JP2015072202A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detector capable of achieving stable position detection performance even when a detection signal of a magnetic sensor is varied significantly.SOLUTION: A position detector 201 of an embodiment is configured so that a threshold for deciding a central coordinate of a rubber magnet tape 107 can be varied according to intensity of a signal obtained from a magnetic sensor array 105, the signal obtained from the magnetic sensor array 105 detects presence and a coordinate of the rubber magnet tape 107. The threshold is set so that the coordinate position of the signal obtained from the magnetic sensor array 105 substantially matches width of the rubber magnet tape 107.

Description

The present invention relates to a position detection device.
More specifically, the present invention relates to a position detection device suitable for use in, for example, a self-propelled unmanned vehicle traveling on a multi-branch road.

As is well known, a self-propelled unmanned vehicle (hereinafter abbreviated as “unmanned vehicle”) has been introduced in a facility such as a factory for the purpose of automating the conveyance of a predetermined load. This unmanned vehicle travels along the guide tape by detecting the presence of the guide tape affixed to the floor through a predetermined sensor.
There are various methods for detecting a guide tape, but the applicant uses a rubber magnet as a guide tape and detects the magnetic flux of this rubber magnet tape, thereby realizing a stable guide tape detection performance that is resistant to noise and the like. Develops, manufactures and sells position detectors for unmanned vehicles.

  The unmanned vehicle detects the center line of the guide tape and performs steering control so that the detected position is directed toward the center of the unmanned vehicle. Therefore, the applicant's position detection device outputs position information of the center in the width direction of the rubber magnet tape as an analog voltage.

  Patent document 1 is a prior art document of the position detection apparatus by the applicant.

Japanese Patent Laid-Open No. 6-258094

  The position detection device according to the prior art has good resistance to noise, but when operating on a floor with many irregularities, the output signal of the magnetic sensor fluctuates greatly, so that the output signal contains a large error was there.

  An object of the present invention is to solve this problem and to provide a position detection device that realizes stable position detection performance even when a detection signal of a magnetic sensor fluctuates greatly.

  In order to solve the above-described problems, a position detection device of the present invention includes a magnetic sensor array including a plurality of magnetic sensors opposed to each other in the width direction of a magnetic tape, and signals output from the magnetic sensor array. And a measured value memory for storing the values. Further, a threshold value calculation unit that sets a threshold value according to the magnitude of the peak value included in the values of the plurality of signals stored in the measurement value memory, and the values and threshold values of the plurality of signals stored in the measurement value memory And a center coordinate calculation unit for calculating the center coordinates of the tape.

According to the present invention, it is possible to provide a position detection device that realizes stable position detection performance even if the detection signal of the magnetic sensor fluctuates greatly.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is the external appearance perspective view of the unmanned vehicle which mounts the position detection apparatus which concerns on embodiment of this invention, and the block diagram which imaged the cross section which looked at the unmanned vehicle from the front. It is a block diagram which shows the hardware constitutions of the position detection apparatus which concerns on embodiment of this invention. It is a functional block diagram of a microcomputer. It is a flowchart which shows the flow of the center coordinate detection process which a microcomputer performs. It is a flowchart which shows the flow of the center coordinate detection process which a microcomputer performs. It is a graph which shows magnetic flux density distribution in the width direction of a rubber magnet tape. It is the schematic explaining the detection method of the center coordinate in the straight advance mode, and the schematic explaining the detection method of the center coordinate in the right turn mode and the left turn mode. It is the graph which shows the relationship between the signal level of a magnetic sensor, and a threshold, the schematic which shows the relationship between an intermediate value, and a threshold, the schematic of a magnetic sensor array, and the schematic of the magnetic sensor array compared with the threshold. It is the schematic explaining the calculation method of the center coordinate in the straight traveling mode.

FIG. 1A is an external perspective view of an unmanned vehicle 101 equipped with a position detection device according to an embodiment of the present invention.
FIG. 1B is a block diagram illustrating a cross section of the unmanned vehicle 101 as viewed from the front.
The unmanned vehicle 101 includes a plurality of wheels 102, such as four wheels or three wheels, that can stably run by themselves. A part of the wheel 102 is rotationally driven by a motor 103 as a drive wheel.
A magnetic sensor array 105 is attached to the bottom of the housing 104 of the unmanned vehicle 101. The magnetic sensor array 105 is configured to be longer than the width of the rubber magnet tape 107 so that the presence of the rubber magnet tape 107 attached to the floor 106 can be detected.
The magnetic sensor array 105 is connected to the center coordinate detection unit 108. The combination of the center coordinate detection unit 108 and the magnetic sensor array 105 is the position detection device according to this embodiment.

The unmanned vehicle control unit 111 is a control device mainly composed of a microcomputer, and stores information on a travel route formed by a rubber magnet tape 107 laid in a facility such as a factory. The unmanned vehicle 101 is controlled so as to reach a predetermined destination in response to a destination command from the outside.
Usually, an address magnet or the like indicating the position is provided on the road surface in front of the branch point of the travel route formed by the rubber magnet tape 107. The unmanned vehicle control unit 111 detects this address magnet with an unillustrated address sensor or the like, grasps the current position of the unmanned vehicle 101, and then determines in which direction the unmanned vehicle 101 is steered. Based on the determined steering direction, a branch command signal is output to the center coordinate detection unit 108. Branch commands are straight, right turn and left turn. The center coordinate detection unit 108 outputs a center coordinate signal corresponding to the branch command, and the unmanned vehicle control unit 111 performs steering control so that the received center coordinate signal becomes the center of the unmanned vehicle 101.

FIG. 2 is a block diagram showing a hardware configuration of the position detection apparatus 201 according to the embodiment of the present invention.
The magnetic sensor array 105 is configured by arranging a plurality of magnetic sensors 202 in a line. In the present embodiment, the magnetic sensor 202 is a saturable coil, but may be a Hall element or the like. The magnetic sensor 202 incorporates a sample and hold circuit, is driven by a pulse signal output from the microcomputer 205 described later, and outputs a voltage proportional to the magnetic intensity. The output signal of the magnetic sensor 202 is connected to each analog input terminal of the microcomputer 205.

In the microcomputer 205, a CPU 206, a ROM 207 that is a flash memory, a RAM 208, an A / D converter 209, a D / A converter 210, and an interface 211 are connected to a bus 212. Further, a plurality of analog input terminals are connected to the A / D converter 209 through the multiplexer 213.
As can be seen with reference to FIGS. 1 and 2, the center coordinate detection unit 108 is constituted by a microcomputer 205.

  An output signal of the magnetic sensor 202 is input to the microcomputer 205. The microcomputer 205 controls the magnetic sensor 202 and the multiplexer 213 according to the program stored in the ROM 207, A / D converts the voltage of the output signal of each magnetic sensor 202 by the A / D converter 209, and stores it in the RAM 208. To do. Then, the microcomputer 205 executes arithmetic processing described later and outputs a center coordinate signal from the D / A converter 210.

FIG. 3 is a functional block diagram of the center coordinate detection unit 108. It is also a functional block diagram of the microcomputer 205.
The signal data of each magnetic sensor 202 input via the A / D converter 209 is temporarily stored in the measurement value memory 302 based on the control of the control unit 301. The control unit 301 also performs operation control of a measurement value verification unit 303, a detection threshold calculation unit 304, a center coordinate calculation unit 305, a mode flag memory 306, a center coordinate memory 307, a switch 308, and the like, which will be described later.
The signal data of each magnetic sensor 202 stored in the measurement value memory 302 is first checked for validity by the measurement value verification unit 303.

  The measurement value verification unit 303 extracts the peak value and the second largest value from the signal data of each magnetic sensor 202 stored in the measurement value memory 302, and compares the difference with a predetermined error determination threshold value. . If the difference is equal to or less than the error determination threshold, it is determined that the signal data of each magnetic sensor 202 is valid. On the other hand, if the difference exceeds the error determination threshold, it is determined that noise is mixed in the signal data of each magnetic sensor 202 so that it cannot be ignored and is not appropriate for calculating the center coordinates. Thus, the measurement value verification unit 303 obtains a peak value from the verification signal, which is a logical signal indicating OK or NG, as the verification result of the signal data of each magnetic sensor 202, and the signal data of each magnetic sensor 202 in the case of OK. The signal data from the magnetic sensor shown (hereinafter referred to as “peak value”) is output.

  The verification signal and the peak value output from the measurement value verification unit 303 are input to the detection threshold value calculation unit 304. When the verification signal is a logical value indicating OK, the detection threshold calculation unit 304 calculates a threshold for the signal data of each magnetic sensor 202 stored in the measurement value memory 302 based on the peak value. This detection threshold is a threshold for determining which magnetic sensor 202 signal data is data facing the rubber magnet tape 107.

The threshold value calculated by the detection threshold value calculation unit 304 is input to the central coordinate calculation unit 305.
The central coordinate calculation unit 305 first refers to the signal data of each magnetic sensor 202 stored in the measurement value memory 302, and the value of the magnetic sensor 202 equal to or higher than the detection threshold across the detection threshold and less than the detection threshold. Find the value of the magnetic sensor 202. Then, an intermediate value between the two values straddling the detection threshold is calculated. This intermediate value is treated as a value of a “virtual magnetic sensor” that assumes that there is a magnetic sensor 202 there. Next, the intermediate values are compared with a threshold value, and two coordinates of the magnetic sensor 202 including the virtual magnetic sensor indicating the lowest value equal to or higher than the threshold value are determined on the left and right.
Next, the center coordinate calculation unit 305 refers to the mode flag memory 306 and calculates center coordinates. The mode flag memory 306 stores information indicating any one of “straight ahead mode”, “right turn mode”, and “left turn mode” in accordance with the branch command signal output from the unmanned vehicle control unit 111.

When the value of the mode flag memory 306 is “straight-ahead mode”, the center coordinate calculation unit 305 outputs a middle point between the coordinates of the left and right magnetic sensors 202 as the center coordinates.
When the value of the mode flag memory 306 is “right turn mode”, a point obtained by giving a distance from the center of the rubber magnet tape 107 as an offset from the coordinates of the magnetic sensor 202 at the right end indicating the minimum value equal to or higher than the threshold Output as.
When the value of the mode flag memory 306 is “left turn mode”, a point where the distance from the center of the rubber magnet tape 107 is given as an offset from the coordinates of the magnetic sensor 202 at the left end indicating the minimum value equal to or greater than the threshold Output as.
The center coordinate information calculated in this way is stored in the center coordinate memory 307 and is output to the outside via the switch 308. The switch 308 is controlled by the verification signal of the measurement value verification unit 303. When the verification signal is NG, the previous central coordinate information stored in the central coordinate memory 307 is output to the D / A converter 210. .

4 and 5 are flowcharts showing the flow of the center coordinate detection process executed by the center coordinate detection unit 108 (microcomputer 205).
When the process is started (S401), first, the control unit 301 stores the signal data of each magnetic sensor 202 input via the A / D converter 209 in the measurement value memory 302 (S402).
When the signal data of all the magnetic sensors 202 are stored in the measurement value memory 302, the control unit 301 causes the measurement value verification unit 303 to operate.
The measured value verification unit 303 extracts the peak value and the second largest value from the signal data of each magnetic sensor 202 stored in the measured value memory 302 (S403). Then, the difference between the peak value and the second largest value is compared with a predetermined error determination threshold value, and it is confirmed whether or not noise is in a state that cannot be ignored (S404). If the difference is equal to or smaller than the error determination threshold (NO in S404), the measurement value verification unit 303 determines that the signal data of each magnetic sensor 202 is valid, and the measurement value verification unit 303 determines the signal data of each magnetic sensor 202. The verification signal indicating OK as the verification result and the peak value of the signal data of each magnetic sensor 202 are output to the detection threshold value calculation unit 304.
Next, the control unit 301 operates the detection threshold value calculation unit 304.
The detection threshold calculation unit 304 calculates a detection threshold for the signal data of each magnetic sensor 202 stored in the measurement value memory 302 based on the peak value output from the measurement value verification unit 303 (S405). Output to the unit 305. Subsequently, the control unit 301 operates the center coordinate calculation unit 305.

  First, the central coordinate calculation unit 305 refers to the signal data of each magnetic sensor 202 stored in the measurement value memory 302, and determines the value of the magnetic sensor 202 that is equal to or greater than the detection threshold across the detection threshold and the magnetic value less than the threshold. Find the value of sensor 202. Then, data interpolation is performed to calculate an intermediate value between the two values straddling these detection thresholds (S406). This intermediate value is handled as signal data from a “virtual magnetic sensor” that is regarded as if the magnetic sensor 202 is present. Next, including the intermediate values obtained as signal data from these virtual magnetic sensors, the signal data from each magnetic sensor is compared with a threshold value, and the magnetic sensor including the virtual magnetic sensor indicates the lowest value above the threshold value. Two detection coordinates 202 are determined on the left and right sides (S407).

Subsequently, the description of the flowchart will be continued with reference to FIG.
Next, the center coordinate calculation unit 305 refers to the mode flag memory 306 and checks whether or not the current operation mode is “straight-ahead mode” (S508).
When the value in the mode flag memory 306 is “straight-ahead mode” (YES in S508), the center coordinate calculation unit 305 calculates an intermediate point between the coordinates of the left and right magnetic sensors 202 as the center coordinate (S509). Then, the calculated center coordinate information is output to the unmanned vehicle control unit 111 through the D / A converter 210 and is stored in the center coordinate memory 307 (S510), and the series of processing ends (S511).

  In step S508, when the value of the mode flag memory 306 is not “straight running mode” (NO in S508), it is confirmed whether or not the current operation mode is “right turn mode” (S512). When the value of the mode flag memory 306 is “right turn mode” (YES in S512), the center coordinate calculation unit 305 determines the center of the rubber magnet tape 107 from the coordinates of the right end magnetic sensor 202 indicating the minimum value equal to or greater than the threshold value. The point given as the offset is calculated as the center coordinate (S513). Then, the calculated center coordinate information is output to the unmanned vehicle control unit 111 through the D / A converter 210 and is stored in the center coordinate memory 307 (S510), and the series of processing ends (S511).

  In step S512, when the value of the mode flag memory 306 is not “right turn mode” (NO in S512), the current operation mode is “left turn mode”. Therefore, the center coordinate calculation unit 305 calculates, as the center coordinates, a point given as a distance from the center of the rubber magnet tape 107 from the coordinates of the leftmost magnetic sensor 202 indicating the minimum value equal to or greater than the threshold value (S514). Then, the calculated center coordinate information is output to the unmanned vehicle control unit 111 through the D / A converter 210 and is stored in the center coordinate memory 307 (S510), and the series of processing ends (S511).

The description of the flowchart will be continued with reference to FIG. 4 again.
In step S404, when the difference exceeds the error determination threshold value (YES in S404), the measurement value verification unit 303 includes noise that cannot be ignored in the signal data of each magnetic sensor 202, and calculates the center coordinates. Therefore, a verification signal indicating NG is output as a verification result of the signal data of each magnetic sensor 202. In response to this, the control unit 301 discards all data in the measurement value memory 302 (S415). Thereafter, the previous center coordinate information stored in the center coordinate memory 307 through the switch 308 is output to the unmanned vehicle control unit 111 through the D / A converter 210 (S416), and a series of processing ends (FIG. 5). Step S511).

[Operation]
FIG. 6 is a graph showing the magnetic flux density distribution in the width direction of the rubber magnet tape 107. In FIG. 6, the magnetic flux density distribution is plotted while changing the distance between the magnetic sensor 202 and the rubber magnet tape 107 to 20 mm, 25 mm, 30 mm, 35 mm, and 40 mm.
As can be seen from FIG. 6, the magnetic flux density distribution of the rubber magnetic tape 107 draws a curve substantially similar to a Gaussian curve. The magnetic flux density distribution changes according to the distance between the magnetic sensor 202 and the rubber magnet tape 107. Here, the magnetic flux density distribution directly corresponds to the signal level obtained from the magnetic sensor 202.

In the prior art, the presence of the rubber magnet tape 107 is detected by using a fixed threshold value for such a signal of the magnetic sensor 202. However, when a fixed threshold value is used, the following problems occur.
For example, in order to enable detection even at a low signal level, such as when the distance between the magnetic sensor 202 and the rubber magnet tape 107 is 40 mm, it is necessary to set the threshold value low. Then, it becomes easy to pick up noise, the resistance to noise is lowered, and it causes malfunction.
Conversely, in order not to pick up noise, it is necessary to set a high threshold. Then, in the case of a low signal level, such as when the distance between the magnetic sensor 202 and the rubber magnet tape 107 is 40 mm, the signals of all the sensors become less than the threshold, and the presence of the rubber magnet tape 107 can be detected. This will cause malfunction.
Therefore, when the unmanned vehicle 101 is operated on the uneven floor 106, the distance between the magnetic sensor 202 and the rubber magnet tape 107 changes, causing a malfunction.

FIG. 7A is a schematic diagram illustrating a center coordinate detection method in the straight traveling mode.
In the straight mode, the coordinates of the right end and the left end of the magnetic sensor 202 that has detected the presence of the rubber magnet tape 107 are acquired, and the intermediate point P701 is output as the center coordinate.
FIG. 7B is a schematic diagram illustrating a center coordinate detection method in the right turn mode and the left turn mode.
In the right turn mode, the right coordinate of the magnetic sensor 202 that has detected the presence of the rubber magnet tape 107 is obtained, and the distance of half the width of the rubber magnet tape 107 is given as an offset to the right coordinate. P702 is output as the center coordinates. At this time, the coordinates of the left end of the magnetic sensor 202 that has detected the presence of the rubber magnet tape 107 are ignored.
In the case of the left turn mode, the coordinates of the left end of the magnetic sensor 202 that detects the presence of the rubber magnet tape 107 are acquired, and the distance of half the width of the rubber magnet tape 107 is given as an offset to the left end coordinates. P703 is output as the center coordinates. At this time, the coordinates of the right end of the magnetic sensor 202 that has detected the presence of the rubber magnet tape 107 are ignored.

  In the case of the prior art, in particular, in the right turn mode and the left turn mode, if the offset distance is given as a fixed value that is half the width of the rubber magnet tape 107, the distance between the magnetic sensor 202 and the rubber magnet tape 107 varies. The center position of the rubber magnet tape 107 and the center coordinates output from the position detection device 201 do not match, and an error occurs. As a result, when the straight-turn mode is switched to the right-turn mode and the left-turn mode, or when the right-turn mode and the left-turn mode are switched to the straight-turn mode, the operation of the unmanned vehicle 101 is suddenly swung to the left and right. .

The description of the operation will be continued with reference to FIG.
In the position detection device 201 of the present embodiment, the detection threshold calculation unit 304 sets the detection threshold variably according to the signal level of the magnetic sensor 202. This detection threshold is set so that the distance between two intersections where the signal level curve of the magnetic sensor 202 and the detection threshold intersect is always constant regardless of the signal level.
In the case of this embodiment, the width of the rubber magnet tape 107 is 50 mm. Therefore, as an example, for the graph shown in FIG. 6, a value corresponding to a coordinate corresponding to ± 20 mm from the center coordinate is set as a detection threshold.
The detection threshold is set so as to maintain a detection width of ± 20 mm from the center coordinate even when the distance between the magnetic sensor 202 and the rubber magnet tape 107 varies. For this reason, even if the offset distance is given as a fixed value of 20 mm in the right turn mode and the left turn mode, a large error does not occur by making the detection threshold value of the magnetic sensor 202 variable. That is, when the straight-turn mode is switched to the right-turn mode and the left-turn mode, or when the right-turn mode and the left-turn mode are switched to the straight-ahead mode, the problem that the operation of the unmanned vehicle 101 is suddenly shaken to the left and right is less likely to occur. The unmanned vehicle 101 achieves stable running performance.

FIG. 8A is a graph showing the relationship between the signal level of the magnetic sensor 202 and the detection threshold. FIG. 8A is a diagram for explaining the operation of the detection threshold value calculation unit 304 in step S405 of FIG.
In the graph of FIG. 6, there are only five variations in the distance between the magnetic sensor 202 and the rubber magnet tape 107. On the other hand, the signal level detected from the magnetic sensor 202 varies widely. Therefore, the detection threshold calculation unit 304 includes an approximate function inside. For example, it is a quadratic function such as y = ax ² + bx + c. Constants a, b, and c are stored in the ROM 207 in advance, the maximum value P801 of the magnetic sensor 202 is given as x, and a threshold value y (threshold value L802 in FIG. 8A) is calculated.

  Thus, the magnetic sensor 202 is set such that the distance between two intersections where the signal level curve of the magnetic sensor 202 intersects the detection threshold is always constant regardless of the strength of the signal level. Appropriate detection processing according to the signal level can be realized. In particular, since the width for detecting the rubber magnet tape 107 can always be detected as a constant width from the magnetic flux density generated by the rubber magnet tape 107 as compared with the prior art, accurate center coordinates are output in the right turn mode or the left turn mode. can do. Therefore, the operation of the unmanned vehicle 101 is suddenly swung to the left and right at the time of switching from the straight-ahead mode to the right-turn mode and the left-turn mode, or from the right-turn mode and the left-turn mode to the straight-ahead mode. Can solve the problem.

FIG. 8B is a schematic diagram illustrating the relationship between the intermediate value and the threshold value. FIG. 8B is a diagram for explaining the operation of the central coordinate calculation unit 305 in step S406 of FIG.
The number of magnetic sensors 202 affects cost and accuracy. Therefore, in order to improve the accuracy of the position detection device 201 by increasing the resolution of the magnetic sensor 202 while keeping the cost low, an intermediate value is calculated based on the signal levels of the two adjacent magnetic sensors 202.
The operation of calculating the intermediate value P803 may be performed only for the values of the adjacent magnetic sensors P804 and P805 with the threshold value L802 interposed therebetween.

FIG. 8C is a schematic diagram of the magnetic sensor array 105. FIG. 8D is a schematic diagram of the magnetic sensor array 105 compared to a threshold. 8C and 8D are diagrams for explaining the operation of the central coordinate calculation unit 305 in step S407 of FIG.
In FIG. 8C, a circle indicated by a solid line is an actual magnetic sensor 202, and a circle indicated by a dotted line is a virtual magnetic sensor 806 created by calculating an intermediate value.
In FIG. 8D, a sensor P803 filled in black is a virtual magnetic sensor 806 that indicates a value equal to or greater than a threshold value. Similarly, the sensors P805 and P807 filled in with black are the magnetic sensors 202 that indicate values greater than or equal to the threshold value. As shown in FIG. 8D, the distance between the sensors P803 and P807, which are painted black at the left and right ends, is approximately equal to the width of the rubber magnet tape 107.

In addition to the embodiment described above, the following application examples are conceivable.
(1) In the case of the straight-ahead mode, the center coordinates of the rubber magnet tape 107 can be calculated by performing the following arithmetic processing without performing the virtual magnetic sensor arithmetic processing.
FIG. 9 is a schematic diagram illustrating a method for calculating center coordinates in the straight traveling mode.
The output of the magnetic sensor exceeding the leftmost detection threshold is Lon, the output of the magnetic sensor less than the left detection threshold is Loff, and Loff (m) is the position coordinate of the magnetic sensor. The output of the magnetic sensor exceeding the rightmost detection threshold is Ron, the output of the magnetic sensor less than the left detection threshold is Roff, and Roff (n) is the position coordinate of the magnetic sensor. The distance between the magnetic sensors is d.
The intersection of two straight lines can be obtained by obtaining x in the following equation (1). Let this intersection be the central coordinates.

That is, two straight lines are drawn using the values of the four magnetic sensors straddling the detection threshold, and the intersection point is set as the central coordinate.
By calculating in this way, the center coordinates of the rubber magnet tape 107 can be calculated without performing the calculation process of the virtual magnetic sensor.

  (2) If the computing power of the one-chip microcomputer used for the microcomputer 205 is high, the coordinates of the intersection of the threshold and the signal level curve may be calculated using linear interpolation instead of the process of calculating the virtual magnetic sensor. Good. In this case, it can be expected to obtain coordinate information with higher accuracy than discrete coordinate information provided by the magnetic sensor 202 and the virtual magnetic sensor.

  (3) In the above-described embodiment, the detection threshold value is calculated using an approximate expression of a quadratic function. However, when accuracy is not so required and the calculation load is to be reduced, an approximate expression of a linear function may be used. A table including a value field and a detection threshold field may be provided, and the detection threshold may be derived from the record having the closest peak value.

  (4) In the above-described embodiment, the center coordinate is output as an analog voltage, but it may be output as parallel or serial digital data.

(5) In the above-described embodiment, in consideration of compatibility with the conventional product manufactured by the applicant, a curve of the signal level at which the magnetic sensor 202 detects the magnetic flux density generated by the rubber magnet tape 107, and detection The detection threshold is set so that the intersection with the threshold is slightly narrower than the width of the rubber magnet tape 107. However, it is not always necessary to set the detection threshold in this way, but it is preferable to set the detection threshold higher.
This is because if the detection threshold is set higher, it can be expected to be stronger against external noise. Further, as the detection threshold increases, the distance between the intersection of the signal level curve and the detection threshold becomes narrower than the width of the rubber magnet tape 107. Then, the range of the relative detection position between the magnetic sensor array 105 and the rubber magnet tape 107 is widened.

In the present embodiment, the position detection device 201 has been disclosed.
In the conventional position detection device, a fixed threshold is used to determine the center coordinates of the rubber magnet tape 107 in the signal obtained from the magnetic sensor array 105 for detecting the presence and coordinates of the rubber magnet tape 107. .
The position detection device 201 of this embodiment makes this threshold variable according to the intensity of the signal obtained from the magnetic sensor array 105. The threshold value is set so that the coordinate position of the signal obtained from the magnetic sensor array 105 substantially matches the width of the rubber magnet tape 107. Thus, the position detection apparatus 201 can output an accurate center coordinate by setting an appropriate threshold according to the intensity of the signal. In particular, in the right turn mode and the left turn mode, the center coordinates can be accurately output regardless of the signal strength, and the traveling stability of the unmanned vehicle 101 can be improved.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and other modifications may be made without departing from the gist of the present invention described in the claims. Includes application examples.

  DESCRIPTION OF SYMBOLS 101 ... Unmanned vehicle, 102 ... Wheel, 103 ... Motor, 104 ... Housing, 105 ... Magnetic sensor array, 106 ... Floor, 107 ... Rubber magnet tape, 108 ... Center coordinate detection part, 109 ... Command receiving part, 110 ... Antenna DESCRIPTION OF SYMBOLS 111 ... Motor drive control part 201 ... Position detection apparatus 202 ... Magnetic sensor 203 ... Preamplifier 204 ... Sample hold circuit 205 ... Microcomputer 206 ... CPU, 207 ... ROM, 208 ... RAM, 209 ... A / D Converter 210 ... D / A converter 211 ... Interface 212 ... Bus 213 ... Multiplexer 301 ... Control unit 302 ... Measured value memory 303 ... Measured value verification unit 304 ... Threshold calculation unit 305 ... Center Coordinate calculation unit, 306 ... mode flag memory, 307 ... center coordinate memory, 308 ... switch, 801 ... virtual The gas sensor

In order to solve the above-described problems, a position detection device of the present invention includes a magnetic sensor array including a plurality of magnetic sensors opposed to each other in the width direction of a magnetic tape, and signals output from the magnetic sensor array. And a measured value memory for storing the values. Further, a detection threshold value is set according to the magnitude of the peak value included in the values of the plurality of signals stored in the measurement value memory, and it is determined that the detection threshold value is effective among the plurality of magnetic sensors. A threshold calculation unit for setting a detection threshold so that the distance between the right end and the left end of the magnetic sensor is equal to or less than the width of the tape and regardless of the distance between the magnetic sensor array and the tape; A central coordinate calculation unit that compares the values of a plurality of signals and a threshold value to calculate the central coordinate of the tape.

Claims (4)

A magnetic sensor array comprising a plurality of magnetic sensors facing in the width direction of the magnetic tape;
A measurement value memory for storing values of signals output from the plurality of magnetic sensors from the magnetic sensor array;
A detection threshold value calculation unit that sets a detection threshold value according to the magnitude of the peak value included in the values of the plurality of signals stored in the measurement value memory;
A position detection apparatus comprising: a center coordinate calculation unit that calculates a center coordinate of the tape by comparing a plurality of signal values stored in the measurement value memory with the detection threshold value.   The detection threshold calculation unit sets the detection threshold so that a distance between a right end and a left end of a magnetic sensor determined to be effective by the detection threshold among the plurality of magnetic sensors is always constant. Item 2. The position detection device according to Item 1.   The center coordinate calculation unit receives a command indicating any one of straight ahead, right turn, or left turn from the outside, and in the case of straight ahead, the center point is the middle point between the right end and the left end of the magnetic sensor determined to be effective by the detection threshold. Output as coordinates, and in the case of a right turn, a point offset by half the width of the tape from the right end of the magnetic sensor determined to be effective by the detection threshold is output as a center coordinate, and in the case of a left turn, the detection threshold The position detection device according to claim 2, wherein a point offset from the left end of the magnetic sensor determined to be effective by half the width of the tape is output as a center coordinate.   The central coordinate calculation unit calculates the coordinate information on the detection threshold by linear interpolation using the magnetic sensor indicating the value closest to the detection threshold among the plurality of magnetic sensors and the detection threshold. The position detection device according to claim 3.

Images