Abstract:
A motor vehicle blind-spot detection system has a remote sensor covering a rear-quadrant blind spot sensing zone and a forward-quadrant side impact sensing zone. A control module receives signals from a side impact sensor and the blind-spot detection sensor, calculates an approach vector of an object in the side impact sensing zone and/or the blind spot sensing zone, determines that the object will impact the vehicle, initializes a side impact algorithm controlling activation of an occupant safety device, detects an impact on the side of the vehicle and determines a magnitude of the impact, compares the magnitude of the impact with a threshold value established at least in part based upon the magnitude of the approach vector, and activates the occupant safety device if the magnitude of the impact exceeds the threshold value.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional Application No. 61/267,205 filed Dec. 7, 2009 the disclosure of which is incorporated in its entirety by reference 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to occupant safety systems for automotive vehicles, and more specifically to such systems for detecting a side impact and activating occupant restraints in response. 
     2. Background Art 
     Known side impact sensing systems use lateral accelerometers and/or air pressure sensors (typically located in a door cavity) to determine when a vehicle is involved in a side impact and to estimate the crash severity level after initial impact. With these sensors, it may take about 10 milliseconds to detect and confirm that the impact event has occurred. In general, it would be advantageous if the detection/confirmation time could be reduced, as this would leave more time for the activation/deployment of restraint systems. 
     SUMMARY 
     A vehicle safety system uses the remote object detection capability of a blind-spot sensing radar to supplement the conventional side impact sensing system described above. The system uses the blind-spot sensors (typically located adjacent the rear corners of the vehicle) to detect objects (fixed or moving) approaching the vehicle from the side, estimate/predict the impact velocity and location on the vehicle of the impact, and uses these estimates for side-impact protection decision-making. With the impact confirmation provided by one or more impact sensors at the side crash zone, the integrated system is able to sense the crash and estimate the crash severity earlier than is possible using the impact sensors alone. In many cases, even a relatively small reduction (e.g. 3-5 milliseconds) in side impact deployment decision-making time can improve occupant protection. 
     In an embodiment disclosed herein, a blind-spot detection system for a motor vehicle comprises at least one remote sensor located adjacent a rear corner of the vehicle. The remote sensor has a beam pattern covering a blind spot sensing zone disposed in a rear quadrant of the vehicle and a side impact sensing zone disposed in a forward quadrant of the vehicle. The vehicle further has at least one side impact sensor mounted at a side impact portion of the vehicle and an occupant safety device operable to protect an occupant during an impact on the side impact portion of the vehicle. A control module receives signals from the side impact sensor and the blind-spot detection sensor and is operative to: 
     calculate an approach vector of an object detected in the side impact sensing zone and/or the blind spot sensing zone; 
     determine, based on the approach vector, that the object is likely to impact the side impact portion of the vehicle; 
     initialize a side impact algorithm controlling activation of the occupant safety device; 
     detect, based on the signals received from the impact sensor, an impact on the side impact portion of the vehicle and determining a magnitude of the impact; 
     compare the magnitude of the impact with a threshold value established at least in part based upon the magnitude of the approach vector; and 
     activate the occupant safety device if the magnitude of the impact exceeds the threshold value. 
     In another embodiment disclosed herein, a method of operating an occupant safety system of a motor vehicle in response to a side impact comprises: 
     operating at least one remote object detection sensor to detect a blind-spot threat object in a first sector rearward of the sensor and to detect a collision threat object in a second sector forward of the sensor; 
     calculating an approach vector of the collision threat object; 
     determining, based on the approach vector, that the collision threat object is likely to impact a side impact portion of the vehicle; 
     in response to the determination, operating a control module to initialize a side impact algorithm controlling activation of an occupant safety device; 
     operating at least one side impact sensor to detect an impact on the side impact portion of the vehicle and determine a magnitude of the impact; 
     comparing the magnitude of the impact with a threshold value established at least in part based upon the magnitude of the approach vector; and 
     activating the occupant safety device if the magnitude of the impact exceeds the threshold value. 
     In another embodiment disclosed herein, a method of operating an occupant safety system of a motor vehicle in response to a side impact comprises: 
     operating an impact sensor to detect a magnitude of an impact on a side impact portion of the vehicle; 
     activating an occupant safety device if the impact magnitude exceeds a contact-only threshold value; 
     operating a blind spot detection sensor to detect an object in a forward quadrant relative to the vehicle; 
     determining, based on information from the blind spot detection sensor, that the object is likely to impact the side impact portion of the vehicle; 
     initializing a side impact algorithm in response to the determination that the impact is likely; 
     determining a magnitude of the impact and comparing the magnitude with a predictive threshold value established at least in part based upon the information from the blind spot detection sensor; and 
     activating the occupant safety device if the magnitude of the impact exceeds the predictive threshold value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic top view showing a host vehicle equipped with a radar-based blind-spot detection (BSD) system; 
         FIG. 2  is a schematic top view showing the host vehicle with a BSD System detecting a target vehicle approaching from the side; 
         FIG. 3  is schematic system diagram showing components of an embodiment of the invention side protection system; 
         FIG. 4  is a schematic top view showing a calculated vector of a target vehicle on a collision-course, and a radar-blanked zone and related threshold line of a blind-spot detection radar sensor; 
         FIG. 5  is a block diagram of side impact algorithm according to an embodiment of the invention; and 
         FIG. 6  is a schematic top view showing a vehicle equipped with both front and rear radar sensors. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     As seen in  FIG. 1 , a host vehicle  10  is equipped with a radar blind-spot detection (BSD) system of a type conventionally known in the automotive safety arts. Such a BSD system is adapted to detect vehicles (or other objects) present in a BSD sensing zone  12 . BSD sensing zone  12  is intended to include the area beside and/or behind host vehicle  10  which may not be easily viewable using rear-view or side-view mirrors. This area is conventionally known as the blind-spot. A BSD system may generate various types of alerts or warnings (audible, visible, haptic, etc.) to notify the driver of the host vehicle that an object is present in the blind-spot. 
     Typically, the desired BSD sensing zone  12  is in the roadway lane adjacent to the lane occupied by the host vehicle  10  and lies within an approximately 90° sector relative the host vehicle. The sector or quadrant extends from a forward-most line extending outwardly (generally parallel with or slightly aft of the vehicle y-axis) from the rear fender or bumper of the host vehicle to a rearward-most line that is almost parallel with the vehicle x-axis. Any object detected within the BSD sensing zone  12  is considered to be a blind-spot threat object. 
     As seen in  FIG. 1 , the BSD sensing zone  12  is covered by radar beams  14   a - 14   d . For ease of description, only the blind-spot on the right side of host vehicle is shown and discussed herein, but it is to be understood that a blind-spot may exist on the left side also, and that a BSD system may include sensors and other components to cover both blind-spots. 
     One known radar BSD system is produced by Valeo Raytheon Systems Inc. and utilizes a multi-beam mono-pulse radar capable of generating eight discrete beams (identified as  14   a - 14   i  in  FIG. 1 ) giving an angular resolution of approximately 20 degrees and a total coverage of 150 degrees. In the Valeo system, a target must be confirmed by at least two beams to be identified as valid and cause an alert to be generated. The potential range of such a radar operating at 24 GHz is up to approximately 50 meters. 
     As seen in  FIG. 1 , the radar beam pattern  14  achievable by such a system may extend well forward of the BSD sensing zone  12 , covering nearly the entire right side of host vehicle  10 . The exact angular extent of coverage depends upon the antenna placement, beam width, number of beams, and other factors. The full amount of coverage available with this beam pattern is not utilized in a conventional BSD system, since the right-forward quadrant covered by beams  14   e - 14   i  is easily viewed by the driver of host vehicle  10  so no driver alert is necessary if an object is detected there. 
       FIG. 2  depicts how the remote object detection function of BSD system  12  may be utilized to advantage in side impact detection. A target vehicle  16  is shown travelling along a collision course relative to host vehicle  10 , as may be the case at a roadway intersection (the vehicle lanes of which are indicated in dashed lines). As it approaches host vehicle  10 , target vehicle  16  is well within the coverage of one or more of the forward beams  14   e - 14   i . Thus, the same radar system hardware used in the conventional BSD system can be used for side impact sensing without incurring additional costs for sensor hardware. Any vehicle or other object detected by beams  14   e - 14   i  and approaching relative to the host vehicle  10  is considered to be a collision threat object. 
       FIG. 3  shows an embodiment of a side impact sensing system as installed on host vehicle  10 . The system comprises one or more side impact sensors of the type well-known in the automotive safety art and which may include, for example, air pressure sensors  18  in the left and right front door cavities, and lateral (y-axis) accelerometers  20  mounted at left and right C-pillar locations. 
     Two BSD radar sensors  22 , as may be used in a conventional BSD system of the type described above, are shown mounted on the vehicle near the left and right rear corners of the vehicle in order to provide optimum coverage of the BSD zones. 
     A restraints control module (RCM)  24  receives inputs from side impact sensors  18 ,  20  and from BSD radar sensors  22 . A radar signal processor  26  may, if required, be used to process the raw radar return data before passing it to RCM  24 . RCM  24  may receive further inputs form other vehicle sensors (not shown) and uses available inputs to make restraint activation decisions and send activation commands to passenger restraints such as side airbags  28 . Various other occupant safety systems (such as restraint belts, front airbags, curtain airbags, knee bolsters, etc.) may also be controlled by RCM  24 , but these are omitted from  FIG. 3  for clarity. 
     RCM  24  may be, as is well known in the art, a microprocessor-based device such as a computer having a central processing unit, memory (RAM and/or ROM), and associated input and output buses. RCM  24  may be an application-specific integrated circuit or other logic devices known in the art, and may include accelerometers for sensing crash pulses along both x and y axes of the vehicle. 
     Conventional blind-spot detection and warning functions based on signals from sensors  22  indicating the presence of a blind spot threat in the rear quadrant of the host vehicle  10  may be carried out by RCM  24  or by a separate control module. 
       FIG. 4  illustrates a collision-course vector V of a target detected by the forward quadrant beams ( 14   e - 14   i ) of a BSD system radar. Vector V is calculated by tracking the target  16  as it moves relative to host vehicle  10  from a first position P 1  to a second position P 2 . The vector V passing through first and second positions P 2 , P 2  indicates the closing velocity, relative direction, and expected impact location on the side of the host vehicle, all of which may be calculated from the radar signal analysis. 
     As seen in  FIG. 4 , a BSD sensor  22  located near a right rear corner of host vehicle  10  may have an angular radar-blocked zone  30  (indicated in cross-hatch in lying close to the side of the vehicle. The radar-blocked zone  30  is a zone which is not covered by the radar antenna field and is a consequence of the BSD sensor  22  being located and aimed so that it provides optimum coverage of the blind-spot sensing zone  12 , which (as described above) lies primarily in the right-rear (and left-rear) quadrant of the host vehicle. For a typical passenger vehicle, for example, the radar-blocked zone  30  may begin at a line approximately 15 degrees outward from the side of the vehicle. If the distance (measured along the x-axis) between the radar sensor  22  and a front door crash zone is 3 meters, then radar blocked zone  30  will extend approximately 0.8 m. along the y-axis from the surface of the front door. This distance is indicated by the threshold line T in  FIG. 4 . At the rear door crash zone, the blocked zone width will be less than 0.8 m. 
     When a target object travelling along vector V crosses threshold line T and enters radar-blocked zone  30 , radar target detection must necessarily cease, however radar processor  26  and/or RCM  24  continue to estimate the track of the target (based upon last known position and relative velocity) until a collision between the target and the host vehicle is confirmed by impact sensors  18 ,  20 . Various known techniques, such as Kalman filtering, may be used to accurately track and predict the path of the target object. 
     It is possible for a target vehicle  16  to be approaching host vehicle  10  on a collision-course from the right-rear quadrant and therefore to be detected by radar beams  14   a - 14   d  covering the blind-spot detection zone in that quadrant. The same tracking and vector calculation as described above is performed in such a case. 
     The side impact algorithm is preferably initialized at or just prior to when the target crosses threshold line T. Algorithm initialization may include (but is not limited to) switching from a steady-state or “background” mode to a crash-preparatory or “active” mode. In the active mode, the computer resources of RCM  24  may focus on side impact prediction and detection. RCM  24  may receives data/signals primarily from the pertinent sensors and perform calculations at a higher data-rate than in the background mode. For example, the signals from pressure sensor(s)  18  and/or satellite accelerometer(s)  20 , and from vehicle state sensors, such as Inertial Measurement Unit (IMU) and wheel speed sensors (not shown) may be sampled/received at higher data rates. Accordingly, the side impact algorithm begins earlier and runs faster than is possible if only information from contact sensors  18 ,  20  is relied upon. 
     The side impact algorithm may involve activation of the appropriate restraint device when the detected level of pressure and/or acceleration (depending upon the type of sensor) reaches a threshold value that is lower than a contact-only (non-predictive) impact threshold value used in the absence of any predictive, pre-contact information from a remote sensor. The resulting reduction in restraint deployment time is achieved without the cost associated with adding remote sensor equipment to the vehicle, since BSD sensors  22  are already present on vehicles equipped with a BSD system. 
       FIG. 5  shows a block diagram ( 100 ) of a side impact algorithm using blind-spot radar data fusion to improve reaction/activation/response time. The radar transmitter generates radio frequency (RF) waves that are broadcast through antennas of the blind-spot detection system ( 110 ). The transmitted RF waves come into contact with a target and are scattered in all directions. The scattered waves that are reflected back toward the host vehicle are received by the receivers, enabling the radar to detect the target ( 120 ). Based on the detected signals, signal processing can broadly classify any target objects ( 125 ) (for example, discriminating between a moving vehicle and a stationary pole), assess the collision threat (expressed as a probability, for example), and determine the expected impact location, impact velocity and impact direction ( 130 ). 
     If the collision threat exceeds a minimum value ( 140 ), and the target crosses the threshold line T ( 145 ) in a position indicating that a side impact is expected, a side impact algorithm is initialized ( 150 ). If the vehicle is equipped with impact sensors associated with a front door crash area and a discrete rear door crash area, the algorithm processing may follow two parallel paths, one for a predicted impact on the front door crash zone area and the other for a predicted impact on the rear door crash zone. For the path of front door crash zone, the signals from impact sensors nearest that zone (in this example assumed to be pressure sensors  18  as shown in the embodiment of  FIG. 3 ) are obtained and processed ( 155 ). Using a predefined threshold value that preferably involves some combination of pressure and incoming velocity values ( 160 ), a deployment decision for restraint(s) associated with the front door crash zone will be made if the detected values exceed the Threshold  1  ( 165 ). For example, if the incoming velocity is relatively high the value of the pressure increase detected by a sensor  18  may be relatively low to meet Threshold  1 , while if the incoming velocity is relatively low a higher detected pressure increase will be required. The lower required pressure increase in the first case will shorten the restraint activation time, which will be necessary if the target velocity is high. In any event, the required pressure increase to meet Threshold  1  will in most cases be a lower value than would be possible without target vector information from the blind-spot detection system, because the risk of a “false positive” activation is substantially reduced by the inclusion of the target vector information. 
     A similar procedure is applied to the path for rear door crash zone ( 175 - 190 ) using data from the impact sensors closet to the rear door crash zone (in this example assumed to be accelerometers  20  as shown in the embodiment of  FIG. 3 ). The Threshold  2  value established (step  180 ) may be different from the Threshold  1  value, depending upon the particular type of impact sensor (pressure or accelerometer). 
     If the vehicle has only one crash zone identified on a side of the vehicle, only one of the two branches ( 155 - 170  and  175 - 190 ) shown in  FIG. 5  is required. 
     As shown in  FIG. 6 , a side impact protection system may include both forward  34  and rear  36  radar sensors providing total side sensing capabilities without any radar blocked zones. Forward sensors  34  may be provided as part of a collision avoidance or mitigation system. In such a system, data from both sets of radar sensors  34 ,  36  can be used for more reliable prediction of side collision details. The two radars can be processed independently or fused together to increase robustness for side collision prediction. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.