Abstract:
An autonomous driver assistance system is integrated with a vehicular control system to constantly detect ambient road environment of the vehicle, identify a vehicle ahead with same driving route to a destination, and follow the vehicle ahead by autonomous driving to the destination. Signals of direction indicators of the vehicle ahead can be recognized to determine a driving direction and driving state of the vehicle ahead beforehand, thereby reducing the chances of emergency brake and collision and increasing driving efficiency. Without expensive radar detection equipment, the present invention can be easily integrated with a vehicular control system to tackle the high installation cost and integration difficulty of conventional autonomous driver assistance apparatuses.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an autonomous driver assistance system and a method therefor, and more particularly to an autonomous driver assistance system and an autonomous driving method thereof combining road detection, autonomous driving, telematics and vehicle safety. 
     2. Description of the Related Art 
     Current vehicles have been equipped with more and more driver assistance apparatuses, such as the early passive driving assistance apparatuses including ABS (Anti-Lock Braking System), air bag, EBD (Electronic Brake Force Distribution), and the like, to provide drivers the capability of controlling the vehicles or protecting drivers&#39; safety upon vehicle collision in an emergency braking condition. However, such passive driving assistance apparatuses still fall short as far as driving safety is concerned. To further improve driving safety and vehicle safety, active safety perception apparatuses, such as LDWS (Lane Departure Warning System), FCWS (Forward Collision Warning System) and the like, have been developed in the market one after the other to alert drivers in advance when detecting any emergency condition in front of the vehicles. The LDWS constantly detects lane or sideline markings in front of vehicles. In the event of any unintentional departure from an original lane or road border, the LDWS will trigger a warning tone to alert drivers. The drawback of the LDWS is that lane and sideline markings must be clearly recognizable. During dusky, snowy or fogy condition, the LDWS may not normally function for failing to clearly recognize lane and sideline markings. The FCWS detects a distance to a vehicle ahead through imaging or radar detection. If the distance is too close, the FCWS immediately triggers an alert or activates the brake system of the vehicle to maintain a safe driving distance or conduct an emergency stop so as to prevent vehicle crash or mitigate impact force. The drawback of the FCWS is that place of collision can never be predicted and the vehicle ahead must enter a system detection zone before the FCWS normally operates (the FCWS does not work when other vehicles are on the lateral sides of the vehicle). 
     The active safety perception apparatuses can only alert drivers or do an emergency stop upon departure from lane or sideline marking or imminent collision. Basically, it is still the responsibility of drivers to drive the vehicles to destinations. When the active safety perception apparatuses are applied to autonomous driving, some deficiencies appear. For example, in addition to detection of obstructions and hazards on the road, autonomous driving further requires route planning and road condition recognition. 
     A recently developed active safety perception apparatus as disclosed in U.S. Pat. No. 8,195,394 entitled “Object detection and classification for autonomous vehicles” is to equip a vehicle with sensors for measuring distance and for imaging, 3D radar (Three-dimensional Light Radar) and GPS (Global Positioning System) maps. The sensors are used to detect moving objects and obstacles on the roadway. The 3D radar and the GPS maps are used to avoid stationary obstacles on the roadway by the comparison with actual scenes of roadways so as to enhance the recognition of neighboring obstacles. Although the 3D radar can accurately scan topography or obstacles, the cost of the 3D radar is rather costly. Besides, a gigantic database is also required to store map information beforehand. The cost of building this active safety perception apparatus is therefore prohibitive. 
     Another U.S. Pat. No. 7,065,245 entitled “Image processing apparatus and the method thereof” involves a method and a device for performing a stereo matching on a pair of color images constituted by a plurality of primary colors. This conventional technique employs image recognition means to recognize signals of direction indicators and predicts a moving direction of the vehicle. However, such technique fails to disclose how to effectively recognize the signals of the direction indicators and how to combine itself with autonomous driving technique or vehicle control technique of the vehicle, making such technique not well-feathered to be combined with autonomous driving applications. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide an autonomous driver assistance system and an autonomous driving method thereof capable of resolving high installation cost and integration difficulty in the conventional autonomous driver assistance apparatuses. 
     To achieve the foregoing objective, the autonomous driver assistance system has an autonomous driving control device, a road detection device, a telemetic device, and a vehicle safety integration device. 
     The autonomous driving control device is adapted to connect to a vehicle control system of the vehicle for issuing an alert or controlling a travelling condition of the vehicle. 
     The road detection device is connected to the autonomous driving control device for acquiring a roadway image in front of the vehicle and detecting a distance to a vehicle ahead and a signal of direction indicators of the vehicle ahead. 
     The telemetic device is connected to the autonomous driving control device for transmitting radio signals out or receiving external radio signals, planning a driving route of the vehicle and positioning the vehicle. 
     The vehicle safety integration device is connected to the autonomous driving control device for detecting a driving condition of a driver of the vehicle. 
     The road detection device determines if the roadway image has lane markings, if the lane markings are available, the telemetic device controls the vehicle to drive along the lane markings to the destination by autonomous driving according to the planned driving route and the positioning of the vehicle, if the lane markings are not available, the telemetic device determines if the vehicle ahead is driving along the same planned route, and if determining that the vehicle ahead follows the same planned route, the telemetic device combines the autonomous driving and the positioning to drive the vehicle and follow the vehicle ahead to the destination. 
     To achieve the foregoing objective, the autonomous driving method has steps of: 
     generating a planned route to a destination; 
     performing road detection of the planned route to obtain roadway information in front of the vehicle including an image of lane markings, a distance to a vehicle ahead, a signal of direction indicators of the vehicle ahead, and a collision alert; 
     performing positioning detection to obtain an actual position of the vehicle compared with the planned route to determine if a driving route of the vehicle matches the planned route; 
     integrating driving safety of the vehicle to detect and determine a driving condition of a driver of the vehicle and actively control a travelling condition of the vehicle upon autonomous driving; and 
     performing the autonomous driving to determine if the image of the lane markings has lane markings, if the lane markings are available, controlling the vehicle to drive along the lane markings to the destination by the autonomous driving according to the steps of generating the planned route and performing road detection of the planned route, if the lane markings are not available, detecting if the vehicle ahead is driving along the same planned route, and if determining that the vehicle ahead follows the same planned route, combining the autonomous driving and the positioning detection to drive the vehicle and follow the vehicle ahead to the destination. 
     The foregoing autonomous driver assistance system is integrated with a vehicular control system. The telemetic device positions the vehicle and compares the detected position of the vehicle with a planned driving route. The road detection device constantly detects an ambient road environment of the vehicle. The autonomous driving control device identifies a vehicle ahead with an identical driving route to a destination, automatically follows the vehicle ahead to drive to the destination, and determines a driving state of the vehicle ahead in advance according to the signal of the direction indicators of the vehicle ahead so as to reduce the possibility of emergency and collision and increasing driving efficiency. The vehicle safety integration device detects a driving condition of the driver. In the event of emergency (for example, the driver is unconscious), the autonomous driving control device forcibly takes control of driving the vehicle, and the telemetic device issues signals for rescue. Without expensive radar detection equipment, the present invention is integratable with a vehicular control system to fully achieve autonomous driving, thereby getting rid of the issues of high installation cost and integratable difficulty of conventional autonomous driver assistance system. 
     Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram of an autonomous driver assistance system in accordance with the present invention; 
         FIG. 2  is a flow diagram of an autonomous driving method in accordance with the present invention; 
         FIG. 3  is a schematic image of a roadway and road borders in accordance with the present invention; 
         FIG. 4  is a graph showing a detection result of road borders in accordance with the present invention; 
         FIG. 5  is a schematic diagram showing calculation curvatures of directions of a road in accordance with the present invention; 
         FIGS. 6A ,  6 B and  6 C are schematic views showing ways for two vehicles on different lanes to maintain a safe distance in accordance with the present invention; 
         FIGS. 7A and 7B  are schematic views showing ways for two vehicles on different lanes to change lane in accordance with the present invention; 
         FIG. 8  is a flow diagram of a method for recognizing signals of direction indicators in accordance with the present invention; 
         FIG. 9  is a flow diagram of a method for detecting collision time of vehicles in accordance with the present invention; 
         FIG. 10  is a flow diagram of a safe driving mechanism in accordance with the present invention; 
         FIG. 11  is a schematic view showing a predicated lane-changing target position in accordance with the present invention; and 
         FIG. 12  is another schematic view showing the predicated lane-changing target position in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , an autonomous driver assistance system in accordance with the present invention is mounted on a vehicle, and has an autonomous driving control device  10 , a road detection device  20 , a telemetic device  30 , and a vehicle safety integration device  40 . 
     The autonomous driving control device  10  is connected to the road detection device  20 , the telemetic device  30  and the vehicle safety integration device  40 , and is further connected to a vehicle control system  50  and a vehicle signal module  60 . The vehicle control system  50  controls an accelerator and a brake of the vehicle. The vehicle signal module  60  acquires vehicle signals, such as signals for acceleration, steering, braking, or throttle control. 
     The autonomous driving control device  10  acquires the vehicle signals from the vehicle signal module  60 , and issues an alert through a prompting device  70  connected with the autonomous driving control device  10  or actively controls the brake or accelerator of the vehicle through the vehicle control system  50  to move the vehicle forward or stop the vehicle after combining and calculating the vehicle signals. In the present embodiment, the autonomous driving control device  10  is a micro-controller unit (MCU) or a digital signal processor (DSP), and the vehicle control system  50  is an electronic control unit (ECU). The autonomous driving control device may be further integrated in the vehicle control system  50 . 
     The road detection device  20  detects a distance to a vehicle ahead, detects signals of direction indicators of the vehicle ahead, and has an image-acquiring module  21  and a distance-detecting module  22 . The image-acquiring module  21  acquires a roadway image in front of the vehicle. The road detection device  20  then recognizes the vehicle ahead, direction indicators of the vehicle ahead or obstacles (such as curb fender or roadside barrier) according the acquired image. The distance-detecting module  22  detects a distance between the vehicle and the vehicle ahead. In the present embodiment, the image-acquiring module  21  is a camera mounted on a front portion of the vehicle or on the windshield to take an image of a road scene in front of the vehicle. The distance-measuring module  22  is mounted on the front portion of the vehicle and uses ultrasonic wave, milli-wave or 2D Lidar (Two-dimensional Light Detection and Ranging) for distance detection. 
     The telemetic device  30  serves to transmit radio signals out or receive external radio signals, and is built in with electronic maps to plan driving routes of the vehicle. The radio signals include GPS signals and Assisted GPS (AGPS) signals. The telemetic device  30  identifies coordinates of the vehicle according to received radio signals, compares the coordinates with a driving route planned on the electronic maps, and wirelessly communicates with a monitoring and control center or an emergency center to report a position of the vehicle and a driving condition of a driver of the vehicle. 
     The vehicle safety integration device  40  serves to detect the driver&#39;s driving condition, such as in a drowsy, unconscious or drunk state, with an on-board camera or a physiological monitoring module, and transmit signals out through the telemetic device  30 . 
     With reference to  FIG. 2 , an autonomous driving method is performed by the autonomous driving control device  10 , and has the following steps. 
     Step  201 : Generate a planned route to a destination. 
     Step  202 : Determine if there is any lane marking (or sideline marking) according to images of road scenes along the planned route taken by the road detection device  20 . If positive, perform Step  203 . If negative, perform Step  206 . 
     Step  203 : Control the steering wheel according to the curvatures of the directions of the lane marking (vehicle-moving direction). 
     Step  204 : Determine if the destination is reached. If positive, perform Step  205 . If negative, perform Step  202 . 
     Step  205 : Terminate autonomous driving. 
     Step  206 : Determine if there are road edges (or sideline markings) that are detected by the distance-detecting module  22  (2D Lidar). If positive, resume Step  203 . If negative, perform Step  207 . 
     Step  207 : Determine if there is any other vehicle on the images acquired by the image-acquiring module  21  (camera). If negative, resume Step  202 . If positive, perform Step  208 . 
     Step  208 : Select a vehicle as a target vehicle and determine if the target vehicle has a same driving route. If positive, perform Step  210 . If negative, perform Step  209 . 
     Step  209 : Update the target vehicle by selecting another vehicle having the same driving route as the target vehicle. 
     Step  210 : Control the steering wheel (vehicle-moving direction) according to the driving route of the target vehicle. 
     With reference to  FIG. 3 , a road image acquired by the image-acquiring module  21  of the road detection device  20  is shown, and includes a roadway and two sideline markings  81 ,  82  of a road  80 . The sideline markings  81 ,  82  are bent as the road  80  winds and are curved. The sideline markings  81 ,  82  on  FIG. 3  are recognized by the road detection device  20  and a recognition result of the sideline markings  81 ,  82  is shown on  FIG. 4 . An X axis along a horizontal direction on  FIG. 4  represents a left side and a right side of the vehicle. A center point (zero meter) corresponds to a mounting position of the image-acquiring module  21  in the vehicle. A right side relative to the center point of the X axis corresponds to the right side of the vehicle, and a left side relative to the center point of the X axis corresponds to the left side of the vehicle. A Y axis represents a distance of the road extending forwards from the vehicle. The two curves shown on  FIG. 4  correspond to the sideline markings  81 ,  82  on  FIG. 3 . It is noted that the curve on the right corresponds to the sideline marking  82  on the right of the vehicle (approximately 30 meters in length) and is bent to the left, and the curve on the left corresponds to the sideline marking  81  on the left of the vehicle (approximately 15 meters in length) and is slightly bent to the left. 
     With reference to  FIG. 5 , after the road detection device  20  acquires the recognition result of the sideline markings  81 ,  82 , as disclosed in Taiwan Patent No. 096145498 entitled “Method and device for detecting lane sway and departure”, a turning angle of the steering wheel tan(α) can be calculated according to a curvature of the sideline marking or a lane marking and is expressed as follows.
 
 L   y   =R ×sin θ
 
 W   L   =R ×cos θ
 
 W   R   =L   y ×tan α= R ×sin θ×tan α
 
     
       
         
           
             
               Radius 
               ⁢ 
               
                   
               
               ⁢ 
               of 
               ⁢ 
               
                   
               
               ⁢ 
               curvature 
               ⁢ 
               
                 : 
               
               ⁢ 
               
                   
               
               ⁢ 
               ρ 
             
             = 
             
               1 
               α 
             
           
         
       
     
     
       
         
           
             
               Turning 
               ⁢ 
               
                   
               
               ⁢ 
               angle 
               ⁢ 
               
                 : 
               
               ⁢ 
               
                   
               
               ⁢ 
               
                 tan 
                 ( 
                 α 
                 ) 
               
             
             = 
             
               
                 L 
                 y 
               
               ρ 
             
           
         
       
     
     Second-order curve of sideline marking: x=k w ×y 2 +m w ×y+b w   
     
       
         
           
             
               Curvature 
               ⁢ 
               
                   
               
               ⁢ 
               of 
               ⁢ 
               
                   
               
               ⁢ 
               sideline 
               ⁢ 
               
                   
               
               ⁢ 
               marking 
               ⁢ 
               
                 : 
               
               ⁢ 
               
                   
               
               ⁢ 
               α 
             
             = 
             
               
                 2 
                 × 
                 
                   k 
                   w 
                 
               
               
                 
                   ( 
                   
                     1 
                     + 
                     
                       
                         ( 
                         
                           
                             2 
                             × 
                             
                               k 
                               w 
                             
                             × 
                             y 
                           
                           + 
                           
                             m 
                             w 
                           
                         
                         ) 
                       
                       2 
                     
                   
                   ) 
                 
                 
                   3 
                   2 
                 
               
             
           
         
       
     
     Distances from a sideline marking to left and right lane markings beside the vehicle:
 
 W   x     r     =W   L   +W   R   −ΔY   R  
 
 W   x   =W   L   +W   R   −ΔY   L  
 
Second-order curve of left and right lane markings beside the vehicle:
 
 x   R   =k   w   ×y   2   +m   w   ×y +( b   w   −W   x     r   )
 
 x   L   =k   w   ×y   2   +m   w   ×y +( b   w   −W   x )
 
Where
 
     k w , m w  and b w  are coefficients of a second-order curve of the lane marking, which are obtained from the image detection; 
     x, y are actual coordinates of the second-order curve of the lane marking in a lateral axis and a longitudinal axis; 
     α represents a curvature of the lane marking; 
     ρ represents a radius of curvature; 
     L y  represents a longitudinal distance from the vehicle to the lane marking; 
     R is a distance from a head of the vehicle to the lane marking; 
     θ is included between a direction from the head of the vehicle to the lane marking and a lateral direction; 
     Tan(α) is the turning angle of the steering wheel. 
     With reference to  FIGS. 6A ,  6 B,  6 C,  7 A and  7 B, the road detection device  20  predicts a possible collision distance and time of the vehicle after recognizing a distance between the vehicle and a vehicle ahead and further analyzing a risk of a moving direction and a moving speed of the vehicle. With reference to  FIGS. 6A and 6B , when the vehicle ahead abruptly cuts into the lane in front of the vehicle from other lane (left or right lane) and a safe distance is not kept, the road detection device  20  determines a signal of the direction indicators of the vehicle for the autonomous driving control device  10  to instruct the prompting module  70  to issue an alert, and the control system  50  activates an timely braking action to prevent the vehicle from hitting the vehicle ahead from behind With reference to  FIG. 6C , when a vehicle ahead in the opposite lane makes a left turn to change to the lane in front of the vehicle, the autonomous driving control device  10  instructs the prompting module  70  immediately issue an alert and the control system  50  generates a braking action to prevent direct collision with the oncoming vehicle. With reference to  FIGS. 7A and 7B , when enough space and safe distance is available is available in the left or right lane ahead of the vehicle for lane change, if the vehicle ahead abruptly changes to the lane on which the vehicle is, the autonomous driving control device  10  can also change to the left or right lane in consideration of reducing braking frequency, thereby increasing driving efficiency and saving gas consumption. 
     With reference to  FIG. 8 , the road detection device  20  recognizes a signal of a vehicle ahead by performing the following steps. 
     Step  801 : Acquire an image in front of the vehicle. 
     Step  802 : Detect a vehicle ahead on the image. 
     Step  803 : Determine if there is any vehicle ahead on the image. If negative, resume Step  801 . If positive, perform Step  804 . 
     Step  804 : Estimate a position and a size (height and width) of the vehicle ahead. 
     Step  805 : Configure an ROI (Region of interest) of the image. 
     Step  806 : Perform image binarization (thresholds are Th_Y, Th_U and Th_V corresponding to different tail lights). 
     Step  807 : Perform subtraction between positions of an identified light spot and a lateral symmetry axis of the vehicle on the image; 
     Step  808 : Perform morphological filtering (dilation and erosion). 
     Step  809 : Estimate a center point. 
     Step  810 : Determine if a signal is on the left or right. 
     Step  811 : Determine if n frames have continuously appeared and n frames have disappeared. If negative, resume Step  801 . If positive, perform Step  812 . 
     Step  812 : Determine that the direction indicator on the left or on the right of the vehicle ahead sends out a signal. 
     As the direction indicators of vehicles in the current market are mostly in orange color, in light yellow or in red. As to the thresholds in Step  806 , the Th_Y may be set to a value in a range of 235˜250 and is 246 preferably, the Th_U may be set to a value in a range of 95˜115 and is 108 preferably, and the th_V may be set to a value in a range of 120˜140 and is 130 preferably. As the direction indicators of vehicles are mounted in bilateral symmetry, only one direction indicator on one side flashes at a time when vehicles change lane. Flashing direction indicators on the left and right sides signals a vehicle failure. Hence, only the flashing direction indicator on one side needs to be recognized. Furthermore, as being once or twice per second, the flashing rate of current direction indicators can be used to calculate the number of the foregoing frames. 
     With reference to  FIG. 9 , the road detection device  20  predicts a collision distance and a collision time by performing the following steps. 
     Step  901 : Detect a surrounding environment of a vehicle with the distance-detecting module  22 . 
     Step  902 : Recognize a type of an obstacle with the image-acquiring module  21 . 
     Step  903 : Determine if the obstacle is a vehicle. If negative, resume Step  901 . If positive, perform Step  904 . 
     Step  904 : Determine if a signal indicated by the direction indicators signal is a left turn or a right turn. 
     Step  905 : Predict a collision time through a collision prevention algorithm after determining the signal of the direction indicators. 
     Step  906 : Activate a driving safety mechanism through the autonomous driving control device  10  and control the vehicle through control system  50 . 
     With reference to  FIG. 10 , the autonomous driving control device  10  activates the driving safety mechanism by performing the following steps. 
     Step  1001 : Determine if a vehicle ahead is detected. If negative, resume Step  1001 . If positive, perform Step  1002 . 
     Step  1002 : Determine if a collision time is less than a braking threshold. If positive, perform step  1003 . If negative, perform Step  1004 . 
     Step  1003 : Activate a braking assistance system. 
     Step  1004 : Determine if enough space around the vehicle is available to avoid a collision. If positive, perform step  1005 . If negative, perform Step  1006 . 
     Step  1005 : Prompt the driver or activate steering intervention to move the vehicle to the space avoiding the collision. 
     Step  1006 : Trigger an alert and prompt the driver for the dangerous collision situation. 
     With reference to  FIGS. 11 and 12 , the foregoing estimated lane-changing target position can be calculated by the following equation. 
     
       
         
           
             
               ∅ 
               est 
             
             = 
             
               
                 π 
                 2 
               
               - 
               
                 atan 
                 ⁡ 
                 
                   ( 
                   
                     y 
                     x 
                   
                   ) 
                 
               
             
           
         
       
     
     where 
     gx, gy are coordinates of the target position; 
     x is a width of a lane; 
     y is an estimated lateral moving distance; and
         is an estimated moving direction.       

     With further reference to  FIG. 12 , the estimated moving direction is added to a moving direction estimated by a tracking algorithm to obtain a final moving direction Ø new =φ±. The final moving direction is substituted into 
               t   ADM     =     ADM     V   A             
and
 
               t   BDM     =     BDM     V   B             
to obtain the estimated collision time for higher accuracy of predication, where ADM represents a distance from a vehicle A to a collision point C, BDM represents a distance from another vehicle B to the collision point C, V A  represents a speed of the vehicle A, V B  represents a speed of the vehicle A, t ADM  represents a time for the vehicle A to reach the collision point C, t ADM  represents a time for the vehicle A to reach the collision point C, t BDM  represents a time for the vehicle B to reach the collision point C, e A  represents an error range for the vehicle A, e B  represents an error range for the vehicle B, H A  represents a heading angle of the vehicle A, H B  represents a heading angle of the vehicle B, H AB  represents an angle of the vehicle A relative to vehicle B, H BA  represents an angle of the vehicle B relative to vehicle A, D is a direct distance between the vehicles A and B, D1 is a driving direction of the vehicle B, D2 is a driving direction of the vehicle A, and θ is an angle formed by extending from the collision point to the vehicles A and B.
 
     Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.