at the current moment, and finally generates a control signal in combination with the preset voltage duty cycle to realize the drive control of the motor, avoids the motor phase being suspended, solves the problem of driving a single-phase motor without a position sensor under a high duty cycle, and uses the motor model to build an estimator, which can realize high-performance control of a single-phase motor without a position sensor. In addition, the method for driving a single-phase brushless DC motor without a position sensor proposed in the present invention can realize the control of a full voltage duty cycle without a position sensor. A strong robust back electromotive force observer is established, which has low sensitivity to the motor inductance and does not require the permanent magnet flux linkage parameters. Through the full-pass filter, a real-time signal with a 90° delay of the back electromotive force signal is obtained. Compared with the method of recording an array, the dynamic response is high, and the rapidity of the drive system is enhanced.

[0047] refer to Figure 3 In order to facilitate the understanding of the present invention, an application example is proposed. Figure 3This is the control block diagram of the motor control system. The motor control system includes a motor, an inverter, a driver, a current sampling module, and a controller. The inverter is connected to a DC voltage source. The DC voltage source supplies power to the entire system. The current sampling module collects the motor phase current and inputs it into the controller. The controller generates control logic based on the motor phase current and the motor phase voltage and sends it to the driver. The driver drives the power device to control the voltage of the first phase of the inverter and the second phase of the inverter, ultimately achieving the effect of controlling the motor.

[0048] The step of generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle comprises: Step S310, determining the voltage sector of the motor at the current moment according to the rotor position angle, the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle; Step S320, generating a voltage reference value and a control signal at the current moment according to a preset voltage duty cycle, a voltage sector of the motor at the current moment, and a voltage sector of the motor at the previous moment.

[0049] It is easy to understand that there are multiple sectors for square wave control of a single-phase motor, and different voltage sectors correspond to different voltage application strategies. By selecting a suitable driving strategy according to the voltage sector in which the rotor is located, the energy loss of the motor can be effectively reduced. The present invention divides the entire electrical cycle into the first to fourth voltage sectors by presetting the first to fourth switching angles, which correspond to the motor in different working stages, such as the first voltage sector, the second voltage sector, the third voltage sector and the fourth voltage sector.

[0050] Optionally, the division method of the voltage sectors and the angle regions corresponding to the voltage sectors will affect the motor control strategy. The position sensorless single-phase brushless DC motor driving method also includes: Calculate a preset first switching angle, a second switching angle, a preset third switching angle, and a preset fourth switching angle according to a preset first freewheeling angle and a preset first commutation angle; It should be noted that the freewheeling angle is the angle at which the two-phase lower bridge is pulled low and the current flows from the ground wire after the motor is driven in one phase. The setting of the freewheeling angle can ensure that the motor current is at a smaller value when the next phase is driven, avoiding the energy in the motor equivalent inductance from flowing into the bus and causing the bus voltage to overshoot. The commutation angle is the angle at which the motor switches between different phases. The setting of the commutation angle determines the relative position of the motor current and the back electromotive force during the rotation of the motor, thereby achieving more efficient drive.

[0051] Specifically, the following is the numerical relationship between the switching angles. The preset first switching angle is equal to the preset first commutation angle, the preset second switching angle is equal to 180 degrees plus the preset first commutation angle minus the preset first freewheeling angle, the preset third switching angle is equal to 180 degrees plus the preset first commutation angle, and the preset fourth switching angle is equal to 360 degrees plus the preset first commutation angle minus the preset first freewheeling angle.

[0052] It is easy to understand that this setting method can generate symmetrical voltage sectors to apply voltage to the first phase of the inverter and the second phase of the inverter respectively and insert the same freewheeling time in the middle. Adjust the preset first commutation angle, that is, adjust the relative position of the current and the motor back electromotive force. Adjust the preset first freewheeling angle, that is, adjust the freewheeling time of the motor. It is worth noting that when the preset first commutation angle is set to a positive number, it is equivalent to all sectors being translated backward by a certain angle relative to the rotor position angle; when the preset first commutation angle is set to a negative number, it is equivalent to all sectors being translated forward by a certain angle relative to the rotor position angle. The preset first freewheeling angle and the preset first commutation angle are determined by the R&D personnel. The preset first freewheeling angle adjusts the length of the controller's freewheeling time. Usually, this value should increase at high speeds, and the specific value can be set by the user according to the actual application. The preset first commutation angle determines the commutation angle, which can be adjusted by the user according to the current waveform or automatically matched by the controller.

[0053] The voltage sector in which the motor is currently located is determined based on the rotor position angle, the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle. Specifically, if the rotor position angle is greater than the preset first switching angle and less than the preset second switching angle, it is in the first voltage sector; if the rotor position angle is greater than the preset second switching angle and less than the preset third switching angle, it is in the second voltage sector; if the rotor position angle is greater than the preset third switching angle and less than the preset fourth switching angle, it is in the third voltage sector; if the rotor position angle is greater than the preset fourth switching angle and less than the preset first switching angle, it is in the fourth voltage sector.

[0054] It is easy to understand that due to the problem of periodic step in angle, the greater than and less than mentioned above are not absolute. For example, 350° is less than 360°, and 360° is equal to 0°, so 350° is less than 0°, that is, when judging the size of the angle, it is necessary to consider the position of the angle in the entire angle period, and what is judged is the lead and lag of the relative position of the angle, rather than directly comparing the absolute size.

[0055] The voltage sector of the motor at the current moment is determined according to the rotor position angle, the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle; the voltage sector of the motor rotor is determined specifically according to the comparison relationship between the rotor position angle and the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle. It should be noted that the specific values ​​of the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle can be independently set by the R&D personnel, or can be determined by the numerical relationship between the above switching angles.

[0056] The method generates a voltage reference value and a control signal at a current moment according to a preset voltage duty cycle, a voltage sector at a current moment, and a voltage sector at a previous moment, including: if the motor is in a first voltage sector at a current moment, a preset voltage duty cycle is applied to the first phase of the inverter, the lower bridge of the second phase of the inverter is turned on, and the voltage reference value is the preset voltage duty cycle multiplied by the bus voltage; if the motor is in a second voltage sector at a current moment, the lower bridge of the first phase of the inverter and the lower bridge of the second phase of the inverter are turned on, and the voltage reference value is zero; if the motor is in a third voltage sector at a current moment, a preset voltage duty cycle is applied to the second phase of the inverter, the lower bridge of the first phase of the inverter is turned on, and the voltage reference value is the preset voltage duty cycle multiplied by the negative of the bus voltage; if the motor is in a fourth voltage sector at a current moment, the lower bridge of the first phase of the inverter and the lower bridge of the second phase of the inverter are turned on, and the voltage reference value is zero.

[0057] It is easy to understand that there are multiple sectors for square wave control of single-phase motors. Different voltage sectors correspond to different voltage application strategies. By selecting the appropriate drive strategy according to the voltage sector where the rotor is located, the energy loss of the motor can be effectively reduced. Different voltage sectors have different current and voltage requirements during motor operation. A reasonable motor control strategy for the voltage sector can enable the motor to operate in the best working state and improve overall energy efficiency.

[0058] In each voltage sector, the driving mode and voltage reference value of the motor will be different. By matching the rotor position angle with the preset voltage sector, the voltage to be applied to the motor at this position and the corresponding control strategy can be determined. In combination with the preset voltage duty cycle, the voltage reference value and control signal at the current sampling moment are generated. Specifically, after determining the voltage duty cycle and the voltage sector, the control system calculates the voltage reference value output at the current rotor position. The voltage reference value is obtained by multiplying the preset voltage duty cycle with the bus voltage. The control signal is an instruction to the motor driver, which determines the actual operating state of the motor. It should be explained that the present position sensorless single-phase brushless DC motor driving method is applied to a motor controller, the motor controller is connected to the motor through a motor driver, and the motor driver is connected to the motor; the motor controller controls the motor driver to realize the drive control of the single-phase motor by sending a control signal to the motor driver.

[0059] Optionally, in order to ensure the smooth operation and control accuracy of the motor when the motor rotor switches between different voltage sectors, the present invention proposes a transition carrier voltage duty cycle. In single-phase motor control, changes in the rotor position angle may cause the switching of voltage sectors. In the carrier switching of the voltage sector, the problem of the front part being the previous voltage sector and the rear part being the next voltage sector occurs. At this time, the transition carrier voltage duty cycle is introduced, and the voltage vectors of the two voltage sectors are synthesized into one by calculation, and the required voltage is accurately output to achieve high-performance and stable control.

[0060] In one embodiment of the present invention, the step of generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle includes: Determine the voltage sector of the motor at the current moment according to the rotor position angle, the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle; The voltage reference value and control signal at the current moment are generated according to the preset voltage duty cycle, the voltage sector of the motor at the current moment, and the voltage sector of the motor at the previous moment.

[0061] Specifically, as the motor rotor rotates, the voltage sector where the rotor is located at the current moment and the previous moment may be the same or may be different.

[0062] If the voltage sector of the motor at the current moment is the same as the voltage sector of the motor at the previous moment, a voltage reference value and a control signal at the current moment are generated according to the voltage sector of the motor at the current moment and a preset voltage duty cycle; If the voltage sector of the motor at the current moment is different from the voltage sector of the motor at the previous moment, the voltage reference value and control signal at the current moment are generated according to the voltage sector of the motor at the current moment, the voltage sector of the motor at the previous moment, the preset voltage duty cycle, the rotor position angle at the previous moment and the rotor position angle at the current moment.

[0063] It is particularly pointed out that at each sampling moment, it is determined whether the voltage sector where the motor rotor is located is the same as the voltage sector where the motor rotor was located at the previous moment, and then corresponding measures are taken according to different situations.

[0064] Reference Figure 4 , Figure 4 is the first phase voltage U1 of the inverter, the second phase voltage U2 of the inverter and the rotor position angle in one electrical cycle θ 1 Waveform diagram of . To preset the first switching angle, To preset the second switching angle, To preset the third switching angle, is a preset fourth switching angle. In the first sector, U1 is a voltage with a preset voltage duty cycle, in the third sector, U2 is a voltage with a preset voltage duty cycle, and in the second voltage sector and the fourth voltage sector, U1 and U2 are zero.

[0065] When the first voltage sector is switched to the second voltage sector, the voltage duty cycle of the transition carrier is calculated by the following formula:

[0066] in, is the voltage duty cycle when the first voltage sector switches to the second voltage sector, is the preset voltage duty cycle, θ 1(k+1) like Figure 4 Where is the rotor position angle at the last sampling moment of the first voltage sector, θ 1(k+2) like Figure 4 Where is the rotor position angle at the first sampling moment of the second voltage sector.

[0067] When the second voltage sector is switched to the third voltage sector, the voltage duty cycle of the transition carrier is calculated by the following formula:

[0068] in, is the voltage duty cycle when the second voltage sector switches to the third voltage sector, θ 1(k+4) like Figure 4 Where is the rotor position angle at the last sampling moment of the second voltage sector, θ1(k+5) like Figure 4 Where is the rotor position angle at the first sampling moment of the third voltage sector.

[0069] Similarly, the voltage duty cycle calculation formula of the transition carrier switching from the third voltage sector to the fourth voltage sector is similar to the voltage duty cycle calculation formula of the transition carrier switching from the first voltage sector to the second voltage sector; the voltage duty cycle calculation formula of the transition carrier switching from the fourth voltage sector to the first voltage sector is similar to the voltage duty cycle calculation formula of the transition carrier switching from the second voltage sector to the third voltage sector, so it will not be repeated here.

[0070] It is easy to understand that the voltage reference value and the control signal need to be matched according to the sectors crossed. For example, when the voltage sector is switched from the first voltage sector to the second voltage sector, the duty is applied to the first phase of the inverter. 12 The voltage duty cycle is 100%, the second phase lower bridge of the inverter is turned on, and the voltage reference value is Duty 12 Multiply the bus voltage; when the voltage sector switches from the second voltage sector to the third voltage sector, a duty is applied to the second phase of the inverter. 23 The voltage duty cycle is 100%, the first phase lower bridge of the inverter is turned on, and the voltage reference value is Duty 23 When the voltage sector is switched from the third voltage sector to the fourth voltage sector and when the voltage sector is switched from the fourth voltage sector to the first voltage sector, the situation is as follows: Figure 4 As shown, no further description is given here.

[0071] The above describes the method for generating the voltage reference value and the control signal in the square wave driving mode. In one embodiment of the present invention, the estimator in the controller of the present invention can also be used in a sine wave driven position sensorless single-phase DC brushless motor driving system. The voltage reference value and the control signal at the current sampling moment are generated according to the preset voltage duty cycle and the rotor position angle, including: generating a sinusoidal voltage duty cycle according to the rotor position angle and a preset voltage duty cycle; A control signal and a voltage reference value are generated according to the duty cycle of the sinusoidal voltage.

[0072] Specifically, the sinusoidal voltage duty cycle is calculated according to a sinusoidal voltage duty cycle generation formula; The sinusoidal voltage duty cycle generation formula is:

[0073] Among them, Duty sin(k) is the duty cycle of the sinusoidal voltage at time k, θ 1(k) is the rotor position angle at time k, and Δθ is the angle offset.

[0074] It is easy to understand that the equation generates a sinusoidal voltage duty cycle signal. By adjusting the magnitude of the preset voltage duty cycle, the amplitude of the sinusoidal signal can be adjusted, thereby adjusting the magnitude of the motor current. By adjusting the angle offset, the phase of the sinusoidal signal can be adjusted, thereby adjusting the phase relationship between the motor current and the motor back electromotive force. The angle offset is adjusted by the user according to the control waveform or automatically adjusted by a designed algorithm by the program.

[0075] Generate a control signal and a voltage reference value according to the voltage duty cycle, and send the control signal to the motor driver to achieve the drive control of the single-phase motor. When the sinusoidal voltage duty cycle is positive, apply the corresponding voltage duty cycle to the first phase of the inverter. When the sinusoidal voltage duty cycle is negative, apply the corresponding voltage duty cycle to the second phase of the inverter. The voltage reference value is the product of the sinusoidal voltage duty cycle and the bus voltage.

[0076] It is easy to understand that the estimator provided by the present invention can also be used in a single-phase motor drive system driven by a sine wave. When using sine wave control, although the maximum output power of the motor is not as good as square wave control, it has certain advantages in terms of motor vibration and noise, so it is also applied to a considerable degree of actual products. At the same time, the estimator proposed by the present invention only needs the current value of the motor and the voltage reference value to estimate the rotor position and speed of the motor. Therefore, it is not limited to the above two voltage drive methods, but can be applied to any drive method that can perform current sampling.

[0077] Refer to Figure 6 , Figure 6 As shown, the motor control system topology only places a sampling resistor on the bus branch, so the current cannot be sampled during freewheeling. The above sensorless single-phase brushless DC motor control technology can also be applied to this topology. When using square wave control, since the phase current cannot be sampled during freewheeling, the preset freewheeling angle should be set to zero or a very small value. It can be approximately considered that the motor phase current does not change during the freewheeling time. When using sine wave control, since the drive signal of the motor is a sinusoidal voltage signal, the phase current flows through the sampling resistor on the bus branch in each carrier cycle, so there is no sampling problem and it can be directly used.

[0078] The present invention also proposes a motor controller. The motor controller is connected to the motor driver. The motor controller includes: a memory, a processor, and a motor drive program stored on the memory and executable on the processor. The motor drive program is configured to implement the steps of the sensorless single-phase brushless DC motor drive method.

[0079] The specific steps of the position sensorless single-phase brushless DC motor driving method refer to the above embodiments. Since the motor controller adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0080] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for driving a position sensorless single-phase brushless DC motor, characterized in that: The method for driving a position sensorless single-phase brushless DC motor comprises: Receiving a current value obtained by sampling a motor phase current, receiving a voltage reference value at a previous sampling moment, and obtaining a first back electromotive force value according to all current values ​​within a preset sampling moment and the voltage reference value; Obtaining the rotor position angle and rotor speed at the current sampling moment according to the first back electromotive force value; According to the preset voltage duty cycle and the rotor position angle, a voltage reference value and a control signal at the current sampling moment are generated, and the control signal is sent to the motor driver to realize the drive control of the single-phase motor.

2. The method for driving a position sensorless single-phase brushless DC motor according to claim 1, wherein: The step of obtaining a first back electromotive force value according to all current values ​​within a preset sampling time and the voltage reference value comprises: Inputting all current values ​​within a preset sampling time and the voltage reference value into a preset back electromotive force estimation formula; The first back electromotive force value is calculated using the preset back electromotive force estimation formula.

3. The method for driving a position sensorless single-phase brushless DC motor as claimed in claim 2, characterized in that: The preset back electromotive force estimation formula is: Where, e(t) is the first back electromotive force value at time t, is the estimation window corresponding to the preset sampling time, α is the preset parameter, i(t) is the current value at time t, and u(t) is the voltage reference value at time t.

4. The method for driving a position sensorless single-phase brushless DC motor according to claim 1, wherein: The obtaining of the rotor position angle and the rotor speed at the current sampling moment according to the first back electromotive force value includes: Performing low-pass filtering on the first back electromotive force value to obtain a second back electromotive force value, and performing full-pass filtering on the second back electromotive force value to obtain a third back electromotive force value; The second back electromotive force value and the third back electromotive force value are input into a phase-locked loop module to obtain a rotor position angle and a rotor speed.

5. The method for driving a position sensorless single-phase brushless DC motor as claimed in claim 4, characterized in that: The method of low-pass filtering the first back electromotive force value to obtain a second back electromotive force value, and full-pass filtering the second back electromotive force value to obtain a third back electromotive force value, further includes: Get the rotor speed at the last sampling moment; The cutoff frequency of the low-pass filter and the center frequency of the all-pass filter are determined according to the rotor speed at the last sampling moment.

6. The method for driving a position sensorless single-phase brushless DC motor as claimed in claim 1, characterized in that: The step of generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle comprises: Determine the voltage sector of the motor at the current moment according to the rotor position angle, the preset first switching angle, the preset second switching angle, the preset third switching angle and the preset fourth switching angle; The voltage reference value and control signal at the current moment are generated according to the preset voltage duty cycle, the voltage sector of the motor at the current moment, and the voltage sector of the motor at the previous moment.

7. The method for driving a position sensorless single-phase brushless DC motor according to claim 6, wherein: The position sensorless single-phase brushless DC motor driving method further comprises: The preset first switching angle, the second switching angle, the preset third switching angle and the preset fourth switching angle are determined according to the preset first freewheeling angle and the preset first commutation angle.

8. The method for driving a position sensorless single-phase brushless DC motor as claimed in claim 6, characterized in that: The method of generating a voltage reference value and a control signal at the current moment according to a preset voltage duty cycle, a voltage sector of the motor at the current moment, and a voltage sector of the motor at the previous moment comprises: If the voltage sector of the motor at the current moment is the same as the voltage sector of the motor at the previous moment, a voltage reference value and a control signal at the current moment are generated according to the voltage sector of the motor at the current moment and a preset voltage duty cycle; If the voltage sector of the motor at the current moment is different from the voltage sector of the motor at the previous moment, the voltage reference value and control signal at the current moment are generated according to the voltage sector of the motor at the current moment, the voltage sector of the motor at the previous moment, the preset voltage duty cycle, the rotor position angle at the previous moment and the rotor position angle at the current moment.

9. The method for driving a position sensorless single-phase brushless DC motor according to claim 1, wherein: The step of generating a voltage reference value and a control signal at a current sampling moment according to a preset voltage duty cycle and the rotor position angle comprises: generating a sinusoidal voltage duty cycle according to the rotor position angle and a preset voltage duty cycle; A control signal and a voltage reference value are generated according to the duty cycle of the sinusoidal voltage.

10. A motor controller, characterized in that: The motor controller is connected to the motor driver, and the motor controller includes: a memory, a processor, and a motor driver program stored in the memory and executable on the processor, wherein the motor driver program is configured to implement the steps of the position sensorless single-phase brushless DC motor driving method as described in any one of claims 1 to 9.

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