JP2987858B2 - Travel control method for carrier vehicles - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling control method for a carrier, and more particularly to a control method for accurately performing autonomous traveling and a traveling position recognition required for performing the control. About the method.

(Conventional technology) The automatic guided vehicle has already been put into practical use in the field of factory automation and has greatly contributed to industrial development. In recent years, OA (Office Autom
In the field of ation), attempts are being made to incorporate this type of transport vehicle and provide services such as e-mail, equipment, and tea service. In particular, a magnetic guiding type transport system in which a carrier travels on a magnetic guiding path having ferrite markers laid in a grid pattern is one of the most suitable systems for such an application [Proceedings of the 5th International].
al Couference Automated Guided Vehicle Systems (AG
VS-5), S5-2, 1987]. As an advanced form of this system, an attempt has been made to realize a shortened lead time by autonomously performing a rotational traveling for changing the traveling direction of the carrier (running ignoring a ferrite marker). I have. In this run, we are trying to achieve this by simply giving a fixed rotational speed difference to the left and right drive wheels [Proceedings of the 6the International Co.
nference Automated Guided Vehicle Systems (AGVS-
6), pp. 233-240, 1988].

FIG. 6 is a view for explaining a conventional autonomous rotational traveling operation of a carrier on a lattice guideway. The automatic guided vehicle 20 includes drive wheels RW1 and RW2, and wheels FW1 and FW2 in front,
Further, a magnetic sensor 12 for guiding along a magnetic guide path (X ₁ , X ₂ ,..., Y ₁ , Y ₂ ,...) Is provided. The AGV, for example autonomous from below along the _{Y 1 P 1 (X 2,} Y 1) up to guide the travel, from P ₁ until P ₂ through _{P 2 (X 4, Y 3} ) until the route R1 to travel (by ignoring the guide, and it is driven only by the rotational speed difference of the left and right wheel RW1, RW2, reaches the rotational speed of the predetermined drive wheel, stopping the running) and again P ₂ Guide ( is made to travel along the X taxiway _4).

(Problems to be Solved by the Invention) However, slip may occur due to unevenness of the floor surface (usually a P-tile is laid and a ferrite marker is provided inside the floor) or an uneven friction coefficient. Since the rotation speed of the wheels is not kept constant, the traveling direction of the carrier may shift, for example, as in the route R2. When such a traveling operation occurs, the carrier 11
It is not possible to ride to the guide on the X ₄ of the P2 point later, a state deviating from exactly the course, put away stop traveling. Such development is a major problem in the reliability of the transport system.

SUMMARY OF THE INVENTION An object of the present invention is to provide a traveling control method of a transport vehicle and a traveling position recognition method for eliminating such a conventional disadvantage.

(Means for Solving the Problems) A traveling control method for a carrier according to the present invention is a method for controlling traveling of a carrier provided with a guide sensor for traveling on a guide marker. When performing autonomous traveling while crossing the marker, the position detection means detects this crossing position, and a value substantially proportional to the magnitude of the deviation between the actual sensor position obtained by this and the predetermined crossing position, left·
The vehicle is caused to travel by setting the difference in the number of rotations of the right drive wheel, and the intersection position and the speed are detected by the position detecting means and the speed detecting means, respectively, and at least the predetermined position and the predetermined speed are determined. Calculate the probable degree for a plurality of control rule data expressed by the membership function of deviation and set the most probable drive wheel rotational speed difference or rotational speed based on these probable degrees. This allows the vehicle to run.

(Operation) By using the traveling control method described in the above-described means, for example, even in the case of autonomously performing a curved rotation traveling, the transport vehicle intermittently sets the intersection position with the guide marker as a guide point, The drive wheel rotational speed difference is proportionally determined according to the magnitude of the deviation so that the deviation from the guide point is reduced, and the travel route is determined for each short distance section so that the deviation is not increased. Changes are made. This means that the autonomous driving is surely performed on a predetermined route, so that the system can realize high reliability and a short lead time.

In addition, the control method that determines the most accurate drive wheel rotational speed difference or rotational speed using the control rule data represented by the membership function and runs the vehicle uses multiple input data such as position and speed deviations. , The driving wheel rotation condition (rotational speed difference or rotational speed) for reducing the deviation of the position can be set in consideration of parameters such as speed. In this case, even in the case where a slip or the like occurs, the vehicle is allowed to travel while more flexibly finding the optimal rotation condition, so that the vehicle does not deviate from the predetermined route first. That is, extremely reliable autonomous traveling is realized.

Further, by using the traveling position recognition method described in the above means, the conventional guide sensor can be used as it is,
The angle of approach to the guide marker is obtained from the difference between the output signals of the left and right detectors, and the position of intersection at the time of entry can be specified, thereby realizing a low-cost, autonomously transportable transport system.

Hereinafter, the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a transport system for explaining a traveling control method of a transport vehicle according to an embodiment of the present invention. Transport system, the X ₁ to X _5, Y ₀ to Y grid-like guide path, such as ₅ (composed of ferrite marker 11 laid on the surface portion of such floor 10 shown in FIG. 2) and the transport vehicle 20. Become. The transport vehicle 20 mainly travels on the lattice-shaped guideway, but performs autonomous traveling in the rotating section. For example, Y ₁ on the transport vehicle 20 has been traveling towards the downward P1 travels up P2 at all ignore the guide markers along when route R1 to perform the rotation from P1 to the right. From the point P2, it continues to travel along the guide markers on the X ₄ to the right.
During such traveling, the carrier has a required size,
The traveling locus S1 at the tip and the traveling locus R1 of the drive wheels RW1, RW2 are different.

In the case of performing such traveling, in the present embodiment, a sensor (angle sensor 21 or magnetic sensor 12) mounted at the leading end of the transport vehicle crosses the position C ₁ ′ (X ₄ ), C ₂ ′ (on Y ₂ ), C ₃ ′ (on Y ₃ ),
C ₄ ′ (on Y ₄ ) are sequentially detected, and relative to the intersection positions C ₁ , C ₂ , C ₃ , C ₄ (coordinates are previously stored as data in the memory unit) that should ideally proceed. The vehicle travels while calculating the deviations and correcting the difference in the rotational speed of the drive wheels so that these deviations become smaller after each position is detected. Means for detecting these intersecting positions include a method using an optical fiber gyro sensor (angle sensor) utilizing the Sagnac effect of light, a geomagnetic sensor (angle sensor) for monitoring the direction of geomagnetism, and a method using the magnetic sensor 12. A method of calculating an angle by detecting a time difference when the two detectors 13 and 13 'cross the guide marker is conceivable, and either method may be used.
With these means, the angle at which the magnetic sensor enters the guide marker is obtained, and the intersection position can be calculated by the following equation. In this case, C ₁ ′, C ₂ ′, C ₃ ′, C ₄ ′ are almost C ₁ , C ₂ , C
₃ and C ₄ are assumed to be close to each other. Also, the guide sensor 12 or the angle sensor 13 and the rear wheels (drive wheels) RW1, RW
The distance between the centers of 2 is l, the average radius of gyration of the rear wheel is R, and the lattice is a square with one side R / 2, and each intersection point C ₁ -C ₄ , C ₁ ′-
Guide marker X ₄ , Y ₂ , Y ₃ , Y of sensor 12 or 21 at C ₄ ′
₄ crossing angle between the respective theta ₁ through? _4, and θ ₁ '~θ _4'. Further, the origin of the coordinates is set to P1 (0, 0).

C ₁ = [lsin θ ₁ + R (1-cos θ ₁ ), R], C ₁ ′ to [lsin θ ₁ ′ + R (1-cos
_{θ 1 '), R] ...} (1) C 2 = [R / 2, lcosθ 2 + R (sinθ 2 -1)], C 2' ~ [R / 2, lcosθ 2 '+ R (sinθ 2'
-1)]. _{(2) C 3 = [R} , lcosθ 3 + R (sinθ 3 -1)], C 3 '~ [R, lcosθ 3' + R (sinθ 3 '-
1)] ... (3) C 4 = [3 / 2R, lcosθ 4 + R (sinθ 4 -1)], C 4 '~ [R, lcosθ 4' + R (sinθ 4 '-
1)]... (4) These intersection points C ₁ ′ to C ₄ ′ are determined by an arithmetic unit (not shown) mounted on the carrier after determining the angle θ _i ′, and the memory unit data are files in C ₁ -C ₄
Is read out, the deviation of the intersection point is also calculated.
After detecting these deviations, the rotational speed difference of the rear drive wheels is set to a value substantially proportional to the deviation amount (it can be said to be a kind of proportional control). That is, when the deviation is large, the difference in the number of rotations is increased, and the direction of the transport vehicle is largely directed to the ideal route S1 to travel. Conversely, if the deviation is small,
The difference in the number of rotations is reduced so that the direction of the transport vehicle is reduced to the route S1 and the vehicle is driven. For example, if the sensor deviation is dn (Cn
And the position of Cn ': dn> 0 when shifted to the right, dn <0 when shifted to the left, where n = 1, 2,...), The rotation of the left drive wheel RW1 Number T1 and the number of rotations of the right drive wheel RW2
Assuming that T2, when traveling in a curve, for example, in the case of clockwise rotation, T1> T2. In that case, the rotation speed of the right driving wheel is T2 · (1−K · dn) without changing T1. However, K is a proportional constant and is determined in a range where (1−K · dn)> 0 in consideration of the size of the vehicle body, the deviation range of the sensor, and the like. By performing such drive wheel speed control, even if a slip with the floor surface occurs or the wheel speed (counted by the encoder) shifts from the set value,
The passing route S1 'of the sensor (12 or 21) provided at the front end of the transport vehicle 20 is shaped like a triangle while always chasing the ideal route S1, and does not protrude greatly from the ideal route S1. That is, while rotating the travel somewhat Omawari than the ideal route S1 through route S1 'from the start of the rotation driving Co (central portion of the rear drive wheels P1), the guide marker X ₄
With interlacing slightly C ₁ on the left side 'than C _1, to direct the traveling direction of the large transport vehicle to the right, and larger than the right driving wheel RW2 the rotational speed of the left driving wheel RW1, to travel. Then
Middle ideal route S1 is across somewhat orientation notwithstanding et al to the right, intermingled with C ₂ 'slightly lower than C ₂ to Y ₂ of the guide markers. Thereafter, in order to direct the traveling direction of the transport vehicle 20 upward, the rotation speed of the right drive wheel RW2 is set to be higher than that of the left drive wheel RW1, and the vehicle is run. While traveling upward across the transport vehicle 20 is ideal route S1 again, than C ₃ to Y ₃ of the guide markers are interlaced in the upper C ₃ '. After C ₃ ′, the left drive wheel RW1 is made to rotate at a higher rotational speed than the right drive wheel RW2 in order to run the carrier in a downward direction. Then, the guide marker Y _4, are interlaced slightly below C ₄ 'than the ideal crossing locations.
Thereafter, when running while changing the direction of travel of slightly upward transporting vehicle enters onto the guide marker X _4. Then, the guide sensor 12 from detecting this marker, thereafter guides travel on guide marker X _4. The starting point of the guide travel substantially corresponds to the time when the center of the subsequent drive wheel has passed through P2.

As described above, when performing the rotational autonomous traveling, the intersection with the guide marker is detected, and the rotation speed difference of the drive wheels is controlled to reduce the deviation from the ideal position (change the traveling direction). ), Highly reliable traveling can be performed without significantly deviating from the ideal traveling route. That is, even if the autonomous traveling is mixed between the guide traveling and the guide traveling, a stable transport system is realized without deviating from the traveling route.

(Embodiment 2) An embodiment of the position detecting means required for realizing the highly reliable traveling will be described below. FIG. 2 is a diagram showing a configuration of a magnetic sensor and a guide marker. FIG. 3 is a diagram showing the principle of detecting the intersection position. A magnetic sensor 12 mounted on a carrier 20 has an excitation coil 14 for generating a magnetic field.
2 for detecting the magnetic field distribution formed by the guide marker 11 (formed of ferrite) laid on the floor 10
And two detection coils 13, 13 '. As shown in FIG. 3 (b), the magnetic sensor moves the guide marker X ₄ at the speed v.
, The left and right detection units (comprising detection coils) 13 and 13 ′ intersect in the order of the left detection unit and the right detection unit. At this time, the output signals from the left and right detectors are Vd
et (L) and as shown in Vdet (R) (FIG. (a)), is detected shifted by a time difference T _1. Therefore, upon entry into the left and right detection unit guide marker X _4, entry angle theta ₁ with respect to the direction perpendicular to the guide marker X _4, when the distance between the left and right detection unit is W, Is represented by When the magnetic sensor 12 mounted on the carrier 20 intersects with the guide markers Y ₂ , Y ₃ , Y ₄ , the signal from the right side detection unit appears before the left side detection unit, so the approach angle θ of the magnetic sensor ₂ , θ ₃ , θ ₄ are the time differences between the output signals Vdet (L) and Vdet (R) from the left and right detection units, respectively, as T ₂ , T ₃ , T ₄ Is represented by If the angle of approach with respect to the guide markers of the magnetic sensors is deviated from the ideal state even (corresponding to the travel route S ₁ '), similar approach angle is calculated, the left and right detection unit of the output signal Vdet (L) and Vdet ( R) and T ₁ ′, T ₂ ′,
T ₃ ′ and T ₄ ′ Crossing angles θ ₁ ′ to θ ₄ ′ can be obtained.

These angles θ _i ′ are obtained by determining the rotational speed v of the drive wheels by measuring encoder pulses per unit time, and determining the time interval between the peak levels of the sensor outputs Vdet (L) and Vdet (R) as the sampling interval. Is calculated by the arithmetic unit. By applying this θ _i ′ to equations (1) to (4), the intersection position of the sensor with the guide marker can be calculated. The method of detecting the intersection position in this way is as follows.
The magnetic sensor is used not only as a guiding sensor when guiding on a guide marker, but also as a position detecting sensor for detecting an intersection in the middle of autonomous traveling (newly a fiber optic gyro sensor). Or the use of a geomagnetic sensor or the like), the number of sensors to be mounted on the carrier can be reduced, and the system can be reduced in cost and simplified in configuration. The guide and position detection sensors are not necessarily limited to the magnetic sensors described here, but may be other optical sensors for detecting tapes such as Al and Cr, and currents flowing through electromagnetic induction wires (guide markers). Or a sensor such as a magnetic sensor for detecting a magnetic field formed by a magnetic sensor or a magnetic sensor for detecting a permanent magnet (guide marker).

(Embodiment 3) FIG. 4 is a configuration diagram of a transport system for explaining a traveling control method of a transport vehicle according to another embodiment of the present invention.
FIG. 5 is a control operation diagram for explaining the traveling control method of the carrier according to the present embodiment. In the present embodiment, when performing autonomous traveling, not only the intersection position with the guide marker but also the speed and the like are detected, and instead of the proportional control described in the first embodiment,
It is characterized in that driving is performed by setting a driving wheel rotation speed or a rotation speed difference according to fuzzy control.
That is, the intersection position C ₁ ″ is detected by the above-described intersection position detection means.
CC ₄ ″, and the speed at the time of entering these intersecting positions is determined by the number of rotations of the drive wheels per unit time using a pulse encoder or the like. (May be the number of rotations) as a plurality of control rule data uniquely identified in a memory unit (not shown) as a membership function (0
This is a function representing the degree of certainty between 1 and 通常 1, and is usually represented by several triangular distribution functions having different regions with respect to the input variable values). In this embodiment, the deviation ΔV from the predetermined value of the speed and the deviation ΔX from the predetermined position of the intersection position (the deviation from the predetermined position in the horizontal axis direction or the vertical axis direction) are set as the antecedent input variables, Using the rotational speed difference Δn (= N _R −N _L ) of the left and right driving wheels as the consequent part output variable, the five control rule data (rules in the form of “if then”) shown in FIGS. ) Is filed in the memory unit. The origin is P1 (0,0). Each control rule data is small (S), large in the positive direction (PB), large in the negative direction (NB), and small in the positive direction (P
S), small in the negative direction (NS), etc. are defined by a triangular membership function as ambiguous information.

if then (a) ΔV = S, Δx = S → Δn = S (b) ΔV = NB, Δx = PB → Δn = NB (c) ΔV = PB, Δx = NB → Δn = NB (d) ΔV = NB , Δx = S → Δn = PS (e) ΔV = S, using Δx = PB → Δn = PS such control rule data, the crossing point C ₁ '(guide marker X ₄ for example shown in Figure 1 (When the sensor enters)
Is performed as follows. When it is measured by a speed sensor (encoder or the like) that the crossing is performed at a speed v ₁ ″ slightly faster than the predetermined value v ₁ , the speed deviation ΔV ₁ = v ₁ ″ −v ₁ becomes a positive slightly larger value. It is input to the calculation unit. Further, at the intersection C ₁ ″, since the intersection is slightly left (X ₁ ″, 0) of the predetermined value (X ₁ , 0), the position deviation ΔX ₁
= X ₁ ″ −X ₁ is input to the calculation unit as a slightly large negative value. The data of the velocity deviation ΔV ₁ and the position deviation ΔX ₁ is applied to the fuzzy control rule, and the driving wheel rotational speed is obtained by the fuzzy calculation. A predicted value of the difference is calculated, and a drive voltage or a drive pulse corresponding to a new number of rotations of the left and right drive wheels is given to the drive unit of the drive motor as control data, thereby obtaining accurate rotation data. , From C ₁ ′ to C ₂ ″ without any significant deviation from the ideal route.

In the fuzzy operation, the membership function values corresponding to the input data ΔV ₁ and ΔX ₁ are obtained for each control rule, and the degree of certainty is set as their minimum values α ₁ , α ₂ , α ₃ , α ₄ and α _5. Derive. The reason why the minimum value is selected for the degree of certainty is that all of the conditions (weight of certainty) in one rule must be satisfied. Next, the minimum value thus calculated and the membership function of the output variable (driving wheel rotational speed difference Δn) are calculated to calculate the driving wheel rotational speed difference according to the certainty of each rule. The distribution of the membership function is obtained (the hatched portion in FIG. 5). Next, each independent rule [(a)-
(E)] to integrate the degree of certainty of Δn
(Logical sum: shaded portion shown in FIG. 5 (f)). Finally, the drive wheel rotational speed difference Δ
In order to obtain the final predicted fixed value Δn ₀ of n, the average value, the center of gravity, and the like of the integrated membership function are calculated.

The thus-obtained predicted value (digital amount) of the drive wheel rotational speed difference Δn is converted into a voltage or a pulse for driving the drive unit of the drive motor, and supplied as an analog amount. Based on the new control data (driving wheel rotational speed difference), the transport vehicle passes through the traveling route S ₁ ″ in FIG. 4 and enters C ₂ ″ (intersection with Y ₂ ). After that, the speed deviation ΔV ₂ and the position deviation ΔX ₂ at the above points are obtained, the same control is performed, and the optimum traveling route S ₁ ″ taking into account the speed change is also considered.
(The same applies after C ₃ ″ and C ₄ ″ crossings). In this case, the calculation time from when the position and speed detection sensors detect the signals at the respective intersections to when the control data is given to the drive motor can be suppressed to at most several hundred μsec to several msec. It is possible to perform drive wheel control immediately. In addition, since the drive wheel control is performed in consideration of a plurality of input variables, highly flexible traveling according to the situation is realized. Further, since the ambiguity is incorporated into the arithmetic processing by using the membership function, even if the detection accuracy of the intersecting position or the speed becomes slightly inaccurate, the change can be absorbed, and as described in the first embodiment. Highly reliable driving performance can be obtained compared to proportional control.

Note that the input variables for performing the fuzzy control are not limited to the two variables of the speed deviation and the position deviation, and a variable such as an acceleration deviation may be added, or a combination of other variables may be used. Good. In addition, the output variable is not limited to the difference between the driving wheel rotational speeds, and the rotational speed and other variables can be used without any problem. Further, even if the number of rules and the number of membership functions are set arbitrarily, the purpose of the present invention is not spoiled.

(Effects of the Invention) As described in detail above, according to the traveling control method for a transport vehicle of the present invention, highly reliable autonomous traveling, which cannot be obtained by the prior art, can be realized. A transport system can be constructed. Further, according to the traveling position recognition method using the sensor shared with the guide sensor, a simple system can be configured at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a transport system for explaining a traveling control method of a transport vehicle according to an embodiment of the present invention, FIG. 2 is a diagram illustrating a configuration of a magnetic sensor system, and FIGS. 4) is a principle diagram of position detection for explaining a traveling position recognition method according to another embodiment of the present invention, and FIG. 4 is a diagram for explaining a traveling control method of a transport vehicle according to another embodiment of the present invention. 5 (a) to 5 (f) are control operation diagrams. FIG. 6 is a view for explaining a conventional round transfer operation of a carrier. In the figure, 10: floor surface, 11: ferrite marker, 12: magnetic sensor, 13, 13 ': detection unit, 14: excitation unit, 20: transport vehicle.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G05D 1/02

Claims (2)

(57) [Claims] 1. A method for controlling the traveling of a transport vehicle provided with a guide sensor for traveling on a grid-like guide marker, wherein the transport vehicle deviates from the guide marker when the transport vehicle rotates and intersects with the guide marker. While performing autonomous traveling, the position detecting means detects the angle of intersection with the guide marker, calculates the intersection position from the detected angle, and calculates the intersection position obtained by the operation with the predetermined intersection position. A traveling control method for a transport vehicle, wherein a traveling speed is set by setting a rotational speed difference between left and right driving wheels by a proportional control to a value substantially proportional to the magnitude of the deviation. 2. A method for controlling the traveling of a transport vehicle provided with a guide sensor for traveling on a grid-like guide marker, wherein the transport vehicle deviates from the guide marker when the transport vehicle rotates and intersects with the guide marker. While performing autonomous traveling, the position detection means detects the angle of intersection with the guide marker, calculates the intersection position from the detected angle, detects the speed of intersection with the speed detection means, and detects the intersection speed. The relationship between the deviation between the position and the speed and the predetermined position and the speed and the rotational speed difference or the rotational speed of the drive wheels is determined by using control rule data defined by a membership function, where the membership function is 0. And a function representing the degree of likelihood between 1 and 1, and the degree of likelihood, which is the output of the function, is usually a function of several triangular distributions in different regions, The degree of likelihood for the speed deviation is obtained, and the minimum value of the degree of likelihood and the difference between the rotational speeds of the drive wheels or the membership function of the rotational speed is calculated to correspond to the rotational speed difference or the rotational speed of the drive wheels. A traveling control method for a transport vehicle, wherein a traveling function is obtained by determining a membership function distribution and determining a rotational speed difference or a rotational speed of a driving wheel having the highest accuracy from the membership function distribution.