Patent Publication Number: US-2019184988-A1

Title: Lane keeping and following system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) to Patent Application No. 201711368885.0 filed in China, P.R.C. on Dec. 18, 2017, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Technical Field 
     The present new invention relates to the field of automobiles, and in particular, to a lane keeping and following system. 
     Related Art 
     An automatic driving system controls a vehicle in a control manner such as acceleration, deceleration, turning, or gear shifting according to global positioning information, road geometry information, and road surrounding conditions. Therefore, as the automatic driving automobile gradually develops from semi-automatic driving to full-automatic driving, higher requirements are imposed on the precision of positioning. 
     Currently, a commercial global position system (GPS) device is usually of a road level, and has an error of approximately 10 meters. During navigation in a common environment, not only the precision of the location decreases, but also loss of accuracy easily occurs on determining in scenarios of turning and going uphill and downhill. The error may result in loss of accuracy of control on an automatic driving vehicle, and the safety of passengers is engendered. 
     Currently, there are high-precision GPS devices of a street or lane level. However, the price of a high-precision GPS device may exceed the price of a vehicle, being inconsistent with the configuration costs. Moreover, the high-precision GPS devices may still be affected by the weather, or the topography such as a tunnel, resulting in malfunction or inaccuracy. 
     SUMMARY 
     To resolve the problem in the prior art, a lane keeping and following system applied to a vehicle is provided herein. The lane keeping and following system includes a global positioning device, a high-precision road map unit, and a following control device. The global positioning device is disposed on the vehicle and used for continuously generating and outputting global positioning information. The high-precision road map unit is disposed on the vehicle and used for storing a plurality of pieces of road information, where each piece of road information includes lane information, and each piece of lane information includes geometry information of a lane line. The following control device is disposed on the vehicle and electrically connected to the global positioning device and the high-precision road map unit, and is used for continuously receiving the global positioning information and continuously matching the road information, to find the lane information currently corresponding to the global positioning information, and retrieving the geometry information of a lane line included in the currently corresponding lane information and controlling the vehicle to travel following the geometry information of a lane line. 
     By using the global positioning device and the high-precision road map unit, high-precision positioning can be implemented, so that the following control device can control the vehicle to travel following the currently corresponding geometry information of a lane line and correct the currently corresponding geometry information of a lane line at any time. In this way, the costs of a conventional high-precision GPS can be greatly reduced, incorrect positioning guidance is avoided, and the vehicle can be correctly and safely controlled to travel, thereby facilitating the development of automatic driving. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block diagram of a lane keeping and following system; 
         FIG. 2  is a schematic top view of a lane keeping and following system; 
         FIG. 3 a    is a schematic diagram of road information in a high-precision map unit; 
         FIG. 3 b    is a schematic diagram of correcting a traveling path of a vehicle by a following control device according to road information; 
         FIG. 3 c    is a schematic diagram of a lane following image generated by a visual tracker; 
         FIG. 4  is a schematic diagram of positioning a vehicle on a lane by a following control device; 
         FIG. 5  is a schematic block diagram of an inertial measurement unit in  FIG. 1 ; 
         FIG. 6  is a schematic diagram of a vehicle control curve; and 
         FIG. 7  is a curve diagram of driving data according to an actual embodiment of vehicle automatic driving. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic block diagram of a lane keeping and following system. As shown in  FIG. 1 , a lane keeping and following system  1  may be mounted on a vehicle  100 . The lane keeping and following system  1  includes a global positioning device  10 , a high-precision road map unit  20 , and a following control device  30 . The global positioning device  10 , the high-precision road map unit  20 , and the following control device  30  are all disposed on the vehicle  100 . The global positioning device  10  is used for continuously generating and outputting global positioning information. The high-precision road map unit  20  is used for storing a plurality of pieces of road information. Each piece of road information includes at least one piece of lane information. Each piece of lane information includes geometry information of a lane line. The following control device  30  is electrically connected to the global positioning device  10  and the high-precision road map unit  20 , and is used for continuously receiving the global positioning information and continuously matching the road information with the global positioning information, to find the lane information currently corresponding to the global positioning information. The following control device  30  is used for retrieving the geometry information of a lane line included in the piece of lane information and controlling the vehicle  100  to travel following the currently corresponding geometry information of a lane line. 
     The global positioning device  10  herein is a common GPS of a commercial road level, and an error of the global positioning information generated by the global positioning device  10  is about 10 meters. The road information of the high-precision road map unit  20  is of a street level or a lane level, and an error of the road information is less than 20 centimeters. The road information provided by the high-precision road map unit  20  may further include a road identifier, a road length, a lane quantity, a road speed limit, coordinates of a road starting point, coordinates of a road end point, coordinates of a stop line, and the like. The lane information may include a lane identifier, a lane width, and the like. Therefore, after receiving the global positioning information, the following control device  30  can match the global positioning information with the currently corresponding lane information and road information, determine a current location of the vehicle  100 , and determine a road on which the vehicle  100  is located and a specific lane on the road, so that the following control device  30  controls the vehicle  100  to travel according to the geometry information of a lane line. The geometry information of a lane line may include coordinates of a starting point, coordinates of an end point, a curvature, and the like of the lane line. 
       FIG. 2  is a schematic top view of a lane keeping and following system. As shown in  FIG. 1  and  FIG. 2 , in some embodiments, the lane keeping and following system  1  further includes a visual tracker  40 . The visual tracker  40  is electrically connected to the following control device  30 , and is used for continuously retrieving and outputting a lane following image, and the following control device  30  is further used for correcting the currently corresponding geometry information of a lane line according to the lane following image, and controlling the vehicle  100  to travel following the corrected currently corresponding geometry information of a lane line. As shown in  FIG. 2 , the visual tracker  40  may be a lens  41  mounted at the front of the vehicle  100 , and can continuously shoot the lane following image in front of the vehicle  100 . In this way, the following control device  30  can perform correction according to an actual road image in addition to the global positioning information and the road information, making the positioning more precise. 
     In some other embodiments, the visual tracker  40  is used for continuously retrieving and outputting a surrounding image, the high-precision road map unit  20  is further used for storing at least one piece of location information of a point of interest, and the following control device  30  is further used for correcting the currently corresponding geometry information of a lane line with reference to the surrounding image and the location information of a point of interest, and controlling the vehicle  100  to travel following the corrected currently corresponding geometry information of a lane line. As shown in  FIG. 2 , the visual tracker  40  may be a lens  41  mounted on a side edge of the vehicle  100  or mounted on a back mirror  110  of the vehicle  100 . The location information of a point of interest may be a traffic light location, a tourist attraction location, a building location, or a combination thereof. The following control device  30  herein further obtains a relative distance between the vehicle  100  and the point of interest by means of analysis according to the surrounding image and the location information of a point of interest, and re-determines the current lane information, so as to correct the currently corresponding geometry information of a lane line and control the vehicle  100  to travel following the currently corresponding geometry information of a lane line. 
       FIG. 3 a    is a schematic diagram of road information in a high-precision map unit.  FIG. 3 b    is a schematic diagram of correcting a traveling path of a vehicle by a following control device according to road information.  FIG. 3 c    is a schematic diagram of a lane following image generated by a visual tracker. A road information image F 1  shown in  FIG. 3 a    is a simulated image and shows geometry information of a lane line included in currently corresponding lane information. In combination with  FIG. 1 , the following control device  30  controls the vehicle  100  to travel following the currently corresponding geometry information of a lane line. As shown in  FIG. 3 b   , correcting the traveling path of the vehicle  100  by the following control device  30  according to the road information is: using a superimposition image F 2 , which is a virtual image, to represent that the geometry information of a lane line included in the currently corresponding lane information is superimposed with the lane following image generated by the visual tracker  40 , so as to perform correction according to a deviation between the lane following image and the geometry information of a lane line included in the currently corresponding lane information, thereby, as shown in  FIG. 3 c   , keeping the geometry information of a lane line included in the lane information currently corresponding to the lane following image F 3 . 
     Further, existing automatic driving systems rely on the visual tracker  40  to perform road tracking. However, the visual tracker  40  may malfunction due to poor parsing in a specific scenario, such as a scenario with insufficient brightness or thick fog. That is, when the lane following image F 3  in  FIG. 3 c    disappears, the following control device  30  can still guide, by using the global positioning information provided by the global positioning device  10  and the road information provided by the high-precision road map unit  20 , the vehicle to travel. 
       FIG. 4  is a schematic diagram of positioning a vehicle on a lane by a following control device. As shown in  FIG. 1 ,  FIG. 2 , and  FIG. 4 , the following control device  30  can determine, by using the global positioning information provided by the global positioning device  10  and the road information provided by the high-precision road map unit  20 , that the vehicle  100  is located on a lane D of a road R. 
     Further, referring again to  FIG. 3 a    to  FIG. 3 c   , the following control device  30  may alternatively use the lane following image F 3  generated by the visual tracker  40  or a surrounding image (not shown) shot by another lens to assist in the positioning and correction, thereby keeping the vehicle  100  traveling on the lane D according to the currently corresponding geometry information of a lane line. This is merely an example herein, and the present invention is not limited thereto. 
       FIG. 5  is a schematic block diagram of an inertial measurement unit in  FIG. 1 . As shown in  FIG. 1  and  FIG. 5 , in some embodiments, the lane keeping and following system  1  further includes an inertial measurement unit  50 . The inertial measurement unit  50  is electrically connected to the following control device  30 , and may include a gyroscope  53 . The gyroscope  53  is used for continuously measuring and outputting a yawing angle and an angular velocity of the vehicle  100 . The lane information further includes a road course angle. The following control device  30  is further used for controlling the vehicle  100  to travel following the currently corresponding geometry information of a lane line according to the yawing angle, the angular velocity, and the road course angle. In other words, the inertial measurement unit  50  measures a turning state of the vehicle  100 , and performs determination based on the road information, so as to constantly track whether the geometry information of a lane line is consistent with the state of the vehicle  100 , and constantly perform correction. In this way, a problem that a conventional GPS has a poor positioning effect on curved paths can be greatly improved. 
     Further, the inertial measurement unit  50  is used for continuously measuring and outputting a pitch angle and an acceleration. The lane information further includes a road slope. The following control device  30  is further used for controlling the vehicle  100  to travel following the currently corresponding geometry information of a lane line according to the pitch angle, the acceleration, and the road slope. Herein, as shown in  FIG. 5 , the inertial measurement unit  50  may include an accelerometer  51 . In other words, the inertial measurement unit  50  continuously measures the pitch angle and the acceleration of the vehicle  100  to determine whether the vehicle  100  is in a state of going uphill or downhill, and further performs determination based on the road information, so as to track constantly whether the geometry information of a lane line is consistent with the state of the vehicle  100 , and constantly perform correction. The foregoing method for measuring inertia of the vehicle  100  is merely an example, and the present invention is not limited thereto. 
     Referring again to  FIG. 2  and  FIG. 4 , in some embodiments, the lane keeping and following system  1  further includes a radar detector  60 . The radar detector  60  may be mounted on the vehicle  100 , for example, mounted at the front of the vehicle  100 . The radar detector  60  is electrically connected to the following control device  30 . The radar detector  60  is used for continuously detecting and outputting a relative distance and a relative velocity of a nearby object. The following control device  30  is further used for controlling, with reference to the relative distance and the relative velocity of the nearby object, the vehicle  100  to travel following the currently corresponding geometry information of a lane line. The nearby object herein is an object, such as a vehicle, a pedestrian, or a traffic light on the lane D on which the vehicle  100  is located and on left and right lanes of the lane D. 
     In this way, the lane keeping and following system  1  controls the vehicle  100  to travel not only according to the road information, but also according to actual conditions surrounding the vehicle  100 . For example, when the radar detector  60  detects that the vehicle  100  is too close to a vehicle ahead, the following control device  30  controls the vehicle  100  to slow down, to avoid collision. This is merely an example herein, and the present invention is not limited thereto. 
     Referring again to  FIG. 2 , in some embodiments, the lane keeping and following system  1  further includes a light sensor  70 . The light sensor  70  is electrically connected to the following control device  30 , and is used for continuously detecting and outputting a relative distance and a relative velocity of a light emitting object. The following control device  30  is further used for controlling, with reference to the relative distance and the relative velocity of the light emitting object, the vehicle  100  to travel following the currently corresponding geometry information of a lane line. In other words, the light sensor  70  may assist in determining under a condition of dim light, and can determine the relative distance and velocity according to light generated by the light emitting object, for example, a brake light of a vehicle ahead. In this way, the vehicle  100  can be controlled to travel according to actual conditions surrounding the vehicle  100 . This is merely an example herein, and the present invention is not limited thereto. 
       FIG. 6  is a schematic diagram of a vehicle control curve. Referring to  FIG. 1 ,  FIG. 4 , and  FIG. 6 , the global positioning device  10  can provide a GPS original location G, and the following control device  30  receives the global positioning information G, and matches the road information provided by the high-precision road map unit  20  and the lane information in the road information, so as to determine that the vehicle  100  is located on the specific lane D of the road R, for example, an ID81 lane. In addition, the following control device  30  sets a deviation threshold T, and when a deviation of the vehicle  100  exceeds the deviation threshold T, the following control device  30  corrects the vehicle  100 , to keep the vehicle  100  traveling on the specific lane D. 
       FIG. 7  is a curve diagram of driving data according to an actual embodiment of vehicle automatic driving.  FIG. 7( a )  and  FIG. 7( b )  are curve diagrams of driving data of driving on different paths. Driving paths of  FIG. 7( a )  and  FIG. 7( b )  each include four lines. A one-dot chain line represents a driving location connection line of a high-precision road map. A three-dot chain line is a driving location connection line of a commercial GPS (PM 220) in coordination with a high-precision road map unit. A dashed line is a driving location connection line of a high-precision GPS device (MB 2000). A solid line is a driving location connection line of a commercial GPS (PM 220) in coordination with an inertial measurement unit (SBG). 
     As shown in  FIG. 7( a )  and  FIG. 7( b ) , a deviation between the driving location of the GPS in coordination with the inertial measurement unit and the driving location of the high-precision road map is relatively large, and a deviation between the driving location connection line of the commercial GPS (PM 220) in coordination with the high-precision road map unit or the high-precision GPS device (MB 2000) and the driving location of the high-precision road map is relatively small. In  FIG. 7( b ) , a driving path of the commercial GPS (PM 220) in coordination with the high-precision road map unit is even closer, than the driving location of the high-precision GPS device (MB 2000), to the driving location of the high-precision road map. Therefore, in this application, correction by using the global positioning device in coordination with the high-precision road map unit by means of a pursuit algorithm actually can achieve an effect similar to that can be achieved by correction by using the high-precision GPS device, and has lower costs over the correction by using the high-precision GPS device. 
     By using the global positioning device and the high-precision road map unit, high-precision positioning can be implemented, so that the following control device can control the vehicle to travel following the currently corresponding geometry information of a lane line and correct the currently corresponding geometry information of a lane line. In this way, the costs can be greatly reduced, incorrect positioning guidance is avoided, and the vehicle can be correctly and safely controlled to travel. 
     Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, the disclosure is not for limiting the scope of the invention. Persons having ordinary skill in the art may make various modifications and changes without departing from the scope and spirit of the invention. Therefore, the scope of the appended claims should not be limited to the description of the preferred embodiments described above.