Patent Publication Number: US-2021173072-A1

Title: Method for detecting the approach of an object on a lateral side of a moving vehicle and on-board associated detection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national phase of International Application No. PCT/EP2019/072152 filed Aug. 19, 2019 which designated the U.S. and claims priority to FR 1857611 filed Aug. 23, 2018, the entire contents of each of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method for detecting the approach of an object on a lateral side of a moving motor vehicle and to an associated detection device which is on board said motor vehicle. 
     Description of the Related Art 
     Nowadays, and despite technological progress, the detection of the approach of an object on a lateral side of a moving motor vehicle by a motorist driving said vehicle, and more specifically the detection of vehicles approaching on one of the lateral sides of the vehicle, either on the side where the driver is located or on the side where the front passenger is located, remains problematic and is the cause of many accidents. If the driver does not see the approaching vehicle in their rearview mirror because said approaching vehicle is in the blind spot of the field of the rearview mirror, they may decide to overtake a vehicle located in front of their vehicle, thus risking a collision with the vehicle that is approaching from one of the rear lateral sides. 
     The solutions of the prior art consist in supplementing the front rearview mirrors with a magnifying mirror or in fitting the vehicle with an additional camera that displays the objects located in the vicinity of the vehicle in the blind spot of the rearview mirrors. 
     The first solution is generally unsatisfactory and does not make it possible to see the entire field located in the blind spot, and the second solution is too costly to be provided in low-end or mid-range vehicles. 
     It is therefore necessary to overcome the drawbacks of the prior art and to be able to offer the driver a means of detecting objects in the blind spot of their rearview mirrors. 
     SUMMARY OF THE INVENTION 
     The invention relates to a method for detecting the approach of an object on a lateral side of a moving motor vehicle, said vehicle being fitted with door handles on said lateral side, each of which includes an ultra-high-frequency antenna designed, when the vehicle is stationary, to detect the presence of a portable user apparatus in the vicinity of the vehicle and to identify said apparatus in order to validate hands-free access to the vehicle for the user, said method being noteworthy in that: 
     the antennas are initially adapted such that each one of said antennas emits an electromagnetic field, a first radiated power per steradian of which, in a first zone oriented toward the outside of the vehicle and defined by a first aperture angle, is greater than a second radiated power per steradian in a second, lateral zone directed toward the other antenna and defined by a second aperture angle, 
     and, when the vehicle is moving, the detection of the approach of the object is validated by the reception, by at least one antenna, of an electromagnetic field emitted by the other antenna and reflected by the object, the received power of which is higher than a predetermined minimum received power. 
     Preferably, the first aperture angle is greater than the second aperture angle. 
     Advantageously, the approach detection method also comprises detecting the overtaking of the vehicle, characterized in that the overtaking detection is validated if the received power of the electromagnetic field remains above the predetermined minimum received power for a period of time longer than a predetermined period of time. 
     Judiciously, the first radiated power is higher than the second radiated power by at least 10 dBi. 
     The method according to the invention is noteworthy in that a slope is calculated for the increase in the value of the received power over time in order to determine a speed of approach of the object on the basis of a driving speed of said vehicle. 
     The invention also relates to a device for detecting the approach of an object on a lateral side of a moving motor vehicle, said device being incorporated in door handles on said lateral side of said vehicle, each of which includes an ultra-high-frequency antenna designed, when the vehicle is stationary, to detect the presence of a portable user apparatus in the vicinity of the vehicle and to identify said apparatus in order to validate hands-free access to the vehicle for the user, said device being noteworthy in that it further comprises: 
     means for adapting the antennas such that each one of said antennas emits an electromagnetic field, a first radiated power per steradian of which, in a first zone oriented toward the outside of the vehicle and defined by a first aperture angle, is greater than a second radiated power per steradian in a second, lateral zone directed toward the other antenna and defined by a second aperture angle, 
     while the vehicle is moving, means for measuring a power of the electromagnetic field received by each antenna, 
     means for comparing the value of the received power with a predetermined minimum received power, 
     means for storing the predetermined received power. 
     The device may comprise: 
     a clock H comprising means for measuring a period of time, 
     means for comparing a measured period of time during which the received power is higher than the minimum received power with a predetermined period of time, 
     additional means for storing the predetermined period of time. 
     Judiciously, the antenna adapting means are in the form of metal shielding and/or unidirectional antennas. 
     The invention also applies to any motor vehicle comprising a detection device according to any one of the features set out above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other aims, features and advantages of the invention will become apparent upon reading the following description provided by way of non-limiting example and upon examining the appended drawings, in which: 
         FIG. 1 a    is a schematic view of an object, in this case of a vehicle, approaching from a position A in dashed lines to a position B on a lateral side of a moving vehicle which is implementing the approach detection method according to the invention, 
         FIG. 1 b    is a schematic view of an object, in this case of a vehicle, which is overtaking a moving vehicle that is implementing the approach detection method, and more specifically the overtaking detection method, according to the invention, 
         FIG. 2  is a schematic view of a door handle P that incorporates the detection device according to the invention, 
         FIG. 3  is a detailed schematic view of the detection device according to the invention, 
         FIG. 4  is a graph illustrating the power that is received by an antenna and is representative of an object approaching and overtaking on a lateral side of a vehicle, and 
         FIG. 5  is a flowchart illustrating the detection method. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As explained above, there is no satisfactory prior art solution for detecting the approach of an object, in this case for detecting the approach of a vehicle on a lateral side of another moving vehicle. 
     It is known practice to use BLE® (Bluetooth Low Energy) ultra-high-frequency antennas on a vehicle and more specifically in the door handles of a vehicle in order to locate a fob or a portable user apparatus around the vehicle and in order to then identify same as being paired with the vehicle and to perform automatic “hands-free” unlocking (or locking) of the vehicle upon the user approaching (or moving away). This detection thus allows the user to unlock/lock their vehicle without physically having to actuate a key. 
     The use of BLE® antennas has several advantages; but in particular BLE® technology is present on most portable user apparatuses. Thus, the user may use a cell phone or the like to access their vehicle, and not only the hands-free access fob that operates with RF, LF (radio frequency and low frequency, respectively) technology, i.e. using a radio frequency between 30 kHz and 300 kHz. 
     BLE is understood to mean any ultra-high-frequency wireless communication, i.e. at a frequency from 300 MHz to 3 GHz or from 100 MHz to over 3 GHz, for example from 2 GHz to 5 GHz for Wi-Fi®. 
     This is illustrated in  FIG. 1 a   ; the vehicle V 1  comprises BLE antennas, a first antenna BLE 1  and a second antenna BLE 2 , in each door handle  10 ,  20  on at least one lateral side of the vehicle, more specifically on the driver side. 
     The vehicle may of course comprise BLE antennas BLE 3 , BLE 4  on the other lateral side, the passenger side, said antennas being incorporated in the handles  30 ,  40 . 
     The BLE antennas are thus called upon only when the vehicle is at a standstill to perform location, identification and locking/unlocking intention validation functions. 
     The method according to the invention proposes also using said BLE antennas when the vehicle is moving, in order to detect the approach of an object on a lateral side of said vehicle. 
     The detection method according to the invention will now be described. 
     Initially (step E 0 , cf.  FIG. 5 ), the antennas BLE 1 , BLE 2  in the handles  10 ,  20  are adapted such that each one of said antennas BLE 1 , BLE 2  emits an electromagnetic field, a first radiated power P 1  per steradian of which, in a first zone Z 1  oriented toward the outside of the vehicle and defined by a first aperture angle α, is greater than a second lateral radiated power P 2  per steradian in a second zone Z 2  directed toward the other antenna and defined by a second aperture angle β. 
     This is illustrated in  FIG. 1 a   . In other words, the antennas BLE 1 , BLE 2  are configured to emit a more powerful electromagnetic field in a first zone Z 1  oriented toward the outside of the vehicle than in a second zone Z 2  oriented toward the other antenna BLE 1 , BLE 2 . Preferably, the first aperture angle α is greater than the second aperture angle β so that the first zone Z 1  covered by the electromagnetic field emitted by the antenna BLE 1 , BLE 2  is larger than the second zone Z 2 . 
     Preferably, the first radiated power P 1  per steradian is at least 10 dBi higher than the second radiated power P 2  per steradian. 
     Thus, in the absence of the detection of an object approaching the vehicle V 1 , whether the vehicle V 1  is stationary or moving, the magnetic field received by one antenna BLE 1 , BLE 2  from the other antenna BLE 1 , BLE 2  will be as weak as possible or even nonexistent. Thus, in the absence of an object in the vicinity of the side where the antennas are located, an antenna BLE 1 , BLE 2  does not receive the electromagnetic field emitted by the other antenna BLE 1 , BLE 2 , or receives it to a limited extent. 
     It is important to note that the first power P 1  per steradian must be higher than the second power per steradian; these are not average powers. In order for the invention to work, for each direction included in the first aperture angle α, the first power P 1  must be higher than the second power P 2  in any direction included in the second aperture angle β. 
     Preferably, the first aperture angle α is greater than the second aperture angle β. 
     When an object approaches on a lateral side of the vehicle, for example when a second vehicle V 2  approaches, from a position A, in dashed lines in  FIG. 1 a   , located behind the vehicle V 1 , to a position B, located on a lateral side of the vehicle V 1 , the electromagnetic field emitted by the second antenna BLE 2  is reflected by the metal structure of the vehicle V 2 , and a part of the reflected electromagnetic field is redirected toward the first antenna BLE 1 . 
     The first antenna BLE 1  then detects an increase in the power of the electromagnetic field that it receives. This is illustrated in  FIG. 4 . 
     If the value of the power of the received signal, also known as RSSI (“Received Signal Strength Indication”), which will be denoted RSSI 1  for the first antenna BLE 1 , increases and exceeds a predetermined minimum received power value RSSI MIN  at the instant t 1  (step E 1 ,  FIG. 5 ), then the approach detection of the object, in the present case of the second vehicle V 2  on a lateral side of the vehicle V 1 , in this case the side where the second antenna BLE 2  is located, is validated (step E 2 ,  FIG. 5 ). 
     In one refinement of the invention, when the value of said received power RSSI 1  remains above the predetermined minimum received power RSSI MIN  for a period of time Δ longer than a predetermined period of time Δmin, (cf.  FIG. 4  and step E 3  in  FIG. 5 ), then the detection not only of the approaching but also of the overtaking of the vehicle V 1  by the second vehicle V 2  is validated. This is illustrated in  FIG. 1   b.    
     When the vehicle V 1  is approached by the second vehicle V 2 , the first antenna BLE 1  also receives a power RSSI 2  of the electromagnetic field emitted by the second antenna BLE 2  and reflected by the second vehicle V 2 , which is higher than a second predetermined threshold, RSSI MIN2 , the value of which is equal to or different from the predetermined power threshold RSSI MIN  of the second antenna BLE 2 . If said received power value RSSI 2  remains above the predetermined minimum value RSSI MIN2  for a period of time Δ 2  longer than a predetermined period of time Δmin 2 , then the detection of the overtaking is validated. 
     Thus, the measurement of the power received by the first antenna BLE 1  makes it possible to confirm the approaching and then the overtaking of the vehicle V 1  by the second vehicle V 2 , which has been detected by the second antenna BLE 2 . 
     Since the location of the antennas BLE 1 , BLE 2  on the vehicle V 1  is known by the central electronic control system of the vehicle, said control system may thus use the analysis of the signals of the power received by the antennas BLE 1 , BLE 2  to determine which antenna the second vehicle V 2  is in the proximity of. 
     Analyzing the increase in the received power over time (i.e. the slope of the signal) makes it possible, on the basis of the driving speed of the vehicle V 1 , to determine the speed of approach of the second vehicle V 2 . This is because the power-over-time slope is proportional to the difference in speed between the two vehicles V 1 , V 2 . 
     This is illustrated in  FIG. 4 ; the received power increases from a received power RSSI 0  at t=t 1  to a received power of RSSI 1  at t=tx. The slope P is thus calculated: 
     
       
         
           
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                       RSSI 
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     and said P is a function of the speeds of the vehicle V 1  and of the approaching vehicle V 2   
         P =ƒ({right arrow over ( v 1)},{right arrow over ( v 2)})
 
     with 
     {right arrow over (v1)}: speed of the vehicle V 1 , 
     {right arrow over (v2)}: speed of the approaching vehicle V 2 . 
     This function may be derived during preliminary calibration tests and then recorded or stored in storage means in a controller of the detection device (see below). 
     Since the speed of the vehicle V 1  is known, the speed of the second vehicle V 2  can thus be derived therefrom by means of this function. 
     The method is implemented by a detection device D incorporated in the handle  10  (cf.  FIG. 2 ), comprising a BLE antenna BLE 1  that is, for example, connected to a control circuit  30  located, for example, in a printed circuit board. 
     In order to carry out the detection method according to the invention, the detection device D further comprises (cf.  FIG. 3 ): 
     an ultra-high-frequency antenna BLE 1 , BLE 2 , 
     means M 1  for adapting antennas such that each one of said antennas BLE 1 , BLE 2  emits an electromagnetic field, a first radiated power P 1  per steradian of which, in a first zone Z 1  oriented toward the outside of the vehicle and defined by a first aperture angle α, is greater than a second lateral radiated power P 2  per steradian in a second zone Z 2  directed toward the other antenna BLE 2 , BLE 1  and defined by a second aperture angle β, 
     while the vehicle V 1  is moving, means M 2  for measuring the electromagnetic field received by each antenna BLE 1 , BLE 2 , 
     means M 3  for comparing the value of the received power RSSI 1 , RSSI 2  with a predetermined minimum received power RSSI MIN , RSSI MIN2 , 
     means M 6  for storing the predetermined minimum received power RSSI MIN , RSSI MIN2  and 
     in the refined embodiment of the invention, the detection device D further comprises: 
     a clock H comprising means for measuring a period of time, 
     means M 4  for comparing a measured period of time Δ, Δ 2  during which the received power is higher than the minimum received power with a predetermined period of time Δmin, Δmin 2 , additional means M 7  for storing the predetermined period of time Δmin, Δmin 2 . 
     The means for adapting antennas BLE 1 , BLE 2  may be in various forms known to a person skilled in the art: 
     either a metal shield around the antenna BLE 1 , BLE 2 , included in the detection device D or optionally on the handle  10 ,  20 , which shield performs the function of an electromagnetic wave reflector, making it possible to orient and/or adjust the power of the electromagnetic field in an aperture angle, 
     or via the use of unidirectional antennas which therefore emit in a favored direction, 
     or any other means known to a person skilled in the art. 
     The means M 2  for measuring the electromagnetic field are in the form of an electronic receiving circuit known to a person skilled in the art. 
     The clock H may be an electronic clock. 
     The comparing means M 3 , M 4  and the storage means M 6  are in the form of software integrated in a microprocessor-type controller located in the printed circuit board. 
     The antenna BLE 1 , BLE 2  is electrically connected to control means  30  comprising: 
     the means M 2  for measuring the electromagnetic field received by each antenna BLE 1 , BLE 2 , 
     the means M 3  for comparing the value of the received power RSSI 1 , RSSI 2  with a predetermined minimum received power RSSI MIN , RSSI MIN2 , 
     the clock H comprising means for measuring a period of time, 
     the means M 4  for comparing a measured period of time Δ, Δ 2  during which the received power is higher than the minimum received power with a predetermined period of time Δmin, Δmin 2 , the means M 6  for storing the predetermined minimum received power RSSI MIN , RSSI MIN2  and the additional means M 7  for storing the predetermined period of time Δmin, Δmin 2 . 
     In order to implement a refinement of the invention set forth above, the detection device D may comprise storage means in the controller for storing the function connecting the received power on the basis of the speeds of the two vehicles, V 1  and V 2   
         P =ƒ({right arrow over ( v 1)},{right arrow over ( v 2)})
 
     with 
     {right arrow over (v1)}: speed of the vehicle V 1 , 
     {right arrow over (v2)}: speed of the approaching vehicle V 2 . 
     The invention thus makes it possible to judiciously use the ultra-high-frequency antennas that are arranged on the vehicle during driving of the vehicle in order to detect the approach of an object on a lateral side of the vehicle, whereas said antennas were hitherto used only during stationary vehicle phases. 
     The method is simple to implement and inexpensive.