JPH10313588A - Rotor position detection device of electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the absolute position of an electric motor within one rotation, by setting the number of rotor poles in a position detection rotor in a rotor pitch position detection means for detecting a relative position to a value that does not have a common divisior for the number of rotor magnet poles of the electric motor, and by performing a fixed processing based on both rotor positions. SOLUTION: When the coil winding of an electric motor is utilized for detecting a position, the change in a coil winding inductance and a rotor position Xmes 2 that is calculated based on the change are 6 periods within a machine angle of 360 deg. since the number of magnetic poles of the rotor is 6. On the other hand, in the case of a rotor pitch position detection means, the degree of magnetic coupling and a position detection value Xmes 1 that is calculated based on it are 7 periods in a machine angle of 360 deg. since the number of rotor poles is 7. In this manner, when the number of rotor poles of the rotor pitch position detection means for detecting a relative position is 7 for the number of magnetic poles of the electric motor of 6 and there us no common divisor a position in the machine angle of 360 deg. of the rotor can be determined based on the Xmes 1 and the Xmes 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor position detecting device used for motor control for controlling the position or speed of a motor.

[0002]

2. Description of the Related Art When controlling the position or speed of a rotor of an electric motor, a current position detection value is usually received from a position detection device provided on the electric motor or a rotating body operated by the electric motor, and a known technique is used. Controls the position or speed of the rotor of the electric motor or the rotating body.

A conventional method for detecting a rotor position of an electric motor will be described with reference to the drawings. First, a description will be given below of an example of a position detection method used in a position control method which is currently most generally performed, in which a position detection device is attached to an electric motor or a rotating body for control. Note that the rotor pitch position detecting device is hereinafter simply referred to as a detector. FIG. 6 is a diagram showing an example of a cross section of the position detection rotor 8 and the position detection stator pole 9 incorporated in the detector. As shown in the figure, the rotor 8 is a portion that rotates in synchronization with the rotor shaft of the electric motor, is provided with rotor poles equally divided into six parts, and is made of a material having high magnetic permeability. . On the other hand, the stator poles 9 are arranged at regular intervals from the outer periphery of the rotor 8 at equal intervals, and are also made of a material having high magnetic permeability. Further, the primary winding for detection is wound on each of the stator poles 9, and the winding manner is such that the windings wound on the stator pole 9 indicated by + S and the stator poles indicated by −S are connected. However, the winding direction is opposite. This is the same for the stator pole 9 indicated by + C and the stator pole 9 indicated by -C, and the number of turns is the same. The winding wound in this way is the primary winding. A winding is also wound around the position detection stator to which the stator pole 9 is attached, and this is called a secondary winding for detection. The relationship between the primary winding and the secondary winding is such that the primary winding is on the input side and the secondary winding is on the output side.
An electric current forming an os wave is supplied. In FIG. 6, the rotor 8
As described above, the rotor poles are divided into six equal parts.
Assuming that it is 60 °, the rotor 60, which is one sixth of one rotation of the rotor 8, corresponds to the electrical angle of 360 °. In addition,
One rotation of the rotor 8 is called a mechanical angle of 360 °. When the rotor 8 rotates by an electrical angle of 360 °, for example, + C
Since the degree of magnetic coupling between the stator pole 9 and the rotor 8 is proportional to the distance between them, the waveform is as shown in the upper part of FIG. This is because the −C stator pole 9 has the smallest magnetic coupling degree at the position where the + C stator pole 9 has the maximum magnetic coupling degree in FIG. 6, and the opposite relationship exists at the position shifted by 180 electrical degrees from the angle. Further, at positions shifted by an electrical angle of 90 ° from each other, the degree of magnetic coupling of the + C and −C stator poles 9 becomes equal and cancel each other. Although not shown in FIG. 7, the magnetic coupling degree of the + S stator pole 9 exists at a position shifted by 90 electrical degrees with respect to the waveform. In this way, by applying a current forming a fixed sine wave and a cos wave to the primary winding, a corresponding electromotive force is generated in the secondary winding depending on the degree of magnetic coupling. When performing position detection by the detector, by calculating the phase difference between the output waveform emitted from the secondary winding and any of the input waveforms applied to the primary winding,
The positions of the rotor 8 and the rotor of the electric motor can be determined. It is to be noted that the details of the above-described series of position detection methods are known in the art, and thus description thereof is omitted.

The above detector has been described as a conventional example in which a motor is provided with a position detecting rotor and a stator. Next, a conventional method for detecting a rotor position of a motor by utilizing windings of the motor itself. The method will be described. Usually, when driving a motor, a current is supplied to a winding in a stator through a power transistor in an amplifier connected to the motor. A conventional position detection method using this energization is to detect the position by measuring the response to the current command Icom of the actual current Imes actually flowing in the winding before or during driving of the motor or both. I do. In particular, in the case where the rotor has a slit structure in which the magnetic resistance of the rotor viewed from the stator side differs according to the rotational position of the rotor as shown in FIG. 8, the difference in the magnetic resistance causes the winding to vary depending on the position of the rotor with respect to the stator. Since the value of the inductance of the wire greatly differs, the position can be easily detected.
Now, assuming that the conduction current is I, the inductance is L, and the voltage is V,

Since it is known that V∝L × (dI / dt) (1), (dI / dt) indicating the response to the current command of the actual current flowing through the winding is measured as described above. By doing so, it becomes possible to perform position detection. Normally, in the magnetic pole pitch position detecting means in the control device, a fixed process based on the above formula is performed to detect the rotor position within the magnetic pole pitch, and the detected position value Xme
s2 is generated.

[0005] On the other hand, in the control device of the electric motor, the following control is performed as is known based on the position of the rotor detected as described above. 9 and 10 are examples of block diagrams showing a conventional control method. FIG. 9 shows an example of a block diagram in the case of using the detector, and FIG. 10 shows an example of a block diagram in the case of performing position detection using the above-described motor winding. In each of the figures, 1 is a first comparator, 2 is a position loop gain, 3 is a second comparator, 4 is a velocity loop gain,
5 is a differentiator. 9 is different from FIG. 10 in that FIG. 9 uses the position data sent from the detector as it is as the position detection value Xmes0, whereas in FIG. 10 the current command Icom and the actual current Imes Processing, and the magnetic pole pitch position detecting means 7 detects the position detection value X
mes0 is required. Other processes are the same for both, and the first comparator 1 uses the position command value Xcom and the position detection value Xmes obtained by using the above-described detector or winding.
The position error Xdiff is calculated from the difference from 0. further,
The position loop gain 2 calculates the speed command value Vcom by multiplying the position error Xdiff by a constant. In the second comparator 3, the speed detection value Vmes and the speed command value V obtained by differentiating the position detection value Xmes0 by the differentiator 5 are shown.
com and a speed error Vdiff is calculated.
Further, at the speed loop gain 4, the current command Icom is calculated by multiplying the speed error Vdiff by a constant. The above is an example of the outline of the processing performed by the motor control device.

[0006]

The position detection method using the detector and the winding of the electric motor has been described above, but in any case, the absolute position of the rotor cannot be obtained by 360 ° in mechanical angle. Normally, in case of detector, mechanical angle 3
In order to detect the absolute position of 60 °, one more set of the rotor 8 and the stator pole 9 as described above is added, and the position of the mechanical angle of 360 ° is detected by combining the two. In this case, the number of rotor poles is set to 1 by a known method such as eccentricity of a circle so that electrical angle = mechanical angle.
It is often realized as being equivalent to a book. However, if a further set of rotors 8 and stator poles 9 are added as described above, the structure of the entire detector becomes complicated and the number of parts increases, resulting in an increase in cost. On the other hand, except for a set of the rotor 8 and the stator pole 9 having six rotor poles such that the mechanical angle of the detector = electrical angle, a set in which the above-mentioned rotor pole is equivalent to one rotor pole is provided. Although it is conceivable to perform position detection only by using this method, the accuracy of position detection is deteriorated in this method as compared with the above method, and it becomes difficult to precisely control the operation of the motor. From the above, in the conventional detector, for reasons such as cost, the mechanical angle 3 is determined only by the combination of the rotor 8 and the stator pole 9 having a plurality of rotor poles.
There has been a demand to detect the absolute position within one rotation of the motor, which is 60 °.

On the other hand, in the method of detecting the position by using the winding of the motor described above, the position can be detected only by the magnetic pole pitch of the rotor of the motor. This is because the inductance change is determined by the positional relationship between the magnetic poles of the rotor and the windings. However, the magnetic pole in the rotor as shown in FIG. 8 is a portion where the slit formed in the rotor in FIG. 8 is substantially orthogonal to the outer periphery of the rotor, and in FIG. Become. As described above, since the inductance of the winding changes one magnetic pole pitch of the rotor in one cycle, in the position detecting method using the winding, position detection can be performed only for one magnetic pole pitch.

As described above, in the prior art, in the above-described detector for detecting the relative position, the method for detecting the position by using the winding of the electric motor is also described.
There is a problem that the absolute position cannot be detected within one rotation of the electric motor corresponding to 360 ° in mechanical angle. The problem to be solved by the present invention lies in what measures should be taken to solve the above problems.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, in a motor control device according to the present invention, the number of rotor poles in a position detecting rotor in a rotor pitch position detecting means for detecting a relative position is determined by the rotation of the motor. By setting a value that does not have a common divisor with respect to the number of slave magnetic poles and performing a constant process based on the rotor positions of both, the absolute position within one rotation of the motor can be detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for describing a detection method according to the present embodiment. FIG. 2 is an example of a sectional view of the position detecting rotor 8 and the position detecting stator pole 9 of the rotor pitch position detecting means for detecting a relative position in the present embodiment. FIG. 1 is composed of four waveforms, the horizontal axis of which is the mechanical angle, and the four waveforms are synchronized from 0 ° to 360 °. In FIG. 1, the upper two waveforms are the same as in FIG. 7, the uppermost waveform is the magnetic coupling degree between the stator pole 9 and the rotor 8 indicated by + C in FIG. 6, and the second waveform from the top is the magnetic coupling. This is the position of the rotor that can be determined using the degree of coupling. However, FIG.
As shown in FIG. 2, the number of rotor poles attached to the rotor 8 here is seven. The arrangement of the stator poles 9 is made up of eight stator poles 9 as in FIG. 6, and the respective stator poles are arranged at equal intervals. In addition,
The manner of winding the primary winding wound on each stator pole 9 and the secondary winding wound on the stator is the same as in the prior art, and therefore the description is omitted. Since there are seven rotor poles as shown in FIG. 2, the degree of magnetic coupling between each of the stator poles 9 and the rotor 8 is the same as that of the prior art. 1 and changes for 7 cycles at a mechanical angle of 360 ° as shown in the top diagram of FIG. Therefore, the position detection value Xmes1 obtained in the same manner as in the related art also has the second waveform from the top in the figure.

On the other hand, the lower two waveforms are waveforms showing a change in the winding inductance and a change in the position detection value Xmes2 when the position of the rotor is detected by using the winding of the motor. As described above, the winding inductance changes with the pitch of the magnetic pole of the rotor as one cycle.
The waveform is as shown at the bottom. The number of magnetic poles of the rotor of the electric motor is 6. Further, the rotor position Xmes2 calculated based on the inductance waveform becomes like the second waveform from the bottom in FIG. 1 by a known technique. As described above, since the number of magnetic poles of the electric rotor is 6, the mechanical angle is 3
The position detection value Xmes2 is six periods between 60 °, while the number of rotor poles of the rotor 8 is seven for the rotor pitch position detection means. Therefore, the position detection value Xmes1 is between 360 ° mechanical angle. There are seven periods.

As described above, for example, the number of rotor poles of the rotor 8 in the rotor pitch position detecting means for detecting the relative position is 7 with respect to the number of magnetic poles 6 of the rotor of the electric motor. If the number does not exist, the position of the rotor within the mechanical angle of 360 ° can be determined from the position detection values Xmes1 and Xmes2. This will be described below. Now, it is assumed that the position of the rotor to be obtained is θx and the position is, for example, as shown in FIG. In this case, assuming that the position detected in Xmes1 is θ1 and the position detected in Xmes2 is θ2, θ1 and θ2 are only the amounts shown in the figure. Here, the cycle of Xmes1 is T1, Xm
Assuming that the cycle of es2 is T2, θx is

## EQU2 ## θx = N1 × T1 + θ1 (2)

## EQU3 ## Two types of expressions can be expressed as follows: θx = N2 × T2 + θ2 (3) Here, in Equation (2), N1 is the number of positions where the period of position detection exists before the period of θx, and N1 = 3 in FIG. Also, N2 in equation (3)
Is the same as N1, and in FIG. 1, N2 = 2
It is. For example, in FIG. 1, T1 = (360/7)
° ≒ 51.4 °, T2 = (360/6) ° = 60 °. Here, the relationship between θ1 and θ2 and N1 and N2 when the mechanical angle is increased from 0 ° is considered. θ
1 and θ2 are both a mechanical angle of 0 ° and N1 = N2 = 0, and are increased while maintaining the mechanical angle = θ1 = θ2.
= T1, the angle returns to θ1 = 0 °, and N1 = 0 is increased by 1 to N1 = 1. When the mechanical angle further increases, this time θ2 = T2
Is returned to θ2 = 0 ° at the point in time, and increases to N2 = 1. By repeating the above, finally N1 = 6, N
In the state of 2 = 5, θ1 = T1, θ2 = T2, and θ1 =
It is continued until it returns to θ2 = 0. FIG. 3 is a diagram illustrating this. In FIG. 3, the horizontal axis is θ1, and the vertical axis is θ2, and T1 and T2 are positions as shown in the figure. In addition, the set of numbers arranged on the upper side and the right side in the figure are the values of N1 and N2. The values of θ1 and θ2 determined in accordance with the above rules are continuously arranged in a solid line in the figure, which is made up of several straight lines. Now, as described above, θ1 and θ2 are obtained by the respective position detections.
Can be determined, if a graph as shown in FIG. 3 is determined in advance, a certain point on the graph can be uniquely determined based on θ1 and θ2. Can be determined up to. That is, in Equations (2) and (3), T1 and T2 are values determined by the number of rotor poles of the rotor 8 of the rotor pitch position detecting means and the number of magnetic poles of the rotor of the electric motor, respectively, as described above. It is possible to have as. In addition, the graph shown in FIG.
When T2 and T2 are determined, the shape of the graph can be uniquely determined. If θ1 and θ2 are detected by storing each point of the graph in advance, a certain point on the graph is determined as described above. can do. By the way, when θx shown in FIG. 1 is obtained, θ1 = θ1
Assuming that 0 and θ2 = θ20, one point on the graph is a point indicated by a circle in FIG. When a certain point on the graph can be determined in this way, which line on a certain graph is a point on the line may be stored simultaneously when each point is stored. While there are several,
Since each graph is a set of points that are constant N1 and N2, the values of N1 and N2 can also be determined. Since T1 and T2 are determined as described above, θx can be obtained from Expression (2) or Expression (3). However, it is preferable to use Equation (2) rather than Equation (3) to determine θx here. This is because the position detection value Xmes2 obtained by using the winding of the electric motor has an error due to noise or the like that is larger than the position detection value Xmes1 by the rotor pitch position detection means, as is known, and performs more precise position detection. That's why.

Further, one point based on θ1 and θ2 detected by the above method because the error of Xmes2 is large,
It is conceivable that the graph does not appear on the graph of FIG. Therefore, as shown in FIG. 4, an error tolerance having a certain width is provided around the graph shown by the solid line. The width of the error allowable range is set in proportion to the number of graphs, and a gap always exists between adjacent error allowable ranges, and the gap is set as an abnormal occurrence range. Therefore,
When θ1 and θ2 detected by the above method are shown as one point on the graph of FIG. 4, if the one point is within the error allowable range, the corresponding N1 and N2 are obtained. If it exists, an abnormality is immediately generated. Various methods can be considered for the processing after the occurrence of the abnormality, such as stopping the motor, stopping the power supply, or using the previous position detection value or the like as a dummy, but the method is not particularly limited here.

By the above processing, the mechanical angle 360 of the rotor
Although the absolute position in ° minutes can be obtained, this processing is executed by the position detection value processing unit 6 in FIG. FIG. 5 is an example of a block diagram showing the processing of the control device when the position is detected using both the rotor pitch position detecting means and the winding of the electric motor. FIG. 9 shows the prior art.
Alternatively, the portions indicated by the same numbers and the same symbols as those in FIG. 10 have the same functions, processes, and the like, and thus description thereof will be omitted. The position detection processing section 6 receives both the position detection value Xmes1 obtained by the rotor pitch position detection means and the position detection value Xmes2 obtained by the magnetic pole pitch position detection means 7, performs the above-described processing, and performs the final position detection value. Ask for Xmes. Other processes are omitted as described above.

The above is the description of the embodiment of the present invention. In the description, various modifications are conceivable with respect to the following matters, and are not limited to those described in the description. Therefore, the present invention is not particularly limited. First, the description has been made on the assumption that the number of magnetic poles of the motor is 6, the number of rotor poles of the rotor 8 of the rotor pitch position detecting means is 7, and the number of stator poles 9 is 8. However, for these numbers, desired position detection is performed, and If there is no common divisor between the number of magnetic poles and the number of rotor poles of the rotor 8 of the rotor pitch position detecting means, the number is not particularly limited. Further, the method of detecting the position using the rotor pitch position detecting means and the windings of the electric motor, and the processing method of the control device are not limited to the methods described in the main text, and it is sufficient if equivalent position detection or control can be performed. This is not particularly the case. Further, the method of determining an allowable error range and matters related to occurrence of an abnormality are not limited to the contents described in the text, and various cases can be considered. In addition, the processing and the realization method of each unit such as the processing of the position detection processing unit 6 are not particularly limited as long as the functions and effects are the same, and various modified examples can be considered.

[0016]

In the motor control device according to the present invention, the number of rotor poles in the position detecting rotor in the rotor pitch position detecting means is set to a value that does not have a common divisor with respect to the number of magnetic poles of the motor, and the rotation of both motors is set. By performing a certain process based on the child position detection value, it is possible to detect the absolute position within one rotation of the electric motor. Therefore, it is not necessary to use a position detector capable of detecting the absolute position within one rotation. However, the same detection accuracy can be achieved with a simple and low-cost structure in which only a simple position detecting means is attached.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a position detection method of the present invention by representing an example of a rotor position detection value in the present invention.

FIG. 2 is a diagram showing an example of a structure of a position detecting rotor and a position detecting stator pole of a rotor pitch position detecting means in the present invention.

FIG. 3 is a diagram illustrating a calculation method of position detection according to the present invention.

FIG. 4 is a diagram illustrating a calculation method of position detection according to the present invention.

FIG. 5 is a block diagram illustrating an example of a process of a control device according to the present invention.

FIG. 6 is a diagram showing an example of a structure of a rotor and a stator pole of a detector according to the related art.

FIG. 7 is a diagram illustrating a magnetic coupling degree and a position detection value in a conventional detector.

FIG. 8 is a cross-sectional view of a rotor in a conventional electric motor having a rotor structure in which the magnetic resistance of the rotor as viewed from the stator side varies depending on the rotational position of the rotor.

FIG. 9 is a block diagram illustrating an example of processing in a conventional control device.

FIG. 10 is a block diagram illustrating an example of processing in a conventional control device.

[Explanation of symbols]

1 first comparator, 2 position loop gain, 3 second comparator, 4 speed loop gain, 5 differentiator, 6 position detection processing unit, 7 magnetic pole pitch position detection means, 8 position detection rotor, 9 position detection stator pole.

Claims (2)

[Claims] 1. A magnetic pole pitch position detecting means for detecting a first rotor position corresponding to a rotor magnetic pole pitch of a motor by measuring a voltage or a current applied to a stator winding of the motor, and a rotor of the motor. And a position detection rotor that rotates synchronously with the rotor. The position detection rotor has a rotor pole equally divided into an integer value having no common divisor with the number of rotor magnetic poles of the electric motor. A rotor pitch position detecting means for electromagnetically detecting a rotor position, and calculating an absolute position within one rotation of the rotor from the first and second rotor positions by the magnetic pole pitch position detecting means and the rotor pitch position detecting means. A rotor position detection device for an electric motor, comprising: 2. The apparatus according to claim 1, wherein said magnetic pole pitch position detecting means and said rotor pitch position detecting means perform a first operation.
When calculating the absolute position within one rotation of the rotor from the second rotor position, a certain error tolerance is provided, and abnormality processing is performed for an absolute position detection value outside the error tolerance. A rotor position detection device for an electric motor, comprising: an absolute position detection processing unit.