JP2590581B2 - Runway judgment device for automatic guided vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel path determination device of an automatic guided vehicle that travels by detecting a magnetic substance or a conductor laid on a travel path.

[Conventional technology]

One of the magnetic detectors for detecting the presence of a magnetic material is a self-excitation type including a detection coil that generates an induced voltage by an AC magnetic field generated by an excitation coil. This is widely used because of its simple structure and great design freedom. As one application field, it is used and useful in various vehicle guidance systems and the like. In these guidance systems, a strip-shaped conductor such as a magnetic material or a metal is laid on a track on which a carrier is guided, and steering is performed by a detector attached to the carrier to guide the vehicle to a target place. .

In the conventional automatic guided vehicle traveling path determination device, a magnetic detector having a coil arrangement shown in FIG. 3 and a circuit configuration shown in FIG. 4 is known.

The excitation coil 2 and the two detection coils 3 and 13 are
It is fixed inside. The two detection coils 3 and 13 are fixed at symmetrical positions with respect to the central axis L.

The operation of the magnetic detector will be described. When the oscillator 1 is connected to the excitation coil 2 and an alternating current flows through the excitation coil 2, an excitation magnetic field 9 is generated from the excitation coil 2. When a part of the excitation magnetic field 9 passes through the detection coils 3 and 13, an induced voltage is generated in the detection coils 3 and 13. This induced voltage is input to the signal processing circuit shown in FIG. The induced voltages of the detection coils 3 and 13 pass through the amplifier circuits 4 and 14 and the rectifier circuits 10 and 20 respectively.
After the rectification, the signals are input to the voltage comparison circuits 11 and 21, and the two signals from the detection coils 3 and 13 are compared with the reference voltage.
The outputs of the voltage comparison circuits 11 and 21 pass through the synthesis circuit 22 and are output as a determination signal for determining a track. In a magnetic detector having such a configuration and function, when a magnetic substance having a magnetic permeability higher than that of air approaches the detection coils 3 and 13, the magnetic field distribution changes and the magnetic flux penetrating the detection coils 3 and 13 also changes. When the conductor approaches, the magnetic field changes due to eddy current generated in the conductor. As a result, the voltage induced in the detection coils 3 and 13 also changes. A magnetic or conductive detection coil 3
When in the 13 close positions, the induction voltage of the two detection coils 3, 13 is large, unattended by the output V _DO of combining circuit 22 for the induction voltage is compared with a reference voltage in the voltage comparator circuit 11, 21 large It is determined that the carrier has not left the track. However, if the magnetic material or the conductor has two sensing coils 3,
When the position is different from one or both of 13, the induced voltage of one or both of the two detection coils 3, 13 is small, and compared with the reference voltage by the voltage comparison circuits 11, 21. Since the side is smaller, the output of the synthesis circuit 22
The _VDO determines that the automatic guided vehicle has left the track.

[Problems to be solved by the invention]

In the above-described conventional method for determining the traveling path of an automatic guided vehicle, since the excitation coil 2 and the detection coils 3 and 13 are close to each other, the voltage generated in the detection coils 3 and 13 is large even when the detected object is not close. In this case, the change in the voltage generated in the detection coils 3 and 13 due to the proximity of the detection object is very small, and it is difficult to detect the voltage change due to the temperature characteristics of the circuit system, mechanical distortion of the case, and the like. In order to solve this, it is necessary to fix the detection coils 3, 13 near a point where the magnetic fields intersecting the detection coils 3, 13 are balanced as shown in FIG. However, near the balance point, there is a drawback that it is difficult to set the position because a change in the magnetic field is large even with a small mounting error.

[Means for solving the problem]

The runway determiner of the automatic guided vehicle of the present invention is a runway determiner attached to an automatic guided vehicle that travels by detecting a magnetic substance or a conductor laid on a runway, wherein an output of an oscillator is supplied to generate an AC magnetic field. An exciting coil, first and second sensing coils respectively outputting first and second induced voltages by the AC magnetic field, and first and second amplifiers respectively amplifying the first and second induced voltages. First and second synchronous detectors for synchronously detecting the outputs from the first and second amplifiers with the output of the oscillator, respectively, and differentially amplifying the outputs from the first and second synchronous detectors And a differential amplifier.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention.

In this embodiment, the excitation coil 2 to which the output of the oscillator 1 is supplied to generate an AC magnetic field 9, and the first and second AC magnetic fields 9 are used.
And second detection coils for respectively outputting induced voltages
3, 13 and the first amplifying the first and second induced voltages, respectively.
And second amplifiers 4 and 14, and a first amplifier for synchronously detecting the outputs from the first and second amplifiers 4 and 14 with the output of the oscillator 1.
And the second synchronous detectors 5, 15 and a differential amplifier 8 for differentially amplifying the output from the first and second synchronous detectors 5, 15. The output of the differential amplifier 8 is a difference voltage detected by the detection coils 3 and 13 and serves as a runway determination signal of the automatic guided vehicle.

Next, the operation of the present embodiment will be described. The oscillator 1 generates an AC signal and drives the excitation coil 2. Excitation coil 2
Generates an AC magnetic field by the AC current from the oscillator 1.
The first and second detection coils 3, 13 generate an induced voltage in response to the AC magnetic field. First and second amplifiers 4,14
Amplifies the induced voltage generated in the first and second detection coils 3 and 13. The first and second synchronous detectors 5 and 15 receive the AC signal of the oscillator 1 as reference signals, respectively, and receive the output signals of the first and second amplifiers 4 and 14 as the other input signals, respectively. Then, the DC component in which the AC component is suppressed is output. The differential amplifier 8 uses the outputs of the first and second synchronous detectors 5 and 15 as input signals, amplifies the differential input voltage, and outputs the amplified signal. The output of the differential amplifier 8 becomes the output signal of the track judgment unit.

For example, the induced voltage generated by the first and second detection coils 3 and 13 when the magnetic detection object laid on the runway is not equidistant from the first and second detection coils 3 and 13 when approaching. A difference is generated between the signals, the signals are amplified by the first and second amplifiers 4 and 14, respectively, synchronously detected by the first and second synchronous detectors 5 and 15, supplied to the differential amplifier 8, and supplied to the first and second amplifiers 8. Is output as a difference signal between the induced voltages of the detection coils 3, 13. When the detected object is between the first and second detection coils 3 and 13 based on this signal, it is determined that the track is not deviated. When the object is not between the first and second detection coils 3 and 13, It is determined that the vehicle is off the track.

In this way, only the change in the induced voltage of the detection coils 3 and 13 when the detection object approaches is output from the differential amplifier 8, and the change in the magnetic field is output on either the left or right side of the detection coils 3 and 13. Therefore, it is possible to determine that the automatic guided vehicle has left the traveling road only by detecting the output voltage of the differential amplifier 8.

FIG. 2 shows input / output voltages of the differential amplifier 8 of the present embodiment. The horizontal axis represents the distance between the magnetic detector and the device under test, and the vertical axis represents the input / output voltage. Curve V _L is the sensing coil 3 side, i.e., shows the output voltage of the synchronous detector 5, the curve V _R sensing coil 13 side, i.e., shows the output voltage of the synchronous detector 15, the curve V _D differential amplifier 8 , That is, a runway determination signal. Located between the detection object when V _D is positive (plus) side of the first detection coil 3 and the second detection coil 13, it indicates that on the runway, curve V _D is negative (minus) side or When zero, the object to be detected is the first detection coil 3 and the second coil
Indicates that he is off the track, not between 13.

〔The invention's effect〕

As described above, the present invention performs synchronous detection of an induced voltage from a detection coil by an excitation voltage of an excitation coil, and thereby provides a vehicle with a runway determination signal that is an output voltage of a differential amplifier when an object to be detected is present. Can easily be determined to have left the runway. Further, there is an effect that the position between the excitation coil and the detection coil can be easily set.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of this embodiment, FIG. 3 is a diagram showing an example of a magnetic detector, and FIG. It is a block diagram showing an example of a runway judgment method of a transportation vehicle. 1 ... Oscillator, 2 ... Exciting coil, 3,13 ... Detection coil, 4,14 ... Amplifier, 5,15 ... Synchronous detector, 8 ... Differential amplifier.

Claims (1)

(57) [Claims] 1. A runway determiner mounted on an automatic guided vehicle that travels by detecting a magnetic or conductive material laid on a runway, an excitation coil supplied with an output of an oscillator to generate an AC magnetic field, and an AC magnetic field. A first and a second sensing coil for outputting first and second induced voltages respectively, a first and a second amplifier for amplifying the first and second induced voltages, respectively, A first and a second synchronous detector for synchronously detecting the output from the second amplifier with the output of the oscillator, and a differential amplifier for differentially amplifying the output from the first and the second synchronous detector. A runway judging device for an automatic guided vehicle, comprising: