JPH0625641B2 - Magnetic detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to position detection required to stop various transport vehicles such as elevators at predetermined positions with high accuracy and smoothly.
Alternatively, the present invention relates to a magnetic detector used for guiding an automatic guided vehicle.

[Conventional technology]

Normally, for positioning stop of the transport vehicle, various proximity switches are used to detect the stop point and before stop, and decelerate and stop. As another method, there is proposed a method using a multiple magnetic detection switch that detects a magnet plate placed at a stop point and produces an output that changes stepwise before and after the stop point (Japanese Patent Application No. 59-241738). reference).

In addition, there are two methods for guiding an automated guided vehicle: an electromagnetic induction method that uses an electric wire buried in the floor and a detection coil on the vehicle, and an optical method that detects a white tape attached to the floor with an optical sensor. As another method, a magnetic guide method has been attempted in which a belt-shaped rubber magnet is attached on the floor and the position of the rubber magnet is detected by the multiple magnetic detection switch to perform steering control (see the above application).

[Problems to be solved by the invention]

The above-mentioned multiple magnetic detection switch has a slight problem in continuous servo control because the control voltage is stepped.
Dozens of magnetic detection switches are required to cover a wide area of up to millimeters, which has a drawback that the circuit is complicated and expensive.

Non-contact potentiometers have already been made by combining a magnetizer and a magnetic detector, but the conventional method not only requires the magnetizer to be provided over the entire change range of the potentiometer, but also a linear magnetometer. In order to generate an output, it is necessary to change the magnetic strength of the magnetized body depending on the location, which is not suitable for a detector for guiding an unmanned vehicle.

The present invention seeks to obtain a positioning magnetic detector that produces a linear output voltage over a change range that is wider than the width of the magnetic body in the displacement direction.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention linearly arranges at least four saturable coils whose inductance is changed by magnetism, or an even number of saturable coils, at intervals substantially equal to or greater than the width of the magnetizer. , And each of these saturable coils is divided into two groups and connected in series in each group,
A high frequency voltage is supplied to each set of saturable coils from a high frequency oscillator through a resistor, the voltage generated in each resistor is rectified by a diode or the like, and the output voltage is taken out differentially.

[Action]

For example, when the magnetizing body comes close to, for example, four saturable coils (multiple magnetic sensors) arranged in a line, the core is saturated and the voltage on the output side of the diode connected to the core rises. Since the coil spacing is set to be larger than the width of the magnetic body, a mountain-shaped voltage is generated each time the magnetic body passes in front of each coil, and
A voltage of (+) is generated from the coil of the second set, and a voltage of (−) is generated from the coil of the second set. The magnitude of the voltage is related to the number of turns of each coil, and the position where the peak appears is determined by the position of the coil.
By appropriately selecting the number of turns and the position of the coil, for example,
By making the detection sensitivity of the outer two saturable coils out of the four saturable coils higher than that of the remaining two inner saturable coils, the linearity over a range wider than the width of the magnetizer. An output voltage having a large slope can be obtained.

〔Example〕

FIG. 1 is a circuit diagram showing a basic embodiment of the present invention.
In the figure, L ₁ , L ₂ , L ₃ , and L ₄ are saturable coils that form a multiple magnetic sensor, and windings are applied to an I-shaped permalloy core, and the magnetic detection sensitivity depends on the thickness and shape of the core. Will change. In this example, height 5 mm width 4 mm thickness 0.05
Millimeter permalloy cores with 200 and 100 turns are used. In FIG. 1, L ₁ and L ₂ are wound 200 times, and L ₃ and L ₄ are wound 100 times. The OSC is a high frequency (for example, 50 kH ₂ ) oscillator, and its pulse width is, for example, 1 μs. R _S is the series resistance (eg 300Ω), D ₁ and D ₂
Is a diode, R ₁ and R ₂ are output resistances, C ₁ , C ₂ and C ₃ are smoothing capacitors, and M is a magnetizer.

In this embodiment, a rubber magnet having a width (moving direction) w of 50 mm and a thickness of 0.8 mm is used as the magnetic body. In the case of an automated guided vehicle guide, the magnetized body has a length of several tens of meters in the longitudinal direction, but in the experiment, a length of 100 mm was used.

FIG. 3 shows the principle of the present invention, and therefore L in FIG.
₃ and L ₄ coils are omitted, only L ₁ and L ₂ 2 coils are provided, and the output voltage curve diagram when the distance l between L ₁ and L ₂ is changed to 60,100,140,180 mm. It shows the output voltage when the magnetism generator M is moved in the width w direction while keeping the interval at 30 mm (constant value).

According to FIG. 3, when the distance l is 60 mm, the output voltage is 40
In the millimeter section, it changes with a linear slope, and the distance between the peak and the valley is
60 mm equals 1 When l is 100 mm, the section of 70 mm has an almost straight slope, but a slight bend is observed in the central part.

When l = 140 mm and l = 180 mm, the output voltage is completely divided into a (+) side peak and a (−) side peak, and the central portion is extremely non-linear. However, the distance between them and the mountains is
In all cases it is equal to l.

The magnitude of the output voltage is related to the magnitude of the distance d between the magnet M and the magnetic sensor of the detector. In the embodiment, the peak value of the output voltage is ± 3 V when d = 30 mm. At this time,
The magnetic field at a distance of 30 mm in front of the magnet M was 8 gauss. From this, it can be seen that the magnetic detector of the example has a very high sensitivity.

When the linear change region is up to about 1.5 times the width w of the magnet M, L ₁ ,
The target magnetic detector can be obtained by appropriately arranging the two saturable coils of L ₂ , but when a linear change range is required over a wider range, as shown in FIG. It is necessary to place L ₃ and L ₄ between L ₁ and L ₂ to correct the bend at the center of the output voltage curve.

FIG. 4 shows the principle. In FIG. 4, V ₁ and V ₂ are curves of l = 180 which are diverted from FIG.
The output voltage produced by the L ₁ and L ₂ coils spaced 180 mm apart is shown. V ₃ and V ₄ represent the voltages generated based on the coils L ₃ and L ₄ placed at 90 mm intervals between L ₁ and L ₂ , respectively. The windings of L ₃ and L ₄ are wound so as to reduce the output voltage by half. V ₁ , V ₂ ,
The combined voltage curve obtained by superposing the voltages of the V ₃ and V ₄ curves is an output voltage curve as a magnetic detector, and is linear over a fairly wide range.

Similarly, by increasing the number of saturable coils, a magnetic detector that produces a linear output voltage over a wider range can be obtained.

Fig. 2 shows L ₁ , L ₂ , L ₃ and L ₄ 4 saturable coils as shown in the circuit of Fig. ₁ with L sat at ± 45 mm from the center.
₃ and L ₄ show the output voltage when L ₁ and L ₂ are placed at ± 90 mm. From this figure, if the distance d between the magnet M and the magnetic sensor of the detector is 30 mm or more,
It can be seen that it shows a linear change over the range of 150 mm. When the carrier travels over a wide range, the magnetic detector of the present invention can detect only a limited range.
In general, in addition to the analog output required for control within a limited range, an ON / OFF section signal indicating this controllable section is required. FIG. 2 also shows a section signal generated by a magnetic switch incorporated with a magnetic detector that produces an analog output on the transport vehicle.

FIG. 5 shows an example of a magnetic switch circuit for generating a section signal. In the figure, K ₁ , K ₂ , ..., K ₆ are saturable coils serving as a sensor of a magnetic switch, and windings are formed on an I-shaped permalloy core, and the magnetic switch sensitivity changes depending on the core thickness and shape. . In this example, a permalloy core having a height of 5 mm, a width of 4 mm, and a thickness of 0.03 mm was wound 200 times. This is almost the same as L ₁ and L _{2 in} FIG. ₁ , but differs only in thickness. OSC is a high frequency (eg 5
00kH ₂ ) Oscillator, R _S is a series resistance, S ₁ , S ₂ , ...
S ₆ is a magnetic switch, and AMP is an amplifier with an OR gate. In this embodiment, the saturable coils K ₁ , K ₂ , ..., K ₆ are arranged on the same line as the saturable coils L ₁ , L ₂ , L ₃ and L ₄ for the magnetic detector that outputs an analog output.
The distance between ₁ , K ₂ , ... K ₆ is about 30 mm. This interval is selected to be narrower than the width of the magnet M (50 mm in this case).

FIG. 6A shows the output voltage of each of the magnetic switches S _{1 to} S ₆ , and when the magnetizing body M comes to the front surface of the saturable coil K ₁ , S ₁ is turned on, and as the M moves, S is sequentially applied. ₂ , ...
·, _{S 6} is turned on. AMP is a magnetic switch S ₁ ~
S ₆ is turned on over the whole section to be operated, and outputs a period signal as shown in FIG. 6 (b). A magnetic switch using one saturable coil operates only in a range covered by the magnetic field of the magnet M, but as described above, by arranging a large number of magnetic switches at appropriate intervals and collecting outputs with an OR circuit, It is possible to obtain a section detection circuit which operates in an arbitrary range wider than the width of the magnetic body. The example shown in FIG. 5 has six magnetic switches and is designed to operate in a 180 mm section.

〔Example of use〕

 Next, preferred applications of the present invention will be described.

FIG. 7 is a plan view showing an example in which the present invention is used to control a stacker crane used in an automatic warehouse. In the figure, a magnetizing body M is attached to a part of the shelf. A rubber magnet having a width of 50 mm, a length of 100 mm, and a thickness of 1.6 mm was used as the magnetism generating body. For an unmanned vehicle moving on a rail, the magnetic detector of the present invention is attached to the side surface that can approach the magnetic generator M, and high-sensitivity magnetic proximity switches SW ₁ and SW ₂ are provided at positions 300 mm before and after the detector. It is provided. When the unmanned vehicle moves, for example, from the top to the bottom of the drawing, the magnetic proximity switch SW ₁ is _first felt by the magnet M and turned on, and then deceleration is started to stop. After traveling about 300 mm, the section signal of the detector turns on, and the unmanned vehicle is stopped at the stop point where the detector output becomes zero by analog control. The distance between the magnet and the detector, SW ₁ and SW ₂ is 50 mm, which is sufficient for operation even if the unmanned vehicle shakes. In addition, since the analog control section for stopping is ± 90 mm, it is possible to smoothly stop by continuous deceleration.

The magnetic detector according to the present invention is extremely effective not only for stacker cranes but also for servo control for stopping an elevator or an automated guided vehicle traveling on the floor at a fixed position.

FIG. 8 is a plan view showing an example in which the present invention is used for trajectory control of an automated guided vehicle. The figure shows a width of 50 mm on the floor and a thickness.
A case in which a 0.8 mm belt-shaped rubber magnet is attached and movement of an unmanned vehicle is controlled along the magnetic belt is shown. Although the unmanned vehicle includes a vehicle drive unit and a control unit, only detectors for track position detection and stop control are shown in the figure.

The orbital detector is mounted on the unmanned vehicle 30 mm away from the floor and perpendicular to the magnetic belt. If the unmanned vehicle is correctly on the magnetic belt, the analog output voltage of the detector will be 0 voltage at the center position, and when the vehicle is displaced to the right or left, the detector will be proportional to the amount of detachment (+) or (- A) voltage is generated. The analog output voltage of the detector is supplied to the vehicle controller, and the vehicle can be correctly moved on the track by servo control.
If the vehicle is orbited and deviates by more than ± 90 mm for some reason, the section signal of the section detection circuit built into the detector turns off and an alarm is issued.

Since both the detector and the section detection circuit operate the saturable coil with a high frequency voltage, the response speed is fast and the maximum response frequency is 4 kHz or more.

〔The invention's effect〕

As described above, according to the present invention, for example, as shown in FIGS. 1 and 4, a plate-shaped or belt-shaped magnetized body (M) having a constant width (w) and this magnetized body (M). ), A saturable coil group (L) arranged at a constant distance (d) from the surface (front surface or back surface) and relatively displaced in the width (w) direction of the magnetic body (M). _{1 to} L ₄ ), an oscillator (OSC) that supplies a high frequency voltage to the saturable coil group (L _{1 to} L ₄ ) via a resistor (R _S ), and each resistor (R 1).
Differential output extracting means (D ₁ , D ₂ , R ₁ , R ₂ , C ₁ , C) for rectifying the voltage generated in _S ) to extract a differential output voltage.
₂ , C ₃ ) and a saturable coil group (L _{1 to} L ₄ ).
Is a 2 (1 + n) saturable coil, where n is a natural number, and these 2 (1 + n) saturable coils are arranged on a straight line parallel to the width (w) direction of the magnet body (M). And the saturable coil groups (L ₃ , L ₁ ) (L ₃ ) each on the left and right with respect to the width (w) direction of the magnetic body (M).
₄ , L ₂ ) and each saturable coil of each saturable coil group of each group is connected in series from the inner side to the outer side, and each saturable coil group of each group connected in series ( L ₃ and L ₁ ) (L ₄ and L ₂ ) respectively have resistance (R _S ).
The high frequency voltage is supplied from the oscillator (OSC) via
In addition, each saturable coil forming each of the (1 + n) saturable coil groups is connected to the outer saturable coil {(L ₃ ) from the inner saturable coil (L ₃ ) (L ₄ ) ((L ₃ )). L ₁ ), (L ₄ ) are symmetrically configured so that the detection sensitivity is sequentially increased toward (L ₂ )}, and the differential output extracting means (D ₁ , D ₂ , R ₁ , R ₂ , C ₁ ,
When trying to make the differential output voltage from C ₂ , C ₃ ) into a linear section with an interval equal to or greater than the width (w) of the magnetizer (M), first, the above-mentioned two sets (1 + n) of each One saturable coil (L ₁ ) (L ₂ ) on each side disposed on the outermost side of each saturable coil that constitutes the saturate coil group has an interval (first 1 in 4 figures
= 180), and the differential output extracting means (D ₁ , D ₂ ,) corresponding to _one saturable coil (L ₁ ) (L ₂ ) on each side arranged so as to substantially coincide with the both ends. R ₁ ,
R ₂ , C ₁ , C ₂ , C ₃ ), so that the central non-linear portion of the differential output voltage (V ₁ , V ₂ ) obtained from R ₂ , C ₁ , C ₂ , C ₃ becomes a straight line,
One saturable coil (L ₃ ) on each of the left and right sides is provided inside each saturable coil (L ₁ ) (L ₂ ) on both sides.
(L ₄ ) are sequentially arranged so that the magnetic body (M) is linearly displaced relative to the saturable coil group in the width (w) direction over a section wider than the width (w). A differential output voltage (see the combined voltage curve shown by the dotted line in FIG. 4) is generated. In the example of FIG. 1, n = 1 and 2
A linear differential output voltage is obtained by (1 + n) = 4 saturable coils L _{1 to} L ₄ , but in order to further widen the linear section, 6, 8, ... The number may be increased experimentally on the basis of (1 + n) and the above configuration and procedure until a linear differential output voltage is obtained by so-called cut-and-try.

By doing so, it is possible to obtain the effect that an output voltage having a linear slope can be obtained over a range wider than the width (w) of the magnetic body (M).

Further, according to the present invention, the following derivative effects can be obtained.

B) Since it is possible to detect the position of the moving magnetic body without contact,
It can be used for general purpose as a kind of scale or potentiometer.

B) Since the output voltage is completely continuous with respect to the displacement of the relative position of the magnetic sensor and the magnetizing body and there is almost no time delay, it can be used also as a speed detector by combining differentiating circuits.

C) Since the distance between the magnet and the detector can be increased by using a highly sensitive saturable coil, it can be used as a detector for guiding and controlling an unmanned vehicle along a strip of rubber magnets laid on the floor. It is suitable.

D) By fixing the magnet to the position that indicates the stop position of the floor or wall, stacker crane, elevator,
It is possible to control the stop position of an automated guided vehicle or the like.

E) The length of the straight line portion of the output voltage signal can be made sufficiently larger than the width of the magnetizing body depending on the control purpose.

F) By combining the magnetic detector that outputs a linearly changing analog output voltage with a section detection circuit that limits the controllable section, it is always possible to determine whether the vehicle is inside or outside the control section. Can be clarified.

G) The circuit configuration is simple and the response speed is fast.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic embodiment of the present invention, FIG. 2 is an output voltage curve diagram showing the operation of the above embodiment, FIG. 3 is an output voltage curve diagram showing the principle of the present invention, and FIG. Is an output voltage curve diagram for explaining the operation of the above-mentioned embodiment, FIG. 5 is a connection diagram showing an essential part of another embodiment of the present invention, FIG. 6 is a waveform diagram showing the operation of FIG. 7 and 8 are schematic diagrams showing examples of use of the present invention. M ... Magnetic body, w ... Magnetic body width, L ₁ , L ₂ , L ₃ ,
L ₄ ... saturable coil, R _S ... resistance, OSC ... high-frequency oscillator, (D ₁ , D ₂ , R ₁ , R ₂ , C ₁ , C ₂ , C
₃ ) ...... Differential output extraction means.

Claims (1)

[Claims] 1. A plate-shaped or belt-shaped magnetic body having a constant width, and a magnetic body arranged so as to be displaced relative to one surface of the magnetic body at constant intervals and relatively in the width direction of the magnetic body. A saturable coil group, an oscillator for supplying a high frequency voltage to the saturable coil group via a resistor, and a differential output extracting means for rectifying the voltage generated in each of the resistors to extract a differential output voltage, In the saturable coil group, when n is a natural number, 2 (1
+ N) saturable coils, and these 2 (1 + n) saturable coils are arranged on a straight line parallel to the width direction of the magnet body, and left and right (1 + n) relative to the width direction of the magnet body. ) Each saturable coil group is divided into two sets, and each saturable coil of each saturable coil group is connected in series from the inside to the outside, and each set of saturable coils connected in series is saturable. A high-frequency voltage is supplied to the coil groups from the oscillator via the resistors, and (1+
n) Each of the saturable coils forming each saturable coil group is symmetrically configured so that the detection sensitivity is sequentially increased from the inner saturable coil toward the outer saturable coil. When trying to make the differential output voltage from the take-out means into a linear section at an interval equal to or greater than the width of the magnet body, first, each of the two sets of (1 + n) saturable coil groups is formed. One saturable coil on each side of the outermost side of the saturation coil was arranged at an interval substantially corresponding to both ends of the linear section to be obtained, and then arranged so as to substantially correspond to both ends thereof. Inside the one saturable coil on each side so that the non-linear portion in the center of the differential output voltage obtained from the differential output extracting means corresponds to one saturable coil on each side. One saturable one on each side The magnets are sequentially arranged so that a linear differential output voltage is generated when the magnetized body is displaced relative to the saturable coil group in the width direction over a section wider than the magnetized body. A magnetic detector characterized in that