JP3405115B2 - Measurement method of electric angle deviation of electric motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection of an electric motor, and more particularly, to a deviation between a position of a reference point when the angular position of a rotor with respect to a stator is represented by a mechanical angle and a position of the reference point when represented by an electrical angle. It relates to a method for measuring an electrical angle deviation.

[0002]

2. Description of the Related Art AC electric motors, particularly synchronous electric motors, require that the electric current supplied be controlled by the angular position of the rotor with respect to the stator. Usually, an encoder or resolver is provided on the rotor shaft to detect the angular position of the rotor. This encoder or the like detects a mechanical relative position (hereinafter, referred to as a mechanical angle) between a stator and a rotor of an electric motor. On the other hand, it is the rotating magnetic field formed by the stator that actually rotates the rotor, and it is desirable to control the electric motor based on the relative position of this magnetic field and the rotor. The encoder or the like detects a mechanical angle, and if there is a deviation (offset) between the mechanical angle origin position and the electrical angle origin position, the rotating magnetic field generated will not be appropriate. The offset occurs due to the winding accuracy of the coil, the accuracy of the permanent magnet attached to the rotor, and the like. If this occurs, there is a problem that the control accuracy of the electric motor deteriorates and the efficiency decreases.

In Japanese Patent Laid-Open No. 63-59783, the angular position (mechanical angle) detected by the encoder when the rotor is stopped after DC excitation is defined as the origin of the electrical angle, and control is performed based on this electrical angle. There is. That is, the offset amount is corrected by the above-mentioned operation.

[0004]

However, according to the method described in the above publication, a DC power supply for performing DC excitation is required. In addition, the rotation of the rotor due to direct-current excitation does not occur until the friction of each part of the rotor is overcome, and the attraction force due to excitation differs depending on the relative position of the rotor and the stator before direct-current excitation. is there. In addition, the stop positions are not always the same even when rotating. Therefore, there is a problem that the offset cannot be corrected accurately and the control accuracy cannot be improved.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for measuring the offset of a motor with high accuracy.

[0006]

If the phase of the rotating magnetic field to be generated is different from that of the actually generated rotating magnetic field, the behavior of the rotor changes according to this phase. That is, if the expected behavior of the rotor cannot be obtained with respect to the rotating magnetic field that is about to be generated, it can be determined that the phase of the rotating magnetic field that is about to be generated is different from the phase of the actually generated rotating magnetic field. On the contrary, if the expected behavior of the rotor is obtained with respect to the rotating magnetic field to be generated, it can be determined that there is no phase difference. The present invention measures the deviation between the mechanical angle origin position and the electrical angle origin position based on the phase of the rotating magnetic field and the behavior of the rotor , particularly the torque value generated by the electric motor .

That is, in the method for measuring the electrical angle deviation according to the present invention, an alternating current determined based on the mechanical angle is supplied to the stator winding, and the torque of the alternating current motor driven by the alternating current is measured. And its measured
The electrical angle deviation is measured based on the Luk value . According to this method, a DC power supply is not required, and an AC power supply that drives the motor to be measured during normal use is used.
The electrical angle deviation can be measured.

Further, the alternating current supplied to the stator winding is made into two types of alternating currents having the same exciting current component, the same absolute value of the torque current component and different polarities.
The electrical angle deviations may be measured by comparing the torque values produced by the alternating currents of the species. According to this method, the electrical angle deviation can be measured under conditions close to those during normal use, that is, under control close to that during normal use, and more effective measured values can be obtained.

Further, the alternating current supplied to the stator windings, a value necessary for the exciting current component to operate power running, as an alternating current torque current component is 0, the torque produced by the alternating current Is measured and that is
The offset can be measured based on the torque value. In this case as well, the electrical angle deviation can be measured under conditions close to those in normal use, that is, under control close to that in normal use, and more effective measured values can be obtained. Further, since the torque to be measured is small, the torque detector may be a small one having a small capacity.

Furthermore, the electrical angle is measured for each of a plurality of different rotation speeds.
Deviation is measured and based on these electrical angle deviations,
The angular deviation can be determined.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below. The output torque T of the electric motor is a torque constant K _T , a d-axis inductance L _d ,
The q-axis inductance is L _q and the d-axis current (excitation current) is I
_{Let d} and q-axis current (torque current) be I _q ,

## EQU1 ## T = {K _T + (L _d −L _q ) I _d } I _q (1) Since the expression (1) is an expression representing the interaction between the rotor and the magnetic field formed by the supplied current, the d-axis current I _d and the q-axis current I _q in this expression are d on the electrical angle.
Axis and q-axis components. If the total current of the motor is I, the d-axis current I _d and the q-axis current I _q on this electrical angle θ are

(2) I _d = (I sin θ) / √3 (2) I _q = (I cos θ) / √3 (3) On the other hand, the current supplied to the electric motor is controlled by θ ″ = nθ ′ based on the mechanical angle θ ′ in the case of an n-pole pair motor, so that the d-axis current I _d ′ and the q-axis current I on the mechanical angle are controlled. _q'is

(3) I _d ″ = (I sin θ ″) / √3 (4) I _q ″ = (I cos θ ″) / √3 (5) In the motor control, the currents being controlled are the d-axis current I _d ″ and the q-axis current I _q ″ on the mechanical angle, so these match the d-axis current I _d and the q-axis current I _q on the electrical angle. Otherwise, equation (1) becomes

[Equation 4] T ″ = {K _T + (L _d −L _q ) I _d ″} I _q ”... (1”), and the expected torque T cannot be generated in the control. If the electrical angle deviation (hereinafter, referred to as an offset) is θ _off (= θ ″ −θ) and the control is performed based on (θ ″ −θ _off ), the d-axis current I _d and the q-axis current I _q on the electrical angle are set. The motor can be controlled based on That is, by replacing θ ″ in the equations (4) and (5) with (θ ″ −θ _off ), I _d = I _d ″, I _q = I _q ″, and the expected torque T is generated in control. . In this embodiment,
If the offset θ _off is provisionally set and the obtained behavior (for example, torque) of the electric motor is expected,
It is determined that the temporarily set offset matches the actual offset.

FIG. 1 is a block diagram showing the arrangement of an offset measuring apparatus according to this embodiment. The output shaft 12 of the motor under test 10 is coupled to the load 16 via the torque detector 14. The test electric motor 10 is operated under the operating conditions controlled by the test electric motor commander 18. Further, the detection value of the torque detector 14 is the offset determination unit 20.
Where the offset measurement is performed.

The test electric motor commander 18 gives a command to the test electric motor 10 based on the set offset value. That is, the motor under test 10 is controlled by a command in which the output of the encoder provided in the motor under test 10 is out of phase by the set offset. The torque of the output shaft 12 at this time is detected by the torque detector 14, and the offset determiner 20 determines whether the current offset setting value is appropriate based on the detected torque value. If the set value of the offset is appropriate, the expected torque should be output from the control command, and if it is inappropriate, the expected torque is not output. When the offset determiner 20 determines that the current offset set value is appropriate, this set value is output as the offset value of the test electric motor 10. If it is determined that the current offset setting value is inappropriate, a command for changing the offset setting value is sent to the test electric motor command device 18. The test motor commander 18 changes the set value based on this change command,
Based on this changed value, the test electric motor 10 is controlled again. Then, the setting value change is repeated until the offset setting unit 20 determines that the setting value of the offset is appropriate.

FIG. 2 shows a flowchart relating to the offset measuring method of this embodiment. In this measurement method, the d-axis current (exciting current) is equal, and the q-axis current (torque current) is driven by two types of alternating currents having the same absolute value and different polarities, and the obtained torque has polarities. , And the offset is measured depending on whether the absolute values are the same.

First, the measured rotation speed is set to the lowest rotation speed in the measurement range (S100), and the initial value of the offset is set (S102). Then, the test motor commander 18
Controls the test electric motor 10 with the d-axis current x and the q-axis current y (S104). The control at this time is performed based on a preset offset value. That is, the current command is issued by shifting the phase by the offset setting value with respect to the mechanical angle detected by the encoder, and thus the rotating magnetic field also has a phase shift. Then, the output torque Ta at this time is detected by the torque detector 14 (S
106).

Next, the test motor commander 18 controls the test motor 10 with the d-axis current x and the q-axis current -y (S).
108). The offset at this time is the step S104.
Is the same as the offset in. In this command, the d-axis currents are equal, the q-axis currents are equal in absolute value, and the polarities are different. The output torque Tb at this time is detected by the torque detector 14 (S110). And the two torque values T
By adding a and Tb, it is determined whether the absolute value of the added value is less than a predetermined threshold value e ₁ (S112). Since the current commands set in steps S104 and S108 differ only in the polarity of the q-axis current, if the set offset setting value is equal to the actual offset, the two output torque values Ta and Tb are calculated from equation (1). Are equal in absolute value,
The signs will be different. On the contrary, if the offset setting value is different from the actual offset, the absolute values of the two output torque values Ta and Tb will not be equal. That is, if the offset setting value is an appropriate value that matches the actual offset, (Ta + Tb) is 0, and if the offset setting value is an inappropriate value that does not match the actual offset, (Ta + Tb) is 0. I won't. In step S112, in order to make this determination, the absolute value of the sum of the output torque values Ta and Tb is compared with the threshold value e ₁ that can be regarded as substantially zero.

If NO is determined in step S112, the offset setting value is changed (S114), and the measurement flow from step S104 is executed again. If YES is determined in step S112, the offset value at the current rotation is stored (S116). It is determined whether this rotation speed is the maximum rotation speed in the measurement range (S11).
8) If the maximum rotation speed has not been reached, the rotation speed is increased by a predetermined rotation speed (S120) and the measurement from step S104 is performed again. If the current rotation speed is the maximum rotation speed in step S118, the offset value of the motor under test 10 is determined based on the measured offset value of each rotation speed (S122). Where the offset value is
It is also possible to determine it as a table of rotation speeds and values at that time, and it is also possible to use an average value of each rotation speed.

FIG. 3 is a flowchart showing an offset measuring method according to another embodiment. The device configuration is the same as that shown in FIG. Further, in the flowchart of FIG. 3, the same steps as those of the flowchart of FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted. After the electric motor under test 10 reaches a predetermined rotation speed, the q-axis current is set to 0 (S200). The d-axis current at this time is a value necessary for the electric motor to perform a powering operation (S200). The torque detector 14 detects the output torque in this state, and in the offset determiner 20, this is the predetermined threshold value e.
_It is determined whether it is less than ₂ (S202). Since the q-axis current is controlled to 0, if the set offset matches the actual offset, the output torque becomes 0 according to the equation (1). The output current does not become zero due to the shaft current component. In step S202, the output torque is compared with a threshold value e ₂ that can be regarded as substantially 0 in order to make this determination. If the output torque can be regarded as 0, the process proceeds to step S116, and if not, the process proceeds to step S114.

According to this embodiment, since the output torque to be detected is a small value, the torque detector 14 can be made small with a small capacity, and the device can be made compact.

FIG. 4 shows a block diagram of the configuration of still another embodiment. As shown in the figure, the configuration of this embodiment includes a test electric motor 10 and a test electric motor commander 18, which are the devices themselves when the electric motor is normally used. That is, no special configuration is required for offset measurement.

FIG. 5 shows a control flow relating to the measurement of the embodiment shown in FIG. First, the initial value of the offset is input (S300). Next, a predetermined d-axis current is supplied to the test electric motor 10 while the test electric motor 10 is stopped (S302). The control at this time is performed based on a preset offset value. And this d
It is determined whether the motor under test 10 rotates by the shaft current (S304). If the set offset matches the actual offset, no torque is generated by the d-axis current supplied from the equation (1), and thus the motor under test 10 does not rotate. If the set offsets do not match, the supplied current has a q-axis component, and the motor under test 10 rotates. The rotation of the electric motor under test 10 is detected by an encoder or a resolver provided in the electric motor. If the motor under test 10 rotates, correct the offset setting value (S30
6) and returns to step S304. On the other hand, the test motor 10
If is not rotated, the set value of the offset at this time is determined as the actual offset (S308). In this embodiment, a special configuration for offset measurement is not required, and the measurement can be performed only by the device during normal operation of the electric motor.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a measuring method of the present embodiment.

FIG. 3 is a flowchart showing a measuring method according to another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a measuring apparatus according to still another embodiment of the present invention.

5 is a flowchart showing a measuring method using the measuring device shown in FIG.

[Explanation of symbols]

10 test motor, 14 torque detector, 16 load,
18 Test motor commander.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 6/20 H02P 21/00

Claims (4)

(57) [Claims] 1. A method of measuring an electrical angle deviation, which is a deviation between a position of a reference point when the angular position of a rotor with respect to a stator of an AC motor is expressed by a mechanical angle and a position of the reference point when expressed by an electrical angle. There, an alternating current determined based on the mechanical angle is supplied to the stator winding, and the torque of the alternating current motor driven by the alternating current.
And measuring the electrical angle deviation based on the measured torque value . 2. A rotor for a stator of an AC motor
When the angular position is expressed by the mechanical angle, the position of the reference point and the electrical angle
Measure the electrical angle deviation, which is the deviation from the position of the reference point when displaying
The method is defined based on the mechanical angle, the excitation current components are equal,
A method of supplying two kinds of alternating currents having the same absolute value of a torque current component and different polarities to a stator winding, and comparing respective torque values generated by the two kinds of alternating currents to measure an electrical angle deviation. 3. The method for measuring the electrical angle deviation of the electric motor according to claim 1, wherein the alternating current supplied to the stator winding is a value required for the exciting current component to perform a powering operation, The torque current component is 0, the torque generated by this AC current is measured, and the measurement is performed.
A method for measuring the electrical angle deviation based on the obtained torque value. 4. The method according to any one of claims 1 to 3.
A method for measuring the electrical angle deviation of a motor, in which the electrical angle deviation is measured for each of a plurality of different rotation speeds.
Based on the electrical angle deviation for each rotation speed, the electrical angle of the motor
Determining the deviation, a method of measuring the electrical angle deviation.