Patent Publication Number: US-2017350713-A1

Title: Map update system for automated vehicles

Description:
TECHNICAL FIELD OF INVENTION 
     This disclosure generally relates to a map-data update system suitable for use by automated vehicles, and more particularly relates to a system that issues an update-request to update the digital-map when the location of a traffic-signal has changed. 
     BACKGROUND OF INVENTION 
     It is known that an automated-vehicle detects light-color emitted by a traffic signal in order to determine how the automated-vehicle should be operated. For example, the automated-vehicle travels through an intersection when the traffic-signal is green, and the automated-vehicle stops when the traffic-signal is red. In order to assist the automated-vehicle to more effectively detect the traffic-signal, it has been suggested that a digital-map could include an indication of an expected-position of a traffic-signal. Having prior knowledge of the expected-location of a traffic-light may also be used by an automated-vehicle to determine when the line-of-site to the traffic light is obstructed, by a truck for example. However, if some event such as construction or natural disaster caused the actual-position of a traffic-signal to change, the process of manually updating the digital-map based on input from, for example, a construction-company employee or government official may not be timely or completely reliable. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment, a map-data update system suitable for use by automated vehicles is provided. The system includes a digital-map, an imager-device, and a controller. The digital-map is used to indicate an expected-position of a traffic-signal relative to a map-location of a host-vehicle. The imager-device is suitable to install on the host-vehicle. The imager-device is used to determine an actual-position of the traffic-signal relative to a present-location of the host-vehicle. The controller is in communication with the digital-map and the imager-device. The controller issues an update-request to update the digital-map when the actual-position differs from the expected-position by greater than an error-threshold. 
     Further features and advantages will appear more clearly on a reading of the following detailed description of the preferred embodiment, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagram of a map-data update system in accordance with one embodiment; and 
         FIG. 2  is a traffic scenario encountered by the system of  FIG. 1  in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a non-limiting example of a map-data update system  10 , hereafter referred to as the system  10 , which is suitable for use by automated vehicles, in particular a host-vehicle  12 . While the teachings presented herein use fully-automated or autonomous (i.e. driverless) vehicles as in the non-limiting examples where a computer operates the vehicle-controls  14  of the host-vehicle  12 , it is contemplated that the advantages of the system  10  described herein are applicable when a vehicle is being operated in a manual mode where an operator (not shown) operates the vehicle-controls  14 . 
     The system  10  includes a digital-map  16  that indicates an expected-position  18  of a traffic-signal  20  (i.e. traffic-light) relative to a map-location  22  of the host-vehicle  12 . While the digital-map  16  is shown as being located within the host-vehicle  12 , it is contemplated that alternatively the digital-map  16  could be stored ‘in the cloud’ for access by the host-vehicle. More likely, a copy of the digital-map  16  will received from a provider  24  of map data, and be stored in the host-vehicle  12  for quick and reliable access. However, the digital-map  16  is expected to be periodically (e.g. daily or weekly) updated so the latest information is available to operate the host-vehicle  12 . 
       FIG. 2  illustrates a non-limiting example of a traffic-scenario  26  that may be encountered by the host-vehicle  12 . The expected-position  18  of the traffic-signal  20  in this example is atop a post adjacent to the intersection  28 . This expected-position  18  is based on information from the digital-map  16 , which may be indicated by world coordinates, e.g. latitude, longitude, and elevation. However, due to construction activity for example, the traffic-signal  20  has been relocated so the actual-position  30  of the traffic-signal  20  is now suspended over the middle of the intersection  28  as illustrated. In order to determine the map-location  22  so the expected-location  18  and the actual-position  30  can be indicated and communicated, the system  10  may include a location-device  32  such as a global-position-system-receiver (GPS-receiver), as will be recognized by those in the art. 
     In order for the system  10  to determine that the traffic-signal  20  is not at the expected-position  18 , and is located at the actual-position  30 , the host-vehicle is equipped with imager-device  34  suitable to install on the host-vehicle  12 . By way of example and not limitation, the imager-device  34  may be a camera, lidar-unit, or any combination of sensors suitable to detect the actual-location  30  of the traffic-signal  20  and what color of light is being emitted by the traffic-signal  20 . That is, the imager-device  34  is used to determine the actual-position  30  of the traffic-signal  20  relative to a present-location  36  of the host-vehicle  12  indicated by the location-device  32 . Ideally, the present-location  36  and the map-location  22  match. However, it is recognized that the present-location  36  (i.e. the actual GPS coordinates) of the host-vehicle  12  may not perfectly match the map-location (i.e. where on the map the host-vehicle  12  is presumed to be located). It is contemplated that if there is a persistent slight difference or offset between the expected-position  18  and the actual-position  30 , less than a quarter-meter (0.25 m) for example, then the system  10  may be further configured to learn and apply a location-offset to the present-location  36  and/or the map-location  22  to compensate for an apparent error in the location-device  32 . 
     Referring again to  FIG. 1 , the system  10  includes a controller  40  in communication with the digital-map  16  and the imager-device  34 . The controller  40  may include a processor (not specifically shown) such as a microprocessor or other control circuitry such as analog and/or digital control circuitry including an application specific integrated circuit (ASIC) for processing data as should be evident to those in the art. The controller  40  may include memory (not specifically shown), including non-volatile memory, such as electrically erasable programmable read-only memory (EEPROM) for storing the digital-map  16 , one or more routines, thresholds, and captured data. The one or more routines may be executed by the processor to perform steps for determining the expected-position  18  and the actual-position  30  based on signals received by the controller  40  from the location-device  32 , the imager-device  34 , and the provider  24  as described herein. 
     If the difference between the expected-position  18  and the actual-position  30  is large enough to not be caused by GPS errors as suggested above, then it may be necessary to update the digital-map  16 . Advantageously, the update may be accomplished if the controller  40  issues an update-request  42  to the provider  24  to update the map-database  44  maintained by the provider  24 , which will result in a update to the digital-map  16  being sent back by the provider  24 . This arrangement is particularly advantageous as other-vehicles (not shown) that will travel through the intersection  28  at some later time, e.g. the next day, will receive an updated version of digital-map from the provider  24  prior to encountering the intersection  28 . Alternatively, or in addition to sending the update-request  42  to the provider  24 , the update-request  42  may initiate operating the controller  40  so that the update is made directly to the digital-map  16  by the controller  40 . In either case, the update-request  42  is made when the actual-position  30  differs from the expected-position  18  by greater than an error-threshold  46 , 0.25 m for example. 
     In addition to detecting when the traffic-signal  20  has been moved or relocated, the system  10 , or more specifically the controller  40 , may be further configured to issue the update-request  42  to update the digital-map  16  when the traffic-signal  20  is not operational, i.e. the operational-state  48  is ‘out-of-order’. This information can forewarn other-vehicles that the traffic-signal  20  is not working so, for example, the intersection  28  can be avoided by taking an alternate route. In addition, this information may be forwarded to the proper entity or authorities so, for example, a police officer may be dispatched to direct traffic through the intersection, and/or a repair-crew can be dispatched to repair the traffic-signal. 
     In contrast to the controller  40  sending or issuing the update-request  42  when the traffic-signal  20  is determined to be at an actual-position  30  other than the expected-position  18 , the controller may be further configured to issue the update-request  42  to update the digital-map  16  when an unexpected-signal  50  not present on the digital-map  16  is detected. That is, if the presence of a traffic-signal is detected and the digital-map  16  has no record of any corresponding traffic-signal within a substantial distance, e.g. twenty-five meters (25 m) from the actual-position  30  of the unexpected-signal  50 , then the update-request  42  may be used to document the presence of a new instance of traffic-signal in the map-database  44 . It is contemplated that the unexpected-signal  50  may be a newly installed traffic-signal, or a traffic-signal that has been in place for some time that for some reason was never documented in the map-database  44 . 
     In order for the controller  40  to communicate with the provider  24 , the system may include a transceiver  52  suitable to install on the host-vehicle  12 . The transceiver  52  may be used to transmit the update-request  42  to the provider  24  of the digital-map  16 , and/or receive updates of the digital-map  16  from the provider  24 . The transceiver  52  may be a WI-FI® type transceiver that establishes a communications link with the provider  24  when a suitable WI-FI® network is available, or the transceiver  52  may be a cellular-phone network type transceiver, or a satellite transceiver. Communications between the controller  40  an the provider  24  may be established continuously if available, or may be established on a periodic basis such as in the middle of the night each day. 
     As noted above, it is recognized that errors can occur in coordinate values used to indicate the present-location  36 . In order to prevent erroneous or malicious revisions to the map-database  44 , the provider  24  may require that a minimum number of similar instances of the update-request  42  are received. That is, the provider  24  may update the digital-map  16  only after a plurality of update-requests (e.g. a request-count  54  more than seven) for the same instance of the traffic-signal  20  is received by the provider  24 . The provider  24  may further require that each of the plurality of update-requests is received from a distinct instance of the controller  40 , i.e. from a different host-vehicle or different customer identification, before accepting the update-request  42  as valid and revising the digital-map  16 . 
     In further view of the recognition that errors can occur in coordinate values used to indicate the present-location  36 , the provider may update the digital-map  16  based on an average-position  56  that is a calculated average of multiple instances of the actual-positions from the plurality of update-requests. It is expected that by basing the update of the digital-map  16  there will be fewer erroneous instance of map-update systems determining that the actual-position  30  differs from the expected-position  18  by greater than the error-threshold  46   
     Accordingly, a map-data update system (the system  10 ), a controller  40  for the system  10  and a method of operating the system  10  is provided. The system  10  provides a reliable way for a map-database  44  to be continuously checked for accuracy and quickly updated when the expected-position  18  of a traffic-signal does not reasonably match the actual-position  30  determined by the controller  40  of the host-vehicle  12 . The system  10  thereby removes the burden on government and/or construction companies to provide manual updates of the map-database  44 . 
     While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.