A control method and device for solving low-speed noise of brushless blower

Abstract

The present invention relates to a control method for solving the low-speed noise of a brushless blower, which comprises the following steps: the motor is started, and the given speed of the brushless motor in the brushless blower is judged by the control chip MCU whether it is less than the set speed; if it is judged to be "yes", the brushless blower is judged to be in a low-speed state, and the back electromotive force detection method is executed; if it is judged to be "no", the brushless blower is judged to be in a medium-high speed state, and the FOC control algorithm is executed; and the angle is seamlessly connected according to the angle calculated in the back electromotive force detection method and the angle estimated by the observer in the FOC control algorithm to realize seamless switching of different speed states; a control device for realizing the control method is also provided, including a single resistor, a three-phase bridge and a control chip MCU connected by signals. The present invention adopts the back electromotive force detection method to run in the low-speed stage to avoid the noise caused by phase shift, and at the same time, the FOC control algorithm is still used for calculation at medium and high speeds through the seamless angle connection, so as to ensure the dynamic response characteristics and measurement accuracy of the motor.

Description

Technical Field

[0001] The invention relates to the technical field of blowers, in particular to a control method and device for solving the low-speed noise of a brushless blower. Background Art

[0002] As people's production and living standards improve, they have higher requirements for the comfort level during vehicle use. Especially with the rapid development of new energy vehicles, without the noise of the engine, the noise of many parts will become prominent. Therefore, it is particularly important to improve the noise of automobile products.

[0003] Nowadays, most of the technical solutions used by blowers are dual-resistor FOC solutions or single-resistor FOC solutions.

[0004] The dual-resistance FOC scheme samples the phase current by connecting a sampling resistor in series to any two lower bridge arms of the full-bridge inverter circuit, collecting voltage signals from both ends of the sampling resistors R1 and R2, passing through the back-end operational amplifier and AD device, and then calculating the phase current. The dual-resistance sampling circuit is shown in Figure 1 As shown, because it requires two sampling resistors and corresponding operational amplifier circuits, it will lead to high costs;

[0005] The principle of single resistor FOC sampling is to reconstruct the phase current of the motor by measuring the instantaneous current of the DC bus according to the different switching states of the power bridge. R is the sampling resistor connected in series in the bus. After the subsequent op amp circuit and AD sampling, the three-phase current reconstruction can be completed. The sampling circuit is as follows: Figure 2 As shown. Since this scheme needs to sample two currents in one cycle and then synthesize the third current. Therefore, when the vector changes to the critical point of another vector, such as Figure 3 In a, the interval between PWM2H and PWM3H is very small, which results in too little time for ADC to measure the phase current, and ADC cannot accurately collect the current. Then the sampling will be biased, resulting in sampling errors. Therefore, phase shifting is required, such as Figure 3 b. Expand the time window of non-zero voltage vector action, modify the modulation mode of SVPWM, and adopt asymmetric PWM output mode to ensure that they are not less than the minimum sampling time. Therefore, such a phase shift strategy will cause a △u between the real voltage and Vs (the vector sum of dq axis voltages Vd and Vq, the size of which can be obtained by taking the square root of the sum of the squares of the two) calculated by the FOC vector control block diagram, thus causing noise;

[0006] The advantages of single-resistance FOC sampling are its simplicity, economy and accuracy. Compared with dual-resistance sampling, single-resistance sampling can save circuit size and cost while still maintaining high measurement accuracy. The dual-resistance solution is more expensive than the single-resistance solution, but the low-speed noise of the single-resistance FOC solution is large, so it is particularly important to improve the low-speed noise of the single-resistance FOC. Summary of the invention

[0007] In view of the above problems, the present invention provides a control method and device for solving the low-speed noise of a brushless blower, which adopts a back-electromotive force detection method to operate at a low speed stage and still adopts a FOC control algorithm to operate at a medium and high speed stage.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a control method for solving the low-speed noise of a brushless blower, comprising the following steps:

[0009] S1, the motor starts, and the control chip MCU determines whether the given speed of the brushless motor in the brushless blower is less than the set speed;

[0010] S2, if the judgment in S1 is "yes", it is determined that the brushless blower is in a low speed state, the back electromotive force detection method is executed, and the process goes to step S4;

[0011] S3, if the judgment in S1 is "No", it is determined that the brushless blower is in a medium-high speed state, and the FOC control algorithm is executed, and the process goes to step S5;

[0012] S4, the motor is running, the back-EMF detection method is executed to calculate the angle, and the FOC control algorithm is executed synchronously to calculate the observer estimated angle;

[0013] S5, the motor runs and the FOC control algorithm is executed;

[0014] S6, step S1 is continuously executed during the operation of the motor, and the angle is seamlessly connected according to the angle calculated in the back electromotive force detection method and the angle estimated by the observer to achieve seamless switching of different speed states.

[0015] Preferably, the back-EMF detection method in step S2 detects the back-EMF voltage of the motor through an ADC, and compares the back-EMF voltage with the suspended phase voltage to obtain the back-EMF zero-crossing point, thereby obtaining the rotor position and realizing motor commutation.

[0016] The present invention also provides a control device for solving the low-speed noise of a brushless blower. The control device includes a single resistor, a three-phase bridge and a control chip MCU, all of which are arranged on a motor control board. The control chip MCU is used to control the execution of a back-electromotive force detection method and a FOC control algorithm. One end of the three-phase bridge is connected to the control chip MCU signal, and the other end of the three-phase bridge is connected to the single resistor signal. At the same time, the single resistor is a sampling resistor connected in series in the bus.

[0017] Preferably, the control chip MCU adopts the SPD1179 chip from Xuanzhi.

[0018] Preferably, the three-phase bridge is composed of six power switch tubes, which are divided into three groups. Each of the three groups contains two upper and lower switch tubes and corresponds to the three-phase winding of the motor respectively. The three-phase bridge generates a three-phase sinusoidal voltage through periodic switching actions, and the operation of each power switch tube is controlled by a pulse width modulation PWM signal.

[0019] Preferably, the power switch tube is MOSFET or IGBT.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Compared with the dual-resistance FOC sampling scheme, the single-resistance FOC sampling scheme in the present invention can save circuit size and cost while still maintaining a high measurement accuracy. Secondly, the single-resistance FOC scheme adopts the back-electromotive force detection method in the low-speed stage to avoid the noise caused by phase shift, and the angle seamless connection is used during the speed switching process to avoid the oscillation of current and speed. At the same time, the present invention still adopts the FOC control algorithm calculation at medium and high speeds to ensure the dynamic response characteristics of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a double resistor sampling circuit diagram;

[0023] Figure 2 It is a single resistor sampling circuit diagram;

[0024] Figure 3 It is a schematic diagram comparing the PWM waveform before and after phase shift in the single resistor FOC solution of the prior art (3a is the waveform diagram before PWM phase shift, 3b is the waveform diagram after PWM phase shift);

[0025] Figure 4 It is a diagram of the back electromotive force (BEMF) voltage detected by the ADC operational amplifier detection method of the present invention;

[0026] Figure 5 is a comparison diagram of BEMF voltage and VBUS / 2 in the present invention;

[0027] Figure 6It is the FOC control block diagram of the present invention;

[0028] Figure 7 It is a schematic diagram of the flow chart of different speed switching execution schemes of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined Figure 1-7 The present invention is described in detail. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0030] A control method and device for solving low-speed noise of a brushless blower, comprising the following steps:

[0031] S1, the motor starts, and the control chip MCU determines whether the given speed of the brushless motor in the brushless blower is less than the set speed;

[0032] S2, if the judgment in S1 is "yes", it is determined that the brushless blower is in a low speed state, the back electromotive force detection method is executed, and the process goes to step S4;

[0033] Specifically, the back-EMF detection method detects the back-EMF voltage of the motor through the ADC, and compares the back-EMF voltage with the suspended phase voltage to obtain the back-EMF zero-crossing point, thereby obtaining the rotor position and realizing the motor commutation;

[0034] S3, if the judgment in S1 is "No", it is determined that the brushless blower is in a medium-high speed state, and the FOC control algorithm is executed, and the process goes to step S5;

[0035] S4, the motor is running, the back-EMF detection method is executed to calculate the angle, and the FOC control algorithm is executed synchronously to calculate the observer estimated angle;

[0036] S5, the motor runs and the FOC control algorithm is executed;

[0037] S6, step S1 is continuously executed during the operation of the motor, and the angle is seamlessly connected according to the angle calculated in the back electromotive force detection method and the angle estimated by the observer to achieve seamless switching of different speed states.

[0038] The present invention also provides a control device for implementing the above-mentioned control method, including a single resistor, a three-phase bridge and a control chip MCU all of which are arranged on a motor control board. The control chip MCU is used to control the execution of the back electromotive force detection method and the FOC control algorithm. In this solution, the control chip MCU includes but is not limited to the Xuanzhi SPD1179 chip. One end of the three-phase bridge is connected to the control chip MCU signal, and the other end of the three-phase bridge is connected to the single resistor signal. At the same time, the single resistor is a sampling resistor connected in series in the bus.

[0039] like Figure 4The figure shows the circuit required for a complete control device. The three-phase bridge consists of six power switch tubes (such as MOSFET or IGBT). The six power switch tubes are usually divided into three groups. Each of the three groups contains two upper and lower switch tubes and corresponds to the three-phase winding (U, V, W) of the motor respectively. In order to realize the conversion from DC to AC, the three-phase bridge generates a three-phase sinusoidal voltage through periodic switching actions. At the same time, the operation of each power switch tube is controlled by a pulse width modulation PWM signal.

[0040] The back electromotive force detection method in the present invention is as follows Figure 4 As shown, the back electromotive force voltage of the motor is detected by the ADC in the voltage sampling circuit, that is, the three-phase terminal voltage of the motor is directly detected in each control cycle to determine the theoretical neutral point voltage and compare it with the terminal voltage of the suspended phase (such as Figure 5 As shown), the back EMF zero crossing point is obtained. The back EMF zero crossing point of the motor winding strictly reflects the position (that is, the angle) of the rotor magnetic pole and the real-time estimated speed. When the back EMF of a phase winding of the motor passes through zero, the rotor direct axis coincides with the quadrature axis of the phase winding. Therefore, as long as the zero crossing signal of the winding back EMF can be accurately detected, the key position of the rotor can be determined. In theory, the ideal commutation point lags the back EMF zero crossing point by 30° electrical angle, so that the motor commutation operation can be realized to ensure that the motor rotates continuously in a fixed direction.

[0041] FOC (such as Figure 6 ) is the field-oriented control, which transforms the collected three-phase current of the motor into coordinates to obtain the excitation current and torque current, i.e., id and iq, and then obtains the rotor electrical angle θ through the observer algorithm (the observer is the position and speed estimator in the figure), and then obtains Vα and Vβ through coordinate transformation, which are passed into SVPWM to calculate the output three-phase voltage.

[0042] Therefore, the present invention is based on Figure 7 In the low speed state, such as below 1500RPM, the above-mentioned back electromotive force zero-crossing detection method (i.e., back electromotive force detection method) is used, and the motor is running, and the FOC block diagram (such as Figure 6 )’s observer estimates the angle and calculates it synchronously. When the speed reaches above 1500 rpm, the two angle algorithms are connected. This can not only solve the noise caused by phase shift at low speed, but also maintain good dynamic response at low and medium speeds.

[0043] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A control method for solving low-speed noise of a brushless blower, characterized in that: The following steps are involved: S1, the motor starts, and the control chip MCU determines whether the given speed of the brushless motor in the brushless blower is less than the set speed; S2, if the judgment in S1 is "yes", it is determined that the brushless blower is in a low speed state, the back electromotive force detection method is executed, and the process goes to step S4; S3, if the judgment in S1 is "No", it is determined that the brushless blower is in a medium-high speed state, and the FOC control algorithm is executed to enter step S5; S4, the motor is running, the back electromotive force detection method is executed to calculate the angle, and the FOC control algorithm is synchronously executed to calculate the observer estimated angle; S5, the motor runs and the FOC control algorithm is executed; S6, step S1 is continuously executed during the operation of the motor, and the angle is seamlessly connected according to the angle calculated in the back electromotive force detection method and the angle estimated by the observer to achieve seamless switching of different speed states.

2. The control method for solving the low-speed noise of a brushless blower according to claim 1, characterized in that: The back electromotive force detection method in step S2 detects the back electromotive force voltage of the motor through the ADC, and compares the back electromotive force voltage with the suspended phase voltage to obtain the back electromotive force zero-crossing point, thereby obtaining the rotor position and realizing motor commutation.

3. A control device for solving the low-speed noise of a brushless blower, characterized in that: The control device includes a single resistor, a three-phase bridge and a control chip MCU, all of which are arranged on a motor control board. The control chip MCU is used to control the execution of a back electromotive force detection method and a FOC control algorithm. One end of the three-phase bridge is connected to the control chip MCU signal, and the other end of the three-phase bridge is connected to the single resistor signal. At the same time, the single resistor is a sampling resistor connected in series in the bus.

4. The control device for solving the low-speed noise of a brushless blower according to claim 3, characterized in that: The control chip MCU adopts the Xuanzhi SPD1179 chip.

5. The control device for solving the low-speed noise of a brushless blower according to claim 3, characterized in that: The three-phase bridge is composed of six power switch tubes, which are divided into three groups. Each of the three groups contains two upper and lower switch tubes and corresponds to the three-phase winding of the motor respectively. The three-phase bridge generates a three-phase sinusoidal voltage through periodic switching actions. At the same time, the operation of each power switch tube is controlled by a pulse width modulation PWM signal.

6. The control device for solving the low-speed noise of a brushless blower according to claim 5, characterized in that: The power switch tube is MOSFET or IGBT.

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