JP2666511B2 - Automatic guided vehicle speed control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an automatic guided vehicle that automatically transports a load in a factory or the like.

[Related Art] In recent years, many automatic transport systems using automatic guided vehicles have been introduced in factories and the like along with FA (factory automation). In this type of system, generally, an automatic guided vehicle travels along a guide line laid on the floor. An example of such an automatic guided vehicle is shown in FIG.
Shown in the figure.

FIG. 6 is a view schematically showing an automatic guided vehicle. In this figure, 1 is a guide wire formed of a magnetic tape or the like,
Reference numeral 2 denotes a three-wheel automatic guided vehicle that can move forward and backward along the guide line 1. 2a is a steering wheel, and 2b is a traveling motor that drives the steering wheel 2a. 2c is a free wheel, and 2d is a steer motor for steering the steer wheel 2a. Reference numerals 2e and 2f denote forward and backward steer sensors for detecting a displacement from the guide line 1, respectively. The forward steering sensor 2e is attached to a rotation shaft (steering shaft) of the steering motor 2d, and moves with steering. On the other hand, the reverse steering sensor 2f is fixed to the rear part of the automatic guided vehicle 2 in the vehicle body. These steer sensors 2e, 2f
The magnetic sensors 2g are installed in pairs at both ends of the. The magnetic sensor 2g detects and outputs the magnetic field of the guide wire 1. 2h is a control box provided with various devices for controlling traveling and various operation switches. According to such a configuration, the forward steering sensor 2e (reverse steering sensor 2f) detects a displacement from the guide line 1, and the steer wheels 2a are steered so as to correct the displacement. Thereby, the automatic guided vehicle 2 travels along the guide line 1.

Next, FIG. 7 is a block diagram showing an example of a speed control device of the automatic guided vehicle 2. In this figure, 3 is a multiplier, which is a reference speed signal Vref and a steering angle signal Sa.
(To be described later) and output. The steering angle signal Sa is a signal supplied from an encoder (not shown) that detects the steering angle (steering angle) of the steering motor 2d. The polarity of the signal Sa becomes negative when the vehicle is steered to the left with respect to the traveling direction, and becomes positive when the vehicle is steered to the right. Reference numeral 4 denotes a speed generator, which generates a signal having a level corresponding to the rotation speed of the traveling motor 2b, and outputs this as a speed feedback signal Vf. 5 is a control circuit,
A speed command signal Sc for controlling the rotation speed of the traveling motor 2b in response to the output signal of the multiplier 3 and the speed feedback signal Vf.
Is output. FIG. 8 shows an example of the control characteristics of the control circuit 5. In the graph shown in this figure, the vertical axis is the speed command signal Sc described above, and the horizontal axis is the steering angle. As shown in this graph, when the steering angle is in the range of ± θ, the automatic guided vehicle 2 runs at the reference speed (4 km / h in this example), while the steering angle is equal to or more than + θ or −. In the case of θ or less, the vehicle runs at a speed inversely proportional to the steering angle. That is, the steering wheel 2a
Is steered, the traveling speed of the automatic guided vehicle 2 decreases.

"Problems to be Solved by the Invention" By the way, considering the case where a human drives such a transport vehicle, the driver first decelerates when approaching a curve from the past experience, and then in the curve, Smooth speed control such as maintaining a constant vehicle speed and accelerating after the end of the curve is performed.

However, in the above-described conventional automatic guided vehicle, since speed control according to the steering angle is performed, there is a disadvantage that smooth speed control such as driving by a human cannot be performed. Also, on a curve with a small turning radius, the vehicle speed may not be sufficiently reduced, and the vehicle may not be able to turn well.

The present invention has been made in view of the above circumstances, and has as its object to provide a speed control device for an automatic guided vehicle that can perform smooth speed control and smoothly turn even on a sharp curve.

Means for Solving the Problems The present invention includes a steering angle control device, and a speed control device that performs speed control for assisting steering control of the steering angle control device, and is laid on a floor or the like. In an automatic guided vehicle traveling along a guide line, a position shift amount detecting means for detecting a position shift amount from the guide line; a first control signal proportional to the position shift amount; Control signal generating means for generating a differentiated second control signal; and receiving the first and second control signals, performing fuzzy inference on a fuzzy set defined by a plurality of membership functions in accordance with a predetermined control rule. Control means for controlling the traveling speed of the automatic guided vehicle according to the inference result, whereby the curve speed control is performed smoothly.

[Operation] According to the above configuration, the first unmanned carrier travels along with the traveling of the automatic guided vehicle.
And a second control signal is output from the control signal generation means. Then, these signals are fuzzy inferred. The traveling speed of the automatic guided vehicle is controlled based on the inference result.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an automatic guided vehicle 2 according to an embodiment of the present invention.
7 is a block diagram showing the configuration of the speed control device of FIG. 6. Parts corresponding to those in FIGS. 6 and 7 are denoted by the same reference numerals, and description thereof is omitted. In this figure, 2g-1,2g
Reference numerals -2 denote magnetic sensors disposed at the left end and the right end of the forward steering sensor 2e, respectively. 6a and 6b are magnetic sensors 2 respectively
An amplifier that amplifies and outputs output signals of g−1 and 2g−2. 7 is a differential amplifier. The differential amplifier 7 outputs a difference signal between the signal supplied to the non-inverting input terminal and the signal supplied to the inverting input terminal, that is, a deviation signal Ds indicating the displacement of the forward steering sensor 2e. This deviation signal Ds is
When the forward steering sensor 2e is located substantially at the center of the above-described guide wire 1, the value becomes "0". When the forward steering sensor 2e is shifted to the left or right from this position, it takes a negative or positive polarity, respectively. Also, the greater the displacement, the greater the signal level. 8 is an input resistor R ₁ , a capacitor C ₁ , and an adjustment resistor
A differential circuit composed of R ₂ and the operational amplifier OP _1. This differentiating circuit 8 differentiates the deviation signal Ds with time and outputs this as a differential signal Δ ² Ds. Reference numeral 9 denotes a comparison circuit including an input resistor R ₃ , an adjustment resistor R _4, and an operational amplifier OP ₂ . The comparison circuit 9 amplifies the deviation signal Ds to a predetermined level and outputs this as a proportional signal ΔDs. Reference numeral 10 denotes a fuzzy controller which receives the differential signal Δ ² Ds and the proportional signal ΔDs, performs fuzzy control, and outputs the result as a speed control command signal Dc.

Next, the fuzzy controller 10 will be described with reference to FIG. 2 and FIG. FIG. 2 is a diagram showing each membership function defined in the fuzzy controller 10. In these figures, the vertical axis is grade (degree), and the horizontal axis is each variable normalized from -1 to 1. A triangular function whose grade continuously changes from 0 to 1 and 1 to 0 is shown. Defines the membership function. FIG. 3A shows a membership function of the proportional signal ΔDs, in which each membership function identified by three labels of L, Z and R is set. L
Is a membership function when the forward steer sensor 2e is shifted to the left of the guide wire 1, and when the steering sensor 2e is shifted to the leftmost (when the comparison signal ΔDs is −1), the grade is 1
Becomes Z is a membership function when the forward steer sensor 2e is located substantially at the center of the guide wire 1, and its grade becomes 1 when it is located at the center. On the other hand, if it deviates left and right from the center, the grade will decrease. R is a membership function when the forward steering sensor 2e is displaced to the right of the guide line 1, and when R is displaced to the far right (the proportional signal Δ
(When Ds is 1), the grade becomes 1.

FIG. 11B shows a membership function of the differential signal Δ ² Ds, and has the same function as FIG.
In this figure, L is a membership function when the forward steering sensor 2e shifts to the left. The grade of the membership function L is 1 when the speed of shifting leftward is the fastest (when the differential signal Δ ² Ds is −1). Z is a membership function when the deviation of the forward steering sensor 2e is substantially constant, and the grade becomes 1 when the deviation speed is 0. R is a membership function when the forward steering sensor 2e shifts rightward. The grade of the membership function R becomes 1 when the speed of shifting rightward is the fastest (when the differential signal Δ ² Ds is 1).

FIG. 3C is a diagram showing each membership function of the speed control command signal Dc obtained by fuzzy inference to be described later. In this figure, N is a membership function when the traveling speed of the automatic guided vehicle 2 is low, Z is a membership function when the traveling speed of the automatic guided vehicle 2 is medium,
P is a membership function for increasing the traveling speed of the automatic guided vehicle 2.

Next, fuzzy inference performed in the fuzzy controller 10 will be described. This fuzzy inference is executed by the fuzzy control rules described below. That is, Rule 1; IF ΔDs = L AND Δ ² Ds = L THEN Dc = N Rule 2; IF ΔDs = L AND Δ ² Ds = Z THEN Dc = Z Rule 3; IF ΔDs = L AND Δ ² Ds = R THEN Dc = P Rule 4; IF ΔDs = Z AND Δ ² Ds = L THEN Dc = Z Rule 5; IF ΔDs = Z AND Δ ² Ds = Z THEN Dc = P Rule 6; IF ΔDs = Z AND Δ ² Ds = R THEN Dc = Z Rule 7; IF ΔDs = R AND Δ ² Ds = L THEN Dc = P Rule 8; IF ΔDs = R AND Δ ² Ds = Z THEN Dc = Z Rule 9; IF ΔDs = R AND Δ ² Ds = R THEN Dc = N The meaning of these rules is, for example, in Rule 1, "if the proportional signal ΔDs is L (if shifted to the left) and the differential signal Δ ² Ds is L (to the left) , The speed control command signal Dc should be set to L (low speed). " Such fuzzy control rules can be displayed in a matrix shown in FIG.

In such a configuration, when the automatic guided vehicle 2 travels forward along the guide line 1, the magnetic sensors 2g-1 and 2g-2 disposed at both ends of the forward steering sensor 2e generate the magnetic field of the guide line 1. To detect. Then, this detection signal is supplied to the differential amplifier 7.
Is supplied to the differentiating circuit 8 and the proportional circuit 9 via Now, for example, when a differential signal Δ ² Ds having a value of “−0.5” is supplied from the differentiating circuit 8 and a proportional signal ΔDs having a value of “0.25” is supplied from the proportional circuit 9 to the fuzzy controller 10, respectively, 10 performs the fuzzy inference described above based on these values.

Hereinafter, the operation of obtaining the speed control command signal Dc by the fuzzy inference will be described in detail. First, in rule 1, in the example described above, the grade of the proportional signal ΔDs is “0” and the grade of the differential signal Δ ² Ds is “0.5” as shown in FIG. 4 (a). And here, "MA
Since the "X-MIN logical product" is adopted, taking these MIN (minimum) values results in "0", which does not conform to Rule 1. Similarly, in the rules 2 and 3, the grade of the proportional signal ΔDs becomes “0”. Next, in rule 4, the grade of the proportional signal ΔDs is “0.75” and the differential signal Δ ² Ds as shown in FIG.
Grade becomes “0.5” and when these MIN values are taken,
It becomes “0.5”. As a result, a trapezoid in which the membership function of the consequent part of Rule 4, that is, the membership function Z of the speed control command signal Dc is truncated at the position of height "0.5" is obtained. Then, in the same manner in rule 5, rule 5
The figure obtained by truncating the membership function P of the consequent part at the position of the height "0.5" is obtained (FIG. 3 (c)). In this way, when the above-described matching is performed for the rules 6 to 9, the rules 6 and 9 do not match, and the rules 7 and 8 obtain the figures shown in FIGS.

When the graphic groups obtained from the above results are combined with MAX (maximum value), the graphic shown in FIG. 5 is obtained. Then, the final inference result determines the output value by defuzzification called the centroid method. In this example, the position at which the area of the figure enclosed by the membership function and the axis shown in FIG. 5 is halved becomes the center of gravity, and the position X is the speed control command signal Dc to be obtained. The speed control command signal Dc thus determined is supplied to the control circuit 5. The control circuit 5 receives the signal Dc and the speed feedback signal Vf,
It outputs a speed command signal Sc for controlling the rotation speed of the traveling motor 2b. As a result, the automatic guided vehicle 2 performs smooth speed control as if driven by a human.

In the above-described embodiment, “MAX-MIN AND” is used as a fuzzy inference method, and “centroid method” is used as a method for determining an output value. It is easy to develop the method.

In the above-described embodiment, the speed control method when the automatic guided vehicle 2 moves forward has been described.
Of course, it can be applied to the case of reverse travel.

[Effects of the Invention] As described above, according to the present invention, the first and second control signals are output from the control signal generation means as the automatic guided vehicle travels. Then, these signals are fuzzy inferred. Since the traveling speed of the automatic guided vehicle is controlled based on the inference result, it is possible to obtain an effect that smooth speed control is performed and a sharp turn can be made smoothly. Also, the rate at which the vehicle speed is accelerated / decelerated can be automatically controlled according to the radius of the curve.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a speed control device according to an embodiment of the present invention, FIG. 2 is a diagram showing a membership function in the embodiment, and FIG. 3 is a fuzzy control rule in the embodiment. FIGS. 4 and 5 are diagrams for explaining fuzzy inference in the embodiment, and FIGS.
FIG. 8 to FIG. 8 are diagrams for explaining a conventional example. 2g-1,2g-2 ... magnetic sensor, 6a, 6b ... amplifier, 7 ...
... Differential amplifier, 8 ... Differentiation circuit, 9 ... Proportional circuit, 10 ...
... Fuzzy controller, 5 ... Control circuit

Claims (1)

(57) [Claims] An unmanned vehicle that travels along a guide line laid on a floor or the like, comprising: a steering angle control device; and a speed control device that performs speed control for assisting steering control of the steering angle control device. In the transport vehicle, a displacement amount detecting means for detecting a displacement amount from the guide line, a first control signal proportional to the displacement amount, and a second control signal obtained by time-differentiating the displacement amount. Receiving the first and second control signals, performing fuzzy inference on a fuzzy set defined by a plurality of membership functions according to a predetermined control rule, and according to the inference result, A speed control device for an automatic guided vehicle, comprising: a control unit for controlling a traveling speed of the automatic guided vehicle;