Motor control device, and washing machine or laundry dryer equipped with the same
By correcting the initial phase of the brushless motor through the inverter circuit and the current detection unit, the problem of inaccurate magnetic pole detection caused by the initial phase estimation deviation is solved, thus enabling smooth start-up of the brushless motor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
- Filing Date
- 2021-10-04
- Publication Date
- 2026-06-12
Smart Images
Figure CN116349128B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a motor control device for sensorless control of the rotation of a brushless motor (permanent magnet synchronous motor) with a rotor having a salient pole configuration, and a washing machine or washer-dryer equipped with the motor control device. Background Technology
[0002] Patent Document 1 discloses a motor control device for sensorless driving of a brushless motor with a salient-pole rotor and for determining the magnetic poles during startup. This motor control device converts DC power to AC power and uses this AC power as motor power to drive the brushless motor with a salient-pole rotor. The motor control device includes a current detector, a three-phase-dq axis conversion unit, a dq axis current control unit, a dq axis-three-phase conversion unit, an AC alternating voltage generator for magnetic pole position estimation, a magnetic pole position estimation unit, a d-axis current DC bias generator, and an NS discrimination unit. The current detector detects the motor current from the inverter to the brushless motor. The three-phase-dq axis conversion unit performs dq axis conversion on the AC current detected by the current detector to output d-axis current detection values and q-axis current detection values. The dq axis current control unit calculates d-axis voltage commands and q-axis voltage commands that cause the d-axis current detection values and q-axis current detection values to follow the d-axis current command input and q-axis current command input, respectively. The dq-axis three-phase conversion unit converts the d-axis voltage command and q-axis voltage command into a three-phase AC voltage command, and uses the converted three-phase AC voltage command as a control signal to supply to the inverter. The pole position estimation unit uses an AC alternating voltage generator to superimpose an auxiliary AC alternating voltage onto the d-axis voltage command. The pole position estimation unit estimates the pole position of the permanent magnet synchronous motor based on the q-axis current detection value and the auxiliary AC alternating voltage. The d-axis current DC bias generator uses the direction of the pole position estimated by the pole position estimation unit as the d-axis, applies a fixed waveform d-axis DC bias current with alternating positive and negative symmetrical switching to the d-axis current command, and inputs the biased d-axis current command to the dq-axis current control unit. The NS discrimination unit estimates the applied d-axis voltage and the rate of change of the d-axis current at the timing of the positive and negative switching of the d-axis DC bias current, determines the direction of the N and S poles of the permanent magnet of the permanent magnet synchronous motor based on the estimated relationship between the applied d-axis voltage and the rate of change of the d-axis current, and outputs an NS discrimination signal.
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-79489 Summary of the Invention
[0006] The problem the invention aims to solve
[0007] This disclosure provides a motor control device that can correctly detect magnetic poles even when the direction of the d-axis obtained from the initial estimation deviates from the correct direction by 90° or 270°, and a washing machine or washer-dryer equipped with the motor control device.
[0008] The motor control device of this disclosure controls a brushless motor with a salient-pole rotor driven by an inverter circuit. The motor control device includes an inverter circuit, a current detection unit, an initial phase estimation unit, and a polarity determination unit. The current detection unit detects the current of the brushless motor. The initial phase estimation unit estimates the initial phase of the brushless motor based on the current detected by the current detection unit. The polarity determination unit determines the polarity of the brushless motor's magnetic poles based on the current detected by the current detection unit. For the initial phase estimated by the initial phase estimation unit, the polarity determination unit determines the polarity of the brushless motor's magnetic poles based on the difference in current amplitude between the positive and negative directions of the d-axis and q-axis detected by the current detection unit after superimposing voltages in the positive and negative directions of the d-axis and q-axis, respectively, and corrects the initial phase.
[0009] In addition, the washing machine or washer-dryer disclosed herein is equipped with the motor control device disclosed herein.
[0010] The motor control device of this disclosure can correctly detect magnetic poles even when the direction of the d-axis obtained from the initial estimation deviates from the correct direction by 90° or 270°.
[0011] Furthermore, the washing machine or washer-dryer disclosed herein is equipped with a motor control device as described above, thus enabling, for example, the washing tub, drum, etc., to rotate smoothly. Attached Figure Description
[0012] Figure 1 This is a diagram showing the structure of the motor control device in Embodiment 1.
[0013] Figure 2 This is a block diagram showing the structure of the sensorless estimation unit of the motor control device in Embodiment 1.
[0014] Figure 3 This is a block diagram showing the detailed structure of the inductor drive section of the motor control device in Embodiment 1.
[0015] Figure 4 This is a block diagram showing the detailed structure of the induced voltage drive unit of the motor control device in Embodiment 1.
[0016] Figure 5 This is a flowchart illustrating the motor drive control process of the motor control device in Embodiment 1.
[0017] Figure 6A This is a diagram used to illustrate a topic related to the initial phase estimation of the rotor.
[0018] Figure 6B This is a diagram used to illustrate a topic related to the initial phase estimation of the rotor.
[0019] Figure 6C This is a diagram used to illustrate a topic related to the initial phase estimation of the rotor.
[0020] Figure 7 This is a graph showing the magnetic saturation characteristics of an electromagnet used in a typical brushless motor.
[0021] Figure 8 This is a flowchart illustrating the polarity determination process of the motor control device in Embodiment 1.
[0022] Figure 9 This is a diagram illustrating an example of the applied voltage and current when the motor control device in Embodiment 1 determines the d-axis.
[0023] Figure 10 This is a diagram illustrating an example of the applied voltage and current when determining the d-axis and q-axis of the motor control device in Embodiment 1.
[0024] Figure 11 This is a diagram illustrating the applied voltage and current during offset correction when the polarity of the motor control device in Embodiment 1 is determined.
[0025] Figure 12 This is a diagram illustrating the outline of polarity determination in the case of current control in the motor control device of Embodiment 2. Detailed Implementation
[0026] The motor control device of this disclosure controls a brushless motor with a salient-pole rotor driven by an inverter circuit. The motor control device includes an inverter circuit, a current detection unit, an initial phase estimation unit, and a polarity determination unit. The current detection unit detects the current of the brushless motor. The initial phase estimation unit estimates the initial phase of the brushless motor based on the current detected by the current detection unit. The polarity determination unit determines the polarity of the brushless motor's magnetic poles based on the current detected by the current detection unit. For the initial phase estimated by the initial phase estimation unit, the polarity determination unit determines the polarity of the brushless motor's magnetic poles based on the difference in current amplitude between the positive and negative directions of the d-axis and q-axis detected by the current detection unit after superimposing voltages in the positive and negative directions of the d-axis and q-axis, respectively, and corrects the initial phase.
[0027] Therefore, the motor control device of this disclosure can correctly detect magnetic poles even when the direction of the d-axis obtained from the initial estimation deviates from the correct direction by 90° or 270°. Thus, the motor control device of this disclosure can suppress reverse start-up and start-up failure during brushless motor startup, and provide smooth acceleration from the start of the brushless motor.
[0028] Alternatively, in the motor control device of this disclosure, if the absolute value of the difference between the current amplitudes in the positive and negative directions of the d-axis, detected by the current detection unit after applying voltages to the positive and negative directions of the d-axis, is greater than a reference value, the polarity determination unit terminates the polarity determination of the brushless motor. If the absolute value of the difference between the current amplitudes in the positive and negative directions of the d-axis is less than the reference value, the polarity determination unit performs the following processing. That is, the polarity determination unit may determine the polarity of the brushless motor's magnetic poles based on the difference between the current amplitudes in the positive and negative directions of the q-axis, detected by the current detection unit after applying voltages to the positive and negative directions of the q-axis, and the difference between the current amplitudes in the positive and negative directions of the d-axis, and correct the initial phase.
[0029] Alternatively, in the motor control device of this disclosure, the polarity determination unit may set the current detected by the current detection unit immediately before the voltage is superimposed in the positive and negative directions of the d-axis and q-axis, respectively, as the offset current value. Alternatively, the polarity determination unit may determine the polarity of the brushless motor's magnetic poles based on the value obtained by subtracting the offset current value from the maximum current amplitude in the positive and negative directions of the d-axis and q-axis, respectively, detected by the current detection unit after the voltage is superimposed in the positive and negative directions of the d-axis and q-axis, respectively. This value also allows for initial phase correction.
[0030] Alternatively, in the motor control device of this disclosure, the polarity determination unit may be controlled such that the current flowing into the brushless motor is 0 during the period of determining the polarity of the magnetic poles of the brushless motor.
[0031] In addition, the washing machine or washer-dryer disclosed herein is equipped with the motor control device disclosed herein.
[0032] (The views, etc., that form the basis of this disclosure)
[0033] When the inventors conceived of this disclosure, they already knew a technique for determining the polarity of magnetic poles based on the estimated initial phase of the rotor. The initial phase of the rotor is estimated during sensorless operation of a brushless motor with a salient pole configuration, at the start of brushless motor operation, and at the stop of the brushless motor before operation.
[0034] In the initial phase estimation, the difference between the inductance L in the direction of the magnetic poles (d-axis direction), which is characteristic of a rotor with salient polarity, and the inductance L in the direction orthogonal to the same magnetic poles (q-axis direction) is used. Furthermore, in the initial phase estimation, a low-amplitude, high-frequency or pulsed voltage and current are applied to the stator windings to estimate the direction of the rotor. At this point in time, at most the rotor direction can be estimated, but the polarity (NS) of the magnetic poles is unknown; therefore, polarity determination is performed to identify the N and S poles.
[0035] In polarity determination, large, pulsed voltages and currents of a certain magnitude in both the positive and negative directions of the estimated d-axis are applied to the stator windings. The direction of the magnetic poles NS is estimated based on the difference between the absolute values of the applied voltage or the detected current. This allows for a smooth start-up of the brushless motor from the moment it begins to rotate, preventing reverse drive or start-up failures.
[0036] However, the following situation occurs at a certain rate: the direction of the d-axis estimated during the initial phase estimation should correctly be the direction of the magnetic poles, but the estimated value is a direction orthogonal to the magnetic poles (the q-axis direction). The inventors discovered the following problem: in this case, even if polarity determination is performed, the correct rotor direction cannot be obtained. Therefore, at the start of brushless motor driving, phenomena such as reverse driving, loss of synchronization, and failure to rotate sometimes occur. In order to solve this problem, the subject of this disclosure was conceived.
[0037] Therefore, this disclosure provides a motor control device that can correctly detect magnetic poles in polarity determination even if the d-axis direction estimated at the initial phase estimation deviates from the correct direction by 90° or 270°.
[0038] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, sometimes unnecessary details are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of substantially the same structures are sometimes omitted. This is to avoid making the following description overly lengthy and to facilitate understanding by those skilled in the art.
[0039] Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.
[0040] (Implementation Method 1)
[0041] The following uses Figures 1 to 11 To illustrate the motor control device 10 in Embodiment 1.
[0042] [1-1. Structure]
[0043] [1-1-1. Structure of the Motor Control Device]
[0044] Figure 1 This is a diagram showing the structure of the motor control device 10 in Embodiment 1.
[0045] The motor control unit 10 receives power from the AC power supply 30. The rectifier circuit 11 converts the received AC power into DC power and supplies power to the inverter circuit 13 via the DC power smoothing capacitor 12. The inverter circuit 13 consists of three sets of six switching elements 14a, 14b, 14c, 14d, 14e, and 14f connected in pairs in series.
[0046] The inverter circuit 13 drives the brushless motor 40 by PWM driving the switching elements 14a, 14b, 14c, 14d, 14e and 14f to turn on / off via the control circuit 20 described later.
[0047] In the inverter circuit 13, resistors 15a, 15b, and 15c are connected to the emitter side of the lower switching elements (i.e., switching elements 14d, 14e, and 14f) that are connected in series in pairs. The other ends of resistors 15a, 15b, and 15c are connected to the output side of the rectifier circuit 11 and the smoothing capacitor 12. The voltage across resistors 15a, 15b, and 15c is input to the current detection unit 21 within the control circuit 20. Various controls are performed using the current value detected by the current detection unit 21, as described later.
[0048] The control circuit 20 includes the aforementioned current detection unit 21, and also includes an initial phase estimation unit 22, a polarity determination unit 23, and a sensorless estimation unit 24. Furthermore, the motor control device 10 includes a computer system with a processor and a memory. The computer system functions as the control circuit 20 by having the processor execute a program stored in the memory. Here, it is assumed that the program executed by the processor is pre-recorded in the computer system's memory, but it can also be provided via a non-transitory recording medium such as a memory card, or via a telecommunications communication line such as the Internet.
[0049] [1-1-2. Structure of the Sensorless Estimation Unit]
[0050] Figure 2 This is a block diagram showing the structure of the sensorless estimation unit 24 of the motor control device 10 in Embodiment 1.
[0051] The sensorless estimation unit 24 includes an inductive drive unit 24b (inductive mode), an induced voltage drive unit 24c (induced voltage mode), and a drive mode switching unit 24a. The inductive drive unit 24b estimates the phase of the magnetic poles using the salient polarity of the rotor 41 of the brushless motor 40. The induced voltage drive unit 24c estimates the magnetic pole position using the back electromotive force generated by the rotation of the brushless motor 40. The drive mode switching unit 24a switches the method of estimating the magnetic pole position between the inductive mode and the induced voltage mode.
[0052] [1-1-3. Structure of the Inductor Drive Section]
[0053] The inductance L varies according to the phase of the magnetic poles of the rotor 41 of the brushless motor 40. Therefore, the inductor drive unit 24b applies a high-frequency current independent of the motor drive current to the motor to detect the motor current, thereby calculating the position estimation error caused by the inductance variation. Then, the inductor drive unit 24b estimates the magnetic pole position in a manner that brings the position estimation error to zero.
[0054] Figure 3 This is a block diagram showing the detailed structure of the inductor drive unit 24b of the motor control device 10 in Embodiment 1.
[0055] The inductor drive unit 24b consists of an uvw→dq current conversion unit 24ba, a position estimation φ calculation unit 24bb, a high-frequency current control unit 24bc, an angular velocity ω calculation unit 24bd, a position angle θ calculation unit 24be, a speed current control unit 24bf, and a dq→uvw voltage conversion unit 24bg. The uvw→dq current conversion unit 24ba uses the three-phase current values (Iu, Iv, Iw) of the brushless motor 40 detected by the current detection unit 21 (see reference). Figure 1 The input is dq, and the output is the current value dq. The position estimation φ calculation unit 24bb estimates the position of the magnetic poles based on the dq current and outputs the position estimation value φ. The high-frequency current control unit 24bc controls the high-frequency current superimposed on the drive current. The angular velocity ω calculation unit 24bd calculates the angular velocity ω based on the position estimation value φ and outputs the calculated angular velocity ω. The position angle θ calculation unit 24be calculates the position angle θ based on the position estimation value φ and the angular velocity ω and outputs the calculated position angle θ. The speed current control unit 24bf feeds back the deviation between the estimated angular velocity (angular velocity ω) and the speed command value ω* to perform speed calculation (PI control), determines the current command value of the brushless motor 40, and outputs the determined current command value of the brushless motor 40. The dq→uvw voltage conversion unit 24bg calculates the voltage (Vu, Vv, Vw) based on the position angle θ and the current command value, and outputs the calculated voltage (Vu, Vv, Vw) to the control circuit 20.
[0056] The dq←→uvw conversion and speed feedback control are the general methods, so the description of the uvw→dq current conversion unit 24ba, the speed current control unit 24bf, and the dq→uvw voltage conversion unit 24bg is omitted here.
[0057] The position estimation φ calculation unit 24bb calculates the position estimate φ based on the following formula 1.
[0058] [Formula 1]
[0059]
[0060] In this embodiment 1, the motor being driven is a brushless motor 40 with a rotor 41 having a salient pole structure (d-axis inductance Ld ≠ q-axis inductance Lq). Therefore, the inductance L (magnetic reluctance) varies according to the phase of the magnetic poles. The change in inductance L is reflected in the current of the brushless motor 40. Therefore, based on the above formula 1, the position estimation error is calculated according to the change in the current of the brushless motor 40.
[0061] The high-frequency current control unit 24bc controls a high-frequency current independent of the motor drive current. In this embodiment 1, a pulse current of 0.4A with a period of 2.56ms is applied in the d-axis direction, and the difference between the q-axis current value when the pulse current is applied and the q-axis current value when the pulse current is not applied is calculated.
[0062] The position angle θ calculation unit 24be and the angular velocity ω calculation unit 24bd calculate the position angle θ and angular velocity ω respectively based on the following formulas 2 and 3.
[0063] [Formula 2]
[0064]
[0065] [Formula 3]
[0066] ω=dθ / dt
[0067] The position angle θ is calculated using the time integral of the position estimation error and the angular velocity ω as inputs, while the angular velocity ω is calculated as the time derivative of the position angle θ. Both the position angle θ and the angular velocity ω are calculated using feedback control to bring the position estimation error to zero.
[0068] [1-1-4. Structure of the Induction Voltage Drive Unit]
[0069] The induced voltage generated by the rotation of the brushless motor 40 varies according to the magnetic pole position. Therefore, the induced voltage drive unit 24c calculates the induced voltage proportional to the speed of the brushless motor 40 based on the applied voltage and current to the brushless motor 40, and estimates the magnetic pole position in a manner that brings the voltage error to zero.
[0070] Figure 4 This is a block diagram showing the detailed structure of the induced voltage drive unit 24c of the motor control device 10 in Embodiment 1.
[0071] The induced voltage drive unit 24c comprises an uvw→dq current conversion unit 24ca, a position estimation εγ calculation unit 24cb, an angular velocity ω calculation unit 24cc, a position angle θ calculation unit 24cd, a speed current control unit 24ce, and a dq→uvw voltage conversion unit 24cf. The uvw→dq current conversion unit 24ca takes the three-phase current values (Iu, Iv, Iw) of the brushless motor 40 detected by the current detection unit 21 as input and outputs the dq current value. The position estimation εγ calculation unit 24cb estimates the position of the magnetic poles based on the dq current and outputs the position estimation value εγ. The angular velocity ω calculation unit 24cc calculates the angular velocity ω based on the position estimation value εγ and outputs the calculated angular velocity ω. The position angle θ calculation unit 24cd calculates the position angle θ based on the position estimation value εγ and the angular velocity ω and outputs the calculated position angle θ. The speed-current control unit 24ce feeds back the deviation between the estimated angular velocity (angular velocity ω) and the speed command value ω* to perform speed calculation (PI control), determines the motor current command value, and outputs the determined motor current command value. The dq→uvw voltage conversion unit 24cf calculates the voltage (Vu, Vv, Vw) based on the position angle θ and the current command value, and outputs the calculated voltage (Vu, Vv, Vw) to the control circuit 20.
[0072] Similar to the inductor drive unit 24b described above, the dq←→uvw conversion and speed feedback control are performed in a general manner. Therefore, the description of the uvw→dq current conversion unit 24ca, the speed current control unit 24ce, and the dq→uvw voltage conversion unit 24cf will be omitted here.
[0073] The position estimation εγ calculation unit 24cb calculates the position estimate εγ based on the following formula 4.
[0074] [Formula 4]
[0075] εγ=Vd-(Ra·Id-ω·Lq·Iq)
[0076] According to Equation 4, the position estimate εγ is calculated using the d-axis current Id, q-axis current Iq, d-axis voltage Vd, and angular velocity ω as inputs, and the parameters of the q-axis inductance Lq and resistance Ra of the brushless motor 40 are applied.
[0077] The angular velocity ω calculation unit 24cc and the position angle θ calculation unit 24cd calculate the angular velocity ω and position angle θ respectively based on the following formulas 5 and 6.
[0078] [Formula 5]
[0079] ω=-∫Ki·εγ·dt
[0080] [Formula 6]
[0081] θ=∫(ω-Kθ·εγ)dt
[0082] The angular velocity ω calculation unit 24cc calculates the angular velocity ω using PI (proportional integral) in a way that makes the position estimate εγ converge to zero. It further calculates the time integral of ω and outputs the estimated phase (position angle θ).
[0083] [1-1-5. Structure of the drive mode switching unit]
[0084] Figure 2 In the block diagram of the sensorless estimation unit 24 shown, the drive mode switching unit 24a switches between the inductive drive unit 24b and the induced voltage drive unit 24c based on the rotational speed of the brushless motor 40, etc. Specifically, the drive mode switching unit 24a exchanges the position angle θ, angular velocity ω, motor current / voltage, and angular velocity feedback control parameters required for motor control in real time to achieve instantaneous switching.
[0085] [1-2. Actions]
[0086] The operation of the motor control device 10 configured as described above will now be explained.
[0087] [1-2-1. Motor Drive Control Actions]
[0088] Figure 5 This is a flowchart illustrating the motor drive control process of the motor control device 10 in Embodiment 1.
[0089] like Figure 5 As shown, in step S001, the motor control device 10 begins motor drive control. In step S002, the motor control device 10 performs initial phase estimation. In step S003, the motor control device 10 performs polarity determination and corrects the phase estimated through the initial phase estimation based on the determination result. Details of the initial phase estimation in step S002 and the polarity determination in step S003 are described later.
[0090] In step S004, the motor control device 10 performs motor start control via the inductor drive unit 24b. In step S005, the motor control device 10 determines whether the rotational speed of the brushless motor 40 is above a certain speed. If the rotational speed of the brushless motor 40 is above a certain speed ("yes" in step S005), in step S006, the motor control device 10 switches the drive mode. That is, the drive mode switching unit 24a switches from the inductor drive unit 24b to the induced voltage drive unit 24c. Next, in step S007, the motor control device 10 performs stable motor rotation control via the induced voltage drive unit 24c. In step S008, the motor control device 10 performs motor deceleration control. In step S009, the motor control device 10 terminates the motor drive control.
[0091] [1-2-2. Operation of the Initial Phase Estimation Unit]
[0092] Figures 6A to 6C This is a diagram used to illustrate a problem related to the initial phase estimation of rotor 41. Furthermore, in Figures 6A to 6C In the diagram, the initial phase estimation d-axis and the initial phase estimation q-axis are represented by solid lines, and the actual d-axis and the actual q-axis are represented by dashed lines.
[0093] Figure 6A The diagram shows the rotor 41, which has magnets 42 inside the brushless motor 40, in the correct relationship with the d-axis and q-axis. The d-axis is the direction of the magnetic poles, and the q-axis is the direction orthogonal to the d-axis. The N-pole direction of the magnetic poles is the positive direction of the d-axis, and the S-pole direction is the negative direction of the d-axis.
[0094] The initial phase estimation unit 22 estimates the initial phase of the rotor 41 through the inductor drive unit 24b. Specifically, the initial phase of the rotor 41 is estimated during a drive period in which the command values for the motor speed and the motor current are both set to 0 for 100ms.
[0095] The inductor drive unit 24b estimates the phase using the difference (Ld≠Lq) between the inductance L in the d-axis direction and the inductance L in the q-axis direction, which is characteristic of the rotor 41 with a salient pole structure as a brushless motor 40. That is, the inductor drive unit 24b distinguishes between the horizontal (d-axis) and vertical (q-axis) directions of the rotor 41, but... Figure 6B As shown, even using the same d-axis, it's impossible to determine whether the orientation is that of the N pole or the S pole. Furthermore, as... Figure 6C As shown, for rotor 41, the inductance L of the d-axis and the inductance L of the q-axis have a periodicity of 2θ, resulting in a problem where the initial phase is misestimated as a q-axis direction that deviates from the actual d-axis by 90° or 270°. To address this problem, the motor control device 10 according to Embodiment 1 of this disclosure is provided with the following polarity determination unit 23.
[0096] [1-2-3. Operation of the polarity discrimination unit]
[0097] Figure 7 This is a diagram showing the magnetic saturation characteristics of the electromagnetic steel plate used as the rotor core in a typical brushless motor.
[0098] like Figure 7 As shown, according to the voltage equation v = L × (di / dt) for inductance L, when the inductance L is large, the time derivative of the current (di / dt) decreases, and the change in current i per unit time decreases. Conversely, when the inductance L is small, the time derivative of the current (di / dt) increases, and the change in current i per unit time increases. That is, when the inductance L changes, the current i also changes.
[0099] The polarity determination unit 23 utilizes the characteristic that the inductance L changes due to magnetic saturation. For example, the polarity determination unit 23 determines the polarity based on the magnitude of the change in current +Id1 and -Id2, which are the magnitudes of the estimated d-axis values obtained by the initial phase estimation unit 22, which are superimposed with voltages +Vd and -Vd of the same magnitude and at the same time in the positive and negative directions respectively.
[0100] Specifically, the polarity of the magnetic poles along the d-axis of the initial phase estimation is determined by comparing the absolute value of the current change |+Id1| when a voltage +Vd is applied to the positive direction of the initial phase estimation d-axis with the absolute value of the current change |-Id2| when a voltage -Vd is applied to the negative direction of the initial phase estimation d-axis. That is, if |-Id2| < |+Id1|, it means that the estimated magnetic pole direction is positive (N pole). Conversely, if |-Id2| > |+Id1|, it means that the estimated magnetic pole direction is negative (S pole).
[0101] [1-2-4. Actions for Polarity Determination]
[0102] Figure 8 This is a flowchart illustrating the polarity determination process of the motor control device 10 in Embodiment 1.
[0103] like Figure 8As shown, in step S101, the polarity determination unit 23 begins polarity determination processing. In step S102, the polarity determination unit 23 performs initialization processing, and in step S103, the polarity determination unit 23 performs Id offset calculation when the initial phase estimation d-axis current is 0. That is, the polarity determination unit 23 sets the d-axis current Id detected by the current detection unit 21 as an offset current value and saves it immediately before the processing of steps S104 to S107, which involve superimposing voltages in the positive and negative directions of the d-axis. Details of the offset calculation of the d-axis current Id and the offset calculation of the q-axis current Iq (described later) will be described later (see [reference]). Figure 11 Therefore, in the following Figure 8 The description does not take into account the offset current value.
[0104] In step S104, the polarity discrimination unit 23 superimposes a voltage +Vd for a certain period of time in the positive direction of the initial phase estimation d-axis. In step S105, the polarity discrimination unit 23 accumulates the maximum current amplitude of the absolute value of the change in current value |+Id| in the positive direction of the initial phase estimation d-axis (Σ+Id). In step S106, the polarity discrimination unit 23 superimposes a voltage -Vd for a certain period of time in the negative direction of the initial phase estimation d-axis. In step S107, the polarity discrimination unit 23 accumulates the maximum current amplitude of the absolute value of the change in current value |-Id| in the negative direction of the initial phase estimation d-axis (Σ-Id). The polarity discrimination unit 23 repeats the processing of steps S104 to S107 three times. Furthermore, in this embodiment 1, it is assumed that the processing of steps S104 to S107 is repeated three times, but the number of repetitions is not limited to this; for example, it could be twice or four times. The same applies to the number of times steps S115 to S118, which will be repeated later, are performed.
[0105] Next, in step S108, the polarity determination unit 23 compares the cumulative maximum value of the current amplitude of the absolute value of the current change after applying a voltage to the positive direction of the d-axis of the initial phase estimation with the cumulative maximum value of the current amplitude of the absolute value of the current change after applying a voltage to the negative direction of the d-axis of the initial phase estimation, and performs processing corresponding to the comparison result. Specifically, if Σ-Id>Σ+Id (yes in step S108), the polarity determination unit 23 proceeds to the processing in step S109; if Σ-Id≤Σ+Id (no in step S108), the polarity determination unit 23 proceeds to the processing in step S110.
[0106] Since there is a possibility that the actual d-axis is in the opposite direction to the initial phase estimation d-axis, in step S109, the polarity determination unit 23 adds 180° to the phase value during the initial phase estimation and stores the result in θtmpD, which serves as a temporary storage location for phase information. Since there is a possibility that the initial phase estimation d-axis direction is correct, in step S110, the polarity determination unit 23 stores the phase value during the initial phase estimation in θtmpD, which serves as a temporary storage location for phase information. The polarity determination unit 23 performs d-axis determination and corrects the estimated phase through the processing in steps S101 to S110 above.
[0107] Next, the polarity discrimination unit 23 confirms the accuracy of the d-axis determination of the initial phase estimation d-axis.
[0108] In step S111, the polarity determination unit 23 calculates the absolute value of the difference between the cumulative maximum current amplitude of the absolute value of the current change after applying voltage to the positive direction of the initial phase estimation d-axis in steps S104 to S107 and the cumulative maximum current amplitude of the absolute value of the current change after applying voltage to the negative direction of the initial phase estimation d-axis, ΔΣId=|Σ+Id-Σ-Id|. In step S112, the polarity determination unit 23 checks whether the absolute value of this difference ΔΣId is greater than a predetermined reference value Idth. If ΔΣId>Idth (e.g., 1A) ("Yes" in step S112), the polarity determination unit 23 proceeds to step S113; if ΔΣId≤Idth ("No" in step S112), the polarity determination unit 23 proceeds to step S114. In step S113, the polarity discrimination unit 23 considers the value of θtmpD stored in the temporary storage location for phase information to be correct, saves the value as the estimated phase, and ends the polarity discrimination process in step S126.
[0109] On the other hand, when the process proceeds to step S114, there is a possibility that the initial phase estimation d-axis has deviated by +90° or +270°. Since this direction is the q-axis direction of the initial phase estimation, the polarity determination unit 23 performs a determination again for the q-axis direction. In step S114, the polarity determination unit 23 calculates the Iq offset when the current on the q-axis of the initial phase estimation is 0.
[0110] In step S115, the polarity discrimination unit 23 superimposes a voltage +Vq for a certain period of time in the positive direction of the initial phase estimation q-axis. In step S116, the polarity discrimination unit 23 accumulates the maximum value of the current amplitude (Σ+Iq) of the absolute value of the change in current value in the positive direction of the initial phase estimation q-axis. In step S117, the polarity discrimination unit 23 superimposes a voltage -Vq for a certain period of time in the negative direction of the initial phase estimation q-axis. In step S118, the polarity discrimination unit 23 accumulates the maximum value of the current amplitude (Σ-Iq) of the absolute value of the change in current value in the negative direction of the initial phase estimation q-axis. The polarity discrimination unit 23 repeats the processing of steps S115 to S118 three times.
[0111] Next, in step S119, the polarity determination unit 23 compares the cumulative maximum value of the current amplitude of the absolute value of the current change after applying a voltage to the positive direction of the initial phase estimation q-axis with the cumulative maximum value of the current amplitude of the absolute value of the current change after applying a voltage to the negative direction of the initial phase estimation q-axis, and performs processing corresponding to the comparison result. Specifically, if Σ-Iq>Σ+Iq (yes in step S119), the polarity determination unit 23 proceeds to the processing in step S120; if Σ-Iq≤Σ+Iq (no in step S119), the polarity determination unit 23 proceeds to the processing in step S121.
[0112] Since there is a possibility that the actual positive direction of the d-axis is the negative direction of the initial phase estimate q-axis, in step S120, the polarity determination unit 23 adds 270° to the phase value during the initial phase estimate and stores the result in θtmpQ, which serves as a temporary storage location for phase information. On the other hand, since there is a possibility that the actual positive direction of the d-axis is the positive direction of the initial phase estimate q-axis, in step S121, the polarity determination unit 23 adds 90° to the phase value during the initial phase estimate and stores the result in θtmpQ, which serves as a temporary storage location for position information.
[0113] The polarity discrimination unit 23 performs q-axis determination and corrects the estimated phase through the processing of steps S114 to S121 as described above.
[0114] Next, in step S122, the polarity determination unit 23 calculates the absolute value of the difference between the cumulative maximum amplitude of the current change after applying a voltage to the positive direction of the initial phase estimation q-axis (as performed in steps S115-S118) and the cumulative maximum amplitude of the current change after applying a voltage to the negative direction of the initial phase estimation q-axis, ΔΣIq=|Σ+Iq-Σ-Iq|. In step S123, the polarity determination unit 23 compares the absolute value of the difference calculated for the d-axis direction, ΔΣId, with the absolute value of the difference calculated for the q-axis direction, ΔΣIq, and performs processing corresponding to the comparison result. Specifically, if ΔΣId≥ΔΣIq ("Yes" in step S123), the polarity determination unit 23 proceeds to the processing in step S124; if ΔΣId<ΔΣIq ("No" in step S123), the polarity determination unit 23 proceeds to the processing in step S125.
[0115] In step S124, the polarity determination unit 23 considers the value of θtmpD, the temporary storage location for phase information, to be correct and saves this value as an estimated phase. In step S125, the polarity determination unit 23 considers the value of θtmpQ, the temporary storage location for phase information, to be correct and saves this value as an estimated phase. Finally, in step S126, the polarity determination unit 23 ends the polarity determination process.
[0116] [1-2-5. Polarity Determination and d-axis Determination]
[0117] Figure 9 This is a diagram showing an example of the applied voltage and current when the motor control device 10 in Embodiment 1 determines the d-axis.
[0118] Next, use Figure 9 The example shown illustrates this in detail. Figure 8 The flowchart of the polarity discrimination process shown includes steps S104 to S107, which involve the superposition of voltages and the accumulation of the maximum current amplitude. Furthermore, in this... Figure 9 In the example, assume the difference between the saved +Id and -Id is greater than the reference value Idth (e.g., 1A). First, a voltage of +Vd is superimposed in the positive direction of the d-axis of the initial phase estimation, and the maximum current amplitude of +Id at this time is saved. Next, a voltage of -Vd is superimposed in the negative direction of the d-axis of the initial phase estimation, and the maximum current amplitude of -Id at this time is saved. If the saved +Id and -Id are in the relationship |-Id| < |+Id|, the estimated phase estimated by the initial phase determination immediately before polarity determination will be used for subsequent motor drive control. If they are in the relationship |-Id| > |+Id|, the estimated phase obtained by adding 180° to the estimated phase estimated by the initial phase determination immediately before polarity determination will be used for subsequent motor drive control. Figure 9In the example, the estimated phase estimated by the initial phase determination immediately before the polarity determination directly becomes the estimated phase.
[0119] Therefore, the motor control device 10 can correct the orientation of the N and S poles even if the d-axis direction obtained from the initial phase estimation deviates by 180°.
[0120] [1-2-6. Polarity Determination: d-axis and q-axis determination]
[0121] Figure 10 This is a diagram showing an example of the applied voltage and current when the motor control device 10 in Embodiment 1 determines the d-axis and q-axis.
[0122] Next, use Figure 10 The example shown illustrates this in detail. Figure 8 The flowchart of the polarity discrimination process shows the superposition of voltages and the accumulation of maximum current amplitude in steps S104-S107 and S115-S118. Figure 9 Similarly, for the d-axis determination, firstly, the voltage of +Vd is superimposed in the positive direction of the d-axis of the initial phase estimate, and the maximum value of the current amplitude of +Id at this time is saved.
[0123] Next, a voltage of -Vd is superimposed in the negative direction of the d-axis of the initial phase estimate, and the maximum value of the current amplitude of -Id at this time is saved. If the difference between the saved +Id and -Id (||+Id|-|-Id||) is less than the reference value Idth, that is, in the relationship of |-Id|≈|+Id|, then there is a possibility that the d-axis estimated by the initial phase estimate deviates from the actual d-axis by 90° or 270°. Therefore, a voltage is also superimposed in the q-axis direction and polarity is determined. Similar to the d-axis above, firstly, a voltage of +Vq is superimposed in the positive direction of the q-axis of the initial phase estimate, and the maximum value of the current amplitude of +Iq at this time is saved.
[0124] Next, a voltage of -Vq is superimposed in the negative direction of the q-axis of the initial phase estimate, and the maximum value of the current amplitude of -Iq at this point is saved. If the saved +Iq and -Iq are in the relationship |-Iq| < |+Iq|, then 90° is added to the estimated phase estimated by the initial phase determination immediately preceding the polarity determination. If they are in the relationship |-Iq| > |+Iq|, then 270° is added to the estimated phase estimated by the initial phase determination immediately preceding the polarity determination. Figure 10 In the example, the relationship is |-Iq|<|+Iq|, and the difference between +Iq and -Iq is greater than the difference between +Id and -Id. Therefore, 90° is added to the estimated phase estimated by the initial phase determination immediately before the polarity determination.
[0125] Therefore, the motor control device 10 can correct the orientation of the N and S poles even if the d-axis direction obtained from the initial phase estimation deviates by 90° or 270°.
[0126] [1-2-7. Polarity Discrimination Offset Correction]
[0127] Figure 11 This is a diagram illustrating the applied voltage and current during offset correction when the motor control device 10 in Embodiment 1 determines the polarity.
[0128] The following is an explanation Figure 8 The content of Id offset calculation in step S103 and Iq offset calculation in step S114. Polarity discrimination unit 23 will Figure 9 , Figure 10 The average value of the current over a certain period before the voltage superposition in the d-axis direction or the voltage superposition in the q-axis direction is set as the offset current value and stored. Figure 8 In steps S105, S107, S116, and S118, after detecting the maximum current amplitude, the polarity discrimination unit 23 subtracts the stored offset current value from the maximum current amplitude and sets the final maximum current amplitude as the value obtained. That is, for the d-axis, when the offset current value is set to +Id0 and the measured maximum current amplitude is set to +Id', the +Id obtained through polarity discrimination can be calculated as +Id = +Id' - Id0 (refer to...). Figure 11 This allows the same operations to be performed regardless of the sign of Id, or whether Id or Iq is positive or negative.
[0129] Therefore, by setting the initial current to the offset current value for correction, the motor control device 10 can suppress the influence on polarity determination even if the current value does not converge to 0. Thus, the motor control device 10 can perform determination with higher accuracy.
[0130] [1-3. Effects, etc.]
[0131] As described above, in this embodiment 1, the motor control device 10 controls a brushless motor 40 with a salient-pole rotor 41 driven by an inverter circuit 13. The motor control device 10 includes an inverter circuit 13, a current detection unit 21, an initial phase estimation unit 22, and a polarity determination unit 23. The current detection unit 21 detects the current of the brushless motor 40. The initial phase estimation unit 22 estimates the initial phase of the brushless motor 40 based on the current detected by the current detection unit 21. The polarity determination unit 23 determines the polarity of the magnetic poles of the brushless motor 40 based on the current detected by the current detection unit 21. For the initial phase estimated by the initial phase estimation unit 22, the polarity determination unit 23 determines the polarity of the magnetic poles of the brushless motor 40 based on the difference in current amplitude between the positive and negative directions of the d-axis and q-axis detected by the current detection unit 21 after superimposing voltages onto the positive and negative directions of the d-axis and q-axis respectively, and corrects the initial phase.
[0132] Therefore, even if the original d-axis direction is incorrectly estimated as the q-axis direction during initial phase estimation, the motor control device 10 can still determine the correct magnetic pole direction during polarity determination. That is, the motor control device 10 can correctly detect magnetic poles even if the d-axis direction obtained from the initial estimation deviates from the correct direction by 90° or 270°. Therefore, the motor control device 10 can perform smooth starting and acceleration of the brushless motor 40 without reversing or losing synchronization during startup.
[0133] As in Embodiment 1, the polarity determination unit 23 of the motor control device 10 terminates the polarity determination of the brushless motor 40 when the absolute value of the difference between the current amplitudes in the positive and negative directions of the d-axis, detected by the current detection unit 21 after applying voltages to the positive and negative directions of the d-axis, is greater than the reference value Idth. Conversely, when the absolute value of the difference between the current amplitudes in the positive and negative directions of the d-axis is less than the reference value Idth, the polarity determination unit 23 performs the following processing: The polarity determination unit 23 determines the polarity of the magnetic poles of the brushless motor 40 based on the difference between the current amplitudes in the positive and negative directions of the q-axis, detected by the current detection unit 21 after applying voltages to the positive and negative directions of the q-axis, and the difference between the current amplitudes in the positive and negative directions of the d-axis, and corrects the initial phase.
[0134] Therefore, even if the original d-axis direction is incorrectly estimated as the q-axis direction during initial phase estimation, the motor control device 10 can still determine the correct magnetic pole direction during polarity determination. That is, the motor control device 10 can correctly detect magnetic poles even if the d-axis direction obtained from the initial estimation deviates from the correct direction by 90° or 270°. Therefore, the motor control device 10 can perform smooth starting and acceleration of the brushless motor 40 without reversing or losing synchronization during startup.
[0135] As in Embodiment 1, the polarity determination unit 23 of the motor control device 10 sets the current detected by the current detection unit 21 immediately before the voltage is superimposed in the positive and negative directions of the d-axis and q-axis, respectively, as the offset current value. The polarity determination unit 23 determines the polarity of the magnetic poles of the brushless motor 40 based on the value obtained by subtracting the offset current value from the maximum current amplitude in the positive and negative directions of the d-axis and q-axis, respectively, detected by the current detection unit 21 after the voltage is superimposed in the positive and negative directions of the d-axis and q-axis, respectively. It also corrects the initial phase.
[0136] Therefore, the motor control device 10 can more accurately determine the correct magnetic pole direction when determining polarity. As a result, it can perform smooth starting and acceleration without reversing or losing synchronization during motor startup.
[0137] (Implementation Method 2)
[0138] The following uses Figure 12 To illustrate the motor control device in Embodiment 2.
[0139] [2-1. Action]
[0140] [2-1-1. Control of Command Current Value]
[0141] The difference between the polarity determination unit of the motor control device in Embodiment 2 and the polarity determination unit 23 of the motor control device 10 in Embodiment 1 is that the polarity determination unit of the motor control device in Embodiment 2 controls the command current value (±Id, ±Iq) to be 0A during the polarity determination period.
[0142] Figure 12 This is a diagram illustrating the outline of polarity determination in the case of current control in the motor control device of Embodiment 2.
[0143] Figure 12 This illustrates the difference between the state of the Id current when current control is applied in polarity discrimination and the state of the Id current when current control is not applied. Furthermore, in Figure 12 In the diagram, solid lines represent the current Id when current control is applied, and dashed lines represent the current Id when current control is not applied.
[0144] like Figure 12 As shown, based on the current state under current control, the current response becomes faster, and therefore the Id current value converges to 0A more quickly.
[0145] [2-2. Effects, etc.]
[0146] As described above, the polarity determination unit of the motor control device in Embodiment 2 controls the current flowing into the brushless motor 40 to be 0 during the period of determining the polarity of the magnetic poles of the brushless motor 40.
[0147] Therefore, the motor control device in Embodiment 2 can shorten the interval of superimposed voltage. Consequently, the motor control device in Embodiment 2 can determine polarity in a shorter period.
[0148] (Other implementation methods)
[0149] As described above, Embodiment 1 and Embodiment 2 have been presented as examples of the technology in this disclosure. However, the technology in this disclosure is not limited thereto, and can also be applied to embodiments obtained by making changes, substitutions, additions, omissions, etc. Furthermore, new embodiments can be formed by combining the constituent elements described in Embodiment 1 and Embodiment 2 above.
[0150] Therefore, other implementation methods are illustrated below.
[0151] The motor control device and the brushless motor with a salient pole configuration disclosed herein can be mounted in a washing machine or washer-dryer. For example, when using the brushless motor with the salient pole configuration and the motor control device disclosed herein as a brushless motor and motor control device for driving the drum in a front-loading washing machine, it is possible to prevent the stopped drum from reversing, to start smoothly without startup failure, and to increase the rotation speed. Therefore, the present disclosure can help improve the washing efficiency, shorten the running time, and provide a high-performance washing machine.
[0152] Furthermore, the motor control device 10 of Embodiment 1 and the motor control device of Embodiment 2 (hereinafter also referred to as "the motor control device of the embodiment") are configured to not include the brushless motor 40. However, the structure of the motor control device of the embodiment is an example of the structure of the motor control device in this disclosure, and the motor control device in this disclosure is not limited to the structure of the motor control device of the embodiment. That is, the motor control device in this disclosure may also include the structure of the brushless motor with a salient pole rotor driven by the inverter circuit in this disclosure.
[0153] Industrial availability
[0154] This disclosure can be applied to a motor control device for sensorless control of the rotation of a brushless motor (permanent magnet synchronous motor) with a rotor having a salient pole structure, and to a washing machine or washer-dryer equipped with such a motor control device. Specifically, this disclosure can be applied, for example, to upright washing machines, front-loading washing machines, and front-loading washer-dryers.
[0155] Explanation of reference numerals in the attached figures
[0156] 10: Motor control device; 11: Rectifier circuit; 12: Smoothing capacitor; 13: Inverter circuit; 14a: Switching element; 14b: Switching element; 14c: Switching element; 14d: Switching element; 14e: Switching element; 14f: Switching element; 15a: Resistor; 15b: Resistor; 15c: Resistor; 20: Control circuit; 21: Current detection unit; 22: Initial phase estimation unit; 23: Polarity determination unit; 24: Sensorless estimation unit; 24a: Drive mode switching unit; 24b: Inductor drive unit; 24ba: uvw→dq current conversion unit; 24bb: Position 24bc: φ estimation calculation unit; 24bd: angular velocity ω calculation unit; 24be: position angle θ calculation unit; 24bf: speed current control unit; 24bg: dq→uvw voltage conversion unit; 24c: induced voltage drive unit; 24ca: uvw→dq current conversion unit; 24cb: position estimation εγ calculation unit; 24cc: angular velocity ω calculation unit; 24cd: position angle θ calculation unit; 24ce: speed current control unit; 24cf: dq→uvw voltage conversion unit; 30: AC power supply; 40: brushless motor; 41: rotor; 42: magnet.
Claims
1. A motor control device for controlling a brushless motor with a salient-pole rotor driven by an inverter circuit, the motor control device comprising: The inverter circuit; A current detection unit detects the current of the brushless motor; An initial phase estimation unit estimates the initial phase of the brushless motor based on the current detected by the current detection unit; and The polarity determination unit determines the polarity of the magnetic poles of the brushless motor based on the current detected by the current detection unit. wherein The polarity discrimination unit determines the polarity of the brushless motor's magnetic poles based on the difference in current amplitude between the positive and negative directions of the d-axis and q-axis detected by the current detection unit after superimposing voltages onto the positive and negative directions of the d-axis and q-axis, respectively, for the initial phase estimated by the initial phase estimation unit, and corrects the initial phase.
2. The motor control device according to claim 1, wherein, If, after applying voltages to both the positive and negative directions of the d-axis, the absolute value of the difference between the current amplitudes in the positive and negative directions of the d-axis, as detected by the current detection unit, is greater than a reference value, the polarity determination unit terminates the polarity determination of the brushless motor. When the absolute value of the current amplitude difference between the positive and negative directions of the d-axis is less than the reference value, the polarity determination unit determines the polarity of the magnetic poles of the brushless motor based on the current amplitude difference between the positive and negative directions of the q-axis detected by the current detection unit after superimposing voltages on the positive and negative directions of the q-axis, and the current amplitude difference between the positive and negative directions of the d-axis, and corrects the initial phase.
3. The motor control device according to claim 1 or 2, wherein, The polarity determination unit sets the current detected by the current detection unit immediately before the voltage is superimposed in the positive and negative directions of the d-axis and q-axis, respectively, as the offset current value. Based on the value obtained by subtracting the offset current value from the maximum current amplitude in the positive and negative directions of the d-axis and q-axis detected by the current detection unit after the voltage is superimposed in the positive and negative directions of the d-axis and q-axis, the polarity of the magnetic poles of the brushless motor is determined, and the initial phase is corrected.
4. The motor control device according to claim 1 or 2, wherein, The polarity determination unit is controlled such that the current flowing into the brushless motor is 0 during the period of determining the polarity of the magnetic poles of the brushless motor.
5. A washing machine or washer-dryer, equipped with a motor control device according to any one of claims 1 to 4.