A method and control system for suppressing torque pulsation of a direct-drive motor of a washing machine

Abstract

This invention discloses a method and control system for suppressing torque ripple in a direct-drive motor of a washing machine. The method includes: using the motor's input speed and real-time speed as the output value of a speed PI controller to obtain a first reference current; using the current motor Hall value, the first reference current, and the real-time current as the output value of a current PI controller to output a compensating electromotive force; obtaining a reference voltage based on the first reference current and the compensating electromotive force; comparing the reference voltage with the motor's rated voltage to obtain the duty cycle; outputting a pulse width modulation (PWM) signal based on the duty cycle; and processing the PWM signal to output a feedback signal to control the motor's output voltage. By employing a dual-closed-loop PI control method, the real-time speed and real-time current of the motor are used for feedback PI control to adjust the motor's input voltage, thereby reducing torque ripple caused by three-phase current fluctuations after load changes, improving the washing machine motor control system's anti-interference capability against load changes, and stabilizing the motor's output torque.

Description

Technical Field

[0001] This invention relates to the field of washing machine control, and in particular to a method and control system for suppressing torque pulsation in a direct drive motor of a washing machine. Background Technology

[0002] Washing machines can be classified into two types based on their drive method: direct drive and indirect drive. In indirect drive washing machines, power is transmitted between the motor and the washing drum via a drive belt. With this method, increasing the washing power and effect can only be achieved by increasing the drum's rotation speed. However, this increased drum rotation speed, while improving washing power, also results in greater noise and vibration, as well as more energy waste. The drive belt is also more prone to wear, significantly reducing the washing machine's lifespan and increasing the failure rate. Therefore, washing machines using direct drive eliminate the drive belt, allowing the motor to directly drive the drum's rotation. This method greatly reduces noise and significantly improves transmission efficiency.

[0003] Current washing machine motors employ single closed-loop control, using a position sensor to detect rotor position and speed. This is then compared to a reference speed via PI control to adjust the voltage amplitude, thus regulating the speed. However, this control method results in significant torque ripple. Such ripple not only generates considerable noise but can also damage bearings over time, reducing the washing machine's lifespan.

[0004] For example, a "bidirectional operation advanced trigger control permanent magnet brushless DC motor" disclosed in Chinese patent literature, publication number CN202334413, includes a rotor position sensor whose sensor rotor is coaxially or integrally set with the main rotor of the permanent magnet motor body. The sensor rotor has the same number of permanent magnet pole pairs as the main rotor. Two sets of detection element groups are set on the sensor stator of the rotor position sensor, respectively located on both sides of the axis of the main stator armature winding of the permanent magnet motor body. The detection elements in the same group have the same deflection angle relative to the axis of the main stator armature winding. The electronic commutation circuit includes a bridge inverter circuit and a logic control circuit, which controls the main stator according to the output signal of the sensor stator. This solution cannot counteract the torque pulsation of motor rotation and speed change; direct rotation will lead to greater torque pulsation and noise. Summary of the Invention

[0005] This invention aims to overcome the problem that existing washing machine motor control systems generate significant torque pulsations when controlling the motor speed, resulting in noise and affecting the washing machine's lifespan. It provides a method and control system for suppressing torque pulsations in the washing machine's direct drive motor, thereby stabilizing the torque and speed of the direct drive motor, reducing motor noise, and extending the washing machine's lifespan.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for suppressing torque pulsation in a direct-drive motor of a washing machine, comprising:

[0007] Acquire the motor rotor input speed, real-time motor rotor speed, real-time current, and current motor Hall value;

[0008] The first reference current is the output value after the motor input speed and the motor real-time speed are controlled by a speed PI controller.

[0009] Based on the current motor Hall value, the first reference current and the real-time current, the current PI control outputs a compensation electromotive force;

[0010] A reference voltage is obtained based on the first reference current and the compensated electromotive force. The duty cycle is obtained by comparing the reference voltage with the motor's rated voltage. A pulse width modulation (PWM) signal is output based on the duty cycle. The PWM signal is processed and output as a feedback signal to control the motor's output voltage. A dual closed-loop PI control method is adopted, using feedback PI control of the motor's real-time speed and real-time current to adjust the motor's input voltage. This reduces torque pulsation caused by three-phase current fluctuations after load changes, improves the washing machine motor control system's anti-interference capability against load changes, and stabilizes the motor's output torque.

[0011] Preferably, the pulse width modulation signal is a PWM_ON signal. This reduces the commutation torque ripple of the motor.

[0012] Preferably, the pulse width modulation signal is output to the three-phase terminals of the motor through the switching of MOSFETs. In PWM_ON modulation mode, the PWM signal is input for the first 60 degrees of the 120 electrical degrees during the conduction of each MOSFET, and remains at a high level for the last 60 degrees.

[0013] Preferably, the step of outputting a compensating electromotive force through a current PI control loop based on the current motor Hall value, the first reference current, and the real-time current includes:

[0014] The phase with the positive back EMF corresponding to the current Hall value is used as the phase for back EMF feedforward control, and the phase with the current flowing into the motor windings corresponding to the current Hall value is used as the positive current phase.

[0015] Preferably, the system includes a speed acquisition unit for acquiring the real-time speed of the motor rotor; a Hall sensor unit for acquiring the Hall position of the motor and converting it into a Hall value; and a current acquisition unit for acquiring the real-time current of the motor.

[0016] Speed ​​regulator: It takes the input speed of the motor rotor and the real-time speed of the motor rotor as input, and outputs the first reference current after PI control;

[0017] Current regulator: The phase with the positive back EMF corresponding to the current Hall value is used as the phase for back EMF feedforward control; the phase with the current flowing into the motor windings corresponding to the current Hall value is used as the positive current phase; the compensation EMF is output through current PI control based on the current motor Hall value, the first reference current and the real-time current; the reference voltage is obtained based on the first reference current and the compensation EMF.

[0018] Synchronous PWM generation unit: Based on the ratio of reference voltage to rated voltage as the duty cycle, the obtained duty cycle is compared with the ratio signal and the PWM signal is output.

[0019] Three-phase voltage inverter circuit: includes several MOSFETs, which switch according to the PWM signal to output three-phase signals to the brushless DC motor.

[0020] Preferably, the three-phase voltage inverter circuit includes a three-phase bridge inverter circuit. The switching on and off of the six IGBT switches Q1-Q6 in the three-phase inverter circuit energizes the corresponding windings, controlling the continuous rotation of the motor.

[0021] Therefore, the present invention has the following beneficial effects: by adopting a dual closed-loop PI control method, the real-time speed and real-time current of the motor are fed back to adjust the input voltage of the motor, thereby reducing the torque pulsation caused by the three-phase current fluctuation after load change, improving the anti-interference ability of the washing machine motor control system to load change, and stabilizing the motor output torque. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the control structure of a washing machine direct drive motor torque pulsation suppression system according to an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the three-phase full-bridge inverter circuit connection of the washing machine direct drive motor torque pulsation suppression system according to an embodiment of the present invention.

[0024] In the diagram: 1. Synchronous PWM generation unit; 2. Three-phase voltage inverter circuit; 3. Speed ​​regulator; 4. Current regulator. Detailed Implementation

[0025] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0026] Example:

[0027] A method for suppressing torque ripple in a direct-drive motor of a washing machine includes acquiring the input speed of the motor rotor, the real-time speed of the motor rotor, the real-time current, and the current motor Hall value;

[0028] The first reference current is the output value after the motor input speed and the motor real-time speed are controlled by a speed PI controller.

[0029] Based on the current motor Hall value, the first reference current and the real-time current, the current PI control outputs a compensation electromotive force;

[0030] A reference voltage is obtained based on the first reference current and the compensated electromotive force. The duty cycle is obtained by comparing the reference voltage with the motor's rated voltage. A pulse width modulation (PWM) signal, specifically a PWM_ON signal, is output based on this duty cycle. This PWM signal is processed and output as a feedback signal to control the motor's output voltage, which is then fed to the motor's three-phase terminals via the switching of a MOSFET. A dual-closed-loop PI control method is employed, using feedback PI control of the motor's real-time speed and current to adjust the motor's input voltage. This reduces torque pulsation caused by three-phase current fluctuations after load changes, improves the washing machine motor control system's immunity to sudden load changes, and stabilizes the motor's output torque.

[0031] This embodiment also discloses a torque ripple suppression control system for a washing machine direct drive motor, employing the aforementioned torque ripple suppression method for a washing machine direct drive motor, such as... Figure 1 As shown, it includes a speed acquisition unit for acquiring the real-time speed of the motor rotor; a Hall sensor unit for acquiring the Hall position of the motor and converting it into a Hall value; and a current acquisition unit for acquiring the real-time current of the motor.

[0032] Speed ​​regulator 3: It takes the input speed of the motor rotor and the real-time speed of the motor rotor as input, and outputs the first reference current after PI control;

[0033] Current regulator 4: The phase with the positive back EMF corresponding to the current Hall value is used as the phase for back EMF feedforward control, and the phase with the current flowing into the motor windings corresponding to the current Hall value is used as the positive current phase; the compensation EMF is output through current PI control based on the current motor Hall value, the first reference current and the real-time current; the reference voltage is obtained based on the first reference current and the compensation EMF.

[0034] Synchronous PWM generation unit 1: Based on the ratio of the reference voltage to the rated voltage as the duty cycle, the obtained duty cycle is compared with the ratio signal and the PWM signal is output.

[0035] Three-phase voltage inverter circuit 2: includes several MOSFETs, which switch according to the PWM signal to output three-phase signals to the brushless DC motor. For example... Figure 2 As shown, the three-phase voltage inverter circuit includes a three-phase bridge inverter circuit. The switching on and off of the six IGBT switches Q1-Q6 in the three-phase inverter circuit energizes the corresponding windings, controlling the continuous rotation of the motor.

[0036] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0037] Although this document uses terms such as PI control, pulse width modulation signal, MOSFET, high level, and low level frequently, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would contradict the spirit of this invention.

Claims

1. A method for suppressing torque pulsation of a direct-drive motor of a washing machine, characterized by, include: Acquire the motor rotor input speed, real-time motor rotor speed, real-time current, and current motor Hall value; The first reference current is the output value after the motor input speed and the motor real-time speed are controlled by a speed PI controller. Based on the current motor Hall value, the first reference current, and the real-time current, the current PI control outputs a compensation electromotive force: the phase with the positive back electromotive force corresponding to the current Hall value is used as the phase for back electromotive force feedforward control, and the phase with the current flowing into the motor windings corresponding to the current Hall value is used as the positive current phase. A reference voltage is obtained based on the first reference current and the compensated electromotive force. The reference voltage is compared with the rated voltage of the motor to obtain the duty cycle. A pulse width modulation signal is output based on the duty cycle. The pulse width modulation signal is processed and output as a feedback signal to control the output voltage of the motor. The pulse width modulation signal is output to the three-phase terminals of the motor through the switching of the MOSFETs. During the 120° conduction angle of each MOSFET, the PWM signal is input for the first 60° and remains at a high level for the last 60°.

2. The method for suppressing torque pulsation in a direct-drive motor of a washing machine according to claim 1, characterized in that, The pulse width modulation signal is a PWM-ON signal.

3. A method for suppressing torque pulsation in a washing machine direct drive motor according to claim 1 or 2, characterized in that, The pulse width modulation signal is processed and output as a feedback signal to control the motor's output voltage, which is then output to the motor's three-phase terminals through the switching of the MOSFET.

4. A torque ripple suppression control system for a washing machine direct drive motor, employing the torque ripple suppression method for a washing machine direct drive motor as described in any one of claims 1 to 3, characterized in that, include The speed acquisition unit is used to acquire the real-time speed of the motor rotor; the Hall sensor unit is used to acquire the Hall position of the motor and convert it into Hall value; the current acquisition unit is used to acquire the real-time current of the motor. Speed ​​regulator: It takes the input speed of the motor rotor and the real-time speed of the motor rotor as input, and outputs the first reference current after PI control; Current regulator: The phase with the positive back EMF corresponding to the current Hall value is used as the phase for back EMF feedforward control; the phase with the current flowing into the motor windings corresponding to the current Hall value is used as the positive current phase; the compensation EMF is output through current PI control based on the current motor Hall value, the first reference current and the real-time current; the reference voltage is obtained based on the first reference current and the compensation EMF. Synchronous PWM generation unit: uses the ratio of reference voltage to rated voltage as the duty cycle, and outputs a PWM signal according to the duty cycle; Three-phase voltage inverter circuit: includes several MOSFETs, which switch according to the PWM signal to output three-phase signals to the brushless DC motor.

5. The torque pulsation suppression control system for a washing machine direct drive motor according to claim 4, characterized in that, The three-phase voltage inverter circuit includes a three-phase bridge inverter circuit.

6. The torque pulsation suppression control system for a washing machine direct drive motor according to claim 5, characterized in that, The three-phase bridge inverter circuit includes six IGBT switches Q1-Q6. The switching on and off of the six IGBT switches Q1-Q6 energizes the corresponding windings and controls the motor to rotate continuously.

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