CN110611464B - Rotor commutation control system and method for brushless direct current motor - Google Patents
Rotor commutation control system and method for brushless direct current motor Download PDFInfo
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- CN110611464B CN110611464B CN201910798273.8A CN201910798273A CN110611464B CN 110611464 B CN110611464 B CN 110611464B CN 201910798273 A CN201910798273 A CN 201910798273A CN 110611464 B CN110611464 B CN 110611464B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
- H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
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Abstract
A rotor commutation control system and method for a brushless DC motor comprises an inverter, a detection module and a main control module. The inverter comprises three upper pipes and three lower pipes, and the inverter adjusts the working states of the upper pipes and the lower pipes according to the received phase-change signals and pulse signals, so that the rotor is controlled to perform phase change to drive the brushless direct current motor. When the detection module detects the zero crossing point of the counter potential of the non-conducting phase in one pulse modulation period, the detection module outputs a zero crossing point signal to the main control module, and the main control module delays a preset electrical angle and then outputs a phase-change signal; the main control module correspondingly outputs a first chopping signal or a second chopping signal according to the counter-potential lifting condition of the current non-conducting phase to correspondingly control the lower tube chopping or the upper tube chopping, so that the zero crossing point of the counter-potential can be detected in any complete pulse modulation period, and the phase change is high in precision and reliability; and moreover, a position sensor is not required to be adopted to detect the position of the rotor, so that the motor structure is simplified and the overall cost is reduced.
Description
Technical Field
The invention belongs to the technical field of brushless direct current motors, and particularly relates to a rotor commutation control system and method for a brushless direct current motor.
Background
Brushless dc motors are widely used in everyday electronic products. For brushless direct current motors adopting two-to-two conduction and three-phase six-state working modes, the rotor needs to be controlled to accurately perform phase inversion. Currently, conventional brushless dc motor control techniques typically employ position sensors to detect rotor position information to determine when the brushless dc motor commutates. However, positional alignment is required when mounting the position sensor; in the using process of the motor, once the position sensor is shifted due to an external force factor, the accuracy of position detection of the position sensor is greatly reduced; also, the use of a position sensor increases the cost of the motor and makes its structure more complex.
Therefore, the conventional brushless dc motor control technology has problems of low reliability and complex motor structure due to the fact that the position sensor is relied on to detect the position information of the rotor.
Disclosure of Invention
In view of the above, the embodiment of the invention provides a rotor commutation control system and a rotor commutation control method for a brushless direct current motor, which aim to solve the problems of low reliability and complex motor structure caused by the fact that a position sensor is relied on to detect the position information of a rotor in the traditional brushless direct current motor control technology, and achieve the beneficial effect that the rotor of the brushless direct current motor can perform accurate commutation without relying on the position sensor.
A first aspect of an embodiment of the present invention provides a rotor commutation control system for a brushless dc motor, where the brushless dc motor adopts a two-to-two conduction and three-phase six-state operation mode, the rotor commutation control system includes:
the inverter comprises three bridge arms which are connected in parallel, each bridge arm comprises an upper pipe and a lower pipe, and the inverter is used for correspondingly adjusting the working states of the three upper pipes and the three lower pipes according to the received phase-change signals and pulse signals so that a rotor of the brushless direct current motor performs phase change to drive the brushless direct current motor;
the detection module is connected with the inverter and is used for detecting zero crossing points of counter electromotive force of the non-conducting phase in one pulse modulation period and outputting zero crossing point signals when detecting the zero crossing points of counter electromotive force of the non-conducting phase; and
the main control module is connected with the inverter and the detection module and is used for delaying a preset electric angle to output the phase conversion signal to the inverter after receiving the zero crossing signal;
the main control module is further used for outputting a first chopping signal to chop the lower pipe corresponding to conduction when judging that the counter-potential of the non-conduction phase in the brushless direct current motor is in an ascending state, or outputting a second chopping signal to chop the upper pipe corresponding to conduction when judging that the counter-potential of the non-conduction phase in the brushless direct current motor is in a descending state.
A second aspect of the embodiment of the present invention provides a rotor commutation control method for a brushless dc motor, where the brushless dc motor adopts a two-to-two conduction and three-phase six-state operation mode, and the rotor commutation control method includes:
the working states of the three upper pipes and the three lower pipes are correspondingly adjusted by adopting an inverter according to the received phase-change signals and pulse signals, so that a rotor of the brushless direct current motor is controlled to perform phase change to drive the brushless direct current motor, the inverter comprises three bridge arms which are mutually connected in parallel, and each bridge arm comprises one upper pipe and one lower pipe;
detecting zero crossing points of counter electromotive force of the non-conducting phase in a pulse modulation period by adopting a detection module, and outputting zero crossing point signals when detecting the zero crossing points of counter electromotive force of the non-conducting phase;
after receiving the zero crossing signal, a main control module delays a preset electrical angle to output the phase conversion signal to the inverter;
judging the lifting condition of counter potential of a non-conducting phase in the current state of the brushless direct current motor by adopting the main control module;
when the main control module is adopted to judge that the counter potential is in a rising state, outputting a first chopping signal to chop the lower pipe corresponding to the conduction;
and when the main control module is adopted to judge that the counter potential is in a descending state, outputting a second chopping signal to chop the upper tube corresponding to the conduction.
According to the rotor commutation control system and method for the brushless direct current motor, when the detection module detects the zero crossing point of the counter potential of the non-conducting phase in one pulse modulation period, the zero crossing point signal is output to the main control module, the main control module delays the preset electrical angle and then outputs the commutation signal to the inverter, a position sensor is not needed to detect the position of the rotor, and the motor structure and the overall cost are simplified; and the main control module correspondingly outputs a first chopping signal or a second chopping signal according to the counter-potential lifting condition of the current non-conducting phase so as to correspondingly control the lower tube chopping or the upper tube chopping, so that the detection module can detect the zero crossing point of the counter-potential in any complete pulse modulation period, thereby carrying out phase change, and having high phase change precision and high reliability.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic block diagram of a rotor commutation control system for a brushless dc motor according to a first aspect of the present invention;
fig. 2 is a schematic block diagram of a rotor commutation control system according to another embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of an inverter in the rotor commutation control system shown in FIG. 1 or FIG. 2;
FIG. 4 is a schematic circuit diagram of a detection module in the rotor commutation control system shown in FIG. 1 or FIG. 2;
FIG. 5 is a waveform of back electromotive force of a three-phase winding of a brushless DC motor in one dot period;
fig. 6 is a flowchart of a rotor commutation control method for a brushless dc motor according to a second aspect of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Fig. 1 is a schematic block diagram of a rotor commutation control system for a brushless dc motor according to a first aspect of the present invention, and for convenience of explanation, only the parts related to the present embodiment are shown, and the details are as follows:
the rotor commutation control system provided in this embodiment includes an inverter 10, a detection module 20 and a main control module 30.
The brushless dc motor M adopts a mode of operation in six states of two-to-two conduction and three-phase, and hereinafter, the "brushless dc motor M" will be simply referred to as a "motor".
The inverter 10 is connected with the detection module 20, the detection module 20 is connected with the main control module 30, and the main control module 30 is connected with the inverter 10.
The inverter 10 includes three parallel bridge arms, each bridge arm includes an upper tube and a lower tube, and the inverter 10 is configured to correspondingly adjust working states of the three upper tubes and the three lower tubes according to the received commutation signals and pulse signals, so that a rotor of the brushless dc motor M performs commutation to drive the brushless dc motor M.
The detection module 20 is configured to detect a zero crossing point of the counter potential of the non-conductive phase in one pulse modulation period, and output a zero crossing point signal when the zero crossing point of the counter potential of the non-conductive phase is detected.
The main control module 30 is configured to delay a preset electrical angle to output a commutation signal to the inverter 10 after receiving the zero crossing signal.
Specifically, the pulse signal is a PWM (pulse width modulation ) signal. The pulse modulation period is a period of a PWM signal, and includes two states, PWM-ON and PWM-OFF, and is referred to as a PWM-ON state when the PWM signal is at a high level and a PWM-OFF state when the PWM signal is at a low level.
Optionally, the preset electrical angle is 30 ° electrical angle, when the main control module 30 receives the zero crossing signal output by the detection module 20, it indicates that the counter potential reaches the zero crossing point at this moment, and the time when the counter potential reaches the zero crossing point is delayed by 30 ° electrical angle to be the phase-change point, so that the phase-change point can be accurately detected by accurately detecting the zero crossing point, and the rotor of the motor M is controlled to perform phase change at the phase-change point, so that phase-change offset is avoided, and normal operation of the motor M is affected.
According to the rotor commutation control system provided by the embodiment, the detection module 20 detects the zero crossing point of the counter potential of the non-conducting phase in one pulse modulation period, when the zero crossing point is detected, the zero crossing point signal is output to the main control module 30, the main control module 30 delays the preset electric angle and then outputs the commutation signal, so that the commutation is realized, the position of the rotor is not required to be detected by adopting the position sensor, the deviation of the installation position of the position sensor or the displacement of the position sensor once caused by the external force factor in the using process of the motor M is avoided, the problem of low system reliability is caused, the power consumption of the system is greatly saved, the energy is saved, the environment is protected, the circuit is simple, and the whole machine cost is low.
In this embodiment, the main control module 30 is further configured to output a first chopping signal to chop the lower tube corresponding to conduction when it is determined that the counter-potential of the non-conducting phase in the brushless dc motor M is in an ascending state, or output a second chopping signal to chop the upper tube corresponding to conduction when it is determined that the counter-potential of the non-conducting phase in the brushless dc motor M is in a descending state.
When the counter potential of the non-conducting phase rises, the lower tube chopping is controlled, so that zero crossing points of the counter potential can be detected in a complete pulse modulation period; when the counter potential of the non-conducting phase is reduced, the upper tube chopping is controlled, so that zero crossing points of the counter potential can be detected in a complete pulse modulation period.
Therefore, compared with the traditional technology capable of detecting zero crossing points only during PWM-ON, the embodiment can correspondingly control the lower tube or the upper tube to chop according to the counter potential lifting condition of the non-conducting phase during any conducting phase sequence, so that the detection module 20 can detect the zero crossing points of the counter potential in a complete pulse modulation period, the detection precision of the zero crossing points is greatly improved, the phase inversion precision is also greatly improved, and the reliability of the system is high.
Fig. 2 is a schematic block diagram of a rotor commutation control system according to another embodiment of the present invention, and for convenience of explanation, only the parts related to the present embodiment are shown, and the details are as follows:
in an alternative embodiment, the rotor commutation control system described above further includes a power module 40 and a calculation module 50.
The power module 40 is connected to the inverter 10, and is configured to provide a dc signal VCC to the inverter 10.
The calculating module 50 is connected to the detecting module 20 and the inverter 10, and is configured to calculate the virtual center point voltage of the motor M in real time, and feed back the virtual center point voltage to the detecting module 20.
Specifically, the calculation formula of the virtual center point voltage is:
wherein, the voltage of the U phase terminal is V B Is a V-phase terminal voltage, said V C Is the W-phase terminal voltage.
Specifically, the detection module 20 outputs the zero crossing signal to the main control module 30 when the terminal voltage of the non-conductive phase jumps from greater than the virtual center point voltage to less than the virtual center point voltage, or when the terminal voltage of the non-conductive phase jumps from less than the virtual center point voltage to greater than the virtual center point voltage, by comparing the terminal voltage of the non-conductive phase with the virtual center point voltage.
Fig. 3 is a schematic circuit diagram of the inverter 10 in the rotor commutation control system shown in fig. 1 or 2, and for convenience of explanation, only the portions related to the present embodiment are shown, and the details are as follows:
in an alternative embodiment, the three upper pipes Q1, Q3 and Q5 and the three lower pipes Q2, Q4 and Q6 are all implemented by power switch pipes, and a gate of each power switch pipe is connected to the main control module 30 and is configured to receive a pulse signal output by the main control module 30.
As shown in fig. 3, an upper tube Q1 and a lower tube Q2 form a bridge arm, an upper tube Q3 and a lower tube Q4 form another bridge arm, and an upper tube Q5 and a lower tube Q6 form a third bridge arm; each bridge arm comprises an upper pipe and a lower pipe, the drains of the three upper pipes are connected with a direct current electric signal VCC, the sources of the three upper pipes are respectively connected with the drains of the corresponding three lower pipes, and the sources of the three lower pipes are grounded; the inverter 10 further includes freewheel diodes connected in one-to-one parallel with the upper and lower tubes, respectively, the freewheel diodes being adapted to provide freewheel paths when the upper tube connected in parallel therewith is disconnected. Alternatively, the freewheeling diode can be replaced by an embedded diode of six power switching transistors Q1-Q6.
The turn-on phase sequence of the motor M and the turn-on sequence of the Q1 to Q6 power switching transistors are shown in table 1 below:
six power switching tubes in tables 1Q 1-Q6 together form a full-bridge driving circuit for controlling the electrified state of the motor M winding, the power switching tubes are electrified in a two-to-two conduction mode, two power switching tubes are electrified in each moment, the motor M rotor is subjected to primary commutation in every 1/6 electric period, namely 60 DEG electric angle, each power switching tube is continuously electrified by 120 DEG electric angle, each phase winding is continuously electrified by 120 DEG electric angle, and the phase current direction is unchanged in the period between two commutation.
When the conducting phase sequence of the motor M is VW phase conduction and the U phase is non-conduction, the counter potential of the U phase is in a descending state according to the counter potential waveform diagram shown in fig. 5, and the counter potential gradually descends from greater than zero to less than zero, so that the main control module 30 controls the upper tube chopping, and the Q3 chopping is controlled, the Q6 is normally open, and the four power switching tubes are all in a cut-off state except for Q3 and Q6 conduction.
When the conducting phase sequence of the motor M is VU phase conduction and the W phase is non-conduction, according to the counter potential waveform diagram shown in fig. 5, the counter potential of the W phase is in a rising state, and the counter potential gradually rises from less than zero to more than zero, and the main control module 30 controls the down tube chopping, so that the Q2 chopping is controlled, the Q3 is normally open, and the four power switching tubes are all in a cut-off state except for Q2 and Q3 conduction.
When the conducting phase sequence of the motor M is WU phase conduction and the V phase is non-conduction, according to the counter potential waveform diagram shown in FIG. 5, the counter potential of the V phase is in a descending state, the counter potential gradually descends from a position larger than zero to a position smaller than zero, the main control module 30 controls the upper tube chopping, so that Q5 chopping is controlled, Q2 is normally open, and other four power switching tubes are in a cut-off state except for Q5 and Q2 conduction.
When the conducting phase sequence of the motor M is WV phase conduction and the U phase is non-conduction, according to the counter potential waveform diagram shown in FIG. 5, the counter potential of the U phase is in a rising state, the counter potential gradually rises from less than zero to more than zero, the main control module 30 controls the down tube chopping, so that the Q4 chopping is controlled, the Q5 is normally open, and the four power switching tubes are all in a cut-off state except for the conduction of the Q4 and the Q5.
When the conducting phase sequence of the motor M is UV phase conduction and the W phase is non-conduction, according to the counter potential waveform diagram shown in FIG. 5, the counter potential of the W phase is in a descending state, the counter potential gradually descends from a position larger than zero to a position smaller than zero, the main control module 30 controls the upper tube chopping, so that Q1 chopping is controlled, Q4 is normally open, and other four power switching tubes are in a cut-off state except that Q1 and Q4 are conducted.
When the conducting phase sequence of the motor M is UW phase conduction and V phase is non-conduction, according to the counter potential waveform diagram shown in fig. 5, the counter potential of the V phase is in a rising state, and the counter potential gradually rises from less than zero to greater than zero, and the main control module 30 controls the down tube chopping, so that the Q6 chopping is controlled, the Q1 is normally open, and the four power switching tubes are all in a cut-off state except for Q6 and Q1 conduction.
The dc brushless motor M operates in a mode of two-by-two conduction and three-phase six-state, wherein two-by-two conduction means that the inverter 10 has only two power switching tubes at any instant, so as to control two phases of three phases to operate, the three phases refer to three states of a winding U-phase, a V-phase and a W-phase of the motor M, and the six states refer to six conduction phase sequences of the motor M shown in table 1.
According to the rotor commutation control system provided by the embodiment, the main control module 30 controls the lower tube chopping when the counter potential of the non-conducting phase rises, and controls the upper tube chopping when the counter potential of the non-conducting phase falls, so that the detection module 20 can detect the zero crossing point of the counter potential in a complete pulse modulation period, the detection precision of the zero crossing point is greatly improved, the commutation precision is also greatly improved, and the system reliability is high.
Fig. 4 is a schematic circuit diagram of the detection module 20 in the rotor commutation control system shown in fig. 1 or 2, and for convenience of explanation, only the portions related to this embodiment are shown, and the details are as follows:
in an alternative embodiment, the detection module 20 described above is implemented using a comparator,
the non-inverting input end of the comparator is connected with the inverter 10 and is used for receiving the end voltage of the non-conducting phase in the brushless direct current motor M in real time; the inverting input of the comparator is connected to the calculation module 50 for receiving the virtual center point voltage in real time.
Specifically, the virtual center point voltage is the virtual center point voltage of the motor M, and the calculation formula is as follows:
wherein the V is A Is the voltage of the U phase terminal, V B Is a V-phase terminal voltage, said V C Is the W-phase terminal voltage.
The comparator outputs a first level signal when the end voltage of the non-conductive phase is greater than the virtual center point voltage, and outputs a second level signal when the end voltage of the non-conductive phase is less than the virtual center point voltage by comparing the end voltage of the non-conductive phase with the virtual center point voltage. Optionally, the first level signal is a high level 1, the second level signal is a low level 0, and when the counter potential of the non-conducting phase crosses zero, the level signal output by the comparator jumps from 1 to 0 or from 0 to 1; when the counter potential of the non-conducting phase is in a rising state and crosses zero, the level signal output by the comparator jumps from 0 to 1, and when the counter potential of the non-conducting phase is in a falling state and crosses zero, the level signal output by the comparator jumps from 1 to 0.
When the counter potential of the non-conducting phase crosses zero, the level signal output by the comparator jumps, after the main control module 30 receives the jump signal, the jump signal is the zero crossing signal, and the main control module 30 delays the 30-degree electrical angle to control the output phase conversion to control the rotor to perform phase conversion.
Optionally, the calculation module 50 is implemented by three resistors, and one end of each of the three resistors is connected to the U-phase terminal voltage, the V-phase terminal voltage, and the W-phase terminal voltage respectively; the other ends of the three resistors are commonly connected, and the common terminal voltage of the three resistors is a virtual center voltage point:
according to the rotor commutation control system provided by the embodiment, the zero crossing point of the counter potential of the non-conducting phase is detected in one pulse modulation period through the comparator, when the zero crossing point is detected, a zero crossing point signal is output to the main control module 30, the main control module 30 delays a preset electrical angle and then outputs a commutation signal, so that commutation is realized, a position sensor is not required to detect the position of a rotor, deviation of the installation position of the position sensor or displacement of the position sensor once caused by external force factors in the using process of the motor M is avoided, the problem of low system reliability is caused, the motor structure is greatly simplified, and the cost is reduced.
As shown in fig. 5, a back electromotive force waveform diagram of the three-phase winding of the brushless dc motor M in one electrical cycle is shown; the motor M performs phase change every 60-degree electric angle, the rotor of the motor M takes the electric time sequence of 60-degree electric angle as a sector, and each sector corresponds to one conducting phase sequence, so that the rotor has six conducting phase sequences, namely six states; each conducting phase sequence is represented by two-phase winding energization, and one-phase winding is suspended, namely two-phase windings are conducted.
The main control module 30 outputs pulse signals to the gates of the power switching transistors in the inverter 10, and modulates the inverter 10 to operate based on the pulse signals. The period of the pulse signal is referred to as a pulse modulation period, and in one pulse modulation period, the state in which the pulse signal is at a high level is referred to as PWM-ON, and the state in which the pulse signal is at a low level is referred to as PWM-OFF.
The working principle of the rotor commutation control system provided by the embodiment of the invention is explained below by taking table 2 as an example and combining table 1, fig. 4 and fig. 5:
TABLE 2
Conventional sensorless rotor position detection techniques detect back emf only once in a pulse modulation period and only at PWM-ON. In the case of a low rotational speed of the motor M, the pulse modulation period is small relative to the electrical period of the motor M, and the influence thereof can be ignored; however, when the rotation speed of the motor M is high, the PWM period is not much different from the electrical period of the motor M, and when the pulse modulation period has an error, a large offset will occur during phase commutation of the motor M, so that the rotor of the motor M performs phase commutation at a non-phase commutation point.
Aiming at the problems of the traditional position sensor-free rotor position detection technology, the embodiment of the invention provides a rotor commutation control system and a rotor commutation control method for a brushless direct current motor, which can detect zero crossing points of counter electromotive force of a non-conducting phase in the whole pulse modulation period, thereby indirectly detecting the rotor position, deducing the commutation point, greatly improving the commutation precision and avoiding commutation offset.
As shown in table 2, taking 270 ° to 330 ° sectors as an example, the principle of controlling down tube chopping and deducing beneficial effects when the counter potential of the non-conducting phase rises by the main control module 30 are illustrated:
in the sector of 270-330 degrees, the conducting phase sequence is UW phase conduction, V phase non-conduction, and the opposite V potential is in the rising state, the main control module 30 controls the lower tube Q6 to chop, and controls the upper tube Q1 to be normally open.
Setting the opposite potential of V as x, and x is less than 0 when theta is less than 300 degrees; when theta is more than 300 DEG, x is more than 0.
During PWM-ON, current flows from power module 40 to ground via upper tube Q1, U-phase winding, W-phase winding, and lower tube Q6; in this process, the neutral point voltage of the motor M is: v (V) N =vcc/2; the terminal voltage of the V phase is:
during PWM-OFF, current flows from the power module 40 back to the power module 40 through the Q1, U-phase winding, W-phase winding, embedded diode of the upper tube Q5; in this process, the neutral point voltage of the motor M is: v (V) N =vcc; the terminal voltage of the V phase is: v (V) B ＝V N +x＝VCC+x。
(1) During PWM-ON, the U-phase terminal voltage is: v (V) A The terminal voltage of the W phase is VCC: v (V) C =0, v-phase terminal voltage isThe virtual center point voltage input to the inverting input of the comparator is: />
It can be seen that when x < 0, V ref ＞V B The comparator outputs a second level signal; when x > 0, V ref ＜V B The comparator outputs a first level signal. Therefore, zero crossing detection of the non-conducting phase is achieved by edge transitions of the comparator.
(2) During PWM-OFF, the U-phase terminal voltage is V A =vcc, W-phase terminal voltage V C =vcc, V-phase terminal voltage V B ＝VCC+x。
When theta is less than 300 DEG, x is less than 0, and the virtual center point voltage isThus V B ＜V ref The comparator outputs a second level signal.
When θ > 300 °, x > 0, at this time V B Clamped to VCC, thusThe output state of the comparator is unstable, but because counter potential x of the non-conducting phase has zero crossing point at the moment, if the comparator outputs a first level signal, the comparator is determined to generate level jump, and a zero crossing point signal is output; if the comparator outputs the second level signal at this time, the zero crossing point can be detected in the PWM-ON phase of the next pulse modulation period.
In summary, in the sectors with rising counter-potential of the non-conducting phase, the main control module 30 outputs the first chopping signal to control the down tube chopping, so that the comparator can judge the zero crossing point of the counter-potential of the non-conducting phase according to whether the output level signal generates edge jump or not in the PWM-ON period and the PWM-OFF period in a complete pulse modulation period.
As shown in table 2, taking a 330 ° to 30 ° sector as an example, the principle of controlling upper tube chopping and deducing beneficial effects when the counter potential of the non-conductive phase decreases by the main control module 30 are illustrated:
in the sector of 330-30 degrees, the conduction phase sequence is VW phase conduction, U phase non-conduction, and U opposite potential is in a descending state, and the main control module 30 controls the lower tube Q3 to chop and controls the upper tube Q6 to be normally open.
Setting the opposite potential of U as x, and when theta is smaller than 360 DEG, x is larger than 0; when theta is more than 360 DEG, x is less than 0.
During PWM-ON, current flows from power module 40 to ground via upper tube Q3, V-phase winding, W-phase winding, and lower tube Q6; in this process, the neutral point voltage of the motor M is: v (V) N =vcc/2; the terminal voltage of the U phase is:
during PWM-OFF, the current V-phase winding, W-phase winding, down tube Q6 and down tube Q4 embedded diodes flow back to the V-phase winding; in this process, the neutral point voltage of the motor M is: v (V) N =0; the back electromotive force of the U phase is x, and the terminal voltage of the U phase is: v (V) A ＝V N +x＝x。
(3) During PWM-ON, the V-phase terminal voltage is: v (V) B The terminal voltage of the W phase is VCC: v (V) C Phase terminal voltage of = 0,UThe virtual center point voltage input to the inverting input of the comparator is: />
It can be seen that when x > 0，V ref ＜V B The comparator outputs a first level signal; when x < 0, V ref ＞V B The comparator outputs a second level signal. Therefore, zero crossing detection of the non-conducting phase is achieved by edge transitions of the comparator.
(4) During PWM-OFF, the U-phase terminal voltage is V A =0, w-phase terminal voltage V C =0, V phase terminal voltage V B ＝x。
When θ < 360 °, x > 0, the virtual center point voltage isThus V B ＜V ref The comparator outputs a first level signal.
When θ > 360 °, x < 0, V A Clamped to 0, thusThe output state of the comparator is unstable, but because counter potential x of the non-conducting phase has zero crossing point at the moment, if the comparator outputs a second level signal, the comparator is determined to generate level jump, and a zero crossing point signal is output; if the comparator outputs the first level signal at this time, the zero crossing point can be detected in the PWM-ON phase of the next pulse modulation period.
In summary, as described in the points (3) and (4), in the sector where the counter electromotive force of the non-conducting phase decreases, the main control module 30 outputs the second chopping signal to control the down tube chopping, so that the comparator can judge the zero crossing point of the counter electromotive force of the non-conducting phase according to whether the output level signal generates edge jump or not in the PWM-ON period and the PWM-OFF period in a complete pulse modulation period.
In summary, as described in the points (1), (2), (3) and (4), when the counter potential of the non-conducting phase rises, the counter potential zero crossing point can be detected in a complete pulse modulation period by controlling the down tube chopper; when the counter potential of the non-conducting phase is reduced, the upper tube chopping is controlled, so that zero crossing points of the counter potential can be detected in a complete pulse modulation period. Therefore, compared with the traditional technology capable of detecting zero crossing points only during PWM-ON, the embodiment can correspondingly control the lower tube or the upper tube to chop according to the counter potential lifting condition of the non-conducting phase during any conducting phase sequence, so that the detection module 20 can detect the zero crossing points of the counter potential in a complete pulse modulation period, the detection precision of the zero crossing points is greatly improved, the phase inversion precision is also greatly improved, and the reliability of the system is high.
Fig. 6 is a specific flowchart of a rotor commutation control method for a brushless dc motor according to a second aspect of the present invention, and for convenience of explanation, only the parts related to the present embodiment are shown, and the details are as follows:
a rotor commutation control method for a brushless direct current motor, wherein the brushless direct current motor M adopts a working mode of two-to-two conduction and three-phase six states; the rotor commutation control method comprises the following steps:
s01: the working states of the three upper pipes and the three lower pipes are correspondingly adjusted by adopting the inverter 10 according to the received phase-change signals and pulse signals, so that a rotor of the brushless direct current motor M is controlled to perform phase change to drive the brushless direct current motor M, the inverter 10 comprises three bridge arms which are mutually connected in parallel, and each bridge arm comprises an upper pipe and a lower pipe;
s02: detecting zero crossing points of counter electromotive force of the non-conducting phase in one pulse modulation period by adopting a detection module 20, and outputting zero crossing point signals when the zero crossing points of counter electromotive force of the non-conducting phase are detected;
s03: after receiving the zero crossing signal, the main control module 30 delays a preset electrical angle to output a phase-change signal to the inverter 10;
s04: judging the lifting condition of the counter potential of the non-conducting phase in the current state of the brushless direct current motor M by adopting a main control module 30;
s05: when the main control module 30 is adopted to judge that the counter potential is in the rising state, a first chopping signal is output to chop the lower tube corresponding to the conduction;
s06: when the main control module 30 is adopted to judge that the counter potential is in a descending state, a second chopping signal is output to chop the upper tube corresponding to the conduction.
Specifically, the pulse modulation period is a period of a PWM signal, and includes two states, PWM-ON and PWM-OFF, and is referred to as a PWM-ON state when the PWM signal is at a high level and a PWM-OFF state when the PWM signal is at a low level.
In an alternative embodiment, the rotor commutation control method further includes the following steps:
s07: the calculation module 50 is adopted to calculate the virtual center point voltage of the brushless direct current motor M in real time and feed back the virtual center point voltage to the detection module 20, and the calculation formula is as follows:
wherein V is ref For virtual centre point voltage, V A Is the voltage of the U phase terminal, V B V is the voltage of the V phase terminal C Is the W-phase terminal voltage.
Specifically, step S07 is performed before step S02.
In an alternative embodiment, step S02 is specifically:
receiving the end voltage of a non-conducting phase of the brushless direct current motor M in real time through a positive phase input end by adopting a comparator;
receiving the virtual center point voltage in real time through an inverting input end by adopting a comparator;
the end voltage of the non-conducting phase is compared with the virtual center point voltage in real time by adopting a comparator, and when the end voltage of the non-conducting phase is larger than the virtual center point voltage, a first level signal is output through the output end, or when the end voltage of the non-conducting phase is smaller than the virtual center point voltage, a second level signal is output through the output end.
When the comparator detects the zero crossing point of the counter potential of the non-conducting phase in one pulse modulation period, the zero crossing point signal is output to the main control module 30, the main control module 30 delays a preset electrical angle and then outputs a phase-change signal to the inverter 10, a position sensor is not needed to be used for detecting the position of the rotor, the motor design is simplified, and the cost is reduced.
In an alternative embodiment, step S04 is specifically:
the main control module 30 judges that the conduction phase sequence is VW phase conduction, and when the U phase is non-conduction, the counter potential of the U phase in the current state is judged to be in a descending state;
the main control module 30 judges that the conducting phase sequence is VU phase conduction, and when the W phase is non-conduction, the counter potential of the W phase is in an ascending state under the current state;
the main control module 30 judges that the conducting phase sequence is WU phase conduction and when the V phase is non-conduction, the counter potential of the V phase is in a descending state under the current state;
the main control module 30 judges that the conducting phase sequence is WV phase conduction, and when the U phase is non-conduction, the counter potential of the U phase is in an ascending state under the current state;
the main control module 30 judges that the conducting phase sequence is UV phase conduction, and when the W phase is non-conduction, the counter potential of the W phase is in a descending state under the current state;
the main control module 30 determines that the conducting phase sequence is UW phase conduction, and when the V phase is non-conduction, determines that the counter potential of the V phase is in an ascending state under the current state.
Of course, in the six states of the motor M corresponding to the six conducting phases, the lifting conditions of the non-conducting phases may be set according to actual needs, and the foregoing shows a correspondence between the lifting conditions of the conducting phases and the non-conducting phases, and other correspondence may be adopted in actual operation.
In summary, the embodiment of the invention provides a rotor commutation control system and a method for a brushless direct current motor, which detect zero crossing points of counter electromotive force of a non-conducting phase in a pulse modulation period through a detection module, output zero crossing point signals to a main control module when the zero crossing points are detected, delay a preset electrical angle through the main control module and output commutation signals, so that commutation is realized, a position sensor is not needed to detect the position of a rotor, deviation of the installation position of the position sensor or displacement of the position sensor due to external force factors once the position sensor is caused in the using process of the motor is avoided, the problem of low system reliability is caused, the power consumption of the system is greatly saved, the energy is saved, the environment is protected, the motor structure is simplified, and the whole cost is reduced.
Compared with the traditional technology capable of detecting zero crossing points only during PWM-ON, the invention correspondingly controls the lower tube or the upper tube to chop according to the counter-potential lifting condition of the non-conducting phase during any conducting phase sequence by the main control module, so that the detection module can detect the zero crossing points of the counter-potential in a complete pulse modulation period, the detection precision of the zero crossing points is greatly improved, the phase-changing precision is also greatly improved, and the reliability of the system is high.
Various embodiments are described herein for various systems, circuits, and methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and shown in the accompanying drawings. However, it will be understood by those skilled in the art that the embodiments may be practiced without such specific details. In other instances, well-known operations, components and elements have been described in detail so as not to obscure the embodiments in the specification. It will be appreciated by persons skilled in the art that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. The utility model provides a rotor commutation control system for brushless DC motor, brushless DC motor adopts two-to-two to switch on and six state's of three-phase mode of operation, its characterized in that, rotor commutation control system includes:
the inverter comprises three bridge arms which are connected in parallel, each bridge arm comprises an upper pipe and a lower pipe, and the inverter is used for correspondingly adjusting the working states of the three upper pipes and the three lower pipes according to the received phase-change signals and pulse signals so that a rotor of the brushless direct current motor performs phase change to drive the brushless direct current motor;
the detection module is connected with the inverter and is used for detecting zero crossing points of counter electromotive force of the non-conducting phase in one pulse modulation period and outputting zero crossing point signals when detecting the zero crossing points of counter electromotive force of the non-conducting phase; and
the main control module is connected with the inverter and the detection module and is used for delaying a preset electric angle to output the phase conversion signal to the inverter after receiving the zero crossing signal;
the main control module is further used for outputting a first chopping signal to chop the lower pipe corresponding to conduction when judging that the counter-potential of the non-conduction phase in the brushless direct current motor is in an ascending state, or outputting a second chopping signal to chop the upper pipe corresponding to conduction when judging that the counter-potential of the non-conduction phase in the brushless direct current motor is in a descending state.
2. The rotor commutation control system of claim 1, further comprising:
the calculating module is connected with the detecting module and the inverter, and is used for calculating the virtual center point voltage of the brushless direct current motor in real time and feeding back the virtual center point voltage to the detecting module.
3. The rotor commutation control system of claim 2, wherein the detection module is implemented using a comparator;
the positive phase input end of the comparator is connected with the inverter and is used for receiving the end voltage of a non-conducting phase in the brushless direct current motor in real time;
and the inverting input end of the comparator is connected with the calculation module and is used for receiving the virtual center point voltage in real time.
4. The rotor commutation control system of claim 1, further comprising:
and the power module is connected with the inverter and used for providing direct current signals for the inverter.
5. The rotor commutation control system of claim 1, wherein the predetermined electrical angle is 30 °.
6. The rotor commutation control system of claim 1, wherein three of the upper tubes and three of the lower tubes are each implemented with a power switching tube; and the grid electrodes of the power switch tubes are connected with the main control module and are used for receiving the pulse signals.
7. A rotor commutation control method for a brushless direct current motor adopts a working mode of two-to-two conduction and three-phase six states; the rotor commutation control method is characterized by comprising the following steps:
the working states of the three upper pipes and the three lower pipes are correspondingly adjusted by adopting an inverter according to the received phase-change signals and pulse signals, so that a rotor of the brushless direct current motor is controlled to perform phase change to drive the brushless direct current motor, the inverter comprises three bridge arms which are mutually connected in parallel, and each bridge arm comprises one upper pipe and one lower pipe;
detecting zero crossing points of counter electromotive force of the non-conducting phase in a pulse modulation period by adopting a detection module, and outputting zero crossing point signals when detecting the zero crossing points of counter electromotive force of the non-conducting phase;
after receiving the zero crossing signal, a main control module delays a preset electrical angle to output the phase conversion signal to the inverter;
judging the lifting condition of counter potential of a non-conducting phase in the current state of the brushless direct current motor by adopting the main control module;
when the main control module is adopted to judge that the counter potential is in a rising state, outputting a first chopping signal to chop the lower pipe corresponding to the conduction;
and when the main control module is adopted to judge that the counter potential is in a descending state, outputting a second chopping signal to chop the upper tube corresponding to the conduction.
8. The rotor commutation control method of claim 7, further comprising:
and calculating the virtual center point voltage of the brushless direct current motor in real time by adopting a calculation module and feeding back the virtual center point voltage to the detection module, wherein the calculation formula is as follows:
wherein the V is ref For the virtual center point voltage, the V A Is the voltage of the U phase terminal, V B Is a V-phase terminal voltage, said V C Is the W-phase terminal voltage.
9. The method for controlling commutation of a rotor according to claim 8, wherein,
the detection module is adopted to detect the zero crossing point of the counter potential of the non-conducting phase in one pulse modulation period, and when the zero crossing point of the counter potential of the non-conducting phase is detected, a zero crossing point signal is output, specifically:
receiving the end voltage of a non-conducting phase of the brushless direct current motor in real time through a positive phase input end by adopting a comparator;
receiving the virtual center point voltage in real time through an inverting input end by adopting a comparator;
and comparing the terminal voltage of the non-conducting phase with the virtual center point voltage in real time by adopting the comparator, and outputting a first level signal through an output end when the terminal voltage of the non-conducting phase is larger than the virtual center point voltage, or outputting a second level signal through the output end when the terminal voltage of the non-conducting phase is smaller than the virtual center point voltage.
10. The method for controlling commutation of a rotor according to claim 7, wherein,
the main control module is adopted to judge the lifting condition of the counter potential of the non-conducting phase under the current state of the brushless direct current motor, and the method specifically comprises the following steps:
the main control module judges that the conduction phase sequence is VW phase conduction, and judges that the counter potential of the U phase is in a descending state under the current state when the U phase is non-conduction;
the main control module judges that the conducting phase sequence is VU phase conduction, and when the W phase is non-conduction, the counter potential of the W phase is in an ascending state under the current state;
the main control module judges that the conducting phase sequence is WU phase conduction, and when the V phase is non-conduction, the counter potential of the V phase is in a descending state under the current state;
the main control module judges that the conducting phase sequence is WV phase conduction, and judges that the counter potential of the U phase is in an ascending state under the current state when the U phase is non-conduction;
the main control module judges that the conducting phase sequence is UV phase conduction, and when the W phase is non-conduction, the counter potential of the W phase is in a descending state under the current state;
and the main control module judges that the conduction phase sequence is UW conduction, and when the V phase is non-conduction, the counter potential of the V phase is in an ascending state under the current state.
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