JP5397354B2 - Position detection system - Google Patents

Description

  The present invention relates to a position detection system.

  In the field of tag detection systems using wireless tags, for example, a wireless tag searching device as disclosed in Patent Document 1 is provided as a technique for detecting the distance and direction of a wireless tag. In the technique of Patent Document 1, the distance and direction of the wireless tag are estimated based on the received intensity of the received electromagnetic wave, the reception characteristic of the antenna, and the transmission characteristic of the wireless tag. According to this technique, since various information recorded in the wireless tag can be acquired on the search device side, it is possible not only to detect the presence / absence of an object but also to acquire specific information about the object.

  In addition, as an arrival wave estimation technique using a variable directivity antenna, a technique as disclosed in Patent Document 2 is also provided. In this technique, a variable directional antenna is configured by an array antenna including a feeding element and a plurality of parasitic elements arranged around the feeding element, and CW while changing the directivity of the variable directional antenna. The direction of the transmitter is detected by transmitting a (Continuous Wave) wave.

JP 2007-74323 A JP 2006-186540 A

  By the way, in the position detection system which detects the position of a wireless tag, the case where a wireless tag is comprised with the active tag etc. provided with the built-in battery is assumed. When a wireless tag having such an internal power source is to be detected, the wireless tag reader must continue to transmit radio waves in order for the wireless tag reader to detect the wireless tag, which increases power consumption. In particular, when a wireless tag is detected while changing its directivity using a variable directivity antenna, it is generally in a time zone where the correlation with the wireless tag is low (for example, the maximum radiation direction of radio waves is wireless). Because the radio tag continues to transmit radio waves even when it is far from the tag position), a large amount of power is consumed even though the radio tag is unlikely to be detected. Will occur. If such waste of electric power continues, it may shorten the battery life and accelerate the battery replacement cycle, and as a result, the operator may be forced to perform complicated battery replacement work.

  The present invention has been made to solve the above-described problems, and an object thereof is to effectively suppress power consumption of a wireless tag in a position detection system capable of tracking the position of the wireless tag by a wireless tag reader. .

The invention of claim 1 includes a wireless tag having an internal power supply and a wireless tag reader that can communicate with the wireless tag, and is configured as a position detection system that detects the position of the wireless tag by the wireless tag reader.
The wireless tag reader controls the scanning direction of the radio wave so that the variable radiation antenna and the maximum radiation and incident direction of the radio wave input / output from the variable directivity antenna are changed around the variable directivity antenna. Directivity control means for transmitting, transmission data generating means for generating transmission data including data relating to the scanning speed of the radio wave whose maximum radiation direction and maximum incident direction are controlled by the directivity control means, and the variable directivity antenna None the configuration in which the wireless tag with a wireless communication radio waves transmitted and received as an intermediary Te, and radio communications means for the transmission data generated by at least said transmission data generation means, and outputs via the directional antenna The maximum radio wave from the variable directional antenna when the radio communication means acquires the radio wave from the radio tag. And azimuth tracking means for tracking the direction of the wireless tag based on the direction morphism has.
In addition, the wireless tag includes an antenna, receiving means for receiving at least the transmission data transmitted from the wireless tag reader, and the scanning speed included in the transmission data received by the receiving means. A transmission time zone determining means for determining a periodic radio wave transmission time zone in the wireless tag based on the data relating to the radio tag, and a radio wave via the antenna according to the radio wave transmission time zone determined by the transmission time zone determination means. Transmitting means for periodically transmitting.
The wireless tag reader or an external device of the wireless tag reader is provided with initial azimuth detecting means for detecting an initial azimuth of the wireless tag, and the wireless tag reader has a radio wave scanning speed controlled by the directivity control means. Start reference timing determination means for determining a start reference timing of the radio wave transmission time zone based on the initial direction of the wireless tag detected by the initial direction detection means. Then, the transmission time zone determining means of the wireless tag determines the start time of the radio wave transmission time zone in the wireless tag after the initial orientation is detected by the initial orientation detection means based on the start reference timing. Yes.

According to a second aspect of the present invention, in the position detection system according to the first aspect, the directivity control means is configured such that a maximum radiation direction and a maximum incident direction of a radio wave output from the variable directional antenna are the variable directional antenna. The radio wave scanning direction and the rotation cycle are controlled so as to rotate at a predetermined rotation cycle as a center, and the transmission data generation unit generates the transmission data including the cycle data related to the predetermined rotation cycle, and determines the transmission time zone A means determines the radio wave transmission time zone based on the periodic data included in the transmission data.

In the invention of claim 3, the initial azimuth detecting means is also used by the azimuth tracking means of the wireless tag reader.

According to a fourth aspect of the present invention, there is provided a laser beam scanning unit that scans a laser beam with an object carrying the radio tag as a detection target, and the laser beam scanned by the laser beam scanning unit includes the radio tag. There is provided a laser device having a light receiving means for receiving the reflected light reflected by the object carrying the light and a detecting means for detecting the orientation of the object based on a light reception result by the light receiving means.
And the said initial direction detection means is comprised by the said laser apparatus.

The invention according to claim 5 is further provided with a reception judging means for judging whether or not a radio wave periodically transmitted by the transmitting means of the wireless tag is periodically received by the wireless communication means. .
The initial azimuth detecting unit redetects the initial azimuth of the wireless tag when the reception determining unit determines that the radio wave from the wireless tag has not been periodically received, and the start reference timing When the initial azimuth detecting unit detects the initial azimuth of the wireless tag again, the determining unit is configured to determine the initial azimuth of the wireless tag detected again and the scanning speed based on the scanning speed. Re-determining the start reference timing, the transmission time zone determining means of the wireless tag resets the start time of the radio wave transmission time zone based on the start reference timing re-determined by the start reference timing determination means ing.

According to a sixth aspect of the present invention, the wireless tag includes a moving speed detecting unit that detects a moving speed of the wireless tag, and the transmission time zone determining unit includes data relating to the scanning speed included in the transmission data; The radio wave transmission time zone is determined based on the moving speed detected by the moving speed detecting means.

According to the first aspect of the present invention, there is provided transmission data generating means for generating transmission data including data relating to a scanning speed of a radio wave whose maximum radiation direction and maximum incident direction are controlled by the directivity control means, and transmission / reception via a variable directivity antenna. Wireless communication means for performing wireless communication with the wireless tag through the transmitted radio wave, at least transmission data generated by the transmission data generation means via the variable directional antenna, and the wireless communication means is a wireless tag Azimuth tracking means for tracking the azimuth of the wireless tag based on the maximum incident direction of the radio wave from the variable directivity antenna when the radio wave from the radio wave is acquired. According to this configuration, the direction of the wireless tag can be tracked based on the radio wave from the variable directional antenna, and further, “data regarding the radio wave scanning speed” can be given from the wireless tag reader to the wireless tag. It becomes like this.
On the other hand, the wireless tag includes transmission time zone determining means for determining a periodic radio wave transmission time zone in the wireless tag based on “data relating to scanning speed” included in the transmission data received by the receiving means, and transmission Transmitting means for periodically transmitting radio waves via an antenna according to the radio wave transmission time zone determined by the time zone determining means is provided. Therefore, the radio tag can be periodically transmitted in accordance with the radio wave transmission time zone determined according to the radio wave scanning speed of the radio tag reader, and the power consumption of the radio tag can be reduced compared to the configuration in which the radio wave is always transmitted. It can be effectively suppressed.
In addition, based on the initial azimuth detecting means for detecting the initial azimuth of the wireless tag, the radio wave scanning speed controlled by the directivity control means, and the initial azimuth of the wireless tag detected by the initial azimuth detecting means, Start reference timing determining means for determining the start reference timing of the time zone is provided. According to this configuration, the wireless tag can acquire an appropriate start reference timing according to the initial orientation of the wireless tag and the radio wave scanning speed, and after the initial orientation is detected based on the obtained start reference timing. The beginning of the radio wave transmission time zone can be determined appropriately.

In the invention of claim 2, the directivity control means scans the radio wave so that the maximum radiation direction and the maximum incident direction of the radio wave output from the variable directional antenna rotate at a predetermined rotation period around the variable directional antenna. The direction and the rotation cycle are controlled, and the transmission data generating means generates transmission data including cycle data relating to a predetermined rotation cycle. On the other hand, the transmission time zone determining means determines the radio wave transmission time zone based on the periodic data included in the transmission data. In this way, the periphery of the wireless tag reader can be scanned more evenly, and further, data related to the rotation period of the radio wave scanned by the wireless tag reader (period data) can be given to the wireless tag. This makes it easier to set an appropriate radio wave transmission time zone according to the radio wave rotation period.

In the invention of claim 3 , the initial direction detecting means is also used as the direction tracking means of the wireless tag reader. In this way, it is possible to detect the initial orientation without providing any special means, and it becomes easy to reduce the size and cost of the apparatus configuration.

The invention of claim 4 further includes a laser beam scanning unit that scans the laser beam, a light receiving unit that receives the reflected light reflected by the object of the laser beam scanned by the laser beam scanning unit, and a light reception result by the light receiving unit. And a detecting means for detecting the azimuth of the object based on the above. The initial orientation detection means is constituted by a laser device.
If it does in this way, it will become easy to detect the initial position of a wireless tag correctly by a laser apparatus.

According to a fifth aspect of the present invention, there is provided reception determination means for determining whether or not radio waves periodically transmitted by the wireless tag transmission means are periodically received by the wireless communication means. The initial azimuth detecting means redetects the initial azimuth of the wireless tag when it is determined that the radio wave from the wireless tag has not been received periodically. Then, the start reference timing determining means, when the initial orientation of the wireless tag is redetected by the initial orientation detection means, the start reference timing in the wireless tag based on the re-detected initial orientation of the wireless tag and the scanning speed. The wireless tag transmission time zone determination means resets the start of the radio wave transmission time zone based on the start reference timing re-determined by the start reference timing determination means.
In this way, when the radio wave from the wireless tag is not periodically received, the initial orientation of the wireless tag can be newly set, and the start reference timing can be corrected to a more appropriate timing accordingly. And since the start of a radio wave transmission time slot | zone can be reset based on the start reference | standard timing reexamined appropriately in this way, favorable communication is attained, suppressing power consumption effectively.

According to a sixth aspect of the present invention, the wireless tag includes a moving speed detecting unit that detects a moving speed of the wireless tag, and the sending time zone determining unit includes the data related to the scanning speed included in the transmission data and the moving speed detecting unit. The radio wave transmission time zone is determined based on the detected moving speed. In this way, the wireless tag can determine the radio wave transmission time zone more appropriately in consideration of not only the radio wave scanning speed but also its moving speed.

FIG. 1 is an explanatory diagram conceptually illustrating the position detection system according to the first embodiment of the present invention. FIG. 2 is a block diagram schematically illustrating an electrical configuration of a wireless tag reader (wireless reader) used in the position detection system of FIG. FIG. 3 is a block diagram schematically illustrating an electrical configuration of a wireless tag used in the position detection system of FIG. FIG. 4 is a flowchart illustrating the flow of communication processing on the wireless tag side in the position detection system of FIG. FIG. 5A is an explanatory diagram conceptually illustrating a request frame transmitted from the wireless tag to the wireless tag reader. FIG. 5B is an explanatory diagram conceptually illustrating an ACK frame from the wireless tag reader. FIG. 5C is an explanatory diagram conceptually illustrating a data frame transmitted from the wireless tag reader to the wireless tag. FIG. 6 is a graph illustrating the relationship between the directivity angle and the received electric field strength when the wireless tag exists in the first radio wave direction. FIG. 7A is an explanatory diagram illustrating the relationship between the time required for one round of scanning in each round and the radio wave radiation time in the Nth radio wave direction for radio wave scanning in the wireless tag reader. FIG. 7B is an explanatory diagram illustrating a method of setting a radio wave transmission time zone with a wireless tag. FIG. 7C is an example of an arithmetic expression that determines the correction time according to the moving speed, and FIG. 7D is an example of a table that determines the correction time according to the moving speed. FIG. 8 is an explanatory diagram conceptually illustrating a position detection system according to the second embodiment of the present invention. FIG. 9 is a cross-sectional view schematically illustrating a laser sensor (laser device) used in the position detection system of FIG. FIG. 10 is an explanatory diagram showing the correspondence between the angle of the laser sensor and the radio wave direction.

[First embodiment]
A first embodiment that embodies the position detection system of the present invention will be described below with reference to the drawings.
(Outline of position detection system)
First, an outline of the position detection system 1 according to the first embodiment will be described. FIG. 1 is an explanatory diagram conceptually illustrating the position detection system according to the first embodiment of the present invention. FIG. 2 is a block diagram schematically illustrating an electrical configuration of a wireless tag reader used in the position detection system of FIG. FIG. 3 is a block diagram schematically illustrating an electrical configuration of a wireless tag used in the position detection system of FIG.

  As shown in FIG. 1, the position detection system 1 according to the first embodiment is configured as a monitoring system that monitors an object (such as an intruder) entering a predetermined monitoring area, for example. , And a wireless tag 50 held by a person (for example, an authorized person). Hereinafter, each of these devices will be described in detail.

(Wireless tag reader)
Next, the wireless tag reader 10 will be described.
As shown in FIG. 2, the wireless tag reader 10 is configured as an RFID tag reader / writer capable of reading an RFID tag, for example, and performs communication using electromagnetic waves with the wireless tag 50 to record information recorded in the wireless tag 50. Reading and writing information to the wireless tag 50 are performed. The wireless tag reader 10 is mainly configured by a control unit 11, a transmission unit 12, a reception unit 13, and a variable directivity antenna 14.

  The control unit 11 includes a CPU 31, a memory 32, a timer circuit 33, and the like, and has a configuration that governs overall control of the wireless tag reader 10.

  The transmission unit 12 includes a coding unit 21, a modulation unit 22, an amplification unit 23, and the like, and is configured to output a carrier (carrier wave) having a predetermined frequency from a carrier oscillator (not shown). The encoding unit 21 is connected to the control unit 11, encodes transmission data output from the control unit 11, and outputs the encoded transmission data to the modulation unit 22. The modulation unit 22 is a part to which the carrier (carrier wave) from the carrier oscillator and the transmission data from the encoding unit are input, and when the command (carrier wave) output from the carrier oscillator is transmitted to the communication target A modulated signal, for example, ASK (Amplitude Shift Keying) modulated by the encoded transmission code (modulated signal) output from the encoding unit 21 is generated and output to the amplifying unit 23.

  The amplifying unit 23 amplifies the input signal (the modulated signal modulated by the modulating unit) with a predetermined gain, and outputs the amplified signal to the variable directivity antenna 14 via a filter, a matching circuit, etc. (not shown). . When a transmission signal is output to the variable directivity antenna 14 in this way, the transmission signal is radiated to the outside from the variable directivity antenna 14 as an electromagnetic wave.

  The variable directivity antenna 14 is configured by a known variable directivity antenna such as an ESPAR antenna, and the directivity is controlled by the control unit 11. Specifically, for example, as shown in FIG. 1, the emission direction of radio waves is switched along the horizontal direction. In the present embodiment, the control unit 11 corresponds to an example of “directivity control means”, and the maximum radiation and the incident direction of the radio wave input / output from the variable directional antenna 14 are set around the variable directional antenna 14. More specifically, the radio wave scanning direction is controlled so that the maximum radiation direction of the radio wave output from the variable directivity antenna 14 is centered on the variable directivity antenna 14 with a predetermined rotation period (2π / The scanning direction and rotation period of the radio wave are controlled so as to rotate at ω).

  The receiving unit 13 includes a demodulating unit 25, a decoding unit 26, and the like, and is configured to receive a radio wave signal received by the variable directivity antenna 14. The receiving unit 13 receives a received signal from the variable directivity antenna 14 via a matching circuit (not shown), filters it with a filter (not shown), amplifies it with an amplifier (not shown), and demodulates the amplified signal. Demodulated by the unit 25. Then, the demodulated signal waveform is binarized by a binarization processing unit (not shown), decoded by the decoding unit 26, and then the decoded signal is output to the control unit 11 as received data. The receiving unit 13 is provided with a carrier sense unit 27 that checks whether a channel for emitting radio waves is available.

(Wireless tag)
The wireless tag 50 is configured, for example, as a known RFID tag in hardware, and includes a control unit 51, an antenna 54, a reception unit 53, a transmission unit 52, a power supply unit 59, and the like as illustrated in FIG. In the example of FIG. 3, the wireless tag 50 is configured as a so-called active tag, and a built-in battery (for example, a lithium coin battery) is provided. The power supply unit 59 receives power supply from the built-in battery, and the control unit Power for operation is supplied to each component including 51.

  The control unit 51 includes a CPU 55, a memory 56, a timer circuit 57, and the like. The CPU 55 performs various controls (such as response processing in FIG. 7) and arithmetic processing in the wireless tag 50. The memory 56 includes various semiconductor memories such as a ROM and an EEPROM, and stores various types of information such as tag identification information (tag ID) for identifying the wireless tag 50 and information handled in communication processing described later. It has come to be.

  The receiving unit 53 includes a demodulating unit 65, a decoding unit 66, a received signal strength detecting unit 67, and the like. In the receiving unit 53, the signal received by the antenna 54 is demodulated by the demodulating unit 65, and the demodulated signal is decoded by the decoding unit 66, thereby outputting the data superimposed on the received signal to the control unit 51. doing. The received signal strength detection unit 67 is a part that detects the radio wave strength of the received signal received by the antenna 54, and outputs the detection signal to the control unit 51. The receiving unit 13 is also provided with a carrier sense unit 68 that checks whether a channel for emitting radio waves is available.

  The transmission unit 52 mainly includes a coding unit 61, a modulation unit 62, and an amplification unit 63. The transmitter 52 encodes the data output from the controller 51 as transmission data by the encoder 61 and then modulates the data by the modulator 62. The modulated signal is amplified by the amplifying unit 63 and output to the antenna 54. Thus, the transmission data output to the antenna 54 is radiated from the antenna 54 as a radio wave signal.

(Detection operation performed by the position detection system)
Next, the detection operation performed by the position detection system 1 will be described.
FIG. 4 is a flowchart illustrating the flow of communication processing on the wireless tag side in the position detection system of FIG. FIG. 5A is an explanatory diagram conceptually illustrating a request frame transmitted from the wireless tag to the wireless tag reader. FIG. 5B is an explanatory diagram conceptually illustrating an ACK frame from the wireless tag reader. FIG. 5C is an explanatory diagram conceptually illustrating a data frame transmitted from the wireless tag reader to the wireless tag. FIG. 6 is a graph illustrating the relationship between the directivity angle and the received electric field strength when the wireless tag exists in the first radio wave direction. FIG. 7A is an explanatory diagram illustrating the relationship between the time required for one round of scanning in each round and the radio wave radiation time in the Nth radio wave direction for radio wave scanning in the wireless tag reader. FIG. 7B is an explanatory diagram illustrating a method of setting a radio wave transmission time zone with a wireless tag. FIG. 7C is an example of an arithmetic expression that determines the correction time according to the moving speed, and FIG. 7D is an example of a table that determines the correction time according to the moving speed.

  In the position detection system 1, as shown in FIG. 1, the direction of the radio wave radiated from the variable directivity antenna 14 is switched in turn at a speed determined in each of 12 preset directions. For example, one round of scanning is performed at T (s). Therefore, the time for which radio wave radiation is maintained in each direction is T / 12. Hereinafter, the scan speed ω (rad / s) is treated as ω = 2π / T.

  For example, the wireless tag 50 performs the processing of FIG. 4 when a predetermined operation is performed or when the power is turned on as a trigger. First, the wireless tag 50 transmits a request frame to the wireless tag reader 10, A detection is requested (S1). For example, as shown in FIG. 5A, the request frame includes a header portion, length data, sequence number, reader ID, tag ID, data transmission request command, checksum, and the like. In the present embodiment, a first request command for requesting a data frame including scan speed information, which will be described later, is determined in advance. In the request frame transmitted in S1, the first request command is used as the data transmission request command. Request commands are included. The reader ID is an ID of the wireless tag reader 10 that is predetermined as a communication target of the wireless tag 50, and the tag ID is a unique ID of the wireless tag 50. Note that both the reader ID and the tag ID are stored in the memory 56 in advance.

  After the process of S1, it is determined whether or not there is an ACK frame response (acknowledgment) from the wireless tag reader 10. The wireless tag reader 10 monitors the radio wave from the radio tag 50 while changing the transmission / reception direction of the radio wave at a predetermined speed as described above. When the radio tag reader 10 can receive the radio wave from the radio tag 50, the ACK frame (acknowledgment) Is supposed to return. Note that the ACK frame returned from the wireless tag reader 10 has a frame configuration as shown in FIG. 5B, for example. In S2, it is determined whether or not such an ACK frame has been received. If not, the process proceeds to No and transmits a request frame again (S1).

  If the reception of the ACK frame is confirmed, the process proceeds to Yes in S2 to receive the data frame (S3). The wireless tag reader 10 used in the present embodiment analyzes the content of the data transmission request command when receiving the request frame. If the first request command is included, the wireless tag reader 10 receives an ACK frame for the wireless tag 50. , The data frame including the scan speed information is transmitted. In S3, the transmitted data frame is received.

  After S3, the scan speed is acquired from the data frame (S4). A data frame transmitted from the wireless tag reader 10 includes a header, a length, a sequence number, a tag ID, a reader ID, data, a checksum, and the like as shown in FIG. Among these, the tag ID is a tag ID included in the request frame transmitted in S1, and identifies the wireless tag 50 that is a transmission target of the data frame. The reader ID is a unique ID that identifies the source wireless tag reader 10 that transmits the data frame. Further, the data frame received in S3 (data frame returned in response to the request frame including the first request command) includes the scan speed information for specifying the scan speed ω as described above. Yes. Note that the scan speed information (for example, the value of the scan speed ω) may be stored in advance in the memory 32 as a set value, and may be calculated and generated by the wireless tag reader 10 when a data frame is transmitted.

  In the present embodiment, the control unit 11 of the wireless tag reader 10 corresponds to an example of a “transmission data generation unit”, and includes data “scanning speed data” of radio waves whose maximum radiation direction is controlled by the “directivity control unit”. Functions to generate a frame (transmission data). The “data relating to the scanning speed of the radio wave” may be data (period data) that can specify the predetermined rotation period T (2π / ω) of the wireless tag reader 10, for example, the scanning speed ω as described above. Alternatively, the predetermined rotation period T (2π / ω) of the wireless tag reader 10 may be used.

  In the present embodiment, the control unit 11, the transmission unit 12, and the reception unit 13 correspond to an example of “wireless communication means”, and the wireless tag 50 and the wireless tag 50 are wirelessly transmitted via radio waves transmitted and received via the variable directivity antenna 14. It is configured to perform communication, and functions to output at least the transmission data generated by the “transmission data generation unit” via the variable directivity antenna 14.

  In S3, the data frame as described above is received from the wireless tag reader 10, and in S4, the data frame is analyzed to obtain scan speed information included in the data frame. In the present embodiment, the control unit 51 and the reception unit 53 correspond to an example of “reception unit” and function to receive at least transmission data transmitted from the wireless tag reader 10 via the antenna 54.

Then, after acquiring the scan speed information in S4, a direction detection radio wave is transmitted (S5). As the direction detection radio wave, for example, an unmodulated wave can be transmitted. In this embodiment, the direction detection radio wave (unmodulated wave) continues to be transmitted until the transmission time Ttx exceeds 2π / ω. 2π / ω is a time T (s) required for one round of radio wave scanning in the radio tag reader 10, and thus a direction detection radio wave (unmodulated wave) from the radio tag 50 is a radio wave from the variable directivity antenna 14. The transmission continues until at least one scan is completed. If the transmission time Ttx of the direction detection radio wave (unmodulated wave) exceeds 2π / ω, the process proceeds to Yes in S6, and the transmission of the direction detection radio wave (unmodulated wave) is stopped (S7). . As described above, since the radio tag 50 transmits the direction detection radio wave (unmodulated wave) until the radio wave scanning from the variable directivity antenna 14 is completed for at least one round, the radio tag reader 10 performs the radio wave scanning of one round. The direction detection radio wave (unmodulated wave) from the wireless tag 50 can be received at any time in the middle, and the initial orientation of the wireless tag 50 can be specified based on the radio wave direction at the time of reception.
In the present embodiment, the control unit 11 of the wireless tag reader 10 corresponds to an example of “initial orientation detection means” and functions to detect the initial orientation of the wireless tag 50.

  After the processing of S7, a request frame shown in FIG. 5A is transmitted to request a radio wave transmission time zone and a radio wave suspension time zone. In the present embodiment, a second request command for requesting a radio wave transmission time zone and a radio wave suspension time zone is determined in advance, and the request frame transmitted in S8 includes the second request command as a data transmission request command. Request commands are included.

Here, calculation of a radio wave transmission time zone and a radio wave suspension time zone performed by the wireless tag reader 10 will be described.
As described above, the wireless tag reader 10 scans radio waves at an average speed of ω (rad / s), and scans for one round at T (s) (= 2π / ω). Is to be done. In the example of FIG. 1, when the predetermined reference direction is the first direction F1 (0 rad) in each direction extending radially from the wireless tag reader 10 in the horizontal direction, the radio waves are concentrated so that the radio waves are concentrated in the first direction F1. One radio wave direction is defined. A range in the first radio wave direction is indicated by a symbol W1. Then, every time 30 ° (π / 6 rad) is shifted clockwise from the reference direction (first direction F1), the second direction F2 and the third direction F3 are sequentially set up to the twelfth direction F12 (fourth). Arrows from the direction to the eleventh direction are omitted), the second direction F2, the third direction F3,..., The radio wave directions concentrated in the twelfth direction F12 are the second radio wave direction (see reference W2) and the third radio wave direction (see FIG. It is defined as the twelfth radio wave direction (see reference W12). In the wireless tag reader 10, the radio wave transmission / reception direction is switched to 12 directions in order of the first radio wave direction, the second radio wave direction, and the third radio wave direction, and the radio wave radiation duration Tbcn in each radio wave direction is T / 12 ( That is, 2π / 12ω).

  Here, assuming that the timing at which radio wave emission in the first radio wave direction (see symbol W1) starts in “a certain round” is the reference time T11, the second, third,... Radio wave transmission / reception start timings in the first radio wave direction are T21 (= T11 + T), T31 (= T11 + 2T)... Tn1 (= T11 + (n−) every period T (s) (= 2π / ω) from the reference time T11. 1) T), and radio waves are concentrated in the first radio wave direction for the time T / 12 (= 2π / 12ω) from the radio wave transmission / reception start timing for each round. Therefore, the time zone in which radio waves concentrate in the first radio wave direction is specified for each lap. FIG. 7A conceptually illustrates the timing from the start of radio wave emission in the first radio wave direction to the end of radio wave emission in the 12th radio wave direction in each lap, and the radio wave emission start timing in the first radio wave direction. For example, in the case of “a certain round”, the reference time T11 is set to “0” for convenience, and the radio wave emission end timing in the twelfth radio wave direction is set to 2π / ω.

The same applies to the second radio wave direction, the third radio wave direction,... The Xth radio wave direction. For example, if the radio wave transmission / reception start timing in the X radio wave direction in the above “certain lap” is T1X, T1X is the following equation using the reference time T11 at the “certain lap”:
That is, it can be expressed by T1X = T11 + (X−1) × T / 12.
Then, when “a certain round” is defined as the first round, the second and third rounds after that, the radio wave transmission / reception start timing in the X radio wave direction of the nth round is the period T (s) (= 2π / Ω), T2X (= T1X + T), T3X (= T1X + 2T)... TnX (= T1X + (n−1) T). Radio waves are concentrated in the X radio wave direction for a time of 2π / 12ω). Therefore, the time zone in which radio waves concentrate in the X-th radio wave direction in each lap is specified.

  For example, when X = 3 (that is, in the case of the third radio wave direction), T13 = T11 + 2 × T / 12, where T13 is the radio wave transmission / reception start timing in the “a certain round”. Then, the radio wave transmission / reception start timing in the third radio wave direction in the second, third,..., Nth round after the first round is T23 (= T13 + T) every period T (s) (= 2π / ω). ), T33 (= T13 + 2T)... Tn3 (= T13 + (n−1) T), and the third radio wave direction for each lap is T / 12 (= 2π / 12ω) from the radio wave transmission / reception start timing. The radio waves will be concentrated on.

  As described above, the wireless tag reader 10 detects the initial azimuth of the wireless tag 50 and holds this azimuth information (that is, information specifying in which radio wave direction the wireless tag 50 exists). The time zone in which the radio tag 50 exists and radiates radio waves in the direction of the radio wave is defined as the “radio wave transmission time zone” in which radio waves are to be transmitted, and the radio wave is suspended in other time zones. Such time zone information is generated as “time zone” and transmitted to the wireless tag 50.

  For example, when the radio wave direction (initial azimuth) of the wireless tag 50 detected on the wireless tag reader 10 side based on the direction detection radio waves of S5 to S7 is the Nth radio wave direction, as shown in FIG. In addition, the timing when (N−1) × T / 12 has elapsed from the reference time (timing at which radio wave emission in the first radio wave direction is started) in each lap is the radio wave radiation start timing (start reference timing in the Nth radio wave direction) ) TNs, and the duration Tbcn during which the radio waves are concentrated in the Nth radio wave direction is T / 12. Therefore, from these, the time zone in which the radio waves concentrate in the Nth radio wave direction in each round (ie, Thus, it is possible to specify a time zone in which radio waves from the radio tag reader 10 are concentrated in the radio wave direction in which the presence of the radio tag 50 is estimated. Accordingly, the Tofs data (that is, (N−1) × T / 12) and the data of the duration Tbcn (that is, T / 12) that specify the radio wave radiation start timing (start reference timing TNs) are stored in the wireless tag 50. The “radio wave transmission time zone” of the radio tag 50 is a time zone in which the radio tag 50 should be suspended, except for the time zone specified by the “radio wave transmission time zone”. This information also functions as “radio wave suspension time” information.

When the wireless tag reader 10 receives the request frame, it analyzes the data transmission request command. If the second request command is included as in the request frame transmitted in S8, the wireless tag reader 10 returns an ACK frame. Thereafter, the “radio wave transmission time zone” information (“radio wave pause time” information) generated as described above is transmitted to the wireless tag 50 in a form included in the data frame of FIG.
In the present embodiment, the control unit 11 of the wireless tag reader 10 corresponds to an example of a “starting reference timing determining unit”. The radio wave scanning speed ω controlled by the “directivity control unit” and the “initial orientation detecting unit” The start reference timing Tofs of the “radio wave transmission time zone” is determined based on the initial orientation of the wireless tag 50 detected by the above.

  If there is an ACK frame response to the request frame transmitted in S8, the wireless tag 50 proceeds to Yes in S9 and receives a data frame transmitted thereafter (S10). Then, by analyzing this data frame, the start reference timing Tofs of each lap and the radio wave emission duration Tbcn are obtained. Further, by acquiring the scanning speed ω in S4, the time T (that is, 2π / ω) required for one round of radio wave scanning can be specified. Accordingly, if the radio tag reader 10 can identify the radio wave radiation start timing in the first radio wave direction (that is, the reference time T11 for any “circumference”) in any of the rounds of the radio tag reader 10, any of the radio tags 50 It is possible to synchronize the reference time of circulation (that is, the timing of “0” in FIG. 7B) with the radio wave radiation start timing in the first radio wave direction (that is, T11 + m × T, where m is an integer). Thus, the radio wave transmission time zone (Tf to Tg) on the radio tag 50 side can be determined to be the same period as the radio wave emission time zone (time TNs to TNe) in the Nth radio wave direction in the radio tag reader 10. . Note that various methods can be used to transmit the timing of the reference time T11 in an arbitrary “circumference”. For example, the wireless tag reader 10 transmits a synchronization signal for specifying the reference time T11 to the wireless tag 50. Alternatively, the wireless tag reader 10 and the wireless tag 50 may each be provided with an internal clock, and the wireless tag reader 10 may transmit time information specifying the reference time T11 to the wireless tag 50. In any case, it is only necessary that the radio tag 50 can specify the radio wave radiation start time (reference time) T11 in the first radio wave direction in any of the laps.

Here, returning to FIG. 4, the description of the communication process will be continued.
As described above, the wireless tag 50 can set the reference time (time “0” in FIG. 7B) at the same timing as the radio wave radiation start timing in the first radio wave direction. To T (= 2π / ω) every reference time is determined. Then, the time Tofs (start reference timing) acquired in S10 is temporarily set as a value indicating the start of the radio wave transmission time zone, and the time Tbcn acquired in S10 is temporarily set as the radio wave transmission duration time in the radio wave transmission time zone. .

Thereafter, the moving speed of the wireless tag 50 in the horizontal direction is measured based on the value detected by the acceleration sensor 80 (S12), and the measured value obtained in S12 is held as the moving speed V of the wireless tag 50 (S13). In the present embodiment, for example, a known triaxial acceleration sensor is provided as the acceleration sensor 80, and the wireless tag 50 can specify the vertical direction and the horizontal direction by a known method. Then, the horizontal speed is calculated from the specified horizontal acceleration component.
In the present embodiment, the acceleration sensor 80 corresponds to an example of “movement speed detecting means” and functions to detect the movement speed of the wireless tag 50.

  Then, based on the moving speed V held in S13, the radio wave transmission time zone temporarily set in S11 is corrected (S14). Specifically, the radio wave is advanced so that the start timing is advanced by the time α from the start reference timing Tf temporarily set in S11, and the end timing is delayed by the time α from the end reference timing Tg after the time Tbcn from the start reference timing Tf. The sending time zone is corrected. In this embodiment, for example, the speed V obtained in S13 is increased by an arithmetic expression in FIG. 7C (for example, a proportional expression using α and V as variables) or a table in FIG. 7D. Accordingly, the speed V and the correction time α are associated with each other so that the correction time α becomes longer. Then, the radio wave transmission time zone is determined so that the time Tf ′ that is earlier by α than the start reference timing Tf is set as the start timing, and Tg ′ that is delayed by α from the end reference timing Tg is set as the end timing. That is, Tf ′ to Tg ′ are set as a radio wave transmission time zone for each period (each cycle) corresponding to the radio wave scanning period of the wireless tag reader 10, and 0 to Tf′Tg ′ to 2π / ω are radio wave pause times. A band is set (S15). Then, in each period (each lap), radio waves are transmitted according to the radio wave transmission time zone and radio wave pause time zone thus set (S16).

In the present embodiment, the control unit 51 of the wireless tag 50 corresponds to an example of “transmission time zone determination means”, and data relating to the scanning speed included in the transmission data received by the “reception means” (period 2π / ω). Based on data (for example, scan speed ω) that can be specified, it functions to determine a periodic radio wave transmission time zone in the wireless tag 50. Specifically, the data (scanning speed ω) relating to the scanning speed included in the transmission data, the start reference timing (Tofs) sent from the wireless tag reader 10, and the moving speed detected by the acceleration sensor (moving speed detecting means). Based on V, the start time of the radio wave transmission time zone in the wireless tag 50 after the initial azimuth is detected by the “initial direction detection means” (start time Tf ′ of the radio wave transmission time zone of each cycle) is determined.
In this embodiment, the control unit 51 and the transmission unit 52 correspond to an example of “transmission unit”, and the radio wave is periodically transmitted via the antenna 54 according to the radio wave transmission time zone determined by the “transmission time zone determination unit”. Function to send automatically.

  The wireless tag 50 determines whether or not a response from the wireless tag reader 10 can be confirmed every time the direction detection radio wave is transmitted in S16 in each cycle, and wirelessly responds to the transmission of the direction detection radio wave in S16. If the response from the tag reader 10 is confirmed, the process proceeds to Yes in S17, returns to S16, and transmits the direction detection radio wave in the radio wave transmission time zone of the next cycle.

  In this manner, the direction detection radio wave is transmitted from the wireless tag 50 for each period, whereas the wireless tag reader 10 checks the direction detection radio wave from the wireless tag 50 for each round in which radio wave scanning is performed. When a direction detection radio wave is detected from the radio tag 50, the radio wave direction detected in association with the ID of the radio tag 50 is recorded. Therefore, the radio wave direction in which the wireless tag 50 is detected is recorded for each turn, and the direction of the wireless tag 50 can be tracked in this way. In addition, in the detection area of the wireless tag reader 10, when radio waves are radiated in order in each radio wave direction, the radio waves are incident on the variable directional antenna 14 when the radio waves are concentrated in the radio wave direction where the radio tag 50 exists as shown in FIG. The intensity of the radio wave to be maximized. FIG. 6 shows a state of detection when the wireless tag 50 is present in the first radio wave direction as shown in FIG. 1. In this case, the variable directional antenna 14 is used when radio waves are concentrated in the first radio wave direction. The intensity of the radio wave incident on is maximum.

  In the present embodiment, the control unit 11 corresponds to an example of a “direction tracking unit”, and the maximum incident direction of the radio wave from the variable directivity antenna 14 when the “wireless communication unit” acquires the radio wave from the radio tag 50. The function of tracking the orientation of the wireless tag 50 based on In the present embodiment, the control unit 11 is configured to serve as both “azimuth tracking means” and “initial orientation detection means”.

  On the other hand, when the response is not confirmed from the wireless tag reader 10 when the direction detection radio wave is transmitted in S16 (that is, the radio wave transmission of the wireless tag 50 and the timing of the radio wave radiation by the wireless tag reader 10 in the direction of the wireless tag 50 match). If no more), the process proceeds to No in S17, and the processes after S1 are repeated.

  On the other hand, on the wireless tag reader 10 side, after transmitting a data frame (such as “radio wave transmission time zone”) in response to the request frame of S8, it is determined whether or not a direction detection radio wave from the wireless tag 50 is periodically received. If a response is returned to the wireless tag 50 every time the direction detection radio wave is received, and the direction detection radio wave from the wireless tag 50 is not periodically checked, the initial direction of the wireless tag 50 Is rediscovered.

  Specifically, as described above with respect to S1, the wireless tag 50 transmits a request frame (a request frame including a first request command) to request direction detection. On the other hand, the wireless tag reader 10 A data frame including the scan speed ω is transmitted with respect to the request frame. Further, as described above with respect to S3 and S4, the wireless tag 50 analyzes the data frame transmitted from the wireless tag reader 10 to acquire the scan speed ω, and then performs the processing of S5 to S7 again. . The wireless tag reader 10 redetects the initial azimuth of the wireless tag 50 based on the transmission of the direction detection radio wave performed in S5 to S7. The processing in the wireless tag 50 after the initial orientation detection is the same as the processing from S8 onward, and the processing on the wireless tag reader 10 side performed in accordance with the operation of the wireless tag 50 from S8 is also as described above. It is.

  As described above, in this embodiment, when the “reception determining unit” determines that the direction detection radio wave (S16) from the wireless tag 50 has not been periodically received, it corresponds to the “initial direction detecting unit”. The control unit 11 redetects the initial orientation of the wireless tag 50, and the control unit 11 corresponding to the “start reference timing determination unit” re-initializes the initial direction of the wireless tag 50 by the “initial orientation detection unit”. When detected, the start reference timing Tofs in the wireless tag 50 is redetermined based on the re-detected initial direction of the wireless tag 50 and the scanning speed (scanning speed ω). Then, the “transmission time zone determination unit” of the wireless tag 50 resets the start period Tg ′ of the “radio wave transmission time zone” based on the start reference timing Tofs re-determined by the “start reference timing determination unit”. Yes.

(Main effects of the first embodiment)
In the position detection system 1 according to the present embodiment, in the wireless tag reader 10, “transmission data generation means” that generates transmission data including data related to the scanning speed of the radio wave whose maximum radiation direction is controlled by the “directivity control means”; The wireless tag 50 is configured to perform wireless communication with radio waves transmitted and received via the variable directional antenna 14, and at least transmission data generated by the “transmission data generating means” is transmitted via the variable directional antenna 14. The “radio communication means” to be output and the “radio communication means” track the orientation of the radio tag 50 based on the maximum incident direction of the radio wave from the variable directivity antenna 14 when the radio wave from the radio tag 50 is acquired. “Direction tracking means” is provided. According to this configuration, the orientation of the wireless tag 50 can be tracked based on the radio wave from the variable directivity antenna 14, and “data relating to the scanning speed of the radio wave” can be transmitted from the wireless tag reader 10 to the wireless tag 50. Will be able to give.
On the other hand, the wireless tag 50 has a “transmission time zone” for determining a periodic radio wave transmission time zone in the wireless tag 50 based on “data relating to scanning speed” included in the transmission data received by the “reception unit”. “Determining means” and “transmitting means” for periodically transmitting radio waves via the antenna 54 according to the radio wave transmitting time zone determined by the “sending time zone determining means” are provided. Therefore, it is possible to periodically transmit radio waves according to a radio wave transmission time zone determined according to the radio wave scanning speed of the radio tag reader 10, and the power of the radio tag 50 can be compared with a configuration in which radio waves are always transmitted. Consumption can be effectively suppressed.

  In the position detection system 1 of the present embodiment, the “directivity control unit” rotates the maximum radiation direction of the radio wave output from the variable directional antenna 14 at a predetermined rotation period T around the variable directional antenna 14. The radio wave scanning direction and rotation period are controlled as described above, and the “transmission data generation means” transmits the period data relating to the predetermined rotation period T (data of T itself or a scan speed ω that can specify T). Data is being generated. On the other hand, the “transmission time zone determining means” determines the radio wave transmission time zone based on the period data included in the transmission data. In this way, the periphery of the wireless tag reader 10 can be scanned more evenly, and further, data (period data) relating to the rotation period of the radio wave scanned by the wireless tag reader 10 can be given to the wireless tag 50. On the tag 50 side, it is easy to set an appropriate radio wave transmission time zone according to the radio wave rotation period.

  Further, in the position detection system 1 of the present embodiment, an “initial azimuth detection unit” that detects the initial azimuth of the wireless tag 50, a radio wave scanning speed controlled by the “directivity control unit”, and an “initial azimuth detection unit” And a start reference timing determining means for determining the start reference timing Tofs of the radio wave transmission time zone based on the initial orientation of the wireless tag 50 detected by “ According to this configuration, the wireless tag 50 can acquire an appropriate start reference timing Tofs according to the initial orientation of the wireless tag 50 and the radio wave scanning speed (scanning speed ω), and based on the obtained start reference timing Tofs. The start time of the radio wave transmission time zone after the initial azimuth is detected can be appropriately determined.

  Further, in the position detection system 1 of the present embodiment, the “initial direction detection unit” is also used by the “direction tracking unit” of the wireless tag reader 10. In this way, it is possible to detect the initial orientation without providing any special means, and it becomes easy to reduce the size and cost of the apparatus configuration.

Further, in the position detection system 1 of the present embodiment, the “reception determination” for determining whether or not the radio wave periodically transmitted by the “transmission means” of the wireless tag 50 is periodically received by the “wireless communication means”. Means "are provided. The “initial orientation detection means” redetects the initial orientation of the wireless tag 50 when it is determined that the radio wave from the wireless tag 50 has not been received periodically. Then, when the initial orientation of the wireless tag 50 is redetected by the “initial orientation detecting means”, the “start reference timing determining means” detects the initial orientation of the wireless tag 50 and the scanning speed (scanning speed ω). ) Based on the start reference timing Tofs re-determined by the “start reference timing determination means”. The start of the radio wave transmission time zone has been reset.
In this way, when the radio wave from the wireless tag 50 is not periodically received, the initial orientation of the wireless tag 50 is newly set, and the start reference timing Tofs is corrected to a more appropriate timing accordingly. it can. And since the start time of a radio wave transmission time zone can be reset based on the start reference timing Tofs appropriately reviewed in this way, it is possible to perform good communication while effectively suppressing power consumption.

  In the position detection system 1 of the present embodiment, the wireless tag 50 includes “movement speed detection means” that detects the movement speed V of the wireless tag 50, and the “transmission time zone determination means” is included in the transmission data. The radio wave transmission time zone is determined based on the data relating to the scanning speed (scanning speed ω) to be detected and the moving speed V detected by the “moving speed detecting means”. In this way, the wireless tag 50 can more appropriately determine the radio wave transmission time zone in consideration of not only the radio wave scanning speed but also its own moving speed.

[Second Embodiment]
Next, a second embodiment will be described.
FIG. 8 is an explanatory diagram conceptually illustrating a position detection system according to the second embodiment of the present invention. FIG. 9 is a cross-sectional view schematically illustrating a laser sensor (laser device) used in the position detection system of FIG. FIG. 10 is an explanatory diagram showing the correspondence between the angle of the laser sensor and the radio wave direction.

  Note that the second embodiment differs from the first embodiment only in that the radio sensor 50 detects which radio wave direction the initial orientation of the wireless tag 50 is, and the rest is the same as the first embodiment. is there. Therefore, only the detection of the initial azimuth by the laser sensor will be described mainly, and the description of the same parts as in the first embodiment will be omitted.

(Position detection system)
As shown in FIG. 8, in the position detection system 1 according to the second embodiment, the wireless tag reader 10 and the laser sensor 100 are arranged close to each other, and the laser sensor 100 lasers toward the detection area of the wireless tag reader 10. It is configured to scan light. The laser sensor 100 and the wireless tag reader 10 are communicably connected to each other, and the wireless tag reader 10 can acquire detection data generated by the laser sensor 100, for example. In the present embodiment, the wireless tag reader 10 is configured to change the radio wave direction along the horizontal direction as in the first embodiment, and the laser sensor 100 is configured to scan the laser beam along the horizontal direction. I am doing.

(Laser device)
As illustrated in FIG. 9, the laser sensor 100 corresponds to an example of a “laser device”, and includes a laser diode 110 and a photodiode 120 that receives reflected light L2 from the detection object. It is comprised as an apparatus which detects the distance and direction of the.

  The laser diode 110 receives a pulse current from a drive circuit (not shown) under the control of a control circuit 170 configured as a microcomputer, for example, and intermittently emits a pulse laser beam (laser light L1) corresponding to the pulse current. Yes. When the laser light L1 is generated from the laser diode 110 and the laser light L1 is reflected by the detection object, the photodiode 120 receives the reflected light L2 and converts it into an electrical signal. In FIG. 9, laser light from the laser diode 110 to the detection object is conceptually indicated by a symbol L1, and reflected light from the detection object to the photodiode is conceptually indicated by a symbol L2. . In addition, as for the reflected light from the detection object, the light of a predetermined region is taken into the deflecting unit 141, and FIG. 9 shows an example in which the reflected light in the region between two lines indicated by reference numeral L2 is taken. ing. In the present embodiment, the photodiode 120 corresponds to an example of “light receiving means”, and functions so that the laser light scanned by the laser light scanning means receives the reflected light reflected by the object.

  A lens 160 is provided on the optical axis of the laser light L1 emitted from the laser diode 110. The lens 160 is configured as a collimating lens, and converts the laser light L1 from the laser diode 110 into parallel light. A mirror 130 is provided on the optical path of the laser light L1 that has passed through the lens 160. The mirror 130 includes a reflecting surface 130 a that is inclined with respect to the optical axis of the laser beam L 1 that has passed through the lens 160, and reflects the laser beam L 1 that has passed through the lens 160 toward the rotation deflection mechanism 140. In the example of FIG. 9, the laser beam L1 in the horizontal direction that has passed through the lens 160 is reflected in the vertical direction (a direction parallel to a center axis 142a described later) by the mirror 130, and the reflected laser beam in the vertical direction. L1 is incident on the deflection unit 141 of the rotation deflection mechanism 140.

  The rotation deflection mechanism 140 includes a deflection unit 141 made of a mirror having a flat reflecting surface 141a, a support base 143 that supports the deflection part 141, a shaft part 142 connected to the support base 143, and the shaft part. And a bearing (not shown) that rotatably supports 142. The deflecting unit 141 is disposed on the optical axis of the laser beam L1 reflected by the mirror 130 and is rotatable about the central axis 142a. The deflecting unit 141 is configured to deflect (reflect) the laser light L1 from the laser diode 110 toward the space and deflect (reflect) reflected light L2 from the detection object toward the photodiode 120. . In addition, the direction of the central axis 142a, which is the rotation center of the deflection unit 141, coincides with the direction of the laser beam L1 incident on the deflection unit 141 from the mirror 130, and the incident position where the laser beam L1 enters the deflection unit 141. P1 is a position on the central axis 142a. In the example of FIG. 9, the direction of the central axis 142a is the vertical direction (Y-axis direction), and the plane direction orthogonal to the central axis 142a is the horizontal direction. Further, a predetermined direction in the horizontal direction is shown as the X-axis direction.

  As shown in FIG. 9, the reflecting surface 141a of the deflecting unit 141 is inclined at an angle of 45 ° with respect to the vertical direction (the direction of the laser beam L1 incident on the reflecting surface 141a) and is incident from the mirror 130 side. The laser beam L1 is reflected in the horizontal direction. Further, since the deflecting unit 141 rotates around the central axis 142a in the direction coinciding with the direction of the incident laser light L1, the incident angle of the laser light L1 is always maintained at 45 ° regardless of the rotational position of the deflecting unit 141. The direction of the laser beam L1 from the position P1 is configured to be constantly in the horizontal direction (direction orthogonal to the central axis 142a). In the present embodiment, the above-described configuration for scanning laser light, that is, the laser diode 110, the mirror 130, and the rotation deflection mechanism 140 correspond to an example of “laser light scanning means”.

  Further, a motor 150 that drives the rotation deflection mechanism 140 is provided. The motor 150 rotates and drives the deflection unit 141 connected to the shaft unit 142 by rotating the shaft unit 142. In addition, as a specific configuration of the motor 150, for example, a servo motor or the like may be used, or a pulsed laser beam is output in synchronization with a timing at which the deflecting unit 141 faces a direction in which distance measurement is desired using a motor that rotates constantly. Thus, detection of a desired direction may be possible. Further, as shown in FIG. 9, a rotation angle position sensor 152 that detects the rotation angle position of the shaft 142 of the motor 150 (that is, the rotation angle position of the deflection unit 141) is provided. As the rotation angle position sensor 152, various types of sensors can be used as long as they can detect the rotation angle position of the shaft portion 142, such as a rotary encoder.

  A condensing lens 162 that condenses the reflected light toward the photodiode 120 is provided on the optical path of the reflected light L2 from the rotation deflection mechanism 140 to the photodiode 120, and the condensing lens 162 and the photodiode. Between 120, a filter 164 is provided. Further, the laser diode 110, the photodiode 120, the mirror 130, the lens 160, the rotation deflection mechanism 140, the motor 150 and the like are accommodated in the case 103, and dust protection and impact protection are achieved. Around the deflection unit 141 in the case 103, a window-shaped light guide unit 104 that allows the laser light L1 and the reflected light L2 to pass is formed so as to surround the deflection unit 141. The light guide unit 104 has an annular shape centering on the optical axis of the laser light L1 incident on the deflecting unit 141, and is configured to extend approximately 360 °. A laser light transmission plate 105 made of a material such as the like is arranged to prevent dust.

  The laser sensor 100 can detect the relative rotation position of the deflecting unit 141 with a predetermined reference position (for example, the origin position of the rotary encoder) as a reference. With reference to the “reference position”, each rotation position of the deflecting unit 141 at each irradiation of the pulsed laser light irradiated intermittently can be detected (that is, each rotation position at each irradiation is It is possible to detect how much the position is rotated with reference to the “reference position”). When the reflected light from the detection object is received by the photodiode 120 at any of the rotation positions, the angle of the deflection unit 141 at the time of the light reception is an angle rotated from the “reference position”. It is possible to identify whether there is. Therefore, the direction of the detection object can be detected using the reference direction as the irradiation direction of the laser beam L1 emitted from the deflecting unit 141 at the “reference position”. Further, when light is received by the photodiode 120 in this way, the laser light is measured by measuring the time from when the laser light L1 is output by the laser diode 110 until the reflected light L2 is detected by the photodiode 120. The distance to the detected object can be obtained in consideration of the speed of light (speed of light). In the present embodiment, the control circuit 170 performs such azimuth and distance detection processing. The control circuit 170 corresponds to an example of “detection means”, and detects an object based on the light reception result of the light reception means. To function.

  In the present embodiment, communication processing is basically performed in the same manner as in FIG. 4, but since the initial orientation detection is not performed by the wireless tag reader 10, the processing of S <b> 5 to S <b> 7 can be omitted. Based on the detection angle of the detection object (the owner of the wireless tag 50) detected by the laser sensor 100, the radio wave direction in which the initial orientation of the wireless tag 50 is located is specified. For example, as shown in FIG. 10, the angle range of the deflecting unit relative to when the deflecting unit is at a predetermined rotational position is associated with each radio wave direction of the wireless tag reader 10 in advance, and the detected object (wireless tag 50 It is possible to specify the corresponding radio wave direction by specifying the range of the angle of the deflecting unit at the time of detection of the owner. For example, in the example of FIG. 10, the laser sensor 100 and the wireless tag reader 10 are positioned so that the vicinity of the first radio wave direction (symbol W1) is scanned by the laser light L1 when the angle range of the deflection unit is θ0 to θ1. When the angle of the deflecting unit is θ0 to θ1 when the detection object (the owner of the wireless tag 50) is detected by the laser sensor 100 at the time of detecting the initial azimuth, the correspondence as shown in FIG. Based on the data, the initial orientation of the wireless tag 50 is specified as “first radio wave direction”. The processing in the wireless tag 50 and the processing in the wireless tag reader 10 after the radio wave direction is specified are the same as those in the first embodiment.

(Main effects of the second embodiment)
The position detection system 1 of this embodiment has the same effect as that of the first embodiment. Furthermore, since the “initial orientation detection means” is constituted by the laser sensor 100, it becomes easy to quickly and accurately detect the initial orientation of the wireless tag 50. In particular, since the initial azimuth of the wireless tag 50 can be detected by laser light, the initial azimuth of the wireless tag 50 can be detected even when radio waves are not radiated from the wireless tag 50.

[Other Embodiments]
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  In the first embodiment, the acceleration sensor 80 is shown as an example of the “movement speed detection unit”, but various known sensors can be adopted as long as the sensor can detect the movement speed of the wireless tag 50.

  In the first embodiment, every time the direction detection radio wave is transmitted in each cycle, the response from the wireless tag reader 10 is confirmed in S17. If the response is confirmed, the process returns to S16 and the next cycle is the same as the previous cycle. The direction detection radio wave is transmitted in the same radio wave transmission time zone, but if the response from the wireless tag reader 10 is confirmed in S17, the process may return to S12. That is, the moving speed of the wireless tag 50 may be obtained every time the period changes, and the correction value α corresponding to the speed may be set for each period.

DESCRIPTION OF SYMBOLS 1 ... Position detection system 10 ... Wireless tag reader 11 ... Control part (Directivity control means, transmission data generation means, wireless communication means, direction tracking means, start reference timing determination means, reception determination means)
12 ... Transmitter (wireless communication means)
13: Receiver (wireless communication means)
14 ... Variable directional antenna 32 ... Memory (storage means)
50. Wireless tag (wireless communication medium)
51. Control unit (receiving means, sending time zone determining means, transmitting means, initial direction detecting means, output adjusting means)
52. Transmission unit (transmission means)
53. Receiving part (receiving means)
54 ... Antenna 70 ... Acceleration sensor (moving speed detecting means)
100: Laser sensor (external device, laser device, initial orientation detection means)
120... Photodiode (light receiving means)
110 ... Laser diode (laser beam scanning means)
130: Mirror (laser beam scanning means)
140... Turning deflection mechanism (laser beam scanning means)
170 ... Control circuit (detection means)

Claims (6)

A wireless tag with an internal power supply;
A wireless tag reader capable of communicating with the wireless tag,
A position detection system for detecting a position of the wireless tag by the wireless tag reader,
The wireless tag reader is
A variable directional antenna,
Directivity control means for controlling the scanning direction of radio waves so as to change the maximum radiation and incident direction of radio waves input and output from the variable directional antenna around the variable directional antenna;
Transmission data generating means for generating transmission data including data relating to the scanning speed of the radio wave whose maximum radiation direction and maximum incident direction are controlled by the directivity control means;
It is configured to perform wireless communication with the wireless tag through a radio wave transmitted / received via the variable directional antenna, and at least the transmission data generated by the transmission data generating means is transmitted via the variable directional antenna. a radio communications means for outputting,
Azimuth tracking means for tracking the azimuth of the radio tag based on the maximum incident direction of the radio wave from the variable directional antenna when the radio communication means acquires the radio wave from the radio tag;
Have
The wireless tag is
An antenna,
Receiving means for receiving at least the transmission data transmitted from the wireless tag reader via the antenna;
A transmission time zone determining means for determining a periodic radio wave transmission time zone in the wireless tag based on data relating to the scanning speed included in the transmission data received by the receiving means;
Transmitting means for periodically transmitting radio waves via the antenna in accordance with the radio wave transmission time zone determined by the transmission time zone determining means;
With
In the wireless tag reader or an external device of the wireless tag reader, an initial azimuth detecting means for detecting an initial azimuth of the wireless tag is provided,
The wireless tag reader has a start reference timing of the radio wave transmission time zone based on a radio wave scanning speed controlled by the directivity control unit and an initial direction of the wireless tag detected by the initial direction detection unit. Start reference timing determination means for determining
The transmission time zone determining unit of the wireless tag determines a start time of the radio wave transmission time zone in the wireless tag after the initial direction is detected by the initial direction detection unit based on the start reference timing. Position detection system. The directivity control means sets the radio wave scanning direction and rotation period so that the maximum radiation direction and maximum incident direction of the radio wave output from the variable directivity antenna rotate at a predetermined rotation period around the variable directivity antenna. Control
The transmission data generation means generates the transmission data including period data related to the predetermined rotation period,
The position detection system according to claim 1, wherein the transmission time zone determination unit determines the radio wave transmission time zone based on the periodic data included in the transmission data. The initial azimuth detection means, position detection system of claim 1 or claim 2 that is characterized in that is shared by the azimuth tracking means of the wireless tag reader. The detection target is an object carrying the wireless tag, laser light scanning means for scanning laser light , and the laser light scanned by the laser light scanning means is the object carrying the wireless tag . A laser device comprising: a light receiving means for receiving reflected reflected light; and a detection means for detecting the orientation of the object based on a light reception result by the light receiving means,
The position detection system of claim 1 or claim 2 wherein the initial azimuth detection means, characterized in that it is constituted by the laser device. A reception determination means for determining whether or not radio waves periodically transmitted by the transmission means of the wireless tag are periodically received by the wireless communication means;
The initial azimuth detecting means performs re-detection of the initial azimuth of the wireless tag when the reception determining means determines that radio waves from the wireless tag have not been received periodically,
When the initial azimuth detection unit detects the initial azimuth of the wireless tag again, the start reference timing determination unit determines the start reference timing determination unit based on the re-detected initial azimuth of the wireless tag and the scanning speed. Re-determining the start reference timing in the wireless tag;
Wherein the delivery time zone determination means of the radio tag, based on the starting reference timing redetermined by the start reference timing determining means, according to claim 1, characterized in that resetting the start of the radio wave transmission time period The position detection system according to claim 1 . The wireless tag includes a moving speed detecting means for detecting a moving speed of the wireless tag,
The transmission time zone determining means determines the radio wave transmission time zone based on data relating to the scanning speed included in the transmission data and the moving speed detected by the moving speed detecting means. The position detection system according to any one of claims 1 to 5 .

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