Patent Publication Number: US-2012041632-A1

Title: Combined lane change assist and rear, cross-traffic alert functionality

Description:
BACKGROUND 
     The present invention relates to safety systems for vehicles. More specifically, the present invention relates to a safety system for alerting a driver of a potential hazard from another vehicle. 
     Some automobiles have safety systems which detect an object outside the vehicle and inform a driver if the object poses a potential hazard. For example a blind spot detection system (BSD) detects objects in a driver&#39;s blind spot and alerts the driver to the presence of the object. Another safety system is a rear, cross-traffic alert system (RCTA). The system detects objects approaching, from the sides, the rear of the vehicle, and warns the driver. The RCTA helps a driver by detecting an approaching object when the driver is backing out of a parking space and the driver&#39;s vision is blocked. Each safety system is autonomous, using individual detection systems and driver warning systems. 
     SUMMARY 
     The invention integrates a plurality of safety systems into a single autonomous system resulting in a reduction in the number of components. This reduction in the number of components reduces the amount of energy consumed by the safety system as well as the cost of the safety system. 
     In one embodiment, the invention provides a system for detecting a potential threat to a vehicle, and generating a warning for a driver of the vehicle of the potential threat. The system includes an object detection device, a controller, and a human-machine interface (HMI). The object detection device is configured to detect objects next to the vehicle, approaching the vehicle from a side, and approaching the vehicle from behind. The controller receives an indication of a detected object from the object detection device, and uses a position, a speed, an acceleration, and a direction of travel of the detected object to categorize the detected object as a potential threat when at least one of (a) the vehicle is moving forward and the detected object is adjacent the vehicle, (b) the vehicle is moving forward at a first speed and the detected object is approaching the vehicle from behind at a second speed relative to the first speed that indicates a time to collision is less than a predetermined threshold, and (c) the vehicle is moving in reverse and the detected object is approaching the vehicle from the side, is within a first distance of the vehicle, and is traveling within a range of speeds. The HMI is coupled to the controller and is configured to receive an indication of the potential threat from the controller and to provide the warning to the driver of the potential threat. 
     The invention also provides a vehicle which includes an object detection device, a controller, and an HMI. The object detection device is configured to detect objects next to the vehicle, approaching the vehicle from a side, and approaching the vehicle from behind. The controller receives an indication of a detected object from the object detection device, and determines a position, a speed, an acceleration, and a direction of travel of the detected object. The controller performs a blind spot detection function, a closing vehicle warning function, and a rear, cross-traffic alert function. The HMI is coupled to the controller and is configured to provide a warning to a driver when the controller determines a potential threat exists. 
     A method of warning a driver of a vehicle, by a single controller and an object detection device, of a potential threat is also provided by the invention. The method detects an object by the object detection device, determines a position of the object relative to the vehicle, determines a direction of travel of the object, determines a speed of the object relative to a speed of the vehicle, determines an acceleration of the object relative to an acceleration of the vehicle, and determines, by a controller, if the object is in a zone of danger. The zone of danger includes a first area adjacent the vehicle, a second area extending perpendicular from the rear of the vehicle, and a third area extending a distance from the back of the vehicle. The controller determines a time to collision for the detected object in the zone of danger, determines a potential threat exists when at least one of the detected object is in the zone of danger adjacent the vehicle or the time to collision is less than a threshold, and provides an indication of the potential threat to the driver. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a vehicle incorporating an embodiment of the invention. 
         FIG. 2  shows positions of vehicles detected by a blind spot detection function and a closing vehicle warning function. 
         FIG. 3  shows exemplary zones of danger for a blind spot detection function and a closing vehicle warning function. 
         FIGS. 4A and 4B  show positions of vehicles detected by a rear crossing traffic alert function. 
         FIGS. 5A-5C  shows an embodiment of the operation of a system incorporating a blind spot detection function, a closing vehicle warning function, and a rear, cross-traffic alert function. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  shows a vehicle  100  incorporating an embodiment of a system which combines lane change assist (LCA) functions (e.g., blind spot detection and closing vehicle warning functions) with rear, cross-traffic alert (RCTA) functions. The vehicle includes an engine  105 , a controller  110 , a first object detection device  115 , a second object detection device  120 , a plurality of wheel speed sensors  125 , and a human-machine interface (HMI)  130 . The controller  110  can be a stand-alone controller (i.e., performing LCA, RCTA, and similar functions) or can incorporate other control functions (e.g., engine control, braking control, etc.). The first and second object detection devices  115  and  120  can be radars, light detecting and ranging (LIDAR) sensors, video cameras, etc. Embodiments of the invention are described herein using mid-range radar sensors (e.g., 24 GHz or 77 GHz) as the object detection devices  115  and  120 . 
     The first and second detection devices  115  and  120  detect objects that are within their field of view (FOV), labeled with reference number  135  and  140 , respectively, in  FIG. 1 . The first and second detection devices  115  and  120  detect where an object is within the FOV  135  or  140  (e.g., using a time-of-flight method), how fast and in what direction the object is moving, and an acceleration of the object (e.g., using Doppler effects). In some embodiments, the first and second object detection devices  115  and  120  communicate the location and motion (e.g., speed, acceleration, and direction) information of objects they detect to the controller  110 . In other embodiments, the first and second object detection devices  115  and  120  communicate raw data (e.g., transmitted and received frequencies, time-of-flight, etc.) to the controller  110  and the controller  110  determines one or more of the location, speed, acceleration, and direction of detected objects. In some embodiments, the controller  110  merges the data from the first and second detection devices  115  and  120  together. In other embodiments, one of the first and second detection devices  115  and  120  merges the data from the first and second detection devices  115  and  120  together and communicates the merged data to the controller  110 . 
     The controller  110  includes a processor  145  (e.g., a microprocessor, microcontroller, ASIC, DSP, etc.) and memory  150  (e.g., flash, ROM, RAM, EEPROM, etc.), which can be internal to the processor  145 , external to the processor  145 , or a combination thereof. The controller  110  also includes other circuits such as input/output circuits and communication circuits. The controller  110  can store information on detected objects in the memory  150  and track the movement of the objects over time. 
     The HMI  130  provides an interface between the system and a driver. The HMI  130  enables the driver to deactivate one or more of the functions of the system (e.g., the LCA function and/or the RCTA function). The HMI  130  provides a suitable input method such as a button, a touch-screen display having menu options, voice recognition, etc. for turning on/off each function. The HMI  130  also provides warnings to the driver of other vehicles that may pose a potential risk. The HMI  130  provides the warning using a suitable indicator such as a tell-tale light on an instrument cluster, a mirror, a heads-up display, etc., an acoustic alarm such as a chime or buzzer, and/or a haptic indicator (e.g., vibrating the steering wheel). The system can provide different warnings based on a level of the potential risk. For example, the system can light an LED when a vehicle is located in the host vehicle&#39;s blind spot. When the system detects that the driver is steering the host vehicle toward the lane in which the vehicle in the blind spot is traveling, the system can provide an acoustic and/or haptic warning in addition to the previously lit LED. 
     An LCA system includes a blind spot detection function and a closing vehicle warning function.  FIG. 2  depicts vehicles that the LCA system warns a driver about. A vehicle  200  is traveling down a three-lane highway  205 . A second vehicle  210  is in the driver&#39;s blind spot where the driver may not be able to see the vehicle  210  (e.g., via a mirror or the driver&#39;s peripheral vision). The LCA system detects the presence of the vehicle  210  in a blind spot area and provides a warning to the driver that the vehicle  210  is in the blind spot area. In some embodiments, the LCA provides a visual indication (e.g., lighting an icon in a side-view mirror) to indicate the presence of the vehicle  210  in the blind spot. The LCA can also use information such as steering wheel angle, yaw rate, etc. to detect a lane change intention of the host vehicle  200  towards the lane where the vehicle  210  is driving. In such a situation, the LCA system can provide an additional warning (e.g., acoustic or haptic) to the driver. 
     A second vehicle  215  is depicted traveling a distance behind vehicle  200 . The LCA detects the vehicle  215  and determines whether the vehicle  215  is closing in on the vehicle  200  such that, were vehicle  200  to move into the lane to its right (i.e., where vehicle  215  is traveling), vehicle  215  would likely collide with vehicle  200 . The LCA makes this determination based on the distance the vehicle  215  is from the vehicle  200 , and how fast the vehicle  215  is moving relative to the vehicle  200 . 
       FIG. 3  shows an embodiment of the operating parameters for an LCA function. The blind spot detection function provides a warning to the driver whenever an object (e.g., a vehicle) is adjacent the vehicle  200  (e.g., within an area bounded by a middle  300  of the vehicle  200  to about 3 meters behind the vehicle  200  and from about 0.5 meters to the left and right of the vehicle  200  to about 3 meters left and right, respectively, of the vehicle  200 ). 
     The LCA function is implemented using one of the three different configurations using one of three different zones of danger A, B, and C, respectively, as shown in  FIG. 3 . Exemplary configurations are defined in ISO/DIS 17387 Intelligent transport systems—Lane change decision aid systems—Performance requirements and test procedures, version 2008. Each configuration includes a common BSD area. Each zone (A, B and C) covers a different area in a lane  305  and a lane  310  adjacent to a lane  315  that vehicle  200  is presently in. Specifically, the area covered by zone A extends from about 3 meters to about 25 meters behind the vehicle  200 , the area covered by zone B extends from about 3 meters to about 45 meters behind the vehicle  200 , and the area covered by zone C extends from about 3 meters to about 70 meters behind the vehicle  200 . For each LCA zone, a different time to collision (TTC) threshold is used. All zones A, B (which includes zone A), and C (which includes zones A and B) are bounded by an area about 0.5 meters from the side of the vehicle  200  to about 3 meters from the side of the vehicle  200 . The LCA configuration using zone A provides a warning to the driver when the speed of a vehicle in zone A, relative to the host vehicle  200 , indicates that a collision will occur in about 2.5 seconds or less (a time to collision). For the LCA configuration using zone B, a warning is given to the driver when the speed of a vehicle in zone B indicates the time to collision is about 3.0 seconds or less. For the LCA configuration using zone C, a warning is given to the driver when a vehicle in zone C indicates the time to collision is about 3.5 seconds or less. 
       FIGS. 4A and 4B  depict vehicles that pose a potential threat and that an RCTA system warns a driver about. In  FIG. 4A , a vehicle  400  is backing out of a parking space  405 . The driver of the vehicle  400  is unable to see vehicles  410  and  415  approaching from the sides (e.g., perpendicular) because the driver&#39;s vision is blocked by other parked vehicles  420  and  425 . The RCTA system detects vehicles  410  and  415  and provides a warning to the driver, enabling the driver to stop the vehicle  400  and avoid a collision.  FIG. 4B  is similar to  FIG. 4A  except that the parking space is an angled parking space. In some embodiments, the RCTA is able to detect approaching vehicles  410  and  415  when the vehicle  400  is parked on an angle (e.g., up to 60 degrees) as well as when the vehicle  400  is parked perpendicular as shown in  FIG. 4A . In addition, in some embodiments, the RCTA can detect approaching vehicles  410  and  415  when the vehicle  400  is parked on a curve or incline (e.g., up to 6 degrees). 
       FIGS. 5A to 5C  illustrate the operation of an embodiment of a system combining LCA and RCTA functions. The system starts when the ignition of the vehicle is turned on (step  505 ). The controller  110  then initializes the system (step  510 ). Initializing the system includes clearing the memory  150  of information from previous operation, and starting the object detection devices  115  and  120 . In some embodiments, the LCA and RCTA functions are enabled each time the system is restarted. In other embodiments, if the LCA and/or RCTA functions were previously disabled (e.g., by the driver using the HMI  130 ), they remain disabled when the system is restarted. 
     Next the controller  110  checks for an error in the system (step  515 ). Errors can include faulty sensors, etc. If the controller  110  detects an error, the controller  110  deactivates any LCA or RCTA warnings that are active (step  520 ) and performs error functions (step  525 ) (e.g., informing a driver of error conditions and checking faulty sensors to determine if they are functioning properly again). The controller  110  then loops back to recheck if an error exists (step  515 ). 
     If there were no errors at step  515 , the controller  110  determines the speed and trajectory of the host vehicle (step  530 ). The controller  110  uses various inputs and sensors to determine the speed and trajectory of the host vehicle. For example, a sensor can detect what gear a transmission of the host vehicle is in or the transmission can provide an indication of the gear (e.g., via a controller area network—CAN). The controller  110  can also receive an indication of the speed and direction of the host vehicle from wheel speed sensors  125 . The use of the wheel speed sensors  125  to determine direction can be important for a manual transmission vehicle which may travel in a direction different than indicated by which gear the transmission is in (e.g., rolling backwards because the clutch is engaged when in a forward gear). An engine control module can also communicate the speed of the host vehicle to the controller. 
     The controller  110  then obtains information on objects around the host vehicle from first and second object detection devices  115  and  120  (step  535 ), and determines a position, speed, acceleration, and direction of each object (step  540 ). The position, speed, acceleration, and direction of each object are relative to the speed and trajectory of the host vehicle. In some embodiments, the first and second object detection devices  115  and  120  provide the position, speed, acceleration, and direction of detected objects to the controller  110 . In other embodiments, the controller  110  determines one or more of the position, speed, acceleration, and direction of the objects based on data received from the first and second object detection devices  115  and  120 . 
     Next the controller  110  determines whether the host vehicle is moving in a forward direction (step  545 ). As discussed above, the determination can be based on a detected gear, a wheel speed, or other method (e.g., an accelerometer). If the host vehicle is moving in a forward direction, the controller  110  deactivates any active RCTA warnings (step  550 ). In some embodiments, the RCTA functions only operate when the vehicle is traveling backward. 
     Next, the controller  110  determines if an object (e.g., a vehicle) is in the host vehicle&#39;s blind spot (step  555 ,  FIG. 5B ). If a vehicle is in one of the blind spots, the controller  110  turns a warning on (step  560 ), and the operation loops back to check for errors (step  515 ). If there is no vehicle in the blind spots, the controller  110  checks if a vehicle is in a closing vehicle warning (CVW) zone of danger for the implemented CVW configuration (step  565 ). If a vehicle is a zone of danger for the implemented configuration, the controller  110  determines if a potential threat exists using the speed and acceleration of the vehicle, relative to the speed and acceleration of the host vehicle. If a time to collision (TTC) is equal to or is below a certain threshold (e.g., about 2.5 seconds for zone A, about 3.0 seconds for zone B, and about 3.5 seconds for zone C), the controller  110  determines that a potential threat exists (step  570 ). If a potential threat exists, the controller  110  turns the warning on (step  560 ), and the operation loops back to check for errors (step  515 ). 
     If at step  565  there was no object in the zone of danger or at step  570  an object in the zone of danger was not approaching fast enough to be considered a potential threat, the controller  110  turns the LCA warning off (step  595 ) and the operation loops back to check for errors (step  515 ). 
     If at step  545 , the controller  110  determines that the host vehicle is not traveling forward, the controller  110  checks if the vehicle is traveling backward (step  600 ). If the host vehicle is moving in a backward direction, the controller  110  deactivates any active LCA warnings (step  605 ). In this embodiment, LCA functions only operate when the vehicle is traveling forward. In some embodiments, the LCA functions only operate when the host vehicle speed exceeds a minimum threshold (e.g., 30 kph). In some embodiments, one or more LCA functions (e.g., blind spot detection) may continue to operate even when the vehicle is traveling backward. 
     Next, the controller  110  determines if a RCTA warning already if turned on (step  610 ,  FIG. 5C ). If the warning is turned on, the controller  110  determines if the potential threat still exists. First, the controller  110  determines if the detected vehicle is within about 20 meters of the host vehicle (step  615 ). If the detected vehicle is within a predetermined distance (e.g., about 20 meters), the controller  110  checks if the speed of the detected vehicle is greater than a threshold (e.g., about 3 kph) (step  620 ). If the detected vehicle is greater than the predetermined distance away from the host vehicle or is traveling at less than about 3 kph, the detected vehicle is not considered to be a potential threat by the controller  110 , and the controller  110  turns the warning off (step  625 ) and loops back to check for errors (step  515 ). 
     If after step  620 , the vehicle still constitutes a potential threat, the controller  110  determines if the detected vehicle is approaching the host vehicle or moving away from the host vehicle (step  630 ). If the detected vehicle is moving away from the host vehicle, the controller  110  assesses whether the detected vehicle is still within about 10 meters of the host vehicle (step  635 ). If the detected vehicle is approaching the host vehicle or the detected vehicle is within about 10 meters of the host vehicle, the controller turns the RCTA warning on (step  640 ), and continues the operation with checking for error conditions (step  515 ). If the detected vehicle is moving away from the host vehicle and is more than about 10 meters away from the host vehicle, the detected vehicle is not considered to be a potential threat, and the controller  110  turns the RCTA warning off (step  625 ), looping back to check for errors (step  515 ). 
     If the RCTA warning was not turned on (step  610 ), the controller  110  checks if a potential threat has appeared. First, the controller  110  checks if an object is within about 20 meters of the host vehicle (step  645 ). If there is an object within about 20 meters, the controller  110  checks if the object is moving within a range of speeds (e.g., between about 7 and about 35 kph) (step  650 ). If the object is moving within the speed range, the controller determines if the object is approaching the host vehicle (step  655 ). If the object is approaching the host vehicle, the controller  110  considers the object to be a potential threat, and turns the RCTA warning on (step  640 ) and continues operation with checking for error conditions (step  515 ). If at any of steps  645 ,  650 , and  655 , the controller  110  determines that a potential threat does not exist, the controller  110  turns the RCTA warning off (step  625 ) and continues operation with checking for errors (step  515 ). In some embodiments, the RCTA warning is issued on a time to collision (TTC) basis. For instance, the RCTA warning is activated if an object is within a certain distance (e.g., less than about 30 meters) of the host vehicle, and is approaching the host vehicle at a speed such that the TTC is less than a threshold (e.g., about 2.5 seconds). 
     If at step  600  ( FIG. 5A ), the controller  110  determines that the host vehicle is not traveling backward (e.g., the vehicle is stopped or parked), the controller deactivates any active LCA and RCTA warnings (step  660 ), and loops back to check for an error condition (step  515 ). In some embodiments, the controller  110  continues to execute one or more LCA and RCTA functions even though the vehicle is not moving, activating the appropriate warnings. In some embodiments, the controller  110  determines whether the vehicle was previously moving (e.g., it has just recently come to a stop) and maintains appropriate warnings for a time period. For example, a vehicle in which a blind spot detection warning is active, may maintain the blind spot warning for a period of time (e.g., twenty seconds) after coming to a stop. This allows the warning to continue while the vehicle is at a stop. 
     Thus, the invention provides, among other things, a system combining LCA and RCTA functionality. Various features and advantages of the invention are set forth in the following claims.