WO2006093162A1

WO2006093162A1 - Ultrasonic distance measuring system and ultrasonic distance measuring method

Info

Publication number: WO2006093162A1
Application number: PCT/JP2006/303782
Authority: WO
Inventors: Hiromichi Hashizume; Masanori Sugimoto
Original assignee: Inter-University Research Institute Corporation Research Organization Of Information And Systems
Priority date: 2005-03-01
Filing date: 2006-02-28
Publication date: 2006-09-08
Also published as: JP4041899B2; JP2006242640A

Abstract

An ultrasonic distance measuring system and an ultrasonic distance measuring method that can perform a distance measurement by use of a simple apparatus structure and particularly can precisely measure the distance between a transmitting node and a receiving node in a short time by use of only ultrasonic waves. In the ultrasonic distance measuring system (100), the transmitting node (102), which generates a communication packet and transmits the communication packet by use of ultrasonic waves, is connected to the receiving node (104), which receives the communication packet to measure the distance between the receiving node and the transmitting node, via an Internet communication network (106) such that they can wirelessly communicate with each other.

Description

Specification

Ultrasonic distance measuring system and ultrasonic distance measuring method

Technical field

[0001] The present invention transmits a communication packet from an information terminal (transmission node) on the transmission side in an ultrasonic wave, and receives the communication packet at an information terminal (reception node) on the reception side. This is related to an ultrasonic distance measuring system and an ultrasonic distance measuring method for measuring the distance between the two.

Background art

[0002] Currently, portable information terminals having a small size and light weight and having a communication function have been developed and are widely used. In addition, the Internet communication network as an infrastructure has been established. It is used in everyday life because it can access the information world (cyber basis) while overcoming the distance through the Internet communication network.

[0003] By the way, when a portable information terminal is targeted, as an information terminal, for example, when another information terminal detects that an information terminal has been moved to a specific location, the other information terminal Can be used for providing services specific to the information terminal, and for each information terminal to start a special operation when specific information terminals detect that they are approaching each other. Specifically, when an information terminal installed in the sales floor detects that a customer who has arrived at a department store is close to the sales floor via the customer's mobile terminal, the customer's information terminal can be provided with product information on the sales floor. In a crowded gathering, it may be possible to display on the information terminals owned by each other what direction and distance the person being interviewed is. These applications are used when the communication distance of the information terminal is not a long distance communication and is a specific value (several meters to several tens of meters).

[0004] Also, when the communication distance of the information terminal is a specific value (several meters to several tens of meters), for example, the information terminal is equipped with a GPS (global positioning system) reception function. By collecting the location information of the members in the central server and installing the mobile phone communication function in the information terminal, it is possible to know the location from the zone information. These technologies are in practical use. There are also techniques for measuring distances and coordinate positions using ultrasonic waves. Electromagnetic waves such as radio waves and light, and electrical signals propagating through cables propagate one million times faster than ultrasonic waves propagating in the air, so they can be regarded as having an almost infinite propagation speed. . Specifically, first, the transmission node generates an electromagnetic wave or an electric signal and an ultrasonic signal at the same time. Next, the receiving node or the concentration node collects signals related to the arrival timing of both signals and knows the propagation delay time of the ultrasonic wave. Then, the interval (distance) between the transmission node and the reception node is calculated by dividing the propagation delay time by the known sound velocity in the air. In other words, the transmitting node transmits a beacon to the ultrasonic channel simultaneously and a timing signal including general information to the radio wave (similar to infrared) channel simultaneously. The receiving node receives both signals, calculates the difference between the arrival times of each signal, and calculates the distance between the nodes. Note that the spatial coordinate position of the specific node can be obtained by performing distance measurement on the three or more pairs of nodes as seen from the specific node.

In addition, for example, there is a technique for measuring the distance between nodes in a system in which a group of nodes whose internal clocks are not synchronized and a central server are connected via a network. Specifically, first, the receiving node receives the ultrasonic beacon transmitted from the transmitting node with ultrasonic waves. Next, the receiving node requests the central server to calculate the distance by transmitting the arrival time of the received ultrasonic beacon to the central server via the LAN. Then, the central server monitoring the operation of each node compares the signals from the transmitting node and the receiving node, calculates the distance between the arrival time differential nodes, and calculates the calculated distance to the receiving node. Send. Then, the receiving node obtains the distance from the transmitting node.

As other related techniques, for example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4 and the like are disclosed.

Patent Document 1: Japanese Patent Laid-Open No. 2003-323357

Patent Document 2: JP-A-2004-289711

Patent Document 3: JP-A-6-82242

Patent Document 4: Japanese Patent Publication No. 2004-530115

Disclosure of the invention

Problems to be solved by the invention [0006] However, in the prior art, the configuration includes a central server, and the configuration includes both a device that generates electromagnetic waves and a device that generates ultrasonic waves, which complicates the device configuration. There was a problem that the control method was also complicated.

On the other hand, there is only a reflection type of measuring the distance using only ultrasonic waves, and it is not possible to grasp the position of the target vaguely, and to transmit general information necessary for information processing with ultrasonic waves. There were problems that couldn't be done.

Furthermore, it is convenient to be able to measure the distance in a single shot in a very short time with a portable terminal, but the conventional method does not necessarily provide sufficient performance when used for such applications. There was also a problem.

[0007] The present invention has been made in view of the above problems, and can measure the distance with a simple device configuration and can accurately measure the distance between the transmission node and the reception node using only ultrasonic waves. An object of the present invention is to provide an ultrasonic distance measuring system and an ultrasonic distance measuring method that can measure well, and in particular have a general data communication function.

Means for solving the problem

[0008] In order to achieve the above object, an ultrasonic distance measurement system according to the present invention uses a predetermined time synchronization method in a plurality of information terminals in a state where their internal clocks are synchronized in advance via a network. An ultrasonic distance measurement system that measures a distance between corresponding information terminals by transmitting a communication packet from one information terminal and receiving the communication packet at another information terminal. A communication packet generating means for generating a transmission time stamp based on the time acquired from the internal clock and generating a communication packet including the transmission time stamp; and a communication packet generated by the communication packet generating means Communication packet transmitting means for transmitting ultrasonically, and the information terminal on the receiving side transmits the communication packet transmitted ultrasonically from the information terminal on the transmitting side A communication packet receiving means for receiving, a reception time stamp generating means for acquiring a time when the communication packet is received by the communication packet receiving means, and generating a reception time stamp based on the time, and the reception time stamp Distance for calculating the distance between the information terminal on the transmission side and the information terminal on the reception side based on the difference between the reception time stamp generated by the generation means and the transmission time stamp included in the communication packet received by the communication packet reception means Calculation And an exit means.

[0009] In addition, the ultrasonic distance measuring system according to the present invention includes a single information terminal among a plurality of information terminals in a state where the internal clock is synchronized in advance via a network using a predetermined time synchronization method. The ultrasonic distance measuring system measures the distance between the corresponding information terminals by transmitting the communication packet and receiving the communication packet at another information terminal. The communication packet transmits and receives the communication packet. The transmission side information terminal actually includes the transmission time obtained from the internal clock and the transmission time, including the transmission time stamp indicating the reference position that is the reference for synchronization and the time when the reference position was transmitted. A transmission time stamp is generated based on a transmission correction value that is a time difference until the reference position of the communication packet is transmitted, and the transmission time stamp is included. A communication packet generating means for generating a communication packet; and a communication packet transmitting means for transmitting the communication packet generated by the communication packet generating means by means of ultrasonic waves. A communication packet receiving means for receiving a communication packet transmitted by sound waves;

The reception time when the communication packet is received by the communication packet receiving means is acquired from the internal clock, and the acquired reception time and the time difference from when the reception time is acquired until the reference position of the communication bucket is actually received. Based on a certain reception correction value, a reception time stamp generating means for generating a reception time stamp representing a time at which the reference position is received, a reception time stamp generated by the reception time stamp generation means and a communication packet received by the reception means Distance calculating means for calculating the distance between the information terminal on the transmission side and the information terminal on the reception side based on the difference from the transmission time stamp included in the communication packet.

[0010] Further, the ultrasonic distance measuring system according to the present invention is the ultrasonic distance measuring system described above, wherein the communication packet includes an identification ID for identifying an information terminal on a transmitting side, arbitrary communication data, a check It further comprises at least one of the thumbs.

[0011] Further, in the ultrasonic distance measuring system according to the present invention, in the ultrasonic distance measuring system described above, the communication packet further includes a coordinate position of an information terminal on a transmitting side, and information on the receiving side When receiving a communication packet continuously from a plurality of different transmission-side information terminals, the terminal and each transmission-side information terminal calculated by the distance calculation means It further comprises position estimating means for estimating the position of the receiving information terminal based on the distance from the receiving information terminal and the coordinate position of each transmitting information terminal.

[0012] Further, in the ultrasonic distance measuring system according to the present invention, in the ultrasonic distance measuring system described above, the information terminal is a portable information terminal such as a PDA, a mobile phone, or a personal computer. It is characterized by.

[0013] Further, in the ultrasonic distance measuring system according to the present invention, in the ultrasonic distance measuring system described above, the information terminal on the transmitting side is fixed, and the information terminal on the receiving side is movable. It is characterized by that.

In addition, the present invention relates to an ultrasonic distance measuring method, and the ultrasonic distance measuring method according to the present invention synchronizes the internal clock in advance via a network using a predetermined time synchronization method. An ultrasonic distance measurement method that measures the distance between corresponding information terminals by transmitting communication packets from one information terminal and receiving communication packets at other information terminals in a plurality of information terminals in a state. Therefore, a transmission time stamp is generated based on the time acquired from the internal clock, and a communication packet including the transmission time stamp is generated, and the generated communication packet is ultrasonically transmitted. The receiving information terminal receives the communication packet transmitted by the transmitting terminal's information terminal power ultrasound and the time when the communication packet was received from the internal clock. A reception time stamp is generated based on the time, and a transmission-side information terminal and the reception-side information terminal are connected based on a difference between the generated reception time stamp and a transmission time stamp included in the received communication packet. It is characterized by calculating the distance.

[0015] In addition, the ultrasonic distance measuring method according to the present invention includes a plurality of information terminals in a state where their internal clocks are synchronized in advance via a network using a predetermined time synchronization method. An ultrasonic distance measurement method for measuring a distance between corresponding information terminals by transmitting a communication packet and receiving the communication packet at another information terminal, wherein the communication packet is used when transmitting / receiving the communication packet. This includes a reference position that is a reference for synchronization and a transmission time stamp that indicates the time when the reference position was transmitted, and the information terminal on the transmitting side actually uses the transmission time acquired from the internal clock and the transmission time. Based on the transmission correction value that is the time difference until the reference position of the communication packet is transmitted, a transmission time stamp is generated, a communication packet including the transmission time stamp is generated, and the generated communication packet is transmitted by ultrasonic waves. The receiving side information terminal receives the communication packet transmitted by the transmitting side information terminal power ultrasound, obtains the reception time when the communication packet was received from the internal clock, and the received reception time and the received time are Based on the reception correction value, which is the time difference from when the reference position of the communication packet is actually received until it is acquired, a reception time stamp indicating the time when the reference position is received is generated, and the generated reception time stamp and Based on the difference from the transmission time stamp included in the received communication packet, the distance between the transmitting information terminal and the receiving information terminal is calculated. To it, it is referred to as Features.

[0016] Further, in the ultrasonic distance measuring method according to the present invention, in the ultrasonic distance measuring method described above, the communication packet includes an identification ID for identifying an information terminal on a transmission side, arbitrary communication data, It further comprises at least one of the checksums.

[0017] Further, in the ultrasonic distance measuring method according to the present invention, in the ultrasonic distance measuring method described above, the communication packet further includes a coordinate position of an information terminal on a transmission side, When an information terminal continuously receives communication packets from a plurality of different transmission side information terminals, the calculated distance between each transmission side information terminal and the reception side information terminal and the coordinates of each transmission side information terminal The position of the information terminal on the receiving side is estimated based on the position.

[0018] Further, in the ultrasonic distance measuring method according to the present invention, in the ultrasonic distance measuring method described above, the information terminal is a portable information terminal such as a PDA, a mobile phone, or a personal computer. It is characterized by.

[0019] Further, in the ultrasonic distance measuring method according to the present invention, in the ultrasonic distance measuring method described above, the information terminal on the transmitting side is fixed, and the information terminal on the receiving side is It is characterized by being movable.

The invention's effect

[0020] According to the ultrasonic distance measuring system and the ultrasonic distance measuring method of the present invention, the internal clock is synchronized in advance via the network using a predetermined time synchronization method. In a plurality of information terminals in a state, a communication packet is transmitted from one information terminal, and a communication packet is received by another information terminal, thereby measuring the distance between the corresponding information terminals. In particular, the information terminal on the transmission side generates a transmission time stamp based on the time acquired from the internal clock, generates a communication packet including the transmission time stamp, and transmits the generated communication packet using ultrasonic waves. Then, the receiving side information terminal receives the communication packet transmitted by the transmitting side information terminal force ultrasonic wave, acquires the time when the communication packet was received, and acquires the internal clock force, and based on the received time stamp And the distance between the transmitting information terminal and the transmitting information terminal is calculated based on the difference between the generated reception time stamp and the transmission time stamp included in the received communication packet. As a result, the distance can be measured with a simple device configuration, and in particular, the distance between the transmission node and the reception node can be accurately measured in a short time using only ultrasonic waves. Further, according to the ultrasonic distance measurement system and the ultrasonic distance measurement method according to the present invention, in a plurality of information terminals in a state where the internal clocks are synchronized in advance via a network using a predetermined time synchronization method, By transmitting communication packets from one information terminal and receiving communication packets at other information terminals, the distance between the corresponding information terminals is measured. In particular, the communication packet includes a reference position serving as a reference for synchronization when the communication packet is transmitted and received and a transmission time stamp indicating the time when the reference position is transmitted. The information terminal on the transmission side generates a transmission time stamp based on the transmission time acquired from the internal clock and the transmission correction value that is the time difference from the transmission time until the reference position of the communication packet is actually transmitted. Then, a communication packet including the transmission time stamp is generated, and the generated communication packet is transmitted by ultrasonic waves. Then, the receiving side information terminal receives the communication packet transmitted by the transmitting side information terminal power ultrasonic wave, acquires the reception time when the communication packet is received from the internal clock, and acquires the acquired reception time and the reception time. Based on the reception correction value that is the time difference from when the reference position of the communication packet is actually received until the reference position of the communication packet is received, a reception time stamp indicating the time when the reference position is received is generated. The distance between the information terminal on the transmission side and the information terminal on the reception side is calculated based on the difference between the reception time stamp and the transmission time stamp included in the received communication packet. This makes it possible to measure distances with a simple device configuration and uses only ultrasonic waves. As a result, the distance between the transmitting node and the receiving node can be accurately measured in a short time.

[0022] Further, according to the ultrasonic distance measurement system and the ultrasonic distance measurement method according to the present invention, the communication packet includes at least one of an identification ID for identifying an information terminal on the transmission side, arbitrary communication data, and a checksum. In addition. As a result, the ability to send and receive multiple pieces of information at once can be achieved.

[0023] Further, according to the ultrasonic distance measuring system and the ultrasonic distance measuring method according to the present invention, the communication packet further includes the coordinate position of the information terminal on the transmitting side, and the information terminal on the receiving side has a plurality of different information terminals. When the communication terminal also continuously receives communication packets, the reception terminal receives the received data based on the calculated distance between each transmission-side information terminal and the reception-side information terminal and the coordinate position of each transmission-side information terminal. The position of the information terminal on the side is estimated. As a result, the coordinate position of the information terminal on the receiving side can be accurately estimated in a short time.

[0024] Further, according to the ultrasonic distance measurement system and the ultrasonic distance measurement method according to the present invention, the information terminal is a portable information terminal such as a PDA, a mobile phone, or a personal computer. As a result, the distance between the information terminals can be accurately measured in a short time while moving.

In addition, according to the ultrasonic distance measuring system and the ultrasonic distance measuring method according to the present invention, the information terminal on the transmission side is fixed, and the information terminal on the reception side is movable. Thus, for example, by installing a plurality of transmitting information terminals indoors, the receiving information terminal can calculate the coordinate position of the information terminal.

Brief Description of Drawings

FIG. 1 is a conceptual diagram showing an example of a configuration of an ultrasonic distance measurement system 100.

FIG. 2 is a block diagram showing an example of a specific configuration of the transmission node 102.

FIG. 3 is a block diagram showing an example of a specific configuration of the receiving node 104.

FIG. 4 is a conceptual diagram showing an example of time synchronization by NTP.

FIG. 5 is a diagram showing an example of a specific configuration of a communication packet. FIG. 6 is a flowchart showing an example of processing performed in the transmission node 102.

FIG. 7 is a flowchart illustrating an example of processing performed in the reception node 104.

FIG. 8 is a diagram showing an example of phase extraction by direct detection.

[Fig. 9] Fig. 9 is a diagram showing an example of expression of a time reference point by a synchronization pattern.

FIG. 10 is a diagram showing an example of an ultrasonic distance measurement system 100 configured with a plurality of fixed transmission nodes 102 and a portable reception node 104.

Explanation of symbols

[0027] 100 ultrasonic distance measuring system

102 Sending node

102a CPU

102b wireless LAN

102c internal β clock

102d: 102f waveform memory

102g to 102i phase shifter

102j DA converter

102k ultrasonic transmitter

104 Receiving node

104a CPU

104b wireless LAN

104c inner clock G clock

104d waveform memory

104e AD converter

104f Ultrasonic transmitter

106 Internet communication network

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of an ultrasonic distance measuring system and an ultrasonic distance measuring method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment. First, the configuration of the ultrasonic distance measuring system 100 of the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram showing an example of the configuration of the ultrasonic distance measuring system 100. As shown in FIG. 1, the ultrasonic distance measurement system 100 generates a communication packet, and transmits the communication packet with ultrasonic waves, and receives the communication packet and measures the distance between the transmission node and the transmission node. The receiving node 104 is connected to the receiving node 104 via the Internet communication network 106 so as to be able to communicate wirelessly. Here, all transmitting nodes 102 and receiving nodes 104 are synchronized in advance with their internal clocks via the Internet communication network 106 using NTP (Network Time Protocol). FIG. 1 shows an example of an ultrasonic distance measuring system 100 force consisting of one transmitting node 102 and three receiving nodes 104. The number of force transmitting nodes 102 and receiving nodes 104 is not limited to this. Les. In this embodiment, the node 102 is described as a transmitting node, and the node 104 is a receiving node. However, the configuration of each node may be the same, and each node plays a role as necessary. Can bear.

[0030] The transmission node 102 generates a transmission time stamp based on the time acquired from the internal clock, generates a communication packet including the transmission time stamp, and transmits the generated communication packet using ultrasonic waves. Here, an example of a specific configuration of the transmission node 102 will be described with reference to FIG. FIG. 2 is a block diagram illustrating an example of a specific configuration of the transmission node 102. As shown in FIG. 2, the transmitting node 102 includes a CPU 102a that controls the entire transmitting node 102 and a wireless LAN 102b that connects the transmitting node 102 to the Internet communication network 106 (the time synchronization communication device in FIG. 1). N), a plurality of waveform memories 102d to 102f that store waveforms to be transmitted, a plurality of phase shifters 102g to 102i, a DA converter 10¾, and an ultrasonic transmission element 102k (Corresponding to the ultrasonic transmitter S in Fig. 1), and these are connected via an arbitrary communication path. The transmission node 102 may further include an ultrasonic receiving element (corresponding to the ultrasonic receiver R in FIG. 1).

In FIG. 2, the CPU 102a includes a communication packet generation unit and a communication packet transmission unit. The communication packet generation unit generates a transmission time stamp based on the time acquired from the internal clock 102c, and generates a communication packet including the transmission time stamp. Specifically Generates a transmission time stamp based on the transmission time acquired from the internal clock 102c and a transmission correction value that is a time difference from the transmission time until the reference position of the communication packet is actually transmitted. A communication packet including is generated. The communication packet transmission unit transmits the communication packet generated by the communication packet generation unit using ultrasonic waves. Note that the communication packet includes at least a reference position serving as a reference for synchronization when the communication packet is transmitted and received and a transmission time stamp indicating the time when the reference position is transmitted.

Here, an example of a specific configuration of the communication packet will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of a specific configuration of a communication packet. As shown in FIG. 5, the communication packet includes a synchronization pattern portion including a reference position (corresponding to a time reference point), which is a characteristic part of the present invention, a packet length (in bytes), a transmission node ID, It consists of a transmission time stamp, user data (arbitrary communication data), and a checksum (CRC16). When the coordinate position of receiving node 104 is estimated, the communication packet includes the coordinate position of transmitting node 102. Further, the order of data included in the communication packet excluding the synchronization pattern part and the checksum may be arbitrarily changed.

[0033] Returning to Fig. 1 again, the receiving node 104 receives the communication packet transmitted by the ultrasonic wave from the transmitting node 102, acquires the time when the communication packet was received from the internal clock, and based on the time, A reception time stamp is generated, and a distance between the transmission node 102 and the reception node 104 is calculated based on a difference between the generated reception time stamp and a transmission time stamp included in the received communication packet. Here, an example of a specific configuration of the receiving node 104 will be described with reference to FIG. FIG. 3 is a block diagram showing an example of a specific configuration of the receiving node 104. As shown in FIG. As shown in FIG. 3, the receiving node 104 includes a CPU 104a that controls the entire receiving node 104 and a wireless LAN 104b that connects the receiving node 104 to the Internet communication network 106 (the time synchronization communicator N in FIG. 1). ), Internal clock 104c for timing, waveform memory 104d for storing received waveforms, AD converter 104e, and ultrasonic receiving element 104f (corresponding to ultrasonic receiver R in FIG. 1) These are configured and connected via an arbitrary communication path. The reception node 104 may further include an ultrasonic transmission element (corresponding to the ultrasonic transmitter S in FIG. 1). In FIG. 3, CPU 104a includes a communication packet receiving unit, a reception time stamp generating unit, a distance calculating unit, and a position estimating unit. The communication packet receiving unit receives a communication packet transmitted from the transmission node 102 by using an ultrasonic wave. The reception time stamp generation unit acquires the time when the communication packet is received by the communication packet reception unit from the internal clock 104c, and generates a reception time stamp based on the time. Specifically, the reception time when the communication packet is received by the communication packet receiver is acquired from the internal clock 104c, and the acquired reception time and the reference position of the communication packet are actually received after the reception time is acquired. Based on the reception correction value, which is the time difference until, a reception time stamp indicating the time when the reference position is received is generated. The distance calculation unit determines the distance between the transmission node 102 and the reception node 104 based on the difference between the reception time stamp generated by the reception time stamp generation unit and the transmission time stamp included in the communication packet received by the communication packet reception unit. Is calculated. When the position estimation unit continuously receives communication packets from a plurality of different transmission nodes 102, the position estimation unit calculates the distance between each transmission node 102 and the reception node 104 calculated by the distance calculation unit and the coordinate position of each transmission node 102. Based on this, the position of the receiving node 104 is estimated.

[0035] In the above configuration, processing performed by the transmission node 102 and the reception node 104 constituting the ultrasonic distance measurement system 100 will be described in order with reference to Figs. Note that all the transmission nodes 102 and reception nodes 104 constituting the ultrasonic distance measurement system 100 are synchronized in advance with the internal clock 102c and the internal clock 104c via the Internet communication network 106 using NTP. And Here, time synchronization by NTP will be briefly described with reference to FIG. Fig. 4 is a conceptual diagram showing an example of time synchronization by NTP. As shown in Fig. 4, the n + 1 layer NTP server that synchronizes the time inquires the NT p server of the n layer for the time. Then, the _n-th layer NTP server transmits the inquiry to the n_l layer NTP server. Thereafter, the communication is repeated between NTP servers in adjacent layers, and finally the inquiry is transmitted to the NTP server in the uppermost layer (0th layer). The top layer NTP server then returns the time to the adjacent layer NTP server. Thereafter, transmission is repeated between NTP servers in adjacent layers, and finally the time is returned to the n + 1 layer NTP server that is the source of the inquiry. This allows the n + 1 layer NTP server to synchronize the time. First, processing performed in the transmission node 102 will be described with reference to FIG. FIG. 6 is a flowchart showing an example of processing performed in the transmission node 102. The sending node sends out communication packets at an appropriate frequency by the following processing.

[0037] First, the initial phase amount p of the waveform (frequency f = 39000 Hz) stored in the waveform memory 102d.

1 1 is determined by the phase shifter 102g (step SA-1), and the initial phase amount p of the waveform (frequency f = 39000Hz) stored in the waveform memory 102e is determined by the phase shifter 102h (step SA_2). ,Waveform

twenty two

The initial phase amount p of the waveform (frequency f = 40000Hz) stored in memory 102f is changed to phase shifter 102

3 3

Determine with i (step SA_3). Specifically, first, the delay times of the transmission circuit and the ultrasonic transmission element are examined, and the delay time s and the waveform of the frequency f corresponding to the waveform of the frequency f are obtained.

1 1 2

Measure the delay time S corresponding to the waveform with the corresponding delay time s and frequency f. Next,

2 3 3

In order to align the phase of the elementary carrier at the time reference point to zero, the initial phase amounts p, p, and p are calculated by Equation 1, Equation 2, and Equation 3 below for each carrier of the synchronization pattern. And

one two Three

Thus, the calculated initial phase amounts p, p, and p are stored in the waveform memories 102d to 102f, respectively.

one two Three

p = 2 π X (l -frac ((0. 0005 + s) X f))) (Equation 1)

1 1 1

p = 2 π X (l -frac ((0. 0005 + s) X f))) (Equation 2)

2 2 2

p = 2 π X (l -frac ((0. 0005 + s) X f))) (Equation 3)

3 3 3

Here, frac (x) is an operation for extracting the fractional part of x.

It should be noted that the processes from step SA— :! to SA—3 may be executed once.

[0038] Here, if the transmission circuit or the transmission element to be used has a property (dispersion characteristic) that changes the phase of the waveform depending on the frequency, correction is applied to the elementary carrier in advance to compensate for it. Anyway. The duration of the synchronization pattern of the transmitted waveform is l / (f -f

max mi

) (F is the highest frequency among multiple carriers, and f is the minimum circumference n max mm

It is wave number. ).

[0039] Next, a transmission time is acquired from the internal clock 102c, and a time obtained by adding a preset time "0.5 ms" as a transmission correction value to the transmission time is generated as a transmission time stamp T.

s

(Step SA_4). Specifically, when starting the transmission operation, one time reference point is determined, the transmission timing of the communication packet can be calculated relative to the time reference point, and the time reference point is time synchronized. Generate and send the value represented by the internal clock Time stamp T. Here, set the time reference point to the center of the synchronization pattern (0

After 5ms), set the waveform transmission phase to zero at this center. More specifically, a carrier waveform composed of a plurality of predetermined frequencies is generated, and an additive synthesis thereof or a result obtained by modulating these with a main carrier is used as a synchronization pattern. Note that the phases of the elementary carriers constituting the plurality of carriers in the synchronization pattern are configured so as to have a predetermined relationship with the time reference point (see FIG. 9). Here, in the present embodiment, the time point when the zero phases of the three frequencies are aligned is defined and set as the time reference point, but the predetermined condition of the time reference point is, for example, the maximum value of the three frequencies Or you can use the point when the minimum values are complete. The time stamp is quantized with 1 μs and expressed as a 48-bit integer. This is a notation that cycles in about nine years.

[0040] Next, simultaneously with the processing of step SA-4, the ultrasonic carrier wave is modulated and a communication packet is transmitted. Specifically, first, the synchronization pattern is transmitted with the initial phase amounts p to p stored in the waveform memories 102d to 102f (step SA-5). Next, the packet length is

13

Send (step SA—6), send sender node ID (step SA—7), send send timestamp T (step SA—8), send user data (step SA—9), bit s

A checksum (CRC16 using a 16-bit generator polynomial in this embodiment) is created from the pattern and transmitted (step SA-10). In other words, the packet length, transmission node ID, transmission time stamp, and CRC16 are sequentially modulated by PSK and transmitted. Here, for data less than the packet length included in the communication packet (see Fig. 5), 8-value PSK modulation is applied to the frequencies f to f.

13

However, a synchronous carrier wave is applied to the phase reference. These are set to zero phase, and a digital value from 0 to 7 is expressed by a phase shifted from here by η / 4 π radians (where n is an integer from 0 to 7). Since there are three types of carrier waves, 24-bit (3 X 8) or 3-byte digital information can be transmitted in 1 ms symbol time. In other words, since the transmission speed in each carrier wave is 1 symbol / ms, the total communication speed is 24 (= 8 × 3 × (1 / 0.001)) kbps. In this embodiment, an example is shown in which transmission is performed using 8-level PSK modulation, but transmission may be performed directly using a carrier wave or other modulation scheme.

This is the end of the description of the processing performed by the transmission node 102.

Next, processing performed at the receiving node 104 will be described with reference to FIG. Figure 7 4 is a flowchart showing an example of processing performed in a trust node 104. For reception, f, f, f

Prepare a signal that is a sine wave with a frequency of 1 2 3 and phase-shifted by 1/2 π radians, and multiply the received waveform as signals equivalent to cos co t and sin co t respectively, and perform quadrature detection. Do. In the following, processing may be performed by force analog demodulation, which describes an example of digital processing.

[0043] First, a carrier is detected, and if it can be detected (step SB-1: Yes), a start time T that is a time when reception starts from the internal clock 104c is acquired (step SB-2).

0

[0044] Next, the received signal is AD converted by the AD converter 104e and stored in the waveform memory 104d (step SB-3).

Next, the beginning portion (synchronization pattern) of the communication packet is extracted (step SB — 4).

[0046] Next, the phase information sine component and cosine component of the subcarrier of frequency f are expressed as cos (2 π f t

1 1

) And sin (2 π f t) (step SB-5). Also, the carrier with frequency f

1 2

Multiplying the wave phase information sine and cosine components by cos (2 n i t) and sin (2 π f t)

twenty two

(Step SB-6). Furthermore, the phase information sine component of the elementary carrier of frequency f and

Three

The cosine component is extracted by multiplying cos (2 π f t) and sin (2 π f t) (Step SB—7

3 3

[0047] Next, the phases φ,, φ at the start time T of the subcarrier of the synchronous pattern portion are calculated.

0 1 2 3 (Step SB-8). In the processing from step SB-4 to SB-7, the data from the beginning of the communication packet to a little less than lms (which is shorter by the carrier detection time) belongs to the synchronous pattern part, and it is orthogonally detected at frequencies f to f. To synchronize the waveform memory 104d.

13

Sine and cosine phase information is extracted for the elementary carrier of the pattern. In step SB_8, by comparing this, the phases φ, φ, φ at the reception start time T can be obtained.

0 1 2 3

it can. Here, if the receiving element or the receiving circuit has a dispersion characteristic related to the phase, the value is corrected. The processing in steps SB_4 to SB_8 will be described in detail. As shown in FIG. 8, the product of the received waveform and the frequency f waveform (cos (2πft)) and the received waveform and the frequency f

1 1 1 Calculate the product of the waveform (sin (2 π f t)) whose phase is shifted by π / 2 from the waveform,

1

Compute the phase Φ by comparison through an integrator. The received waveform and frequency f

1 Phase shift from product of 2 waveform (cos (2 π ft)) and received waveform and frequency f waveform by π Ζ2. Compute the product of the phased waveforms (sin (2 π ft)) and pass each through an integrator.

2

To calculate the phase Φ. Furthermore, the product of the received waveform and the frequency f waveform (cos (2 f t))

2 3 3 and the waveform (sin (2 π f t)) with the phase shifted by π / 2 from the received waveform and the frequency f waveform

Compute the phase Φ by computing the products of 3 3 and comparing each through an integrator.

Three

[0048] Returning again to FIG.

13

Time reference points T 1, T 2, T 3 are determined based on the transmission delay times r to r (step SB—9

1 3 12 23 31

). Specifically, from the reception phase Φ, Φ of the elementary carrier of frequency f and the elementary carrier of frequency f

1 2 1 2

The time reference point T is calculated by the following formula 4. Also, an elementary carrier with frequency f and frequency f

The time reference point T is calculated using Equation 5 below from the received phases φ and φ of 12 2 3 elementary carriers. The

2 3 23

In addition, the time base is determined from the reception phases Φ and Φ of the elementary carrier with frequency f and the elementary carrier with frequency f.

3 1 3 1

Point T is calculated using Equation 6 below.

31

Τ = Τ + (((φ --φ) / 2π) + (rf -rf)) / (f -f)

12 0 1 2 1 1 2 2 1 2

• · · (Formula 4)

T = T-(((Φ --Φ) / 2π) + (rf -rf)) / (f -f)

(Formula 5)

Τ = Τ-(((Φ --Φ) / 2π) + (rf -rf)) / (f -f)

(Formula 6)

In other words, the time reference point is reproduced by calculating the time when the phase relationship of the subcarriers becomes a specific value.

[0049] Next, based on the time reference points T to T and the start time Τ determined in step SB-9.

12 31 0 and the reception time stamp Τ is determined (step SB-10). Specifically, the arithmetic mean shown in Equation 7 below is the reception time stamp T. Note that variations and confidence intervals may be considered in the reception time stamp.

T = T + (T + Τ + Τ) / 3 (Equation 7)

r 0 12 23 31

[0050] Next, the quadrature detection is continued on the data in the waveform memory 104d, and the phases φ, small, φ are used as a reference.

1 2 3 Demodulation obtains the packet length, transmission node ID, transmission time stamp T, user data, and checksum (CRC16) (step SB-11).

[0051] Next, the checksum is verified, and if it matches (step SB—12: Yes), the communication bucket The distance D between nodes is calculated using Equation 8 below (step SB-13).

D = (T -T) / c (8)

r s

Where c is the speed of sound, about 340mZs in a dry atmosphere of 20 degrees Celsius and 1 atmosphere. In other environments, correction is performed in advance. Specifically, when this system or method is implemented in a wide range of other temperature environments, a thermometer is installed in the receiver (receiving node 104) to correct changes in sound velocity due to temperature.

[0052] Here, when a communication packet further including the coordinate position of transmitting node 102 is continuously received from a plurality of different transmitting nodes, each transmitting node 102 calculated in step SB-13 and the receiving node concerned The position of the receiving node 104 may be estimated based on the distance to the transmitting terminal 104 and the coordinate position of each transmitting node 102.

[0053] This is the end of the description of the processing performed by the receiving node 104.

The embodiment of the ultrasonic distance measurement system 100 has been described above. Here, the process up to the development of this system is explained.

[0055] Until now, the conventional technology for measuring distances using ultrasonic waves, for example, required a central server for collecting information. Therefore, an access from each node to the central server occurs in determining the distance, which becomes a load on the server. Furthermore, the load increases in proportion to the square of the number of nodes (the number of nodes involved), and the system may fail if the number of nodes increases. In addition, it takes time to determine each distance by the communication time for access and response.

Also, with the conventional technology that measures distance using electromagnetic waves and ultrasonic waves, the receiving node must receive ultrasonic waves and electromagnetic waves. Therefore, for example, if either one of the receptions fails, the measurement cannot be performed and the reliability is bad. In addition, when a reception routine is created with the processor software of a small digital device, high-speed and high-precision processing is required for reception of both channels, which increases costs. In addition, when the number of measurement processes between nodes increases, the number of receive interrupt processes is approximately twice that of this system, making it unsuitable for large-scale applications.

In addition, with conventional technologies that measure distances with GPS, etc., it is generally only possible to achieve accuracy of several meters, and it is difficult to measure with accuracy of several centimeters like this system. Mobile phone The method of tracking in a talk or PHS antenna zone cannot measure distances finer than the zone grid (generally hundreds of meters). In addition, with the method of estimating the distance from the decrease in the level of the received signal by installing radio waves or infrared beacons, if the radio wave shielding object is lost, the signal attenuation will result in a measurement error, and accurate distance measurement will not be possible. Have difficulty. In addition, these measurement methods cannot be used indoors where radio waves do not reach if the radio sources are outdoors.

[0056] By the way, many information terminals currently have an Internet access function. By using a widely used time synchronization method such as NTP, the information terminal can always synchronize the internal clock with sufficient accuracy by network communication once every few minutes. In this way, distance measurement and coordinate position measurement can be performed simply by transmitting and receiving an ultrasonic signal without simultaneously generating timing with an electric signal and an ultrasonic signal.

However, when distance measurement is performed only by ultrasonic communication, it is necessary to transmit information necessary for distance measurement (for example, ID of transmission node, transmission time stamp). In conventional ultrasonic measurement, the ultrasonic wave is transmitted only by a burst indicating the timing, and the time stamp and the transmission node ID are transmitted through an electrical communication channel. However, in measurement using only ultrasonic waves, it must be designed to transmit both timing and general digital information using ultrasonic waves.

However, the widely used piezoelectric ultrasonic wave transmitting and receiving elements are characterized by a narrow communication band and uneven amplitude and phase propagation characteristics in the transmission band. Due to this feature, even if it is attempted to convey the timing start point with a carrier burst, the received signal is subjected to another amplitude change or phase change for each frequency component, and is decomposed to make the start point ambiguous. That is, the delay time becomes ambiguous. As a result, it becomes difficult to accurately measure the distance. Therefore, the present inventors have developed a mechanism capable of accurately transmitting timing information even in a narrowband communication path such as ultrasonic communication. Portable information terminals are constantly moving, and there are always people around who can interfere with communication. Therefore, it is necessary to complete a single distance measurement including information transmission in a short time. In addition, if there is an error in communication, it is necessary to consider detecting the error and avoiding erroneous measurements.

[0059] According to this system developed based on the above circumstances, while performing general information communication in a network in which portable or fixed information terminals communicate with each other by ultrasonic waves, The distance of the information terminal power on the transmitting side can be measured. This makes it possible to provide various advanced mobile information services such as information services based on the location of information terminals and services based on mutual relationships. In addition, it is possible to know the approach of the information terminal, and to post information several meters in advance. In addition, it is possible to know the distance and direction to the target in the crowd. In addition, a plurality of transmission nodes are fixedly installed in the building, and the coordinate position of the reception node can be known by the reception node knowing the distance to each transmission node. In addition, this system can be used when designing various information services using the absolute position and mutual position of portable information terminals such as mobile terminals and PDAs. All nodes are basically in the reception state and transition to the transmission state at random timing.

[0060] Specifically, according to this system, information terminals (nodes) communicate with each other via a bucket-type digital communication network using ultrasonic waves. For example, one node (transmission node) performs a transmission operation, and the other nodes (reception nodes) perform a reception operation. All nodes have the same internal clock value in advance using a time synchronization method such as NTP. The transmitting node transmits the information communication packet including the time reference point information and the time stamp information of the time when it was transmitted. The receiving node determines the position of the time reference point from the received packet and generates a reception time stamp again. At the same time, it is possible to obtain the packet propagation delay time by calculating the difference compared with the transmission time stamp obtained by decoding the communication information. The receiving node can calculate the distance from the transmitting node by converting the delay time in consideration of the speed of sound. In other words, according to the present system, each node is synchronized in time with an accuracy of, for example, 1/1000 second by a highly synchronized internal clock or time synchronization method such as NTP. Then, one transmitting node transmits a packet composed of a node identification number and a time stamp using an ultrasonic channel. Then, the receiving node can calculate the distance from the transmitting node by obtaining the reception time (reception time stamp) of the specific bit position of the packet. By further including the transmission node ID and coordinate information in the packet, a receiving node that has received three or more sets of this packet can determine the three-dimensional coordinate position of the receiving node.

Further, as a modification of the present embodiment, for example, as shown in FIG. It is also possible to place the receiving node in a portable position, make the receiving node portable, and measure the distance from the transmitting node in the room.

[0062] Further, according to this system, as a result of experiments, digital communication (several to several) of information including node IDs and transmission time stamps by ultrasonic packets is performed in a room with a distance of several tens of meters. 10 kbps) was possible, and it was confirmed that the distance could be measured with an error of several centimeters.

Industrial applicability

As described above, the ultrasonic distance measurement system and the ultrasonic distance measurement method according to the present invention can accurately measure the distance between the transmission node and the reception node in a short time using only the ultrasonic waves. In particular, it is suitable for distance measurement indoors and within a range of several meters to several tens of meters, and is extremely useful.

Claims

The scope of the claims

[1] A plurality of information terminals with their internal clocks synchronized in advance via a network using a predetermined time synchronization method, one information terminal power communication packet is transmitted, and another information terminal transmits a communication packet. An ultrasonic distance measurement system that measures the distance between corresponding information terminals by receiving

The sending information terminal

Communication packet generation means for generating a transmission time stamp based on the time acquired from the internal clock and generating a communication packet including the transmission time stamp;

A communication bucket transmitting means for transmitting the communication packet generated by the communication packet generating means with ultrasonic waves;

With

The information terminal on the receiving side

A communication packet receiving means for receiving a communication packet transmitted by ultrasonic waves from an information terminal on the transmitting side;

The time when the communication packet is received by the communication packet receiving means is acquired from an internal clock, the reception time stamp generating means for generating a reception time stamp based on the time, the reception time stamp generated by the reception time stamp generating means, Distance calculating means for calculating the distance between the information terminal on the transmission side and the information terminal on the reception side based on the difference from the transmission time stamp included in the communication packet received by the communication packet receiving means. A characteristic ultrasonic distance measuring system.

[2] In a plurality of information terminals in which the internal clock is synchronized in advance via a network using a predetermined time synchronization method, one information terminal power communication packet is transmitted, and the communication packet is transmitted to another information terminal. An ultrasonic distance measurement system that measures the distance between corresponding information terminals by receiving

The communication packet includes a reference position serving as a reference for synchronization when the communication packet is transmitted and received and a transmission time stamp indicating a time when the reference position is transmitted,

The sending information terminal A transmission time stamp is generated based on a transmission time acquired from the internal clock and a transmission correction value that is a time difference from the transmission time until the reference position of the communication packet is actually transmitted, and the communication packet including the transmission time stamp is generated. Communication packet generation means for generating

With

The information terminal on the receiving side

This is the time difference between the reception time when the communication packet is received by the communication packet receiving means from the internal clock, and the reference position of the communication bucket is actually received after the acquired reception time and the reception time are acquired. Based on the reception correction value, a reception time stamp generating means for generating a reception time stamp indicating the time when the reference position is received, a reception time stamp generated by the reception time stamp generating means, and a communication received by the communication packet receiving means An ultrasonic distance measuring system comprising: distance calculating means for calculating a distance between a transmitting information terminal and a receiving information terminal based on a difference from a transmission time stamp included in a packet. .

[3] The communication packet further includes a coordinate position of an information terminal on the transmission side,

The receiving information terminal is

When communication packets are successively received from a plurality of different transmission side information terminals, the distance between each transmission side information terminal calculated by the distance calculation means and the reception side information terminal and each transmission side information terminal Position estimating means for estimating the position of the receiving information terminal based on the coordinate position of

The ultrasonic distance measuring system according to claim 1, further comprising:

[4] The internal clock is synchronized in advance via the network using a predetermined time synchronization method. Ultrasonic distance measurement method for measuring the distance between corresponding information terminals by transmitting one information terminal power communication packet and receiving the communication packet at another information terminal Because

In the information terminal on the transmission side, a transmission time stamp is generated based on the time acquired from the internal clock, a communication packet including the transmission time stamp is generated, and the generated communication packet is transmitted with ultrasonic waves.

The receiving information terminal receives the communication packet transmitted by the ultrasonic wave from the transmitting information terminal, acquires the time when the communication packet was received from the internal clock, and receives the time stamp based on the time. And calculating a distance between the information terminal on the transmission side and the information terminal on the reception side based on the difference between the generated reception time stamp and the transmission time stamp included in the received communication packet,

An ultrasonic distance measuring method characterized by the above.

[5] In a plurality of information terminals in which the internal clock is synchronized in advance via a network using a predetermined time synchronization method, one information terminal power communication packet is transmitted, and the other information terminal transmits the communication packet. Is an ultrasonic distance measurement method for measuring the distance between corresponding information terminals by receiving

In the information terminal on the transmission side, a transmission time stamp is generated based on the transmission time acquired from the internal clock and the transmission correction value that is the time difference from the transmission time until the reference position of the communication packet is actually transmitted. A communication packet including a transmission time stamp is generated, and the generated communication packet is transmitted with ultrasonic waves.

The information terminal on the receiving side receives the communication packet transmitted by ultrasonic waves from the information terminal on the transmitting side, acquires the reception time when the communication packet is received from the internal clock, and acquires the acquired reception time and the relevant reception time. Based on the reception correction value, which is the time difference from when the reference position of the communication packet is actually received, to the reception time stamp indicating the time when the reference position was received. Based on the difference from the transmission time stamp included in the communication packet, the transmitting side information terminal and the receiving side Calculating the distance to the information terminal

An ultrasonic distance measuring method characterized by the above.

The communication packet further includes a coordinate position of an information terminal on the transmission side,

When the receiving information terminal continuously receives communication packets from a plurality of different transmitting information terminals, the calculated distance between each transmitting information terminal and the receiving information terminal and each transmitting side Estimating the position of the receiving information terminal based on the coordinate position of the information terminal,

The ultrasonic distance measuring method according to claim 4 or 5, wherein: