JP7684830B2 - Motor Control Device - Google Patents

Description

The present invention relates to a motor control device.

Patent Document 1 discloses a technology for reducing torque pulsation in motor drive control. Specifically, the drive control in Patent Document 1 is configured to prepare correction wave information in advance in a storage unit and monitor state quantities (torque command, motor speed) that define the drive state that causes pulsation in the torque generated by the motor. Then, a sinusoidal correction wave is generated based on the monitoring results, and the motor is driven and controlled based on a correction torque command that is a combination of a torque command input from a higher-level device and the generated correction wave.

Patent No. 5755334

However, motors have the problem that cogging torque caused by magnetic flux nonuniformity generates electromagnetic noise according to the motor's electrical angular velocity. In washing machines, this electromagnetic noise is the main cause of noise, especially during the spin-drying process.

In the technology of Patent Document 1, a correction torque command is generated using correction wave information stored in a memory unit, and the motor is controlled using the correction torque command. However, there is a problem in that the effect of the correction (for example, the effect of reducing noise) varies due to individual differences between motors.

The present invention was made in consideration of these points, and its purpose is to eliminate the variation in noise reduction effect caused by individual motor variations (variations in magnet characteristics, manufacturing variations, etc.) and current response variations in motor control.

To solve the above problem, the motor control device according to the first aspect of the present invention includes a current detection means for detecting a motor current flowing through a motor, and a control unit for applying a cancellation current of opposite phase to a cogging component calculated based on the phase and amplitude of the motor current detected by the current detection means, and the control unit corrects the phase and amplitude of the cancellation current based on the motor current during operation of the motor.

The motor control device of this embodiment corrects the phase and amplitude of the cancellation current for canceling the cogging component based on the motor current during motor operation, making it possible to apply a cancellation current with optimized phase and amplitude for individual motor variations and current response variations. This makes it possible to eliminate variations in the noise reduction effect due to individual motor variations and current response variations.

In the motor control device according to the second aspect of the present invention, in the first aspect, the control unit changes the phase of the canceling current while fixing the amplitude of the canceling current in a low-speed rotation region where the motor does not generate noise, to set the initial value of the cogging component.

According to this embodiment, the state of individual variation of the motor can be identified in the low rotation speed region. This makes it possible to shorten the time required for correction while the motor is in operation. In addition, since the individual variation component of the motor can be eliminated in the low rotation speed region, the impact of noise can be reduced.

In the motor control device according to the third aspect of the present invention, in the first aspect, the control unit corrects the phase and amplitude of the cancellation current in a predetermined rotation speed range where noise of the motor is expected to occur.

In this way, by identifying the rotation speed range in which the phase and amplitude of the cancellation current are corrected, it is possible to reduce the current consumption required for control while still achieving a noise reduction effect.

The motor control device according to the fourth aspect of the present invention is the motor control device according to the first aspect, in which the control unit corrects the amplitude of the cancel current so that the amplitude of the cancel current is minimized.

Here, a specific manner is specified for correcting the amplitude of the canceling current. By correcting the amplitude of the canceling current so that it is minimized, the noise generated by the motor can be minimized.

In the motor control device according to the fifth aspect of the present invention, in the fourth aspect, the control unit corrects the phase of the cancellation current so that the phase of the cancellation current is minimized.

Here, a specific manner of correcting the phase of the cancellation current is specified. By correcting the phase of the cancellation current so that it is minimized, the noise generated by the motor can be minimized.

In the motor control device according to the sixth aspect of the present invention, in the fourth aspect, the control unit corrects the phase of the cancellation current so that the delay error of the motor current approaches zero.

Here, a specific embodiment of the phase correction of the cancel current is specified. According to this embodiment, the phase and amplitude of the cancel current can be corrected independently.

The motor control device according to the seventh aspect of the present invention is the sixth aspect, in which a pulse current is input to the motor to provide a phase error in addition to the motor current during phase correction of the cancellation current.

This allows phase correction of the cancellation current to be performed regardless of the amplitude of the current response to the cancellation current.

According to the present invention, by applying a cancellation current according to the individual variations and current response variations of the motor, it is possible to eliminate the variations in the noise reduction effect caused by the individual variations and current response variations of the motor.

Schematic cross-sectional view of a washing machine according to an embodiment. An exploded perspective view showing the main components of the motor. FIG. 1 is a diagram for explaining a cancellation current. A flowchart showing the process of setting the cancel current by the control unit. A waveform showing how the control unit sets the initial value of the cancellation current. A waveform diagram showing the cancellation current set by the control unit while the motor is running. A diagram showing a waveform of a modification of the setting of the cancel current by the control unit while the motor is operating.

The following describes an embodiment of the present invention with reference to the drawings. Note that the following description of the preferred embodiment is essentially merely illustrative and is not intended to limit the present invention, its applications, or its uses.

-washing machine-
1 shows an example of a washing machine 1 to which the motor control method according to the present disclosure is applied. The washing machine 1 is, for example, a fully automatic washing machine in which each process from washing to rinsing and spin-drying can be performed by automatic control.

The washing machine 1 in FIG. 1 has a vertically long rectangular box-shaped housing 2, and an input port 4 that can be opened and closed with a lid 3 is formed at the top. Laundry is loaded and unloaded through this input port 4 (a so-called vertical washing machine). Various switches and displays that the user can operate are provided behind the input port 4.

Inside the housing 2, a tub 10, a drum 11, a motor 12, a pulsator 13, a balancer 14, a motor control device 15, etc. are installed.

The tub 10 is a cylindrical container with a bottom that can store water, and is suspended inside the housing 2 by multiple hanging members 16 with its opening facing the upper inlet 4. Water can be poured into the inside of the tub 10 through a water injection mechanism (not shown). A drain pipe 17 that is controlled to open and close by a valve is connected to the bottom of the tub 10, and unnecessary water is drained outside the washing machine 1 through this drain pipe 17.

The drum 11 is a cylindrical container with a bottom that is slightly smaller than the tub 10 and that receives the laundry. The drum 11 is housed in the tub 10 in a state in which it can rotate around a vertical axis J that extends vertically, with its opening facing the loading port 4. All laundry processing is carried out inside the drum 11. A large number of drain holes 11a are formed over the entire surface of the cylindrical peripheral wall of the drum 11 (only a portion is shown in the figure). A balancer 14 is installed at the opening of the drum 11. The balancer 14 is an annular member that contains multiple balls and a viscous fluid inside, and adjusts the imbalance in weight caused by the uneven distribution of laundry when the drum 11 rotates. A disk-shaped pulsator 13 with a stirring blade on its upper surface is installed rotatably at the bottom of the drum 11.

The motor 12 has a flat cylindrical appearance with a diameter smaller than that of the tub 10, and is mounted below the tub 10 so that the vertical axis J passes through its center.

Figure 2 shows an example of the configuration of the motor 12. The motor 12 is composed of, for example, an outer rotor 20, an inner rotor 30, an inner shaft 40, an outer shaft 50, and a stator 60.

The outer rotor 20 is a flat, bottomed, cylindrical member that has a disk-shaped bottom wall 21 with an open center, a cylindrical peripheral wall 22 erected on the periphery of the bottom wall 21, a boss 23 integrated into the center of the bottom wall 21, and multiple outer magnets 24. Each outer magnet 24 is made of a rectangular plate-shaped permanent magnet and is fixed to the inner surface of the peripheral wall 22.

The inner rotor 30 is a flat, bottomed, cylindrical member with a smaller outer diameter than the outer rotor 20, and has a trapezoidal inner bottom wall 31 with an open center, a cylindrical inner peripheral wall 32 erected around the inner bottom wall 31, an inner boss 33 integrated into the center of the inner bottom wall 31, and multiple inner magnets 34. Each inner magnet 34 is made of a rectangular plate-shaped permanent magnet and is fixed to the outer surface of the inner peripheral wall 32.

The motor control device 15 includes a current detection means 18 for detecting the current flowing through the motor 12 (hereinafter referred to as the "motor current"), and a control unit 151 for applying a cancellation current of opposite phase to the cogging component calculated based on the phase and amplitude of the motor current detected by the current detection means 18. The current detection means 18 is, for example, a circuit mounted on a control board (not shown), connected to the coils (not shown) of each phase (U-phase, V-phase, W-phase) of the motor 12, and detects the current flowing through the coils.

The control unit 151 is composed of hardware such as a CPU and ROM, and software such as a control program, and comprehensively controls each process performed by the washing machine 1. The control unit 151 is electrically connected to various switches and the motor 12, and the control program executes the washing, rinsing, and spin-drying processes according to the user's instructions. For example, in the washing and rinsing processes, the motor 12 rotates the pulsator 13 while rotating it in a constant cycle, agitating the laundry together with water and detergent. In the spin-drying process, the motor 12 rotates the drum 11 in a constant direction at high speed, and centrifugal force is used to press the laundry against the peripheral wall to spin it out.

- Current control by control device -
3, in the spin-drying process of washing machine 1, control unit 151 controls to pass a torque current in the opposite phase to the periodic fluctuation of the cogging torque of motor 12. This cancels the cogging component of motor 12, and reduces the electromagnetic noise of motor 12 (e.g., noise during the spin-drying process). In the following description, unless otherwise specified, the main control unit is control unit 151.

As mentioned above, in the washing machine 1, the cogging torque varies due to the characteristic variations of the outer magnet 24 and the inner magnet 34, the manufacturing variations of the motor 12, the variations in the current response delay, and the like. That is, when a preset correction command is used to cancel the cogging component, as shown by the dashed line in FIG. 3, amplitude errors and phase errors occur with respect to the ideal cancellation current, resulting in individual variations in the noise reduction effect. In contrast, the motor control disclosed herein has the characteristic that, even in the presence of individual variations, the amplitude errors and phase errors can be suppressed, and the noise reduction effect in the spin-drying process can be obtained. A specific description will be given below with reference to the flowchart in FIG. 4.

In step S11, the control unit 151 sets initial values for the phase correction value and the amplitude correction value of the cancellation current in the low-speed rotation region of the motor 12.

Here, the low-speed rotation range of motor 12 refers to a rotation speed range that is sufficiently lower than the range where noise occurs. For example, in a washing machine 1, noise generally occurs at around 450-600 rpm due to the relationship with the resonance point of housing 2 and motor 12, while noise due to cogging torque is small in a speed range of about 100 rpm. Therefore, sensing is performed to set the initial value at a constant speed of, for example, 100 rpm. The reason for setting the initial value at a constant speed is to avoid the effect of the current amplitude changing according to the speed when the speed changes.

Figure 5 shows an example of how the initial value is set in the form of a waveform. In the example of Figure 5, the control unit 151 rotates the motor 12 at a constant speed of 100 [rpm], fixes the amplitude of the cancel current to 0.007 [A], and changes the phase of the cancel current by 360 [deg] to set the initial value. This makes it possible to sense the individual variation of the motor 12. Note that the amplitude of the cancel current when setting the initial value is not particularly limited, but if it is too small it becomes difficult to distinguish the difference, and if it is too large noise is generated, so it is preferable to set it at a value that does not generate noise and allows the difference to be distinguished.

As shown in FIG. 5, the control unit 151 changes the phase of the canceling current by 360 degrees, and sets the phase at which the sensed current amplitude is at its minimum as the "initial value of the phase of the canceling current". Hereinafter, the "initial value of the phase of the canceling current" will be simply referred to as the "initial phase value". Similarly, the control unit 151 changes the phase of the canceling current by 360 degrees, and sets the amplitude at which the sensed current amplitude is at its maximum as the "initial value of the amplitude of the canceling current". Hereinafter, the "initial value of the amplitude of the canceling current" will be simply referred to as the "initial amplitude value". This makes it possible to quantify the individual variation of the motor 12.

In the above example, the phase is changed by 360 degrees to perform sensing for setting the initial value, but this is not limiting. For example, if the phase at which the "initial phase value" and/or the "initial amplitude value" is obtained can be estimated to some extent, the control unit 151 may change the phase of the cancellation current near the estimated phase to set the "initial phase value" and/or the "initial amplitude value." In addition, data may be collected every 90 degrees and narrowed down from there, or other search methods such as a binary tree search method may be used.

In the above example, the control unit 151 fixes the amplitude of the cancel current and changes the phase of the cancel current to set the initial value, but the phase of the cancel current may be fixed and the amplitude of the cancel current may be changed to set the initial value. However, it is easier to determine the maximum value when the amplitude of the cancel current is fixed.

When the initial value setting in step S11 is completed and the spin-drying process of the washing machine 1 is started, the control unit 151 repeatedly executes the processes from step S12 to step S13 at a predetermined time interval.

In step S12, the control unit 151 checks the amplitude of the current response (hereinafter simply referred to as "current response") of the canceling current shown in FIG. 6(a) to the current command at a predetermined time period, and adjusts the phase of the canceling current so that the amount of fluctuation of this current response (amplitude of the current response) is minimized. For example, the phase of the canceling current is adjusted so that it faces the direction of the arrow in FIG. 6(b). The current detected by the current detection means 18 is an example of a current response.

After the adjustment of the phase of the cancel current in step S12 is completed, in the next step S13, the control unit 151 adjusts the amplitude of the cancel current. Specifically, the amplitude of the cancel current is adjusted so that the amount of fluctuation in the current response (amplitude of the current response) is minimized. For example, the amplitude of the cancel current is adjusted so that it moves in the direction of the arrow in Figure 6 (c).

In this way, by repeatedly performing the adjustments of steps S12 and S13, it becomes possible to adjust the cancellation current to the optimum in real time in response to individual variations in the motor and variations in current response. In addition, even if changes in characteristics occur due to changes in the operating temperature while the washing machine 1 is operating, it becomes possible to adjust the cancellation current to the optimum.

The control unit 151 may execute the processes of steps S12 and S13 in a rotational speed range where the motor 12 is expected to generate noise. More specifically, the rotational speed range where the motor 12 is expected to generate noise is a range including rotational speeds with a predetermined rotational speed range before and after the rotational speed range where the noise is expected to generate. Specifically, the control unit 151 may start the processes of steps S12 and S13 when approaching the rotational speed range where the motor 12 is expected to generate noise, and stop the processes of steps S12 and S13 after completely leaving the rotational speed range where the noise is expected to generate. For example, when it is expected that the motor 12 will generate noise at a rotational speed of 450-600 [rpm] based on design information, prior evaluation results, etc., the processes of steps S12 and S13 may be started when the motor 12 reaches a rotational speed of 400 [rpm]. For example, when the rotation speed of the motor 12 exceeds 650 rpm, the processes in steps S12 and S13 may be stopped. This can reduce current consumption.

The repeated process of steps S12 and S13 is terminated, for example, when the spin cycle of the washing machine 1 is completed and the motor 12 falls below a predetermined rotation speed or when the motor 12 is stopped. As described above, if the process is started when approaching the rotation region where noise is generated and stopped when the rotation region where noise is generated is passed, the repeated process of steps S12 and S13 may be executed only in the rotation region where noise is generated.

As described above, according to this embodiment, the amplitude and phase of the cancel current can be adjusted while monitoring the operating state of the motor 12 (washing machine 1), making it possible to apply a cancel current with an optimized phase and amplitude for individual variations and current response variations of the motor 12.

A preferred embodiment has been described as an example of the technology of this disclosure. However, the technology of this disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate.

<Modification 1>
For example, Fig. 7 shows another example of the phase correction of the cancel current in step S12 in Fig. 4. More specifically, when determining the initial values of the phase correction value and the amplitude correction value of the cancel current in step S11 in Fig. 4, the behavior of the cogging in the low speed rotation region (hereinafter referred to as the low speed cogging component) is known, and therefore the low speed cogging component is used. In Fig. 7, an example of the low speed cogging component is shown by a thick solid line.

Specifically, step S11 is executed in the same manner as in the above embodiment. Then, in the control unit 151, initial values of the phase correction value and the amplitude correction value of the cancellation current are set, and the aforementioned low-speed cogging component is calculated.

When the operation of the washing machine 1 is started, in step S12, phase correction of the cancellation current is performed at a predetermined time period. Specifically, when the rotation speed of the motor 12 of the washing machine 1 increases, a delay error occurs in the phase of the cancellation current (see the dashed line in FIG. 7(b)).

Therefore, the control unit 151 corrects the phase of the cancellation current so that the phase error of the cancellation current approaches "0". Specifically, the control unit 151 generates a pseudo waveform of the low-speed cogging component based on the result of step S11, and corrects the phase of the cancellation current so that the phase shift with the measurement result of the detected current response approaches "0".

In addition, in this modified example, the amplitude correction of the cancellation current is performed in step S13 at the same time as the phase correction of the cancellation current. The amplitude correction of the cancellation current is performed in the same manner as in the above-described embodiment.

By performing the processing of this modified example, it becomes possible to apply a cancellation current whose phase and amplitude are independently optimized for the individual variations and current response variations of the motor 12.

In this modified example, the control unit 151 may start the processing of steps S12 and S13 when approaching the rotation region where noise occurs, and stop the processing when passing the rotation region where noise occurs. For example, if it is expected that noise will occur at a rotation speed of 450-600 [rpm] based on design information or prior evaluation results, the processing of steps S12 and S13 may be started when the rotation speed of the motor 12 reaches 400 [rpm]. Then, for example, when the rotation speed of the motor 12 reaches 600 [rpm] and exceeds 650 [rpm], the processing of steps S12 and S13 may be stopped. This can reduce current consumption.

<Modification 2>
In the first modification, when the correction results of the phase correction and the amplitude correction of the cancellation current approach an optimized state, the amplitude of the current response shown in FIG. 7A decreases, and the current delay error decreases.

Therefore, when correcting the phase of the cancellation current in step S12, for example, the phase error of the cancellation current may be input as a pulse signal to perform phase correction of the cancellation current. As the phase error pulse signal, it is preferable to input a pulse signal that does not cause noise problems. For example, as the phase error pulse signal, an error of 90 degrees at 5 ms is input for 1 second.

Then, after step S12, in the absence of a pulse signal, the amplitude correction of the cancellation current is performed in step S13. The amplitude correction of the cancellation current is performed in the same manner as in the above-described embodiment.

In this modified example, the process of step S12 and the process of step S13 are repeated at a predetermined cycle. That is, the control unit 151 executes the process in the same flow as in the above-described embodiment.

By performing the processing of this modified example, phase correction of the cancellation current can be performed regardless of the amplitude of the current response.

In this modified example, the control unit 151 may start the processing of steps S12 and S13 when the rotation region where noise is generated is approached, and stop the processing when the rotation region where noise is generated is passed. This can reduce current consumption.

As explained above, the present invention is extremely useful and has high industrial applicability because it can correct the current applied to a motor according to individual variations in motors and variations in current response.

15 Motor control device 18 Current detection means 151 Control unit

Claims (6)

A motor control device for controlling a motor, comprising:
A current detection means for detecting a motor current flowing through the motor;
a control unit that applies a cancel current having an opposite phase to a cogging component calculated based on the phase and amplitude of the motor current detected by the current detection means,
The control unit corrects the phase and amplitude of the canceling current based on the motor current while the motor is operating , and in a low-speed rotation region where the motor does not generate noise, changes the phase of the canceling current while keeping the amplitude of the canceling current fixed, to set an initial value of the cogging component . 2. The motor control device according to claim 1,
The control unit corrects the phase and amplitude of the cancellation current in a predetermined rotation speed range in which noise of the motor is expected to be generated. 2. The motor control device according to claim 1,
The control unit corrects the amplitude of the canceling current so that the amplitude of the canceling current is minimized. 4. The motor control device according to claim 3 ,
The control unit corrects the phase of the canceling current so that the phase of the canceling current is minimized. 4. The motor control device according to claim 3 ,
The control unit corrects the phase of the cancellation current so that a delay error of the motor current approaches zero. A motor control device for controlling a motor, comprising:
A current detection means for detecting a motor current flowing through the motor;
a control unit that applies a cancel current having an opposite phase to a cogging component calculated based on the phase and amplitude of the motor current detected by the current detection means,
The control unit is
correcting a phase and an amplitude of the cancellation current based on the motor current during operation of the motor;
correcting the amplitude of the canceling current so that the amplitude of the canceling current is minimized;
correcting the phase of the cancellation current so that the delay error of the motor current approaches zero;
A motor control device that inputs a pulse current to the motor during correction of the phase of the cancellation current, in addition to the motor current, for imparting a phase error.

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