JP2006214992A - Tracking system and self-traveling body used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tracking system capable of measuring precisely a relative position of a moving object to allow tracking of high reliability, and a self-traveling body used therefor. <P>SOLUTION: This tracking system includes a transponder 20 arranged in the moving object 2, and the self-traveling body 1 for tracking the transponder 20. The tracking system conducts position estimation processing including (i) a step of transmitting the first ultrasonic wave containing information as to a time T (0≤T), from the self-traveling body 1, (ii) a step of receiving the first ultrasonic wave, by the transponder 20, to transmit the second ultrasonic wave after the time T lapses, and (iii) a step of estimating a position of the transponder 20 by receiving the second ultrasonic wave, in the self-traveling body 1. The time T is set to discriminate the second ultrasonic wave from the first ultrasonic wave received reflected with an object existing in the periphery of the self-traveling body 1. The information as to the time T is determined in response to an existing condition of the object to increase or decrease the time T in response to the existing condition of the object. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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.

  Generally, in these apparatuses, an echo method and a transponder method are used. In the echo method, only the self-propelled body has an ultrasonic transmitter / receiver, 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, thereby moving The relative position of the body is measured. On the other hand, in the transponder method, each of the mobile body and the self-propelled body includes an ultrasonic transmitter / receiver, and the relative position of the mobile body is measured by mutually transmitting and receiving ultrasonic waves.

  When there are many objects other than a moving object around the self-propelled object, if ultrasonic waves are transmitted from the self-propelled object to the moving object, in the echo method, it exists in the surroundings in addition to the reflected ultrasonic waves from the moving object. The reflected ultrasonic wave from the object (reflector) to be received 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.

  In the transponder method, reflected ultrasonic waves from a reflector (including a moving body) existing around the self-propelled body may be superimposed on an ultrasonic signal from the moving body. In that case, as in the echo method, a large error may occur in the measurement of the relative position of the moving object.

In order to remove the influence of such reflected ultrasonic waves, a method has been proposed in which a delay operation is introduced into the processing on the moving object side in the transponder tracking device (Patent Document 1). In this method, after the apparatus on the moving body receives the ultrasonic wave from the self-propelled body, the reflected wave from the reflector existing in the surroundings is sufficiently attenuated and does not affect the measurement of the relative position of the moving body. The transmission of ultrasonic waves from the moving body is delayed for a predetermined time until. The delay time is set so that the reflected wave from the reflector is sufficiently attenuated so as not to affect the measurement of the propagation time in any situation. Therefore, an invariable delay time is set regardless of the change in the situation around the self-propelled body.
Japanese Examined Patent Publication No. 7-31244

  However, in the conventional method, the delay time must be set in consideration of the time during which the reflected ultrasonic wave from the reflector is sufficiently attenuated regardless of the presence of the reflector, so a long delay time is set. There was a need. Therefore, in the conventional method, it takes time to measure the relative position of the moving body, and if the moving body moves at a high speed, it may be difficult to perform highly reliable tracking.

  Under such circumstances, an object of the present invention is to provide a tracking system capable of measuring the relative position of a moving body with high accuracy and performing highly reliable tracking, and a self-propelled body used therefor. .

In order to achieve the above object, the tracking system of the present invention is a tracking system including a transponder arranged in a moving body and a self-propelled body that estimates the position of the transponder and tracks the transponder. Comprises a first ultrasonic transceiver, and the transponder comprises a second ultrasonic transceiver,
(I) The self-propelled body transmits a first ultrasonic wave including information on time T (0 ≦ T) from the first ultrasonic wave transmitting / receiving device,
(Ii) The transponder receives the first ultrasonic wave by the second ultrasonic transmission / reception device, transmits the second ultrasonic wave from the second ultrasonic transmission / reception device after the elapse of the time T,
(Iii) The self-propelled body performs a position estimation process including a step of estimating the position of the transponder by receiving the second ultrasonic wave by the first ultrasonic transmission / reception device; T is such that the second ultrasonic wave can be distinguished from the first ultrasonic wave reflected by an object existing around the self-propelled body and received by the first ultrasonic transmission / reception device. The information related to the time T is determined according to the presence status of the object so that the time T is set and increased or decreased according to the presence status of the object.

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

In addition, the self-propelled body of the present invention is an ultrasonic transmission / reception in a self-propelled body used in a tracking system including a transponder arranged in a moving body and a self-propelled body that estimates the position of the transponder and tracks the transponder. Equipped with equipment,
(I) transmitting a first ultrasonic wave including information related to time T (0 ≦ T) from the ultrasonic wave transmitting / receiving device;
(II) By receiving the second ultrasonic wave transmitted from the transponder as a response signal to the first ultrasonic wave after the elapse of the time T from the reception of the first ultrasonic wave by the ultrasonic transmitting / receiving apparatus. A position estimation process including a step of estimating the position of the transponder is executed, and during the time T, the second ultrasonic wave is reflected by an object existing around the self-propelled body and the ultrasonic transmission / reception is performed. It is set so that it can be distinguished from the first ultrasonic wave received by the apparatus, and the time T according to the presence state of the object is increased or decreased according to the presence state of the object. The information regarding is determined.

  According to the tracking system of the present invention, the measurement cycle for measuring the relative position of the moving body can be shortened according to the reflection state of the ultrasonic wave in the surrounding environment. Therefore, according to the present invention, it is possible to obtain a tracking system capable of measuring the relative position of the moving body with high accuracy and performing highly reliable tracking, and a self-propelled body used for the tracking system. The system of the present invention is effective when the distance between the self-propelled body and the reflector existing around the self-propelled body is short. In addition, the system of the present invention is effective when there are many situations in which there are no reflectors other than the moving body within the measurement range.

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

  The tracking system of the present invention includes a transponder arranged in a moving body and a self-propelled body that tracks the transponder by estimating the position of the transponder. The self-propelled body includes a first ultrasonic transmission / reception device, and the transponder includes a second ultrasonic transmission / reception device. In this system, position estimation processing including the following three steps (i) to (iii) is performed.

  (I) A self-propelled body transmits the 1st ultrasonic wave containing information about time T (0 <= T) from the 1st ultrasonic wave transceiver. The time T is distinguishable from the first ultrasonic wave that is reflected by an object (ultrasonic reflector) existing around the self-propelled body and received by the first ultrasonic transmission / reception device. Is set to be Further, the time T is increased or decreased according to the presence state of an object existing around the self-propelled body. Information regarding the time T is determined according to the presence state of an object existing around the self-propelled body so that the time T is increased or decreased in this manner. The presence state of an object (an ultrasonic reflector) existing around the self-propelled body can be detected using ultrasonic waves as will be described later. However, the presence state of the reflector may be detected by a method other than ultrasonic waves, for example, a known method using an image sensor. The information relating to the time T may be information necessary for determining the time T, and may be the time T itself or information suggesting the time T.

  (Ii) The transponder receives the first ultrasonic wave by the second ultrasonic transmission / reception device, and transmits the second ultrasonic wave from the second ultrasonic transmission / reception device after the elapse of time T. At this time, the transponder obtains information regarding the time T from the first ultrasonic wave.

  (Iii) The self-propelled body estimates the position of the transponder by receiving the second ultrasonic wave by the first ultrasonic transmitting / receiving apparatus. The distance and direction of the transponder can be calculated from the reception time of the second ultrasonic wave, and as a result, the relative position of the transponder can be estimated. Based on the position of the transponder 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 / reception apparatus is an apparatus for transmitting / receiving ultrasonic waves, and includes an ultrasonic transmission apparatus and an ultrasonic reception apparatus. The ultrasonic transmission device 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. Note that the first ultrasonic transmission / reception apparatus usually includes two or more ultrasonic receivers arranged at a certain distance. By using two or more ultrasonic receivers, the direction of the reached ultrasonic waves can be specified. Usually, two ultrasonic receivers are used. The two ultrasonic receivers are usually arranged at a constant interval (for example, about 10 cm to 1 m) so that a straight line connecting each other is substantially parallel to the floor surface.

  In the tracking system of the present invention, the second ultrasonic wave is reflected after the first ultrasonic wave reflected by the object and received by the first ultrasonic transmission / reception apparatus becomes smaller than a predetermined intensity. It may be set to reach one ultrasonic transmission / reception device.

  In the tracking system of the present invention, the self-propelled body may execute a reflection state detection process including the following steps. (A) A third ultrasonic wave is transmitted from the first ultrasonic transmission / reception device. (B) The third ultrasonic wave reflected by the object is received by the first ultrasonic transmission / reception device. (C) The maximum time d is acquired from the time required to transmit the third ultrasonic wave having a predetermined intensity or higher after the third ultrasonic wave is transmitted. (D) Information on time T is determined based on time d.

  In the tracking system of the present invention, the time T may be a time obtained by adding the adjustment time M to the time d.

  In the tracking system of the present invention, the self-propelled body may calculate a time t expected to be required for the ultrasonic wave to reciprocate between the self-propelled body and the transponder. The time T may be a time obtained by subtracting the time t from the time d and adding the adjustment time M.

  The adjustment time M is a margin time set to increase the reliability of the transponder position estimation. The adjustment time M may be fixed at a predetermined time or may be changed according to the tracking situation. However, when the adjustment time M is fixed at the predetermined time, the process becomes easy. The adjustment time M is determined in consideration of, for example, the measurement cycle in the previous position estimation process and the moving speed of the self-propelled body. The adjustment time M may be a positive time, a negative time, or zero.

  In the tracking system of the present invention, the self-propelled body may execute a reflection state detection process including the following steps. (A) The first ultrasonic wave reflected by the object is received by the first ultrasonic wave transmitting / receiving device. (B) The maximum time d is obtained from the time required for transmitting the first ultrasonic wave until receiving the first ultrasonic wave having a predetermined intensity or higher. (C) Information on time T is determined based on time d.

  Further, in the tracking system of the present invention, the time T may be increased or decreased in consideration of only the presence state of an object within a predetermined distance from the self-propelled body among the objects. The predetermined distance (measurement range) is determined on the basis that the reflected wave from the object existing within the distance affects the position estimation. That is, the reflected wave reflected at a position far from the measurement range has little influence on the position estimation.

  In the tracking system of the present invention, the first ultrasonic wave may be an ultrasonic pulse including information related to the time T in a state encoded by the number of pulses.

  In the tracking system of the present invention, the first ultrasonic wave may be an ultrasonic pulse that includes information related to the time T in a state encoded by the phase of the pulse.

  In the tracking system of the present invention, a cycle in which the position estimation process is performed once or more after the reflection state detection process is performed once may be repeated. Usually, tracking is performed by repeating a cycle in which the position estimation process is performed a plurality of times after the reflection state detection process is performed once. As the number of position estimation processes performed for one reflection state detection process increases, the average time required for one position estimation process can be shortened. On the other hand, if the number of times of position estimation processing is increased, there is a high possibility that the change in the reflection state cannot be accommodated, and the tracking reliability may be lowered. Therefore, it is preferable to change the number of position estimation processes performed for one reflection state detection process according to the surrounding environment. An example of the method is described in Embodiment 2.

  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.

  In the tracking system of the present invention, the difference between the frequency of the first ultrasonic wave and the frequency of the second ultrasonic wave may be 10 kHz or less (for example, 5 kHz or less).

  Further, the self-propelled body of the present invention is a self-propelled system used in the tracking system of the present invention, that is, the tracking system including the transponder arranged in the mobile body and the self-propelled body that tracks the transponder by estimating the position of the transponder. Is the body. This self-propelled body includes an ultrasonic transmission / reception device (first ultrasonic transmission / reception device). This self-propelled body executes position estimation processing including the following two steps (I) and (II).

  (I) The 1st ultrasonic wave containing the information regarding time T (0 <= T) is transmitted from an ultrasonic transmitter / receiver. (II) The position of the transponder is estimated by receiving the second ultrasonic wave transmitted from the transponder as a response signal to the first ultrasonic wave after the elapse of time T from the reception of the first ultrasonic wave by the ultrasonic transmitting / receiving apparatus. A position estimation process including the step of performing is performed. The time T is set so that the second ultrasonic wave can be discriminated from the first ultrasonic wave reflected by an object existing around the self-propelled body and received by the ultrasonic transmitting / receiving device. Then, information related to the time T is determined according to the presence state of the object so that the time T is increased or decreased according to the presence state of the object.

  The steps (I) and (II) correspond to the steps (i) and (iii) described above, respectively. The self-propelled body of the present invention may have the features described for the tracking system of the present invention. For example, the reflection state detection process including the steps (a) to (d) may be executed.

(Embodiment 1)
The configuration of the tracking system in the first embodiment is schematically shown in FIG. A transponder 20 is disposed on the moving body (person) 2. The self-propelled body 1 estimates the position of the transponder 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 transponder 20.

  The configurations of the tracking device 10 and the transponder 20 are schematically shown in FIG. The tracking device 10 includes a first ultrasonic transmission / reception device (a first ultrasonic transmission device 11 and a first ultrasonic reception device 12). The ultrasonic transmitter 11 includes an ultrasonic transmitter 11a and a transmission circuit 11b connected thereto. The ultrasonic receiving device 12 includes two ultrasonic receivers 12a and 12b and receiving circuits 12c and 12d connected to them. The ultrasonic receivers 12a and 12b are arranged at a constant interval so that a straight line connecting them is substantially parallel to the floor surface. These devices and sensors are connected to an arithmetic processing unit (CPU) 13. The arithmetic processing unit 13 includes a storage unit (memory) for storing predetermined parameters and measured data, or is connected to an external storage device. The arithmetic processing unit 13 estimates the relative position of the transponder 20 using the received ultrasonic signal. In addition, the arithmetic processing unit 13 detects the presence state of an object that exists around the self-propelled body 1 and reflects the ultrasonic wave by using the received ultrasonic signal, and determines the time T.

  The transponder 20 includes a second ultrasonic transmission / reception device (a second ultrasonic transmission device 21 and a second ultrasonic reception device 22). The ultrasonic transmission device 21 includes an ultrasonic transmitter 21a and a transmission circuit 21b. The ultrasonic receiver 22 includes an ultrasonic receiver 22a and a receiving circuit 22b. These devices are connected to the arithmetic processing unit 23.

  The arithmetic processing devices 13 and 23 drive an ultrasonic transmitter via a transmission circuit and transmit ultrasonic waves. The ultrasonic transmitter 11 transmits the first ultrasonic wave W1 and the third ultrasonic wave W3, and the ultrasonic transmitter 21 transmits the second ultrasonic wave W2. The arithmetic processing devices 13 and 23 obtain an ultrasonic signal received by the ultrasonic receiver via a receiving circuit and analyze the signal. The ultrasonic waves W1 and W3 are received by the ultrasonic receiver 22, and the ultrasonic wave W2 is received by the ultrasonic receiver 12. Further, as shown in FIG. 2, when an object 3 that reflects ultrasonic waves exists around the tracking device 10 (self-propelled body 1), the ultrasonic waves W1 and W3 reflected by the object 3 are converted into an ultrasonic receiver 12a. And 12b. The ultrasonic waves W1 and W3 are also reflected by the moving body 2 and received by the ultrasonic receivers 12a and 12b.

  Note that the first ultrasonic transmission / reception apparatus may include an ultrasonic transmission apparatus other than the first ultrasonic transmission apparatus 11, a transmission apparatus that transmits the ultrasonic wave W1, and a transmission apparatus that transmits the ultrasonic wave W3. May be separated. Further, the first ultrasonic transmission / reception apparatus may include an ultrasonic reception apparatus other than the first ultrasonic reception apparatus 12, and the reception apparatus used for reception may be changed depending on the ultrasonic wave to be received.

  There is no limitation in particular in the frequency of ultrasonic waves W1-W3, and a preferable frequency is selected according to a 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.

  In a specific situation, the frequency of the ultrasonic wave W1 transmitted from the tracking device 10 and the frequency of the ultrasonic wave W2 transmitted from the transponder 20 may be required to be close (for example, the frequency difference between the two is within 10 kHz). is there. In such a case, the influence of the reflected wave of the ultrasonic wave W1 is particularly problematic in the conventional method, but according to the present invention, the influence of the reflected wave of the ultrasonic wave W1 can be eliminated. Therefore, the frequency of the ultrasonic wave W1 and the frequency of W2 may be the same or different. However, when the frequency difference between the ultrasonic wave W1 and the frequency W2 is within 10 kHz, the transmitter, receiver, transmission circuit, and reception circuit used in the first ultrasonic transmission / reception device and the second ultrasonic transmission / reception device are the same. Since it may have a characteristic, an advantage of being economical is obtained.

  The frequency of the ultrasonic wave W3 may be the same as or different from the frequencies of the ultrasonic waves W1 and W2. However, when the difference between the frequency of the ultrasonic wave W2 and the frequency of W3 is within 10 kHz, the bands of the ultrasonic receivers 12a and 12b and the receiving circuits 12c and 12d connected to the ultrasonic receivers 12a and 12b can be narrowed. The advantage that the S / N of the signal is improved is obtained.

  As an ultrasonic transmitter and an ultrasonic receiver, an ultrasonic transmitter and an ultrasonic receiver using a piezoelectric ceramic flexible vibrator, or an ultrasonic transmitter and an ultrasonic receiver using a PVDF piezoelectric polymer film as an oscillator. Can be used.

  The ultrasonic receiver 12 includes two ultrasonic receivers 12a and 12b that are arranged at regular intervals. The distance from each receiver to the ultrasonic transmitter 21a of the transponder 20 can be calculated from the ultrasonic propagation time. If the distance from the ultrasonic receiver 12a to the ultrasonic transmitter 21a and the distance from the ultrasonic receiver 12b to the ultrasonic transmitter 21a are known, the distance and direction of the transponder 20 with respect to the tracking device 10 can be calculated. . An example of the positional relationship between the ultrasonic receivers 12a and 12b and the ultrasonic transmitter 21a is shown in FIG.

  In FIG. 3, a triangle is constituted by the ultrasonic transmitter 21 a of the transponder 20 and the ultrasonic receivers 12 a and 12 b of the self-propelled body 1. The ultrasonic receiver 12a and the ultrasonic receiver 12b are arranged apart from each other by a predetermined distance L. It is assumed that the ultrasonic transmitter 21a and the ultrasonic receiver 12a are separated by a distance L1, and the ultrasonic transmitter 21a and the ultrasonic receiver 12b are separated by a distance L2. The distances L1 and L2 are estimated using the time required for propagation of the ultrasonic waves and the sound speed in the air, respectively. The time required for the propagation of the ultrasonic wave is calculated in consideration of the time required from the transmission of the ultrasonic wave W1 to the reception of the ultrasonic wave W2 and the time required for processing in the transponder 20. When the distances L1, L2, and L are clarified, the triangle formed by the ultrasonic transmitter 21a, the ultrasonic receiver 12a, and the ultrasonic receiver 12b is uniquely determined. Therefore, the distance and relative orientation of the transponder 20 with respect to the tracking device 10 can be easily obtained from these distances using a trigonometric function.

  In the tracking system of the first embodiment, one reflection state detection process and one or more (preferably a plurality of) position estimation processes are alternately performed. By the reflection state detection process, the presence state of an object that exists around the self-propelled body 1 and reflects ultrasonic waves is detected, and information about the time T is obtained. Further, the relative position of the transponder 20 with respect to the tracking device 10 is estimated by the position estimation process.

  An outline of the operation of the self-propelled vehicle 1 (tracking device 10) in the reflection state detection process is shown in the flowchart of FIG. First, the self-propelled body 1 (tracking device 10) transmits (radiates) the third ultrasonic wave W3 (S41).

  The third ultrasonic wave W3 is reflected by objects (moving body 2 and object 3) existing around the self-propelled body 1. The tracking device 10 obtains the time d by receiving the reflected wave of the ultrasonic wave W3 (S42). The time d is the maximum time among the times from when the ultrasonic wave W3 is transmitted to when a reflected wave having a predetermined intensity or higher is received. Here, the predetermined intensity is an intensity that makes it difficult to distinguish from the ultrasonic wave W2. At this time, the time d is determined using only the signal of the reflected wave from the object existing within the set measurement range (within the measurement limit). That is, when the time estimated to reach the reflected wave from the measurement range has elapsed, the process proceeds to the next step.

  Next, the self-propelled body 1 determines information on the time T using the time d (S43). Time T is a time for delaying the transmission of the second ultrasonic wave W2 by the transponder 20. This time T is increased or decreased according to the presence state of the object 3 present around the self-propelled body 1. In the conventional tracking device described in Japanese Examined Patent Publication No. 7-31244, the transmission of the second ultrasonic wave W2 is delayed by a fixed delay time regardless of the presence of an object existing around the self-propelled body 1. The In this conventional apparatus, the delay time is set so that the reflected wave from the reflector is sufficiently attenuated to the extent that it does not affect the measurement of the propagation time in any situation. Therefore, in most situations, the set delay time is longer than the delay time actually required in that situation, and as a result, the time required for estimating the position of the transponder 20 becomes longer. On the other hand, in the tracking system of the present invention, the time T is increased / decreased according to the presence state of the object existing around the self-propelled body 1, and therefore it is possible to prevent an unnecessarily long delay time from being set, The time required for estimating the position of the transponder 20 can be shortened.

  The information related to the time T included in the ultrasonic wave W1 only needs to include information necessary to determine the time T. For example, the information indicating the time d may be information indicating the time T itself. There may be. Below, the case where the information regarding the time T is the time T itself is mainly demonstrated.

  If the ultrasonic wave W2 reaches the self-propelled body 1 after the elapse of time d since the transmission of the ultrasonic wave W1, the ultrasonic wave W2 can be received without being affected by the reflected wave of the ultrasonic wave W1. Become. Therefore, it is possible to determine the time T based on the time d.

  After determining the time T, position estimation processing is performed. An outline of the operation of the self-propelled vehicle 1 (tracking device 10) in the position estimation process is shown in the flowchart of FIG. First, the first ultrasonic wave W1 is transmitted from the ultrasonic transmitter 11a of the tracking device 10 (S44). The ultrasonic wave W1 includes information regarding the time T (0 ≦ T).

  The arithmetic processing unit 23 of the transponder 20 that has detected reception of the ultrasonic wave W1 reads information on the time T included in the ultrasonic wave W1. Then, the transponder 20 sends a drive command to the transmission circuit 21b so that the second ultrasonic wave W2 is transmitted after the time T has elapsed. The ultrasonic transmitter 21a driven by the transmission circuit 21b transmits the second ultrasonic wave W2. At this time, the time T is set so that the ultrasonic wave W2 reflected by the object 3 and received by the ultrasonic receiver 12 is sufficiently attenuated and then the ultrasonic wave W2 reaches the ultrasonic receiver 12. . A specific example of the operation of the transponder 20 will be described in the second embodiment.

  The tracking device 10 receives the ultrasonic wave W2 (S45). Since the ultrasonic wave W2 is received after the reflected wave of the ultrasonic wave W1 is sufficiently attenuated, the reflected wave of the ultrasonic wave W1 and the ultrasonic wave W2 are prevented from interfering with difficulty in estimating the position of the transponder 20. Is done. The self-propelled body 1 analyzes the received signal, calculates the relative position of the transponder 20, and outputs it (S46). The relative position data is sent to a traveling control unit (not shown) of the self-propelled body 1 to control the tracking traveling.

  Next, it is determined whether or not to perform the reflection state detection process (S47). If the reflection state detection process is performed, the process proceeds to the reflection state detection process. If not, the position estimation process is performed again. Regarding this determination, the number of position estimation processes for one reflection state detection process may be determined in advance. In addition, it may be determined which process is to be executed according to a change in the surrounding situation. An example of such determination will be described in Embodiment 2. In this way, the estimation of the position of the transponder 20 and the tracking based thereon are executed.

  Information relating to the time T can be included in the ultrasonic wave W1 in various forms, and a known method can be applied. In one example, the ultrasonic wave W1 is composed of one or more ultrasonic pulses. In this case, for example, the time T may be discretized within an appropriate range, and a unique number of pulses may be associated with each. When the maximum distance between the tracking device 10 and the transponder 20 is 5 m, it is sufficient to assume a delay time of about 5 m in terms of distance. At this time, if the delay time (time T) to be set is converted into a distance and divided in units of 1 m, it is divided into five levels. For example, 2 burst waves can be set for 0 to 1 m, 3 burst waves for 1 m to 2 m, 4 burst waves for 2 m to 3 m, 5 burst waves for 3 m to 4 m, and 6 burst waves for 4 m to 5 m can be set. Information on the time T can be transmitted by transmitting the ultrasonic wave W <b> 1 composed of a pulse train in this way.

  FIG. 5 shows an example of 3 burst waves corresponding to 1 m to 2 m. The ultrasonic wave W1 includes three ultrasonic pulses 51a to 51c. In this example, the information about time T is coded by a pulse train. The tracking device 10 and the transponder 20 share pulse train coding information. As long as the tracking device 10 and the transponder 20 share information on the encoding method, various types of encoding can be applied.

  Unlike the ultrasonic wave W1, the ultrasonic wave W3 for detecting the reflection state may be an ultrasonic wave that can measure the existence range of the reflector in the surrounding environment, and does not need to include specific information. However, the ultrasonic wave W3 and the ultrasonic wave W1 need to be distinguishable. When the ultrasonic wave W1 is composed of the burst wave described above, the ultrasonic wave W3 and the ultrasonic wave W3 can be distinguished by making the ultrasonic wave W3 a single ultrasonic pulse, for example.

  Another example of the ultrasonic wave W1 is shown in FIG. In the ultrasonic wave W1 of FIG. 6, information regarding the delay time (time T) is encoded by the phase of the ultrasonic pulse. 6A shows a driving waveform of the ultrasonic transmitter of the tracking device 10, FIG. 6B shows a received waveform in the transponder 20, and FIG. 6C shows a phase detection signal in the transponder 20. . As shown in FIG. 6A, the ultrasonic wave W1 is transmitted using a drive waveform whose phase is reversed halfway. As a result, as shown in FIG. 6C, the phase detection signal is inverted once from positive to negative.

  Even when the information is coded by the phase, the delay time information may be discretized within an appropriate range, and the number of phase inversions may be associated with each, as in the case of coding the information by the pulse train. When the maximum distance between the tracking device 10 and the transponder 20 is 5 m, when the delay time to be set is converted into a distance and divided in units of 1 m, for example, 0 to 1 m is inverted by 1 phase, and 1 m to 2 m is 2 phases. Inversion, 2m to 3m can be set to 3 phase inversion, 3m to 4m can be set to 4 phase inversion, and 4m to 5m can be set to 5 phase inversion. In this case, for example, an ultrasonic pulse without phase inversion can be used as the ultrasonic wave W3.

  Hereinafter, the relationship between the reception state of ultrasonic waves in a specific situation and the time T set based on the reception state will be described. An example of a situation where an object 3 (obstacle) other than the moving body 2 exists in the measurable range is schematically shown in FIG. The object 3 is an object that reflects ultrasonic waves, and is an obstacle such as a passerby or a pillar. In FIG. 7A, the measurement range 70 is a range of 5 m, the distance between the tracking device 10 (the self-propelled body 1) and the object 3 is about 5 m, and the tracking device 10 and the transponder 20 (the moving body 2). ) Is assumed to be about 2.5 m.

  FIG. 7B schematically shows the ultrasonic reception state and the time T determination method in the state of FIG. In the state of FIG. 7A, the reflected wave 71 by the moving body 2 is observed about 15 milliseconds after transmitting the ultrasonic wave W3, and the reflected wave 72 by the object 3 is observed after about 30 milliseconds. Assume that the time for which the received reflected wave 72 is received at a predetermined intensity or higher is about 2.5 milliseconds. By observing these reflected waves, the maximum time d (about 32.5 milliseconds) is obtained from the time from when the ultrasonic wave W3 is transmitted until the reflected wave having a predetermined intensity or higher is received. .

  On the other hand, in the state of FIG. 7A, the total time of the time required for the ultrasonic wave to move from the tracking device 10 to the transponder 20 and the time required for the ultrasonic wave to move from the transponder 20 to the tracking device 10. Is about 15 milliseconds. This time is predicted as time t, and can be predicted based on the distance between the tracking device 10 and the transponder 20 determined in the immediately preceding position estimation process. Here, it is assumed that the distance between the tracking device 10 and the transponder 20 determined in the immediately preceding position estimation process is about 2.5 m, which is the same as the situation in FIG. In this case, the predicted time t is about 15 milliseconds. When the moving speed of the moving body 2 is about 1.6 m / sec at the maximum, the distance traveled from the previous position estimation process to the next position estimation process is estimated to be several tens of centimeters or less. Therefore, even in actual measurement, the error in the predicted time t is small. Note that in the first reflection state detection process at the start of tracking, there is no information for determining the time t, and therefore only the first time may calculate the time T with the time t set to zero, for example.

  When the time required for signal processing in the transponder 20 is not taken into consideration, the delay time predicted to be the minimum is about 17.5 milliseconds obtained by subtracting the time t from the time d. It takes time t (about 15 milliseconds) for the ultrasonic wave W1 to propagate from the tracking device 10 to the transponder 20 and for the ultrasonic wave W2 to propagate from the transponder 20 to the tracking device 10. Therefore, if the delay time is longer than 17.5 milliseconds, the tracking device 10 receives the ultrasonic wave W2 after about 32.5 milliseconds have elapsed since the transmission of the ultrasonic wave W1. Therefore, the ultrasonic wave W2 is received by the tracking device 10 after the reflected wave of the ultrasonic wave W1 is sufficiently attenuated.

  In the processing of the first embodiment, the time T is obtained by adding an adjustment time M (for example, 3 milliseconds) that is a margin time to the minimum required delay time. The adjustment time M is determined in consideration of an error between the predicted time t and the actual time, a change in state from the execution of the reflection state detection process to the execution of the position estimation process, and the like. In determining the adjustment time M, the time required for signal processing may be taken into consideration. For example, when the time required for signal processing in the transponder 20 is longer than the margin time, the adjustment time M may be a negative time. Depending on the value of the adjustment time M, the time T may be zero.

  If the adjustment time M is 3 milliseconds, the time required from the transmission of the ultrasonic wave W1 to the reception of the ultrasonic wave W2 is the total time of the time d and the adjustment time M (about 35.5 milliseconds). In the vicinity of that time, the wave 73 of the ultrasonic wave W2 (see FIG. 7B) is received. On the other hand, in the conventional method that does not detect the reflection state, it is necessary to delay the transmission of the ultrasonic wave W2 by a time during which the reflected wave from within the measurement range may be received. Therefore, the delay time in the conventional method is about 32.5 milliseconds even when the adjustment time is zero, and is about 35.5 milliseconds when the adjustment time is 3 milliseconds. Also in the conventional method, the time required from the transmission of the ultrasonic wave W1 to the reception of the ultrasonic wave W2 is equal to or longer than the sum of the delay time and the time t, and is approximately 47.5 milliseconds or longer. As described above, the time required from the transmission of the ultrasonic wave W1 to the reception of the ultrasonic wave W2 is about 47.5 milliseconds or more in the conventional method, whereas the time required for the method of the present invention is about 35.5. Milliseconds.

  Next, processing in the situation of FIG. In FIG. 8A, the distance between the tracking device 10 (self-propelled body 1) and the object 3 is about 2 m, and the distance between the tracking device 10 and the transponder 20 (moving body 2) is about 3.m. The case of 5 m is assumed. FIG. 8B shows the relationship between the ultrasonic reception state in the situation of FIG. 8A and the time T set based on the reception state.

  In the state of FIG. 8A, the reflected wave 81 by the object 3 is observed about 12 milliseconds after the transmission of the ultrasonic wave W1, and the reflected wave 82 by the moving body 2 is observed after about 21 milliseconds. Assume that the time for which the received reflected wave 82 is received at a predetermined intensity or higher is about 2.5 milliseconds. By observing these reflected waves, time d (about 23.5 milliseconds) is obtained.

  On the other hand, it is assumed that the time t predicted to be required for the ultrasonic wave to reciprocate between the tracking device 10 and the transponder 20 was about 21 milliseconds from the previous position estimation process. In this case, the delay time predicted to be the minimum is about 2.5 milliseconds obtained by subtracting time t from time d. That is, in the case of FIG. 8A, the time width of the reflected wave 82 is a delay time predicted to be the minimum necessary. In the processing of the first embodiment, the adjustment time M (for example, 3 milliseconds) is added to the minimum required delay time, and the time T is about 5.5 milliseconds. When the time required for signal processing in the transponder 20 is longer than 2.5 milliseconds, the time T may be zero.

  In the tracking system of the present invention, the time required to receive the wave 83 of the ultrasonic wave W2 (see FIG. 8B) after transmitting the ultrasonic wave W1 in the situation of FIG. 23.5 milliseconds) plus adjustment time M (3 milliseconds). On the other hand, in the conventional method that does not detect the reflection state, a time longer than the sum of the fixed delay time (about 32.5 milliseconds) and the time t (about 21 milliseconds) (about 53.5 milliseconds or more). Cost. As described above, the time required from the transmission of the ultrasonic wave W1 to the reception of the ultrasonic wave W2 is about 53.5 milliseconds or more in the conventional method, whereas it is about 26.5 in the method of the present invention. Milliseconds.

  As described above, in the situation of FIG. 8 (a), the effect of the present invention on the conventional method of fixing the delay time is further increased as compared with the situation of FIG. 7 (a). In the tracking system of the present invention, the shorter the distance between the self-propelled body 1 and the reflector (the moving body 2 and other objects), the longer it takes to estimate the position of the transponder 20 than in the conventional method of fixing the delay time. Can be greatly shortened. Therefore, the tracking system of the present invention is particularly effective when there is no object other than the moving body 2 around the self-running body 1 and the distance between the self-running body 1 and the moving body 2 is short.

  As described above, in the tracking system of the present invention, the time T for delaying the transmission of the ultrasonic wave W2 from the transponder 20 is increased or decreased according to the presence state of the objects existing around the self-propelled body 1. As a result, it is possible to estimate the position of the transponder 20 with high accuracy by transmitting and receiving ultrasonic waves in a shorter time than the conventional method.

  In the above method, [Time T] = [Time d] − [Time t] + [Adjustment time M], but the time T is calculated as [Time T] = [Time d] + [Adjustment time M]. May be. Also in this case, since the time d is shortened depending on the situation around the self-propelled body 1, the position estimation process can be performed in a shorter time than the conventional method depending on the situation. For example, in the situation of FIG. 7A, the time T is 35.5 milliseconds, which is the same as the conventional method. However, in the situation of FIG. 8A, the time T is 26.5 milliseconds, the conventional method. Can be shorter.

  In the above description, the case where the ultrasonic wave W1 and the ultrasonic wave W3 are separate has been described. However, the reflection state detection process may be performed using the reflected wave of the ultrasonic wave W1. In this case, the reflection state detection process and the position estimation process are performed in parallel. In the position estimation process in this case, the time T is determined based on the reflection situation detected by the reflection situation detection process performed in parallel with the previous position estimation process.

(Embodiment 2)
In the second embodiment, an example of processing will be described in more detail. In addition, the description which overlaps about the part similar to Embodiment 1, for example, the structure of the tracking apparatus 10 and the transponder 20, an ultrasonic wave transmitted, etc. is abbreviate | omitted.

  The operation of the self-propelled vehicle 1 (tracking device 10) in the reflection state detection processing 90 and the position estimation processing 100 of the second embodiment is shown in the flowchart of FIG.

  The tracking device 10 performs processing for detecting a reflection state. First, the third ultrasonic wave W3 is transmitted (S91). In order to prevent the ultrasonic wave W3 transmitted from the ultrasonic transmitter 11 from being directly received by the ultrasonic receiver 12 and being mistakenly recognized as a reflected wave by an obstacle, reception by the ultrasonic receiver 12 is performed. Is stopped for a certain time (S92). Thereafter, the ultrasonic receiver 12 enters a reception waiting state.

  The ultrasonic wave W3 is reflected by an object existing around the self-propelled body 1, for example, the object 3 in FIG. 7A, and is received by the ultrasonic receivers 12a and 12b. The arithmetic processing unit 13 analyzes the reflected waves received by the two receivers and determines whether or not a reflected wave of a certain level or higher has been received (S93). If there is no reception, the process proceeds to step S95. When it is determined that a reflected wave of a certain level or more has been received, the received reflected wave is analyzed, and distance data between the object (reflector) that has produced the reflected wave and the tracking device 10 is output ( S94). The distance data is calculated from the time elapsed from transmission to reception of the ultrasonic wave W3 and the sound speed. Since the tracking device 10 according to the second embodiment has two ultrasonic receivers, two distance data can be obtained for one reflector, but the far one of the two distance data is selected.

  Next, it is determined whether the time elapsed since the transmission of the ultrasonic wave W3 is longer than the time corresponding to the set measurement range (S95). If the elapsed time is within the measurement range, the reception state is entered again. The distance data is updated every time a new reflected wave is received (S94).

  By the above processing, the distance of the farthest reflector that is expected to affect the measurement within the initially set measurement range can be estimated. Based on the estimated data regarding the distance of the reflector, a time T (delay time) and a transmission waveform of the ultrasonic wave W1 including information on the time T are determined (S96). These are determined by the method described in the first embodiment. Next, the reception stop time in the position estimation process 100 (see S102), the number of repeated executions of the position estimation process 100, and the movement range of the self-propelled body 1 are determined (S97).

  After the reflection state detection process 90 is performed, the position estimation process 100 is performed. First, the first ultrasonic wave W1 having the transmission waveform determined in the reflection state detection process 90 is transmitted (S101). After transmission, in order to eliminate the influence of receiving the reflected wave of the ultrasonic wave W1, reception of the ultrasonic wave is stopped for a certain time (S102).

  The transponder 20 that has received the ultrasonic wave W1 reads the information contained in the ultrasonic wave W1, and transmits the second ultrasonic wave W2 after the elapse of time T (0 ≦ T). The tracking device 10 in the reception waiting state monitors reception of the ultrasonic wave W2 by the ultrasonic receivers 12a and 12b until a time corresponding to the measurement range has elapsed (S103, S104).

  There is no particular limitation on the method of determining the presence or absence of a received signal (S93, S103) and the method of measuring the arrival time of the received signal in the reflection state detection process 90 and the position estimation process 100, and a known method can be applied. For example, a method of determining that the received signal is received when the amplitude of the received signal exceeds a predetermined threshold value may be used. Further, a method may be applied in which a transmission signal waveform corresponding to each received signal is assumed and used as a reference signal, a correlation process is performed, and a determination is made based on a correlation peak value.

  When the signal of the ultrasonic wave W2 is received, the distance and direction of the transponder 20 are calculated using the arrival times of the signals in the ultrasonic receivers 12a and 12b, and the data is output (S105). On the other hand, when the signal of the ultrasonic wave W2 is not received within the measurement range, an error flag is output as a measurement error (S106), and the process proceeds to the next step.

  After the distance and azimuth data are output or the error flag is output, it is determined whether or not the number of executions of the position estimation process 100 and the movement range determined in the reflection state detection process 90 are exceeded (S107). . If any one of them is exceeded, the process proceeds to the reflection state detection process 90. If both of them are within the set range, the position estimation process 100 is performed again. In this manner, one reflection state detection process 90 and one or more position estimation processes 100 are alternately repeated until the tracking of the moving object 2 by the self-propelled object 1 is completed.

  Hereinafter, switching between the reflection state detection process and the position estimation process will be described. As an example, it is assumed that the distance that the ultrasonic wave propagates during the adjustment time M is 1 m, the moving speed of the self-propelled body is 1 m / sec, and the current measurement cycle of the position estimation process is 30 Hz. The one-way distance (margin distance) through which the ultrasonic wave propagates during the adjustment time M is 50 cm, which is half of 1 m. Moreover, the moving distance of the self-propelled body per measurement cycle is about 3.3 cm.

  Based on the above assumptions, assuming that a new reflector appears due to the movement of the self-propelled body, in one example, each time the self-propelled body travels a distance of 25 cm, which is ½ of the margin distance, the reflection state is detected. What is necessary is just to process. The position estimation process that can be performed while the self-propelled body travels a distance of 25 cm is about 7.5 times. Therefore, after performing the reflection state detection process once, the cycle of performing the position estimation process seven times may be repeated as one cycle to perform tracking. In the actual environment where the tracking system is operating, the status of the reflector rarely changes rapidly while the self-propelled body moves 25 cm. In addition, seven cycles of 30 Hz are about 0.23 seconds, and it is almost impossible for the distance between the self-propelled body and the moving body to change suddenly within the marginal distance or more in a short time. Therefore, a good tracking operation can be realized by the above setting.

  When tracking is performed in an environment where obstacles serving as ultrasonic reflectors can be almost ignored, high-speed tracking is possible. However, in order to realize good tracking, it is necessary to measure the relative position at a higher speed as the moving speed of the moving body 2 increases. Therefore, in such a situation, it is preferable to set the adjustment time M short. On the other hand, when tracking is performed in a situation where there are many obstacles, for example, indoor passages, it is expected that the delay time will be long. However, in such a situation, the moving speed of the moving body 2 tends to be slow according to the environment. Accordingly, although the measurement cycle is delayed, it is preferable to set the adjustment time M longer. Thus, tracking can be executed while ensuring the accuracy of position estimation of the transponder 20.

  When there are many reflectors around the self-propelled object and the distance between the self-propelled object and the reflector is long and the measurement cycle is long, or when the moving speed of the self-propelled object and the moving object becomes faster Can be dealt with by setting the adjustment time M (margin distance) longer. In addition, another mobile object such as a person unexpectedly appears in the vicinity of the tracked mobile object 2, and a new unexpected reflection signal is generated within the margin distance, so that the relative position of the mobile object 2 is estimated. A large error may occur. In such a situation, a mismatch (discontinuity) occurs between the estimated value in the current position estimation process and the estimated value in the previous position estimation process. When such a mismatch occurs, it is preferable to shift from the position estimation process to the reflection state detection process and reacquire information on the surrounding reflection state. Then, in consideration of past relative position data before inconsistency occurs, settings such as margin distance (adjustment time M) and delay time (time T) may be updated.

  Thus, in the tracking system of the present invention, the reflection state detection process and the position estimation process may be switched according to the surrounding situation. The determination of switching between them can be performed using the margin time (adjustment time M) used when determining the time T, the moving speed of the self-propelled body, and the current measurement cycle as basic parameters.

  Next, the process in the mobile body 2 (transponder 20) will be described with reference to the flowchart of FIG. When the tracking system is activated, the transponder 20 waits for reception and monitors whether an ultrasonic signal has been received (S111).

  And when an ultrasonic wave is received, the waveform analysis of the received signal is performed (S112). Next, based on the result of waveform analysis, it is determined whether or not the received signal is the position estimation ultrasonic wave W1 (S113). If it is determined that the received signal is not the signal of the ultrasonic wave W1, the state returns to the reception waiting state. On the other hand, when it is determined that the received signal is a signal of the ultrasonic wave W1, the time T is set using the information related to the time T extracted by the waveform analysis (S112) (S114).

  Next, the process is delayed until the time T elapses (S115). Next, the second ultrasonic wave W2 is transmitted (S116). In order to prevent the ultrasonic wave W2 from being directly received by the ultrasonic wave receiver 22a of the transponder 20, after the ultrasonic wave W2 is transmitted, reception by the ultrasonic wave receiver 22a is stopped for a certain period (S117). Then, it returns to the state of waiting for reception. In this way, processing on the transponder 20 side is performed.

  Below, an example of the method of waveform analysis (S112) is demonstrated. FIG. 11A is a time chart showing the waveform of the ultrasonic wave W 1 received by the ultrasonic receiver 22 a and the control state of the transponder 20.

  The ultrasonic wave W1 is first received at time 121. The ultrasonic wave W1 includes information related to the time T in a form encoded by the number of pulse trains, and specifically includes three pulse trains. Waveform analysis (S112) is performed on the received waveform data. Hereinafter, an example of the waveform analysis process will be described with reference to the flowchart of FIG.

  When the first signal is received when the transponder 20 is in a reception waiting state, the reception time 121 is recorded (S112a). Next, reception is stopped for a certain time (S112b). This reception stop time is set in advance according to a signal coding rule. After the reception stop time elapses, the device again waits for reception for a predetermined period. FIG. 11A shows the reception waiting period 122. It is determined whether or not a signal is received during this reception waiting period (S112c). If it is determined that a signal has been received during the reception waiting period, the count of the number of receptions is increased (S112d), and the count is set to 2 including the first signal. After the count number is increased, the process returns to the previous step (S112b), and the count number is increased every time a new signal is received. If no signal is received during the reception waiting period, the waveform analysis process is terminated, and the process proceeds to the next step.

  Based on the number of receptions counted by the above process, it can be determined whether or not the received signal is the ultrasonic wave W1 for position estimation. For example, in the example of the coding rule described with reference to FIG. 5, if the counted number of receptions is two or more, it is determined that the ultrasonic wave W1 is used, and information on the time T can be obtained according to the number of receptions.

  In FIG. 11, the case where the information regarding the time T is coded using the number of pulse trains has been described. On the other hand, when the information about the time T is coded using the number of phase inversions, the number of phase inversions can be counted by incorporating a phase detection circuit in the receiving circuit 22a of the transponder 20. Also in this case, as in the case of using the pulse train, it is possible to determine whether or not the received signal is a signal of the ultrasonic wave W1, and information about the time T can be obtained.

  As described above, also in the tracking system of the second embodiment, as described in the first embodiment, the time T is increased or decreased according to the arrangement of objects (reflectors) existing around the self-propelled body 1. As a result, the average time required for one position estimation process can be shortened.

  As described above, in the tracking system of the present invention, the state of the reflector existing around the self-propelled body and the relative position of the mobile body are measured by the ultrasonic transceiver of the self-propelled body. From these two pieces of information, the delay time set on the mobile body side can be optimized. By superimposing this delay time information on the ultrasonic wave and transmitting it from the self-propelled body to the moving body, the optimum delay time is always set. As a result, a tracking system that can flexibly cope with changes in the surrounding environment can be realized. According to this tracking system, good tracking characteristics can be realized both at high speed tracking and at low speed tracking.

  The embodiments of the present invention have been described above with examples. However, the present invention is not limited to the above-described embodiments, and can be applied to other embodiments based on the technical idea of the present invention.

  The tracking system of the present invention has means for changing the measurement cycle according to the surrounding conditions, and can flexibly respond to changes in the surrounding environment, so it is useful as a transport robot for railway stations, airports, etc. . 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 transponder in the tracking system of this invention. The figure which shows typically an example of the method of estimating the position of a transponder. The flowchart which shows an example of the process by the side of the self-propelled body in the tracking system of this invention. The figure which shows an example of the 1st ultrasonic wave used in the tracking system of this invention. The figure which shows another example of the 1st ultrasonic wave used in the tracking system of this invention. The figure which shows typically an example of the setting method of the time T in the tracking system of this invention. The figure which shows typically an example of the setting method of the time T in the condition different from FIG. The flowchart which shows another example of the process by the side of the self-propelled body in the tracking system of this invention. The flowchart which shows an example of the process by the side of the transponder in the tracking system of this invention. The timing chart of the waveform analysis which shows typically the method of the waveform analysis in the tracking system of this invention, and the flowchart of the process of (b).

Explanation of symbols

1 Self-propelled object 2 Moving object 3 Object (reflector)
DESCRIPTION OF SYMBOLS 10 Tracking apparatus 11 1st ultrasonic transmitter 12 First ultrasonic receiver 13 Arithmetic processor 20 Transponder 21 2nd ultrasonic transmitter 22 2nd ultrasonic receiver 23 Arithmetic processor 51a-51c Pulse 70 Measurement range W1 First ultrasonic wave W2 Second ultrasonic wave W3 Third ultrasonic wave

Claims (14)

In a tracking system including a transponder arranged in a moving body and a self-propelled body that tracks the transponder by estimating the position of the transponder,
The self-propelled body includes a first ultrasonic transmission / reception device,
The transponder includes a second ultrasonic transmission / reception device,
(I) The self-propelled body transmits a first ultrasonic wave including information on time T (0 ≦ T) from the first ultrasonic wave transmitting / receiving device,
(Ii) The transponder receives the first ultrasonic wave by the second ultrasonic transmission / reception device, transmits the second ultrasonic wave from the second ultrasonic transmission / reception device after the elapse of the time T,
(Iii) The self-propelled body performs a position estimation process including a step of estimating the position of the transponder by receiving the second ultrasonic wave by the first ultrasonic transmission / reception device,
The time T can be distinguished from the first ultrasonic wave that is reflected by an object existing around the self-propelled body and received by the first ultrasonic transmission / reception device. Is set to
The tracking system according to claim 1, wherein information relating to the time T is determined in accordance with the presence state of the object so that the time T is increased or decreased according to the presence state of the object.   The time T is the time when the second ultrasonic wave is reflected by the object and received by the first ultrasonic transmission / reception apparatus after the first ultrasonic wave becomes smaller than a predetermined intensity. The tracking system according to claim 1, wherein the tracking system is set to reach an ultrasonic transmission / reception device. The self-propelled body is
(A) transmitting a third ultrasonic wave from the first ultrasonic transmitting / receiving device;
(B) receiving the third ultrasonic wave reflected by the object by the first ultrasonic transmitting / receiving device;
(C) obtaining a maximum time d from a time required for transmitting the third ultrasonic wave to receiving the third ultrasonic wave having a predetermined intensity or more;
(D) The tracking system according to claim 1, wherein a reflection state detection process including a step of determining information on the time T based on the time d is executed.   The tracking system according to claim 3, wherein the time T is a time obtained by adding an adjustment time M to the time d. The self-propelled body calculates a time t expected to be required for ultrasonic waves to reciprocate between the self-propelled body and the transponder,
The tracking system according to claim 3, wherein the time T is a time obtained by subtracting the time t from the time d and adding an adjustment time M. The self-propelled body is
(A) The first ultrasonic wave reflected by the object is received by the first ultrasonic transmission / reception device,
(B) Obtaining the maximum time d from the time required to transmit the first ultrasonic wave until receiving the first ultrasonic wave having a predetermined intensity or higher,
(C) The tracking system according to claim 1, wherein a reflection state detection process including a step of determining information on the time T based on the time d is executed.   2. The tracking system according to claim 1, wherein the time T is increased or decreased in consideration of only the presence of an object within a predetermined distance from the self-propelled body among the objects.   2. The tracking system according to claim 1, wherein the first ultrasonic wave is an ultrasonic pulse including information related to the time T in a state encoded by a pulse number.   The tracking system according to claim 1, wherein the first ultrasonic wave is an ultrasonic pulse including information related to the time T in a state encoded by a phase of the pulse.   The tracking system according to claim 1, wherein a cycle in which the position estimation process is performed once or more is repeated after the reflection state detection process is performed once.   The tracking system according to claim 1, wherein the moving body is a person and the self-propelled body is a cart.   The tracking system according to claim 1, wherein a difference between the frequency of the first ultrasonic wave and the frequency of the second ultrasonic wave is 10 kHz or less. In a self-propelled vehicle used in a tracking system including a transponder arranged in a moving object and a self-propelled vehicle that estimates the position of the transponder and tracks the transponder,
Equipped with an ultrasonic transceiver,
(I) transmitting a first ultrasonic wave including information related to time T (0 ≦ T) from the ultrasonic wave transmitting / receiving device;
(II) By receiving the second ultrasonic wave transmitted from the transponder as a response signal to the first ultrasonic wave after the elapse of the time T from the reception of the first ultrasonic wave by the ultrasonic transmitting / receiving apparatus. Performing a position estimation process including the step of estimating the position of the transponder;
The time T is set so that the second ultrasonic wave can be discriminated from the first ultrasonic wave reflected by an object existing around the self-propelled body and received by the ultrasonic transmission / reception device. And
The self-propelled vehicle according to claim 1, wherein information relating to the time T is determined according to the presence state of the object so that the time T is increased or decreased according to the presence state of the object. (A) transmitting a third ultrasonic wave from the ultrasonic transmitting / receiving device;
(B) The third ultrasonic wave reflected by the object is received by the ultrasonic wave transmitting / receiving device,
(C) obtaining a maximum time d from a time required for transmitting the third ultrasonic wave to receiving the third ultrasonic wave having a predetermined intensity or more;
The self-propelled body according to claim 13, wherein a reflection state detection process including a step (d) of determining information on the time T based on the time d is performed.

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