JP4123877B2 - Motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device that controls a synchronous motor without using a position sensor.
[0002]
[Prior art]
Conventionally, there is a so-called position sensorless driving method in which the electrical angle position of the rotor is driven without being detected by a position sensor (see, for example, Patent Document 1).
However, the position sensorless driving method has a problem that synchronous operation cannot be performed unless the position and speed of the rotor are known at the time of startup. To solve this problem, a method has been proposed in which when the rotor is stopped, a voltage is applied to the stator winding for a short time to measure the inductance value, and the rotor stop position is detected by comparison with a previously measured reference inductance value ( For example, see Patent Document 2).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-236789 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-136779
[Problems to be solved by the invention]
However, in Patent Document 1 and Patent Document 2, it is assumed that the rotor is stopped at the time of starting, and even when the rotor is rotated by an external force or the like before starting, the rotation of the rotor is temporarily stopped. There is a need. For this reason, there has been a problem that it cannot be started smoothly in a state where it is rotating before starting.
The present invention has been made based on the above circumstances, and its object is to provide a motor that can be smoothly started without having to stop the rotation of the rotor even when the rotor is rotating before the start. It is to provide a control device.
[0005]
[Means for Solving the Problems]
(Invention of Claim 1)
The present invention is a control device for controlling a synchronous motor including a stator having a plurality of phase coils and a rotor having saliency,
Current detecting means for detecting a coil current of a specific phase by applying a voltage having a predetermined frequency higher than the winding inductance cycle of the specific phase to a coil of at least one phase (specific phase) of the plurality of phases; Current amplitude value calculating means for calculating a current amplitude value from the current value, and rotor speed estimating means for estimating the rotational speed of the rotor from the change period of the calculated current amplitude value.
[0006]
The winding inductance of each phase is synchronized with the rotor position. Here, if a voltage having a predetermined frequency higher than the winding inductance cycle is applied to the coil of a specific phase, the current value flowing through the coil is affected by the change in the winding inductance, so that the current that is the envelope of the current value The amplitude value is a waveform synchronized with the rotor position. Therefore, the rotor speed (rotor rotational speed) can be estimated from the change period of the current amplitude value. According to this method, the rotor speed before startup can be detected without using a position sensor or a speed sensor.
In the motor control device of the present invention, the rotor speed estimation means estimates the rotor rotational speed, and the output frequency of the inverter circuit that drives the synchronous motor is equal to or lower than the frequency determined from the rotor estimated speed (estimated rotational speed). And synchronous operation starting means for starting the synchronous operation.
In this case, when the synchronous operation is started (before starting), the synchronous operation can be smoothly started by setting the output frequency of the inverter circuit to a frequency corresponding to the rotor speed.
[0007]
(Invention of Claim 2)
In the motor control device according to claim 1,
The current amplitude value calculation means samples the coil current at a predetermined cycle and reverses again after the polarity of the sampled current value is reversed or the period of the sampled current value is reversed. The current amplitude values are calculated by integrating the current values sampled during the period until the current time.
In this configuration, by integrating the sampled current value, when current noise is mixed in the coil, the influence can be reduced, so that the current amplitude value can be calculated with high accuracy.
[0008]
(Invention of Claim 3)
In the motor control device according to claim 1,
The rotor speed estimating means is characterized in that, after a voltage having a predetermined frequency is applied to a coil of a specific phase, a rotation period of the rotor is estimated by calculating a change period of a current amplitude value after a predetermined period has elapsed.
[0009]
Immediately after the voltage is applied to the coil of a specific phase, the current is not stable, so even if the change period is calculated using the current amplitude value calculated during that time (while the current is not stable), the exact rotor speed Cannot be calculated. Therefore, while the current is not stabilized, the change period of the current amplitude value is not calculated. In other words, after the current has stabilized (after a predetermined period of time has elapsed after applying a voltage of a specific frequency to a coil of a specific phase), the change period of the current amplitude value is calculated to estimate the rotor speed. The rotor speed can be obtained well.
[0010]
(Invention of Claim 4)
In the motor control device according to claim 1,
The rotor speed estimating means includes two current amplitude values calculated before and after the apex of the current amplitude value calculated by the current amplitude value calculating means and a region where the polarity of the current value is the same as the apex of the current amplitude value. The position of the vertex is corrected using.
Even when the period of the current amplitude value calculated by the current amplitude value calculation means does not match the true period (winding inductance period), the detection error due to the sampling period is corrected at the calculated vertex and the points before and after it. It is possible to find the true vertex.
[0012]
(Invention of Claim 5 )
In the motor control device according to claim 1 ,
The synchronous operation starting means estimates the rotational position (rotor position) of the rotor from the change in the current amplitude value, and determines the initial voltage phase when starting the synchronous operation from the estimated position of the rotor.
According to this configuration, the voltage phase of the inverter circuit can be matched to the rotor phase at the time of startup, so that the startup can be performed smoothly.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a block diagram showing a basic configuration of the motor control device.
As shown in FIG. 2, the motor control device 1 of the present embodiment includes a stator (not shown) having three-phase (U-phase, V-phase, and W-phase) coils U, V, and W and a rotor having saliency ( As a basic configuration common to each embodiment described below, an inverter circuit 3 composed of a plurality of switching elements and an alternating voltage is converted into a direct current. The control circuit 5 includes a rectifier circuit 4 for applying to the inverter circuit 3 and a control unit 5 for ON / OFF control of each switching element of the inverter circuit 3.
[0014]
(First embodiment)
In addition to the above basic configuration, the motor control device 1 of the present embodiment, as shown in FIG. 1, takes in a coil current (phase current) detected by a current sensor 6 and performs A / D conversion. Current amplitude value calculating means 8 for calculating the current amplitude value from the detected current value, and rotor speed estimating means 9 for estimating the rotor rotational speed (rotor speed) from the change period of the current amplitude value. Yes.
[0015]
The rotor speed can be estimated based on the following logic.
The winding inductance of each phase is synchronized with the rotor position. Here, as shown in FIG. 3, when a voltage (b) having a predetermined frequency higher than the period of the winding inductance is applied to the coil of the specific phase, the current value (c) flowing through the coil of the specific phase becomes the winding inductance. Therefore, the current amplitude value, which is an envelope of the current value, becomes a waveform (d) synchronized with the rotor position. Therefore, it is possible to estimate the rotor speed from the change period of the current amplitude value.
[0016]
Next, a rotor speed estimation method will be described based on a rotor speed estimation subroutine shown in FIG.
Step101… Change the frequency of the command voltage applied to the coil of the specific phase.
Step 102 ... The time t that has elapsed since the frequency of the command voltage was changed is determined (the reason why Step 102 is performed will be described later). When the determination result is YES (t> t1), the process proceeds to Step 103, and when the determination result is NO (t ≦ t1), Step 102 is executed again.
Step 103 ... A current amplitude value calculation subroutine described later in the second embodiment is executed, and the calculated current amplitude value is stored in the memory.
[0017]
Step 104: It is determined whether or not the number of current amplitude values stored in the memory is n (n ≧ 3). When the determination result is YES (current amplitude value stored in the memory = n), the process proceeds to Step 105, and when the determination result is NO, the process returns to Step 103.
Step 105 ... The change period of the current amplitude value of the specific phase is obtained, and the rotor speed is estimated from the change period. In FIG. 3D, n = 40 current amplitude values are used, and the periods t1 and t2 when the current amplitude values become maximum are measured to obtain the period.
As described above, in the first embodiment, the rotor speed can be estimated from the change period of the current amplitude value of the specific phase without using a position sensor or a speed sensor.
[0018]
(Second embodiment)
In the present embodiment, an example of the current amplitude value calculation means 8 described in the first embodiment will be described.
The current amplitude value calculation means 8 samples the coil current of any one phase at a predetermined period, and the period of the sampled current value having the same polarity twice or more continuously, or the sampled current value During the period from when the polarity is inverted to when it is inverted again, the sampled current values are integrated to calculate the current amplitude value.
[0019]
Next, a method of calculating an actual current amplitude value will be described based on the flowchart shown in FIG.
Step 201 ... The memory S is cleared (S ← 0).
Step 202 ... Shift the memory for storing the current amplitude value (I1 ← I0).
Step 203: The current value is sampled at a predetermined cycle by the current detection means 7 (A / D converter) and stored in the memory I0.
Step204… Compare the polarity of the sampled current value. If the polarities are the same (determination result: YES), the process proceeds to Step 205. If the polarities are different (determination result: NO), the process proceeds to Step 206.
Step 205 ... After accumulating the current value (absolute value) stored in the memory I0 in the memory S, the process returns to Step 202.
Step 206 ... The value integrated in the memory S is set as the current amplitude value.
[0020]
According to this method, as shown in FIG. 6, if the polarities of the current values sampled at a predetermined period are the same (sections t1 to t2, sections t2 to t3), the sampled current values (absolute values) are obtained. Since the sum of the current values (absolute values) accumulated in the memory S is used as the current amplitude value at the timing (t2, t3) at which the polarity of the sampled current value changes after being added to the memory S, the coil When current noise is mixed in U, V, and W, the influence can be reduced, and the current amplitude value can be calculated with high accuracy.
[0021]
(Third embodiment)
In this embodiment, Step 102 of the first embodiment will be described.
When estimating the rotor speed, a voltage having a predetermined frequency is applied to at least one phase (specific phase) coil to detect a current flowing in the specific phase coil. As shown in FIG. Immediately after the voltage is applied, the current is not stable, so even if the change period is obtained using the current amplitude value calculated during that time (while the current is not stable), the accurate rotor speed cannot be calculated.
Therefore, while the current is not stable, the current amplitude value is not used for calculating the change period. That is, after the current is stabilized (after a predetermined period of time t1 has elapsed after applying a voltage of a predetermined frequency to the coil of a specific phase), by calculating the change period of the current amplitude value and estimating the rotor speed, The rotor speed can be obtained with high accuracy.
[0022]
(Fourth embodiment)
In this embodiment, in the rotor speed estimation subroutine described in the first embodiment, a method for correcting the peak of the current amplitude value when determining the change period of the current amplitude value in Step 105 will be described.
When the difference between the voltage frequency of the inverter circuit 3 and the inductance frequency of the rotor (winding inductance change period) becomes smaller, the change period T2 of the current amplitude value obtained from the current value is true as shown in FIG. The period T1 shifts (T1 ≠ T2). At this time, the detection accuracy is one cycle of the applied voltage. For example, when the frequency of the applied voltage is 300 Hz and the rotor frequency is 60 Hz (1800 rpm), if there is an error for one voltage cycle, an error of about ± 400 rpm occurs in the detected rotational speed.
[0023]
Therefore, as shown in FIG. 9A, the vertex y of the current amplitude value calculated by the current amplitude value calculation means 8 is calculated before and after the vertex in the region where the polarity of the current value and the vertex y is the same. The position of the vertex is corrected using the two current amplitude values x and z, and the change period is calculated with the corrected vertex as the true vertex.
As a correction method, there is a method by linear approximation shown in FIG. 9B or a method of calculating a true vertex by calculating from a sine wave.
[0024]
(5th Example)
In this embodiment, a method for starting synchronous operation from a state in which the rotor is rotated by an external force or the like will be described.
A specific method will be described based on the synchronous operation start subroutine shown in FIG.
Step 301 ... The rotor speed estimation subroutine (see FIG. 4) described in the first embodiment is executed to estimate the rotor speed.
Step 302 ... The output frequency of the inverter circuit 3 is determined from a rotational speed lower than the estimated rotor speed (rotor estimated speed-predetermined amount a).
[0025]
Step 303 ... The applied voltage phase of the inverter circuit 3 is set to a predetermined value. Here, the rotational position (rotor position) of the rotor is estimated from the change in the current amplitude value detected when the rotor speed is estimated, and the applied voltage phase of the inverter circuit 3 is determined from the rotor position.
According to the present embodiment, the synchronous operation can be started as it is without stopping the rotor from the state where the rotor is rotating. Further, when the synchronous operation is started, the applied voltage phase of the inverter circuit 3 can be matched with the rotor phase, so that the synchronous operation can be smoothly started.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration for estimating a rotor speed (first embodiment).
FIG. 2 is a block diagram showing a basic configuration of a motor control device.
FIG. 3 is a diagram showing changes in winding inductance waveform diagram (a), voltage waveform diagram (b), current waveform diagram (c), and current amplitude value (d) in a specific phase (first embodiment); .
FIG. 4 is a rotor speed estimation subroutine (first embodiment).
FIG. 5 is a current amplitude value calculation subroutine (second embodiment);
FIG. 6 is an explanatory diagram showing a method of calculating a current amplitude value (second embodiment).
FIG. 7 is a waveform diagram showing changes in current value with respect to applied voltage (third embodiment).
FIG. 8 is a waveform diagram for explaining a difference between a rotor frequency and a change period of a current amplitude value (fourth embodiment).
FIG. 9A is a waveform diagram for explaining a deviation between a detected vertex and a true vertex of a current amplitude value, and FIG. 9B is a diagram for explaining a method for correcting the vertex of the current amplitude value (fourth) Example).
FIG. 10 is a synchronous operation starting subroutine (fifth embodiment).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor control apparatus 2 Synchronous motor 3 Inverter circuit 7 Current detection means 8 Current amplitude value calculation means 9 Rotor speed estimation means U, V, W Coil

Claims (5)

A motor control device for controlling a synchronous motor including a stator having a plurality of phase coils and a rotor having saliency,
Voltage applying means for applying a voltage having a predetermined frequency higher than a winding inductance cycle in the specific phase to a coil of at least one phase (specific phase) of the plurality of phases;
Current detecting means for detecting the coil current of the specific phase;
Current amplitude value calculating means for calculating a current amplitude value from the detected current value;
Rotor speed estimating means for estimating the rotational speed of the rotor from the change period of the calculated current amplitude value ;
Synchronous operation starting means for estimating the rotational speed of the rotor by the rotor speed estimating means and then setting the output frequency of the inverter circuit for driving the synchronous motor to be equal to or lower than the frequency determined from the estimated speed of the rotor to start synchronous operation motor controller having and. In the motor control device according to claim 1,
The current amplitude value calculating means samples the coil current at a predetermined cycle, and the period when the polarity of the sampled current value is the same polarity continuously twice or more, or after the polarity of the sampled current value is inverted A motor control device characterized in that a current amplitude value is calculated by integrating current values sampled during a period until reversing again. In the motor control device according to claim 1,
The rotor speed estimation means calculates a change period of the current amplitude value after a predetermined period of time after applying a voltage of a predetermined frequency to the coil of the specific phase, and estimates the rotation speed of the rotor. A motor control device. In the motor control device according to claim 1,
The rotor speed estimation means includes two currents calculated before and after the apex of the current amplitude value calculated by the current amplitude value calculating means and a region where the polarity of the apex and the current value is the same. A motor control device that corrects the position of the vertex using an amplitude value. In the motor control device according to claim 1,
The synchronous operation starting means estimates a rotational position (rotor position) of the rotor from a change in the current amplitude value, and determines an initial voltage phase when starting synchronous operation from the estimated position of the rotor. Motor control device .

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