Control system

Abstract

Provided is a control system that suppresses power consumption and is highly convenient. A control system (1), which is mounted in a vehicle and controls communication with a communicator present around the vehicle, is provided with: a detection unit (20) that generates an electromagnetic field around an antenna (10) in a first mode in which operation is performed under a preset first condition, and that detects a disorder in the electromagnetic field on the basis of a change in impedance of the antenna (10); a communication unit (30) that outputs information to a communicator associated with the vehicle to the surroundings of the vehicle by means of short-range wireless communication when the disorder is detected; and a counting unit (40) that counts the number of times the information has been output even if the communication unit (30) has output the information but has no response to the information, and that counts the number of times the information has been output if the counting result of the counting unit (40) exceeds a preset number within a preset first time period. The detection unit (20) shifts to a second mode in which the detection unit (20) operates under a second condition in which power consumption is lower than that of the first condition.

Description

Technical Field

[0001] The present invention relates to a control system which is mounted on a vehicle and controls communication with a communicator existing around the vehicle. Background Art

[0002] Conventionally, the following technology has been used: based on the disturbance of the magnetic field, the presence of a communicator is detected around the vehicle, and when the presence of the communicator is detected, the vehicle switches to a communication state in which the vehicle communicates with the communicator.

[0003] Patent document 1 describes a door handle device provided on a door handle of a vehicle. The door handle device includes an antenna and an NFC reader disposed on the handle portion. The antenna generates a magnetic field around it, and the NFC reader detects disturbances in the magnetic field. The NFC reader is configured to shift from a power saving operation state to an active operation state in response to the proximity of an NFC tag.

[0004] Patent document 2 describes a vehicle authentication system. The vehicle authentication system includes an onboard device mounted on a vehicle and an electronic key held by a user of the vehicle. Authentication is performed by wireless communication between the onboard device and the electronic key, and when the user leaves the vehicle, if there is an intentional operation by the user, the authentication is stopped for a certain period of time.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent document 1: U.S. Patent Application Publication No. 2021 / 0370877.

[0008] Patent document 2: Japanese Patent Application Publication No. 2016-79600.

[0009] In the door handle device described in Patent Document 1, when a metal object different from the NFC tag approaches due to a prank, the magnetic field is disturbed, and the NFC reader switches to an active operation state. In addition, when the magnetic field is disturbed in an EMI environment, the NFC reader also switches to an active operation state. In this way, even if the NFC reader cannot communicate, unnecessary communication will be performed if it is in an active operation state, thereby increasing power consumption.

[0010] In addition, in the vehicle authentication system described in Patent Document 2, if the user wants to lock and unlock the vehicle earlier than originally expected, a different operation is required, so the convenience is poor. In addition, after a certain period of time, the authentication can be restarted, so the dark current increases. Summary of the invention

[0011] Therefore, a control system capable of suppressing power consumption is required.

[0012] The characteristic structure of the control system involved in the present invention lies in the following point, that is, a control system is installed in a vehicle, controls the communication with the communicator existing in the vicinity of the vehicle, wherein it comprises: a detection unit, which generates an electromagnetic field around the antenna in a first mode operating under a predetermined first condition, and detects the disturbance of the electromagnetic field based on the change of the impedance of the antenna; a communication unit, which outputs information directed to the communicator associated with the vehicle to the vicinity of the vehicle through short-range wireless communication when the disturbance is detected; and a counting unit, which counts the number of times the information is output when there is no response to the information even though the communication unit outputs the information, and when the counting result of the counting unit within the predetermined first time exceeds the predetermined number, the detection unit shifts to a second mode operating under a second condition with lower power consumption than the first condition.

[0013] If such a characteristic structure is used, when the detection unit detects the disturbance of the electromagnetic field, although the communication unit outputs information to the communicator through short-range wireless communication, if there is no response to the information within the first time, the operation of the detection unit can be transferred to the operation in the second mode with reduced power consumption. Therefore, when there is no response to the information within the first time, power consumption can be suppressed. Moreover, when there is no response to the information within the first time, the counting by the counting unit can be used to prevent the false detection of the approach of metal objects different from the NFC tag due to pranks, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A diagram showing a vehicle equipped with a control system.

[0015] Figure 2 It is a block diagram showing the structure of a control system.

[0016] Figure 3 It is a timing diagram showing the operation of the control system.

[0017] Figure 4 It is a flowchart which shows the process of a control system.

[0018] Figure 5 This is a flowchart showing the process of transitioning to the first mode (recovery process).

[0019] Explanation of symbols

[0020] 1: control system, 2: vehicle, 3: smart key (communicator), 10: antenna, 20: detection unit, 30: communication unit, 40: counting unit. DETAILED DESCRIPTION

[0021] The control system involved in the present invention is configured to control communication with a communicator existing around a vehicle. The control system 1 of this embodiment is described below. However, the control system 1 is not limited to the following embodiment, and various modifications can be made within the scope of the gist thereof.

[0022] Figure 1 2 is a diagram showing a vehicle 2 equipped with a control system 1. Figure 1 As shown, the control system 1 is provided on the door handle 4 of the vehicle 2. The control system 1 of the present embodiment detects a smart key (an example of a "communicator") 3 present around the vehicle 2. The smart key 3 is a key corresponding to the vehicle 2, and by pressing the lock / unlock switch of the smart key 3 or touching a specified part of the door, the locking mechanism of the door of the vehicle 2 can be set to a locked state or an unlocked state. In addition, when the communicator is a portable terminal such as a smart phone, it can also be locked and unlocked by an application operation.

[0023] Next, the configuration of the control system 1 will be described. Figure 2 Schematic diagram showing the structure of the control system 1. Figure 2 As shown, the control system 1 includes an antenna 10 , a detection unit 20 , a communication unit 30 , and a counting unit 40 . Each functional unit is constructed by hardware or software or both with a CPU as a core component to perform processing related to communication with the smart key 3 .

[0024] The antenna 10 is powered from a power supply unit (not shown) to generate an electromagnetic field around the antenna 10. In the present embodiment, the antenna 10 is powered so that an electromagnetic field is periodically generated around the antenna 10 with a period of several hundred milliseconds.

[0025] The antenna 10 is configured to be able to switch the operating state (the operation of generating an electromagnetic field) between a first mode and a second mode. The first mode is a mode in which the antenna 10 operates under a first condition that is set in advance. The first condition specifies the power supplied to the antenna 10, the generation cycle of the electromagnetic field from the antenna 10, and the like. On the other hand, the second mode is a mode in which the antenna 10 operates under a second condition that reduces power consumption compared to the first mode. The so-called "reduced power consumption compared to the first mode" means that the antenna 10 is powered with a power smaller than the power specified in the first condition. The so-called "power smaller than the power specified in the first condition" can mean that the power supplied itself is small, or that the power supply cycle is long. Therefore, the second condition specifies a power smaller than the power specified in the first condition and a long power supply cycle. Of course, in the second condition, only one of the power and the power supply cycle can be specified.

[0026] The detection unit 20 detects the disturbance of the electromagnetic field based on the change of the impedance of the antenna 10. As described above, an electromagnetic field is periodically generated around the antenna 10. If a metal body including the smart key 3 exists in the area where the electromagnetic field is generated, the electromagnetic field is disturbed. If such an electromagnetic field is disturbed, the impedance of the antenna 10 changes. The detection unit 20 detects the disturbance of the electromagnetic field based on such a change of impedance, and when the disturbance is detected, the detection information indicating the detection of the disturbance of the electromagnetic field is transmitted to the communication unit 30 described later. The disturbance of the electromagnetic field caused by the presence of the metal body will occur even when the battery of the smart key 3 is exhausted, so it is highly convenient.

[0027] When the disturbance of the electromagnetic field is detected, the communication unit 30 outputs information directed to the smart key 3 associated with the vehicle 2 to the vicinity of the vehicle 2 through short-range wireless communication. As described above, when the detection unit 20 detects the disturbance of the electromagnetic field, the detection information indicating the detection of the disturbance of the electromagnetic field is transmitted to the communication unit 30. The smart key 3 associated with the vehicle 2 is a smart key 3 capable of operating the locking mechanism of the door of the vehicle 2. The so-called information is information that can switch the locking mechanism from one of an unlocked state and a locked state to the other. Specifically, it is equivalent to an electronic lock. Here, the communication unit 30 outputs information from the antenna 10 that has generated the disturbance. The so-called short-range wireless communication is specifically equivalent to NFC (near field communication).

[0028] When the smart key 3 obtains the information output by the communication unit 30, the smart key 3 responds to the information, and the communication unit 30 checks whether the smart key 3 is associated with the vehicle 2. If the check result indicates that the smart key 3 is associated with the vehicle 2, the communication unit 30 continues to communicate with the smart key 3. On the other hand, if the check result does not indicate that the smart key 3 is associated with the vehicle 2, the communication unit 30 ends the communication with the smart key 3.

[0029] As described above, the detection object detected by the detection unit 20 is the disturbance of the electromagnetic field, which is caused not only by the presence of the smart key 3 but also by the presence of the metal body. If the smart key 3 obtains information from the communication unit 30, it will respond to the information, but the metal body will not respond even if the information from the communication unit 30 arrives. In addition, even if the smart key 3 is another smart key that is not associated with the vehicle 2, it cannot properly respond to the information from the communication unit 30. Therefore, in the case where there is no response to the information even though the communication unit 30 outputs the information, the counting unit 40 counts the number of times the communication unit 30 outputs the information. The number of times the information is output is equivalent to the number of times the communication unit 30 fails to communicate. Therefore, the counting unit 40 counts the number of times the communication unit 30 fails to communicate. The counting result of the counting unit 40 is transmitted to the detection unit 20.

[0030] The number of times the communication unit 30 fails in communication may be counted only when TD (Technology Detection) in the NFC Forum fails, or may be counted when both TD and CR (Collision Resolution) in the NFC Forum fail.

[0031] When the counting result of the counting unit 40 within the preset first time exceeds the preset number, the detection unit 20 shifts to the second mode. The preset first time can be appropriately changed, but as mentioned above, although there is no response to the information, if the communication unit 30 continues to output the information, the power is wasted. Therefore, the first time can be set based on the power consumption of the communication unit 30 and the capacity of the battery that serves as the power supply for the communication unit 30 to output the information. The first time can be set to, for example, tens of seconds (for example, about 30 seconds). When the number of communication failures of the communication unit 30 during the first time exceeds the preset number, it shifts to the second mode that operates under the second condition that reduces the power consumption compared to the first mode.

[0032] When the detection unit 20 is transferred to the second mode, the generation of the electromagnetic field is terminated within a pre-set second time. The second time can be set to, for example, a few minutes (for example, about 5 minutes). Even in the case of communication failure of the communication unit 30 as described above, if there is a metal body in the range of the electromagnetic field generation or a smart key that is not associated with the locking mechanism of the vehicle 2, the detection of electromagnetic field disturbance by the detection unit 20 and the communication by the communication unit 30 are continued. Therefore, by terminating the generation of the electromagnetic field, the failure of communication can be eliminated and the power consumption required for communication within the specified time can be reduced.

[0033] The detection unit 20 measures the disturbance of the electromagnetic field within a preset third time after the second time. If the disturbance is detected within the third time, it determines whether there is a response to the information output from the communication unit 30 based on the detected disturbance of the electromagnetic field. If there is a response to the information output from the communication unit 30, the action in the first mode is transferred, and if there is no response to the information, the action in the second mode is continued. The third time can be a time of the same degree as the first time mentioned above. Of course, the third time can be longer or shorter than the first time. In addition, the detection unit 20 can also be configured to measure the disturbance of the electromagnetic field within the third time, and if the disturbance is detected within the third time, it determines whether the disturbance is continuing based on the detected disturbance. In such a structure, if the disturbance of the electromagnetic field is not detected, there is no possibility of an increase in current consumption caused by false detection, so it can be configured to prepare for the use of the device (card, smart key in this text) of the next user and transfer to the action in the first mode.

[0034] In addition, it is also possible to determine whether the disturbance of the magnetic field caused by the surrounding environment is continuing by driving the antenna of the communication unit 30. Specifically, when the number of disturbances detected in the antenna driving of the communication unit 30 is less than the specified number of times after multiple implementations, it is determined that the disturbance of the electromagnetic field is not continuing, and when the number of disturbances detected in the antenna driving of the communication unit 30 is more than the specified number of times after multiple implementations, it is determined that the disturbance of the electromagnetic field is continuing. In addition, in such a determination, when the disturbance of the electromagnetic field is detected, the action in the second mode can also be continued without transferring to the communication (TD, CR in NFC Forum) performed by the communication unit 30. In such a determination, the structure of not transferring to the communication performed by the communication unit 30 when the disturbance of the electromagnetic field is detected is compared with the structure in which the communication unit 30 outputs information to the smart key 3 through short-range wireless communication when the above-mentioned disturbance of the electromagnetic field is detected. The power consumption reduction effect is high, so it is preferred. In addition, at this time, if the third time is set to, for example, hundreds of milliseconds (for example, about 100 milliseconds-500 milliseconds), the power consumption reduction effect is higher, so it is preferred.

[0035] When the detection unit 20 continues the operation in the second mode, it is preferable to stop the generation of the electromagnetic field for a time longer than the second time. This can further reduce power consumption.

[0036] Next, use Figure 3 The operation of the control system 1 will be described using a timing chart. Figure 3 2 is a timing diagram when the detection unit 20 and the communication unit 30 are driven based on the NFC standard (hereinafter referred to as "NFC drive"). First, in order to use the antenna 10 as an inductive sensor for detecting the presence or distance of an object, calibration (#1) is performed (in Figure 3 After the calibration is completed, the low-power card detection function is used to send signals in a 200-millisecond cycle (#2-#5). One transmission can be around tens of microseconds. In addition, the "card" in the "low-power card detection function" includes not only cards but also smart devices.

[0037] For example, regarding the transmission in #6, when the detection unit 20 detects disturbance of the electromagnetic field, the communication unit 30 outputs information via NFC (#7) (in Figure 3 In the case of no response to the output information, the NFC communication is deemed to have failed, and calibration is performed again (#8). When the calibration is completed, the low-power card detection function is used to send a signal again (#9). When the detection unit 20 detects the disturbance of the electromagnetic field, the communication unit 30 outputs information through NFC (#10). This calibration, the sending of signals through the low-power card detection function, and the sending of information by the communication unit 30 are repeated. If the number of communication failures within the preset first time exceeds the preset number (in Figure 3 In the example, 4 times), the NFC drive is stopped within the second time.

[0038] When the second time has passed, NFC driving is performed within a third time, that is, calibration is performed (#17) and transmission is performed (#18, #19).

[0039] Next, use Figure 4 The processing of the control system 1 is described with reference to the flowchart of FIG. First, calibration is performed (step #100). When the calibration is completed, detection by the antenna 10 is started (step #101). Specifically, the signal is transmitted through the low-power card detection function. When the detection unit 20 does not detect the disturbance of the magnetic field (step #102: No), the detection by the antenna 10 is continued (#101).

[0040] When the detector 20 detects disturbance of the magnetic field (step #102: Yes), the communication unit 30 outputs information (#103). If there is a response to the output information (step #104: Yes), communication is performed (step #105) and continues until the communication is terminated (step #106: Yes).

[0041] In step #104, if there is no response to the output information (step #104: No), the counting unit 40 counts the number of times the information has been output (step #107). If the counting result of the counting unit 40 within the first time exceeds the preset number (prescribed value) (step #108: Yes), the detection by the antenna 10 is suspended during the second time (step #109). In the case of restarting the detection by the antenna 10 (step #110: Yes), the process returns to step #100 to continue. In the case of not restarting the detection by the antenna 10 (step #110: No), the process returns to step #109 to continue. In addition, in step #108, if the counting result of the counting unit 40 within the first time is less than the preset number (prescribed value) (step #108: No), the process returns to step #100 to continue. The process is performed according to the above flow.

[0042] Next, use Figure 5 The flowchart of will explain the transition from the second mode to the first mode (recovery process). As described above, when the counting result of the counting unit 40 within the preset first time exceeds the preset number, the detection unit 20 transitions to the second mode. When the detection unit 20 is performing detection in such a second mode (step #200), if there is a recovery trigger (step #201: yes) and the recovery trigger comes from the upper system (step #202: yes), the detection unit 20 transitions to the first mode (step #203).

[0043] In step #201, if there is no recovery trigger (step #201: No), detection in the second mode is continued (step #200). In addition, in step #202, if the recovery trigger is not from the upper system (step #202: No), calibration is performed (step #204) and detection is performed using antenna 10 (step #205).

[0044] If the electromagnetic field disturbance is detected by the detector 20 (step #206: Yes) and the number of detections is greater than the specified value (step #207: Yes), the process returns to step #200 to continue. On the other hand, if the number of detections is less than the specified value (step #207: No), the process shifts to the first mode (step #203).

[0045] In addition, in step #206, if the electromagnetic field disturbance is not detected by the detection unit 20 (step #206: No) and the number of detections performed by the antenna 10 is greater than the specified value (step #208: Yes), the process is transferred to the first mode (step #203). On the other hand, if the number of detections performed by the antenna 10 is less than the specified value (step #208: No), the process returns to step #205 and continues processing.

[0046] Here, the so-called recovery trigger of step #201 is, for example, information indicating the approach / contact of a person from an electrostatic sensor provided on the door handle 4. In this case, the information can be directly transmitted from the electrostatic sensor to the control unit (not shown) of the control system 1, or the information can be transmitted from the electrostatic sensor to the control unit of the locking mechanism, and from the control unit of the locking mechanism or other control units to the control unit of the control system 1. Moreover, the control unit of the locking mechanism or other control units can also be polled. In addition, the recovery trigger can also be set to the operation of a locking switch or an unlocking switch provided with a smart key 3. In addition, in the case of operating the locking mechanism using a digital key, it can also be set to a locking instruction or an unlocking instruction based on the digital key.

[0047] When the electrostatic sensor provided on the door handle 4 detects the approach / contact of a person (for example, when the user holds the unlocking sensor), the function can be naturally restarted (i.e., the low-power card detection function can be automatically restarted) when the user gets into the vehicle, thereby improving convenience.

[0048] In addition, although the communication unit 30 implements TD in the communication based on NFC, if there is no response to the TD, it can be regarded as an erroneous detection and processed. In addition, if there is a response to the TD, CR can be implemented, and if the card type is a specific type (such as "T4AT"), the processing is continued, and if it is not a specific type (such as "T2T"), it is regarded as an erroneous detection and processed.

[0049] [Other implementation methods]

[0050] Next, other embodiments of the control system 1 will be described.

[0051] In the above embodiment, it is described that the detection unit 20 stops the generation of the electromagnetic field within the preset second time when the second mode is transferred, but the detection unit 20 may also lengthen the generation cycle of the electromagnetic field within the preset second time when the second mode is transferred. Alternatively, the threshold for detecting the disturbance of the electromagnetic field may be changed. Even in this case, power consumption can be reduced.

[0052] In the above embodiment, the detection unit 20 detects the disturbance of the electromagnetic field within the third time after the second time has passed, and when there is a response to the information output from the communication unit 30 based on the disturbance of the electromagnetic field detected within the third time, the operation is transferred to the first mode, and when there is no response to the information, the operation is continued in the second mode. The detection unit 20 may also be configured to detect the disturbance of the electromagnetic field within the third time after the second time has passed, and transfer to the operation in the first mode regardless of whether there is a response to the information output from the communication unit 30 based on the disturbance of the electromagnetic field detected within the third time.

[0053] In the above embodiment, the detection unit 20 suspends the generation of the electromagnetic field for a time longer than the second time while continuing the operation in the second mode. However, the detection unit 20 may also be configured to extend the generation cycle of the electromagnetic field for a time longer than the second time while continuing the operation in the second mode.

[0054] In the above-mentioned embodiment, the example in which the communication device is the smart key 3 is described, but the communication device may be a card key or a portable terminal such as a smart phone.

[0055] [Overview of the above-mentioned embodiment]

[0056] Hereinafter, the outline of the control system 1 described above will be described.

[0057] (1) A control system 1 is mounted on a vehicle 2 and controls communication with a smart key 3 (communicator) present in the vicinity of the vehicle 2. The control system 1 is configured to include: a detection unit 20 which generates an electromagnetic field in the vicinity of an antenna 10 in a first mode operating under a first condition set in advance and detects disturbance of the electromagnetic field based on a change in the impedance of the antenna 10; a communication unit 30 which, when disturbance is detected, outputs information directed to the smart key 3 associated with the vehicle 2 to the vicinity of the vehicle 2 through short-range wireless communication; and a counting unit 40 which, when there is no response to the information despite the output of the information by the communication unit 30, counts the number of times the information is output, and when the count result of the counting unit 40 within the first time set in advance exceeds a predetermined number, the detection unit 20 shifts to a second mode operating under a second condition which reduces power consumption compared to the first condition.

[0058] According to this structure, when the detection unit 20 detects the disturbance of the electromagnetic field, although the communication unit 30 outputs information to the smart key (communicator) 3 through short-range wireless communication, if there is no response to the information within the first time, the action of the detection unit 20 can be transferred to the action in the second mode with reduced power consumption. Therefore, if there is no response to the information within the first time, power consumption can be suppressed. Moreover, if there is no response to the information within the first time, a simple structure such as counting by the counting unit 40 can be used to prevent erroneous detection of metal objects approaching the NFC tag due to pranks, etc.

[0059] (2) In the control system 1 described in (1), preferably, when the detection unit 20 shifts to the second mode, the detection unit 20 stops the generation of the electromagnetic field or lengthens the generation cycle of the electromagnetic field for a preset second time.

[0060] According to this configuration, in the second mode, the detection unit 20 stops generating the electromagnetic field or lengthens the generation cycle of the electromagnetic field, thereby reducing power consumption compared to the case where the detection unit 20 continues generating the electromagnetic field or does not change the generation cycle of the electromagnetic field.

[0061] (3) The control system 1 described in (2) is preferably configured such that the detection unit 20 measures the disturbance of the electromagnetic field within a predetermined third time after the second time has passed. When the disturbance is detected within the third time, it is determined whether the disturbance is continuing based on the detected disturbance. When it is determined that the disturbance is continuing, the communication unit 30 does not communicate and continues the operation in the second mode. When it is determined that the disturbance is not continuing, the communication unit 30 switches to the operation in the first mode.

[0062] According to this structure, when electromagnetic field disturbance is not detected, there is no possibility of increased current consumption due to false detection, so the use of the device (card, smart key in this article) of the next user can be prepared. On the other hand, when electromagnetic field disturbance is continuously detected, the operation in the second mode is continued, so that power consumption can be continuously reduced.

[0063] Furthermore, when disturbance of the electromagnetic field is detected during the determination, the communication may not be switched to communication (TD, CR in NFC Forum) by the communication unit 30. In this case, the power consumption required for communication can be further reduced.

[0064] (4) In the control system 1 described in (3), it is preferred that, when it is determined that the disorder is continuing, the operation in the second mode is continued, and when the operation in the second mode is continued, the generation of the electromagnetic field is terminated for a time longer than the second time or the generation cycle of the electromagnetic field is lengthened.

[0065] According to this configuration, power consumption can be further reduced, thereby improving the power saving effect.

[0066] Industrial Applicability

[0067] The technology according to the present invention can be used in a control system that is mounted on a vehicle and controls communication with a communication device that exists around the vehicle.

Claims

1. A control system mounted on a vehicle, for controlling communication with a communicator existing around the vehicle, wherein: have: a detection unit that generates an electromagnetic field around an antenna in a first mode that operates under a first condition set in advance, and detects disturbance of the electromagnetic field based on a change in impedance of the antenna; a communication unit that outputs information directed to a communicator associated with the vehicle to the periphery of the vehicle through short-range wireless communication when the turbulence is detected; and a counting unit that counts the number of times the information has been output when there is no response to the information even though the communication unit has output the information, When the count result of the counting unit within a preset first time exceeds a preset number, the detection unit shifts to a second mode in which the detection unit operates under a second condition in which power consumption is reduced compared to the first condition.

2. The control system according to claim 1, wherein: When the detection unit shifts to the second mode, the detection unit stops the generation of the electromagnetic field or lengthens the generation cycle of the electromagnetic field for a preset second time.

3. The control system according to claim 2, wherein: It is composed of The detection unit measures the disturbance of the electromagnetic field within a preset third time after the second time has passed, and if the disturbance is detected within the third time, determines whether the disturbance is continuing based on the detected disturbance, If it is determined that the disturbance is continuing, the communication unit does not perform communication and continues the operation in the second mode. If it is determined that the disturbance is not continuing, the communication unit shifts to the operation in the first mode.

4. The control system according to claim 3, wherein: When it is determined through the determination that the disturbance is continuing, the detection unit continues the operation in the second mode. When continuing the operation in the second mode, the detection unit stops the generation of the electromagnetic field for a time longer than the second time or lengthens the generation cycle of the electromagnetic field.

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