JP3592435B2 - Automatic guided vehicle stop control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stop positioning device for an automatic guided vehicle.
[0002]
[Prior art]
A conventional automatic guided vehicle stop positioning device that automatically moves through a plurality of stations with a load placed thereon is equipped with a permanent magnet embedded in the floor at the stop position, and attached to the automatic guided vehicle body to displace the vehicle. And a magnetic sensor for measuring. Then, control is performed such that the deviation between the sensor output indicating the current position and the target sensor output becomes zero using the correlation between the output of the magnetic sensor and the displacement of the magnetic sensor.
[0003]
[Problems to be solved by the invention]
However, the conventional apparatus uses a large number of magnets and a magnetic sensor and utilizes the correlation between the output of the magnetic sensor and the position of the permanent magnet, and thus has the following problems.
{Circle around (1)} When the output of the magnetic sensor fluctuates for some reason, an error occurs in the stop position.
{Circle around (2)} When a plurality of automatic guided vehicles are operated, the characteristics of the individual magnetic sensors do not match, which causes an error in the stop position.
{Circle around (3)} Since the distance between the permanent magnet and the stop position must be within the effective operating range of the magnetic sensor, a deviation from the range may cause malfunction.
[0004]
Factors that cause the output of the magnetic sensor to fluctuate include changes with time of the permanent magnet, changes in the magnetic field due to a magnetic material such as a reinforcing bar buried near the permanent magnet buried on the floor, and inconsistencies in characteristics of individual sensors. And errors in the mounting position of the magnetic sensor and errors in the burying depth of the permanent magnet.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic guided vehicle positioning apparatus capable of accurately performing stop control of a stop position with a simple configuration.
[0006]
According to a second aspect of the present invention, in addition to the object of the first aspect, there is provided an automatic guided vehicle capable of accurately stopping even when the characteristics of the magnet and the magnetic sensor do not match by detecting a zero point of the output. It is intended to provide a positioning device.
[0007]
A third aspect of the present invention provides, in addition to the object of the first aspect, an automatic guided vehicle positioning device that can efficiently operate without lowering the bogie speed near a stop position. And
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present invention includes a magnet provided near a stop position of the automatic guided vehicle, and a magnet provided substantially at a center portion and a front portion of the vehicle body of the automatic guided vehicle, respectively. A first magnetic sensor that detects a deviation between the magnet and the vehicle body position, a second magnetic sensor that operates with a magnetic flux density equal to or higher than a predetermined value, an encoder that measures the amount of movement of the vehicle body, and a control unit. The control unit sets and stores a coarse distance between the current position and the stop position of the vehicle body at the time of starting, and sets a distance between the second magnetic sensor and the first magnetic sensor when the second magnetic sensor detects a magnet. When the coarse distance set in the interval is updated and changed to a low speed, further, when the first magnetic sensor detects a magnet and detects a zero position where the output becomes zero, the distance between the stop position and the zero position is calculated. Further update values Updating, is characterized in that so as to travel while measuring the amount of movement through the encoder to the stop position.
[0009]
According to a second aspect of the present invention, in the configuration of the first aspect of the present invention, the first magnetic sensor outputs the displacement between the center of the sensor and the magnet as a signal, and outputs the signal when the first magnetic sensor coincides with the center point of the magnet. Is arranged to be zero.
[0010]
According to a third aspect of the present invention, in the first aspect of the invention, the second magnetic sensor is configured to have a low operation accuracy for performing on / off operation in response to a magnetic flux density of a predetermined value or more. Features.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an automatic guided vehicle stop control device (hereinafter, referred to as the present invention device) according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a front view illustrating the configuration of an automatic guided vehicle, FIG. 2 is a diagram illustrating the operation of a magnet and a first magnetic sensor, and FIG. 3 is a diagram illustrating the output of the first magnetic sensor and the position of a permanent magnet and the same sensor. FIG. 4 is a block diagram of the control unit, FIG. 5 is an explanatory diagram of the operation of the first nonlinear element function, FIG. 6 is an explanatory diagram of the operation of the second nonlinear element, and FIG. 7 is a control variable. FIG. 8 is a flowchart for explaining the operation of the control unit, and FIG. 9 is an explanatory diagram showing a change in the moving speed at the time of stop.
[0012]
The apparatus of the present invention includes a magnet 11 made of a permanent magnet or the like buried in a floor 10 near a stop position P, a first magnetic sensor 21 and a second magnetic sensor 21 disposed at two places on a body 20 of an automatic guided vehicle. It includes a magnetic sensor 22, an encoder 24, and a control unit 30.
[0013]
As shown in FIG. 2, the first magnetic sensor 21 is provided on the lower surface of the substantially central portion of the vehicle body 20 so as to face the magnet 11 at a predetermined distance E, and the center of the first magnetic sensor 21 and the magnet 11 Is continuously output as a signal. FIG. 3 is a characteristic diagram showing a relationship between a position error (distance) between the first magnetic sensor 21 and the magnet 11 and a sensor output (voltage).
[0014]
The sensor output (voltage) of the first magnetic sensor 21 changes as shown in FIG. 3 depending on the magnitude of the position deviation. In the figure, a to d indicate the magnitude of the distance interval E, where a>b>c> d, and b and c are appropriate values of the distance interval. F indicates the effective operating range of the first magnetic sensor 21.
[0015]
In FIG. 3, when the center positions of the first magnetic sensor 21 and the magnet 11 match, that is, when the deviation is zero, a pair of Hall elements (not shown) incorporated in the first magnetic sensor 21 is used. The differential signal of the signal of the magnetic detection element is zero if the distance between the magnet and the magnetic detection element is equal, regardless of the magnetic flux density. At other positions, the magnetic flux density changes, so that the sensor output of the first magnetic sensor 21 changes.
[0016]
The second magnetic sensor 22 is provided on the lower surface of the front part of the vehicle body 20 at a predetermined distance L2 from the first magnetic sensor 21 and at a predetermined distance D from the magnet 11 to be fixed. It is configured to perform on / off operation with a magnetic flux density equal to or greater than the value. Therefore, the second magnetic sensor 22 may have low operation accuracy.
[0017]
The encoder 24 measures a moving amount, that is, a deviation of the vehicle body 20, and is connected to a driven wheel 26 via a belt 25, a gear, or the like. Then, the detection value of the encoder 24 is input to the control unit 30. 23 is a running wheel.
[0018]
The control unit 30 includes a microcomputer, and is provided with a positioning function and the like in addition to a guidance, steering, traveling, and load transfer function for the automatic guided vehicle to travel. FIG. 7 is a block diagram showing the positioning function of the control unit 30 in terms of hardware. The first comparison 31, the proportional element amplification 32, the first nonlinear element 33, the second nonlinear element 34, the differentiation 35, the second , A proportional-integral element 37, and an addition 38.
[0019]
The stop position P and the current position (start position) measured by the encoder 20 are compared by a comparison function 31, and the deviation is input to a first nonlinear element function 33 via a proportional element function 32.
[0020]
As shown in FIG. 5, the first non-linear element function 33 has a function of saturating positive and negative outputs with respect to an input having a certain value or more. In this embodiment, the positive and negative saturation outputs are set to the maximum moving speed VX in the positive and negative directions.
[0021]
Then, the output of the first nonlinear element function 33 is input to the second nonlinear element function 34. The second non-linear element function 34 has a function of holding the output value at a constant value for an input less than a certain value. In this embodiment, the constant value is set as the minimum moving speed VN in the positive and negative directions. FIG. 6 shows the input / output characteristics of the second nonlinear element function 34.
[0022]
Further, the count value of the encoder 24 is differentiated with respect to time through a differentiating function 35 to calculate the speed of the vehicle body 20, and the output of the second nonlinear element function 34 and the deviation thereof are calculated via a second comparing function 36. Is obtained.
[0023]
The deviation signal is proportionally integrated via a proportional integration function 37, added to the output of the second nonlinear element function 34 via an addition function 38, and output as a speed command signal for the servo motor 40. Then, the bogie 20 is input to a servo amplifier 39 that drives a travel motor, and travels with its speed controlled so as to follow the input of the servo amplifier 39.
[0024]
Next, the operation of the device of the present invention will be described with reference to FIGS. FIG. 7 shows the contents of the update of the control variables, which are performed at the time of control switching of the device of the present invention, that is, at the time of startup (A), at the time of operation of the second magnetic sensor 22 (B), and at the time of zero point detection of the first magnetic sensor 21. The set distance, the maximum moving speed VX, and the minimum moving speed VN at the time (C) are displayed. In addition, the cleave speed VC is set to a low speed so as not to give an impact to the load when stopped. In this embodiment, it is set to a value of 1/10 to 1/20 of the rated traveling speed.
[0025]
The distance between the current center position R and the stop position P of the vehicle body at the time of startup is L1, the distance interval between the first and second magnetic sensors 21 and 22 is L2, and the zero point position Q detected by the first magnetic sensor 21, that is, the magnet 11 Is defined as L3. Needless to say, the distance intervals L2 and L3 are known.
[0026]
(1) A distance L1 from the current position R of the vehicle body 20 to the target stop position P (hereinafter, roughly set distance) is set (S1). Note that the distance L1 does not require accuracy, and may be an approximate value.
(2) Also, the minimum moving speed VN is set to zero for the maximum moving speed VX, the rated speed, or the speed limit V1 of the corresponding section (S2) (see FIG. 7A).
[0027]
(3) The maximum moving speed in the positive and negative directions that defines the range of discontinuity of input and output of the first nonlinear element 33 is set to VX. The minimum moving speed that defines the range of discontinuity of input and output of the second nonlinear element 34 is set to zero.
(4) The automatic guided vehicle starts up (S3) (see FIG. 9A), and detects the second magnetic sensor 22 while traveling.
[0028]
(5) When the second magnetic sensor 22 detects the magnet 11 (S4), the coarse interval L1 is updated and set to the distance L2 by software set in advance (S5).
[0029]
(6) At the same time, the maximum moving speed VX is kept at V1 by the above software, and the minimum moving speed is updated and set to the creep speed VC (S6) (see FIG. 7B). As a result, the automatic guided vehicle gradually decelerates to the creep speed VC (S7) (see FIG. 9B. Thereafter, the speed is maintained. This state corresponds to the area of the hatched portion S shown in FIG. 9).
[0030]
(7) After the second magnetic sensor 22 detects the magnet 11, the output of the first magnetic sensor 21 gradually increases as it approaches the magnet 11, and after passing the maximum output point, the output decreases. When it reaches the center line, a zero point Q at which the output becomes zero is detected (S8).
Then, as the distance from the magnet 11 increases, a signal of the opposite polarity is output when approaching (see FIG. 3).
[0031]
At this time, in order to prevent the signal of the first magnetic sensor 21 from malfunctioning due to disturbance or the like, before and after the output of the first magnetic sensor 21 reaches the maximum value or the minimum value, the signal of the sensor is differentiated at the position. It is also monitored that the value of the differential coefficient is inverted and that the differential coefficient keeps a substantially constant value near the output of the first magnetic sensor 21 becomes zero.
Therefore, the zero point Q can be accurately detected.
[0032]
(9) Simultaneously with the detection of the zero point Q, the distance interval L2 is updated to L3 (hereinafter, referred to as a precision set distance) (S9).
(10) The maximum moving speed VX is set to the creep speed VC and the minimum moving speed VN is set to zero (S10) (see FIGS. 7C and 9C).
[0033]
(11) The vehicle travels along the precisely set distance L3 at the creep speed VC based on the detection value of the encoder 24 (S11), and stops when L3 becomes zero (S12).
Since the precision setting distance L3 is extremely short as compared with the coarse setting distance L1, the measurement can be stopped accurately with very few measurement errors.
[0034]
【The invention's effect】
As described above, the invention according to claim 1 of the present invention includes the magnet 11 provided near the stop target position, the two magnetic sensors provided on the automatic guided vehicle, the encoder, and the control unit. At startup, the coarse set distance L1 is stored, the operating set distance of the second magnetic sensor is updated to L2 and decelerated, and the set point of the first magnetic sensor at zero point detection is set to L3. It is configured to stop at the stop target position based on the detected value of the encoder.
[0035]
As described above, since the first magnetic sensor 21 detects the amount of movement every moment for the distance between the magnet 11 and the stop position P set after the detection of the zero point, the positioning can be stopped accurately with a relatively simple configuration.
[0036]
Further, it is not necessary to accurately provide the magnet at the stop position P, and an error may occur in the embedding position and the embedding depth.
Therefore, the setting can be performed without being affected by the structure of the floor or the structure such as the reinforcing bar, so that the mounting work for disposing a large number of magnets and the layout change can be extremely easily performed, and the number of working steps can be reduced. Furthermore, since the coarse setting distance set at the time of starting does not require accuracy, the preparation work for setting is simplified.
In addition, since the distance between the magnet and the stop position does not have to be within the effective operating range of the magnetic sensor, it can be arbitrarily installed.
[0037]
The invention according to claim 2 uses the magnetic sensor that detects the position of the vehicle body based on the difference in the magnetic flux density of the magnet. Therefore, in addition to the effect of claim 1, the characteristics of the magnet and the magnetic sensor do not match. In this case, no error occurs, so that the vehicle can be stopped accurately. Further, since it is not necessary to strictly match the characteristics of the magnets and the magnetic sensors used in many cases, the work for selecting the products to be used can be reduced.
[0038]
Since the invention according to claim 3 may be a magnetic sensor that operates with a magnetic flux density equal to or higher than a predetermined value, it can operate reliably without using a special sensor, so that cost can be reduced and a target stop can be achieved. Since the speed of the carriage does not need to be reduced to the vicinity of the position, there is an effect that the automatic guided vehicle can be operated efficiently.
[Brief description of the drawings]
FIG. 1 is a front view illustrating a configuration of an automatic guided vehicle used in the present invention.
FIG. 2 is an explanatory diagram of an operation of a magnet and a first magnetic sensor.
FIG. 3 is a characteristic diagram showing a relationship between an output of a first magnetic sensor and a deviation between the position of a magnet and the position of the sensor.
FIG. 4 is a block diagram of a control unit.
FIG. 5 is an explanatory diagram of an operation of a first nonlinear element function.
FIG. 6 is an explanatory diagram of an operation of a second nonlinear element function.
FIG. 7 is a list of updated contents of control variables.
FIG. 8 is a flowchart illustrating an operation of a control unit.
FIG. 9 is an explanatory diagram of a change in a moving speed at the time of stop.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Magnet 20 Body 21 First magnetic sensor 22 Second magnetic sensor 24 Encoder 30 Control unit 40 Servo motor

Claims (3)

A magnet provided near the stop position of the automatic guided vehicle, a first magnetic sensor provided at substantially the center and front of the vehicle body of the automatic guided vehicle to detect a deviation between the magnet and the vehicle body, and a first magnetic sensor having a predetermined value or more. A second magnetic sensor that operates with the magnetic flux density, an encoder that measures the amount of movement of the vehicle body, and a control unit, wherein the control unit sets a coarse distance between the current position and the stop position of the vehicle body at startup. When the second magnetic sensor detects a magnet, the coarse distance is updated to the distance between the second magnetic sensor and the first magnetic sensor, and the speed is changed to a low speed. When the magnetic sensor detects a magnet and detects a zero position at which the output becomes zero, the updated value is further updated to the distance between the stop position and the zero position, and the movement amount is measured via an encoder to the stop position. Run AGV stop control device being characterized in that as. 2. The sensor according to claim 1, wherein the first magnetic sensor outputs a displacement between the center of the sensor and the magnet as a signal, and the output becomes zero when the first magnetic sensor coincides with the center point of the magnet. An automatic guided vehicle stop control device as described in the above. 2. The stop control device for an automatic guided vehicle according to claim 1, wherein the second magnetic sensor has a low operation accuracy for performing on / off operation in response to a magnetic flux density equal to or higher than a predetermined value. 3.

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