CN109861595B

CN109861595B - Position-sensorless control method for high-electric-speed brushless direct current motor

Info

Publication number: CN109861595B
Application number: CN201910162791.0A
Authority: CN
Inventors: 祁宏
Original assignee: Suzhou Zhiying Electronic Technology Co ltd
Current assignee: Suzhou Zhiying Electronic Technology Co ltd
Priority date: 2019-03-05
Filing date: 2019-03-05
Publication date: 2021-09-07
Anticipated expiration: 2039-03-05
Also published as: CN109861595A

Abstract

The invention discloses a high-power rotating speed brushless direct current motor position sensorless control method, which comprises the steps of starting and running a motor, wherein the running and starting of the motor are respectively as follows: motor positioning, motor starting, low-speed running and high-speed running; in the running process of the motor, the motor positioning and starting process runs once, and the low-speed and high-speed processes run repeatedly according to the speed setting. The integral control method is simple, saves energy consumption, greatly improves the working efficiency of the motor, and is worthy of popularization.

Description

Position-sensorless control method for high-electric-speed brushless direct current motor

Technical Field

The invention relates to the technical field of motor control, in particular to a sensorless control method for a high-electric-speed brushless direct current motor.

Background

With the development of semiconductor technology and motor control technology, the application field of the brushless dc motor is wider and wider due to the advantages of high efficiency, large torque, long service life and the like. Meanwhile, the brushless direct current motor can be reliably operated only by correctly commutating the position signal of the permanent magnet rotor, so that higher requirements on correct detection of the position of the rotor are provided. The application of the control technology without the position sensor can avoid a plurality of problems of installing the sensor, and can also be applied to certain motor applications which are not suitable for installing the position sensor.

At present, the application of the sensorless control mode of the brushless direct current motor is more and more extensive. And among them, the most applied is the back electromotive force control manner, that is, the position of the rotor of the motor is detected by detecting the back electromotive force of the non-energized phase in rotation; the most common mode 1 is a commutation mode in which the zero-crossing point of the opposite potential that is not energized is detected with a further 30-degree delay. Because the speed regulation of the motor generally adopts PWM pulse width speed regulation, interference signals of PWM signals must be filtered, and the zero crossing point of an unpowered phase is detected by comparing a voltage value of the unpowered phase sampled by an A/D port of a control MCU or a DSP chip when the PWM is switched on with the direct current voltage of 1/2. However, under the condition of high rotation speed of the motor, when each switching period (60 degrees electrical angle) is less than 8 times of the PWM period, the error of position detection is too large and the phase is lost due to too low sampling precision, for example, when the electrical rotation speed of the motor reaches 20000 revolutions, each commutation time is 500us, the carrier frequency of the PWM must be greater than 16K (62.5 us of carrier period) to ensure the commutation precision of the motor, as described in CN105680740A "a control method for a high rotation speed brushless dc motor without position sensor", the maximum electrical rotation speed of the motor using this method can only reach 2 ten thousand revolutions per minute. When the rotating speed of the motor is required to be higher, the pwm carrier frequency must be increased again, the high pwm carrier brings higher switching loss of the power tube, the failure rate of the power tube is increased, and the mode cannot be applied to the motor with higher rotating speed due to the limitation of the highest switching frequency of the IGBT tube in some high-voltage occasions; meanwhile, the A/D sampling interrupt processing must be completed in one pwm period, which requires a DSP and an MCU with high processing speed, and increases the control cost. Another control mode 2 is to detect the zero crossing point of the non-energized phase by filtering the PWM carrier signal through RC low-pass filtering and comparing with the center point of the motor. However, in the method, when the motor is at a low speed, the counter potential amplitude value is too low after low-pass filtering, phase loss can be caused by small parameter difference, the motor cannot be started well under the condition of low speed (particularly under a high load), meanwhile, the low-pass filter brings phase shift, the phase shift angle after filtering needs to be calculated for compensation, and a high-end MCU or DSP needs to be used for processing to obtain a good effect. In view of the above, how to invent a sensorless control method for a high-electric-speed brushless dc motor becomes a problem to be solved.

Disclosure of Invention

The invention aims to provide a sensorless control method of a high-electric-speed brushless direct current motor, which solves the problems in the background art.

In order to solve the above problems, the present invention provides the following technical solutions: a control method for a high-electric-speed brushless direct current motor without a position sensor comprises the steps of starting and running the motor, wherein the running and starting of the motor are respectively as follows: motor positioning, motor starting, low-speed running and high-speed running; in the running process of the motor, the motor positioning and starting process runs once, and the low-speed and high-speed processes run repeatedly according to the speed setting.

The brushless motor rotor is divided into 6 states in 360-degree electrical angle, wherein the states are 001,101,100,110,010,011 respectively, and the corresponding 6 driving states are AH and BL; AH. CL; BH. CL; BH. AL; CH. AL; CH. BL, when determining that the motor rotor is in a certain state of 6 states, output corresponding signal control 3 looks bridge type power tube, make the motor rotate, foresee the next state of motor namely the corresponding order of switching power tube.

The motor is positioned: when the motor stops, the motor is rotated to a fixed position by repeatedly applying voltage of 2 phases, the voltage applied by the motor can control the phase current through the width of PWM, and the application time is determined according to the parameters and the load characteristics of the motor; the motor is positioned: the initial position of the motor rotor can be determined by 6 pulses of detection current, and the stationary phase electrification positioning mode is sampled.

The motor is started: the power tube of the corresponding bridge arm can be switched on after the position of a motor rotor is determined, the motor rotates in the required direction, 6 driving states can be sequentially powered by gradually increasing PWM pulse width, the power supply time of each state is gradually reduced, the motor is enabled to be started forcibly according to the sequence, in the process, the counter electromotive force of the unpowered phase is monitored, the software can preset the number of times of reversing for forced starting, and the mode is switched to the counter electromotive force control mode after the number of times reaches a set threshold.

The motor runs at a low speed: the sampling center is aligned with a PWM mode, A/D sampling interruption of a non-conduction phase is triggered when each PWM period is matched, the voltage value is read in the A/D interruption, and meanwhile, according to the previous commutation time (60 degrees electrical angle), data of the previous 15 degrees are not reserved by software, and the follow current influence (namely interference time) after the motor is commutated is removed; when the read A/D sampling data is larger than 1/2 DC bus voltage (ascending channel) or smaller than 1/2 DC bus voltage (descending channel), setting the central point to be effective, calculating the time from the switching point to the point, putting the switching timer into the switching point, closing the A/D interruption, and running the main program at the time from the switching point; waiting for timer interruption, when entering the timer interruption, indicating that the motor is fully rotated by 60 degrees, carrying out phase switching in the timer interruption, reading the rotor state of the next motor, determining the control state of the next switching according to the rotor state, simultaneously calculating the real-time motor speed according to the whole switching length of the timer, judging whether the speed enters high-speed mode control, if so, starting a hardware trigger Hall mode state, closing A/D sampling interruption, and entering a high-speed running mode of the motor; if the speed is below threshold 1, continuing to turn on the PWM trigger should detect the A/D interruption of the phase.

The motor runs at a high speed: applying the state of the Hall interrupt mode, and applying the port interrupt mode if the MCU does not have the function; the 3 phase voltages generate three sinusoidal signals with phase shift close to 90 degrees through low-pass filtering signals, the sinusoidal signals are compared with a simulation central point, 6 motor rotor states with phase lag of 90 degrees are generated, the time from the switching to an interruption point is recorded, the time is 30 degrees, and the time is put into a switching timer; when entering timer interruption, the motor is indicated to be rotated for 60 degrees, phase switching is carried out in the timer interruption, the next motor rotor state is read, the control state of the next switching is determined according to the rotor state, meanwhile, the real-time motor speed is calculated according to the whole switching length of the timer, whether the speed is in a high-speed mode or not is judged, if yes, the high-speed running mode is continuously executed, if the speed is lower than a threshold value 2, the Hall interruption mode is closed, A/D sampling interruption is triggered, the motor enters a low-speed running mode, and the speed threshold value 2 is lower than a speed threshold value 1.

The switching process of the motor is processed in the timer interrupt, the PWM period is matched to trigger the A/D sampling interrupt and the Hall interrupt processing programs to respectively run in a low-speed running mode and a high-speed running mode, and the priority levels of the 3 interrupts are set to be the same.

Compared with the prior art, the invention has the following beneficial effects:

the invention samples the counter electromotive force of the non-electrified phase by a PWM period interruption mode during starting and low speed, avoids the interference of PWM signals in a digital mode, correctly obtains the zero crossing point (1/2 bus voltage) of the counter electromotive force and delays the commutation by 30 degrees of electrical angle; when the rotating speed is increased, the effective amplitude of the counter electromotive force is also increased, the PWM interference signal is filtered through RC low-pass filtering, a counter electromotive force waveform which is approximately 90-degree phase shift and is attenuated is obtained, a zero crossing point after the phase shift is obtained after the comparison of a hardware comparator and a simulated motor central point, and 30-degree electrical angle reversing is delayed.

Drawings

FIG. 1 is a block diagram of the overall main program of the present invention;

FIG. 2 is a schematic diagram of a motor start-up sequence according to the present invention;

FIG. 3 is a motor shutdown subroutine diagram of the present invention;

FIG. 4 is a diagram of a timer interrupt subroutine of the present invention;

FIG. 5 is a diagram of the A/D interrupt subroutine of the present invention;

FIG. 6 is a Hall interrupt subroutine diagram of the present invention;

fig. 7 is a schematic diagram of the circuit principle structure of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-7, the present invention provides a technical solution: a control method for a high-electric-speed brushless direct current motor without a position sensor comprises the steps of starting and running the motor, wherein the running and starting of the motor are respectively as follows: motor positioning, motor starting, low-speed running and high-speed running; in the running process of the motor, the motor positioning and starting process runs once, and the low-speed and high-speed processes run repeatedly according to the speed setting.

Description of the main circuit:

in the figure, phase lines U, V, W of a motor 3 are respectively input to A/D ports AN0, AN1 and AN2 of AN MCU after being divided by voltage division resistors R64, R38, R65, R39, R66 and R40; the small-capacitance capacitors C1, C2 and C3 absorb the transient interference effect of the switch; the voltage of the direct current bus is input to AN A/D sampling port AN7 of the MCU through voltage dividing resistors R67 and R42 with the same resistance value. Detecting the zero crossing point of the non-electrified phase during starting and low-speed running; and U, V, W through R68, R51, C36; r69, R52, C37; RC low-pass filtering composed of R70, R53 and C38 is respectively input to the negative-polarity input end of a comparator U8, 3 filtered signals are subjected to analog central points after filtering through resistors R21, R22 and R23 and are respectively connected to the positive-polarity input end of the U8, and the outputs of the 3 comparators are connected to the Hall port input ends P1.5, P1.6 and P1.7 of the MCU. A zero crossing point circuit for detecting the non-electrified phase when the motor runs at high speed is formed, and when 3 Hall input pins have level change, the zero crossing point circuit is the zero crossing generation time of a certain non-electrified phase.

In conclusion, the voltage of the non-electrified phase is detected by triggering A/D through PWM cycle interruption at low speed, the zero crossing point is determined by comparing the voltage of the non-electrified phase with the voltage of 1/2 bus, and the commutation is delayed by 30 degrees; and when the counter potential reaches a certain value, switching to a zero crossing point obtained by a hardware comparator, and delaying for 30 degrees to obtain a commutation point. The method has the advantages that the correct back electromotive force voltage of the non-electrified phase can be detected through the interruption of the PWM period during starting and low-speed running, so that the correct commutation can be realized, the starting performance and the low-speed running stability of the motor are ensured, the PWM carrier signal is filtered through the low-pass RC filtering at high speed, a zero-crossing signal with the phase shift close to 90 degrees is obtained, the commutation is delayed by 30 degrees, and the commutation failure caused by the poor sampling precision of the back electromotive force of the non-electrified phase due to the fact that the PWM period is too long relative to the commutation period can be avoided. The problem of seamless switching between high and low speeds is solved by controlling the operation of the whole speed adjusting range of the brushless direct current motor without a sensor at a high electric rotating speed. The invention adopts the control mode of delaying 30-degree switching after detecting the non-electrified phase zero crossing point of the brushless motor at both low speed and high speed, so that the software overhead becomes simple, the performance requirement on the MCU is reduced, and the application of the motor control MCU with low cost becomes possible.

While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A high electric speed brushless DC motor position sensorless control method, including the start and operation of the motor, characterized by that: the operation and the starting of the motor are respectively as follows: motor positioning, motor starting, low-speed running and high-speed running; in the running process of the motor, the motor positioning and starting process runs once, and the low-speed and high-speed processes are repeatedly run according to the speed setting;

the motor runs at a low speed: aligning a sampling center with a PWM mode, triggering A/D sampling interruption of a non-conduction phase when each PWM period is matched, reading a voltage value at the moment in the A/D interruption, and simultaneously, according to the previous commutation time, keeping data of 15 degrees in the front by software, and removing the follow current influence after the motor commutates; when the read A/D sampling data is larger than 1/2 DC bus voltage or smaller than 1/2 DC bus voltage, setting the center point to be effective, calculating the time from the switching point to the point, putting the switching timer into the switching point, closing the A/D interruption, and running the main program at the time from the switching point; waiting for timer interruption, when entering the timer interruption, indicating that the motor is fully rotated by 60 degrees, carrying out phase switching in the timer interruption, reading the rotor state of the next motor, determining the control state of the next switching according to the rotor state, simultaneously calculating the real-time motor speed according to the whole switching length of the timer, judging whether the speed enters high-speed mode control, if so, starting a hardware trigger Hall mode state, closing A/D sampling interruption, and entering a high-speed running mode of the motor; if the speed is lower than the threshold value 1, continuously starting PWM to trigger A/D interruption of the phase to be detected;

2. The sensorless control method of a high electric speed brushless dc motor according to claim 1, wherein: the brushless motor rotor is divided into 6 states in 360-degree electrical angle, wherein the 6 states are 001,101,100,110,010 and 011, and the corresponding 6 driving states are AH and BL; AH. CL; BH. CL; BH. AL; CH. AL; CH. BL, when determining that the motor rotor is in a certain state of 6 states, output corresponding signal control 3 looks bridge type power tube, make the motor rotate, foresee the next state of motor namely the corresponding order of switching power tube.

3. The sensorless control method of a high electric speed brushless dc motor according to claim 1, wherein: the motor is positioned: when the motor stops, the motor is rotated to a fixed position by repeatedly applying voltage of 2 phases, the voltage applied by the motor controls phase current through the width of PWM, and the application time is determined according to the parameters and the load characteristics of the motor; the motor is positioned: and (3) a stationary phase is sampled and a positioning mode is adopted.

4. The sensorless control method of a high electric speed brushless dc motor according to claim 1, wherein: the motor is started: when the position of a rotor of the motor is determined, the power tube of the corresponding bridge arm is switched on, the motor rotates in the required direction, 6 driving states are sequentially powered by gradually increasing PWM pulse width, the power supply time of each state is gradually reduced, the motor is enabled to be started forcibly according to the sequence, in the process, the counter electromotive force of the unpowered phase is monitored, the software presets a commutation frequency of forced starting, and the counter electromotive force control mode is switched to after the frequency reaches a set threshold.

5. The sensorless control method of a high electric speed brushless dc motor according to claim 1, wherein: the switching process of the motor is processed in the timer interrupt, the PWM period is matched to trigger the A/D sampling interrupt and the Hall interrupt processing programs to respectively run in a low-speed running mode and a high-speed running mode, and the priority levels of the 3 interrupts are set to be the same.