JP2005069892A - System for computing self-position of moving object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that in the case a position of an automatic guided vehicle is computed from differences between respective signals, its computation process easily gets complicated, and to simplify the process for calculating the position of a moving object 30. <P>SOLUTION: Each of base stations 20a, 20b and 20c has a reference signal receiver 22; a memory meas 24 storing time interval data of the base stations 20 which differ from each other; and an ultrasonic transmitter 26 transmitting ultrasonic waves (propagation waves) at a second timing defined by adding the time interval stored in the memory means 24 to a first timing at which a reference signal is received by the reference signal receiver 22. The mobile object 30 has an ultrasonic receiver 34 which receives the ultrasonic waves; a timing difference calculating means 58 calculating differences between a third timing being approximately equal to the second timing and a fourth timing at which the ultrasonic wave is received by the ultrasonic receiver, with respect to base stations 20; and a self-position computing means 60 which computes the self-position of the moving object 30 on the basis of sonic velocity data, position data of respective base stations 20 and the timing differences calculated by the timing difference calculating means 58 with respect to base stations 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for calculating the position of a moving body.

Patent Document 1 discloses a system for guiding an automatic guided vehicle, which receives a master station that transmits an ultrasonic signal modulated at a constant period and receives a signal from the master station, A plurality of slave stations that transmit sonic wave self-station identification signals, and a calculation unit provided in the automatic guided vehicle that receives each signal from the master station and the slave station and calculates a position from a time difference between the received signals. System is described. An automated guided vehicle is an example of a moving body.
JP-A-6-266432

When the position of the automatic guided vehicle is calculated from the time difference between the signals as in the system described in Patent Document 1, there is a problem that the calculation process is likely to be complicated.
Specifically, as a system described in Patent Document 1, there is an automatic guided vehicle guidance system including a master station and three slave stations (first slave station, second slave station, and third slave station). To do. As shown in FIG. 1, a signal transmitted from the master station and A, and the transmission time and t _1. The timing of the automatic guided vehicle receives the signal A and t _2. The ultrasonic waves transmitted from the first slave station, the second slave station, and the third slave station are B ₁ , B ₂ , and B ₃ , respectively, and the transmission timings are t ₃ , t ₅ , and t ₇ , respectively. The timings when the automatic guided vehicle receives the ultrasonic waves B ₁ , B ₂ , and B ₃ are t ₄ , t ₆ , and t ₈ , respectively.
The difference between the transmission timings t ₃ and t ₅ is Tm. Tm is assumed to be known. Differences in the receiving timing _{t 4} and _{t 6} is Ta. Ta corresponds to the “time difference between received signals (received ultrasonic waves B ₁ and B ₂ )” described above. Ta can be calculated.
The difference in reception timing _{t 4} the transmission timing _{t 3} of ultrasonic _{B 1} and _{T 1.} The difference in reception timing _{t 6} the transmission timing _{t 5} of the ultrasonic _{B 2} and _{T 2.}

As well shown in FIG. 1, Tm = T ₁ + R and Ta = R + T ₂ . Taking the difference between the left sides of these equations and taking the difference between the right sides, R is eliminated, and Tm−Ta = T ₁ −T ₂ . That is, only the difference between T ₁ and T ₂ can be obtained from the known Tm and the calculable Ta, and the value of T ₁ itself and the value of T ₂ itself cannot be obtained. Knowing the value of T ₁ itself can calculate the distance of the first child station and the AGV. Knowing the value of T ₂ itself may calculate the length of the second slave station and the AGV. However, the only difference T ₁ and T _2, and the distance of the first slave station and the AGV can only be calculated difference in distance of the second slave station and the AGV. As a result, there is a problem that the calculation process of the position of the automatic guided vehicle (moving body) is likely to be complicated.

  An object of this invention is to simplify the calculation process of the position of a moving body.

A mobile body self-position calculation system according to one aspect of the present invention includes reference signal transmission means for transmitting a reference signal, a plurality of base stations, and a mobile body. Each base station includes a reference signal receiving unit that receives the reference signal, a storage unit that stores time interval data different for each base station, and a first timing at which the reference signal receiving unit receives the reference signal. Propagating wave transmission means for transmitting the propagation wave at the second timing with the time interval stored in the storage means.
The mobile unit determines a difference between a propagation wave receiving unit that receives the propagation wave, a third timing substantially equal to the second timing, and a fourth timing at which the propagation wave reception unit receives the propagation wave for each base station. A timing difference calculating means for calculating, and a self-position for calculating the position of the mobile itself based on the timing difference calculated for each base station by the timing difference calculating means, velocity data of propagation waves and position data of each base station It has a calculation means.

The “third timing substantially equal to the second timing” is intended to allow a case where the third timing is slightly deviated from the second timing. Specifically, when the difference between the second timing and the third timing is 1/20 (preferably 1/50) or less of the minimum value of the time interval data, the second timing is almost equal to the third timing. Included at least.
The “first timing” to “fourth timing” described above exist for each base station. For example, the second timing of the first base station and the second timing of the second base station are different.
The above-mentioned propagation wave indicates an electromagnetic wave propagating in an electromagnetic field, a sound wave propagating in a gas, a liquid, or a solid. Electromagnetic waves include radio waves and light. The sound wave is not limited to an acoustic wave having an audio frequency, but includes an ultrasonic wave having a frequency equal to or higher than an audio frequency.

  According to the said aspect, the arrival time itself of the propagation wave from each base station to a mobile body can be known from the difference (timing difference) between the third timing and the fourth timing for each base station. And, since the position of the mobile body is calculated based on the timing difference calculated for each base station, the velocity data of the propagation wave, and the position data of each base station, it is possible to simplify the process of calculating the position of the mobile body. It becomes possible.

The reference signal transmitted by the reference signal transmission means is a radio wave signal, and the mobile body includes reference signal reception means for receiving the reference signal, storage means for storing the time interval data for each base station, and Timing deriving means for obtaining the third timing for each base station based on the fifth timing when the reference signal receiving means of the mobile body receives the reference signal and the time interval data stored in the storage means of the mobile body It is preferable to further have.
In the above aspect, since the reference signal is a radio wave signal and is very fast, the difference between the first timing at which the base station receives the reference signal and the fifth timing at which the mobile body receives the reference signal is very high. small. Therefore, the third timing substantially equal to the second timing can be obtained from the fifth timing and the time interval data.

Reference signal transmission means for transmitting a reference signal including information sufficient to specify the third timing for each base station is further included, and the mobile unit further includes reference signal reception means for receiving the reference signal. Is preferred. This reference signal transmission means may be included in the apparatus having the reference signal transmission means, may be included in the base station, or may be in another form.
According to the said aspect, even if it does not require | calculate the 3rd timing on the mobile body side, the mobile body can obtain sufficient information to specify the 3rd timing.

Each time the self-position calculating means calculates a new timing difference for one base station by the timing difference calculating means, the self-position calculating means has already been calculated for base stations other than the one base station. It is preferable to calculate the position of the moving body itself based on the latest timing difference.
According to the above aspect, the position of the moving body can be calculated at short time intervals.

There are four base stations, two of which make up the first set, the remaining two base stations make up the second set, and a line connecting the first set of base stations and the second Each base station is preferably arranged such that the lines connecting the pair of base stations are orthogonal to each other.
According to the above aspect, it is possible to further simplify the calculation process when calculating the position of the moving object.

  In the self-position calculation system of the present invention, an ultrasonic wave can be suitably used as the propagation wave. According to this aspect, it is possible to further simplify the calculation process when calculating the position of the moving object.

The mobile unit according to another aspect of the present invention calculates a position using a plurality of base stations that sequentially transmit a propagation wave at a predetermined time interval from the first timing when the reference signal receiving unit receives the reference signal. It is a moving body. The mobile unit includes: a propagation wave receiving unit that receives the propagation wave; a third timing that is substantially equal to a timing at which the base station transmits the propagation wave; and a fourth timing at which the propagation wave reception unit receives the propagation wave. Timing difference calculating means for calculating the difference for each base station, and calculating its own position based on the timing difference, propagation wave velocity data, and position data of each base station calculated for each base station by the timing difference calculating means. Self-position calculating means.
Furthermore, in the moving body according to the present invention, an ultrasonic wave can be suitably used as the propagation wave.

  In this specification (including the embodiments), the “means” is not limited to hardware, and includes cases where the functions of the respective means are realized by software. Further, the function of one means may be realized by two or more hardware or software, or the functions of two or more means may be realized by one hardware or software. Specifically, the reference signal transmission means, the base station, the mobile body, and the like may be configured by dedicated hardware, or at least a part of a general-purpose computer (CPU, ROM, RAM, external storage device, etc.) The reference signal transmission means, the base station, the mobile unit, and the like may be realized by causing the computer to execute the program.

  According to the present invention, it is possible to simplify the calculation process of the position of the moving object. Thereby, the calculation time can be shortened. As a result, it can be expected to improve the calculation accuracy of the position of the moving body.

First, some of the technical ideas grasped from the embodiments of the present invention to be described later are listed.
(Embodiment 1) The frequency of the ultrasonic wave transmitted from the ultrasonic wave transmitting means of each base station is equal.
According to this, it is possible to reduce the burden of processing the ultrasonic wave received by the moving body.
(Mode 2) The moving body converts the ultrasonic wave received by the ultrasonic wave receiving means into an electric signal, and converts the conversion signal obtained by the conversion means to a predetermined threshold value or more. It further has extraction means for extracting.
(Mode 3) The mobile unit recognizes and processes the ultrasonic wave received by the ultrasonic wave receiving unit within a predetermined time width as the ultrasonic wave transmitted by the ultrasonic wave transmitting unit of the specific base station. Have means.
According to the above form 2 or 3, even when the received ultrasonic wave includes a noise component (including a reflected wave component), it is difficult to be adversely affected by the noise component.

First Embodiment FIG. 2 is a diagram schematically illustrating a configuration of a mobile body self-position calculation (self-position measurement) system according to a first embodiment. FIG. 3 shows a block diagram of the system. FIG. 4 is a timing chart showing the operation of the system.
As shown in FIGS. 2 and 3, the self-position calculation system includes a reference signal transmission device 10, three base stations 20 a, 20 b, and 20 c, and a moving body 30. Although only one moving body 30 is shown in FIG. 2, the position of a plurality of moving bodies 30 that move independently can be calculated in this system. In this embodiment, the moving range 70 of the moving body 30 shown in FIG. 2 is set to 20 m × 20 m.

As shown in FIG. 3, the reference signal transmission device 10 includes a storage unit 12, a reference signal generation unit 14, a reference signal transmitter 16, and a reference signal transmission control unit 18. The reference signal generation means 14 and the reference signal transmission control means 18 are constituted by a CPU or the like.
The reference signal transmitted from the reference signal transmission device 10 is a radio signal. The reference signal may be used only to inform each base station 20a, 20b, 20c and the mobile unit 30 of the reference timing, or information that can be used by the base station 20 and / or the mobile unit 30. You may make it transmit on board. For example, time interval data from when the base station 20 receives the reference signal to when an ultrasonic wave is transmitted may be added to the reference signal. The storage means 12 stores reference signal generation data and reference signal transmission data. The reference signal generation data includes the time interval data described above. The reference signal transmission data includes reference signal transmission timing information and the like.

The reference signal generation unit 14 generates a reference signal based on the reference signal generation data stored in the storage unit 12. The generated reference signal data is stored in the storage unit 12. The reference signal transmitter 16 can transmit a reference signal toward each base station 20 a, 20 b, 20 c and the mobile body 30. The reference signal transmitter 16 has a transmitting antenna 16a as shown in FIG. The reference signal transmission control unit 18 controls the reference signal transmitter 16 to transmit the reference signal at the transmission timing included in the reference signal transmission data stored in the storage unit 12. In this embodiment, the reference signal transmitting control means 18 as a reference signal transmitter 16 transmits the timing t ₁ the reference signal A, as shown in FIG. 4 controls.

  Each base station 20a, 20b, 20c is fixed at a position that is not on the same straight line as illustrated in FIG. The position of each base station 20a, 20b, 20c is known. As shown in FIG. 3, each of the base stations 20a, 20b, and 20c includes reference signal receivers 22a, 22b, and 22c, storage means 24a, 24b, and 24c, ultrasonic transmitters 26a, 26b, and 26c, It has sound wave transmission control means 28a, 28b, 28c. The ultrasonic transmission control means 28 is constituted by a CPU or the like. In the following, except for the case where necessary, the subscripts (a and the like) are omitted for descriptions common to the base stations (or their constituent elements) 20a, 20b, and 20c.

The reference signal receiver 22 can receive the reference signal transmitted from the reference signal transmission device 10. The reference signal receivers 22a, 22b, and 22c have reception antennas 22a-1, 22b-1, and 22c-1, respectively, as shown in FIG. Each base station 20a, 20b, 20c is assumed that receives the reference signal A, as shown in FIG. 4 the timing _{t 2.} Since the reference signal A is a radio signal and is very high speed, even if the distance between the reference signal transmission device 10 and the base station 20 is different for each base station 20, each base station 20a, 20b, 20c is substantially different. It can be considered that it was received at the same timing.

Storage means 24, the reference signal receiver 22 stores the timing t _2, which has received the reference signal A. The storage unit 24 stores the time interval data from the timing t _2, which has received the reference signal A to the timing of transmitting ultrasonic waves. The value of the time interval data differs for each base station 20. As shown in FIG. 4, from the first base station 20a, ultrasonic _{B 1} is being transmitted to the timing _{t 2.} That is, the time from the timing t ₂ is zero. From the second base station 20b, ultrasonic _{B 2} is transmitted to the timing _{t 5.} That is, the time from the timing t ₂ is t ₅ −t ₂ = Tm. From the third base station 20c, ultrasonic _{B 3} is transmitted to the timing _{t 7.} That is, the time from the timing _{t 2} is _t 7 _-t 2 = 2Tm. These time interval data (zero, Tm, 2Tm) may be obtained from the reference signal, or may be input in advance by the operator. Strictly speaking, for example, from the timing t ₂ of the first base station 20a receives the reference signal and before transmitting the ultrasonic B ₁ represents the processing time is required. Therefore, the timing of transmitting ultrasonic waves B ₁ represents a little later than t _2. Here, however, it describes the transmission timing as approximately t _2.

The ultrasonic transmitter (also referred to as an ultrasonic sound source) 26 can transmit ultrasonic waves (ultrasonic pulses) to the moving body 30. Each ultrasonic transmitter 26a, 26b, 26c has transmitting antennas 26a-1, 26b-1, 26c-1, as shown in FIG. The ultrasonic transmitters 26a, 26b, and 26c are transmitters of the same specification that transmit ultrasonic waves having the same frequency. In this embodiment, it is assumed that each of the ultrasonic transmitters 26a, 26b, and 26c transmits an ultrasonic wave having a frequency of 40 kHz. This frequency is preferably 40 ± 5 kHz. Each ultrasonic transmitter 26a, 26b, 26c is a timing _{t 2} of the reference signal receiver 22 receives the reference signal as a reference, the first base station 20a, the second base station 20b, the third time the base station 20c is equal to Control is performed by the ultrasonic transmission control means 28a, 28b, and 28c so as to perform the operation of transmitting ultrasonic waves in order at intervals of Tm.
Note that this time interval may be different. For example, the timing at which the first base station 20a to transmit ultrasonic waves _{B 1,} the difference in timing of the second base station 20b originates ultrasound _{B 2} (time interval) at 2Tm, the second base station 20b ultrasound and timing for transmitting a B _2, the difference in timing of the third base station 20c to transmit ultrasonic waves B ₃ (time interval) may be Tm.

  As described above, in this embodiment, the ultrasonic transmitters 26a, 26b, and 26c do not transmit ultrasonic waves having different frequencies at the same timing, but transmit ultrasonic waves having the same frequency at different timings. ing. Therefore, on the mobile body 30 side, it is possible to recognize which base station 20 is the received ultrasonic wave from the difference in the reception timing. As a result, on the mobile body 30 side, complicated signal analysis processing that is required when ultrasonic waves having different frequencies are received separately is unnecessary. For this reason, the processing burden on the moving body 30 side is small.

  The moving body 30 has wheels 66a (a part of the moving mechanism 66 in FIG. 3) as schematically shown in FIG. 2, and can be said to be a wheel traveling robot. The moving body 30 can move at a speed of about 1 m / sec. As shown in FIG. 3, the moving body 30 includes a reference signal receiver 32, two ultrasonic receivers 34 and 38, two ultrasonic transducers 36 and 40, an isolation circuit 42, and a waveform shaping board. 44 and a USB communication board 46.

The reference signal receiver 32 can receive the reference signal transmitted from the reference signal transmission device 10. The reference signal receiver 32 has a receiving antenna 32a as shown in FIG. Reference signal receiver 32 (moving body 30), and receives the reference signal A in the timing t _2, as shown in FIG. For the same reason as described above, it can be considered that the mobile unit 30 has received the reference signal A at substantially the same timing as the base stations 20a, 20b, and 20c. When the reference signal receiver 32 receives the reference signal A, it outputs a signal. The output signal is input to the USB communication board 46.

  The two ultrasonic receivers (ultrasonic sensors) 34 and 38 can receive ultrasonic waves transmitted from the ultrasonic transmitters 26 of the base stations 20a, 20b, and 20c. As shown in FIG. 2, the two ultrasonic receivers 34 and 38 are arranged at positions separated by a predetermined interval in the front-rear direction of the moving body 30. In this embodiment, the two ultrasonic receivers 34 and 38 are separated by 200 mm. By using the two ultrasonic receivers 34 and 38, the inclination of the moving body 30 can be obtained. For example, the position of each ultrasonic receiver 34, 38 is calculated, and the inclination of the moving body 30 can be obtained by calculating the inclination of a line connecting the two positions and a preset reference line.

  Further, by using the two ultrasonic receivers 34 and 38, it is possible to know the accuracy of the position calculation and the abnormality of the position calculation system. For example, the position of each ultrasonic receiver 34, 38 is calculated, the distance between the two positions is calculated, and the accuracy of position calculation can be known from the difference between the calculated distance and the actual distance. If the difference between the calculated distance and the actual distance is greater than or equal to a predetermined value, it can be recognized that an abnormality has occurred in the position calculation system.

The ultrasonic waves received by the first ultrasonic receiver 34 are sent to the first ultrasonic transducer 36. The ultrasonic waves received by the second ultrasonic transmitter 38 are sent to the second ultrasonic transducer 40. Each of the ultrasonic transducers 36 and 40 converts the ultrasonic wave transmitted from the ultrasonic receivers 34 and 38 into an electric signal. D (D _1A , D _1B, etc.) shown in FIG. 4 is a converted signal obtained by converting an ultrasonic wave into an electric signal by the first ultrasonic transducer 36. The waveform of the converted signal is corrupted compared to the ultrasonic pulse transmitted from the base stations 20a, 20b, and 20c. _D1A shown in FIG. 4 corresponds to the ultrasonic wave transmitted directly from the first base station 20a and directly reached (direct wave). D _1B corresponds to an ultrasonic wave transmitted from the first base station 20a and reflected by a wall or the like (reflected wave). E (E _1A , E _1B, etc.) shown in FIG. 4 is a converted signal obtained by converting an ultrasonic wave into an electric signal by the second ultrasonic transducer 40. In the example of FIG. 4, the conversion signals D and E are slightly out of timing. The outputs of the ultrasonic transducers 36 and 40 are input to the isolation circuit 42. The isolation circuit 42 switches the output on the side to be processed by the waveform shaping board 44 among the outputs of the first ultrasonic transducer 36 and the second ultrasonic transducer 40 as necessary.

The output of the isolation circuit 42 is input to the waveform shaping board 44. The waveform shaping board 44 extracts a signal having an amplitude value greater than or equal to a predetermined threshold value K from the converted signal that is the output of the isolation circuit 42 (the output of the ultrasonic transducers 36 and 40), and Outputs a shaped signal with a shaped waveform. F (F _1A , F _1B, etc.) shown in FIG. 4 is a shaping signal of the converted signal D (D _1A , D _1B, etc.) converted by the first ultrasonic transducer 36. G (G _1A , G _1B, etc.) shown in FIG. 4 is a shaping signal of the converted signal E (E _1A , E _1B, etc.) converted by the second ultrasonic transducer 40. The output of the waveform shaping board 44 is input to the USB communication board 46.

  The moving body 30 also has storage means 48. The moving body 30 further includes a timing deriving unit 50, a reference signal output unit 52, a timing difference calculating unit 58, a self position calculating unit 60, a self position correcting unit 62, and a movement control unit 64. These are constituted by a CPU or the like. The moving body 30 further includes a moving mechanism 66. These means are connected to the USB communication board 46. Thus, the moving body 30 has the self-position calculating means 60, and the apparatus other than the moving body 30 does not calculate the position of the moving body 30, but the moving body 30 itself calculates its own position. .

Storage means 48, the reference signal receiver 32 stores the timing t _2, which has received the reference signal A. The timing data can be obtained by referring to the output of the USB communication board 46 to which the output signal of the reference signal receiver 32 is input. The storage means 48, the base station 20 from the timing _{t 2,} which has received the reference signal A is the time interval data from the timing of transmitting ultrasonic waves, and stores the base station 20a, 20b, for 20c. As described above, the time interval data is zero for the first base station 20a, Tm for the second base station 20b, and 2Tm for the third base station 20c (see FIG. 4). . These time interval data (zero, Tm, 2Tm) may be obtained from the reference signal, or may be input in advance by the operator. In this embodiment, Tm = 50 milliseconds is set. Further, the storage means 48 stores the timing at which the ultrasonic receivers 34 and 38 receive ultrasonic waves that satisfy a predetermined condition. Specifically, as described above, the timings t _3F , t _4F , t _{6F at which} the converted signal D (shaped signal F) equal to or higher than the threshold value K is present in the output of the first ultrasonic transducer 36. , T _8F , t _9F are stored. Among the outputs of the second ultrasonic transducer 40, the timings t _3G , t _4G , t _6G , t _8G , t _{9G at} which the converted signal E (shaped signal G) equal to or higher than the threshold value K is stored.

The timing deriving unit 50 sets the timing substantially equal to the timing at which the ultrasonic transmitter 26 of the base station 20 transmits ultrasonic waves (hereinafter, the expression “substantially equal” is omitted) to each base station 20a, It calculates | requires about 20b and 20c. Specifically, the timing deriving unit 50 compares the timing with the timing t ₂ when the reference signal receiver 32 of the moving body 30 receives the reference signal and the time interval data ( Zero, Tm, 2Tm). The timing is determined as t ₂ + zero = t ₂ for the first base station 20a, t ₂ + Tm = t ₅ for the second base station 20b, and t ₂ + 2Tm = t ₇ for the third base station 20c.

The reference signal output means 52 outputs a reference signal at timings t ₂ , t ₅ , and t _{7 at} which the base stations 20a, 20b, and 20c transmit ultrasonic waves. The reference signal output unit 52 includes a parent signal output unit 54 and a parent signal frequency dividing unit 56. As shown in FIG. 4, when the time intervals at which the base stations 20a, 20b, and 20c transmit ultrasonic waves are equal (time interval Tm in FIG. 4), the parent signal output from the parent signal output means 54 is the parent signal. A child signal divided by the frequency dividing means 56 can be output as a reference signal. In the present embodiment, child signals C _1A , C _1B , and C _{1C obtained} by dividing the parent signal C ₁ having a period of 3Tm by 3 are output as reference signals. The timing data output by the reference signal output means 52 may use the timing data obtained by the timing derivation means 50 described above, or may use timing data obtained in advance by other means.

  The timing difference calculation means 58 is a difference between the timing at which the ultrasonic transmitter 26 of the base station 20 transmits ultrasonic waves (transmission timing) and the timing at which the ultrasonic receivers 34 and 36 receive the ultrasonic waves (reception timing). (Ultrasonic arrival time) is calculated for each base station 20a, 20b, 20c.

The first base station 20a, the timing deriving section 50, transmission timing of ultrasound _{B 1} is being sought and _{t 2.} Also, the first ultrasonic receiver 34, the timing of receiving a direct wave (adjusting signal _{F 1A)} of the ultrasonic _{B 1} represents a _{t 3F,} receiving ultrasonic _{B 1} of the reflected wave (adjusting signal _{F 1B)} The timing is t _4F . t _4F is later than t _3F . Therefore, the reception timing of the ultrasonic B ₁ of the first ultrasonic receiver 34, the transmission timing t ₂ subsequent ultrasound B _1, shaping signal F is a timing timing initially present (shaping signal F _1A is present t _3F ).

As a result, the timing difference calculating means 58, for the first base station 20a, transmission timing of ultrasound B ₁ is a t _2, since the reception timing of the first ultrasonic transmitter 34 is t _3F, its timing The difference is calculated as t _3F −t ₂ = T ₁ . Similarly, for the second base station 20b, transmission timing of ultrasound _{B 2} is _{t 5,} since the reception timing of the first ultrasonic transmitter 34 is _{t 6F,} the timing difference _t 6 -t ₅ = _{T 2} to be calculated. For the third base station 20c, transmission timing of ultrasound B3 is _{t 7,} since the reception timing of the first ultrasonic transmitter 34 is _{t 8F,} the difference in timing _t 8 _-t 7 = _{T 3} And calculate. If the second ultrasonic transmitter 38 is similarly calculated, the timing differences are T ₅ (= t _3G −t ₂ ), T ₆ (= t _6G −t ₅ ), T ₇ (= t _8G −t _7). ) Is required.

  The self-position calculation means 60 is based on the timing difference calculated for each base station 20a, 20b, 20c by the timing difference calculation means 58, the sound speed data, and the position data of each base station 20a, 20b, 20c. Calculate its own position. Below, the case where a timing difference is calculated | required based on the ultrasonic reception timing of the 1st ultrasonic receiver 34, and a position is calculated based on the timing difference etc. is demonstrated. The position is calculated in the same manner for the second ultrasonic receiver 38.

First, the distance L ₁ between the first base station 20a and the moving body 30 at timing t _3F is calculated as Vs × T ₁ from the timing difference (ultrasound arrival time) T ₁ calculated for the first base station 20a and the sound speed Vs. To do. Similarly, the distance _{L 2} of the moving body 30 and the second base station 20b at the timing _{t 6F} calculates the Vs × _{T 2.} The distance _{L 3} of the moving body 30 and the third base station 20c at the timing _{t 8F} calculates the Vs × _{T 3.}

The sound speed Vs can be expressed as 331.5 + 0.6 J (m / second). J is the temperature. As described above, the distances L ₁ , L ₂ , and L ₃ between the base stations 20a, 20b, and 20c and the moving body 30 indicate distances at different timings. However, if the time intervals of the timings t _3F , t _6F , and t _8F are short, the distances L ₁ , L ₂ , and L ₃ can be approximated to the distances at substantially the same timing.

When approximated in this way, the moving body 30 can be regarded as being in a position that satisfies the relationships of the following equations (1) to (3). Here, the position coordinates of the moving body 30 are assumed to be (X, Y). The position coordinates of the first base station 20a are assumed to be (X ₁ , Y ₁ ). The position coordinates of the second base station 20b are assumed to be (X ₂ , Y ₂ ). The position coordinates of the third base station 20c are (X ₃ , Y ₃ ).
(X−X ₁ ) ² + (Y−Y ₁ ) ² = L ₁ ² (1)
(X−X ₂ ) ² + (Y−Y ₂ ) ² = L ₂ ² (2)
(X−X ₃ ) ² + (Y−Y ₃ ) ² = L ₃ ² (3)

Equation (1) indicates that the moving body 30 is located on the circumference of the radius L ₁ centered on the first base station 20a (see FIG. 5). (2) indicates that the mobile body 30 is positioned on the circumference of a radius L ₂ around the second base station 20b (see FIG. 5). Therefore, as shown in FIG. 5, it can be seen that the moving body 30 is located at one of two intersections of the circle represented by the expression (1) and the circle represented by the expression (2). If it is known that one of the intersections is outside the moving range of the moving body 30, it can be narrowed down that the moving body 30 is located at the other intersection. In this case, the position of the moving body 30 can be specified only from the expressions (1) and (2).

L ₁ in the equation (1) is obtained from the timing difference T ₁ and the sound speed Vs as described above. X ₁ and Y _{1 in} equation (1) are obtained from the position coordinates (X ₁ , Y ₁ ) of the first base station 20a. (2) of the _{L 2} is determined from the timing difference _{T 2} and the sound velocity Vs as described above. X ₂ and Y _{2 in} equation (2) are obtained from the position coordinates (X ₂ , Y ₂ ) of the second base station 20b.
Therefore, the timing differences T ₁ and T ₂ calculated by the timing difference calculating unit 58 for the first base station 20a and the second base station 20b, the sound velocity data Vs, and the first base station 20a Based on the position data (X ₁ , Y ₁ ) and (X ₂ , Y ₂ ) of the second base station 20b, the position of the moving body 30 itself can be calculated.

According to the method of Patent Document 1 described above, as shown in FIG. 1, only the difference between T ₁ and T ₂ can be obtained from Ta and Tm, and T ₁ itself and T ₂ itself cannot be obtained. As a result, the distance between the first slave station and the automated guided vehicle and the distance between the second slave station and the automated guided vehicle cannot be determined. That is, in this case, it can only be understood that the automatic guided vehicle is on a hyperbola with the first slave station and the second slave station as focal points. Therefore, in order to narrow down the location of the AGV determines the Tb ₍₌ t 8 -t ₆₎ shown in FIG. 1, from the Tb and Tm, it must be determined difference between _{T 2} and _{T 3.} T ₃ is the difference between t ₈ and t ₇ . If the difference between T ₂ and T ₃ are known, it can be seen that there the AGV is a further second child station third child station on hyperbola focus. As a result, the position of the automatic guided vehicle can be narrowed down from the intersection of the two hyperbolic curves.

However, in order to determine the Tb shown in FIG. 1, it must obtain the difference of the timing t ₈ and t _6. In other words, it is not possible to refine the position of the automatic guided vehicle to wait for the timing t _8. Moreover, the burden of calculation processing is large. For these reasons, the calculation time becomes longer. Since the moving body is moving during the calculation time, if the calculation time becomes long, the position where the calculation position is obtained and the actual position of the moving body will become large. .

In contrast, according to the method of Example, without seeking the timing difference T _3, it may identify the position of the moving body 30. That is, the position of the moving body 30 can be specified without waiting for the timing t _8F (corresponding to the timing t ₈ in FIG. 1) shown in FIG. That is, the position of the moving body 30 can be specified at an earlier stage than that of Patent Document 1. Moreover, the burden of calculation processing is also small. For these reasons, the calculation time can be shortened. As a result, the deviation between the calculated position and the actual position can be reduced. Thus, the accuracy of position calculation can be improved.

Of course, from the viewpoint of more accurately determining the position of the moving body 30, it may identify the position of the movable body 30 in consideration of the timing difference T _3. In this case, since the position of the moving body 30 is specified from the intersection of the three circles represented by the expressions (1) to (3), the position of the moving body 30 can be obtained with higher accuracy.

In the above description, an example in which the position coordinates are a two-dimensional plane has been described. However, the position of the moving body 30 in the three-dimensional space can also be specified. In this case, the position coordinates (X, Y, Z) of the moving body 30 that satisfy the relationships of the following expressions (4) to (6) may be obtained. Here, the position coordinates of the first base station 20a are assumed to be (X ₁ , Y ₁ , Z ₁ ). Let the position coordinates of the second base station 20b be (X ₂ , Y ₂ , Z ₂ ). The position coordinates of the third base station 20c are assumed to be (X ₃ , Y ₃ , Z ₃ ).

(X−X ₁ ) ² + (Y−Y ₁ ) ² + (Z−Z ₁ ) ² = L ₁ ² (4)
(X−X ₂ ) ² + (Y−Y ₂ ) ² + (Z−Z ₂ ) ² = L ₂ ² (5)
(X−X ₃ ) ² + (Y−Y ₃ ) ² + (Z−Z ₃ ) ² = L ₃ ² (6)
The moving body 30 exists at a position where the spheres represented by the equations (4) to (6) intersect.

A method for obtaining the timing differences T ₁ , T ₂ , T ₃ used in the self-position calculating means 60 in the above case will be described with reference to FIG. FIG. 6 shows only the ultrasonic shaping signal received by the first ultrasonic receiver 34 from FIG.
(1) As indicated by reference numeral 72 in FIG. 6, position calculation is performed using timing differences T ₁ , T ₂ , and T ₃ that are sequentially calculated based on data obtained during the period 74.
(2) The next position calculation is performed using timing differences T ₁ , T ₂ , and T ₃ that are sequentially calculated based on data obtained during the period 76 that does not overlap the period 74.
According to this method, position calculation processing is performed every 3 Tm.

Preferably, the timing differences T ₁ , T ₂ , T ₃ are obtained by the following method.
(1) As indicated by reference numeral 78 in FIG. 6, position calculation is performed using timing differences T ₁ , T ₂ , and T ₃ that are sequentially calculated based on data obtained during the period 80.
(2) The next position calculation is performed using the latest timing differences T ₂ and T ₃ that have already been calculated together with the newly calculated timing difference T ₁ . In this case, position calculation is performed based on data obtained during the period 82 that overlaps the period 80.
(3) the next position calculation is newly calculated with the timing difference T _2, performed by using the latest timing difference T ₁ and T ₃ that are already calculated. In this case, position calculation is performed based on data obtained during the period 84 that overlaps the period 82.
(4) the next position calculation is newly with timing difference T ₃ calculated, performed already using the latest timing difference T ₁ and T ₂ which are calculated. In this case, position calculation is performed based on data obtained during a period 86 that overlaps the period 84.
According to this method, position calculation processing is performed for each Tm. For this reason, the position of the moving body 30 can be calculated at a short time interval compared to the method described above.

Incidentally, when, for example, can not receive ultrasonic waves (adjusting signal) from the first base station 20a between the reference signal C _1A and the reference signal C _1B shown in FIG. 4, it was not determined timing difference T _1, already computed and performs position calculation using the latest timing difference T ₁ is. If the timing difference T ₁ that already calculated does not exist, the position calculation is not performed until calculate the timing difference T ₁ next time.

The self-position correcting unit 62 obtains a difference between the position of the moving body 30 calculated by the self-position calculating unit 60 and the target position of the moving body 30 and corrects the position of the moving body 30 so as to approach the target position. Generate data for The data is sent to the movement control means 64.
If a device other than the moving body 30 calculates the position of the moving body 30 and the moving body 30 corrects the position based on the calculated position, the calculated position from the device other than the moving body 30 to the moving body 30 is calculated. You need to send data. In this case, a communication system for that purpose is required. On the other hand, in the position calculation system of the present embodiment, the moving body 30 itself calculates its own position. Then, the mobile body 30 itself corrects its own position. Therefore, in order to correct the position of the moving body 30, it is not necessary to construct a communication system as described above.

  The movement control means 64 controls the movement direction and movement speed of the moving body 30 by controlling the operation of the movement mechanism 66 (including the wheel 66a shown in FIG. 2). The movement control means 64 controls the operation of the movement mechanism 66 based on (1) data input by the operator, (2) pre-programmed contents, or (3) data sent from the self-position correction means 62. Do it.

By the way, in the above, the reference signals (C _1A , C _1B , C _{1C in} FIG. 4) are generated by the reference signal output means of the moving body 30 and output to the timing difference calculation means 58. The reference signal may be obtained from a device different from the moving body 30. For example, the reference signal transmission device 10 is configured to function as a reference signal transmission device, and the reference signals C _1A , C _1B , and C _1C illustrated in FIG. 4 are transmitted from the transmission device 10. Good. The first base station 20a, the second base station 20b, at the same time when the third base station 20c to transmit ultrasonic waves to the timing _{t 3,} t 5, _{t 7} respectively, be transmitting a radio signal as a reference signal Good. According to this, the timing at which the mobile body 30 obtains the radio wave signal (reference signal) is substantially equal to the timings t ₃ , t ₅ , and t ₇ . That is, the timings t ₃ , t ₅ , and t ₇ can be known from the timing at which the moving body 30 obtains the radio wave signal (reference signal).

Second Embodiment FIG. 7 is a diagram schematically showing the positions of the base stations and the mobile body in the mobile body self-position calculation system of the second embodiment. FIG. 8 shows a timing chart for explaining the operation of the system.
The self-position calculation system according to the second embodiment includes a reference signal transmission device 10, a base station 20, and a moving body 30 having the same configuration as that of the first embodiment. However, this system has four base stations 20a, 20b, 20c, and 20d as schematically shown in FIG. Two of these base stations (the first base station 20a and the third base station 20c) constitute the first set. The remaining two base stations (the second base station 20b and the fourth base station 20d) constitute the second set.

  The base stations 20a, 20b, 20c, and 20d are arranged so that the line connecting the first set of base stations 20a and 20c and the line connecting the second set of base stations 20b and 20d are orthogonal to each other. The first base station 20a is located at coordinates (a, 0, 0). The third base station 20c is located at coordinates (−a, 0, 0). The second base station 20b is located at coordinates (0, b, 0). The fourth base station 20d is located at coordinates (0, -b, 0). The moving body 30 is located at coordinates (X, Y, Z).

The first base station 20a to the third base station 20c transmit ultrasonic waves at the same timing as the first base station 20a to the third base station 20c of the first embodiment. As shown in FIG. 8, the fourth base station 20d, ultrasonic _{B 4} is transmitted to the timing _{t 10.} The timing _{t 10,} the time from the timing _{t 2} is 3Tm. That is, in this embodiment, each base station 20a, 20b, 20c, ultrasonic transmitter 26 of the 20d is a timing _{t 2} of the reference signal receiver 32 receives the reference signal as a reference, the first base station 20a, the The two base stations 20b, the third base station 20c, and the fourth base station 20d are controlled by the ultrasonic transmission control means 28 (see FIG. 3) so as to transmit ultrasonic waves in order at equal time intervals Tm. .

Storage means 48 of the moving body 30 (see FIG. 3) is, as the time interval data from the timing t _2, which has received the reference signal A to the timing of transmitting ultrasonic waves, also stores those of the fourth base station 20d. The time is 3 Tm for the fourth base station 20d. The storage unit 48 stores the timings t _11F and t _{11G at} which the two ultrasonic receivers 34 and 38 (see FIG. 3) have received the ultrasonic waves that satisfy the predetermined condition from the fourth base station 20d.

The timing deriving means 50 also obtains the timing at which the ultrasonic transmitter of the fourth base station 20d transmits ultrasonic waves. Specifically, t ₂ + 3Tm = t ₁₀ is obtained. The reference signal output means 52 outputs child signals C _1A , C _1B , C _1C , and C _{1D obtained} by dividing the parent signal C ₁ having a cycle of 4Tm (4 × 50 msec = 200 msec) by 4 as reference signals. Timing difference calculating means 58, transmission timing of ultrasound _{B 4} from the fourth base station 20d is _{t 10,} since the reception timing of the first ultrasonic receiver 36 is _{t 11F,} the difference between the timing t calculated to _11F -t ₁₀ = _{T 4.} Own position calculating means 60, in addition to the distance _{L 1,} L 2, _{L 3} described in the first embodiment, the distance _{L 4} of the moving body 30 and the fourth base station 20d at the timing _{t 11} and Vs × _{T 4} calculate.

From the above, it can be considered that the moving body 30 is in a position that satisfies the relationships of the following expressions (7) to (10).
(X-a) ² + Y ² + Z ² = L ₁ ² (7)
^{X 2 + (Y-b)} 2 + Z 2 = L 2 2 (8)
(X + a) ² + Y ² + Z ² = L ₃ ² (9)
X ² + (Y + b) ² + Z ² = L ₄ ² (10)

From Expression (9) -Expression (7), X ² , Y ² , and Z ² can be eliminated, and a linear equation with one unknown (X) is obtained as shown in the following Expression (11).
X = (L ₃ ² −L ₁ ² ) / 4a (11)
From Formula (10) -Formula (8), X ² , Y ² and Z ² can be eliminated, and a linear equation with one unknown (Y) is obtained as shown in the following Formula (12).
Y = (L ₄ ² -L ₂ ² ) / 4b (12)
From the equation (7), the z coordinate Z of the moving body 30 is obtained as the following equation (13). When X is obtained from equation (11), Y is obtained from equation (12), and these are substituted into equation (13), equation (13) is also a linear equation with one unknown (Z).
Z = root (L ₁ ² − (X−a) ² −Y ² ) (13)

Thus, according to the present embodiment, the position of the moving body 30 can be calculated by solving the linear equations (11) to (13) each having one unknown.
That is, the position of the moving body 30 is calculated without solving the quadratic simultaneous equations with three unknowns (X, Y, Z) represented by the equations (4) to (6) as described above. it can. When solving the equations (4) to (6), there is a solution when the difference between the distances L ₁ , L ₂ , L ₃ obtained by calculation and the actual distance becomes large due to the influence of temperature, wind, etc. There may be no solution, or vice versa. In this case, it takes time and effort to improve the situation. On the other hand, when solving the equations (11) to (13), it is only necessary to solve a linear equation with one unknown, so that the solution can be obtained reliably with less effort. Thus, according to the present embodiment, a position calculation system that is strong against temperature, wind, and the like can be realized.

  Further, when Z is the height of the moving body 30, Z is known when the height of the moving body 30 does not substantially change. In this case, the position calculation accuracy is calculated from the difference between the X value obtained from Expression (11), the Y value obtained by substituting Y obtained from Expression (12) into Expression (13), and the known Z value. It is also possible to know the abnormality of the position calculation system.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, the frequency of the ultrasonic wave transmitted from each of the base stations 20a to 20c is different, and the ultrasonic wave received by the moving body 30 is distinguished from which of the base stations 20a to 20c is transmitted by the difference in the frequency. Consider when possible. In this case, the moving body 30, the ultrasonic wave received by the ultrasonic receiver 34 only (shaping signal), recognizes that the ultrasonic wave first base station 20a is sent between the timing t ₂ and t ₅ shown in FIG. 4 Then, a processing unit that performs processing may be provided. According to this, can not receive the direct wave of the ultrasonic wave from the first base station 20a of should receive the moving body 30 between the timing t ₂ and t ₅ would normally for some reason, the reflection of the ultrasonic waves even if the wave reaches the ultrasonic receiver 34 after the timing t _5, it can be prevented erroneously recognize the direct wave of the ultrasonic wave and the reflected wave from the first base station 20a.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings can achieve a plurality of purposes at the same time, and has technical utility by achieving one of the purposes.

  The present invention can be expected to be widely used in the field of calculating the position of a moving body such as a mobile robot.

An explanatory view of prior art is shown. The block diagram of the self-position calculation system of the moving body of 1st Example is shown (1). The block diagram of the self-position calculation system of the moving body of 1st Example is shown (2). The timing chart for demonstrating operation | movement of the self-position calculation system of 1st Example is shown. An explanatory view of a self-position calculation method by a self-position calculation system of a 1st example is shown (1). An explanatory view of a self-position calculation method by the self-position calculation system of the first embodiment is shown (2). It is the figure which showed typically the position of each base station and mobile body of the self-position calculation system of the mobile body of 2nd Example. The timing chart for demonstrating operation | movement of the self-position calculation system of 2nd Example is shown.

Explanation of symbols

10. Reference signal transmitter 20 Base station 30 Mobile unit

Claims (8)

A reference signal transmission means for transmitting a reference signal, a plurality of base stations, and a mobile unit;
Each base station includes a reference signal receiving unit that receives the reference signal, a storage unit that stores time interval data different for each base station, and a first timing at which the reference signal receiving unit receives the reference signal. Propagating wave transmission means for transmitting a propagation wave at the second timing with the time interval stored in the storage means,
The mobile unit determines a difference between a propagation wave receiving unit that receives the propagation wave, a third timing substantially equal to the second timing, and a fourth timing at which the propagation wave reception unit receives the propagation wave for each base station. A timing difference calculating means for calculating, and a self calculating the position of the mobile body based on the timing difference calculated for each base station by the timing difference calculating means, velocity data of the propagation wave and position data of each base station A mobile body self-position calculation system having position calculation means. The reference signal transmitted by the reference signal transmission means is a radio signal,
The mobile unit includes a reference signal receiving unit that receives the reference signal, a storage unit that stores the time interval data for each base station, and a fifth unit that receives the reference signal from the reference signal receiving unit of the mobile unit. The mobile unit according to claim 1, further comprising a timing deriving unit that obtains the third timing for each base station based on the timing and the time interval data stored in the storage unit of the mobile unit. Self-position calculation system. Reference signal transmission means for transmitting a reference signal including information sufficient to specify the third timing for each base station,
The mobile body self-position calculation system according to claim 1, wherein the mobile body further includes reference signal receiving means for receiving the reference signal.   Each time the self-position calculating means calculates a new timing difference for one base station by the timing difference calculating means, the self-position calculating means has already been calculated for base stations other than the one base station. 4. The mobile body self-position calculation system according to claim 1, wherein the position of the mobile body itself is calculated based on the latest timing difference.   There are four base stations, two of which make up the first set, the remaining two base stations make up the second set, and a line connecting the first set of base stations and the second 5. The mobile unit self-position calculation system according to claim 1, wherein the base stations are arranged so that lines connecting the pair of base stations are orthogonal to each other.   6. The self-position calculation system according to claim 1, wherein an ultrasonic wave is used as the propagation wave. A mobile unit whose position is calculated using a plurality of base stations that transmit propagation waves in order at predetermined time intervals from a first timing at which the reference signal receiving means receives the reference signal,
The difference between the propagation wave receiving means for receiving the propagation wave, the third timing substantially equal to the timing at which the base station transmits the propagation wave, and the fourth timing at which the propagation wave reception means has received the propagation wave is determined for each base station. A timing difference calculating means for calculating the position of the base station based on the timing difference calculated for each base station by the timing difference calculating means, velocity data of propagation waves and position data of each base station. A moving body having. The moving body according to claim 7, wherein an ultrasonic wave is used as the propagation wave.

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