CN103986377A - Direct-current brushless motor control method - Google Patents

Abstract

The invention discloses a direct-current brushless motor control method. An adopted control system is characterized in that an upper switching tube and a lower switching tube on a bridge arm in one phase are controlled to be turned on in a complementary mode in an on interval of 120 degrees for a three-phase inverter and lower bridge arms of the other two phases are alternately constantly turned on for 60 degrees, namely in the interval of 0-60 degrees, T1 and T4 are turned on in the complementary mode, and T6 is turned on constantly; in the interval of 60-120 degrees, T1 and T4 are turned on in the complementary mode, and T2 is constantly turned on; in the interval of 120-180 degrees, T3 and T6 are turned on in the complementary mode, and T2 is constantly turned on; in the interval of 180-240 degrees, T3 and T6 are turned on in the complementary mode, and T4 is constantly turned on; in the interval of 240-300 degrees, T2 and T5 are turned on in the complementary mode, and T4 is constantly turned on; in the interval of 300-360 degrees, T2 and T5 are turned on in the complementary mode, and T6 is constantly turned on.

Description

A kind of DC Brushless Motor Control method

Technical field

The present invention relates to a kind of DC Brushless Motor Control method.

Background technology

The main modulation system of DC Brushless Motor generally has five kinds at present, is respectively PWM-ON type, ON-PWM type, H_PWM-L_ON type, H_ON-L_PWM type, H_PWM-L_PWM type, and its control method is as follows:

(1) PWM-ON type: in 120 ° of conducting intervals, first 60 ° of each switching tube adopts PWM modulation, rear 60 ° of Heng Tongs;

(2) ON-PWM type: in 120 ° of conducting intervals, the front 60 ° of Heng Tongs of each switching tube, latter 60 ° adopt PWM modulation;

(3) H_PWM-L_ON type: in 120 ° of conducting intervals, upper brachium pontis switching tube adopts PWM modulation, lower brachium pontis Heng Tong;

(4) H_ON-L_PWM type: in 120 ° of conducting intervals separately, upper brachium pontis switching tube Heng Tong, lower brachium pontis adopts PWM modulation;

(5) H_PWM-L_PWM type: in 120 ° of conducting intervals, upper and lower bridge arm all adopts PWM modulation.

Can find out; front four kinds of modulation systems; owing to being all the time 2 out of phase switching tube actions; in deceleration or stopping process; can only, by descending accordingly brachium pontis diode continuousing flow, form inner afterflow, and not have corresponding Boost booster circuit to make energy back passage; make capacity usage ratio not high, the braking ability of motor is not good.The 5th kind of mode, owing to being bipolarity modulation, its feedback path comes afterflow to complete by respective diode.Motor load has energy exchange with power supply all the time, but switching loss is approximately 2 times of other modes, has affected its range of application.

In sum, there is following shortcoming in traditional control strategy:

1, the torque pulsation when commutation of traditional DC Brushless Motor Control strategy is larger, has limited the extensive use of DC Brushless Motor.

2, it is more that traditional PI controls required transducer, and parameter adjustment is more complicated.

Summary of the invention

The present invention, in order to address the above problem, has proposed a kind of DC Brushless Motor Control method, and that the method has advantages of is torque pulsation inhibited, realize energy transmits fast.

To achieve these goals, the present invention adopts following technical scheme:

A kind of DC brushless motor control system, comprise three phase full bridge inverter circuit, three phase full bridge inverter circuit comprises three branch roads in parallel, every branch road comprises the power transistor of two series connection, every branch road neutral point is in series with respectively resistance, inductance and a phase stator winding, threephase stator winding is star-like connection, and the two ends of every branch road connect DC power supply, and power transistor two ends are parallel with a diode.

Described threephase stator winding is respectively A, B, C three-phase; On corresponding branch road, brachium pontis power transistor is respectively T1, T3, T5, and lower brachium pontis power transistor is respectively T2, T4, T6.

Control method based on above-mentioned control system is: a three-phase inverter, and in 120 ° of conducting intervals, wherein the upper and lower switch controlled complementation of a phase brachium pontis is open-minded, and under other two-phase, brachium pontis replaces 60 ° of Heng Tongs.

The concrete mode of described control method is:

In 0 °～60 ° intervals, T1 and T4 complementation are open-minded, and T6 often opens; In 60 °～120 ° intervals, T1 and T4 complementation are open-minded, and T2 often opens; In 120 °～180 ° intervals, T3 and T6 complementation are open-minded, and T2 often opens; In 180 °～240 ° intervals, T3 and T6 complementation are open-minded, and T4 often opens; In 240 °～300 ° intervals, T2 and T5 complementation are open-minded, and T4 often opens; In 300 °～360 ° intervals, T2 and T5 complementation are open-minded, and T6 often opens.

Beneficial effect of the present invention is:

1. torque pulsation while effectively suppressing DC Brushless Motor commutation;

2. the feedback that is conducive to energy, realizes quick shutdown and the reversion of motor;

3. torque pulsation in the time of can effectively reducing commutation.

Accompanying drawing explanation

Fig. 1 is DC brushless motor control system figure;

Fig. 2 is PWM-ON type Motor Control policy map;

Fig. 3 is ON-PWM type Motor Control policy map;

Fig. 4 is H_PWM-L_ON type Motor Control policy map;

Fig. 5 is H_ON-L_PWM type Motor Control policy map;

Fig. 6 is H_PWM-L_PWM type Motor Control policy map;

Fig. 7 is DC Brushless Motor Control policy map;

Fig. 8 is the two-way road of rationing the power supply of electric current;

Fig. 9 is DSP input signal voltage stabilizing fidelity circuit;

Figure 10 is that duty ratio is under 0.5 condition, A phase current and line voltage U when motor low speed is underloading _aBoscillogram;

Figure 11 is motor band torque pulsating waveform figure in commutation process while carrying.

Embodiment:

Below in conjunction with accompanying drawing and embodiment, the invention will be further described.

As shown in Figure 1, the core of DC brushless motor control system is inverter.Whole circuit is by direct current supply, and the core devices inverter of control system is generally realized and being controlled by 6 power transistors (T1～T6), and wherein going up brachium pontis is T1, T3, T5, and lower brachium pontis is T2, T4, T6.Inverter is to control motor coil to have currentless switch.And the core of inverter is control strategy, it produces pulse width modulating signal control transistor and opens and close short frequency and the time of rotating.

The main modulation system of DC Brushless Motor generally has five kinds at present, is respectively PWM-ON type, ON-PWM type, H_PWM-L_ON type, H_ON-L_PWM type, H_PWM-L_PWM type.As Fig. 2-6.

(1) PWM-ON type: in 120 ° of conducting intervals, first 60 ° of each switching tube adopts PWM modulation, rear 60 ° of Heng Tongs;

(2) ON-PWM type: in 120 ° of conducting intervals, the front 60 ° of Heng Tongs of each switching tube, latter 60 ° adopt PWM modulation;

(3) H_PWM-L_ON type: in 120 ° of conducting intervals, upper brachium pontis switching tube adopts PWM modulation, lower brachium pontis Heng Tong;

(4) H_ON-L_PWM type: in 120 ° of conducting intervals separately, upper brachium pontis switching tube Heng Tong, lower brachium pontis adopts PWM modulation;

(5) H_PWM-L_PWM type: in 120 ° of conducting intervals, upper and lower bridge arm all adopts PWM modulation.

Can find out; front four kinds of modulation systems; owing to being all the time 2 out of phase switching tube actions; in deceleration or stopping process; can only, by descending accordingly brachium pontis diode continuousing flow, form inner afterflow, and not have corresponding Boost booster circuit to make energy back passage; make capacity usage ratio not high, the braking ability of motor is not good.The 5th kind of mode, owing to being bipolarity modulation, its feedback path comes afterflow to complete by respective diode.Motor load has energy exchange with power supply all the time, but switching loss is approximately 2 times of other modes, has affected its range of application.

Three-phase symmetrical sine wave signal, its amplitude size every 60 ° of changes once, and is compared with sine wave freuqency when enough high when the switching frequency of PWM, and the modulation signal amplitude in a PWM switch periods can be similar to constant.Therefore, according to three-phase voltage amplitude magnitude relationship, carry out subregion, a sine wave period can be divided into 6 districts.As Fig. 2, the Novel direct-current brushless Motor Control strategy of proposition, is characterized in that, for three-phase inverter, in 120 ° of conducting intervals, wherein the upper and lower switch controlled complementation of a phase brachium pontis is open-minded, and in addition under two-phase brachium pontis replace the mode of 60 ° of Heng Tongs.In 0 °～60 ° intervals, T1 and T4 complementation are open-minded, and T6 often opens; In 60 °～120 ° intervals, T1 and T4 complementation are open-minded, and T2 often opens; In 120 °～180 ° intervals, T3 and T6 complementation are open-minded, and T2 often opens; In 180 °～240 ° intervals, T3 and T6 complementation are open-minded, and T4 often opens; In 240 °～300 ° intervals, T2 and T5 complementation are open-minded, and T4 often opens; In 300 °～360 ° intervals, T2 and T5 complementation are open-minded, and T6 often opens.

In lower six states of this modulation system, arbitrary state has three switching tube work, is different from five kinds above.Its advantage is when motor moves, and is conducive to the feedback of energy, makes the shutdown of motor and reversion rapider.Because when motor moves, from single-phase be electric current dual quadrant circuit.

As carved at a time, be T ₁, T ₄modulated on pipe, and T6 pipe Heng Tong, motor runs on a certain duty ratio.Its circuit is as being simplified to Fig. 8.U in figure _a0for motor load wye connection mid-point voltage U _nwith back electromotive force sum.

From electric current just always, power supply, T ₁, D ₄with load be Buck circuit; When electric energy reverse flow, switch transistor T ₄and D ₁form Boost booster circuit.When motor duty ratio reduces (slowing down) or requires to shut down, cause voltage U _a<U _a0, electric current can reduce even oppositely, and now this circuit is Boost circuit.Energy feeds back to power supply from motor load, can realize forward braking, reaches energy-conservation and object quick shutdown.

The pulsation of torque is mainly from the pulsation of electric current, and especially pulsation is maximum during commutation.Reason is: no matter be upper brachium pontis or lower brachium pontis commutation, it closes broken phase current can be not all 0 moment, opens mutually and also can moment not reach stationary value, and during this, current pulsation causes torque pulsation.And this time Δ t (commutation is to stable) is generally that several times of switch periods are even longer.

During first split-phase motor even running, i.e. electromagnetic torque size during not commutation.If T _erepresent the electromagnetic torque (Nm of unit) that brushless motor produces, three-phase electromagnetic torque sum total can be expressed as:

T _e＝(e _Ai _A+e _Bi _B+e _Ci _C)/ω

In formula, ω represents rotor mechanical angular speed.

Because the magnetic potential of DC Brushless Motor is trapezoidal wave, so any time in motor operation course only has back-emf value the maximum open-minded, only have two-phase to open (if A phase T now ₁t ₄complementation is open-minded, B phase T ₆heng Tong), obtain:

$\begin{array}{cc}\left(\begin{array}{c}{e}_A=E\\ e_B=-E\end{array}\right.& \left(\begin{array}{c}{i}_A=-i_B=I_A\\ i_A+i_B+i_C=0\end{array}\right.\end{array}$

There is total electromagnetic torque to be: T _e=2EI _a/ ω

I in formula _athe mean value of A phase current while being stable operation.

Because commutation is divided into upper brachium pontis commutation and lower brachium pontis commutation, the current pulsation in the time of therefore need to comparing upper and lower bridge arm commutation respectively.Current pulsation situation while first relatively descending brachium pontis commutation.

With A, be modulated to up and down mutually example, now, switch is from T ₁t ₄t ₆, be transformed into T ₁t ₄t ₂, electric current mutually brachium pontis to change to C from B and descends mutually brachium pontis.

Now, have $\left(\begin{array}{c}{e}_A=E\\ e_B=e_C=-E\end{array}\right.$

Due to the continuity of electric current, in commutation moment, T ₆pipe can turn-off, but i _bcan be not 0 at once, cause diode D ₃afterflow conducting, therefore there is following equation:

$\left\{\begin{array}{c}{U}_A={\mathrm{DU}}_d={\mathrm{Ri}}_A+L\frac{{\mathrm{di}}_A}{\mathrm{dt}}+e_A+U_N\\ U_B=U_d={\mathrm{Ri}}_B+L\frac{{\mathrm{di}}_B}{\mathrm{dt}}+e_B+U_N\\ U_C=0={\mathrm{Ri}}_C+L\frac{{\mathrm{di}}_C}{\mathrm{dt}}+e_C+U_N\end{array}\right.---\left(1\right)$

Therefrom three formulas are added, and obtain:

(1+D)U _d＝e _A+e _B+e _C+3U _N＝-E+3U _N

Solve: $U_N=\frac{(1+D)U_d+E}{3}---\left(2\right)$

Substitution formula again (1) in the first formula, obtain:

$U_A={\mathrm{DU}}_d={\mathrm{Ri}}_A+L\frac{{\mathrm{di}}_A}{\mathrm{dt}}+e_A+\frac{(1+D)U_d+E}{3}$ Change in voltage in negligible resistance:

${\mathrm{\&Delta;i}}_{A1}=\frac{(2D-1)U_d-4E}{3L}\mathrm{\&Delta;t}---\left(3\right)$

In like manner, the variation of electric current in the time of can analyzing this three kinds of PWM strategy commutation of PWM-ON, ON-PWM and H-PWM-L-PWM, can obtain the curent change that commutation causes and be:

$\left\{\begin{array}{c}{\mathrm{\&Delta;i}}_{A2}=\frac{{\mathrm{DU}}_d-4E}{3L}\mathrm{\&Delta;t}\\ {\mathrm{\&Delta;i}}_{A3}=\frac{(2D-1)U_d-4E}{3L}\mathrm{\&Delta;t}\\ {\mathrm{\&Delta;i}}_{A4}=\frac{(2D-1)U_d-4E}{3L}\mathrm{\&Delta;t}\end{array}\right.---\left(4\right)$

Due to $\left\{\begin{array}{c}{\mathrm{\&Delta;i}}_{A1}={\mathrm{\&Delta;i}}_{A3}={\mathrm{\&Delta;i}}_{A4}\\ {\mathrm{\&Delta;i}}_{A1}-{\mathrm{\&Delta;i}}_{A2}<0\end{array}\right.---\left(5\right)$

So it is very little a kind of that this kind of modulation system current pulsation belongs to, torque pulsation is little.

While relatively going up brachium pontis commutation again, T ₁change to T ₃torque pulsation, as T ₁t ₄t ₂change to T ₃t ₆t ₂.Now A phase current will reduce and each opposite potential meets following formula: $\left(\begin{array}{c}{e}_A=e_B=E\\ e_C=-E\end{array}\right.$

According to same thinking, can draw, under different modulating mode there is following relation in current pulsation absolute value:

$\left\{\begin{array}{c}{\mathrm{\&Delta;i}}_{A1}={\mathrm{\&Delta;i}}_{A2}\\ {\mathrm{\&Delta;i}}_{A1}<{\mathrm{\&Delta;i}}_{A4}<{\mathrm{\&Delta;i}}_{A3}\end{array}---\left(6\right)\right.$

From formula (5), (6) can find out Δ i _a1all very little, show under the Novel direct-current brushless Motor Control mode of this patent proposition, no matter while being upper brachium pontis or lower brachium pontis commutation, current pulsation is all very little.

By above analysis comparison, the torque pulsation of the Novel direct-current brushless Motor Control mode strategy that this patent proposes is very little, is conducive to the even running of motor.

The present invention adopts DSP to realize control procedure as control unit, for improving high-fidelity, the high-quality of input signal, designed DSP input signal voltage stabilizing fidelity circuit, as Fig. 9, its principle is at current sensor output, to install voltage-stabiliser tube and the RC filter circuit of 3.3V additional, thereby realizes the high-fidelity of sensor output signal.Meanwhile, if when output voltage is excessive, the voltage of DSP input below 3.3V, can not burn DSP original paper all the time, and DSP is formed to protection system.

Experiment parameter is as follows: the rated power of motor is 550W, voltage range 220-240V, and number of pole-pairs is 2, and rated current is 3.5A, and torque is 1.7Nm, rated speed 3000r/m.

In experiment, adopt the switching frequency of 3KHz.Figure 10 be duty ratio than under 0.5 condition, A phase current and line voltage U when motor low speed is underloading _aBwaveform.

As can be seen from Figure 10, T ₁, T ₄upper modulated, T ₆while opening, line voltage U _aBfor timing, A phase current is in rising trend; Line voltage U _aBfor timing, A phase current is on a declining curve.

If Figure 11 is motor band torque pulsating waveform in commutation process while carrying, can find out that the Novel direct-current brushless Motor Control mode strategy of proposition shows good dynamic property in motor commutation process, be conducive to the even running of motor.

Although above-mentioned, by reference to the accompanying drawings the specific embodiment of the present invention is described; but be not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various modifications that creative work can make or distortion still in protection scope of the present invention.

Claims (4)

1. a DC brushless motor control system, it is characterized in that: comprise three phase full bridge inverter circuit, three phase full bridge inverter circuit comprises three branch roads in parallel, every branch road comprises the power transistor of two series connection, every branch road neutral point is in series with respectively resistance, inductance and a phase stator winding, threephase stator winding is star-like connection, and the two ends of every branch road connect DC power supply, and power transistor two ends are parallel with a diode.

2. a kind of DC brushless motor control system as claimed in claim 1, is characterized in that: described threephase stator winding is respectively A, B, C three-phase; On corresponding branch road, brachium pontis power transistor is respectively T1, T3, T5, and lower brachium pontis power transistor is respectively T2, T4, T6.

3. the control method of the control system based on described in any one in claim 1-2, it is characterized in that: concrete grammar is: three-phase inverter is in 120 ° of conducting intervals, wherein the upper and lower switch controlled complementation of a phase brachium pontis is open-minded, and under other two-phase, brachium pontis replaces 60 ° of Heng Tongs.

4. control method as claimed in claim 3, is characterized in that: concrete mode is: in 0 °～60 ° intervals, T1 and T4 complementation are open-minded, and T6 often opens; In 60 °～120 ° intervals, T1 and T4 complementation are open-minded, and T2 often opens; In 120 °～180 ° intervals, T3 and T6 complementation are open-minded, and T2 often opens; In 180 °～240 ° intervals, T3 and T6 complementation are open-minded, and T4 often opens; In 240 °～300 ° intervals, T2 and T5 complementation are open-minded, and T4 often opens; In 300 °～360 ° intervals, T2 and T5 complementation are open-minded, and T6 often opens.