JPH03260706A - Course deciding method for unmanned carrier - Google Patents

Abstract

PURPOSE:To easily decide a fact that an unmanned carrier gets out of its course with a course deciding signal, i.e., the output voltage of a differential amplifier obtained at presence of an object to be detected by detecting synchronously the voltage induced from a detection coil based on the exciting voltage of an exciting coil. CONSTITUTION:An exciting coil 2 generates an AC magnetic field with reception of the output of an oscillator 1, and the detection coils 3 and 13 output the induced voltage via the AC magnetic field, respectively. The synchronizing detectors 5 and 15 detect synchronously the outputs sent from the amplifiers 4 and 14 with the output of the oscillator 1. The output of a differential ampli fier 8 is identical with the differential voltage between both coils 3 and 13 and serves as a course deciding signal of an unmanned carrier. Thus, only the changing components of the induced voltage produced by both coils 3 and 13 with approximation of an object to be detected are outputted from the ampli fier 8. Then the magnetic field change is outputted at either one of right and left sides of the coils 3 and 13, respectively. Thus, it is possible to decide a fact that the carrier gets out of its course just by detecting the output voltage of the amplifier 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a route determination method for an automatic guided vehicle that travels by detecting a magnetic material or a conductive material installed on the route.

[Conventional technology]

One type of magnetic detector that detects the presence of a magnetic substance is a self-excitation type that includes a detection coil that generates an induced voltage by an alternating magnetic field generated by an excitation coil. This is widely used because it has a simple structure and a high degree of freedom in design.

One field of application is that it is used and useful in various vehicle guidance systems. In these guidance systems, a conductive material such as a magnetic or metal strip is laid on the track where the vehicle is guided, and the vehicle is steered by a detector attached to the vehicle to guide the vehicle to the desired location. .

In the conventional method for determining the route of an automatic guided vehicle, a magnetic detector having a coil arrangement as shown in FIG. 3 and a circuit configuration as shown in FIG. 4 is known.

An excitation coil 2 and two detection coils 3.13 are fixed in a metal case 12. The two detection coils 3 and 13 are fixed at symmetrical positions around the center axis.

To explain the operation of this magnetic detector, when an oscillator 1 is connected to an excitation coil 2 and an alternating current is passed through the excitation coil 2, an excitation magnetic field 9 is generated from the excitation coil 2. When a part of this excitation magnetic field 9 penetrates the detection coil 3.13,
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 3.13 are each passed through amplifier circuits 4.14, rectified by rectifier circuits 10.20, and then rectified by voltage comparison circuits 11.
．． 21, and the two signals from the detection coils 3 and 13 are compared with a reference voltage. The outputs of the voltage comparison circuits 11 and 21 are passed through the synthesis circuit 22 and output as a determination signal for determining the running route. In a magnetic detector with such a configuration and function, when a magnetic body with magnetic permeability greater than air approaches the detection coil 3.13, the magnetic field distribution changes and the detection coil 3.
．． The magnetic flux passing through 13 also changes. Furthermore, when a conductor approaches, the magnetic field changes due to an overcurrent generated in the conductor. As a result, the voltage induced in the sensing coil 3.13 also changes. When a magnetic material or a conductive material is located close to the two detection coils 3.13, the induced voltage in the two detection coils 3, 13 is also large, and the induced voltage in the voltage comparison circuit 11.21 is small even when compared with the reference voltage. Since the output VDO of the synthesis circuit 22 is large, it is determined that the automatic guided vehicle has not left the running route. However, if the magnetic material or the conductive material is located at a different position from one or both of the two sensing coils 3, 13, the induced voltage in one or both of the two sensing coils 3, 13 is small; Voltage comparison circuit 11
．． Since the induced voltage side is smaller than the reference voltage at step 21, it is determined that the automatic guided vehicle has left the running path based on the output VDO of the combining circuit 22.

[Problem to be solved by the invention]

In the above-described conventional route determination method for an automatic guided vehicle, since the excitation coil 2 and the detection coil 3.13 are close to each other, the voltage generated in the detection coil 3.13 is large even when the object to be detected is not close to each other. In this case, the change in voltage that occurs in the detection coils 3 and 13 due to the proximity of the object to be detected is very small, and it is difficult to detect the voltage change due to the temperature characteristics of the circuit system, the chance strain of the case, etc. To solve this,
As shown in FIG. 3, it is necessary to fix the sensing coil 3° 13 near the point where the magnetic fields intersecting the sensing coils 3 and 13 are balanced. However, the magnetic field changes significantly near this balance point even with a small installation error, so there is a drawback that position setting is difficult.

[Means to solve the problem]

The route determination method for an automatic guided vehicle according to the present invention includes an excitation coil that is supplied with the output of an oscillator and generates an alternating magnetic field, and a first coil that outputs first and second induced voltages by the alternating magnetic field, respectively.
and a second sensing coil, first and second amplifiers that amplify the first and second induced voltages, respectively;
a first and a second synchronous detector that synchronously detects the output from the amplifier with the output of the oscillator, and a differential amplifier that differentially amplifies the output from the first and second synchronous detector. ing.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

This embodiment includes an excitation coil 2 that is supplied with the output of an oscillator 1 and generates an alternating current magnetic field 9, and first and second detection coils 3 that output first and second induced voltages by the alternating magnetic field 9, respectively.
, 13, first and second amplifiers 4.14 that amplify the first and second induced voltages, respectively, and the outputs from the first and second amplifiers 4.14 are synchronously detected by the output of the oscillator 1. The first and second synchronous detectors 5.15 and the differential amplifier 8 differentially amplify the outputs from the first and second synchronous detectors 5.15. The output of the differential amplifier 8 is the differential voltage detected by the detection coils 3 and 13, and serves as a route determination signal for the automatic guided vehicle.

It should be noted that the same operation can be achieved even if the first and second amplifiers 4.14 of the above embodiment are configured as differential amplifiers and the output thereof is configured with one synchronous detector.

In this way, only the change in the induced voltage of the detection coil 3.13 when the object to be detected approaches is output from the differential amplifier 8, and the change in the magnetic field is output from either the left or right side of the detection coil 3.13. Therefore, by simply detecting the output voltage of the differential amplifier 8, it is possible to determine that the automatic guided vehicle has left the running path.

FIG. 2 shows the input and output voltages of the differential amplifier 8 of this embodiment.
The horizontal axis is the distance between the magnetic detector and the object to be measured, and the vertical axis is the input/output voltage. The curve VL shows the output voltage of the detection coil 3 side, that is, the synchronous detector 5, the curve ■R shows the output voltage of the detection coil 13 side, that is, the synchronous detector 15, and the curve VD shows the output voltage of the differential amplifier 8. It shows the voltage, that is, the route determination signal. When VD is on the positive side, it is determined that the automatic guided vehicle has not left the running path.

〔Effect of the invention〕

As explained above, the present invention detects the induced voltage from the detection coil synchronously with the excitation voltage of the excitation coil, and uses the route determination signal, which is the output voltage of the differential amplifier when a detected object is present, to drive the conveyed vehicle. It can be easily determined that the vehicle has left the running track. Further, there is an effect that the position between the excitation coil and the detection coil can be easily set.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an 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. 4 is a diagram of a conventional unmanned sensor. FIG. 2 is a block diagram illustrating an example of a method for determining a route for a guided vehicle. 1... Oscillator, 2... Excitation coil, 3.13...
Detection coil, 4, 14... Amplifier, 5, 15... Synchronous detector, 8... Differential amplifier.

Claims (1)

[Scope of Claims] 1. An excitation coil that is supplied with the output of an oscillator and generates an alternating magnetic field; first and second detection coils that output first and second induced voltages, respectively, by the alternating magnetic field; first and second amplifiers that amplify first and second induced voltages, respectively; and first and second synchronous detectors that synchronously detect outputs from the first and second amplifiers with the output of the oscillator. and a differential amplifier that differentially amplifies the outputs from the first and second synchronous detectors. 2. The method for determining a route for an automatic guided vehicle according to claim 1, wherein the first and second induced voltages are differentially amplified and synchronously detected.