JP7382880B2 - Motor control device, motor system and motor control method - Google Patents

Description

The present disclosure relates to a motor control device, a motor system, and a motor control method.

Conventionally, in a constant current control state, the attenuating current flowing through each phase of the synchronous motor is detected after the gates of the switching elements of each phase of the synchronous motor are cut off, and the rotor is controlled based on the detected attenuating current. A technique for estimating the initial magnetic pole position is known (for example, see Patent Document 1).

Japanese Patent Application Publication No. 2016-19454

However, since the conventional technology detects the current flowing through each phase of a synchronous motor, it cannot be applied to the so-called one-shunt current detection method. Furthermore, since the initial magnetic pole position is estimated based only on the current that is attenuating, it may be difficult to ensure the estimation accuracy.

The present disclosure provides a motor control device, a motor system, and a motor control method that can ensure magnetic pole position estimation accuracy in a one-shunt current detection method.

A motor control device according to an embodiment of the present disclosure includes:
an inverter that energizes a motor whose rotor is stopped or at an extremely low speed by turning on some of the arms according to an energization pattern;
a current detector connected to the DC side of the inverter;
When the current flowing through the current detector reaches the current threshold due to turning on of some of the arms, all the arms are turned off, and the same arm as the some of the arms is turned off during the current reduction period after all the arms are turned off. and an initial position estimating unit that measures the current by turning on the current, and estimates the magnetic pole position of the rotor in the state based on the difference in the measured value for each energization pattern of the current.

According to the present disclosure, the accuracy of estimating the magnetic pole position can be ensured in the one-shunt current detection method.

1 is a diagram showing a configuration example of a motor system according to Embodiment 1 of the present disclosure. FIG. 3 is a diagram showing an example of a voltage vector. It is a table showing the phases of voltages applied to a two-phase energization pattern. It is a table showing the phases of voltages applied to a three-phase energization pattern. FIG. 3 is an image diagram of voltage vector directions for each energization pattern. FIG. 3 is a diagram showing an example of current response characteristics when applying a step voltage. It is a figure showing an example of composition and operation of an initial position estimating part. 7 is a timing chart for explaining inductive sensing of a comparative example. 5 is a timing chart for explaining inductive sensing according to the present disclosure.

Hereinafter, a motor control device, a motor system, and a motor control method according to embodiments of the present disclosure will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a motor system 1-1 according to Embodiment 1 of the present disclosure. Motor system 1-1 shown in FIG. 1 controls the rotational operation of motor 4. Motor system 1-1 shown in FIG. Examples of devices equipped with the motor system 1-1 include a copy machine, a personal computer, a refrigerator, and a pump, but the devices are not limited to these. Motor system 1-1 includes at least a motor 4 and a motor control device 100-1.

Motor 4 is a permanent magnet synchronous motor with multiple coils. The motor 4 has, for example, a three-phase coil including a U-phase coil, a V-phase coil, and a W-phase coil. A specific example of the motor 4 is a three-phase brushless DC motor. The motor 4 has a rotor on which at least one permanent magnet is arranged, and a stator. The motor 4 is a sensorless motor that does not use a position sensor that detects the angular position (magnetic pole position) of the magnet of the rotor. The motor 4 is, for example, a fan motor that rotates a fan for blowing air.

The motor control device 100-1 controls an inverter that converts direct current into three-phase alternating current by controlling on/off (ON, OFF) a plurality of switching elements connected in a three-phase bridge according to an energization pattern including three-phase PWM signals. Drive the motor through. The motor control device 100-1 includes an inverter 23, a current detection section 27, a current detection timing adjustment section 34, a drive circuit 33, an energization pattern generation section 35, a carrier generation section 37, and a clock generation section 36.

The inverter 23 is a circuit that converts the DC supplied from the DC power supply 21 into three-phase AC by switching a plurality of switching elements, and rotates the rotor of the motor 4 by passing the three-phase AC drive current to the motor 4. be. The inverter 23 operates based on a plurality of energization patterns generated by the energization pattern generation section 35 (more specifically, three-phase PWM signals generated by the PWM signal generation section 32 in the energization pattern generation section 35). Drive the motor 4. PWM means Pulse Width Modulation.

The inverter 23 has a plurality of arms Up, Vp, Wp, Un, Vn, and Wn connected in a three-phase bridge. Upper arms Up, Vp, and Wp are high-side switching elements that are each connected to the positive electrode side of the DC power supply 21 via the positive bus bar 22a. Lower arms Un, Vn, and Wn are low-side switching elements connected to the negative electrode side (specifically, the ground side) of the DC power supply 21, respectively. The plurality of arms Up, Vp, Wp, Un, Vn, and Wn each follow a corresponding drive signal among the plurality of drive signals supplied from the drive circuit 33 based on the PWM signal included in the above-mentioned energization pattern. Turns on or off. Below, the plurality of arms Up, Vp, Wp, Un, Vn, and Wn may be simply referred to as arms unless they are particularly distinguished.

A connection point between the U-phase upper arm Up and the U-phase lower arm Un is connected to one end of the U-phase coil of the motor 4. A connection point between the V-phase upper arm Vp and the V-phase lower arm Vn is connected to one end of the V-phase coil of the motor 4. A connection point between the W-phase upper arm Wp and the W-phase lower arm Wn is connected to one end of the W-phase coil of the motor 4 . The other ends of the U-phase coil, V-phase coil, and W-phase coil are connected to each other.

Specific examples of the arm include an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor). However, the arms are not limited to these.

The current detector 24 is connected to the DC side of the inverter 23 and outputs a detection signal Sd corresponding to the current value of the current flowing to the DC side of the inverter 23. The current detector 24 shown in FIG. 1 generates a detection signal Sd corresponding to the current value of the current flowing through the negative bus 22b. The current detector 24 is, for example, a current detection element placed on the negative bus 22b, and more specifically, a shunt resistor inserted in the negative bus 22b. A current detection element such as a shunt resistor generates a voltage signal corresponding to the current value of the current flowing through itself as a detection signal Sd.

The current detection unit 27 detects the U flowing through the motor 4 by acquiring the detection signal Sd based on the plurality of energization patterns (more specifically, three-phase PWM signals) generated by the energization pattern generation unit 35. , V, W phase currents Iu, Iv, and Iw of each phase are detected. More specifically, the current detection unit 27 detects the U and V flowing through the motor 4 by acquiring the detection signal Sd at an acquisition timing synchronized with a plurality of energization patterns (more specifically, three-phase PWM signals). , W detect the phase currents Iu, Iv, and Iw of each phase. The acquisition timing of the detection signal Sd is set by the current detection timing adjustment section 34.

For example, the current detection unit 27 captures the analog voltage detection signal Sd generated by the current detector 24 into an AD (Analog to Digital) converter at the acquisition timing set by the current detection timing adjustment unit 34. The AD converter is provided in the current detection section 27. Then, the current detection unit 27 AD converts the captured analog detection signal Sd into a digital detection signal Sd, and digitally processes the digital detection signal Sd after the AD conversion. Detect phase currents Iu, Iv, and Iw of each phase. The detected values of the phase currents Iu, Iv, and Iw of each phase detected by the current detection section 27 are supplied to the energization pattern generation section 35.

The clock generator 36 is a circuit that generates a clock of a predetermined frequency using a built-in oscillation circuit and outputs the generated clock to the carrier generator 37. Note that the clock generator 36 starts operating, for example, at the same time as the motor control device 100-1 is powered on.

The carrier generating section 37 generates the carrier C based on the clock generated by the clock generating section 36. Carrier C is a carrier signal whose level increases and decreases periodically.

The energization pattern generation unit 35 generates a pattern for energizing the inverter 23 (an energization pattern for the inverter 23). The energization pattern of the inverter 23 may be rephrased as the pattern for energizing the motor 4 (the energization pattern of the motor 4). The energization pattern of the inverter 23 includes three-phase PWM signals that energize the inverter 23 . The energization pattern generation unit 35 generates a three-phase PWM signal to energize the inverter 23 so that the motor 4 rotates, based on the detected values of the phase currents Iu, Iv, and Iw of the motor 4 detected by the current detection unit 27. It has a PWM signal generation section 32 that generates a PWM signal.

The energization pattern generation section 35 further includes a vector control section 30 when generating the energization pattern of the inverter 23 by vector control. Note that in this embodiment, the energization pattern of the inverter is generated by vector control, but the present invention is not limited to this, and the phase voltage of each phase may be determined using vf control or the like.

When the rotational speed command ωref of the motor 4 is given from the outside, the vector control unit 30 controls the torque current command Iqref and the excitation based on the difference between the measured value or estimated value of the rotational speed of the motor 4 and the rotational speed command ωref. Generate current command Idref. The vector control unit 30 calculates the torque current Iq and the excitation current Id based on the phase currents Iu, Iv, and Iw of the U, V, and W phases of the motor 4 through vector control calculation using the rotor position θ. The vector control unit 30 performs, for example, a PI control calculation on the difference between the torque current command Iqref and the torque current Iq, and generates a voltage command Vq. The vector control unit 30 performs, for example, PI control calculation on the difference between the excitation current command Idref and the excitation current Id, and generates a voltage command Vd. The vector control unit 30 converts the voltage commands Vq and Vd into phase voltage commands Vu*, Vv*, and Vw* for each phase of U, V, and W using the rotor position θ. The rotor position θ represents the magnetic pole position of the rotor of the motor 4.

The PWM signal generation section 32 generates a three-phase PWM signal by comparing the phase voltage commands Vu*, Vv*, Vw* generated by the vector control section 30 with the level of the carrier C generated by the carrier generation section 37. Generate an energization pattern that includes a signal. The PWM signal generation unit 32 also generates a PWM signal for lower arm drive which is an inversion of the three-phase PWM signal for upper arm drive, and after adding dead time as necessary, energization including the generated PWM signal is performed. The pattern is output to the drive circuit 33.

The drive circuit 33 outputs a drive signal that switches the six arms Up, Vp, Wp, Un, Vn, and Wn included in the inverter 23 in accordance with the energization pattern including the applied PWM signal. As a result, a three-phase AC drive current is supplied to the motor 4, and the rotor of the motor 4 rotates.

The current detection timing adjustment unit 34 allows the current detection unit 27 to control one cycle of the carrier C based on the carrier C supplied from the carrier generation unit 37 and the energization pattern including the PWM signal generated by the PWM signal generation unit 32. The acquisition timing for detecting the phase current of any one of the three phases is determined.

The current detection unit 27 detects the phase currents Iu, Iv, and Iw by acquiring the detection signal Sd at a plurality of acquisition timings determined by the current detection timing adjustment unit 34. The current detection unit 27 detects the phase currents Iu, Iv, and Iw using a method of detecting a plurality of phase currents from one current detector 24 (so-called one-shunt current detection method).

By the way, there is a method called inductive sensing as a method for estimating the magnetic pole position (initial position) of a rotor when a sensorless permanent magnet synchronous motor is stopped. Inductive sensing is a method of detecting the magnetic pole position of a rotor magnet of a permanent magnet synchronous motor by using the dependence of inductance on the rotor position. Since this position detection method does not use the induced voltage of the motor, the magnetic pole position of the rotor magnet can be detected even when the rotor of the motor is stopped or at an extremely low speed. The state in which the rotor is at extremely low speed refers to a state in which the rotor is rotating at such a low speed that the motor control device cannot detect the induced voltage. In this specification, for convenience of explanation, "a state in which the rotor is stopped or at an extremely low speed" is simply referred to as a "state in which the rotor is stopped".

The motor control device 100-1 according to the first embodiment includes an initial position estimation unit 38 that estimates an initial position θs, which is the magnetic pole position of the motor rotor in a stopped state, by inductive sensing. The energization pattern generation unit 35 uses the initial position θs estimated by the initial position estimation unit 38 to output an energization pattern including a PWM signal for rotating the rotor of the motor 4 to the drive circuit 33.

Inductive sensing detects the initial position of a magnetic pole by detecting a difference in inductance, but it is not a method for extracting magnetic pole position information by directly determining the inductance itself. Inductive sensing is a method that regards a stopped motor as an RL series circuit and extracts magnetic pole position information from the response of the current flowing through the motor when a step-shaped voltage is applied to the motor for a desired phase.

Applying a voltage to a desired phase means considering the voltage to be applied to the motor as a vector and adjusting its direction to the desired phase. For example, when the W-phase upper arm Wp and the U-phase lower arm Un of a three-phase inverter are turned on, a voltage vector as shown in FIG. 2 is applied. That is, the voltage was applied in the 30 degree direction. The current vector (vector of the composite current of the current flowing in the W-phase coil and the current flowing in the U-phase coil) and magnetic flux vector (the composite magnetic flux of the magnetic flux generated in the W-phase coil and the magnetic flux generated in the U-phase coil) generated at this time vector) also occurs in approximately the same phase as the voltage vector. However, the magnetic flux vector may be 180 degrees opposite depending on the winding direction of the coil.

Therefore, the initial position estimation unit 38 causes the drive circuit 33 to sequentially output a drive signal that turns on or off each arm according to the 12 energization patterns p1 to p12 shown in FIGS. Voltages can be applied to 12 different phases (see Figure 5). FIG. 3 is a table showing the phases of voltages applied to the two-phase energization patterns p1 to p6. FIG. 4 is a table showing the phases of voltages applied to the three-phase energization patterns p7 to p12. FIG. 5 is an image diagram of voltage vector directions for each energization pattern.

For example, in FIG. 3, when the initial position estimation unit 38 causes the drive circuit 33 to output a drive signal that turns on the upper arm Wp and the lower arm Vn and turns off the remaining four arms according to the energization pattern p2, the U-phase coil A voltage can be applied in a direction of 90 degrees to (see FIG. 5). Similarly, voltage can be applied in each direction in the other two-phase current pattern shown in FIG. 3.

For example, in FIG. 4, the initial position estimation unit 38 causes the drive circuit 33 to output a drive signal that turns on the upper arms Up, Wp and the lower arm Vn and turns off the remaining three arms according to the energization pattern p9. A voltage can be applied to the phase coil in a direction of 120 degrees (see FIG. 5). Similarly, voltage can be applied in each direction in the other three-phase current pattern shown in FIG. 4.

Note that when using the microcontroller's general-purpose port to output only on or off, there are the 12 types of energization patterns mentioned above, but if you use the microcontroller's PWM function, the voltage can be divided into finer phases as long as the resolution of the PWM timer allows. can be applied.

Next, in inductive sensing, extracting magnetic pole position information from a response of a current flowing through a motor when a step-shaped voltage (step voltage) is applied will be described with reference to FIG.

FIG. 6 is a diagram showing an example of current response characteristics when a step voltage is applied. Due to the current transient phenomenon in the RL series circuit, the current i flowing through the motor responds to the applied step voltage E of 5V as shown in FIG. R represents the resistance value of the coil, and L represents the inductance of the coil.

The rise time of the current at this time depends on the resistance value R and inductance L of the coil, and when the rotor position changes, it changes only according to the inductance L, which has a different value depending on the rotor position. In other words, as the inductance becomes larger (as the magnetic resistance becomes smaller), the time constant L/R becomes larger, so the current i responds more slowly. Conversely, the smaller the inductance (the larger the magnetic resistance), the smaller the time constant L/R becomes, so the current i responds more quickly.

The initial position estimating unit 38 estimates the initial position of the magnetic pole using the relationship between inductance and current response as described above. First, the initial position estimation unit 38 applies a step-shaped voltage to a desired phase until the current i flowing through the motor 4 (current detector 24) reaches a predetermined current value (current threshold). The rise time Tr is measured. Then, the initial position estimating unit 38 uses at least the difference in the measured value of the rise time Tr for each energization pattern to read the magnitude relationship and distribution of inductance depending on the rotor position, and extracts magnetic pole position information.

Note that the initial position estimation unit 38 compares the rise times Tr measured with the two-phase energization pattern, and compares the rise times Tr measured with the three-phase energization pattern. This is because although the time constant is almost the same between two-phase energization and three-phase energization, the current value that converges after rising changes, so the rise time Tr cannot be simply compared.

Next, before explaining the inductive sensing according to the present disclosure performed by the initial position estimating unit 38, in order to compare with the inductive sensing according to the present disclosure performed by the initial position estimating unit 38, referring to FIG. Inductive sensing as a comparative example will be explained.

FIG. 8 is a timing chart for explaining inductive sensing as a comparative example. One comparative example of inductive sensing is to apply current to the motor until it reaches a current threshold, read out the counter value of a timer counter that starts counting from the start of energization, and measure it in the same way with other energization patterns. Compare with the counter value. Inductive sensing as a comparative example that utilizes magnetic saturation characteristics estimates that the magnetic pole position exists in the direction determined by the energization pattern that minimizes the counter value. In the example shown in FIG. 8, since the counter value Cp2 is smaller than the counter value Cp1, the 90-degree direction is determined by the energization pattern p2 (see FIG. 3) in which the upper arm Wp and the lower arm Vn are on and the remaining arms are off. It is estimated that a magnetic pole position exists nearby.

Here, it is considered that the larger the difference in the rise time Tr between the case where a magnetic pole exists and the case where a magnetic pole does not exist, the higher the estimation accuracy of the magnetic pole position becomes. For example, the higher the current flowing through the motor, the more the slope of the transient response due to inductance changes, resulting in a larger difference in the counter value, making it easier to detect the difference in inductance (that is, the difference in rise time Tr). However, if the current is large, the motor is likely to generate abnormal noise, which may impair comfort.

It is true that the slope change when the current increases due to the inductance difference occurs even when a relatively low current is passed through the motor. However, the lower the current value, the smaller the difference in counter values, and even if a timer counter is used to capture the difference in counter values, it may be difficult to estimate the magnetic pole position. Therefore, from the viewpoint of reducing current consumption, it is preferable that the value of the current flowing through the motor for inductive sensing is small.

In addition, for applications such as fan motors that have low friction and rotate with low current (small torque), the value of the current flowing through the motor for inductive sensing should be set to minimize the effect on the application status. Smaller is preferable.

The inductive sensing according to the present disclosure, which is executed by the initial position estimating unit 38, is a method that can ensure the estimation accuracy of the magnetic pole position even with a relatively low current value. The method will be explained below.

FIG. 9 is a timing chart for explaining inductive sensing according to the present disclosure. Even after the current i flowing through the current detector 24 reaches the current threshold and the energization of the motor 4 is turned off, the behavior when the current i decreases is influenced by the inductance of the coil of the motor 4. Utilizing this characteristic, inductive sensing according to the present disclosure measures the difference in inductance by combining current behavior during energization and current behavior after energization is turned off. This makes it easier to understand the difference in inductance compared to measuring the difference in inductance based only on the current behavior during energization, as in the comparative example above, and the magnetic pole position can be measured even at relatively low current values. The estimation accuracy can be ensured.

However, during the energization-off period, current cannot be detected using the one-shunt current detection method. Therefore, as shown in FIG. 9, a period (for example, about 2 μs) in which current is temporarily applied for current detection is provided during the period when the current is turned off. In FIG. 9, a period t3-t4 and a period t7-t8 are illustrated as temporary energization periods for current detection.

In realizing the inductive sensing according to the present disclosure, the initial position estimation unit 38 according to the present disclosure estimates the magnetic pole position of the rotor in the stopped state according to the following steps S1 to S4.

(Step S1) The initial position estimation unit 38 turns on some of the arms of the inverter 23 according to one energization pattern selected from a plurality of energization patterns, so that the rotor is in a stopped state. The motor 4 is energized.

(Step S2) The initial position estimation unit 38 turns on some of the arms in step S1, and when the current i flowing through the current detector 24 connected to the DC side of the inverter 23 reaches a current threshold value, the initial position estimation unit 38 turns on the inverter 23. Turn off all arms.

(Step S3) The initial position estimating unit 38 temporarily turns on some of the arms that were turned on in step S1 during the decreasing period of the current i after turning off all the arms in step S2, thereby increasing the current. Measure i.

(Step S4) The initial position estimation unit 38 estimates the magnetic pole position of the rotor in the stopped state based on the difference in the measured value of the current i for each energization pattern.

The initial position estimation unit 38 measures the difference in inductance by combining the current behavior during energization and the current behavior after energization is turned off by estimating the magnetic pole position of the rotor in the stopped state according to the above steps S1 to S4. can. Therefore, in the one-shunt current detection method, the accuracy of estimating the magnetic pole position can be ensured even if the current threshold is set relatively small. Furthermore, since the current threshold value can be lowered, the level of abnormal noise generated by the motor during inductive sensing can be lowered.

By performing such inductive sensing according to the present disclosure, the initial position estimation unit 38 can detect current values (ip1 and ip2 in the example of FIG. 9) during the energization off period without increasing the applied current. The magnetic pole position can be estimated based on the magnitude of . The more obvious the magnetic saturation is, the greater the degree of decrease in the inductance of the coil. Therefore, in the energization off period immediately after the current i reaches the current threshold, the current i is more likely to decrease in the direction where the rotor's magnetic pole position is present than in the direction where the rotor's magnetic pole position is not present. Therefore, in the example shown in FIG. 9, since the detected current value ip2 is lower than the detected current value ip1, the initial position estimating unit 38 uses an energization pattern p2 in which the upper arm Wp and the lower arm Vn are on and the remaining arms are off. It is estimated that the magnetic pole position exists near the 90 degree direction determined by (see FIG. 3).

Although only two types of energization patterns are shown in FIG. 9, the initial position of the rotor magnet may be estimated using three or more types of energization patterns. For example, in step S4, the initial position estimation unit 38 estimates that the magnetic pole position of the rotor in the stopped state exists in the direction determined by the energization pattern with the smallest measured value of current i among the plurality of energization patterns.

It is preferable that the elapsed time from when the initial position estimation unit 38 turns on some of the arms in step S1 until it temporarily turns on some of the arms in step S3 be the same among the plurality of energization patterns. . Thereby, the initial position estimating unit 38 can measure the current i in step S3 at the elapsed timing of a certain period of time common to a plurality of energization patterns after turning on some of the arms in step S1. Therefore, since the initial position estimating unit 38 can compare the measured values of the current i measured at a common timing for a plurality of energization patterns, the accuracy of estimating the magnetic pole position is improved. For example, in the example shown in FIG. 9, the elapsed time from t1 to t3 (period t1-t3) and the elapsed time from t5 to t7 (period t5-t7) are the same.

The initial position estimating unit 38 makes the period during which some of the arms are temporarily turned on in step S3 shorter than the time from when the certain arms are turned on until the current i reaches the current threshold value. By shortening the period during which some of the arms are temporarily turned on for current detection, an increase in abnormal noise due to a temporary increase in the current flowing through the motor 4 can be suppressed.

FIG. 7 is a diagram illustrating an example of the configuration and operation of the initial position estimation section. The initial position estimation unit 38 calculates the rise time from when a step voltage is applied to the motor 4 (after turning on some arms in step S1) until the current i flowing through the current detector 24 reaches a current threshold value. A timer count value representing Tr is recorded in memory.

The initial position estimation unit 38 includes, for example, a threshold voltage generation circuit 39, a comparator 40, and a timer counter 41. The threshold voltage generation circuit 39 generates an analog voltage threshold Vth corresponding to the current threshold Ith by D/A (Digital to Analog) conversion of a digital current threshold Ith stored in advance in a memory. The comparator 40 is connected in parallel with the AD converter of the current detection section 27 (see FIG. 1), which is connected to the current detector 24. The comparator 40 compares the voltage v generated according to the current i flowing through the current detector 24 inserted in series with the negative bus 22b with a voltage threshold Vth, and outputs the comparison result. Comparator 40 inverts its output when voltage v reaches voltage threshold Vth. The timer counter 41 starts counting at the timing when a pulsed step voltage starts to be applied to some arms in one of the 12 energization patterns (for example, energization pattern p1), and when the output of the comparator 40 is Continue counting until it is reversed. The initial position estimation unit 38 records the timer count value when the output of the comparator 40 is inverted (when the count is stopped) in the memory, and also records the timer count values sequentially measured with other energization patterns in the memory. Thereby, the initial position estimation unit 38 can measure the rise time Tr (in the example of FIG. 9, t1-t2, t5-t6). In this way, the period t1-t3 (period t5-t7) can be reliably set to be longer than the period t1-t2 (period t5-t6). Thereby, it is possible to prevent the current i from being measured before the rise time Tr reaches its maximum value, thereby preventing an incorrect value from being detected.

The initial position estimation unit 38 turns off all of the arms that were turned on in step S1 when the output of the comparator 40 is inverted (when the first interrupt signal for stopping the timer counter 41 is generated). On the other hand, the timer counter 41 outputs a second interrupt signal at a timing when a certain period of time common to the plurality of energization patterns has elapsed after some arms are turned on in step S1 using one of the plurality of energization patterns. to occur. When the second interrupt signal is generated after the first interrupt signal is generated, the initial position estimating unit 38 temporarily turns on some of the arms that were once turned off. The initial position estimation unit 38 detects the measured value of the current i during the current reduction period (ip1 or ip2 in the example of FIG. 9) from the voltage generated in the current detector 24 during this temporarily turned-on period. do. For example, the initial position estimation unit 38 estimates that the magnetic pole position of the rotor in the stopped state exists in the direction determined by the energization pattern with the smallest measured value of current i among the plurality of energization patterns.

Note that each function of the current detection section 27, energization pattern generation section 35, current detection timing adjustment section 34, and initial position estimation section 38 is executed by a CPU (Central Processing Unit) by a program readably stored in a storage device (not shown). This is realized by the operation of For example, each of these functions is realized by cooperation between hardware and software in a microcomputer including a CPU.

Although the motor control device, motor system, and motor control method have been described above using the embodiments, the present invention is not limited to the above embodiments. Various modifications and improvements, such as combinations and substitutions with part or all of other embodiments, are possible within the scope of the present invention.

For example, a current detector that outputs a detection signal corresponding to the current value of the current flowing to the DC side of the inverter may output a detection signal corresponding to the current value of the current flowing to the positive side bus. Further, the current detector may be a sensor such as a CT (Current Transformer).

1-1 Motor system 4 Motor 21 DC power supply 22a Positive bus 22b Negative bus 23 Inverter 24 Current detector 27 Current detection section 30 Vector control section 32 PWM signal generation section 33 Drive circuit 34 Current detection timing adjustment section 35 Energization pattern generation Section 36 Clock generation section 37 Carrier generation section 38 Initial position estimation section 100-1 Motor control device Up, Vp, Wp, Un, Vn, Wn Arm

Claims (6)

an inverter that energizes a motor whose rotor is stopped or at an extremely low speed by turning on some of the arms according to an energization pattern;
a current detector connected to the DC side of the inverter;
When the current flowing through the current detector reaches the current threshold due to turning on of some of the arms, all the arms are turned off, and the same arm as the some of the arms is turned off during the current reduction period after all the arms are turned off. an initial position estimation unit that measures the current by turning on the current, and estimates the magnetic pole position of the rotor in the state based on the difference in the measured value for each energization pattern of the current. . The motor control device according to claim 1, wherein an elapsed time from when the some arms are turned on until when the same arm is turned on during the reduction period is the same among the plurality of energization patterns. 3. The motor control device according to claim 1, wherein the period during which the same arm is on is shorter than the time from when the some of the arms are turned on until the current reaches the current threshold value. A motor control device according to any one of claims 1 to 3,
A motor system comprising: the motor. A motor control method performed by a motor control device, comprising:
By turning on some of the arms of the inverter according to the energization pattern, the motor is energized when the rotor is stopped or at extremely low speed.
When a current flowing through a current detector connected to the DC side of the inverter reaches a current threshold by turning on some of the arms, turning off all the arms;
Measuring the current by turning on the same arm as some of the arms during a decreasing period of the current after all the arms are turned off,
A motor control method that estimates a magnetic pole position of the rotor in the state based on a difference in measured values for each current application pattern. 6. The motor control method according to claim 5, wherein the time during which the arms are turned on during the reduction period is shorter than the time from when some of the arms are turned on until the current reaches the current threshold.

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