WO2018214979A1

WO2018214979A1 - Control method for brushless dc motor, control device, and electric tool

Info

Publication number: WO2018214979A1
Application number: PCT/CN2018/088520
Authority: WO
Inventors: 张传兵; 朱行
Original assignee: 苏州宝时得电动工具有限公司
Priority date: 2017-05-26
Filing date: 2018-05-25
Publication date: 2018-11-29

Abstract

The present invention relates to a control method for a brushless DC motor, a control device, and an electric tool, for controlling a brushless DC motor lacking a position sensor and having three phases (A, B, C). The method comprises: sequentially applying a pulse in a first direction for a first duration and a pulse in a second direction for a second duration to phase A of the brushless DC motor, so as to obtain a bus current value Ia when the pulse is applied in the first direction to phase A; repeating the above operation for phases B and C, so as to obtain a bus current value Ib when applying a pulse in the first direction to phase B and a bus current value Ic when applying a pulse in the first direction to phase C; and comparing the values of the obtained Ia, Ib, and Ic, so as to determine an initial position of a rotor, and transmitting, according to the initial position of the rotor, a drive signal to drive phase commutation of the brushless DC motor. The method for detecting the position of a rotor of a brushless DC motor, the control device, and the electric tool as described above use a pulse method to detect the position of a rotor in a rest position, and enable phase commutation according to the position of the rotor, thus improving accuracy of phase commutation and probability of a successful start.

Description

Brushless DC motor control method, control device and power tool

Technical field

The invention relates to the technical field of electromechanical integration, in particular to a brushless DC motor control method, a control device and a power tool.

Background technique

Brushless DC motor is composed of motor main body and driver. It is a typical mechatronic product. It has the advantages of good speed regulation performance, small size and high efficiency. It has been widely used in many fields. The position sensor plays an important role in the normal operation of the brushless DC motor. It provides basic commutation information for the motor, but the position sensor signal is susceptible to interference in some high precision and complex environments, and increases the cost and motor structure. The complexity, so the study of sensorless brushless DC motors has become one of the hot spots in the field of brushless DC motors.

In the control of the brushless DC motor, the key is to detect the rotor position, and then obtain the commutation point according to the position information, the corresponding winding conducts the commutation, and the conduction current is synchronized with the phase of the back electromotive force of the winding. For power tools, most applications require full torque start-up, so the acquisition and dynamic adjustment of the commutation timing is particularly important.

There are currently two ways to get the position of the rotor: Hall sensor mode and sensorless mode. Since the installation accuracy of the sensor directly affects the use effect of the brushless DC motor and the cost is high, the sensorless method is the goal pursued by the brushless controller. At present, most motors only use the back-EMF zero-crossing method in the whole process. The circuit is simple and the cost is low. However, the motor is in a static or low-speed phase. There is no back EMF or back EMF in this stage, which makes the timing of commutation usually not optimal. Timing, which can easily lead to startup failure.

Summary of the invention

The technical problem to be solved by the present invention is how to improve the inaccurate timing of the commutation timing of the brushless DC motor of the conventional position sensorless. To solve the above problem, the present invention provides a brush position detection method for a brushless DC motor, control method and control thereof. Devices and power tools.

A brushless DC motor rotor position detecting method for controlling a three-phase (A, B, C) brushless DC motor without a position sensor, the method comprising the following steps:

Applying a first direction pulse of a first time and a second direction pulse of a second time to the phase A of the brushless DC motor to obtain a bus current value Ia when the first direction pulse is applied to the phase A;

Repeating the above operations for the B and C phases, obtaining the bus current value Ib when the B phase is applied with the first direction pulse and the bus current value Ic when the first direction pulse is applied to the C phase;

The size of the obtained Ia, Ib, Ic is compared to obtain the initial position of the rotor.

A brushless DC motor control method for controlling a three-phase (A, B, C) brushless DC motor without a position sensor, the method comprising the following steps:

Comparing the obtained sizes of Ia, Ib, and Ic to determine the initial position of the rotor;

Transmitting the brushless DC motor by a control signal according to an initial position of the rotor.

Preferably, a specific step of applying the first direction pulse of the first time and the second direction pulse of the second time to the phase A of the brushless DC motor to obtain the bus current value Ia when the first direction pulse is applied to the phase A is performed. include:

Controlling the A phase of the brushless DC motor to be forwarded, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, and controlling the A of the brushless DC motor to be oppositely turned on, and A voltage pulse of a second time is applied to the phase A.

Preferably, a specific step of applying the first direction pulse of the first time and the second direction pulse of the second time to the phase A of the brushless DC motor to obtain the bus current value Ia when the first direction pulse is applied to the phase A is performed. Also includes:

Controlling A of the brushless DC motor to be oppositely turned on, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia', and controlling the A phase of the brushless DC motor to be forwarded. And applying a voltage pulse of the second time to the phase A.

Preferably, the control method further comprises the steps of:

Applying a second direction pulse of the first time and a first direction pulse of the second time to the phase A of the brushless DC motor to obtain a bus current value Ia' when the second direction pulse is applied to the phase A;

Repeating the above operations for the B and C phases, obtaining the bus current value Ib' of the B phase applied with the second direction pulse and the bus current value Ic' when the C phase applying the pulse of the second direction;

The size of the obtained Ia, Ib, Ic, Ia', Ib', Ic' is compared to determine the initial position of the rotor.

Preferably, the control method is specifically:

Controlling the A phase of the brushless DC motor to be forwarded, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, and controlling the A of the brushless DC motor to be oppositely turned on, and Applying a voltage pulse of a second time to the phase A;

Repeat the above operations for the B and C phases, and obtain the bus current value Ib when the B phase is forwarded and the bus current value Ic when the C phase is forwarded;

Controlling A of the brushless DC motor to be oppositely turned on, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia', and controlling the A phase of the brushless DC motor to be forwarded. And applying a voltage pulse of the second time to the phase A;

Repeat the above operations for the B and C phases to obtain the bus current value Ib' when B is oppositely turned on and the bus current value Ic' when C is oppositely turned on;

Comparing the obtained sizes of Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor;

Preferably, the control method is specifically:

Preferably, the control method comprises:

Controlling the A phase of the brushless DC motor to be forwarded, B is oppositely conducting (A+B-), and applying a voltage pulse of the first time to the AB phase to obtain a corresponding bus current value Iab, and the control A is oppositely guided. , phase B is forward-conducting (A-B+), and a voltage pulse of a second time is applied to the BA phase;

Controlling the B-phase forward conduction of the brushless DC motor, C is oppositely conducting (B+C-), and applying a voltage pulse of the first time to the BC phase to obtain a corresponding bus current value Ibc, and the control B is oppositely guided. , phase C is forward-guided (B-C+), and a voltage pulse of a second time is applied to the CB phase;

Controlling the C-phase of the brushless DC motor to be forwarded, A is oppositely conducting (C+A-), and applying a voltage pulse of the first time to the CA phase to obtain a corresponding bus current value Ica, and the control C is oppositely guided. , phase A is forward-conducting (C-A+), and a voltage pulse of a second time is applied to the AC phase;

Controlling the B-phase forward conduction of the brushless DC motor, A is oppositely conducting (B+A-), and applying a voltage pulse of the first time to the BA phase to obtain a corresponding bus current value Iba, and the control B is oppositely guided. , phase A is forward-conducting (B-A+), and a voltage pulse of a second time is applied to the AB phase;

Controlling the C-phase of the brushless DC motor to be forwarded, B is opposite to the conduction (C+B-), and applying a voltage pulse of the first time to the CB phase to obtain a corresponding bus current value Icb, and the control C is oppositely guided. , phase B is forward-conducting (C-B+), and a voltage pulse of a second time is applied to the BC phase;

Controlling the A phase of the brushless DC motor is forward-conducting, C is oppositely conducting (A+C-), and applying a voltage pulse of the first time to the AC phase to obtain a corresponding bus current value Iac;

Compare the Iab, Ibc, Ica, Iba, Icb, Iac size to determine the initial position of the rotor;

Preferably, the comparing Iab, Ibc, Ica, Iba, Icb, Iac size, determining the initial position of the rotor comprises:

If Ibc>Iab>Ica, and Iba>Icb>Iac, the rotor is located in the first sector;

If Ibc>Ica>Iab, and Iac>Icb>Iba, the rotor is located in the third sector;

If Iab>Ica>Ibc, and Iac>Iba>Icb, the rotor is located in the second sector;

If Iab>Ibc>Ica, and Icb>Iba>Iac, the rotor is located in the sixth sector;

If Ica>Ibc>Iab, and Icb>Iac>Iba, the rotor is located in the fourth sector;

If Ica>Iab>Ibc, and Iba>Iac>Icb, the rotor is located in the fifth sector;

Wherein, the BC phase is rotated counterclockwise by 0°, and the electrical angle ranges of the first sector to the sixth sector are (0°60°), (240°300°), and (300°360°), respectively. , (120 ° 180 °), (60 ° 120 °), (180 ° 240 °).

Preferably, the steps of the control method comprise:

Controlling the A phase of the brushless DC motor to be forwarded, B and C are oppositely conducting (A+BC-), applying a voltage pulse of the first time to the ABC phase, acquiring a corresponding bus current value Ia, and controlling the The brush A of the DC motor is oppositely turned on, and the B and C phases are forwardly guided (A-B+C+), and a voltage pulse of the second time is applied to the BCA phase;

Controlling the B phase of the brushless DC motor to be forwarded, and A and C are oppositely conducting (B+AC-), applying a voltage pulse of the first time to the BAC phase, acquiring a corresponding bus current value Ib, and controlling the B of the brush DC motor is oppositely turned on, and the A and C phases are forwardly guided (B-A+C+), and a voltage pulse of the second time is applied to the ACB phase;

Controlling the C phase of the brushless DC motor to be forwarded, and A and B are oppositely conducting (C+AB-), applying a voltage pulse of the first time to the CAB phase, acquiring a corresponding bus current value Ic, and controlling the The C of the brush DC motor is oppositely turned on, and the A and B phases are forwardly guided (C-A+B+), and a voltage pulse of the second time is applied to the ABC phase;

Controlling the A of the brushless DC motor is reversed, and the B and C phases are forward-conducting (A-B+C+), and a voltage pulse of the first time is applied to the BCA phase to obtain a corresponding bus current value Ia', and the control station The phase A of the brushless DC motor is forwardly guided, and B and C are oppositely connected (A+BC-), and a voltage pulse of the second time is applied to the ABC phase;

Controlling the brushless DC motor B to conduct the opposite direction, and the A and C phases are forward-conducting (B-A+C+), applying a voltage pulse of the first time to the ACB phase, and obtaining a corresponding bus current value Ib', the control station The B phase of the brushless DC motor is forwardly guided, and A and C are oppositely connected (B+AC-), and a voltage pulse of the second time is applied to the BAC phase;

Controlling the C of the brushless DC motor to conduct the opposite direction, and the A and B phases are forward-conducting (C-A+B+), and applying a voltage pulse of the first time to the ABC phase to obtain a corresponding bus current value Ic';

Comparing the sizes of Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor;

Preferably, the comparing the Ia, Ib, Ic, Ia', Ib', Ic' size, the step of determining the initial position of the rotor comprises:

If Ia>Ib, Ia>Ic, Ia<Ia’, the rotor is located in the first sector;

If Ib>Ia, Ib>Ic, Ib<Ib', the rotor is located in the third sector;

If Ic>Ia, Ic>Ib, Ic<Ic', the rotor is located in the second sector;

If Ia>Ib, Ia>Ic, Ia>Ia’, the rotor is located in the sixth sector;

If Ib>Ia, Ib>Ic, Ib>Ib’, the rotor is located in the fourth sector;

If Ic>Ia, Ic>Ib, Ic>Ic’, the rotor is located in the fifth sector;

Wherein, the BC phase is rotated counterclockwise by 0°, and the electrical angle ranges of the first sector to the sixth sector are (0°60°), (240°300°), and (300°360°), respectively. , (120°180°), (60°120°), (180°240°)

Preferably, the second time is equal to the first time.

The invention also provides a method for detecting a rotor position of a brushless DC motor, the detection method comprising:

After obtaining the initial position of the brushless DC motor and before detecting the zero-crossing point of the back electromotive force, short-time voltage pulses are sequentially applied to the three phases of the brushless DC motor to obtain corresponding voltage values and current values;

The voltage value and current value of each of the above phases are brought into a flux linkage function for processing, and the rotor position is determined.

A brushless DC motor control method, characterized in that the control method comprises:

Obtaining a current value flowing through the brushless DC motor and a voltage value of the brushless DC motor after obtaining the initial position of the brushless DC motor until a zero-crossing point of the back electromotive force is detected;

Obtaining the rotor position according to the method of the flux linkage function; transmitting a control signal according to the obtained rotor position

Controlling the brushless DC motor commutation.

Preferably, the voltage value includes a voltage value of a conducting phase of the brushless DC motor and a voltage value of a non-conducting phase.

Preferably, the current value comprises any one of a bus current value or a phase current value.

Preferably, the back electromotive force zero-crossing point is a stable back electromotive force zero-crossing point, and the number of times of the counter electromotive force zero-crossing point reaches a preset value or the slope of the terminal voltage rise reaches a preset value.

Preferably, the above method further comprises the steps of:

When it is determined that the brushless DC motor detects the zero-crossing of the back electromotive force, the position of the rotor is determined by the zero-crossing point of the counter electromotive force.

The invention also provides a method for detecting a rotor position of a brushless DC motor, the method comprising the following steps:

And sequentially inputting a pulse to the three phases of the brushless DC motor to detect an initial position of the rotor of the brushless DC motor;

After obtaining the initial position of the brushless DC motor until the zero-crossing point of the back electromotive force is detected, the position of the rotor is determined by a flux linkage function to perform commutation;

When it is determined that the brushless DC motor detects the zero-crossing point of the back electromotive force, the position of the rotor is determined by the zero-crossing point of the counter electromotive force.

A brushless DC motor control method, the control method comprising:

The sensorless control of the full speed range of the brushless DC motor is divided into three stages according to a preset condition, and each stage acquires an electrical signal of the brushless DC motor, and the rotor position of the brushless DC motor is obtained according to the electrical signal. The brushless DC motor is commutated according to the rotor position.

Preferably, the control method comprises:

In the first stage, when the brushless DC motor is stationary, a pulse is sequentially applied to the three phases of the brushless DC motor to obtain a current value flowing through the brushless DC motor, and the brushless DC motor rotor is obtained according to the current value. The initial position, and the control signal is sent according to the initial position to control the commutation of the brushless DC motor;

In the second stage, after the brushless motor rotates, the current value flowing through the brushless DC motor and the voltage value of the brushless DC motor are obtained, and the rotor position of the brushless DC motor is obtained according to the method of the flux linkage function, according to the The rotor position transmission control signal controls the commutation of the brushless DC motor;

In the third stage, when it is determined that the brushless DC motor detects the zero-crossing point of the back electromotive force, the rotor position of the brushless DC motor is obtained by the zero-crossing point of the back electromotive force, and the commutation of the brushless DC motor is controlled according to the sending position control signal of the rotor position. .

Preferably, a pulse is sequentially applied to the three phases of the brushless DC motor to obtain a current value flowing through the brushless DC motor, and an initial position of the rotor of the brushless DC motor is obtained according to the current value, and according to the The step of the initial position transmission control signal controlling the commutation of the brushless DC motor includes the steps of the brushless DC motor control method according to any of the above.

Preferably, the method of the flux linkage function comprises the above brushless DC motor control method.

The present invention also provides a control device for detecting a rotor position of a brushless DC motor to control motor commutation, the control device being configured to perform the brushless DC motor control method according to any of the above.

The invention also provides a power tool comprising a housing; a control device; a motor located in the housing; a power source for supplying electrical power to the motor; and a switch, optionally opening and closing, for controlling the power source to the The control device and the motor provide electrical energy; wherein, after the switch is closed, the first phase pulse of the first time and the second direction pulse of the second time are sequentially applied to the phase A of the brushless DC motor to obtain the phase A The bus current value Ia when the first direction pulse is applied; the above operation is repeated for the B and C phases, and the bus current value Ib when the B phase is applied with the first direction pulse and the bus current value Ic when the first direction pulse is applied to the C phase; Comparing the obtained sizes of Ia, Ib, Ic, determining the initial position of the rotor; and transmitting a control signal according to the initial position of the rotor to control the commutation of the brushless DC motor.

The invention also provides a power tool comprising a housing; a control device; a motor located in the housing; a power source for supplying electrical power to the motor; and a switch, optionally opening and closing, for controlling the power source to the The control device and the motor provide electrical energy; after the switch is closed, the control device obtains a current value flowing through the motor and a voltage value of the motor after obtaining an initial position of the rotor until a zero-crossing point of the back electromotive force is detected, The rotor position is obtained according to the method of the flux linkage function, and the motor commutation is controlled according to the rotor position transmitting control signal.

The invention also provides a power tool comprising a housing; a control device; a motor located in the housing; a power source for supplying electrical power to the motor; and a switch, optionally opening and closing, for controlling the power source to the The control device and the motor provide electric energy; the sensorless control of the brushless DC motor in the full speed range is divided into three stages according to a preset condition, and after the switch is closed, the electric signal of the brushless DC motor is obtained in each stage, according to the The electrical signal obtains the rotor position of the brushless DC motor, and the brushless DC motor is commutated according to the rotor position.

Preferably, the switch is closed, and further comprising: after the switch is closed, the control device receives the trigger signal from the switch and determines whether the trigger signal meets a preset condition, and if yes, the motor starts.

Preferably, the preset condition includes that the voltage signal set at different positions of the switch is greater than a preset voltage value previously stored in the control device.

Preferably, the motor is a brushless DC motor.

Preferably, the first direction is opposite to the second direction.

Preferably, the control device comprises the control device described above.

The above brushless DC motor control method, control device and power tool have the beneficial effects that the brushless DC motor uses different methods to detect the position of the rotor according to different states of the motor during operation, and the detection effect is more accurate. When the motor is stationary, the position of the rotor is detected by pulse injection method, and a positive pulse and a negative pulse of the same time are sequentially input to a certain phase of the motor, wherein the negative pulse is mainly used to cancel the current generated by the positive pulse to the next phase. The effect of the current detection result, so that the detection of the current is more accurate by the cancellation of the negative pulse, and the commutation of the rotor is more accurate. When the motor is running at low speed, the zero-crossing point of the back electromotive force cannot be detected. At this time, the position of the rotor is detected by the method of flux linkage function; when it is judged that the zero-crossing point of the back electromotive force can be detected, the speed of the brushless DC motor reaches the medium-high speed. In the stage, the use of the flux linkage function method to stop the rotor seat by the back electromotive force method is reduced, and the calculation amount is reduced to improve the accuracy of the commutation, thereby increasing the probability of successful startup.

DRAWINGS

The objects, technical solutions, and advantageous effects of the present invention described above can be achieved by the following figures:

1 is a flow chart of a first embodiment of a control method of a brushless DC motor according to the present invention,

2 is a circuit diagram of a brushless DC motor control circuit of the present invention.

Figure 3 is a flow chart showing a second embodiment of the brushless DC motor control method of the present invention.

4 is a flow chart showing a fourth embodiment of the brushless DC motor control method of the present invention.

Figure 5 is a flow chart showing a fifth embodiment of the brushless DC motor control method of the present invention.

Figure 6 is a flow chart showing a seventh embodiment of the brushless DC motor control method of the present invention.

Figure 7 is a diagram showing the position of a sector of a brushless DC motor of the present invention.

Figure 8 is a flow chart showing an eighth embodiment of the brushless DC motor control method of the present invention.

Figure 9 is a flow chart showing a ninth embodiment of the brushless DC motor control method of the present invention.

Figure 10 is a diagram showing the back electromotive force waveform of the brushless DC motor control method of the present invention.

detailed description

In order to facilitate the understanding of the present invention, the present invention will be described more fully hereinafter with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the understanding of the present disclosure will be more fully understood.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning meaning meaning The terminology used herein is for the purpose of describing the particular embodiments, The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

1 is a flow chart of a first embodiment of a brushless DC motor control method according to the present invention, including the steps of:

Step S1. The first phase pulse of the first time and the second direction pulse of the second time are sequentially applied to the phase A of the brushless DC motor, and the bus current value Ia when the first phase pulse is applied to the phase A is obtained;

Step S2. Repeat the above operations for the B and C phases, and obtain the bus current value Ib when the B phase is applied with the first direction pulse and the bus current value Ic when the first direction pulse is applied to the C phase;

Step S3. Comparing the obtained sizes of Ia, Ib, and Ic, and determining the initial position of the rotor;

Step S4. The control signal is sent according to the initial position of the rotor to control the commutation of the brushless DC motor.

Among them, steps S1, S0, S3 are used to detect the initial position of the rotor. In practical applications, the accurate detection and positioning of the initial position of the rotor is directly related to the smooth start of the motor.

Specifically, FIG. 2 is a schematic diagram of a commutation drive circuit of a brushless DC motor. In the figure, Ud is the DC power supply voltage, g is the reference point of the DC voltage, Q1-Q6 is the high power MOSFET, and D1-D6 is the parasitic body diode in the MOSFET.

In the commutation control of brushless DC motor, two-way conduction mode and three-three conduction mode are usually adopted. In the two-conduction mode, in one rotation cycle, in order to rotate the motor in one direction, the winding energization state is changed six times, and each commutation is dependent on the position of the rotor. Therefore, only accurate access to these positions can be correctly commutated.

The invention adopts the pulse method to detect the initial position angle of the rotor, and applies a short time positive and negative voltage pulse to the motor winding, then calculates the pulse current value, and queries the defined relationship table to determine the current position of the rotor and the conduction phase of the next state. sequence. Wherein, in step S1, the first direction is opposite to the second direction, and the two are different by 180°, that is, the present invention sequentially applies positive and negative pulses to each phase of the brushless DC motor to compare the positive pulses when each phase is applied. The magnitude of the bus current value is obtained, or the position of the rotor of the motor is obtained, or a negative pulse and a positive pulse are sequentially applied to each phase of the brushless DC motor, and the magnitude of the bus current when each phase is applied with a negative pulse is compared to obtain the position of the rotor of the motor.

Please refer to FIG. 3, which is a flowchart of a second embodiment of a method for controlling a brushless DC motor according to the present invention.

The three pairs of positive and negative pulses are used to detect the rotor position and then control the rotor commutation, including:

Step S10. Control the A phase of the brushless DC motor to be forwarded, and apply a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, control the A of the brushless DC motor to be oppositely directed, and to the A phase. Applying a voltage pulse of a second time;

Step S20. Repeat the above operations for the B and C phases, and obtain the bus current value Ib when the B phase is applied with the first direction pulse and the bus current value Ic when the first direction pulse is applied to the C phase;

Step S30. Comparing the obtained sizes of Ia, Ib, and Ic, and determining the initial position of the rotor;

Step S40. The control signal is sent according to the initial position of the rotor to control the commutation of the brushless DC motor.

In the third embodiment of the brushless DC motor control method of the present invention, the difference from the second embodiment is that the step S10 in the first embodiment specifically includes: controlling the A of the brushless DC motor in the embodiment. Conversely, the conduction is performed, and a voltage pulse of the first time is applied to the phase A to obtain a corresponding bus current value Ia', and the phase A of the brushless DC motor is controlled to be forwarded, and the second phase is applied to the phase A. The voltage pulse of time.

In the fourth embodiment of the brushless DC motor control method of the present invention, as shown in FIG. 4, on the basis of the three pairs of positive and negative pulses in the first embodiment, the present embodiment uses six pairs of positive and negative pulses to determine The initial position of the rotor, which in turn controls the commutation of the brushless DC motor. The specific steps include:

Step S100. The first phase pulse of the first time and the second direction pulse of the second time are sequentially applied to the phase A of the brushless DC motor to obtain the bus current value Ia when the first phase pulse is applied to the phase A;

Step S200. Repeat the above operations for the B and C phases, and obtain the bus current value Ib when the B phase applies the first direction pulse and the bus current value Ic when the C phase applies the first direction pulse;

Step S300. sequentially applying a second direction pulse of the first time and a first direction pulse of the second time to the phase A of the brushless DC motor to obtain the bus current value Ia' when the second direction pulse is applied to the phase A;

Step S400. Repeat the above operations for the B and C phases to obtain the bus current value Ib' to which the B phase applies the second direction pulse and the bus current value Ic' when the C phase applies the pulse in the second direction.

Step S500. Comparing the obtained sizes of Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor;

Step S600. The control signal is sent according to the initial position of the rotor to control the commutation of the brushless DC motor.

Of course, the above embodiment can first input a negative pulse to the three phases of the motor, and then input a positive pulse, compare the magnitudes of the obtained six current values, and determine the initial position of the rotor, which will not be described in detail herein.

In the above embodiment, during the operation, the driving method of the brushless DC motor may be: the control device performs logic transformation according to the change of the rotor position to generate a pulse width modulation signal, and then is amplified by the driving circuit and sent to the inverter for each power. The switch tube, in turn, switches the current of the stator winding according to a certain logic relationship to drive the rotor to start accelerating operation.

In the above three embodiments, the three windings of the three-phase motors A, B, and C have two combinations (AB, BC, CA), (BA, AC, CB), and the above embodiments are for the brushless DC motor A. The phase sequentially applies the first direction pulse of the first time and the second direction pulse of the second time, and repeats the above operations for the B and C phases, wherein one specific manner is to apply the positive pulse and the second time of the first time to the AB phase. Negative pulse, the positive pulse of the first time and the negative pulse of the second time are applied to the BC phase, the positive pulse of the first time of the CA phase time and the negative pulse of the second time; another specific way is to apply the phase of the BA The negative pulse of the first time and the positive pulse of the second time apply a positive pulse of the first time and a negative pulse of the second time to the AC phase, and a positive pulse of the first time and a negative pulse of the second time are applied to the CB phase.

In the fifth embodiment of the present invention, the steps in the fourth embodiment are specifically refined, as shown in FIG. 5:

Step S101, controlling the A-phase forward conduction (A+) of the brushless DC motor, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, and controlling the opposite direction of the brushless DC motor A (A -), and apply a voltage pulse of the second time to phase A.

In step S201, the above operations are repeated for the B and C phases, and the bus current value Ib when the B phase is forwarded and the bus current value Ic when the C phase is forwarded are obtained.

Step S301, controlling A of the brushless DC motor to be oppositely turned on, and applying a voltage pulse of the first time to the A phase, obtaining a corresponding bus current value Ia', controlling the A phase of the brushless DC motor to be forwarded, and to A The phase applies a voltage pulse of a second time.

In step S401, the above operation is repeated for the B and C phases, and the bus current value Ib' when B is reversely turned on and the bus current value Ic' when C is turned on in the opposite direction are obtained.

In step S501, the sizes of the acquired Ia, Ib, Ic, Ia', Ib', Ic' are compared to determine the initial position of the rotor.

Step S601. The control signal is sent according to the initial position of the rotor to control the commutation of the brushless DC motor.

In the sixth embodiment of the present invention, the difference from the fifth embodiment is that the first control A, B, and C are oppositely turned on, and a voltage pulse of a certain time is applied to obtain a corresponding bus current, and then in the control A. The B and C phases are forwarded, and a voltage pulse is applied for a certain period of time to obtain a corresponding bus current. The initial position of the rotor is obtained by comparing the obtained bus currents. In the sixth embodiment, steps S301 and S401 are performed first. Steps S101, S201, S501, and S601 are performed.

In the fifth and sixth embodiments, the phase A is forward-conducted, and the MOSFET of the upper arm of the corresponding driving circuit of A is turned on, specifically, the Q1 in FIG. 2 is turned on, and the other two phases are used. The lower arm of one phase is turned on, that is, Q2 or Q6 is turned on; A is opposite to the MOSFET of the lower arm of the corresponding driving circuit of A, specifically, Q4 is turned on in FIG. 2, Q3 or Q5 is turned on.

6 is a flow chart of a seventh embodiment of a control method of a brushless DC motor according to the present invention, specifically adopting a three-phase two-two conduction manner, and the steps of the method include:

Step S110: Control the A phase of the brushless DC motor to be forwarded, B to conduct the opposite direction, and apply a voltage pulse of the first time to the AB phase to obtain the corresponding bus current value Iab, and the control A is oppositely guided, and the B phase is guided. Passing, and applying a voltage pulse of a second time to the BA phase;

Specifically, the voltage pulse Vab of the first time is applied to the stator winding through the Q1 and Q6 power tube conduction (A+B-) of the driving circuit shown in FIG. 2, that is, the current flows from the A-phase winding, and the B-direction winding Flow out, detect the corresponding bus current value Iab; pass the Q3 and Q4 power tube conduction (A-B+) of the drive circuit, and apply a second time voltage pulse Vba to the stator winding, that is, the current flows from the B-phase winding, by A The winding flows out to cancel the interference of the current Iab to the next detected current, so that the detection accuracy of the initial position of the rotor can be improved.

Step S210: Control the B-phase forward conduction of the brushless DC motor, C reversely conducts, and applies a voltage pulse of the first time to the BC phase to obtain a corresponding bus current value Ibc, and the control B is oppositely guided, and the C phase is guiding. Passing, applying a voltage pulse of a second time to the CB phase;

Specifically, the voltage pulse Vbc of the first time is applied to the stator winding through the Q3 and Q2 power tube conduction (B+C-) of the driving circuit, that is, the current flows from the B-phase winding, and the C flows out to the winding, and the corresponding detection is performed. The bus current value Ibc is applied by the driving current Q5 and the Q6 power tube (B-C+), and the second time voltage pulse Vcb is applied to the stator winding, that is, the current flows in from the C-phase winding and flows out from the B to the winding. It is used to cancel the interference of the current Ibc to the next detection current, so that the detection accuracy of the initial position of the rotor can be improved.

Step S310: controlling the C-phase of the brushless DC motor to be forwarded, A is oppositely turned on, and applies a voltage pulse of the first time to the CA phase to obtain a corresponding bus current value Ica, and the control C is oppositely guided, and the A phase is positively guided. Passing, and applying a voltage pulse of a second time to the AC phase;

Specifically, the voltage pulse Vca of the first time is applied to the stator winding through the Q5 and Q4 power tube conduction (C+A-) of the driving circuit, that is, the current flows in from the C-phase winding, and flows out from the A to the winding, and the corresponding detection is performed. The bus current value Ica is applied by the driving current Q1 and the Q2 power tube (C-A+), and the second time voltage pulse Vac is applied to the stator winding, that is, the current flows in from the A-phase winding and flows out from the C to the winding. It is used to cancel the interference of the current Ica to the next detection current, so that the detection accuracy of the initial position of the rotor can be improved.

Step S410: Control the B phase of the brushless DC motor to be forwarded, A is oppositely turned on, and applies a voltage pulse of the first time to the BA phase to obtain a corresponding bus current value Iba, and the control B is oppositely guided, and the A phase is positively guided. Passing, and applying a voltage pulse of a second time to the AB phase;

Specifically, the voltage pulse Vba of the first time is applied to the stator winding through the Q3 and Q4 power tube conduction (B+A-) of the driving circuit, that is, the current flows from the B-phase winding, and the A-direction winding flows out, and the corresponding detection is performed. The bus current value Iba is applied to the stator winding through the Q1 and Q6 power tube conduction (B-A+) of the driving circuit, and the second time voltage pulse Vab is applied to the stator winding, that is, the current flows in from the A-phase winding and flows out from the B-to-winding. It is used to cancel the interference of the current Iba to the next detection current, so that the detection accuracy of the initial position of the rotor can be improved.

Step S510: Control the C-phase of the brushless DC motor to be forwarded, B to conduct the opposite direction, and apply a voltage pulse of the first time to the CB phase to obtain a corresponding bus current value Icb, and the control C is oppositely guided, and the B phase is guided. Passing, and applying a voltage pulse of a second time to the BC phase;

Specifically, the voltage pulse Vcb of the first time is applied to the stator winding by the driving current Q5 and the Q6 power tube conducting (C+B-), that is, the current flows from the C-phase winding, and the B flows out to the winding, and the corresponding detection is performed. The bus current value Icb is applied to the stator winding through the Q3 and Q2 power tube conduction (C-B+) of the driving circuit, and the second time voltage pulse Vbc is applied to the stator winding, that is, the current flows in from the B-phase winding and flows out from the C to the winding. It is used to cancel the interference of the current Icb to the next detection current, so that the detection accuracy of the initial position of the rotor can be improved.

Step S610: controlling the A phase of the brushless DC motor to be forwarded, C is oppositely turned on, and applying a voltage pulse of the first time to the AC phase to obtain a corresponding bus current value Iac, and the control A is oppositely guided, and the C phase is guiding. Passing, and applying a pulse of the second time to the CA phase;

Specifically, by driving the current Q1 and Q2 power tube conduction (A+C-), a voltage pulse Vac of the first time is applied to the stator winding, that is, the current flows in from the A-phase winding, and flows out from the C to the winding, and the corresponding detection is performed. Bus current value Iac.

Step S710: Comparing the Iab, Ibc, Ica, Iba, Icb, and Iac sizes, and determining the initial position of the rotor, that is, the sector in which the rotor is located. For the specific six sectors, please refer to FIG.

If Ibc>Iab>Ica, and Iba>Icb>Iac, the rotor is located in the first sector;

If Ibc>Ica>Iab, and Iac>Icb>Iba, the rotor is located in the third sector;

If Iab>Ica>Ibc, and Iac>Iba>Icb, the rotor is located in the second sector;

If Iab>Ibc>Ica, and Icb>Iba>Iac, the rotor is located in the sixth sector;

If Ica>Ibc>Iab, and Icb>Iac>Iba, the rotor is located in the fourth sector;

If Ica>Iab>Ibc and Iba>Iac>Icb, the rotor is in the fifth sector.

In the above embodiment, the BC phase is 0°, and the counterclockwise rotation is performed, and the electrical angle ranges of the first sector to the sixth sector are respectively (0°60°), (240°300°), and (300°360). °), (120°180°), (60°120°), (180°240°). Among them, A, B, and C three phases are three AC circuits with the same frequency, the same amplitude, and 120° phase difference. Specifically, the above A, B, and C may be U phase, V phase, and W phase; or may be L1, L2, and L3 phases.

Step S810: The control signal is sent according to the initial position of the rotor to control the commutation of the brushless DC motor.

In the present invention, after a forward voltage (for example, Uab) is applied, a reverse voltage (Uba) is applied, and the reverse voltage is used to cancel the current generated by the forward voltage at the second time to avoid the next input voltage Ubc. When the current Ibc is detected, the current Ibc causes interference, making the detection result inaccurate.

In the present invention, the first time is equal to the second time, and the time is shorter, and the voltage pulse that is input at the second time is used to cancel the interference of the current generated by the voltage applied at the first time to the next detection current, thereby improving The accuracy of the detection of the initial position of the rotor.

In the embodiment of the present invention, the three phases A, B, and C are three alternating current circuits having the same frequency, the same amplitude, and 120° phase difference. Specifically, the above A, B, and C may be U phase, V phase, and W phase; or may be L1, L2, and L3 phases.

Figure 8 is a flow chart showing an eighth embodiment of the brushless DC motor control method of the present invention. The brushless DC motor of this embodiment adopts a three-phase three-tube conduction mode, and the brushless DC motor adopts a full-bridge drive, that is, six MOSFETs respectively constitute an upper bridge arm and a lower bridge arm, and specifically includes:

Step S111. Control the A phase of the brushless DC motor to be forwarded, B and C are oppositely connected, and apply a voltage pulse of the first time to the ABC phase to obtain a corresponding bus current value Ia, and control the opposite direction of the brushless DC motor A. Passing, B, C phase forward conduction, applying a voltage pulse of the second time to the BCA phase;

Specifically, the Q2 and the C-phase winding corresponding to the Q1 and B-phase windings of the A-phase winding of the brushless DC motor are controlled to be connected to the Q2 (A+BC-), and the first time voltage pulse is applied to the stator winding. Detecting the corresponding bus current value Ia, controlling the Q4 and B phase windings corresponding to the A phase winding of the brushless DC motor to be connected to the corresponding Q5 according to the Q3 and C phases, and applying a voltage pulse of the second time to the stator winding, The detection of the current detected by the voltage pulse of the first time cancels the current detected by applying the forward voltage to the next B phase, thereby improving the detection accuracy of the initial position of the rotor.

Step S211. Control the B phase of the brushless DC motor to be forwarded, and A and C are oppositely connected, and apply a voltage pulse of the first time to the BAC phase to obtain a corresponding bus current value Ib, and control the opposite direction of the brushless DC motor B. Pass, the A and C phases are forwarded, and a voltage pulse of the second time is applied to the ACB phase;

Specifically, the Q3 corresponding to the B-phase winding of the brushless DC motor is controlled, the Q4 corresponding to the A-phase winding is turned on, the Q2 corresponding to the C-phase winding is turned on (B+AC-), and the voltage of the first time is applied to the stator winding. Pulse, detecting the corresponding bus current value Ib, controlling the Q6 corresponding to the B-phase winding of the brushless DC motor, the Q1 corresponding to the A-phase winding is turned on, the Q5 corresponding to the C-phase winding is turned on, and applying the second time to the stator winding The voltage pulse is used to cancel the interference of the current generated by the voltage pulse of the first time to the current detected when the forward voltage is applied to the next C phase, thereby improving the detection accuracy of the initial position of the rotor.

Step S311. Control the C-phase of the brushless DC motor to be forwarded, and A and B are oppositely connected, and apply a voltage pulse of the first time to the CAB phase to obtain a corresponding bus current value Ic; and control the opposite direction of the brushless DC motor C Pass, the A and B phases are forwarded, and a voltage pulse of the second time is applied to the ABC phase;

Specifically, the Q4 of the C-phase winding of the brushless DC motor is controlled, and the Q6 of the A-phase winding corresponding to the Q-phase winding is turned on (C+AB-), and the voltage pulse of the first time is applied to the stator winding. Detecting the corresponding bus current value Ic, controlling the Q2 corresponding to the C-phase winding of the brushless DC motor, the Q1 corresponding to the A-phase winding is turned on, the Q3 corresponding to the B-phase winding is turned on, and applying the voltage pulse of the second time to the stator winding It is used to cancel the interference of the current generated by the voltage pulse of the first time to the current detected when the forward voltage is applied, so that the detection accuracy of the initial position of the rotor can be improved.

Step S411. Control A of the brushless DC motor to conduct the opposite direction, and the B and C phases are forwarded to each other, and apply a voltage pulse of the first time to the BCA phase to obtain a corresponding bus current value Ia', and control the phase A of the brushless DC motor. Positive conduction, B and C are oppositely connected, and a voltage pulse of the second time is applied to the ABC phase;

Specifically, the Q3 and C phases corresponding to the Q4 and B phase windings of the A-phase winding of the brushless DC motor are controlled to be connected to the corresponding Q5 (A-B+C+), and the voltage of the first time is applied to the stator winding. Pulse, detecting the corresponding bus current value Ia', controlling the Q2 corresponding to the Q1 and C phase windings corresponding to the Q1 and B phase windings of the A-phase winding of the brushless DC motor, and applying the second time voltage to the stator winding The pulse is used to cancel the interference of the current generated by the voltage pulse Ubca at the first time on the current detected when the next voltage is applied, thereby improving the detection accuracy of the initial position of the rotor.

Step S511. Control B of the brushless DC motor to conduct the opposite direction, and the phases A and C are forwarded, and the voltage pulse of the first time is applied to the ACB phase to obtain the corresponding bus current value Ib', and the phase B of the brushless DC motor is controlled. Positive conduction, A and C are oppositely connected, and a voltage pulse of a second time is applied to the BAC phase;

Specifically, the Q1 and C phases corresponding to the Q6 and A phase windings of the B-phase winding of the brushless DC motor are controlled to be connected to the corresponding Q5 (B-A+C+), and the voltage of the first time is applied to the stator winding. Pulse, detecting the corresponding bus current value Ib', controlling the Q3 of the B-phase winding of the brushless DC motor, and the Q4 and C phases corresponding to the A-phase winding are turned on around the corresponding Q2, and applying the second time to the stator winding The voltage pulse is used to cancel the interference of the current generated by the voltage pulse Ubac of the first time on the current detected when the forward voltage is applied, thereby improving the detection accuracy of the initial position of the rotor.

Step S611. Control the brushless DC motor C to conduct the opposite direction, and the A and B phases are forwardly connected, and apply a voltage pulse of the first time to the ABC phase to obtain a corresponding bus current value Ic';

Specifically, the Q1 and the C-phase winding corresponding to the Q2 winding of the brushless DC motor are controlled to correspond to the Q3 conduction (C-A+B+), and the first time voltage pulse is applied to the stator winding. , the corresponding bus current value Ic' is detected.

Step S711. Compare the sizes Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor. That is, the magnitude of the six current values obtained is compared to determine the 600 electrical angle interval (sector) where the rotor is located.

Please refer to FIG. 7 for a schematic diagram of six sectors.

If Ia>Ib, Ia>Ic, Ia<Ia’, the rotor is located in the first sector;

If Ib>Ia, Ib>Ic, Ib<Ib', the rotor is located in the third sector;

If Ic>Ia, Ic>Ib, Ic<Ic', the rotor is located in the second sector;

If Ia>Ib, Ia>Ic, Ia>Ia’, the rotor is located in the sixth sector;

If Ib>Ia, Ib>Ic, Ib>Ib’, the rotor is located in the fourth sector;

If Ic > Ia, Ic > Ib, Ic > Ic', the rotor is located in the fifth sector.

In the above embodiments, the bus current value refers to the current sampling value on the DC side of the inverter. When a short-time voltage pulse of different width and direction is applied to the stator windings respectively, the saturation state of the stator core is different, and the inductance of the magnetic circuit is different, so that the current response is different, so according to each current response The relationship between the two determines the position information of the rotor. The amplitude of each voltage pulse is less than the minimum of the safety thresholds that all power devices in the brushless DC motor can withstand. The width of each pulse is smaller than the corresponding width of the brushless DC motor when the inductance reaches saturation, and the width of each pulse needs to ensure that the pulses can be distinguished and the position of the rotor can be determined. In addition, the width of each pulse should be as short as possible to improve the response speed of the whole machine.

When the motor starts from the rest position, during the operation, the mode of driving the brushless DC motor can be: the controller performs logic transformation according to the change of the rotor position to generate a pulse width modulation signal, and then is amplified by the driving circuit and sent to Each power switch tube of the inverter further switches the current of the stator winding according to a certain logic relationship to drive the rotor to start accelerating operation.

When the brushless DC motor starts running, it is in the low speed phase, and the rotational speed is gradually increasing. At this time, there is no back electromotive force or the back electromotive force is not obvious, so that the position of the rotor cannot be obtained according to the back electromotive force zero crossing point.

In a ninth embodiment of the control method of the brushless DC motor of the present invention, before the brushless DC motor starts to operate until the zero point of the back electromotive force is detected, the current value flowing through the brushless DC motor and the voltage value of the motor are detected; The value, voltage value and flux linkage function are used to calculate the rotor position; the drive signal is sent according to the calculated rotor position to drive the brushless DC motor commutation.

Preferably, the brushless DC motor obtains the initial position and starts to run until the zero point of the back electromotive force is detected. At this time, the motor has started to rotate, and the controller controls the two phases to be turned on and the other phase is not turned on by the closed loop control mode. Detecting the current value of the motor, the voltage value of the conduction phase, and the voltage value of the non-conduction phase, and calculating in the flux linkage function according to the detected current value, the conduction phase voltage value, and the non-conduction phase voltage value, according to the calculation result The position of the rotor is determined, and the drive signal is sent according to the position of the rotor to drive the commutation of the brushless DC motor.

In the above embodiment, the basic idea of the flux linkage function method is: construct a function related to the flux linkage to describe the rotor position, estimate the flux linkage by using the measured voltage applied to the stator winding and the detected bus current, and then The relationship between the flux linkage and the rotor position estimates the position of the rotor. The specific implementation manner may be: writing a phase voltage equation, and writing the phase voltage as a function of phase current, resistance, inductance, mutual inductance, rotor position, and flux linkage. The flux linkage function is the flux linkage generated on the rotor permanent magnet and is a function of the rotor position. Ignore current saturation, leakage inductance and iron loss, and write the flux linkage into current, inductance and flux linkage functions. The line voltage expression is derived by using the three-phase windings with the same mutual inductance and the sum of the three-phase currents to zero. The line voltage expression is a function of resistance, current, self-inductance, mutual inductance, and line flux linkage function, wherein the line voltage is replaced by the voltage applied to the stator winding, and the line flux function is the difference between the two flux linkage functions. The differential of the linear flux linkage function is positioned as a line function, and the expression of the function is derived from the expression of the voltage, and the function also has the amount of rotation, which is further transformed in order to eliminate the amount of rotation. The ratio of the two line functions is defined as an estimation function. This estimation function is independent of the rotational speed. It is only a function of the rotor position. The estimated function value can be used to estimate the rotor position to achieve stator commutation. Therefore, the flux linkage function method can estimate the rotational speed from near zero (e.g., 1.5% of the rated rotational speed) to the high-speed commutation instant by the application of the rotational speed independent estimation function, and because the form of the estimation function is in the entire speed range. The same is true, so accurate commutation pulses can be provided in both transient and steady state.

Specifically, the derivation of the flux linkage function is as follows:

Assume that the current phase sequence of the motor is A+C-, phase A is the commutation phase, phase B is the non-conducting phase, phase C is the non-commutation phase, U _an is the phase voltage of the conducting phase A, i _a — - Phase A current, R _a - phase resistance, θ - rotor position angle

L _aa - self-inductance, L _ab - mutual inductance

Let L _aa = L _bb = L _cc = L _s , L _ba = L _ab = L _ca = L _ac = L _bc = L _cb = L _m , L = L _{s -} L _m , R _a = R _b = R _c =R,i _a +i _b +i _c =0, and λ _ar (θ) is expressed as the back-EMF constant K _e and the position-dependent flux linkage function f _ar (θ)

Where, U _ab - motor line voltage, ω - motor instantaneous angular velocity, U _a is the motor's conduction phase terminal voltage, defines a new line-to-line flux function

Wherein, when the AB phase winding is turned on (A+B-):

It can be seen from the above formula that the conduction phase voltage value, the non-conduction phase voltage value, and the current value are obtained, and G(θ) at a certain position can be obtained.

make

Where U _BC is the voltage value when the BC phase winding is turned on, and U _AB is the voltage value when the AB phase winding is turned on.

In the above G(θ) formula, the current value includes any one of a bus current value or a phase current value.

The above G(θ) function is independent of the speed and includes a continuous position signal. When the above G(θ) tends to be infinite, it is a commutation point. In the present invention, when G(θ) is greater than a preset value, Reversing point. Since the motor's expression is the same when the motor is running at any speed, a precise commutation pulse can be obtained in both the transient and steady state of the motor.

The above method of flux linkage function detects the position of the rotor. Although the motor runs at any speed, the expression of the function is the same, that is, the control method is applicable to the entire rotational speed range of the brushless DC motor, but the method of obtaining the flux linkage function Calculating the position of the rotor is relatively large. When the motor is running at high speed, it will happen that the position of the rotor has not yet been calculated and the commutation time has been reached. Therefore, when the motor is running at high speed, the position of the rotor is calculated by the method of flux linkage function. Will result in inaccurate calculation results.

In summary, the brushless DC motor control method provided by the embodiment of the present invention can detect the position of the rotor by using a flux linkage function in a low speed stage, thereby being capable of commutating according to the position information of the rotor, and improving the commutation. Accuracy and increased starting torque, which increases the probability of successful startup.

When the motor speed reaches a certain speed, that is, the medium-high speed phase, a stable back-EMF zero-crossing point can be detected. The position of the rotor can be determined by the back-EMF zero-crossing point. For example, the opposite potential method, the terminal voltage method, and the line voltage can be used. The difference method, the third harmonic method, etc. are used to determine the position of the rotor, and then the commutation control of the stator winding is performed to drive the rotor to rotate. At this time, the brushless DC motor operates in a self-synchronizing state, indicating that the rotor has been successfully started.

Wherein, the stable back electromotive force zero-crossing point includes the number of times the back electromotive force zero-crossing reaches a preset value or the slope of the terminal voltage rise reaches a preset value.

In summary, in the full speed process of the motor, the sensorless control of the full speed range of the brushless DC motor is divided into three stages according to the preset conditions. The electric signals of the brushless DC motor are obtained in each stage, and the brushless DC is obtained according to the electric signal. The rotor position of the motor controls the commutation of the brushless DC motor according to the rotor position.

9 is a tenth embodiment of the control method of the brushless DC motor of the present invention. In the present embodiment, the brushless DC motor is divided into three stages according to the speed in the full speed range, and the motor is separately controlled by different methods. include:

Step S01: In the first stage, when the brushless DC motor is stationary, a pulse is sequentially applied to the three phases of the brushless DC motor to obtain a current value flowing through the brushless DC motor, and the rotor of the brushless DC motor is obtained according to the current value. The initial position, and the control signal is sent according to the initial position to control the commutation of the brushless DC motor;

Step S02: In the second stage, after the brushless motor rotates, the current value flowing through the brushless DC motor and the voltage value of the brushless DC motor are obtained, and the rotor position of the brushless DC motor is obtained according to the method of the flux linkage function, according to the rotor The position transmission control signal controls the commutation of the brushless DC motor; the second stage is mainly when the motor is running at low speed, the back electromotive force is not obvious or the back electromotive force cannot be detected, and the position of the rotor can be accurately obtained by the method of flux linkage function.

Step S03: In the third stage, when the brushless DC motor detects the zero-crossing of the back electromotive force, the rotor position of the brushless DC motor is obtained by the zero-crossing point of the back electromotive force, and the commutation of the brushless DC motor is controlled according to the rotor position transmission control signal.

Specifically, the third stage mainly refers to the motor running at medium and high speeds. At this time, the back electromotive force is relatively obvious. The position of the motor rotor can be obtained according to the method of zero-crossing of the back electromotive force, and the motor is commutated according to the position of the rotor. At this stage, the motor runs at a relatively high speed. If the flux linkage function is used, the calculation amount will increase, and the commutation delay may occur, which makes the commutation inaccurate. Therefore, the back electromotive force method can be used to obtain the rotor position accurately.

In the eleventh embodiment of the control method of the brushless DC motor of the present invention, the step S01 may be the method of any one of the first to eighth embodiments.

In this embodiment, the present invention S02 may be the flux linkage function method described in the above embodiment 9, that is,

make

Among them, UBC is the voltage when the BC phase winding is turned on, and UAB is the voltage when the AB phase winding is turned on.

The above G(θ) function is independent of speed and includes a continuous position signal. When the above G(θ) tends to be infinite, it is a commutation point. In the present invention, when G(θ)) is greater than a preset value. Extremely commutating point. Since the motor's expression is the same when the motor is running at any speed, a precise commutation pulse can be obtained in both the transient and steady state of the motor.

The above method of flux linkage function detects the position of the rotor. Although the motor runs at any speed, the expression of the function is the same, that is, the detection method is applicable to the entire rotational speed range of the brushless DC motor, but the method of obtaining the flux linkage function Calculating the position of the rotor is relatively large. When the motor is running at high speed, it will happen that the position of the rotor has not yet been calculated and the commutation time has been reached. Therefore, when the motor is running at high speed, the position of the rotor is calculated by the method of flux linkage function. Will result in inaccurate calculation results.

The S03 of the present invention includes the back electromotive force zero-crossing method described in one embodiment of the above-described brushless DC motor control method for detecting the initial position of the rotor.

Wherein, the zero-crossing point of the back electromotive force is a stable zero-electrode zero-crossing point, and the number of times of the zero-crossing of the counter electromotive force reaches a preset value or the slope of the terminal voltage rise reaches a preset value. The zero-crossing of the back EMF can be detected by the terminal voltage detection method. The basic principle is: by detecting the terminal voltage and performing passive filtering, filtering out the influence of the switching noise on the low-frequency back EMF, and estimating the phase shift caused by the filtering. Then compensated by software, after comparing with the neutral point voltage of the brushless DC motor, the zero-crossing point of the obtained difference is the zero-crossing point of the back electromotive force. After finding the zero-crossing point of the back electromotive force, the 30° electrical angle is the commutation moment of the brushless DC motor.

Referring to FIG. 10, in a three-phase brushless DC motor whose back electromotive force is a trapezoidal wave, the back electromotive force of each phase has two zero crossing points in one electric cycle, and six commutation positions in three opposite electromotive force waveforms. Corresponding to b, d, f, h, j, i in the figure respectively; because the back electromotive force corresponding to these positions is not special, it is not easy to detect. The rotor position detecting method for the zero-crossing point of the back electromotive force of the present invention is to obtain the key position of the rotor of the motor by detecting the zero-crossing point of the counter electromotive force of the suspended phase when the two motors are turned on, and then perform the commutation.

Specifically, please refer to FIG. 2 and FIG. 10. If the Q1-Q6 power tube is turned on, A+B- is turned on, and the C phase is suspended. The opposite electromotive force conditions are as shown in the interval 1 of FIG. 10, so after running 30 degrees, C The back electromotive force of the phase winding will cross the zero point S1, and then run 30 degrees to reach the b position, which is the key position that can be commutated. It is conceivable that by detecting the back electromotive force zero crossing point S1-S6, the position of the relevant key can be known. In a preferred embodiment of the present invention, the position of S1 is determined by detecting the bus current value of phase C. When i _t1 >0, i _t2 <0, then S1 is located between t1 and t2, because the time difference between the two is very high. Short, it can be approximated that the time at which S1 is located is t=(t1+t2)/2.

In the brushless DC motor control method of the present invention, the initial position of the rotor is detected by the short-time pulse positioning method in the initial stage, and the rotor position is detected by the flux linkage method before the back electromotive force cannot be detected, and when the counter electromotive force is detected, according to the counter electromotive force method Detect the rotor position. The detection method adopts closed-loop control in the whole process, which makes the motor start more stable, avoids the phenomenon of jitter, and improves the accuracy of the commutation. When the counter electromotive force cannot be obtained in the low speed stage, the flux position is detected by the flux linkage method, and the detection result is more Accurate, and improve the starting torque, which increases the probability of successful start-up. The high-speed phase uses the back electromotive force method instead of the flux linkage method, which can accurately obtain the rotor position and avoid the use of the flux linkage method in high-speed operation. Large problems that may result in inaccurate commutation.

The present invention also provides a control device for closed-loop communication with a brushless DC motor and for detecting a position of a brushless DC motor rotor without a position sensor, the control device being configured to include the one described in any of the above embodiments Brushless DC motor rotor position detection method or control method.

That is, the control device of the present invention integrates the brushless DC motor rotor position detecting method in the above embodiment into a controller, so that the motor is detected by pulse injection at different speeds, that is, when the motor is stationary. The initial position, when the motor is running at low speed, the position of the rotor is detected by the flux linkage function method. When the motor is running at high speed, the position of the rotor is calculated by the flux linkage function method, the calculation amount is large, and the calculation speed is slow. When the motor runs at high speed, the calculation result of the rotor position is not accurate. Therefore, when the motor runs at medium and high speed, the back electromotive force is obvious at this time, and the position of the rotor is detected by the back electromotive force method, and the commutation is better and more accurate. The invention detects the position of the rotor in different ways by the motor at different speeds, and fully utilizes the characteristics of the motor itself, and the detection effect is better and more accurate.

The invention also protects a power tool, comprising a casing; a control device; a motor, located in the casing; a power source for supplying electric energy to the motor; a switch for controlling the power source to supply electric power to the control device and the motor; the trigger switch triggering, the power source is given The control device and the motor provide electrical energy, and the control device receives the voltage signal from different positions of the trigger switch, and the control device compares the received voltage signal with a preset voltage value pre-stored in the control device, if the voltage value is greater than the preset voltage value And the control device sequentially applies a first direction pulse of the first time and a second direction pulse of the second time to each of the three phase motors, and the controller compares the bus current value when the first direction pulse is applied to each phase. Size, obtain the position of the motor rotor and control the motor commutation.

Another embodiment of a power tool according to the present invention includes a housing; a control device; a motor located in the housing; a power source for supplying power to the motor; a switch for controlling power to supply power to the control device and the motor; and a trigger switch Triggering, the power supply supplies power to the control device and the motor, the control device receives the voltage signal set from different positions of the trigger switch, and the control device compares the received voltage signal with a preset voltage value pre-stored in the control device, if the voltage value is greater than Presetting the voltage value, and controlling the current value flowing through the brushless DC motor and the phase voltage value of the motor after obtaining the initial position without the motor until the zero point of the back electromotive force is detected, according to the voltage value and the current value and the flux linkage The relationship of the function calculates the rotor position and sends a drive signal to drive the motor commutation based on the calculated rotor position.

Preferably, the voltage value includes a voltage value of the conduction phase of the brushless DC motor and a voltage value of the non-conduction phase.

Another embodiment of a power tool according to the present invention includes a housing; a control device; a motor located in the housing; a power source for supplying power to the motor; a switch for controlling power to supply power to the control device and the motor; and a trigger switch Triggering, the power supply supplies power to the control device and the motor, the control device receives the voltage signal set from different positions of the trigger switch, and the control device compares the received voltage signal with a preset voltage value pre-stored in the control device, if the voltage value is greater than The preset voltage value is sequentially applied to the three-phase of the brushless DC motor to detect the initial position of the rotor of the brushless DC motor; after obtaining the initial position of the brushless DC motor until the zero-crossing point of the back electromotive force is detected, according to the function of the flux linkage The method determines the position of the rotor for commutation; when the brushless DC motor detects the zero-crossing of the back electromotive force, the position of the rotor is determined by the zero-crossing point of the counter electromotive force.

Another embodiment of a power tool according to the present invention includes a housing; a control device; a motor located in the housing; a power source for supplying power to the motor; and a trigger switch for controlling the power supply to supply power to the control device and the motor; The switch triggers, the power supply supplies power to the control device and the motor, and the control device sequentially applies a first direction pulse of the first time and a second direction pulse of the second time to each phase of the motor, and compares the phases when the first direction pulse is applied. The magnitude of the bus current value is obtained by taking the position of the motor rotor and controlling the motor commutation.

Another embodiment of a power tool according to the present invention includes a housing; a control device; a motor located in the housing; a power source for supplying power to the motor; and a trigger switch for controlling the power supply to supply power to the control device and the motor; The switch triggers, the power supply supplies power to the control device and the motor, and controls the current value flowing through the brushless DC motor and the phase voltage value of the motor after obtaining the initial position without the motor until the back electromotive force is detected; according to the current value and phase The relationship between the voltage value and the flux linkage function calculates the rotor position; the drive signal is transmitted according to the calculated rotor position to drive the brushless DC motor commutation.

Another embodiment of a power tool according to the present invention includes a housing; a control device; a motor located in the housing; a power source for supplying power to the motor; and a trigger switch for controlling the power supply to supply power to the control device and the motor; The switch triggers, the power supply supplies power to the control device and the motor, and the three phases of the brushless DC motor sequentially pass pulses to detect the initial position of the rotor of the brushless DC motor; after obtaining the initial position of the brushless DC motor, the zero-crossing point of the back electromotive force is detected. Previously, the position of the rotor was determined according to the method of the flux linkage function for commutation; when the brushless DC motor detected the zero-crossing of the back electromotive force, the position of the rotor was determined by the zero-crossing point of the counter electromotive force.

The motor of each of the above embodiments is a brushless DC motor, and the first direction is opposite to the second direction. The voltage value includes a voltage value of the conduction phase of the brushless DC motor and a voltage value of the non-conduction phase, and the current value includes any one of a bus current value or a phase current value, and the counter electromotive force zero crossing point is a stable back electromotive force. The zero-crossing point, including the number of zero-crossings of the back electromotive force, reaches a preset value or the slope of the terminal voltage rises to a preset value.

The electric tool of the invention comprises an electric wrench, the electric wrench is provided with a trigger switch, the trigger switch is used for controlling the starting of the electric wrench, when the user triggers the trigger switch, the electric wrench is energized, the above control device is activated, and the position of the motor rotor is detected, And control the motor commutation according to the test result.

The above-described embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A brushless DC motor control method for controlling a three-phase (A, B, C) brushless DC motor without a position sensor, characterized in that the method comprises the following steps:

Applying a first direction pulse of a first time and a second direction pulse of a second time to the phase A of the brushless DC motor to obtain a bus current value Ia when the first direction pulse is applied to the phase A;

Repeating the above operations for the B and C phases, obtaining the bus current value Ib when the B phase is applied with the first direction pulse and the bus current value Ic when the first direction pulse is applied to the C phase;

Comparing the obtained sizes of Ia, Ib, and Ic to determine the initial position of the rotor;

Transmitting the brushless DC motor by a control signal according to an initial position of the rotor.
The brushless DC motor control method according to claim 1, wherein the first direction pulse of the first time and the second direction pulse of the second time are sequentially applied to the phase A of the brushless DC motor to obtain A. The specific steps of applying the bus current value Ia when the first direction pulse is applied include:

Controlling the A phase of the brushless DC motor to be forwarded, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, and controlling the A of the brushless DC motor to be oppositely turned on, and A voltage pulse of a second time is applied to the phase A.
The brushless DC motor control method according to claim 1, wherein the first direction pulse of the first time and the second direction pulse of the second time are sequentially applied to the phase A of the brushless DC motor to obtain A. The specific steps of applying the bus current value Ia when the first direction pulse is applied further include:

Controlling A of the brushless DC motor to be oppositely turned on, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia', and controlling the A phase of the brushless DC motor to be forwarded. And applying a voltage pulse of the second time to the phase A.
The brushless DC motor control method according to claim 1, wherein the control method further comprises the steps of:

Applying a second direction pulse of the first time and a first direction pulse of the second time to the phase A of the brushless DC motor to obtain a bus current value Ia' when the second direction pulse is applied to the phase A;

Repeating the above operations for the B and C phases, obtaining the bus current value Ib' of the B phase applied with the second direction pulse and the bus current value Ic' when the C phase applying the pulse of the second direction;

The size of the obtained Ia, Ib, Ic, Ia', Ib', Ic' is compared to determine the initial position of the rotor.
The control method of the brushless DC motor according to claim 4, wherein the control method is specifically:

Controlling the A phase of the brushless DC motor to be forwarded, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, and controlling the A of the brushless DC motor to be oppositely turned on, and Applying a voltage pulse of a second time to the phase A;

Repeat the above operations for the B and C phases, and obtain the bus current value Ib when the B phase is forwarded and the bus current value Ic when the C phase is forwarded;

Controlling A of the brushless DC motor to be oppositely turned on, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia', and controlling the A phase of the brushless DC motor to be forwarded. And applying a voltage pulse of the second time to the phase A;

Repeat the above operations for the B and C phases to obtain the bus current value Ib' when B is oppositely turned on and the bus current value Ic' when C is oppositely turned on;

Comparing the obtained sizes of Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor;

Transmitting the brushless DC motor by a control signal according to an initial position of the rotor.
The control method of the brushless DC motor according to claim 4, wherein the control method is specifically:

Controlling A of the brushless DC motor to be oppositely turned on, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia', and controlling the A phase of the brushless DC motor to be forwarded. And applying a voltage pulse of the second time to the phase A;

Repeat the above operations for the B and C phases to obtain the bus current value Ib' when B is oppositely turned on and the bus current value Ic' when C is oppositely turned on;

Controlling the A phase of the brushless DC motor to be forwarded, and applying a voltage pulse of the first time to the A phase to obtain a corresponding bus current value Ia, and controlling the A of the brushless DC motor to be oppositely turned on, and Applying a voltage pulse of a second time to the phase A;

Repeat the above operations for the B and C phases, and obtain the bus current value Ib when the B phase is forwarded and the bus current value Ic when the C phase is forwarded;

Comparing the obtained sizes of Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor;

Transmitting the brushless DC motor by a control signal according to an initial position of the rotor.
The brushless DC motor control method according to claim 5, wherein the control method comprises:

Controlling the A phase of the brushless DC motor to be forwarded, B is oppositely conducting (A+B-), and applying a voltage pulse of the first time to the AB phase to obtain a corresponding bus current value Iab, and the control A is oppositely guided. , phase B is forward-conducting (A-B+), and a voltage pulse of a second time is applied to the BA phase;

Controlling the B-phase forward conduction of the brushless DC motor, C is oppositely conducting (B+C-), and applying a voltage pulse of the first time to the BC phase to obtain a corresponding bus current value Ibc, and the control B is oppositely guided. , phase C is forward-guided (B-C+), and a voltage pulse of a second time is applied to the CB phase;

Controlling the C-phase of the brushless DC motor to be forwarded, A is oppositely conducting (C+A-), and applying a voltage pulse of the first time to the CA phase to obtain a corresponding bus current value Ica, and the control C is oppositely guided. , phase A is forward-conducting (C-A+), and a voltage pulse of a second time is applied to the AC phase;

Controlling the B-phase forward conduction of the brushless DC motor, A is oppositely conducting (B+A-), and applying a voltage pulse of the first time to the BA phase to obtain a corresponding bus current value Iba, and the control B is oppositely guided. , phase A is forward-conducting (B-A+), and a voltage pulse of a second time is applied to the AB phase;

Controlling the C-phase of the brushless DC motor to be forwarded, B is opposite to the conduction (C+B-), and applying a voltage pulse of the first time to the CB phase to obtain a corresponding bus current value Icb, and the control C is oppositely guided. , phase B is forward-conducting (C-B+), and a voltage pulse of a second time is applied to the BC phase;

Controlling the A phase of the brushless DC motor is forward-conducting, C is oppositely conducting (A+C-), and applying a voltage pulse of the first time to the AC phase to obtain a corresponding bus current value Iac;

Compare the Iab, Ibc, Ica, Iba, Icb, Iac size to determine the initial position of the rotor;

Transmitting the brushless DC motor by a control signal according to an initial position of the rotor.
The brushless DC motor control method according to claim 7, wherein the comparing the Iab, Ibc, Ica, Iba, Icb, Iac size, and determining the initial position of the rotor comprises:

If Ibc>Iab>Ica, and Iba>Icb>Iac, the rotor is located in the first sector;

If Ibc>Ica>Iab, and Iac>Icb>Iba, the rotor is located in the third sector;

If Iab>Ica>Ibc, and Iac>Iba>Icb, the rotor is located in the second sector;

If Iab>Ibc>Ica, and Icb>Iba>Iac, the rotor is located in the sixth sector;

If Ica>Ibc>Iab, and Icb>Iac>Iba, the rotor is located in the fourth sector;

If Ica>Iab>Ibc, and Iba>Iac>Icb, the rotor is located in the fifth sector;

Wherein, the BC phase is rotated counterclockwise by 0°, and the electrical angle ranges of the first sector to the sixth sector are (0° 60°), (240° 300°), and (300° 360°), respectively. , (120 ° 180 °), (60 ° 120 °), (180 ° 240 °).
The brushless DC motor control method according to claim 5, wherein the step of the control method comprises:

Controlling the A phase of the brushless DC motor to be forwarded, B and C are oppositely conducting (A+BC-), applying a voltage pulse of the first time to the ABC phase, acquiring a corresponding bus current value Ia, and controlling the The brush A of the DC motor is oppositely turned on, and the B and C phases are forwardly guided (A-B+C+), and a voltage pulse of the second time is applied to the BCA phase;

Controlling the B phase of the brushless DC motor to be forwarded, and A and C are oppositely conducting (B+AC-), applying a voltage pulse of the first time to the BAC phase, acquiring a corresponding bus current value Ib, and controlling the B of the brush DC motor is oppositely turned on, and the A and C phases are forwardly guided (B-A+C+), and a voltage pulse of the second time is applied to the ACB phase;

Controlling the C phase of the brushless DC motor to be forwarded, and A and B are oppositely conducting (C+AB-), applying a voltage pulse of the first time to the CAB phase, acquiring a corresponding bus current value Ic, and controlling the The C of the brush DC motor is oppositely turned on, and the A and B phases are forwardly guided (C-A+B+), and a voltage pulse of the second time is applied to the ABC phase;

Controlling the A of the brushless DC motor is reversed, and the B and C phases are forward-conducting (A-B+C+), and a voltage pulse of the first time is applied to the BCA phase to obtain a corresponding bus current value Ia', and the control station The phase A of the brushless DC motor is forwardly guided, and B and C are oppositely connected (A+BC-), and a voltage pulse of the second time is applied to the ABC phase;

Controlling the brushless DC motor B to conduct the opposite direction, and the A and C phases are forward-conducting (B-A+C+), applying a voltage pulse of the first time to the ACB phase, and obtaining a corresponding bus current value Ib', the control station The B phase of the brushless DC motor is forwardly guided, and A and C are oppositely connected (B+AC-), and a voltage pulse of the second time is applied to the BAC phase;

Controlling the C of the brushless DC motor to conduct the opposite direction, and the A and B phases are forward-conducting (C-A+B+), and applying a voltage pulse of the first time to the ABC phase to obtain a corresponding bus current value Ic';

Comparing the sizes of Ia, Ib, Ic, Ia', Ib', Ic' to determine the initial position of the rotor;

Transmitting the brushless DC motor by a control signal according to an initial position of the rotor.
A brushless DC motor control method according to claim 9, wherein said comparing Ia, Ib, Ic, Ia', Ib', Ic' and determining the initial position of the rotor comprises:

If Ia>Ib, Ia>Ic, Ia<Ia’, the rotor is located in the first sector;

If Ib>Ia, Ib>Ic, Ib<Ib', the rotor is located in the third sector;

If Ic>Ia, Ic>Ib, Ic<Ic', the rotor is located in the second sector;

If Ia>Ib, Ia>Ic, Ia>Ia’, the rotor is located in the sixth sector;

If Ib>Ia, Ib>Ic, Ib>Ib’, the rotor is located in the fourth sector;

If Ic>Ia, Ic>Ib, Ic>Ic’, the rotor is located in the fifth sector;

Wherein, the BC phase is rotated counterclockwise by 0°, and the electrical angle ranges of the first sector to the sixth sector are (0° 60°), (240° 300°), and (300° 360°), respectively. , (120 ° 180 °), (60 ° 120 °), (180 ° 240 °).
The brushless DC motor control method according to claim 1, wherein the second time is equal to the first time.
A brushless DC motor control method, characterized in that the control method comprises:

Obtaining a current value flowing through the brushless DC motor and a voltage value of the brushless DC motor after obtaining the initial position of the brushless DC motor until a zero-crossing point of the back electromotive force is detected;

The rotor position is obtained according to the method of the flux linkage function; the brushless DC motor commutation is controlled according to the obtained rotor position transmission control signal.
The brushless DC motor control method according to claim 12, wherein the voltage value comprises a voltage value of a conduction phase of the brushless DC motor and a voltage value of a non-conduction phase.
The brushless DC motor control method according to claim 12, wherein the current value comprises any one of a bus current value or a phase current value.
The brushless DC motor control method according to claim 12, wherein the zero-crossing point of the counter electromotive force is a stable zero-crossing point of the back electromotive force, and the number of times of the zero-crossing point of the counter electromotive force reaches a preset value or the slope of the terminal voltage rises Any of the preset values.
The brushless DC motor control method according to claim 12, further comprising the steps of:

When it is determined that the brushless DC motor detects the zero-crossing point of the back electromotive force, the position of the rotor is determined by the zero-crossing point of the counter electromotive force.
A brushless DC motor control method, characterized in that the control method comprises:

The sensorless control of the full speed range of the brushless DC motor is divided into three stages according to a preset condition, and each stage acquires an electrical signal of the brushless DC motor, and the rotor position of the brushless DC motor is obtained according to the electrical signal. The brushless DC motor is commutated according to the rotor position.
The brushless DC motor control method according to claim 17, wherein the control method comprises:

In the first stage, when the brushless DC motor is stationary, a pulse is sequentially applied to the three phases of the brushless DC motor to obtain a current value flowing through the brushless DC motor, and the brushless DC motor rotor is obtained according to the current value. The initial position, and the control signal is sent according to the initial position to control the commutation of the brushless DC motor;

In the second stage, after the brushless motor rotates, the current value flowing through the brushless DC motor and the voltage value of the brushless DC motor are obtained, and the rotor position of the brushless DC motor is obtained according to the method of the flux linkage function, according to the The rotor position transmission control signal controls the commutation of the brushless DC motor;

In the third stage, when it is determined that the brushless DC motor detects the zero-crossing point of the back electromotive force, the rotor position of the brushless DC motor is obtained by the zero-crossing point of the back electromotive force, and the commutation of the brushless DC motor is controlled according to the sending position control signal of the rotor position. .
The brushless DC motor control method according to claim 18, wherein a pulse is sequentially applied to the three phases of the brushless DC motor to obtain a current value flowing through the brushless DC motor, and the current value is obtained according to the current value. The step of controlling the brushless DC motor commutation according to the initial position of the rotor of the brushless DC motor and transmitting the control signal according to the initial position comprises the steps of the brushless DC motor control method according to any one of claims 1-11.
The brushless DC motor control method according to claim 18, wherein the method of the flux linkage function comprises the brushless DC motor control method according to any one of claims 12-16.
A control device for detecting a rotor position of a brushless DC motor to control motor commutation, characterized in that said control device is configured to perform a brushless DC motor control according to any of claims 1-18 method.
A power tool including a housing;

Control device

a motor located in the housing;

a power source for supplying electrical power to the motor;

a switch, an optional opening and closing, for controlling the power supply to supply power to the control device and the motor; wherein, after the switch is closed, the first phase of the first time is applied to the phase A of the brushless DC motor The direction pulse and the second direction pulse of the second time are used to obtain the bus current value Ia when the first direction pulse is applied to the A phase; the above operation is repeated for the B and C phases, and the bus current value Ib when the B phase is applied with the first direction pulse is obtained. a bus current value Ic when the first direction pulse is applied to the C phase; comparing the obtained sizes of Ia, Ib, and Ic to determine an initial position of the rotor; and transmitting a control signal according to the initial position of the rotor to control the brushless DC motor phase.
A power tool including a housing;

Control device

a motor located in the housing;

a power source for supplying electrical power to the motor;

a switch, an optional opening and closing, for controlling a power source to supply electric power to the control device and the motor; wherein, after the switch is closed, the control device detects a zero-crossing point of the back electromotive force after obtaining the initial position of the rotor Previously, the current value flowing through the motor and the voltage value of the motor are obtained, the rotor position is obtained according to the method of the flux linkage function, and the motor commutation is controlled according to the rotor position transmission control signal.
A power tool including a housing;

Control device

a motor located in the housing;

a power source for supplying electrical power to the motor;

a switch, an optional opening and closing, for controlling the power supply to supply power to the control device and the motor; wherein the sensorless control of the full speed range of the brushless DC motor is divided into three stages according to a preset condition, After the switch is closed, the electrical signal of the brushless DC motor is obtained at each stage, the rotor position of the brushless DC motor is obtained according to the electrical signal, and the brushless DC motor is commutated according to the rotor position.
The power tool according to claim 22-24, wherein the switch is closed, further comprising: after the switch is closed, the control device receives the trigger signal from the switch and determines whether the trigger signal satisfies a preset condition, if , the motor starts.
The power tool according to claim 25, wherein said preset condition comprises a voltage signal set at a different position of the switch being greater than a preset voltage value previously stored in the control device.
A power tool according to any one of claims 22 to 24, wherein the motor is a brushless DC motor.
The power tool according to claim 22, wherein said first direction is opposite to said second direction.
The electric power tool according to any one of claims 22 to 24, wherein the control device comprises the control device according to claim 21.