Patent Document

BACKGROUND 
       [0001]    Tracking lane markings is important for various kinds of driver assistance systems in modern motor vehicles. For example, a lane departure warning (LDW) can use the tracking of lane markings to determine the position of the vehicle within the lane and can emit a warning signal if the vehicle gets too close to, or crosses, a lane boundary. However, mechanisms are lacking for vehicles to identify lane markings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a block diagram of an exemplary vehicle on a highway roadway detecting a left and a right roadway marking. 
           [0003]      FIG. 2  is a detailed block diagram illustrating a portion of the highway roadway of  FIG. 1  including an exemplary vehicle detecting a change in the left lane marking indicating a highway exit ramp. 
           [0004]      FIG. 3  is an exemplary transition chart which can predict the vehicle response at certain locations. 
           [0005]      FIG. 4  is an exemplary resultant action matrix which may represent one of the cells of the exemplary transition chart of  FIG. 3 . 
           [0006]      FIG. 5  is a flowchart of an exemplary process that may be implemented by the vehicle&#39;s computer. 
           [0007]      FIG. 6  is a flowchart of a second exemplary process that may be implemented by the vehicle&#39;s computer. 
       
    
    
     DETAILED DESCRIPTION 
     Learning the Road 
       [0008]    Referring to  FIG. 1 , illustrated is an exemplary vehicle lane marker detection system  5  for a vehicle  10  on a highway lane  13 , which for purposes of this example is a highway such as a beltway around a city  20 . The vehicle  10  lane has a left lane marker  11 , which is a single broken line (e.g., a conventional painted lane marking on a roadway) to the left of the vehicle  10  and a single unbroken line at the right lane marker  16 , which changes to a second single broken line  19  at an exit ramp  17 . The vehicle  10  has one or more image capture devices, such as forward facing camera  12  with a left view site line  15  and a right view site line  14 . 
         [0009]    Now with reference to  FIG. 2 , which is a detail blocked diagram of the system  5  of  FIG. 1  which better illustrates the left lane marker  11  to the left of the vehicle  10  and the single unbroken line right lane marker  16  to the right, which changes to the second single broken line  19  at the beginning of the exit ramp  17 . Also shown is a computer  8 , which can also be referred to as an imaging electronic control unit (ECU). The computer  8  has at least one processor and memory to store computer instructions, register values, and temporary and permanent variables. The instructions include one or more predetermined detection criteria for a lane marker. 
         [0010]    The computer  8  may also include an additional special processor, such as an image processor or a digital signal processor (DSP) to aid the processor with signal interpretation. The computer  8  is communicatively coupled to the camera  12 , e.g., via a vehicle communications bus or other vehicle network such as is known. 
         [0011]    As the vehicle  10  traverses around the highway lane  13 , the camera  12  can substantially continuously capture images of the highway lane  13  ahead. The computer  8  substantially continuously receives images of the highway and the right and left lane markers. The computer  8  includes program instructions to determine the occurrence of a detected transition identifier, for example, when the right lane marker  16  is a solid white line having a width of 50 cm and the left lane marker is a dashed line having a width of 50 cm. Several data entries can be recorded into memory when the right lane marker  16  changes to a dashed line with a width of 50 cm, even if there was not a change in the left lane marker  11 . The entries can include, for example, a geolocation of the transition, a lane marker type of change, a change of direction of the vehicle  10 , etc. 
         [0012]      FIG. 3  is an example of a transition chart  25  which can be assembled from historical data as the vehicle  10  traverses the highway lane  13 . A “transition,” as that term is used herein, encompasses an event in which a vehicle  10  changes lanes. For example, when the vehicle  10  approaches a first exit ramp  17 , as indicated in row  27  in the chart  25  as the intersection of I-85 and Main Street, the vehicle  10  exited the highway lane  13  twenty-six times of the last fifty times the vehicle  10  identified the exit ramp  17 . However, when the vehicle  10  approached second exit ramp  18 , identified in row  21 , which is at the intersection of I-85 and Central Avenue, the vehicle  10  exited the highway lane  13  five times of the last fifty times. Therefore, at each transition position, i.e., an instance in which the vehicle  10  traverses a portion of a highway that can be a subject of the chart  25 , i.e., a place where the vehicle  10  could be exiting, changing lanes and/or turning, and is identified by, for example, a change in the lane markings, can be represented by the values of the cells in the transition chart  25 . These values are incremented each time the vehicle  10  traverses a transition position. A “location column”  22  of the chart  25  identifies the location of the transition position and a “times exited” column  23  has a number of times the vehicle  10  exited, changed lanes or took some other identifiable action. A “total number of trips” column  24  has a running total of the number of trips the vehicle has taken on a particular route and an “earliest date” column  26  keeps track of an earliest date the vehicle  10  has come across the transition position indicated in the column  22 . The earliest date  26  can be used to keep the chart  25  current, for example, any trips recorded that are more than a year old can be removed from the “times exited” column  23  and the “total number trips” column  24 . 
         [0013]      FIG. 4  is an example resultant action matrix  30  which can include an entry for each lane transition. A resultant action matrix  30  maps data represented in the aggregate in a transition chart  25 , e.g., the times exited column  23  from the chart  25  shown for the transition location of the row  27  is shown in detail in the matrix  30  of  FIG. 4 . More specifically, the action matrix  30  represents one of the cells of the exemplary transition chart  25  of  FIG. 3  of vehicle  10  positions relative to the left lane marker  11  for twenty-eight distance increments (indexes 1 to 28 along the vertical axis) as the vehicle  10  approaches the exit ramp  17 . An index 0 is a location on the highway lane  13  designated as a reference location for a transition location; the indexes may then represent predetermined distance increments, e.g., 1 meter, 3 meters, 5 meters, etc., along the highway lane  13  with reference to the 0 index location. (For example, with 28 rows in the index of the matrix  30 , a transition from one row to the next row represents approximately 3.5 meters.) Values in each cell in the matrix  30  thus represent a number of times that a vehicle  10  had been at the lateral offset indicated by the left lane offset shown on the vertical axis for each time that the vehicle  10  has passed the transition location&#39;s 0 index, the 0 position for the lateral offset being a leftmost border of a leftmost lane of the highway lane  13 . Thus, the matrix  30  provides a history of vehicle  10  passages through the approach to the exit ramp  17 , e.g., forty different trips in this example. 
         [0014]    As stated above, each time a transition occurs, the appropriate cells of the resultant action matrix  30  are updated, for example, when the vehicle travels through the transition area, the cells representing the lateral and longitudinal positon at each of the longitudinal indexes 0 to 28 will be incremented by one. 
         [0015]    The datum in each row and column of the matrix  30  therefore provides a number of times that a response to a lane marking was recorded at a particular lateral position in the lane (i.e., at a particular distance from the left lane marker) at a particular distance index. Thus, over time the resultant action matrix  30  will provide a history of travel either through the transition location, where higher numbers represent a higher probability of the vehicle  10  tendency to follow the matrix learned path. For example, with reference to row  31  (at index 0), the value “2” is provided at the intersection of the lateral position 0 and longitudinal index of 0, reading from left to right, where each adjacent box represents a segment of the width of the lane of approximately equal to 20 cm (centimeters), which can total the width of the highway lane  13 , which in this example is approximately 3.2 meters. That is, the vehicle  10  determined that it was at the extreme left of the highway lane  13  two times of the last forty passages through this location on the highway lane  13 . The vehicle was 100 cm from the left lane marker  11  one time of the forty passages. The vehicle was 120 cm from the left lane marker  11 , one time. The vehicle was 140 cm from the left lane marker  11  eight times and the vehicle  10  was 160 cm from the left lane marker  11  thirteen times. Continuing, the vehicle  10  was 180 cm away nine times, 200 cm away three times, 220 cm away one time, 280 cm away one time and 300 cm away from the left lane marker  11  one time. 
         [0016]    In the next row, row  32 , with a longitudinal index of one, it can be seen that the vehicle  10  was 160 cm away from the left lane marker  11  fourteen times, 180-220 cm away from the left lane marker  11  eight times and 240-320 cm away three times. In the next row, row  34  (longitudinal index  2 ), it can be seen that the vehicle was 160 cm away from the left lane marker  11  fourteen times, 180-220 cm away from the left lane marker  11  eleven times and 240-320 cm away two times. At a row  35  (longitudinal index of 7), the vehicle  10  was 160 cm away from the left lane marker  11  thirteen times, 180-220 cm away from the left lane marker  11  eleven times and 240-320 cm away three times. At a row  36  (longitudinal index of 9), the vehicle  10  was 160 cm away from the left lane marker  11  eleven times, 180-220 cm away from the left lane marker  11  ten times and 240-320 cm away six times. At a row  38  (longitudinal index of 11), the vehicle  10  was 160 cm away from the left lane marker  11  eleven times, 180-220 cm away from the left lane marker  11  eight times and 240-320 cm away eight times. At a row  40  (longitudinal index of 16), the vehicle  10  was 160 cm away from the left lane marker  11  twelve times, 180-220 cm away from the left lane marker  11  seven times and 240-320 cm away seven times.  FIG. 4  shows that the vehicle  10  tended to stay in the middle of the highway lane  13 , however, the number of times the vehicle  10  exited the highway lane  13  is apparent by noting the number of times the vehicle  10  had entries in the 140-300 cm columns. An arrow  29  is superimposed upon the center columns of  FIG. 4  to represent the tendency for the vehicle  10  to stay in the middle of the highway lane  13 . A second arrow  28  is representative of the occasional tendency when the vehicle  10  leaves the highway lane  13  and exits via the exit ramp  17 . 
         [0017]    When the computer  8  is detecting lane markers and lane maker transitions, the computer  8  can classify the lane markings into an invalid lane category and a valid lane category. The valid lane category can include, for example, a single unbroken line, a double unbroken line, a single broken line, a double broken line, a broken and unbroken line, a wide broken line, a line with surface profile and a single unbroken with single broken line. The invalid lane marker can be, for example, a guide rail or a land mark. 
         [0018]    The vehicle  10  position can be obtained via several methods including a global navigation satellite system (GNSS) or a Global Positioning System (GPS) receiver, a dead reckoning system, an inertial navigation system and can be calculated using the number of tire rotations to determine the distance from a known start reference point. 
         [0019]    The GNSS is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude/elevation) to high precision (within a few meters) using time signals transmitted along a line of sight by radio from satellites. The signals also allow the electronic receivers to calculate the current local time to high precision, which allows time synchronization. GPS is United States of America term for a space-based navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. 
         [0020]    Dead reckoning is the process of calculating one&#39;s current position by using a previously determined position, or “fix”, and advancing that position based upon known or estimated speeds over elapsed time and course. The vehicle  10  would obtain a “fix” and calculate the direction and distance traveled for a certain time and determine the vehicle  10  new location. The internal navigation system is course plotting aid that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references. 
         [0021]    The geolocation of the vehicle  10  can be in Universal Transverse Mercator (UTM), coordinate system, a vehicle coordinate system as defined by the International Organization for Standardization (ISO) for a vehicle coordinate system, a military grid reference system (MGRS) and a universal polar stereographic (UPS) system. The UTM system divides the Earth between 80° S and 84° N latitude into 60 zones, each 6° of longitude in width. Zone  1  covers longitude 180° to 174° W; zone numbering increases eastward to zone  60 , which covers longitude 174° to 180° E. Each of the 60 zones uses a transverse Mercator projection that can map a region of large north-south extent with low distortion. By using narrow zones of 6° of longitude (up to 800 km) in width, and reducing the scale factor along the central meridian to 0.9996 (a reduction of 1:2500), the amount of distortion is held below 1 part in 1,000 inside each zone. 
         [0022]    The MGRS is the geocoordinate standard used by NATO militaries for locating points on the earth. The MGRS is derived from the Universal Transverse Mercator (UTM) grid system and the universal polar stereographic (UPS) grid system, but uses a different labeling convention. The MGRS is used for the entire earth. 
         [0023]    The UPS coordinate system is used in conjunction with the universal transverse Mercator (UTM) coordinate system to locate positions on the surface of the earth. Like the UTM coordinate system, the UPS coordinate system uses a metric-based Cartesian grid laid out on a conformally projected surface. 
         [0024]    In addition, the path may be filtered into the driving path using known Kalman or other filtering techniques. Providing a Kalman filter, for example, can compensate for noisy readings which can ‘jump around’ rapidly, though always remaining within a few meters of the real position. In addition, since the vehicle  10  is expected to follow the laws of physics, its position can also be estimated by integrating its velocity over time, determined by keeping track of wheel revolutions and the angle of the steering wheel. As discussed above, this is a technique known as dead reckoning. Typically, the dead reckoning will provide a very smooth estimate of the vehicle  10  position, but it will drift over time as small errors accumulate. 
         [0025]    The Kalman filter can be thought of as operating in two distinct phases: predict and update. In the prediction phase, the vehicle  10  position will be modified according to the physical laws of motion (the dynamic or “state transition” model) plus any changes produced by the accelerator pedal and steering wheel. A new position estimate can be calculated and inserted into the transition chart as well as an update to the resultant action matrix. 
         [0026]    In operation, the vehicle lane marker detection system  5  may erroneously determine that the vehicle  10  is in traveling through a center median. Since it is physically impossible to travel through a solid, the erroneous positional determination will be treated as noise and the Kalman filter can eliminate and/or suppress such spurious calculated vehicle  10  positions. The Kalman filter can use coefficients based upon the vehicle  10  travel history, for example, previous trips on the highway lane  13 . 
         [0027]    A dead reckoning positional error of the vehicle  10  position is in part, proportional to the speed of the vehicle  10 . This is due to the uncertainty about the accuracy of the dead reckoning position estimates at higher speeds, as a small amount of positional errors grow rapidly at higher speeds than at slower speeds. Therefore, once the vehicle  10  detects a “known position”, such as a lane marker, the system can correct for any dead reckoning drift form the actual position. Other “known positions,” for example, can be a lane marker transition, a lane marker at a known intersection, a road sign, a land marks, etc. 
       Process Flows 
       [0028]      FIG. 5  is a flow chart illustrating an exemplary process  100  of the computer  8  to capture an image of lane markings, determine the vehicle&#39;s relative position in the lane and the vehicle&#39;s geolocation and save the values in a transition matrix. 
         [0029]    The process  100  begins in a block  105 , which can also follow in a block  115  or in a block  125 . The camera  12  captures a forward facing image (relative to the vehicle  10 ) of the highway lane  13 . The image is stored in memory on the computer  8 , which can also be known as an imagining electronic control unit (ECU), and the right and left lane marker types are identified, e.g., using image recognition techniques such as are known and that can be included in program instructions in the computer  8 . As discussed above, the lane marker types can include a single unbroken line, a double unbroken line, a single broken line, a double broken line, a broken and unbroken line, a wide broken line, a line with surface profile and a single unbroken with single broken line. The computer  8  can also usually differentiate an invalid image object from a lane marking, for example, the computer  8  can determine that the lane marker is not a lane marker, but rather a guard rail. 
         [0030]    In a block  110 , a counter is incremented to a next position dicating an image and its characteristics have been loaded into memory. The characteristics can include the right and left lane marker types and the geolocation of the vehicle  10 . 
         [0031]    Next, in the block  115 , the computer  8  determines if the image stored in a most recent iteration of the block  105  is a first image captured, and if it is the first image captured, the system will return to in the block  105  and capture a next sequential image, else the system  100  will continue in a block  120 . 
         [0032]    Next, in a block  120 , the current image characteristics are compared to the previous image&#39;s characteristics, for example, the computer  8  determines that the current right lane marker has changed from a single unbroken to a single broken line. If there is a difference in image characteristics, the process  100  continues in a block  125 , else the process returns to the block  105 . 
         [0033]    Next, in a block  130 , the system  100  determines a lane offset distance of the vehicle  10  with respect to the lane the vehicle  10  is in, for example, if the vehicle  10  is in the center of the highway lane  13  and the lane is three meters wide, the left lane marker offset can be 150 cm to the center of the vehicle  10 . Additionally, the vehicle  10  geolocation can be determined from the methods cited above, including a global navigation satellite system (GNSS) or a Global Positioning System (GPS) receiver, a dead reckoning system, an inertial navigation system and can be calculated using the number of tire rotations to determine the distance from a known start reference point. 
         [0034]    Next, a block  135 , the computer stores the left lane marker offset, the left lane marker type, the right lane marker type and a geolocation of the vehicle  10  into a memory. 
         [0035]    Next, in a block  140 , the computer  8  determines if the segment of the trip requiring collecting images and lane marking data is complete, and if it is the process  100  ends, else the process  100  returns to the block  105 . 
         [0036]      FIG. 6  is a flow chart illustrating an exemplary process  200  of the computer  8  for determining the location of the vehicle  10  and an exit ramp. 
         [0037]    The process  200  begins in a block  205 , which can also follow in a block  220  or in a block  240 . The camera  12  captures a forward facing image (relative to the vehicle  10 ) of the highway lane  13 . The image is stored in memory on the computer  8 . 
         [0038]    Next in a block  210 , the computer  8  determines the position of the vehicle  10 . The position can be generally determined using GNSS or dead reckoning from a known start point 
         [0039]    Next, in a block  215 , the processor compares the captured image characteristics with known geolocations and their characteristics. For example, when the right lane marker  16  changes from the single unbroken line to the second single broken line  19  at the exit ramp  17 . The computer  8  can then determine the vehicle  10  position on the highway lane  13 . 
         [0040]    Next, in the block  220 , the computer  8  makes a determination in any of the recently captured image&#39;s characteristics matches any characteristics of previously stored images in the transition matrix. If there is a match, the process continues to in a block  225 , else the process returns to in the block  205  to capture and process another image from the camera  12 . 
         [0041]    Next, in the block  225 , the process  200  can optionally capture another image from the camera  12  and its lane marking characteristics are extracted. 
         [0042]    Next in a block  230 , the optional image lane characteristics from in the block  225  are checked against the database to verify the positioning of the vehicle  10 . 
         [0043]    Next, profile in a block  235 , the computer  8  sends a control signal to the vehicle  10  to commence the egress of the highway lane  13  onto the exit ramp  17 . If the vehicle  10  is an autonomous vehicle, the vehicle&#39;s onboard control and navigation system will maneuver the vehicle by controlling one or more of steering, braking, and acceleration. If the vehicle is a non-autonomous vehicle, the computer  8  will send an alert to the vehicle  10  and the operator that the vehicle  10  is approaching a desired exit. 
         [0044]    In other words, if the exit and the highway path have been traveled repeatedly, then there will be a statistical preference of which path is a preferred path and its preferred shape of travel relative to the resultant action matrix  30 , starting at the transition point of the particular transition matrix cell. When a detection of a particular transition is detected then driver can be alerted of the preferred learned decision and take action unless canceled by the driver or passenger. 
         [0045]    Next in a block  240 , the computer  8  verifies that the vehicle  10  is on the exit ramp. This can be accomplished with another image capture of the lane markings or by taking a GNSS position. If the vehicle is on the exit ramp  17 , the process continues to in a block  250 , else the process returns to in the block  205 . 
         [0046]    Next, in a block  250 , the computer  8  sends a message to the vehicle&#39;s onboard control and navigation system confirm the egress or a message to the operator. Following the block  250 , the process  200  ends. 
       Conclusion 
       [0047]    As used herein, the adverb “substantially” modifying an adjective means that a shape, structure, measurement, value, calculation, etc. may deviate from an exact described geometry, distance, measurement, value, calculation, etc., because of imperfections in the materials, machining, manufacturing, sensor measurements, computations, processing time, communications time, etc. 
         [0048]    Computing devices such as those discussed herein generally each include instructions executable by one or more computing devices such as those identified above, and for carrying out blocks or steps of processes described above. Computer executable instructions may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java™, C, C++, C#, Visual Basic, Python, Java Script, Perl, HTML, PHP, etc. In general, a processor (e.g., a microprocessor) receives instructions, e.g., from a memory, a computer readable medium, etc., and executes these instructions, thereby performing one or more processes, including one or more of the processes described herein. Such instructions and other data may be stored and transmitted using a variety of computer readable media. A file in a computing device is generally a collection of data stored on a computer readable medium, such as a storage medium, a random access memory, etc. 
         [0049]    A computer readable medium includes any medium that participates in providing data (e.g., instructions), which may be read by a computer. Such a medium may take many forms, including, but not limited to, non-volatile media, volatile media, etc. Non-volatile media include, for example, optical or magnetic disks and other persistent memory. Volatile media include dynamic random access memory (DRAM), which typically constitutes a main memory. Common forms of computer readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read. 
         [0050]    With regard to the media, processes, systems, methods, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of systems and/or processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the disclosed subject matter. 
         [0051]    Accordingly, it is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to claims appended hereto and/or included in a non-provisional patent application based hereon, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the disclosed subject matter is capable of modification and variation.

Technology Category: g