JP2000105133A - Position detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detecting apparatus whose accuracy is practically sufficient. SOLUTION: A position detecting apparatus is composed of a stator which contains an exciting winding and an output winding. In addition, it is composed of a stator which contains a core only having N pieces as integral numbers of salient poles equal to the sum or the difference of the number of pole pairs of the exciting winding and the output winding and which does not contain a winding. An output signal which expresses the position of the angle of rotation of the rotor is obtained from the output winding. In the position detecting apparatus, a conversion means 40 which converts the output signal into a digital signal is provided, and a correction means 50 which receives the digital signal, which corrects a position error generated due to the shape of the rotor and which outputs a digital position signal is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device widely used for a machine device requiring positioning of a machine tool, a robot, an FA device, and the like. And a position detection device employed for a position sensor for measuring the water level of a dam.

[0002]

2. Description of the Related Art A rotary encoder and a resolver are known as position detecting devices widely used in conventional mechanical devices requiring positioning. Of these, rotary encoders that use light are mainly used, but this rotary encoder has a problem that an error occurs when used in a place where environmental conditions are poor.

[0003] On the other hand, the resolver uses a slip ring or a rotary transformer to supply current to the excitation winding of the rotor, but the former has a problem in maintenance, and the latter has a complicated structure and is expensive. Problem.

In order to solve this problem, an exciting winding and an output winding are provided on a stator, and a rotor is not provided with a winding.
An R-type resolver is known, but has not been put to practical use due to a problem in accuracy.

One of the present inventors has previously proposed in Japanese Patent No. 2698013 a position detecting device using a VR-type resolver having sufficient practical accuracy and a simple structure.

In general, the resolver modulates the amplitude of an AC voltage of a power supply frequency (carrier wave sinωt) according to an input rotation angle θ and sends out the signal as a trigonometric function output signal (AC voltage) of the rotation angle θ. This output voltage is a two-phase trigonometric function with respect to the rotation angle θ as shown in FIG.

As shown in FIG. 10, an R / D converter (resolver-to-digital converter) 40 converts an AC voltage (analog amount) representing rotation angle θ information of the resolver 30 into a binary digital amount. Calling. Further, in the combination system of the resolver 30 and the R / D converter 40 connected to the power supply 20 shown in FIG. 10, the resolver 30 converts an input rotation angle into an analog voltage, and converts the rotation angle of the input into an analog voltage. And the other R / D converter 40
Is a static converter for converting the electric signal converted by the resolver 30 into a digital signal again.

The output data of the R / D converter 40 is
The data can be output to a computer in the same manner as the data of the ordinary A / D converter 40.

[0009]

In the resolver proposed in the above patent, the excitation winding is single-phase and the output winding is two-phase.
In the case of a phase, the voltage induced in the output winding is sin which changes by 2π when the rotor moves 1 / N of the entire circumference.
The position is detected using the wave voltage and the cos wave voltage. In this case, the cause of the position detection error is the harmonic component included in the induced voltage waveform of the output winding.However, since the variation due to the rotor position of the gap permeance due to the salient pole is used, the harmonic component is used. The shape of the salient pole of the rotor has the greatest influence on the wave component.

Therefore, the rotor shape is such that the harmonic components are minimized. The logic derived from this shape is developed under the assumption that the magnetic flux lines pass in the radial direction. The permeance coefficient may include a harmonic component.

Therefore, there is a disadvantage that a practical rotor shape includes some errors. This error is not removed by digital conversion through the A / D converter 40.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a position detecting device which can easily remove an error in a digital signal of a position caused by the shape of a rotor.

It is another object of the present invention to provide a position detecting device which has a simple structure, requires no maintenance, and can detect a position with sufficient accuracy for practical use.

[0014]

According to the present invention, a stator in which excitation windings and output windings having different numbers of pole pairs are accommodated in slots provided in an iron core, the excitation windings and the output windings are provided. A rotor having no winding with only an integer N salient poles equal to the sum or difference of the number of pole pairs, and when the excitation winding is single-phase, the output winding is two-phase or three-phase. Wherein the output winding is single-phase when the excitation winding is two-phase, and a position detection device that obtains an output signal indicating the rotation angle position of the rotor from the output winding, wherein the output signal is digitally output. A converter for receiving the digital signal, correcting a position error caused by the shape of the rotor, and outputting a corrected digital position signal. A position detecting device is obtained.

Further, according to the present invention, a stator in which exciting windings and output windings having different numbers of pole pairs are accommodated in slots provided in an iron core, and a stator having the same number of pole pairs as the exciting windings and the output windings. A rotor having no winding with only an integer N cores of salient poles equal to the sum or difference, and taking the center of the salient poles of the rotor as an origin, a spatial angle representing the position of the rotor circumference is defined as When θ ₂ , the minimum air gap length at the center of the salient pole is δ ₁
And then, when k takes a value between 1 and 2, the air gap length in the position of the theta ₂ is, kδ ₁ / {1+ (k-
1) a rotor having cos (Nθ ₂ )｝, wherein the output winding is two-phase or three-phase when the excitation winding is single-phase, and the output winding is two-phase or three-phase when the excitation winding is two-phase The line is single-phase, and in a position detection device that obtains an output signal representing the rotation angle position of the rotor from the output winding, a conversion unit that converts the output signal into a digital signal, and receives the digital signal, Correct the position error caused by the shape of the rotor,
And a correcting means for outputting a corrected digital position signal.

[0016]

In the position detecting device according to the present invention, the exciting winding and the output winding have different numbers of poles, all of which are housed in slots of the stator core, the number of pole pairs of the exciting winding is p ₁ , and the output winding is p. of pole pairs as p _2, the rotor is constructed without the windings in core having N salient poles. That is, p ₁ + p ₂
= N or p ₁ −p ₂ = ± N, when the excitation winding is single-phase and the output winding is two-phase or three-phase, the movement of 1 / N of the entire circumference of the rotor is A two-phase or three-phase sine wave voltage having one cycle is induced in the output winding.

When the excitation winding has two phases and the output winding has a single phase, the voltage induced in the output winding changes by 2π when the rotor moves 1 / N of the entire circumference. It becomes a sine wave voltage.

In any case, the cause of the position detection error is a harmonic component contained in the induced voltage waveform of the output winding. This varies with the position of the rotor, but is constant with the shape of the rotor. Find this error in advance,
The correction data is stored in a correction table.

The analog position detection signal from the output winding is converted into a digital signal, and this digital signal is corrected by the correction data in the correction table to obtain a digital signal indicating a correct position.

[0020]

FIG. 1 shows an embodiment of a position detecting device according to the present invention. Note that the same parts as those of the conventional position detecting device shown in FIG.

Referring to FIG. 1, a position detecting device according to an embodiment has a resolver 30 supplied with power from a power supply 20 and an R / D converter 40 for converting the output of the resolver 30 into digital signals. A correction processing circuit 50 for correcting the output signal after the conversion by the R / D converter 40 is provided.

The correction processing circuit 50 stores correction data (function)
And a correction processing circuit 50B comprising an arithmetic circuit for correcting a digital signal input thereto based on the correction data of the correction table 50A.
Note that the correction processing circuit 50B can be realized by a microcomputer or a personal computer.

As described above, the output signal of the R / D converter 40 usually includes error components Δε and Δα, and θ + Δε +
Δα is a digital signal.

The error component Δε is caused by a shape error of the rotor 10 and is a fixed error component.
The correction data is stored in 0A.

On the other hand, since the error component Δα is an error generated due to a problem in manufacturing the resolver 30, it is not a problem in accuracy as a very small component. Accordingly, the error component Δα can be regarded as substantially zero, and is ignored here.

In this position detecting device, the correction table 50
A function table is created in advance as correction data in A, and R / D
By providing a correction processing circuit 50 having this correction table 50A after the converter 40, the error component Δε is corrected, and the final output signal is made as close as possible to an ideal digital output.

Next, a specific structure of the resolver 30 will be described with reference to FIGS.

FIG. 2 shows a rotor 10 and a stator 1 which are iron cores.
1 is shown. In the stator 11, slots 11a are formed at equal intervals on the entire inner circumference thereof.
only a portion of a is shown), this slot 11a, the output winding of the excitation winding and pole pairs p ₂ of pole pairs p ₁ to be described later is housed. The rotor 10 has N
The number of salient poles 10a is formed, and between the number of pole pairs p ₁ and p ₂ and the number N of salient poles (rotor salient poles) 10a, p ₁ + p ₂ = N (1) or p ₁ −p ₂ = ± N (2)

In this case, assuming that the excitation winding has a single phase and the output winding has two or three phases, the output winding has a sinusoidal waveform with 1 / N movement of the entire circumference of the rotor as one cycle. To obtain a two-phase or three-phase voltage whose amplitude changes.

[0030] Incidentally, in FIG. 2, theta ₁ is a coordinates set on the stator 11, _.theta.2 is the spatial angle representing the position of the rotor 10. Further, in FIG. 2, as the origin the center of the entire coil theta ₁ is constituting the excitation winding of one pole, the coordinates indicated by the spatial angle of any point circumferential inside the stator, _.theta.2 is the t = 0 instant a coordinates fixed to the rotor a central rotor salient pole as the origin in the position closest to the theta ₁ origin expressed by spatial angle.

If the excitation winding has two phases and the output winding has a single phase, a sine wave voltage whose phase changes by 2π when the rotor 10 moves 1 / N of the entire circumference can be obtained. These voltages become output signals indicating the rotational angle position.

However, when the induced voltage of the output winding is not a perfect sine wave but contains a harmonic component, which causes an error, it is necessary to minimize the harmonic component. For this reason, one method is to use a winding that makes the third harmonic zero. When the output winding has three phases, no harmonic component of an integral multiple of three is induced in the terminal voltage. Even in the case of a single-phase or two-phase winding, two-phase windings of a three-phase winding are connected by a U-phase winding 12 and a V-phase winding 13 as shown in FIG. If used as a winding, no harmonic component that is an integral multiple of 3 is induced, as in the case of a three-phase winding. Also, if this winding is used as the exciting winding, the magnetomotive force generated by the exciting current does not include harmonics that are integral multiples of three.

On the other hand, one of the present inventors considers that the shape of the salient poles 10a of the rotor 10 has a large effect on the harmonic components of the induced voltage of the output winding, and thus minimizes the salient pole components. It has been clarified in the patent that the shape of the pole 10a may be expressed by the following equation (3).

R _θ2 = R ₁ −kδ ₁ / {1+ (k−1) cos (Nθ ₂ )} (3) FIG. 4 shows an example of the shape of the salient pole 10a when N = 4.
Particularly, an example of the salient pole 10a for reducing harmful harmonic components is shown.

Here, R _θ2 is the distance between the outer circumference and the center of the rotor core at the space angle θ ₂ , R ₁ is the radius of the inner circumference of the stator core, and δ ₁ is the minimum gap length. Therefore, determined the value of the dimensions and k in [delta] _1, the outer peripheral shape of the rotor 10, that is, to determine the salient poles 10a shape.

Incidentally, since the shape shown in the expression (3) is developed under the assumption that the magnetic flux lines pass in the radial direction, the magnetic flux density obtained by the rotor shape obtained by the expression (3) is It may contain harmonic components. here,
In particular, a case where N = 1 where accuracy is a problem will be described.

Now, the model of the stator 11 shown in FIG. 5 will be described as an example. The number of slots of the stator 11 is Z ₁ = 12
As shown in FIGS. 6 and 7, the output windings 11c and 11d are two-phase two-phase windings and the exciting windings 11b.
Is a 4-pole single-phase winding. As described above, the exciting winding 11b is a winding that does not generate a harmonic component that is an integral multiple of three.

In this structure, when a current having an angular frequency ω flows through the exciting winding 11b, the output windings 11c and 11c
The voltage induced in d is given by equation (4) of equation (1) and equation (5) of equation (2).

[0039]

(Equation 1)

(Equation 2)

This is described in Japanese Patent No. 2698013. Here, θ is the coordinate of θ ₁ indicating the position where the air gap length is minimum. Γ is the rotor 10
Represents the order of the pulsation of the gap permeance due to the shape of. In this case, an effective component actually used for position detection is a component corresponding to γ = −1, and a component having an absolute value of γ of 2 or more is caused by the rotor shape. In order to achieve this, it is considered to minimize this by using the shape shown in the above formula (3), but even with this shape, some components remain and cause errors.

For example, in the iron core shape of the model example shown in FIG. 5, when δ ₁ = 0.4 [mm] and k = 1.6, an error caused by the shape of the rotor 10 is as shown in FIG. become. It has been verified that this is almost the same if the rotor 10 has the same shape.

Accordingly, the correct rotation angle θ can be obtained by correcting the output of the R / D converter 40 by the error Δε (θ) in the correction processing circuit 50B.

The angle θ is obtained by precision measurement using a high precision encoder directly connected to the resolver, and Δε (θ) = E (θ) −θ is obtained from the output E (θ) of the R / D converter 40. A correction table for the output E (θ) and Δε (θ) is created as a correction table 50A.

[0044]

As described above, according to the position detecting device of the present invention, by providing a correction circuit having a correction table prepared in advance after the R / D converter, errors caused by the shape of the rotor can be reduced. By compensating, the final output signal will be as close as possible to the ideal digital output,
Correct position detection can be easily performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system in an embodiment of a position detecting device according to the present invention.

FIG. 2 is a sectional view of an iron core for explaining the principle of the position detecting device of the present invention.

FIG. 3 is an explanatory diagram showing an example of a winding configuration of the position detection device of the present invention.

FIG. 4 is a cross-sectional view of a rotor showing an example of the shape of a salient pole for reducing harmful harmonic components in the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of the position detection device of the present invention when N = 1.

FIG. 6 is a development view of a stator core showing an example of a winding arrangement in a slot when N = 1 in the position detection device of the present invention.

FIG. 7 is an explanatory diagram showing an example of the shape and arrangement of windings when N = 1 in the position detecting device of the present invention.

FIG. 8 is a graph showing a relationship between an error component of an output caused by a shape of a rotor of the present invention and a rotation angle.

FIG. 9 is a graph showing a relationship between an output voltage of a resolver and a rotation angle in a conventional position detection device.

FIG. 10 is a block diagram showing a digital processing system in a conventional position detecting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotor 10a Salient pole 11 Stator 11a Slot 11b Excitation winding 11c, 11d Output winding 12 U-phase winding 13 V-phase winding 20 Power supply 30 Resolver 40 R / D converter 50 Correction circuit 50A Correction table 50B Correction processing circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA35 BA21 BA22 BA24 BC04 BD16 CA40 CB20 CC01 DA01 DA24 DB07 EA20 GA22 LA20 LA23 LA29 2F077 AA20 FF34 PP26 TT06 TT38 TT66 VV01

Claims (2)

[Claims] 1. A stator in which exciting windings and output windings having different numbers of pole pairs are accommodated in slots provided in an iron core, and equal to the sum or difference of the number of pole pairs between the exciting windings and the output windings. A rotor having only an integral number of N salient poles and no winding, wherein the output winding is two-phase or three-phase when the excitation winding is single-phase, and the excitation winding is two-phase. When the output winding is a single phase, in a position detection device that obtains an output signal representing the rotational angle position of the rotor from the output winding, a conversion unit that converts the output signal into a digital signal; A position detecting device for receiving a signal, correcting a position error caused by the shape of the rotor, and outputting a corrected digital position signal. 2. A stator in which excitation windings and output windings having different numbers of pole pairs are accommodated in slots provided in an iron core, and an integer equal to the sum or difference of the number of pole pairs between the excitation windings and the output windings. When the rotor is composed of a rotor having no windings with only N cores of salient poles and the center of the salient poles of the rotor as an origin, and a spatial angle representing the position of the rotor circumference as θ ₂ , When the minimum air gap length at the center of the salient pole is δ ₁ and k takes a value between 1 and 2, the air gap length at the position of θ ₂ is k δ ₁ / ｛1+ (k−1). cos (Nθ ₂ )}, wherein the output winding is two-phase or three-phase when the excitation winding is single-phase, and the output winding is two-phase or three-phase when the excitation winding is two-phase. A position detection device that is single-phase and obtains an output signal representing the rotational angle position of the rotor from the output winding, And a correction unit that receives the digital signal, corrects a position error caused by the shape of the rotor, and outputs a corrected digital position signal. Position detection device.