JP2021164192A - Motor controller, motor system, and motor control method - Google Patents

Abstract

To secure estimation accuracy of a magnetic pole position.SOLUTION: A motor controller comprises: an inverter for turning on arms of all arms to energize a motor having a rotor in a stopped or extremely low speed state, the arms varying among energization patterns; a current detector connected to a DC side of the inverter; and an initial position estimation unit for estimating an initial position, a magnetic pole position of the rotor in the state. The initial position estimation unit measures a first time until a value of current flowing through the current detector reaches a first current threshold after the arms are turned on in each energization pattern and measures a second time until the value of current flowing through the current detector reaches a second current threshold after the arms are turned on in a first energization pattern in which a voltage vector is generated in a first intermediate direction in a first angular range and in a second energization pattern in which a voltage vector is generated in a second intermediate direction in a second angular range to narrow down an angular range in which the magnetic pole position exists.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to motor control devices, motor systems and motor control methods.

Conventionally, in the constant current control state, after shutting off the gate of the switching element of each phase of the synchronous motor, the decaying current flowing through each phase of the synchronous motor is detected, and based on the detected decaying current, the rotor A technique for estimating the initial magnetic pole position is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-19454

However, the conventional technique cannot be applied to the so-called one-shunt current detection method because it is a type that detects the current flowing through each phase of the synchronous motor. Further, since the initial magnetic pole position is estimated based only on the current being attenuated, it may be difficult to secure the estimation accuracy.

The present disclosure provides a motor control device, a motor system, and a motor control method capable of ensuring the estimation accuracy of the magnetic pole position in the one-shunt current detection method.

The motor control device according to the embodiment of the present disclosure is
An inverter that energizes a motor in a state where the rotor is stopped or extremely low speed by turning on some of the arms that are different for each energization pattern among all arms.
A current detector connected to the DC side of the inverter and
An initial position estimation unit that estimates an initial position that is a magnetic pole position of the rotor in the above state is provided.
When a threshold value higher than the first current threshold value is set as the second current threshold value,
The initial position estimation unit
The first time from when the part of the arm is turned on until the current flowing through the current detector reaches the first current threshold is measured for each energization pattern.
The first angle range is defined as an angle range including the first direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on the part of the arms in the energization pattern having the longest first time. An angular range including a second direction shifted 90 degrees in the negative direction from the direction of the voltage vector generated by turning on the part of the arm with the energization pattern having the longest time, or the energization pattern having the second longest time. When the angle range including the second direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on the part of the arm is set as the second angle range.
The voltage vector is set in the first intermediate angle direction included in the first angle range for the second time from when the part of the arms is turned on until the current flowing through the current detector reaches the second current threshold. Measured with the generated first energizing pattern and the second energizing pattern in which the voltage vector is generated in the second intermediate angle direction included in the second angle range.
The angle range including the direction of the voltage vector generated in the energization pattern having the shorter second time of the first angle range and the second angle range is defined as the third angle range, and one end of the third angle range. When the angular direction of is the first end direction, the angular direction of the other end of the third angle range is the second end direction, and a threshold higher than the first current threshold is the third current threshold.
The third energization pattern in which a voltage vector is generated in the first end direction and the third energization pattern for the third time from when the part of the arms are turned on until the current flowing through the current detector reaches the third current threshold. Measured with the 4th energization pattern in which a voltage vector is generated in the two-end direction,
When the angle range including the first end direction of the third angle range is defined as the fourth angle range and the angle range including the second end direction of the third angle range is defined as the fifth angle range.
It is presumed that the initial position is in the angle range including the direction of the voltage vector generated in the energization pattern in which the third time is shorter of the fourth angle range and the fifth angle range.

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

It is a figure which shows the structural example of the motor system which concerns on Embodiment 1 of this disclosure. It is a figure which shows an example of a voltage vector. It is a table which shows the phase of the voltage applied with respect to a two-phase energization pattern. It is a table which shows the phase of the voltage applied with respect to the three-phase energization pattern. It is an image diagram of the voltage vector direction for each energization pattern. It is a figure which shows an example of the current response characteristic at the time of applying a step voltage. It is a figure which shows an example of the structure and operation of the initial position estimation part. It is a vector figure for demonstrating the detection example of the magnetic pole position information in the magnetic saturation characteristic utilization method. It is a figure for demonstrating the detection example of the magnetic pole position information in the magnetic saturation characteristic utilization method. It is a vector figure for demonstrating the detection example of the magnetic pole position information in the saliency utilization method. It is a figure for demonstrating the detection example of the magnetic pole position information in the salient pole use system. It is a vector figure for demonstrating the detection example of the magnetic pole position information in the static state-oriented method used in the high-precision inductive sensing which concerns on this disclosure. It is a figure for demonstrating the detection example of the magnetic pole position information in the static state-oriented method used in the high-precision inductive sensing which concerns on this disclosure. It is a vector figure for demonstrating the detection example of the magnetic pole position information in the static state-oriented method used in the high-precision inductive sensing which concerns on this disclosure. It is a vector figure for demonstrating the detection example of the magnetic pole position information in the magnetic saturation characteristic utilization method used in the high-precision inductive sensing which concerns on this disclosure. It is a figure for demonstrating the detection example of the magnetic pole position information in the magnetic saturation characteristic utilization method used in the high-precision inductive sensing which concerns on this disclosure. It is a figure which shows the structural example of the motor system which concerns on Embodiment 2 of this disclosure. It is a vector figure for demonstrating the motor start method after inductive. It is a timing chart when the rotation speed of a motor is increased by the method of starting a motor by passing a γ-axis current at the time of starting (pull-in type starting method). It is a timing chart when the rotation speed of a motor is increased by the method of starting the rotation of a motor at the time of starting (the initial rotation type starting method). It is a timing chart when the rotation speed of a motor is increased by the method of shifting to sensorless vector control using the induced voltage at the time of pulling (sensorless vector control type starting method at the time of starting). It is an actual waveform at the time of motor start with open loop control (FIG. 20). It is an actual waveform at the time of motor start when there is no open loop control (FIG. 22).

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

FIG. 1 is a diagram showing a configuration example of the motor system 1-1 according to the first embodiment of the present disclosure. The motor system 1-1 shown in FIG. 1 controls the rotational operation of the motor 4. The equipment on which the motor system 1-1 is mounted is, for example, a copier, a personal computer, a refrigerator, a pump, and the like, but the equipment is not limited thereto. The motor system 1-1 includes at least a motor 4 and a motor control device 100-1.

The motor 4 is a permanent magnet synchronous motor having a plurality of 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. Specific examples of the motor 4 include a three-phase brushless DC motor. The motor 4 has a rotor in which at least one permanent magnet is arranged and a stator. The motor 4 is a sensorless type motor that does not use a position sensor that detects the angular position (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) of a plurality of switching elements connected by a three-phase bridge according to an energization pattern including a three-phase PWM signal. Drive the motor through. The motor control device 100-1 includes an inverter 23, a current detection unit 27, a current detection timing adjustment unit 34, a drive circuit 33, an energization pattern generation unit 35, a carrier generation unit 37, and a clock generation unit 36.

The inverter 23 is a circuit that rotates the rotor of the motor 4 by converting the direct current supplied from the DC power supply 21 into a three-phase alternating current by switching a plurality of switching elements and passing a driving current of the three-phase alternating current through the motor 4. be. The inverter 23 is based on a plurality of energization patterns generated by the energization pattern generation unit 35 (more specifically, a three-phase PWM signal generated by the PWM signal generation unit 32 in the energization pattern generation unit 35). Drives the motor 4. PWM means Pulse Width Modulation.

The inverter 23 has a plurality of arms Up, Vp, Wp, Un, Vn, and Wn connected by a three-phase bridge. The upper arms Up, Vp, and Wp are high-side switching elements connected to the positive electrode side of the DC power supply 21 via the positive bus 22a, respectively. The 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 the 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. In the following, a plurality of arms Up, Vp, Wp, Un, Vn, and Wn may be simply referred to as arms unless otherwise specified.

The 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. The 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. The 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, the V-phase coil, and the 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 arm is 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 on 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 arranged 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 it as a detection signal Sd.

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

For example, the current detection unit 27 takes in the detection signal Sd of the analog voltage generated by the current detector 24 into the 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 unit 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, thereby U, V, W of the motor 4. The phase currents Iu, Iv, and Iw of each phase are detected. The detected values of the phase currents Iu, Iv, and Iw of each phase detected by the current detection unit 27 are supplied to the energization pattern generation unit 35.

The clock generation unit 36 is a circuit that generates a clock having a predetermined frequency by a built-in oscillation circuit and outputs the generated clock to the carrier generation unit 37. The clock generation unit 36 starts operation at the same time when the power of the motor control device 100-1 is turned on, for example.

The carrier generation unit 37 generates the carrier C based on the clock generated by the clock generation unit 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 (the energization pattern of the inverter 23). The energization pattern of the inverter 23 may be rephrased as a pattern for energizing the motor 4 (energization pattern of the motor 4). The energization pattern of the inverter 23 includes a three-phase PWM signal for energizing the inverter 23. The energization pattern generation unit 35 generates a three-phase PWM signal for energizing 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 unit 32 to generate.

The energization pattern generation unit 35 further includes a vector control unit 30 when the energization pattern of the inverter 23 is generated by vector control. In the present 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 obtained by using vf control or the like.

When the rotation speed command ωref of the motor 4 is given from the outside, the vector control unit 30 excites the torque current command Iqref based on the difference between the measured value or the estimated value of the rotation speed of the motor 4 and the rotation speed command ωref. Generates the current command Idref. The vector control unit 30 calculates the torque current Iq and the exciting current Id by the vector control calculation using the rotor position θ based on the phase currents Iu, Iv, and Iw of the U, V, and W phases of the motor 4. The vector control unit 30 performs, for example, a PI control operation on the difference between the torque current command Iqref and the torque current Iq, and generates the voltage command Vq. The vector control unit 30 performs, for example, a PI control calculation on the difference between the exciting current command Idref and the exciting current Id, and generates the 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 of the U, V and W phases 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 unit 32 compares the phase voltage commands Vu *, Vv *, Vw * generated by the vector control unit 30 with the level of the carrier C generated by the carrier generation unit 37, thereby performing a three-phase PWM. Generate an energization pattern that includes a signal. The PWM signal generation unit 32 also generates a PWM signal for driving the lower arm by inverting the three-phase PWM signal for driving the upper arm, adds a dead time as necessary, and then energizes the generated PWM signal. The pattern is output to the drive circuit 33.

The drive circuit 33 outputs a drive signal for switching the six arms Up, Vp, Wp, Un, Vn, and Wn included in the inverter 23 according to the energization pattern including the given PWM signal. As a result, a three-phase alternating current drive current is supplied to the motor 4, and the rotor of the motor 4 rotates.

In the current detection timing adjustment unit 34, the current detection unit 27 performs 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 signals 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 by 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 of estimating the magnetic pole position (initial position) of the rotor when the sensorless permanent magnet synchronous motor is stopped. Inductive sensing is a method of detecting the magnetic pole position of the rotor magnet of a permanent magnet synchronous motor by utilizing the rotor position dependence of inductance. 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 extremely low speed means a state in which the rotor is rotating at such a low speed that the motor control device cannot detect the induced voltage. In the present specification, for convenience of explanation, the "rotor stopped or extremely low speed state" is simply referred to as the "rotor stopped state".

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 a magnetic pole position of the motor in a stopped state, by inductive sensing. The energization pattern generation unit 35 outputs an energization pattern including a PWM signal for rotating the rotor of the motor 4 to the drive circuit 33 using the initial position θs estimated by the initial position estimation unit 38. The vector control unit 30 uses the initial position θs estimated by the initial position estimation unit 38 as the initial value of the rotor position θ, and converts the voltage commands Vδ and Vγ into the phase voltage commands Vu *, Vv *, and Vw *. In the present disclosure, the initial position θs is a value having a width of 30 degrees as an example. In such a case, the motor 4 is controlled by using a predetermined value determined based on the initial position θs.

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

Applying a voltage to a desired phase means considering the voltage applied to the motor as a vector and adjusting the direction to the desired phase. For example, when the W-phase upper arm Wp and the U-phase lower arm Un of the three-phase inverter are turned on, the voltage vector as shown in FIG. 2 is applied. That is, the voltage is applied in the direction of 30 degrees. The current vector generated at this time (the vector of the combined current of the current flowing in the W-phase coil and the current flowing in the U-phase coil) and the magnetic flux vector (the combined magnetic flux of the magnetic flux generated in the W-phase coil and the magnetic flux generated in the U-phase coil). Vector) also occurs in almost 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 drive signals for turning on or off each arm according to the 12 energization patterns p1 to p12 shown in FIGS. 3 and 4, so that the initial position estimation unit 38 sequentially outputs every 30 degrees. Voltages can be applied to 12 types of phases (see FIG. 5). FIG. 3 is a table showing the phases of the voltages applied to the two-phase energization patterns p1 to p6. FIG. 4 is a table showing the phases of the voltages applied to the three-phase energization patterns p7 to p12. FIG. 5 is an image diagram in the voltage vector direction for each energization pattern.

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

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

In the case of output only on or off using the general-purpose port of the microcomputer, the above-mentioned 12 types of energization patterns are used, but when the PWM function of the microcomputer is used, the voltage is applied to a finer phase as long as the resolution of the PWM timer is allowed. Can be applied.

Next, in inductive sensing, extracting magnetic pole position information from the response of the current flowing through the 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 transient phenomenon of the current of 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 the inductance L of the coil, and when the rotor position changes, it changes only according to the inductance L which becomes a different value depending on the rotor position. That is, as the inductance increases (the magnetic resistance decreases), the time constant L / R increases, so that the current i responds slowly. On the contrary, as the inductance becomes smaller (the magnetic resistance becomes larger), the time constant L / R becomes smaller, so that the current i responds quickly.

Utilizing the relationship between the inductance and the current response as described above, the initial position estimation unit 38 estimates the initial position of the magnetic pole. 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 value). The rise time Tr of is measured. Then, the initial position estimation unit 38 reads the magnitude relation and distribution of the inductance depending on the rotor position by at least utilizing the difference in the measured values for each energization pattern of the rise time Tr, and extracts the magnetic pole position information.

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

As described above, the inductive sensing extracts the magnetic pole position information from the response of the current (rise time Tr) when the voltage is applied to the step shape with respect to the desired phase. There are multiple sensing methods for inductive sensing. As an example, there is a method of extracting magnetic pole position information from a change in inductance due to magnetic saturation characteristics (here, referred to as a magnetic saturation characteristic utilization method). Further, as another example, there is a method of extracting magnetic pole position information from the rotor position dependence of the inductance in a motor having a salient polarity such as a magnet-embedded synchronous motor (here, referred to as a salient polarity utilization method).

The method of setting the current threshold value and the information to be extracted differ between the magnetic saturation characteristic utilization method and the salient polarity utilization method. Next, the method of setting the current threshold value and the information to be extracted will be described for each method including the procedure.

FIG. 8 is a vector diagram for explaining a detection example of magnetic pole position information in the magnetic saturation characteristic utilization method. FIG. 9 is a chart for explaining a detection example of magnetic pole position information in the magnetic saturation characteristic utilization method. In the magnetic saturation characteristic utilization method, voltages are applied in order for six types of two-phase energization patterns (see FIG. 3). When a part of the arms of the inverter 23 is turned on and a voltage is applied to the motor 4, a current flows through the two-phase coils in the motor 4 to generate a combined magnetic flux (see FIG. 8). FIG. 8 illustrates the combined magnetic flux generated when the upper arm Wp and the lower arm Vn are turned on and the remaining four arms are turned off according to the energization pattern p2. When the current i flowing through the current detector 24 reaches the current threshold value Is2, the application of the voltage is stopped, and the rise time Tr2 from the application of the voltage until the current i reaches the current threshold value Is1 is measured. Each of the energization patterns of is carried out in order (see FIG. 9). Since this method utilizes the magnetic saturation characteristic of the motor, a current sufficient to cause magnetic saturation is passed through the motor 4, so that the current threshold value Is2 is set large enough to make the magnetic saturation characteristic manifest.

The initial position estimation unit 38 specifies the energization pattern having the shortest rise time Tr2 among the six types of energization patterns p1 to p6. The fact that the current response is fast (that is, the rise time Tr2 is short) can be regarded as the actualization of the magnetic saturation characteristic (decrease in the inductance L). The reason why the rise time Tr2 is shortened (the inductance L is lowered) in some specific energization patterns is that the direction of the magnetic flux generated by the coil is the same as the direction of the magnetic flux generated by the magnet of the rotor. Therefore, the initial position estimation unit 38 sets the rotor in an angle range centered on the direction of the voltage vector generated by turning on a part of the energization patterns in which the measured value of the rise time Tr2 is the shortest among the plurality of energization patterns. It can be estimated that there is a magnetic pole position of. Here, when there are n types of energization patterns, there are n angle range candidates, and the central angle of each angle range candidate is (360 / n) degrees.

In the example shown in FIG. 9, the measured value of the rise time Tr2 at the time of the energization pattern p2 that generates the voltage vector in the 90-degree direction is the shortest. Therefore, the initial position estimation unit 38 estimates that the magnetic pole position exists in an angle range (60 degree direction to 120 degree direction) centered on the 90 degree direction (see FIG. 8).

FIG. 10 is a vector diagram for explaining a detection example of magnetic pole position information in the salient polarity utilization method. FIG. 11 is a chart for explaining a detection example of magnetic pole position information in the salient pole utilization method. Even in the salient polarity utilization method, voltages are applied in order for six types of two-phase energization patterns (see FIG. 3). When a part of the arms of the inverter 23 is turned on and a voltage is applied to the motor 4, a current flows through the two-phase coils in the motor 4 to generate a combined magnetic flux (see FIG. 10). When the current i flowing through the current detector 24 reaches the current threshold value Is1, the application of the voltage is stopped, and the rise time Tr1 from the application of the voltage until the current i reaches the current threshold value Is1 is measured. Each of the energization patterns of is carried out in order (see FIG. 11). Since this method does not utilize the magnetic saturation characteristic of the motor, a current that does not cause magnetic saturation is passed through the motor 4, so that the current threshold Is1 is set small enough that the magnetic saturation characteristic does not become apparent. That is, the current threshold value Is1 is smaller than the current threshold value Is2.

The current threshold value Is1 is an example of a first current threshold value, and the current threshold value Is2 is an example of a second current threshold value higher than the first current threshold value. The rise time Tr1 is an example of the first time from when a part of the arms are turned on until the current flowing through the current detector 24 reaches the first current threshold value. The rise time Tr2 is an example of the second time from when a part of the arms are turned on until the current flowing through the current detector 24 reaches the second current threshold value.

The initial position estimation unit 38 specifies at least one of the six types of energization patterns p1 to p6, the energization pattern having the longest rise time Tr1 and the energization pattern having the second longest rise time Tr1. A slow current response (that is, a long rise time Tr1) can be regarded as a place (direction) where the magnetoresistance is low (a place (direction) where the inductance L is large). The reason why the rise time Tr1 is long (inductance L is large) in some specific energization patterns is that the direction of the magnetic flux generated by the coil is different from the direction of the magnetic flux generated by the magnet of the rotor. That is, the rotor magnet does not exist in the same direction as the magnetic flux generated by the coil.

Therefore, the initial position estimation unit 38 shifts 90 degrees from the direction of the voltage vector generated by turning on some of the arms in the energization pattern having the longest measured value of the rise time Tr1 among the plurality of energization patterns in the positive and negative directions. It can be estimated that the magnetic pole position of the rotor exists in the angle range centered on the right angle. Alternatively, the initial position estimation unit 38 is 90 in each of the positive and negative directions from the direction of the voltage vector generated by turning on some arms in the energization pattern in which the measured value of the rise time Tr1 is the second longest among the plurality of energization patterns. It can be estimated that the magnetic pole position of the rotor exists in the angle range centered on the shifted direction. Alternatively, the initial position estimation unit 38 is positive or negative from the direction of the voltage vector generated by turning on some arms in the energization pattern in which the measured value of the rise time Tr1 is the longest and the second longest among the plurality of energization patterns. It can be estimated that the magnetic pole position of the rotor exists in the angle range centered on the direction shifted by 90 degrees.

Theoretically, the response is slowed to the same extent with the two types of energization patterns. In the example shown in FIG. 11, the current response is slower in the energization patterns p1 and p4, and the current response is slightly slower in the energization pattern p1. However, in the actual machine, various variation factors are assumed. Therefore, the initial position estimation unit 38 identifies the energization pattern having the longest rise time Tr1 among the six types of energization patterns p1 to p6, and turns on a part of the arms with the longest energization pattern to generate 180. The energization pattern that generates the voltage vector in different directions may be specified as the second longest energization pattern.

In the example shown in FIG. 11, the measured value of the rise time Tr1 of the energization pattern p1 that generates the voltage vector in the 30-degree direction is the longest, and the measured value of the rise time Tr1 of the energization pattern p4 that generates the voltage vector in the 210-degree direction. Is the second longest. Therefore, the initial position estimation unit 38 is 90 degrees in the angle range (from 90 degrees to 150 degrees) centered on the 120 degree direction shifted 90 degrees in the positive direction from the 30 degree direction, or 90 in the negative direction from the 30 degree direction. It is estimated that the magnetic pole position exists in the angle range (from 270 degrees to 330 degrees) centered on the 300 degree direction shifted by 300 degrees or the 300 degree direction shifted 90 degrees in the positive direction from the 210 degree direction (see FIG. 10). ..

The initial position estimation unit 38 combines the above two types of inductive sensing to execute "high-precision inductive sensing" that estimates the initial position θs, which is the magnetic pole position of the motor in the stopped state, with high accuracy. The high-precision inductive sensing according to the present disclosure combines a method that emphasizes the stillness of the rotor (here, referred to as a method that emphasizes staticity) and the above-mentioned magnetic saturation characteristic utilization method to make the initial position θs highly accurate. This is an estimation method. Next, the high-precision inductive sensing according to the present disclosure will be described.

FIG. 12 is a vector diagram for explaining an example of detecting magnetic pole position information in the static state-oriented method used in the high-precision inductive sensing according to the present disclosure. FIG. 13 is a chart for explaining an example of detecting magnetic pole position information in the static state-oriented method used in the high-precision inductive sensing according to the present disclosure. The staticity-oriented method is a method that combines a salient polarity utilization method and a magnetic saturation characteristic utilization method, and after the magnetic pole position estimation by the salient polarity utilization method, the magnetic pole position is estimated by the magnetic saturation characteristic utilization method.

In the case of an application such as a fan motor that has low friction and rotates with a low current (small torque), the value of the current flowing through the motor for inductive sensing is set in order to minimize the effect on the application state. Smaller is preferable. The static-oriented method of high-precision inductive sensing according to the present disclosure does not narrow down the initial position θs only by the magnetic saturation characteristic utilization method that requires a relatively large current, but within the angle range narrowed down by the salient polarity utilization method. The initial position is narrowed down by the magnetic saturation characteristic utilization method. This can minimize the impact on the application (eg, the magnitude and duration of the current flowing through the motor).

First, the initial position estimation unit 38 narrows the range in which the magnetic pole position exists to two angular ranges by the salient pole utilization method. The initial position estimation unit 38 uses a salient polarity utilization method to set the first rise time Tr1 for each energization pattern from when a part of the arms is turned on until the current flowing through the current detector 24 reaches the current threshold value Is1. measure. For example, in the example shown in FIG. 12, the initial position estimation unit 38 is in the first angle range including the 120-degree direction (in this example, the 90-degree direction to the 150-degree direction), or in the second angle range including the 300-degree direction. (In this example, it is estimated that the magnetic pole position exists in the direction from 270 degrees to 330 degrees). The 120-degree direction in this example is an example of the first direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on a part of the arms in the energization pattern with the longest rise time Tr1. The 300-degree direction in this example is an example of a second direction in which the rise time Tr1 is shifted 90 degrees in the negative direction from the direction of the voltage vector generated by turning on a part of the arms in the longest energization pattern, or the rise time Tr1. Is an example of the second direction shifted by 90 degrees in the positive direction from the direction of the voltage vector generated by turning on a part of the arms in the second longest energization pattern.

Next, the initial position estimation unit 38 uses the first intermediate angle direction (120 degree direction in this example), which is the intermediate phase of the first angle range, and the second intermediate angle direction (120 degree direction, which is the intermediate phase of the second angle range). In this example, a step-shaped voltage is applied in the direction of 300 degrees). The initial position estimation unit 38 determines whether the polarities of the magnets located in the first intermediate angle direction and the second intermediate angle direction are N pole or S pole by the magnetic saturation characteristic utilization method.

Specifically, the initial position estimation unit 38 has a shorter rise time Tr2 among the first energization pattern in which the voltage vector is generated in the first intermediate angle direction and the second energization pattern in which the voltage vector is generated in the second intermediate angle direction. Identify the energization pattern on the other side. The fact that the current response is fast (that is, the rise time Tr2 is short) can be regarded as the actualization of the magnetic saturation characteristic (decrease in the inductance L). The reason why the rise time Tr2 is shortened (inductance L is lowered) in one of the two energization patterns is that the direction of the magnetic flux generated by the coil is the same as the direction of the magnetic flux generated by the magnet of the rotor. be. Therefore, the initial position estimation unit 38 has the magnetic pole position of the rotor in the third angle range including the direction of the voltage vector generated in the energization pattern having the shorter rise time Tr2 of the first angle range and the second angle range. Can be estimated.

In the example shown in FIG. 13, the measured value of the rise time Tr2 when the energization pattern p9 that generates the voltage vector in the 120-degree direction is the measurement of the rise time Tr2 when the energization pattern p12 that generates the voltage vector in the 300-degree direction. Shorter than the value. Therefore, the initial position estimation unit 38 estimates that the magnetic pole position exists in the third angle range (in this example, the range from the 90 degree direction to the 150 degree direction centered on the 120 degree direction) (see FIG. 14). ..

In this example, the first intermediate angle direction is the same as the above-mentioned first direction, but if it is within the first angle range, it may be deviated from the first direction, and the second intermediate angle direction is It is the same direction as the above-mentioned second direction, but may be a direction deviated from the second direction as long as it is within the second angle range.

Next, the initial position estimation unit 38 steps in each of the first end direction, which is the angular direction of one end of the third angle range, and the second end direction, which is the angular direction of the other end of the third angle range. Apply the voltage of the shape. The initial position estimation unit 38 narrows down which angle range the magnetic pole position exists in when the third angle range is divided into the fourth angle range and the fifth angle range by using the magnetic saturation characteristic utilization method ( (See FIG. 15).

FIG. 15 is a vector diagram for explaining a detection example of magnetic pole position information in the magnetic saturation characteristic utilization method used in the high-precision inductive sensing according to the present disclosure. In this example, the 90 degree direction is an example of the first end direction, the 150 degree direction is an example of the second end direction, and the angle range from the 90 degree direction to the 120 degree direction is the fourth angle range. As an example, the angle range from 120 degrees to 150 degrees is an example of the fifth angle range.

The initial position estimation unit 38 has a rise time Tr3 up to the current threshold Is3 (see FIG. 16) among the third energization pattern in which the voltage vector is generated in the first end direction and the fourth energization pattern in which the voltage vector is generated in the second end direction. Identify the energization pattern with the shorter one. The rise time Tr3 is an example of a third time from when a part of the arms is turned on until the current flowing through the current detector 24 reaches the third current threshold value. The third current threshold is a threshold higher than the first current threshold, and is set so large that the magnetic saturation characteristic becomes apparent. The current threshold Is3 is an example of the third current threshold. The current threshold value Is3 may be the same value as the current threshold value Is2 as long as it is set large enough to make the magnetic saturation characteristic manifest.

The fact that the current response is fast (that is, the rise time Tr3 is short) can be regarded as the actualization of the magnetic saturation characteristic (decrease in the inductance L). The reason why the rise time Tr3 is shortened (inductance L is lowered) in one of the two energization patterns is that the direction of the magnetic flux generated by the coil is the same as the direction of the magnetic flux generated by the magnet of the rotor. be. Therefore, the initial position estimation unit 38 considers that the magnetic pole position of the rotor exists in the angle range including the direction of the voltage vector generated in the energization pattern having the shorter rise time Tr3 among the fourth angle range and the fifth angle range. Can be estimated.

In the example shown in FIG. 16, the measurement value of the rise time Tr3 when the energization pattern p2 that generates the voltage vector in the 90-degree direction is the measurement of the rise time Tr3 when the energization pattern p3 that generates the voltage vector in the 150-degree direction is used. Shorter than the value. Therefore, the initial position estimation unit 38 estimates that the magnetic pole position exists in the fourth angle range (in this example, the range from the 90 degree direction to the 120 degree direction with the 90 degree direction as the end direction) (see FIG. 15). ).

Therefore, according to the high-precision inductive sensing according to the present disclosure, the magnetic pole position information can be narrowed down to a range of 30 degrees, so that the estimation accuracy of the initial position, which is the magnetic pole position of the rotor in the stopped state, can be improved. Further, after narrowing down to two angle ranges by the salient pole utilization method, a current for magnetic saturation is passed in the intermediate angle direction of these two angle ranges. Since the two intermediate angular directions are close to the direction in which the magnetic pole positions are oriented, torque is unlikely to be generated in the motor even if a relatively large current for magnetic saturation is passed in these two intermediate angular directions. Therefore, even if a current for detecting the initial position is passed, it is possible to prevent the motor in the stopped state from inadvertently moving.

FIG. 7 is a diagram showing an example of the configuration and operation of the initial position estimation unit. The initial position estimation unit 38 represents the rise time Tr from when the step voltage is applied to the motor 4 (after turning on some arms) until the current i flowing through the current detector 24 reaches the current threshold value. Record the timer count value in the 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 Is by D / A (Digital to Analog) conversion of the digital current threshold Is stored in the memory in advance. The comparator 40 is connected in parallel with the AD converter of the current detection unit 27 (see FIG. 1) 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 the voltage threshold Vth, and outputs the comparison result. When the voltage v reaches the voltage threshold Vth, the comparator 40 inverts its output. The timer counter 41 starts counting at the timing when a pulsed step voltage is applied to some arms in one of the 12 energization patterns (for example, energization pattern p1), and the output of the comparator 40 is output. Continue counting until it reverses. The initial position estimation unit 38 records the timer count value at the time of output inversion (when the count is stopped) of the comparator 40 in the memory, and also records the timer count value sequentially measured by other energization patterns in the memory. As a result, the initial position estimation unit 38 can measure the rise time Tr.

The functions of the current detection unit 27, the energization pattern generation unit 35, the current detection timing adjustment unit 34, and the initial position estimation unit 38 are CPUs (Central Processing Units) by a program readable and stored in a storage device (not shown). Is realized by the operation of. For example, each of these functions is realized by the collaboration of hardware and software in a microcomputer including a CPU.

FIG. 17 is a diagram showing a configuration example of the motor system 1-2 according to the second embodiment of the present disclosure. The description of the configuration similar to that of the first embodiment will be omitted by referring to the above description. The motor system 1-2 shown in FIG. 17 includes a motor 4 and a motor control device 100-2. The motor control device 100-2 is different from the motor control device 100-1 in the first embodiment in that the energization pattern generation unit 35 has the position / speed estimation unit 45.

By the above-mentioned or known inductive sensing, it is possible to estimate the rotor magnetic pole position (initial magnetic pole position) during stop even without a position sensor. In many conventional sensorless controls, after estimating the initial magnetic pole position, the motor is started and accelerated by speed open loop control until the induced voltage is large enough to obtain position information. However, in the speed open loop control, since the output cannot be changed by an external factor, it is difficult to smoothly start the rotation speed of the motor when the load of the motor changes due to disturbance or the like. There is also a method of extending the inductive sensing to the state of driving and starting and accelerating the motor by speed closed control, but the quietness is relatively low and it is often impractical.

The vector control unit 30 according to the present disclosure operates the inverter 23 in an energization pattern that generates a voltage vector in a direction deviated by an angle α in the positive direction from the initial magnetic pole position estimated by the above-mentioned or known inductive sensing. As a result, the stopped motor can be started up smoothly. The angle α is greater than 0 degrees and less than 180 degrees, but is preferably 45 to 135 degrees, more preferably 60 to 120 degrees, and even more preferably 90 degrees. This is because the most torque can be generated in the motor by passing a current in a direction deviated by 90 degrees with respect to the magnetic pole position.

For example, as shown in FIG. 18, it is assumed that the initial position estimation unit 38 estimates that the magnetic pole position of the rotor magnet exists in an angle range of 30 to 90 degrees. When rotating the rotor in the forward direction CW, the vector control unit 30 first generates a current vector in the direction of 150 (= 60 + 90) degrees. Then, the rotor is started so as to be drawn into the current vector in the 150 degree direction. If nothing is done as it is, the rotor magnetic pole position faces the direction of about 150 degrees and becomes a stopped state or a vibrating state centered on the 150 degree direction. However, before such a state occurs, the position / velocity estimation unit 45 detects or estimates the induced voltage of the motor. The position / velocity estimation unit 45 extracts the position / velocity information from the induced voltage and shifts to the velocity closed control to realize the velocity closed control in almost all the velocity regions except the extremely low speed. As a result, the influence of load fluctuations such as disturbance can be minimized.

The position / speed detection method of the position / speed estimation unit 45 is not particularly limited. It may be "detected" by using AD conversion or the like, or it may be "estimated" by using an extended induced voltage observer or the like. In addition, the magnitude and direction of the current vector are adjusted according to the operating environment of the motor and the characteristics of the motor itself in order to generate a sufficient speed when the rotor is pulled in, that is, a sufficient induced voltage to obtain position / speed information. Is preferable.

FIG. 19 is a timing chart when the rotational speed of the motor is increased by a method of starting the motor by passing a γ-axis current at the time of starting (pull-in type starting method). FIG. 20 is a timing chart in the case of increasing the rotation speed of the motor by a method of starting the rotation of the motor at the time of starting (initial rotation type starting method). FIG. 21 is a timing chart in the case of increasing the rotation speed of the motor by a method of shifting to sensorless vector control using the induced voltage at the time of pulling (sensorless vector control type starting method at the time of starting). The γ axis is an axis in the estimated angle direction representing the estimated magnetic pole position, and is deviated from the direction of the reference coil (for example, the U-phase coil) of the motor by an estimated angle of θm. The δ axis is an axis in a direction deviated by 90 degrees from the γ axis by an electric angle. The γ-δ coordinate system deviates from the reference coil by an estimated angle of θm.

In the case of the sensorless vector control type starting method at the time of starting, the motor is started to rotate by using the induced voltage generated by the pull-in by the γ-axis current. Therefore, there are merits such as being able to be driven by vector control after starting, a short starting time, no damping, and a wide usable acceleration range.

FIG. 22 is an actual waveform at the time of motor start when there is open loop control (FIG. 19). FIG. 23 is an actual waveform at the time of motor start when there is no open loop control (FIG. 21). As shown in FIG. 23, the rotational speed of the motor can be smoothly increased even when there is no open loop control.

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

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

1-1, 1-2 Motor system 4 Motor 21 DC power supply 22a Positive side bus 22b Negative side bus 23 Inverter 24 Current detector 27 Current detection unit 30 Vector control unit 32 PWM signal generation unit 33 Drive circuit 34 Current detection timing adjustment unit 35 Currenting pattern generator 36 Clock generator 37 Carrier generator 38 Initial position estimation unit 45 Position / speed estimation unit 100-1,100-2 Motor control device Up, Vp, Wp, Un, Vn, Wn arm

Claims (6)

An inverter that energizes a motor in a state where the rotor is stopped or extremely low speed by turning on some of the arms that are different for each energization pattern among all arms.
A current detector connected to the DC side of the inverter and
An initial position estimation unit that estimates an initial position that is a magnetic pole position of the rotor in the above state is provided.
When a threshold value higher than the first current threshold value is set as the second current threshold value,
The initial position estimation unit
The first time from when the part of the arm is turned on until the current flowing through the current detector reaches the first current threshold is measured for each energization pattern.
The first angle range is defined as an angle range including the first direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on the part of the arms in the energization pattern having the longest first time. An angular range including a second direction shifted 90 degrees in the negative direction from the direction of the voltage vector generated by turning on the part of the arm with the energization pattern having the longest time, or the energization pattern having the second longest time. When the angle range including the second direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on the part of the arm is set as the second angle range.
The voltage vector is set in the first intermediate angle direction included in the first angle range for the second time from when the part of the arms is turned on until the current flowing through the current detector reaches the second current threshold. Measured with the generated first energizing pattern and the second energizing pattern in which the voltage vector is generated in the second intermediate angle direction included in the second angle range.
The angle range including the direction of the voltage vector generated in the energization pattern having the shorter second time of the first angle range and the second angle range is defined as the third angle range, and one end of the third angle range. When the angular direction of is the first end direction, the angular direction of the other end of the third angle range is the second end direction, and a threshold higher than the first current threshold is the third current threshold.
The third energization pattern in which a voltage vector is generated in the first end direction and the third energization pattern for the third time from when the part of the arms are turned on until the current flowing through the current detector reaches the third current threshold. Measured with the 4th energization pattern in which a voltage vector is generated in the two-end direction,
When the angle range including the first end direction of the third angle range is defined as the fourth angle range and the angle range including the second end direction of the third angle range is defined as the fifth angle range.
A motor control device that estimates that the initial position is in an angle range including the direction of a voltage vector generated in an energization pattern having a shorter third time of the fourth angle range and the fifth angle range. The motor control device according to claim 1, wherein the first intermediate angle direction is the same direction as the first direction, or the second intermediate angle direction is the same direction as the second direction. The motor control device according to claim 1 or 2, wherein the third current threshold value is the same value as the second current threshold value. Any of claims 1 to 3, wherein the inverter generates a voltage vector in a direction deviated from the estimated initial position by an angle larger than 0 degrees and smaller than 180 degrees in the positive direction to start the motor. The motor control device according to item 1. The motor control device according to any one of claims 1 to 4.
A motor system comprising the motor. This is a motor control method performed by a motor control device that energizes a motor in a state where the rotor is stopped or at an extremely low speed by turning on some of the arms of the inverter that are different for each energization pattern.
When a threshold value higher than the first current threshold value is set as the second current threshold value,
The first time from when the partial arm is turned on until the current flowing through the current detector connected to the DC side of the inverter reaches the first current threshold value is measured for each energization pattern.
The first angle range is defined as an angle range including the first direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on the part of the arms in the energization pattern having the longest first time. An angular range including a second direction shifted 90 degrees in the negative direction from the direction of the voltage vector generated by turning on the part of the arm with the energization pattern having the longest time, or the energization pattern having the second longest time. When the angle range including the second direction shifted 90 degrees in the positive direction from the direction of the voltage vector generated by turning on the part of the arm is set as the second angle range.
The voltage vector is set in the first intermediate angle direction included in the first angle range for the second time from when the part of the arms is turned on until the current flowing through the current detector reaches the second current threshold. Measured with the generated first energizing pattern and the second energizing pattern in which the voltage vector is generated in the second intermediate angle direction included in the second angle range.
The angle range including the direction of the voltage vector generated in the energization pattern having the shorter second time of the first angle range and the second angle range is defined as the third angle range, and one end of the third angle range. When the angular direction of is the first end direction, the angular direction of the other end of the third angle range is the second end direction, and a threshold higher than the first current threshold is the third current threshold.
The third energization pattern in which a voltage vector is generated in the first end direction and the third energization pattern for the third time from when the part of the arms are turned on until the current flowing through the current detector reaches the third current threshold. Measured with the 4th energization pattern in which a voltage vector is generated in the two-end direction,
When the angle range including the first end direction of the third angle range is defined as the fourth angle range and the angle range including the second end direction of the third angle range is defined as the fifth angle range.
The initial position, which is the magnetic pole position of the rotor in the above state, is in the angle range including the direction of the voltage vector generated in the energization pattern in which the third time is shorter of the fourth angle range and the fifth angle range. A motor control method that presumes that there is.

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