JPH10312215A - Traveling control method and unmanned vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply execute the right/left traveling control and the stopping position control of a traveling path by only one guiding cable. SOLUTION: This method detects the intensity of a magnetic field generated from a guiding cable 1 arranged along a guiding route by a left/right pair of two magnetic sensors P1 and P2 provided at a traveling vehicle and calculates the displacement of the traveling vehicle with respect to the cable 1 from the output values of these magnetic sensors P1 and P2 to travel-control in the direction of reducing this displacement. In this case the cable 1 at the stopping position of the unmanned vehicle is coiled in the form of a figure eight in parallel with a road surface to locally form the inversion part of magnetic field distribution at the part of a cable 1b to detect the inversion of the magnetic field by the sensors P1 and P2 to control the stoppage of the unmanned vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the traveling of an automatic guided vehicle applied to a left-right traveling control and a stop position control of the automatic guided vehicle in an automatic warehouse or the like.

[0002]

2. Description of the Related Art An automatic guided vehicle used in an automatic warehouse or the like detects a magnetic field generated by an electric current flowing through an induction cable provided along a traveling path with a magnetic sensor provided in the automatic guided vehicle and thereby detects the magnetic field. The method of controlling the traveling control in the left-right direction and the control of the stop position is widely used. Such a conventional traveling control method for an automatic guided vehicle will be described below.

FIG. 4A shows a current i flowing on a straight conductor.
And the magnetic field h induced by the current i. The magnetic field h is induced in the direction in which the right-hand screw turns with respect to the current i traveling straight. FIG. 4B shows the current i shown in FIG.
And a magnetic field h is shown in a plan view. When a current i flows from left to right on the paper in the direction indicated by the arrow, the magnetic field h flows from the back of the paper to the front at the upper part of the conductor and to the surface of the paper at the lower part. It occurs in the direction of breaking through from behind.

Next, the principle of running control of the automatic guided vehicle in the left-right direction using the guide cable will be described with reference to FIG. The guide cable 1 is buried in the road surface 2, and the automatic guided vehicle 3 runs along the guide cable 1 directly below and runs along the longitudinal direction. When an induction current i is applied to the induction cable 1 in a direction from the front to the back of the drawing, the magnetic field h induces a circular magnetic field around the cable as indicated by a dotted line. The magnetic sensors P ₁ and P ₂ for detecting the magnetic field h by the induction cable 1 are symmetrical with respect to the center of the guided vehicle on the floor of the automatic guided vehicle 3 (x ₁ =
x ₂ ), and a magneto-electric conversion element such as a coil or a Hall element is used.

The outputs of the magnetic sensors P ₁ and P ₂ are connected to each other as shown in FIG. ± the output of P ₁
Assuming that the outputs of e ₁ and P ₂ are ± e ₂ , the difference between the absolute values of both e _x = | e ₁ | − | e ₂ | is detected. The difference of the horizontal distance x ₁ and x ₂ from the center of the magnetic sensors P _1, P ₂ and the induction cable 1 when the center of the AGV 3 is shifted to the left or right from the induction cable _{1 (x = x 1 -x 2} ) in proportion to, e _x = the difference between the magnetic sensors _{P 1, P 2 | e 1} | - | e 2 | changes as shown in FIG. 4 (c). The polarity of the e _x (±)
Then, the steering of the automatic guided vehicle 3 (not shown) is controlled so that _ex = 0.

Next, a description will be given of a conventional example of a traveling control method of an automatic guided vehicle to which the above-described principle of the induction cable is applied and control of a stop position is added as well as left and right traveling control with reference to FIGS. I do. Reference numeral 1 shown by a solid line in FIG. 5A is an induction cable for controlling the left and right deviation of the automatic guided vehicle 3. Reference numeral 4 indicated by a dotted line denotes a stop guide cable for controlling a stop position, which is buried in the traveling path orthogonal to the guide cable 1. The guide cable 4 for stopping is orthogonally arranged in a zigzag pattern at each stopping position.

FIG. 5B shows the connection of a magnetic sensor for detecting a magnetic field induced by the induction cable 1 and the stop induction cable 4. 4A and 4B, magnetic sensors P ₁ and P ₂ that detect left and right deviations from the induction cable 1 are arranged on the lower surface of the induction cable 1 symmetrically with respect to the center of the carrier, as in FIGS. to detect the output e _x. The magnetic field induced by the stopping induction cable 4 is, as shown in FIG.
₃ by detecting the peak e _y of the horizontal component. The polarity of the detection signal of the magnetic sensor P ₃ is reversed at the position where the induction cable 1 and the stop for the induction cable 4 is orthogonal to the reverse position and the stop position. Current i ₁ and i ₂ flowing the induction cables 1 to stop the induction cable 4, a magnetic sensor (P ₁ -P
₂ ) The frequencies f ₁ and f ₂ are changed so that the outputs of P ₃ and P ₃ do not interfere with each other.

With such a configuration, the traveling of the automatic guided vehicle 3 is controlled by the guide cable 1 and the magnetic sensors P ₁ and P ₂ , and the stop of the automatic guided vehicle is controlled by the stop guide cable 4 and the magnetic sensor P _3. .

However, in this method, since the portions 4a, 4b, 4c,... Connecting the respective stop positions are single wires, an induced magnetic field is generated, and the pipes, other signal lines or other signal lines to be laid in close proximity are generated. An induction fault may occur in a pipe or the like passing through the cables 4a, 4b, 4c,.

[0010] In order to prevent this guidance failure, the cable 4
FIG. 6 shows an example in which the portions a, 4b, 4c,. The outgoing line and the return line of the stop guide cable 5 for controlling the stop position of the automatic guided vehicle are paired. At the stop position, these two lines are arranged in parallel at a predetermined interval and are orthogonal to the guide cable 1. While stranding in portions other than the stop position, the vehicle is detected by the magnetic sensor P _4, P ₅ and a horizontal component e _h and a vertical component e _v separately to each of the induced magnetic field of each lead cable at the stop position, these The stop position is detected by calculating the ratio of the detected values.
In this way, the inductive magnetic field generated by the outgoing line and the return line is canceled out by twisting the outgoing line and the return line in pairs, so that no induction failure occurs.

As another method related to the control of the stop position of the automatic guided vehicle 3, there is a well-known method in which a target such as a magnet is separately buried at the stop position and detected by another magnetic sensor. is there.

[0012]

In the above-mentioned conventional traveling control method for an automatic guided vehicle, in the case of one guide cable, stop position control cannot be performed only by controlling the left and right direction of the automatic guided vehicle. In order to add a stop position control function in addition to the left and right cruise control, a stop position control guide cable may be provided in addition to the left and right cruise control guide cables, or a target such as a magnet and a sensor corresponding thereto may be provided. Is required. Therefore, there is a problem that the installation cost of the taxiway is high, and the sensor on the automatic guided vehicle side needs to have a multi-function and is expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to easily control the traveling of the traveling road in the left-right direction and the stop position with only one guide cable. It is an object of the present invention to provide a traveling control method of an automatic guided vehicle that enables the following.

[0014]

According to a method of detecting a stop position of an automatic guided vehicle according to the present invention, the traveling vehicle is provided with two magnetic sensors on the left and right sides with respect to the traveling direction of the traveling vehicle. Detects the intensity of the magnetic field generated from the guide cable arranged along the traveling lane, calculates the amount of deviation of the traveling vehicle with respect to the guide cable from the detected value, and controls traveling in the direction in which the amount of deviation decreases. In the traveling control method for an automatic guided vehicle, an inversion cable of a magnetic field distribution is formed on the left and right sides of the traveling lane by winding an induction cable at a stop position of the automatic guided vehicle in a figure 8 parallel to a road surface, The stop position control of the automatic guided vehicle is performed by detecting reversal of a magnetic field by two magnetic sensors.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a view of an induction cable used in a method for controlling travel of an automatic guided vehicle according to an embodiment of the present invention, as viewed from above a road surface. FIG. 2 is a circuit showing signal processing of travel control in the embodiment. FIG. 3 and FIG. 3 are diagrams showing the principle of running control of the automatic guided vehicle in the left-right direction. In FIG. 1, reference numeral 1 denotes an induction cable for inducing a magnetic field used for traveling control of an automatic guided vehicle. Parts 1a and 1c are single-wire cables provided along the traveling direction of the automatic guided vehicle. While the automatic guided vehicle is traveling on the guide cable 1, the traveling control of the automatic guided vehicle is detected by detecting the left and right traveling deviation and the stop position of the automatic guided vehicle by the magnetic sensors P ₁ and P ₂ provided on the automatic guided vehicle. I do.

The principle of running control in the left-right direction at the portions of the guide cables 1a and 1c in FIG. 1 will be described in detail with reference to FIG. The guide cable 1 is buried in the road surface 2, and the automatic guided vehicle 3 runs along the guide cable 1 right below and along the longitudinal direction. An induction current i flows through the induction cable 1 perpendicularly to the front direction from the back of the paper, and the induction current i is a circular magnetic field h around the induction cable 1 as indicated by a dotted line.
Is induced. The strength of the magnetic field h attenuates in inverse proportion to the square of the distance around the induction cable 1.

The magnetic sensors P ₁ and P ₂ are connected to the induction cable 1
Is detected on the floor of the automatic guided vehicle 3 and is symmetrical with respect to the center of the automatic guided vehicle 3 (x ₁ = x ₂ ). Magnetic sensors P ₁ , P
Height from lateral spacing and the induction cables 1 of _2, the induced magnetic field h (proportional to the current i) is set within a detectable range. Magnetoelectric conversion elements such as coils and Hall elements are used as the magnetic sensors P ₁ and P ₂ . The magnetic field h may be detected by detecting only one of the horizontal and vertical components with respect to the road surface, or by detecting the vector sum of these components.

The outputs of the magnetic sensors P ₁ and P ₂ are connected to each other as shown in FIG. That is, when the output of ± e _1, P ₂ the output of P ₁ and ± e _2, the difference between the absolute value of both _{e x = | e 1 | -} | e 2 | detected. When the center of the automatic guided vehicle 3 is shifted to the left or right from the guide cable 1, the difference between the magnetic sensors P ₁ and P ₂ and the horizontal distance x ₁ and x ₂ from the center of the guide cable 1 (x = x ₁ −x ₂₎ of the difference between the magnetic sensors P _1, P ₂ in response _{to) e x = | e 1 |} - | e 2 |
Changes as shown in FIG. So that e _x = 0 by detecting the polarity (±) and the size of this e _x, controls the steering of the AGV 3 (not shown).

Next, the guide cable 1 shown in FIG.
The stop position control in the part b will be described. The guide cable 1 detours horizontally on the road in a figure 8 at the portion 1b. As for the order of detour, draw a figure of 8 in the order of →→→ as shown by the arrow. Further, the winding is performed so that the center interval of the figure-eight circle coincides with the interval between the magnetic sensors P ₁ and P ₂ shown in FIG.

The current i is applied to the wound cable pattern.
Pay attention to the direction of the induced magnetic field when flowing. According to the principle of FIG. 4 described above, the direction of the center magnetic field of the figure-eight circle in the portion 1b is reversed with respect to the portions 1a and 1c. This reversal of the magnetic field is performed by the magnetic sensor P which is also used for the left-right running control.
_1, is detected at P _2, the magnetic field reversing position is the stop position.

Next, will be described with reference to FIG. 2 the signal processing of the magnetic sensor P _1, P _2. 1 is an induction cable, S ₁ ,
S ₂ ,..., _Sn are figure-eight detours that determine the stop position of the automatic guided vehicle 3, and correspond to the portion of the guide cable 1b in FIG. Reference numeral 12 denotes an AC power supply that supplies a current to the induction cable 1, and 13 denotes a constant current control unit that controls the current supplied from the AC power supply 12 to a constant current and supplies the current to the induction cable 1. The case where an alternating current is used as the current flowing through the induction cable 1 is described below. However, the present invention is applicable to both the alternating current and the direct current.

First, the signal processing for performing the left-right control will be described. The differential outputs of the magnetic sensors P ₁ and P ₂ are output to the differential amplifier 14. The differential amplifier 14 amplifies this differential output and outputs it to the polarity discrimination circuit 15. The polarity discrimination circuit 15 discriminates the polarity of the output signal of the differential amplifier 14. For example, when the output signals of the alternating currents of the magnetic sensors P ₁ and P ₂ have a relationship of P ₁ > P _2, a positive signal is output. When the relationship P ₁ <P ₂ is satisfied, a negative signal is output. The polarity discrimination circuit 15 includes a filtering circuit that cuts off the AC component and extracts only the DC component. When the automatic guided vehicle 3 (not shown) meanders to the left and right with respect to the guide cable 1, a DC voltage corresponding to the polarity (±) of one of the right and left and its deviation is output to the A / D converter 16. Is done. The A / D converter 16 converts the DC analog output of the polarity discrimination circuit 15 into a digital signal, and outputs the digital output to a control unit 21 including a CPU described later.

Next, the signal processing for controlling the stop position will be described. The output signal of the magnetic sensor P ₁ is amplified by the amplifier 17 and output to the polarity discrimination circuit 18. The polarity discrimination circuit 18 is a circuit for discriminating the polarity of the output signal of the magnetic sensor P ₁ and includes a filtering circuit, similarly to 15. The obtained polarity discrimination signal is output to the comparator 19.

The comparator 19 compares the polarity discrimination signal with a preset threshold of the same level of ± bipolarity.
When the output signal of the polarity discriminating circuit 18 is equal to or more than the threshold value, either "H" or "L" signal is output. The unmanned guided vehicle 3 (not shown) stops at the stop positions (S ₁ , S ₂ ,...,
At S _n ), when the output signal of the polarity discrimination signal 18 becomes higher than the threshold value, the polarity “H” or “L” of the comparator 19 is inverted, and the inverted signal is input to the control unit 21 including the CPU. Is done. The control unit 21 including the CPU receives the inverted output signal of the comparator 19 and outputs a stop output signal to a stop position control device of the automatic guided vehicle 3 (not shown).

In order to detect the stop position with higher accuracy, it is possible to search for the middle point of the stop position. That is, the analog output of the polarity discrimination circuit 18 is output to the A / D converter 20, converted into a digital signal, and converted into a digital signal by the control unit 21 including the CPU.
Take in. Then, the time-series data is recorded in a memory (not shown), the maximum value is searched, and the position having the maximum value is set as the middle point. By determining the middle point as the stop position and outputting the stop output signal, it is possible to detect the stop position with high accuracy.

The above has been described stop position control for only the magnetic sensor P ₁ side, a circuit similar to the P ₁ side to the output from the magnetic sensor P ₂ side 22 (amplifier 17, the polarity discrimination circuit 1
8, the comparator 19, the same configuration as the A / D converter 20) and performs the same detection operation and P ₁ side is provided, via an OR circuit (not shown) the output of P ₁ side and the P ₂ side both CPU May be output to the control unit 21 including By adopting such a configuration, P ₁ side or P ₂
Since the stop output signal is output even when the output of one of the comparators is inverted, the reliability of the stop position control can be improved.

The operation of the traveling control method for an automatic guided vehicle according to the above embodiment will be described.

As shown in FIG. 3, the automatic guided vehicle 3 travels on the road surface 2 on which the guide cable 1 is provided. An induction current i flows through the induction cable 1 in a direction from the front to the back of the drawing, and this current i induces a circular magnetic field h as shown by a broken line. X = 0 when the automatic guided vehicle 3 is traveling around the guide cable 1 without shifting in the left-right direction.
Next, the voltage value to detect the magnetic sensor P ₁ and the magnetic sensor P ₂ is _{equal, e x = | e 1 |} - | a = 0 | e _2. Therefore, the signal input to the differential amplifier 14 becomes zero, and the traveling control in the left-right direction is not performed.

[0030] When the AGV 3 is serpentine for example to the left in FIG. 3 (a), since the _{x = x 1 -x 2> 0} , e x = | e 1 | - | e 2 |> 0 and Become. The differential voltage e _x is outputted to the differential amplifier 14, is amplified. The amplified differential voltage is output to the polarity discrimination circuit 15, the positive and negative polarities are discriminated, and output to the A / D converter 16.
The A / D converter 16 converts the polarity discrimination signal into a digital signal and outputs the signal to the control unit 21 including the CPU. Based on this digital signal, the control unit 21 including the CPU generates and outputs a guidance output signal for controlling the steering of the automatic guided vehicle 3 so that x = 0. When the automatic guided vehicle 3 meanders to the right, the same signal processing as described above is performed.

Next, control of the stop position of the automatic guided vehicle will be described.

While the automatic guided vehicle 3 is traveling on the guide cables 1a and 1c shown in FIG. 1A, an induced magnetic field is detected by a magnetic sensor in the same manner as in the case of the left-right traveling control. Detection signals of the magnetic sensors P ₁ is amplified is output to the amplifier 17. The amplified signal is supplied to the polarity discrimination circuit 18.
Is output to The polarity discrimination circuit 18 discriminates between the positive and negative polarities of the output signal of the amplifier 17 and outputs the signal to the A / D converter 20 and the comparator 19. During traveling along the induction cables 1a and 1c, the vehicle travels while receiving an induction magnetic field in the same direction, so that the polarity is constant, and the output of the comparator 19 is always "H" or "L".

When the automatic guided vehicle 3 reaches the guide cable 1b, the induced magnetic field induced on the left and right sides of the automatic guided vehicle 3 is reversed. Therefore, the polarity of the output signal detected by the magnetic sensor P ₁ is inverted, and an inverted signal is output to the amplifier 17. The amplifier 17 amplifies this signal and outputs it to the polarity discrimination circuit 18. Polarity discrimination circuit 18 discriminates the polarity detected magnetic sensor P _1.

The inverted polarity discrimination signal is output to the comparator 19, and a signal opposite to the output from the induction cables 1a and 1c is output to the control unit 21 including the CPU. The control unit 21 including the CPU controls the automatic guided vehicle 3 (not shown) based on the inverted output signal from the comparator 19.
A stop output signal is output to the stop position control device of (1), and the automatic guided vehicle 3 stops based on this signal.

As described above, using one guide cable 1, the guide cable 1b at the stop position of the automatic guided vehicle 3 is used.
By winding the portion in a figure eight, the magnetic field at that position can be reversed. Therefore, by detecting the reversal of the magnetic field with the magnetic sensor, the stop point of the automatic guided vehicle 3 can be detected, and the cable laying ratio can be reduced, and a low-cost and highly reliable system can be constructed. Further, both left and right and stop positions can be controlled only by a magnetic sensor used for left and right traveling control without newly providing a magnetic sensor for stop position control different from that for left and right traveling control.

The stop position is detected by the magnetic sensor P ₁
Or it has been described a method for detecting an inversion of the output of P _2, P ₁ and P ₂ is used as a circuit of the left and right travel control
Differential amplifier 14 which is the differential output of → polarity discrimination circuit 15 →
The output of the series of the A / D converter 16 is also the stop point S ₁ ,
Since the polarity is inverted at S ₂ ,..., _Sn , the stop position can be detected using this inverted signal.

[0037]

As described above, according to the present invention, the guide cable at the stop position of the automatic guided vehicle is wound in a figure 8 parallel to the road surface, so that it can be wound on the left and right of the traveling lane of the automatic guided vehicle. A stop position control is performed by forming a reversal part of the magnetic field distribution and detecting reversal of the magnetic field by two pairs of left and right magnetic sensors provided on the traveling vehicle, so that only one induction cable is used to control the left and right traveling only. In addition, the stop position can be detected. Therefore, the cable laying ratio is low, and a single set of magnetic sensors can also be used for detecting both the left-right direction control and the stop position control, and a low-cost and highly reliable traveling control system for an automatic guided vehicle can be constructed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an induction cable and a magnetic sensor used for traveling control of an automatic guided vehicle according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing signal processing of traveling control in the embodiment.

FIG. 3 is a view for explaining left-right traveling control of the automatic guided vehicle to which the present invention is applied.

FIG. 4 is a diagram showing a relationship between a current and a magnetic field.

FIG. 5 is a diagram showing a guide cable and a magnetic sensor used for traveling control of a conventional automatic guided vehicle.

FIG. 6 is a diagram showing an induction cable and a magnetic sensor used for traveling control of a conventional automatic guided vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Induction cable 2 Road surface 3 Automatic guided vehicle 4,5 Stopping induction cable 12 AC power supply 13 Constant current control unit 14 Differential amplifier 15,18 Polarity discrimination circuit 16,20 A / D converter 17 Amplifier 19 Comparator 21 Control including CPU Department

Claims (1)

[Claims] 1. A pair of right and left sides with respect to a traveling direction of a traveling vehicle.
The traveling vehicle is provided with two magnetic sensors, and the two magnetic sensors detect the strength of a magnetic field generated from an induction cable disposed along the traveling lane. In the traveling control method of the automatic guided vehicle, in which the traveling amount is controlled in a direction in which the deviation amount is reduced, the guide cable at the stop position of the automatic guided vehicle is wound in a figure 8 parallel to the road surface. A method for controlling the stop position of the automatic guided vehicle by forming inversion portions of a magnetic field distribution on the left and right sides of the traveling lane and detecting the inversion of the magnetic field by the two magnetic sensors. .