JP2012063324A - Foreign matter detection system, foreign matter sensor, and detection device - Google Patents

Abstract

Disclosed is a foreign object detection system capable of remote communication that is small, inexpensive, and consumes less power.
A foreign matter detection system 100 includes a foreign matter sensor 200 having an antenna 204 and a resistance element 206 electrically connected on a surface of a reflection tag 202, an antenna 302, and first and second antennas 302. A radio wave transmission unit 304 that transmits radio waves of a frequency, and a first reflected wave of radio waves of the first and second frequencies transmitted from the radio wave transmission unit 304 in a reference state in which there is no foreign object around the foreign object sensor 200 And the storage unit 308 storing the reflected power of the second reflected wave, and the third and fourth reflected waves that are the reflected waves of the first and second frequency radio waves transmitted from the radio wave transmitting unit 304 The determination unit 3 determines that the foreign object is present around the foreign matter sensor if the signs of the first difference and the second difference, which are differences obtained by subtracting the reflected power of the first and second reflected waves, are different. And a detection device 300 and a 6.
[Selection] Figure 2

Description

  The present invention relates to a foreign matter detection system, a foreign matter sensor, and a detection device.

  In recent years, with the advancement of wireless technology and small sensor development technology, the development of measurement systems in which a control device acquires and uses various information of people and the real environment using multiple sensors (patents) Literatures 1-3).

  In general, a sensor capable of remote communication used in such a measurement system is required to be small, inexpensive, and power-saving.

  For example, in Patent Document 1, an attempt is made to reduce the size and power consumption by omitting a part of an electronic circuit that processes a result measured by a sensor and making an appropriate communication timing.

  In Patent Document 2, an attempt is made to reduce the size of the sensor by simplifying the configuration of the sensor.

  Furthermore, in patent document 3, it is trying the power saving by devising the protocol and communication processing part of the wireless communication which a sensor performs.

JP 2010-123033 A JP 2009-250843 A JP 2008-072414 A

  However, there is a problem that conventional sensors capable of remote communication have not yet been sufficiently reduced in size and power saving.

  For example, in Patent Document 1, the power consumption itself required for one wireless transmission is the same as that in the past, and a large amount of power must be consumed when frequent transmission from the sensor is required.

  Patent Document 2 does not disclose a technique for suppressing power consumption in the communication unit of the sensor.

  Patent Document 3 does not disclose a technique for reducing power consumption required for sensing.

  Furthermore, since these wirelessly communicable sensors have a wireless communication module added to a normal sensor for detecting a physical quantity, they must be large and expensive compared to a normal sensor. It has become a challenge.

  Thus, a sensor capable of remote communication that is sufficiently small, inexpensive, and consumes little power has not been realized.

  Accordingly, an object of the present invention is to provide a foreign matter detection system, a foreign matter sensor, and a detection device that use a foreign matter sensor that can be remotely communicated more compactly, inexpensively, and consumes less power.

  A foreign matter detection system according to an aspect of the present invention is a foreign matter detection system including a foreign matter sensor and a detection device that detects the presence or absence of foreign matter around the foreign matter sensor, wherein the foreign matter sensor includes a first antenna, A resistance element electrically coupled to the first antenna, and a reflection tag which is a substrate on which the first antenna and the resistance element are arranged, and in a state where there is no foreign object around the foreign object sensor In a certain reference state, the reflected power of the first reflected wave, which is a reflected wave when a radio wave of the first frequency is received by the first antenna, is a first frequency defined in advance including the first frequency. The reflected power of the second reflected wave, which is a reflected wave when taking a local minimum value in the region and receiving a radio wave of the second frequency by the first antenna, is defined in advance including the second frequency. Within the second frequency domain The detection device reflects a radio wave so as to take a local maximum value, the detection device includes a second antenna, a radio wave transmission unit that transmits the radio wave of the first frequency and the second frequency from the second antenna, and the reference state , The reflected power of the first reflected wave, which is a reflected wave reflected by the foreign matter sensor, is transmitted from the radio wave transmission unit, part of the radio wave of the first frequency transmitted from the radio wave transmission unit A storage unit storing a reflected power of a second reflected wave, which is a reflected wave reflected by the foreign object sensor, and a part of the second frequency radio wave transmitted from the radio wave transmitting unit; A third reflected wave, which is a reflected wave reflected by the foreign object sensor, and a part of the second frequency wave transmitted from the radio wave transmitter are reflected by the foreign object sensor. Reflected wave A fourth reflected wave is obtained from the second antenna, and the reflected power of the first reflected wave and the second reflected wave are reflected from the reflected power of the third reflected wave and the reflected power of the fourth reflected wave. And a determination unit that determines that the foreign object is present around the foreign object sensor if the first difference and the second difference, which are differences obtained by subtracting the reflected power of the waves, have different signs.

  According to this configuration, when there is a foreign object around the foreign object sensor, the apparent dielectric constant of the reflective tag changes, and as a result, the frequency characteristic of the power intensity of the radio wave transmitted from the detection device and reflected by the reflective tag changes. To do. In addition, the reflection tag has a maximum value and a minimum value in the frequency characteristics of the reflected power. Therefore, when the apparent dielectric constant of the foreign matter sensor substrate changes due to foreign matter adhering to the foreign matter sensor substrate (especially the periphery of the antenna), the reflected power at one frequency increases, and the other The reflected power of the frequency decreases.

  As a result, the detection apparatus can distinguish between a change in the reflected power due to a foreign object and a change in the reflected power due to a distance variation. Therefore, it is possible to accurately detect foreign matter around the foreign matter sensor while suppressing excessive detection of foreign matter.

  At this time, the foreign matter sensor only reflects the radio wave transmitted from the detection device, and does not transmit the radio wave itself. Therefore, so-called wireless modules and power supplies are unnecessary. Therefore, a foreign object detection system using a foreign object sensor with a wireless communication function that is small, inexpensive, and consumes less power can be realized.

  The radio wave transmission unit includes a first transmission unit that transmits radio waves of the first frequency, and a second transmission unit that transmits radio waves of the second frequency, and the first transmission unit and the first transmission unit The two transmitters transmit the radio waves of the first frequency and the second frequency at the same time.

  According to this configuration, the detection device can transmit radio waves of two frequencies necessary for detecting a foreign object at the same time. Therefore, even when the distance between the detection device and the foreign matter sensor is constantly changing and the reflected power is constantly changing accordingly, a foreign matter detection system that accurately detects the foreign matter using the reflected power at the same time can be realized.

  The reflective tag is made of a hygroscopic member.

  According to this configuration, since the substrate of the foreign matter sensor has hygroscopicity, when a liquid such as water adheres to a part of the substrate, the liquid penetrates the entire substrate of the foreign matter sensor. As a result, the apparent dielectric constant around the antenna of the foreign matter sensor is likely to change, and the change in reflected power becomes significant, thereby improving the foreign matter detection accuracy by the detection device.

  In addition, a detection apparatus according to an aspect of the present invention includes an antenna, a radio wave transmission unit that transmits radio waves of the first and second frequencies from the antenna, and a reference state in which there is no foreign object around the foreign object sensor. The reflected power of the first reflected wave, which is a reflected wave reflected by the foreign object sensor, is a part of the first frequency radio wave transmitted from the radio wave transmitting unit, and the radio wave transmitted from the radio wave transmitting unit. A storage unit storing a reflected power of a second reflected wave, which is a reflected wave reflected by the foreign object sensor, with a part of the second frequency radio wave, and the first transmitted from the radio wave transmitting unit A third reflected wave, which is a reflected wave reflected by the foreign object sensor, and a part of the second frequency wave transmitted from the radio wave transmitter are reflected by the foreign object sensor. Counter A fourth reflected wave that is a wave is acquired from the antenna, and the reflected power of the first reflected wave and the second reflected wave are reflected from the reflected power of the third reflected wave and the reflected power of the fourth reflected wave. And a determination unit that determines that the foreign object is present around the foreign object sensor if the first difference and the second difference, which are differences obtained by subtracting the reflected power of the waves, have different signs.

  According to this configuration, the detection apparatus can detect whether or not the reflected power with respect to radio waves having two predetermined frequencies has changed.

  In addition, when the reflected power changes, the determination unit included in the detection device determines whether the cause is that there is a foreign object around the foreign object sensor or whether the distance between the foreign object sensor and the detection apparatus has changed. It can be determined from the increase / decrease.

  Specifically, since the frequency characteristic of reflected power includes a maximum point and a minimum point, when a foreign substance adheres to the foreign matter sensor (particularly, the periphery of the antenna) and its dielectric constant changes, The reflected power at one frequency increases and the reflected power at the other frequency decreases.

  As described above, the detection device can distinguish between the change in the reflected power due to the foreign matter and the change in the reflected power due to the distance variation, so that the foreign matter around the foreign matter sensor can be accurately detected while suppressing the excessive detection of the foreign matter. be able to.

  The radio wave transmission unit includes a first transmission unit that transmits radio waves of the first frequency, and a second transmission unit that transmits radio waves of the second frequency, and the first transmission unit and the first transmission unit The two transmitters transmit the radio waves of the first frequency and the second frequency at the same time.

  According to this configuration, the detection device can transmit radio waves of two frequencies necessary for detecting a foreign object at the same time. Therefore, even when the distance between the detection device and the foreign matter sensor is constantly changing and the reflected power is constantly changing accordingly, the foreign matter can be accurately detected using the reflected power at the same time.

  The determination unit determines that the distance between the foreign matter sensor and the detection device has changed if the product of the first difference and the second difference has the same sign. According to this configuration, the detection device can determine and detect whether or not the foreign matter sensor is moving in addition to the presence or absence of foreign matter around the foreign matter sensor.

  Further, a foreign matter sensor according to an aspect of the present invention includes an antenna, a resistance element electrically coupled to the antenna, and a reflection tag that is a substrate on which the antenna and the resistance element are arranged. The reflected power of the first reflected wave, which is a reflected wave when a radio wave of the first frequency is received by the antenna in a reference state in which there is no foreign object around the foreign object sensor, The reflected power of the second reflected wave, which is a reflected wave when the antenna takes a local minimum value within a predefined first frequency region including the first frequency and receives a radio wave of the second frequency by the antenna. However, the radio wave is reflected so as to have a maximum value within a second frequency range defined in advance including the second frequency.

  According to this configuration, when a foreign substance exists around the foreign substance sensor, the apparent dielectric constant of the reflective tag changes, and as a result, the frequency characteristic of the reflected power changes. The frequency characteristic of the reflected power from the reflection tag has a maximum value and a minimum value.

  Therefore, by comparing the reflected power of the frequency within a certain region including the frequency at which these extreme values are taken (for example, within a range of about 6 MHz before and after the maximum point and the minimum point), it is possible to compare the reflected power with a reference state where no foreign object exists. The presence or absence of can be determined.

  At that time, the foreign matter sensor only reflects radio waves and does not transmit radio waves by itself, so that a so-called wireless module or power source is unnecessary. Therefore, it is possible to realize a foreign sensor with a wireless communication function that is small and inexpensive and consumes less power.

  Specifically, the antenna has a shape in which two or more antennas having different lengths are connected in parallel.

  With this configuration, it is possible to realize a reflective tag in which the frequency characteristic of reflected power has a maximum value and a minimum value.

  The reflective tag is made of a hygroscopic member.

  According to this configuration, the apparent dielectric constant around the antenna of the foreign matter sensor is likely to change, the change in reflected power becomes remarkable, and the foreign matter detection accuracy is improved.

  The present invention can be realized not only as such a foreign matter detection system, detection device and foreign matter sensor, but also as a foreign matter detection method including steps of characteristic means included in the detection device and foreign matter detection system. Such characteristic steps can also be realized as a program for causing a computer to execute. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  Furthermore, the present invention can be realized as a semiconductor integrated circuit (LSI) that realizes part or all of the functions of such a detection device.

  As described above, the present invention can provide a foreign object detection system, a foreign object sensor, and a detection apparatus using a foreign object sensor capable of remote communication that is small, inexpensive, and consumes less power.

FIG. 1 is a conceptual diagram showing an example of sweat detection by a foreign object detection system using a foreign object sensor and a detection device according to an embodiment of the present invention. FIG. 2 is a block diagram of the foreign matter sensor and detection apparatus according to the embodiment of the present invention. FIG. 3 is a conceptual diagram illustrating the basic principle used for detecting the presence or absence of foreign matter in the present invention. FIG. 4 is a diagram illustrating a result of verifying the relationship between the dielectric constant of the reflective tag and the frequency characteristic of the reflected power using an electromagnetic field simulator. FIG. 5 is a diagram illustrating the influence of the dielectric constant of the reflection tag and the distance between the detection device and the foreign matter sensor on the frequency characteristics of the reflected power. FIG. 6 is a diagram illustrating frequency characteristics of reflected power having a maximum point and a minimum point. FIG. 7 is a conceptual diagram illustrating a method of separating a change in dielectric constant and a change in distance using a reflection tag having a maximum point and a minimum point in the frequency characteristic of reflected power. FIG. 8 is a flowchart showing the flow of foreign object detection processing by the detection apparatus according to the embodiment of the present invention. FIG. 9 is a flowchart showing the flow of processing of the determination unit provided in the detection apparatus according to the embodiment of the present invention. FIG. 10 is a block diagram of a detection apparatus according to a modification of the embodiment of the present invention. FIG. 11 is a diagram for explaining conditions to be satisfied by the reflective tag according to the embodiment of the present invention. FIG. 12 is an external view showing an example of a computer system that realizes the detection apparatus according to the embodiment of the present invention. FIG. 13 is a block diagram showing a hardware configuration of a computer system that realizes the detection apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of a foreign matter detection system, a detection device, and a foreign matter sensor according to the present invention will be described in detail with reference to the drawings.

  The foreign object detection system 100 according to the embodiment of the present invention can be used mainly for moisture detection. Therefore, as a use, the thing of the perspiration detection for health management or the leak of a building, or the detection of dew condensation can be considered.

  FIG. 1 is a conceptual diagram showing an example of sweat detection by the foreign object detection system 100 according to the embodiment of the present invention.

  As shown in FIG. 1, the foreign object detection system 100 includes a foreign object sensor 200 and a detection device 300.

  The foreign matter sensor 200 has a function of reflecting and absorbing (consuming as electric power in an internal circuit) a part of the radio wave transmitted from the detection device 300.

  The detection device 300 transmits radio waves having two predetermined frequencies to the foreign matter sensor 200 and receives the reflected waves. The detection apparatus 300 determines the presence or absence of a foreign substance based on the intensity change of the received reflected wave.

  For example, the foreign object sensor 200 is installed on the clothes of the trainees 700 and 701.

  Here, when the foreign matter sensor detects a foreign matter (sweat in this example), the detection device 300 issues an alarm. For example, if excessive sweating is left during exercise, dehydration may occur. Therefore, it is desirable that the sweating state of the trainees 700 and 701 can be grasped. However, it is difficult for a limited number of trainers 702 to keep an eye on the sweating conditions of many trainees.

  With the foreign object detection system 100 using the foreign object sensor 200 and the detection apparatus 300 according to the present embodiment, the trainer 702 can record and monitor the sweating state of the trainees 700 and 701 in real time.

  FIG. 2 is a block diagram of the foreign matter sensor 200 and the detection device 300 according to the embodiment of the present invention.

  As shown in FIG. 2, the foreign matter sensor 200 includes a reflection tag 202, an antenna 204, and a resistance element 206.

  The reflection tag 202 is a substrate on which an antenna 204 and a resistance element 206 are arranged. As the material of the substrate, for example, it is conceivable to use a resin having a low dielectric constant or a hygroscopic member (paper, cloth, etc.), but is not limited thereto.

  In addition, by using a hygroscopic member as a substrate, when a liquid foreign matter adheres to a part of the reflective tag 202, the foreign matter is likely to permeate more widely. The detection device 300 detects a change in the apparent dielectric constant of the reflective tag 202 as a change in the reflected power. In particular, the reflected power changes due to a foreign substance adhering to the reflective tag 202 near the antenna 204 and a change in the dielectric constant. Tend to change significantly. Therefore, it is considered that the use of a hygroscopic member for the reflective tag 202 facilitates detection of liquid foreign matter.

  Note that the change in the apparent dielectric constant of the reflective tag 202 means that the apparent dielectric constant of the tag 202 changes due to the change in the dielectric constant in the space near the antenna 204 or a part thereof. Specifically, it means that the apparent dielectric constant of the entire reflection tag 202 changes when air that fills the periphery of the reflection tag 202 is replaced with other foreign matters in a reference state where there is no foreign matter.

  Theoretically, the change in the dielectric constant is not limited to the periphery of the antenna 204, but in practice, it is considered that only the change in the dielectric constant around the antenna 204 can be detected.

  The antenna 204 receives radio waves transmitted from the detection device. As will be described later, the shape of the antenna 204 is designed so that the foreign matter sensor 200 reflects and absorbs radio waves at a specific frequency.

  The resistance element 206 adjusts the intensity of reflected power by consuming radio waves received by the antenna 204 as power. The resistance value of the resistance element 206 is one of the design parameters for mounting the foreign matter sensor 200 having the characteristic of reflecting or absorbing radio waves at a specific frequency, like the shape of the antenna 204. The resistance element 206 may be a variable resistance element or a fixed resistance element.

  For example, the antenna 204 is printed on the paper reflection tag 202 with a conductive ink having a high conductivity, and the resistance element 206 is printed with a conductive ink having a conductivity lower than that of the antenna 204. It can be produced in large quantities at low cost.

  The detection apparatus 300 includes an antenna 302, a radio wave transmission unit 304, a determination unit 306, and a storage unit 308.

  The antenna 302 is an antenna having a three-dimensional or planar structure, and transmits a radio wave having a specific frequency output from the radio wave transmission unit 304 to the reflection tag 202.

  The radio wave transmission unit 304 generates two types of radio waves having different frequencies and transmits them via the antenna 302. For example, it is conceivable to alternately transmit 950 MHz and 2.4 GHz radio waves, which will be described later in detail.

  The determination unit 306 compares the radio wave intensity of the reflected wave received from the antenna 302 with a reference value acquired from the storage unit 308 to determine the presence or absence of a foreign object. Details of the determination unit 306 will be described later.

  The storage unit 308 reflects reflected power from the foreign matter sensor 200 when transmitting radio waves of two types of frequencies determined in advance from the detection device 300 in a reference state (for example, a state where there is no foreign matter around the foreign matter sensor 200). I remember the intensity of. The storage unit 308 can be realized using, for example, a ROM (Read Only Memory) or a RAM (Random Access Memory).

  Note that the storage unit 308 is not necessarily provided in the detection device 300, and may be provided in a device outside the detection device 300. In that case, the detection device 300 obtains the same effect as when the detection device 300 includes the storage unit 308 by acquiring the reflected power intensity in the reference state from the device including the storage unit 308, for example, by wireless communication.

  More specifically, the foreign matter sensor 200 includes a storage unit 308, and applies identification information transmission means in so-called RFID (Radio Frequency IDentification), and uses reflected power from the foreign matter sensor 200 for radio waves transmitted from the antenna 302. Thus, it is conceivable to notify the detection apparatus 300 of the reflected power intensity in the reference state from the foreign matter sensor 200.

  FIG. 3 is a conceptual diagram illustrating the basic principle used for detecting the presence or absence of foreign matter in the present invention.

  In the present invention, the presence or absence of a foreign object is detected by using the fact that the frequency characteristic of reflected power changes depending on the dielectric constant of an object that reflects radio waves.

  The horizontal axis in FIG. 3A indicates the frequency of radio waves transmitted from the detection device 300 to the foreign object sensor 200, and the vertical axis indicates the intensity of reflected power from the foreign object sensor 200 to the detection device 300.

  For example, it is assumed that the frequency characteristic of the reflected power when a radio wave is transmitted to the foreign object sensor 200 in the reference state is indicated by a graph 460 having a minimum point 401 at the frequency fa.

  Next, when a foreign substance having a dielectric constant larger than that of the reflective tag 202 adheres to the reflective tag 202, the apparent dielectric constant of the reflective tag 202 increases.

  In this case, generally, as the dielectric constant increases, the graph of the frequency characteristic of the reflected power shifts toward a smaller frequency (to the left in FIG. 3A). A graph 461 is an example of the frequency characteristics of the reflective tag 202 whose dielectric constant has increased due to foreign matter adhering thereto.

  Therefore, when a radio wave having the frequency fa is transmitted in a state where foreign matter is attached, the reflected power becomes larger than that in a state where the foreign matter is not attached (minimum point 401).

  Conversely, when a foreign substance having a dielectric constant smaller than that of the reflective tag 202 adheres to the reflective tag 202, the dielectric constant of the reflective tag 202 decreases. As a result, the frequency characteristic of the reflection tag 202 is shifted to the higher frequency (right side) as indicated by the graph 462. Also in this case, the intensity of the reflected power when the radio wave having the frequency fa is transmitted to the reflection tag 202 is larger than the reflected power in the reference state (the minimum point 401 in the graph 460).

  FIG. 3B shows the foreign matter sensor 200 in which moisture adheres to the back surface of the reflective tag 202 as the foreign matter 601.

  The dielectric constant of water is about 80, which is very high compared to the dielectric constant of air (about 1). Therefore, as shown in FIG. 3B, when water adheres to the back surface of the reflective tag 202, the apparent dielectric constant of the reflective tag 202 increases.

  As a result, when radio waves having the frequency fa are transmitted to the foreign matter sensor 200 in FIG. 3B, the reflected power becomes larger than the value of the minimum point 401 in the reference state.

  Thus, the detection apparatus 300 can detect a foreign object using the difference from the reflected power intensity in the reference state where there is no foreign object.

  As described above, the place where the foreign object adheres to the reflective tag 202 is preferably the vicinity of the antenna 204 including the place where the antenna 204 is arranged and the back surface thereof (because the change in reflected power is large). However, any other place on the reflection tag 202 may be used as long as the characteristic impedance of the antenna 204 changes to such an extent that the detection device 300 can detect the change in the reflected power.

  Even if the foreign matter does not completely adhere to the reflective tag 202, the apparent dielectric constant of the reflective tag 202 changes even when the foreign matter exists, for example, several millimeters away from the reflective tag 202. Therefore, it is considered that the foreign matter sensor 200 can detect the foreign matter in a non-contact manner based on the above principle.

  FIG. 4 is a diagram illustrating a result of verifying the relationship between the apparent dielectric constant of the reflection tag 202 and the frequency characteristics of the reflected power using an electromagnetic field simulator.

  In the simulation, it was assumed that radio waves having a plurality of frequencies were sequentially transmitted to the foreign matter sensor 200 having the dielectric constant of the reflection tag 202 of 4.6, and the magnitude of the reflected power was calculated.

  A graph 410 is a characteristic of the reflected power of the foreign matter sensor 200 in the air having a dielectric constant of 1. As shown in the graph 410, the foreign object sensor 200 is designed so that the intensity of the reflected power becomes a minimum value when a 2.4 GHz radio wave is transmitted.

  A graph 411 shows frequency characteristics of reflected power from the foreign matter sensor 200 when it is assumed that a 10 mm-thick water (dielectric constant 80) layer is on the back surface of the reflective tag 202 as a foreign matter. The graph 411 has a shape in which the graph 410 is moved to the left side, and the intensity of reflected power when a 2.4 GHz radio wave is transmitted due to a change in dielectric constant is compared to that measured in air. You can see that it is getting bigger.

  As described above, the principle of the present invention is that the frequency characteristic of the reflected power from the foreign matter sensor 200 changes with the change in the dielectric constant of the reflection tag 202, and as a result, the reflected power intensity measured at a specific frequency changes. Is used.

  However, the intensity of the reflected power varies depending on the distance between the foreign matter sensor 200 and the detection device 300 in addition to the dielectric constant of the reflective tag 202. Therefore, the foreign matter cannot be accurately detected unless it is possible to determine whether the cause of the change in the reflected power intensity is a change in the dielectric constant or a change in the distance. This problem will be described in more detail with reference to FIG.

  FIG. 5 is a diagram illustrating the influence of the dielectric constant of the reflective tag 202 and the distance between the detection device 300 and the foreign matter sensor 200 on the frequency characteristics of the reflected power.

  A graph 450 shown in FIG. 5 shows the intensity of the reflected power from the reflection tag 202 with respect to radio waves of various frequencies transmitted around the frequency f1 in the reference state. At the frequency f1, the reflected power takes the minimum value P1.

  A graph 451 shows frequency characteristics of the reflected power intensity when the dielectric constant increases as a result of wetting the reflection tag 202 with water. As a result of the graph moving to the left, the reflected power at the frequency f1 becomes Pm.

  A graph 452 shows the characteristic of the reflected power intensity when the foreign object sensor 200 is brought closer to the detection device 300 than when the graph 450 is measured. Since the dielectric constant does not change, the graph 452 has a minimum value at the frequency f1, but the value is not P1 but Pm.

  That is, just detecting that the reflected power at the frequency f1 has changed from P1 to Pm indicates whether the dielectric constant of the reflection tag 202 has increased due to the foreign matter or whether the distance between the foreign matter sensor 200 and the detection device 300 has changed. The problem that it cannot be separated remains.

  The foreign matter sensor 200 according to the present embodiment solves this problem by devising the frequency characteristic of the reflected power. This will be described in detail with reference to FIG.

  FIG. 6 is a diagram illustrating the frequency characteristics of the reflected power having the maximum point and the minimum point of the foreign matter sensor 200.

  As shown in FIG. 6, the graph 450 showing the intensity of the reflected power in the reference state has a minimum point 415 at the frequency f1 and a maximum point 417 at the frequency f2.

  That is, foreign object sensor 200 is designed to absorb the most radio waves when receiving radio waves of frequency f1 and to absorb the least radio waves when receiving radio waves of frequency f2. Here, the frequencies f1 and f2 are frequencies of radio waves transmitted from the detection device 300 in order to detect a foreign object.

  FIG. 7 is a conceptual diagram illustrating a method for separating the change in the dielectric constant and the change in the distance using the foreign matter sensor 200 having the maximum point and the minimum point in the frequency characteristic of the reflected power shown in FIG.

  Now, it is assumed that moisture has adhered to the reflective tag 202 and the apparent dielectric constant of the reflective tag 202 has increased. In that case, as shown in FIG. 7A, the frequency characteristic of the reflected power from the foreign matter sensor 200 changes from the graph 450 to the graph 451.

  In this case, the reflected power when the detection device 300 transmits radio waves having the frequency f1 and the frequency f2 to the foreign matter sensor 200 has values indicated by points 416 and 418 on the graph 451, respectively.

  When these values are compared with the intensity of the reflected power at the frequency f1 and the frequency f2 in the graph 450, it can be seen that the reflected power increases at the frequency f1, and the reflected power decreases at the frequency f2.

  On the other hand, when the distance between the foreign matter sensor 200 and the detection device 300 becomes long, the frequency characteristic of the reflected power changes from the graph 450 to the graph 454 as shown in FIG. 7B.

  In this case, the reflected power from the foreign matter sensor 200 at the frequency f1 and the frequency f2 has values indicated by the minimum point 420 and the maximum point 421 on the graph 454, respectively.

  When these values are compared with the intensity of the reflected power at the frequency f1 and the frequency f2 in the graph 450, it can be seen that both the reflected power becomes small at the frequency f1 and the frequency f2.

  Further, when the distance between the reflection tag 202 and the detection device 300 is shortened, the frequency characteristic of the reflected power changes from the graph 450 to the graph 452 as shown in FIG. 7B.

  In this case, the reflected power from the foreign matter sensor 200 at the frequency f1 and the frequency f2 has values indicated by the minimum point 422 and the maximum point 423 on the graph 452, respectively.

  When these values are compared with the intensity of the reflected power at the frequency f1 and the frequency f2 in the graph 450, it can be seen that the reflected power increases at the frequency f1 and the frequency f2.

  FIG. 7C is a table summarizing changes in reflected power for each of the factors described above.

  When the apparent dielectric constant of the reflection tag 202 increases, the reflected power at the frequency f1 increases from the reference state, and the reflected power at the frequency f2 decreases from the reference state.

  On the other hand, when the dielectric constant of the reflective tag 202 does not change and the distance between the foreign matter sensor 200 and the detection device 300 changes, the reflected power at the frequency f1 and the frequency f2 both increases or decreases. Become.

  Therefore, by determining how the reflected power at the frequencies f1 and f2 changes from the reference state, a change in the dielectric constant (that is, the presence of a foreign substance) and a change in the distance from the detection device 300 (for example, The change in the posture of the trainees 700 and 701 in which the foreign matter sensor 200 is installed can be detected separately.

  FIG. 8 is a flowchart showing a flow of foreign object detection processing by the detection apparatus 300 according to the present embodiment.

  First, the detection apparatus 300 transmits a radio wave having a frequency f1 from the radio wave transmission unit 304 to the foreign object sensor 200 (S320).

  Foreign object sensor 200 receives this radio wave via antenna 204. Thereafter, the foreign matter sensor 200 consumes a part of the received radio wave by the antenna 204, the resistance element 206, and the like, and reflects a part thereof as a reflected wave to the detection device 300.

  The detection apparatus 300 receives the reflected wave from the foreign matter sensor 200 through the antenna 302 (S321). For the sake of explanation, this reflected wave is referred to as a third reflected wave. The determination unit 306 temporarily stores the value of the reflected power of the third reflected wave in the storage unit 308.

  Next, the detection apparatus 300 transmits a radio wave having a frequency of f2 from the radio wave transmission unit 304 to the foreign matter sensor 200 (S322).

  Next, the foreign matter sensor 200 receives this radio wave via the antenna 204. Thereafter, the foreign matter sensor 200 consumes a part of the received radio wave by the antenna 204, the resistance element 206, and the like, and reflects a part thereof as a reflected wave to the detection device 300.

  Next, the detection apparatus 300 receives the reflected wave from the foreign matter sensor 200 by the antenna 302 (S323). For the sake of explanation, this reflected wave is referred to as a fourth reflected wave. The determination unit 306 temporarily stores the value of the reflected power of the fourth reflected wave in the storage unit 308.

  Next, the determination unit 306 acquires from the storage unit 308 the value of each reflected power when radio waves having the frequency f1 and the frequency f2 are transmitted to the reflection tag 202 in a reference state where there is no foreign object. For the sake of explanation, these are called the reflected power of the first reflected wave and the reflected power of the second reflected wave, respectively.

  Further, the determination unit 306 acquires the values of the reflected power of the third reflected wave and the reflected power of the fourth reflected wave from the storage unit 308.

  Thereafter, the determination unit 306 determines increase / decrease in the reflected power of the third and fourth reflected waves based on the reflected power of the first and second reflected waves, and determines the presence / absence of a foreign object near the reflective tag 202. (S324).

  FIG. 9 is a flowchart showing a process flow of the determination unit 306 provided in the detection apparatus 300 according to the present embodiment.

  First, as described above, the determination unit 306 obtains increase / decrease in the reflected power of the third and fourth reflected waves with reference to the reflected power of the first and second reflected waves (S304).

  Specifically, the determination unit 306 determines the first difference, which is a difference obtained by subtracting the reflected power of the first reflected wave from the reflected power of the third reflected wave, and the second difference from the reflected power of the fourth reflected wave. And a second difference that is a difference obtained by subtracting the reflected power of the reflected wave.

  Next, the determination unit 306 determines whether one of the reflected powers of the third and fourth reflected waves is increased and one of the reflected powers is decreased compared to the reflected power of the first and second reflected waves. Is determined (S305).

  Specifically, it can be considered that the determination unit 306 determines whether the positive and negative signs of the first difference and the second difference are different.

  As a result of the determination, if the signs of the first difference and the second difference are different (Yes in S305), the determination unit 306 outputs a foreign object detection signal on the assumption that a foreign object has been detected in the vicinity of the reflection tag 202. (S306).

  On the other hand, if the signs of the first difference and the second difference are the same (No in S305), the determination unit 306 does not output a foreign object detection signal.

  That is, foreign object detection system 100 according to the present embodiment includes foreign object sensor 200 and detection device 300 that detects the presence or absence of foreign objects around foreign object sensor 200.

  Here, the foreign matter sensor 200 includes an antenna 204, a resistance element 206 that is electrically coupled to the antenna 204, and a reflection tag 202 that is a substrate on which the antenna 204 and the resistance element 206 are arranged. .

  The foreign matter sensor 200 has a reflected power of the first reflected wave, which is a reflected wave when the antenna 204 receives a radio wave of the first frequency in a reference state in which no foreign matter is present around the foreign matter sensor 200, The reflected power of the second reflected wave, which is a reflected wave when the antenna 204 receives a radio wave of the second frequency, takes a local minimum value within a first frequency region defined in advance including the first frequency, The radio wave is reflected so as to have a maximum value within a second frequency range defined in advance including two frequencies.

  In addition, the detection apparatus 300 includes an antenna 302, a radio wave transmission unit 304 that transmits radio waves of the first frequency and the second frequency from the antenna 302, and a first frequency transmitted from the radio wave transmission unit 304 in the reference state. The reflected power of the first reflected wave, which is a reflected wave reflected by the foreign object sensor 200, and a part of the second frequency wave transmitted from the radio wave transmission unit 304 are reflected by the foreign object sensor 200. The foreign substance sensor 200 reflects a part of the first frequency radio wave transmitted from the storage unit 308 that stores the reflected power of the second reflected wave that is the reflected wave and the radio wave transmission unit 304. The third reflected wave, which is a reflected wave, and the fourth reflected wave, which is a reflected wave that is reflected by the foreign object sensor 200, are partly reflected by the antenna. The first difference is obtained by subtracting the reflected power of the first reflected wave and the reflected power of the second reflected wave from the reflected power of the third reflected wave and the reflected power of the fourth reflected wave. The determination unit 306 determines that there is a foreign object around the foreign object sensor 200 if the difference and the second difference have different signs.

  Note that a hygroscopic member may be used as the member of the reflective tag 202.

  In addition, the detection apparatus 300 according to the present embodiment includes an antenna 302, a radio wave transmission unit 304 that transmits radio waves of the first and second frequencies from the antenna 302, and a reference that is free of foreign matter around the foreign matter sensor 200. In the state, a part of the first frequency radio wave transmitted from the radio wave transmitting unit 304 is reflected from the first reflected wave, which is a reflected wave reflected by the foreign object sensor 200, and transmitted from the radio wave transmitting unit 304. A storage unit 308 that stores the reflected power of the second reflected wave, which is a reflected wave reflected by the foreign object sensor 200, with a part of the radio wave of the second frequency, and the first transmitted from the radio wave transmitting unit 304 Part of the second frequency wave transmitted from the third reflected wave and the radio wave transmission unit 304 is a reflected wave reflected by the foreign object sensor 200. A fourth reflected wave that is a reflected wave reflected by the first reflected wave is obtained from the antenna 302, and the reflected power of the first reflected wave and the second reflected wave are reflected from the reflected power of the third reflected wave and the reflected power of the fourth reflected wave. And a determination unit 306 that determines that there is a foreign object around the foreign object sensor 200 if the first difference and the second difference, which are differences obtained by subtracting the reflected power of the reflected waves, have different signs.

  Further, foreign matter sensor 200 according to the present embodiment includes an antenna 204, a resistance element 206 electrically coupled to antenna 204, and a reflective tag that is a substrate on which antenna 204 and resistance element 206 are arranged on the surface. 202.

  The foreign matter sensor 200 has a reflected power of a first reflected wave that is a reflected wave when the antenna 204 receives a radio wave of the first frequency in a reference state where no foreign matter is present around the foreign matter sensor 200. The reflected power of the second reflected wave, which is a reflected wave when the antenna 204 receives a radio wave of the second frequency in the first frequency region defined in advance including the first frequency, is received. The radio wave is reflected so as to have a maximum value within a second frequency range defined in advance including the second frequency.

  Here, if the first and second frequency regions are too wide, the possibility of overdetection of foreign matters increases, and if the first and second frequency regions are too narrow, the possibility of overlooking foreign matters increases. For example, the first frequency region includes the first frequency and is set to about 6 MHz before and after the first frequency region, and the second frequency region includes the second frequency and is set to about 6 MHz before and after the second frequency region.

  According to this configuration, when foreign matter is present around the foreign matter sensor 200 (for example, around several millimeters) without contact with foreign matter, the apparent dielectric constant of the reflective tag 202 changes, and as a result, the frequency characteristic of reflected power changes. To do.

  More specifically, the antenna 204 included in the foreign matter sensor 200 may be designed to have a shape in which two or more antennas having different lengths are connected in parallel.

  That is, if the antenna 204 is provided with two resonance points having different frequencies, there is a maximum point and a minimum point between them.

  Therefore, it is conceivable to design the antenna 204 as a shape in which two antennas whose resonance points are changed by changing the length are connected in parallel.

  Since the foreign matter sensor 200 described above only reflects radio waves and does not transmit radio waves by itself, a so-called wireless module is unnecessary. Therefore, the foreign object detection system 100 using the foreign object sensor 200 with a wireless communication function that is small, inexpensive, and consumes less power can be realized.

  Further, in foreign object detection system 100 according to the present embodiment, measurement can be performed using characteristics including a maximum value and a minimum value among frequency characteristics of reflected power, that is, only two frequencies. Therefore, there is no need to measure the spectrum of frequency characteristics, and there are advantages such as simplification of the detection device, cost reduction, and energy saving.

  Further, in the foreign object detection system 100 according to the present embodiment, since impedance matching (power loss due to resistance) between the load and the antenna is used for the design, a perfect reflection state and a perfect absorption state (theoretically transmission power Half absorbed). A larger reflected power change can be obtained. Specifically, the amount of change in the reflected power (the peak depth of the minimum point) can be controlled. As a result, it becomes easy to detect the reflected power change, and the detection accuracy of the foreign matter can be increased.

  The foreign object sensor 200 according to the present embodiment is similar to a so-called passive RFID in that communication is performed using a reflected wave without transmitting a radio wave by itself.

  However, since passive RFID returns ID information on a reflected wave, the tag needs to have an IC (Integrated Circuit). On the other hand, foreign object sensor 200 according to the present embodiment need only include an antenna and a resistance element for absorbing radio waves, and does not require an IC.

  In other words, the foreign matter sensor 200 does not require power for driving the IC required for the passive RFID.

  As a result, it is possible to extend the communication distance of the foreign matter sensor 200 as compared to the passive RFID, and to reduce the output of radio waves output by the detection device 300 (corresponding to a reader in the passive RFID).

More specifically, the maximum value of the communication distance by the passive RFID (that is, the communicable distance between the reader and the tag) can be obtained by Equation 1. Here, λ is the wavelength of the radio wave to be transmitted, P _TX is the transmission power of the _reader , G _reader is the antenna gain of the reader, G _tag is the antenna gain of _{the tag} , and P _{min, tag} Is the threshold power (sensitivity) of the tag.

On the other hand, the maximum value of the communication distance between the foreign matter sensor 200 and the detection apparatus 300 according to the present embodiment is obtained by Expression 2. Here, λ is the wavelength of the radio wave to be transmitted, P _TX is the transmission power of the detection apparatus 300, G _reader is the antenna gain of the detection apparatus 300, and G _tag is the antenna gain of the foreign object sensor 200. _Yes , P _{min, reader} is the sensitivity of the detection apparatus 300, and T _b is the backward spread transmission loss.

Assuming that the transmission frequency is 950 MHz, P _{min, tag} is −10 dBm, and P _{min, reader} is −80 dBm, from Equation 1, the communication distance of passive RFID is 6 m.

  On the other hand, the maximum value of the communication distance between the foreign matter sensor 200 and the detection apparatus 300 according to the present embodiment is 45 m from Equation 2.

  Since these are theoretical values, the communication distance actually varies depending on the matching state of the IC and the antenna, and the foreign object detection system 100 according to the present embodiment is compared with the conventional passive RFID. Long-distance communication is possible with low power consumption.

  The foreign object detection system 100, the detection device 300, and the foreign object sensor 200 according to the present embodiment have been described above.

  Next, a detection apparatus 300 according to a modification of the present embodiment will be described.

(Modification)
FIG. 10 is a block diagram of a foreign object detection system 100 including a detection device 300 according to this modification. Components similar to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this modification, the detection apparatus 300 further includes an antenna 303. The radio wave transmission unit 304 includes a first transmission unit 311 and a second transmission unit 312. The determination unit 306 includes a first reception unit 313 and a second reception unit 314.

  The antenna 302 and the antenna 303 are antennas that perform transmission of radio waves transmitted from the first transmission unit and the second transmission unit and reception of reflected waves, respectively.

  The first transmission unit 311 transmits a radio wave having a first frequency from the antenna 302.

  The second transmission unit 312 transmits a radio wave having the second frequency from the antenna 303.

  These transmissions may be performed, for example, at the timing when the user instructs the detection apparatus 300 to detect a foreign object, or may be performed periodically (for example, every several tens of seconds).

  Further, the first transmission unit 311 and the second transmission unit 312 may transmit radio waves at the same time, or may transmit radio waves at different times by several tens of milliseconds.

  The first reception unit 313 receives the reflected wave of the radio wave transmitted from the first transmission unit 311 using the antenna 302.

  The second reception unit 314 receives the reflected wave of the radio wave transmitted from the second transmission unit 312 using the antenna 303.

  The first receiving unit 313 and the second receiving unit 314 temporarily store the received reflected wave power in the storage unit 308.

  That is, the radio wave transmission unit 304 according to the present modification includes a first transmission unit 311 that transmits radio waves of a first frequency and a second transmission unit 312 that transmits radio waves of a second frequency, and the first transmission The unit 311 and the second transmission unit 312 transmit radio waves of the first frequency and the second frequency, respectively, at the same time.

  According to this modification, the detection apparatus 300 can transmit the radio wave of the first frequency and the radio wave of the second frequency to the foreign object sensor 200 at independent timings, and can receive the reflected wave.

  Therefore, the detection apparatus 300 can transmit the second reflected wave before the measurement of the reflected power of the first reflected wave is completed. More specifically, the detection device 300 can simultaneously transmit radio waves having the first frequency and the second frequency.

  As a result, even when the distance between the foreign matter sensor 200 and the detection device 300 constantly changes and the reflected power changes correspondingly, the reflected power of the first reflected wave and the second reflected wave at the same distance is changed. It can be measured. Therefore, the detection apparatus 300 can detect a foreign object more accurately.

  In the embodiment and the modification, when the frequency interval between the two types of radio waves transmitted by the detection device 300 is narrow, the determination unit 306 determines the change in reflected power due to the foreign material and the distance between the detection device 300 and the foreign material sensor 200. Therefore, it is difficult to distinguish the change in the reflected power due to the change in the number of foreign matters, and overdetection of foreign matters is likely to occur. This will be described in more detail with reference to FIGS.

  In FIG. 6, the reflected power indicated by the graph 451 increases at the frequency f1 and decreases at the frequency f2, compared with the reference state 450. As summarized in FIG. 7C, the determination unit 306 determines whether or not the reflected power increases for one of the two frequencies and decreases for the other frequency. Thus, it is possible to determine whether the change in the reflected power is due to a foreign matter or a change in distance.

  However, for example, in the relationship between the graph 450 and the graph 490 illustrated in FIG. 11, the graph 490 is a graph in which the graph 450 which is the reference state is shifted to the left due to a change in the dielectric constant of the reflective tag 202. The value of the reflected power decreases for both frequency f1 and frequency f2.

  That is, when the difference between the frequencies f1 and f2 is small and the amount of change in the dielectric constant of the reflection tag 202 due to foreign matter is large, the determination unit 306 may overdetect the foreign matter. In particular, when the difference between the frequencies f1 and f2 is small (the interval is narrow), it can be said that foreign matter is easily detected excessively.

  In order to avoid this, it is necessary to appropriately separate the frequencies f1 and f2 in accordance with the assumed change in dielectric constant (that is, the type and amount of foreign matter to be detected by the detection device 300).

  More specifically, for example, f1 may be set to 940 MHz and f2 may be set to 2.45 GHz.

  Note that the frequency characteristic of the reflected power of the foreign object sensor 200 may not be a shape in which a plurality of straight lines are combined as shown in FIG. 6, for example. For example, a shape in which a downwardly convex curve having a minimum point and an upwardly convex curve having a maximum point are combined, and one reflected power is determined for one frequency.

  The frequency characteristic of the reflected power of the reflection tag 202 does not necessarily have one local maximum point and one local minimum point. However, in the range where the frequency characteristic can be changed by a foreign object to be detected, it is necessary to have one local maximum point and one local minimum point.

  For example, in FIG. 6, the frequency characteristic of the reflected power when water (dielectric constant 80), which is a foreign substance to be detected, is in contact with the reflective tag 202 is shown by a graph 451. When it is known that the upper dielectric constant does not increase (for example, when the reflective tag 202 is in contact with a sufficient amount of water), the frequency characteristic of the reflected power from the foreign matter sensor 200 is represented by a graph 451. It is sufficient that there is no inflection point other than one maximum point between the minimum point and the point 418.

  In the present embodiment, a state without foreign matter is used as the reference state, but a state with a specific foreign matter may be used as the reference state. For example, it is possible to detect that there is no water as a foreign object by detecting a deviation from the maximum point and the minimum point of the reflected power of the submerged reflection tag 202.

  In this embodiment, as an example of the foreign matter, description has been made using water having a dielectric constant larger than a value (about 10 or less) assumed as the dielectric constant of the reflective tag 202, but the presence or absence of a substance having a smaller dielectric constant is present. Can also be detected.

  In addition to simply detecting the presence or absence of foreign matter, it is also possible to measure the value of the dielectric constant by evaluating the magnitude of the reflected power deviation. That is, the determination unit 306 included in the detection device 300 further includes a dielectric constant calculation unit, and the dielectric constant calculation unit detects the dielectric constant by calculating the dielectric constant as the first difference and the second difference are larger. The device 300 can calculate the magnitude of the dielectric constant.

  Note that the detection apparatus 300 described in the embodiment and the modifications can be realized by a computer. Referring to FIG. 12, the detection apparatus 300 includes a computer 34, a keyboard 36 and a mouse 38 for giving instructions to the computer 34, a display 32 for presenting information such as calculation results of the computer 34, and the computer 34. A CD-ROM (Compact Disc-Read Only Memory) device 40 and a communication modem (not shown) are included.

  A program that is processing performed by the detection device 300 is stored in the CD-ROM 42 that is a computer-readable medium, and is read by the CD-ROM device 40. Alternatively, the data is read by the communication modem 52 through a computer network.

  FIG. 13 is a block diagram illustrating a hardware configuration of a computer system that implements the detection apparatus 300. The computer 34 includes a CPU (Central Processing Unit) 44, a ROM (Read Only Memory) 46, a RAM (Random Access Memory) 48, a hard disk 50, a communication modem 52, and a bus 54.

  The CPU 44 executes a program read via the CD-ROM device 40 or the communication modem 52. The ROM 46 stores programs and data necessary for the operation of the computer 34. The RAM 48 stores data such as parameters at the time of program execution. The hard disk 50 stores programs and data. The communication modem 52 communicates with other computers via a computer network. The bus 54 connects the CPU 44, the ROM 46, the RAM 48, the hard disk 50, the communication modem 52, the display 32, the keyboard 36, the mouse 38, and the CD-ROM device 40 to each other.

  Furthermore, some or all of the constituent elements constituting each of the above-described devices may be configured by one system LSI (Large Scale Integration). The system LSI is an ultra-multifunctional LSI manufactured by integrating a plurality of components on a single chip, and specifically, a computer system including a microprocessor, ROM, RAM, and the like. . A computer program is stored in the RAM. The system LSI achieves its functions by the microprocessor operating according to the computer program.

  Furthermore, some or all of the constituent elements constituting each of the above-described devices may be configured from an IC card that can be attached to and detached from each device or a single module. The IC card or module is a computer system that includes a microprocessor, ROM, RAM, and the like. The IC card or the module may include the super multifunctional LSI described above. The IC card or the module achieves its function by the microprocessor operating according to the computer program. This IC card or this module may have tamper resistance.

  Further, the present invention may be the method described above. Further, the present invention may be a computer program that realizes these methods by a computer, or may be a digital signal composed of the computer program.

  Furthermore, the present invention provides a computer-readable recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray Disc). (Registered trademark)), a memory card such as a USB memory or an SD card, or a semiconductor memory. Further, the digital signal may be recorded on these recording media.

  Further, the present invention may transmit the computer program or the digital signal via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.

  The present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program.

  In addition, the program or the digital signal is recorded on the recording medium and transferred, or the program or the digital signal is transferred via the network or the like and executed by another independent computer system. You may do that.

  Furthermore, the above embodiment and the above modification examples may be combined.

  The embodiments and modifications disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to a foreign object detection system, a detection device, and a foreign object detection sensor.

32 Display 34 Computer 36 Keyboard 38 Mouse 40 CD-ROM device 42 CD-ROM
44 CPU
46 ROM
48 RAM
50 Hard disk 52 Communication modem 54 Bus 100 Foreign matter detection system 200 Foreign matter sensors 204, 302, 303 Antenna 202 Reflection tag 204 Antenna 206 Resistance element 300 Detection device 304 Radio wave transmission unit 306 Determination unit 308 Storage unit 311 First transmission unit 312 Second transmission Unit 313 first receiving unit 314 second receiving unit 401, 402, 403, 415, 420, 422 minimum point 417, 421, 423 maximum point 416, 418 point 410, 411, 450, 451, 452, 454, 460, 461 , 462, 490 Graph 601 Foreign object 700, 701 Trainee 702 Trainer

Claims (10)

A foreign matter sensor;
A foreign matter detection system comprising a detection device for detecting the presence or absence of foreign matter around the foreign matter sensor,
The foreign matter sensor is
A first antenna;
A resistive element electrically coupled to the first antenna;
A reflection tag that is a substrate on which the first antenna and the resistance element are arranged;
In a reference state in which there is no foreign matter around the foreign matter sensor, the reflected power of the first reflected wave that is a reflected wave when a radio wave having a first frequency is received by the first antenna is the first reflected wave. The reflected power of the second reflected wave, which is a reflected wave when the first antenna receives a radio wave of the second frequency and takes a local minimum value within the first frequency region defined in advance including the frequency, Reflect the radio wave so that it takes a maximum value within a predefined second frequency range including the second frequency,
The detection device includes:
A second antenna;
A radio wave transmitter that transmits radio waves of the first frequency and the second frequency from the second antenna;
In the reference state, the reflected power of the first reflected wave, which is a reflected wave reflected by the foreign object sensor, is a part of the first frequency radio wave transmitted from the radio wave transmitter, and from the radio wave transmitter. A storage unit storing a reflected power of a second reflected wave, which is a reflected wave reflected by the foreign object sensor, in which part of the transmitted radio wave of the second frequency is reflected;
A third reflected wave, which is a reflected wave reflected by the foreign object sensor, and a part of the second frequency transmitted from the radio wave transmitter are transmitted from the radio wave transmitter. A fourth reflected wave, which is a reflected wave reflected by the foreign object sensor, is obtained from the second antenna, and the reflected power of the third reflected wave and the reflected power of the fourth reflected wave are acquired from the second antenna. If the signs of the first difference and the second difference, which are differences obtained by subtracting the reflected power of the first reflected wave and the reflected power of the second reflected wave, are different, the foreign object is present around the foreign object sensor. A foreign matter detection system comprising a determination unit for determining The radio wave transmitter is
A first transmitter that transmits radio waves of the first frequency;
A second transmitter that transmits radio waves of the second frequency,
The foreign object detection system according to claim 1, wherein the first transmission unit and the second transmission unit transmit radio waves of the first frequency and the second frequency, respectively, at the same time. The foreign object detection system according to claim 1, wherein the reflective tag is configured by a hygroscopic member. A detection device for detecting the presence or absence of foreign matter around the foreign matter sensor,
An antenna,
A radio wave transmitter that transmits radio waves of the first and second frequencies from the antenna;
In a reference state in which there is no foreign object around the foreign object sensor, a first reflected wave that is a reflected wave reflected by the foreign object sensor is a part of the first frequency radio wave transmitted from the radio wave transmitter. And a reflected power of the second reflected wave, which is a reflected wave reflected by the foreign matter sensor, in part of the second frequency radio wave transmitted from the radio wave transmitter. And
A third reflected wave, which is a reflected wave reflected by the foreign object sensor, and a part of the second frequency transmitted from the radio wave transmitter are transmitted from the radio wave transmitter. A fourth reflected wave, which is a reflected wave reflected by the foreign object sensor, is acquired from the antenna, and the first reflected wave is reflected from the reflected power of the third reflected wave and the reflected power of the fourth reflected wave. If the sign of the first difference and the second difference, which are differences obtained by subtracting the reflected power of the first reflected wave and the reflected power of the second reflected wave, is different, it is determined that the foreign object exists around the foreign object sensor. And a determination unit. The radio wave transmitter is
A first transmitter that transmits radio waves of the first frequency;
A second transmitter that transmits radio waves of the second frequency,
The detection device according to claim 4, wherein the first transmission unit and the second transmission unit transmit radio waves of the first frequency and the second frequency, respectively, at the same time. The determination unit
The detection device according to claim 4, wherein if the product of the first difference and the second difference has the same sign, it is determined that the distance between the foreign matter sensor and the detection device has changed. An antenna,
A resistive element electrically coupled to the antenna;
A foreign matter sensor comprising a reflective tag that is a substrate on which the antenna and the resistive element are arranged on a surface,
In a reference state where there is no foreign matter around the foreign matter sensor, the reflected power of the first reflected wave, which is a reflected wave when a radio wave of the first frequency is received by the antenna, is the first frequency. The reflected power of the second reflected wave, which is a reflected wave when the antenna receives a radio wave of the second frequency and takes a local minimum value in the first frequency region defined in advance, includes the second frequency. A foreign object sensor that reflects radio waves so as to have a maximum value within a second frequency range defined in advance. The foreign matter sensor according to claim 7, wherein the antenna has a shape in which two or more antennas having different lengths are connected in parallel. The foreign matter sensor according to claim 7, wherein the reflective tag is formed of a hygroscopic member. A foreign matter detection method for detecting the presence or absence of foreign matter around a foreign matter sensor,
A radio wave transmitting step of transmitting radio waves of the first and second frequencies;
In a reference state where there is no foreign matter around the foreign matter sensor, the reflected power of the first reflected wave, which is a reflected wave reflected by the foreign matter sensor, part of the first frequency radio wave, and the second A storage step of storing a reflected power of a second reflected wave, which is a reflected wave reflected by the foreign matter sensor, with a part of a radio wave having a frequency of
A third reflected wave, which is a reflected wave reflected by the foreign object sensor, and a reflected wave where a part of the second frequency wave is reflected by the foreign object sensor. The fourth reflected wave is acquired, and the reflected power of the first reflected wave and the reflected power of the second reflected wave are respectively obtained from the reflected power of the third reflected wave and the reflected power of the fourth reflected wave. A foreign matter detection method comprising: a step of determining that the foreign matter is present around the foreign matter sensor if signs of the first difference and the second difference as subtracted differences are different.

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