CN114362603A - Control Method for Suppressing Starting Torque Ripple of Brushless DC Motor - Google Patents

Abstract

The invention provides a control method for restraining starting torque pulsation of a brushless direct current motor, which comprises the following steps: setting the commutation time of the commutation timer as the preset commutation time, and starting the commutation timer and the period timer; detecting the rising or falling edge zero-crossing point moment of a position signal of the three-phase Hall sensor, and determining the conduction state and the phase-changing time sequence of the power switch tube; acquiring a corresponding electrical angle during each phase change, and determining A, B, C three-phase vector relation during each phase change; and changing the PWM duty ratio during phase conversion to ensure that the vector size synthesized before and after the two-two conduction and the three-three conduction are switched is the same. The two-two conduction mode and the three-three conduction mode are combined, the traditional six-step phase change is converted into the twelve-step phase change in one electric cycle, the Hall sensor acquires the initial position of the rotor, and the torque pulsation problem generated when the brushless direct current motor is started is restrained through multiple phase changes, so that the motor is stably started.

Description

Control Method for Suppressing Starting Torque Ripple of Brushless DC Motor

technical field

The invention relates to the technical field of brushless direct current motors, in particular to a brushless direct current motor control method for suppressing starting torque ripple.

Background technique

With the increasing maturity and rapid development of power electronics technology, brushless DC motors have continuously achieved breakthroughs in technology and have been widely used in various fields, such as electric vehicles, household appliances, etc., and due to the innovation of machining technology, their Production costs are also greatly reduced.

The brushless DC motor is composed of a motor body and a driver. It is a typical mechatronic product. It not only has the characteristics of high torque, high efficiency, small size, high reliability, and simple structure, but also has excellent speed regulation performance. And smaller steady-state speed error, in terms of operation efficiency, speed accuracy and low-speed torque, it is better than other technology-controlled frequency converters. The traditional brushless DC motor mostly adopts the two-two conduction mode, and the phases are commutated six times in one electrical cycle. Due to the inductance of the armature winding of the motor, there is a delay when the winding current switches from one phase to the next phase. Torque ripple is generated. For numerous well-made DC motors, its cogging torque ripple and harmonic torque ripple are relatively small, but the commutation torque ripple can reach about 50% of the average torque.

In the prior art, the application publication number CN107171605A discloses a BLDCM two-two conduction and three-three conduction switching method, and specifically discloses the use of the Hall position signal of the brushless DC motor, the DSP chip, and the CPLD module to logically calculate the two The two-on and three-three-on program modules allow the brushless DC motor to switch from two-two-on to three-three-on operation at 3s. It mainly uses software programming to realize the switching between two-two conduction and three-three conduction of the brushless DC motor.

The present invention provides a control method combining two-two conduction and three-three conduction, which is converted from a traditional six-step commutation to a twelve-step commutation in one electrical cycle, and is acquired by a Hall sensor. The initial position of the rotor is used to suppress the torque ripple problem during commutation and realize the smooth start of the brushless DC motor.

SUMMARY OF THE INVENTION

The invention provides a control method for suppressing the starting torque ripple of a brushless DC motor, which combines the two-two conduction mode and the three-three conduction mode, and transforms from the traditional six-step commutation to ten-step commutation in one electrical cycle. Two-step commutation, and the initial position of the rotor is obtained by the Hall sensor, and the torque ripple problem generated when the brushless DC motor is started is suppressed by multiple commutation, so as to realize the smooth start of the motor.

In order to achieve the above object, the present invention is achieved through the following technical solutions:

The present invention relates to a control method for suppressing starting torque ripple of a brushless DC motor, comprising the following steps:

Step 1: Set the commutation time of the commutation timer as the preset commutation time, and start the commutation timer and the period timer;

Step 2: Detect the time when the rising or falling edge of the three-phase Hall sensor position signal crosses the zero point, determine the conduction state of the power switch tube, and the commutation sequence;

Step 3: Calculate the real-time commutation time, and set the commutation timer to the commutation time at this time;

Step 4: Obtain the electrical angle corresponding to each step of commutation, and determine the vector relationship of the three phases of A, B, and C during each step of commutation;

Step 5: Change the size of the PWM duty cycle during commutation, so that the size of the vector synthesized before and after switching between two-two and three-three-on is the same.

The further improvement of the present invention lies in that the BLDC motor commutation circuit controls the conduction sequence of the MOS transistor as follows: T1, T4→T1, T4, T6→T1, T6→T1, T3, T6→T3, T6→T2, T3, T6→T2, T3→T2, T3, T5→T2, T5→T2, T4, T5→T4, T5→T1, T4, T5.

A further improvement of the present invention lies in that the specific commutation control logic is as follows: when detecting the zero-crossing point of the rising edge of the A-phase of the Hall sensor, the power switch tubes T1 and T4 are turned on, the corresponding A-phase windings are positively energized, and the B-phase windings are turned on. Negative electricity, the commutation sequence is 30° at this time, the commutation time at this time is calculated as t and the time of the commutation timer is set as t;

When it is detected that the real-time commutation time is 2t, the commutation timer is set to zero, the power switch tubes T1, T4, and T6 are turned on, the A-phase winding is positively energized, and the B-phase and C-phase windings are negatively energized. At this time, the commutation sequence is 60°;

When the zero-crossing point of the falling edge of the C-phase of the Hall sensor is detected, the power switches T1 and T6 are turned on, the corresponding A-phase winding is positively energized, and the C-phase winding is negatively energized. The commutation sequence is 90°, and the commutation at this time is calculated. The time is 3t and the time of the commutation timer is set to t;

When it is detected that the real-time commutation time is 4t, the commutation timer is set to zero, the power switch tubes T1, T3, T6 are turned on, the A-phase and B-phase windings are positively energized, and the C-phase winding is negatively energized. At this time, the commutation sequence is 120°;

When the zero-crossing point of the rising and falling edges of the B-phase of the Hall sensor is detected, the power switches T3 and T6 are turned on, the corresponding B-phase windings are positively energized, and the C-phase windings are negatively energized, and the commutation sequence is 150°. The direction time is 5t and the time of setting the commutation timer is t;

When it is detected that the real-time commutation time is 6t, the commutation timer is set to zero, the power switch tubes T2, T3, and T6 are turned on, the B-phase winding is positively energized, and the A-phase and C-phase windings are negatively energized. At this time, the commutation sequence is 180°;

When the zero-crossing point of the falling edge of phase A of the Hall sensor is detected, the power switches T2 and T3 are turned on, the corresponding B-phase winding is positively energized, and the A-phase winding is negatively energized. The commutation sequence is 210°, and the commutation at this time is calculated. The time is 7t and the time of setting the commutation timer is t;

When it is detected that the real-time commutation time is 8t, the commutation timer is set to zero, the power switch tubes T2, T3, and T5 are turned on, the B-phase and C-phase windings are positively energized, and the A-phase windings are negatively energized. At this time, the commutation sequence is 240°;

When the zero-crossing point of the rising edge of the C-phase of the Hall sensor is detected, the power switches T2 and T3 are turned on, the corresponding B-phase winding is positively energized, and the A-phase winding is negatively energized. The commutation sequence is 270°, and the commutation at this time is calculated. The time is 9t and the time of the commutation timer is set to t;

When it is detected that the real-time commutation time is 10t, the commutation timer is set to zero, the power switch tubes T2, T4, and T5 are turned on, the C-phase winding is positively energized, and the A-phase and B-phase windings are negatively energized. At this time, the commutation sequence is 300°;

When the zero-crossing point of the falling edge of the B phase of the Hall sensor is detected, the power switches T4 and T5 are turned on, the corresponding C-phase winding is positively energized, and the B-phase winding is negatively energized. The commutation sequence is 330°, and the commutation at this time is calculated. The time is 11t and the time of the commutation timer is set to t;

When it is detected that the real-time commutation time is 12t, the commutation timer is set to zero, the power switch tubes T1, T4, and T5 are turned on, the corresponding A-phase and C-phase windings are positively energized, and the B-phase windings are negatively energized. The phase timing is 360°.

A further improvement of the present invention is: in step 3, the real-time commutation time is calculated as follows:

Wherein, T _t is the value of the real-time commutation time, T _d is the duty cycle of the preset PWM, _ne is the rated speed of the brushless DC motor, and p is the number of pole pairs of the brushless DC motor.

A further improvement of the present invention is: when the load of the brushless DC motor is less than 40% of the rated load, the PWM preset duty cycle of the brushless DC motor is 0-1%, and when the load is greater than 40%, the brushless DC motor The preset PWM duty cycle is 5% to 6%.

三三导通时的合成转矩大小为

为了保证两种导通方式的合成矢量大小相等，调节PWM占空比，使得调节后的PWM占空比为二二导通使得

倍。A further improvement of the present invention is: in step 5, the torque generated by the current flowing into the winding is positive when the two are turned on, and the torque generated by the outflow winding is negative, then the combined torque is

The combined torque size when the three and three are turned on is

In order to ensure that the combined vector size of the two conduction modes is equal, the PWM duty cycle is adjusted so that the adjusted PWM duty cycle is two-two conduction so that

times.

The beneficial effects of the present invention are as follows: 1. The control method for suppressing the starting torque ripple of the countless DC motors proposed by the present invention adopts the complementary combination of two-two conduction and three-three conduction, which suppresses the rotation in the two-two conduction mode. Torque pulsation, effectively reducing the influence of noise at start-up.

2. In the scheme of the present invention, the commutation time is calculated according to the rated speed of the brushless DC motor, the duty cycle of the PWM and the number of pole pairs, and the torque ripple during the commutation is suppressed by changing the commutation time, so as to realize the commutation of the brushless DC motor. Stable start.

Description of drawings

FIG. 1 is a flowchart of a control method for suppressing starting torque ripple of a brushless DC motor according to the present invention.

FIG. 2 is a vector relationship diagram of three phases under each commutation sequence of the control method for suppressing starting torque ripple of a brushless DC motor according to the present invention.

FIG. 3 is a commutation circuit diagram of the control method for suppressing the starting torque ripple of the brushless DC motor according to the present invention.

Detailed ways

In order to make the purpose and advantages of the technical solutions of the embodiments of the present invention clearer, 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. Obviously, the described embodiments are Some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figures 1-3, the present invention provides a control method for suppressing starting torque ripple of a brushless DC motor, which specifically includes the following steps:

Step S1: setting the commutation time of the commutation timer as the preset commutation time, and starting the commutation timer and the period timer; wherein, the preset period value of the brushless DC motor is 100ms;

Step S2: Detect the time when the rising edge or the falling edge of each phase of the Hall sensor crosses the zero point, and determine the commutation sequence and the conduction state of the power switch tube;

The brushless DC motor commutation circuit of the present invention controls the conduction sequence of the MOS transistor as: T1, T4→T1, T4, T6→T1, T6→T1, T3, T6→T3, T6→T2, T3, T6→T2, T3→T2, T3, T5→T2, T5→T2, T4, T5→T4, T5→T1, T4, T5, the specific commutation control logic is as follows:

When the zero-crossing point of the rising edge of the A-phase of the Hall sensor is detected, the power switch tubes T1 and T4 are turned on, the corresponding A-phase windings are positively energized, and the B-phase windings are negatively energized. At this time, the commutation sequence is 30°. The commutation time is t and the time of setting the commutation timer is t;

When it is detected that the real-time commutation time is 2t, the commutation timer is set to zero, the power switch tubes T1, T4, and T6 are turned on, the A-phase winding is positively energized, and the B-phase and C-phase windings are negatively energized. At this time, the commutation sequence is 60°;

When the zero-crossing point of the falling edge of the C-phase of the Hall sensor is detected, the power switches T1 and T6 are turned on, the corresponding A-phase winding is positively energized, and the C-phase winding is negatively energized. The commutation sequence is 90°, and the commutation at this time is calculated. The time is 3t and the time of the commutation timer is set to t;

When it is detected that the real-time commutation time is 4t, the commutation timer is set to zero, the power switch tubes T1, T3, T6 are turned on, the A-phase and B-phase windings are positively energized, and the C-phase winding is negatively energized. At this time, the commutation sequence is 120°;

When the zero-crossing point of the rising and falling edges of the B-phase of the Hall sensor is detected, the power switches T3 and T6 are turned on, the corresponding B-phase windings are positively energized, and the C-phase windings are negatively energized, and the commutation sequence is 150°. The direction time is 5t and the time of setting the commutation timer is t;

When it is detected that the real-time commutation time is 6t, the commutation timer is set to zero, the power switch tubes T2, T3, and T6 are turned on, the B-phase winding is positively energized, and the A-phase and C-phase windings are negatively energized. At this time, the commutation sequence is 180°;

When the zero-crossing point of the falling edge of phase A of the Hall sensor is detected, the power switches T2 and T3 are turned on, the corresponding B-phase winding is positively energized, and the A-phase winding is negatively energized. The commutation sequence is 210°, and the commutation at this time is calculated. The time is 7t and the time of setting the commutation timer is t;

When it is detected that the real-time commutation time is 8t, the commutation timer is set to zero, the power switch tubes T2, T3, and T5 are turned on, the B-phase and C-phase windings are positively energized, and the A-phase windings are negatively energized. At this time, the commutation sequence is 240°;

When the zero-crossing point of the rising edge of the C-phase of the Hall sensor is detected, the power switches T2 and T3 are turned on, the corresponding B-phase winding is positively energized, and the A-phase winding is negatively energized. The commutation sequence is 270°, and the commutation at this time is calculated. The time is 9t and the time of the commutation timer is set to t;

When it is detected that the real-time commutation time is 10t, the commutation timer is set to zero, the power switch tubes T2, T4, and T5 are turned on, the C-phase winding is positively energized, and the A-phase and B-phase windings are negatively energized. At this time, the commutation sequence is 300°;

When the zero-crossing point of the falling edge of the B phase of the Hall sensor is detected, the power switches T4 and T5 are turned on, the corresponding C-phase winding is positively energized, and the B-phase winding is negatively energized. The commutation sequence is 330°, and the commutation at this time is calculated. The time is 11t and the time of the commutation timer is set to t;

When it is detected that the real-time commutation time is 12t, the commutation timer is set to zero, the power switch tubes T1, T4, and T5 are turned on, the corresponding A-phase and C-phase windings are positively energized, and the B-phase windings are negatively energized. The phase timing is 360°.

Step S3: Calculate the real-time commutation time, and set the commutation timer to be the commutation time at this time;

If the load of the brushless DC motor is less than 40% of the rated load, the preset PWM duty cycle of the brushless DC motor is 0-1%; if the load is greater than 40%, the brushless DC motor The duty cycle of the preset PWM of the DC motor is 5% to 6%.

The commutation time of the brushless DC motor can be accurately calculated according to the preset PWM duty cycle, the rated speed of the brushless DC motor and the number of pole pairs, that is, the calculation formula of the commutation time of the brushless DC motor is as follows:

In the above formula, T _t is the value of real-time commutation time, T _d is the duty cycle of the preset PWM, _ne is the rated speed of the brushless DC motor, and p is the number of pole pairs of the brushless DC motor.

Step S4: obtaining the electrical angle corresponding to the commutation step of each step, and determining the vector relationship of the three phases of A, B, and C during the commutation step of each step;

Step S5 : changing the size of the PWM duty cycle during commutation, so that the size of the vector synthesized before and after switching between two-two and three-three-on is the same.

同理，三三导通时的合成转矩大小为

为了保证两种导通方式的合成矢量大小相等，调节PWM占空比，使得调节后的PWM占空比为二二导通使得

倍。As shown in Fig. 2, the present invention provides a vector relationship diagram of three phases at each time sequence. When two and two are turned on, the torque generated by the current flowing into the winding is positive, and the torque generated by the outflow winding is negative, so the combined torque is

In the same way, the combined torque when the three and three are turned on is

In order to ensure that the combined vector size of the two conduction modes is equal, the PWM duty cycle is adjusted so that the adjusted PWM duty cycle is two-two conduction so that

times.

By combining the two-two conduction mode with the three-three conduction mode, the present invention transforms the traditional six-step commutation into twelve-step commutation within one electrical cycle, so as to suppress the brushless by multiple commutation. The torque ripple problem generated when the DC motor starts to ensure the smooth start of the motor.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the present invention, such modifications and variations falling within the scope of the appended claims within the limited scope.

Claims (6)

1. The control method for suppressing the starting torque pulsation of the brushless direct current motor is characterized by comprising the following steps of: the method comprises the following steps:

step 1: setting the commutation time of the commutation timer as the preset commutation time, and starting the commutation timer and the period timer;

step 2: detecting the rising or falling edge zero-crossing point moment of a position signal of the three-phase Hall sensor, and determining the conduction state and the phase-changing time sequence of the power switch tube;

and step 3: calculating real-time commutation time, and setting a commutation timer as the commutation time at the moment;

and 4, step 4: acquiring a corresponding electrical angle during each phase change, and determining A, B, C three-phase vector relation during each phase change;

and 5: and changing the PWM duty ratio during phase conversion to ensure that the vector size synthesized before and after the two-two conduction and the three-three conduction are switched is the same.

2. The control method of suppressing the starting torque ripple of the brushless dc motor according to claim 1, wherein: the specific sequence of the conducting states of the power switch tube in the step 2 is as follows: t1, T4 → T1, T4, T6 → T1, T6 → T1, T3, T6 → T3, T6 → T2, T3, T6 → T2, T3 → T2, T3, T5 → T2, T5 → T2, T4, T5 → T4, T5 → T1, T4, T5.

3. The control method of suppressing the starting torque ripple of the brushless dc motor according to claim 2, characterized in that: the specific commutation control logic is as follows: when the rising edge zero crossing point of the phase A of the Hall sensor is detected, the power switch tubes T1 and T4 are conducted, the corresponding phase A winding is electrified positively, the phase B winding is electrified negatively, the commutation time sequence is 30 degrees, the commutation time is calculated to be T, and the time of the commutation timer is set to be T;

when the real-time phase change time is detected to be 2T, the phase change timer is set to be zero, the power switch tubes T1, T4 and T6 are conducted, the phase A winding is conducted with positive electricity, the phase B winding and the phase C winding are conducted with negative electricity, and the phase change time sequence is 60 degrees at the moment;

when the falling edge zero crossing point of the C phase of the Hall sensor is detected, the power switches T1 and T6 are switched on, the corresponding A phase winding is switched on positively, the C phase winding is switched on negatively, the commutation time sequence is 90 degrees, the commutation time at the moment is calculated to be 3T, and the time of the commutation timer is set to be T;

when the real-time phase change time is detected to be 4T, the phase change timer is set to be zero, the power switch tubes T1, T3 and T6 are conducted, the A-phase winding and the B-phase winding are conducted with positive electricity, the C-phase winding is conducted with negative electricity, and the phase change time sequence is 120 degrees at the moment;

when the rising edge zero crossing point of the B phase of the Hall sensor is detected, the power switches T3 and T6 are switched on, the corresponding B phase winding is electrified positively, the C phase winding is electrified negatively, the commutation time sequence is 150 degrees, the commutation time at the moment is calculated to be 5T, and the time of the commutation timer is set to be T;

when the real-time phase change time is detected to be 6T, the phase change timer is set to be zero, the power switch tubes T2, T3 and T6 are conducted, the phase B winding is conducted with positive electricity, the phase A winding and the phase C winding are conducted with negative electricity, and the phase change time sequence is 180 degrees at the moment;

when the falling edge zero crossing point of the phase A of the Hall sensor is detected, the power switches T2 and T3 are switched on, the corresponding phase B winding is switched on positively, the phase A winding is switched on negatively, the commutation time sequence is 210 degrees, the commutation time at the moment is calculated to be 7T, and the time of the commutation timer is set to be T;

when the real-time phase change time is detected to be 8T, the phase change timer is set to be zero, the power switch tubes T2, T3 and T5 are conducted, the phase B winding and the phase C winding are conducted with positive electricity, the phase A winding is conducted with negative electricity, and the phase change time sequence is 240 degrees at the moment;

when the rising edge zero crossing point of the phase C of the Hall sensor is detected, the power switches T2 and T3 are switched on, the corresponding phase B winding is switched on positively, the phase A winding is switched on negatively, the commutation time sequence is 270 degrees, the commutation time at the moment is calculated to be 9T, and the time of the commutation timer is set to be T;

when the real-time phase change time is 10T, the phase change timer is set to be zero, the power switch tubes T2, T4 and T5 are conducted, the phase C winding is conducted with positive electricity, the phase A winding and the phase B winding are conducted with negative electricity, and the phase change time sequence is 300 degrees at the moment;

when the falling edge zero crossing point of the B phase of the Hall sensor is detected, the power switches T4 and T5 are switched on, the corresponding C phase winding is switched on positively, the B phase winding is switched on negatively, the commutation time sequence is 330 degrees, the commutation time at the moment is calculated to be 11T, and the time of the commutation timer is set to be T;

when the real-time commutation time is 12T, the commutation timer is set to zero, the power switch tubes T1, T4 and T5 are conducted, corresponding A-phase and C-phase windings are electrified positively, corresponding B-phase windings are electrified negatively, and at the moment, the commutation time sequence is 360 degrees.

4. The control method of suppressing the starting torque ripple of the brushless dc motor according to claim 3, wherein: the real-time commutation time in step 3 is calculated as follows:

wherein, T_tFor the value of the real-time commutation time, T_dFor presetting the duty ratio of PWM, n_eAnd p is the pole pair number of the brushless direct current motor, wherein the rated rotating speed of the brushless direct current motor is the rated rotating speed of the brushless direct current motor.

5. The control method of suppressing the starting torque ripple of the brushless dc motor according to claim 4, wherein: when the load of the brushless direct current motor is less than 40% of the rated load, the duty ratio of the preset PWM of the brushless direct current motor is 0-1%, and when the load is more than 40%, the duty ratio of the preset PWM of the brushless direct current motor is 5% -6%.

6. The control method of suppressing the starting torque ripple of the brushless dc motor according to claim 5, wherein: in step 5, when the two-two conduction state is adopted, the torque generated by the current flowing into the winding is positive, the torque generated by the current flowing out of the winding is negative, and the magnitude of the resultant torque is

The resultant torque at three-three conduction is

In order to ensure that the magnitude of the resultant vector of the two conduction modes is equal, the PWM duty ratio is adjusted, so that the adjusted PWM duty ratio is switched on twice, and the two conduction modes are realized

And (4) doubling.

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