JPS59228168A - Detection for speed of linear motor - Google Patents

Abstract

PURPOSE:To detect the speed of a linear motor simply and accurately by measuring either or both of the amplitude ratio and the phase difference of a magnetic field at different two points between a stator and the secondary conductor of the linear motor. CONSTITUTION:A search coil is fixed on a stator core 1 in such a manner that the distance from the secondary conductor 3 on the same vertical surface is positioned at two different points C1 and C2 between the stator core 1 and the second conductor 3. Magnetic fields at two points C1 and C2 are measured with the search coil and the output voltage of the search coil is converted into a digital signal indicating the amplitude ratio or the phase difference of the magnetic fields at the two points C1 and C2 with a proper A/D converter. The digital signal is inputted into a computer to determine the running speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for detecting the speed of a linear induction motor used as a drive source for a floating railway system and other various transportation systems.

[Prior art]

Conventionally, the running speed of a linear motor car that uses a linear motor as its drive source has been determined by installing optical or wireless detecting objects or objects at equal intervals along the track of the linear motor car installed on the ground. Detection is performed by counting the number of objects to be detected or objects to be detected that the linear motor car passes per unit time when the motor car is guided by the track section and travels.

However, this conventional speed detection method requires ground equipment as described above and on-board equipment for counting the ground equipment, which makes the speed detection device complicated and increases manufacturing costs. Disadvantages: Company owned.

In addition, when the body of a linear motor car is supported on the track by wheels, etc., the speed of the linear motor can be detected by measuring the number of rotations of the wheels. However, it has the disadvantage that it cannot be used with linear motor cars whose bodies are suspended above the track due to magnetic force or the like.

[Purpose of the invention]

An object of the present invention is to provide a method that can easily and reliably detect the speed of a linear motor even in a floating linear motor car by eliminating the above-mentioned drawbacks of the conventional method for detecting the speed of a linear motor.

[Key points of the invention]

The present invention attempts to detect the speed of a linear motor by measuring either or both of the amplitude ratio and phase difference of magnetic fields at two different points between the stator and the secondary conductor of the linear motor. It is.

[Structure of the invention]

Below, the configuration of the present invention will be explained along with examples and drawings.

In Figures 1 and 2, reference numeral 1 denotes a stator core of a single-sided linear motor, and the stator core 1, which is elongated and flat along the running direction, has a plurality of grooves perpendicular to the running direction. The stator is formed by winding the conductive wire 2 of the primary coil of the 18 linear motor around the stator iron core 1 along these grooves. Further, 3 is a secondary conductor of the linear motor, which is located parallel to the stator core 1.

The stator 1 of the linear motor having such a structure is
The secondary conductor 3 is attached to the bottom of the vehicle body of a linear motor car (not shown), and the secondary conductor 3 is attached to the track section 4 of the linear motor car.
A flotation facility (not shown) installed above gives the car body buoyancy that balances the weight of the car body, and the stator core 1
A propulsion force is applied from the secondary conductor 3 in, for example, the left direction in FIG. 2, and the body of the linear motor car travels with the track section 4 also floating.

In Figure 2, the reverse running direction parallel to the secondary conductor 3 is
The upper direction of FIG. 2, which is perpendicular to the secondary conductor 3, is taken as the positive direction of the y-axis, and y=o on the upper surface of the secondary conductor 3, and the stator iron core ■ At the bottom of y=g(g
is a constant).

In addition, if the traveling direction of the current wave in the stator iron core 1 is in the X direction, the stator iron core 1 moves at a speed V in the −X direction with respect to the secondary conductor 3, and the magnetic permeability is infinite, the thickness of the secondary conductor 3 is zero, and the surface conductivity of the secondary conductor 3 is σt.

Furthermore, it is assumed that the magnetic field does not change in the direction perpendicular to the xy plane, and the magnetomotive force exists as a surface current flowing in the direction perpendicular to the xy plane at the y-g position.

Then, the magnetic field (Hx H7) in the atmosphere between the stator iron core 1 and the secondary conductor 3 is expressed as follows. Here, A and B are complex constants.

From the boundary condition at y=Q, the following holds true between A and B. Here, ■8 is the synchronous speed, and μO is the magnetic permeability in the atmosphere.

Therefore, by measuring the magnetic field (Hx Hy ), the equation
By calculating 5A and B and substituting them into equation (2), the traveling speed V can be detected.

Next, an embodiment of the present invention for detecting speed as described above will be described.

First, in equation (2), since (A+B)/(A-B) is a purely imaginary number, IAI = IB+ holds true, and A.

B It can be expressed as Here, a is a real number.

From formulas ■, ■, ■, the X coordinates are equal to each other and 3""3
The y component of the magnetic field at two points C, , C2, which is 'l,y-y2, is expressed as follows. However, exp(j(ωx−kx)) is omitted.

From the formulas ■ and ■, eXP(jp)1exp(jq) is -
It is expressed as However, here, hl”Hy(71 meja, b2=Hy(7z)/j
a e) P=exp(2ky1)-exp
(2ky2), Q=exp(-2ky+)-exp(-
2kyz).

Therefore, from the formulas ■, ■, ■, A+B aexp(jp) + aexp(jq)A
-B aexp(jp) -aexp(jq) holds true. However, here, P(EQexp(kyl) −Pexp(−kyl)P
2 E Qexp(kyl) -Pexp('to 3'
2) QIE Qexp(kyl) + Pexp(
−kyl)(4=Qexp(kyl)+Pexp
(-kyl) From equation O, IP+h+ -P2h21 1Q+h+ -Q2h21 holds true. However, here it is assumed that h+=Ih+IZdato h2=Ihzltda2.

According to equations (2) and (2), the traveling speed can be calculated by detecting the amplitude ratio and phase difference of the magnetic fields at the two points C1 and C2.

Figure 3 shows 1■1y(
The results of a computer experiment to determine the changes in yl)/■y(72 months and 1ψ1−ψ21) are shown.

In this computer experiment, each numerical value is k -112,2m-', f = 60I (Z, v
s = 2 f/ = 3.36 m/e, μo = 4πX
100-7k1σt= 3.7X101J-g= 0
．． 003myl=0. oo1m, y2=o, 00
It was set to 2m.

From Figure 3, the magnetic field l-17(y,) at two points CI and C2,
Amplitude ratio 1Hy of H3'(3'z) (yt column y (y2)
l and the phase difference 1ψ1-ψ21 are the speed ratio IV/vS
1, it can be seen that the amount of change is monotonous and has a sufficiently distinguishable magnitude.

Therefore, conversely, the traveling speed V can be detected by measuring the amplitude ratio or phase difference of the magnetic fields at the two points C1 and C2.

To implement the above speed detection method, the search coil is
The search coil is fixed to the stator core 1 so as to be located at two points C1 and C2 at different distances from the secondary conductor 3 on the same vertical plane between the stator core 1 and the secondary conductor 3. The magnetic fields at the two points C1 and C2 are measured, and an appropriate A/D converter is used to convert the output voltage of the search coil into a digital signal indicating the amplitude ratio or phase difference of the magnetic fields at the two points C1 and C2.

Next, using a storage device that stores in advance the relationship between the running speed and the amplitude ratio of the magnetic field or the relationship between the running speed and the phase difference of the magnetic field shown in FIG. Just convert it to speed.

Also, input the above digital signal to the computer,
The traveling speed may be determined by performing calculations as described above.

Note that when the linear motor is coasting, no magnetic field acts between the stator iron core 1 and the secondary conductor 3, but the stator iron is If a weak magnetic field is applied between the core 1 and the secondary conductor 3 and this magnetic field is measured,
Speed detection is possible even while coasting.

〔Effect of the invention〕

As detailed above, according to the present invention, the magnetic field acting between the primary coil and the secondary conductor of the linear motor is
The running speed is detected by measuring with a search coil etc. attached to the moving object driven by the linear motor.
Even in a floating moving system, it is possible to provide a speed detection method that can detect the running speed simply and at low cost using only equipment on the moving body.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the structure of a linear motor, Figure 2 is a sectional view of Figure 1, and Figure 3 is the amplitude ratio IHy (yθ/''V) of the magnetic field at two points CI and C2 in Figure 2. (72) l and phase difference 1ψ1−ψ21 and running speed ratio I V/■8+
FIG. 1. Stake iron core, 2. - secondary coil conductor, 3.
...Secondary side conductor patent applicant Sumitomo Electric Industries Co., Ltd. Patent attorney Aoyama Shugai 1 master craftsman\ Figure 2 0 Figure 3 V/Vs

Claims (1)

[Claims] (1) Between the primary coil and secondary conductor of a linear motor, the amplitude ratio of the magnetic fields at two points on a plane perpendicular to the running direction of the linear motor and at different distances from the secondary conductor. Alternatively, a speed detection method is characterized in that the running speed of a linear motor is detected from one or both values of the phase difference.