JP2006317161A - Tracking system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tracking system of high reliability capable of highly reliable tracking by highly precisely measuring the relative position of a moving body, and a self-propelled body used for it. <P>SOLUTION: The tracking system is composed of the ultrasonic transmission source 20 arranged on the moving body 2 and the self-propelled body 1 for tracking the ultrasonic transmission source 20. The tracking system is provided with four ultrasonic receivers in a line on the self-propelled body 1, wherein two receivers among the four receivers are arranged near by positions and the remaining two receivers are arranged near by positions but apart from the former two receivers. The position estimation process is composed of the steps: (i) the ultrasonic transmission source 20 is transmitting the ultrasound in a certain interval; (ii) the self-propelled body 1 is obtaining a phase after receiving ultrasound; (iii) extracting the optimum phase information from among the phase data; (vi) estimating the correct position from the phase differences of two pairs of receivers. The time zone when the optimum phase information is existing is obtained by each ultrasonic receiver separately. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tracking system using ultrasonic waves and a self-propelled body used therefor.

  Systems that control the movement of autonomous mobile bodies such as transport robots (hereinafter sometimes referred to as “self-propelled bodies”) and track mobile bodies such as people are used in factories and the like. As an example of such a tracking system, a tracking device that measures the position of a moving body using ultrasonic waves is known.

  Basically, the position of a moving object is measured using the propagation time of ultrasonic waves. Only the self-propelled body is equipped with an ultrasonic transmission / reception device, transmits ultrasonic waves from the self-propelled body to the moving body, and receives the ultrasonic waves reflected by the moving body on the self-propelled body side. And a method of measuring the relative position of the moving body by transmitting and receiving ultrasonic waves to and from each other.

  However, when there are many objects other than the moving body around the self-propelled body, if ultrasonic waves are transmitted from the self-propelled body to the moving body, objects existing in the surroundings (reflection) The reflected ultrasound from the body is received. In particular, if there is a reflector near the moving body, the reflected ultrasonic waves from the moving body and the reflected ultrasonic waves from other reflectors may be superimposed, resulting in a large error in measurement of the relative position of the moving body.

  Therefore, the mobile body is equipped with an ultrasonic transmission device, the self-propelled body is equipped with an ultrasonic reception device, and the time at which the ultrasonic wave is transmitted is self-propelled by means of radio waves or infrared (high-speed) means (radio signals) There is a method to inform the body and measure the relative position of the moving body. Since the propagation direction of ultrasonic waves is only one direction, the influence of reflected ultrasonic waves from surrounding objects is small.

  However, for example, radio waves cannot be used in environments where radio waves cannot be used. If it is light such as infrared, it cannot be used in an environment where external light or the like is directly incident.

  Therefore, there is a method in which the moving body is provided with an ultrasonic transmission device, the self-propelled body is provided with a plurality of ultrasonic reception devices, and the relative position of the moving body is measured using the arrival time difference of the received ultrasonic waves. In particular, in order to accurately measure the arrival time difference, a method of converting from the received ultrasonic phase difference is used (Patent Document 1 and Patent Document 2).

FIG. 7 schematically shows a conventional example. The ultrasonic wave transmitted from the ultrasonic wave transmission source 78 is received by the wave receiving device 79. The ultrasonic transmission source 78 includes an ultrasonic transmission device 71. The ultrasonic transmission device 71 includes an ultrasonic transmitter 71a and a transmission circuit 71b. These devices are connected to a transmission signal generator 76. The wave receiving device 79 includes an ultrasonic wave receiving device 72. The ultrasonic receiving device 72 includes two ultrasonic receivers 72a and 72b and receiving circuits 72c and 72d connected to them. The ultrasonic receivers 72 a and 72 b are fixed to the rotating shaft of the motor 73 so that they are separated from each other. By applying electric power according to the phase difference of the received ultrasonic waves to the motor 73 by the power amplifier 77, the ultrasonic receivers 72 a and 72 b can face the ultrasonic transmission source 78. This utilizes the fact that a phase difference occurs in the ultrasonic waves received by the ultrasonic receiver 72a and the ultrasonic receiver 72b depending on the direction of the ultrasonic transmission source 78. The ultrasonic wave transmitted from the ultrasonic transmitter 71 a is frequency-modulated by the transmission signal generator 76. For this reason, the ultrasonic wave received by the ultrasonic wave receiving device 72 is demodulated by the demodulator 74, and the phase difference of the demodulated signal is obtained by the phase difference detector 75. This compares the phase at a frequency lower than that of the ultrasonic signal by modulating and demodulating the phase difference range −π to π in a one-to-one correspondence with a wide range of directions.
JP 56-76066 A JP-A-56-137173

  However, the conventional method requires a broadband transmitter and receiver for transmitting and receiving frequency-modulated ultrasonic waves. In addition, in order to obtain an accurate phase difference from received waves having different arrival times, it is necessary to overlap time zones having necessary phase information. Further, since a low-frequency phase is demodulated and the frequency is lowered, the transmission signal is inevitably a long signal. When the signal becomes long, a large power source is required for the ultrasonic transmission device, and reflected ultrasonic waves from surrounding obstacles are likely to interfere with each other, which increases the possibility of an erroneous result. Also, when the arrival time difference of the received ultrasonic waves is determined using the phase difference between the two receivers, the influence of refraction due to air fluctuations varies depending on the location, and if the ultrasonic waves are broadband, the frequency components included in them Since the directivity is different for each receiver, the correlation between the receivers is lowered, which causes a problem that the measurement accuracy of the phase difference is deteriorated.

  Under such circumstances, the present invention does not use a broadband ultrasonic transmitter / receiver, and enables tracking with high reliability by accurately measuring the relative position of a moving object even with a shorter transmission signal. An object is to provide a system and a self-propelled body used for the system.

In order to achieve the above object, a tracking system of the present invention includes an ultrasonic transmission source arranged on a moving body and a self-propelled body that estimates the position of the ultrasonic transmission source and tracks the ultrasonic transmission source. In the tracking system including, the ultrasonic transmission source includes an ultrasonic transmission device. The self-propelled body is provided with four ultrasonic receivers configured by narrow-band ultrasonic receivers on a straight line, two of the ultrasonic receivers are arranged in close proximity, and the remaining two are Arranged close to each other at a position away from the two,
(A) The moving body transmits a short burst ultrasonic wave from the ultrasonic transmission device,
(B) The self-propelled body receives the ultrasonic waves with the ultrasonic receiver,
(C) obtaining a phase signal from the received signal of each ultrasonic receiving device;
(D) determining a time zone in which the frequency of the reception signal and the transmission drive signal is the same from the phase signal;
(E) obtaining a representative value of the phase of the time zone;
(F) obtaining a phase difference between the ultrasonic receivers disposed in the adjacent positions;
(G) A position estimation process including a step of estimating the position of the ultrasonic transmission source from the positional relationship between the phase difference and the ultrasonic receiver is performed, and the phase difference is determined between adjacent ultrasonic receivers. Obtaining and the time zone are obtained independently for each ultrasonic receiver.

  In this specification, “ultrasonic wave” means a sound wave having a frequency of 20 kHz or more.

  According to the tracking system of the present invention, a phase difference can be measured with high accuracy even when a short transmission drive signal is used in a narrow band. For this reason, according to this invention, the relative position of a mobile body is measured with high precision, and the tracking system which can track with high reliability and the self-propelled body used for it are obtained. The system of the present invention is effective when there are many reflectors around the self-propelled body. In addition, the system of the present invention is effective in a situation where environmental changes such as air fluctuation are large.

  Hereinafter, embodiments of the present invention will be described with reference to examples.

  The tracking system of the present invention includes an ultrasonic transmission source arranged on a moving body and a self-propelled body that estimates the position of the ultrasonic transmission source and tracks the ultrasonic transmission source. The ultrasonic transmission source includes an ultrasonic transmission device. The self-propelled body includes four ultrasonic receiving devices. The ultrasonic receiver is composed of an ultrasonic receiver with a narrow band, all provided on a straight line, two of which are arranged close to each other, and the other two are arranged close to each other at a position away from the two. Is done. Further, in this system, a position estimation process including the following steps is performed.

  (A) The moving body transmits a short burst ultrasonic wave from the ultrasonic transmission device. The frequency is single, and the length of the burst ultrasonic wave does not need to be increased in consideration of the temporal overlap of phase information due to the arrival time difference to each ultrasonic receiver.

  (B) The self-propelled body receives the ultrasonic waves by the ultrasonic receiver.

  (C) A phase signal is obtained from the received signal of each ultrasonic receiver. The phase signal is obtained using the frequency at which the ultrasonic transmitter is driven.

  (D) A time zone in which the frequency of the reception signal and the transmission drive signal is the same is determined from the phase signal. A time zone representing phase information of the same frequency as the transmission drive signal is extracted from the characteristics of the phase signal. The said time slot | zone may differ for every receiver.

  (E) A representative value of the phase in the time zone is obtained. The representative value of the phase may be an average value of the phase in the time zone or a median value. Further, the phase reliability may be evaluated by evaluating the variation of the phase in the time zone.

  (F) The phase difference between the ultrasonic receivers arranged at the adjacent positions is obtained. The phase difference is obtained by comparing the representative values of the phase in the time zone.

  (G) The position of the ultrasonic transmission source is estimated from the positional relationship between the phase difference and the ultrasonic receiver.

  Based on the position of the ultrasonic wave transmission source estimated by such processing, the self-propelled body tracks the moving body by controlling the self-propelled device. In addition, although there is no limitation in particular in a self-propelled apparatus, it is provided with drive devices, such as an engine and a motor, and the wheel driven by it, for example.

  The ultrasonic transmission device is a device for transmitting ultrasonic waves, includes an ultrasonic transmitter, and may further include a transmission circuit for driving the ultrasonic transmitter. The ultrasonic receiver includes an ultrasonic receiver and may further include a receiving circuit for driving the ultrasonic receiver. The self-propelled body includes two sets of two ultrasonic receivers in which the ultrasonic receivers are arranged close to each other (for example, the distance between the centers of the ultrasonic receivers is 8.5 mm to 17 mm). Further, the two sets are arranged at a certain distance (for example, about 10 cm to 1 m). By using two ultrasonic receivers arranged close to each other, the phase difference can be obtained, and the direction of the ultrasonic wave that has reached can be identified from the phase difference. And the distance to an ultrasonic wave transmission source can be specified from the phase difference of another set arranged at a fixed interval and the positional relationship of two sets. The two sets of ultrasonic receivers are usually arranged such that the straight line connecting each other is substantially parallel to the floor surface.

  In the tracking system of the present invention, the moving body may be a person and the self-propelled body may be a cart. Such a system can be used in situations such as factories, shopping centers, airports, stations, etc. where it is necessary to transport packages with people.

(Embodiment 1)
The configuration of the tracking system in the first embodiment is schematically shown in FIG. An ultrasonic transmission source 20 is disposed on the moving body (person) 2. The self-propelled body 1 estimates the position of the ultrasonic transmission source 20 and tracks the moving body 2 based on the estimated position. The self-propelled body 1 includes a tracking device 10 for estimating the position of the ultrasonic transmission source 20. The configurations of the tracking device 10 and the ultrasonic transmission source 20 are schematically shown in FIG.

  The tracking device 10 includes an ultrasonic receiving device 11. The ultrasonic receiver 11 includes four ultrasonic receivers 11a, 11b, 11c and 11d, and receiving circuits 11e, 11f, 11g and 11h connected to them. The ultrasonic receivers 11a, 11b, 11c, and 11d are arranged at regular intervals so that the straight line connecting them is substantially parallel to the floor surface. These devices are connected to phase detectors 12a, 12b, 12c and 12d. In addition, any one of the receiving circuits 11e, 11f, 11g, or 11h is connected to the comparator 14. The phase detector 12 and the comparator 14 are connected to an arithmetic processing unit (CPU) 13. The arithmetic processing unit 13 internally includes storage means (memory) for A / D converting predetermined parameters and measured signals and storing them as digital data, or is connected to an external storage device. The sampling frequency of the A / D converter for A / D conversion is preferably higher than the frequency of the ultrasonic wave W1. If the ultrasonic wave W1 is 40 kHz, it may be about 200 kHz to 1 MHz. The arithmetic processing unit 13 estimates the relative position of the ultrasonic transmission source 20 using the received ultrasonic signal. The arithmetic processing device 13 analyzes the phase signal of the received ultrasonic signal and determines the time zone of the phase signal used for the phase difference calculation.

  The ultrasonic transmission source 20 includes an ultrasonic transmission device 21. The ultrasonic transmission device 21 includes an ultrasonic transmitter 21a and a transmission circuit 21b. These devices are connected to the arithmetic processing unit 22.

  The arithmetic processing unit 22 gives a transmission drive command to the transmission circuit 21b at a certain period. The transmission circuit 21b generates a transmission drive signal, and the ultrasonic wave W1 is radiated from the ultrasonic transmitter 21a to the surrounding environment. The transmission drive signal is a burst wave and has a single frequency. The wave number depends on the characteristics of the ultrasonic transmitter and the ultrasonic receiver. For example, when the ultrasonic transmitter and the ultrasonic receiver having a resonance frequency of 40 kHz and a bandwidth of about 5 to 10% are used, the wave number is 30. A wave is enough.

  A part of the emitted ultrasonic waves reaches the ultrasonic receivers 11a, 11b, 11c and 11d of the self-propelled body. If there is no obstacle in the surroundings, the fixed period may be such that the ultrasonic wave that arrives at the ultrasonic receiver 11 does not overlap with the ultrasonic wave transmitted in the next period (about 3 ms to 10 ms). However, as shown in FIG. 2, when the object 3 that reflects ultrasonic waves exists around the tracking device 10 (self-propelled body 1), the ultrasonic wave W1 reflected by the object 3 is converted into ultrasonic receivers 11a and 11b. , 11c and 11d. Then, it is impossible to distinguish whether the arrived ultrasonic wave W1 is directly propagated from the ultrasonic wave transmission source 20 or reflected by the object 3. If the maximum distance that can be measured by the reached ultrasonic tracking device 10 is 5 m and the sound velocity is 340 m / second, it takes about 15 milliseconds for the ultrasonic wave to reach the tracking device 10 from the ultrasonic transmission source 20. It is desirable that the certain period is about 20 milliseconds with a slight margin in this value.

  The frequency of the ultrasonic wave W1 is not particularly limited, and a preferable frequency is selected according to the measurement environment. When the moving body 2 is a person, the normal speed can be set to about 4 km / h, and the maximum speed can be set to about 6 km / h (about 1.6 m / s). In that case, the traveling speed of the self-propelled vehicle 1 may be almost equal to the human body, and considering the time delay when the self-propelled vehicle 1 starts moving from the stationary state at the start of tracking, the self-propelled vehicle 1 and the mobile vehicle 2 If the maximum relative distance (measurement limit) is set to about 5 m to 10 m, a smooth tracking operation is possible. Considering this measurement limit and the attenuation characteristics of ultrasonic waves in the atmosphere, the frequency of ultrasonic waves to be used is suitably 100 kHz or less.

  As an ultrasonic transmitter and an ultrasonic receiver, an ultrasonic transmitter and an ultrasonic receiver using a piezoelectric ceramic flexural vibration, or an PVDF piezoelectric polymer film ultrasonic transmitter and an ultrasonic receiver can be used. .

  The ultrasonic receiving device 11 includes two ultrasonic receivers 11a and 11b arranged close to each other and two ultrasonic receivers 11c and 11d arranged close to each other.

  The direction of the ultrasonic transmission source 20 from the ultrasonic receivers 11a and 11b can be calculated from the difference between the arrival times of the ultrasonic waves of the two ultrasonic receivers 11a and 11b. Similarly, the direction of the ultrasonic transmission source 20 from the ultrasonic receivers 11c and 11d can be calculated from the difference in the arrival times of the ultrasonic waves of the two ultrasonic receivers 11c and 11d. If the two orientations are known, the distance and orientation of the ultrasonic transmission source 20 with respect to the tracking device 10 can be calculated. An example of the positional relationship with the ultrasonic transmitter 21a is shown in FIG.

  In FIG. 3, the ultrasonic transmitter 21a of the ultrasonic transmission source 20, the ultrasonic receivers 11a and 11b of the self-propelled body 1, and the ultrasonic receivers 11c and 11d form a triangle. The ultrasonic receivers 11a and 11b are arranged apart from each other by a predetermined distance a. The ultrasonic receivers 11c and 11d are arranged apart from each other by a predetermined distance a. The ultrasonic receivers 11a and 11b and the ultrasonic receivers 11c and 11d are arranged apart from each other by a predetermined distance L. It is assumed that the ultrasonic transmitter 21a is in the direction of angle θ1 from the center of the ultrasonic receivers 11a and 11b, and the ultrasonic transmitter 21a is in the direction of angle θ2 from the center of the ultrasonic receivers 11c and 11d. The angles θ1 and θ2 are estimated using the difference in arrival time of ultrasonic waves and the sound speed in the air, respectively. This is an ultrasonic transmitter using a distance a between two ultrasonic receivers, where ΔT is the time difference when ultrasonic waves from a sufficiently far sound source are detected by two ultrasonic receivers, and v is the sound velocity of the ultrasonic waves. It is known that the angles θ1 and θ2 indicating the direction of 21a can be obtained from the following equation.

  The ultrasonic arrival time difference ΔT is calculated from the phase difference between adjacent ultrasonic receivers. If the ultrasonic wave is 40 kHz, one wavelength is 25 μs (= 1/40 kHz), and this phase 2π (one wavelength) corresponds to 25 μs. Therefore, the phase difference can be converted into a time difference. If the sound speed is 340 m / sec, one wavelength is 8.5 mm, and in order to make the phase difference and the angles θ1 and θ2 correspond one-to-one, a is set to 8.5 mm or less from Equation 1. There is a need.

  When the angles θ1, θ2, and L are clarified, the triangle formed by the ultrasonic transmitter 21a, the ultrasonic receivers 11a and 11b, and the ultrasonic receivers 11c and 11d is uniquely determined. Therefore, the distance and relative orientation of the ultrasonic transmission source 20 with respect to the tracking device 10 can be easily obtained using a trigonometric function.

  An outline of the operation of the tracking device 10 is shown in the flowchart of FIG. When the tracking device 10 is activated, the arithmetic processing unit 13 determines whether or not the ultrasonic wave W1 from the ultrasonic wave transmission source 20 has been received by the ultrasonic wave receivers 11a, 11b, 11c, and 11d, and phase information from the ultrasonic wave W1. Is extracted (S41). Details of the operation of S41 will be described later. Using the extracted phase information, the difference in phase information in the ultrasonic receivers 11a and 11b and the difference in phase information in the ultrasonic receivers 11c and 11d are calculated, and the azimuth of the ultrasonic transmission source 20 is calculated using Equation 1. Is obtained (S42). Then, as shown in FIG. 3, the azimuth and distance of the ultrasonic transmission source 20 are obtained (S43).

  An outline of the operation of S41 is shown in the flowchart of FIG.

  When the tracking device 10 is activated, the arithmetic processing device 13 enters a reception waiting mode in which the ultrasonic receivers 11a, 11b, 11c, and 11d determine whether the ultrasonic wave W1 from the ultrasonic transmission source 20 has been received. If the received signal exceeds a certain level, it is determined that there is reception (S51).

  In the determination of the presence or absence of the received signal and the arrival time measurement associated therewith, a threshold is set for the amplitude of the received signal used in the conventional method, and when it exceeds the threshold, it is determined that the signal has been received, Envelope detection of each received signal, setting a threshold for the detected waveform, and determining that the signal has been received when the threshold is exceeded, and cross-correlation between each received signal and the transmission drive signal And a method of judging from the peak value of the correlation can be applied.

  During the reception waiting mode, the output of the phase detector 12 is A / D converted and then stored as phase data in a ring memory in the arithmetic processing unit 13.

  The phase data from a predetermined time before and after a time determined to be received is read from the memory (S52). Then, after the phase data suddenly changes in the positive direction, it takes a constant value and records from what number to what number in the memory the changing range (S53). Then, using this range, the average value of the phases is obtained (S54).

  FIG. 6 shows an example of the waveform of the ultrasonic wave W1 reaching the tracking device 10 and its phase signal. FIG. 6A shows the output waveform 61 of the receiving circuit 11 e and the reference signal 63 of the comparator 14. The reference signal 63 of the comparator 14 is compared with the output waveform 61, and when the output waveform 61 exceeds the reference signal 63 of the comparator 14, it is determined that there is a received signal. FIG. 6C shows an output waveform 62 of the receiving circuit 11f.

  FIG. 6B shows an example of the phase signal 64 after the phase detector 12a. FIG. 6D shows an example of the phase signal 65 after the phase detector 12b. From the time when the received signal is determined to be present, the phase data ranges 66 and 67 to be read from the memory are determined.

  Next, phase information having the same frequency as that of the transmission drive signal is extracted from the phase data ranges 66 and 67. This is because the resonance frequency of the ultrasonic receiver and the frequency of the rising edge of the ultrasonic reception signal are lower than the frequency of the transmission drive signal, so that the phase at the frequency of the transmission drive signal appears to gradually increase. Utilizing this, a time zone 68 and a time zone 69 indicating phase information having the same frequency as the transmission drive signal are extracted.

  In the phase signal, a region having phase information of the same frequency as that of the transmission drive signal is flat. In the flat part of the phase, the flatness of the flat part is lowered when interference due to ambient noise or air fluctuation is large. As the flatness is lowered, the accuracy of the angle obtained therefrom is deteriorated. Therefore, only a time zone in which the phase is as flat as possible is extracted. Further, the width of this time zone is also determined within an optimum range for each received signal. However, if the flat time zone is small, the data parameter decreases accordingly, and the accuracy deteriorates. By utilizing this fact, the reliability of data may be obtained from the time length of the flat portion of the phase used in the calculation or the flatness of the phase. By using the reliability, when the reliability is low, it becomes effective information in the control of the self-propelled body 1 such as repeatedly obtaining and averaging the azimuth and distance.

  The ultrasonic receivers 11a and 11b are arranged as close to each other as possible in order to reduce the influence of ultrasonic fluctuations due to air fluctuations. Therefore, since the ultrasonic wave propagation paths are received at substantially the same position, there is almost no difference in the waveform at the reception position due to the air fluctuation in the propagation path and the directivity of the ultrasonic transmitter 21a. The system can prepare conditions suitable for phase difference measurement. The same applies to the ultrasonic receivers 11c and 11d. However, there is a difference of individual variation between the ultrasonic receivers 11a and 11b and between the ultrasonic receivers 11c and 11d. Therefore, the ultrasonic reception signal is different. Therefore, the phase signal is similarly different.

  The phase signal is lower than the resonance frequency of the ultrasonic receiver when the ultrasonic reception signal rises, and then vibrates at the frequency of the transmission drive signal due to forced vibration caused by the transmission drive signal. However, after that, the influence of vibration due to the resonance frequency of the ultrasonic receiver appears.

  The phase detector obtains the phase for the same frequency as the transmission drive signal. Therefore, when the frequency of the received signal is different from the transmission drive signal, an error occurs in the phase. Conventionally, in order to avoid this, the transmission drive signal is lengthened, and the received signal is passed through a narrow band-pass filter to stretch the signal, and the phase stabilization time is lengthened to make a simple phase difference. The accuracy was ensured. By doing so, the time shift of the phase signal due to the arrival time difference was absorbed. However, if the transmission drive signal is lengthened or the reception signal is passed through a narrow band-pass filter, the ultrasonic transmission device 10 can be used when there is an obstacle 3 between the mobile body 2 and the self-propelled body 1. Is reflected on the obstacle 3, and the probability that this signal interferes increases.

Therefore, the tracking system of the present invention is
(1) By shortening the distance between the ultrasonic receivers for obtaining the phase difference, it is difficult to be affected by the difference depending on the location of the air fluctuation, and it is not necessary to use a low-frequency phase by modulation / demodulation processing.

  (2) Since modulation / demodulation processing is not used, this can be realized with a narrow-band ultrasonic transceiver.

(3) Since the range oscillating at the frequency of the transmission drive signal is extracted independently from each ultrasonic reception signal, the transmission drive signal may be short, and it is affected by interference even in an environment with many obstacles. Hateful.
It is possible to realize a good tracking characteristic.

  The tracking system according to the present invention has means for extracting accurate phase information from a short burst wave, and can reduce the influence of an obstacle. Therefore, the tracking system is useful as a transport robot in a railway station or an airport. It can also be used for shopping carts in mass retailers such as supermarkets and home centers.

The figure which shows the outline of the tracking system of this invention typically The figure which shows typically an example of a structure of the tracking apparatus and ultrasonic transmission source in the tracking system of this invention The figure which shows typically an example of the method of estimating the position of an ultrasonic transmission source The flowchart which shows an example of the process by the side of the self-propelled body in the tracking system of the present invention The flowchart which shows the detail of the process of S41 in the flowchart of FIG. The figure which shows typically the method of the waveform analysis in the tracking system of this invention The figure which shows typically the conventional example which estimates the position of an ultrasonic transmission source

Explanation of symbols

1 Self-propelled object 2 Moving object 3 Object (reflector)
DESCRIPTION OF SYMBOLS 10 Tracking apparatus 11 Ultrasonic receiver 12 Phase detector 13 Computation processing apparatus 14 Comparator 20 Ultrasonic transmission source 21 Ultrasonic transmission apparatus 22 Arithmetic processing apparatus 61 Ultrasonic reception signal 62 Ultrasonic reception signal 63 Reference signal 64 of comparator 14 Phase Signal 65 Phase signal 66 Phase signal stored in memory 67 Phase signal stored in memory 68 Phase signal having the same frequency as the transmission drive signal 69 Phase signal having the same frequency as the transmission drive signal 71 Ultrasonic transmitter 72 Ultrasonic receiver 73 Motor 74 Demodulator 75 Phase difference detector 76 Transmission signal generator 77 Power amplifier 78 Ultrasonic transmission source 79 Receiving device W1 Ultrasonic

Claims (6)

The ultrasonic wave from the ultrasonic wave transmission source attached to the moving body is received by a plurality of ultrasonic receiving devices, and the position of the moving body is estimated from the phase difference between the received ultrasonic wave receivers. In the tracking system including the self-propelled body that tracks the ultrasonic wave, the ultrasonic receiving device is disposed at a position close to each other as a unit, and the phase difference of the received ultrasonic wave obtained for each unit and a plurality of units A tracking system, characterized in that the position of a moving object is obtained from the arrangement relationship of. The ultrasonic wave from the ultrasonic wave transmission source attached to the moving body is received by a plurality of ultrasonic receiving devices, and the position of the moving body is estimated from the phase difference between the received ultrasonic wave receivers. In the tracking system including the self-propelled body that tracks the phase, the time of the phase value extracted from the phase waveform may be different for each ultrasonic receiving device. The time zone of the phase waveform is between a time point when the slope of the phase waveform is positive from a region where the slope of the phase waveform is positive and a time point when the slope of the next phase waveform changes. The tracking system described. 4. The reception time difference of the ultrasonic receiving apparatus is evaluated by using the flatness of the phase difference of the ultrasonic reception signal, and the higher the flatness, the higher the reliability of the data. Tracking system. 4. The reception time difference of the ultrasonic receiving apparatus is evaluated by using the flatness of the phase difference of the ultrasonic reception signal, and it is evaluated that the reliability of the data is higher as the flat range is larger. Tracking system described in. The ultrasonic wave from the ultrasonic wave transmission source attached to the moving body is received by a plurality of ultrasonic receiving devices, and the position of the moving body is estimated from the phase difference between the received ultrasonic wave receivers. In the tracking system including the self-propelled body that tracks the ultrasonic wave, the ultrasonic receiving device is disposed at a position close to each other as a unit, and the received ultrasonic wave is obtained from a time zone that may be different for each unit. 6. The tracking system according to claim 1, wherein the position of the moving body is obtained from the phase difference and the arrangement relationship of the plurality of units.

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