Magnetic pole position detection device

Abstract

A magnetic pole position detection device capable of shortening the time required to detect the initial magnetic pole position of a synchronous motor rotor is provided. A magnetic pole position detection device (1) detects the magnetic pole position of a synchronous motor rotor, the magnetic pole position detection device (1) comprising: an excitation command unit (10) for exciting the synchronous motor while changing the current phase of the excitation current from a preset initial value; and a zero torque determination unit (12) for determining whether the torque generated by the rotor is zero. The excitation command unit (10) continuously excites the synchronous motor by setting the current phase of the excitation current to a value obtained by subtracting a phase angle from the initial value, the phase angle corresponding to the cumulative value of the rotor movement amount from the start of excitation at the initial current phase, when the torque is determined to be zero. The excitation command unit acquires the value obtained by the subtraction as the initial magnetic pole position when the torque is determined to be zero.

Description

Technical Field

[0001] The invention relates to a magnetic pole position detection device. Background Art

[0002] Synchronous motors use a dq coordinate control system to generate the desired torque by flowing current through the appropriate field phase winding according to the rotor's magnetic pole position. Synchronous motors include those with a magnetic pole position sensor, such as an encoder, to detect the rotor's magnetic pole position, and those without.

[0003] In the case of a synchronous motor without a magnetic pole position sensor, a magnetic pole position detection process is performed to detect the initial position of the magnetic pole (hereinafter referred to as the "initial magnetic pole position") each time the synchronous motor is powered on (started). The rotation of the synchronous motor is controlled based on the magnetic pole position with this initial magnetic pole position as a reference. For example, a DC excitation method is used to detect the initial magnetic pole position, in which a fixed excitation current is continuously passed through the synchronous motor with the current phase fixed, and the final stop position is set to the initial magnetic pole position.

[0004] Regarding the detection of the magnetic pole position of a synchronous motor, Patent Document 1 states that "Taking advantage of this, in the present embodiment, first, a direct current is caused to flow through the stator excitation phase of 180 degrees to detect the rotation direction of the rotor. If the rotation is in the positive direction, the rotor magnetic pole position (the position of the magnetic flux Φ) is within the range of 180 degrees to 360 degrees of the stator excitation phase, and if the rotation is in the negative direction, the rotor magnetic pole position is within the range of 0 degrees to 180 degrees. Next, a direct current is similarly caused to flow through the excitation phase in the middle of the region where the rotor magnetic pole position is located (the region of 180 degrees to 360 degrees or the region of 0 degrees to 180 degrees) to detect the rotation direction of the rotor, thereby detecting the region where the rotor magnetic pole position is located. This process is repeated below, and the region where the rotor magnetic pole position is located is successively set to a smaller region, thereby finally detecting the rotor magnetic pole position." (Paragraph 0014).

[0005] Regarding the detection of the magnetic pole position of a synchronous motor, Patent Document 2 states that "a rotation sensor 330 is used that outputs two analog signals, such as a sine wave and a cosine wave, and has multiple periods within one period of the electrical angle of the motor 300. At startup, multiple electrical angles corresponding to multiple absolute angle candidates obtained from the rotation sensor signal are set as the motor's initial position. Each of the angles is energized for a specified time, and the electrical angle at which the motor acceleration is maximum is determined as the absolute angle." (Abstract).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 3971741

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-220472 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] In the process of detecting the initial magnetic pole position using a DC excitation method, for example, a synchronous motor is DC-excited at a magnetic pole angle of 0 degrees, and the rotor of the synchronous motor is allowed to stop. The position after the stop is then acquired as the initial magnetic pole position. This takes a very long time from the start of DC excitation of the synchronous motor until the rotor stops, and acquiring the initial magnetic pole position takes time. In particular, in synchronous motors with very low friction and high acceleration performance, such as those with hydrostatic bearings, acquiring the initial magnetic pole position can sometimes take several minutes. A magnetic pole position detection device that can shorten the time it takes to detect the initial magnetic pole position of a synchronous motor's rotor is desired.

[0012] Solutions for solving problems

[0013] One embodiment of the present disclosure is a magnetic pole position detection device for detecting the magnetic pole position of a rotor of a synchronous motor. The magnetic pole position detection device includes: an excitation command unit for exciting the synchronous motor while changing the current phase of an excitation current for exciting the synchronous motor from a preset initial value; and a zero torque determination unit for determining whether torque generated by the rotor is zero when the excitation current flows through the synchronous motor. The excitation command unit continuously excites the synchronous motor by setting the current phase of the excitation current as a value obtained by subtracting a phase angle from the initial value, the phase angle corresponding to a cumulative value of the rotor movement amount since the start of excitation of the synchronous motor at the initial current phase, from the initial value, until the zero torque determination unit determines that the torque has become zero. When the zero torque determination unit determines that the torque has become zero, the excitation command unit acquires the value obtained by the subtraction as the magnetic pole initial position.

[0014] Effects of the Invention

[0015] According to the above configuration, the time required for detecting the magnetic pole position can be shortened compared to the case where the magnetic pole initial value is detected by performing excitation with a fixed current phase.

[0016] These and other objects, features, and advantages of the present invention will become more apparent from the detailed description of typical embodiments of the present invention as shown in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a block diagram showing the configuration of the magnetic pole position detection device according to this embodiment.

[0018] Figure 2 It is a diagram for explaining the detection operation of the magnetic pole position in the magnetic pole position detection device.

[0019] Figure 3 This is a diagram showing the relationship between a dq coordinate system related to a synchronous motor and a dq coordinate system related to a motor control device that controls the synchronous motor.

[0020] Figure 4A This is a diagram explaining the magnitude of the exciting current flowing to obtain the initial magnetic pole position of a synchronous motor having salient polarity.

[0021] Figure 4B This is a diagram explaining the magnitude of the exciting current flowing to obtain the initial magnetic pole position of a synchronous motor having salient polarity.

[0022] Figure 5 This is a diagram illustrating the relationship between the temperature of a permanent magnet provided in a synchronous motor and the magnetic flux density of the main magnetic flux of the synchronous motor.

[0023] Figure 6 This is a waveform diagram showing an example of changes in the exciting current, exciting phase, acceleration, and speed of the rotor during the magnetic pole position detection operation.

[0024] Figure 7 The graphs respectively show the changes in the acceleration, speed, and total movement amount (cumulative movement amount) of the rotor in the magnetic pole position detection action involved in this embodiment, and as a comparative example, respectively show the changes in the acceleration, speed, and total movement amount (cumulative movement amount) of the rotor when excitation is performed with the current phase fixed.

[0025] Figure 8 This is a flowchart showing the processing of the magnetic pole position detection operation.

[0026] Figure 9 This is a diagram for explaining a first example of the error correction operation.

[0027] Figure 10 This is a diagram for explaining a second example of the error correction operation.

[0028] Figure 11 1 is a block diagram showing a motor control device including the magnetic pole position detection device according to the present embodiment.

[0029] Figure 12 This is a block diagram showing another configuration example of the magnetic pole position detection device.

[0030] Figure 13A This is a diagram illustrating the behavior of the rotor of the synchronous motor when a fixed excitation current is continuously supplied to the synchronous motor so as to fix the current phase.

[0031] Figure 13B It will Figure 13A A diagram that is magnified along the time axis. DETAILED DESCRIPTION

[0032] Next, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, identical structural components or functional components are denoted by the same reference numerals. For ease of understanding, the scales of these drawings have been appropriately altered. The embodiments shown in the accompanying drawings are merely examples for implementing the present invention, and the present invention is not limited to the illustrated embodiments.

[0033] Figure 1 : is a block diagram showing the structure of the magnetic pole position detection device 1 according to the embodiment of the present disclosure. Figure 2 This is a diagram for explaining the detection operation of the magnetic pole position in the magnetic pole position detection device 1. When explaining the detection operation of the magnetic pole position by the magnetic pole position detection device 1, refer to Figure 13A and Figure 13B The following describes the behavior of the rotor when a fixed excitation current is continuously supplied to the synchronous motor (DC excitation is performed) so as to keep the current phase fixed.

[0034] Figure 13A and Figure 13B This is a diagram illustrating the behavior of the rotor of the synchronous motor when a fixed excitation current is continuously supplied to the synchronous motor so as to fix the current phase. Figure 13A is a diagram illustrating the time course of the rotor speed and position. Figure 13B It will Figure 13A The image is enlarged in the time axis direction. Figure 13A and Figure 13B In the figure, the solid line shows the actual position of the synchronous motor rotor over time, and the dashed line shows the speed (rotational angular velocity) of the synchronous motor. Figure 13A and Figure 13B As shown in the example, the rotor of the synchronous motor vibrates in the rotational direction. The vibration of the synchronous motor gradually decays, and the rotor eventually stops at a phase angle position that matches the excitation phase.

[0035] By performing DC excitation in this manner and waiting for the rotor to stop, the initial magnetic pole position can be acquired, but this requires a very long time until the rotor stops. The magnetic pole position detection device 1 according to this embodiment significantly shortens the time required to acquire the initial magnetic pole position compared to a case using such excitation with a fixed current phase (using a DC excitation method).

[0036] like Figure 1 As shown, the magnetic pole position detection device 1 includes an excitation command unit 10 and a zero torque determination unit 12. The excitation command unit 10 excites the synchronous motor 2 while changing the current phase of the excitation current used to excite the synchronous motor 2 from a preset initial value. The zero torque determination unit 12 determines whether the torque generated by the rotor when the excitation current flows through the synchronous motor 2 is zero. As will be described in detail later, the excitation command unit 10 continuously executes an operation of exciting the synchronous motor 2 by using a value obtained by subtracting a phase angle (electrical angle) corresponding to a cumulative value of the amount of movement of the rotor from the start of excitation of the synchronous motor 2 at the initial value of the current phase, from the initial value until the zero torque determination unit 12 determines that the torque has become zero, as the current phase of the excitation current. When the zero torque determination unit 12 determines that the torque has become zero, the excitation command unit 10 obtains the value obtained by the above subtraction as the initial magnetic pole position.

[0037] like Figure 1 As shown, the excitation command unit 10 includes an excitation phase calculation unit 13 that calculates the current phase during the magnetic pole detection operation, and an excitation command generation unit 11 that generates an excitation command for the synchronous motor 2. The excitation phase calculation unit 13 includes a storage unit 13a that stores an initial excitation phase, which is an initial value of the excitation phase. The excitation phase calculation unit 13 sets the initial value of the excitation phase during the magnetic pole detection operation as the initial excitation phase, and continuously outputs a value obtained by subtracting a phase angle (electrical angle) corresponding to the cumulative value of the rotor movement amount from the start time of the magnetic pole detection operation as the current phase of the excitation current from the initial excitation phase, from the start of the magnetic pole detection operation until the zero torque determination unit 12 determines that the torque has become zero. The excitation command generation unit 11 includes a storage unit 11a that stores a set value for the excitation current amplitude. The excitation command generation unit 11 generates an excitation command for flowing a current having the set value for the excitation current amplitude based on the excitation phase output from the excitation phase calculation unit 13. The excitation phase calculation unit 13 also includes a storage unit 13c that stores the number of pole pairs.

[0038] The command generated by the excitation command generating unit 11 is sent to the current control unit 33 (see FIG. 1 ) in the motor control device 1000 for controlling the driving of the synchronous motor 2. Figure 11 The current control unit 33 within the motor control device 1000 generates a voltage command based on the command received from the excitation command generation unit 11 and current feedback obtained by converting the current with a fixed current phase. The power conversion unit 35 applies a voltage to the synchronous motor 2 based on the received voltage command, thereby generating a fixed excitation current with a fixed current phase.

[0039] Reference Figure 1 and Figure 2 The excitation operation performed by the magnetic pole position detection device 1 will be described in more detail. Figure 2 This is a diagram showing the transition of the excitation phase generated by the excitation phase calculation unit 13 on the dq coordinate system on the motor control device side. ) is located at the initial position denoted by reference numeral 201. The switching unit 13b in the excitation phase calculation unit 13 operates as follows: while the zero torque determination unit 12 has not determined that the torque generated by the rotor of the synchronous motor 2 is zero, the output terminal 13b3 is connected to the input terminal 13b2. When the zero torque determination unit 12 determines that the torque generated by the rotor has become zero, the switching unit 13b3 is switched to the input terminal 13b1.

[0040] According to this configuration, until the zero torque determination unit 12 determines that the torque generated by the rotor has become zero, the excitation phase calculation unit 13 outputs the phase angle represented by the following equation as the excitation phase.

[0041] Excitation phase (θ) = Initial excitation phase value - ΣΔθ…(A1)

[0042] In the above formula (A1), Δθ is the increase in phase angle (electric angle) obtained by multiplying the amount of movement of the rotor by the number of pole pairs, and ΣΔθ is the cumulative value of the amount of movement of the rotor from the start time of the magnetic pole detection action. This formula (A1) means that the excitation phase is reduced from the initial excitation phase value as the rotor moves. Such an update of the excitation phase can be performed, for example, at a predetermined period. Here, as an example, the initial excitation phase value is set to 0°. In this case, as Figure 2 As shown in FIG, at the start of the magnetic pole position detection operation, a fixed excitation current (excitation current amplitude value) with a phase angle of 0° is used for excitation. Figure 2 In FIG, the excitation current Ie at this time is represented by reference numeral 301. Figure 2In the figure, the counterclockwise direction is the positive direction and the clockwise direction is the negative direction. Due to the torque acting on the rotor by the excitation based on the excitation current (reference numeral 301), the rotor is attracted toward the phase position of the excitation current (reference numeral 301) and starts to rotate (at Figure 2 In the example, it rotates in the positive direction). As the rotor moves, the excitation phase is reduced, and the current phase of the excitation current is as follows Figure 2 As shown by reference numerals 302 and 303 in FIG. Figure 2 At this time, the rotor continues to rotate in the positive direction, and the phase angle position of the rotor and the phase angle position of the excitation current are close to each other.

[0043] When the excitation current is at the position indicated by reference numeral 302, the rotor is still in the negative direction relative to the excitation current (reference numeral 202), so the rotor continues to rotate in the positive direction. Then, when the excitation current reaches the position indicated by reference numeral 303, the rotor position (indicated by reference numeral 203) matches the position (phase angle) of the excitation current. The zero torque determination unit 12 detects this state as a zero torque state.

[0044] The excitation phase (θ) expressed by equation (A1) when zero torque is detected by the zero torque determination unit 12 represents the magnetic pole position (the actual position of the rotor). Specifically, the magnetic pole position detection device 1 detects the magnetic pole position by detecting zero torque during the above-described operation. The magnetic pole position obtained by detecting zero torque in this manner is referred to as the initial magnetic pole position.

[0045] When zero torque is detected by the zero torque determination unit 12, the switching unit 13b switches the input terminal selection. Consequently, the excitation phase calculation unit 13 outputs the magnetic pole position (the value obtained by multiplying the pulse increment from the sensor 51 by the number of pole pairs) as the cumulative value of the rotor movement added to the initial magnetic pole position (Formula (A2) below).

[0046] Magnetic pole position = initial magnetic pole position + ΣΔθ…(A2)

[0047] That is, after the magnetic pole initial position is detected, the excitation phase calculation unit 13 functions as a magnetic pole position counter.

[0048] Here, a method of determining zero torque in the zero torque determination unit 12 will be described in detail. Figure 3 This is a diagram showing the relationship between the dq coordinate system related to the synchronous motor and the dq coordinate system related to the motor control device that controls the synchronous motor. m and q m, the coordinate axis of the dq coordinate system involved in the motor control device for controlling the synchronous motor is set to d c and q c In addition, the offset of the d axis between the coordinate systems (i.e. the coordinate axis d m With coordinate axis d c The angle formed by the coordinate system is set as θ. In addition, the offset θ is also the offset of the q axis between the coordinate systems (i.e., the coordinate axis q m With the coordinate axis q c angle formed by the ).

[0049] The fixed excitation current that fixes the current phase to 0 degrees in the dq coordinate system of the motor control device is defined as I e At this time, the excitation current I e In the dq coordinate system related to the synchronous motor, it is expressed as shown in Formula (1).

[0050] [Number 1]

[0051]

[0052] Assuming the number of pole pairs of the synchronous motor 2 is pp, the main magnetic flux is Φ, and the d-phase inductance is L d , let the q-phase inductance be L q When the excitation current I e The torque T generated when flowing through a synchronous motor with salient polarity r It is expressed as formula (2).

[0053] [Number 2]

[0054] T r =pp·{Φ-(L q -L d )·I dm}·I qm

[0055] =pp·{Φ-(L q -L d )·I e ·cosθ}·(-I e ·sinθ)

[0056] …(2)

[0057] In addition, in a non-salient synchronous motor (i.e., a synchronous motor without salient polarity), the d-phase inductance L d and q-phase inductance L q Therefore, after transforming equation (2) into equation (3), it is expressed as follows: e The torque T generated when the current flows through a non-salient synchronous motor r .

[0058] [Number 3]

[0059] T r =pp·Φ·(-I e ·sinθ)…(3)

[0060] As described above, when the excitation current flows through the synchronous motor, the rotor moves in the direction of rotation, and the offset θ changes every moment. Although "sinθ" is included in equations (2) and (3), when the offset θ is zero, "sinθ" is zero, so the torque T r is zero. On the contrary, when the torque T r When the value of is zero, the "sinθ" in equations (2) and (3) may be zero, that is, the offset θ may be zero. Therefore, when a fixed excitation current flows through the synchronous motor, the torque T is detected. r At the time point when the magnetic pole becomes zero, the initial position of the magnetic pole can be obtained.

[0061] However, in the case of a synchronous motor having salient polarity, according to the excitation current I e When θ is other than zero, the value of “{Φ-(L q -L d )·I e ·cosθ}" may be zero, that is, the torque T expressed by Equation 2 r That is, in the case of a synchronous motor with salient polarity, even if the torque T r Therefore, when the present embodiment is applied to a synchronous motor having salient polarity, it is necessary to make it so that the non-circulation will cause "{Φ-(L q -L d )·I e ·cosθ}" so that the excitation current I e On the other hand, in the case of a non-salient synchronous motor, the torque T r As shown in equation (3), the torque T is only r Therefore, when this embodiment is applied to a non-salient synchronous motor, it is not necessary to fix the current phase to the fixed excitation current I e Set the upper limit value.

[0062] Here, refer to Figure 4A 、 Figure 4B and Figure 5 The excitation current I that should flow to obtain the initial magnetic pole position of a synchronous motor with salient polarity is explained below. e size.

[0063] Figure 4A and Figure 4BThis is a diagram illustrating the magnitude of the excitation current flowing in order to obtain the initial position of the magnetic pole of a synchronous motor having salient polarity. Figure 4A In the figure, the horizontal axis represents the offset θ, and the vertical axis represents the torque T r .exist Figure 4B In the equation, the horizontal axis represents the offset θ, and the vertical axis represents the value obtained by dividing the torque generating equation by the q-phase current. Figure 4A and Figure 4B In the figure, the double-dotted line represents the excitation current I e For the case of 30Arms, the single-dot chain line represents the excitation current I e For the case of 60Arms, the solid line represents the excitation current I e For the case of 80Arms. In addition, Figure 4A and Figure 4B The excitation current I shown e The size is just one example.

[0064] The excitation current I e For the case of 30Arms and 60Arms, Figure 4A As shown, the torque T is only when the offset θ is zero. r becomes zero. In contrast, when the excitation current I e When the offset θ is 80 Arms, the torque T is not only when the offset θ is zero, but also when it is near "-44 degrees". r Also becomes zero. Thus, when the excitation current I e When the offset θ is 80 Arms, the torque T is generated even when the offset θ is not zero. r is zero, because Figure 4B As shown in FIG. 2 , the value obtained by dividing the torque generating equation by the q-phase current produces a negative region. Therefore, when this embodiment is applied to a synchronous motor having salient polarity, it is necessary to set the torque T represented by equation 2 to be equal to 0 in all cases except when the offset θ is zero. r The excitation current I is positive (i.e. greater than zero) e . The details are as follows.

[0065] If “T1>0” and “θ≠0” are applied to Equation 2 and rearranged, Inequality 4 is obtained.

[0066] [Number 4]

[0067] Φ-(L q -L d )·I e ·cosθ>0…(4)

[0068] In inequality 4, “−1≤cosθ≤1” holds true, so inequality 5 is obtained based on inequality 4.

[0069] [Number 5]

[0070] Φ-(L q -L d )·I e >0…(5)

[0071] If we rearrange inequality 5, we get inequality 6.

[0072] [Number 6]

[0073]

[0074] Therefore, when the present embodiment is applied to a synchronous motor having salient polarity, the fixed excitation current I e The magnitude should be set to satisfy Inequality 6. In this embodiment, when the synchronous motor for which the initial magnetic pole position is to be obtained is a synchronous motor with salient polarity, the excitation command generating unit 11 generates a magnetic field to be supplied to the synchronous motor 2 that is less than the upper limit value "Φ / (L q -L d )” excitation current I e Such instructions.

[0075] In addition, the main magnetic flux Φ decreases as the temperature of the permanent magnets provided in the synchronous motor 2 increases. Therefore, the excitation current I may be set in consideration of the expected temperature increase of the permanent magnets when driving the synchronous motor 2 having salient polarity. e Here, refer to Figure 5 The excitation current I that should flow in order to obtain the initial magnetic pole position in consideration of the temperature rise of the permanent magnet of the synchronous motor having saliency will be described. e size.

[0076] Figure 5 This is a diagram illustrating the relationship between the temperature of a permanent magnet provided in a synchronous motor and the magnetic flux density of the main magnetic flux of the synchronous motor. Figure 5 In FIG, the horizontal axis represents the temperature of the permanent magnet provided in the synchronous motor 2, and the vertical axis represents the ratio of the magnetic flux density when the magnetic flux density is set to 100% when the permanent magnet is at 20°C. Figure 5 The numerical values ​​shown are just examples and other numerical values ​​may be used. For example, when the maximum temperature of the permanent magnets assumed to be 160 degrees Celsius when driving the synchronous motor 2 having salient polarity, the magnetic flux Φ at the maximum temperature of the permanent magnets assumed to be the synchronous motor 2 is min (minimum magnetic flux density) to limit the excitation current I e , so that even when the permanent magnet is at 160 degrees, the offset θ does not become zero, and the generated torque does not become zero. That is, Inequality 7 can be obtained from Inequality 6.

[0077] [Number 7]

[0078]

[0079] Therefore, when the present embodiment is applied to a synchronous motor having salient polarity, the fixed excitation current I which fixes the current phase may be changed to the fixed excitation current I in consideration of the temperature rise of the permanent magnets assumed when the synchronous motor is driven. e The magnitude is set to satisfy Inequality 7. In this case, the excitation command generating unit 11 generates a current smaller than the upper limit value "Φ" to be supplied to the synchronous motor 2. min / (L q -L d )” excitation current I e Such instructions.

[0080] The torque T generated by the rotor of the synchronous motor 2 r When the acceleration is zero, the acceleration of the rotor of the synchronous motor 2 is zero. Zero acceleration can be detected as the time point when the polarity of the acceleration changes from positive to negative, or from negative to positive. Furthermore, when the polarity of the acceleration of the synchronous motor 2 changes from positive to negative, the speed of the synchronous motor 2 reaches its maximum (maximum), and when the polarity of the acceleration of the synchronous motor 2 changes from negative to positive, the speed of the synchronous motor 2 reaches its minimum (minimum). Therefore, in this embodiment, the zero torque determination unit 12 obtains the acceleration of the synchronous motor 2 (rotor) and determines the time point when the polarity of the acceleration of the synchronous motor 2 changes as the time point when the torque reaches zero. Alternatively, the zero torque determination unit 12 obtains the speed of the synchronous motor 2 (rotor) and determines the time point when the speed of the synchronous motor 2 reaches its maximum or minimum as the time point when the torque reaches zero. The acceleration of the synchronous motor 2 can be obtained by performing a second-order differential on the actual rotor position represented by the pulse increment from the sensor 51. The speed of the synchronous motor 2 can be obtained by first-order differentiation of the actual rotor position indicated by the pulse increment from the sensor 51. The zero torque determination unit 12 executes the differential calculation process of the actual rotor position.

[0081] Figure 6 It means reference Figure 2 The waveform diagram of an example of the changes in the excitation current, excitation phase, rotor acceleration and speed during the magnetic pole position detection operation is shown. Figure 6 In FIG, the waveform representing the excitation current is labeled with reference numeral 61 (hereinafter referred to as excitation current 61), the waveform representing the change in the excitation phase is labeled with reference numeral 62 (hereinafter referred to as excitation phase 62), the waveform representing the change in the acceleration of the rotor is labeled with reference numeral 63 (hereinafter referred to as acceleration 63), and the waveform representing the change in the speed of the rotor is labeled with reference numeral 64 (hereinafter referred to as speed 64). Figure 6Also shown is a detection completion signal 65 (high level active signal) indicating that the initial position of the magnetic pole has been detected. Figure 6 In the figure, the horizontal axis represents time and the vertical axis represents the size of each physical quantity. Figure 6 In FIG. 1 , time t0 is the time when the magnetic pole position detection operation starts, and time t1 is the time when the magnetic pole position detection operation is completed.

[0082] As described above, when the magnetic pole position detection operation starts (time t0), excitation is performed with a fixed excitation current at the initial excitation phase (see excitation current 61 and excitation phase 62). The excitation phase 62 gradually changes from the initial excitation phase value as the rotor moves. Figure 6 , an example of operation is shown in which the excitation phase 62 is gradually changed in the positive direction from the initial excitation phase value (0 degrees) by making the initial position of the rotor be located at a position more positive than the initial excitation phase value. As the excitation current 61 is applied, a torque is generated on the rotor, and the rotor begins to move. As a result, acceleration 63 is generated. Due to the change in the excitation phase 62, the excitation phase 62 and the position of the rotor will soon coincide, and the acceleration becomes zero (time t1). The zero torque determination unit 12 determines that the torque has become zero, for example, by detecting a reversal of the acceleration near time t1. The zero torque determination unit 12 may also generate a detection completion signal 65 after determining zero torque. The detection completion signal 65 can be used to switch the switching unit 13b.

[0083] In addition, if Figure 13B As shown in FIG. 1 , the rotor speed shows a peak value at the timing of the acceleration polarity reversal. Zero torque can also be detected by detecting such a peak value (maximum value or minimum value) of the speed.

[0084] Figure 7 The following figures show the changes in rotor acceleration, speed, and total movement (cumulative movement) during the magnetic pole position detection operation (i.e., excitation operation with a variable excitation phase) according to this embodiment. Furthermore, as a comparative example, the following figures show the changes in rotor acceleration, speed, and total movement (cumulative movement) when excitation is performed with the current phase fixed. The relationship between the excitation phase and the initial rotor position at the start of the magnetic pole position detection operation is made consistent between this embodiment and the comparative example.

[0085] Figure 7 The solid line curve 371 in the acceleration characteristic 70A shows an example of the time transition of the acceleration in the magnetic pole position detection operation involved in this embodiment, and the dotted line curve 372 shows an example of the time transition of the acceleration of the rotor in the comparative example. Figure 7As shown in the acceleration characteristic 70A, in the case of the comparative example, it takes about 80 ms until the acceleration becomes zero for the first time. In contrast, in the case of the magnetic pole position detection action involved in this embodiment, the acceleration becomes zero in about 60 ms (the excitation phase is consistent with the rotor position). It is understood that the time required to obtain the initial position of the magnetic pole is shortened compared with the case of the comparative example (the case where the excitation phase is fixed).

[0086] Figure 7 The solid line curve 381 in the speed characteristic 70B shows the time transition of the rotor speed in the magnetic pole position detection operation according to the present embodiment, and the dotted line curve 382 shows the time transition of the rotor speed in the case of the comparative example. Figure 7 It can be understood from the speed characteristic 70B that, in the case of the magnetic pole position detection operation according to this embodiment, the rotor speed at the time of detecting the magnetic pole initial value can be reduced compared to the case of the comparative example.

[0087] Figure 7 The solid line curve 391 in the total movement amount characteristic 70C shows the time transition of the cumulative movement amount of the rotor in the magnetic pole position detection operation involved in this embodiment, and the dotted line curve 392 shows the time transition of the cumulative movement amount of the rotor in the case of the comparative example. Figure 7 It can be understood from the total movement amount characteristic 70C that, in the case of the magnetic pole position detection operation involved in this embodiment, the cumulative movement amount of the rotor at the time of detecting the magnetic pole initial value can be reduced compared with the case of the comparative example.

[0088] Figure 8 It is used to implement reference Figure 1 The flowchart of the magnetic pole position detection operation is as follows. In the first step S1, the rotor movement amount (in Figure 8 , which is recorded as the excitation phase feedback amount in the figure), and the rotor speed and acceleration are calculated. Next, the value of the variable STAGE is checked (step S2). It is assumed that the variable STAGE is initially initialized to zero. In this case, the process proceeds to step S3 to determine whether magnetic pole detection can be performed. Unless there are any factors that would interrupt or prevent the magnetic pole position detection operation, the process proceeds to step S4 (S3: Execute). If there are any factors that would interrupt or prevent the magnetic pole position detection operation, this process flow is exited.

[0089] Next, in step S4, the value of the variable STAGE is checked. Since STAGE = 0 in the initial stage, the process proceeds to step S5. In step S5, the variable TIME, which represents the elapsed time, is initialized to zero, and the value zero representing the initial excitation phase value of 0° is substituted into the variable EPOFS. Next, in step S6, the excitation phase is initialized to zero, and the variable SUMFB, which represents the accumulated value (ΣΔθ) of the excitation phase feedback amount, is initialized to zero. Next, the excitation current amplitude value stored in the storage unit 11a is substituted into the variable IDCMD, which represents the dc-axis excitation current command, and zero is substituted into the variable IQCMD, which represents the qc-axis excitation current command, to execute excitation (step S7). In other words, excitation begins with the initial excitation phase value of 0°. The variable STAGE is then updated to 1 (step S8), the process flow exits, and the process from step S1 is executed again.

[0090] When the process from step S1 is executed with variable STAGE = 1, it is determined in step S4 that variable STAGE is 1, and the process proceeds to step S9. In step S9, the excitation current amplitude value stored in the storage unit 11a is substituted into the variable IDCMD representing the dc-axis excitation current command, and zero is substituted into the variable IQCMD representing the qc-axis excitation current command. In addition, here, the cumulative value ΣΔθ of the excitation phase feedback amount (Δθ) obtained in step S1 is substituted into the variable SUMFB, and the value of the cumulative value ΣΔθ is substituted into the variable SUMFB.

[0091] Excitation phase = EPOFS-SUMFB

[0092] The excitation phase is updated. That is, the excitation phase is set to a value obtained by subtracting a phase angle corresponding to the amount of movement of the rotor from the initial excitation phase value. In step S9, excitation is executed based on these excitation commands.

[0093] Next, in step S10, the value of the variable STAGE is checked. At this stage, since the variable STAGE = 1, the process proceeds to step S11. In step S11, it is determined whether the rotor speed has exceeded a predetermined speed threshold. If the rotor speed has not exceeded the speed threshold (S11: No), the process proceeds to step S17. If the rotor speed has exceeded the speed threshold (S11: Yes), the process proceeds to step S12. Here, it is assumed that the rotor speed has not yet exceeded the speed threshold (S11: No).

[0094] In step S17, the variable TIME is incremented. Then, in step S18, it is determined whether the variable TIME has exceeded a predetermined time threshold. Here, since the variable TIME has not exceeded the time threshold (S18: No), the process flow is exited and the process continues from step S1.

[0095] If the process from step S1 onward is started after a "No" determination in step S18, the variable STAGE is determined to be 1 in step S4. Then, in step S9, excitation is performed using the excitation phase updated by ΣΔθ corresponding to the amount of rotor movement. Next, in step S10, it is determined that the variable STAGTE is not 3 (S10: No), and the process proceeds to step S11. Here, it is assumed that the rotor speed has exceeded the speed threshold due to an increase in rotor speed (S11: Yes). In this case, the process proceeds to step S12, where the variable STAGE is updated to 3.

[0096] Next, in step S13, a determination is made as to whether the rotor acceleration is zero (i.e., whether the polarity of the rotor acceleration has reversed). If the acceleration is determined to be zero (S13: "Yes"), the process proceeds to step S14. If the acceleration is not zero (S13: "No"), the process exits and continues with step S1. If the acceleration is not zero (S13: "No"), the process resumes with step S1, then a "Yes" determination is made in step S10, and the determination in step S13 is repeated.

[0097] Assuming that the rotor acceleration is determined to be zero as the rotor moves (S13: YES), in this case, in step S14, the calculation formula for updating the excitation phase is switched to a formula that adds the excitation phase feedback amount (ΣΔθ) to the excitation phase as follows.

[0098] Excitation phase = excitation phase + excitation phase feedback

[0099] The excitation phase expressed by this equation indicates the magnetic pole position (current value) of the rotor.

[0100] Next, in step S15, the variable IDCCMD representing the dc-axis excitation command is set to 0, and the variable IQCCMD representing the qc-axis excitation command is set to 0. This completes magnetic pole position detection, and the variable STAGE is updated to 4 (step S16). If magnetic pole position detection is complete and this process is executed from step S1, STAGE = 4 is determined in step S2, and the process of updating the counter representing the magnetic pole position (i.e., updating the counter as the rotor moves) continues (step S23).

[0101] If the determination in step S11 is "No" and the variable TIME is determined to have exceeded the time threshold in step S18 (S18: "Yes"), it can be considered that the rotor's magnetic pole position is 180° reversed relative to the excitation phase and the rotor is not moving, or that the rotor is in a constrained state and cannot move. In this case, the initial excitation phase (EPOFS) is changed from 0° to 90°, and the variables TIME and SUMFB are initialized to 0 (step S19). Then, if the variable STAGE is 1 (S20: "Yes"), the variable STAGE is updated to 2 (step S21) to start the magnetic pole position detection operation with the initial excitation phase of 90°, and the current process flow is exited, continuing with the process from step S1.

[0102] On the other hand, if the variable STAGE is not 1 in step S20, it is considered that the rotor is in a restrained state, such as being fixed by a fastener. Therefore, the variable STAGE is set to 7, an alarm is issued, and the current processing flow is exited (step S22). If the variable STAGE is 7, the magnetic pole position detection operation will not be executed based on the determination in step S2.

[0103] As described above, the magnetic pole position (initial magnetic pole position) detected by the magnetic pole position detection device 1 may contain errors, depending on, for example, the sampling period of the signal from the sensor 51. The magnetic pole position detection device 1 may also include an error correction unit 14 that performs operations to eliminate errors included in the detected magnetic pole position. The error correction unit 14 performs at least one of the error correction operations 1 and 2 described below.

[0104] (Error correction action 1)

[0105] In the error correction operation 1, the magnetic pole position detected by the above-mentioned magnetic pole position detection operation is used as a temporary determination value, and error correction is performed through the following procedure.

[0106] (Process A1) After the detection of the magnetic pole position by the magnetic pole position detection operation is completed, a zero speed command is issued to stop the rotor.

[0107] (Process A2) After the rotor stops, the excitation current is passed so as to be fixed to the stopped current phase. After a predetermined time has passed since the stop, the excitation position of the fixed current phase is used as the magnetic pole initial position.

[0108] Figure 9 is a diagram for explaining error correction operation 1. Figure 9 In the example, the phase of the position where the speed stops at zero is θ. Let the main magnetic flux be The direction of the excitation current (reference numeral 211) is offset by Δθ relative to the fixed excitation current direction (dc axis direction) due to the error in the magnetic pole position detection. In this case, when the excitation current I is passed in a manner fixed to the stopped dc axis phase, e (reference numeral 311), the main magnetic flux The magnetic pole is attracted to the dc axis, moves by Δθ, and then stops. Then, after a certain period of time (predetermined time) has passed, the error correction is considered complete. As a result, the error Δθ in the magnetic pole position is eliminated.

[0109] (Error Correction Action 2)

[0110] In the error correction operation 2, the magnetic pole position detected by the above-mentioned magnetic pole position detection operation is used as a temporary determination value, and error correction is performed through the following procedure.

[0111] (Process B1) After the detection of the magnetic pole position by the magnetic pole position detection operation is completed, the rotor is rotated at a fixed speed.

[0112] (Process B2) Using the preset magnetic pole position offset (θ ofs ) replaces the magnetic pole position at the time when one rotation signal from the sensor 51 provided in the synchronous motor 2 is detected.

[0113] Figure 10 This is a diagram for explaining error correction operation 2. Figure 10 The graph 470 shown on the left side of the middle shows the relationship between the actual magnetic pole position and the position at which the sensor 51 generates a rotation signal. As shown in the graph 470, the sensor 51 uses the actual magnetic pole position 0° as a reference and adjusts the magnetic pole offset (θ ofs ) generates a rotation signal. The magnetic pole offset (θ ofs ) is stored in advance in the error correction unit 14.

[0114] Figure 10 The curve 471 on the right side of the diagram shows the time transition of the magnetic pole position, and the dotted curve 361 shows the time transition of the magnetic pole position without correction processing. Without correction processing, the magnetic pole position starts from the magnetic pole detection position θ1 at the completion of the magnetic pole position detection operation described above, and changes as shown by the dotted curve 361 while including errors. By the above process B2, at the time point T1 when the one-rotation signal is generated, the magnetic pole position is corrected to θ ofs Therefore, the magnetic pole position then shifts as shown by the solid line 362 in a state where the error is corrected.

[0115] Figure 111 is a block diagram showing a motor control device 1000 including the magnetic pole position detection device 1 according to an embodiment of the present disclosure. The motor control device 1000 includes the magnetic pole position detection device 1, a speed control unit 31, a current command generating unit 32, a current control unit 33, a dq three-phase conversion unit 34, a power conversion unit 35, a three-phase dq conversion unit 36, and a speed acquisition unit 37. The speed control unit 31 generates a current command based on the speed command ω. cmd and the speed ω of the rotor of the synchronous motor 2 acquired by the speed acquisition unit 37 m To generate the torque command T cmd The current command generating unit 32 generates a torque command T based on the torque command T cmd and the speed ω of the rotor of the synchronous motor 2 acquired by the speed acquisition unit 37 m To generate the d-axis current command I dc and q-axis current command I qc .

[0116] The three-phase dq converter 36 converts the three-phase current I output from the power converter 35 based on the magnetic pole position detected by the magnetic pole position detector 1 . u , I v , I w Perform three-phase dq conversion and convert the d-axis current I d and q-axis current I q The current control unit 33 outputs the d-axis current command I to the current control unit 33. dc , q-axis current command I qc , d-axis current I d and the q-axis current I q , to generate the d-axis voltage command V dc and q-axis voltage command V qc In addition, during the magnetic pole position detection operation, the current control unit 33 is based on the excitation command (for example, I d =I e , I q =0), to generate the d-axis voltage command V for flowing a fixed excitation current. dc and q-axis voltage command V qc The dq three-phase converter 34 converts the d-axis voltage command V based on the magnetic pole position detected by the magnetic pole position detector 1. dc and q-axis voltage command V qc Perform dq three-phase conversion and convert the three-phase voltage command V uc 、V vc 、V wc Output to the power conversion unit 35.

[0117] The power conversion unit 35 is composed of, for example, an inverter (three-phase inverter) of a full-bridge circuit including semiconductor switching elements, and generates a power supply voltage based on the received three-phase voltage command V uc 、V vc 、V wc To control the on and off of the semiconductor switching element, output the three-phase current I for driving the synchronous motor 2 u , I v , I w .

[0118] The excitation command generation unit 11, zero torque determination unit 12, speed control unit 31, current command generation unit 32, current control unit 33, dq three-phase conversion unit 34, three-phase dq conversion unit 36, speed acquisition unit 37, and magnetic pole position update unit 41 described above can be implemented, for example, in the form of software programs, or can be implemented primarily using hardware such as various electronic circuits or ASICs (Application Specific Integrated Circuits). For example, when implemented in the form of software programs, the functions of each of the aforementioned units can be realized by causing the CPU (central processing unit) within the motor control device 1000 to operate according to the software programs.

[0119] As described above, the magnetic pole position detection device according to this embodiment, which detects the magnetic pole position by performing excitation with a variable excitation phase, can shorten the time required for detecting the magnetic pole position compared to the case of performing excitation with a fixed current phase and detecting the magnetic pole initial value.

[0120] While the present invention has been described above using representative embodiments, it will be understood by those skilled in the art that changes to the above-described embodiments and various other changes, omissions, and additions may be made without departing from the scope of the present invention.

[0121] In the above-mentioned magnetic pole position detection action, an action of determining zero torque by detecting the time point when the acceleration of the rotor becomes zero is performed, but it is also possible to detect zero torque by additionally performing the following action in such an action. Here, it is assumed that the initial value of the excitation phase (initial excitation phase) deviates from the initial position of the rotor (magnetic pole) at the start time point of the magnetic pole detection action by more than 90 degrees. If the torque generated by the rotor is re-recorded, it is expressed by the following formula. Here, for simplicity, a non-salient synchronous motor is considered. In addition, let the excitation phase be θ e . θ is the position of the rotor.

[0122]

[0123] According to the above torque formula, it can be understood that in (θe When the angle (-θ) is 90° or -90°, the absolute value of the torque reaches its maximum. That is, when the magnetic pole position detection operation is performed from a position where the rotor position has deviated by more than 90° from the initial value of the excitation phase, the rotor acceleration reaches its maximum value before reaching zero. Therefore, by detecting the time when the rotor acceleration reaches its maximum value, it is possible to detect whether the initial magnetic pole position is -90° (when the rotor acceleration is positive) or +90° (when the rotor acceleration is negative).

[0124] Figure 7 Curve 371, showing the rotor acceleration change shown in acceleration characteristic 70A, shows the time-dependent acceleration when the rotor's initial position deviates by more than 90° in the negative direction relative to the initial excitation phase at the start of magnetic pole position detection. In this case, the acceleration reaches a maximum value from the start of magnetic pole position detection until it reaches zero. This maximum value occurs when the magnetic pole position reaches -90° (when the initial excitation phase is 0°).

[0125] Figure 12 The following illustrates the structure of a magnetic pole position detection device 1A that implements this operation. In this case, an acceleration peak determination unit 112 is added to the zero torque determination unit 12a. This acceleration peak determination unit 112 detects the peak value of the rotor acceleration when the excitation current is flowing through the synchronous motor 2. Thus, even if the zero torque determination unit 12a detects a maximum absolute value of the rotor acceleration before zero torque is detected, it switches the connection of the output terminal 13b3 of the switching unit 13b to the input terminal 13b1. At the time when the peak value of the rotor acceleration is detected by the acceleration peak determination unit 112, the excitation phase calculation unit 13D is configured to obtain a value obtained by adding -90° or +90° to the initial excitation phase value, depending on the polarity of the rotor acceleration, as the initial magnetic pole position.

[0126] The program for executing various processes such as the magnetic pole position detection operation in the above-mentioned embodiment can be recorded on various computer-readable recording media (for example, semiconductor memories such as ROM, EEPROM, and flash memory, magnetic recording media, and optical disks such as CD-ROM and DVD-ROM).

[0127] Description of Reference Numerals

[0128] 1. 1A: Magnetic pole position detection device; 2: Synchronous motor; 10: Excitation command unit; 11: Excitation command generation unit; 12. 12a: Zero torque determination unit; 13. 13D: Excitation phase calculation unit; 13b: Switching unit; 14: Error correction unit; 31: Speed ​​control unit; 32: Current command generation unit; 33: Current control unit; 34: D / Q three-phase conversion unit; 35: Power conversion unit; 36: Three-phase D / Q conversion unit; 37: Speed ​​acquisition unit; 51: Sensor; 112: Acceleration peak determination unit.

Claims

1. A magnetic pole position detection device for detecting the magnetic pole position of a rotor of a synchronous motor, the magnetic pole position detection device comprising: an excitation command unit that excites the synchronous motor while changing a current phase of an excitation current for exciting the synchronous motor from a preset initial value; and a zero torque determination unit for determining whether the torque generated by the rotor is zero when the excitation current flows through the synchronous motor; in, The excitation command unit continuously executes an operation of exciting the synchronous motor by setting a value obtained by subtracting a phase angle from the initial value to the current phase of the excitation current, the phase angle corresponding to a cumulative value of a movement amount of the rotor from a start time of excitation of the synchronous motor at the initial value of the current phase, during a period from when the synchronous motor is excited at the initial value of the current phase until the zero torque determination unit determines that the torque has become zero. When the zero torque determination unit determines that the torque has become zero, the excitation command unit acquires the value obtained by the subtraction process as the magnetic pole initial position.

2. The magnetic pole position detection device according to claim 1, wherein: After the zero torque determination unit determines that the torque has become zero, the excitation command unit acquires a current value of the magnetic pole position by adding a phase angle corresponding to a cumulative value of the rotor movement amount after the time when the torque has become zero to the magnetic pole initial position.

3. The magnetic pole position detection device according to claim 2, wherein: The invention further includes an error correction unit that issues a zero speed command to the synchronous motor to stop the synchronous motor after the acquisition of the initial magnetic pole position is completed, excites the synchronous motor in a manner fixed to a current phase at which the synchronous motor stops after the synchronous motor stops, and sets the fixed current phase as the current value of the magnetic pole position of the synchronous motor after a predetermined time has passed.

4. The magnetic pole position detection device according to claim 2, wherein: The invention further comprises an error correction unit that rotates the synchronous motor at a fixed speed after the acquisition of the initial position of the magnetic pole is completed, and replaces the current value of the magnetic pole position with a specified value corresponding to the position of the rotor that generates the pulse signal in the synchronous motor at a time point when a pulse signal outputted by the sensor provided in the synchronous motor for each rotation of the rotor is received.

5. The magnetic pole position detection device according to any one of claims 1 to 4, wherein: further comprising an acceleration peak value determination unit for detecting a peak value of acceleration of the rotor when the excitation current flows through the synchronous motor; At the time point when the acceleration peak determination unit detects the peak value of the rotor acceleration, the excitation command unit obtains a value obtained by adding -90° or +90° to the initial value of the current phase according to the polarity of the rotor acceleration as the magnetic pole initial position.

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