Patent Publication Number: US-7712776-B2

Title: Method and control system for predictive deployment of side-impact restraints

Description:
TECHNICAL FIELD 
   The present invention relates to vehicle safety restraints and deployment systems. More particularly, the present invention relates to a method and system for deployment control of side-impact adaptive restraints within a vehicle. 
   BACKGROUND OF THE INVENTION 
   To improve the safety aspects of vehicles, many manufacturers are now including side and curtain airbags. Side and curtain airbags may be employed in a vehicle side door, an A-pillar, a B-pillar, and other side structures and components of a vehicle. Side airbags are presently deployed in response to the information collected from side or lateral accelerometers and crush or pressure sensors. The accelerometers are used to determine or estimate severity of a collision and the pressure sensors are used to determine the condition of a vehicle or an estimated amount of intrusion into a vehicle of an object, after contact therewith. Upon receipt of the stated information, algorithms are used to evaluated conditions of a collision for restraint deployment. 
   For a 30 mph vehicle-to-vehicle collision, current deployment systems require a short activation time for restraint deployment, which is the time difference between when a host vehicle contacts an object and when a restraint is deployed. It is common for this period to be approximately 3-5 ms. From the onset of a collision, side airbags typically fully inflate in approximately 10-15 ms after activation. The stringent activation time requirements are due to the limited side structure of a vehicle and the limited available space between the interior side of the vehicle and an occupant, such as for example between an inside door panel and a vehicle occupant. 
   It is desirable to deploy airbags at different rates depending upon the severity of a collision. It is also desirable to deploy an airbag such that it is fully deployed at the appropriate time to maximize collision energy absorption and prevent injury to a vehicle occupant. It is understood that injury mitigation is not maximized when airbag deployment inaccurately occurs at an inappropriate time. 
   Also, current side airbag deployment systems, in certain scenarios, may be limited in their ability to differentiate between severe collisions and marginal collisions. For example, an accelerometer, installed in one selected area of a vehicle, may not detect or fully detect the energy experienced in a localized collision event in another or nearby area of the vehicle. Subsequently, non-deployment, or late deployment of side-restraints can occur. 
   Additionally, some airbag deployment systems, that include front airbags, can accidentally deploy the front airbags during a side collision. The National Automotive Sampling System indicates that 16% of frontal airbags have deployed for 3 o&#39;clock side-collisions, while 22% of frontal airbags have deployed for 9 o&#39;clock side-collisions. 
   Furthermore, current side airbag deployment systems do not account for occupant characteristics, such as occupant size, weight, and position within a seat system. As an example, it can be undesirable for a side airbag to deploy when an occupant is resting against a door panel or when a small occupant, such as a young child, is located in the seat system of concern. 
   Thus, there exists a need for an improved airbag deployment system for a vehicle that provides improved side airbag deployment control with accurate and appropriate deployment timing. The system should account for localized collisions, varying degrees of collision severity, and occupant characteristics, and prevent inadvertent deployment of front airbags during a side collision event. 
   SUMMARY OF THE INVENTION 
   The present invention provides systems and methods of controlling the deployment of side restraints within a vehicle. A control system for a vehicle is provided and includes an adaptive restraint. A side sensor is configured to detect an object, in a detection zone along a side of the vehicle, and generate an object detection signal. A controller determines a decision-making zone for the adaptive restraint, an activation time for and a deployment status of the adaptive restraint, and activates the adaptive restraint before or after contact between the object and the vehicle side structure. 
   The embodiments of the present invention provide several advantages. One such advantage, provided by several embodiments of the present invention, is the provision of a side restraint deployment control system that accurately and appropriately deploys side collision related restraints. In so providing, the stated embodiments are capable of determining restraint deployment times and are capable of activating restraints before or after contact between an impending collision object and a host vehicle. The stated embodiments also account for localized collisions and minimize inadvertent deployment. In addition, the stated embodiments account for collision severity. 
   Another advantage provided by an embodiment of the present invention is the provision of a side restraint deployment control system that accounts for various occupant characteristics when determining deployment times and whether to activate a restraint. As such, the stated embodiment minimizes injury to vehicle occupants. 
   Yet another advantage provided by an embodiment of the present invention is the provision of a side restraint deployment control system that performs a side collision confirmation and signals frontal restraint systems of side collision status, which aids in the prevention of unwarranted deployment of side and frontal restraints. 
   The present invention itself, together with attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of this invention reference should now be made to embodiments illustrated in greater detail in the accompanying figures and described below by way of examples of the invention wherein: 
       FIG. 1  is a block diagrammatic view of an integrated control system architecture for a vehicle in accordance with an embodiment of the present invention; 
       FIG. 2  is a logic flow diagram illustrating a method of controlling activation of adaptive restraints within a vehicle in accordance with an embodiment of the present invention; 
       FIG. 3  is a top view of the vehicle of  FIG. 1  illustrating the side collision sensor fields-of-view and corresponding detection zones in accordance with an embodiment of the present invention; and 
       FIG. 4  is a decision-zone predictive time plot in accordance with an embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   In the following figures the same reference numerals will be used to refer to the same components. Also, in the following description, various operating parameters and components are described for multiple constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
   Additionally, in the following description, the term “performing” may include activating, deploying, initiating, powering, and other terms known in the art that may describe the manner in which a safety restraint system or a comfort and convenience feature may be operated. 
   As well, in the following description, various safety restraints are discussed. The restraints may be reversible or irreversible. Reversible restraints refer to restraints that may be reset to their original form or used repeatedly without a significant amount of functional deficiency, which may be determined by a system designer. Irreversible restraints refer to restraints such as airbags that, once deployed, are not reusable. 
   Furthermore, a control signal may include information pertaining to the above-stated reversible and irreversible restraints or may include other information, such as collision warning information. For example, the control signal may contain object detection information, which may be used to indicate to a vehicle operator the presence or close proximity of a detected object. 
   In addition, the term “object” may refer to any animate or inanimate object. An object may be a vehicle, a pedestrian, a road sign, a vehicle occupant, or other object known in the art. 
   Also, although the present invention is primarily described with respect to side restraint deployment, the present invention may be applied to various other safety system deployments known in the art. 
   Referring now to  FIG. 1 , a block diagrammatic view of an integrated control system architecture  10  for a host vehicle  12  in accordance with an embodiment of the present invention is shown. The vehicle  12  has sides  13  that extend longitudinally between the front and rear  14  of the vehicle  12 . The system architecture  10  includes a main controller  16  that determines activation times and the deployment status for selected adaptive restraints  15  and in response to various parameters described below performs activation thereof. 
   The system architecture  10  includes the main controller  16  that has an object and host vehicle accident state prediction (ASP) module  18  and a side restraint deployment (SRD) module  20 . The ASP module  18  receives object related information from object detection sensors  22 , host vehicle dynamic related information from dynamic sensors  24 , and in response thereto determines various side collision related parameters. The side collision related parameters may include range, range rate, position, and heading of an object relative to the vehicle  12 . The side collision related parameters may also include the amount of time that an object is within a detection zone, lateral velocity of the vehicle  12 , as well as other related parameters known in the art. The ASP module  18  in response to the side collision parameters selects or determines a decision zone, which is utilized in performing various restraint deployment related tasks, and estimates time-to-collision and desired activation time of one or more of the restraints  15 . 
   The SRD module  20  receives the host vehicle and obstacle trajectories, the time-to-collision, and the activation time of the restraints  15  from the ASP module  18 , occupant characteristics from occupant characteristic sensors  26 , collision confirmation information from collision confirmation or contact sensors  28 , and in response thereto controls activation of the restraints  15 . The SRD module  20  obtains information corresponding to the vehicle  12 , detected objects of concern, and occupants within the vehicle  12  to tailor activation and deployment of the restraints  15 . The SRD module  20  also determines the appropriate stage of deployment for situations when multi-stage deployable restraints are utilized. The SRD module  20  includes an internal counter  21 . The counter  21  is used to assure that deployments of the restraints  15  occur at the appropriate times. 
   The above-stated features of the ASP module  18  and the SRD module  20 , as well as further features and performance tasks are described in greater detail below. 
   The main controller  16  may perform as a signal processor and may include analog-to-digital converters, filters, or amplifiers, as well as other signal conditioning components known in the art. The information collected from the various sensors of the present invention may be signal processed at the sensors, by the controller  16 , by a separate processor, or by a combination thereof. The controller  16  may be microprocessor based, such as a computer having a central processing unit, have memory (RAM and/or ROM), and associated input and output buses. The controller  16  may be an application-specific integrated circuit or be formed of other logic devices known in the art. The controller  16  may be a portion of a central vehicle main control unit, an interactive vehicle dynamics module, a restraints control module, a main safety controller, or may be a stand-alone controller as shown. 
   The object detection sensors  22  include side remote sensors  30 , such as driver side remote sensors  32  and passenger side remote sensors  34 . The side sensors  30  are used to detect objects within detection zones along side of the vehicle  12  and to collect object related information associated therewith and generate object detection signals. The term “side” does not refer to the front and rear of the vehicle  12 . Sample detection zones are best seen and described below with respect to the embodiment of  FIG. 3 . The side sensors  30  may be located in various locations along the sides of the vehicle  12 . The side sensors  30  may be located in a vehicle door, in a vehicle pillar, such as an A-pillar or B-pillar, in a side rail or frame, or in various other vehicle structures. The side sensors  30  may be of various styles and types, for example the side sensors  30  may be in the form of radar sensors, lidar sensors, vision sensors, ultrasonic sensors, infrared sensors, or in some other form known in the art. In one embodiment of the present invention, the side sensors  30  are located within the B-pillars of the vehicle  12  and are in the form of radar sensors. 
   The vehicle dynamic sensors  24  are used to determine dynamics, such as velocity, acceleration, and yaw rate of the vehicle  12  and to generate vehicle dynamic signals. The vehicle dynamic sensors  24  may include a vehicle speed sensor  36 , a yaw rate sensor  38 , and a steering angle sensor  40 . The vehicle speed sensor  36  may be in the form of a transmission rotation sensor, a wheel speed sensor, or other vehicle speed sensor known in the art. The vehicle dynamic sensors  24  may include accelerometers, optical sensors, or other velocity or acceleration sensors known in the art. 
   The occupant sensors  26  are used to determine various occupant characteristics, such as occupant positioning within a seat system, occupant size, shape, and weight, and to generate occupant signals indicative thereof. The occupant sensors  26  may also be of various styles. The occupant sensors  26  may be in the form of radar sensors, lidar sensors, vision sensors, ultrasonic sensors, infrared sensors, pressure sensors, weight sensors, strain gauges, piezoelectric or piezoresistive sensors, or may be in some other form known in the art. The occupant sensors  26  may also include remote and local accelerometers, seat belt sensors, occupant position sensors, and seat track sensors. 
   The contact sensors  28  are utilized to verify that a side collision has occurred and to generate collision confirmation signals. The contact sensors  28 , like the side sensors  30 , may also be in various locations along the side of the vehicle  12  and may even be more internally located within the vehicle  12 . The contact sensors  28  may be in the form of accelerometers, pressure-sensors, piezoelectric or piezoresistive sensors, or may be in some other form known in the art. 
   The restraints  15  are generally in the form of passive safety systems electronically augmented, and include front airbags  42 , side airbags  44 , and side curtains  46 . The front airbags  42  are controlled via a front airbag control module  48 . The side restraints  44  and  46  are deployed via inflators  50 . The side airbags  44  may be in the form of seat integrated or door mounted airbags. The side curtains  46  may be in the form of pillar or roof supported head restraints. The restraints  15  may also include other airbags or deployable restraints, as well as seatbelt control, knee bolster control, head restraint control, pretensioner control, airbag control, and other side impact passive safety system control known in the art. 
   Referring now also to  FIG. 2 , a logic flow diagram illustrating a method of controlling the activation of the restraints  15  in accordance with an embodiment of the present invention is shown. 
   In step  100 , the object detection sensors  22  generate object detection signals. The object detection sensors  22  monitor detection zones, such as the detection zones  60  shown in  FIG. 3 . Although only a pair of detection zones  60  is shown for a pair of side sensors  62 , any number of detection zones may be utilized with any number of side sensors. The detection zones  60  may include various areas along each side  13 . 
   In the embodiment of  FIG. 3 , the detection zones  60  include a first detection zone  63  and a second detection zone  64 . The first zone  63  includes an area between 2 o&#39;clock and 4 o&#39;clock, 2 o&#39;clock and 4 o&#39;clock refer to positions at approximately 60° and 120° from a longitudinal line  67  extending along the right side  69  and as represented by lines  66 , and up to approximately two meters from the vehicle  12 . The second zone  64  includes an area between 8 o&#39;clock and 10 o&#39;clock, 8 o&#39;clock and 10 o&#39;clock refer to positions at approximately 240° and 300° from the longitudinal line  71  extending along a left side  73  and as represented by lines  68 , and up to approximately two meters from the vehicle  12 . The side sensors  62  are in the form of radar sensors that have a field-of-view of approximately 55°. The detection zones  60  are sized, in general, to cover or monitor one detected vehicle at a time, even though three detected vehicles  70  are shown. 
   The decision-making zones based on the detection zones  60  may be determined in response to adaptive restraint time constants and trajectories of detected objects, as well as in response to other vehicle and object related parameters known in the art, some of which mentioned herein. 
   In step  102 , the ASP module  18  determines range and range-rate or velocity of the detected objects of concern relative to the vehicle  12 . The range-rate information may be obtained via the range information or may be determined directly, depending upon the type of object detection sensors utilized. 
   In step  104 , the ASP module determines whether the objects are within the detection zones  60  and whether their impending relative velocity is greater than or equal to a minimum velocity threshold V min . The ASP module  18  may track electromagnetic reflections of the detected objects using radar sensors and may ignore or filter tracked objects that are not in a collision path with the vehicle  12 . In so doing, the ASP module  18  may utilize equations 1-3, where R m (k) is the relative range of an object for a given time k, R max  is the decision-making zone range threshold, which as stated may be set equal to approximately two meters, and V rel  is the relative velocity or closing velocity of the object.
 
| R   m ( k )|≦ R   max   (1)
 
| R   m ( k+ 1)|−| R   m ( k )|&lt; R   max   (2)
 
V rel ≧V min   (3)
 
   The minimum velocity threshold V min  is used to prevent restraint deployment in situations where restraint deployment is not desired or warranted. For example, it is undesirable to deploy a restraint in a situation when a detected object is traveling at a slow relative velocity such that deployment of a restraint does not assist in the prevention of an occupant injury, but rather increases vehicle repair costs, due replacement of the deployed restraints and other associated repairs. 
   In step  106 , the detection zones  60  are evaluated. Detected objects within the detection zones  60  are tracked for a minimum time period, represented by O t     —     num  in equation 4, where T sens  is the sampling time of the object detection sensors  22  used in the detection of the objects. As an example, a radar sensor sampling frequency can range from approximately 50-100 Hz. The minimum time period O t     —     num  corresponds to a number of sample returns wherein a particular object of interest has been detected; each return has an associated time interval. Thus, the minimum time period O t     —     num  is equal to the number of detected object samples multiplied by a sampling rate. 
   
     
       
         
           
             
               
                 
                   O 
                   t_num 
                 
                 ≥ 
                 
                   
                     R 
                     max 
                   
                   
                     
                       V 
                       rel 
                     
                     ⁢ 
                     
                       T 
                       sens 
                     
                   
                 
               
             
             
               
                 ( 
                 4 
                 ) 
               
             
           
         
       
     
   
   In step  108 , the ASP module  18  block filters objects, which are parallel to the vehicle  12 . The ASP module  18  compares the relative velocity V rel  with the minimum velocity threshold V min , where the relative velocity V rel  is determined using equation 5, T is time, and 
           1   τ         
is the bandwidth of the filter.
 
                   V   rel     =           Δ   ⁢           ⁢     R   meas         Δ   ⁢           ⁢   t       ⁡     [     1   -     ⅇ     -     T   τ           ]       ≥     V   min               (   5   )               
When the relative velocity V rel  is greater than or equal to the minimum velocity threshold V min  the ASP module  18  proceeds to step  110 , otherwise the ASP module  18  discards or ceases to monitor the object and returns to step  102 .
 
   In step  110 , position and dynamics of the vehicle  12  are determined. The vehicle dynamic sensors  24  are used to generate the vehicle longitudinal speed U h , a yaw rate signal ψ, and a steering dynamics or heading angle signal δ. The ASP module  18  determines the position of the vehicle (x h , y h ) and lateral velocity of the vehicle ν h     —     lat  in response to the vehicle longitudinal speed U h , the yaw rate ψ, and the heading angle δ by combining vehicle dynamics equations with vehicle position equations in a state-space representation as know in the art, using equations 6-13.
 
{dot over (r)}=ν r   (6)
 
{dot over (ν)} r =α r   (7)
 
 {dot over (x)}   h   =U   h  cosδ−ν h     —     lat  sinδ   (8)
 
 {dot over (y)}   h = U   h  sinδ+ν h     —     lat  cosδ   (9)
 
   {dot over (x)} =M x +I u +F w     (10)
 
   y =C x + v     (11)
 
 x =[r ν r  ψ δ ν h     —     lat  x h  y h ] T   (12)
 
   {circumflex over ({dot over (x)} =M  {circumflex over (x)} +I u +K (   y −C  {circumflex over (x)}   )  (13)
 
   In equations 10-13, M is the host vehicle dynamic matrix, I is the host vehicle matrix for the input u, F is the input noise matrix, C is the output matrix, and y is the output vector. The input random noise disturbance and measurement noise are represented by vectors w and v respectively. A gain matrix is represented by K, which is selected to minimize the error of the estimates due to the process and measurement noise. The state variables of the system  10  are given by equation 12. The estimated path of the vehicle  12  and the closing velocity V rel  of an object are given by equation 13, which may be referred to as an “observer”. Equation 13 is designed to filter the yaw rate and steering angle measurements. 
   In step  114 , the ASP module  18  determines whether an object is a moving or stationary object in response to the lateral velocity ν h     —     lat , relative velocity V rel , and a tolerance value β 1  using equation 14. When equation 14 is satisfied a collision with a stationary object may occur.
 
ν h     —     lat = V   rel ±β 1   (14)
 
   In step  116 , the ASP module  18  determines whether the vehicle  12  and the detected object are on a collision course. When the vehicle  12  and the detected object are on a collision course, the ASP module  18  proceeds to step  118 , otherwise the ASP module  18  returns to step  102 . 
   In step  118 , once the measured radial distance or range of the objects are confirmed, the latest detected objects that are of concern are compared and the closest detected object relative to the vehicle  12  is used to determine the time-to-collision (TTC). The time-to-collision TTC is determined in response to the estimated closing velocity V rel . The approximate time available for estimating the time-to-collision TTC is provided in the plot of  FIG. 4 . The time available is plotted in relation to the range and the range rate of an object relative to the vehicle  12 . Of course, this plot may be altered depending upon the direction of travel or heading of the object, the sophistication level of the object detection sensors  22 , and the ability of corresponding hardware and software to monitor and track detected objects. 
   In step  120 , the ASP module  18  determines an estimated speed dependent potential collision severity λ sev  of the collision in response to the above-stated vehicle and object dynamics. 
   In step  122 , the occupant sensors  26  generate occupant signals, as stated above, providing size, weight, and positioning information of the occupants. In one embodiment, the occupant sensors  26  are used to determine the distance between the occupants and the interior sides of the vehicle  12  or the distance between the occupants and the side airbags  44 . 
   In step  124 , the SRD module  20  determines the type of restraint to deploy and the activation or restraint deployment time RDT in response to the collision severity λ sev  and the occupant signals. The SRD module  20  determines and verifies plausibility of range, change in range, range-rate, position, last predicted closest position, and heading of the object of concern relative to the vehicle  12 . 
   In step  126 , the SRD module  20  determines whether the magnitude of the time-to-collision TTC is less than the restraint deployment time RDT plus a sensor and microprocessor dependent time delay ε. When this is the case the SRD module  20  proceeds to step  128 , otherwise the SRD module  20  returns to step  102 . 
   In step  128 , the SRD module  20  determines whether a confirmation of an actual collision is desired. When a confirmation is not desired the SRD module  20  proceeds to step  130 , otherwise the SRD module  20  proceeds to step  140 . 
   In step  130  the SRD module  20  initializes the synchronization internal clock counter  21 , to track the activation difference time α time  between the predicted contact time with the object and the activation time of a restraint, to assure precise time deployment of the restraint. 
   In step  132 , the SRD module  20  determines whether the magnitude difference between the time-to-collision TTC and the restraint deployment time RDT is approximately equal to the activation difference time α time . The SRD module  20  monitors the activation difference time α time  using the internal clock counter  21  to assure that restraint activation is performed at the proper time. When the difference is equal to the activation difference time α time  the SRD module  20  proceeds to step  134 , otherwise the SRD module  20  returns to step  130 . 
   In step  134 , the SRD module  20  may signal the front airbag module  48  the activation status of the side restraints  30 . The front airbag module  48  may then determine whether frontal airbag deployment is appropriate. 
   In step  136 , the controller  16  determines whether to deploy single state restraints, multi-stage restraints, or a combination thereof. Step  138  is performed for single stage deployment of restraints. A restraint, such as one of the side restraints  44  or  46  is deployed for a single-stage deployment. Steps  150  through  156  are performed when multi-stage deployment of restraints is performed. 
   In situations when collision confirmation is not desired equation 15 is used and provides a first restraint deployment status RDS 1  and represents tasks performed in steps corresponding to such situations. Seat integrated/door mounted airbags for torso protection and pillar/roof-supported airbags for head protection, as examples, may be activated based on the characteristics of a potential collision. 
   
     
       
         
           
             
               
                 
                   RDS 
                   1 
                 
                 = 
                 
                   { 
                   
                     
                       
                         1 
                       
                       
                         
                           
                             if 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               ( 
                               
                                 
                                    
                                   TTC 
                                    
                                 
                                 ≤ 
                                 
                                   RDT 
                                   + 
                                   ɛ 
                                 
                               
                               ) 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
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                             ⁢ 
                             
                               ( 
                               
                                 
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                                     TTC 
                                     - 
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                                    
                                 
                                 = 
                                 
                                   α 
                                   time 
                                 
                               
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                           ⁢ 
                           
                               
                           
                         
                       
                     
                     
                       
                         0 
                       
                       
                         otherwise 
                       
                     
                   
                 
               
             
             
               
                 ( 
                 15 
                 ) 
               
             
           
         
       
     
   
   The following steps  140 - 156  describe deployment tasks that are performed after collision confirmation is detected and desired by an airbag collision contact sensor. 
   In step  140 , the SRD module  20  adjusts a contact sensor threshold δ thres  to satisfy a second restraint deployment status RDS 2  of equation 16, where K s  is the gain-scheduled parameter for adjusting the accelerometer threshold, V cal  is the threshold velocity, δ cal  is the calibrated confirmation signal constant, and β 2  is the contact sensor output. Equation 16 represents tasks performed in steps  126 ,  140 ,  146 , and  150 . 
   
     
       
         
           
             
               
                 
                   RDS 
                   2 
                 
                 = 
                 
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                         1 
                       
                       
                         
                           
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                               ( 
                               
                                 
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                                    
                                 
                                 = 
                                 
                                   α 
                                   time 
                                 
                               
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                                 β 
                                 2 
                               
                             
                             &gt; 
                             
                               
                                 δ 
                                 thres 
                               
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               where 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 δ 
                                 thres 
                               
                             
                           
                           = 
                           
                             
                               K 
                               s 
                             
                             ⁢ 
                             
                               
                                 V 
                                 
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                                   ⁢ 
                                   
                                       
                                   
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                                 rel 
                               
                             
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                               δ 
                               
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                                 ⁢ 
                                 
                                     
                                 
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                         0 
                       
                       
                         otherwise 
                       
                     
                   
                 
               
             
             
               
                 ( 
                 16 
                 ) 
               
             
           
         
       
     
   
   For localized side-collision events, such as a collision with a pole, the collision energy is concentrated at the onset of the collision and tends to “fold” the impacted location of a vehicle. In certain situations, conventional side restraint controllers may detect and classify a localized collision as a minor collision, which in turn may cause the controller to determine that deployment of a side restraint is not warranted. A side restraint may therefore not be deployed or deployment thereof may be delayed. When the lateral velocity ν h     —     lat  is approximately equal to the closing-velocity V rel , the SRD module  20  determines that the object of interest is a stationary object and adjusts the threshold δ thres  accordingly to account for a potential localized collision and provide improved and appropriate airbag deployment. 
   In step  142 , the SRD module  20  determines side restraints to deploy and conditions those side restraints for deployment after confirmation of a collision. In step  144 , the SRD module  20  initializes the synchronization internal clock counter  21  to track the activation difference time, to assure precise deployment time. 
   In step  146 , as in step  132 , the SRD module  20  determines whether the magnitude difference between the time-to-collision TTC and the restraint deployment time RDT is approximately equal to an activation difference time α time . The SRD module  20  monitors the activation difference time α time  to assure that restraint activation is performed at the proper time. When the difference is equal to the activation difference time α time  the SRD module  20  proceeds to step  148 , otherwise the SRD module returns to step  144 . 
   In step  148 , the contact sensor  28  generates a collision confirmation signal in response to the detection of a collision or contact with an object. In step  150 , the SRD module  20  determines whether the contact sensor output β 2  is greater than the threshold δ thres . When the contact sensor output β 2  is greater than the threshold δ thres  the SRD module  20  proceeds to step  152 , otherwise the SRD module  20  does not deploy a side restraint and returns to step  102 . 
   In step  152 , the SRD module  20  may signal to the front airbag control module  48  and other supporting componentry the activation status of the side restraints  44  and  46 . The SRD module  20  also monitors the internal counter  21 . 
   In step  154 , the controller  16  determines whether to deploy one or more of the side restraints  44  and  46  in a single stage mode, a multi-stage mode, or a combination thereof. When it is determined to deploy a side restraint in the single stage mode, step  156  is performed. When it is determined to deploy a side restraint in the multi-stage mode, steps  158 - 164  are performed. 
   In steps  158 - 164 , the SRD module  20  activates selected side restraints in the multi-stage mode in response to a collision severity value and current occupant characteristics. In step  158 , the collision severity value λ sev  is determined according to equation 17, where G rs  is a gain that is adjusted based on the confidence in or reliability of an object detection sensor to accurately detect an object. G 1  is the relative velocity regulatory gain, and V 0  is the threshold velocity. 
   
     
       
         
           
             
               
                 
                   λ 
                   sev 
                 
                 = 
                 
                   
                     G 
                     rs 
                   
                   ⁢ 
                   
                     
                       
                         G 
                         1 
                       
                       ⁡ 
                       
                         ( 
                         
                           
                             V 
                             rel 
                           
                           
                             V 
                             0 
                           
                         
                         ) 
                       
                     
                     . 
                   
                 
               
             
             
               
                 ( 
                 17 
                 ) 
               
             
           
         
       
     
   
   In step  160 , the SRD module  20  determines a restraint determining value Res det  using equation 18, where G ws  is the weight sensor reliability gain, G 2  is the weight regulatory gain, W occ  is the occupant weight, W 0  is the weight threshold, G ps  is the occupant proximity sensor reliability gain, p occ  is the occupant position relative to a side airbag, side panel, or interior side of the vehicle  12 , and p 0  is the threshold position. 
   
     
       
         
           
             
               
                 
                   Res 
                   det 
                 
                 = 
                 
                   
                     
                       G 
                       ws 
                     
                     ⁢ 
                     
                       
                         G 
                         2 
                       
                       ⁡ 
                       
                         ( 
                         
                           
                             W 
                             occ 
                           
                           
                             W 
                             0 
                           
                         
                         ) 
                       
                     
                     ⁢ 
                     
                       λ 
                       sev 
                     
                   
                   + 
                   
                     
                       G 
                       
                         p 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         s 
                       
                     
                     ⁡ 
                     
                       ( 
                       
                         
                           p 
                           occ 
                         
                         - 
                         
                           p 
                           0 
                         
                       
                       ) 
                     
                   
                 
               
             
             
               
                 ( 
                 18 
                 ) 
               
             
           
         
       
     
   
   In step  162 , the restraint determining value Res det  is used to determine an inflation stage selection Res_stage using equation 19 where L 3 -L 0  represent a series of progressively less severe deployment stages, including a potentially no deployment stage, and γ 1 -γ 3  are the thresholds corresponding to each stage level of deployment. 
   
     
       
         
           
             
               
                 Res_stage 
                 = 
                 
                   { 
                   
                     
                       
                         
                           L 
                           3 
                         
                       
                       
                         if 
                       
                       
                         
                           ( 
                           
                             
                               Res 
                               det 
                             
                             ≥ 
                             
                               γ 
                               3 
                             
                           
                           ) 
                         
                       
                     
                     
                       
                         
                           L 
                           2 
                         
                       
                       
                         if 
                       
                       
                         
                           ( 
                           
                             
                               γ 
                               2 
                             
                             ≤ 
                             
                               Res 
                               det 
                             
                             &lt; 
                             
                               γ 
                               3 
                             
                           
                           ) 
                         
                       
                     
                     
                       
                         
                           L 
                           1 
                         
                       
                       
                         if 
                       
                       
                         
                           ( 
                           
                             
                               γ 
                               1 
                             
                             ≤ 
                             
                               Res 
                               det 
                             
                             &lt; 
                             
                               γ 
                               2 
                             
                           
                           ) 
                         
                       
                     
                     
                       
                         
                           L 
                           0 
                         
                       
                       
                         if 
                       
                       
                         
                           ( 
                           
                             
                               Res 
                               det 
                             
                             &lt; 
                             
                               γ 
                               1 
                             
                           
                           ) 
                         
                       
                     
                   
                 
               
             
             
               
                 ( 
                 19 
                 ) 
               
             
           
         
       
     
   
   In step  164 , the SRD module  20  deploys one or more multi-stage side restraints in response to the inflation stage selection Res_stage. 
   The above-described steps are meant to be illustrative examples; the steps may be performed sequentially, synchronously, simultaneously, or in a different order depending upon the application. 
   The present invention provides a deployment control system for accurate and proper control of side restraint deployment. The control system deploys respective restraints in response to determined relative heading and dynamics of an impending collision object relative to a host vehicle. The control system determines an early deployment time, for activation of an adaptive restraint before or shortly after a collision occurs, to provide enhanced occupant protection. The control system minimizes inadvertent deployment of side-restraints and front airbags, minimizes late deployment of side restraints, and provides effective deployment decisions for localized collisions. Restraints are deployed in response to occupant characteristics in conjunction with predicted velocity dependent potential collision severity estimation. The algorithms utilized within the control system are tailored to dissipate the kinetic energy of occupants during a side collision event such that injuries can be avoided or effectively mitigated. Coordinated activation of multi-stage airbag deployment is also provided. The control system accounts for sensor availability and performance. 
   While the present invention has been described in connection with one or more embodiments, it is to be understood that the specific mechanisms and techniques which have been described are merely illustrative of the principles of the invention, numerous modifications may be made to the methods and apparatus described without departing from the spirit and scope of the invention as defined by the appended claims.