Patent Publication Number: US-2023133362-A1

Title: Control device, control system, and non-transitory computer readable medium

Description:
TECHNICAL FIELD 
     The present invention relates to a control device, a control system, and a program. 
     BACKGROUND ART 
     In recent years, various technologies that measure a distance between devices (that may be also referred to as distance measurement below) have been developed. For example, following Patent Literature 1 discloses a technology that measures a distance between devices based on a time (also referred to as a propagation time below) taken until a signal is received after the signal is transmitted. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: U.S. Pat. No. 9,566,945 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     Measuring a distance between devices can be also regarded as estimating a position of the other device for which the one device serves as a reference point. However, it is desirable that the positions of the devices are more finely estimated. 
     Accordingly, the present invention is made in view of the aforementioned issue, and an object of the present invention is to provide a mechanism that can more finely estimate positions of devices. 
     Solution to Problem 
     To solve the above described problem, according to an aspect of the present invention, there is provided a control device comprising a control section configured to obtain one or more distance measurement values, and estimate a relative position of a position changeable type communication device with respect to a target space based on the one or more distance measurement values, the one or more distance measurement values being obtained when one or more position fixed type communication devices and the position changeable type communication device perform wireless communication, and indicating a distance between each of the one or more position fixed type communication devices and the position changeable type communication device, the one or more position fixed type communication devices being communication devices whose relative positions with respect to the target space that is a space partitioned by an object are fixed, and the position changeable type communication device being a communication device whose relative position with respect to the target space is changeable. 
     To solve the above described problem, according to another aspect of the present invention, there is provided a control system comprising: one or more position fixed type communication devices that are communication devices whose relative positions with respect to a target space that is a space partitioned by an object are fixed, and a control device configured to obtain one or more distance measurement values, and estimate the relative position of a position changeable type communication device with respect to the target space based on the one or more distance measurement values, the one or more distance measurement values being obtained when each of the one or more position fixed type communication devices and the position changeable type communication device perform wireless communication, and indicating a distance between each of the one or more position fixed type communication devices and the position changeable type communication device, and the position changeable type communication device being a communication device whose relative position with respect to the target space is changeable. 
     To solve the above described problem, according to another aspect of the present invention, there is provided a program causing a computer to function as a control section configured to obtain one or more distance measurement values, and estimate a relative position of a position changeable type communication device with respect to a target space based on the one or more distance measurement values, the one or more distance measurement values being obtained when one or more position fixed type communication devices and the position changeable type communication device perform wireless communication, and indicating a distance between each of the one or more position fixed type communication devices and the position changeable type communication device, the one or more position fixed type communication devices being communication devices whose relative positions with respect to the target space that is a space partitioned by an object are fixed, and the position changeable type communication device being a communication device whose relative position with respect to the target space is changeable. 
     Advantageous Effects of Invention 
     As described above, the present invention provides a mechanism that can more finely estimate positions of devices. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating an example of a configuration of a system according to an embodiment of the present invention. 
         FIG.  2    is a sequence diagram illustrating an example of a flow of a distance measurement process executed by the system according to the present embodiment. 
         FIG.  3    is a view illustrating an example of arrangement of communication devices according to the present embodiment. 
         FIG.  4    is a view for explaining position estimation that is based on a first condition according to the present embodiment. 
         FIG.  5    is a view for explaining position estimation that is based on a second condition according to the present embodiment. 
         FIG.  6    is a view for explaining position estimation that is based on the first condition and the second condition according to the present embodiment. 
         FIG.  7    is a sequence diagram illustrating an example of a flow of a position estimation process executed by the system according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, referring to the appended drawings, preferred embodiments of the present invention will be described in detail. It should be noted that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation thereof is omitted. 
     Furthermore, elements employing substantial identical functional configurations in the description and the drawings are distinguished by assigning different alphabets to tails of identical reference numerals in some cases. For example, a plurality of elements employing substantially identical functional configurations are distinguished as communication devices  210 A,  210 B, and  210 C when necessary. In this regard, in a case where each of a plurality of elements employing the substantially identical functional configurations does not need to be distinguished in particular, each of a plurality of elements is assigned only an identical reference numeral. For example, in a case where the communication devices  210 A,  210 B, and  210 C do not need to be distinguished in particular, the communication devices  210 A,  210 B, and  210 C will be referred to simply as a communication device  210 . 
     1. Configuration Example 
       FIG.  1    is a diagram illustrating an example of a configuration of a system  1  according to an embodiment of the present invention. As illustrated in  FIG.  1   , the system  1  according to the present embodiment includes a portable device  100  and a communication unit  200 . The communication unit  200  according to the present embodiment is mounted on a vehicle  202 . The vehicle  202  is an example of a movable body. Furthermore, the vehicle  202  is an example of a user&#39;s use target. 
     A device of an authenticatee side and a device of an authenticator side are involved in the present invention. The portable device  100  is an example of the device of the authenticatee side. The communication unit  200  is an example of the device of the authenticator side. 
     When the user (e.g., a driver of the vehicle  202 ) approaches the vehicle  202  carrying the portable device  100 , the portable device  100  and the communication unit  200  perform wireless communication for authentication. Furthermore, when authentication succeeds, a door lock of the vehicle  202  is unlocked or an engine is started, and then the vehicle  202  becomes usable for the user. The system  1  is also referred to as a smart entry system. Hereinafter, each component will be described in order. 
     (1) Portable Device  100   
     The portable device  100  is an example of a device that the user of the movable body carries to use. The portable device  100  is configured as an arbitrary device carried by the user. The arbitrary device includes, for example, an electronic key, a smartphone, and a wearable terminal. 
     As illustrated in  FIG.  1   , the portable device  100  includes a wireless communication section  110 , a storage section  120 , and a control section  130 . 
     The wireless communication section  110  has a function of performing communication that conforms to predetermined wireless communication standards with the communication unit  200 . The wireless communication section  110  performs wireless communication with each of the plurality of communication devices  210  included in the communication unit  200 . The wireless communication section  110  is configured as, for example, a communication interface that can perform communication that conforms to the predetermined wireless communication standards. 
     According to, for example, the predetermined wireless communication standards, a signal that uses an Ultra-Wide Band (UWB) may be used. A signal of an impulse system that uses the UWB has characteristics that it is possible to precisely measure a distance. That is, the signal of the impulse system that uses the UWB makes it possible to precisely measure a radio wave propagation time by using a radio wave of a very short pulse width equal to or less than nano seconds, and makes it possible to precisely measure a distance based on the propagation time. In this regard, distance measurement refers to measuring a distance between devices that transmit and receive signals. 
     Hereinafter, it is assumed that the wireless communication section  110  transmits and receives signals that use the UWB. 
     The storage section  120  has a function of storing various pieces of information for an operation of the portable device  100 . For example, the storage section  120  stores, for example, programs for operations of the portable device  100 , and an Identifier (ID), a password and an authentication algorithm for authentication. The storage section  120  is configured as, for example, a storage medium such as a flash memory, and a processing device that executes recording and playback with respect to the storage medium. 
     The control section  130  has a function of controlling all operations of the portable device  100 . In an example, the control section  130  controls the wireless communication section  110 , and communicates with the communication unit  200 . Furthermore, the control section  130  reads information from the storage section  120 , and writes the information in the storage section  120 . The control section  130  is configured as, for example, an electronic circuit such as a Central Processing Unit (CPU) and a microprocessor. 
     (2) Communication Unit  200   
     The communication unit  200  is provided in association with the vehicle  202 . In this regard, the communication unit  200  is mounted on the vehicle  202 . 
     The communication unit  200  includes the one or more communication devices  210 . In the example illustrated in  FIG.  1   , the communication unit  200  includes the plurality of communication devices  210  (such as  210 A and  210 B) and a control device  220 . In addition, the communication unit  200  may include the three or more communication devices  210 . Furthermore, as illustrated in  FIG.  1   , the communication unit  200  includes the control device  220 . The communication unit  200  is an example of a control system. 
     Communication Device  210   
     The communication device  210  is a device that performs wireless communication with the portable device  100 . 
     As illustrated in  FIG.  1   , the communication device  210 A includes a wireless communication section  211 , an intra-unit communication section  212 , a storage section  213 , and a control section  214 . In this regard, the other communication devices  210  such as the communication device  210 B also include components similar to those of the communication device  210 A. 
     The wireless communication section  211  has a function of performing communication that conforms to predetermined wireless communication standards with the portable device  100 . The wireless communication section  211  is configured as, for example, a communication interface that can perform communication that conforms to the predetermined wireless communication standards. Hereinafter, it is assumed that the wireless communication section  211  transmits and receives a signal that uses the UWB. 
     The intra-unit communication section  212  has a function of performing communication with the other devices included in the communication unit  200 . In an example, the intra-unit communication section  212  communicates with the control device  220 . In another example, the intra-unit communication section  212  communicates with the other communication devices  210 . The intra-unit communication section  212  is configured as, for example, a communication interface that can perform communication that conforms to standards of an arbitrary in-vehicle network such as a Local Interconnect Network (LIN) or a Controller Area Network (CAN). 
     The storage section  213  has a function of storing various pieces of information for operations of the communication device  210 . For example, the storage section  213  stores, for example, programs for operations of the communication device  210 , and an Identifier (ID), a password and an authentication algorithm for authentication. The storage section  213  is configured as, for example, a storage medium such as a flash memory, and a processing device that executes recording and playback with respect to the storage medium. 
     The control section  214  has a function of controlling operations of the communication device  210 . In an example, the control section  214  controls the wireless communication section  211 , and communicates with the portable device  100 . In another example, the control section  214  controls the intra-unit communication section  212 , and communicates with the other devices included in the communication unit  200 . In still another example, the control section  214  reads information from the storage section  213 , and writes the information in the storage section  213 . The control section  214  is configured as, for example, an Electronic Control Unit (ECU). 
     Control Device  220   
     The control device  220  is a device that executes communication with the plurality of communication devices  210 . 
     As illustrated in  FIG.  1   , the control device  220  includes an intra-unit communication section  222 , a storage section  223 , and a control section  224 . 
     The intra-unit communication section  222  has a function of performing communication with the other devices included in the communication unit  200 . In an example, the intra-unit communication section  222  communicates with the communication device  210 . The intra-unit communication section  222  is configured as, for example, a communication interface that can perform communication that conforms to standards of an arbitrary in-vehicle network such as a Local Interconnect Network (LIN) or a Controller Area Network (CAN). 
     The storage section  223  has a function of storing various pieces of information for operations of the control device  220 . For example, the storage section  223  stores, for example, programs for operations of the control device  220 , and an Identifier (ID), a password and an authentication algorithm for authentication. The storage section  213  is configured as, for example, a storage medium such as a flash memory, and a processing device that executes recording and playback with respect to the storage medium. 
     The control section  224  has a function of controlling operations of the control device  220 . In one example, the control section  224  controls the intra-unit communication section  222 , and communicates with the other devices included in the communication unit  200 . In another example, the control section  224  reads information from the storage section  223 , and writes the information in the storage section  223 . The control section  224  is configured as, for example, an Electronic Control Unit (ECU). 
     Above all, the control section  224  executes a process that is based on information obtained by wireless communication between each of the plurality of communication devices  210  and the portable device  100 . 
     An example of the process is an authentication process of authenticating the portable device  100 . Another example of the process is a process of controlling the door lock such as locking and unlocking of the door lock of the vehicle  202 . Still another example of the process is a process of controlling a power source such as start/stop of the engine of the vehicle  202 . In addition, the power source included in the vehicle  202  may be, for example, a motor in addition to the engine. 
     2. Technical Features 
     (1) Distance Measurement Process 
     The portable device  100  and the communication unit  200  perform a distance measurement process. The distance measurement process is a process of measuring a distance between the portable device  100  and the communication unit  200 . The distance measured by the distance measurement process is also referred to as a distance measurement value below. 
     During the distance measurement process, a signal may be wirelessly transmitted and received. 
     An example of the signal transmitted and received during the distance measurement process is a distance measurement signal. The distance measurement signal is a signal that is transmitted and received to measure a distance between devices. The distance measurement signal is also a signal that is a measurement target. For example, a time taken to transmit and receive the distance measurement signal is measured. Typically, the distance measurement signal includes a frame format that does not include a payload part in which data is stored. The distance measurement signal may naturally include a frame format that includes a payload part in which data is stored. 
     During the distance measurement process, a plurality of distance measurement signals may be transmitted and received between devices. The distance measurement signal transmitted from the one device to the other device among the plurality of distance measurement signals is also referred to as a first distance measurement signal. Furthermore, the distance measurement signal transmitted from the device that has received the first distance measurement signal to the device that has transmitted the first distance measurement signal is also referred to as a second distance measurement signal. 
     Another example of the signal transmitted and received during the distance measurement process is a data signal. The data signal is a signal in which data is stored to transport. The data signal includes a frame format that includes a payload part in which data is stored. 
     Transmitting and receiving a signal during the distance measurement process is also referred to as distance measurement communication below. In the present embodiment, the portable device  100  and each of the plurality of communication devices  210  perform distance measurement communication. 
     During the distance measurement process, a distance between the portable device  100  and the communication device  210  that have performed the distance measurement communication is measured as a distance between the portable device  100  and the communication unit  200 . 
     An example of the distance measurement process will be described with reference to  FIG.  2   . 
       FIG.  2    is a sequence diagram illustrating an example of a flow of the distance measurement process executed by the system  1  according to the present embodiment. The portable device  100  and the communication device  210  are involved in this sequence. 
     As illustrated in  FIG.  2   , the wireless communication section  110  of the portable device  100  first transmits the first distance measurement signal (step S 12 ). The first distance measurement signal is transmitted as a signal that uses the UWB. 
     When receiving the first distance measurement signal from the portable device  100 , the wireless communication section  211  of the communication device  210  transmits the second distance measurement signal as a response to the first distance measurement signal (step S 14 ). The second distance measurement signal is transmitted as a signal that uses the UWB. 
     When the wireless communication section  110  receives the second distance measurement signal, the control section  130  of the portable device  100  measures a time ΔT 1  from a transmission time of the first distance measurement signal to a reception time of the second distance measurement signal. Next, the wireless communication section  110  of the portable device  100  transmits a data signal that includes information obtained by encrypting information that indicates measured ΔT 1  (step S 16 ). The data signal is transmitted as a signal that uses the UWB. 
     On the other hand, the control section  214  of the communication device  210  measures a time ΔT 2  from a reception time of the first distance measurement signal to a transmission time of the second distance measurement signal. Furthermore, when the wireless communication section  211  receives the data signal from the portable device  100 , the control section  214  of the communication device  210  obtains a distance measurement value that indicates the distance between the portable device  100  and the communication device  210  based on ΔT 1  indicated by the received data signal and measured ΔT 2  (step S 18 ). For example, the communication device  210  first calculates a propagation time by dividing ΔT 1 −ΔT 2  by 2. The propagation time described herein is a time taken for one-way signal transmission/reception between the portable device  100  and the communication device  210 . Furthermore, the communication device  210  calculates the distance measurement value that indicates the distance between the portable device  100  and the communication device  210  by multiplying the propagation time with a signal speed. 
     In this regard, during distance measurement communication, a signal that uses the UWB is desirably transmitted and received. At least the distance measurement signal is desirably transmitted and received as a signal that uses the UWB. According to this configuration, it is possible to precisely perform distance measurement as described above on the UWB. 
     In recent years, it is studied to mount on a vehicle a wireless communication function that can transmit and receive signals of Ultra-High Frequency (UHF) and Low Frequency (LF) bands or a signal of Bluetooth Low Energy (BLE and registered trademark). Furthermore, it is studied to measure a distance between a vehicle and another device based on a radio field strength on a reception side of a wirelessly transmitted signal. 
     However, it is less probable that a function of transmitting and receiving the signal of the UHF band and the signal of the LF band is mounted on smartphones. On the other hand, it is highly probable that a function of transmitting and receiving a signal that uses the UWB is mounted on smartphones. The technology according to the present embodiment performs distance measurement communication that uses the UWB, and therefore it can be said that it is highly probable that the technology is mounted on smartphones. 
     Furthermore, BLE has a relatively great variation of the radio field strength, and therefore provides low distance measurement accuracy. In this regard, the technology according to the present embodiment performs distance measurement that is based on a propagation time by using a signal that uses the UWB, so that it is possible to exhibit high distance measurement accuracy compared to distance measurement that uses a signal using BLE and is based on a radio field strength. 
     (2) Arrangement of Communication Devices 
     The communication device  210  is mounted on the vehicle  202 . The communication device  210  is an example of a position fixed type communication device. The position fixed type communication device is a communication device whose relative position with respect to a target space that is a space partitioned by an object is fixed. 
     A vehicle interior of the vehicle  202  is an example of the target space. In this regard, the vehicle interior is a space that is provided in the vehicle  202  for the user to get on the vehicle  202 . In a case where the target space is the vehicle interior, an example of the object that partitions the target space is a component that makes up an outermost shell of the vehicle  202 . The component that makes up the outermost shell of the vehicle  202  is a layer that is the most distant layer seen from the vehicle interior among components that make up the vehicle interior. An example of the component that makes up the outermost shell of the vehicle  202  is a steel plate that makes up a body of the vehicle  202 , a steel plate that makes up doors, and glass windows that are fitted to the doors. Note that interior parts are applied using a resin to the vehicle interior side of the steel plate that makes up the body and the steel plate that makes up the doors in some cases. These interior parts are also included in the vehicle interior. 
       FIG.  3    is a view illustrating an example of arrangement of the communication devices  210  according to the present embodiment. In the example illustrated in  FIG.  3   , the vehicle  202  is provided with communication devices  210 A to  210 F. As illustrated in  FIG.  3   , a traveling direction of the vehicle  202  is also referred to as a forward direction. A direction opposite to the traveling direction of the vehicle  202  is also referred to as a backward direction. Furthermore, a direction perpendicular to the traveling direction of the vehicle  202  is also referred to as a right direction and a left direction. 
     The position fixed type communication device includes one or more first position fixed type communication devices that are position fixed type communication devices arranged inside the target space. In the example illustrated in  FIG.  3   , the communication device  210 A and the communication device  210 B are examples of the first position fixed type communication devices. That is, the communication device  210 A and the communication device  210 B are arranged inside the vehicle interior of the vehicle  202 . According to this configuration, it is possible to suppress that it is estimated by mistake that the portable device  100  is located inside the vehicle interior even though the portable device  100  is actually located outside the vehicle interior during position estimation that is based on a first condition described below. 
     More specifically, the first position fixed type communication devices may be arranged between an end part on the traveling direction side of the vehicle  202  and an end part on the opposite direction side to the traveling direction of the vehicle  202 . In the example illustrated in  FIG.  3   , the communication device  210 A and the communication device  210 B are arranged at center parts in a front-back direction of the vehicle  202 . According to this configuration, it is possible to appropriately set a first virtual space during the position estimation that is based on the first condition described below. 
     The position fixed type communication device includes one or more second position fixed type communication devices that are the position fixed type communication devices arranged outside the target space. In the example illustrated in  FIG.  3   , the communication device  210 C to the communication device  210 F are examples of the second position fixed type devices. According to this configuration, it is possible to suppress that it is estimated by mistake that the portable device  100  is located outside the vehicle interior even though the portable device  100  is actually located inside the vehicle interior during position estimation that is based on a second condition described below. 
     More specifically, the second position fixed type communication devices may be arranged at each of end parts on the traveling direction side of the vehicle  202  and end parts on the opposite direction side to the traveling direction of the vehicle  202 . In the example illustrated in  FIG.  3   , the communication device  210 C and the communication device  210 F are arranged at the end parts in the forward direction of the vehicle  202 . On the other hand, the communication device  210 D and the communication device  210 E are arranged at end parts in the backward direction of the vehicle  202 . In an example, the communication device  210 C to the communication device  210 F may be arranged at bumpers of the vehicle  202 . Note that the bumper is a buffer device that buffers an impact and vibration caused when the vehicle  202  contacts other objects. According to this configuration, it is possible to appropriately set a second virtual space during the position estimation that is based on the second condition described below. 
     Furthermore, the second position fixed type communication devices may be arranged at end parts in the direction perpendicular to the traveling direction of the vehicle  202 . In the example illustrated in  FIG.  3   , the communication device  210 C and the communication device  210 D are arranged at the end parts in the right direction of the vehicle  202 . On the other hand, the communication device  210 E and the communication device  210 F are arranged at the end parts in the left direction of the vehicle  202 . According to this configuration, it is possible to appropriately set the second virtual space during the position estimation that is based on the second condition described below. 
     The arrangement of the communication unit  200  that is the example of the position fixed type communication device has been described. On the other hand, the portable device  100  is an example of the position changeable type communication device. The position changeable type communication device is a communication device whose relative position with respect to the target space is changeable. The portable device  100  is carried by the user, and moves as the user moves. For example, the portable device  100  may be located inside the vehicle interior or located outside the vehicle interior. 
     (3) Position Estimation Based on Distance Measurement Value 
     The control device  220  obtains one or more distance measurement values that are obtained when each of the one or more communication devices  210  and the portable device  100  perform wireless communication, and indicate a distance between each of the one or more communication devices  210  and the portable device  100 . The wireless communication described herein is distance measurement communication. Each of the one or more communication devices  210  obtains the distance measurement value by performing a process of measuring a distance to the portable device  100 , and transmits the distance measurement value to the control device  220 . Consequently, the control device  220  can obtain the distance measurement value obtained by each of the one or more communication devices  210 . 
     Furthermore, the control device  220  estimates the relative position of the position changeable type communication device with respect to the target space based on the one or more distance measurement values. For example, the control device  220  estimates the relative position of the portable device  100  with respect to the vehicle interior. According to this configuration, it is possible to estimate the relative position of the portable device  100  with respect to the vehicle interior as a position of the portable device  100 . Consequently, it is possible to more finely estimate the position of the portable device  100  compared to the simple distance measurement values. 
     The control device  220  may estimate whether or not the position changeable type communication device is located inside the target space to estimate the relative position of position changeable type communication device with respect to the target space. For example, the control device  220  estimates whether or not whether or not the portable device  100  is located inside the vehicle interior. According to this configuration, based on the estimation result, the control device  220  can appropriately execute a process that needs to be executed based on a condition that the portable device  100  is located inside the vehicle interior. An example of the process that needs to be executed based on the condition that the portable device  100  is located inside the vehicle interior is to permit start of the engine. 
     The control device  220  may estimate whether or not the position changeable type communication device is located outside the target space to estimate the relative position of the position changeable type communication device with respect to the target space. For example, the control device  220  estimates whether or not the portable device  100  is located outside the vehicle interior. According to this configuration, based on the estimation result, the control device  220  can appropriately execute the process that needs to be executed based on a condition that the portable device  100  is located outside the vehicle interior. An example of the process that needs to be executed based on the condition that the portable device  100  is located outside the vehicle interior is to park the vehicle by a remote operation. 
     Position Estimation Based on First Condition 
     The first condition is a condition that the distance measurement value satisfies when the position changeable type communication device is located inside the first virtual space that is the virtual space at least part of which overlaps the target space. That is, when the portable device  100  is located inside the first virtual space, the first condition is satisfied. On the other hand, when the portable device  100  is located outside the first virtual space, the first condition is not satisfied. 
     The control device  220  estimates whether or not the position changeable type communication device is located inside the target space by deciding whether or not the distance measurement values satisfy the first condition. For example, the control device  220  decides whether or not the distance measurement value satisfies the first condition. Furthermore, the control device  220  estimates that the portable device  100  is located inside the vehicle interior when the first condition is satisfied. On the other hand, the control device  220  estimates that the portable device  100  is located outside the vehicle interior when the first condition is not satisfied. According to this configuration, the control device  220  can estimate whether or not the portable device  100  is located inside the vehicle interior based on the distance measurement value. 
     The control device  220  decides whether or not the one or more distance measurement values that indicate the distance between each of the one or more first position fixed type communication devices and the position changeable type communication device satisfy the first condition to decide whether or not the distance measurement values satisfy the first condition. For example, the control device  220  decides whether or not the distance measurement value obtained by the communication device  210 A and the distance measurement value obtained by the communication device  210 B satisfy the first condition. According to this configuration, the control device  220  can decide whether or not the first condition is satisfied based on the distance measurement value of the first position fixed type communication device. 
     The first condition is that a sum of the one or more distance measurement values that indicate the distance between each of the one or more first position fixed type communication devices and the position changeable type communication device is equal to or less than a first threshold. That is, the first virtual space is a space in which, when the position changeable type communication device is located inside the first virtual space, the sum of the one or more distance measurement values that indicate the distance between each of the one or more first position fixed type communication devices and the position changeable type communication device is equal to or less than the first threshold. The first condition is expressed by, for example, a following equation. 
       [Mathematical 1] 
         L   A   +L   B   ≤Th   1   (1)
 
     In this regard, LA represents a distance measurement value obtained by the communication device  210 A. LB represents a distance measurement value obtained by the communication device  210 A. Th 1  represents the first threshold. 
     The first condition indicated in above equation (1) will be more specifically described with reference to  FIG.  4   .  FIG.  4    is a view for explaining position estimation that is based on the first condition according to the present embodiment. 
     The control device  220  decides whether or not the sum of the one or more distance measurement values that indicate the distance between each of the one or more first position fixed type communication devices and the position changeable type communication device is equal to or less than the first threshold to decide whether or not the distance measurement values satisfy the first condition. For example, the control device  220  decides whether or not the sum of the distance measurement value LA obtained by the communication device  210 A and the distance measurement value LB obtained by the communication device  210 B is equal to or less than the first threshold Th 1  as indicated in above equation (1). 
     When the portable device  100  is located inside a first virtual space  10  as illustrated in  FIG.  4   , the sum of the distance measurement value LA obtained by the communication device  210 A and the distance measurement value LB obtained by the communication device  210 B is equal to or less than the first threshold Th 1 . Hence, when the sum of the distance measurement value LA and the distance measurement value LB is equal to or less than the first threshold Th 1 , the control device  220  decides that the first condition is satisfied. That is, the control device  220  estimates that the portable device  100  is located inside the first virtual space. Furthermore, the control device  220  estimates the portable device  100  is located inside the vehicle interior. 
     On the other hand, when the portable device  100  is located outside the first virtual space  10  as illustrated in  FIG.  4   , the sum of the distance measurement value LA obtained by the communication device  210 A and the distance measurement value LB obtained by the communication device  210 B exceeds the first threshold Th 1 . 
     Hence, when the sum of the distance measurement value LA and the distance measurement value LB exceeds the first threshold Th 1 , the control device  220  decides that the first condition is not satisfied. That is, the control device  220  estimates that the portable device  100  is located outside the first virtual space. Furthermore, the control device  220  estimates that the portable device  100  is not located inside the vehicle interior (that is, located outside the vehicle interior). 
     According to this configuration, the control device  220  can estimate whether or not the portable device  100  is located inside the vehicle interior based on the sum of the distance measurement values of the first position fixed type communication devices. 
     In this regard, the communication device  210 A and the communication device  210 B are arranged inside the vehicle interior (that is, inside the target space). Hence, when the portable device  100  is located outside the vehicle interior, the distance measurement value of each of the communication device  210 A and the communication device  210 B becomes longer than an actual distance due to an influence of an obstacle such as the door. Hence, when the portable device  100  is located outside the vehicle interior, the first condition indicated by above equation (1) is hardly satisfied. Consequently, in a case where the first virtual space goes beyond the vehicle interior and includes a space outside the vehicle interior, too, even when the portable device  100  is located at this extended part, it is possible to suppress that it is estimated by mistake that the portable device  100  is located inside the vehicle interior. 
     Furthermore, as illustrated in  FIG.  4   , the first virtual space  10  that matches above equation (1) is formed in an elliptical shape whose center is the communication device  210 A and the communication device  210 B. Furthermore, the communication device  210 A and the communication device  210 B are arranged between the end part on the traveling direction side of the vehicle  202  and the end part on the opposite direction side to the traveling direction of the vehicle  202 . Consequently, it is possible to appropriately set the first virtual space  10  as a space that is provided at the center in the front-back direction of the vehicle  202  and includes the vehicle interior. 
     Position Estimation Based on Second Condition 
     The second condition is a condition that a distance measurement value satisfies when the position changeable type communication device is located outside the second virtual space that is a virtual space at least part of which overlaps a non-target space that is a space outside the target space. That is, when the portable device  100  is located outside the second virtual space, the second condition is satisfied. On the other hand, when the portable device  100  is located inside the second virtual space, the second condition is not satisfied. 
     The non-target space is a space that is outside the vehicle interior of the vehicle  202 . Above all, a space (also referred to as a door vicinity space below) in the vicinity of the door outside the vehicle interior of the vehicle  202  is an example of the non-target space. 
     The control device  220  estimates whether or not the position changeable type communication device is located in the non-target space by deciding whether or not the distance measurement values satisfy the second condition. Furthermore, when estimating that the position changeable type communication device is located in the non-target space, the control device  220  estimates that the position changeable type communication device is not located in the target space. When, for example, the second condition is not satisfied, the control device  220  estimate that the portable device  100  is located in the door vicinity space. Furthermore, the control device  220  estimates that the portable device  100  is not located inside the vehicle interior. On the other hand, when the second condition is satisfied, the control device  220  estimate that the portable device  100  is not located in the door vicinity space. Furthermore, the control device  220  estimates that the portable device  100  may be located inside the vehicle interior. According to this configuration, the control device  220  can estimate whether or not the portable device  100  is located in the door vicinity space based on the second virtual space. As a result, the control device  220  can estimate that the portable device  100  is not located inside the vehicle interior or the portable device  100  may be located inside the vehicle interior. 
     The control device  220  decides whether or not the one or more distance measurement values that indicate the distance between each of the one or more second position fixed type communication devices and the position changeable type communication device satisfy the second condition to decide whether or not the distance measurement values satisfy the second condition. For example, the control device  220  decides whether or not the distance measurement value obtained by each of the communication device  210 C to the communication device  210 F satisfies the second condition. According to this configuration, the control device  220  can decide whether or not the second condition is satisfied based on the distance measurement values of the second position fixed type communication devices. 
     Position estimation that is based on the second condition will be specifically described below with reference to  FIG.  5   . 
       FIG.  5    is a view for explaining the position estimation that is based on the second condition according to the present embodiment. As illustrated in  FIG.  5   , a second virtual space  20 R is set to a right side of the vehicle  202 . The second virtual space  20 R corresponds to the communication device  210 C and the communication device  210 D arranged on the right side of the vehicle  202 . A second virtual space  20 L is set to a left side of the vehicle  202 . The second virtual space  20 L corresponds to the communication device  210 E and the communication device  210 F arranged on the left side of the vehicle  202 . At least part of each of the second virtual space  20 R and the second virtual space  20 L overlaps the door vicinity space that is the non-target space. 
     The second condition is that the sum of the one or more distance measurement values that indicate the distance between each of the one or more second position fixed type communication devices and the position changeable type communication device is equal to or more than a second threshold. That is, the second virtual space is a space in which, when the position changeable type communication device is located outside the second virtual space, the sum of the one or more distance measurement values that indicate the distance between each of the one or more second position fixed type communication devices and the position changeable type communication device is equal to or more than the second threshold. Note that, as illustrated in  FIG.  5   , in a case where the plurality of second virtual spaces  20  are set, the second condition can be set to each of the plurality of set second virtual spaces. 
     The second condition set to the second virtual space  20 R is expressed by, for example, a following equation. 
       [Mathematical 2] 
         L   C   +L   D   ≥Th   2R   (2)
 
     LC represents a distance measurement value that is obtained by the communication device  210 C. LD represents a distance measurement value that is obtained by the communication device  210 D. Th 2 R represents the second threshold that is associated with the second virtual space  20 R. 
     The control device  220  decides whether or not the sum of the one or more distance measurement values that indicate the distance between each of the one or more second position fixed type communication devices and the position changeable type communication device is equal to or more than the second threshold to decide whether or not the distance measurement values satisfy the second condition. For example, the control device  220  decides whether or not the sum of the distance measurement value LC obtained by the communication device  210 C and the distance measurement value LD obtained by the communication device  210 D is equal to or more than the second threshold TH 2 R as indicated in above equation (2). 
     When the portable device  100  is located inside the second virtual space  20 R as illustrated in  FIG.  5   , the sum of the distance measurement value LC obtained by the communication device  210 C and the distance measurement value LD obtained by the communication device  210 D is less than the second threshold TH 2 R. Hence, when the sum of the distance measurement value LC and the distance measurement value LD is less than the second threshold TH 2 R, the control device  220  decides that the second condition is not satisfied. Furthermore, when deciding that the second condition is not satisfied, the control device  220  estimates that the portable device  100  is located in the door vicinity space. That is, the control device  220  estimates that the portable device  100  is located outside the vehicle interior. 
     On the other hand, when the portable device  100  is located outside the second virtual space  20 R as illustrated in  FIG.  5   , the sum of the distance measurement value LC obtained by the communication device  210 C and the distance measurement value LD obtained by the communication device  210 D is equal to or more than the second threshold TH 2 R. Hence, when the sum of the distance measurement value LC and the distance measurement value LD is equal to or more than the second threshold TH 2 R, the control device  220  decides that the second condition is satisfied. Furthermore, when deciding that the second condition is satisfied, the control device  220  estimates that the portable device  100  is not located in the door vicinity space. That is, the control device  220  estimates that the portable device  100  may be located inside the vehicle interior. 
     According to this configuration, the control device  220  can estimate whether or not the portable device  100  is located in the door vicinity space based on the sum of the distance measurement values of the second position fixed type communication devices, and, as a result, estimate whether or not the portable device  100  is located outside the vehicle interior or may be located inside the vehicle interior. 
     In this regard, the communication device  210 C and the communication device  210 D are arranged outside the vehicle interior. Therefore, when the portable device  100  is located inside the vehicle interior, the distance measurement value of each of the communication device  210 C and the communication device  210 D becomes longer than an actual distance due to an influence of an obstacle such as the door. Hence, when the portable device  100  is located inside the vehicle interior, the second condition indicated in above equation (2) is readily satisfied. Consequently, in a case where the second virtual space goes beyond the door and includes a space inside the vehicle interior, too, even when the portable device  100  is located at this extended part, it is possible to suppress that it is estimated by mistake that the portable device  100  is located outside the vehicle interior. 
     Furthermore, as illustrated in  FIG.  5   , the second virtual space  20 R that matches above equation (2) is formed in an elliptical shape whose center is the communication device  210 C and the communication device  210 D. Furthermore, the communication device  210 C and the communication device  210 D are arranged at each of the end part on the traveling direction side of the vehicle  202  and the end part on the opposite direction side to the traveling direction of the vehicle  202 . Hence, as illustrated in  FIG.  5   , it is possible to finely set the second virtual space  20 R in the left-right direction, so that it is possible to prevent the space inside the vehicle interior from being included in the second virtual space as much as possible. From another viewpoint, the communication device  210 C and the communication device  210 D are arranged at end parts in a direction (right direction) perpendicular to the traveling direction of the vehicle  202 . Consequently, as illustrated in  FIG.  5   , the door vicinity space on the right side that is the non-target space can be included in the second virtual space. Consequently, it is possible to appropriately set the second virtual space  20  that is the space that does not include the space inside the vehicle interior as much as possible and includes the door vicinity space. 
     The second condition set to the second virtual space  20 L is expressed by, for example, a following equation. 
       [Mathematical 3] 
         L   E   +L   F   ≥Th   2L   (3)
 
     LE represents a distance measurement value that is obtained by the communication device  210 E. LF represents a distance measurement value that is obtained by the communication device  210 F. Th 2 L represents the second threshold that is associated with the second virtual space  20 L. 
     The control device  220  performs a process similar to the process related to the second condition set to the above-described second virtual space  20 R as a process related to the second condition set to the second virtual space  20 L. 
     Position Estimation Based on First Condition and Second Condition 
     When both of the first condition and the second condition are satisfied, the control device  220  estimates that the position changeable type communication device is located inside the target space. When, for example, both of the first condition and the second condition are satisfied, the control device  220  estimates that the portable device  100  is located inside the vehicle interior. This point will be described with reference to  FIG.  6   . 
       FIG.  6    is a view for explaining position estimation that is based on the first condition and the second condition according to the present embodiment. A third virtual space  30  illustrated in  FIG.  6    is a space that is inside the first virtual space  10  and is outside the second virtual space  20 . When the portable device  100  is located inside the first virtual space  10 , the first condition is satisfied. On the other hand, when the portable device  100  is located outside the second virtual space  20 , the second condition is satisfied. Hence, when the portable device  100  is located inside the third virtual space  30 , both of the first condition and the second condition are satisfied. 
     Hence, when both of the first condition and the second condition are satisfied, the control device  220  estimates that the portable device  100  is located inside the third virtual space  30 . Furthermore, the control device  220  estimates that the portable device  100  is located inside the vehicle interior. On the other hand, when one of the first condition and the second condition is not satisfied or is satisfied, the control device  220  estimates that the portable device  100  is located outside the third virtual space  30 . Furthermore, the control device  220  estimates that the portable device  100  is located outside the vehicle interior. 
     According to this configuration, it is possible to estimate whether or not the portable device  100  is located inside the vehicle interior based on whether or not the portable device  100  is located inside the third virtual space that is a space of the first virtual space that does not overlap the second virtual space. Even when the first virtual space goes beyond the vehicle interior and includes a space outside the vehicle interior, too, it is possible to exclude this extended part by the second virtual space. Consequently, it is possible to reduce that it is decided by mistake that the portable device  100  is located inside the vehicle interior even though the portable device  100  is located outside the vehicle interior (e.g., door vicinity space). 
     Note that, regarding the second condition, the control device  220  may decide which one of above equations (2) and (3) to use according to which one of the left and the right of the vehicle  202  the portable device  100  is located on. When, for example, the distance measurement value LA obtained by the communication device  210 A is equal to or less than the distance measurement value LB obtained by the communication device  210 B, the control device  220  decides that the portable device  100  is located on the right side of the vehicle  202 . In this case, the control device  220  decides based on equation (2) whether or not the second condition is satisfied. On the other hand, when the distance measurement value LA obtained by the communication device  210 A exceeds the distance measurement value LB obtained by the communication device  210 B, the control device  220  decides that the portable device  100  is located on the left side of the vehicle  202 . In this case, the control device  220  decides based on equation (3) whether or the second condition is satisfied. 
     That is, the control device  220  may estimate whether or not the portable device  100  is located inside the vehicle interior according to a conditional expression indicated by a following equation. 
     
       
         
           
             
               
                 
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     When equation (1) is satisfied and one of equations (2) and (3) is satisfied as indicated in equation (4), the control device  220  decides that the portable device  100  is located inside the vehicle interior. 
     (4) Flow of Process 
       FIG.  7    is a sequence diagram illustrating an example of a flow of a position estimation process executed by the system  1  according to the present embodiment. The portable device  100  and the communication unit  200  are involved in this sequence. 
     As illustrated in  FIG.  7   , the portable device  100  and the communication device  210 A first perform the distance measurement process (step S 102 A). The distance measurement process is as described above with reference to  FIG.  2   . The control device  220  obtains the distance measurement value LA that is obtained by the distance measurement process and indicates a distance between the portable device  100  and the communication device  210 A. 
     Next, the portable device  100  and the communication device  210 B perform the distance measurement process (step S 102 B). The control device  220  obtains the distance measurement value LB that is obtained by the distance measurement process and indicates a distance between the portable device  100  and the communication device  210 B. 
     Furthermore, the control device  220  decides whether or not the distance measurement value LA and the distance measurement value LB satisfy the first condition (step S 104 ). For example, the control device  220  decides whether or not above equation (1) is satisfied. 
     Next, the portable device  100  and the communication device  210 C perform the distance measurement process (step S 106 C). The control device  220  obtains the distance measurement value LC that is obtained by the distance measurement process and indicates a distance between the portable device  100  and the communication device  210 C. 
     Although omitted in  FIG.  7   , the portable device  100  and the communication device  210 D also perform the distance measurement process. The control device  220  obtains the distance measurement value LD that is obtained by the distance measurement process and indicates a distance between the portable device  100  and the communication device  210 D. Similarly, as for the portable device  100  and the communication device  210 E, too, the control device  220  that performs the distance measurement process obtains the distance measurement value LE that is obtained by the distance measurement process and indicates a distance between the portable device  100  and the communication device  210 E. 
     Subsequently, the portable device  100  and the communication device  210 F perform the distance measurement process (step S 106 F). The control device  220  obtains the distance measurement value LF that is obtained by the distance measurement process and indicates a distance between the portable device  100  and the communication device  210 F. 
     Furthermore, the control device  220  decides whether or not the distance measurement values LC, LD, LE and LF satisfy the second condition (step S 108 ). For example, the control device  220  decides whether or not above equation (2) or equation (3) is satisfied. 
     Subsequently, the control device  220  decides whether or not the portable device  100  is located inside the vehicle interior (step S 110 ). When, for example, both of the first condition and the second condition are satisfied, the control device  220  decides that the portable device  100  is located inside the vehicle interior. On the other hand, when at least one of the first condition and the second condition is not satisfied, the control device  220  decides that the portable device  100  is not located inside the vehicle interior. 
     Note that, when it is decided in step S 104  that the first condition is not satisfied, steps S 106 C to S 108  may be omitted. In this case, it is possible to improve responsiveness. The responsiveness described herein refers to how fast whether or not the portable device  100  is located inside the vehicle interior is decided after the distance measurement process is started. 
     3. Supplementary Explanation 
     Heretofore, the preferred embodiment of the present invention has been described in detail with reference to the appended drawings. However, the present invention is not limited to this embodiment. It should be understood by those who have common knowledge in the technical field to which the present invention belongs that it is obvious that various change examples or alteration examples can be arrived at within the scope of the technical idea recited in the claims, and these change examples and alteration examples also naturally belong to the technical scope of the present invention. 
     For example, although the above embodiment has described the example where the spaces in the vicinity of the left and right doors of the vehicle  202  are the non-target spaces, and the second virtual spaces corresponding to the non-target spaces are set, the present invention is not limited to this example. For example, the second virtual space corresponding to the rear door of the vehicle  202  may be set. In this case, that the sum of the distance measurement value of the communication device  210 C and the distance measurement value of the communication device  210 D is equal to or more than the second threshold may be the second condition. 
     For example, although the above embodiment has described the example where the second position fixed type communication devices are arranged at the bumpers, the present invention is not limited to this example. In an example, the second position fixed type communication devices may be arranged at headlights and taillights of the vehicle  202 . Note that the headlights are light emitting devices that are provided at a front side of the vehicle  202 . The taillights are light emitting devices that are provided at a rear side of the vehicle  202 . In another example, the second position fixed type communication devices may be arranged at side mirror parts of the vehicle  202 . Note that the side mirrors are mirrors that are arranged on outer sides of the front seat doors of the vehicle  202 . 
     For example, although the above embodiment has described the example where the communication devices  210  calculate the distance measurement values, the present invention is not limited to this example. For example, the control device  220  may calculate a distance measurement value. In this case, the communication devices  210  report the information that indicates ΔT 1  and ΔT 2  to the control device  220 . 
     For example, although the above embodiment has described that the information that indicates the time ΔT 1  from the transmission time of the first distance measurement signal to the reception time of the second distance measurement signal in the portable device  100  is included in the data signal, the present invention is not limited to this example. The data signal only needs to include information related to the transmission time of the first distance measurement signal and the reception time of the second distance measurement signal. Another example of information included in the data signal will be described below. 
     The another example of the information included in the data signal is information that indicates the transmission time of the first distance measurement signal and the reception time of the second distance measurement signal in the portable device  100 . That is, the portable device  100  may transmit time stamps of a start time and an end time of ΔT 1  without calculating ΔT 1 . 
     The another example of the information included in the data signal is information that indicates a distance between the portable device  100  and the communication device  210  calculated based on the time from the transmission time of the first distance measurement signal to the reception time of the second distance measurement signal. That is, the portable device  100  may calculate the distance between the portable device  100  and the communication device  210 , and transmit the information that indicates the calculated distance to the communication device  210 . When, for example, ΔT 2  is a fixed value, the portable device  100  can calculate the distance measurement value by measuring ΔT 1 . 
     For example, although the above embodiment has described the example where the portable device  100  transmits the first distance measurement signal, the present invention is not limited to this example. For example, the communication device  210  may transmit the first distance measurement signal. In this case, when receiving the first distance measurement signal, the portable device  100  transmits the second distance measurement signal as a response to the first distance measurement signal. Furthermore, the portable device  100  transmits the data signal including information that indicates the time ΔT 2  from the reception time of the first distance measurement signal to the reception time of the second distance measurement signal. On the other hand, the communication device  210  calculates a distance measurement value based on the time ΔT 1  from the transmission time of the first distance measurement signal to the reception time of the second distance measurement signal and the time ΔT 2  included in the data signal. 
     For example, although the above embodiment has described the example where the distance measurement value is calculated based on the propagation time, the present invention is not limited to this example. For example, the distance measurement value may be calculated based on the radio field strength. 
     For example, although the above embodiment has described the example where the UWB is used as wireless communication standards, the present invention is not limited to this example. In one example, wireless communication standards that use a signal of the UHF band and a signal of the LF band may be used. In another example, wireless communication standards that use Wi-Fi (registered trademark), Near Field Communication (NFC) and an infrared ray may be used. 
     For example, although the above embodiment has described the example where the control device  220  is included in the communication unit  200 , the present invention is not limited to this example. In one example, the control device  220  may be included in the portable device  100 . In another example, the control device  220  may be included in another device other than the portable device  100  and the communication unit  200 . 
     For example, although the above embodiment has described the example where the communication unit  200  is a communication device that is mounted on the vehicle, the present invention is not limited to this example. The communication unit  200  may be mounted on an arbitrary movable body such as an airplane or a ship other than the vehicle. In this regard, the movable body refers to a device that moves. 
     For example, although the above embodiment has described the example where the present invention is applied to the smart entry system, the present invention is not limited to this example. The present invention is applicable to arbitrary systems that perform wireless communication. The present invention is applicable to, for example, a pair including two arbitrary devices of a portable device, a vehicle, a smartphone, a drone, a house, and a home electric appliance. Note that the pair may include two devices of the same type or may include two devices of different types. 
     Note that, a series of processes performed by the devices described in this specification may be achieved by any of software, hardware, and a combination of software and hardware. A program that configures software is stored in advance in, for example, a recording medium (non-transitory medium) installed inside or outside the devices. In addition, for example, when a computer executes the programs, the programs are read into random access memory (RAM), and executed by a processor such as a CPU. The recording medium may be a magnetic disk, an optical disc, a magneto-optical disc, flash memory, or the like. Alternatively, the above-described computer program may be distributed via a network without using the recording medium, for example. 
     Further, in the present specification, the processes described using the flowcharts and the sequence diagrams are not necessarily executed in the order illustrated in the drawings. Some processing steps may be executed in parallel. In addition, additional processing steps may be employed and some processing steps may be omitted. 
     REFERENCE SIGNS LIST 
     
         
           1  system 
           100  portable device 
           110  wireless communication section 
           120  storage section 
           130  control section 
           200  communication unit 
           202  vehicle 
           210  communication device 
           211  wireless communication section 
           212  intra-unit communication section 
           213  storage section 
           214  control section 
           220  control device 
           222  intra-unit communication section 
           223  storage section 
           224  control section