Patent Publication Number: US-2021179020-A1

Title: Vehicle control apparatus, vehicle control method, recording medium with program for control recorded, and vehicle control system

Description:
INCORPORATION BY REFERENCE 
     The present application claims priority under 35 U.S.C.§ 119 to Japanese Patent Application No. 2019-227114 filed on Dec. 17, 2019. The content of the application is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a vehicle control apparatus, a vehicle control method, a recording medium with program for control recorded, and a vehicle control system. 
     Description of the Related Art 
     Conventionally, a vehicle control system has been proposed that includes a security device and an interior reader/writer in a vehicle and thus enables operations on the vehicle by using a vehicle key and a mobile terminal such as a smartphone (see Japanese Patent Laid-Open No. 2014-54902, for example). In the vehicle control system, the security device permits locking/unlocking of a door with a vehicle key if authentication of the vehicle key is succeeded within a communication area outside of the vehicle. The security device further permits to start an engine of the vehicle with the vehicle key if the authentication of the vehicle key is succeeded within a communication area within the vehicle. 
     The interior reader/writer permits operations on the vehicle (such as locking/unlocking of a door and start of the engine) with a mobile terminal carried onto the vehicle if authentication via near field communication (NFC) with the mobile terminal is succeeded. 
     Although the operations on a vehicle with a mobile terminal are enabled when the mobile terminal is carried onto the vehicle in the conventional vehicle control system, enabling operations on the vehicle from outside of the vehicle with the mobile terminal like a vehicle key is also desired. With respect to a vehicle key, operations on a vehicle with the vehicle key can be permitted based on a distance between the vehicle and the vehicle key measured with relatively low power consumption achieved by a combination of low-frequency (LF) and ultra-high frequency (UHF). Therefore, also in order to enable operations on a vehicle from outside of the vehicle with a mobile terminal, enabling measurement of a distance between the vehicle and the mobile terminal with reduced power consumption is desirable. 
     The present invention has been made in view of such background, and it is an object of the present invention to provide a vehicle control apparatus, a vehicle control method, a recording medium with program for control recorded, and a vehicle control system that enable measurement of a distance between a vehicle and a mobile terminal with reduced power consumption and with high precision. 
     SUMMARY OF THE INVENTION 
     As a first aspect for achieving the object, there is provided a vehicle control apparatus including a vehicle communication control unit performing communication by a first communication specification with a mobile terminal used by a user of a vehicle when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, a first distance measuring unit measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining unit obtaining vehicle position information including current position information on the vehicle, a terminal position information obtaining unit obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through the vehicle communication control unit, a second distance measuring unit measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining unit determining whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured by the second distance measuring unit. 
     In the vehicle control apparatus, the high-precision distance measurement determining unit may determine to cause the first distance measuring unit to measure the vehicle-terminal distance when the vehicle-terminal distance decreases by a predetermined distance or larger in a plurality of the vehicle-terminal distances measured at different points in time by the second distance measuring unit. 
     The vehicle control apparatus may further include a battery remaining-amount recognizing unit recognizing a remaining amount of a battery included in the vehicle. In this case, the high-precision distance measurement determining unit may determine not to cause the first distance measuring unit to measure the vehicle-terminal distance when the remaining amount of the battery recognized by the battery remaining-amount recognizing unit is equal to or lower than a predetermined remaining amount even though the vehicle-terminal distance decreases by a predetermined distance or larger in a plurality of the vehicle-terminal distances measured at different points in time by the second distance measuring unit. 
     The vehicle control apparatus may further include an electronic-key-app operation recognizing unit recognizing that an electronic key app for remotely operating the vehicle with the mobile terminal is in operation based on operating state information on the mobile terminal transmitted from the mobile terminal to the vehicle communication control unit. In this case, the high-precision distance measurement determining unit may determine to cause the first distance measuring unit to measure the vehicle-terminal distance when the electronic-key-app operation recognizing unit recognizes that the electronic key app is in operation even though the vehicle-terminal distance does not decrease by a predetermined distance or larger in a plurality of the vehicle-terminal distances measured at different points in time by the second distance measuring unit. 
     In the vehicle control apparatus, the terminal position information may include current position information on the mobile terminal detected by a terminal global positioning system (GPS) sensor provided in the mobile terminal, the vehicle position information may include current position information on the vehicle detected by a vehicle GPS sensor provided in the vehicle, the second distance measuring unit may measure the vehicle-terminal distance with the second precision based on a current position of the vehicle detected by the vehicle GPS sensor and recognized from the vehicle position information and the terminal position information detected by the terminal GPS sensor and recognized from the terminal position information, and the first distance measuring unit may measure the vehicle-terminal distance with the first precision by performing, by the vehicle communication control unit, communication with the mobile terminal by a second communication specification involving larger power consumption for communication than the first communication specification. 
     In the vehicle control apparatus, the first communication specification may be a communication specification by Bluetooth Low Energy (BLE where Bluetooth is a registered trademark), and the second communication specification is a communication specification by Ultra Wide Band (UWB). 
     As a second aspect for achieving the object, there is provided a vehicle control method to be executed by a vehicle control apparatus performing communication with a mobile terminal used by a user of a vehicle, the method including a vehicle communication control step of performing communication by a first communication specification with the mobile terminal when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, a first distance measuring step of measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining step of obtaining vehicle position information including current position information on the vehicle, a terminal position information obtaining step of obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through processing in the vehicle communication control step, a second distance measuring step of measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining step of determining whether the first distance measuring step is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured in the second distance measuring step. 
     As a third aspect for achieving the object, there is provided a recording medium with a program for control recorded, the program being executed by a vehicle control apparatus performing communication with a mobile terminal used by a user of a vehicle and causing the vehicle control apparatus to function as a vehicle communication control unit performing communication by a first communication specification with the mobile terminal when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, a first distance measuring unit measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining unit obtaining vehicle position information including current position information on the vehicle, a terminal, position information obtaining unit obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through the vehicle communication control unit, a second distance measuring unit measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining unit determining whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured by the second distance measuring unit. 
     As a fourth aspect for achieving the object, there is provided a vehicle control system including a vehicle control apparatus having a vehicle communication control unit and a mobile terminal used by a user of a vehicle. In this case, the vehicle communication control unit and the mobile terminal perform communication by a first communication specification by establishing communication with each other when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, and the vehicle control apparatus includes a first distance measuring unit measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining unit obtaining vehicle position information including current position information on the vehicle, a terminal position information obtaining unit obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through the vehicle communication control unit, a second distance measuring unit measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining unit determining whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured by the second distance measuring unit. 
     Advantageous Effect of Invention 
     According to the above-described vehicle control apparatus, when the mobile terminal is within an out-vehicle communication area and communication is performed by the first communication specification between the mobile terminal and the vehicle communication control unit, a vehicle-terminal distance is measured, by the second distance measuring unit, with low precision based on terminal position information transmitted from the mobile terminal. The high-precision distance measurement determining unit determines whether the first distance measuring unit is caused to measure the vehicle-terminal distance with first precision being high precision based on the vehicle-terminal distance measured by the second distance measuring unit. Thus, the power consumption required for measurement of the vehicle-terminal distance can be reduced more than a case where the vehicle-terminal distance is unconditionally measured with the high precision by the first distance measuring unit when the mobile terminal positions within the out-vehicle communication area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram of an aspect in which a distance between a vehicle and a mobile terminal is measured by a vehicle control system; 
         FIG. 2  is an explanatory diagram of configurations of a vehicle on which a vehicle control apparatus is mounted and a mobile terminal; 
         FIG. 3  is a first flowchart of distance measurement processing between the vehicle and the mobile terminal; and 
         FIG. 4  is a second flowchart of the distance measurement processing between the vehicle and the mobile terminal. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     1. Measurement of Distance Between Vehicle and Mobile Terminal by Vehicle Control Apparatus 
     With reference to  FIG. 1 , an aspect is described in which a distance (hereinafter, “vehicle-terminal distance”) M between a vehicle  100  and a mobile terminal  10  is measured in a vehicle control system  1  of an embodiment. The vehicle control system  1  includes a vehicle control apparatus  110  mounted on the vehicle  100  and the mobile terminal  10  to be used by a user U of the vehicle  200 . The vehicle control apparatus  110  is an electronic control unit (ECU) that includes a central processing unit (CPU), a memory, an interface circuit and so on, not shown, and controls operations of the vehicle  100 . 
     In order to permit a remote operation on the vehicle  100  by the mobile terminal  10 , the vehicle control apparatus  110  measures the vehicle-terminal distance M by performing communication with the mobile terminal  10 . The mobile terminal  10  is, for example, a smartphone, a mobile phone, a tablet terminal, or a wearable device such as a smart watch and is carried or worn by the user U for use. 
     An electronic key application (app) is installed in the mobile terminal  10 , and the mobile terminal  10  can function as an electronic key including a function that remotely operates the vehicle  100  by executing the electronic key app. The vehicle  100  and the mobile terminal  10  mutually perform communication by communication specifications of Bluetooth Low Energy (BLE where Bluetooth is a registered trademark) and Ultra Wide Band (UWB). In UWB communication, a bandwidth of 500 MHz to ten-odd GHz (such as around an 8 GHz band) is used. 
     The vehicle  100  includes a first vehicle communication unit  130  performing communication by BLE, a second vehicle communication unit  140  performing communication by UWB, and a vehicle global positioning system (GPS) sensor  145  receiving radio waves transmitted from a GPS satellite and detecting a current position (latitude, longitude) of the vehicle  100 . The communication specification by BLE corresponds to a first communication specification of the present invention. The communication specification by UWB corresponds to a second communication specification of the present invention. 
     The vehicle  100  has a BLE antenna  131  connected to the first vehicle communication unit  130  and UWB antennas  141 ,  142  and  143  connected to the second vehicle communication unit  140 . The BLE antenna  131  is arranged substantially in a center part of the vehicle  100 . The UWB antenna  141  is arranged in a front part of the vehicle  100 , the UWB antenna  142  is arranged in the center part, and the UWB antenna  143  is arranged in a rear part of the vehicle  100 . 
     The vehicle control apparatus  110  performs polling by BLE communication through the first vehicle communication unit  130 , and, when the mobile terminal  10  enters from outside (the state indicated by C 1 ) to inside (the state indicated by C 2 ) of an out-vehicle communication area Ar 1  of BLE communication by the first vehicle communication unit  130 , establishes communication by BLE with the mobile terminal  10 . 
     The vehicle control apparatus  110  confirms that the mobile terminal  10  is registered as an electronic key of the vehicle  100  by performing authentication of the electronic key between the vehicle control apparatus  110  and the mobile terminal  10 . More specifically, the vehicle control apparatus  110  confirms that the mobile terminal  10  is registered as an electronic key of the vehicle  100  by comparing an authentication code transmitted from the mobile terminal  10  and an authentication code saved in the memory of the vehicle control apparatus  110 . 
     The vehicle control apparatus  110  measures the vehicle-terminal distance M in order to permit use of the mobile terminal  10  as an electronic key. The vehicle control apparatus  110  performs UWB communication through the second vehicle communication unit  140  with the mobile terminal  10  and measures a distance X between the UWB antenna  141  and the mobile terminal  10 , a distance Y between the UWB antenna  142  and the mobile terminal  10 , and a distance Z between the UWB antenna  143  and the mobile terminal  10  based on Time of Flight (ToF). Because a position Pa of the UWB antenna  141 , a position Pb of the UWB antenna  142  and a position Pc of the UWB antenna  143  in the vehicle  100  are known, a relative position Pd of the mobile terminal  10  with respect to the vehicle  100  is calculated by trilateration by measuring X, Y and Z, and the vehicle-terminal distance M can thus be measured with first precision being high precision. 
     While communication by BLE is being established between the first vehicle communication unit  130  and the mobile terminal  10 , the vehicle control apparatus  110  performs UWB communication between the second vehicle communication unit  140  and the mobile terminal  10  and measures the vehicle-terminal distance M with the first precision. When the vehicle control apparatus  110  recognizes from the vehicle-terminal distance M measured by UWB communication that the mobile terminal  10  has entered a monitoring area Ar 2  near the vehicle  100 , the vehicle control apparatus  110  permits use of the mobile terminal  10  as the electronic key. 
     Thus, the user U can unlock and lock a door of the vehicle  100 , open and close an electric door (such as a power slide door, a power hinge door or a power tail gate), start the engine, turn on/off an air conditioner, and cause a buzzer to go off, for example, by operating the mobile terminal  10 . When the vehicle control apparatus  110  recognizes that the mobile terminal  10  has entered the monitoring area Ar 2 , the vehicle control apparatus  110  performs processing for, for example, putting on a welcome light (not shown) included in the vehicle  100 . 
     The mobile terminal  10  further includes a terminal GPS sensor  20  (see  FIG. 2 ), and the mobile terminal  10  transmits to the vehicle  100  terminal position information Spi including current position information on the mobile terminal  10  detected by the terminal GPS sensor  20 . Based on the terminal position information Spi received through the first vehicle communication unit  130  and the current position of the vehicle  100  detected by the vehicle GPS sensor  145 , the vehicle control apparatus  110  measures the vehicle-terminal distance M with second precision lower than the first precision. 
     Limitedly when the vehicle control apparatus  110  recognizes that the mobile terminal  10  is approaching the vehicle  100  from time-series data of the vehicle-terminal distance M measured with the second precision, the vehicle control apparatus  110  measures the vehicle-terminal distance M with the first precision by performing UWB communication. Here, power consumption required for the BLE communication is lower than power consumption required for UWB communication. Thus, the power consumption required for measurement of the vehicle-terminal distance M with the first precision can be reduced more than a case where the vehicle-terminal distances M are measured with the first precision by unconditionally performing UWB communication between the vehicle  100  and the mobile terminal  10  when the mobile terminal  10  positions within the out-vehicle communication area Ar 1  of the first vehicle communication unit  330 . 
     2. Configurations of Vehicle and Mobile Terminal 
     With reference to  FIG. 2 , configurations of the vehicle  100  on which the vehicle control apparatus  110  is mounted and the mobile terminal  10  are described. The vehicle  100  includes, in addition to the vehicle control apparatus  110 , the first vehicle communication unit  130 , the second vehicle communication unit  140  and the vehicle GPS sensor  145  described above, a door lock mechanism  150 , a power window  151 , an electric door  152  (such as a power slide door, a power hinge door or a power tail gate), an air conditioner  153 , an engine starting unit  154 , a speaker  155 , and a battery  160 . 
     The battery  160  provides power supply to the vehicle control apparatus  110 , the first vehicle communication unit  130 , the second vehicle communication unit  140 , the vehicle GPS sensor  145  and so on. The battery  160  has a voltage sensor  161  that detects inter-terminal voltage in the battery  160  and a current sensor  162  that detects input and output currents of the battery  160 . 
     The mobile terminal  10  includes a terminal GPS sensor  20  that detects a current position of the mobile terminal  10  and functions as an electronic key of the vehicle  100  by executing the electronic key app  30 . The mobile terminal  10  transmits to the vehicle  100  the terminal position information Spi including current position information of the mobile terminal  10  detected by the GPS sensor  20  and operating state information Sci including execution information on the electronic key app  30 . 
     The CPU (not shown) included in the vehicle control apparatus  110  reads and executes a program for control  121  for the vehicle  100  saved in the memory  120  (recording medium) to function as a vehicle communication control unit  111 , a vehicle position information obtaining unit  112 , a terminal position information obtaining unit  113 , a first distance measuring unit  114 , a second distance measuring unit  115 , a battery remaining-amount recognizing unit  116 , an electronic-key-app operation recognizing unit  117 , a high-precision distance measurement determining unit  118 , and a vehicle electronic-key control unit  119 . The program for control  121  may be recorded in an external recording medium (flash memory, magnetic disk, optical disk or the like), and transferred from the external recording medium to the memory  120 . 
     Processing to be executed by the vehicle communication control unit  111  corresponds to a vehicle communication control step in a vehicle control method of the present Invention, and processing to be executed by the first distance measuring unit  114  corresponds to a first distance measuring step in the vehicle control method of the present invention. Processing to be executed by the vehicle position information obtaining unit  112  corresponds to a vehicle position information obtaining step in the vehicle control method of the present invention, and processing to be executed by the terminal position information obtaining unit  113  corresponds to a terminal position information obtaining step in the vehicle control method of the present invention. Processing to be executed by the second distance measuring unit  115  corresponds to a second distance measuring step in the vehicle control method of the present invention, and processing to be executed by the high-precision distance measurement determining unit  118  corresponds to a high-precision distance measurement determining step in the vehicle control method of the present invention. 
     The vehicle communication control unit  111  performs control over BLE communication through the first vehicle communication unit  130  and performs control over UWB communication through the second vehicle communication unit  140 . The vehicle position information obtaining unit  112  obtains vehicle position information Cpi including current position information on the vehicle  100  detected by the GPS sensor  145 . The terminal position information obtaining unit  113  obtains the terminal position information Spi transmitted from the mobile terminal  10 . The first distance measuring unit  114  measures the vehicle-terminal distance M with the first precision by performing UWB communication with the mobile terminal  10  through the second vehicle communication unit  140  as described above with reference to  FIG. 1 . 
     The second distance measuring unit  115  measures the vehicle-terminal distance M with the second precision that is a measurement precision lower than the first precision based on the current position of the vehicle  100  detected by the vehicle GPS sensor  145  and recognized from the vehicle position information Cpi and the current position of the mobile terminal  10  detected by the terminal GPS sensor  20  and recognized from the terminal position information Spi. The battery remaining-amount recognizing unit  116  recognizes the remaining amount (residual accumulated electrical quantity) of the battery  160  based on the integrated quantity of input and output currents of the battery  160  detected by the current sensor  162 , output voltage of the battery  160  detected by the voltage sensor  161  and so on. 
     The electronic-key-app operation recognizing unit  117  recognizes that the electronic key app  30  is in operation in the mobile terminal  10  from the operating state information Sci transmitted from the mobile terminal  10 . The high-precision distance measurement determining unit  118  determines whether the first distance measuring unit  114  is caused to measure the vehicle-terminal distance M with the first precision or not to permit use of the mobile terminal  10  as the electronic key by confirming the satisfaction of the following first to third conditions. 
     First condition: The vehicle-terminal distance M decreases by a predetermined distance or larger in a plurality of vehicle-terminal distances M measured with the second precision at different points in time by the second distance measuring unit  115 . If the vehicle-terminal distance M decreases by a predetermined distance or larger, it is presumed that the user U carrying the mobile terminal  10  is approaching the vehicle  100  for using the vehicle  100 . Thus, if the first condition is satisfied, the high-precision distance measurement determining unit  118  determines to cause the first distance measuring unit  114  to measure the vehicle-terminal distance M. 
     Second condition: The remaining amount of the battery  160  recognized by the battery remaining-amount recognizing unit  116  is equal to or lower than a predetermined remaining amount. If the remaining amount of the battery  160  is equal to or lower than the predetermined remaining amount, reduction of the consumption of the battery  160  is required. For that, if the second condition is satisfied, the high-precision distance measurement determining unit  118  determines not to cause the first distance measuring unit  114  to measure the vehicle-terminal distance M. 
     Third condition: It is recognized by the electronic-key-app operation recognizing unit  117  that the electronic key app  30  is in operation in the mobile terminal  10 . If the third condition is satisfied, it may be considered that the user U has started the electronic key app  30  for using the vehicle  100 . Therefore, if the third condition is satisfied, the high-precision distance measurement determining unit  118  determines to cause the first distance measuring unit  114  to measure the vehicle-terminal distance M. 
     3. Distance Measurement Processing on Distance between Vehicle and Terminal 
     With reference to the flowcharts shown in  FIGS. 3 and 4 , processing for measuring a distance between the vehicle and the mobile terminal to be executed by the vehicle control apparatus  110  is described. 
     In step S 1  in  FIG. 3 , the vehicle communication control unit  111  performs polling by BLE and performs pairing processing with the mobile terminal  10  positioning within the out-vehicle communication area Ar 1  (see  FIG. 1 ) of the first vehicle communication unit  130 . In the subsequent step S 2 , when communication with the mobile terminal  10  by BLE is established by the pairing processing with the mobile terminal  10 , the vehicle communication control unit  111  advances the processing to step S 3 . 
     The vehicle communication control unit  111  transmits a polling signal through the first vehicle communication unit  130  and receives, through the first vehicle communication unit  130 , a response signal transmitted from the mobile terminal  10  having received the polling signal and thus detects the mobile terminal  10  and performs pairing with the mobile terminal  10 . As the procedure of the pairing, the polling signal may be transmitted from the mobile terminal  10 , and a response signal transmitted from the vehicle  100  having received the polling signal may be received by the mobile terminal  10  to perform pairing between the vehicle  100  and the mobile terminal  10 . 
     The battery remaining-amount recognizing unit  116  in step S 3  recognizes the remaining amount of the battery  160 , and the high-precision distance measurement determining unit  118  in the subsequent step S 4  determines whether the remaining amount of the battery  160  is equal to or lower than a predetermined remaining amount or not (the third condition described above). If the remaining amount of the battery  160  is equal to or lower than the predetermined remaining amount, the high-precision distance measurement determining unit  118  advances the processing to step S 14  in  FIG. 4 , and, in this case, the measurement of the vehicle-terminal distance M by the first distance measuring unit  114  is inhibited. On the other hand, if the remaining amount of the battery  160  is higher than the predetermined remaining amount, the high-precision distance measurement determining unit  118  advances the processing to step S 5 . 
     In step S 5 , the electronic-key-app operation recognizing unit  117  requests the mobile terminal  10  to transmit the operating state information Sci by BLE communication and obtains the operating state information Sci transmitted from the mobile terminal  10  in response to the request. Then, the electronic-key-app operation recognizing unit  117  recognizes whether the electronic key app  30  is in operation in the mobile terminal  10  or not from the operating state information Sci. 
     In the subsequent step S 6 , the high-precision distance measurement determining unit  118  determines whether the electronic-key-app operation recognizing unit  117  recognizes that the electronic key app  30  is in operation in the mobile terminal  10  or not. If it is recognized that the electronic key app  30  is in operation in the mobile terminal  10 , the high-precision distance measurement determining unit  118  advances the processing to step S 20  in  FIG. 4 . In this case, the first distance measuring unit  114  measures the vehicle-terminal distance M with the first precision by performing UWB communication with the mobile terminal  10  in step S 20 , and the processing then moves to step S 12 . Hereinafter, the vehicle-terminal distance M measured with the first precision by the first distance measuring unit  114  is also called “vehicle-terminal distance MH”. 
     On the other hand, if it is not recognized that the electronic key app  30  is in operation in the mobile terminal  10 , the high-precision distance measurement determining unit  118  advances the processing from step S 6  to step S 7 . In step S 7 , the terminal position information obtaining unit  113  requests the mobile terminal  10  to transmit the terminal position information Spi by BLE communication and obtains the terminal position information Spi transmitted from the mobile terminal  10  in response to the request. 
     In the subsequent step S 8 , the vehicle position information obtaining unit  112  obtains the vehicle position information Cpi including detection information on the current position of the vehicle  100  output from the GPS sensor  145 . In the next step S 9 , the second distance measuring unit  115  measures the vehicle-terminal distance M with the second precision based on the current position of the mobile terminal  10  recognized from the terminal position information Spi and the current position of the vehicle  100  recognized from the vehicle position information Cpi. Hereinafter, the vehicle-terminal distance M measured by the second distance measuring unit  115  is also called “vehicle-terminal distance ML”. The second distance measuring unit  115  saves, in the memory  120 , the data of the vehicle-terminal distance ML measured in step S 9 . 
     In the subsequent step S 10  in  FIG. 4 , the high-precision distance measurement determining unit  118  calculates a change amount ΔML (=ML 2 −ML 1 ) of the vehicle-terminal distance ML 2  measured at the current sampling time with respect to the vehicle-terminal distance ML 1  measured at the last sampling time with reference to the time-series data of the vehicle-terminal distance ML measured by the second distance measuring unit  115  and saved in the memory  120 . 
     In the next step S 11 , the high-precision distance measurement determining unit  118  determines whether the change amount ΔML is negative and the magnitude is equal to or higher than a predetermined value or not. If the change amount ΔML is negative and the magnitude is equal to or higher than the predetermined value, the high-precision distance measurement determining unit  118  advances the processing to step S 20 . In this case, as described above, the vehicle-terminal distance MH is measured with the first precision by the first distance measuring unit  114 . 
     On the other hand, if the change amount ΔML is positive and the user U carrying the mobile terminal  10  is moving away from the vehicle  100 , or if the magnitude of the change amount ΔML is lower than the predetermined value and it is recognized that the user U carrying the mobile terminal  10  is staying still, the high-precision distance measurement determining unit  118  advances the processing from step S 11  to step S 12 . In this case, the measurement of the vehicle-terminal distance MH by the first distance measuring unit  114  is not performed. 
     In step S 12 , the high-precision distance measurement determining unit  118  waits for the passage of the sampling time and then advances the processing to step S 13 . In step S 13 , the vehicle communication control unit  111  determines whether the BLE communication between the first vehicle communication unit  130  and the mobile terminal  10  has been disconnected or not. If the BLE communication between the first vehicle communication unit  130  and the mobile terminal  10  has been disconnected, the vehicle communication control unit  111  then advances the processing to step S 14  where the processing by the flowcharts in  FIGS. 3 and 4  ends. 
     On the other hand, if the BLE communication between the first vehicle communication unit  130  and the mobile terminal  10  is being established, the vehicle communication control unit  111  advances the processing to step S 3  in  FIG. 3 , and, in this case, the processing in step S 3  and subsequent steps is repeatedly executed, and whether the measurement of the vehicle-terminal distance MH with the first precision by the first distance measuring unit  114  is to be performed or not is determined by the high-precision distance measurement determining unit  118 . 
     4. Other Embodiments 
     Although, in the embodiment above, the high-precision distance measurement determining unit  118  determines the satisfaction of the first to third conditions, the determination of the satisfaction of the second and third conditions may be omitted. 
     Although, in the embodiment above, the vehicle position information obtaining unit  112  is provided and the vehicle position information Cpi is obtained by the vehicle GPS sensor  145 , information on a parking point of the vehicle  100  (point where use of the vehicle  100  starts) may be included in the terminal position information Spi which may then be transmitted to the vehicle  200  if the user U recognizes the parking point of the vehicle  100 . In this case, the vehicle position Information obtaining unit  112  obtains vehicle position information including current position information of the vehicle from the terminal position information Spi. The vehicle position information obtaining unit  112  may obtain vehicle position information including current position information on the vehicle  100  by obtaining a position signal output from a beacon placed at a parking location of the vehicle  100 . 
     Although, in the embodiment above, the second distance measuring unit  115  measures the vehicle-terminal distance MH with the first precision by performing UWB communication between the second vehicle communication unit  140  and the mobile terminal  10 , the vehicle-terminal distance MH may be measured with the first precision by other measurement methods. 
       FIGS. 1 and 2  are schematic diagrams showing the configuration of the vehicle control apparatus  110  by dividing it based on main processing details for easy understanding of the present invention of the subject application, but the vehicle control apparatus  110  may be configured based on other divisions. Processing by the constituent elements may be executed by one hardware unit or may be executed by a plurality of hardware units. The processing by the constituent elements shown in  FIGS. 3 and 4  may be executed by one program or may be executed by a plurality of programs. 
     5. Configuration Supported by Embodiments Above 
     The embodiments above are specific examples of the following configuration. 
     (1) A vehicle control apparatus including a vehicle communication control unit performing communication by a first communication specification with a mobile terminal used by a user of a vehicle when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, a first distance measuring unit measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining unit obtaining vehicle position information including current position information on the vehicle, a terminal position information obtaining unit obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through the vehicle communication control unit, a second distance measuring unit measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining unit determining whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured by the second distance measuring unit. 
     According to the vehicle control apparatus under (1), when the mobile terminal positions within an out-vehicle communication area and communication is performed by the first communication specification between the mobile terminal and the vehicle communication control unit, a vehicle-terminal distance is measured, by the second distance measuring unit, with low precision based on terminal position information transmitted from the mobile terminal. The high-precision distance measurement determining unit determines whether the first distance measuring unit is caused to measure the vehicle-terminal distance with first precision being high precision or not based on the vehicle-terminal distance measured by the second distance measuring unit. Thus, the power consumption required for measurement of the vehicle-terminal distance can be reduced more than a case where the vehicle-terminal distances are unconditionally measured with the high precision by the first distance measuring unit when the mobile terminal positions within the out-vehicle communication area. 
     (2) The vehicle control apparatus according to (1), wherein the high-precision distance measurement determining unit determines to cause the first distance measuring unit to measure the vehicle-terminal distance when the vehicle-terminal distance decreases by a predetermined distance or larger in a plurality of the vehicle-terminal distances measured at different points in time by the second distance measuring unit. 
     According to the vehicle control apparatus under (2), when it is presumed from a measurement state by the second distance measuring unit that a user carrying the mobile terminal is approaching the vehicle for using the vehicle, the first distance measuring unit can be caused to measure the vehicle-terminal distance with the high precision. 
     (3) The vehicle control apparatus under (2), further including a battery remaining-amount recognizing unit recognizing a remaining amount of a battery included in the vehicle, wherein the high-precision distance measurement determining unit determines not to cause the first distance measuring unit to measure the vehicle-terminal distance when the remaining amount of the battery recognized by the battery remaining-amount recognizing unit is equal to or lower than a predetermined remaining amount even though the vehicle-terminal distance decreases by a predetermined distance or larger in a plurality of the vehicle-terminal distances measured at different points in time by the second distance measuring unit. 
     According to the vehicle control apparatus under (3), when the remaining amount of the battery is low, the measurement of the vehicle-terminal distance by the first distance measuring unit is inhibited so that the decrease of the remaining amount of the battery can be reduced. 
     (4) The vehicle control apparatus under (2) or (3), further including an electronic-key-app operation recognizing unit recognizing that an electronic key app for remotely operating the vehicle with the mobile terminal is in operation based on operating state information on the mobile terminal transmitted from the mobile terminal to the vehicle communication control unit, wherein the high-precision distance measurement determining unit determines to cause the first distance measuring unit to measure the vehicle-terminal distance when the electronic-key-app operation recognizing unit recognizes that the electronic key app is in operation even though the vehicle-terminal distance does not decrease by a predetermined distance or larger in a plurality of the vehicle-terminal distances measured at different points in time by the second distance measuring unit. 
     According to the vehicle control apparatus under (4), when the electronic key app is in operation in the mobile terminal, it is presumed that there is a high possibility that the user uses the vehicle, and the first distance measuring unit can be caused to measure the vehicle-terminal distance with the high precision. 
     (5) The vehicle control apparatus according to any one of (1) to (4), wherein the terminal position information includes current position information on the mobile terminal detected by a terminal global positioning system (GPS) sensor provided in the mobile terminal, the vehicle position information includes current position information on the vehicle detected by a vehicle GPS sensor provided in the vehicle, the second distance measuring unit measures the vehicle-terminal distance with the second precision based on a current position of the vehicle detected by the vehicle GPS sensor and recognized from the vehicle position information and the terminal position information detected by the terminal GPS sensor and recognized from the terminal position information, and the first distance measuring unit measures the vehicle-terminal distance with the first precision by performing, by the vehicle communication control unit, communication with the mobile terminal by a second communication specification involving larger power consumption for communication than the first communication specification. 
     According to the vehicle control apparatus under (5), the second distance measuring unit measures the vehicle-terminal distance with the second precision based on current positions of the mobile terminal and the vehicle by the terminal GPS sensor and the vehicle GPS sensor where the precision of the position measurement may be decreased by communication between the mobile terminal and the vehicle by the first communication specification with lower power consumption for communication. Based on the vehicle-terminal distance by the second distance measuring unit, the high-precision distance measurement determining unit then determines whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not by performing communication between the mobile terminal and the vehicle by the second communication specification with higher power consumption for communication than the first communication specification. Thus, the power consumption required for the measurement of the vehicle-terminal distance can be reduced more than a case where the vehicle-terminal distances are unconditionally measured by the first distance measuring unit. 
     (6) The vehicle control apparatus under (5), wherein the first communication specification is a communication specification by Bluetooth Low Energy (BLE), and the second communication specification is a communication specification by Ultra Wide Band (UWB). 
     According to the vehicle control apparatus under (6), the power consumption is reduced by performing BLE communication for the measurement of the vehicle-terminal distance by the second distance measuring unit and performing UWB communication for the measurement of the vehicle-terminal distance by the first distance measuring unit so that the vehicle-terminal distance can be measured with high precision. 
     (7) A vehicle control method to be executed by a vehicle control apparatus performing communication with a mobile terminal used by a user of a vehicle, the method including a vehicle communication control step of performing communication by a first communication specification with the mobile terminal when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, a first distance measuring step of measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining step of obtaining vehicle position information including current position information on the vehicle, a terminal position information obtaining step of obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through processing in the vehicle communication control step, a second distance measuring step of measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining step of determining whether the first distance measuring step is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured in the second distance measuring step. 
     By executing the vehicle control method under (7) by the vehicle control apparatus, the configuration of the vehicle control apparatus under (1) above can be implemented. 
     (8) A recording medium with a program for control recorded, the program being executed by a vehicle control apparatus performing communication with a mobile terminal used by a user of a vehicle and causing the vehicle control apparatus to function as a vehicle communication control unit performing communication by a first communication specification with the mobile terminal when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, a first distance measuring unit measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining unit obtaining vehicle position information Including current position information on the vehicle, a terminal position information obtaining unit obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through the vehicle communication control unit, a second distance measuring unit measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining unit determining whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured by the second distance measuring unit. 
     By executing the program for control under (8) by the vehicle control apparatus, the configuration of the vehicle control apparatus under (1) above can be implemented. 
     (5) A vehicle control system including a vehicle control apparatus having a vehicle communication control unit and a mobile terminal used by a user of a vehicle, wherein the vehicle communication control unit and the mobile terminal perform communication by a first communication specification by establishing communication with each other when the mobile terminal positions within an out-vehicle communication area within a predetermined distance from the vehicle, and the vehicle control apparatus includes a first distance measuring unit measuring a vehicle-terminal distance with first precision, the vehicle-terminal distance being a distance between the vehicle and the mobile terminal, a vehicle position information obtaining unit obtaining vehicle position information including current position information on the vehicle, a terminal position information obtaining unit obtaining terminal position information including current position information on the mobile terminal transmitted from the mobile terminal by the first communication specification by receiving the terminal position information from the mobile terminal through the vehicle communication control unit, a second distance measuring unit measuring the vehicle-terminal distance with second precision based on the vehicle position information and the terminal position information, the second precision being measurement precision lower than the first precision, and a high-precision distance measurement determining unit determining whether the first distance measuring unit is caused to measure the vehicle-terminal distance or not based on the vehicle-terminal distance measured by the second distance measuring unit. 
     According to the vehicle control system under (9), when the mobile terminal positions within an out-vehicle communication area of the vehicle communication control unit and communication is established by the first communication specification between the mobile terminal and the vehicle communication control unit, a vehicle-terminal distance is measured, by the second distance measuring unit, with low precision based on terminal position information transmitted from the mobile terminal. The high-precision distance measurement determining unit determines whether the first distance measuring unit is caused to measure the vehicle-terminal distance with first precision being high precision or not based on the vehicle-terminal distance measured by the second distance measuring unit. Thus, the power consumption required for measurement of the vehicle-terminal distance can be reduced more than a case where the vehicle-terminal distances are unconditionally measured with the high precision by the first distance measuring unit when the mobile terminal positions within the out-vehicle communication area. 
     REFERENCE SIGNS LIST 
       1 : vehicle control system,  10 : mobile terminal,  20 : terminal GPS sensor,  30 : electronic key app,  100 : vehicle,  110 : vehicle control apparatus,  111 : vehicle communication control unit,  112 : vehicle position information obtaining unit,  113 : terminal position information obtaining unit,  114 : first distance measuring unit,  115 : second distance measuring unit,  116 : battery remaining-amount recognizing unit,  117 : electronic-key-app operation recognizing unit,  118 : high-precision distance measurement determining unit,  120 : memory,  121 : program for control,  130 : first vehicle communication unit,  131 : BLE antenna,  140 : second vehicle communication unit,  141 ,  142 ,  143 : UWB antenna,  145 : vehicle GPS sensor,  160 : battery, U: user