Torque pulse suppression method of brushless DC motor in all speed regulation range

[0043] The present invention will be further explained below in conjunction with the embodiments and the drawings of the specification.

[0044] When applying the present invention to power a brushless DC motor, firstly, the AC power supply 1 is rectified by the rectifier 2, and then filtered by the filter capacitor 3 to obtain the DC power. Finally, the inverter 4 converts the DC power into AC power To supply power to the brushless DC motor, the torque ripple control method in the full speed regulation range of the brushless DC motor of the present invention is:

[0045] According to the motor speed obtained by the speed calculation module 12, it is divided into two states of low-speed operation and high-speed operation for corresponding control:

[0046] ① When the motor is running at low speed, the position feedback module 5 is used to detect the rotor angular speed signal of the brushless DC motor, and the speed calculation module 11 calculates the motor speed ω according to the rotor angular speed signal, which is combined with the given speed ω* The obtained speed difference is input into the PI speed regulator 6 to obtain the reference electromagnetic torque Te* of the motor; at the same time, the feedback values ​​ij and ik of any two-phase current of the motor are input to the torque calculation module 10 to estimate the electromagnetic torque of the motor Te;

[0047] Make the difference between the electromagnetic torque Te and the given torque Te*, and the obtained torque difference is adjusted by the torque hysteresis regulator 7 to obtain the control parameter τ, which is input to the switch table selection module 8, and then combined with the fan The output signal of the zone judgment module 9 selects the corresponding switch signal to control the inverter 4, thereby driving the brushless DC motor to run, and realizes the direct torque control of the brushless DC motor at low speed operation without flux linkage;

[0048] ② When the motor is running at high speed, the position feedback module 5 is used to detect the rotor angular speed signal of the brushless DC motor, and the speed calculation module 11 calculates the motor speed ω according to the rotor angular speed signal, which is combined with the given speed ω* The obtained speed difference is input into PI speed regulator 6 to obtain the reference electromagnetic torque Te* of the motor; at the same time, the feedback value i of any two-phase current of the motor j , I k Input to the torque calculation module 10 to estimate the electromagnetic torque Te of the motor;

[0049] Make the difference between the electromagnetic torque Te and the given torque Te*, and the obtained torque difference is adjusted by the torque hysteresis regulator 7 to obtain the control parameter τ, which is input to the switch table selection module 8, except for In addition, the commutation judgment module, which does not participate in the function at low speed, participates in the control. Input the feedback values ​​ij, ik of any two-phase currents of the motor to the commutation judgment module 12, and judge whether the current shut-off phase needs to be delayed shut-off control according to whether its output is zero, and if necessary, delay the shut-off phase Turn off, so that 3 switch tubes will be turned on at the same time during the turn off. The two-phase conduction switch table at low speed becomes a three-phase conduction switch table. Finally, the switch table selection module 8 is based on the torque hysteresis regulator. 7 Output signal τ, sector judgment module 9 output signal Q and commutation judgment unit 12 output signal K determine the current switching signal to be applied to control the inverter module 4, thereby driving the brushless DC motor to achieve high-speed brushless DC motor Direct torque control without flux linkage during operation.

[0050] The position feedback module 5 can use photoelectric encoder, Hall element or no position sensor; the calculation method of the reference electromagnetic torque Te* is to make the difference between the motor speed ω and the given speed ω*, and the speed difference is input to the speed regulator After 6 get the reference electromagnetic torque of the brushless DC motor.

[0051] In the torque ripple control in the low-speed operation state and the high-speed operation state, the torque Te is calculated according to the following formula:

[0052] T e =Ke(|i j |+|i k |+|i j +i k |)

[0053] Among them, Ke is the no-load back-EMF constant of the motor, and ij, ik are any two-phase currents among the three-phase currents of the motor.

[0054] The specific implementation method of the commutation judgment module 12 is: detect the two-phase current at any time and calculate the third-phase current to obtain the three-phase currents Ia, Ib, and Ic, and then add the three-phase currents in pairs and take the absolute value. Get the minimum value m. During the non-commutation period, the non-conducting phase current is zero, and the sum of the other two phase currents is also zero. During the commutation period, since the change rates of the on-phase current and the off-phase current are different, the three current values ​​are not 0, and the value of m is also not 0. The switch table selection module 8 can judge whether the motor is in the commutation period at this time by judging whether m is 0. If it is in the non-commutation period, use the two-phase continuity meter when running at low speed; if it is in the commutation period, use the replaced three-phase continuity meter for high-speed control to drive the brushless DC motor.

[0055] In the torque ripple control in the low-speed operation state and the high-speed operation state, the switch table selection module 8 generates a corresponding switch signal according to the input data, and the switch table selection module 8 outputs the signal τ according to the torque hysteresis regulator 7. The output signal Q of the judgment module 9 and the output signal K of the commutation judgment unit 12 are used to select the voltage vector to be applied to the brushless DC motor according to the following table, and generate the corresponding switching signal:

[0056]

[0057]

[0058] In the table, S 1 ~S 6 Indicates the 6 switching tubes of the inverter module 4. In the table, 1 means on, and 0 means off.

[0059] The space voltage vector used in the present invention:

[0060] Define the voltage space vector U s for:

[0061] Where U an , U bn , U cn These are the motor phase voltages.

[0062] Image 6 It is the torque simulation waveform of brushless DC motor running at low speed under traditional hysteresis control mode; Figure 7 It is the torque simulation waveform of the non-magnetic linkage direct torque control method proposed by the present invention at low speed; Figure 8 It is the simulation waveform diagram of the rotation speed when the rotation speed is increased from low speed to high speed after using the method proposed by the present invention; Picture 9 It is the torque simulation waveform diagram when the rotation speed is increased from low speed to high speed when the method of suppressing torque ripple at high speed proposed by the present invention is not applied; Picture 10 It is a torque simulation waveform diagram when the rotation speed is increased from low speed to high speed by using the method of the present invention at high speed;

[0063] According to the simulated torque result graph, it can be seen that the method of the present invention is effective.

[0064] The above-mentioned embodiments are only preferred implementations of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and equivalent substitutions can be made, and these have rights to the present invention. All technical solutions requiring improvements and equivalent replacements fall within the protection scope of the present invention.